DE976392C - Process for the production of metal carbides - Google Patents

Description

Process for Making Metal Carbides The invention relates to a process for the production of simple or mixed metal carbides from carbon and metal hydride or from carbon, metal hydride and metal.

It is of decisive importance for the later use of the metal carbides Meaning that they are not only always in a precisely defined composition, but always with consistently good physical properties. Adhering to these conditions., Is not or only under Difficulties possible.

A method for producing metal carbides is proposed which is the mixing of metal hydride and carbon into a completely homogeneous one Comprises mass, the incomplete combustion of gases or carbon can originate from organic liquids. The powdery mass obtained is in this process to compacts compressed, which in a graphite crucible in a cold oven must first be used. Depending on the nature of the hydride, the Temperature rise slowly, this more or less quickly in metal and hydrogen decomposes to form a porous mass. The temperature is then increased until the carbon starts to react with the metal. As a result of Porosity, which the mass during of heating has assumed it happens that the reaction does not go to completion. Therefore one submits the product in a second step, consisting of kneading, drying and compression and burning, thus obtaining a dense compact of pure carbide. He owns however, the disadvantage that it is even with light impacts or low vibrations falls apart. Such masses generally consist of a mixture of Metal carbides, unreacted carbon and metal. It has been shown that this disadvantage can be eliminated with the method according to the invention.

The process of making simple or mixed metal carbides in the form of a fine powder of great purity from a homogeneous mixture of Carbon and metal hydride or carbon, metal hydride and metal, compression the mass and heating it at a low temperature and for such a short time Time that the pressed part does not bake together in such a way that the reaction product has to be ground is required, according to the invention, that finely divided, previously in carbon annealed in a hydrogen atmosphere is used and the compressed The mixture is heated to a temperature of 2000 ° to 200 ° C.

The product thus obtained is ground and recompressed before Its reheating proved to be advantageous in particularly difficult cases.

The annealing of carbon in a hydrogen atmosphere and the like the repetition of a grinding, compressing and heating process is among others Circumstances and known for other purposes. To this extent is used for these measures in itself no legal protection is claimed.

The invention is explained in detail below using a few exemplary embodiments explained which without application of the invention would not be a satisfactory one with certainty Would lead to success.

Mix zooo g of titanium hydride, practically of the formula TiH2 (the The hydrides of niobium and titanium that the industry is currently making actually have a basic composition corresponding to the formulas HNb and H.Ti), and 243 g ash-free lamp soot, previously in hydrogen at a temperature of about 80o ° C has been annealed with each other. This mixture is for example in a small pan mill; how it is used for processing molding sand, after adding just enough gasoline to run a To obtain a mass of the consistency of a paste.

The excess gasoline is heated to around zoo ° C in a Removed hydrogen atmosphere. The powder then becomes conical, truncated pellets each of 20 g weight compressed under a pressure of 20 kg / mm2. The compacts will then placed in a graphite crucible and in a furnace with graphite resistance, which must be cold at the beginning of the work process, heats up, creating a hydrogen atnosphere forms. Hydrogen is released as soon as the temperature has reached 50o ° C, and that Leakage of hydrogen occurs particularly strongly between goo and iooo'C. Man the heating continues until a temperature of 200 ° C is reached, which is 50 Sustains for minutes. After cooling, a disjointed one is obtained Mass, which you consecutively the process steps of kneading (two hours in the presence of gasoline), drying, pressing and heating for 50 minutes exposes at z100 ° C. An apparently dense block of titanium carbide is obtained, the but falls apart by a few blows and is easily converted into a fine powder can be. The carbides of zirconium, hafnium, Thorium, niobium and tantalum are produced - being one of the hydrides of these Metals ZrH2, HfH2, ThH4, NbH and TaH run out.

The formula for niobium hydride is in the "Handbook of -für and Physic", 30th year, 1948, p. Q: 08, and in a treatise by Paul Pascal in "Mineral-Chernie", Vol. IV, p. 40. In the last-mentioned treatise, on the pages 4,72 and q.73_ of the same volume pointed out the difficulties involved in the Trying to determine the exact formula of the tantalum hydride due to its easy absorption of the hydrogen arise through the metal. The extensive analogy of properties of tantalum and niobium on the one hand and the formation of technical hydrides on the other has led to the use of the formula HTa as the most suitable.

To z. B. produce the -Doppelcarbid of titanium and tungsten having about 2o0 / 9 titanium carbide (TiC) and 8o11 / 9 tungsten carbide (WC), to set -a mixture of 164.7 g of titanium hydride, 751 9 _ metallic tungsten and carbon 89,36g after the latter had previously been annealed in a hydrogen atmosphere at around 80o ° C. The mixture is brought to the consistency of a thick paste with gasoline and kneaded for 2 hours. After kneading, the mass is dried, the powder obtained is compressed and the pellets produced are heated very slowly in the oven, which must be cold at the beginning of the process. It comes to the surprising finding that the hydrogen is released slowly enough to preserve the compact such cohesion that when the temperature is increased to 2ooo ° C and held for 50 minutes, the complete connection of the metals with the Carbon is going on.

It is sufficient to grind the double carbide thus obtained, which is very much a short time is going on, it is replaced by a binding metal, such as B. cobalt, at a Wrap a dosage of 5.50 / a, shape and sinter the desired objects, these operations can be carried out sequentially or simultaneously in order to so to get welding platelets for cutting tools whose quality z. B. by the unprecedented number of machined without regrinding Share is marked.

Claims (2)

PATENT CLAIMS: 1. Process for the manufacture of simple or mixed Metal carbides in the form of a fine powder of great purity from a homogeneous Mixture of carbon and metal hydride or of carbon, metal hydride and Metal by compressing the mass and heating the pellets, characterized in that finely divided carbon previously annealed in a hydrogen atmosphere used and the compressed mixture to temperatures of about 2ooo to 2loo ° C is heated. 2. The method according to claim I, characterized in that the compressed, sintered mixture is finely ground, compressed again and then heated again. Publications considered: Swiss Patent No. 159719; . USA. Patent Nos 2,163,224, 2,287,771; Chemisches Zentralblatt, 1939 / I, p. 2473 (referred to in Russian patent specification No. 53 592) "Metals and Alloys", 1938, pp. 179 to 181; "Powder Metallurgy", 1942, p. 150; Hönigschmid: "Karbide und Silicide", 1914, p.141. Older patents considered: German Patent No. 858547.