Cold cracking typically forms at temperatures below what threshold?

The phenomenon of cold cracking, also known as hydrogen-induced cracking or delayed cracking, typically occurs in metals that are exposed to certain conditions, particularly low temperatures. It usually manifests when the temperature drops below a significant threshold where the mechanical properties of the material can become compromised.

In the context of the options given, it is well-established in welding and metallurgy that cold cracking is a concern at temperatures below 100° C. This threshold is crucial because it represents a critical limit where the risk of brittle fracture due to hydrogen embrittlement in weldments is heightened. As the temperature decreases, materials, especially high-strength steels, can become less ductile and more prone to cracking when subjected to stress.

This understanding is critical for welders and engineers, as they must take precautions, such as preheating or controlling the cooling rate, to prevent cold cracking in welded joints that are subjected to low temperatures.