DE1150264B - Organic suspending agent in the manufacture of molded bodies to be sintered using the slip casting process - Google Patents

Description

Objects made of tungsten, molybdenum, tungsten carbide and other refractory metals and their Connections are mainly made according to the usual powder metallurgy processes, wherein powder of the starting material is pressed into the desired shape at high pressure and the Compact is sintered. Equipment for this process is expensive because of the wide variety of press sizes and shapes required. The forms wear out quickly and need to be replaced frequently. Another disadvantage of manufacturing by Pressing consists in that, due to the flow properties of certain powders during pressing, the manufacturable sizes and shapes are limited. Entangled objects, e.g. B. those with re-entrant angles, external threads, two or more lateral protrusions, etc., can through Presses are cumbersome to manufacture.

There have been other methods of making articles from the heavier ones Tried metals and metal compounds. A well-known and well-known in the ceramic industry the successfully used process is the slip casting process. Ceramic particles collide as a result the nature of their ionic charge in a suspending agent, causing the for the Slurry casting suitable, dispersed state is achieved. With metal powder particles such as tungsten and Molybdenum, on the other hand, does not tend to disperse easily. Continuation of the suspension of the However, metal powder in the slip is necessary to prevent premature settling and, consequently, uneven To prevent wall thickness, however, it was because of the excessive weight of the heavy metal powder particles heretofore difficult, if not impossible, consistently high density articles and satisfactory produce uniform wall thickness. For these reasons, so far was the manufacture unusual shapes made from these metals and their compounds costly or even impossible.

Furthermore, water is usually used as a suspending agent for the particulate matter. As a result the application of these methods is limited to materials that cannot be used in an aqueous environment react.

It is also already known to produce stainless steel powders by means of the slip casting process in US Pat Way to process that from the metal powder, water, a polyvinyl alcohol as organic Suspending agent and ammonium alginate a slip is formed. This slip is in

Organic suspending agent
in the manufacture of to be sintered
Moldings after the slip casting process

Applicant:

Union Carbide Corporation,
New York, NY (V. St. A.)

Representative:

Dr.-Ing. R. v. Kreisler, Dr.-Ing. K. Schönwald

and Dr.-Ing. Th. Meyer, patent attorneys,

Kölnl, Deichmannhaus

Claimed priority:
V. St. v. America, December 27, 1957 (No. 705 475)

Jan Walter Szymaszek, Niagara Falls, Ontario

(Canada),
has been named as the inventor

poured a porous mold and the formed body sintered after demolding. Through this procedure however, neither the problem of the uneven settling of the metal powder particles is solved, another useful instruction is given, such as a suspension in an organic suspending medium can be achieved.

The invention relates to an organic suspending agent in the manufacture of products to be sintered Objects with an intricate shape and high density made from the heavier metals and their compounds by slip casting.

With the help of this suspension medium, hollow moldings with a uniform wall thickness can pass through Slip casting are produced. The suspension agent according to the invention allows metals or Metal compounds that are normally reactive in the presence of water by slip casting to shape.

According to the invention, the suspending agent is non-polar, such as in particular toluene and / or hylene,

309 600/130

Claims (1)

