Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
46 Cards in this Set
- Front
- Back
|
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
-convexity of fillet welds to a minimum -somewhat controlled if the heat input is evenly distributed on both sides of the weld 120102g pg 8 |
|
|
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 it 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 |
