Dayang Welding Materials Lecture Hall | Resistance Welding Method
Resistance welding refers to a method of locally heating a welding piece by using the resistance heat generated by a current passing through the welding piece and the contact as a heat source, and applying pressure at the same time. When performing this type of resistance welding, the surface of the workpiece to be welded is very important to obtain stable welding quality. Therefore, the contact surfaces between the electrode and the workpiece and between the workpiece and the workpiece must be cleaned before welding. When welding, there is no need for filler metal, high productivity, small deformation of the weldment, and easy automation.
There are four main types of resistance welding, spot welding, seam welding, projection welding, and butt welding.
Spot welding (Spot Welding) is a resistance welding method for assembling weldments into lap joints and pressing them between two columnar electrodes to fuse the base metal with resistance heat to form a solder joint.
The process of seam welding is similar to spot welding, except that the cylindrical electrode is replaced by a rotating disk-shaped roller electrode. The weldment is assembled into an overlap or butt joint and placed between the two roller electrodes. The resistance welding method of continuous rotation and intermittent power transmission to form a continuous welding seam is mainly used for welding structures where the welding seam is relatively regular and requires sealing. The thickness of the plate is generally below 3mm.
Projection Welding is a variant of spot welding; there are pre-made bumps on a workpiece. During projection welding, one or more nuggets can be formed at the joint at one time.
Butt Welding is a resistance welding method that welds the weldment along the entire contact surface, including Resistance Butt Welding and Flash Butt Welding.
The quality of resistance welding is determined by the current, energization time, pressure, and tip diameter of the resistor.
Lots of highlights in resistance welding
When the nugget is formed, it is always surrounded by a plastic ring, the molten metal is isolated from the air, and the metallurgical process is simple.
The heating time is short and the heat is concentrated, so the heat-affected zone is small, and the deformation and stress are also small. Generally, it is not necessary to arrange correction and heat treatment processes after welding.
Filling metals such as welding wires and electrodes are not required, and welding materials such as oxygen, acetylene, and hydrogen are low, and the welding cost is low.
High productivity, no noise and harmful gas, in mass production, it can be combined with other manufacturing processes on the assembly line. However, flash butt welding needs to be isolated due to spark spray.
Simple operation, easy to realize mechanization and automation, improve working conditions.
Resistance welding has many advantages, but also lacks reliable non-destructive testing methods. The joints in spot and seam welding have low tensile strength and fatigue strength, high equipment costs, and difficult maintenance.
With the development of China's microelectronic technology and the development of high-power thyristors and rectifiers, favorable conditions have been provided for the improvement of resistance welding technology. Chinese-made high performance secondary rectifier welding machine. The control box composed of integrated circuits and microcomputers has been used for supporting new welding machines and rebuilding old welding machines. Advanced closed-loop monitoring technologies such as constant current, dynamic resistance, and thermal expansion have begun to be applied in production. All this will help improve the quality of resistance welding technology and expand its application areas.