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Welding

Resistance Welding

Resistance, or spot, welding (RW) is a process where two or more layers or pieces of metal, stacked together, are welded together by a combination of pressure and heat. An electrical current, along with an appropriate amount of pressure, is applied to the area or spot of the desired weld. When the electricity flows through the metal, it heats up, due to the metal's resistance to the flow of electricity. When two or more metals are touching, the heat flows through from one piece to the next. The greatest amount of heat is generated at the spot where the two metals are touching. As the temperature reaches the critical point where the metals melt, a weld is created. Pressure is applied through air pressure, hydraulic pressure, or mechanical leverage. Electrodes used for spot welding are not consumable, and can be manufactured into specific shapes. Some electrodes are shaped like wheels for seam welding.

See also Metallurgy; Solder and soldering iron.


Resources

Books

Althouse, Andrew D., et al. Modern Welding. South Holland, IL: Goodheart-Willcox, 1988.

Bowditch, W., and K. Bowditch. Welding Technology Fundamentals. South Holland, IL: Goodheart-Willcox, 1992.

Jeffus, L., and H. Johnson. Welding, Principles and Applications. 2nd ed. Albany, NY: Delmar, 1988.


Christine Miner Minderovic

KEY TERMS


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Acetylene

—Colorless fuel gas. When burned with oxygen, acetylene produces one of the highest flame temperatures.

Arc

—A stream of bright light or sparks formed as a strong electric current jumps from one conductor to another. In welding, an arc is formed when an electrode connected to a power supply touches the base metal.

Base metal

—Metal to be welded or joined. It is also called workpiece or work.

Brazing

—Process of welding in which two base metals are joined with a filler metal heated to above 800°F (427°C), but below the melting point of the base metals. The piecework is grooved, the brazing rod is melted, and the molten filler metal flows into the grooves via "capillary action."

Chemical properties

—The way in which a material reacts in a given environment. Some examples are oxidation resistance and corrosion resistance.

Electrode

—Terminal point to which electricity is brought to produce the arc for welding. Some electrodes are melted and become part of the weld.

Electron beam welding

—Process in which a focused beam of electrons heats and fuses the material being welded.

Filler metal

—Metal or alloy added to the base metal to make welded, brazed, or soldered joints.

Flux

—A material to facilitate melting and the removal of unwanted contaminants.

Laser beam welding

—Welding process that uses the energy of a laser beam to fuse materials.

Mechanical properties

—The way a material reacts under loads or forces, such as hardness, brittleness, ductility, and toughness.

Physical properties

—The characteristics used to describe or identify a metal, such as color, melting temperature, or density.

Resistance

—The property of a material to oppose the passage of an electric current. In welding, metal "resists" the electrical current and heats up.

Shielding gas

—A gas that is used to guard the weld from surrounding air contamination.

Soldering

—A group of welding processes that join materials by heating a filler metal or solder to around 800°F (427°C), which is below the melting point of the base metal.

Additional topics

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