What is Tempering

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Tempering

Tempering is used to increase the toughness of iron metal, particularly steel. Untampered steel is very hard but is too brittle for most application. Tempering is commonly used after hardening to reduce extra hardness.

Tempering is used to alter:

• Hardness
• Ductility
• Toughness
• Strength
• Structural stability

Tempering involves heating the metal to a temperature below the critical point, and is often done in air, vacuum or inner atmospheres.

The temperature is adjusted depending on the Qty of hardness that needs to be reduced. While it’s varies depending on the metal type, generally, low temperatures will reduce brittleness while maintaining most of the hardness, while higher temperatures reduce hardness which increases elasticity and plasticity, but causes some yield and tensile strength to be lost.

It is essential to heat the metal gradually to avoid the steel being cracked. The metal is then held at this temperature for a fixed Time period. A rough guideline is one hour per inch of thickness. During this time the internal stresses in the metal are relieved. The metal is then cooled in still air.