US2291685A - Manufacture of manganese alloys and the like - Google Patents

Description

Fatented Aug. 4,

MANUFACTURE OF MANGANESE ALLQYS AND THE LIKE of Delaware No Drawing. Application February 7, 1940,

Serial No. 317.659

3 Claims.

This invention relates to the manufacture of term-manganese, spiegeleisen and other manganese alloys and relates more particularly to the preparation of. manganiferous materials in the term of briquettes or in other convenient form form in the manufacture of steel.

Farm-manganese, which contains about 80% manganese and about 12% iron, and the balance principally carbon and phosphorus, is used widely in the steel industry for deoxidiz'ing practically all grades of steel. This, as well as the lower grades of manganese-iron alloys are mostly made by reducing and smelting the manganese ore in a blast furnace and forming the molten metal into pigs. The production of ferro-manganese or other manganese alloys by a melting process is comparatively expensive because of relatively high manganese losses, especially when made in a blast furnace where there is a loss of between 12% and 20% of the original manganese content of the ore in the slag and gases removed from the furnace. Such high losses do not occur when manganese alloys are prepared in electric furnaces, but the high cost of power and electrodes makes production cost by this method relatively high. Moreover, these alloys as now produced, are not of a high degree of purity, for they absorb carbon from the coke, or from the electrodes. Also, most of the phosphorus contained in the ore remains n the metal. The carbon cannot be removed and is absorbed by the steel, which is objectionable when the steel is a low carbon steel; the phosphorus brought into the steel by the ferro-manganese is detrimental to almost all grades of steel.

Another disadvantage of the manganese alloys that are now available is that they are cast in the form of pigs or slabs which must be broken up or crushed in order to place them in better physical condition to be absorbed by the molten steel. If, in the act of crushing some of'the material becomes too small, it readily oxidizes and,

unless used promptly, partially reverts to the I,

' steel, eliminating the usual breaking or crushing with the consequent loss through oxidation, and restricting oxidation during longer storage by greater density of grain structure. Moreover, the briquettes or tablets are of controllable grain structure, density and specific gravity, so that they are readily submerged and absorbed in the bath of liquid steel.

Generally the process of this invention conslsts in charging a finely-divided manganese ore into a furnace where it .is reduced by gaseous, liquid or solid fuel in a reducing atmosphere without fusing or melting the powdered material, and pressing it while hot into tablet form.

More specifically, in practicing the process, the manganese ore which may contain oxides of manganese and oxides of other metals, if not already in a finely-divided condition, is reduced to such condition by crushing and grinding, and the fineness of the powdered ore must be such as to free the valuable portion of the ore from the gangue which is associated therewith. The gangue may then be separated from the remainder of the ore in any suitable way, for example, by flotation, thus leaving a comparatively pure form of the oxides for further treatment. This partially purified ore is then passed through the reducing furnace in which and subsequent collectors, for instance of the cyclone separation type, a further removal of the gangue, or ash if solid fuel is used, takes place by reason of the difierence in specific gravity of the metals and the gangue, the former being precipitated first and the latter being carried along in the stream of gases, The reduced ore is recovered as a finely-divided powder or spongy mass similar to powdered or granular sponge iron; which if not sumciently finely-divided, may be recrushed and ground to that state.

The reduced powder, while still hot or further heated, is then passed to a press where it is compacted to form briquettes or tablets of a suitable size for use as a deoxidizer of molten steel. In some cases this may be done cold.

The heated metal in pulverulent form is particularly susceptible to oxidation and, therefore, all of the processing of the metal to shape it into briquettes or tablets is preferably carried out in a non-oxidizing atmosphere of inert or reducing gases which precludes the reoxidation of the material.

Preferably moderately high pressures are used for compacting the material in a single operation into self-sustaining briquettes or tablets, or the density of the material may be increased by repeated pressing operations. Whether or not it is desired to repeat the compacting treatment of the material, the briquettes or tablets are then heated to a higher temperature than that at which they were originally formed, and preferably to about the surface fusion temperature of the material, so that the surface of the briquette or tablet is relatively denser than the interior thereof, this denser surface reducing the penetration of the air and thus inhibiting material oxidation without interfering with the absorbability of the briquette or tablet in the steel. If more accurate dimensions of the briquettes are wanted, or a harder surface, they are further compacted as by pressing. The pressure applied should preferably be such that the density of the tablets is substantially greater than that. of the molten steel, so that they will quickly submerge and become absorbed in the lower as well as upper part of the molten steel in the ladle or furnace.

