Chapter 32:Resistance and Solid-State Welding Processes

DeGarmo’s Materials and Processes in Manufacturing

32.2 Theory of Resistance Welding

Basic Resistive Welding

FIGURE 32-1 The basic resistance welding circuit.

Resistive Welding Temperature Distribution

FIGURE 32-2 The desiredtemperature distribution acrossthe electrodes and workpiecesduring resistance welding.

Current and Pressure for Resistive Welding

FIGURE 32-3 A typical current and pressure cycle for resistance welding. This cycle includes forging and postheating operations.

Schematic of Resistive Welding

FIGURE 32-4 Thearrangement of the electrodesand workpieces in resistancespot welding.

32.3 Resistance Welding Processes

Microstructure of a Resistance Weld

FIGURE 32-5 A spot-weld nugget between two sheets of 1.3-mm (0.05-in.) aluminum alloy. The nugget is not symmetrical because the radius of the upper electrode is greater than that of the lower electrode. (Courtesy Lockheed Martin Corporation, Bethesda, MD.)

Tear Test

FIGURE 32-6 Tear test of a satisfactory spotweld, showing how failure occurs outside ofthe weld.

Resistive Welder

FIGURE 32-7 Three-phase, air-operated, press-type resistance welder with microprocessor control. (Courtesy Sciaky Inc., Chicago, IL.)

Spot Welding Seams

FIGURE 32-8 Seam weldsmade with overlapping spotsof varied spacing. (CourtesyTaylor-Winfield Corporation,Brookfield, OH.)

Schematic of Seam Welding

FIGURE 32-9 Schematicrepresentation of theseam-welding process.those

Tube Welding

FIGURE 32-10 Using high- Squeeze rollfrequency AC current to producea resistance seam weld in buttweldedtubing. Arrows from thecontacts indicate the path of thehigh-frequency current

Projection Welding

FIGURE 32-11 Principle ofprojection welding (a) prior toapplication of current andpressure and (b) after formationof the welds.

Process Summary for RW