US1947735A - Process of producing steel - Google Patents

Description

Patented Feb. 20, 1934 UNITED STATES PATENT OFFICE .Minnesota Metallurgical 00.,

Minn, a corporation Minneapolis, of Minnesota No Drawing. Application April 14, 1932 Serial No. 605,351

5 Claims.

My invention relates particularly to the reduction of iron ore admixed with the ores of other metals, and provides an improved process whereby iron and its alloys, by a single or one-step process,

may be reduced to the form of steel, either pure steel or steel alloy. The steel or steel alloy thus produced may, by certain variations of the process, be brought down in various forms ranging from what is properly designated as a soft or mild steel to'a very hard steel, such as tool steel or even a harder steel, and to a degree of hardness and tensile strength which resists cutting and forging. The process can be best carried out in an electrical induction furnace, (although the H process is not limited to the use of such a furnace) in which the ores and the reducing agents and flux hereinafter described, should be placed before the heat is turned entirely on to the furnace.

For several years I have been engaged in experimenting with the process disclosed and claimed in Letters Patent of the United States, No. 1,850,381, issued to George A. Code of date March 22, 1932; and in my experiments I have discovered that the salts of certain acids may be utilized with as good and in many instances,

better results than with the acids.

Before discussing the broad features of the invention, I will describe in detail one of the several successful ways in which the process has been carried out in actual practice. It is understood that I am not limited in my invention by the exact proportion of reacting materials, by the time or by the exact temperature cited in the example given below. 1

Example Into the furnace place twenty-five (25) grams of a salt of mucic acid, such as sodium mucate, then place therein approximately fifteen (15) pounds of dressed ore (e. g. 63% iron content), such for example, as comes direct from Minnesota mines. On top of the above mixture place a flux consisting of two and one-half (2 /2) pounds of lime and one hundred (100) grams fluorspar. Turn on the heat to produce temperatures as follows:

First hour, twenty-five hundred (2500) degrees F.; second hour, two thousand six hundred fifty (2650) degrees F.; third hour, two thousand eight hundred fifty (2850) degrees F.; and during approximately one-half of the fourth hour a furnace temperature of two thousand nine hundred (2900) degrees F.

During the last approximate half hour in the above process, if the steel is found deficient in the requisite amount of carbon, a proper amount of charcoal can be mixed into the molten mass, or if too much carbon is present, the high temperature can be maintained until a proper percentage 01' carbon in the molten steel is attained. The above suggested addition of carbon is not for the purpose of reduction, but to supply a carbon content necessary for the inter-crystalline cement of the steel. In many instances, the addition of further carbon will not be necessary.

The end product produced by the above process, where the metal of the ore is entirely iron will be a true steel, but where the ore contains other metals such as manganese, nickel, cobalt, cop-' per, tungsten, vanadium, chromium, lead etc.,the end product will be as'teel alloy; but the final product will be produced by a single step process, as distinguished from a two-step process such as has been hitherto employed and wherein the ore is first reduced to pig iron, and by a second step, is reduced from pig iron to the form of a steel or to a steel alloy.

I am unable to state the exact chemical or physical reactions that take place in the above process, but the results of the process have been definitely established. The fact that the desired results have been and may be attained by quantities of reducing agencies which in themselves are too small (as small as three-fourths of one per cent) for the requirements of the accepted chemical equations depicting the reduction of iron ore, seems to indicate that the organic compound which is added, or some subsequent decomposition product of such added organic compound, is the active agent and acts as a catalyst.

To date, I have obtained the best results by the use of a salt of mucic acid, such as sodium mucate, which, of course, is an organic compound; but I have obtained results differing only in degree by the use of other organic salts which are more or less closely related in their chemical structure to salts of mucic acid, such as salts of citric acid, tartaric acid, and oxalic acid. These substances are all salts of polycarboxylic acids. The polycarboxylic acid salts employed may or may not contain one or more substituted groups in the organic acid. I have found that various different polycarboxylic acid salts will combine with the flux to produce the desired action with the general results above stated, but so far as my present experiments have gone, the polycarboxylic acid salts which produce the above action in the flux are of the aliphitic or chain type. As to time and temperature, I have found that while under the conditions of my experimentation, the best results can be obtained by quite closely following the instructions of the above given Example 1, I do not wish to be limited to the exact temperatures and the conditions which are noted.

The results obtained indicate that the action of the organic reagent is a catalytic reaction hitherto unknown, and that, in connection with the flux or other elements present, such a process serves to free the iron from oxygen, but at the present date I am unable to state just what this catalytic agent is, or exactly in what manner it reacts. I do know however, that by the use of a certain class of organic chemical compounds which, in themselves have insufficient carbon and hydrogen content to efiect the reduction by exchange of their carbon and hydrogen elements, neverthelesathe reaction produced causes a disassociation of the oxygen from the iron ore at approximately the temperatures indicated and by approximately the treatment outlined in the example above. This action, for lack of a more definite term, I have designated as a catalytic action that causes a disassociation oi the oxygen from the iron ore, the iron of the ore being recoverable in the form of steel or of steel alloys in the event that the original ore batch contained other admixed metallic ores or oxides.

In practice, I have found that while the proportions of ingredients used may be greatly varied, that they should be kept within the following ranges of proportion, to wit: from fifteen (15) to thirty-five (35) grams of polycarboxylic acid salt for fifteen (15) pounds of ore.

I What I claim is:

1. The process or" reducing oxide iron ores and admixtures of ores to the form of true steel and its alloys, which consists in melting the ore or ores while commingled with a flux and with a salt of polycarboxylic acid, and in which the polycarboxylic acid is in the proportion of from fifteen (15) to thirty-five (35) grams to fifteen (15) pounds of ore.

2. The process of reducing oxide iron ores and admixtures of ores to the form of true steel and its alloys, which consists in melting the ore or ores while commingled with a flux and with a salt of mucic acid, and in which the salt of-mucic acid is in the proportion of from fifteen (15) to thirty-five (35) grams to fifteen (15) pounds of ore.

3. The process of reducing oxide iron ores and admixtures of ores to the form of true steel and its alloys, which consists in melting the ore or ores while connningled with a flux and with sodium mucate, and in which the sodium mucate is in the proportion of fifteen (15) to thirty-five (35) grams to fifteen (15) pounds of ore.

4. The process of reducing oxide iron ores and suitable admixtures of ores to the form of true steel orlstecl alloys, which consists in melting the same while comniingled'with a salt of polycarhoxylic acid and a flux, and which acid, in the presence of the flux has the property of effecting a catalytic action that causes disassociation of the non-metallic from the metallic substances, thereby reducing the same to the form of steel or its alloys, and in which the salt of polycarboxylic acid is in the pro-portion of from fifteen (15) to thirty-five (35) grams to fifteen (15) pounds of ore.

5. The process of reducing oxide iron ores and admixtures of ores to the form of true steel and its alloys, which consists in melting the ore or ores while commingled with a flux and with a salt of polycarboxylic acid, and in which process the polycarboxylic acid is in a quantity less than sufficient to directly react with the oxygen of the ore, but is sufiicient to produce a catalytic action accomplished in the said reduction.

WILLIAM J. POPI-IAIVI.