US2222035A

US2222035A - Production of alloys

Info

Publication number: US2222035A
Application number: US226962A
Authority: US
Inventors: Robert R Jones
Original assignee: Ohio Ferro-Alloys Corp
Current assignee: Ohio Ferro-Alloys Corp
Priority date: 1938-08-26
Filing date: 1938-08-26
Publication date: 1940-11-19
Anticipated expiration: 1957-11-19

Description

Patented Nov. 19, 1940 STATES gzzzpas FFHC PRODUCTION or ALLOYS poration of Ohio No Drawing. Application August as, 1938, Serial No. 226,962

9 Claims.

This invention relates to the production of alloys. Although the invention is adapted generally to the production of metallic alloys, both ferrous and non-ferrouait'is suited particularly to the production of iron and steel, 1. e., ferrous, alloys for which reason it will be described with particular reference thereto by way of illustration but not of limitation.

In the production of ferrous metal alloys the 10 common practice is to add the requisite alloying element or elements to the furnace charge prior to bringing it to the molten condition, or to add the alloying element or elements to the molten bath. Such alloying elements are, for example,

35 silicon, chromium, manganese, titanium, tungsten, vanadium, molybdenum, and others well known in the art. These may be added as such or in combination with other alloying elements or in the form of ferro-alloys, and commonly they are used in either lump or similar massive form, or in sub-divided form such as powder.

In such practices dimculties are encountered in the production of metals of these and other added alloying elements in consequence of their oxidation during the process of forming the metals. Not only does such oxidation increase the cost of the metal through loss of the alloying element, some of which are quite expensive, but also it is necessary to insure removal of the oxi- 80 dation product from the metal, and in some instances surface oxidation of the particles of the alloying element may substantially decrease the rate of solution in the molten bath. These factors become more prominent, generally speaking,

when the alloying element is used in powdered form. Although in such form they shouldalioy more rapidly, due to the increase in exposed surface, than lumps or similar large particles, the

increase in exposed surface likewise increases oxidation losses, and losses may be encountered through dusting. Also, such material may tend to float on the surface of the bath, which further enhances oxidation and makes it difficult to produce a uniform melt.

It has been proposed heretofore to protect alloying elements against oxidation by coating the particles with refractory protective material. For example, it has been proposed to mix the alloying element with a silicate, such as Portland cement, which acts as a binder for the formation of aggregates of briquettes and serves to protect the element against oxidation in forming a metal. These proposals are objectionable in that such silicates serve no useful function in the alloying operation and are not required in the bath,

and they must be removed. Where the protective materials are highly refractory their use is limited to smelting Operations and applications, for such briquettes are not commercially applicable to molten bath or ladle additions. On the other 5 hand, if the protective material be modified to confer lower softening or melting point, its protective action is adversely affected;

It is among the objects of this invention to produce alloys without the foregoing and related 30 disadvantages.

Another object is to provide alloying elements in a form in which they are adequately protected against oxidation without the use of agents possessing objectionable characteristics.

Other objects will appear from the following description.

In the practice of this invention use is made of the reducing properties of carbon when heated to protect alloying elements against oxidation. In accordance with the invention the alloying element is mixed intimately with carbonaceous material capable of being coked upon heating, and the resulting mixture is then subjected to a temperature such as to effect coking. In this manner there are produced coked aggregates through which the alloying element is disseminated, and the carbon of the coke acts to reduce or minimize oxidation of the aggregates when added to a furnace charge or a molten bath for the purpose of producing an alloy containing the element. Such coked aggregates may then be used to supply one or more alloying elements with avoidance of the disadvantages encountered heretoiore in the use of such alloying elements io producing metallic alloys or metals.

A variety of coking agents are available, such as asphalt, pitch, starch, and other carbonaceous materials which coke when heated to an appropriate temperature. For many purposes I prefer to use coking coals. For that reason they will be referred to as exemplifying the coking agents in the following more detailed description of the invention.

