Molding sand for amorphous casting and its manufacturing method

Abstract

The invention discloses molding sand for amorphous-state casting. The molding sand is formed by mixing crude sand with a binding agent; the crude sand comprises the following components in percentageby weight: 30-52% of SiO2, 15-20% of Al2O3, 15-30% of ZrO2, 0-3% of K2O, 2-10% of Na2O, K2O+Na2O less than 12%, and 1-5% of Ca2O; and the average particle size of the crude sand is within 0.03-2 mm. In the molding sand for casting, the crude sand thereof is an amorphous-state solid, is free of cleavage planes during crushing, and is low in expansion coefficient and excellent in thermochemical stability.

Description

technical field [0001] The invention relates to molding sand for casting, in particular to molding sand for amorphous casting and a manufacturing method thereof, belonging to the technical field of casting materials. Background technique [0002] At present, the most commonly used casting sand is quartz sand. Quartz sand is commonly known as silica sand. The main component is silicon dioxide. Generally, the sand consumption per ton of castings requires more than one ton of molding sand. The relationship is very important. The cost of molding and core making accounts for half of the cost of castings. Among the common casting defects, defects such as casting welding repair defects, shovel cleaning work, sand holes, pores, peeling, and water leakage are basically caused by core making factors. The waste rate caused by the quality of casting sand is about 6% to 10%. 60% of casting waste is caused by molding and core-making factors. If the quality of foundry sand is not good, it ...

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Problems solved by technology

[0002] At present, the most commonly used casting sand is quartz sand. Quartz sand is commonly known as silica sand. The main component is silicon dioxide. Generally, the sand consumption per ton of castings requires more than one ton of molding sand. The relationship is very important. The cost of molding and core making accounts for half of the cost of castings. Among the common casting defects, defects such as casting welding repair defects, shovel cleaning work, sand holes, pores, peeling, and water leakage are basically caused by core making factors. The waste rate caused by the quality of casting sand is about 6% ~ 10%. 60% of casting waste is caused by molding and core making factors. If the quality of casting sand is not good, it will cause a lot of casting waste

For quartz sand for casting, the first disadvantage is that the expansion coefficient is large, and its expansion coefficient is 5.3-5.8*10 -7 ppm / °C, resulting in low precision castings; second, because natural quartz sand is a crystalline crystal, due to the anisotropy of the crystal, crystal cleavage will occur when it is broken, that is, it will break along the cleavage plane of the quartz crystal, resulting in broken The angle coefficient of the final quartz particles (the detection unit of the average grain shape of the sand in the sand test, the smaller the angle coefficient, the closer the sand shape is to a circle) is relatively large. Generally, the angle coefficient of the molding sand is required to be below 1.3, but untreated in actual production The angle coefficient of quartz sand is difficult to meet this standard. If the angle coefficient is too large, the fluidity of the molding sand will be poor, and the cracking performance will decrease, which is not conducive to the subsequent processing of castings. Moreover, due to the large specific surface area, too much auxiliary material is added during the sand mixing process. , which not only increases the manufacturing cost, but also reduces the physical properties of the molding sand, reduces the air permeability of the molding sand, increases the gas generation, and causes defects such as casting pores; thirdly, because the melting point of quartz sand is about 1750 degrees Celsius, and it does not have compressibility When using a lower casting temperature, the yield of the molding sand is not good, and the casting is prone to internal stress or cracking. The tighter the sand, the worse the yield. Sometimes adding sawdust to the sand can improve the yield, but Adding too many auxiliary additives further reduces the quality controllability of foundry sand and increases the risk of product quality

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