What happens to the properties of alloy steels when they are improperly welded?

When alloy steels are improperly welded, one of the significant outcomes is the development of residual stresses. This phenomenon occurs due to differential cooling rates during the welding process. When molten metal cools, it contracts, and if there are portions of the weld that cool at different rates, it can lead to internal stresses in the material. These residual stresses are critical because they can affect the performance of the welded joint, potentially leading to distortion or premature failure under load.

Residual stresses can cause unexpected behavior in the steel during operation, such as crack initiation or propagation, which ultimately compromises the structural integrity of the component. The presence of these stresses is a common concern in welding practices for alloy steels and must be managed through proper welding techniques, post-weld heat treatment, or other stress-relieving methods.

In contrast, while issues like loss of ductility or a strengthening effect might occur under certain conditions, they are typically not the primary consequences associated with improper welding. Similarly, the original properties of the alloy steels would not remain unaffected, as the welding process inherently alters the material structure due to the heat input and the thermal gradients experienced during the process.