US2579369A - Addition alloy for treatment of steel - Google Patents

Description

Patented Dec. 18, 1951 ADDITION ALLOY FOR TREATMENT OF STEEL Charles N. Dawe, Detroit, Mich., assignor to Vanadium Corporation of America, New York, N. Y. a corporation of Delaware No Drawing. Application September 13, 194 Serial No. 49,119 v 9 Claims. (01. 75-138) This invention pertains to a composition of matter used to improve the properties of ferrous metals and particularly of carbon and low alloy steels. It is especially efiective in improving the balance of physical properties of steels'ranging from .05% to 1.00% carbon, either with incidental alloying elements or with specified alloy-' ing elements up to 6% content by weight of the steel though its use is not limited thereto. This application is a continuation in-part of application Serial No. 623,169, filed October 18, 1945, now abandoned.

When a steel of proper composition is cooled rapidly from within its hardening temperature range, for example by quenching in oil, water, or some other medium, those portions which are most rapidly cooled harden while those portions which cool more slowly, for example the center of a bar, harden to a lesser extent. The depth of hardening depends upon the temperature from which the bar is cooled, the nature of the cooling medium, and the composition and other characteristics of the steel itself. The hardening capacity of a given steel is referred to as its hardenability, and this, as is well known, increasesas the carbon content and the amount of certain other elements in the steel are increased and also as the grain size of the steel is increased (i. e., coarsened).

- There are, however, certain advantages for which it is desirable to maintain fine grain in a steel even. though increased hardenablility is desired. The novel alloy which I have invented will serve this dual purpose, namely, to increase the hardenability of steel while at the same time producing fineness of grain so valuable in commercial utilization of the steel for numerous purposes.

In steel production, whether in the open-hearth furnace or electric furnace, it is customary to obtain fine grain size by the addition of about one pound or more of aluminum per ton of steel, depending on the composition and the steelmaking process employed. The aluminum, having an afllnity for oxygen greater than that of mostother elements, must be added late in the inelting operation and just before the steel is cast, so asto avoid possible loss of its grain refining properties. In open-hearth furnace marinfactu're it is customary to add the aluminumto the-ladle while the heat is being tapped, but in the electric furnace the aluminum addition may be added either to the ladle or to the furnace just beforetapping. As the amounts of aluminum are increased, within limits for a giverl type of steel, the grain size become liner and to this extent the hardenability is diminished. Grain refinement is accompanied by greater uni-' formity of composition and by smaller variations in mechanical. properties of castings or of bars, plates, and other shapes rolled or forged from the ingots. v

Fineness of grain is often specified along with high hardenability in order toobtain the accompanying benefits of uniformity of composition and uniformity of properties. The combination of fine grain and high hardenability is generally obtained by the addition of aluminum, together with the addition of alloying elements (usually a combination of several) designed to increase the depth of hardness. Some oi these elements are easily oxidized in the'steel bath and at the same timeare rather diflicult to melt or cause to diffuse. This may be due to the fact that the required temperatures are too high or because such an amount of the elements' must be added to bring about the desired effect upon hardenability that, unless they can be added in the liquid state, they cool the molten steel to such an extent that its manufacture will be impeded or its quality impaired. It is necessary, therefore, to engage the skill of the steelmaker in adding these elements a sufficiently short time before tapping to prevent eifective oxidation, but a sufficiently long time before tap to permit complete absorption by the steel. I

The situation becomes critical in the case of elements such as titanium, zirconium, and boron where the-heats of combination with oxygen and nitrogen are exceedingly high; and critical also, insofar as the use of boron is concerned, due to the exceedingly small amount of addition. required (from about 0.0002 to 0.003 per cent'of the steel weight) and the consequent effects of very low recoveryor of segregation.

