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497 Cards in this Set
- Front
- Back
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What do drawings do? |
Conveys information to the fabricator and supplies a permanent record of the fabrication
120102a pg 4 |
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Who draw up plans?
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The draftsman |
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What are the copies of original drawing called?
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Blueprints
120102a pg 4 |
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What are working drawings?
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The drawings created during the process of producing the blueprints before the final draft |
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What do working drawings allow for?
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Needed changes and revisions before the final draft is approved |
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What is CAD?
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Computer Aided Drafting
120102a pg 5 |
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What are specifications?
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written instructions necessary for that particular job |
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When there is a conflict between the specifications and the drawings what do you assume is correct? |
the information in the specifications is usually assumed to be correct(best to confirm with the engineer or architect |
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What are the 5 divisions of working drawings and blueprints?
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-architectural |
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What are architectural drawings? |
a line drawing that shows plan and/or elevation views of the proposed building for showing it’s overall appearance
(may contain perspectives of the finished structure) 120102a pg 6 |
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What are structural drawings?
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All the drawings that describe the structural members of the building and their relationship to each other |
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What drawings can structural drawings contain?
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-foundation plans and details |
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What are mechanical drawings?
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they show all the required mechanical components of the building |
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What items can Mechanical drawings include?
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-heating |
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What are electrical Drawings?
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they locate the various outlets, indicate the routing of circuits, show the location and size of panel boards and illustrate other electrical details |
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What are landscaping drawings?
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They show the elevations of the ground that surrounds the building and location of trees and plants |
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What are the three basic elements found on a blue prints?
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-lines |
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What do lines convey?
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-the shape of the object |
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Dimensions give what information?
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sizes and locations
120102a pg 7 |
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What do notes give information on?
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details of construction not shown by lines.(may be symbols or abbreviations) |
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What are object lines? |
(visible line) |
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What are Hidden lines?
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Broken lines that of medium thickness used to show edges and outlines not visible to the eye |
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What are section lines?
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-They represent different types of material when there is an imaginary cut surface |
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What are centerlines?
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-Thin broken line made up of a series of short and long dashes that are alternately spaced |
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What are Extension lines?
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-Thin lines that extend from the object with a slight break between |
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What are dimension lines?
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-Thin lines with arrowheads, unbroken except where the dimension is placed |
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What are terminals?
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arrows, slashes, or dots at the end of dimension lines |
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What are leader lines?
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-Thin straight line or a fine curved line |
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What are cutting plane lines?
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Indicates where an imaginary cut is made through an object |
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What do the arrows on cutting lines indicate?
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-The direction in which the section is to be viewed |
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What are viewing lines?
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line used outside an object to show the direction of viewing(similar to cutting plane lines) |
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What are short break lines?
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-A thick irregular line drawn freehand to show where a portion of an object is broken away to show detail behind the object |
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What are long break lines?
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-A thin straight light line with freehand zigzags |
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What are phantom lines?
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thin, broken line made up of a series of one long and two short dashes |
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What are the three different ways of placing dimensions
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-Unidirectional
-Aligned -Architectural 120102a pg 12 |
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What are unidirectional dimensions?
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Dimensions placed inside the arrows with numbers placed in the horizontal position |
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What are aligned dimensions?
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Dimensions placed inside arrows with numbers in the directions the arrows are running |
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What are architectural dimensions?
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Dimensions placed beside the arrows running the same way as arrows. Solid arrows |
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What is the seam line? |
the line between the shell and the vessel and the head of the vessel |
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What is the tangent line?
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the line that touches the curved head of a vessel at the highest point of the curvature |
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What is the datum line? |
The line that runs around the circumference of the shell of a vessel near one end of the shell |
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What is the best line for reference on vessels? |
The datum line |
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What can notes provide?
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-Details of constructions |
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Where is a note placed?
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near one of the views and a leader line indicates the exact point of reference
120102a pg 13 |
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Where is a general note placed?
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Away from the views so that it can be readily seen
120102a pg 13 |
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What is a note called if it specifies the materials required, the welding processto be used and the type and size of filler material?
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A Specification |
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Where is the title block normally located on a drawing?
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Lower right corner |
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Where is the bill of materials located on a drawing?
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top right corner
120102a pg 14 |
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What are symbols on drawings used to draw your attention to?
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-corrections or revisions
-detail drawings 120102a pg 17 |
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How are corrections shown on blueprints?
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letters or numbers that have a circle or triangle drawn around them |
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All changes must be initialed by authorized personnel and include the date of change. |
a)True |
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When an entire section of a drawing has been changed the section may be enclosed in what?
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a revision cloud |
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What is an as built drawing?
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A drawing that represents the final project, which may differ from the original drawing because of field changes or other add ons |
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What does a detailed drawing show?
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larger scale drawing which clearly shows all information needed to complete a specific part of a larger whole |
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When many pieces in a drawing need to be shown in detail what is done?
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Each part is given a number or letter on the main drawing and detailed drawings are given similar letters or numbers
120102a pg 18 |
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What is an auxiliary view used for? |
to show the true size and shape of a slanted surface |
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What is a developed view show?
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-Shows a part before bending, rolling, or any other fabrication method shapes it |
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What does a revolved view do to an object?
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A portion of the object is rotated to obtain a straight axis for better detail and dimensioning |
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What is a sectional view?
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any view seen when a portion of the object nearest the observer is imagined to be removed by means of cutting planes |
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What is a full section view?
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-A view of an object that is imagined to be cut through top to bottom |
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What is a half section view?
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-A view that is imagined to be only cut in halfway through |
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When does an offset section have an advantage?
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If you want to obtain certain details of the object |
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If a true cross sectional is desired what section view do you use?
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Revolved section view |
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What is an aligned section view?
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When a revolved projection is incorporated within a sectional view |
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Define Alternating current.
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Current that flows in one direction during any half cycle, then reverses and flows in the other direction during the next half cycle |
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What is Amperage?
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-Electrical property that causes the electrode and/or parent metal to be melted together |
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What is the Arc?
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Created when there is enough amperage and voltage available at the electrode tip to overcome the natural resistance to the flow of electricity
120102b pg 2 |
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What is Arc Blow?
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A condition encountered during DC welding when the arc flares uncontrollably from side to side. Caused by magnetic fields being set up around the work
120102b pg 2 |
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What is Arc voltage?
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-The voltage output of the machine during welding.
-force that maintains the arc between the electrode and the work piece 120102b pg 3 |
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What is a Buzz Box?
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Describes an AC transformer welding machine because of the typical buzzing sound made when welding with them |
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What is a circuit?
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Any system of conductors that is designed to complete the path of an electric current |
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What is a core?
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-The magnetic link between the primary and secondary coils of a welding transformer |
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What is a movable shunt?
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A core that can be moved into different positions which will alter the magnetic link between the primary and secondary coils
-Allows for any setting between minimum and maximum of the machine’s output potential 120102b pg 3 |
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What is a conductor?
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A material or substance that is capable of transmitting electricity |
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What is current flow?
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-the movement of electrons in an electrical circuit.
-measured in amperes 120102b pg 4 |
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What is a diode?
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A one way electrical valve
-allows current to flow in one direction only |
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What is a diode used for in welding machines?
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used to change AC current to DC current
120102b pg 5 |
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What is direct current?
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-electrical current that flows in one direction only
- either a positive or negative value 120102b pg 5 |
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What is a cycle?
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A complete rotation of a sine wave pattern |
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What direction do electrons flow in?
