What Happens When Metals Undergo Heat Treatment? – Part 2
The Precipitation Hardening Process
Precipitation hardening is also known as age hardening. It is a heat treatment process that creates uniformity in a metal’s grain structure, a process that makes the material stronger.
The process occurs by heating a solution treatment to high temperatures after a fast cooling process. Precipitation hardening is usually executed in an inert atmosphere at temperatures ranging from 900 to 1150°F. It can take anywhere from an hour to four hours to carry out this process. The length of time typically depends on the thickness of the metal and similar factors.
Why Are Metals Tempered?
Commonly used in steelmaking today, tempering is a heat treatment used to improve hardness and toughness in steel as well as to reduce brittleness. The tempering process creates a more ductile and stable structure. The aim of tempering is to achieve the best combination of mechanical properties in metals.
What Is Stress Relieving?
Stress relieving is a heat treatment process that decreases stress in metals after they have been quenched, casted, normalized, etc. by heating them to a temperature under the transformation range. After this process, the metal is then slow cooled.
The Benefits of Cryogenic Treatments
When a metal part is cryogenically treated, it is slowly cooled with liquid nitrogen.
The slow cooling process helps prevent thermal stress of the metal. Next, the metal part is maintained at a temperature of roughly −190 °C for about a day.
When it is later heat tempered, the metal part undergoes an increase of temperature–up to approximately +149 °C. This heat tempering helps to lower the amount of brittleness that may be caused as martensite forms during cryogenic treatment.