I have discovered that when certain of the alloying elements used to increase the hardenabil-ity of steel aredissolved or intimately dispersedin aluminum through combination in the molten state, the resulting composition of matter when added to steel in the proper amount will increase the hardenability of the steel, while simultaneously insuring against very low recovery and segregation of the added elements and at the same time refine the grain size. The liquefying temperature of such a composition is above that of aluminum, yet far below that of the ferro-alloys in which form the hardening "elements are usually added so that thealloys of ill Qmyinventionare more easily absorbed by the zirconium alone or in combination, as hereinafter more specifically described, as dispersed in alumi mum and, if desired, accompanied by incidental amounts of manganese and silicon alone or in association. Some iron mayalsqbe added asacarrier. I have discovered that the desired effects oi increased hardenability in thepresencenf fine amount within or without this range is dependent upon the desired quantities of the other elements.

The alloy of my invention may be produced by any convenient method, either by direct alumino- 5 thermic reduction of oxides or other suitable compounds, with an excess of aluminum. present, or added after the reaction-is complete; or it may be produced by silico-thermic reduction or by reduction with an electric are using aluminum or V silicon as reducing agents and operating on a bath of aluminum or aluminum-silicon alloy, or excess aluminum maybe combined with the alloy afterelectric-reduction. These are just examples of methods that may be employed and this de- 5 scription should not be interpreted as placing any grain size are especially pronounced in steelsw-ith 0.05 to 1.00% carbon (preferably 0.05 to 0.65%.)

containing additionally ,either incidental" alloyare typical of my invention:

ing elements or specifiedalloying elements upto 6%"content' by Weigh'twf the steel though the alloy' is "also useful in; the treatment o-f'oth'er ferrous metals, ,j By th'e 'additi'on to steels in this composition" ranga while'the molten state, of alloys containing between 35 7;; and 65 alum'i num, along with suitable combinations of boron, titanium, zirconium and vanadium, I have been able to develop large" increases in hardbnabil ity along with thedesiredfine-grain sizewhile avoidi'ngthe usual large-losses incident tar-the addition of th'e'sepoweriul hardeners. r y

Y In" addition to the aluminum content, the alloy of my;' invention containsboron all cases, this element beingthemost powerful of the hardening agentsper unit of weight and the mostdifiic-ult to add-to steels insuch manneras to insure uniformityof distribution along' vvi-th h-igl-i recovery in effective form. The novel alloy preferab'lycontains one or both-ofthe-- elements titanium and zirconium, elementswliich are also-very diificul't toadd' to steels without large losses, in total amountvaryi-ngirom about 5% to about 35%, but preferably in the "range of l 0'% -to %"tota1. The boron content is ordinarily from about: 432% to about 5% intliese alloys; preferably, however, in the range '.l5% to l.5%-. F-br the absolute maximum contribution tohardenabi lityand grain size; with minimum'los ses and 'al's'o to prevent the formation of reaction-products which. may be detrimental to steel'qiiality, some vanadium Usually as azresult -of the method of maxim facture, though they may be purposely. included, there-is present in. thealley as a remainder of relatively minor: significanceone, ormore; oi the elements, manganese. and silicon in. an amount not to exceed about"%jof" the-ztotal and-prefera-bly notyover' 20% of the total. It will be realizedthatboth manganeseand silicon may contribute to: the hardenabilityoi: the: finished Steel, bu-twith thfi; amounts-thatcan possibly be addedwhen considering the; fact; thatgthe, gross weight of this alloy addition isusually about /1 to 2% ofthe steel-weight; this contribution. to hardenability :isrelatively niinor and insignificant. -The balance of the alloy-ispreferably iron which serves asa carrier-ior the, other elements, and, of course, has the desirable. property. of a: melting point nohiglier than thatloi the ,iierrous metal to thealloy isgladded. ,Qrdi'narily the. iron will. be present-in,amountoflfrom about. l5=%.to 40% though 'itwillb'e understood that the precise limitationuponthemode of manufacture, which .method is not considered to be part of this invention.