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Negative to Positive |
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What is duty cycle?
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percentage of time that a machine can run at maximum rated output current before over a 10 minute period before it must be cooled down
120102b pg 6 |
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What is an electron?
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Negatively charged particle
120102b pg 6 |
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What is frequency?
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Relates to the speed at which alternating current changes it’s direction of flow
120102b pg 6 |
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What is a generator?
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a machine used to create electricity of sufficient volume for welding
120102b pg 6 |
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What are AC generators called?
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Alternators
120102b pg 6 |
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What is inductance?
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The ability of a conductor to transfer current onto a neighboring body without physical contact
120102b pg 6 |
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What is an insulator?
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Any material that does not allow current to flow through it
120102b pg 6 |
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What is an inverter?
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A device that changes DC to AC current
120102b pg 6 |
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What is line transformer?
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used to describe an AC transformer welding machine
120102b pg 6 |
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What is open circuit voltage?
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when a welding machine is turned on but no current is flowing in the circuit
120102b pg 7 |
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What does the primary coil do?
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takes power directly from the AC input power line
-causes magnetic fields to form 120102b pg 7 |
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What is a rectifier? |
A device that changes AC to DC by allowing current to flow in one direction only
120102b pg 7 |
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What is a relay?
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a switch that is operated by electro-mechanical force rather than by the application of external mechanical force |
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What is resistance?
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the property of an electrical conductor to oppose the flow of current, which causes electrical energy to turn into heat
120102b pg 7 |
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What does the secondary coil do?
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Takes the magnetic field generated by the primary coil is then induced into the secondary coil
120102b pg 9 |
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What is a switch?
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a device with points of contact that can complete a circuit
120102b pg 9 |
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What is Voltage?
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Electrical pressure of force that causes current to flow in a conductor or to cross an arc gap
120102b pg 9 |
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What is EMF?
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Electromotive force
120102b pg 9 |
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What is voltage responsible for in arc welding?
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-starting the arc |
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To maintain the arc what must be present?
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Arc voltage
120102b pg 9 |
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What does arc voltage control in the weld puddle?
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the width of the weld bead and the fluidity
120102b pg 9 |
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What is an atom?
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the smallest particle of any element that can exist
120102b pg 11 |
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What does the selection of DCEP, DCEN, or AC depend on? |
-filler metal type
the material being welded -welding process being used 120102b pg 12 |
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60 cycles per second(AC) changes direction how many time per second?
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120 times per second
120102b pg 13 |
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what does three phase allow for?
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fewer gaps in the current flow
120102b pg 13 |
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what are the three distinct advantages of three phase over single phase?
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-constant power
-smaller equipment -more efficient 120102b pg 14 |
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constant power from three phase results in what in machines?
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less vibration and better performance
120102b pg 14 |
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What does a transformer do?
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Takes electricity from the power grid and converts it into welding current
120102b pg 15 |
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How does a AC transformer convert voltage and amperage?
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high voltage, low amperage to low voltage to high amperage suitable for welding
120102b pg 15 |
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How does an adjustable coil transformer work?
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moves the primary and secondary coils closer together or further apart
-greater distance between coils, greater the resistance causes decreased voltage (same opposite) 120102b pg 16 |
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How does a Metal shunt adjustable coil work?
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-Moves a metal bar between the two coils |
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What is one advantage of AC transformers?
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-low initial cost
-low maintenance costs -lower operating costs -generally quiet operation -no accumulative arc blow 120102b pg 17 |
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What is one disadvantage of AC transformers? |
-not portable
-no choice of polarity -limited electrode selection -more difficult to strike and maintain an arc -restricted welding process 120102b pg 17 |
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What is an AC-DC Transformer-Rectifier?
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welding machine that are AC transformers with an added rectifier(made up of diodes that are capable of allowing current to flow in one direction only, changing AC to DC)
120102b pg 18 |
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What is one advantage of AC-DC transformer-Rectifiers?
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-May have AC or DC output capability |
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What is one disadvantage of AC-DC Transformer Rectifiers?
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-Generally more costly than transformers |
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What do generators and alternators do?
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convert mechanical energy into electrical energy |
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What type of current does a generator create?
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DC
120102b pg 20 |
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What type of current does an alternator produce?
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AC
120102b pg 20 |
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What does a basic generator consist of? |
a wire loop that can rotate in a stationary magnetic field
120102b pg 21 |
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What is one advantage of AC Alternators? |
-No arc blow |
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What is one disadvantage of an AC Alternator?
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-higher initial cost |
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On DC generator there is a split ring that rectifies the current what it called?
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a commutator |
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What is one advantage of DC Generators and Alternators?
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-choice of polarity
-smoother arc than with AC -may be portable -full choice of electrodes -often have auxiliary power outout 120102b pg 25 |
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What is one disadvantage of DC Generators and Alternators?
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-high initial cost
-higher maintenance costs than transformers sets -higher operating costs than transformer sets -Generally noisier than transformer sets -Arc blow is a factor with DC 120102b pg 25 |
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What is an inverter?
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an electronic circuit that is capable of transmitting DC imput to AC output
120102b pg 27 |
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Metal is an element or mixture of elements that has all or most of what characteristics?
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-solid at room tepurature
-opaque -conducts heat and electricity -reflects light when polished -expands when heated and contracts when cooled(except bismuth) -has a crystalline structure 120102c pg 2 |
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What is ferrous metals main ingredient?
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Iron
120102c pg 2 |
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What are the most common ferrous metals?
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Carbon steels and cast irons
120102c pg 2 |
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What are tooled or high speed steels?
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very high carbon steels used to make punches, dies, shear blades, cutting tools, and other components
120102c pg 2 |
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What is the main ways to identify a metal? |
-visual appearance and color |
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When looking at the fractured surface of a metal what are you looking at? |
the exposed grain structure |
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What can relative weight be measured in?
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g/cm3 or lb/ft3 |
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When looking at your shape of a metal what can you see that tells you it’s been cast? |
A cast seam is visible
120102c pg 5 |
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What does a rough outer texture of a metal object usually suggest?
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a casting
120102c pg 6 |
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If a solid metal has a smooth outer surface usually means it’s a formed product. a)True |
a)True
120102c pg 6 |
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What are the four tests used for identifying metals? |
-chip test
-spark test -file test -flame test 120102c pg 7 |
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When doing the spark test what pressure should you use on different test pieces?
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constant equal pressure
120102c pg 8 |
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What sparks do low carbon steels give off?
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bright long, straight and yellow
very little branching and few carbon bursts 120102c pg 8 |
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What sparks do high carbon steels give off? |
-burst and branch off more than low carbon steels
-darker yellow orange and burst nearer to the wheel |
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What type of sparks are produced by cast iron? |
red bursts near the grinder yellow bursts further out
-not as long as carbon steels -may require considerably more pressure 120102c pg 9 |
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What sparks are created by high speed steel?
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lines are orange with very little branching and end in ball shaps
120102c pg 10 |
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What can you observe from a flame test?
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-Speed of melting
-Changes in color -appearance and action of the slag -appearance of the molten puddle of -action of the molten puddle under the flame 120102c pg 11 |
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What is the melting point of aluminum?
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659°C (1218°F)
120102c pg 11 |
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What is the melting point of carbon steel? |
1510°C (2750°F)
120102c pg 11 |
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What is the most accurate way to identify a metal? |
A Mill Test Report |
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Where is the heat number identified?
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specification tag and mill test report
120102c pg 14 |
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Why are tag numbers used?
