What are the characteristics of magnesium alloy furnaces?
Magnesium alloy smelters say the process must be conducted in a protective atmosphere because of the need to prevent oxidation and safety measures such as combustion and explosion. Therefore, magnesium alloy die casting needs to be equipped with a special melting furnace, and melting is also the key link of magnesium alloy die casting. For the hot chamber machine, the magnesium alloy melting furnace used should not only meet the higher temperature requirements than the zinc alloy, but also have the passage of input protective gas and the sealing mechanism of the melting furnace.
Before 1970, the smelting of magnesium alloys mainly used flux protection, its main components are some fluorinated salts. Although this method can play a good role in flame retardant, but it is easy to produce slag inclusion, resulting in the mechanical properties and corrosion resistance of the product decline. In addition, the flux reacts with magnesium liquid to produce corrosive gas, which causes serious corrosion to crucible and die casting equipment, affects the service life of equipment and deteriorates the chemical environment.
Magnesium alloy smelters say that modern magnesium alloy smelting mainly uses gas protection technology, among which the application of protective gas SF 6 is of great significance to the development of magnesium alloy industry. At present, most magnesium alloy die casting plants in the world adopt gas protected melting process. The flame retardant mechanism of the protective gas is that the gas reacts with magnesium liquid to form a surface film, which has different protective effects on the melt surface. These membranes are dense enough to prevent the reaction from continuing and the magnesium solution from evaporating. In addition, these gases are denser than air, somewhat blocking the reaction between magnesium and oxygen.
Magnesium alloy furnace manufacturers said that advanced magnesium alloy melting furnaces are double-chamber structure, that is, the melting chamber is separated from the greenhouse, which can avoid large fluctuations in the temperature of the metal liquid in the insulation area. At the same time, the position of the baffle can prevent slag from entering the pressure chamber and affecting the casting quality. In designing melting furnaces, the surface area to volume ratio of molten magnesium should be small, and the crucible and lid should be well matched and sealed.
The furnace body of magnesium alloy furnace is generally made of double-layer material, the inner layer is corrosion-resistant stainless steel, and the stainless steel without Ni is generally selected, because even if a small amount of Ni enters the magnesium alloy, the corrosion resistance of the magnesium raw material will be greatly reduced. The outer layer is heat-resistant steel, and it is welded together as far as possible.
Because the smelting of magnesium alloy is carried out under closed conditions, the charging tank and the charging system are also immersed in the magnesium liquid for the hot chamber die casting machine, which can realize the automatic charging and charging. For a cold chamber die casting machine, a quantitative pouring system is required to pour from the melting furnace to the press chamber of the die casting machine. At present, magnesium alloy quantitative pouring system has been developed and applied, including impeller type, pneumatic type and piston type.
In order to facilitate the connection between magnesium alloy melting furnace and die casting machine and facilitate the production, some other devices are needed, such as the three-dimensional positioning device of cold chamber die casting machine melting furnace, which can realize the rotation, translation and lifting of the melting furnace, so as to facilitate the matching and daily maintenance of the die casting machine.
Magnesium alloy continuous ingot casting machine manufacturers said that, at present, lead ingot casting equipment has been widely used in domestic lead smelters, the main operation has achieved varying degrees of mechanization or automation, casting, the use of lead pump molten lead pot liquid lead pump into the casting bag, liquid lead through the casting bag quantitative pouring device injected into the ingot mold for casting, scraper liquid lead ingot surface slag layer, Then, after cooling forming, printing and demudding process, the demudding lead ingot is stacked by cantilever hanging. It plays an active role in improving the working conditions and reducing the labor intensity of finished lead ingot.
The core of magnesium alloy continuous ingot casting machine is continuous casting technology. Continuous casting is a casting method in which liquid metal is continuously injected into one end of the die and molding materials are continuously pulled out from the other end. When the casting is drawn from the metal form to a certain length, the casting can be cut off while pouring; It is also possible to stop pouring when the casting reaches a certain length in order to obtain a certain length of casting. Magnesium alloy continuous ingot casting machine can be used for casting various high density plate, round bar, hollow pipe and other profiles.
Magnesium alloy smelters say that magnesium alloys are very active among all metals because they have an ignition point of 550℃ and a melting point of 650℃. At high temperatures, it reacts with oxygen to form magnesium oxide, while it reacts with water to form hydrogen and magnesium oxide, which causes an explosion. Therefore, metal oxidation or combustion must be prevented effectively in the process of melting magnesium alloy, which is usually achieved in the process of flux or no flux on the surface of metal melt. A large number of experimental studies show that gases such as C02.S02.SF6 can play a good protective role on magnesium and its alloy melt, but these substances will react with magnesium to form other substances. Such substances constitute impurities in magnesium soup, and a large number of impurities will float on the surface of the molten soup or adhere to the furnace side wall, and the dense ones will sink to the bottom of the furnace. When the substance becomes thicker and more concentrated, a large amount of this substance adheres to the crucible wall of the furnace. After a period of time, it will form a hard solid layer of material, causing a decrease in the volume of crucible. At the same time, heat from the external heating device of crucible cannot be properly transmitted into crucible, which reduces the melting speed and cannot meet the production requirements, thus reducing the production efficiency of die casting and seriously affecting the service life and product quality of crucible.
The shell of magnesium alloy furnace is made of high quality steel plate and high quality insulation material. The furnace has advanced structure, low energy consumption and fast melting speed. The design of double chamber crucible is reasonable and can be used in two die casting machines at the same time. High quality imported radiation processing thermal components, long service life, high thermal efficiency.
What are the advantages of magnesium alloy smelters? Let's find out.
In magnesium alloy smelting process, metal oxidation reaction should be avoided to prevent metal combustion. To achieve this effect, we usually sprinkle some flux on the metal melt. Sometimes, we can also use fluxless processes. The common flux is beryllium metal, and the common flux free process is flux free melting. The melting process of magnesium alloy is mainly flux melting. The flux removes impurities from the magnesium and forms a protective film on the surface of the magnesium alloy melt to isolate air. However, the effect of flux film on air isolation is not very ideal, and the magnesium loss caused by oxidation combustion in smelting process is relatively large.