Process for manufacturing hard objects in silicidized carbon or other similar substances

Nov. 27, 1934. a. l. mingard 1,982,012

PROCESS FOR MANUFACTURING HARD OBJECTS IN SILICIDIZED CARBON OR OTHER SIMILAR SUBSTANCES

Filed April 20, 1932

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INVENTOR

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Patented Nov. 27, 1934

1,982,012

UNITED STATES PATENT OFFICE

1,982,012

PROCESS FOR MANUFACTURING HARD OBJECTS IN SILICIDIZED CARBON OR OTHER SIMILAR SUBSTANCES

Aurele Louis Mingard, Lausanne, Switzerland

Application April 20, 1932, Serial No. 606,490 In France May 11, 1931

Claim. (CI. 51—278)

The object of this invention is a process for manufacturing very hard objects, particularly grinding stones, in silicidized carbon or other very hard materials.

i The process consists essentially in transforming objects of any shape, made of carbon, into another very hard substance particularly into silicidized carbon, without altering their shape and by chemical reaction at high temperature.

) The crucible in which the reactions take place is filled with a mixture of substances capable of reacting upon each other at the temperature produced by an electric arc struck between electrodes. By the influence of this arc and as a result of the $ chemical reactions between the substances forming the charge, metallic vapors are produced, which reach a certain pressure, forming a pocket with the arc in the center, and which pocket gradually increases in volume until the objects 0 to be transformed, and which at the commencement of the operation were embedded in the charge, are enclosed within the pocket charged with metallic vapors, without having changed their position, and are subjected to the action of 5 these vapors, until the transformation into a very hard material particularly silicidized carbon, is completed.

The transformation is preferably produced in a furnace consisting of a crucible 1 of any desired 0 shape, containing a lining of refractory bricks. This furnace is placed either vertically or horizontally and may be of the tilting type. It is provided with electrodes 2 of carbon or other material capable of resisting high temperatures.

These electrodes may be placed into the furnace in any position with respect to the furnace, and at any variable position with regard to each other. They can, for instance, be placed along the center line of the furnace in line with each other and 10 at any distance from each other. Each electrode is fitted on the end inside the furnace with a piece of carbon 3 of any suitable shape, cylindrical, coneshaped etc. The object or objects of carbon 4 to be transformed are attached to the electrodes in any suitable manner, along their center line for instance if they are cylindrical. The other electrode may also be provided with a similar object or an object of different shape to the one attached to the first electrode.

>0 In the case of a body of carbon in the form of a grinding wheel, the body may be mounted on the electrode by means of the axial bore formed therein. When so mounted the body is held in place on the electrode by friction between the (5 bore in the body and the electrode.

The electrodes are fixed in a suitable way and maintained in a vertical or any other position, along the center line of the hollow cylinder forming the furnace. If this furnace is used exclusively in a vertical position, the lower part is °® closed, thus forming a crucible through the bottom of which the lower electrode only passes through an aperture.

The transformation of the objects made of carbon, into silicidized carbon or other material proceeds in the following manner.

The furnace is charged with a mixture of substances capable of producing by chemical reaction at high temperature the transformation of the objects of carbon into silicidized carbon or other 70 very hard substances.

As an example of such substances forming the charge the following mixture is mentioned:

For obtaining silicidized carbon:

. Parts ⁷⁸

Silica____________________________r--------30

Carbon__________________________________— ⁷

The proportions of materials employed as stated, have no limitative character and may vary 80 within wide limits.

A continuous or alternating electric current is then sent through the electrodes by means.of .electric conduits in metal, or other conductive material, to which conduits the electrodes are 85 attached in any suitable manner, along their axis for instance.

The arc is struck between the electrodes and as a result of the heat produced a chemical reaction takes place between the substances forming 90 the charge in the furnace, liberating from one of the constituents silicon vapors, or other vapors according to the nature of the charge.

This reaction may be represented as follows:

SiOa+2C=Si+2CO

These vapors reach a certain pressure and rapidly form around the arc a pocket 5 with the arc in the center. The pocket gradually increases in volume until the objects of carbon which it 100 is desired to transform are enclosed within this pocket. These objects are then subjected to the action of metallic vapors of silicon or other elements and are transformed into silicidized carbon or as the case may be into other very hard 105 materials with carbon as a base, without changing in shape or position in the furnace and without passing through any other physical changes. The objects may then be removed from the furnace and the operation can be repeated. 110