As is well known [1][2][3][4], the isostatic method of pressing is one of the prospective methods in the production of refractories. The authors*of the present article developed a mold for making crucibles 150 mm high and 220 mm in diameter by the isostatic method using a "free matrix" scheme. The mold is shown in Fig. 1. It consists of a rigid matrix-ring 1, fitted on a thread in a flange 2 placed on the columns 3, and spring loaded on the axle of the press mold with springs 4. The external rigid-plunger 5 is connected with the upper plate 6. The internal elastically deformable plunger (press buffer) 7 made of polyurethane is fitted to the rigid cylindrical table-pusher 8 connected by means of a shaft 9 and an ejector 10 with the press ejector 11. The annular ejector 12 is installed concentrically on the table-pusher 8 on a cross piece 13, connected with a locking device 14. Two electromechanical vibrators 15 of the type PV-66 are fitted to the flange 2, and the intermediate plate 16 --to the bottom plate 17. The regulating supports 18 are placed on the upper plate 6.
Earlier [1][2][3] there was developed and approved a mold for production by quasiisostatic pressing of parts in the form of crucibles with a height of up to 320 mm, an outer diameter of 150 mm, and a wall thickness of 15-18 mm.In contrast to a mold [3] with internal compression as the result of deformation of the elastic punch in the mold, that proposed by the authors of this article causes external compression of the powder being pressed by an elastically deformed die.The design of the mold is as follows.On the lower plate 1 (Fig. i) is located the rigid (inner) punch 2, which has the capability of axial movement with the help of the push rod 3 in the metal holder 4 fastened by the flange 5 in the guide columns 6 and spring loaded in the axial direction.Inside the holder 4 is located the elastic polyurethane die 7 tightly in contact on the outer surface with the inner surface of the holder.On its lower face the die is located on the shoulder of the punch and on its face during pressing presses the rigid punch 8 fastened to the upper plate 9. The interchangeable elastic polyurethane insert i0 fastened in the bore of the punch 8 is used for forming the outer surface of the bottom of the part during pressing.The lower plate 1 is fastened to the table of the press and the upper plate 9 to the slide block.Normally in isostatic pressing the powder is subjected to preliminary vibropacking [4][5][6]. In this case type IV-66 unbalanced vibrators fastened to the flange 5 are used for preliminary packing of the powder to be pressed.The vibrators transmit to the holder 4 together with the polyurethane die 7 harmonic oscillations in the axial direction.Damping of these oscillations from below is provided by springs and from above by rubber packings. The parameters of vibration are selected experimentally in relation to the properties of the powder being pressed.In pressing of parts of powders of corundum-zircon composition with grain sizes of corundum of 0.1-0.63 mm and of zircon of less than 0.i mm with a binder in the form of a solution of K-9 silicoorganic resin in acetone [7] in a quantity of 4-7%, the vibration parameters were rate of vibration 20,000 oscillations/min, amplitude 0.5 mm, and length of vibration 30-60 sec.The mold operates in the following manner.With the press slide block raised into the upper position, the powder is poured into the gap between the surface of the punch 2 and the inner surface of the die 7. The thickness of the layer of powder poured on the upper face of the punch 2 is selected experimentally based on the properties of the powder being pressed. The poured powder is packed by the vibrator.Then the vibrators are turned off and movement of the slide block downward is started.After contact of the faces of the punch 8 and the die 7 gradual comp&ction of the side surface of the part being pressed occurs as the result of elastic deformation in the radial direction (from the periphery to the axis) of the die, which is compressed from the side of the faces by the pressure of the press. Simultane...
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