US2470935A - Alloy addition agents - Google Patents

Description

Patented May 24, 1949 f "S T'A'TES FATE FIGE ALLOY ADDITION AGENTS No Drawing. Application September 3, 1947, Serial No. 772,011

7 Claims. (01-. 7527) '{T'he-present-invention relates to new and useful improvements in alloy addition agents.

Objects and advantages of the invention will be set forth in part hereinafter *and in part will aloe obvious herefrom, or may be learned by prac- -,.tice.- .with--- the invention, the same being realized Land-attained by-meansof the steps, instrumen- .,;t'ali tiesandcombinations pointed out in the ap- Lpendedclaims.

The-invention consists in the novel steps, compo's'itions and improvements herein shown and .sdescribed.

mvHeretofore, i many different addition agents havebeen proposed for the addition of alloy- Qing elements, such as molybdenum, chromium, tungsten, vanadium to ferrous alloys. Among ,l-such addition agents are the ferro-metal agents, .gsuch as ferro-molybdenum and Terra-chromium, briquettes formed from the metal oxide and a reducing agents, such as ferro-silicon, silicon, lalu-minum, calcium silicide and other reducing ;,inetals or carbon, bound together with a binder iiivhich may be a carbonaceous material such as pitch. Many of these addition agents are rel- ,atively expensive to produce, while others introduce arrelatively large amount of foreign mat- ,ter -into'the alloy and which may appear in the finished alloy as inclusions of slag, while other .addition -ag entsgive a poor recovery of the allo'ying metal in the finished alloy and are thus relatively expensive to use.

"The present invention has for its object the provision of -a-novelandimproved alloy addition agent which can be produced with very little eiipensebeyond the cost of the alloying metal contained in the addition agent, does not require elaborate equipment for their production, gives. good recovery of the alloying metal in the ,finishd .alloy, can be used without radical iichange in alloying technique, and does not result in the addition ofabn'ormal large amounts of foreign material such as slag-forming ingredients. The invention has for a further object the provision of novel and improved alloy addition agents which are economical to produce, are economical to use, are of general application and give excellent results in use.

In accordance with the present invention the alloying addition agent comprises a proportioned, mixture of an oxide of the alloying metal to be added to the ferrous alloy and a reducing agent comprising a stable form of calcium carbide, which agent may be formed into convenient briquettes by briquetting under powerful pressure with or Without a carbonaceous binder,

or may be merely packaged in bags of "convenient size or in packages and added to the molten iron or steel in the ladle or otherwise as desired. Calcium carbide, as such, is not suitable for-*use in such alloyin addition agents as thecalcium carbide contained therein is so unstable' and when briquetted, there is a danger "that the briquettes will explode or disintegrate due to the accumulation of gas therein caused by the decomposition of the carbide. Howeven thel-calcium carbide reducing agent may be economically and effectively protected against premature place. The quantity of binder used i fromabout decomposition without deleteriously affectin'guts reducing action on the metallic oxide or the effect of the alloying additionagent as a whole-on the ferrous alloy to be produced.

In accordance with the present invention-this protection is afforded by treating the calcium carbide particles, whether lumps, rains or-dust, with a waterproofing material which is'preferably a film-forming material and is in its lfia reducing agent and generally a binder ofgnsufiicient adhesive force to materially assist in holding themetallic oxide and calcium carbide-in intimate contact until the reducin -action takes 1% to about 5% based on the weight oftheical- =cium-carbide, and theamount of calciumcarbide is generally approximately the stoichiometric quantity required to convert the oxygenof the metallic oxide into carbonmonoxide.

Suitable stabilizing agents for the calcium carbide-are crude petroleum, refined'mineraliioil, paraifin and other mineral waXes,"-drying:and non-drying vegetable oils, rosin, asphalt,.:r.=still pitch, all of which are film-forming andwaterproofing carbonaceous materials which-in themselves can serve as reducing agents of a mild *kind for the metallic oxide. Other'carbonaceous 40 reducing agents which are waterproof-maylso be used, but I prefer to use the petroleunr mraterials, such as crude petroleum,mineral oil or mineral wax, as these materialswmay be easily applied to the calcium carbide, as by spraying, to completely coat the external surfaces of the calcium carbide particles and serve to impregnate at least the outer portion of the particles sufficiently So that the particles are effectively waterproofed and thus rendered immune to the action of atmospheric moisture, even to the extent that the particles will withstand immersion in water for a considerable period Without reacting with the water.

