Refractories for vacuum Casting equipment
High temperature operating departments are required to resist high-temperature heat load performance, but due to different operating departments, and even in the same furnace in different parts of the working conditions are not consistent. Therefore, the requirements of refractory materials are also different. It is based on general working conditions of ordinary industrial furnaces, and puts forward the following requirements on the performance of Refractories:
Resistance to high-temperature heat load, not softening, not melting. Refractories are required to have a fairly high degree of fire resistance. Resistance to high-temperature heat load, volume does not shrink and only homogeneous expansion. The material has high volume stability, residual shrinkage and residual swelling should be small, no crystal type transition and serious volume effect. The joint action of resisting high temperature heat load and heavy load does not lose strength and does not creep and collapse. It is required that the material has fairly high temperature strength and high thermal strength, high load softening temperature, high creep resistance. Resistance to sudden changes in temperature or uneven heating, not cracking, not peeling. The material has good thermal shock resistance. Resist the chemical erosion of molten liquid, dust and gas. The material has good slag resistance. Resistance to flame and charge, material dust scouring, impact and wear, the surface does not wear. The material has a very high compactness and wear resistance at room temperature and high temperature.
Vacuum casting equipment is affected by high temperature vacuum operation and atmosphere change, not volatile, not damaged. The materials have low vapor pressure and high chemical stability. In addition, in order to ensure that the bulk refractory masonry structure or the overall quality of lining. Slag resistance and airtight good, and easy to construction, but also required the appearance of materials neat, accurate size, to ensure a certain tolerance, and du must not allow the existence of defects. In order to withstand the impact of handling and possible mechanical vibration and extrusion, the material must have a very high ambient temperature strength. The thermal conductivity and conductivity of some special requirements are sometimes considered. It should be noted that although the above points can be used as a basis for evaluating the quality of refractories, none of the refractories can fully meet all of the above requirements. In selecting or evaluating refractory materials, it is necessary to make use of the material's outstanding characteristics and conditions. At the same time, economic accounting is considered.