US1597001A - Alloy steel - Google Patents

Description

' tion,-as the process of oxidizing the carbon v "alloying metal, results in a substantlally 49 sequent waste, of the valuable alloying eleofjthe charge. The freshly reduced alloyingmetal is in direct contact with the melting steel,. and therefore. the best conditions hatented 'Aijug unorsrnnn w ing elements, in the already reduced metallic state, mostly in the form of a ferro-aL.

' loy, are added to a molten bath of steel. For example, to obtain the respective steels thereof, term-manganese, ferro-chromium, ferro-titanium, form-tungsten, .ferro-vanadium, term-uranium, ferr c-molybdenum,

. term-nickel or metallic nickel and ferro-cobalt or cobalt metal, are added't'o'the steel, in the molten state in the furnace, or after it is tapped in. the ladle. -'As--the regular commercial grades of such ferro-alloys conv tain an appreciable amount of carbon, this practice introduces an undue amount of carbon in the steel. If special grades of lowcarbon-lerro-alloys arn used, the cost of such alloysis comparatively so high as to prohib-' itively' increase the cost of steel produced, These defects are especially apparent in the case'of steels where the content of the alloy- 39 ing element'has to be high and the carbon content low, as in the case of the so-called stainless steels or irons, which have a; '"'chromium content'o f between 9 and 15% v and a low carbon contonh It is not commercially practicable to usethe regular high carbon ferro-alloys, and:

then decarbonize the steel after their addiis accompanied by an'oxidation, and con- .ments. w Jul: 5. V ,Another deficiency of the existing" methods 'ofmanufacturmg alloy steels, by the addition of metallic 'ferro-alloys to -molten steel, is the henomenon of segregation. The alloy being added in the solid state in the form of lumps scattered .oyer the surface of the molten steel, causes points: of concentration of the alloying element at the 1 location of each of the'lumpsi 'As the'steelis' tapped immediately after melting of-the lum s in order to avoid an undue oxidation 1 of t e alloying element, "the'sepoints of higher concentration have no. opportunity V to equalize themselves over the. ent1r'e mass of metal by difiusion. Moreover, the ferro --ment content will persist in I the stee on mixed together, and then melted. On the 1923, Serial m5. 650,157.

alloys have various constituents of different meltingpoints and de ees of, solubility, as p for example the carbides in the ordinary grades of alloy. Such carbides have a higher melting 'point than the remainder of the alloy. Such a carbide-containi ferro alloy, when added to molten steel, Will have. the result that when the rest of the alloy will be completel assimilated, the carbide content will still e in the solid state, floatg in the molten steel, without giving up its alloying element content to the bath. Such solid particles with a high alloy' 1 ele- 7 0 solidification and present, segregation...

I overcome the above mentioned difiicul ties by introducing the alloying metal in unreduced form, such as an oxide or an-ore, and reducing it simultaneously with the melting of the cold metal, such as the steel scrap to be melted. The alloying metal 0rd or the scrap and the reducing agent may all be charged cold into the furnace, preferably other hand, a molten bath containing a part of the iron and steel, together with the reducing agent if desired, may be formed, and then the cold scrap and alloying ore, with or withouta reducing agent, may

or steel. In each case thejuninelted metal,

' such as steel scrap, is a'substantial qua tit go;

of proportion ofthe' whole charge-niche so that the dissemination of the. alloyin metal into the steel which is being melted simultaneously with the reduction of the thorough dissemination throughout the body are obtained for the alloying'and uniform out-the. molten steel,

tion*-of -added fluxing material, generally.

lime, absorbing and neutraliai" the I oxidized r'educf agent together with undesirable 'metalloi ,such. as phosphorus and sulphur, .cause-.;a" refining ofthe steel to take it be as w 7 charged into the furnace. In either case, I the alloying ore is reduced simultaneously a with the melting "of some or all of thev iron 10o;- disseminating-of the all gymg metal throughe alloying element f isobtained from acheap source Thein it place simultaneous] with p the .production of the alloy and me ting of the scrap.

