Slim shaft vacuum hardening

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The slender shaft used in a product of our factory is heated and quenched in a converter, which has different degrees of heating and quenching deformation, and the straightening workload is large. We study the application of vacuum furnace quenching equipment instead of converter for heating and quenching the workpiece, so that the workpiece heat treatment hardness is more uniform, the surface is smooth and free of oxidation, the problem of large heat treatment deformation is solved, and the working environment is improved.

The shape of the slender shaft is slender rod-shaped. The heat treatment is carried out after forming. The surface does not allow oxidation and decarburization. The converter propane atmosphere is used for protection and heating. Although the quenching heating and oxidation decarburization are prevented, the heat treatment deformation of the thin rod of the workpiece is different. Existing, the straightening workload after heat is large, and the straightening rejection rate of large deformation after heat is as high as 1.5%.

The double-chamber high-vacuum furnace is used to replace the converter, which realizes the high-vacuum heating and quenching of the workpiece, and the internal and external quality is significantly improved, which can effectively solve the problem of heat treatment deformation and scrapping.

Overview of Vacuum Furnace

The double-chamber high vacuum furnace fully meets the requirements of non-oxidative decarburization heating and quenching of the workpiece under the vacuum degree of <10Pa. In addition, the process parameters of the new equipment are set to automatic program control, which can eliminate the influence of human uncertain factors. The temperature control system adopts PID adjustment and automatic control. The uniformity of the furnace temperature is guaranteed to be ±3°C. The workpiece is uniformly heated at the quenching temperature by program control, the heat treatment hardness is small, and the surface is smooth and free of oxidation.

For the slender shaft, the material box tooling is used for heating and quenching, which effectively ensures that the workpiece has no surface cooling, uneven quenching hardness, and small heat treatment deformation.

Process flow:

(1) Equipment selection: high vacuum double-chamber quenching furnace.

(2) Design and process vacuum heating tooling, and change the converter bulk heating and quenching to vacuum charging box-mounted flat heating and quenching on the heating aids. Among them, there is 1 set of supports and 20 stainless steel trays. The structure is shown in the figure.

(3) The quenching cooling medium KR328 vacuum quenching oil, the operating temperature is 20 ~ 70 ℃.

(4) Furnace loading method: 240-260 pieces/box, 10-20 boxes in total, 1000-3000 pieces/box.

(5) The workpiece is laid flat in layers, and the head of the workpiece and the thin rod are placed horizontally in the material box to ensure that there is no warped part.

(6) In view of the slow heat transfer of vacuum heating, in order to ensure that the workpiece is heated evenly and has a good structure, the process parameters are adjusted, and the quenching heating time is changed from 15min of the converter to 60-80min, and the holding time is changed from the original 30min to 60min. After the vacuum oil temperature rises to 20°C, select the automatic button to automatically reclaim and quench the oil.

(7) The tempering equipment is RJ-35-6 strong convection well-type tempering furnace, with a furnace capacity of 1000 to 3000 pieces, a tempering temperature of 200 °C ± 10 °C, and a holding time of 1.5 to 2 hours. The new process parameters of slender shaft vacuum heat treatment are shown in the figure:

Production effect

After the batch production verification, the tooling capacity is 240 to 260 boxes, 2453 pieces per furnace. Quenching process 850 ~ 870 ℃ × 60min tempering process 190 ~ 210 ℃ × 90 ~ 120min. The test hardness is 46-50HRC, the surface is bright, and there is no warpage. The metallographic examination is tempered troostite. Meet product design requirements. After heat treatment, the surface is smooth without oxidation, and there is no obvious deformation after heat treatment, and the pass rate is 100%, which fundamentally solves the problem of scrapping due to deformation.

Since the mass production, not only the internal and external quality of heat treatment has been significantly improved, but also the working environment has been greatly improved and the labor intensity of workers has been reduced.

Equipment selection: The VOGQ series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment process 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 air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.