technical case study
By calculating the likely movement before welding begins, fabricators can improve dimensional accuracy, reduce costly rework and prevent distortion from compromising the finished assembly. Before the arc strikes: How to predict and control stainless steel weld shrinkage
The rule of thumb every fabricator should know as a preliminary rule of thumb, fabricators can allow between 3 mm and 6 mm of movement across the joint for every 25 mm of weld throat thickness. On single-V groove joints, angular distortion can also develop rapidly and may fall in the range of 1° to 3° per weld pass. These figures should be treated as workshop planning guides rather than substitutes for an engineering calculation or a representative welding trial. Actual movement will depend on the stainless steel grade, joint design, plate thickness, welding process, heat input, number and size of passes, restraint and overall stiffness of the fabrication. The practical message is nevertheless important: stainless steel is unlikely to remain exactly where it was positioned unless the likely direction and magnitude of movement have been considered in advance. Turning movement into a number For a butt joint, transverse shrinkage can be estimated using the following engineering formula: ΔW=4.5×A÷t
In stainless steel fabrication, weld distortion should not be regarded as an unexpected event. It is a predictable consequence of localised heating, thermal expansion, weld- metal solidification, contraction and restraint. The challenge is particularly significant when welding austenitic stainless steels. These grades have relatively low thermal conductivity and a higher rate of thermal expansion than carbon steel. Heat remains concentrated around the weld for longer, while the material expands and contracts more significantly during the welding cycle. A joint that is correctly aligned before the first arc is struck can therefore pull, bow or twist as it cools. In precision fabrications, even relatively small dimensional changes can move holes and flanges out of alignment, alter the profile of a component or create difficulties during final assembly. Experienced fabricators consequently treat shrinkage as part of the production plan. Before welding begins, they consider how much filler metal will be deposited, how the joint geometry will contract, how the welding sequence will distribute heat and how clamps or fixtures will influence the final movement.
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Issue 3 – 2026
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