Engineers need to alter the way that metals perform and react during precision machining. One of the most widely used methods of altering metals is heat treatment. There are many options to consider, including age hardening before or after a part has been machined. Heat treating is used to alter and enhance final part characteristics, including hardness, strength, machinability, ductility, and toughness. Heat treating is often used to alter future work on metal. There are five types of heat treatments. Knowing what each is and how they affect precision machining allows engineers to design and create the best possible products.
This is a heat treatment method where metal is heated to a specific temperature and then held at that temperature until transformation occurs. Finally, the part is cooled. The process is ideal for those that need metal to be ductile with a decreased hardness (making the metal workable). When materials are annealed before machining, it improves the material’s overall stability, which means it is much less likely to fracture or crack.
This is an annealing process meant for steel that is being heated over 150°F of normal annealing temperatures. When steel is heated in this way, it must then be air-cooled. The main goal of this heat treatment is to create small austenitic grains in final parts. This improves ductility, machinability, and the strength of steel.
During this process, metal is heated to a high enough temperature where the metal elements become a solution. Heat treating addresses defects in the crystal lattice structure of a metal. Once the metal is heated to the right temperature, it produces a solid solution. After that, the metal is quenched to trap the particles within the solution.
This process only hardens the external layer of metal; the interior metal remains soft. Additional carbon is infused in metals the boast a low carbon content (steel and iron). This process is often the final step of production (after being machined). A combination of chemicals, elements, and high heat produces a hardened outer layer.