Heat Treatment – An Overview

Heat treatment is the process of changing the properties of metal parts by subjecting them to precisely controlled temperatures. Hardness and toughness are the two main properties affected by heat treatment. A metal can be made harder so that it resists wear, but it will also become more brittle (easily cracked); or it can also be made tougher (less easily cracked), but it will also become softer and less durable. Metals can be treated before and during processing, to make them easier to work, and after processing, to make them more durable.

Annealing is a heat treatment process in which metal is held at a high temperature for some time and then allowed to cool slowly. Depending on the times and temperatures used, annealing can make the metal more workable or relieve the internal stresses created by manufacturing processes. Tempering is a process in which a metal is heated and then rapidly cooled in a liquid. Tempering makes the metal tougher but also reduces its hardness.

Case hardening is the process of making the surface of a part harder without reducing the toughness of the inside of the part. This achieves the best of both worlds since the hard surface makes the part last a long time without wear, and the tough core keeps it from cracking. The hardening can be accomplished in many ways. In induction hardening, the part is placed inside a coil of wire. Electricity running back and forth through the wire creates a strong magnetic field around the part, and this causes electrical currents to move across the surface of the part. These electrical currents, in turn, cause the outside of the part to heat up. When the part is removed, it cools rapidly and now has a much harder surface layer. Nitriding is a method of case hardening steel that uses chemistry instead of high heat. The part is heated and kept in an environment of nitrogen and hydrogen for up to 40 hours. The nitrogen penetrates into the surface of the steel and forms a nitride alloy, which is much harder than the steel alone.

Heat Treatment Processes Supported

• Annealing
• Hardening
• Case Hardening
• Induction Hardening
• Through Hardening
• Nitriding
• Stress Relieving
• Tempering
• Vacuum Treatment