US1969886A - Method of manufacturing ferro alloys - Google Patents

Description

1934- E. A. JONES 1,969,886

METHOD OF MANUFACTURING FERRO ALLOYS Filed May 25. 1932 Gas Emma: 15

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Patented Aug. 14, 1934 UNITED STATES PATENT (OFFICE METHOD or MANUFACTURING FERRO' armors Edwin A. Jones, Jackson, Ohio Application May 23, 1932, Serial No. 613,099

Claims. (01. 75-17) My invention relates to the manufacture of alloys, such for instance as those designed to be remelted and usedin the manufacture of' cast iron, steel, or special alloy castings; particularly 5 ferro alloys having a. high silicon content.

One of the principal objects of my invention is to provide a method of manufacturing alloys which is of great advantage from the standpoint of economy of time and expenserequired in the electric furnace operation for the refining of the alloy and bringing it to the desired characteristics.

Another object is to provide a method of manufacturing alloys which is characterized by more economical use of alloy additions, due to the comparatively short heating and refining period for conditioning the metal; equally good results being obtained by my method with the use of smaller additions of costly alloying materials .as with other methods requiring longer periods of time and the additions of greater amounts of alloying materials. I

A further object of my invention is to provide a method of manufacturing alloys which has the advantage of affording better conditions than in the usual methods for eliminating possible harmful effects from the formation of oxides or the absorption of carbon. For instance, the metal may be obtained from the blast furnace at relatively low temperatures, thus preventing harmful foreign elements from being absorbed by the iron that would, if the smelting were done at higher temperatures, go over into the finished alloy and contaminate the same, and the purer metal thus obtained from the blast furnace at relatively low temperatures can be brought in the electric furnace to the required composition by making the desired alloying additions. Another object to provide a method which allows the electrodes to be lowered to the proper extent into the charge at the beginning of the operation in the electric furnace, to thereby lower the smelting zone and prevent the current from shunting into'the top of the charge and thus result in less effective smelting.

While I have chosen as an illustration an apparatus and method for the manufacture of iron alloys high in silicious content, it will be understood that this is done for purposes of illustration only, and it is not intended that the invention as hereinafter more particularly described and claimed shall be confined, except as restricted by the priorart, to-the particular method and apparatus described.

The present commercial methodsused in the manufacture of ferro alloys in the electric fur-' nace have many difiicult problems. Usually metallicscrap, such as borings, turnings, sheet bundies, etc. is charged into the electric furnace with iron is desired).

with the proper proportions of manganeseores. silicon in the form of silica sand or ground quartz (SiOz), chrome, nickel, titanium, etc., (depending upon what alloy or combination of alloys Carbon, usually in the form of coke breeze, is introduced throughout the'melt'to facilitate the passing of the current through the melt, particularly at the beginning of a heat when the furnace burden is cold. It requires several minutes after the current bar been turned on for the metal to become molten. after which the electrodes may be lowered into the bath, to thereby come into better contact and effect 'a more even and economical operation. The current is allowed to pass into the melt to bring the charge to the desired character. after which the content of the furnace is poured into molds or blocks, and when cool is ready for shipment.

But this method, as stated, has objectionable features which my invention is designed to overcome. One of the several difliculties with the commercial methods is the high cost of the melting down period or the initial melt period which brings the charge into a molten condition. for during the melting down period, notwithstandingthe carbon addition, the electric load is irregular and is at itspeak due to uneven contact with the burden, and to contact with cold scrap. In addition to the high cost of power, the irregular and peak load is injurious both to the carbon electrodes and to the refractory linings of the electricfurnace.

According to my method this costly meltin down period, or initial stage in the electrc furnace, is greatly reduced or totally eliminated. depending upon the particular alloy being made, the period in every case being partially eliminated. In addition to this saving, my process as a whole is speeded, and the conditions thus prevailing favor the elimination of harmful effects upon the alloy which may result fromthe present methods, such as the forming of harmful oxides or the picking up of carbon.

In the drawing, which is a diagrammatic vertical sectional view, I have illustrated an installation suitable for the carrying out of my process. In the drawing, 1 represents a blast furnace, equipped with a tapping notch 2, the furnace being supplied with tuyres 3. A receiving ladle is illustrated at 4, a gas furnace at 5, equipped with a gas burner 6 and a gas head connecting the blast furnace with the gas furnace is indicated at 6'. The contents of the gas furnace may be tapped off at 7 into the ladle 4.

