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79 Cards in this Set
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SMAW |
Shielded metal arc welding. An electric arc that develops when an electric current is forced to leap a small gap in the circuit Also commonly called stick welding |
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Pressure and Voltage |
Pressure created by generator. Also called voltage and measured in volts (v) Flow of electricity is called current and measured in amperes (a) |
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SMAW Welding Circuit |
Consists of: 1. A welding power source 2. A work piece lead cable and ground clamp 3. An electrode lead cable 4. A welding electrode and electrode holder 5. The work piece |
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Arc Path |
Circuit completed > Current > Electrode > Arc >Workpiece > Ground Clamp > Work place lead > Back to power source |
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Open Circuit Voltage |
Power source for circuit on but no arc has been struck. Highest voltage generated |
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Arc Voltage |
Circuit close resulting in drop of voltage. Is also the current that flows through the entire welding circuit |
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SMAW Heat |
Heat generated is 5500 - 6600 c |
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Applications of SMAW |
1. Shipbuilding 2. CT and automotive 3. Industrial and Agricultural 4. Engineering Applications 5. Boiler and Pressure Vessels 6. Piping and Pipelines 7. Bridge Building 8. Building and Structural |
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PPE Welding Helmets |
Shade depends upon the intensity of the arc. Higher intensity requires a darker shade
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PPE
Arc Burn |
Infrared and UV radiation that arc welding can damage eyes and skin. Proper PPE such as flame resistant clothing must be worn |
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Electric Shock |
SMAW generates currents strong enough to severely hurt or kill you. Know how to d/c machine. |
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Electrode Studs |
Electrodes can be used down to a length of 50mm or 2inches. Should be disposed of in a fire proof metal container. |
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Ventilation |
Booths or welding stations should be equipped to extract harmful fumes at 2.8m3/min The pickup duct must be located so fumes cannot reach welders face |
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Alternating Current |
An electric current that reverses its direction many times a second at regular intervals, typically used in power supplies. |
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Single Phase Alternating Current |
Most useful for domestic and light industrial operations. Has a considerable amount of time where peak power is not utilized |
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Three Phase Alternating Current |
Made up of 3 single phase at measured intervals to allow one of the three phases to be supplying maximum power at a given time. Best used for industrial settings |
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Direct Current |
The electrons in the current flow steadily from the negative pole to the positive pole. |
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GMAW |
Gas Metal Arc Welding |
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FCAW |
Flux Cored Arc Welding |
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GMAW Principle |
An electric arc is drawn between a filler metal electrode and the base metal. The heat from the arc melts the end of the wire and area of base metal while shielding gas protects the arc from contamination |
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Main Components of GMAW |
1. DC power source 2. Welding gun with hose and cables 3. Feed mechanism for wire with contractor 4. Shielding gas system with hose and flowmeter 5. Continuous bare electrode filler wire |
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GMAW Power Source |
DCEP - Direct Current electrode positive |
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FLUX CORED ARC WELDING (FCAW) |
A GMAW process that uses the tubular electrode wire with powdered flux inside. Suitable for welding low carbon steel, low alloy, and stainless steel. Widely used for hardfacing appllications |
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FCAW Advantages |
1. Deeper penetration 2. Higher deposition rates 3. High deposition efficiency |
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FCAW Disadvantages |
1. Limited application 2. Only used on ferrous metals, low alloy steels and limited stainless steels 3. Initial cost of equipment high that SMAW |
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METAL CORED ARC WELDING (MCAW) |
Like FCAW but the metal cored wire has no fluxing ingredients inside but is filled with powdered metal. Usually iron powder with alloying elements. |
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Advantages of MCAW |
1. Low smoke and fume levels 2. High deposition efficiency 3. Broad range of alloy choices 4. No Slag 5. Minimal Slag 6. Good Penetration 7. Good bead appearance |
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Safety Req Electric Shock |
1. Never permit contact between hot circuit and bare skin. 2. Wear dry, hole free gloves 3. Always insulate yourself from welding circuit 4. Always ensure work lead ground clamp has a good electrical connection 5. Ground work piece to secondary ground to earth 6. Maintain equipment in good working condition 7. Use proper PPE and fall prevention equip |
