US2221624A - Treatment of manganese alloys - Google Patents

Description

Patented Nov. 12, 1940 UNITED STATES PATENT OFFICE TREATMENT OF MANGANESE ALLOYS No Drawing. Application February 20, 1939, Serial No. 257,455

14 Claims.

This invention relates to the treatment of manganese alloys and is particularly concerned with the removal of sulphur therefrom in order to provide alloys essentially free of sulphur.

The presence of sulphur in manganese alloys and manganese base alloys is most likely to occur by virtue of the employment of electrolytic manga-nese as a constituent of such alloys. Electrolytic manganese, as prepared in accordance with.

ing or fabricating operations impossible as well as deleteriously aifecting various properties and characteristics of said alloys. While, in many instances, it is of advantage to remove the sulphur from the electrolytic manganese prior to alloying the manganese with such other elements as may comprise the alloys, there are occasions when it may be preferable initially to form the manganese alloy from the electrolytic manganese containing the aforementioned amounts of sulphur and then to treat the resulting alloy ,to effect desulphurization.

It will be clear that if electrolytic manganese containing 0.3% sulphur is employed in an alloy containing say 40% of manganese, the sulphur content of the finished alloy will be 0.12% assuming that sulphur has not been introduced into the alloy from any other source. If, however, the manganese content of the alloy is say 90%, then the sulphur content of the finished alloy would be 0.27%. In the usual case,.-the sulphur content of the alloys should be reduced to not substantially in excess of 0;02% and should preferably be substantially less than that or in other words of the order of a few thousandths of a percent.

In accordance with my present invention, the sulphur, however it may have been introduced into the manganese alloys, is effectively removed in a simple and inexpensive manner.

In general, the removal of the sulphur from the manganese alloys containing the same is efiected by mixing the latter, in the molten state, with an oxygenated boron compound. This treatment effectively removes the sulphur but introduces boron into the alloy. The latter is then treated, in a molten condition, with an oxide of manganese, particularly manganese dioxide. In this manner, the boron may be removed to such an extent that it is below the point of accurate analytical determination. The result is the preparation of a substantially sulphur-free manganese alloy. In those cases where I boron is not a deleterious constituent of the alloy,

it may be permitted to remain in the alloy and the subsequent step of treatment with manganese oxides may be eliminated. Indeed, in certain alloys, the presence of small amounts of boron 1 is highly desirable. The present invention enables the production of such alloys simultaneously with the efiective reduction or substantial elimination of sulphur therefrom.

The oxygenated boron compounds which I employ for the sulphur removal treatment may be selected from a group which includes B203, boric acids, and salts, particularly alkali metal salts, of boric acids such as sodium and potassium metaborates and tetraborates. Of particular utility is sodium tetraborate or borax. The sulphur is removed in the form' of a gas, namely, sulphur dioxide.

The reaction of the sulphur-containing manganese alloy with the oxygenated boron compound is not a surface reaction but the oxygenated boron compound appears to disperse or dissolve in the molten manganese alloy and is apparently in equilibrium with the dispersed or dissolved manganese or other sulphide present in 30 the manganese alloy. As a result, a substantial, though minor, amount of oxygenated boron compound must be added in some cases to obtain efiective desulphurization. It should be understood that I do not wish to be limited by 35 what the exact mechanism of the reaction may be since the inventionis predicated upon discoveries and results entirely independently of theoretical considerations.

The following examples are illustrative of my 40 invention, although it will be appreciated that they are subject to variations with respect to temperatures, times of treatment and character of manganese alloys being treated without departing from the spirit of the invention and the 4.5 novel teachings herein as defined in the appended claims.

Erample I (a) pounds of an alloy, comprising 20% 50 nickel, 30% copper and 50% ofelectrolytic manganese containing 0.25% sulphur (the sulphur content based on the alloy as a whole being 0.125%), are melted in a high frequency induction furnace at a temperature between 1300 de- 66 grees C. and 1400 degrees C. To the molten alloy, maintained at the indicated temperature, 8 pounds of borax are added. The stirring which ls produced by the high frequency current is allowed to proceed for 15 to 20 minutes. The borax is then removed as completely as possible from the melt.

