The main reason why high alumina balls appears nail grain
Nail grain defect exists in the domestic and foreign products of wear resistant ceramic balls , and presented the larger dimensions, the more grain nail situation. There are lines of high alumina balls nails will appear dregs, wear big problems when used as grinding media. Nail patterns and the emergence of high aluminum balls production process technology systems related. To sum up the following main reasons:
1, the use of raw materials
wear resistant ceramic balls using a phase alumina powder as the main raw material, a phase alumina powder conversion rate directly determines how much product in the nail folds. If a phase conversion rate of less than 92%, which contains a lot of Y phase alumina powder will produce a phase change in the product shrinkage during firing, resulting in the appearance of the nail pattern.
2, the milling process problems
High alumina balls are made of powder slurry is pressure-type spray drying, the slurry viscosity, moisture determines the resulting powder particle size distribution, sphericity, powder bulk density and viscosity index. If the majority of spherical powder is not enough, poor mobility, the presence of spaghetti, closed pores appeared in the press of the semi-finished product. In high alumina balls sintering process because of the pores with the grain boundary will pass, will eventually form China Unicom closed pores, the closed pores in the milling process due to the intensity lower than the surrounding environment, and bending nails pattern.
3, the problem of adhesive
High alumina balls are used in powder molding, in order to improve the half-isostatic pressing and isostatic pressing process semi-finished products and semi-finished products rate intensity, often adding a lot of binder in the formulation. Binder will produce a large number of the product sintering of ash and gas high pressure, can not be smoothly discharged internally generated nail pattern, it should reduce the amount of binder or using no residue after burning additive.
4, the molding pressure problems
When high alumina balls isostatic and semi-isostatic pressing, due to the design pressure of the crushed raw material powder can not achieve complete request internal structure of semi-finished non-dense, resulting in products occur within the nail firing pattern.
5, firing question
When fired at high wear resistant ceramic balls nails eliminate pattern defects is also important to exclude furnace design problems, firing temperature, holding time, heating curve will determine how much the nail folds. High alumina balls presence in the firing process the volatile free water and crystal water, shrink, phase transformation, recrystallization and other complex processes. To this end, in the range of 1000 -1350 ℃, abrupt firing shrinkage in the process, to extend the holding time, while burning zone temperature difference should not exceed 5 ℃, in order to try to avoid firing inconsistencies appear.
1, the use of raw materials
wear resistant ceramic balls using a phase alumina powder as the main raw material, a phase alumina powder conversion rate directly determines how much product in the nail folds. If a phase conversion rate of less than 92%, which contains a lot of Y phase alumina powder will produce a phase change in the product shrinkage during firing, resulting in the appearance of the nail pattern.
2, the milling process problems
High alumina balls are made of powder slurry is pressure-type spray drying, the slurry viscosity, moisture determines the resulting powder particle size distribution, sphericity, powder bulk density and viscosity index. If the majority of spherical powder is not enough, poor mobility, the presence of spaghetti, closed pores appeared in the press of the semi-finished product. In high alumina balls sintering process because of the pores with the grain boundary will pass, will eventually form China Unicom closed pores, the closed pores in the milling process due to the intensity lower than the surrounding environment, and bending nails pattern.
3, the problem of adhesive
High alumina balls are used in powder molding, in order to improve the half-isostatic pressing and isostatic pressing process semi-finished products and semi-finished products rate intensity, often adding a lot of binder in the formulation. Binder will produce a large number of the product sintering of ash and gas high pressure, can not be smoothly discharged internally generated nail pattern, it should reduce the amount of binder or using no residue after burning additive.
4, the molding pressure problems
When high alumina balls isostatic and semi-isostatic pressing, due to the design pressure of the crushed raw material powder can not achieve complete request internal structure of semi-finished non-dense, resulting in products occur within the nail firing pattern.
5, firing question
When fired at high wear resistant ceramic balls nails eliminate pattern defects is also important to exclude furnace design problems, firing temperature, holding time, heating curve will determine how much the nail folds. High alumina balls presence in the firing process the volatile free water and crystal water, shrink, phase transformation, recrystallization and other complex processes. To this end, in the range of 1000 -1350 ℃, abrupt firing shrinkage in the process, to extend the holding time, while burning zone temperature difference should not exceed 5 ℃, in order to try to avoid firing inconsistencies appear.
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