T e process may be carried out inthefol-- lowing manner: I? g 1 e steel or ironscrap desired to be melted to the alloy steel paratively small sizes, such as borings, turnetc, is mixed with a reducing agent, w ich may be a metallic reducing agent such as silicon, manganese, calcium magnesium or I the like, either alone or in combination with a carbonaceous reducing material, for mpreferably in the ofreducin are figure centage of. alloying weight of finished steel.

asto eflectiyely'remove by chemical-combination the roduct formed by oxidation of a metallic re ucing agent, such as silicon. In

the case of silicon,

the silica produced by its oxidation goes into chemical combination with the slag, principallyin theform of calcium silicate,.and is thereby removed from the metal. The

' the flux, therefore,'is" the prevention of "the presence of the reducing agent in the 'finished steel. The

' ders the oxide more amenabletoreduction mixture "of raw materials is charged into any well ten, it is advantageous temperature in' order 8 traces of'the reducingscrap or pig, the a-llOyingpre, I agent .and the slag-forming or at short intervals to hy-"the reducing agent;

' 'tion then ismelted-and the reduced alloying or electric furnace at a for the reaction. After electricfurnace, Th

proceeds at the same time the scrap element is directly in contact with the melt ng scrap and is readily absorbed in the liquid steel;

As-this operation takes lace in the presence uxing materia s, molten scrap proceeds simultaneously. The

furnace such as an open-hearth, or crucible, temperature suitable "the reaction is 'complete and the entire charge thorougl-ilymolto raisethe'furnace to eliminate .;the-: last ageht in the finished steel, acceleratin ,theefiect produced; by fluxing agents-ad ed for this he process i's-particularly applicable to the manufacture ofalloy'steel ,or iron in an e, furnace may be operated continuously, 3 the steel Lor iron b'ei tapped out as collected, and the unmelt d the reducing charged continuously the bath, which is continuously .-mainta ined preferably selected in comagent andalloying raw material give the requisite perpractical result achieved by flux also combines with the "refractory gangue elements of ore and rena The reducing reac- .a-refining of the as above describedknown steel makingam the hearth. This allows an electric furnace to be operated continuously at sub- ...stantially constant load, thus obviating the. ,power fluctuations incident toipleriodicoper "'a'tion of 'a'n"electric sufelt' rna'ce.

The most generally .ducing a con meta or I silicon alloy containing one of the alloyin metals may also be 'advantageously'use I For instance, in the case of the manufacture =,of-so-called stainless steel 21' silico-ch'ro-' mium alloy may be added to the rawfcold charge and its silicon content utilized-tore duce a further quantity of chromium from chrome orepresent in the charge. This procedure'is especially advantageous in the case of a steel containing a alloying element.

T-tended as a'term of'gen'eral description and 7 not of limitation, and is intended to include .not only substantially pure silicon, but also silicon alloyed w'thother metals or metalloids.

In the case-of alloy steels jcont-aini-ng' a plurality .ofalloying elements,

*the raw materials in the right containingthe plural elements, being charged together with the scrap and reducing agent. The flux maybe added sepa- -rately or' the raw alloying materials may be selected of'such a composition as to have in their gangue the 'nents,

together and the adapted metallic. re- 7 nt is ferro-siliconl However,-s1liany other silicon alloysuchzas a The term silicon reducing agent is innecessary fluxing compohigh percentage of the this; proce dure may be carried out in the same-manner,

proportions Thesteel scrap and the ore-may be mixed mixture charged. into the rnace 'or' the steel scrap and the ore may be introduced in separate batches-"or charges, "so long as they simultaneously or. within that the melting down of the scrap will proreduction ofthe' ore.

used, such as a mixtureof carbonaceous and metallic reducing agentsi'or several different jmetallic reducing stance, a ferro-silicon alloy containing car bon'may he'nse'd, both its a bntents being utilized -for, =th'e reduction *YJPIH'POSBQQAISO any reducing agents" origin lliy presentinjthe' sc'ra I I use thus eli-minating their presence-dram are chargedsubstantially such time interval ceed substantially simultaneously wants I .Also a plurality 'ofreducing' agent fma 1 agents. "For in- .325 silicon and carbon may be effectively the charge will have the effect "of refining.

the molten sc'rap busly with the-. melting 'o calloymg "with ther-alloying'elemena ii deoxidizing If desired, after the'ineltin'gof the chase.

is ended,.a "small,.