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because there may be more than one bundle of metal all with the same heat number
120102c pg 14 |
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Define mechanical properties? |
a materials ability to resist or withstand a particular kind of physical force |
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What is compressive strength?
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the resistance of a material to a force that tends to deform or fail by crushing
120102c pg 15 |
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What is shear strength?
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the maximum load required to punch through a material
120102c pg 15 |
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What is tensile strength?
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the ultimate pull that a material will stand without fracture(measured in psi or MPa)
120102c pg 16 |
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What is yield strength?
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-The stress point where deformation takes place
-point where force applied causes the metal to bend or deform and not return to it’s original shape 120102c pg 16 |
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What is impact strength?
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the ability of a metal to withstand a high velocity blow
120102c pg 17 |
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What is ductility?
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ability of a material to stretch or deform under a load without breaking
120102c pg 18 |
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What is Brittleness?
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The tendency of a material to fail suddenly by breaking without any permanent deformation before failure
120102c pg 18 |
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What is hardness?
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a materials ability to resist penetration or indentation
120102c pg 19 |
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What are the two common types of hardness tests?
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Rockwell and Brinell
120102c pg 19 |
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What does a Rockwell test punch have on its punch tip? |
diamond cone
120102c pg 19 |
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What does a brinell test punch have on its punch tip? |
ball
120102c pg 19 |
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What is toughness?
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-the ability of a metal to withstand a rapidly applied load without breaking
-ability to absorb considerable energy without fracturing 120102c pg 20 |
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What is Elasticity?
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the ability of a metal to return to it’s original shape and dimension once the load has been removed
120102c pg 20 |
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What is malleability?
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metals ability to be cold worked without a great deal of resistance
120102c pg 21 |
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What are physical properties?
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They describe the nature of the metal
120102c pg 22 |
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What is Density? |
a materials weight per unit of volume
120102c pg 22 |
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What is corrosion resistance?
|
ability of a material to resist chemical attack by compounds or other elements that tend to waste is away
120102c pg 22 |
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What is electrical conductivity?
|
a materials ability to conduct an electrical current
120102c pg 23 |
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What is thermal conductivity?
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measure of rate at which heat travels through a material(higher the thermal conductivity the faster the heat loss)
120102c pg 23 |
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What is thermal expansion?
|
the increase in physical dimension due to an increase in the material’s temperature
120102c pg 24 |
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What is Melting point? |
The point at which a material becomes a liquid
120102c pg 25 |
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What is the electrical conductivity of copper?
|
100
120102c pg 23 |
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What is the electrical conductivity of steel?
|
3-15
120102c pg 23 |
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What is the thermal conductivity of copper?
|
93
120102c pg 24 |
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What is the thermal conductivity of Aluminum?
|
50
120102c pg 24 |
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What is the thermal expansion coefficient of aluminum?
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0.000013in/in/°F
120102c pg 24 |
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What is the thermal expansion coefficient of steel? |
0.0000065in/in/°F
120102c pg 24 |
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What is the melting temperature of mild steel?
|
1510°C(2750°F)
120102c pg 25 |
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What is the melting point of stainless steel?
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1449°C(2640°F)
120102c pg 25 |
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What is the melting point of aluminum?
|
659°C(1218°F)
120102c pg 25 |
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What is the heat affected zone(HAZ)?
|
It is the area on both sides of a weld directly adjacent to where the weld metal mixes with the parent metal
120102d pg 2 |
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The HAZ consists of what four areas?
|
-the solid/liquid transition zone
-the grain growth zone -the recrystalized zone -the partially transformed zone 120102d pg 2 |
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What is the end grain result in a multi-pass weld? |
finer grain structure(finer grain=stronger weld)
120102d pg 3 |
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Why must HAZ be controlled? |
To maintain the required mechanical properties
120102d pg 4 |
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A finer grain provides a higher _________ and __________ strength.
|
tensile and yield
120102d pg 4 |
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A welding procedure that generates too fine a grain structure may result in the formation of a hard and brittle martensitic structure prone to what?
|
Cracking
120102d pg 4 |
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Temperature refers to what?
|
a degree or intensity and is expressed in degrees Fahrenheit (°F) or in degrees Celsius (°C)
120102d pg 5 |
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What is heat as a volume measured in? |
British Thermal Units(BTU) or Joules(J)
120102d pg 5 |
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How do you convert BTUs to joules? |
Multiply the number of BTUs by 1055.056
120102d pg 6 |
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How do you convert joules to BTUs? |
Multiply the number of joules by 0.000948
120102d pg 6 |
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What are the three forms of heat transfer?
|
radiation
-convection -conduction 120102d pg 7 |
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What is radiation?
|
heat that travels on light waves, such as ultraviolet and infrared rays from the sun or from the welding arc
120102d pg 7 |
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What is convection?
|
the transfer of heat from one body to another
120102d pg 7 |
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What is conduction?
|
The transfer of heat within a body
120102d pg 7 |
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What is expansion?
|
increasing in size or swelling and is usually associated with a rise in temperature
120102d pg 9 |
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What is solid expansion?
|
occurs when the metal is in a solid condition and has not reached its transition temperature
120102d pg 9 |
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When does transition expansion occur?
|
Above the transition temperature
120102d pg 9 |
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Where does fluid expansion occur?
|
Molten metal
120102d pg 9 |
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What is free expansion and contraction?
|
metal is allowed to expand and contract in all directions
120102d pg 9 |
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What is restrained expansion and free contraction?
|
the longitudinal expansion is prevented so that expansion upon heating only occurs on the height and width of the bar
120102d pg 10 |
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What method can you use to remove broken studs?
|
Dimensional upset
120102d pg 12 |
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What are the two methods of preheating? |
-a local preheat on a small surface area
-total preheat of the material 120102d pg 13 |
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What does preheating prevent?
|
high stress or cracking
-reduces or prevents hardness 120102d pg 15 |
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What arc characteristics does preheating make easier?
|
striking the arc
120102d pg 15 |
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What effects does preheating have?
|
-lowers the tensile strength
-reduces residual hardness -improves ductility -increases the notch toughness 120102d pg 15 |
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What do preheat temperatures usually range from?
|
40°C to 250°C(100°F to 400°F)can be as high as 425°C(800°F)
120102d pg 15 |
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What is postheating ?
|
the application of heat immediately after welding
120102d pg 16 |
|
|
What is the primary purpose of postheating? |
to slow the cooling process
120102d pg 16 |
|
|
Name two specific purposes of post heating?
|
-prevention of hydrogen-induced cracking
-reduction or prevention of martensite formation in the weld metal or HAZ -relief of residual stress -reduction of the preheat temperature 120102d pg 16 |
|
|
How does postheating prevent hydrogen-induced cracking?
|
Postheating allows hydrogen trapped in the HAZ to come to migrate out of the metal
120102d pg 16 |
|
|
How does post heating prevent martensite formation?
|
Postheating slows down the cooling rate and allows the carbon to escape to the grain boundary and not become trapped
120102d pg 17 |
|
|
The higher the postheat temperature the ________ the residual stress is.
|
Lower
120102d pg 17 |
|
|
Postheating allows for a what in your preheat temperature?
|
reduction
120102d pg 17 |
|
|
Temperature for postheating depends on what three factors?
|
-Material thickness
-carbon and other alloy content -weather the material was subjected to heat treatment when it was manufactured 120102d pg 17 |
|
|
What two categories can postweld heat treatments be divided into?
|
high temperature heat treatments and low temperature heat treatments
120102d pg 19 |
|
|
What is transformation temperature (lower critical temperature)?
|
When a metal begins to change to it’s crystalline form
120102d pg 19 |
|
|
What is upper critical temperature?
|
The transformation from one crystalline form to another
120102d pg 19 |
|
|
What is one postweld heat treatment that involves temperature above the upper critical limit?
|
-normalizing
-annealing -hardening 120102d pg 19 |
|
|
Normalizing heat treatment is heated above the upper critical temperature by how many degrees and how is it cooled?
|
-10°C to 40°C (50°F to 100°F)
-allowed to cool in still air at room temperature 120102d pg 20 |
|
|
What is annealing?
|
The process of softening a material or bringing it to its softest, toughest, weakest state.
