15CrMo material
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In equipment, 15CrMo material is primarily used for nozzles and forged flanges. Is post-weld heat treatment required for its Class D welds?
Since the entire equipment does not undergo post-weld heat treatment, should local heat treatment be applied to this weld?
For weld joints between different steel grades, it is determined whether heat treatment is necessary based on the more stringent heat treatment requirements. For 15CrMo material, heat treatment is required regardless of its thickness; therefore, in the situation described by the original poster, heat treatment is necessary.
It depends on what the main material is and what welding materials are used. If the main body is austenitic stainless steel, and austenitic welding materials are used for Class D welds between the fittings and the main body material, no post-weld heat treatment is required.
The main material is Q245R, and the welding material is J427.
Thank you; according to the standard requirements, heat treatment is necessary.
In other words, apart from this situation, is heat treatment necessary?
What is the reason why the covering material is different from the main material?
Not necessarily. This type of material has requirements regarding thickness for heat treatment; not all of it requires post-weld heat treatment. You see, for thinner materials, preheating and post-heating are sufficient.
Please refer to Table 5 in GB150.4; the 15CrMo material requires heat treatment at any thickness.
GB150 only specifies the requirements for welding steel of the same type; it does not address welding 15CrMo with other types of steel such as carbon steel or alloy steel. Each case must be analyzed on its own.