Distortion

Weld distortion can be identified by a change in the weld joint – either shrinkage, a change in the angle or buckling.

Distortion is a problem that most welders will experience at some point.

It can affect the appearance of a weld, prevent it being assembled with other parts, or even stop the finished piece from performing its intended purpose.

In this guide we look at the causes of distortion to help you minimise its impact on your welding.

What causes weld distortion?

Distortion occurs during the expansion and contraction of the weld and base metals during the heating and cooling cycle.

It means that the welded component fails to maintain its original shape and may result in shrinkage, angular movement, or buckling. Not only can the appearance of the weld be unacceptable but, more importantly, distortion can mean that it’s unable to meet its design requirements or perform correctly.

Picture a weld metal in a vice. During heating it expands, but because it is held in a vice, it can only expand vertically. As it solidifies and joins the base metal, it does so in this expanded form and when it cools, is unable to contract to the right shape because of the join.

Stresses then develop between the weld and the adjacent base metal and the weld stretches and thins out, to adjust to the volume requirements of the lower temperature. When the restraints are removed, these stresses are partially relieved as they cause the base metal to move, but the weld is then distorted.

What can you do to minimise weld distortion?

Shrinkage during heating and cooling can’t be prevented, but it can be controlled.

If the following steps are taken and distortion still occurs, some corrective measures can be attempted, including flame straightening. However, these methods are expensive and require particular skill to be successful.

Consider your design

Is it possible to keep welding to a minimum? If it can’t be eliminated entirely, try to reduce the need to weld as much as possible.
Avoid overwelding

The more weld metal that’s put in the joint, the higher the forces that can cause shrinkage. Make sure the weld is correctly sized for the joint.
Use restraints

Tack welds, jigs, clamps and heavy strongbacks can help to hold the assembly in place and restrict movement during welding.
Use intermittent welding

Intermittent, rather than continuous welds, can significantly reduce the weld metal and reduce the risk of distortion.

Use high travel speeds and low heat input to limit heat buildup

Mechanised or automated processes can help.
Balance your weld around the neutral axis

If the weld is placed right at the neutral axis, distortion can be better controlled.
Use a backstep weld sequence or preset the joint

If you can anticipate distortion and predict which way the welded piece will bend, the part can be pre-bent or set out of alignment, so that after welding, the part is straight.
Use a square edge or narrow gap procedure

This is the best way to avoid angular distortion.

Choosing the right shielding gas for MIG/MAG welding

Are you MIG/MAG welding carbon or low-alloy steels?

By using the right shielding gas, you can actually reduce the risk of distortion. Take a look at some of our most popular gases.

ARGOSHIELD Universal

Easy to use, Argoshield Universal is ideal for semi-automatic, automatic and robotic applications. It produces smooth, flat welds with good penetration and sidewall fusion, and creates less spatter. Because welding speeds are kept high over a wide range of welding conditions, it’s particularly effective at keeping distortion to a minimum.

Buy ARGOSHIELD Universal online

ARGOSHIELD Light

Argoshield Light is designed for welding thinner materials. Because it can be used at faster welding speeds on a lower heat, welding distortion is reduced, but it also contains oxygen, meaning the arc is stabilised for less spatter. It’s a great choice for welding components that are painted or powder coated after welding. Welding different metals? View our extensive range of shielding gases.

Buy ARGOSHIELD Light online