Unravelling the Mystery of Heat Treatment
This article originally appeared in Connector Magazine, Fall 2020 Edition
Erectors can save cost and time by taking this welding technique in-house
Large steel erection projects commonly require heat treatment for welding because of the thick materials used in structural steel construction. Proper implementation is critical; so often this work is outsourced. The perceived level of expertise to perform this work can make the prospect of using in-house personnel daunting. However, most welding contractors are actually fully capable of performing on-site heat treatment operations.
The two primary methods for heat treating metal are preheating and post-weld heat treatment (PWHT). Preheating is the process of heating the base metal to a specific temperature prior to welding to minimize the temperature difference between the welding arc and the base metal. This process helps to reduce internal stresses that occur as substantial temperature differences between the weld and the base metal normalize, which can cause cracking and distortion. Slowing the cooling rate also allows hydrogen to escape from the weld, which minimizes the potential for cracking.
