Heat treatment process of HPM75 non magnetic steel
Introduction: HPM75 non-magnetic steel has many die characteristics, such as high hardness, wear resistance, corrosion resistance and non-magnetic properties, which are comparable with stainless steel SUS304. Therefore, it is most suitable for corrosion resistance and wear resistance of mold products.
1, HPM75 without magnetic steel
HPM75 is a non-magnetic, high hardness, easy cutting plastic die steel produced by a special smelting process. It is a non-magnetic, high strength, austenitic, non-magnetic die steel in the HPM series. It remains stable austenite under all conditions and has very low permeability. HPM75 non-magnetic steel has high hardness, wear resistance, corrosion resistance, non-magnetic and other die characteristics comparable to stainless steel SUS304; Therefore, it is most suitable for mold products with high corrosion resistance and wear resistance. Gas - nitrogen carburizing heat treatment can further improve the surface hardness and wear resistance, so as to prolong the service life of the die.
2. Heat treatment process of HPM75 non-magnetic 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
High hardness of mould material and poor machining performance; The purpose of high temperature annealing is to improve machining performance, eliminate forging stress, facilitate mold manufacturing and shorten machining cycle. Annealing process: annealing temperature 870-890℃, heat preservation 3-6h, control the cooling rate from annealing temperature to 500℃, cooling time is not less than 6 hours, hardness: 28-30HRC.
(2) Solution softening process
Solid solution process is to dissolve material carbide into the matrix to prepare for the aging hardening treatment, but also improve the cutting performance. Also known as softening treatment in production; Equipment: box electric furnace (preheating), high temperature salt bath furnace (solution) or box high temperature electric furnace; Solution softening process: when the allowance is greater than 1.5-2mm, high-temperature box-type furnace is used for solution heating, heating temperature is 1150-1180℃, salt bath furnace insulation is 15-*20min/mm, box-type furnace insulation is 30min/mm, water cooling, HPM75 solution hardness is 20-22HRC, material microstructure: Austenite + undissolved primary carbides.
(3) Aging hardening process
The aging hardening treatment after the mold manufacturing process is to make the carbides dissolved in the matrix dispersed and deposited on the matrix, so as to strengthen the matrix, improve the hardness and wear resistance, also known as hardening treatment in production; Adopt box-type electric furnace, aging temperature 650-700℃, aging 15-20h, water-cooled or air-cooled, hardness up to 45-50HRC.