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Safety Req Handling of cylinders |
1. Properly secure cylinder 2. Crack valve to clean threads. Stand to side 3. Adjust pressure slowly to avoid damage to regulators. Stand to one side again. |
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Safety Req Toxic Gases |
Main Gases that are toxic 1. Ozone 2. Nitrogen Dioxide 3. Carbon Monoxide Can be controlled by general ventilation or by proper resp. ppe |
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Safety Req Toxic Gases - Shielding Gases |
GMAW and FCAW shielding gas displace oxygen and can cause lung damage or death via suffocation. |
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Safety Req Protection against Radiation |
Proper filter lens according to OHS Reg is 10 - 12 depending on current level. (p 210) Non-reflective, fire retardant clothing. |
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Wire Feed Push Type |
Consists of an assembly that pulls wire from the spool and pushes it through the cable assembly to the welding gun. Usually one unit but can also be from an overhead crane. Pressure and alignment must be correct to properly work. |
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Wire Feed Pull Type |
A smaller but higher speed motor is located in the welding gun to pull filler metal wire through the conduit. This system makes it possible to increase distance between spool and gun. |
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Pull Type Wire Feed Disadvantages |
1. Welding gun is heavier and more difficult to use. 2. Rethreading wire more time consuming. 3. Operating life shorter |
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Push-Pull Wire Feed |
Uses synchronized feed motors to pull wire to the assembly and push it out to the gun. Advantages are extended distance, faster feed, longer operating life. Disadvantages are the complexity and cost. |
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Basic Components of a GMAW or FCAW gun |
1. Contact Tip 2. Shielding Gas Nozzle 3. Shielding Gas Nozzle Insulator 4. Filler Metal Electrode Wire Conduit 5. Shielding Gas Hose 6. Welding Electrode Cable Assembly 7. Welding Gun Trigger 8. Shielding Gas Diffuser |
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Contact Tip |
Usually made of copper or copper alloy. Conducts welding current and directs work Must be centered in shielding gas nozzle Attached via slide or screw Important to keep clean and clog free |
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Shielding Gas Nozzle |
Directs an even flowing column of shielding gas to welding zone. Protect with anti-spatter |
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Air Carbon Arc Cutting |
Known as CAC-A, AAC. Can cut and gouge all types of ferrous and non ferrous metals quicker than flame cutting. Can partial cut, gouge, or wash off a surface or prepare joints for welding. Can remove metal, weld faults, bolts nuts and fasteners. |
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CAC-A (Carbon Arc Cutting) Principles |
Works by melting base metal with an electric arc and using jets of air to blow molten metal to form a kerf or groove. Works by melting and not oxidizing like oxy-fuel. Can be used on anything that conducts electricity |
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Components of CAC-A |
1. Welding power source 2. Electrode Holder 3. Compressed air supply system. |
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CAC-A Power |
Can use AC or DC power |
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Safe Work CAC-A Ventilation |
Must ventilate as metals may release toxic fumes when heated. Must also wear a ventilator when cutting metal that contains chromium |
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Safe Work CAC-A Noise |
Noise level from the compressed air is high. Wear ear plugs or ear muffs |
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Safe Work CAC-A Radiation |
Need a standard welding helmet with a darker lens than SMAW. Filter 12-14. Cover all exposed skin |
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Safe Work CAC-A Fire |
Can spray sparks 6 meters away. Place sheet metal shield. Have a fire extinguisher or water hose near Never use oxygen instead of compressed air |
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Electrode Holders |
Carries welding current to welding electrode. 2 types - twist head type - jaw type Need to check for broken parts or insulation to ensure safety and efficiency |
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Ground Clamps |
Needed to make welding circuit complete. Needs to be checked for good connection otherwise a loss of power may occur. 2 Types - Spring loaded Clamp - C Clamp |
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Spring Loaded Clamp |
Most common type. Advantage is that you can easily change location of connection |
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C-Clamp |
Allows for a secure connection, preventing arcing on the base metal and ensures a solid electrical connection |
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Electrode Size |
Measured as the diameter of the inner core wire excluding flux coating. Sizes: 1/16, 5/64, 3/32, 1/8, 5/32, 3/16, 7/32, 1/4, 5/16 |
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Electrode Type Fast Fill |
Deposits substantial amounts of filler material at a fast rate. Used often for production work.
