Welding technology of medium carbon steel and cw50 cemented carbide

When cw50 steel bonded carbide and 45 steel are welded by continuous flash butt welding, the following two processes are mainly experienced:

One is the burning process. During the burning process of the two base metals, the average resistance on the contact surface is much greater than the resistance of the weldment itself, and the heat evolution on the contact surface plays a leading role in heating. Due to the extremely low pressure between the weldments during firing, the weldments are connected only by liquid metal droplets called "transition". During the burning process, a thin layer of liquid metal is formed on the whole end face to protect the internal metal from oxidation. The liquid metal itself is extruded from the joint under the action of upsetting force, and the oxide on the liquid surface is also extruded, avoiding the defect of slag inclusion.

The second is the upsetting process. After the two base metal joints are burned, they should quickly close together to squeeze the liquid metal and oxide out of the joint before solidification. At this time, under the action of upsetting force, the joint will produce large plastic deformation locally, so that common grains can be formed on the joint surface of the two base metals, so that a solid welded joint without pollution can be obtained.

The third is the welding process parameters. Un1-75 universal flash butt welding machine is used. The rated power is 75kW, the secondary no-load voltage is 3.5 ~ 7V, the upsetting pressure is 300mpa, the feeding mechanism of the welding machine is a lever, the cross-sectional area of flash butt welding is 600mm2, and the clamping mode of the welding machine is screw clamping mode. When using flash butt welding process to weld cw50 steel bonded carbide with 45 steel, the process parameters

The flash butt welding process is adopted to weld the welded joint between cw50 steel bonded carbide and 45 steel. The characteristics of metallographic structure after heat treatment are as follows:

① On one side of the heat affected zone of cw50 steel bonded carbide, carbide agglomeration occurs, so the hardening tendency is large.

② On one side of heat affected zone of 45 steel, cw50 alloy is distributed in strip or network, with martensite and carbide structure and hardness up to 730hv.

③ The strength of the flash butt welded joint of cw50 steel bonded carbide and 45 steel is high, but the plasticity of the joint is usually low due to the existence of carbides.