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Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

Some characteristics of vacuum heat treatment metal materials

High vacuum heat treatment has the following characteristics:

①The chemical activity of the high vacuum atmosphere is extremely low. During the vacuum heat treatment, the reactions occurring at the interface between the gas phase and the solid phase, such as oxidation, reduction, decarburization, carburization, etc., will not proceed to the extent that it affects;

②The high-vacuum atmosphere changes the volume of the gas very rapidly, which can cause the metal or alloy to release dissolved gas or cause the metal oxide to decompose. The pressure is very low and the oxidation is inhibited, so in order to achieve the purpose of no oxidation, the partial pressure of oxygen must be lower than the decomposition pressure of the oxide.

Advantages of vacuum heat treatment:

Vacuum heat treatment can maintain the original surface finish, dimensional accuracy and performance requirements of all metal materials. For workpieces that need to be ground again, the machining allowance before heat treatment can be greatly reduced, and the surface cleaning process (such as acid cleaning, sand blasting, shot blasting, etc.), so vacuum heat treatment is the most promising process method, and it is also the most ideal heat treatment “atmosphere”. Its share in heat treatment equipment has reached more than 20%, especially in aviation and aerospace. , electronic components, textiles, tooling and other fields have been widely used.

Advantages of metal materials after vacuum heat treatment:

Compared with conventional heat treatment, the mechanical properties (especially plasticity and toughness) of metal material workpieces after vacuum heat treatment have been significantly increased. The reason is that vacuum heat treatment has a good degassing effect.

Surface purification and degreasing The workpiece is heated in a vacuum state, and the oxide film, slight rust, nitride, hydride, etc. on the surface are reduced, decomposed or volatilized and disappear, so that the metal obtains a smooth surface. This is a vacuum A characteristic of heat treatment.

It should be noted that when the oxide on the metal surface is heated in vacuum, it may also react with H₂ and C diffusing outward from the inside of the metal material, thereby reducing the oxide on the metal surface. In the decomposition process of oxides, it is also accompanied by the effect of removing organic substances such as grease. Even without special cleaning to remove surface organic substances, the surface of the workpiece can also have a bright surface. The reason is that these greases and lubricants are all Belonging to the aliphatic group, it is a compound of carbon, hydrogen and oxygen. It has a high decomposition pressure, so it is easy to decompose into gases such as hydrogen, water vapor and carbon dioxide when heated in a vacuum, and then it is sucked away by a vacuum pump, so that it will not be separated from the parts at high temperature. Any reaction on the surface can still get a clean surface without oxidation and corrosion. The vacuum purification effect enhances the activity of the metal surface, which is conducive to the absorption of C, N, Cr, Si and other atoms, making carburizing, nitriding and nitrogen carbon The speed of co-infiltration is faster, and the infiltration layer is more uniform.

Features of vacuum heat treatment: evaporation of metal surface elements

Vacuum evaporation When the workpiece is heated in a vacuum furnace, the moisture in the furnace and the nitrogen, oxygen and carbon monoxide in the air will be evaporated and escaped at low temperature, and hydrogen and nitrogen will be released from the surface of the workpiece above 800°C And the decomposition gas of oxides completes the surface degassing effect, and the evaporation and dissipation formed by thermal decomposition makes the metal surface bright, which is the characteristic of vacuum heat treatment.

Another feature of vacuum heat treatment is the evaporation of metal surface elements, which is reflected in the bonding between parts and parts after heat treatment of high chromium cold work die steel or chromium stainless steel, or between parts and baskets (tooling), and the surface is Orange peel, very rough, and the corrosion resistance is significantly reduced. This is the shortcoming of vacuum heat treatment-the evaporation of metal. Regarding the evaporation of metal, it comes from the theory of phase equilibrium. The equilibrium pressure of steam acting on the metal surface (steam pressure) is different, the higher the temperature, the higher the vapor pressure, and the larger the evaporation of solid metal; the lower the temperature, the lower the vapor pressure. If the temperature is constant, the vapor pressure will have a certain value. When the vapor pressure is lower than the temperature, the metal will evaporate (sublimate). The lower the external pressure, that is, the higher the vacuum degree, the easier it is to evaporate. Similarly, metals with higher vapor pressures are easier to evaporate.

Commonly used elements in steel such as Mn, Ni, Co, and Cr, as well as elements such as Zn, Pb, and Cu, which are the main components of non-ferrous metals, have high vapor pressures, and vacuum evaporation is easy to occur during vacuum heating to cause workpieces ( Or with tooling) mutual adhesion. In fact, there is a certain relationship between the vapor pressure and the heating temperature. As long as the vacuum degree is properly selected, the evaporation of alloying elements can be prevented.

In addition, when heating in vacuum, the type of metal material can be considered, and a high-purity inert gas (that is, reverse inflation such as high-purity nitrogen, high-purity argon, etc.) can be introduced at a certain temperature to adjust the vacuum in the furnace. To prevent the evaporation of alloy elements on the surface of the workpiece by heating in a low vacuum, this measure is more effective for high-speed tool steel, high-alloy steel and other workpieces.

Vacuum furnace selection: The vacuum heat treatment furnace produced by SIMUWU is a high-quality product for vacuum heat treatment process. Good temperature control accuracy and temperature control uniformity ensure the effective vacuum heat treatment process. The equipment is easy to manage and maintain, greatly reducing maintenance costs. SIMUWU company focuses on 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.