Resistance welding

Conti……

• Resistance Welding is a welding process, in which work pieces are welded due to a combination of a pressure applied to them and a localized heat generated by a high electric current flowing through the contact area of the weld.

• Heat produced by the current is sufficient for local melting of the work piece at the contact point and formation of small weld pool (”nugget”). The molten metal is then solidifies under a pressure and joins the pieces. AC electric current (up to 100 000 A) is supplied through copper electrodes connected to the secondary coil of a welding transformer.

The following metals may be welded by Resistance Welding:• Low carbon steels - the widest application of Resistance Welding• Aluminum alloys• Medium carbon steels, high carbon steels and Alloy steels (may be welded,

but the weld is brittle)

Advantages,disadvantages & applications

Advantages of Resistance Welding: • High welding rates;• Low fumes;• Cost effectiveness;• Easy automation;• No filler materials are required;• Low distortions.

Disadvantages of Resistance Welding: • High equipment cost;• Low strength of discontinuous welds;• Thickness of welded sheets is limited - up to 1/4” (6 mm);

applicationsResistance Welding (RW) is used for joining vehicle body parts, fuel tanks, domestic radiators, pipes of gas oil and water pipelines, wire ends, turbine blades, railway tracks.

Resistance spot welding

Conti…….

• Spot Welding is a Resistance Welding (RW) process, in which two or more overlapped metal sheets are joined by spot welds.

• The method uses pointed copper electrodes providing passage of electric current. The electrodes also transmit pressure required for formation of strong weld.Diameter of the weld spot is in the range 1/8” - 1/2” (3 - 12 mm).

• Spot welding is widely used in automotive industry for joining vehicle body parts.

Resistance spot welding

• 3000 – 40000 A,

depending on the

material and thickness.

• Steel, Copper, Brass and

light alloys can be joined.

• Application: Fabrication

of sheet metal products.

Resistance butt welding

• Upset Welding