A subtractive manufacturing technique, CNC machining exposes the shape of an object by removing material from a solid block using cutting tools. Metals must be machinable for the machining process to be efficient and successful. After machining metal items, it is also possible to improve the material quality. Heat treatments can help with that.
Let us understand the heating procedure.
Stay ahead of the industry with exclusive feature stories on the top companies, expert insights and the latest news delivered straight to your inbox. Subscribe today.
The heating procedure
Heat treatment involves heating metal until its microstructure is altered, soaking it, then cooling it to harden it. With a longer soak time, the metal's microstructure will change more significantly, affecting its mechanical properties.
Size, metal type, and heat treatment method all influence the soaking time.
The cooling rate and the environment can also change the metal's structure. Oil, water, forced air, and furnaces are other methods of cooling metals.
Heat treatments can give items their initial, intermediate, or final qualities. It is possible to start CNC machining after heat-treating the component. The process can reduce lead times and make it easy to work with the metals. Heat treatment can increase the toughness and durability of metal after machining.
Following are the frequently used CNC heat treatments;
Annealing
During annealing, metal is heated and immersed, then cooled. This reduces the metal's hardness and enhances its ductility. This reduces internal tensions, reducing machining damage risks. Various annealing procedures can be used, including full annealing, recrystallization annealing, partial annealing, and final annealing.
Hardening of cases
Case hardening hardens a part's appearance without changing its interior. Case hardening produces less brittle, more workable pieces than other methods of increasing metal hardness. A carburization process increases a metal's surface strength and carbon content by heating it in a carbon-rich atmosphere.
Hardening of precipitation
Aerospace sector components are heat-treated using precipitation hardening or aging because they produce robust and lightweight metals. It is possible to distribute precipitates uniformly throughout a malleable metal by heating it to a high temperature, quenching it, and then heating it to a low temperature.
Stress reduction
In CNC machining, shaping, rolling, and straightening, stress can accumulate inside parts, weakening them. The relative stresses will be reduced, improving the mechanical characteristics of the part without changing its structure. This technique heats metal below its lower critical boundary. Gradual cooling produces uniform pieces with consistent mechanical properties.
Tempering and quenching
This two-part heat treatment improves iron-based alloys' hardness, ductility, and resilience. Quenching causes the metal's crystalline structure to change from ferrite to austenite, allowing it to absorb more carbon. The metal will then be quickly cooled.
Advantages of heating metal
Metals are often heat treated in the automotive and aerospace industries to increase their strength. Strengthening a material may also reduce its toughness and increase its brittleness. The metal may need to be annealed or tempered to release internal stresses. After stress-relieving treatments, heat-treated metals will be easier to work with and machine.
Heat can also change the microstructure or chemical composition of metal alloys, which affects corrosion resistance, magnetism, durability, heat conductivity, and electrical conductivity.
More in News