120102d pg 21 |
|
|
For the annealing process how far above the upper critical temperature does the material get heated and how is it cooled?
|
About 40°C(100°F)
- cooled through the use of an oven or other means 120102d pg 21 |
|
|
What are two of the main purposes of annealing?
|
softens the steel so it can be more readily formed or cold worked
-aid in machining -refine the grain structure -removes residual stresses 120102d pg 22 |
|
|
Annealing improves softness and toughness but what does it lower in the material?
|
Tensile strength
120102d pg 22 |
|
|
Hardening is an immediate process to tempering and to combat wear.
a)True b)False |
a)True
120102d pg 22 |
|
|
What is one facto that influences the desired degree of hardness?
|
-The composition of the steel
-the recommended quenching temperature -the degree of hardness required -the proper quenching medium 120102d pg 22 |
|
|
What is the most severe quenching media in hardening?
|
iced brine
120102d pg 23 |
|
|
What are the two temperature hardening processes that use quenching are?
|
-flame hardening
-induction hardening 120102d pg 24 |
|
|
What is flame hardening?
|
The process of hardening the outer surface of the material without hardening the material within
120102d pg 24 |
|
|
What is induction hardening?
|
The process of hardening through the use of high-frequency magnetic resonance that is set up between a water-cooled magnetic heating coil and the work
120102d pg 26 |
|
|
What are the two types of post weld heat treatments that involve temperatures below the lower critical temperature?
|
stress relieving and tempering
120102d pg 27 |
|
|
When stress relieving you must control the rising and lowering of what?
|
Temperature
120102d pg 27 |
|
|
What does Tempering do?
|
Reduces hardness and promotes toughness
120102d pg 28 |
|
|
The process of tempering involves a thermal cycle after hardening that includes what?
|
reheating below lower critical limit
-subsequent cooling in a liquid or in air 120102d pg 28 |
|
|
How is the temper heat determined?
|
By the impact the object will be subjected to
120102d pg 29 |
|
|
What is the most common temperature-indicating devices?
|
temperature indicating crayons and pellets
120102d pg 31 |
|
|
What is the range of temperature indicating crayons come in?
|
40°C-815°C(100°F-1500°F) increments of 50°F
120102d pg 31 |
|
|
Thermocouples provide what when heating treating?
|
continuous indication of the material’s temperature
120102d pg 33 |
|
|
What are the five basic joint types?
|
-Butt
-corner -tee -edge -lap (BCTEL) 120102e pg 2 |
|
|
What are the four weld types? |
-surfacing
-plug or slot -fillet -groove 120102e pg 3 |
|
|
What is surface welding?
|
when a bead or beads are used in place a layer of weld metal over a surface
120102e pg 3 |
|
|
What is surface welding used for? |
-Reclaim worn surfaces |
|
|
What is the two step process to reclaim worn parts? |
1.Layer of softer less expensive weld metal returns metal to original thickness |
|
|
What joint are plug or slot welds commonly used with?
|
lap joints |
|
|
What joints are fillet welds found on?
|
lap, Tee and corner joints
120102e pg 4 |
|
|
What is the size of a fillet weld determined by?
|
the largest equal leg triangle that may be drawn within the cross section of the weld |
|
|
What is a fillet welds strength determined by?
|
it’s effective throat dimension
120102e pg 5 |
|
|
What can excessive convexity lead to on a fillet weld?
|
tends to produce a notch effect
120102e pg 5 |
|
|
What can over welding a joint with a fillet weld lead to?
|
increased distortion
120102e pg 5 |
|
|
What is the size of an unequal leg fillet weld determined by?
|
it’s shortest leg
120102e pg 6 |
|
|
What are the 4 variations of fillet welds?
|
-continuous
-intermittent -chain intermittent -staggered intermittent 120102e pg 7 |
|
|
The length and centre to centre distance of fillet welds is called what?
|
Pitch
120102e pg 7 |
|
|
What joint types are groove welds commonly used with?
|
butt joints
120102e pg 8 |
|
|
What is the size of a groove weld determined by?
|
The throat size
-full penetration = material thickness is the size -less than full penetration = less than material size is weld size 120102e pg 8 |
|
|
Name two factors you use to determine what type of groove weld to use on a joint?
|
-intended service
-material thickness -cost of preperation -accessibility -total joint economy -residual stresses leading to distortion 120102e pg 9 |
|
|
What are square groove welds generally restricted to due to limited penetration?
|
Thin gauge material
120102e pg 9 |
|
|
Where is the bevel groove used most often?
|
Where you only have access to one member of the joint or where the joint is set in the horizontal position
120102e pg 10 |
|
|
What is the most widely used groove joint for materials 9.6mm(3/8”) to 25.4(1”) thickness?
|
Vee Grove
120102e pg 10 |
|
|
What is the advantage of a U-groove weld over a Vee groove?
|
smaller included angle which requires less filler metal
120102e pg 11 |
|
|
What advantage does a J groove weld have over a bevel groove?
|
J groove affords better access for welding, which promotes good penetration and fusion to the bottom of the joint
120102e pg 12 |
|
|
What is a corner joint used mainly on?
|
sheet metal fabrications
120102e pg 14 |
|
|
To make a corner joint stronger what can you add to the inside of the joint?
|
a fillet weld
120102e pg 14 |
|
|
What is an edge joint used extensively to do?
|
join light gauge sheet metal
120102e pg 15 |
|
|
What advantages does edge joining light gauge sheet metal give you?
|
-less danger of burn through
-reduces distortion 120102e pg 15 |
|
|
What is the disadvantage of edge joints?
|
Cannot withstand dynamic loads
120102e pg 15 |
|
|
How are thin gauge material edge joints generally welded?
|
autogenously(without the need for additional filler metals)
120102e pg 15 |
|
|
What weld are Tee joints generally joined with?
|
fillet welds
120102e pg 15 |
|
|
What is the lap joint highly successful at joining?
|
Metals of different sizes
120102e pg 16 |
|
|
Why are Lap joints preferred for soldering, brazing and braze welding operations? |
Total joining surface area is greater than that of the butt joint
120102e pg 16 |
|
|
Where maximum strength joint is needed what joint is used?
|
The butt joint
120102e pg 17 |
|
|
In the two digit code 1G what does the
a)the number denote? b)the letter indicate? |
a)the position |
|
|
What are the primary considerations in deciding what joint and weld type to use?
|
strength requirements and load conditions
120102e pg 20 |
|
|
What do welding symbols provide?
|
A shorthand method for conveying complete welding information from the designer to the welder |
|
|
Weld symbols represents what?
|
-types of desired welds |
|
|
Supplementary weld symbols are necessary to what?
