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Vacuum Quenching Technology of Aluminum Extrusion Die

Aluminum extrusion products are durable, light and solid, with good thermal conductivity and fashionable appearance. Moreover, the aluminum extrusion process has a wide range of applications and is easy to conduct secondary processing. The overall processing cycle is short, the cost is low and environmental protection. It is widely used in aviation and aerospace industry, transportation industry, construction industry, daily consumer goods and even the manufacturing of electronic equipment.

If you want to carry out aluminum extrusion process, you can’t do without the production of aluminum extrusion die. In recent years, due to the thinning of the wall thickness of aluminum profiles, the quality of die materials is required to have higher strength and toughness and better surface quality. Vacuum heat treatment can obtain many excellent properties that are difficult to obtain in conventional heat treatment, so it has become the preferred process for producing high-performance aluminum extrusion dies.

Advantages of vacuum quenching

Under the same quenching process conditions, vacuum heat treatment and salt bath furnace heat treatment and other traditional heat treatment have obvious differences in the surface structure of parts. Serious oxidative decarburization occurs after heating and quenching in salt bath furnace, while vacuum heat treated workpieces are free of oxidation and decarburization no matter from the appearance quality or measured with a microhardness tester. It ensures the consistency of internal and external organization, and obtains bright grinding surface.

Compared with salt bath quenching, vacuum quenching has higher tensile strength, higher impact toughness and more uniform hardness. Vacuum quenched steel has high mechanical properties. Quenching in vacuum can greatly reduce the hydrogen content and other gas content of high-strength steel, thus resisting brittle fracture.

Technological process:

VOGQ double chamber vacuum oil quenching furnace produced by SIMUWU is selected for the process. VOGQ series vacuum furnace is a high performance and cost-effective vacuum furnace product produced by SIMUWU. The VOGQ vacuum oil quenching furnace is a double chamber structure. All actions of the furnace are controlled by PLC. The heating speed is fast and uniform. It is a high-quality production equipment for processing aluminum extrusion dies. The following is a brief introduction to the process using VOGQ vacuum furnace:

Quenching heating:

Heating and quenching is the main way to obtain the strength of die. With the increase of quenching heating temperature, the tensile strength after tempering can also be enhanced, improving the thermal fatigue performance, but the plastic toughness is slightly reduced, so the ideal heating temperature is 1080 ℃ or 1100 ℃. Proper temperature selection can ensure the strength of the product, so that deformation will not occur during extrusion, and ideal impact toughness will be obtained, thus improving the product life.

Key points of using vacuum furnace for quenching:

1) Preheating and heat preservation: the vacuum heating adopts the radiation heat transfer with the heating body (graphite) evenly distributed on all sides. In the low temperature stage (≤ 600 ℃) of the heating process, the radiation efficiency is relatively low, and the temperature difference between the furnace temperature and the workpiece surface, as well as the temperature difference inside and outside the workpiece, is still large. Therefore, it should be noted to slowly heat up. Preheating sufficiently near the transformation point (800~850 ℃) of the steel to ensure that the workpiece is burned through can reduce the temperature difference between the inside and outside of the workpiece and reduce the stress and deformation. For small workpieces and small amount of furnace charging, this part can be omitted and directly slowly raised to the quenching temperature.

2) Selection of vacuum degree

The higher the vacuum degree, the better the degassing and degreasing effect, and the better the oxidation prevention effect. However, pumping high vacuum will consume more time, and will cause alloy elements (such as Cr, Mo, Al, etc.) to evaporate under high vacuum, thus making the workpiece surface rough and reducing the brightness. In addition, the volatile high vapor pressure elements will also lead to the pollution of the vacuum element and furnace body, and the workpiece will adhere to each other, affecting the electrical insulation performance. Therefore, it is necessary to control the vacuum degree or fill protective gas in actual production. The VOGQ vacuum oil quenching furnace can adapt to different vacuum degrees, and is equipped with a pressure dividing pipeline, which can prevent the evaporation of workpiece elements under high vacuum by filling nitrogen or argon.

3) Cooling process

VOGQ double chamber vacuum oil quenching furnace mainly uses vacuum oil quenching as the workpiece cooling mode, and has certain requirements on quenching oil, oil temperature and oil surface pressure. Vacuum quenching oil requires good chemical stability, less impurities and carbon residue, and low acid value. The quenching oil temperature should be about 30~80 ℃. Filling the cooling chamber with pure nitrogen to 0.04~0.06MPa during the process can effectively improve the cooling rate. Gas filling can also increase the oil level pressure, improve the evaporation and condensation temperature of quenching oil, and avoid pollution of equipment due to oil volatilization.

4)Vacuum tempering process

In order to maintain the excellent quality of vacuum quenching, vacuum tempering shall be carried out for vacuum quenched workpieces. Vacuum tempering can effectively reduce the subsequent grinding, polishing, wire cutting and other operations of the extrusion die. Reduce production cost and improve production efficiency.

Selection of vacuum quenching furnace: The VOGQ series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment process of tools and dies. Good temperature control accuracy and uniformity ensure the effective implementation of the vacuum heat treatment process. SIMUWU focuses on the manufacturing 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 gas quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.