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Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

Gear shaft vacuum heat treatment

The traditional gear shaft heat treatment process relies on atmosphere carburizing, oil quenching, tempering and other processes to obtain parts that meet the design requirements.

The heat treatment equipment takes a long time to start and stop the furnace. When the equipment fails during full-load production, a large number of parts are scrapped and a large amount of carbon dioxide gas emissions are generated. The parts of this heat treatment method often need to be cleaned and shot blasted to remove the residual grease and oxide skin after heat treatment. The working environment of employees is poor, which is inconvenient to use and greatly increases the cost and cycle of parts production. This paper mainly introduces the application advantages of the world’s most advanced vacuum heat treatment production lines in the heat treatment of gear shafts of dual clutch gearboxes.

1.Introduction to vacuum

Vacuum refers to a gas state below one atmospheric pressure in a given space, that is, a standard atmospheric pressure: 1.013x 105Pa.

Compared with the atmospheric state, the vacuum state has the main characteristics: the number of molecules per unit volume is less; between the gas molecules inside the gas

Fewer collisions; fewer gas molecules hitting the walls of the container.

The degree of thinness of the gas in the vacuum state is called the degree of vacuum, which is usually expressed by the pressure value, the type of vacuum and the conversion of pressure units

See Table 1.

2.Introduction to the process

Under the low pressure vacuum, the pulse carburizing method is adopted to realize the carburizing process and satisfy the depth of the product carburized layer through multiple strong infiltration (passing through the carburizing medium acetylene) + diffusion (passing in the protective gas nitrogen) and a centralized diffusion process and metallographic requirements. Components

After the carburization is completed, it enters the quenching chamber through the moving chamber, and a large amount of helium gas is instantly introduced to make the gas flow at a high speed to achieve the purpose of cooling and quenching. The specific process is shown in Figure 2. The pulse carburizing process parameters are based on the sum of the surface area of the parts, the material of the parts,

The layer depth requirements are simulated by the simulation software, and the parameters include carburizing temperature, number of carburizing pulses, pulse time and pulse process gas flow.

3.Advantages of vacuum heat treatment over traditional heat treatment

According to the comparison and conclusion after using the vacuum heat treatment production line and the double gauge continuous atmosphere heat treatment production line, the vacuum heat treatment production is the best.

The situation is as follows:

(1) After the continuous furnace heat treatment parts are released, there are oxide scales and grease residues; while the carburization of the vacuum production line is carried out in a vacuum environment, and gas quenching is used. There is no oxidation and no quenching oil in the whole process, so the surface of the parts after being released from the furnace is smooth and free of oxidation.

(2) The metallographic structure has no intergranular oxidation, and the surface fatigue resistance of the parts is good. The non-martensitic structure produced by the continuous furnace is often between 0.02 and 0.025mm, and the vacuum heat treatment parts have almost no non-martensitic structure and internal oxidation, as shown in the figure below.

(3) The thermal deformation of vacuum furnace parts is smaller than that of continuous furnace parts. The vacuum furnace adopts gas quenching, and there is only a convection cooling process in the whole process.

The heat transfer coefficient remains unchanged, while the oil quenching cooling process has three stages: film boiling, bubble boiling and convection, and the heat transfer coefficient is different in each stage.

(4) The same part process is produced, with short time and high energy efficiency. Compared with the production efficiency of continuous furnace and vacuum furnace, according to the different effective hardening layer required by the parts, the time for producing parts in vacuum furnace is 40%~60% less than that of traditional continuous furnace, and the furnace load is 50%~50% more than that of traditional continuous furnace. 60%, and the maximum carburizing temperature of the vacuum furnace can reach 1050C, which greatly improves the carburizing efficiency, and the process is flexible and adjustable. If the vacuum furnace wants to achieve different carburizing layers, it is only necessary to adjust the gas flow and time in a single process. , there is no need to wait for the continuous furnace to wait for an empty furnace, switch programs, and stabilize the carbon potential.

(5) Good working environment and less production pollution. The traditional continuous furnace needs to burn the exhaust gas in the furnace with an open flame, which emits carbon dioxide, and requires a large amount of cleaning agent to clean the parts after heat treatment, and the overall operating environment is poor. There will be no related problems in the vacuum furnace. The whole process is oil-free and oxidation-free, and the parts do not need to be cleaned. The vacuum furnace of our company uses acetylene as the carburizing medium, and there is no carbon dioxide emission. The decomposition formula of acetylene is as follows: C2H2→[C]+H2

4.Application examples of vacuum heat treatment

The production process of the heat treatment workshop of the input shaft of the 6DCT250 dual clutch transmission is: heat treatment → cleaning shot blasting → strong shot blasting → straightening → inner hole cleaning.

Due to the limitation of the part structure and the traditional heat treatment process, a large amount of steel shot will remain in the center hole after the part is cleaned and shot blasted.

Seriously affect the assembly quality of the part. After the introduction of vacuum heat treatment equipment, it is planned to transfer the part to vacuum furnace heat treatment, the surface of vacuum heat treatment parts is light heat treated, the surface of vacuum heat treatment parts is smooth, no need to clean the shot blasting process, there will be no steel shot residue in the center hole of the part, and no manual 100% cleaning is required. Bore. After conversion, the process flow of this part is as follows: heat treatment → strong

Shot blasting → straightening. After the conversion, the production efficiency of the part has been greatly improved, and the production cost has been reduced.

Recommended vacuum heat treatment equipment: The 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 air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.