The normalizing process is a metal heat treatment process in which the steel is heated to 30-50℃ above the critical temperature (the temperature of complete austenitizing), and then taken out from the furnace to be cooled in air or by a water spray, spray, or air blow after holding the steel for an appropriate time.
(1) To make grain refinement and carbide distribution uniform;
(2) Remove the internal stress of the material;
(3) Increase the hardness of the material.
Material: Subeutectic tinplate
Tissue: graphite brown, martensite light yellow, pearlite green and dark yellow, cementite brown
Materials: A – 299
Tissue: brown ferrite yellow, blue, white pearlite brown
Material: 13 minions
Tissue: light brown pearlite taupe, ferrite red, yellow, blue
Material: 45 steel
Structure: light blue ferrite and pearlite in various colors
Advantages of the normalizing process :
(1) the normalizing cooling rate is slightly faster than the annealing cooling rate, so the pearlite lamellar space obtained is smaller, the normalizing structure is finer than the annealed structure, so its hardness and strength are higher;
(2) External cooling of a normalizing furnace does not occupy equipment and has high productivity.
Application of normalizing process: suitable only for carbon steel and low and medium alloy steel, not for high alloy steel. Because the austenite of high alloy steel is very stable, air cooling will also result in martensite tissue.