US891898A - Process of making low-carbon metals or alloys. - Google Patents

Description

UNITED STATES PATENT OFFICE.

FREDERICK M. BECKET, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO ELECTRO METAL- LURGICAL COMPANY, A CORPORATION OF WEST VIRGINIA.

EROCES S OF MAKING LOW-CARBON METALS OR ALLOYS.

Specification of Letters Patent.

Patented June 30, 1908.

Application filed August 24, 1905. Serial No. 275,667.

agara and State of New York, have invented certain new and useful Improvements in Processes of Making Low-Carbon Metals or Alloys, of which the following is a specification.

This invention is a process for the production of metals and alloys of low carbon content, and is more particularly applicable to the metals chromium, molybdenum, vanadium and tungsten and to the alloys of these metals with iron or nickel.

The invention consists in first producing from a suitable ore an alloy high in silicon and low in carbon, and thereafter eliminating all or part of the silicon by reacting upon further quantities of ore.

As is well known, the presence of carbon is undesirable in the various metals and alloys such as ferro-chromium, ferro-tungsten, etc., which are used for imparting s ecial roperties to steel, and the value of t ese a oys increases greatl as their carbon content decreases. Wit the object of producing metale and alloys of low carbon content many processes have been devised in which reducmg agents other than carbon are employed, such reducing agents being, however, very costl Processes have also been devised in whio a high carbon alloy is produced and thereafter subjected in a secondary stage to the refining action of various decarburizmg agents which are also either costly or cause large losses of the metal produced in the first stage.

According to my invention an economlcal process is provided for the production of the above mentioned metals and alloys with a' content of. carbon and silicon which may be easil controlled.

I have found that if the oxids or oxygen containing compounds of chromium, molybdenum, vanadium or tungsten are mixed with varying quantities of silicious material and subjected to the reducing action of carbon, the resulting product containing the metals chromium, molybdenum, vanadium, tungsten or their alloys, contains silicon and carbon in vary-in proportion, the percentage of carbon being Tower as the ercentage of silicon is higher; I have also lbund that by incorporating silicious material and carbon in the charge in certain proportions it is possible to produce these metals and alloys containing a very small proportion of carbon. I.

have also found that if the products made in the manner just described are suitably treated with a new supply of ores or compounds of the desired metals, the silicon may be practically eliminated and the carbon content still further diminished.

In order that my invention may be fully understood I shall describe its application to the manufacture of low carbon ferrochro mium, it being understood that this alloy is typical only of those heretofore mentioned. As a source of chromium and iron I generally use the mineral chromite containing from 50 to 52 percent. chromium sesquioxid, Cr O and from 16 to 17 percent. ferrous oxid, FeO.

With chromite I mix a quantity of sand or.

other silicious material, sufficient carbon to reduce not only the oxide of chromium and of &

iron but also a part or all of the silicious material, and a flux, such as lime, to form a suitable slag with the impurities generally existing in the chromite and with any portion of the silicious material which may be unre- (luced. This mixture is then subjected to a hi h tern erature by means of electrically developed eat and yields an alloy containing chromium, iron, silicon and a small percentage of carbon. This ,is the first stage of my rocess. mg the alloy thus produced, preferably in another electric furnace which when a very 'low carbon product is desired should have a hearth of material other than carbon, with a mixture of chromite or other suitable oxid ore and any fiuxing material such as lime. As a result of this treatment the silicon of the alloy produced in the first sta e of the process combmes with the oxygen of tained in the chromite or other ore and forms silica which passes into the slag, an e uivalent proportion of chromium and iron eing reduced and accumulating with the chromium and iron produced in the first stage. As one ound of silicon will liberate from the oxid of chromium, Cr O 2.44 pounds of chromium, and as this same uantity of silicon will liberate from the oxi of iron, FeO, 3.9 pounds of .iron, it will be understood that the silicon in the alloy produced in the first stage is replaced by a greater weight of The second stage consists in treat the oxids conchromium and iron, and that therefore the percentage of carbon in the finished product may be further reduced.

The roportions of carbon and silica incororated with a given quantity of chromite to e smelted in the first stage of my process depend upon the uality of the chromite and the ercenta e 0 carbon which it is desired the finished erro-chromiumshould contain. To make a ferro-chromium containing about one percent. carbon from chromite of the qtlliality above referred to, I have found that t e charge may advantageously consist of equal parts by weight of chromite, sand and ordinary coke. The alloy obtained when this charge is smelted in the electric furnace has approximately the following analysis: chromium 51.3%; iron '17 .5%; silicon 30.0%; carbon 1.2%. In the second stage of the process this alloy is treated in the electric furnace with a new supply of chromite in the proportion of about six pounds of chromite to every pound of silicon in the alloy, this pro ortion of chromite to silicon being very slig tly in excess of that theoretically necessary to sup ly sufficient oxygen for the conversion of t e silicon to silica. As a result of this treatment the silicon is practically eliminated, and more chromium and iron have been produced, and the alloy will now analyze practically as follows: chromium 70.0% iron 28.9%; carbon 1.0%; silicon 0.10%. If an alloy of even lower carbon content is required, a higher percenta e of "silicon is obtained in the metallic rmIucts from the first stage of the process y using an increased proportion of both sand and coke to chro mite, with the result that the carbon content is still lower. Similarly by using a lower proportion of sand and coke, metallic products containing less silicon and more carbon are obtained. It will beseen that by thus controlling, in the first sta e of the process, the carbon content of the a oy, the percentage of carbon in the finished product may be controlled within very narrow limits.

