Plastic and nonmetallic article shaping or treating: processes – Including step of generating heat by friction
Patent
1989-07-05
1991-09-10
Derrington, James
Plastic and nonmetallic article shaping or treating: processes
Including step of generating heat by friction
264517, C04B 3576
Patent
active
050471856
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for producing moldings in the form of composite bodies, which include ceramic material, fired after a molding operation, and a reinforcement embedded in the ceramic material, the strength of which is greater than the strength of the ceramic material.
The German patent 440,745 describes a method for the production of moldings using a reinforcement formed by metal fabric, on which a ceramic material in an unfired paste form is spread. A disadvantage of this method is that such a ceramic paste is only able to penetrate a wire fabric with a comparatively coarse mesh. The fabric, thus, has to be very coarse and is not able to take on every desired fine configuration. In many cases it is thus not possible to provide the supporting skeleton with a geometry substantially adapted to the geometry of the molding and with a density which is properly related to the forces to be resisted. The overall strength which is obtainable in the known system is therefore limited. A further factor is that the wire of the metal fabric is melted during firing and then solidifies again. This involves changes in structure, which often lead to a loss in strength. Apart from this, the ceramic paste spread on the fabric is not able to be applied very densely so that there is an imperfect bonding with the support skeleton and this in turn means that the overall strength obtainable is also impaired. At the same time, in the method disclosured by the cited prior art there is also a lack of trueness. This is also due to the fact that the ceramic paste may be not be applied very densely so that during firing there is a considerable shrinkage. This disadvantage is made even more significant by the fact that the metal fabric forming the reinforcement is also changed in size by the change in structure due to firing. Apart from this the spreading of the ceramic paste is practically a modeling operation with which it is in any case not possible to obtain any great accuracy to size or trueness. A further shortcoming is to be seen in the fact that owing to the use of a ceramic paste the unfired blanks are insufficient in strength and are thus difficult to transport and therefore, there is a further reason for failure to keep to the desired dimensions.
In a further process as proposed in the German patent 1,181,114 for the production of refractory bricks, there is admittedly the use of pulverulent ceramic material, which is incorporated in a molding cavity containing the reinforcement in the form of sheet metal parts which, during the introduction of the ceramic material, practically have the effect of baffles so that it is not possible to fluidize the pulverulent ceramic material and to introduce it into the mold cavity. This is because the sheet metal parts forming the reinforcement would cause an excessive deflection and retardation. The ceramic material is accordingly only poured into the mold, cavity. In the case of complex molds as occur less in the case of refractory bricks and are more likely in the case of the production of parts of machines, there would thus be the danger of the mold cavity not being completely filled and the consequence of this would be a high reject quota. A further factor is that the metallic plates forming the reinforcement are only able to conform to a complicated configuration to an insufficient extent so that, in the case of complicated forms or molds, it would only be possible to reinforce the core part and not the marginal zones near to the surface. Apart from this it is to be assumed that the pieces of metal sheet used in this case would also melt during the firing operation so that there would be the same resultant disadvantages as regards to strength and loss of accuracy. This known method is thus quite unsuited to the production of machine components.
In the case of a further method as proposed in the German patent 2,048,358 of the initially mentioned type the reinforcement consists exclusively of short metal fibers, which have the basic ceramic material mixed with them even pr
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Patent Abstract of Japan, vol. 7, No. 203 (M-241) (1348) Sep. 8, 1983.
Derrington James
Schindler Edwin D.
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