What kind of welded joints are prone to reheat cracking or delayed cracking?

The main contact with the tendency of reheat cracking is austenitic stainless steel. The main contact with the tendency of delayed cracking is generally low-hydrogen welding rod, preheating before welding, and hydrogen elimination heat treatment after welding.

Most of them refer to materials with Rm greater than 540MPa

Welded joints with reheat cracking tendency or delayed cracking tendency generally refer to the cracking tendency caused by the uneven internal stress of the metal material during the welding process due to high temperature and cooling process. Here are a few situations where this tendency may be present: 1. High hardness materials, such as high carbon steel and high alloy steel. These materials are prone to high stress during welding, which can lead to crack formation. 2. Welded joints with large thickness or large rigid structure. Due to the high rigidity, welding shrinkage and deformation are large, and the residual stress near the weld is also large, making cracks more likely to occur. 3. Severely constrained welded structures. That is, the area around the weld cannot shrink and expand freely for some reason, which will increase the stress at the weld and easily cause cracks. 4. During the welding process, the microstructure in the welding heat-affected zone changes, especially for materials containing easily precipitated phases and brittle phases, which are more likely to cause cracks to form. 5. Improper selection of welding process parameters, such as excessive current, too fast welding speed, etc., may increase the possibility of cracks. Welded joints under these conditions require surface inspection to confirm whether there are cracks to ensure the safety performance of the welded structure. .

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For some high-strength steels and high-temperature alloys containing precipitation-strengthening elements (including low-alloy high-strength steels, pearlitic heat-resistant steels, precipitation-strengthened high-temperature alloys, and some austenitic stainless steels), cracks did not appear after welding, but cracks appeared during the heat treatment. This type of crack is called "stress relief crack". Some welded structures work under certain temperature conditions. For example, cracks will occur when working at 500~600℃ for a long time. In engineering, cracks generated in the above two situations (stress relief process and service process) are often collectively referred to as "reheat cracks".