3 4 and it contains a resin, which is a non-oxidizing atmosphere necessary on the sintering. Metal or metal compound powder particles are agile. Hydrogen is suitable, with the exception of many Coating forms. easily in a graphite furnace where argon is preferred The phenomenon that allows the slip or another gas that does not have an oxidizing effect and casting process successful for the production of counter- 5 with which carbon does not react in the furnace, use stands in particular from heavy metals and is det. Applying their connections is based on the fact that _n ■ . ₁ the particles of the metal or the metal compound are coated with a resin and 904 g of tungsten powder with an effective purity of 99.6% in the organic, non-polar suspension and an average particle size can be dispersed as a result, with Slips between 2.0 and 2.2 microns were formed in 90 cm ^{3 of} one that had the properties required for the slip casting process of methylphenylpolysiloxane in xylene solution. in which the resin was present in an amount of 9 g (approx. Suitable are powders with a particle diameter of 1 "/", based on the weight of the tungsten), knife from 1 to 5 microns. The resin can be 15 The solids content of the tungsten exchange slip was up to 1%, based on the weight of the powder, was 90%, the slip density 8.5 g / cm ³ . For this purpose, if the powder was a particle slip, crucibles of 50 and 100 cm ³ fiber diameter of 5 microns were used. If the particle size is between 0.1 and 2 microns with a wall thickness of 2.4 mm and a diameter of between 0.1 and 2 microns, then 4% plaster of paris is cast. The cast and getrock resin, based on the total weight of the powder, 20 neth crucibles were required for 1 hour in a graphite tube, oven at 1900 ⁰ C in an argon atmosphere, all organic resins or silicone resins, the tert. After sintering, the crucibles had a density capable of enveloping the individual metal particles of 18.3 to 18.6 g / cm ³ . The maximum deviation can be used. Methylphenylpolysiloxane in mixture 35 was between 0.35 and 0.75 mm particularly effective in terms of the wall thickness of the individual crucibles. with toluene (CH ₃ C ₆ H ₃ ) and / or xylene (C ₆ H ₄ (GEy ₈ ), the latter serving as an organic remedy. However, Example 2 can also be used any other organosiloxane resin. It was further found that the 906 g of molybdenum powder can be formed with a purity of organosiloxane resin directly in the organic 30 99% and a particle size of less as a solvent by using a 5 micron with 90% of the particles were dispersed in 188 cm ³ hydrolyzable silane, the residue by an organic solution of methylphenylpolysiloxane in xylene, e.g. B. a methyl or ethyl radical, substituted, which contained 40 g of the resin. This formed, together with an amount of water sufficient to form the organic slip with a density of 3.93 g / cm ^{3 of} siloxane resin, in a 35 and a solids content of 85 ° / ». This organic, non-polar suspending agent was put into plaster molds of 50 and will. In the same way, any organic, non-100 cm ³ capacity with a wall thickness of polar liquid in which the resins are soluble can be poured as of 2.4 mm. Subsequently, the tie suspending agents were used. In addition to its gel peptizing effect in a graphite furnace at 1900 ° C. for 1 hour, the silicone resin is also used when sintered in an argon atmosphere. The density of the to increase the strength of the green body. The crucible after sintering was 9.2 g / cm ³ , ie 90%. When the method is carried out, the theoretical density of molybdenum metal is added. The next the solid resin dissolved in the solvent in order to achieve wall thickness of the individual crucibles from above to achieve maximum dispersion. Then the bottom will be a maximum deviation of 0.35 to powder of the metal or metal compound directly 45 0.75 mm. added to the resin-solvent mixture. The above examples serve only for the material content can be between 80 and 98%, while the invention is not limited to tungsten and molybdenum suitable for casting. The inventive act of the slip is retained. The slip is a suspension medium suitable for all metals or then slowly poured into a plaster mold. The gypsum 50 metal compounds and in particular has the pre-suction of the liquid slightly, while the powder part on that metallic materials, the density of which is too small to adhere to the walls of the mold and are high, to make suitable slips from it after progressing there up to to form the desired wall thickness according to the usual method, after the slip build-up. Some of the resin will be able to be processed by the molding process. That in the solvent is transferred into the form, where it is sucked up on the expression »metal compound. The greater part of the resin remains "contains" intermetallic compounds and yet remains attached to the particles. If necessary, additional slurry is added to metalloids, such as carbides, nitrides, borides and silicides, until the required wall thickness is reached, whereupon the excess slurry, such as metal salts or halides, is drained from the mold will. As soon as it turns 60, provided that it has become sufficiently jest in the organic object, it will be insoluble from suspending agent. It can also be removed from the mold and placed in an oven for sintering at room temperature for highly reactive metals that are air-dried in counterrature until they have been handled and are easily oxidized by water. That
Resin that envelops the particles is released during the 65th ! - .., ■. 111, Smtering process decomposes and charred. Sintering takes place at temperatures from 1700 to 1. Organic agent for suspending 2000 ⁰ C, preferably at 1900 ⁰ C. During the metal or metal compound powder particles 5 6 in the production of molded bodies to be sintered 2. Means according to claim 1, characterized in that from such powders after the slip casting draws that silicone resin is used as the resin method, characterized in that that is. Suspending agent is non-polar, such as in particular Toluene and / or xylene, and that in it a resin 5 publications considered: is included, which is based on the metal or metal journal Materials & Methods, May 1956, p. 132 Compound powder particles form a coating. to 134. ® 309 600/130 6.63