In the process of producing refractory balls, a hydroforming method is usually used. The following is an introduction to the press forming method and some suggestions for equipment selection.
1. The press forming method is the most used forming method in the production of refractory balls. The method uses a ball press and a steel die to compress the formulated refractory ball material into a sphere. Since general machine forming refers to a semi-dry material forming method having a water content of 4% to 9%, it is also called semi-dry molding. The equipment commonly used in this method includes a friction brick press, a lever press, and a hydraulic press.
2. The press forming process is essentially a process in which the particles in the ball are densely packed and the air is discharged to form a dense sphere. The machine-formed refractory ball has the advantages of high density, high strength, small shrinkage and shrinkage, and easy control of the size of the refractory ball. Therefore, this method plays a major role in the production of refractory balls.
3. In order to obtain a dense sphere during press forming, sufficient pressure must be given to the pellet. The pressure should be such that it can overcome the internal friction between the pellets, overcome the external friction between the pellet and the mold wall, and overcome the pressure distribution caused by the moisture of the pellet, the particles and the uneven filling in the mold. Uniformity.
The proportional relationship between the three depends on the dispersion of the pellets, the composition of the pellets, the moisture of the pellets, the size and shape of the spheres, and the like. Although there are several theoretical formulas for calculating the relationship between pressure and sphere densification, such as the change of the spherical pores with the logarithm of the pressure, the test method is usually used to determine the pressure per unit area of the sphere, and the pressure is determined accordingly. The total pressure that the brick machine should have.
The requirements of the ball forming machine for the ball material should have a certain fluctuation range except for the moisture, and there are certain requirements for the particle size. For example, there should be a reasonable particle size ratio, and the bulk density should be as large as possible. Generally, the critical particle size is 3 to 5 mm, and the fine powder content of less than 0. 088 mm should be in the range of 35% to 45%.
The most common defects of machine-formed refractory balls are spallation and layer density. A spallation is a lamellar crack formed perpendicular to the direction of pressurization formed during pressurization. Excessive moisture in the ball, excessive fines, too little binder and excessive pressure can lead to spalling.
Therefore, these parameters must be controlled in production. The layer density phenomenon, that is, the density of the refractory balls after molding, is reversed in the direction of pressurization. The unidirectionally pressurized refractory ball from the top is generally dense and sparse, and the same horizontal plane is medium-density and sparse. This is due to the friction between the ball particles and the friction between the ball and the die wall. The method of reducing the external friction by double-sided pressing and lubricating the four walls of the mold can reduce the phenomenon and reduce the porosity of the sphere.
The selection of molding equipment should be considered comprehensively according to the quality requirements, size and production quantity of the refractory ball. Generally, the refractory ball for the heating furnace or the product with simple shape, large quantity and general quality requirements can be selected with the lever ball press with high production efficiency; the refractory ball with higher quality requirement can adopt the friction with the nominal pressure not lower than 2000K•N. Pressure ball machine.