US2179167A - Method of making steel - Google Patents

Description

Patented Nov. 7, 1939 PATENT OFFlCE 2,119,151 ma'rnon or MAKING STEEL James G. Vignos, Canton, Ohio, assignor to Ohio- Fern-Alloys Corporation, Canton, Ohio, a corporation of Ohio No Drawing. Application February 5, 1937. Serial No.- 124,281

, 4 Claims. (Cl. 75-45) The invention relates to the manufacture of iron and steel, and more especially to the production of iron andsteel and its alloys from a molten bath of iron, comparatively low in carbon 5 and commercially satisfactorily low in other metallic and non-metallic impurities, with the exception of iron oxide, by removing the excess iron oxide, recarburizing and, if desirable, alloying a this base metal to give the desired finished analyl sis.

The invention contemplates primarily the production of the relatively pure iron base metal by oxidizing the carbon, manganese, silicon and other impurities, removing them from the metal, in so far as the equilibrium reactions between an oxidizing slag and metal low in carbon will permit. To obtain an iron or steel that is low in carbon and other impurities is extremely difficult and costly under present practice, due to the type of raw materials required and the time necessary for completing the reactions. Under the methods now in use it is almost impossible to have a metal free from the products of deoxidation, when this is accomplished by the use of manganese, silicon,

aluminum or other deoxidizers.

The objects of the invention are to provide a method of making iron and steel and its alloys of high quality, by shortening the time required an using cheaper raw materials. These objects may be attained by obtaining a molten metal that is cheaply produced and having a higher carbon content than desired in the base metal to be produced,'and intermixing the molten metal with a molten oxidizing slag in such manner that the carbon content of the metal is reduced and manganese oxide, silicon oxide and other oxides, are removed in the slag, producing a base metal low in carbon, and substantially free from impurities except iron oxide. Said base 40 vmetal may then be transferred to a suitable furnace where the iron oxide is reduced and additions are made to produce any desired analysis by standard and well known methods.

The method implied in this invention consists in first obtaining a molten metal containing at least .05% carbon, and mixing the metal with a a molten oxidizing slag, in such a way that a reaction is set up between the carbon and the slag, causing considerable evolution of gas, and reduction of the carbon content. The manganese oxide, silicon oxide, and other oxides, are taken up in the slag. .This produces a metal lower in carbon, higher in iron oxide, but almost free from other impurities.

The molten metal produced in this operation may then be transferred to an electric furnace, or other suitable furnace, the iron oxide reduced, and additions made to make any desired analysis 1 by. standard and well known methods.

From the above, it is apparent that elimination 5 of carbon is extremely rapid, and that the oxidizing slag must have sufficient iron oxide content, so that it can react with the carbon in the metal.

To further illustrate the invention, but not to 10 limit the scope of the invention in any way, molten metal of high carbon content can be blown down in a Bessemer furnace to a suitable carbon content, or a metal of suitable carboncontent can be produced in an open hearth fur- 1E nace; for example-approximately .15 to .50 carbon.

To produce a metal of that carbon range'is a comparatively easy operation under our present methods of refining iron and steel. However, to 20 carry the carbon content lower requires considerable time and fuel, and is hard on the furnace refractories; thus making the removal of the carbon expensive. Further, before it can be properly deoxidized it is necessary to remove the slag, 25 I which is high in iron oxide, or lower the iron oxide in the slag and metal by using ferro-manganese, ferro-silicon, etc., in which there is considerable loss of these costly deoxidizers and alloy agents. The products of this deoxidization are 30 always a source of contamination and give rise to dirty steels if considerable skill is not employed in their use. The present invention overcomes these difilculties by removing from the furnace the metal when it has reached the desired carbon 35 content and separating it from its slag.

For further lowering. the carbon and removing the impurities from this metal it is mixed with a slag containing a sufficient amount 'of iron oxide, preferably at least 10%, which has been 40 previously melted and made fluid by suitable additions in a separate furnace. The mixing of the metal and slag can be accomplished in many ways, suchas pouring the metal into the slag, rolling it in a rotary furnace, etc. In this inve'ntion the mixing is mainly accomplished by the v evolution of the carbon monoxide produced by the chemical reaction of the carbon on the iron oxide in the slag. After the reaction between the metal and slag is complete, which is evident by 50 the quieting of the boiling action dueto the evolution of gas, the metal then separates from the slag by gravity and the metal is lower in carbon and richer in iron oxide. This metal while still molten is then transferred to anelectric furnace 55 or other suitable furnace for removal of the iron oxide by standard and well known methods and. can be alloyed in any desired manner to give the required analysis.

