US1794401A - Process for producing metals and alloys - Google Patents

Description

Patented Mar. 3, 1931 PATENT OFFICE TUBE ROBERT HAGLUND, OF STOCKHOLM, SWEDEN PROCESS FOR PRODUCING METALS AND ALLOYS No Drawing. Application filed July 31, 1924, Serial No. 729,354, and in Sweden October 8, 1923.

The present invention relates to a process for producing metals and alloys, which makes it possible to obtain an improved regulation of the quantity of metals to be alloyed with a metal or alloy as compared with the results of hitherto known processes for the production of metals and alloys in electric furnaces. The chief object of the invention is a process for reducing metals and alloys with a low percentage of carbon but the process may in many cases also be used with. great advanta e for the production of metals and alloys with higher percentages of carbon. In the hitherto known electro-metallurgical processes Where carbon or carboniferous reducing agents are used, the ores or other raw materials, from which the metals or alloys are to be produced, are reduced either directly with carbon or, as is the case when producing pig iron, partly with carbon and partly with the carbon-mono-oxide containing gases formed in the process. To produce a product with low percentage of carbon by such means has as a rule hitherto not been possible. Instead it has been necessary, in order to get such a product with low percentage of carbon,

to refine the product with great costs.

The present process renders it possible to produce directly metals and alloys with low percentage of carbon, even such metals and alloys that will easily absorb carbon. This object is attained by reducing the ore or the like entirely or mainly not directly but-indirectly with carbon or carboniferous reducing agents. A suitable mixture of oxidiferous material and carboniferous reducing agents are formed into bricks or lumps of rectangular or other form which lumps are charged in a furnace together with the ore or the like from which the. metal or alloy is to be produced. The ingredients for the bricks or lumps should be pulverized and intimately mixed. The specially prepared material in the lumps will first be reduced in the furnace r and the metal or the like thus produced will in its turn act as a reducing agent upon the other material.

The oxidiferous materials in the bricks or lumps must be of such quality that, when it is 5 reduced by carbon, such elements, alloys or carbides are formed, as will have a reducing action upon the raw material proper for the metal or alloy to be produced. For example the following oxides may be used as an ingredient in the bricks or lumps, namely alumlnum oxide, magnesium oxide, barium oxide, calcium oxide, silica, manganese oxide, boric acid, chrome oxide, zinc oxide and others. Each of these oxides or a mixture of two or more of them may be used in the bricks or lumps, different sorts of which may be used together. It may be advantageous to use special agents in the process for getting a suitable consistency and melting point of the slag and such agents may be mixed into the bricks. As a rule, however, it will be more suitable to add separately such agents, that are not to be influenced by the reducing carboniferous agents. These agents which naturally must be chosen with due regard to the nature of the oxidiferous materials in the bricks or lumps and of the slag forming ingredients in the other materials may consist of lime, quartz, fluor-spar, sulfides such as Gas and others. As reducing agents in the bricks or lumps one or more carboniferous materials may be used such as charcoal, graphite, anthracite, coal, lignite, coke, lignite coke (or dust or grits of said Carboniferous materials), peat, sawdust and others. If a carboniferous material other than a coke is an ingredient in the bricks or lumps thesemay be previously heated to make the fuel to coke. This will also make the bricks hard and porous. A binding agent for the content of the bricks or lumps may, if necessary, be used such as the usual agents for brick-making namely tar, marl, lime-water, clay, waterglass, sulphite, waste lye and others. VVhen bricks of special strength are required they may be previously sintered or burnt.

Metals or alloys which with great advantage may be produced by the present process are for example, chromium, iron, manganese, titanium, vanadium, tungsten. molybdenum and alloys containing the metals named.

For the production of ferro-chromium from the commercial chromium oxide ore (chromite) or for" the roduction of ferrochromium alloys with ower percentage of chromium, for example rustless iron and steel, out of mixtures of such ore and iron ore (or metallic iron), it is suitable to use bricks or lumps containing one or more oxides such as aluminum oxide, calcium oxide or magnesium oxide. Upon the reduction of the bricks in the furnace in this case aluminum, calciumor magnesium metal will be produced (or, according to the percentage of carbon in the bricks, carbides, for example calcium carbide), which metals (or carbides) will rapidly reduce the chromium oxide ore charged together with the bricks or lumps. hereupon aluminum oxide, calcium oxide or magnesium oxide will again be formed, which oxides are taken up in, the slag. As suitable aluminum oxide contain ing raw material in the bricks or lumps may be used aluminum oxide, alundum, bauxite and others. As suitable magnesium oxide containing raw material may be used magnesite or dolomite and others, and as suitable calcium oxide containing raw material may be used limestone, burnt, lime, marl and others. As the slag forming ingredients by reduction of chromite mainly will be aluminum oxide and magnesium oxide, the slag produced may be used for the brick-making. The temperature in the reduction zone of the furnace will be higher than by the reduction of chromium oxide ore directly by means of carboniferous reducing agents, and the slag will accordingly be hotter and more easily tapped than by the hitherto used processes for the production of ferro-chromium.

