Welding Processes Handbook
This explanatory guide to the commercially significant and commonly-used welding processes covers the design of welded joints, quality assurance and costing, and can be applied to all instruction levels.
TABLE OF CONTENTS Welding Processes Handbook
Chapter 8: Pressure Welding Methods
Pressure welding can be carried out by several welding methods, having in common the fact that the surfaces of the joint are pressed or worked together. Smiths in traditional forges used forge welding, which involved heating the metal in a fire until it was plastic, then it could be forged together. This means that forge welding could be classified among methods of pressure welding. In some cases (e.g. spot welding), the surfaces to be joined are heated to melting point, while in other methods the weld can be made without significant heating.
8.1 Resistance Welding
Resistance welding is one of the oldest types of welding. Heat is generated by the passage of an electric current through the resistance formed by the contact between two metal surfaces. The current density is so high that a local pool of molten metal is formed, joining the two parts. The current is often in the range 1 000 100 000 A, and the voltage in the range 1 30 V.
We usually distinguish between five different types of resistance welding:
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spot welding
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seam welding
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projection welding
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resistance butt welding
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flash welding
Resistance welding methods are generally fast, efficient and low-polluting. No filler materials are required. The drawbacks can be high capital cost and a somewhat limited range of applications. In principle, each machine can be used for only one type of welding.
Spot Welding
Spot welding is the best-known resistance welding method. It is used for joining thin sheet materials (up to 3 + 3 mm)...
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