|
proper weld completion
120102f pg 3 |
|
|
What are three elements of a welding symbol?
|
-reference line |
|
|
What is the reference line?
|
forms the base for welding symbols (always drawn horizontally) |
|
|
What side of the reference line is the |
a)the bottom |
|
|
When is a broken Arrow line used?
|
Used with J groove and bevel groove preparation when it is necessary to indicate which member of the joint is to be prepared |
|
|
When drawing a surface welding symbol what side is it always on? |
The arrow side |
|
|
What symbol is an isosceles drawn with the left leg perpendicular to the reference line?
|
Fillet weld symbol |
|
|
What does a dotted U or J indicate? |
The preparation of the groove by the carbon arc-air process |
|
|
When a backing weld symbol is put on a single reference line what is indicated by the note in the tail? |
whether the backing weld should be welded before or after the joint weld |
|
|
In the AWS letter designation for joints with backing what does M mean? |
materials to be located in the tail |
|
|
In the CSA letter designation what is does each letter mean?
a)M b)MR c)S d)SR e)T f)F |
a)material identification(by means of assigned letter
b)material identification, but remover after welding c)steel or other material as specified d)The same as S, but removed after welding e)Tape f)Flux 120102f pg 12 |
|
|
What are the three contour symbols?
|
-flat |
|
|
Each letter mean the contour means it should be finished how?a)M
b)C d)G e)H f)R g)U |
a)machine |
|
|
When reference is made to what a tail added to the end of a reference line? |
-specification data |
|
|
Multiple reference lines provide information relative to what?
|
-the sequence of welding operations |
|
|
What dimensions are shown on a plug and slot weld symbol? |
-diameter of the hole |
|
|
Where is the length of a fillet weld shown? |
to the right of the weld symbol |
|
What is this symbol? |
plug or slot weld |
|
What is this symbol? |
Square Groove weld
120102f pg 8 |
|
What is this symbol? |
Vee Groove weld |
|
What is this symbol? |
U Groove weld |
|
What is this symbol? |
Bevel Groove weld |
|
What is this symbol? |
J Groove |
|
What does this weld symbol mean? |
the joint requires welding all around one side(or both sides, if shown) |
|
What is this weld symbol? |
Field weld |
|
What is this symbol and what does the R mean? |
Joints with backing
-backing is to be removed after welding 120102f pg 12 |
|
What is this symbols general classification? |
joint with spacer |
|
What does the solid black semi circle in this symbol mean? |
Melt through(full penetration is required) |
|
What does this symbol mean? |
a 3mm deep surface is needed on the whole face of the object |
|
What does this symbol mean? |
a 3mm deep surface weld is only required to the 75mm section |
|
What does this symbol mean? |
Fillet weld is an equal leg fillet weld |
|
What does this symbol mean? |
Fillet weld with unequal legs |
|
What does this symbol show? |
a intermittent fillet 50mm weld with a pitch of 100mm |
|
What does this symbol show? |
A chain intermittent 50mm fillet weld with a pitch of 125mm
120102f pg 23 |
|
What does this symbol mean? |
A staggered 75mm fillet weld with a pitch of 250mm |
|
A)What is S? |
A)effective throat size |
|
In this picture what is the 3 the measurement of and what is the 50°? |
The root measurement and the bevel angle
120102f pg 25 |
|
What does this symbol indicate? |
direction of radiation(in relation to the weld joint
120102f pg 31 |
|
What does this symbol show? |
the percentage of a weld to be tested with a radiographic test
120102f pg 33 |
|
What does this symbol show? |
weld test is to be done in the field all around the weld with a penetrant test
120102f pg 33 |
|
|
What is distortion the result of?
|
stresses being set up in the work through heating, coupled with factors such as expansion, upset and contraction
120102g pg 6 |
|
|
Where is angular distortion?
|
rotation around the weld line
120102g pg 6 |
|
|
Where is it most angular distortion most prominent?
|
Tee joints and butt joints that are welded on one side only
120102g pg 6 |
|
|
Angular distortion causes what?
|
Warpage
120102g pg 6 |
|
|
Transverse and longitudinal distortions are sometimes classed as what?
|
Dimensional distortions
120102g pg 6 |
|
|
Where is Transverse distortion? |
perpendicular to the weld line
120102g pg 6 |
|
|
Transverse distortion refers to what?
|
-The tendency in butt joints for the plates to draw together
-can also refer to a change in dimension caused by weld shrinkage 120102g pg 7 |
|
|
How can Transverse distortion be prevented?
|
-Tack welds placed at both ends
-wedge ahead of the joint 120102g pg 7 |
|
|
Where is longitudinal distortion?
|
Parallel to the weld line
120102g pg 6 |
|
|
Longitudinal Distortion refers to what? |
Distortion or shrinkage along the length of the weldment
120102g pg 8 |
|
|
How can you reduce longitudinal distortion?
|
-keeping the reinforcement on groove welds |
|
|
What are the tree ways of controlling distortion?
|
-mechanical
-procedural -design 120102g pg 9 |
|
|
What does pre-setting allow for?
|
shrinkage due to heat in the welds
120102g pg 9 |
|
|
How does pre-bending differ from pre-setting?
|
Pre-bending usually involves using clamps set up along the weld seam
120102g pg 9 |
|
|
What is ridged clamping and fixturing?
|
Weldments are rigidly clamped to heavy slabs or bases during welding
120102g pg 10 |
|
|
What is Residual stress?
|
refers to the buildup of internal stresses within the weld or the parent metal
120102g pg 10 |
|
|
What is a jig?
|
a fixture or device made for the express purpose of aligning and holding parts or components of a weldment
120102g pg 10 |
|
|
What does a jig ensure?
|
-accuracy and dimension
-uniformity of product -cost reduction by speeding up production 120102g pg 10 |
|
|
What is a skeleton frame?
|
is an internal frame or skeleton around which parts are clamped or otherwise held in place for welding
120102g pg 10 |
|
|
What is a strongback?
|
is heavily built, high strength object placed opposite the parts to be welded
120102g pg 11 |
|
|
What are chill strips?
|
Heavy strips of metal that are placed on either side of the weld shoulders and are generally clamped to a heavy backer
120102g pg 12 |
|
|
What are chill strips most often used on?
|
light gauge sheet metal fabrications
120102g pg 12 |
|
|
What are backing strips?
|
strips of metal or other material that are placed at the back (root) side of groove weld joint preparations
120102g pg 13 |
|
|
What is the method called when an object it is broken down into parts to be welded? |
Sub-Assembly
120102g pg 13 |
|
|
What is a welding sequence?
|
The order in which the welds of a structure or project are completed
120102g pg 14 |
|
|
When you are planning a weld so one welds pull is counteracted another welds pull what are you doing? |
working around the neutral axis
120102g pg 15 |
|
|
What is the neutral axis?
|
The theoretical centre of an object or an imaginary line where neither tension nor compression would exist if the object were bent
120102g pg 15 |
|
|
What is the principle involved in stagger welding?
|
spreading of heat throughout the joint
120102g pg 17 |
|
|
How does skip welding work?
|
weld deposits are applied in increments on each side of the centre of the joint
120102g pg 17 |
|
|
What is the back stepping method of welding?
|
The first weld begins a short distance from the end with the direction of travel towards that end and the following welds use the same process
120102g pg 18 |
|
|
How does Tack welding parts help control distortion?