From about 1% to about 5% of the stabilizing agent is added to the calcium carbide, but I prefer to use about 3% of the stabilizing agent and apply it to the calcium carbide by spraying it on the carbide at that rate, care being taken that the particles are substantially completely coated with the stabilizing material.

Examples of the metal oxides suitable for use in the alloy addition agents of the present invention are the various oxides of chromium, molybdenum, tungsten, vanadium, comprising the ferrous-alloying metals of the fifth, and sixth periodic groups. These oxides include the trioxide and all the lower oxides of molybdenum, the trioxide and lower oxides of chromium, tungsten trioxide and its lower oxides, and the pentoxide and the lower oxides of vanadium, some of which are not ordinarily desirable in view of their relative high cost on the basis of the metal contained in them.

Impure oxides, usually in the form of ores of the alloying metals are useful and may be mixed directly with the stabilized calcium carbide without preliminary reduction or extensive chemical treatment of the ore, the ore of course being concentrated to remove from it most or all of the mechanically separable impurities and other undesirable impurities such as sulfur. Among the natural impure oxides which are useful are the following: wolframite, scheelite, hubnerite and ferberite. Of course, many ores may contain impurities which are undesirable from one point of View or another, such as lead, sulfur, arsenic, tin and the like, and the choice of such naturally impure oxides will be determined by the eiTect of the impurities on the eventual alloy.

In the event that a more active reducing agent metallic oxide, 14 pounds of it are mixed with about '75 pounds of the stabilized calcium carbide and preferably formed into briquettes which are added in the desired quantity to the molten iron or steel in the ladle. Under the heat of the molten metal, the oxide is reduced according to the equation:

MoO3+CaCz+CaO+2CO+Mo If molybdenum dioxide is used, 384 pounds of it are mixed with about 75 pounds of the stable calcium carbide and the reaction proceeds according to the equation:

3MoO2+CaC2- 2CaO+4CO+3Mo Using about 75 pounds of the stable calcium carbide in each of the following instances, the

equations are:

Using 232 pounds of tungsten trioxide Using 150 pounds of vanadium sesquioxide V2Os+CaC2 CaO+2CO+2V Using 166 pounds of chromite, calculated as pure FeCrzOs In each instance it will be noted that the quantity of calcium carbide is substantially the quantity needed on a stoichiometric basis to convert the metallic oxide into metal with the resulting reaction products of carbon monoxide, and lime. The carbonaceous material forming the stabilizing agent for the calcium carbide has been disregarded in the above calculations but introduces no great change in the calculations due to its relatively small quantity.

The invention in its broader aspects is not limited to the specific steps shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

l. A self-reducing alloy addition agent comprising a mixture of an oxide of a metal selected from the group consisting of molybdenum, chromium, tungsten and vanadium, and calcium carbide, said particles of calcium carbide being stabilized by a coating of a waterproofing carbonaceous material which acts as a reducing agent for the metal oxide.

2. A composition as claimed in claim 1 in which the quantity of stabilized calcium carbide is approximately the quantity necessary to reduce the metal oxide with the formation of lime and carbon monoxide.

3. A composition as claimed in claim 2 in which the calcium carbide is stabilized by coating the particles with a substantially nonvolatile petroleum oil.

4. A composition as claimed in claim 1 in which the calcium carbide is stabilized by coating the particles with a substantially nonvolatile petroleum oil.

5. A composition as claimed in claim 1 in which the metal oxide is a molybdenum oxide.

6. A composition as claimed in claim 1 in which the metal oxide is a chromium oxide.

7. A composition as claimed in claim 1 in which the metal oxide is chromite.

ARTHUR LINZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 866,562 Becket Sept. 17, 1907 1,275,449 Lemon Aug. 13, 1918