In ferritic steels, hydrogen embrittlement occurs at temperatures close to ambient temperature. HIC typically occurs when the weldment has a sensitive microstructure, a high level of stress, and/or a sufficient level of hydrogen. Post heating is utilized to decrease the potential for hydrogen-induced cracking (HIC). Application and code requirements as well as service environment primarily drive the need for PWHT. Stress relieving and post-heating are the most commonly used PWHT procedures. Additionally, PWHT can also lead to material strength enhancements and hardness reduction.
Typically, PWHT is used to reduce the residual stresses and enhance the resistance to brittle fracture. The resultant residual stresses in the structure increase substantially due to solidification and melting and their magnitudes become almost equal to the yield strength of the base material. Moreover, the magnitude of stresses increases in more complex or bigger parts/structures.ĭuring the welding process when the metals are joined together, hardening occurs in different degrees based on the carbon content in metals, specifically in the heat-affected zone near the weld metal deposit. Welding induces residual stresses in a structure, which cause distortions in the structure in the long term. Post weld heat treatment (PWHT) refers to any heat treatment performed after machining/welding to improve the mechanical and chemical properties of the machined surfaces/weldment. This article discusses the post weld heat treatment (PWHT) process and its effectiveness in reducing the residual stresses and improving the mechanical properties of weldments.
0 kommentar(er)
