US2301360A - Purification of high silicon iron alloys - Google Patents

Description

Patented Nov. 10, 1942 UNITED STATES PATENT OFFICE 7 2,301,360 PURIFICATION-0F men SILICON moN mors Joseph H. Brennan, Niagara Falls, N. Y., assignor to Electro Metallurgical Company, a. corpora.-

tion of West Virginia No Drawing. Application August 3, 1940,

Serial No. 351,125

I 3 Claims.

This invention relates to the purification of molten silicides and alloys containing a large proportion of silicon and refers more particularly to a process of removing calcium and aluminum from such molten silicides and alloys. The raw materials used in the production of silicides and such alloys as ferrosilicon frequently contain alumina and lime as impurities, and

when the usual manufacturing processes are pursued, using such materials, the silicides or alloys produced are contaminated with aluminum and calcium. There is a demand, notably in the production of electrical steel sheet, for silicides and high silicon alloys practically free from such contaminants, and to achievethe desired purity it has heretofore been necessary to use very pure grades of raw materials. These special raw materials are more expensive than the ordinary materials utilized, and there is a demand for a method utilizing cheaper grades of rawmaterials but at the same time producing silicides or high silicon alloys containing little or no aluminum or calcium. It is a principal object of this invention to'provide such a method.

This object is achieved by the invention which comprises adding to a molten high silicon alloy or silicide produced in the usual way from the usual raw materials a quantity of a metal sulphide sufiicient to remove aluminum and calcium. A preferred material for refining aluminum and calcium from high silicon alloys is iron pyrites. If iron is an objectionable impurity in the alloy or silicide being produced, nickel sulphide or cobalt sulphide or other appropriate sulphide may be employed. The sulphide may a be added to the molten silicide or alloy either in the ladle or in an auxiliary refining furnace. 1

In either event aluminum and calcium are removed in a fluid slag, probably as aluminum and calcium sulphides. Under properly controlled conditions, there is no substantial loss of silicon incurred in the treatment of the invention, and

In the practice of the invention the sulphide treatment is preferably carried out in the ladle. Thus, a silicide or high silicon alloy is produced in the 'usual way, and a part of it may then be tapped'into a ladle. The desiredamount of sulphide is added to the material in the ladle, and the remainder of the silicide or alloy is then tapped rapidly to provide a stirring action. The molten material in the ladle is allowed to cool 10 to proper pouring temperature. The sulphide treatment apparently raises the temperature-of the material in the ladle and a longer time is necessary for cooling than is necessary when no sulphide addition is made, but this longer cool- 1 ing period is advantageous because it insures completion of the refining'action of the sulphide before pouring.

The following specific examples of the application of the method of the invention to the refining of ferrosilicon illustrate the principles and practice of the invention. It is to be understood, however, that the invention is not limited to the treatment of ferrosilicon but is equally applicable to the refining of other high silicon alloys or silicides.

Two hundred and-fifty pounds of iron pyrites containing about 41% iron and 48% sulphur, the remainder principally silica, were added to the ladle during the tapping of about 7500 pounds of ferrosilicon containing 47.16% silicon, 1.5%

aluminum. 0.08% calcium, 0.003% sulphur, .re -ma1'nder principally iron. The molten ferrosili con was tapped rapidly to give a good stirring action. The molten material'in the ladle Was- 'al1owed to cool to a low pouring temperature and was then poured into chills. The ferrosilicon produced contained 47.23% silicon, 1.07% aluminum, 0.006% sulphur and nil calcium. Thus,

- the silicon to aluminum ratio was improved from 40 31.4 to 1 to 44.2 to 1, there was no loss of silicon,

no appreciable increase in sulphur content, and the calcium was entirely eliminated.

In another test of the method of the invention 6500 pounds of-amolten ferrosilicon contain- I ing 50.65% silicon, 1.45% aluminum, 0.26% calcium, 0.005% sulphur, the remainder principally iron, were tapped into a ladle. A portion of the molten ferrosilic'on' was then poured from this ladle into a second ladle and 275 pounds of iron pyrites containing about 41% iron and 48% sulphur were rapidly added tothe small portion of molten metal in the second ladle. The remain-' ing ferrosilicon in the first ladle was then poured into the second ladle, the stream stirring the material already in the second ladle. After all of 1 2 asonaeo the ferrosilicon'had been poured into the second ladle, the contents or the second ladle were repoured into the first ladle to obtain further stirring. The molten metal was then allowed to cool to pouring temperature and was then poured into chills. The product contained 49.84% silicon, 0.73% aluminum, 0.02% calcium and 0.003% sulphur. Thus, by'the-"sulphide treatment the aluminum in the ferrosilicon was decreased from 1.45% to 0.73%, the calcium was decreased from 0.26% to 0.02%, there was no increase in sulphur content. and the silicon content was not rail a lltially decreased.

' another test of the method of the invention 250 pounds oi iron pyrit'es of the same lot usedin the previous examples were added to a ladle containing 7000 pounds of a ferrosilicon contain-'- a treatment or the invention not only contain as aluminum and calcium than alloys or, silicides which have not been given this treatment, but the material produced is exceptionally sound and dense and is considerably tougher than alloys or silicides which have not been given the treatment of the invention. v

While specific examples have been given of the application of the invention to the production of ierrosilicon these examples merely illustrate the principles of the invention and the invention is not limited to such examples. For instance, it may be used to advantage in the treatment of nickel-silicon alloys, cobalt-silicon ing li.8% aluminum and 0.07% calcium. Jitter the writes-treatment the ferrosillcon produced contained'QBV; aluminum and 0.0l%.'calcium.

tent of the lei-rosilicon was reduced from 0.39%

to 0.19% and the calcium content was reduced from 0.06%150 0.04%.

it has been found that high silicon alloys or silicides which have been given the sulphide I alloys, and other high silicon alloys or silicides.

' I'claim:

l-. A process of purifying iron alloys containing a large proportion of silicon-and only small proportions of the impurities aluminum and caloium which comprises subjecting a molten bath of such high silicon alloy1-t0 the action of a metallic sulphide. I e

2. A process of preparing ferrosilicon containing unobjectionable proportions of aluminumand calcium which comprises subjecting a molten ierrosilicon containing objectionable proportions oi such elements to the action of iron sulphide.

3. A process of preparing a ferrosilicon comtaining unobjectionable proportions of aluminum and calcium as impurities which comprises forming a molten 'bath of a ferro-silicon containin objectionable proportions of such elements and adding to such bath a quantity of iron sulphide, sumcient to remove at least a portion of the aluminum and calcium present in said ferrosilicon.

JOSEPH H. BRENNAN.