Development of vacuum induction furnace melting technology
Along with the rapid development of modern industrial technology, people are increasingly demanding the use of mechanical parts, the use of increasingly stringent environment on the metal material of high temperature resistance, abrasion resistance, fatigue resistance higher requirements are put forward. For some specific metal or alloy materials, in the late prophase development test or put into use in mass production, research or get a high performance metal alloy materials require metal smelting equipment, heat treatment equipment and so on the surface of the support. In numerous special heating or melting method, induction heating technology for preparation of smelting metal material or to a certain process to sintering material, heat treatment, etc., have played a vital role.
1. 1 the principle
Induction heating technology usually refers to the technology of making the materials with good inductive magnetism obtain the induction current through the principle of electromagnetic induction in the vacuum condition, so as to achieve the purpose of heating. Current at a certain frequency through the electromagnetic coil around metal materials, change the current induced magnetic field, and the metal internal produce induced current, and produce a lot of heat used to heat the material. When the heat is relatively low, it can be used in vacuum induction heat treatment and other processes, when the heat is high
When, enough heat is produced to melt metal and be used to prepare metal or alloy materials.
1. 2. 1. Vacuum induction melting
Vacuum induction melting technology is the most efficient, fastest and environmentally friendly induction heating technology for metal materials at present. This technology is mainly used in induction melting furnace and other equipment.
Solid metal raw materials in crucible by coil winding, when current flows through the induction coil, induction electromotive force and eddy current is generated in metal furnace charge current calorific value is greater than the metal furnace charge when the rate of heat release, as the heat is piling up, arrived
At a certain degree, the metal melts from solid state to liquid state to achieve the purpose of smelting metal. In this process, because the whole process takes place in a vacuum environment, it is beneficial to remove the gas impurities inside the metal and the metal alloy material is more pure. At the same time smelting
During the process, the melting temperature can be adjusted and the alloy metal can be added in time through the control of vacuum environment and induction heating, so as to achieve the purpose of refining. In the melting process, because of the characteristics of the induction melting technology, liquid metal materials in the crucible of internal due to the interaction of electromagnetic force, can automatically realize stirring, make more uniform composition, that is a big advantage of induction smelting technology.
Compared with traditional smelting, vacuum induction smelting has great advantages in energy saving, environmental protection, good working environment and low labor intensity. With induction melting technology, less impurities are added in the final casting of alloy materials, and the alloy proportion added is more suitable, which can meet the requirements of the process for various properties of materials.
Vacuum induction melting technology has been widespread use, the current from a few kilograms induction furnace used for experimental study to used in the actual production of dozens of tons capacity of large induction furnace, due to its simple operation process, melting warming faster melting process easier to control, the advantages of smelting metal components uniform, has great application prospect, and got rapid development in recent years.
Vacuum sintering refers to the sintering of metal, alloy or metal compound powder in a vacuum environment (10 ~ 1O approximately Pa) at a temperature lower than the melting point to form metal products and metal billets. Under the condition of vacuum sintering, there is no reaction between the metal and gas, and no gas adsorption effect, not only the densification effect is good, and can rise to purify and restore function, reduce the sintering temperature, and sintering at room temperature than can reduce 100 ℃ ~ 150 oc, save energy, improve the sintering furnace life and get high quality products.
For some materials, the combination of particles can be achieved by means of atomic migration when heated, while induction sintering technology plays a heating role in this process. Under the condition of vacuum induction sintering has the advantage that the vacuum atmosphere helps to reduce the harmful substances (water vapor and oxygen, nitrogen and other impurities), avoid decarburization, nitriding and carburizing, reduction, oxidation and so on a series of reactions. Reduce the amount of gas in the pore in the process, reduce the gas molecules of chemical reaction, at the same time in the oxide film on the surface of the liquid phase out before the onset of the material, which when melt material in combination with each other to make materials with more dense, improve its wear resistance and strength. In addition, vacuum induction sintering has certain effect on reducing product cost.
Due to the vacuum environment, is in a state of relative low gas content, so you can ignore the heat convection and conduction, mainly by the heating components in the form of radiation heat transfer to the surface of a material, depending on the sintering temperature, physical and chemical properties of material, it is also important to choose appropriate heating components. Compared with vacuum resistance heating, induction sintering is heated by medium frequency power supply, which avoids the high temperature insulation problem of vacuum furnace with resistance internal heating.
At present, induction sintering technology is mainly used in steel and metallurgy. In addition, in special ceramic materials, induction sintering enhances the bonding of solid particles, which helps the grains grow up and compress the gap, thus increasing the density and forming a dense polycrystalline sintering body. Induction sintering technology is also widely used in the research of new materials.
At present, there should be more induction heat treatment technology mainly focused on induction quenching technology. When the workpiece is put into a sensor (coil), the alternating magnetic field is generated around the sensor when the sensor is connected with alternating current of a certain frequency. The electromagnetic induction of alternating magnetic field causes closed eddy current in workpiece. Due to skin effect, namely, the distribution of induction current on the workpiece section is very uneven, the surface current density of the workpiece is very high, and gradually decreases inward.