Martensitic stainless steel quenching vacuum heat treatment process

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Martensitic stainless steel is a type of stainless steel whose properties can be adjusted by vacuum heat treatment (quenching, cryogenic, tempering). Martensitic stainless steel has high strength and corrosion resistance, and can be used to manufacture machine parts such as blades of steam turbines (1Cr13), shafts and tie rods of steam equipment (2Cr13), and parts that work in corrosive media such as valves, Bolts, etc. (4Cr13). Steel grades with higher carbon content (4Cr13, 9Cr18) are suitable for the manufacture of medical equipment, table knives, measuring instruments, springs, etc.

The product in the picture is martensitic stainless steel, and the material is 4Cr13. This quenching is the vacuum heat treatment furnace used. The maximum production temperature of the vacuum heat treatment gas quenching furnace can reach 1300 ℃. The degree of vacuum is generally  10^-3 or  10 ^-4 power, depending on the product, the required heating rate. The holding temperature, holding time and cooling speed are different. No oxidation will occur on the surface of the product under vacuum. Therefore, the appearance of the product will not change after the product is released. There is no oxide layer or scale on the surface.

The quenched product enters the next production link, cryogenic treatment. For cryogenic treatment technology, the treatment process is the key to determining the treatment effect. The key influencing factors in the cryogenic treatment process mainly include: cryogenic treatment method, heating and cooling speed, pre-tempering or post-tempering treatment, holding time, cryogenic times, etc.

Changes in tissue after cryogenic treatment can lead to improved properties:

The reduction of retained austenite can improve the dimensional stability of the workpiece; the hardness can be improved due to the increase of martensite; the wear resistance can be improved due to the increase of martensite and the precipitation of fine carbides. However, due to the reduction of retained austenite after cryogenic treatment, the impact absorption work of the workpiece will decrease to a certain extent.

After cryogenic cooling, the product is tempered, and the tempering adopts a vacuum tempering furnace. Different from the quenching furnace, the tempering furnace is heated by positive pressure, which is to make the temperature in the furnace more uniform.

The finished product needs to be tested for its hardness, toughness and metallography. The hardness of 4Cr13 should be between 500-620 of HV Vickers hardness, and the converted Rockwell hardness of HRC should be between 5-60. If the hardness exceeds this range, it is easy to cause the product to be too brittle, easy to break, and not durable. There is a greater risk. For cast martensite, its selection and acceptance are mainly based on mechanical properties, and no special requirements are generally made for its corrosion resistance.

Equipment selection: The RVGQ series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment of tooling and molds. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum heat treatment process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum tempering furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.