From these examples it is apparent that. the present invention departs very radically from our present methods employed in making iron and steel and its alloys. The main point of deviation in this invention from present practice is that the metal is removed from the refining furnace and separated from its slag for the final elimination of carbon and impurities by a new slag prepared in a separate furnace. After removing the carbon to the desired point, the metal while still molten is finished in another furnace. This deviation from present practice can be readily understood when we consider our present methods of making iron and steel and its alloys.

The present open hearth practice is to eliminate the carbon and finish the heat to the desired point in one furnace, using the same slag throughout by making suitable additions to it as required. Present electric furnace practice varies a great deal in regard to the slags and methods of handling the slag. The conventional practice in both acid and basic furnaces is to melt down, slag oil and put on new slag for finishing the heat. In some cases the same slag is used throughout the heat and additions are made to the slag to bring about the desired finished slag and metal to the correct analysis. practice is to blow the heat down to the desired carbon and remove it from the converter.

In each of the above examples of our present practice we find that the metal is finished under a desirable slag without removing it from the furnace or converter. In no case is the metal removed from the melting furnace separated from its slag for the final elimination of carbon by mixing it with a new molten slag obtained from a suitable slag melting furnace, and the resulting metal while still molten placed in a refining furnace for bringing the analysis to the desired point.

For anyone who is conversant with our present metallurgical practice, it is obvious that the above process is capable of wide application because the process is extremely flexible and can be applied to make any of our present analyses of iron and steel and its alloys.

I claim:

1. The process of treating ferrous metals which comprises forming a bath of molten ferrous metal having a higher carbon content than desired in the base metal to be produced, oxidizing this bath of metal until the carbon content is lowered to approximately .05% to .50%, then forming a separate bath of molten oxidizing slag containing sumcient oxide to appreciably reduce the carbon content in the metal and incapable of eliminat ing an appreciable amount of phosphorus, intermixing the molten metal containing the above mentioned amount of carbon with the molten oxidizing slag whereby a reaction is set up between the slag and the carbon in the metal causing a reduction of the carbon content in the metal accompanied by a strong evolution of gas, and eliminating from the metal and absorbing by the slag the manganese, silicon and similar oxidizable elements that are oxidized, and separating the metal from the slag, producing a base metal Bessemer lower in carbon, higher in iron oxide, and substantially i'ree from other impurities.

2. The process of treating ferrous metals which comprises forming a bath of molten ferrous metal having a higher carbon content than desired in the base metal to be produced, oxidizing this bath of metal until the carbon content is lowered to approximately .05% to .50%, then forming a separate bath of molten oxidizing slag containing sufiicient oxide to appreciably reduce the carbon content in the metal and incapable of eliminating an, appreciable amount of phosphorus, intermixing the molten metal containing the above mentioned amount of carbon with the molten oxidizing slag whereby a reaction is set up between the slag and the carbon in the metal causing a reduction of the carbon content in the metal accompanied by a strong evolution of gas and eliminating from the metal and absorbing by the slag the manganese, silicon and similar oxidizable elements that are oxidized, and separating the metal from the slag, producing a base metal lower in carbon, higher in iron oxide, and substantially free from other impurities and then reducing the iron oxide in the metal.

3. The process of treating ferrous metals which comprises forming a bath of molten ferrous metal having a higher carbon content than desired in the base metal to be produced, oxidizing this bath of metal until the carbon content is lowered to approximately .05% to 50%, then forming a separate bath of molten oxidizing slag incapable of eliminating an appreciable amount of phosphorus and containing over 10% iron oxide, intermixing the molten metal containing the above mentioned amount of carbon with the molten oxidizing slag whereby a reaction is set up between the slag and the carbon in the metal causing reduction of the carbon content in the metal accompanied by a strong evolution of gas and eliminating from the metal and absorbing by the slag the manganese, silicon andsimilar oxidizable elements that are oxidized, and separating the metal from the slag, producing a base metal lower in carbon, higher in iron oxide, and substantially free from other impurities.

4. The process of treating ferrous metals which comprises forming a bath of molten ferrous metal having a higher carbon content than desired in the base metal to be produced, oxidizing this bath of metal until the carbon content is lowered to approximately .05% to .50%, then forming a separate bath of molten oxidizing slag containing suflicient oxide to appreciably reduce the carbon content in the metal and incapable of eliminating an appreciable amount of phosphorus, intermixing the molten metal containing the above mentioned amount of carbon with the molten oxidizing slag whereby a reaction is set up between the slag and the carbon in the metal causing a reduction of the carbon content in the metal accompanied by a strong evolution of gas and eliminating from the metal and absorbing by the slag the manganese, silicon and similar oxidizable elements that are oxidized, and separating the metal from the slag, producing a base metal lower in carbon, higher in iron oxide, and substantially free from other impurities, then reducing the iron oxide in the metal and alloying the metal to any desired analysis.

' JAMES C. VIGNOS.