Silicon or erro i'ofdts metalloidleontents, -such as sulphur andphesihorus, simultanev thestgrapf'and its cleanser, before'tappin the steel, as is the common ractice in ma ingalloy steels."

, The a vantages of this process of simultaneous melting, refining and alloying are steels or iron with a high alloy content an very low carbon content. As such an instance may be cited the manufacture of'so called stainless iron containing 9 to 15% chromium and less than 0.1% carbon. Also the advantages of this process are apparent in the case of alloying a highly oxidizable and difiicultly soluble element as uranium in steel. The alloying element being produced in the nascent'state and directly in contact with the melting steel, the chances of its oxidizing or not dissolving are reduced to a minimum.' Also, as the carbon content of the finished steel can be eliminated to any desired extent, simultaneously during the process of reducing and alloying, the exact percentageof carbon in the finished alloy steel can be arrived at more accurately by recarburizing before tapping. In the case of metallic reducing agents being used, their presence in the finlshed steel is practically eliminated by the action of fluxes. Thus by the process of this invention a steel of predetermined given composition can be more accurately produced. than by the use of ferro-alloys. Also by this process, as the valuable alloying elements do not exist at 7 any time in the metallic state, unless disas in the older processes, there is no loss sufiered through oxidation, rendering th s1l1con re ucing agent and steelscrap and "an nnreduced chronium ,cOmpound solved and alloyed in the steelitself, and as after their solution in the steel there is no occasion to subject such steel to an oxidizing process forremoval of carbon, for instance,

process extremely ec0nomical.- The charge put into the furnace contains a suflicient proportion of steel scrap so that themetal as tapped fromthe furnace is a finished steel, as contrasted with a cast iron" or a ferro-alloy. The term steel, however, as herein employed, is intended as a term of general definition and not of limitation, and

is intended to include steels having very low carbon and metalloid contents and which are sometimes called irons, as for example, the

- sorbmg lime containln flux material and so-called stainless irons.

The process also assures a thorough and uniform dissemination of the alloying metal throughout the body of the molten iron or Y steel before tapping. j While the preferredimethod of carrying out my process has-been specificall de. scribed, it is to be understood that t e-1n vention is not limited to all of the described details, but may be otherwise embodied in processes of making alloy steels or irons, ivithin the scope of the following claims.

' Iclaim:

1. The process of making chrome steel 68..

chrome steel in the furnace, tapping the steel Y into the bath as refluired a silicon reducing agent and a meta oid-absorbing lime-contaimng flux material and steel scrap and an unreduced chromium compound in amounts sufficient to furnish the major portion, if not all, of the iron and chromium contents of the steel and proportioned to maintain the desired composition of the steel bath, substantially as described.

2. The process of making alloy steel, comtherefrom from time to time, and charging prising maintaining a molten bath of alloy steel in a furnace, tapping the steel there-' from from time to time, and chargin into the bath as required a metallic re ucing agent and a metalloid-absorbing lime-con.- taining fiux material and steel scrap and an unreduced compound of the alloying metal .in amounts suflicient to furnish the major portion, if'not all, of the iron aludalloyin metal contents of the steel and p'roportione to maintain the desired composition of the steel, substantially as described. 3. The process of making chrome steel, comprising maintaining amolten both ofchrome steel in a furnace, and charging intothe bath as required a silicon reducing agent and steel scrap and an'unreduced. chronium compound in amounts sufiicient to' furnish the major portion, if not all, of the iron and chromium contents of the steel and proportioned to maintain the desired composition of the steel bath, substantially as described. 4. The process of making chrome steel, comprisin forming a. charge containing a in amounts sufiicient'to furnish the major portron, if not all, of the iron and chromium contents :of the steel, and simultaneously melting'the charge and reducing the chro- "15 steel scrap and an unre need chronium compound {amounts suflicient to. furnish the major portion, if not all, of the iron and...

scribed.

my hand.

BYRAMJI n. SAKLATWALLA.

'i chromiuni content-s of'the steel, and simul: vtaneously melting-the charge, reducing the chromium- -from its unreduced compound and refining. the steel, substantially as de- 1 I, In testimony whereof I have hereunto set v I Q