Vacuum Air Quenching and High Temperature Tempering of 4Cr5MoSiV1 Parts

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4Cr5MoSiV1 is a domestic hot work tool steel listed in GB/T 1299-2000. Labels H13, W320, 1.2344, GS244, SKD61, DHA1, KDA1S, 8407, DAC, etc. all have basically similar chemical composition to this steel grade. According to the importance and life requirements of the parts, the mold manufacturer selects rolling materials or forgings of different quality grades and different price levels from ordinary electric furnaces, out-of-furnace refining, electroslag remelting, and vacuum electroslag. In addition to the above-mentioned mechanical properties, since 4Cr5MoSiV1 also has relatively low coefficient of thermal expansion, high thermal conductivity, good forgeability, repair welding, hardenability, hardenability and machining and other technological properties, it is gradually It replaces the traditional manufacturing of small and medium-sized aluminum alloy die-casting mold parts.

During the heat treatment and heating of the parts, the decarburization, carburization, and depletion of alloying elements on the surface will lead to early cracks in the use of the parts. They require vacuum heat treatment, which is especially important for parts that have been finish formed and then heat treated. The harmful gas and some non-metallic inclusions remaining in the steel are first diffused from the inside to the outside under the vacuum heating condition, and then separated from the workpiece and pulled out of the furnace with the system to complete the solid phase transformation and further vacuum purification of the workpiece material.

Process flow:

Preheat:

The main purpose of the first preheating is to eliminate the machining stress generated in the machining of the parts before quenching, and to prevent and reduce the quenching deformation caused by the heating process. The preheating temperature is high, and the stress relief effect is obvious. The preheating temperature is selected as 580°C; the heating speed V1=8°C/min; the holding time h1 is twice the final heating holding time h of quenching, that is, h1=h2; the vacuum degree is set to 2.66644Pa. The second preheating adopts 850℃, the heating rate is V2=12℃/min(1, the vacuum degree is set to 26.6644Pa, and the holding time is h2=1/3h.

Gas quenching: After heat preservation, move it to the cooling chamber, and select 0.2~0.55MPa high-purity nitrogen for high-pressure gas quenching according to the size of the workpiece and the amount of furnace installed. The cooling rate is not only related to the nitrogen pressure but also related to the heat exchange capacity of the cooling chamber. Due to the large power of the cooling fan in the quenching furnace and the water flow of the heat exchanger, it can ensure that the larger size parts have a sufficiently high post-quenching hardness and hardening depth. During the cooling process, no isothermal stay was performed, and the furnace was continuously cooled to 80°C.

Tempering: 4Cr5MoSiV1 adopts three high temperature tempering, and the three tempering temperatures are 580 ℃, 590 ℃, 580 ℃ respectively. The heating rate was 8°C/min for each heating. According to the specific requirements of the parts of each heat, the cooling speed is selected to be 0.05~0.12MPa for fast cooling, or 300 ℃ to continue fan cooling, or cool to room temperature.

Equipment selection: SIMUWU is a domestic enterprise that designs and produces vacuum tempering furnaces, vacuum air quenching furnaces, vacuum oil quenching furnaces, vacuum sintering furnaces, vacuum brazing furnaces and other products. The equipments produced by SIMUWU are exported to many overseas countries and are well received.

This processing is carried out using the RVGQ vacuum air quenching furnace produced by SIMUWU. The surface gloss and strength of the parts meet the requirements, the production process is stable and reliable, and the degree of automation is high.