Resistance welding refers to a method of using electric current through the weldment and the resistance heat generated by the contact as a heat source to locally heat the weldment, and at the same time pressurize the welding method. When resistance spot welding, no filler metal is required, the productivity is high, the deformation of the weldment is small, and it is easy to realize automation.

Resistance projection welding is a method of using the resistance heating effect generated by the current flowing through the contact surface and adjacent areas of the workpiece to heat it to a molten or plastic state to form a metal bond. There are four main methods of resistance flash welding, namely spot welding, seam welding, projection welding and butt welding.

Electric resistance welding is a type of welding method that uses resistance heat as energy, including electroslag welding using slag resistance heat as energy and resistance seam welding using solid resistance heat as energy.Resistance percussion welding is generally a welding method in which the workpiece is placed under the action of a certain electrode pressure and the contact surface between the two workpieces is melted by the resistance heat generated when the current passes through the workpiece to realize the connection. Usually larger currents are used. To prevent arcing on the contact surfaces and to forge the weld metal, pressure is always applied during welding. When performing this type of resistance butt welding, the surface goodness of the workpiece to be welded is of prime importance to obtain stable welding quality. Therefore, the contact surface between the electrode and the workpiece and the workpiece and the workpiece must be cleaned before welding.

The principle of resistance welding

The generation of welding heat and the factors that affect the heat generation The heat generated during spot welding is determined by the following formula: 

Q =I2Rt

Where Q - the heat generated (J)

I2——The square of welding current (A)

R——Resistance between electrodes (Ω)

t——Welding time (s)

Resistance R and the factors affecting R, the resistance between electrodes in the above formula includes the resistance R of the workpiece itself, the contact resistance R between the two workpieces, and the contact resistance R between the electrode and the work.

When the workpiece and electrodes are timed, the resistance of the workpiece depends on its resistivity. Therefore, resistivity is an important property of the material being welded. Metals with high resistivity have poor thermal conductivity (such as stainless steel), and metals with low resistivity have good thermal conductivity (such as aluminum alloys). Therefore, it is easy to generate heat and difficult to dissipate heat when spot welding stainless steel, and it is difficult to generate heat and easy to dissipate heat when spot welding aluminum alloy. When spot welding, the former can use a small current (several thousand amperes), while the latter must use a large current (tens of thousands of amperes) for the resistance element welding.