Layer formation problem of white corundum fine-grained abrasives
Release date: 2019-08-19 Browse times: Article source: Henan Ruishi Group
Introduction: White corundum is a relatively common abrasive in the abrasive market. It is made from industrial alumina powder and smelted in an arc at a high temperature above 2000 degrees. The main chemical composition of white corundum sand is AL2O3
White corundum is a relatively common abrasive in the abrasive market. It is made from industrial alumina powder and smelted in an arc at a high temperature above 2000 degrees. The main chemical composition of white corundum sand is AL2O3, whose content is 98.65% -99.37%, and it also contains a small amount of Fe, Si, Ti and so on. White corundum is suitable for the manufacture of ceramics, resin-consolidated abrasives, grinding, polishing, sandblasting, precision casting, etc., and can also be used to make high-grade refractory materials. There are many properties of white corundum such as abrasion resistance; brittleness; toughness; permanent corrosion resistance; reduced dust; impact resistance; not afraid of fire; metal aggregates can also be antistatic; etc. Today, this article mainly introduces the fine grain abrasives Layer formation problems during forming.
White corundum fine-grained products are composed of fine particles. The fine particles have a large surface, and the particles contact each other more, so the hardness is higher. When the hardness is the same, the porosity is large. The large contact surface also relatively increases the forming pressure. Coarse particles have larger pores, while fine particles have smaller pores.
It is best to use mixed particle sizes for the manufacture of high-density products, so that the proportion of different particles can be made into products with high filling density and low porosity. Strict control of the particle size range can be considered for manufacturing low porosity products.
Reasons for the formation of fine-grained products
1. Pressing fast during molding: the gas in the molding material does not run out, both sides have been compacted and concentrated in the middle to form an air layer. After the external pressure is cancelled, the gas expands into an intermediate layer.
2. Aftereffect of elasticity: Under high pressure, the blank has a high elastic expansion and contraction effect. The closer the particle size is, the closer the contact between particles is, the smaller this kind of stress transmission changes. In the pressing, double-sided pressing is used, and the intermediate layer of the product is the weakest. The friction force is different from upper to lower, and the elasticity is different. Therefore, layer cracks occur under the effect of elastic stress.
3. Moisture concentration: Moisture moves from the pressure side downwards. The double-sided pressure causes moisture concentration in the middle and lower parts, which reduces the strength, so it also causes layer waste. Even if no cracks occur after molding, cracks may occur during firing. Therefore, if it can be turned over to dry, it is more reasonable.
4. The mold sleeve becomes larger when subjected to high pressure, and shrinks when not pressurized, causing the middle layer to crack and bulge up and down.
Fine-grained products are almost bound to produce layer waste under high pressure. Therefore, it is especially necessary to find a new molding method to avoid layer formation.
◎ Press slowly to make the gas run out.
◎ It is maintained under the prescribed pressure for a certain period of time, so that the profile can be fully moved, so that the density is uniform, the strength is uniform, and the elastic stress is eased to eliminate the stress aftereffect.
◎ Vacuum forming. Or use vibration, pressure reduction and other methods.
◎ Pouring or plastic molding.
◎ Reduce the pressure and increase the maintenance time when forming the semi-dry material.
◎ It adopts dry material molding, and the adhesive uses adhesives. After bonding, the particle surface is covered with a layer of adhesive film. Under normal circumstances, the particles do not cause cementation and agglomeration, and when pressed, the film is in close contact with the film and cemented. Or use thermoplastic materials to form a wrapping film, and then mold. When hot air is passed into the mold, plastic cement such as paraffin wax and asphalt is produced. Dry material forming can make the weighing process that is not easy to mechanize adopt fixed volume weighing. The dry material is easy to disperse and has good fluidity. It is also beneficial to eliminate imbalance.
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