An electric furnace is indicated at 10 and it may be mounted for tilting'as at 11. The electrodes are indicated at 12, and the holders at 13. Apparatus for handling the electrode and actuating the furnace is indicated generally at 14. Molds into-which the electric furnace contents may be poured are indicated at 15. An overhead crane is indicated at 16.

Briefly stated, according to one method I may follow, the ore, etc., is charged into the blast furnace and smelted, resulting in the manufacture of a silicon iron ranging from 6% to 16% in sili- -con content. This special high silicon iron is tapped from the furnace into a ladle, and is transferred by means of the crane and introduced into the electric furnace.- To this molten metal any one or more raw additions are made in the form of chrome ore, manganese ore, quartz, nickel, etc. Also scrapadditions may be made, such as borings and turnings, to give-necessaryiron additions. The raw additions may be added to the molten metal in the electric furnace in a cold state, or they may have been put through a preliminary heating in the gas furnace 5, which furnace is supplied by gas through the header 6 from that taken off of the blast furnace operation.

After melting in the gas furnace, (if this intermediate step has been used) the additions may be tapped off into the receiving ladle 4, and transferred by the crane to the electric furnace to be added to the melt therein. Whether the inter- 'the ordinary processes of steel or cast iron making.

I may, in those instances where it is found desirable, transfer the iron from the blast furnace to the gas furnace, and there make the additions of other materials desired for the particu-' lar alloy being made. These materials may be in a pre-heated condition in the gas furnace atv the time of the introduction of the silicon iron,

or may be introduced into the gas furnace in a cold state. After the treating in the gas furnace the melt may be transferred to the electric furnace and there refined; whatever small additions, if any are needed to bring the alloy to'the desired composition, being made during the refining period in the electric furnace.

As a specific example of making an alloy (in this case a 50% ferro-silicon) by my process, I note the following:

(a) Making 10% Si. pig in. the blastjurnace The following charge of iron ore, lime stone,

and fuel is fed into the top of the blast furnace Tilden 4200# Bennett 2000# Morris 3000# Gardner 1200# Pig iron 10% silicon Limestone 2800# Coke 4500# Coal 2000# The compositions of the iron ores referred to above may, by way of an illustrative example, be as follows:

Phos- Man- Alu- Mag- Loss Iron phor- Silica gami- Lime nesiby igus nese um um nition Tilden 40. 35 050 40. 30 07 .96 .35 29 40 Bennett 56. 30 .076 8.80 1. 25 2. 10 20 l7 6. 20 Morris 59. 15 066' 8.30 44 2. 47 1. 06 29 2. 83 Gardner 51.00 .086 3. 42 24 l. 41 2. 50 1. 14

(Above Dried 212 F.)

. As the charge passes down through the furnace, it is pre-heated by the combustion of carbonmonoxide rising from the tuyere zone below. As

the charge passes through the tuyere zone, the reduction of the alloy of iron and silicon takes place. The iron and silicon passes on down into the final zone, or hearth zone, and is tapped oil.

The wash or slag lies directly above the iron and is tapped oif metal.

(1)) Introduction into the gas furnace prior to tapping the furnace for The high-silicon iron (pig iron 10% silicon) is then transferred by ladle into the gas furnace 5 in which have been placed other materials to bring the alloy to the desired composition (in this example 50% ferro-silicon). The charge placed in the gas furnace may be as follows,

4480# 10% silicon pig 1690# Millscale (often referred to as mill cinder and which contains a high percentage of a solid solution of ferrous silicate and iron oxide) ,8690# Silica rock 2600# Coke The gas furnace is operated over a suflicient period of time to bring the entire charge to a preheated or a molten state before its introduction into the.e1ectric furnace for its final refining.

During the treatment in the gas furnace, the following re-action isinitiatedr Fe,o3+4sio2+ac.=zFsi,+55+3E,

(0) Treatment in the electric furnace The molten mixture tapped oil from the gas furnace is then'transferred to the electric furnace. Here the refining period takes place and the reaction is completed; Small additions, if needed, may be used to bring the alloy to the desired composition. After suiilcient heat has been passed through the charge in the electric furnace to refine the alloy and bring it to the desired characteristics, the electrodes are raised and the furnace is tilted and the alloypoured in the molds 15 for cooling. The final-productobtained in the electric furnace will be,-

1300o#-5 0% Perm-Silicon It will be understoodthat my process is not limited to this alloy, but may be used for the manufacture of a number of ferro-alloys by the introduction into the gas or electric furnace, or both, ofmaterials differing, in part, from those used'in the foregoing example.