(b) The manganese alloy, containing several tenths of one percent of boron, which is produced in part, (a) hereinabove, is mixed, in the molten state, at a temperature of about 1500 degrees C. with 2 pounds of manganese dioxide, the mass being maintained at a temperature of 1500 degrees C. to 1550 degrees C. for between 5 and 15 minutes. The manganese oxide slag is then removed and the metal cast into ingots. On analysis, the resulting manganese alloy contains .005% sulphur and .002% boron.

Example II (a) 100 pounds of an alloy, comprising 15% chromium, 48% iron and 37% electrolytic manga'nese containing 0.28% sulphur (the sulphur content based on the alloy as a whole being about 0.10%), are melted in a high frequency induction furnace at a temperature between 1600 degrees C. and 1650 degrees C. To the molten alloy, maintained at such temperature, 10 pounds of borax are added. The reaction is allowed to proceed for 10 to 20 minutes. The borax is then removed as completely as possible from the melt.

. (b) The manganese alloy, containing several tenths of one percent of boron, which is produced in part (a) of this example, is mixed, in the molten state, at a temperature of about 1600 degrees 0., with 2 pounds of manganese dioxide, the mass being maintained at a temperature of 1600 degrees C. to 1650 degrees C. for between 10 and 20 minutes. The manganese oxide slag 40 is then removed and the metal cast into ingots.

.On analysis, the resulting manganese alloy contains .005% sulphur and .002% boron.

Example III (a) 100 pounds of an alloy, comprising 10% copper and electrolytic manganese containing 0.24% sulphur (the sulphur content based on the alloy as a whole being about 0.21%), are melted as described in the previous examples at a temperature between 1400 degrees C. and 1450 degrees C. To the molten alloy, maintained at the indicated temperature, 10 pounds of borax are added and the reaction is allowed to proceed for from 10 to 20 minutes. The borax is then removed as completely as possible from the melt.

(b) The manganese alloy, containing several tenths of one percent of boron, which in produced in part (a) of this example, is mixed, in the molten state, at a temperature of about 1450 degrees C. with 5 pounds of manganese oxide, the mass being maintained at a temperature of 1450 degrees C. to 1500 degrees C. for between 10 and 20 minutes. The manganese oxide slag is then removed and the metal cast into ingots. On analysis, the resulting manganese alloy contains .005% sulphur and .009% boron.

While the practice of the invention is illustrated in the above examples with respect to certain alloys, it is of utility in connection with the treatment of all manganese-base alloys, particularly those having a manganese content in excess of 30%. The alloys may contain one or more of the elements nickel, copper, iron, carbon, zinc, vanadium, chromium, tungsten, molybdenum, tin, aluminum, beryllium. silver, magnesium, titanium and/or other elements in varying amounts, some from a fraction of one percent to several percent and others as high as about 70%.

The melting of the manganese alloys is preferably carried out in a highly dense alumina crucible although magnesia crucibles may be used in certain cases. If it is desired to avoid the introduction of silicon into the manganese alloy, crucibles containing silica or silicates should be avoided or, in general, the melt should not be exposed in any way to contact with silica or silicates.

The proportions of oxygenated boron compounds and oxides of manganese are subject to relatively Wide variations. The proportions utilized depend, among other things, on the amount of sulphur present and the amount of boron introduced into the manganese alloy, it being understood that the smaller the percentage of sul- I phur and boron the less oxygenated boron derivatives and oxides of manganese, respectively, will be required. In the average case, from 5% to 10% of borax or the like and from 1% to to 4% of a manganese oxide, based on the weight of the manganese alloy, will be suflicient to achieve the desired results.

The temperature at which the manganese alloys and borax or the like and the oxides of manganese, respectively, are mixed is variable. It should not be so high as to cause undesired volatilization. About 1300 degrees C. to 1600 degrees C. represents a preferred working range, although, of course, the temperature employed will depend upon the nature of the manganese alloy and the nature of the oxygenated boron compound or oxide of manganese, as the case may be. In general, a satisfactory range is from 50 degrees C. to degrees C. above the melting point of the manganese alloy.

