High carbon steel has poor weldability because of its high carbon content. Its welding has the following characteristics:
(1) Poor thermal conductivity, resulting in a significant temperature difference between the welded part and the unheated part. When the molten pool is rapidly cooled, the internal stress in the weld may form cracks.
(2) It is more sensitive to quenching and easy to form martensite in the joint area. Due to the effect of tissue stress, cold cracks occur in the vicinity of joints.
(3) Because of the influence of high temperature welding, the grain growth is fast, the carbide is easy to aggregate and grow at the grain boundary, the weld is weak, and the strength of the welded joint decreases.
(4) Hot cracking of high carbon steel is easier than that of medium carbon steel in welding.