Is preheating required before cladding welding?

This post was last edited by Shutong on 2022-12-20 at 19:12. Weld evaluation can fully cover the composite layer. Whether preheating is required before welding is determined by the base metal and the coating material. In the current standard for welding procedure qualification, NB/T 47014-2011 \"Welding Procedure Qualification for Pressure Equipment\", welding procedure qualification is primarily based on the mechanical properties of the welded joint to assess the welding process; it specifies only the methods for evaluating the mechanical properties of the welded joint, its bending performance, the chemical composition of the surfacing layer, and the shear strength of the welds between the heat exchange tubes and the tube sheet. For specimens of stainless steel clad plates, it is sometimes necessary to determine or test additional characteristics such as the chemical composition of their cladding and their susceptibility to intergranular corrosion. The factors influencing these additional characteristics are different from those affecting mechanical properties. However, standards such as NB/T 47014-2011 “Welding procedure qualification for pressure equipment” only specify evaluation rules and requirements based on mechanical properties, without addressing this aspect at all. Does the surfacing layer also need to be evaluated? Personally, I believe that when other special inspection requirements are specified in the design documents of pressure vessels made from stainless steel clad plates (in this method, specifically the determination of the cladding’s chemical composition and the intergranular corrosion susceptibility test), it is necessary to conduct an additional evaluation of the welding procedure alongside the regular welding procedure qualification ； If no other special requirements are specified, it is considered that no such requirements exist in the design; therefore, only a welding procedure qualification is necessary, without the need for any additional welding procedure assessments.

Preheating is required before welding; without preheating, it cannot be used for root welding when S=60； See Table 16, Column 1 continued, of NB/T47014.

It seems like something was said, but it also seems like nothing was said: lol

This post was last edited by Shutong on 2022-12-22 at 18:49. Please share your thoughts on this post; I’d like to learn from it as well and be more active in discussions. Please correct me if there’s anything wrong in what I say

What’s the preheating temperature? Is it 100 or higher?