DE3045838C2 - Process for the production of metallic semi-finished products - Google Patents

Description

55

The invention relates to a method of manufacture metallic semi-finished product, in which a Metal powder is hot isostatically pressed.

According to the state of the art, metal objects are used made by powder metallurgy essentially in such a way that a vacuum-tight closed Container that holds the material for the object to be manufactured with the interposition of a secondary Pressure medium encloses, in the evacuated state after heating to the compression temperature, an isostatic Is subjected to hot pressing. The object to be produced can already be a prefabricated one Pre-pressed bodies are present or, according to DE-PS 22 00 066, by one in the interior of a non-vacuum-tight closable form filled with the shape of the object to be manufactured Powder batch are hot isostatically pressed. The disadvantage is that a secondary pressure medium is required for this in powder form for isostatic pressure transfer to the metal powder actually to be pressed bring about. The secondary pressure medium compresses to become more compact as the pressure increases ceramic material, so that with increasing compression of the secondary pressure medium finally the pressure transfer to the metal powder actually to be compacted becomes weaker because the compacted Ceramic supports itself In addition, it is known that poured and compacted by knocking Ceramic powder locally can have very different densities than the intended uniform counteract isostatic pressure transfer differently.

These disadvantages are avoided if you use metallic pre-contoured capsules into which the powder is filled, and then the powder and the capsule are ^{degassed at pressures of ΙΟ- 4} mbar and temperatures up to 450 " Powder compacted using hot isostatic pressing, which is known in principle.As a rule, however, the pre-contoured capsules can only be produced in simple geometric shapes, so that the process described here has a limit in terms of the wealth of shapes, since the production of unusual geometric shapes is in most cases uneconomical is.

It is the object of the invention to provide a method of the type mentioned at the outset, which is carried out according to the known disadvantages of the prior art bypasses and an easy-to-use, as economical as possible Manufacture of metallic semi-finished products in a wide variety of geometric shapes and sizes allowed.

The object on which the invention is based is achieved by the method characterized in claim 1 solved, which makes it possible to design any, in particular geometrically complex shape. The models are coated in layers with hardenable ceramic and backfilled to the extent that a large, in its outer dimensions simple geometric body arises, compared to the previous one pre-contoured capsules used has several advantages. This ceramic body can easily be used for cleaning placed in a metal container for isostatic pressing, with the entire ceramic body is tightly enclosed, on the other hand, the isostatic pressure transfer to the one located in the ceramic body Metal powder can be made evenly, as this also affects the pressure conditions in the ceramic body influence can be exerted through its shaping.

Another advantage associated with its external shape is that the can be easily stored and stacked Ceramic body. After all, the sheet metal capsule with a welded-in ceramic body is better than before evacuable.

An advantageous mixture of the outer casing consists of 50 to 90% by weight chamotte, 10 to 50% by weight of aluminum oxide and 1 to 15% by weight Water glass, with chamotte of grain size 0.5 to

1.25 mm and aluminum oxide with a grain size of <0.1 mm can be used.

Advantageously, however, ceramics can also be used which plasticize at the process temperature. Such a ceramic consists of a mixture of up to 10% by weight MgO, 1 to 12% by weight CaO, up to 16% by weight Na ₂ O, up to 8% by weight K ₂ O, up to 40% by weight B ₂ O _3, 1 wt .-% Al oh 20 ₂ O _3, balance SiO _2. A mixture of 3 to _{4% by weight of MgO 1,} 6 to 7% by weight of CaO, 3 to 4% by weight of Na ₂ O, 2 to 3% by weight of K _2, 0.8 to 9% by weight, is preferably used. - ° / o B ₂ O ₃ , 15 to 16% by weight Al ₂ O. The remainder SiO ₂ . The mixtures are made into a paste with water glass and cured with CO ₂ and finally fired at temperatures of about 70o C ^0.

According to a further development of the invention, several models are wrapped in such a way that only a single one Molded body is created.

According to a further embodiment of the invention, the model consists of wax and / or another organic filler and is melted out when heated or burned or gasified without residue

The metal or alloy powder is in a known manner in the vibrating ceramic body filled so that it is extremely dense. h. under E: range the optimal tap density is filled.