If the bricks are of high specific gravity it may in some cases be advantageous for easing the Work of the furnace to add a part of the reducing agents in'the charge in the form of lumps of carbon material, for example lumps of charcoal. Only a small quantity of such charcoal will be needed if a specially high percentage of carbon in the alloy is not desired. An excess of chromium oxide'ore may be eventually added for the compensation of such additional charges of Carboniferous material. It is however more convenient to use carboniferous reducing agents in the bricks or lumps of such quality that light and porous bricks are formed, in which case no supplementary addition of carboniferous materials is needed.

By using a surplus of bricks in proportion to the quantity of chromium oxide ore it will be possible to produce chromium alloys with for example'a high percentage of aluminum. In this case a slag of low specific gravity may suitably be used. As in dients in the slag, efiecting a low speci c gravity of same may be mentioned calcium sulphide, aluminumsulphide, magnesium sulphide and magnesium oxide. These named sulphides may be brought into the slag by adding charges of material already containing such sulphides, or additional, charges may be made of some other sulfidiferous material such as sulphide of iron, magnetic lIOIl pyrite and others. These materials will during the process, for example by reaction with the metal reduced out of the bricks, form in the furnace one or more of the light sulphides above mentioned, whereby the iron or other metal content in the sulfidiferous material is separated out.

If, however a chromium alloy with low or no percentage of aluminum is to be produced by means of bricks or lumps containing aluminum oxide the content of chromium oxide ore in the charge is accordingly regulated so that aluminum metal reduced out will wholly or substantially be oxidized through reaction with the chromium oxide ore. In this case it will be advantageous to work with a slag of comparatively high specific gravity, the reason for this being that i the reduction of the chromium oxide ore mainly will take place in the zone above the slag and accordingly a quicker reduction effected than will be the case if the chromium oxide first-is solved in the slag from which it must be reduced out.

' Upon the reduction of bricks or lumps containing magnesium oxide or calcium oxide, the magnesium or calcium metal will be obtained in the form of gas which vastly facilitates the reducing action on the ore. This appearance of the metal in the form of gas in the furnace will also take place to a great extent when aluminum metal is reduced out of bricks. The furnaces for the production of chromium or chromium alloys with the described method may suitably be the usual furnacesof the carbide furnace type.

The production of other metals and alloys with the present method is efi'ected in a similar way to that described above with {eference to the production-of chromium aloys.

Forthe production by means of the present process of iron "or steel it is especially advantageous to determine the ingredients in the bricks or lumps and the rest of the charge in such a manner that the slag formed by the smelting has such quality as to be suitable" for the production of cement. The working of the slaginto cement may be effected by means of the usual methods. By means of thepresent process it will thus be possible to produce as a by-product not only cement of the usual Portland composition but also more rapidly hardening aluminate cement and lime-aluminate cement. For the production of Portland cement the oxide containing raw material in the bricks or lumps may suitably consist of one or more CaO containing materials such as lime-stone, marl or burnt lime and of clay, bauxite or other A1 0 containing material and if necessary also of quartz or other SiO containing material. For the production of cement richer in aluminum oxide it will be best to use bauxite as an A1 0 containing raw material. The bricks or lumps are suitably. made with use of lime-water, clay or cement as a'binding agent. For this purpose a part of the cement obtained inv the process may be used, therebycirculating it in the process.

If however, the production of cement clare that what I claim is:

slags is not desired, bricks may be used with a high percentage of silica such as for-example quartz or sand. If the iron ore con-- tains lime, bricks-may be used which contain, besides'reducing agents, mainly silica. In other cases slag-forming materials other than silica must as a rule also be added, either forming part of the bricks or being charged separate. Two or more sorts of bricks or. lumps may be used, for example bricks containing one or more .of the oxides of calcium, magnesium or aluminum and carboniferous materials together with bricks containing SiO and carboniferous materials. Slags such as for example calciumsilicates or manganese-silicates may also be used as oxidiferolls ingredients incthe bricks.

In this case calcium-silicid or manganesesilicid will first be formed and these silicides thereupon reduce the iron ore. Aluminiumsilicates such as chamotte, clays and others may also be used as suitable raw materials a for the bricks.

