Heat Treatment of DZ4 Alloy in High Pressure Gas Quenching Vacuum Furnace

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The vacuum high pressure gas quenching process has been used for more than ten years since the 1980s. Especially in the aviation I plant, equipment has been purchased, but due to the lag in process research, the equipment has been put on hold for a long time. The vacuum high pressure gas quenching process of DZ4 alloy was studied in order to facilitate its popularization and application.

DZ4 alloy is usually used to manufacture aircraft engine turbine blades. The extension between the blade body and the tenon is not processed, and the blade itself has no machining allowance. Compared with the conventional process, the vacuum high-pressure gas quenching process is used for heat treatment. The heating temperature, After the holding time is determined, the key to the research is to use the cooling rate to cool the alloy so that the alloy can obtain a good combination of strength and toughness.

There are two types of vacuum air quenching furnaces, horizontal and vertical. The horizontal vacuum air quenching furnace has no special requirements for the shape of the workpiece, and the vertical vacuum air quenching furnace is especially suitable for the vacuum air quenching process of large and easily deformed workpieces such as long rod-shaped parts, shafts, and plate parts. , The deformation of the parts after gas quenching is small, and the cooling effect is good.

The horizontal vacuum air quenching furnace is mainly used for gas quenching of tool steel, die steel, high-speed steel, ultra-high-strength steel and other materials. It is suitable for the vacuum air quenching process of large and easily deformed workpieces such as long rod-shaped parts, shafts, and plate parts. After air quenching, the deformation of the parts is small and the cooling effect is good.

There are two types of vertical vacuum air quenching furnaces: top-loading and bottom-loading. Mainly used for ring die, pellet die, tool steel, die steel, high-speed steel, ultra-high strength steel, etc. The vertical vacuum air quenching furnace is especially suitable for the vacuum air quenching process of easily deformed large workpieces such as long rods, shafts and plates. After gas quenching, the deformation of the parts is small and the cooling effect is good.

Vacuum air quenching furnace is mainly used to strengthen the surface of some metal equipment, and it is widely used in fine technology such as aviation.

The working principle and composition of vacuum air quenching furnace: quenching in vacuum has two types: gas quenching and liquid quenching. Gas quenching means that the workpiece is heated in vacuum and then filled with high-purity neutral gas (such as nitrogen) in the cooling chamber for cooling. Suitable for gas quenching are high-speed steel and high-carbon high-chromium steel with low critical cooling rate of martensite. Liquid quenching is to heat the workpiece in the heating chamber, move it to the cooling chamber, fill it with high-purity nitrogen, and immediately send it to the quenching oil tank for rapid cooling. If a high surface quality is required, tempering and precipitation hardening after vacuum quenching and solution heat treatment of the workpiece should still be carried out in a vacuum furnace.

Precautions for the use of vacuum air quenching furnace:

1.Strictly squeezed vacuum sealing: most parts are subjected to vacuum heat treatment in a closed vacuum air quenching furnace. Therefore, to obtain the original air leakage rate of the furnace and to ensure the vacuum degree of the vacuum furnace, it is necessary to ensure the parts The quality of vacuum heat treatment is of great significance. Therefore, a key issue of vacuum heat treatment furnaces is to have a reliable vacuum sealing structure. In order to ensure the vacuum performance of vacuum furnaces, a basic principle must be followed in the structural design of vacuum heat treatment furnaces. That is, the furnace body should be welded with airtightness, and at the same time, the furnace body should be opened as little or no holes as possible, and the dynamic sealing structure should be used less or avoided to minimize the chance of vacuum leakage. Components and accessories installed on the vacuum furnace body, etc. For example, water-cooled electrodes and thermocouples must also be designed with a sealing structure.

2.Most of the heating and heat insulating materials can only be used in the open state: the heating and heat insulating linings of the typical air heat treatment furnace work under vacuum and high temperature, so for this material, high temperature resistance, steam Low pressure, good radiation effect, small thermal conductivity and other requirements, but not high requirements for oxidation performance, therefore, tungsten, platinum and graphite are widely used as heating and heat insulation materials in the air heat treatment furnace. Derailment, therefore, conventional heat treatment furnaces cannot use these heating and insulating materials.

3.Using low voltage and high current: In the stone vacuum container, the energized conductor in the vacuum container will generate a glow discharge under high voltage. Therefore, the working voltage of the electric heating element of the vacuum heat treatment furnace is generally not more than 80-100 volts. At the same time, effective measures should be taken in the structural design of the electric heating parts, such as avoiding sharp edges as much as possible. The distance between the electrodes should not be too small and narrow to prevent the occurrence of glow discharge or arc discharge.

4.the high degree of automation: the high degree of automation of the vacuum heat treatment furnace is because the heating and cooling of metal workpieces require dozens or even dozens of actions to complete. These actions are carried out in the vacuum heat treatment furnace. Personnel cannot approach, and at the same time, if there is such an action, such as after heating and heat preservation, the quenching process of the workpiece requires six actions and must be completed within 15 seconds. In such a rapid condition, many tasks are completed, which is easy to cause the operator’s injury. It is stressful and constitutes a misoperation. Therefore, only a higher self-efficacy can be accurately and timely coordinated according to the procedure.

5.Water-cooling device, furnace shell, furnace cover, electric heating element of vacuum heat treatment furnace, separately disposed (water-cooled electrode), intermediate vacuum insulation door and other components, all work in vacuum and heated state, and work under such extremely unfavorable conditions , It is necessary to ensure that the structure of each component is not deformed or damaged, and the air seal is not overheated or burned. Therefore, each component should be equipped with a water cooling device according to different conditions to ensure that the vacuum heat treatment furnace can operate normally and have enough use. life.

(1) DZA alloy vacuum positive pressure gas gloss process: solution treatment: 220 ℃ x 215h, 0105MPa, 011MPa, 012MPa nitrogen cooling; aging treatment 870 ℃ x 3215h, air cooling.

(2) The surface of DZ4 alloy after solution treatment is bright, no pollution, small deformation, and the strength and plasticity indicators can meet the design requirements.

Equipment selection: The RVGQ series vacuum air quenching furnace produced by SIMUWU is a high-quality product for this type of vacuum heat treatment process. The good temperature control accuracy and temperature control uniformity ensure the effective operation of the vacuum air quenching furnace. 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 oil quenching furnace, vacuum brazing furnace, vacuum sintering furnace, etc., which are widely sold in developed and developing countries.