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Electrode Type Fast-Freeze |
Deposits a weld bead with the ability to solidify quickly Suitable for vertical and overhead position welding |
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Electrode Type Fill Freeze |
Deposits thin narrow beads best used for thin metals with shallow penetration |
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Electrode Type Low Hydrogen |
Electrodes that contain or lessen hydrogen. Tested by dipping in glycerin. |
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Electrode Coatings Cellulose |
Made from wood pulp. Forms a envelope of carbon dioxide and water vapor that excludes oxygen and nitrogen. Sodium or potassium is added to coating to stabilize arc |
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Electrode Coatings Rutile |
Another term for titanium dioxide. Makes the arc smooth and stable and forms a hard black slag that gives a smooth finish. Freq. combined with sodium and potassium |
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Electrode Coatings China Clay, Silica, Mica |
Used to provide slag volume and used in controlling viscosity and rate in which slag freezes. |
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Electrode Coatings Potassium |
Used as an arc stabilizer and an ionizer. As ionizer, alters electrical characteristics and helps ease and stabilize flow of current. |
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Electrode Coatings Ferro-manganese |
An alloy containing 80 percent manganese. Helps remove oxygen when used as an electrode coating |
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Electrode Classification |
First letter - designates electric welding 2 numbers - tensile strength in tens of megapascal 3rd number - designates welding positions 4th number - designates composition of coating |
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Electrode Position |
1. all positions except vertical down 2. flat and horizontal fillet 3. flat position only 4. vertical down |
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Weld joint Design Lap Joint |
Two pieces of metal overlap for weld |
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Weld Joint Design Tee Joint |
Joins 2 pieces of metal at 90 degrees to each other |
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Weld Joint Design Corner Joint |
Also joined at right angles but in an L shape |
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Weld Joint Design Butt Joint |
Joins 2 metals lying on the same plane |
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Weld Joint Design Edge Joint |
Joins two pieces of metal that are turned up at the edges. Also called a flange joint |
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Tee Joints |
Allows for maximum access but requires more filler material. Chances of distortion are high. |
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Corner Joints |
2 types open and closed Open - Used more often as full penetration is achieved and results in full strength weld |
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Weld Types Surfacing Weld |
Deposits of weld material that are used to build up surface of metal or replace worn metal Types - Build Up, Buttering, Hardfacing, Cladding |
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Surfacing Weld Build Up |
Intended to change dimension such as thickness |
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Surfacing Weld Buttering |
Provide a base for another surface weld |
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Surfacing Weld Hardfacing |
Intended to create a hard or tough surface to control wear |
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Surfacing Weld Cladding |
Create a corrosion or heat resistant layer |
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Weld Types Tack Welds |
Short temporary welds used to hold assembly on a short term |
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Weld Types Fillet Welds |
Used extensively on lap, tee, and corner joints. Consists of beads that are triangular. |
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Ideal Fillet Weld |
Joint faces at 90 Face flat or slightly convex Toes that merge smoothly Legs of equal length |
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Structural Discontinuities In Weld |
1. Undercut 2. Incomplete Penetration 3. Underfill 4. Incomplete Fusion 5. Porosity 6. Slag Inclusion 7. Cracking |