US3515524A - Sintered carbide compound - Google Patents

Description

United States Patent O 3,515,524 SINTERED CARBIDE COMPOUND Jini'ich Grambal, Brno, Czechoslovakia, assignor to Zavody Jana Svermy, narodni podnik, Brno, Czechoslovakia No Drawing. Filed July 18, 1967, Ser. No. 654,057 Int. Cl. 1322f 7/06 US. Cl. 29182.7 2 Claims ABSTRACT OF THE DISCLOSURE Composition of a sintered carbide composite using an admixture of phosporus and possibly also of boron resulting in a reduction of the temperature for sintering the composite by about 300 to 400 C. A grinding tool comprising diamond particles bonded by said sintered carbide compound.

BACKGROUND OF THE INVENTION Sintered carbide is substantially a powder mixture of at east one of the metals having an elevated melting point and of at least one of the ferrous metals, which at a temperature close to the melting point of the ferrous metal sinters and forms a stable material suitable, for example, for the manufacture of tools for working of metals. The product receives in the course of the sintering process its proper shape and dimensions. Carbides of tungsten, titanium, tantalum and similar materials are examples of carbides of metals which have elevated melting points. The ferrous metals act as the sintering agent, i.e. as means enabling a sintering of the mixture at temperatures substantially below the sintering temperature of the carbides of metals having elevated melting temperatures. In the course of sintering, the volume of the product is reduced by about 40%, which fact must be borne in mind when designing the dimensions of the end prdouct. The sintering of the mixture at the relatively elevated temperatures reqiures a rather complicated and sophisticated design of the sintering furance and special material for its manufacture. In order to lower the required sintering temperature, pressure is applied on the mixture while it is arranged in a graphite mold, said pressure being generally within the range of 12 to 15 l g./cm. while simultaneously heating the mixture for example, by passing an electric current therethrough. The required sintering temperature can in this way be reduced by about 100 C. If some boron in powder form is added an amount up to by weight, a further lowering of the sintering temperature by about 100 C. can be achieved.

A drawback of the known sintered carbides lies in that they cannot be used as binding agents for diamond abrasives for the manufacture of diamond grinding tools and similar tools. This is primarily due to the relatively high sintering temperatures of the mixture, which causes the structure of the diamonds to be impaired due to their tendency to react with oxygen, which is released from the surface of the metal particles of the mixture.

A metal binding agent is therefore used at present for such tools, such as for example bronze, nickel, zinc, aluminum alloys and similar materials. The binding metal is however substantially softer than the diamond abrasives and, due to the large stress to which such tools are subjected in the course of grinding, the diamond grains are loosened and fall off without being fully used.

SUMMARY OF THE INVENTION It is an object of this invention to provide a sintered carbide composite particularly suitable in the manufacture of grinding tools with diamonds. In accordance with this invention an admixture for phosphorus in an amount 'ice up to 5% of the total weight is used for this purpose. An additional admixture of boron in an amount up to 5% by weight can be furthermore added in order to lower even further the required sintering temperature.

By adding phosphrous, the required sintering temperature 1s lowered up to 300 C. The combination of admixtures of phosphorus and boron results in a lowering of the required sintering temperature by up to 400 C. when compared to sintering temperatures of the prior art compounds.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples are given for sintered carbide composltolns.

EXAMPLE 1 Percent b wei ht Tungsten carbide Cobalt 24 Red phosphorus l The mixture is pre-pressed into the required shape with an addition for shrinking and is placed on a graphite support. The sintering proceeds at normal pressure in a continuous sintering furnace at a temperature of 1090 C. The sintering time depends on the weight of the product.

EXAMPLE 2 Percent b h Tungsten carbide f 75 Cobalt 23.5 Red phosphorus 1 Boron 0.5

The mixture is prepressed into the required shape with an addition for shrinking and laced on a graphite support. The s ntering proceeds at normal pressure in a continuous sintering furnace at 1040 C. The sintering time depends on the weight of the product.

The sintered carbide according to this invention offers a better resistivity to abrading then sintered carbides used at present. It can be therefore advantageously used as binding agent of diamond edges in the headpiece of an apparatus for measuring the hardness of materials; as bll'ldll'lg agent of diamond grains for boring bits used, for example, in geological survey; as binding agent of diamond particles used in wheel trueing and many other uses, where at present the rather elevated sintering temperature has prevented the use of sintered carbides.

What is claimed is:

1. A sintered composite adapted for use as an abrasive tool, consisting essentially of diamond particles bonded by a sintered carbide composition, consisting of:

a carbide of at least one metal selected from tungsten, molybdenum, titanium, tantalum, vandium and chromium;

at least one metal selected from the group of iron, co-

balt and nickel;

up to 5% phosphorus of the total weight of the cemented carbide composition.

2. A sintered composite adapted for use as an abrasive tool, consisting essentially of diamond particles bonded by a sintered carbide composition, consisting of a carbide of at least one metal selected from tungsten, molybdenum, titanium tantalum, vanadium and chromium;

at least one metal selected from the group of iron, co-

balt and nickel;

up to 5% phosphorus of the total weight of the cemented carbide composition;

with an addition of boron up to 5% of the total weight of the cemented carbide composition.

(References on following page) 3 References Cited UNITED STATES PATENTS 4 FOREIGN PATENTS 528,324 7/1956 Canada.