|
it preheats the metal and holds the joint in alignment
120102g pg 19 |
|
|
What one of the four guidelines when deciding on the number and frequency of tack welds? |
-thinner the material, closer together the tack welds must be
-Narrow strips require more tack welds than wide strips -flat objects require more tack welds than curved or cylindrical pieces -tack welds should be neat clean and small enough to fuse into the finished weld 120102g pg 19 |
|
|
Why do you decide if pre set is required?
|
to prepare the joint properly so that travel in welding is not slowed down for wide sections or speeded up for narrow sections
120102g pg 19 |
|
|
Why should you avoid to many passes when welding?
|
the heating and cooling leads to higher distortion, particularly on welds that may be subjected to transverse shrinkage
120102g pg 20 |
|
|
To avoid distortion why should you weld at a fast even rate? |
to keep the heat affected zone narrow and to prevent to much heat from creeping ahead of the weld
120102g pg 20 |
|
|
Local preheating can alleviate what?
|
stress and distortion
120102g pg 20 |
|
|
A water jet cutting machine is a form of what that minimizes distortion?
|
specialized equipment
120102g pg 21 |
|
|
Good welding design uses what?
|
-smooth flowing lines
-few or no rapid changes in direction or cross-section 120102g pg 21 |
|
|
To capitalize on strength and minimize the number of welds what can you use?
|
rolled or formed sections(shapes, beams, and tubing)
120102g pg 22 |
|
|
Welding in the flat position allows what?
|
high heats and larger electrodes allowing for increased welding speed
120102g pg 22 |
|
|
What does the use of rounded corners prevent?
|
Prevents a rapid change in direction of the stress flow lines, which cause a notching effect
120102g pg 22 |
|
|
What can welding across a frame cause?
|
high stresses that can lead to cracking when the frame is stress loaded
120102g pg 22 |
|
|
Why is weld seams that line up a poor design?
|
concentration of heating and cooling is localized to the area where the weld joins
120102g pg 23 |
|
|
What are two design methods of distortion control?
|
-minimizing the number of pieces
-welding in the flat position -rounding corners -not welding across carrying members -not accumulating weld intersections 120102g pg 21 |
|
|
What are two procedural methods of controlling distortion?
|
-planning the welding sequence
-welding around the neutral axis -stagger welding -skip welding -back step welding -tack welding -pre-set and joint preparation -using fewer weld passes -welding at a fast and even rate of travel -preheating the work -specialized equipment 120102g pg 14 |
|
|
What are two mechanical methods of minimizing distortion?
|
-pre-setting and pre-bending |
|
What is this material? |
Cast Iron or General Use
120102a pg 9 |
|
What is this material? |
Steel
120102a pg 9 |
|
What is this material? |
Bronze, Brass, Copper
120102a pg 9 |
|
What is this material? |
White Metal, Lead, Zinc, Babbit and Alloys |
|
What is this material? |
Magnesium, Aluminum, and aluminum alloys |
|
|
Satisfactory welds depend upon maintaining specified dimensions related to what?
|
–preparation and fit up
–the size and shape of completed welds –the finished dimensions of a welded assembly 120102h pg 3 |
|
|
Dimensional defects include what?
|
–poor or incorrect material preparation
–poor or incorrect fit–up –incorrect weld size and profile –distortion and warping 120102h pg 3 |
|
|
When are structural discontinuities in the weld zone generally caused?
|
During the welding process
120102h pg 3 |
|
|
Structural discontinuities can ultimately lead to the failure of the weld while in service.
A)True B)False |
A)True
120102h pg 3 |
|
|
What are two structural discontinuities weld faults?
|
–porosity
–slag inclusion –oxidation –lack of fusion –incomplete penetration –cracking –stray arc strikes 120102h pg 3 |
|
|
How are structural discontinuities normally tested for?
|
Through non–destructive testing
120102h pg 3 |
|
|
What are Defective properties?
|
Any departure from the specified mechanical and chemical requirements
120102h pg 3 |
|
|
What is intergranular carbide precipitation?
|
A serious metallurgical condition that leads to a loss of corrosion resistance in the area adjacent to the weld zone
120102h pg 4 |
|
|
When does the notch effect occur?
|
Whenever a notch is placed or formed within the cross section of a material creating a point of weakness or as a result of:
–poor joint design –poor weld profile –structural discontinuities in the weld zone 120102h pg 6 |
|
|
What are stress flow lines?
|
imaginary lines that run through an object when stress is applied to it
120102h pg 6 |
|
|
When joints are to be made between parts of unequal thickness what should you do to prevent severe notching effect and possible failure of the weldment?
|
taper the transition
120102h pg 7 |
|
|
What is a good taper ratio to use?
|
3:1
120102h pg 7 |
|
|
Excess what in a lap weld can lead to a severe notching effect?
|
–concavity or convexity
120102h pg 8 |
|
|
What on frames and support structures provides a more gradual flow in stress lines?
|
Gussets and corner braces
120102h pg9 |
|
|
Weld craters at the end of a weld should always be?
|
filled and apply a wash coat if necessary
120102h pg 9 |
|
|
What are the three types of faults that occur before welding?
|
incorrect preparation and fit up
–irregularities in the surface of the joint preparation –surface discontinuities 120102h pg 10 |
|
|
What can poor material preparation and fit up cause?
|
–difficulty in maintaining dimensions
–high stresses –structural discontinuities –defective properties within the weld zone 120102h pg 11 |
|
|
Surface discontinuities can lead to what types of weld faults?
|
–sheared surfaces
–flame–cut surfaces –gouged surfaces 120102h pg 11 |
|
|
Depending on the condition of the shear blades various undesirable foreign materials may become embedded on the joint edges possibly leading to what?
|
–porosity
–slag entrapment –lack of fusion 120102h pg 11 |
|
|
How can flame cut surfaces lead to weld faults?
|
notches and irregularities may occur when flame cutting and slag may adhere to these leading to slag entrapment, porosity, lack of fusion or chemical composition defects
120102h pg 11 |
|
|
What can Carbon arc gouging operations leave leading to weld fault defects?
|
deposits of carbon, copper, and/or oxidized metal in the joint area
120102h pg 11 |
|
|
What are the two general types of faults that can occur after welding?
|
–distortion and warpage
–incorrect weld profile 120102h pg 13 |
|
|
What is one cause of distortion?
|
–lack of control over heat imput
–inadequate control of weld pass sequencing –inaccurate preparation of the joint –inadequate control of fit up –incorrect joint design 120102h pg 13 |
|
|
What are the effects of distortion?
|
welded components so badly out of shape that extensive work is needed to straighten them or they may need to be replaced
120102h pg 13 |
|
|
How can you control distortion?
|
–ensuring accuracy during preparation
–strict adherence to welding specifications and procedures –using jigs, braces, and supports when required 120102h pg 13 |
|
|
What are the four types of incorrect weld profiles?
|
–convex reinforcment
–insufficient throat or leg –overlap –undercut 120102h pg 13 |
|
|
The convexity of a weld or individual surface bead shall not exceed 0.0___ times the actual face width of the weld or individual face bead, respectively plus 1.6mm (1/16 inch)
|
0.07
120102h pg 14 |
|
|
The Reinforcement of a groove weld shall not exceed what?
|
3mm
120102h pg 14 |
|
|
Excessive convexity tends to produce what in multi–pass welds?
|
notch effect
120102h pg 15 |
|
|
Why is excessive weld reinforcement undesirable?
|
It can lead to increased shrinkage stresses and to create a notch effect
120102h pg 15 |
|
|
What is a cause of convexity and excessive reinforcement?