A suitable apparatus for treating the material and shaping it into briquettes is disclosed in my copending application Serial No. 316,717, filed February 1, 1940, now Patent No. 2,252,697, which includes a chamber into which the granular, pulverulent or metallic sponge is delivered in charges of predetermined size and then compacted into briquettes by means of a hydraulic ram. Such briquettes may, if desired, be subjected to repeated treatment with hydraulic rams of similar type after reheating or they may be rolled while heated and thus compacted into a dense mass. All of these operations should be carried out in a non-oxidizing atmosphere in order to preclude re-oxidation.

The briquettes may be made in any desired shape, form or size, such as, for example, rectangular tablets, like cakes of soap, or cylindrical or polygonal tablets, and if desired, of small volume, so as to be rapidly absorbed and melted in the bath of steel, but always of a high density so as to quickly submerge in the bath of liquid steel.

If desired, a flux, such as soda or fiuorspar, or a binder for binding the particles, such as sodium silicate, or both, may be added to the material before it is compacted into the briquettes or tablets, the requirement of either of these additions being. that they must have a materially lower fusion point than the steel to be treated in order to avoid slag enclosures in the ingot formed from the treated steel.

An advantage of the above described process is that there is no carbon included in the tablets for the reason that the manganese is not reduced to a molten condition in the presence of blast furnace coke or carbon electrodes, and the carbon and other impurities therefore. are not dissolved or occluded in the metallic materials. Inasmuch as the reduced material is in a pulverulent form, the reduced metal may be separated to almost any degree desired from ash or nonmetallic materials which may have been present in the ore, thereby providing a simple and effective way of obtaining a material of a high degree of purity and having a low carbon content. This material, therefore, may readily be used in the purification of all types of steel and because of its convenient briquette or tablet form it need not be broken up or even weighed to provide the required amount of manganese in readily absorbed form. Any desired number of briquettes providing the required manganese content can be added to the steel, thus providing a convenient method ofdetermining the actual amount of manganese supplied to the furnace.

It will be understood that various methods of reducing the ore to a metallic powder may be used in the process, and the example of the process given above should be considered as illustrative only and not as limiting the scope of the following claims.

I claim:

1. The method of pre aring manganese products which consists in concentrating, in finely divided condition, an oxide of manganese, reducing said oxide at a temperature below that at which the manganese will melt, and effecting, in a non-oxidizing atmosphere while retaining the residual heatof the reduction operation, compression of the finely divided metal particles into self-sustaining briquettes and then, while maintaining each briquette in a non-0;.ldizing atmosphere, heating it to a higher. temperature and further compressing it to provide it with a surface substantially impenetrable to oxidation gases when cooled.

2. The method of preparing manganese products, which consists in concentrating, in finely divided condition, an oxide of manganese, reducing said oxide at a temperature below that at which the manganese will melt, forthwith effecting, in a non-oxidizing atmosphere and while said finely divided metal particles are still hot from the reducing operation, compression of said particles into self-sustaining briquettes and then, while still maintaining each briquette in a non-oxidizing atmosphere, heating it to a higher temperature and further compressing it to a density such that the specific gravity of the briquette is greater than that of molten steel to be treated thereby and that its outer surface is sufficiently compact to exclude oxygen from the interior thereof.

3. The method of preparing manganese products, which consists in concentrating, in finely divided condition, an oxide of manganese, reducing said oxide at a temperature below that at which the manganese will melt and, while said reduced finely divided ore is still hot from the reducing operation and is still in a non-oxidizing atmosphere, effecting a separation of the reduced metal particles fromother solid products of the reduction operation and forthwith compressing the finely divided metal particles into self-sustaining briquettesand then, while still maintaining the briquettes in a non-oxidizing atmosphere, fusing the surfaces thereof inorder to provide each with a surface sufiiciently compact to 'exclude oxygen from the interior thereof.

HERMAN A. BRASSERT.