It is sometimes advantageous, in carrying out the step of removing the boron, to mix the oxide of manganese with a small amount of a fluxing material such as sodium carbonate, calcium carbonate or calcium fluoride. In general, however, good results are obtained without resorting to such practice.

My copending application, Serial No. 250,377, filed January 11, 1939, discloses and claims the use of oxygenated boron compounds for the desulphurization of electrolytic manganese, while my copending applications, Serial No. 257,456, filed February 20, 1939, and Serial No. 257,457, filed February 20, 1939, relate to the treatment of manganese and manganese alloys, respectively, by means of acidic oxides, of which class of substances, boric acid is a member.

What I claim as new and desire to protect by Letters P-atent of the United States is:

1. The method of substantially reducing the sulphur content of a manganese alloy containing relatively high proportion of manganese, which comprises contacting said alloy, in molten condition, with an oxygenated boron compound for a period of time suflicient to efi'ect the desired removal of thesulphur, whereby boron is introduced into the manganese alloy, and then mixing the resulting manganese alloy, in molten con- 7 tion, with an alkali metal salt of boric acid tor a a of time suficient to effect the desired removal of the boron.

3. The method of substantially reducing the sulphur content of a manganese alloy containing at least 30% manganese and simultaneously said manganese alloy, in molten condition, with an oxide of manganese for a period of time sufficient to efiect the desired removal of the boron. 6. The method of reducing the boron-content of a manganese alloy from approximately 0.1% I

or more to approximately 0.02% or less which comprises mixing said manganese alloy, in molten condition, with manganese dioxide for a period of time sufficient to efiect the desired removal of the boron.

'7. The method of substantially reducing th sulphur content of a manganese alloy containing the same which comprises contacting said alloy, in molten condition, with from about to about of an oxygenated boron compound for a period of time sufficient to efiect the desired removal of the sulphur, whereby boron is introduced intorthe manganese alloy, and then.

mixing the resulting manganese alloy, in molten condition, with from about 1% to 4% of an oxide of manganese for a periodof time sufficient to effect the desired removal of the boron. 8. The method of substantially reducing the sulphur content of a manganese alloy containing at least 30% of electrolytic manganese which comprises contacting said manganese alloy, in

molten condition, with borax for a period of time suflicient to effect the desired removal of the sulphur, whereby boron is introduced into the man ganese alloy, and then mixing the resulting manganese alloy, in molten condition, with manganese dioxide for a period of time sufiicient to effect the desired removal of the boron.

9. The method of substantially reducing the sulphur content of a manganese alloy containing at least 30% electrolytic manganese which comprises agitating said-manganese alloy, at a temperature about-50 degrees C. ormore above its melting point, with borax for a period of time sufiicient to e'fiect the desired removal of the sulphur.

10. Themethod of-substantially reducing the boron content of a manganese alloy containing at least 30%'manganese which comprises mixing said manganese alloy, in molten condition, with manganese dioxide at a temperature between about 1300 degrees C. and 1500 degrees C. for a period of time suflicient to effect the desired removal of the boron.

11.- The method of reducing the boron content of manganese alloys from approximately 0.1% or more to approximately 0.02% or less which com-.

agitating said manganese alloys, in a molten condition, with an alkali metal'salt of boric acid for a period of time suflicient to efiect the desired removal of the sulphur.

13. The method of reducing the sulphur content of manganese alloys containing at least 30% electrolyticmanganese from approximately 0.2% or more to approximately 0.02% or less which comprisesmelting said manganese alloys and mixing the same with borax at a temperature of from about 1300 degrees C. to 1500 degrees C.

14. In a method of producing a substantially sulphur-free manganese alloy from an alloy prepared from electrolytic manganesasaid alloy initially containing at least 0.05% sulphur, which comprises agitating said manganese alloy, in a molten condition, with an oxygenated boron compound for a period of time suflicient to effect the desired removal of the sulphur.

C. TRAVIS ANDERSON.