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Heat treatment process of HPM75 non-magnetic steel
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Heat treatment process of HPM75 nonmagnetic steel;
The heat treatment process mainly includes: high temperature annealing process, solution softening process and aging hardening process; They are as follows:
1. High temperature annealing process
The die material has high hardness and poor machinability. The purpose of annealing die at high temperature is to improve machinability, eliminate forging stress, facilitate die manufacturing and shorten machining cycle. Annealing process flow: annealing temperature is 870-890℃, heat preservation is 3-6h, the cooling rate from annealing temperature to 500℃ should be controlled, the cooling time should not be less than 6h, and the hardness is 28-30HRC.
2. Solution softening treatment process
The solid solution process is to make the carbide of the material dissolve into the matrix, prepare the structure for the aging hardening treatment, and also improve the cutting performance, which is also called softening treatment in production; Equipment used: box type electric furnace (for preheating), high temperature salt bath furnace (for solid solution) or box type high temperature electric furnace; Technological process of solution softening treatment: when the balance is greater than 1.5-2mm, adopt high temperature box furnace for solution heating at 1150-1180℃, keep the temperature in salt bath furnace for 15-20min/mm, keep the temperature in box furnace for 30min/mm, and water-cool, the solution hardness of HPM75 is 20-22HRC, and the metallographic structure of the material is austenite+undissolved primary carbide.
3. Age hardening treatment process
The purpose of aging hardening treatment after mold manufacturing and processing is to disperse and precipitate carbides dissolved in the matrix, so as to strengthen the matrix and improve hardness and wear resistance, which is also called hardening treatment in production; Adopt a box-type electric furnace, aging at 650-700℃ for 15-20h, water cooling or air cooling, and the hardness can reach 42-45HRC.
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