US1037713A - Method of making silicon articles. - Google Patents

Description

" anion,

THOMAS IB. ALLEN, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO THE CARIBORU'NDUM COMPANY, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF PENNSYLVANIA.

METHOD OF MAKING- SILICON ARTICLES.

No Drawing.

T all whom it may concern:

Be it known that I, THOMAS B. ALLEN, a resident of Niagara Falls, Niagara county, State of New York, have invented a new and useful Improvement in Methods of Making Silicon Articles, of which the'following is a full, clear, and exact description.

This invention has relation to a new and useful improvement in the method of making silicon articles.

Heretofore, the production of silicon articles by casting molten metal into the desired shape has been attended with very great difficulties, which have been so great as to practically prevent the format-ion of suitable articles. The main difliculties in casting the ordinary molten metal have been, first, that the cast metal is very spongy and porous, being filled with blow holes and pin holes; second, that the cast article is mechanically unsound, this being largely occasioned by the presence of How marks due to the lapping of the metal which causes folds in the surfaces of the cast silicon; and third, that the cast metal is rather coarsely crystalline which tends to make the article mechanically weak. 7 I

I have discovered that electric furnace silicon and silicon alloys and compounds contain dissolved silicon dioxid and dissolved nitrogen and oxygen, and that by removing these substances, I am able to obtain castings which are stronger, denser and more perfect than any castings so far obtained. I have further discovered that I can obtain the improvements and remove the-impurities by means of a large number of substances, such as the alkali metals, the alkaline earth metals, magnesium, vanadium, titanium,

aluminum, boron, etc., and in general, any

element which has a combining heat with the impurities, which is greater than that of silicon. To obtain especially advanta geous results, I preferably use a material, :uch as calcium, magnesium, vanadium, etc., vvhich, besides acting as a deoxidizing agent, :an act as a denitrogenizing agent. I may, iowever, also add an element, such as solium, to remove the oxygen or oxids, and a. mbstance, such as vanadlum, to remove the iitrogen or nitrids.

I will now describe a preferred method of arrying out my invent-ion with reference to Specification of Letters Patent.

Application filed June 26, 1911.

Patented Sept. 3, 1912. Serial No. 635,500.

for about one to two hours, having preferably placed a layer of coke on the surface of the silicon to prevent loss by oxidation and volatilization. When the silicon is in a very fluid condition, I remove the crucible from the furnace, skim off the coke and add the magnesium to the molten silicon in the form of a fine powder or in small lumps by means of an implement commonly called a phosphorizer. I have found that I can obtain the desired results by adding from one-half per cent. to three per cent. magnesium and I contemplate adding only such a quantity of this substance which will combine with the impurities and pass off to the surface of the silicon as a slag. The magnesium silicate formed when magnesium is used is readily fusible and comes to the surface of the fused silicon. When the silicon shows no further reaction due to magnesium and is in a quiescent condition, I preferably pour it from-the bottom of the crucible in order to prevent any of the slag from the surface getting into the molten silicon.

In making the mold of the desired shape for the silicon article, I prefer to use what is commonly known as a dry sand mold and to coat the surfaces of this mold with which the molten silicon comes in contact with talc. I have further found it desirable to pour the metal into the mold through a gate entering at the bottom of the mold and to use a comparatively large riser, so that the casting cools under considerable fluid pressure. By this means I aid the production of dense sound castings. The articles produced in this manner are mechanically sound and show a marked absence of blow holes and flow marks. The metal crystallizes in very fine crystals and shows a marked interpenetration of the same which causes the articles produced to have considerable mechanical strength.

It will be evident to others skilled in the art of making castings that I may make many changes in the described method with out departing from the spirit of the invention. Further, by the term silicon used sired form, substantially as described.

2. The method of removing impurities from silicon, which consists in adding thereto an element having a combining heat with said impurities higher than the combining heat of silicon, substantially as described.

3. The method of making silicon tastings, which consists in adding an element whose oxids has a higher heat of formation than the oxids of silicon and whose nitrid has a higher heat of formation than the nitrid of silicon, removing the reaction products, and pouring the molten silicon into the desired form, substantially as described.

4. The method of making silicon articles, which consists in adding to molten silicon an element whose afiinity for oxygen and nitro gen is greater that that of silicon, removing the reaction products, and pouring the molten silicon into the desired form, subsantially as described. 5

5. The method of making silicon articles, which consists in adding to silicon an element whose oxid has a higher formation heat than oxid of silicon, and an elementwhose nit-rid has a higher formation heat than nitrid of silicon, removing the reaction products, and casting the molten silicon into the desired form, substantially as described.

6. The method of making silicon articles, which consists in adding to silicon an element whose formation heat with the impurities in the molten silicon is greater thanthat of silicon, removing the reaction products, and casting the molten silicon into the desired form under pressure, substantially as described.

7. The herein described method of treating molten silicon to remove therefrom silicon dioxid and nitrogen and oxygen, which consists in adding thereto a metal which will combine with said impurities to form a slag, substantially as described.

8. The herein described method of treating molten silicon to remove therefrom silicon dioxid, andnitrogen and oxygen, which consists in adding thereto an alkaline metal, which willcombine with said impurities to form a slag, substantially as described.

9. The herein described method of treating molten silicon to remove therefrom silicon dioxid and nitrogen and oxygen, which consists in adding thereto magnesium, which will combine with said impurities to form a slag; substantially as described.

10. The herein described method of treating molten silicon to remove impurities therefrom, which consists in tapping the metal from the furnace with a crucible, and

heating it to bring it to a highly fluid condition, protecting the metal While being so heated to prevent oxidation and volatilization losses, and then adding thereto a metal which has a combination heat with the impurities in the silicon higher than the combining heat of silicon, and separating the silicon from the resulting slag, substantially as described.

11. The herein described method of making articles in which silicon is the principal constituent part, which consists 111 tapping molten silicon into a vessel and heating the same until the silicon is in a very fluid condition, then adding thereto an element which has a. higher formation heat with the 1mpurities existing in the silicon than of silicon, and which will unite with said 1 m purities to form a slag, and then separating the purified silicon and slag and casting the silicon, substantially as described.

In testimony whereof, I have hereunto set my hand.

THOS. B. ALLEN. Witnesses:

L. B. COULTER, F. T. PIERCE.