The mixture of alloying element and coking coal may be charged into a coking oven and coked therein, the resulting coked mass being broken up into masses of desired size. For most purposes, however, it is preferred to form the mixture into briquettes of predetermined size or alloy content which are then heated to a coking temperature, and in this embodiment there may be incorporated with the mixture, if desired, a small amount of temporary binder so that the briquette will be form-retaining, for handling until it has been coked. Such temporary binders should be of a. character such as to be unobiectionable in the ultimate use of the briquette, various binders of this character being known in the art, such as water, asphalt, goulac, dextrine, and the like. The temperature at which the material is coked will vary depending upon the properties of the particular coking agent used, but with many coking coals it suffices to heat to, for instance, 300

to 600 C.

Enough coking coal is added to the alloying element to afford protection against oxidation of the alloying element in the coked aggregate or briquette. The minimum quantity of coking coal or other coking agent will vary with its coking characteristics. Apart from such factors, however, there is nothing critical in the proportions of the alloying element and the coking coal, although in most instances it is desirable to have as high a proportion of alloying element present in the coked product as possible. For some purposes, as in recarburization of ferrous alloys, the presence of an excess of carbon may be desirable. In view of these considerations it is not possible to fix proportional limits for the constituents of the material applicable to all alloy elements, coals and purposes.

The alloying element may be finely divided or in the form of rather coarse particles or lumps,

depending upon the conditions and requirements of use. The chief criterion is that in the coked product the coke shall adequately surround the alloying element and be in an amount sufiicient to protect it against oxidation.

Although for reasons just stated exact limits can not be set for the amounts of alloying element and coking coal to be used, which proportions may vary also depending upon the ease of oxidation of the particular element, the following examples are illustrative of the invention:

Example 1.20-mesh ferrosilicon containing 50 per cent of silicon and Pittsburgh No. 8 coal powdered so that 80 per cent passesa ZOO-mesh sieve are mixed in the proportions of 84 per cent of ferrosilicon to 16 per cent of coal. ture is coked at 600 C.

Example 2.-Ferrochrome powdered to pass a ZOO-mesh sieve is mixed with coal as in Example 1 in the proportions of 80 per cent of ferrochrome and 20 per cent of coal. The mixture is coked at 600 0.

Example 3.50 per cent ferrosilicon in the form of inch lump and down is mixed with Pittsburgh No. 8 coal crushed to pass a screen having a mesh, the fines being retained in the coal. The two are mixed in the same proportions as in Example 1, and the mixture is coked at 600 C.

It will be understood that the practice of the invention is not limited to the use of a single alloying element. Two or more such elements as such or as ferro-alloys, for instance, may be mixed with coking coal and treated as described above. Also, other beneficial agents may be added to the mixture, such as a flux, whose presence during the alloying operation is as advantageous as in other operations, for instance welding. By mixing a suitable fluxing agent with the coking coal and alloying element prior to coking there are produced self-fluxing briquettes which more readily alloy when used. This is advantageous particularly because the flux, if required, will take care of the ash contained in the coke and thus expedite and improve the alloying operation. For most purposes I prefer to use lime as the flux, if one is required, not only The mix-v because it exerts the functions just described, but also because it tends to produce a harder and less porous coke than is produced when it is not present. The quantity of lime or other fluxing' agent used is dependent upon the composition and quantity of ash in the coke, but the amount necessary can be calculated readily. Similarly,

more than suificient flux to take care of the ash in the coke may be incorporated to form either a basic or acid low melting residue as the nature of the alloying operation requires.

Various modifications may be made without departing from the essence of the invention. For example, the coking may be effected under pressure if it is desired to produce briquettes of greater density than would otherwise result. Also, some cokes tend to be rather porous and slightly brittle when rubbed, and to improve the briquettes in handling for shipment and charging they may be coated with a material to minimize such factors. For instance, they may be dipped in an asphalt bath after coking, or dipped in or sprayed with a glazing material, such as a mixture of bentonite clay and silica flour, after pressing and before coking. For ease of selection and to avoid errors, it is contemplated that a characteristic color will be applied to the exterior of the briquettes to distinguish those of different alloying materials, and those of varying contentsof a particular alloying element. This may be done by applying color to the coked briquette, or through suitable glazing compositions.

