Tool Steel Weldability

Cemented carbide is simply not weldable by conventional methods, it is composed of ceramic particles held together with a metal binder. It is extremly brittle and its capable of withstanding thermal shock of the type that occur in welding procceses.
Cooling from the welding temperature is the same as a quench from a hardening temperature. Some material are very prone to cracking with drastic quenches. Mass effect cooling can produce the equivalent of a liquid quench. The brittle structure that result from the rapid quench is strained by the shrinkage stresses from the weld solidification and this produces a combination of effect that tend to crack tool steel when they are welded.

Solution

The best approach to welding of tool steel is never to do it. Never do it by design . If welding must be done to save a mismachined partt or the like , it should be done only with the knowledge that there is considerable risk of cracking, and then special procedures should be used. It is best to weld hardenable steel in the annealed condition, slow cool from the welding temperature and re-anneal after welding. If the parts are already hardened they must be preheated to their original tempering temperature before welding. They must be maintained at this temperature during welding. After welding the parts are slowly to hand warm and imediately tempered again at the original tempering temperature. Wherever possible use a nonhardenable filler metal such as type 310 stainles steel use a matching composition filler metal. Always dye penetrant inspect for crack after welding. Never weld free machining tool steel , they crack from hot shortness, the weld is weak when cooling from the weld temperature

The best approach to welding of tool steel is never to do it. Never do it by design . If welding must be done to save a mismachined partt or the like , it should be done only with the knowledge that there is considerable risk of cracking, and then special procedures should be used. It is best to weld hardenable steel in the annealed condition, slow cool from the welding temperature and re-anneal after welding. If the parts are already hardened they must be preheated to their original tempering temperature before welding. They must be maintained at this temperature during welding. After welding the parts are slowly to hand warm and imediately tempered again at the original tempering temperature. Wherever possible use a nonhardenable filler metal such as type 310 stainles steel use a matching composition filler metal. Always dye penetrant inspect for crack after welding. Never weld free machining tool steel , they crack from hot shortness, the weld is weak when cooling from the weld temperature