The hardening of steels and irons involve heating of materials to a temperature greater than its austentizing temperature which changes the structure of the material to austenite. Once the material is completely transformed into austetite, it undergoes a quenching in transforming process to its material structure, changing it into martensite which enhances its strength and hardness. After the quenching process is complete, a process of reheating to a lower subcritical temperature tempers the metal down to the desired final strength and hardness, increasing its toughness and ductility. This comprises the hardening and tempering steel process.
Neutral Hardening
The process of neutral hardening is implemented in a neutral atmosphere in which no net loss or gain of nitrogen, carbon, or other element to the surface of the material takes place. It is typically used for nearly finished or completely finished parts where decarburization of the surface of the parts is not permitted.
Open Fire Hardening
Within an air atmosphere furnace, open fire hardening is performed during which carbon exits the surface of the material when it reacts with the air, resulting in surface decarburization. This process is often performed on rough parts are raw materials in which all the surfaces are to be machined or ground subsequent to hardening, which then removes the decarburized layer of the surface.
The process of hardening and tempering steel is often called harden and temper, quench and temper, or through hardening.
Application for Hardened Stainless Steel
Applications in which wear protection and corrosion resistance are demanded often make use of hardened stainless steel. Surfaces may be produced that are up to five times harder and extend the operating limits of the previously soft steel.
Industry applications for hardening and tempering include a household and consumer goods sector, medical technology, construction, mechanical engineering, and automotive industries.
Various types of equipment and different methods can be chosen for the neutral hardening process. The atmospheres used, processing parameters selected, and type of furnace chosen may be based on the particular iron or steel grade that requires hardening and the volume of the parts involved – whether a large production order, small lot, or individual piece.
Contact an experienced heat treatment supplier today to find out more about your hardening and tempering steel options and benefits.