Technological processes of production and processing of various materials often include the stage of thermal exposure. Thus, hardening, drying at high temperatures, soldering and other procedures are performed. It is not always possible to implement such measures in conventional furnaces even for industrial purposes. Restrictions may be related to the inadmissibility of contact with the air. Therefore, to solve such problems, a vacuum furnace is used, processing in which also eliminates the processes of excessive deformation and warping of workpieces.
Appointment and scope of vacuum furnaces
Thermal firing operations in vacuum are used in machine and instrument making, in the construction industry, in various industries, etc. For example, in instrument making with the help of such a unit, an operation is performed to degass the elements, which later become components of various equipment. In the same direction, the vacuum furnace allows for high-quality soldering and finishing sealing of individual sections on electrical boards.
Sintering is also common. With its help, the necessary operational qualities are given to ceramic products, solid alloys, refractory metal powders in construction and production. The metallurgical industry, which is also interested in heat treatment operations, is also worth mentioning. For example, a vacuum furnace allows you to implement procedures for quenching, aging and tempering alloys. Various steels, bronze and magnesium can be subjected to such treatments.
Key Specifications
The productivity of the furnace construction often becomes the main criterion for choosing a model. In this case, the plants have a potential of 3 to 20 kW. Moreover, this indicator affects the quality and effectiveness in providing thermal exposure to a minimum. As a rule, power increases as the load volume increases, which depends on the dimensions of the structure. So, in standard industrial models of this type, you can load from 15 to 40 kg of material on average. But there are also units that allow serving up to 100 kg at a time. Endowed with average characteristics, an induction melting furnace is capable of serving up to 9000 kg per shift. As for the quality and effectiveness of the exposure inside the chamber, the temperature range should be taken into account directly. It ranges from 1800 to 2000 ° C.
Smelting process
The technology in traditional units is based on the action of an arc discharge. There is a contact of an electric current and a gas mixture. Further, the resulting arc due to the high concentration in vacuum provides increased thermal effect. Even with low power, a vacuum arc furnace is able to melt steel billets.
There are two principles of heat transfer in relation to the material. This is a direct and indirect effect. In the first case, the arc generates energy between the electrode and the workpiece, which with this configuration receives the maximum heat. Indirect heating involves working with two electrodes that act on an object at some distance. It is obvious that a direct heat transfer vacuum furnace is more efficient, but it allows a larger percentage of negative heat treatment factors.
Varieties of furnaces
The basic model of a vacuum furnace structure is the arc design described above. With this tool, you can serve most varieties of complex metal alloys, including refractory products. Another variety is an induction melting furnace, in the device of which an inclined crucible is provided. It is in the crucible that the process of melting the material loaded into the working chamber is realized. The induction principle of operation is considered the most expensive to maintain, so it is used less often and only when necessary when working with complex metals. Special types of vacuum furnaces include electron beam aggregates. Such a device produces refined alloys and metal ingots at the output. Structurally, the equipment is a thermal gun, which implements beam firing of the product by means of directed action.
Advantages and disadvantages of vacuum furnaces
Compared to conventional heat treatment furnaces, vacuum allows for highly efficient heat treatment of workpieces. At the same time, the operator has the possibility of flexible adjustment of the heating parameters, which, for example, provides a vacuum induction furnace with a crucible. The advantages of such structures include the possibility of obtaining a relatively pure metal material. That is, the technology itself eliminates excessive contamination of the array with foreign particles - heat treatment products.
As for the disadvantages, they are associated with a low resource of the parts forming the structure. It is not even a matter of flaws in the material of the constituent elements, but in the harsh conditions that are required to ensure efficient heat treatment and which affect the structure of the working surfaces. In addition, a vacuum furnace, the average price of which is 500-700 thousand rubles, is available to few enterprises. Nevertheless, high quality sintering and melt is an expensive method that limits its application.
Manufacturers
Only large enterprises cooperating with institutes of design and development of industrial equipment are engaged in the supply of vacuum furnaces. Today, high-quality units of this type are supplied to the domestic market by foreign manufacturers SCHMETZ and XERION. These products are oriented both to performing typical thermal operations and to specialized tasks like diffuse annealing. The Moscow factory of industrial equipment, specializing in the production of vacuum electric furnaces, also offers units worthy of performance. With this equipment, the owner can carry out metal tempering, sintering and standard thermal processes. Automatic models are offered by Spetszhelezobeton Plant, which develops high-vacuum units with volumetric loading chambers.
Conclusion
An example of vacuum annealing technology shows that not always new solutions justify themselves during operation. Although the same Moscow factory of industrial equipment seeks to optimize units for the needs of a wide range of consumer enterprises, the high cost of vacuum heat treatment processes for many potential customers makes this method unavailable. The refusal from such furnaces is due not only to their cost, but to the lack of the need to obtain a high-quality product. Nevertheless, advanced companies working in high-tech industries can no longer do without the use of such heat treatment means.