|
–travel speed to slow
–incorrect electrode angle –incorrect electrode filler size –incorrect welding technique –insufficient current 120102h pg 15 |
|
|
What are effects of convexity?
|
–distortion
–points of high stress –poor weld profile that can cause a notch effect 120102h pg 15 |
|
|
How can you avoid convexity and excessive reinforcement?
|
–increased travel speeds
–use appropriately sized electrodes and filler metals –use recommended welding techniques –preheat if requires –use the proper current settings for the electrode 120102h pg 15 |
|
|
What is excessive concavity is more often associated with what type of weld?
|
fillet welds
|
|
|
When is a concave fillet weld not a weld fault?
|
when the drawing calls for it
120102h pg 16 |
|
|
What is a cause of insufficient throat or leg size?
|
–travel speed to fast
–insufficient number of passes or layers –incorrect welding technique –excessive groove angle 120102h pg 16 |
|
|
What problems can insufficient throat or leg cause?
|
–weld size does not meet specification
–strength is low –notch effect occurs –excessive groove angle 120102h pg 16 |
|
|
What can you do to remedy insufficient throat or leg?
|
–use proper joint preparation
–maintain correct current settings –use recommended welding techniques –visually inspect weld 120102h pg 16 |
|
|
Poor profile may be detected with visual examination or with a what?
|
With suitable gauges
120102h pg 17 |
|
|
What is overlap?
|
a condition in which an excess of weld metal exists at the toe of a weld beyond the limits of fusion
120102h pg 17 |
|
|
What can cause overlap?
|
–incorrect electrode angle
–incorrect travel speed –excessive passes or layers –incorrect welding techniques 120102h pg 18 |
|
|
What are the effects of overlap?
|
–weld size does not meet specification
–strength is low –Notch effect occurs(in more severe cases) –poor weld metal appearance results 120102h pg 18 |
|
|
What can you do to remedy overlap?
|
–use proper joint preparation
–maintain correct current settings –use recommended welding techniques –use recommended electrode angles –do not over–weld 120102h pg 18 |
|
|
What is under cut?
|
the melting away of the parent material during the welding process
120102h pg 18 |
|
|
Elongated slag lines as a result of undercut left in the weld between the root bead and the fill pass are known as what?
|
Wagon Tracks
120102h pg 19 |
|
|
Undercut of the side walls of a groove weld does not affect the completed weld if what?
|
sufficient care is taken to correct the condition before depositing the next bead
120102h pg 19 |
|
|
What is a cause of undercutting?
|
Poor joint preparation
–incorrect travel speed –improper electrode angles –incorrect electrode selection –improper welding techniques –wrong electrode diameter –improper current settings –impurities –poor joint accessibility 120102h pg 20 |
|
|
What are the effects of undercutting?
|
notch effect
–lack of strength –structural discontinuities –poor weld appearance 120102h pg 20 |
|
|
What is a remedy to undercut?
|
–remove all impurities from the weld zone
–maintain the correct electrode angle angle –use correct settings a and polarity for the electrode –use proper welding technique –remove internal undercut between passes by grinding or melting out with successive passes –external undercut should be filled in with another pass and blended in by grinding if necessary 120102h pg 20 |
|
|
What are the two categories of structural distortion?
|
–surface defects
–internal defects 120102h pg 20 |
|
|
What do surface defects include?
|
–surface porosity
–badly shaped surface ripples –excessive spatter –craters –stray arc strikes 120102h pg 20 |
|
|
The welder is responsible for surface defects as a result of what?
|
improper base metal preparation
–incorrect technique –improper current setting 120102h pg 21 |
|
|
Why are bead irregularities a defect?
|
they constitute a change of cross–section and may create a notch effect
120102h pg 21 |
|
|
What does spatter indicate?
|
improper welding technique
120102h pg 21 |
|
|
What do stray arc flashes cause?
|
They create a quenched, hard brittle condition(often called a metallurgical notch)
120102h pg 21 |
|
|
What is a stray arc flashed area prone to?
|
cracking
120102h pg 21 |
|
|
What are the two categories of internal discontinuities?
|
spherical and laminar
120102h pg 22 |
|
|
Spherical faults are serious if they are what?
|
present in large quantities or are positioned in line
120102h pg 22 |
|
|
What are the three spherical faults?
|
–porosity
–slag inclusion –other inclusions 120102h pg 22 |
|
|
What are the three types of laminar faults?
|
–lack of fusion
–incomplete penetration –cracking 120102h pg 22 |
|
|
What is porosity?
|
gaseous voids trapped within the weld metal
120102h pg 22 |
|
|
What are the causes of porosity?
|
–moistuer in the electrodeor parent metal
chemistry and structure of the parent metal –surface impurities and contaminants –faulty electrodes, fluxes, insufficient gas shielding , trapped slag –incorrect welding techniques 120102h pg 23 |
|
|
What surface contaminants cause porosity?
|
(DOGROMP)
–Dirt –Oil –Grease –Rust –Oxides –Mill scale –Paint 120102h pg 24 |
|
|
Insufficient flux covering in submerged arc welding may cause what?
|
scattered surface porosity
120102h pg 25 |
|
|
How can porosity be avoided?
|
–properly prepare and clean joints
–select correct filler metal –good condition filler metal –set up welding equipment properly –adhere to recommended welding procedures 120102h pg 25 |
|
|
What are slag inclusions?
|
oxides and other non–metallic solids that are sometimes found as elongated or irregular shaped inclusion in welds
120102h pg 25 |
|
|
What can cause slag inclusion?
|
high viscosity of weld metal
–rapid solidification –to low temperature –current setting too low improper manipulation of the electrode –undercut from previous passes –foreign material trapped in weld 120102h pg 26 |
|
|
Slag inclusions have much the same effect as porosity.
a)true b)false |
a)true
120102h pg 26 |
|
|
Majority of slag inclusions may be prevented by what?
|
–proper preparation of the joint
–correct filler metal selection –correct current settings –complete removal of slag between passes –proper welding techniques 120102h pg 26 |
|
|
How can you prevent oxidation on the inside of a pipe or tube?
|
purge it with an inert shielding gas
120102h pg 28 |
|
|
Lack of fusion(cold lapping)describes what?
|
the failure to fuse the weld metal to the base material or adjacent layers of weld metal to each other
120102h pg 28 |
|
|
Lack of fusion is normally only detectable by what non–destructive test?
|
Ultrasonic testing
120102h pg 29 |
|
|
What does incomplete penetration (IP) describe?
|
failure of the deposited weld metal to fuse fully and completely with the parent material at the root of the weld
120102h pg 29 |
|
|
How can you remedy incomplete penetration?
|
–prepare the joint properly
–select correct filler metal –use the correct current settings –use the correct voltage settings –use proper welding technique 120102h pg 30 |
|
|
Why is cracking the most serious of all faults?
|
–difficult to detect
–usually lead to a complete failure of the joint –can occur after all welding operations are complete 120102h pg 30 |
|
|
What are the two categories of cracking causes?
|
–metallurgical
–mechanical 120102h pg 30 |
|
|
What are the metallurgical causes of cracking?
|
–hydrogen–induced cold cracking
–solidification cracking –hot cracking –crater cracking 120102h pg 30 |
|
|
Cold cracks develop when?
|
after the weld metal has cooled(weld metal or HAZ)
120102h pg 31 |
|
|
What steels are more susceptible to cold cracks?
|
higher carbon steels
120102h pg 32 |
|
|
What causes solidification cracking?
|
contraction strains across the weld
120102h pg 32 |
|
|
What causes hot cracking?
|
combined effects of metallurgical and mechanical factors
120102h pg 32 |
|
|
What causes crater cracking?
|
improper termination of the welding arc
120102h pg 32 |
|
|
What is a mechanical cause of a crack?
|
–high restraint on the joint |
|
|
What are the purposes of hard facing?
|
-combat wear
-prolong the life of the object -reduce costly down time -reduce the cost of replacement parts 120102i pg 2 |
|
|
What is spalling?
|
The breaking away of the weld metal from the base metal
120102i pg 2 |
|
|
What does ABR stand for?
|
Abrasive resistant material
120102i pg 5 |
|
|
In Pulsed DC GMAW surfacing allows for better control of electrode melting rate and bead shape.
