“What are the definitions of "delayed cracking tendency" and "reheat cracking tendency"?

Cracks that occur after a period of time after welding are delayed cracks. Delayed cracking is a common defect of cold cracking. It does not occur immediately after welding, but appears after a delay of several hours, days or longer. Materials prone to delayed cracking: 16MnR, 15MnNbR, 18MnMoNbR (not easy to buy), 13MnMoNbR, 07MnCrMoVR, 07MnNiMoVDR and Japan’s CF-62 series steel. reheat crack: After welding is completed, the cracks caused by the welded joint being heated again within a certain temperature range (stress-relieving heat treatment or other heating processes) are reheat cracks. Reheat cracks generated during stress relief heat treatment are also called stress relief treatment cracks, also called SR cracks. There are two reasons for the occurrence of reheat cracks:: One is related to the carbide-forming elements (Cr, Mo, V, Ti, B, etc.) contained in the steel. For example, the V element in pearlitic heat-resistant steel will significantly increase SR crack sensitivity. ； The second is related to the heating speed and heating time. Different steel types have different sensitive temperature ranges that are prone to reheat cracking. Therefore, when formulating the post-weld heat treatment process, the residence time of the weldment in the sensitive temperature range should be minimized. The former is an internal factor and the latter is an external cause.