The electric furnace may be of any standard type. It may be of the tilting or stationary type. The most economical type .of furnace for this method of'alloying is the arc type where the electrodes, by a lowering and raising device,can be allowed to submerge into the bath to thereby o lower the smelting zone, and to allow the current to come into better contact with the. alloy.

In the case where introduction of the silicon iron into the electric furnace in the molten state directly from the blast furnace takes place, the iron may be mixed with metals or alloys, one or both, in the cold state; or after having been first pre-heated in the gas furnace. In either case, the introduction of the molten silicon iron tends to melt the additions so as to make the electric furnace operation a short and steady process, without undue wear on the electrodes or the lining materials of the furnace.

My method requires only'from fifteen to fortyfive minutes treatment of the melt in the electric furnace, the time depending upon the kind of alloy being manufactured, some requiring a longer period to be properly mixed and brought to the required characteristics. This electric furnace operation period required in my method is of much shorter duration however than that of any existing methods for the production of alloys known to me.

It will be observed from the foregoing that my process has the advantage of greater economy in the manufacture of alloys from the standpoint of time required in the electric furnace operation, which operation is very costly. Further,

my invention has the advantage of more economical use in alloy additions, due to the shorter heating and refining period, with as good results being obtained by the use of smaller additions of costly alloying materials as with other methods in which greater additions of alloying materials are required. Also, my method has the advantage of better conditions for eliminating possible harmful materials which the alloy may abso'rb from being held over longer periods of time at high temperatures. Due to the molten condition of the charge when it comes in contact with the electric furnace, my method has the advantage of permitting the electrode to be lowered to the proper degree into the charge with ease, thereby lowering the smelting zone and preventing the electric current from shunting into the top of the charge and causing less effective smelting. Furthermore, where the intermediate step of treating the melt from the blast furnace in the gas furnace, or of pre-heating the additions in the gas furnace, is used, great economy results from the use of the products of combustion generated in the blast furnace, thus effecting material savings to render the process extremely economical in commercial operation.

Having-thus described my invention what I claim as new and desire to secure by U. S. Letters Patent is:

1. The method of manufacturing a high silicon alloy comprising smelting a charge suitable for the production of a high silicon pig iron in a blast furnace, transferring the high silicon iron from the blast furnace into a gas furnace and there introducing into the high silicon iron materials for bringing the alloy to the desired composition, heating the charge in the gas furnace until it has obtained the proper fluidity, transferring the charge from the gas furnace to an electric furnace and therein refining the charge and making suchsmall additions of materials as are required to bring the alloy to the desired characteristics while regulating the temperature of the charge.

2. The method of manufacturing ferro alloys which comprises smelting a charge of silicious iron ore, lime stone, and fuel in a blast furnace, tapping off the high silicon ferro alloy resulting from the smelting of the charge, and transferring it to an electric furnace, adding to the charge in theeletcric furnace additional silicious alloying materials required to bring the finished alloy to the desired composition, and heating the mixture in the electric furnace until it is completely alloyed.

3. The method of manufacturing ferro alloys such for instance as those used in steel making and special alloyed cast steel or cast iron which comprises smelting a silicious charge in a blast furnace, tapping off the alloy resulting from the smelting of the charge, transferring it to an electric furnace and therein making such additions of silicious and other materials as are required to bring the finished alloy to the desired composition while regulating the temperature of the charge.

4. The method of manufacturing ferro alloys which comprises smelting a charge of silicious iron ore, limestone, and fuel in a blast furnace,-

tapping off the silicon ferro alloy resulting from 1 the smelting of the charge and transferring it to an electric furnace, adding to the charge in the electric furnace a silicious compound and a reducing agent in quantities sufficient to introduce upon the reaction of the materials added, sufiicient silicon into the alloy to raise it to the desired final content, and heating the mixture in the electric furnace until completely alloyed.

5. The method of producing ferro alloys as end products which comprises producing a ferro alloy having a high silicon content in a blast furnace, transferring such alloy while molten to an electric furnace, adding to the charge in the electric furnace such additions as are required to raise the silicon content to the desired percentage in the finished alloy, and heating the mixture in the electric furnace until it is completely alloyed.

EDWIN A. JONES.

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