Auto body spot welder online store
Spot welding of very dissimilar metals, such as aluminum and steel, is generally not possible because of different melting characteristics and conductivities. Some types of coated low-carbon steels require special techniques. Steels plated with chrome and nickel for electrical conductivity can usually be resistance welded as readily as uncoated material. Aluminum, tin, zinc and terne-coated steels are also spot weldable with special precautions and welding equipment. Some coatings can emit poisonous fumes that must be safely handled when spot welded, thereby increasing cost. Spot welding of coated substrates creates burn marks in the coating which can be unsightly and may corrode in severe environments. Designers should carefully consider the product’s appearance and service requirements before specifying spot welding of pre-plated materials.
Position the welding torch with the wire in the center of the hole contacting the back sheet of metal. It is important to arc against this back sheet rather than on the edge of the hole, otherwise the weld might not penetrate into the back sheet. The torch should ideally be pointing directly into the hole rather than at the angle in the photograph. Start welding in this position and don’t move the welder until the hole is almost full of weld. Then move the welder outwards in ever increasing circles until the weld is completed.
Materials Appropriate for Spot Welding: Due to its lower thermal conductivity and higher electrical resistance, steel is comparatively easy to spot weld, with low carbon steel being most suited to spot welding. However, high carbon content steels (Carbon equivalence > 0.4wt%) are prone to poor fracture toughness or cracking in the welds as they tend to form hard and brittle microstructures. Galvanised steel (zinc coated) requires slightly higher welding currents to weld than uncoated steels. Also, with zinc alloys, the copper electrodes rapidly degrade the surface and lead to a loss of weld quality. When spot welding zinc coated steels, electrodes must either be frequently exchanged or the electrode tip surface should be ‘dressed’, where a cutter removes contaminated material to expose a clean copper surface and reshapes the electrode. See more info at Auto Body Spot Welder.
To make sure your welding settings are correct, you should carry out a test run using metal offcuts, followed by a destructive test where you separate the welded parts with a hammer and a forked chisel. After separation, a hole must be made in one of the two conjoined sheets – a process known as “unbuttoning” in metalworking jargon – as proof that the settings are right for the metals and thicknesses involved. Apologies for the abstruse technical term! When welding radiators, make sure you also carry out a leak test.
