DE862723C - Process for the production of dense bodies from aluminum oxide - Google Patents

Description

Process for the production of dense bodies from aluminum oxide Beim Manufacture of dense bodies from aluminum oxide by pressing powdery Aluminum oxide and subsequent sintering of the pressed body shows the disadvantage, that the very hard aluminum oxide powder attacks the pressing tools extremely strongly. In order to avoid this disadvantage, one already has recourse to pressing tools made of hard metal taken, which are difficult and can only be produced at great cost.

The aim of the invention has been previously used in the manufacture of dense bodies from aluminum oxide, there is always a strong risk of wear and tear on common pressing tools from common metals of the trade largely to be avoided. This is achieved if, according to the invention, the powdery aluminum oxide is powdery or bloomed Aluminum (aluminum bronze) incorporated in amounts of 0.05 to 20% and the pressed body in a manner known per se by firing in an oxidizing atmosphere, e.g. B. air, is sintered. During the sintering process, the added aluminum turns into aluminum oxide transformed so that the finished product consists entirely of aluminum oxide. By the addition of aluminum during the pressing process has been found to be the The pressing or molding jaws of the pressing tools are significantly spared. As shown Has, A few percent suffice, in some cases only Fractions of a single percent of the aluminum added to the purpose of the To achieve protection of the pressing tools.

When using lighter aluminum oxide, it is advisable to use a to use a larger percentage of powdered or flaky aluminum, since the greater loss of the lighter aluminum oxide is compensated for by the Volume increase with the oxidation of the added aluminum.

Instead of adding aluminum to the starting powder, it is also possible; the aluminum is only incorporated into the aluminum oxide during the pressing process. It is sufficient for this purpose, the pressing or molding jaws of the pressing tools with an aluminum slurry to be coated, as a larger proportion of the aluminum then during the pressing process into the Pores of the pressed body is pressed.

A very special advantage and a particularly extensive avoidance the wear and tear of the pressing tools results if the starting material is not powdery Aluminum oxide, but such an aluminum compound is taken that at lesser Hardness as aluminum oxide is transformed into aluminum oxide by decomposition during sintering, such as B. aluminum oxalate. With regard to the strong change in volume of the oxalate in the case of decomposition, it is advisable to use particularly high percentages in this case to add aluminum to the starting material. Also a partial replacement of the aluminum oxide through _ aluminum oxalate can be advantageous under certain circumstances.

Claims (3)

PATENT CLAIMS: i. Process for the production of dense bodies from aluminum oxide by pressing powdery oxide and subsequent sintering of the pressed body, characterized in that the powdery aluminum oxide incorporates powdery or flaky aluminum (aluminum bronze) in amounts of 0.05 to 20 °% and the pressed body in .an is sintered in a known manner by firing in an oxidizing atmosphere. 2. The method according to claim i, characterized in that that only when the aluminum oxide powder is pressed into the outer layers of the pressed body Aluminum is introduced, e.g. B. by covering the pressing or molding jaws Pressing tools with aluminum. 3. The method according to claim i and 2, characterized in that that instead of powdery aluminum oxide one when sintering in aluminum oxide passing aluminum compound of lower hardness, e.g. B. aluminum oxalate is used will. Referred publications: German Patent No. 68o, 648.