In order to obtain satisfactory results with the metals named it is ractically necessary that the first stage of the process should be carried out at the high temperature of the electric furnace, and it'is preferred that the second or refining stage should also be carried out in the same or other electric furnace. To obtain the advantages of continuous operation and in ener-a1 to conduct the process in the most a vantageous manner I prefer to employ two electrlc furnaces in close proximityto each other, so that the metal or alloy containing considerable silicon produced in one-furnace may be ta ped directly into the other furnace, in whic the second stage of the rocess is carried out and from which the finished roducts are ta ped as desired. By. this method the total e ectrical ener consumed in the process is less than when t e metallic products of one furnace are allowed to cool before treatment in the same or other furnace.

In the production of chromium, molybdenum, vanadium, tungsten or alloys of these metals in the electric furnace it is known that if sufficient carbon-is used in the charge to obtain a high yield of these metals from the quantity of ore furnaced, the resulting metallic products contain a relatively high proportion of carbon; and as is commonly practiced, if less than the theoretical quantity of carbon is supplied to the charge, poor yields are obtained and the carbon or graphite in the very expensive form of electrodes is rapidly consumed. Referring to the above exam le of production of ferro-chromium, ha the silicious material not been used in the charge and had the theoretical quantity, 'orslight excess of carbon, been employed, the carbon in the resulting product Would have been about 8-10 percent. Had considerably less than the theoretical carbon been used in the charge, the resulting ferro-chromium' One of the advantages of my process lies in the possibility of using almost any excess of carbon as a reducing agent in the charge employed in the first stage, thereby o taining very high yields of the desired metals and causing a great saving in consumption of carbon or gra hite electrodes. 4 As a further advantage Ihave found it possible to produce low carbon, hi h silicon products in an electric furnace in w 'ch not only the side walls but the hearth on which the metal rests during the first stage of the process are made of the cheap and durable material carbon. As other advantages it may be pointed out that ores which are usually considered as low grade on account of the presence'of undue roportions of silica, and which are there- -fore considered unfit for the manufacture of the specified metals or alloys, can be successfully and economically used in this process. The same remark applies to the purity of the carbonaceous reducmg agents such as coke. When the ores contain sufficient silica for the purpose, no addi 'on of silicious material is required, and it is then only necessary to so pro ortion the coke that the desired amount 0 silicon is obtained. This is the case when low carbon ferro-vanadium is producedfirom vanadiferous sandstone.

As the reaction between silicon and the metallic oxids em loyed is strongly exothermic, a relatively very small amount of electrical energy is required to eliminate the 1 silicon in the second stage of the process with the production of a further quantity of the desired metals almost equivalent to that theoretically possible wlth a given amount of silicon.

The silicon can readily be so far eliminated that the final product chromlte.

I claim:

1. The process of producing low carbon metals or alloys which consists in producing under electric furnace conditions a metallic product low in carbon and high in silicon, and then oxidizing part or all of the silicon, substantially as described.

2. The process of roducing low carbon metals or alloys whic consists in reacting under electric furnace conditions with carbon on a charge containing an oxid ore and silica to roduqe a metallic productlow in carbon am high in silicon, and then oxidizing part or all of the silicon, substantially as described.

3. The process of producing low carbon metals or alloys which consistsin producing under electric furnace conditions a metallic product low in carbon and hi h in silicon and then reacting on said pro uct with an oxid ore to oxidize the silicon, substantially as described.

4. The process of roducing low carbon metals or alloys whic fi consists in reacting under electric furnace conditions with carbon on a charge containing an oxid ore and silica to roduce a metallic product low in carbon and high in silicon and then reacting on said product with additional quantities of the same oxid ore to oxidize silicon, substantially as described.

5. The process of producing low-carbon ferrochrome, which consists in reacting under electric furnace conditions with carbon on a char e containing an oxid ore of chromium an silica to produce a metallic product low in carbon and high in chromium and silicon, and then oxidizing part or all of the silicon, substantially as described.

6. The process of producing low-carbon ferrochrome, which consists in reacting under electric furnace conditions with carbon on a charge containing an oxid ore of chromium and silica to produce a metallic product low in carbon and high in chromium and silicon, and then reacting on said product with additional uantities of the same oxid ore to oxidize s1 icon, substantially'as described.

In testimony whereof, I affix my signature in presence of two witnesses.

FREDERICK M. BEOKET.

Witnesses JASPER WHITING,

WM. L. HEIM.