On account of the fact that the temperature in the furnace mainly is determined by the reduction temperature for the bricks, the products snielted' by the process will reach' a higher temperature than will bethe case when producing for example pig iron in the usual way in an electric furnace.- Thus the temperature will be sufliciently. high ,even for the tapping of iron with low content of carbon. u

- If the bricks or lumps are'used in excessof iron ore, the iron may be obtained with the metal reduced out of'the bricks, for example silicon, manganese, aluminum, chromium and others. If however such amount of iron ore is used that a part of the iron oxide remains, un'reduced in the charge, it is possible by the present method to'obtain a product poor in carbon and other alloy ingredients. This product should h o\\'cvcr,-as a rule, be subsequently treated in specialv electric furnace for adjustment of the percentage of carbon and sulfur cleaning and so on. This subsequent treatment can however be made in much shorter time and Willbe" much cheaper than the refining of pigiron. The production of iron with the present process may if the iron ore mainly is in form of lumps be carried out in the usual electric shaft furnace.' If the iron ore is finely granulated or pulverized it will be more advantageous to work in an electric furnace of the carbide furnace type.

' For the production bythe present method .of metals and alloys with extremely low percentage of carbon, the quantity of carboniferous material in the bricks or lumps should-as a rule be less than the quantity of carbon required for the complete reduction of the oxidiferous material in the bricks or lumps.

Having thus described my invention I deprises reducing ores by fusing them in an electric furnace together with a quantity of reducing agent for the ores added in the 'form of lumps of material containing bauxite and carbonaceous reducing agents and lumps of material containing'magnesium oxide material and carbonaceous reducing agents.

3. A process for producing ferro-chromium alloys, which comprises reducing chromite ore by fusing it in an electric furnace together with a quantity of carbonaceous reducing agents added for the greater part in the form I of ingredients of lumps of material containing in addition to the carbonaceous agents a considerable amount of magnesium oxide.

4. Process for producing the elements with atomic number from22 to 26 in the periodic system, or alloys containing at least one of said elements, which comprises preparing a chargecontaining an oxide of at least one of saidelements and at least one oxide having a heat of formation equal to or higher than that of said first oxide; and carbon reducing agents in amounts insuflicient for the reduction of more than a part of the whole oxide content; keeping in the unfused condition the oxide of the first named kind, keepm sald oxide, compared with the last named k nd, in

less intimate contact with the reducing agents by adding a considerablepart'of the carbon reducing agents in. the form oflumps, said. lumps besides the reducing agents containing mainly an oxide of the last named kind; and reducm the oxide oft-he first named kind by fusing tlle charge in an electric furnace.

5. Process of producing the elements with atomic number from 22 to 26 in the periodic system, namely titanium, vanadium, chromium, manganese or iron, or alloys containing at least one of said elements, which comprises preparing a charge containing an ox ide ore of at least one of said elements and at least one of the oxides of aluminum, mag

tion of more than a part of the whole oxide content; keepingin the unfused condition the oxide of the first named kind, said oxide, compared with the last named kind, being kept in less intimate contact with the carbon material by adding at least a considerable part of the carbon reducing agents in form of lumps which besides the reducing agents mainly contain a considerable amount of at least one of the oxides of aluminum, magnesium and calcium; and reducing the oxide of the first named kind by fusing the charge in an electric furnace.

6. Process for producing ferrochromium alloys, which comprises preparing a charge containing chromite ore and material containing at least one of the oxides of aluminum, magnesium and calcium, and carbon reducing agents in amount insuflicient for the reduction of the whole content of oxides of iron and chromium; keeping in the unfused condition the chromite compared. with the material containing at least one of the oxides of aluminum, magnesium and calcium,

' said chromite being kept in less intimate contact with the'carbon material by adding at least a considerable part of the carbon ma terial in the form of lumps, said lumps besides the carbon'material mainly containing at least one of the oxides of aluminum, magnesium and calcium; and reducing the oxides of iron and chromium out of the chromite by fusing the charge in an electric furnace.

7. Process for producing chromium-alloyed iron or steel, which comprises preparing a charge containing chromite ore and iron and a material containing at least one oxide which has a higher heat of formation than that of chromium oxide; and carbon reducing agents in amounts insufiicient for the reduction of more than a part of the whole oxide content; keeping in the unfused con- 7 dition the chromite andthe iron, said materials, compared with the oxide of the higher heat of formation, being kept in 'less intimate contact with the carbon material by adding at least a considerable partof the car- 'bon material in form of lumps, which besides the carbon material mainly contain an oxide of .the last named kind; and reducing the oxide in the chromite ore by fusing the charge.

in an electric furnace.

8. Process of producing chromium-alloyed iron or steel, which comprises preparing a charge containing chromium oxide ore. iron ore, material containing at least one of the oxides of aluminum, magnesium and calcium, and carbon reducing agents in amounts insufficient for the reduction of the whole .content of oxides of iron and chromium,

intimate contact with the carbon material by adding a portion of the reducing agents as