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Alumina Sand

When the cooling speed is slow, the temperature gradient of liquid steel in the cavity is small, and the heat transfer directionality of the mold wall is weak, which is conducive to the formation of equiaxed products(alumina sand). At this time, non-metallic inclusions will float up into the slag and be absorbed, and the molten steel will become clean(sandblasting grit). 


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When the pouring temperature is the same and the wall thickness of the casting is the same, the difference of heat storage capacity and thermal conductivity of the mold will also change the distribution characteristics of liquid steel temperature in the mold cavity(alumina sand). The relationship between the wall thickness of the imitation part and the loose box time is shown in the figure(120 grit aluminum oxide blasting media).


The sedation time is given in table 2-29(brown corundum). When the cooling rate is very fast, the liquid steel temperature gradient from the mold wall to the center is large, and the heat transfer direction of the mold wall is strong, which is conducive to the formation of columnar crystal zone(alumina sand). During pouring, in order not to lift the upper box and core under the buoyancy of molten steel, it shall be fixed with pressurized iron(aluminium oxide abrasive grit). 


Especially for complex castings, the delivery time can refer to the empirical formula of the former Soviet Union Nochik factory: high manganese steel castings need to be cut and cleaned after they are unpacked(alumina sand). The technical requirements of the external cooling iron are: the working surface of the direct external cooling iron shall be smooth and free of rust(refractory materials); When in use, paint shall be brushed and dried together with the mold. 


The spacing of external cooling iron shall be 20 ~ 25mm, and the vertical and horizontal gaps shall be staggered to avoid cracks in castings between cooling iron due to the formation of regular cooling weak surface(glass bead blasting media suppliers). The relationship between the size of the external cooling iron and the thickness of the corresponding section of the casting can be referred to the data in the table(alumina sand). 


The general principle is that with the improvement of mold cooling capacity, it is conducive to the formation of columnar crystals, especially at higher pouring temperature, columnar crystals develop more seriously and form transgranular structure(aluminium oxide grit suppliers). If necessary, the molding sand near the riser should be removed to avoid excessively hindering the shrinkage of the casting and causing cracks(alumina sand).


Pouring temperature is limited by tapping temperature(steel grid). Tapping temperature = pouring temperature + temperature drop in ladle during tapping + temperature drop in ladle during sedation(alumina sand). The pouring time depends on the specific situation of the casting(aluminium oxide powder). For thin-walled parts and complex parts, rapid pouring should be adopted to avoid insufficient pouring. Pouring can be carried out after the completion of sedation.


If there is a large plane on the upper surface of the mold (such as lining plate and toothed plate), rapid pouring should also be adopted to avoid casting defects such as peeling and sand inclusion caused by high temperature baking of liquid steel for a long time(abrasive blast media). Generally, refer to table 2-28 for pouring time of small and medium-sized parts(alumina sand). The molten steel shall be killed with slag after pouring into the ladle.


It is absolutely not difficult to adopt the sedation and purification process(aluminum oxide suppliers usa). However, for the mixing and injection of induction furnace refining subcontracting, there are difficulties in the sedation process, mainly due to less furnace overflow and low temperature, it is difficult to cover the whole ladle of molten steel, and even sedation can not fully capture the non-metallic inclusions in the molten steel(alumina sand).


Generally, the steel slag is mixed out of the plug ladle, and the top of the ladle is covered with a thick layer of high-temperature slag(aluminium oxide blast media). Generally, molten steel is poured into the ladle at the bottom of the ceramic plug rod from the steelmaking furnace, and then poured into the mold(alumina sand). Therefore, after tapping, a layer of expanded perlite (about 20 ~ 30mm thick) is immediately covered on the steel level in the ladle.


The melting point of perlite is low (1300 ℃)(alumina sand). After melting, molten slag is formed to absorb the floating non-metallic inclusions in the molten steel(aluminum oxide sandblasting). Generally, the slag is removed immediately after reaching the sedation time, During pouring, a piece of aluminum silicate refractory fiber is covered on the nozzle to block slag(green silicon carbide). The principle of "low temperature and fast pouring" shall be implemented as far as possible.


Changes make the steel brittle and easy to crack(aluminium oxide suppliers south africa). In addition, for effective castings after pouring and solidification, the box must be loosened in time, the fastening bolts of the flask and the weight must be removed to reduce the shrinkage resistance, which is of great benefit to reducing the cracks of the casting(aluminum oxide sandblast media). Of course, it should not be too early to loosen the box, which will cause deformation of the casting(alumina sand). 


Strictly control the tapping temperature, have sufficient pouring speed, reduce the secondary oxidation of molten steel in the pouring process, and adapt to the pouring temperature, mold structure, and the layout of the pouring system(garnet sand). For castings with simple shapes, the out-of-box time can be shortened appropriately(alumina sand). After heat treatment, the oxide scale on the surface of the incision falls off and the cracks are exposed. 


After cutting, high manganese steel castings often have mesh patterns on the surface, and the depth is about 5mm or less(alumina sand). If cold cutting is performed with a suspended grinder, it is ideal to remove gates, mesh openings and burrs, but it has the characteristics of low production efficiency, high labor intensity and poor working environment, so oxygen-acetylene flames are generally used for heating(white aluminum oxide blast media). 


Because the plasticity and toughness of high manganese steel castings are greatly improved after heat treatment(alumina abrasive), but when the oxygen-acetylene flame is used for hot cutting, the heating of the casting will cause carbides to precipitate, resulting in greater composition, structure and performance of the steel near the incision(alumina sand). After cutting and air cooling, observe that there are no cracks on the surface of the incision.


The cutting process of high manganese steel is more difficult(aluminum oxide blast media canada). In order to improve the flow, filling and feeding conditions, increase the rising speed of molten steel and reduce slag inclusion, it is advisable to adopt inclined pouring for castings with large surface areas, such as bucket bottom doors(alumina grit). State cutting. The micro-cracks formed during cutting in the as-cast state may expand during the heat treatment(alumina sand). 


The special properties of high manganese steel in performance and structure(silicon carbide grit), such as low thermal conductivity of steel, large linear expansion coefficient, a large number of network carbides in the as-cast structure, very brittle performance, and easy cracking during as-cast cutting, etc., make the cutting A series of problems and difficulties arise(alumina sand). But in fact, it has been formed when cutting in the as-cast state.


High manganese steel has poor thermal conductivity, large shrinkage, low as-cast strength, and high casting stress(100 grit aluminum oxide). Therefore, high manganese steel should take longer to leave the box than carbon steel, and the shape of complex and thick castings should be lower than 200 ℃(alumina sand). The casting is pre-heated to 300~800℃ for cutting(150 grit aluminum oxide). But after heat treatment, there are still net-like cracks on the surface of the incision.


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