How about weldability of 40Cr structural steel

Attention should be paid to preheating before welding of 40Cr structural steel to prevent quenching crack inside weld due to heat dissipation of base metal. It is best to normalize before welding.

Weldability of 40Cr structural steel:
It is easy to segregate during crystallization and is sensitive to crystallization crack (a kind of hot crack). 40Cr alloy steel is easy to crack in crater and concave part of weld during welding. When the carbon content is high, the quenched structure (martensite structure), which is very sensitive to cold crack can be easily obtained. When the cooling rate is high in the superheated zone, it is easy to form hard and brittle high carbon martensite, which makes the superheated zone brittle.

Key points of welding process of 40Cr structural steel:
1. Welding is usually carried out in the annealed (normalized) state.
2. The welding method is not limited.
3. Generally, the preheating temperature can be increased between 250℃ and 300℃.
4. Welding materials should ensure that the composition of deposited metal is basically the same as that of base metal, such as J107 CR.
5. Quenching and tempering heat treatment shall be carried out in time after welding. If it is difficult to carry out quenching and tempering treatment in time, intermediate annealing or holding at a temperature higher than preheating for a period of time can be carried out to eliminate diffusive hydrogen and soften the structure. For products with complex structure and more welds, an intermediate annealing can be carried out after a certain number of welds are welded.