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Vacuum Heat Treatment Furnace

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Application of vacuum pump system in vacuum heat treatment

Points to note for heat treatment of vacuum pump system:

1. When disposing of titanium alloys in a vacuum furnace, nitrogen should not be used as a cooling gas, because titanium and nitrogen react at high temperatures to form golden-yellow titanium nitride.

2. The movable connection part of the vacuum furnace is all sealed and connected by O-shaped rubber ring, and this part is cooled by water.

3. When the workpiece is quenched in a vacuum state, vacuum quenching oil should be used, which has a lower saturated vapor pressure.

4. The maintenance of the vacuum furnace should be in a vacuum or pure nitrogen state to prevent inhalation and moisture absorption when it is not in use.

5. The pressure rise rate of the domestic vacuum furnace should not be greater than 1.33Pa/h, and the specification of some foreign companies is 0.67Pa/h.

6. Vacuum heating is mainly based on radiation, and the distance between the workpieces in the furnace should be maintained.

7. During the heating process, the workpiece and the materials in the furnace will deflate, causing the vacuum to drop.

8. The heating temperature for vacuum tempering, vacuum annealing, vacuum solid solution treatment and vacuum aging is generally the same as the heating temperature for conventional treatment.

9. The vacuum tempering furnace should have a quick cooling installation. The pressure of the cooling water should be greater than 0.2Mpa, and the flow rate should be adjustable.

10. Cooling gas: 99.995% purity nitrogen is generally used for steel, 99.999% nitrogen or argon is used for high-temperature alloys, and 99.995% argon is used for titanium alloys.

11. Heating up: After putting in the workpiece, it can be heated up when the workpiece is pre-pumped to 6.67Pa.

Gehang vacuum furnace adopts internationally famous Leybold and EVP brand vacuum pumps, which have excellent performance, energy-saving and silent effect. Vacuum pumps are widely used in various types of vacuum furnaces, especially vacuum heat treatment furnaces equipped with EVP brand H-150G vertical sliding The valve vacuum pump has the ability to deal with moisture and impurities, and is especially suitable for vacuum oil quenching and vacuum oil quenching furnaces.

2. Several common heat treatment methods for metals:

A metal heat treatment process that heats a metal workpiece under 1 atmosphere pressure (that is, under negative pressure). In the late 1920s, with the development of electric vacuum technology, a vacuum heat treatment process was presented, which was only used for annealing and degassing at that time. Due to equipment limitations, this process failed to achieve a large pause for a long time. From the 1960s to the 1970s, the Shengli air-cooled vacuum heat treatment furnace, cold wall vacuum oil quenching furnace and vacuum heating high-pressure gas quenching furnace were successively developed, which enabled the vacuum heat treatment process to be newly developed. The technology of stopping carburizing in vacuum and stopping carburizing, nitriding or infiltration of other elements under the action of the plasma field in vacuum has further expanded the scope of application of vacuum heat treatment.
The heat treatment of metal parts in vacuum can avoid oxidative decarburization and has a degassing effect, but the metal elements may evaporate.

The heating chamber of the vacuum heat treatment furnace is close to vacuum when it is working. There are only traces of carbon monoxide and hydrogen, etc., which are restorative to the heated metal and do not produce oxidative decarburization. At the same time, it can also make the formed The oxide film is restored, so that the appearance of the heated metal workpiece can maintain the original metallic luster and good appearance performance.

When metal parts are heated in a vacuum environment, harmful gases in the metal, such as hydrogen and oxygen in titanium alloys, will escape at high temperatures, which is conducive to improving the mechanical properties of the metal.

Various elements have their own vapor pressure. If the pressure in the environment is lower than the vapor pressure of a certain element, this element will evaporate. In vacuum heat treatment, the vacuum degree or temperature during heating should be selected according to the vapor pressure of the alloy elements contained in the steel to prevent the alloy elements from evaporating.

Vacuum heat treatment equipment can be used for vacuum annealing, vacuum degassing, solution heat treatment, vacuum quenching, vacuum tempering and other processes. After passing the appropriate medium, it can also be used for chemical heat treatment.

Annealing, degassing, and solution treatment in vacuum are mainly used for workpieces with high purity level or high surface quality requirements, such as the softening and stress relief of refractory metals, the solution treatment of stainless steel and nickel-based alloys, and the removal of titanium and titanium alloys. Gas treatment, annealing of soft magnetic alloys to improve permeability and coercivity, and bright annealing of carbon steel, low alloy steel and copper that require bright. There are two types of quenching in vacuum: gas quenching and liquid quenching. The SIMUWU brand vacuum heat treatment furnace has two types of heat treatment equipment, namely the RVGQ series vacuum quenching furnace and the VOGQ series vacuum oil quenching furnace.

RVGQ series vacuum air quenching furnace is to fill the cooling chamber with high purity neutral gas (such as nitrogen) to cool the workpiece after being heated in vacuum. Suitable for gas quenching are high-speed steel and high-carbon high-chromium steel and other materials with low critical cooling rate of martensite. Liquid quenching is to heat the workpiece in the heating chamber, then move it to the cooling chamber to fill with high-purity nitrogen and immediately send it to the quenching oil tank for rapid cooling. If high appearance quality is required, the tempering and precipitation hardening of the workpiece after vacuum quenching and solution heat treatment should still be stopped in the vacuum furnace.

Vacuum carburizing is to load the workpiece into a vacuum furnace, vacuum and heat to purify the furnace. When the carburizing temperature is reached, hydrocarbons (such as propane) are introduced to stop carburizing, and the carburizing agent is cut off after a certain period of time. Vacuum to stop diffusion. This method can complete high temperature carburizing (1040℃) and shorten the carburizing time. There is no internal oxidation in the carburized layer, and there is no problem that the carbon content on the surface of the carburized layer is lower than that of the sub-layer. It can be vacuum carburized by pulse mode to make blind holes and small holes get an average carburized layer. SIMUWU’s low-pressure carburizing technology LPC has excellent performance in the carburizing of gears, screws and other products.

After vacuum heat treatment of the parts, the distortion is small, the quality is high, and the process itself is sensitive and pollution-free. Therefore, vacuum heat treatment is not only a necessary means for heat treatment of some special alloys, but also used in the heat treatment of ordinary engineering steels, especially tools, molds and fine coupling parts. After vacuum heat treatment, the service life is relatively ordinary. Heat treatment has made great progress. For example, after vacuum heat treatment, some molds have a lifespan that is 40 to 400% higher than that of the original salt bath treatment, while the life of many tools can be increased by about 3 to 4 times. In addition, the Gehang vacuum heating furnace can work at a higher temperature, and the workpiece can maintain a clean appearance, so it can accelerate the adsorption and response process of chemical heat treatment. Therefore, certain chemical heat treatments, such as carburizing, nitriding, chromizing, boronizing, and multiple co-infiltration can get faster and better results.