True or False |
True
120102i pg 6 |
|
|
What is the advantage of MCAW surfacing?
|
has a large variety of alloy classifications
120102i pg 7 |
|
|
With SAW what are coiled trip electrodes most commonly used for?
|
corrosion resistant surfacing
120102i pg 8 |
|
|
When using SAW for surfacing full properties of the surfacing metal are not attained until when?
|
two or more layers are deposited
120102i pg 8 |
|
|
SMAW surfacing is popular, low cost, and convenient.
true or false |
true
120102i pg 9 |
|
|
What current can be used with SMAW surfacing?
|
DC or AC
120102i pg 9 |
|
|
What positions can SMAW surfacing be used in?
|
all positions
120102i pg 9 |
|
|
GTAW surfacing has what type of deposition rate that produces high quality deposit with minimum dilution and low distortion?
|
low deposition rates
120102i pg 10 |
|
|
Low temperature limits the base metal dilution in what surfacing methods?
|
OAW
120102i pg 10 |
|
|
What is critical when thermal spray surfacing?
|
Distance and heat input
120102i pg 11 |
|
|
How is a hardfacing material determined for a specific task?
|
the type of wear that the base metal is subjected to
120102i pg 12 |
|
|
Define abrasion.
|
a sliding/scraping type of wear that removes metal by gouging or grinding
120102i pg 12 |
|
|
What causes abrasions?
|
continuous exposure of metal parts to rubbing friction against earth, sand, gravel or other gritty substances
120102i pg 12 |
|
|
Define impact.
|
A pounding or battering type of wear that splits, breaks, chips, mushrooms or otherwise deforms the metal surface
120102i pg 13 |
|
|
Define erosion.
|
a gouging type of wear that washes away or grooves out the metal surface
120102i pg 13 |
|
|
What can cause erosion?
|
steam, water, liquids, or solids moving rapidly across or against a metal surface
120102i pg 13 |
|
|
Define Metal to metal wear.
|
the seizing or galling(wearing away by friction) that rips and tears out portions of a metal surface
120102i pg 14 |
|
|
Define corrosion.
|
the type of wear that pits, perforates and eventually dissolves metal parts
120102i pg 14 |
|
|
What can cause corrosion?
|
acid and acid fumes, gas fumes and salts can cause corrosion
120102i pg 14 |
|
|
Define oxidation.
|
a special form of corrosion that takes place when some metals are exposed to a combination of heat and air
120102i pg 15 |
|
|
Define compression?
|
a squeezing type of wear usually cause by a heavy static load or by loads that gradually increase pressure on a metal surface
120102i pg 15 |
|
|
What does thermal shock refer to?
|
cracking or splitting wear caused by exposing metal parts to temperature extremes such as rapid heating and cooling cycles
120102i pg 16 |
|
|
What is the hardest and most abrasive-resistant of all hard surfacing filler metals?
|
tungsten Carbide
120102i pg 19 |
|
|
What filler metal is slightly superior to tungsten carbide for impact resistance?
|
chromium carbide
120102i pg 19 |
|
|
What are martensitic stainless steels filler metal are used for?
|
metal to metal wear applications
120102i pg 19 |
|
|
Semi-austenitic steels are probably the most widely used filler metal.
True or false |
true
120102i pg 19 |
|
|
Austenitic manganese steels filler metals are good alloys of resistance to what?
|
Impact
120102i pg 20 |
|
|
Austenitic Stainless Steels filler metals provide a tough ductile coating with good resistance to what?
|
chipping and corrosion
120102i pg 20 |
|
|
Heat treatable steels are high carbon steels, medium carbon alloy steels or tool and die steels
true or false |
true
120102i pg 20 |
|
|
What filler metal is good for salt water resistance?
|
copper alloys
120102i pg 20 |
|
|
Define dilution?
|
the mixing of the base metal with the hardfacing filler metal
120102i pg 22 |
|
|
What are five common hardfacing problems?
|
-dilution
-spalling -stress failure -underbead cracking -distortion 120102i pg 22 |
|
|
If there is to dilution what can happen to the hardfacing material characteristics?
|
They are watered down by the softer base metal
120102i pg 22 |
|
|
How can you avoid excessive dilution?
|
-use low current settings
-use slower rate of travel -use correct polarity -change welding position -use more overlap between beads -use weave beads -select a shielding gas that produces minimum dilution 120102i pg 22 |
|
|
Define spalling.
|
when the weld metal breaks away from the base metal
120102i pg 23 |
|
|
How can spalling be avoided?
|
-prepare the surface
-Control the cooling rate -limit deposit thickness -if thicker deposit is necessary, build up the object with a filler metal that matches the chemistry of the base metal before hard surfacing -use a base layer for brittle hardfacing deposits -apply a base layer of austenitic stainless steel -when surfacing high manganese steels(12% to 14% manganese), keep interpass temperatures below 260°C(500°F) 120102i pg 24 |
|
|
Define stress failure?
|
occurs when welding stresses are added to parts that contain high retained internal stresses
120102i pg 24 |
|
|
How can stress failures be avoided?
|
-preheat slowly and uniformly
-controlled heating and slow cooling to achieve specified preheat tempuratures -avoid interuptions during the weld process -cool the part slowly and evenly 120102i pg 24 |
|
|
Define underbead cracking.
|
occurs in the base metal just under the weld.cracks may not be visible but can lead to more serious defects such as spalling or weld cracking
120102i pg 25 |
|
|
How can you prevent underbead cracking?
|
make sure material is at 21°C-38°C(70°F-100°F)
-preheat metal to the specified preheat temperature -slow the cooling rate 120102i pg 25 |
|
|
Define Distortion?
|
occurs when unbalanced stresses are created during uneven expansion and contraction
120102i pg 25 |
|
|
What are ways to avoid surfacing distortion?
|
-allow distortion forces to work positively
-balance the stresses -Do not overheat the part -relieve internal stresses 120102i pg 25 |
|
|
What temperature should materials be at before hardfacing?
|
21°C-38°C(70°F-100°F)
120102i pg 27 |
|
|
Medium to high carbon and low alloy steels may require a higher what?
|
preheat
120102i pg 27 |
|
|
How can you control the cooling rate when hardfacing?
|
-preheat the materials
-maintaining the correct interpass temperature -retaining the heat by insulating the surface 120102i pg 28 |
|
|
What does the waffle pattern work well for?
|
earth moving equipment(built up dirt and sand provide additional base metal protection
120102i pg 28 |
|
|
What does the dot pattern works well on?
|
base metals that should not be overheated during welding |
|
|
What hardfacing pattern is used when larger pieces of ore, rock or slag?
|
Stringer beads |
