US1711052A - Method of producing steel ingots - Google Patents

Description

April 30, 1929. E. GATHMANN METHOD OF PRODUCING STEEL INGOTS ZSheetS- -Sheet 1 Filed June 22, 1928 I NTOR lmla mam /JM M36 ATTORNEYS Patented App 30, 1929.

UNITED STATES nun. ca'rmrann, or BALTIMORE, mmrmrn.

METHOD OF PRODUCINGfi'IEEL INGOTS.

Application filed June 22,

My invention relates primarily to the method of producing steel or allo ingots which shrink or contract in passing rom the liquid to the solid state and which are subsequently rolled, pressed or otherwlse worked into commercial shapes or forglngs.

In speaking of an ingot it is to beunderstood that I refer to one cast in a suitably proportioned big-end-up tapered mold, suc

as is described in Patents No. 1,049,573 of January 7, 1913 and No. 1,643,241 of September 20, 1927 granted to me.

A fundamental requirement in the production of a physically sound and relatively homogeneous steel ingot is that of suitable deoxidation of the bath after proper chemical analysis has been obtained. In addltion to this, the metal must be properly finished 1n the ladle prior to teeming it into the mold. When teemed at suitable temperature into an iron mold having relatively heavy chamber walls, metal so finished will solidify in several distinct phases, the initial solidificat on being due to contact of the molten metal with the walls defining the mold chamber.- This solidification is practically coincident with the entrance of the steel into the mold and is only of skin thickness. The greater mass of the ingot then solidifies within this initially formed skin by crystallization of a dendritic form, which starts at right angles to the skinsurface and progresses from the sides and bottom to the center of the ingot. The rate of solidification decreases as the ingot skin increases in thickness and the matrix walls of the mold become heated, at which time solidification proceeds not only by the formation of dendritic crystals, but also by the formation of equiaxial or free crystallization. The more rapid the solidification of the body of the ingot, the greater will be the number of independent nuclei from which solidification proceeds. As a result of such rapid solid1fication, the formation of the dendritic crystals, which proceeds inwardly and at right angles to the initial skin or the ingot, prevents or at least greatly reduces so-called clotted segre-. 'gation. What may be termed a land-locking type of solidification occurs due to the growt of the dendrites retarding free emigration or segregation of nonmetallic impurities, or matter not in solid solution in the molten steel. 9

It is now well-known to those familiar with the art that thoroughly deoxidized steel is of greater volume when molten than the same ms. Serial 110. 287,557.

weight of metal when solidified this reductron in volume or shrinkage having been ascertained to be somewhere between 3% and 5% in ordinary carbon steels, the exact amount of shrinkage dependin primarily upon the pouring temperature. he method of solidification, or the extent of wth of dendritic and uiaxial cr stals, etermines the position an type of t e shrinkage cav- 1ty formed in the ingot during the process of solidification. By keeping a continuous supply of molten metal above the solidifying crystals it is theoretically possible to produce an ingot without any shrinkage cavit at all, the shrinkage in volume of the meta result- 1n only in a shortening of the ingot.

' he primary ob'ect of my invention is to so shape and solidify steel ingots that a greater yield of physically sound, substantially homo eneous material is obtainable from the solidified ingot than has heretofore been considered possible in tonnage practice.

A further object of my invention is to so cool and solidify the molten mass of the in ct from the bottom progressively upwardly t at molten metal is continuously su erim sed upon the crystallizing portion 0 the ingot, until finally the uppermost art of the metal, or that contained within t e to zone .of a suitably constructed shrink hea casing, has cooled or frozen. In otherwords, I abstract the heat of the ingot first at the bottom and thence progressively upward causing the isotherms or lines of abstr tion of heat to be swun downwardly from the usual nearly vertical lines to lines progressively flattening out from bottom to top of theingot structure. Since the isothermal lines at the top of the ingot are nearly horizontal, I obtain a flatter and a shallower shrinkage cavity, all of which is contained in the uppermost portron of the ingot, so that only 10% or even less of the total volume of the molten ingot metal need be contained within the hot top in order to assure of physical soundness in the ingot body.

' The method covered by U. S. Patent No.

1,049,57 3, issued to me January 7, 1913, provides for the rapid cooling of approximately 85% of the mass of molten metal from the bottom towards the to and the retarding of the cooling and soli ification of approximately 15% at the to Many million tons of ingots have since been produced by this method, an averageyield of from 80% to 82% of sound, finished product being obtained j ever, as before state fromleach ingoe My1resentinventiomhow ofsound substantiallyhomogeneousproduct from the solidified ingot g The accompanying drawings illustrate' a fftypeofzinold andhottop for carrying-out my.

