Introduction to "normalizing" process of heat treatment
Normalizing is a metal heat treatment process in which steel parts are heated to 30-50 ℃ above the critical temperature (fully austenitized temperature), and then taken out of the furnace for cooling in air or water spray, spray or air blast after holding for an appropriate time.
(1) to refine the grain and homogenize the distribution of carbides;
(2) Remove the internal stress of the material;
(3) Increase the hardness of the material.
(1) The cooling rate of normalizing is slightly faster than that of annealing, so the pearlite lamellar spacing is smaller, and the normalizing structure is finer than that of annealing, so its hardness and strength are also higher;
(2) The cooling outside the normalizing furnace does not occupy equipment and has high productivity.
Application: it is only applicable to carbon steel and low and medium alloy steel, not high alloy steel. Because the austenite of high alloy steel is very stable, martensite structure will also be obtained by cooling in air.
(1) For low carbon steel and low alloy steel, normalizing can improve its hardness and machinability;
(2) For medium carbon steel, normalizing can replace quenching and tempering treatment to prepare the structure for high-frequency quenching, reduce the deformation of steel parts and reduce the processing cost;
(3) For high carbon steel, normalizing can eliminate the network cementite structure and facilitate spheroidizing annealing;
(4) For large steel forgings or steel castings with sharp changes in section, normalizing can be used instead of quenching to reduce the tendency of deformation and cracking, or make organizational preparations for quenching;
(5) For the quenched and repaired parts of steel, the influence of overheating can be eliminated by normalizing, so that they can be quenched again;
(6) It is used in iron castings to increase the pearlescent volume of the matrix and improve the strength and wear resistance of castings.