With the development of industry, there are many different types of metal materials that have emerged. The common ones are plated steel sheets, stainless steel sheets, aluminum alloys, copper alloys and other materials. When spot welding machine is used to weld these corresponding metal materials, different welding means are used to weld each material well.
Coated steel is also called coated steel. It is a general term for products made of low carbon steel plates with excellent deep-drawing properties coated with organic coatings of SnsZn, Al, Cr, Pb-Ssn alloys and plastics. When welding with a spot welder, it differs from ordinary steel plates because it has a coating on its surface. The welding should pay attention to these conditions.
The spot weldability is better, the welding should pay attention to the problem:The electrode is easy to adhere with the plating, which reduces the electrode life. The melting point of the plating metal is lower than that of mild steel. When heated, the plated metal melts first to increase the contact surface in the middle of the two plates and reduce the current density - thus the welding current density is greater than when there is no plating.
Austenitic stainless steel, ferritic stainless steel: because of high resistivity, poor thermal conductivity, thermal sensitivity, can choose a smaller welding current, shorter welding time and relatively large electrode pressure. Martensitic stainless steel because of the tendency to quench, can choose a longer welding time.
Aluminum alloy should be a non-ferrous metal materials. In the industrial use of a wide range of applications, for aviation, aerospace, automotive, machinery manufacturing, chemical industry, etc., so far the aluminum alloy should be the application of more alloys.
Spot welding of aluminum alloys: the electrical and thermal conductivity is high, so it is necessary to choose a relatively large welding current and a short welding time. The coefficient of linear expansion of the narrow plastic temperature range is large, so it is necessary to choose a relatively large electrode pressure, and the electrode followability should also be good. The surface of the workpiece is easy to generate oxide film, must be strictly clean before welding.
Copper alloy spot welding: compared with aluminum alloy, spot welding is relatively easy, but pure copper spot welding is more difficult, so it is necessary to choose the corresponding countermeasures, such as adding shims between electrode and workpiece.