Resistance welding
1.Resistance spot welding of low carbon steel sheets
sheet thickness Electrode tip dia. Force. Current time
mm. mm. Kgf amps. sec
0.5 4 30 2000 02
1 5 100 3000 0.4
2 7 200 5000 1
3 9 300 8000 2
4 11 380 10000 3.2
5. 13. 450 12000. 4.5
2.Resistance spot welding of Aluminium and alloys
Sheet 0.5 mm
welding current 25000 -30000 amps
welding time 12- 15 cycles (50cps frequency)
welding force 150 – 180 kgf
Cleaning : Mechanical and chemical methods
Machine : Programmable controls with display and recording of parameters.
3.Electrode tips
Electrolytic copper
Chromium copper alloy
Cadmium copper alloy
Beryllium copper alloy
Tungsten copper alloy
ODS copper alloy
The choice depends on production rate and material to be welded.
4.WELD BONDING
Weld bonding is a resistance spot welding process variation in which the spot-weld strength is augmented by an adhesive at the faying surfaces. Weld bonding is a combination of resistance spot welding and adhesive bonding. An adhesive in the form of paste or film is placed between the workpieces; resistance welds are then made.
Structures common to the aerospace and transportation industries are joined by weld bonding. For example, weld bonding is used to attach beaded panels to aircraft skins, and aircraft or truck skins to channels, angles, and other types of reinforcement.
5.Coated Steels.
The various coatings and types of plating applied to carbon steel sheet metal to provide corrosion resistance or to enhance appearance lend themselves satisfactorily to welding with resistance welding processes, with few exceptions. In general, good results may be obtained without special cleaning processes. However, the surfaces of aluminized steel should be wire brushed before welding to minimize expulsion and electrode pickup.
Phosphate coatings can increase the electrical resis- tance of the surfaces to a degree that welding current cannot pass through the sheets with low welding pressures. Higher pressures will produce welds, but slight variations in coating thickness may prevent welding.