Lifting rod vacuum heat treatment

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Vacuum heat treatment is a heat treatment technique in which the workpiece is heated under vacuum conditions. The so-called vacuum refers to a state in which the density of gas molecules in a given space is much lower than that of gas molecules under one atmospheric pressure.

When heated in vacuum, due to the low partial pressure of oxygen and other gases, the oxidation effect of oxygen on the workpiece is inhibited, and the residual gas elements inside the workpiece material (inhaled during hot processing such as smelting and welding) are also easier. Escape to the outside world, the grease and oxides on the surface of the workpiece are also easy to volatilize or decompose. Therefore, the vacuum can protect, degas, degrease and clean the surface of the workpiece. At the same time, the vacuum heating of the workpiece has the characteristics of slow heating and automatic mechanical movement in the production process, so the vacuum heat treatment also has the advantages of less quenching deformation and improved heat treatment working conditions.

The material of the key part of a key model product produced by our factory is 30CrMnSiA. The technical requirements are that the hardness of quenching and tempering is HRC28~32, and the hardness of surface quenching is HRC50~55. The production process of this part is: roughing → quenching and tempering Treatment→finishing→surface quenching→finishing and forming. Since this process requires two heat treatment processes, and due to the small size and complex shape of the parts, it is not easy to facilitate the operation during surface quenching, and it is not easy to ensure the quenching quality, and the deformation is large. For this reason, the production process of this part has been improved from the point of view of heat treatment.

Vacuum heat treatment process

The unique heating characteristics of vacuum quenching are beneficial to the improvement of the comprehensive performance of the parts. At the same time, from the inspection process of the finished product, it is also beneficial to improve the surface finish of the parts.

Vacuum heat treatment not only has the advantages of no oxidation, no decarburization, and no residual salt corrosion, but also an effective way to solve the problems of finishing deformation and anti-cracking of some parts.

By improving the heat treatment process of the lifting rod, we replaced the traditional process of quenching and tempering + surface quenching with vacuum heat treatment, and realized the process progress of replacing aerobic operation with anaerobic operation, which provided an effective reference idea for improving the heat treatment quality of parts. Since the vacuum heat treatment is applied to the lifting rod, the mechanical properties of the parts and the requirements for various performance indicators have always been stable. Thereby, the technical problems of dimensional deformation of the lifting rod during heat treatment and difficult control of quenching cracking are completely solved. At present, this process improvement method has been maturely applied to the heat treatment production of various key components such as poppet valve cores, multi-stage valve cores, valve stems and valve sleeves.

Since vacuum quenching can obtain better mechanical properties than furnace heating, the risk of deformation of parts is reduced, and vacuum heating can ensure the surface finish of product parts. Therefore, it is decided that after the parts are formed, vacuum heat treatment is performed at HRC40~45, and then the parts can be finely ground.

Process drawing of vacuum heat treatment

1) After entering the furnace, slowly heat up to 550°C for 20 minutes;

2) Incubate at 550°C for 40 minutes;

3) Warm up from 550°C to 860°C for 20 minutes;

4) Incubate at 860°C for 30 minutes and oil-cool;

5) The tempering temperature is 400°C, and high-purity nitrogen is introduced for strong cooling.

1) The measured hardness after vacuum quenching and tempering is HRC42~43, and the surface smoothness is good. Only simple manual grinding is carried out to load the finished product;

2) The parts after the improved process did not have any quality problems in the assembly test;

3) During the various tests of subsequent products, the parts have guaranteed various performance index requirements;

4) After the improvement of the heat treatment process, the production progress of this part is greatly advanced, and the product quality requirements are guaranteed at the same time.

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.