Annealing: Steel and Quench Media

Annealing is a process where a metal is heated at certain temperature, then it is slowly cooled. First, the steel is heated at a temperature of about 16000F (8710C) for a certain amount of time (“Annealing of Tool Steel”). During annealing, ferrite, which is pure iron, turns into austenite, another type of iron (“Full Annealing”). The heating time is dependent upon the size of the specimen to be annealed, which is about two hours per inch thickness of the specimen (“Annealing of Tool Steel”). After the metal is heated for the desired amount of time, it is slowly cooled at a rate of 50-1000F per hour (“Annealing of Tool Steel”). Usually, this process is done by turning off the furnace, where the metal was heated, and keeping the door shut (“Annealing of Tool Steel”). Once the material has reached room temperature, it is soft, malleable, and easier to use with a machine (“Annealing of Tool Steel”).
The process of annealing softens metals, reduces stress between the bonds, and improves corrosion resistance (“Annealing”). These changes make the material easier to machine and less brittle (“Annealing”). Welding and magnetic properties also improve as a result of annealing (“Annealing”). Annealing makes metals more ductile and malleable than it was in its original condition (“Annealing of Tool Steel”).
After testing the hardness of the annealed specimen with a 3,000 kg load, a 5.7 mm diameter indent was left on the surface, while the control had a 5.2 mm diameter indent. The hardness on the Brinell scale was HB 107 for the annealed specimen while the control had a hardness of HB 131. These results showed that the slow cooling of the steel softened the material.
“Annealing”. Mamesta. N.p. N.d. Web. 15 Dec 2013.
“Annealing of Tool Steel”. Simply Tool Steel. N.p. N.d. Web. 15 Dec 2013.
“Full Annealing”. eFunda. eFunda. N.d. Web 15 Dec 2013.

Quenching is a heat treatment process where a metal is heated at about 16000F (8710C) and quickly plunged into water