Welding Services: Minimising Weld Distortions in Welded Structures

10 April 2019

Welding journeymen, including those that work for structural steel fabrication services, are expected to produce fused joints that conform to the highest engineering standards. A welding inspector will even swing around an erection project at some point to assess the metallic unions and greenlight them as high-quality structural connections. That being said, the temperatures delivered to those metal surfaces can have unforeseen consequences, which will inevitably make themselves known.

Studying Weld Distortion Energies

Understanding a problem always helps when we’re trying to come up with an effective solution. That principle applies to many engineering fields, so there’s a good chance it’ll work here, too. Anyway, where are those excess energies coming from? No one wants to hear this, but there’s no avoiding certain hard truths. Sometimes a welder gets it wrong. An over-welded joint is applied when an intermittent approach should’ve been selected. Too much fill material or too high an arc temperature caused excess thermal strain. Alloy surfaces can cause trouble, too. Thin-walled sections don’t dissipate heat in the same way as thickly plated segments, for example. These effects cycle, too, so metal joints expand and contract, again and again. Indeed, cyclic stress is a major contributor to weld distortion problems.

Minimising Weld Area Stresses

Cycling temperatures cause weld joints to expand and contract. Welders can use fewer electrode passes as a shrinkage controlling mechanism. Follow up this approach with a series of maneuvers that sees the thermal energies applied uniformly, not just to one localised area. A welder’s goal is to spread the temperature, to distribute the energy while keeping the weld pool hot and flowing. Next on the list of weld distortion minimising tips, don’t over-weld. Don’t apply too much filler, and don’t use an overly high arc temperature. As a journeyman, expert welders use purpose-designed weld heads and edge preparation techniques to retain control of the job at hand. For instance, edge bevels work well on thicker plate sections as an energy minimising aid.

There are other techniques available. They all form a theme of sorts. They’re part of a good practices approach. There’s the concept that welds should be applied in and around the joint neutral axis. Intermittent heat application work yields good results, too, but that technique requires a mindful approach, one where the weld pool stays hot and liquid. Ultimately, the weld site, the thick plate or thin-walled elements on a fabrication project, all require a seasoned eye and trained hand. Then, knowing the mechanical stresses that will occur if the job isn’t handled right, the above good practices techniques, plus a whole series of work-relevant welding codes, acts to prevent any structure destabilising weld distortion.