"Alloys of the following percentage compositions ,Alloy Al B 'li 21 v Si Mn Fe The weight of. alloy per ton of steel varies 0 ordinarily from about-2 to, about 20 pounds. but

results that it is desired to obtain, and, as those in theart will,understand, it isadj ustedin accordance with preliminary experienced-n each .im stance-1 1 Whati sclaimedis: V

1. A grainrefini-ng. and-hardenabiliw impart-,- ing; agent for; addition to: molten steel consisting essentially of about 35 -65 aluminum, about 02-95% bqron and' abound-35% of. atleast one of :the elements selected from: the group consista ing; of titaniumand zircon'mmrii e balancesubstantially all iron, saidironubeing .nfl llessthan -12. A grain refining and hardenability impart.- ing agent for addition to moltemsteel consist, ing essentially of a'boi1t 35-65%v aluminurmabout .02-5 %v boron; and about 2-35%, vanadium, the balanceasubstantially all i-ron,, said. iron beingnot less-than 15%.

-3. A grain refining: and hardenabi-lity impart, i-ng. agent. for addition to molten steel consisting essentially of about -35-65.%- aluminum, about .0-2 -.-5 boron,. a.-bout 5--35 of at .leastzone of. the elements selected from the group consistingoi titanium. andzi-rconium, about vanadium, the. balance substantially-all iron, said. iron being notless than-15%,. l

4 A. grainrefining and hardenability impart! ing, agent for addition to moltensteel-consist ing essentially of about 35-65% aluminum, about .02-5.% boron,.,up,to.30,% oi'at-least one ofv elements selected fizom the group, consisting. of manganese ands'ilicon .thelbalancesubstantially a'lliron..

5. .A. grain .refining. hardenab'ilityv imparting, agent for, addition. to molten steel, consistingessentially or about 35-65% aluminum, about 02- 5 boron, and thebalance. substantially all ron. a 6';

teens .for addition entrances ami'stmg,essentiauyoi about.ssiwssyz about 0.021265%" boron. about 5% 3 5% or one or more elements selected from the group titanium and zirconium, and up to 80% of one or more elements selected from the group consisting of silicon and manganese, the balance substantially iron, said iron being not less than 7. An agent for addition to molten steel con sisting essentially of about 35 to 65% aluminum, about 0.02 to 5% boron, about 2 to 35% vanadium and up to of at least one'of the elements selected from the group consisting of silicon and manganese, the balance substantially iron.

8. An alloy for addition to molten steel and efiective in increasing the hardenability and refining the grain size of the steel composed of about to 65% aluminum, about 0.02 to 5% boron, about 5 to 35% of at least one of the elements selected from the group consisting of titanium and zirconium, about 2 to 35% vanadium, and up to about 30% of an element selected from the group consisting of silicon and manganese, the remainder being iron and incidental impurities, said iron being at least 15 9. An alloy for addition to molten steel and efiective in increasing the hardenability and refining the grain size of the steel consisting essentially of about 35 to 65% aluminum, about 0.02 to 5% boron, about 5 to 35% of at leastone of the elements selected from the group consisting of titanium and zirconium, about 2 to 35% vanadium, the total of said boron, titanium, zirconium, and vanadium being less than 40%, up to about 30% of an element selected from the group consisting of silicon and manganese, and about 15 to 40% iron.

CHARLES N. DAWE.

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

UNITED STATES PATENTS Number Name Date 2,291,842 Strauss Aug. 4, 1942 2,295,706 Comstock Sept. 15, 1942 FOREIGN PATENTS Number Country Date 478,462 Germany July 2, 1929

Claims (1)

1. 8. AN ALLOY FOR ADDITION TO MOLTEN STEEL AND EFFECTIVE IN INCREASING THE HARDENABILITY AND REFINING THE GRAIN SIZE OF THE STEEL COMPOSED OF ABOUT 35 TO 65% ALUMINUM, ABOUT 0.02 TO 5% BORON, ABOUT 5 TO 35% OF AT LEAST ONE OF THE ELEMENTS SELECTED FROM THE GROUP CONSISTING OF TITANIUM AND ZIRCONIUM, ABOUT 2 TO 35% VANADIUM, AND UP TO ABOUT 30% OF AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF SILICON AND MANGANESE, THE REMAINDER BEING IRON AND INCIDENTAL IMPURITIES, SAID IRON BEING AT LEAST 15%.