This imperfection is formed when excessive weld metal is added to the joint, which is usually a result of poor welder technique for manual processes but may be due to poor parameter selection when the process is mechanised. That is, too much filler metal for the travel speed. In simple terms, weldment distortion is the permanent bending, twisting, or warping of metal that occurs after welding. It results from the uneven heating and cooling during welding, which creates residual stresses that literally pull and push the metal out of shape. The heated zone wants to grow, the surrounding material restrains it, and the cooled weld zone then wants to shrink while the rest holds position. Once clamps. This case study details the failure of recently replaced inlet pigtail pipes for a hydrogen reformer furnace. The pigtail connection to the catalyst tube consisted of a ASME A-335 P22 pipe welded to an Incoloy 800HT weldolet.
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