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Aluminium Oxide Sandblasting Grit

Although general cracks only appear after heat treatment, for castings that cannot be immersed in water for cutting, water shall be used to cool the cut parts in time during cutting(aluminium oxide sandblasting grit). The surface cut by oxygen acetylene flame shall be grinded for another 3 ~ 5mm to eliminate the micro cracks generated in cutting and the metal layer with deteriorated microstructure and performance in the heat affected zone(aluminium oxide blasting). 


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The linear shrinkage rate of high manganese steel is more than twice that of ordinary carbon steel, but the thermal conductivity is far lower than that of ordinary steel(aluminium oxide grit suppliers). This tensile stress is caused by uneven heating during flame cutting and the final cooling shrinkage at the notch is restrained by the region with low surrounding temperature(aluminium oxide sandblasting grit). The relationship between the diameter of the electrode and the current is shown in the table.


If there are defects on the surface of the casting, it is usually repaired by welding after cutting and cleaning(aluminium oxide sandblasting grit). Generally, the riser is not used, and only the molded outer chilled iron is directly placed on the lower type (used surface), which cooperates with the pouring riser to expand the effective feeding distance of the remaining mouth, improve the feeding efficiency, and cause the sequential solidification of the riser direction(glass bead abrasive). 


The composition of the electrode should ensure that the weld and transition zone are all austenitic. In production, electrodes with higher manganese content or nickel-manganese electrodes with low phosphorus are often used(white aluminium oxide powder). The diameter of the electrode should be small, and the current should be as small and stable as possible to ensure penetration and reduce the width and depth of the heat-affected zone(aluminium oxide sandblasting grit).


When using DC welding, the electrode should be connected to the positive electrode, otherwise the casting will be seriously heated and difficult to penetrate(220 grit aluminum oxide blast media). The surface should be free of rust, oil, etc(aluminium oxide sandblasting grit). The castings should be treated with water toughening first, and no preheating is allowed before welding repairs(aluminum oxide suppliers usa). To sum up, the out-of-box temperature of simple and thin-walled castings should be lower than 400℃.


Hammering at the weld can form compressive stress inside the metal, which can offset the effect of tensile stress to a certain extent and reduce heat(steel shot abrasive). The possibility of cracking. Before welding and repairing the surface defects of the castings, the surface should be cleaned up, and a layer should be polished(aluminium oxide sandblasting grit). Due to the special chemical composition, structure and performance of high manganese steel, it is difficult to weld and repair.


The principle of cutting high manganese steel castings with oxygen-acetylene flame is to minimize the heat-affected zone(aluminium oxide sandblasting grit); the cutting operation is completed quickly at one time(240 grit aluminum oxide), avoiding repeated cutting, and repeated trimming to reduce casting cracks and prevent the renewed precipitation of carbides(aluminium oxide sandblasting). After cutting, the cutting surface shall be polished off with a grinding wheel before heat treatment (the thickness is less than 5mm).


Water immersion castings are mostly used for large-scale high-manganese steel castings(aluminium oxide suppliers south africa). If the cutting can be achieved after slow cooling and then rapid cooling, the cutting quality can be greatly improved. When coating the paint, you can use the shower brush method to coat the large castings, and the small castings use the dip coating method(aluminium oxide sandblasting grit). The best coating thickness depends on the size and complexity of the casting.


The final requirement is that the prepared coating has good spreadability, high strength, and certain air permeability(aluminium oxide blasting media). Generally simple thin-walled parts adopt the principle of simultaneous solidification. It is advisable to use more flat and thin cross-section gates to introduce molten steel evenly, dispersedly and steadily(aluminium oxide sandblasting grit). No risers are provided, but more openings are required on the opposite or side of the inner gate(garnet mesh 30 60). Stomata.


At the same time(aluminium oxide blasting grit), coating thickness is another important factor affecting the quality of castings(aluminium oxide sandblasting grit). The coating thickness is controlled by adjusting the coating concentration, coating times and coating operations. Generally, coating Three times, the thickness is controlled at about 0.5 ~ 3mm, and then dried at 40 ~ 50 ℃(aluminum oxide blast media canada). In addition, when the spacer mesh cannot meet the needs of casting feeding, a cutting riser is used.


In particular, when cutting is carried out in the as cast state, and after cutting, it is heated in the furnace to 1050 ℃ for thermal insulation and water quenching, cracks will also be found at the notch(garnet blasting media). On the one hand, it is due to the effect of thermal stress during heating and water-soluble chilling during heat treatment(aluminium oxide sandblasting grit). In these two cases, when the cutting temperature is below 950 ℃, it shall be cooled as soon as possible.


On the other hand, it is due to serious decarburization of notch surface at high temperature, reduction of manganese content, formation of a large amount of martensite after water quenching, embrittlement of steel properties and crack propagation under stress(120 grit aluminum oxide). The semi closed gating system can not only stop the slag, but also make the liquid steel fill the mold smoothly and reduce the casting defects(aluminium oxide sandblasting grit). The process flow is shown in the figure.


The cutting surface shall be polished with a grinding wheel with a thickness of 4 ~ 5mm to prevent residual cracks(aluminum oxide blast media 60 grit), and the surface layer with a large amount of martensite structure shall be removed by grinding(aluminium oxide sandblasting grit). During cutting, the eutectic with low melting point, such as phosphorus or other low melting point substances, often melts at high temperature and is subjected to tensile stress during cooling after cutting(refractory materials).


As a result, the eutectic weak region between grains is pulled and cracked under stress, so the chemical composition of steel has a significant effect on the formation of cracks in the cutting process(black silicon carbide). The following points should be paid attention to in the cutting of gating and riser and defect welding repair of high manganese steel castings, so as to reduce the occurrence of casting cracks and ensure the quality of castings(aluminium oxide sandblasting grit).


This method is applicable to castings after heat treatment(aluminium oxide sandblasting grit). When cutting as cast high manganese steel castings, thermal cutting can be used. In order to gradually transition the chilling capacity of the cold iron, the outer cold iron is made into a 45 inclined plane with the edge(100 grit aluminum oxide blast media). When cutting the casting riser, it can be immersed in water and the eye part is exposed to prevent the casting body from heating up after heating.


The casting shall be boxed in the red hot state, and the eye opening shall be hot poured at 500 ~ 700 ℃(aluminium oxide sandblasting grit). Thermal cutting during heat treatment(80 grit aluminum oxide). This method is to heat the casting to 500 ~ 700 ℃ for thermal cutting, polish the cutting surface after cutting, and then immediately enter the furnace to continue heating(silicon carbide powder). Compared with the thermal cutting in as cast state, this method can reduce one-time heating process.


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