Through the practice of the invention there is provided material for producing alloys. and metals in which the alloying element is adequately protected against oxidation during the melting of a furnace charge or after addition to a bath of molten metal, and with other advantages which will be understood by those familiar with the art from the foregoing description. The use of briquettes is likewise advantageous because they can be produced with standard, predetermined amounts of alloying element so that a given alloy may be produced by adding the necessary number of briquettes, thus eliminating weighing operations.

The briquettes may be used generally for alloy addition to metals, as in open hearth, electric furnace, cupola, and the like practice. They may be added with the charge, to the bath, to the runner or ladle, or otherwise as circumstances may make desirable.

A particular advantage of the briquettes as applied to the production of ferrous metal alloys is that they not only protect the alloying elements against oxidation, but also may be used to effect increase of the. carbon content of the bath where that is necessary or desirable. Thus alloying and carbon introduction are carried on together under especially advantageous conditions for the carbonaceous material is weighted by the alloy and carried into the molten bath, thus facilitating carburization of the bath.

According to the provisions of the patent statutes, I have explained the principle and mode of practicing my invention, and have described what I now consider to be its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

-I claim:

1. That method of minimizing oxidation of an alloying element in producing an alloy thereof with a metal which comprises melting said metal and adding thereto coked aggregates of an intimate mixture of coking coal and said alloying element, oxidation of said alloying element during alloying thereof with said metal being prevented primarily by the coke of said aggregates.

2. That method of minimizing oxidation of an alloying element in producing an alloy thereof with a metal which comprises melting said metal and addin'gthereto coked aggregates of an intimate mixture of coking coal, said alloying "element and a flux, oxidation of said alloying element during alloying thereof with said metal being prevented primarily by the coke of said aggregates. v

' 3. That method of minimizing oxidation of ferro-alloy alloying element in producing an alloythereof with a metal which comprises melting said metal and adding thereto coked aggregates of an intimate mixture of coking coal, finely divided ferro-alloy metal and lime, oxidation of said ferro-alloy metal during alloying thereof with said metal being prevented primarily by the coke of said aggregates.

4. That method of producing an alloy of a metal with an alloying element which comprises melting said metal and heating with it coked aggregates of an intimate mixture of coking coal and said alloying element in which oxidation of said element during alloying is prevented primarily by the coke of said aggregates, said alloying element constituting the major component by weight I of said coked aggregates.

5. As a new article of manufacture, coked aggregates of coked carbonaceous matter havin distributed therethrough an alloying element to be alloyed with another metal to which said aggregates are added, said coked carbonaceous matter substantially preventing oxidation of said alwloying element during alloying with said other metal and thereby effecting alloying of substantially the entire content of said element, said alloying element constituting "the major component by weight of said coked aggregates.

6. Asa new article of manufacture, coked aggregates of coked coal having distributed therethrough an alloying element to be" alloyed with another metal to which said aggregates are added, said coked coal substantially preventing oxidation of said alloying element during alloying with said other metal and thereby eflecting alloying of substantially the entire content of said element, said alloying element constituting the major component by weight of said coked aggregates.

7. As a new article of manufacture, coked aggregates of coked coal having distributed therethrough ferro-alloy metal to be alloyed with another inetal to which said aggregateaare added, said coked coal substantially preventing oxidation of said ferro-alloy metal during its alloying with said other metal and thereby eilecting all o ing of substantially the entire content of' s d ferro-alloy metal, said ferro-alloy metal constituting the major component by weight of said coked aggregates.

8, As a new article of manufacture, coked aggregates of coked coal having distributed therethrough ferro-ailoy metal to be alloyed with another metal to which .said aggregates are added, and lime in an amount to flux ash of said coal,

said coked coal'substantially preventing oxida- "tion of said ierro-allo'ymtal during its alloying with said other metal and thereby eifecting alloying ofsubstantially the entire content oi said ferro-alloy nietal.

9. As a new article of manufacture, coked aggregates of coked coal having distributed therethrough ferro-alloy metal to be alloyed with another metal to which said aggregates are added, said coked coal subs antially preventing oxidation of said ferro-all metal during its alloying with said other metal and thereby efiecting alloy ing of substantially the entire content of said ferro-alloy metal, and said aggregates being provided with a separate non-metallic coating protective against dusting due to abrasion and shock and against oxidation of said ferro-alloy metal.

ROBERT R. JONES.