Spot welder According to use, there are universal (general-purpose), special-purpose; In accordance with the number of welding points, there is a single point, two-point type, multi-point; According to the conduction method, there are unilateral, bilateral; According to the transmission mode of the pressure mechanism, there are pedal-type, motor-cam type, pneumatic type, hydraulic type, compound type (gas hydraulic); According to the characteristics of operation, there is no automation, automation, according to the installation method, there are fixed, movable or portable (suspension); According to the movable electrode of the welding machine The moving direction of (an ordinary electrode) there are vertical travel (electrode for linear motion), circular arc stroke, according to the power supply mode, there are power frequency welder (50 Hz alternating current), Pulse welder (DC pulse welder, storage welding machine, etc.), inverter welder (such as low-frequency welder).
When the workpiece and the electrode are fixed, the resistance of the workpiece depends on its resistivity. Therefore, the resistivity is the important energy of the welded material. A metal with a high resistivity (such as stainless steel) has a good conductivity (such as aluminum alloy) with low electrical conductivity. Therefore, spot welding stainless steel When the heat is easy and heat dissipation, spot welding aluminum alloy when the heat is difficult and heat. When spot welding, the former can use a small current (thousands of amps), the latter must be very large current (tens of thousands of amps). Resistivity not only depends on the type of metal, but also with the metal heat treatment State, processing mode and temperature.
In order to ensure the size of the fusion core and the strength of solder joint, welding time and welding current can complement each other in a certain range. In order to obtain a certain strength of the solder joints, you can use large current and short time (strong conditions, also known as hard specifications), can also be used small current and long time (weak conditions, also known as soft specifications). The use of hard or soft specifications, depending on the performance of the metal, thickness and the power of the welder. For the different performance and thickness of the metal required by the current and time, there is a limit, use this as the prevail.
The electrode pressure has a significant effect on the total resistance r of the two electrodes, and the r is significantly reduced with the increase of the electrode pressure, but the amplitude of the welding current increase is not large, which can not affect the decrease of heat production caused by R reduction. Therefore, the strength of solder joints decreases with the increase of welding pressure. The solution is to increase the welding pressure while increasing the welding current.