The weldability of GBT 8162 35CrMo steel pipes

The most commonly used GBT 8162 35CrMo steel pipes are seamless pipes, it is seldom to find 35CrMo welded pipe. One of the main reason is that the weldability of GBT 8162 35CrMo steel is not that good.

According to the International Institute of Welding (IIW), when Ceq<0.40%, the hard tendency of steel is not obvious, the weldability is excellent, the welding is not necessary to be preheated and can be welded directly. When Ceq=0.40 to 0.60%, the hard tendency of the steel is obvious, the weldability is still available, the steel needs to be properly preheated before welding,. Meanwhile, the post weld slow colding and other technical measures need to be adopted to control the welding connection energy. When Ceq>0.60%, the hard tendency of steel is strong, and the weldability is poor. It belongs to hard welding steel, such as GBT 8162 35CrMo steel pipes. It is necessary to adopt high preheating temperature and strict technical measures, and select suitable welding material to weld 35CrMo steel, etc such hard welding steel.

It is calculated that the carbon equivalent of GBT 8162 35CrMo steel pipe is Ceq=0.72%. It can be seen that the weldability of 35CrMo steel material is bad, the hard tendency of the welding is larger, the hot cracking and cold cracking tendency of the heat affected zone will be larger, especially in the tempering state, and the cold cracking tendency in the heat affected zone will be very prominent.

Therefore, based on selecting suitable welding materials and welding methods, we also need to adopt higher preheating temperature before welding, strict technological measures and proper interlayer temperature control to achieve welding purpose of GBT 8162 35CrMo steel pipes.