Application of tungsten alloy as high temperature refractory material in the aerospace industry and military aspects is highly valued by the industry in developed countries. In recent years, special metal tungsten and tungsten alloy products are widely used in pipeline spacecraft, reactor and penetrator. Because it also has excellent corrosion resistance, thus it can also be used as electrical contacts used in high temperature and corrosive environment. High density tungsten alloy has a special application in the military field, such as aircraft, rocket, missile, submarine, the torpedo navigation gyroscope etc.
The crucible is vessels or melting pot which is made of extremely refractory materials (such as clay, graphite, kaolin, quartz or difficult molten metal iron). When a solid needs to be heated with big fire, you must use the crucible. Because it can withstand higher temperature than the glass vessels. In the using process of crucible, the crucible cover usually obliquely placed on the crucible, this can prevent the heating material jumping out, and allowing air to have free access to have the possible oxidation reaction. Because the bottom of crucible is very small, generally it can be heated directly with fire after it was framed in the pipe clay triangle. The crucible can be placed in the iron triangle with lay or obliquely, and it can be placed according to the experiment demand. After the crucible is heated, it can not be immediately placed in cold metal on the desktop, in order to avoid the rupture because of the rapid cooling.
The type and specification of crucible is more, so it can't be limited by the scale of production, batch size and melting material varieties in application, and it with arbitrarily chosen, strong applicability, and can guarantee the purity of the smelting materials.
1. Place the dry place, avoid rainwater intrusion; It must be slowly baked to 500 degrees, and then it can be used.
2. The charging should be based on the volume of crucible, avoid crowded too tight, avoide the crack of crucible because of the metal thermal expansion.
3. When the molten metal is removed, it is best to use spoon to scoop out, to minimize the use of caliper, if using calipers and other tools should be consistent with the crucible shapes, to avoid excessive local stress and shorten the service life.
4. The service life of the crucible is relevant with the usage, should avoid strong oxidizing flame sprayed directly into the crucible, which will make the oxidation of crucible materials and short-lived
Under normal temperature, tungsten can be quickly dissolved in hydrofluoric acid and the mixed acid of concentrated nitric acid, but it doesn't work in alkaline solution. With the presence of air, molten alkali can take tungsten oxide into tungstate, where oxidants (NaNO3, NaNO2, KClO3, and PbO2) exist; the reacting of forming tungstate is more violently. What's more, it can combine with chlorine, bromine, iodine, carbon, nitrogen, sulfur in high temperature, but it doesn't work with hydrogen.