The invention is to be explained in more detail below on the basis of exemplary embodiments. A wax model, in which the shrinkage allowances of the later powder-metallurgically manufactured component are taken into account and which is additionally provided with a powder filling nozzle, is coated in layers with ceramic of different densities the quality of the subsequent component surface depends. After the first ceramic layers have been applied, the model is surrounded by a mixture of fireclay and water glass in a molding box. The mixed dough-like mass consists of 75% fireclay with a grain size of 0.5 to 1.25 mm and 25% aluminum oxide with a grain size of <0.1 mm, to which 15% of the weight of the premixed ceramic waterglass is added and which is mixed intensively. The chamotte-waterglass mixture is then _{cured with CO 2} and the resulting mold block is dewaxed in the autoclave after it has been removed from the mold box and finally fired in the kiln at a temperature of approx. 1000 ° C. The firing process removes all volatile constituents expelled from the mass and a body of uniform density is created. The mixtures used create a very porous, gas-permeable ceramic body. The ceramic body is simple because of its external structure

ίο easy to stack, largely against mechanical influences stable and, if necessary, easy to work with by sawing, drilling or similar. For the production of the metallic In the semi-finished product, the ceramic body 1 shown in the figure is inserted into a metal container 2 and its cavity 3 with the powder to be compacted, in the present case powder of the titanium alloy TiAl6V4, filled This is preferably done on a vibration device The rigidity of the ceramic body 1 supports the filling with powder d '; n vibrating process intensively, since the compact ceramic body makes the Vibration is transmitted directly to the metal powder. After filling the cavity 3 becomes d "filler neck closed with a metal plug and the metal container 2 welded shut and via a suction nozzle 4 evacuated The metal container 2 is now ready to be brought into a hot isostatic pressing plant, where it is compressed at the pressing parameters necessary for the filled metal powder. After the hot isostatic Pressing the metal container 2 is separated and the ceramic coating from the finished metallic semi-finished product removed.

Another embodiment of the invention is based on a plastic model that is encased in a mold frame with a mixture of chamotte and Al ₂ O ₃ , approximately in a ratio of 1: 1, with the addition of 15% by weight of water glass and hardened _{with CO 2.} The mold block is then removed from the frame and placed in a kiln. In the furnace, a temperature of 100O ⁰ C is then set at which the plastic model burns residue-free and the remaining body is hardened. With regard to the production of the metallic semifinished product, the procedure was then carried out in accordance with the exemplary embodiment described above.

1 sheet of drawings

Claims (8)

Patent claims: l. Process for the production of metallic semifinished product, in which a metal powder filled into an internally pre-contoured monolithic ceramic housing with a geometrically simple outer shape is hot isostatically pressed, characterized in that a model with a powder filler neck is provided in layers with a powder filler neck taking into account the contours of the metallic semifinished product to be produced, taking into account the shrinkage Curable ceramic is encased in such a way that a geometrically simple outer shape is created, and with simultaneous removal of the model material is continuously ^{heated to 700 to 1000 0} C, then the finished ceramic body is tightly filled with metal powder and welded into a metal container, which is then evacuated and then hot isostatic is pressed. 2. The method according to claim 1, characterized in that that ceramic layers of different densities are applied to the model. 3. The method according to claim 1 or 2, characterized in that several models to one single ceramic body are encased. 4. The method according to any one of claims 1 to 3, characterized in that the model (s) melted out of wax and / or another organic filler during heating or is or will be gassed without residue. 5. The method according to any one of claims 1 to 3, characterized in that a mixture of 50 up to 90% by weight chamotte, 10 to 50% by weight Alumina and '. up to 15% by weight of water glass as outer coating is applied. 6. Application of the procedure according to one of the Claims I to 4 on a ceramic mixture with chamotte of grain size 0.5 to 1.25 mm and with Alumina grain size <0.1 mm. 7. Application of the method according to one of claims 1 to 5 to a ceramic mixture made of up to 10% by weight of MgO and made into a paste with water glass. 1 to 12% by weight CaO, up to 16% by weight Na ₇ O, up to 8% by weight K ₂ O, up to 40 _{% by weight B 2} O ₃ , 10 to 20% by weight. -% Al ₂ O ₃ , remainder SiO ₂ . 8. Use according to claim 7 to a ceramic mixture of 3 to 4 wt .-% MgO, 6 to 7 wt .-% CaO. 3 to 4% by weight Na ₂ O, 2 to 3% by weight K ₂ O, 8 to 9% by weight B ₂ Oj. 15 to 16% by weight Al ₂ O ₅ , the remainder SiO ₂ .