Hardening & Tempering
Hardening and tempering is a heating and cooling treatment which we use to change the properties and structure of a metal. It serves to strengthen the metal, which increases its machining capabilities. As its name implies, hardening is done to increase the hardness of a metal or alloy. Tempering is the process of heating a material to a temperature below its critical range, holding it, and then cooling it in order to reduce the brittleness of a quenched metal or alloy. Hardening and tempering techniques we employ include:
Salt bath hardening can offer distinct advantages over other forms of hardening and tempering, because molten salt can be an ideal heat treatment medium. Heat is transferred to the surface when parts are immersed in the molten salt, and air cannot come into contact with the material surface.
Induction hardening increases the surface strength of steel and other alloy components. The part is first induction-heated inside a water-cooled copper coil. Alternating current is then applied to the coil to heat the metal above its transformation temperature. It is then quenched, which increases the part’s hardness and brittleness.
This is the process of heating alloys in a special vacuum chamber at pressures down to .0001 - .2 Torr. Oxygen is removed and replaced with another gas, the chamber is heated to a specified temperature, and cooling is then performed with inert gas. The tightly-controlled environment produces high-quality parts that have no scaling or discoloration, and require no further cleaning processes.
Age, or precipitation, hardening imparts strength to metals and their alloys. It makes use of precipitates, or solid impurities, for this strengthening process. The metal can be aged by either heating it, or storing it at lower temperatures until the necessary precipitates are formed.