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Through Hardening

Our Through Hardening is one of the most widely applied heat-treating processes. Through Hardening refers to a group of processes in which parts are heated in a furnace and then cooled in an accelerated manner–quenched in other words–to increase the hardness and strength of the part. After hardening, parts are then tempered to improve the toughness to the desired strength/toughness balance as dictated by the customer.


Common Alloys

  • Carbon Steels, e.g., 1045, 1144
  • Alloy Steels, e.g., 4140, 4340, 8630
  • Tool Steels, e.g.,  A2, D2, M4, H13
  • Martensitic Stainless Steels, e.g., 420, 440

TMT Equipment/Variations

Parts can be hardened in air, endothermic, or vacuum furnaces.

  • Parts run through air furnaces will exhibit some scaling due to the high temperature exposure to oxygen. They can be quenched in polymer or water.
  • Parts run through endothermic furnaces can be quenched in oil, polymer, or water quenches.
  • Parts run through in vacuum furnaces are cooled in the furnace with a gas or fan quench.

Applications of Through Hardening

  • ​Through Hardening, also called ‘Quench and Temper’, is one of the most widely applied heat-treating processes. The fundamental part of Through Hardening is the heating of a part above its critical temperature so that a phase change occurs to Austenite. The part must then be rapidly cooled to form a Martensite microstructure. Untempered Martensite is extremely brittle, so a subsequent tempering operation is needed.
  • In general, steels with a higher carbon content will be able to achieve higher maximum hardness. Increasing the alloy content is required to improve the hardenability of a material. A material with higher hardenability will be able to achieve higher hardness as the part size increases and will be more consistent, surface to core.
  • After hardening, parts are tempered to increase the toughness. In general, as the tempering temperature is increased the hardness and strength will drop while the toughness will increase.
  • Tool steels are a special group of steels that generally feature very high alloy contents.  They are frequently used in applications requiring extreme wear, hot work, or impact resistance. Some will contain carbide-forming alloys that create extremely hard spots within the material requiring special heat-treating techniques to realize their full potential.

Associated Specs/Standards

  • AMS 2759/1, 2759/2​, 2759/5, 2759, 6875
  • ASTM A350, A668
  • MIL 1684, 2710, 24093
  • NACE MR0103, MR0175
  • W-HTX

What To Consider When Specifying

  • Material
  • Furnace Atmosphere
  • Hardness (if required)
  • Mechanical Testing (if required)
  • Specification (if required)

Still have questions?

For more information, or if you’re ready to get started, feel free to contact us today!