For GGC cladding, is heat treatment necessary?
Thread Content
For the three types of GGC valves specified in API 600, the valve sealing surfaces are weld-clad; is heat treatment required? How to choose the heat treatment temperature? The surfacing materials are 13CR for carbon steel surfacing, and Stellite for carbon steel surfacing
The heat treatment after cladding is primarily aimed at preventing cracking after welding and ensuring the quality of the cladded layer. In general, no pre-warming or post-welding heat treatment is required for 13Cr cladding; however, for Stellite cladding, pre-warming to 300°C is necessary before welding, followed by tempering at 630°C for 2 hours, after which the material is cooled slowly in the furnace. If appropriate conditions are not available, it can also be placed in a bucket filled with plant ash, with the aim of achieving a slow cooling process.
Are there any dissenting opinions? Expert opinion?
Well, according to normal welding procedure qualification, post-weld heat treatment is required; I have carried out such welding evaluations, and it is necessary for the stability of quality. Because both 410 and STL are relatively hard, they are prone to cracks after welding.
For 13CR, preheating is not required before welding, and air cooling is used after welding; however, it is necessary to control the welding current, speed, and layer thickness. STL: preheating before welding, and maintaining heat for slow cooling after welding.
Factory STL surfacing welding was performed without preheating, and no cracking was observed.