Distortion Control



The effect of heat on weldments can cause all kinds of distortions problems. Many of these problems can be eliminated by planning the sequence, size, and location of the welds. Some general rules that have been outlined in many of the texts published by the Lincoln Electric Company are listed below. 1) Do not overweld 2) Use intermittent welding. 3) Use as few weld passes as possible. 4) Place welds near the neutral axis. 5) Balance the welds about the neutral axis. 6) Use backstep welding 7) Anticipate the shrinkage forces. 8) Plan the welding sequence. 9) Remove weld shrinkage forces after welding. 10 Minimize welding time.



An excellent text for reference is The Procedure Handbook from which the above list was taken. The Lincoln Electric Company, 22801 St. Clair Ave. Clevland, Ohio

The Welding Institute has an informative website:

http://www.twi.co.uk/bestprac/jobknol/jk36.html

The following discussion shows some examples for problems encountered and possible solutions.





Distortion of a simple Tee joint

The first example is very common and has several possible solutions. The tee joint using plate is a common subject of examples in text and has some problems that many people fail to visualize.

In example A the bracing prevents movement and forces the weld to stretch or yield as it cools. There will be some tension on the bead faces . It will be the amount of tension that would match the yield strength of the weld metal. Some minor distortion will be evident when the braces are released but it usually is within acceptable tolerances.

In Example B the brace will ensure that the relationship between the right side and the upright will stay close to ninety degrees however the left side is free to shrink and distort. Often the braces will be placed as in this example because braces on the left interfere with the welder's free access to that side.

Example C is the result of welding equally on both sides. The upright remains vertical but the base piece is bowed.

Example D is the best solution to prevent C however it requires that the assembly be pre-bent against the brace or strongback.

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Tee Joints

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