-' that --mo1d"s and hottops of other -.contours, either 3invertical or horizontal crosssection, v

1 may beem' loyedf-withinthelimitsherein;-' after speci ed withoutdepartin'g from 'the' a -invention-.. It is t'o beunderst'ood, however,

eiof mylinvention, i

sco iguregl shows averticalcentral sect on of I an ingotmo1 1 and the'. molten metal of an lingot immediately after being cast; therein.v Figure 2shows ajvertica-l section of an in ct mold containing an ingot which'has-solidi ed" j Figurejli-is'a {sectional viewthrouglilline "3-3-ofFigure4. f p; as I Figure'a'is asectio'nalview on line of- F 23 i 1 I 11 carry ng" out my jin'yentioniit isessential;

that the metallic-mold employedis-so "constructed that'the heat of the ingot'me'tal cast f "therein will, be extracted and the ingot solidio Sively'flatten'out iromthe bottom-to-the top fied along isothermal line,s-'1,lwhich progress of the ingot structure as {the solidification of w-themoltenjmetal proceeds progressively, from bOt Q f o't0'p. V

he chamber of the metallic mold 2-formjingor defining thefbodyof'the ingot 3 has relativel heavy bottom and side Walls/l, the

combine cross-sectional area-of whichis approximately twice-that of the horizontal sectionalarea-of the-mold chamber'at the lower lic, heat-absorbing mo body'2 is a hot tog "or shrink head, casing of the type describe I in my U. S. Patent No; 1,696,395fof December 25, 1928; The shrink head casin "as aiwhole in its preferred form is'de'si ate v by? and is .constructedprimarily of a ighly refractory fire.'-clay 8, the 'sintering'point ofwhich isreferably somewhat higher thanthe pour mg temperature of liquid steely The core portion 9 of'thehot'top-orshrink'head cas 1mg walls is of an exceedingly porous nature,

' being permeated-with microscopiccells. For -this core portion I preferabl employ infusorial earth andia binder,;w ich'all'ows but .llittle absorption and practicallylno' conduc- -pxfoyides' means for relatively rapid coolin'g -of,fromi 9( to 92%. of the-mass of molten steehwhereby I obtain" agreater yield, approximately 88% to 90% tiou of heat throuthe wallsofthe casing. The} eir'terior-wal s 8, however, .are made homogeneous,',dense' and highly refractory to the hea't' ofi-the molten ingot metal; 3 The casing7, as described, 'canbe formedin various ways, details of several methodso'finanufac- -ture-vbeing described 1n theaforenained cop'en'ding applicationl =In carrying out my-pres'cnt methodofingot production, Ihave found it'essential, inorder to obtain the best results, to notonly' conserve the heat at the yertical'port-ions of the shrink head: of the ingot, -but also. at the upper face thereofis'ubstantiall 'asdescribed-in my Patem; No, 1,-04 9,573j7 J n ary-1,. 191 3 For this -.purpo's'e I employ a material-"1O that is neutralwhen 'infcontact with the moltenflsteel and :the particles of 'whichmaterial contain microsoopic'cellsso that the escape fheat from the top of the ingot'i's prevented.- I have found that complete insulation-j may be ;'obtained with as :little' as an inch thicknes of such" materi-a'l, powdered fv-i'nfusorialnearth, diatomiteor the-like, indicated at ,10' in Figjnr'es l and-2 ofthe drawingsbeingt preferre "By the use of amold" and shrin head'casing'of the type described; I' prevent radiation of heatfromthe upper 's'ides'and top portion of the ingotl-and l am'enabled to materially reducethe volume of'flthe chamber of the 'shrinkhead casing. ,I. ha've'found from experiments that thefpercent'age of steel in the heat-conserving mold top or shrink head-casing may be reduced toas'l'ittlelas 8%to 10% ofIthe entire volume of the molten ingot."- 'The 'yield'of sound steel in the body" of'the ingot 1s 'thusincreased some 1 1%"to13% above that previously considered possible in the '-,com-

mercialprodu'ct-ion of mill ingots, efi'ecting a ,savin'g of $2.50 to $3100 a ton'in the ordinary grades ofcarbon'forging steel.- 7

It is thus apparent-tliatin practicing my methodof ingot productiomwherein the proportion of rapid cooling and solidification extend to at least 90%.of the vertical massof the ingot and wherein ja-reservoir of molten steel' amounting to 10%v or'less,is' superim'. posed upon the solidifying crystals in the ody of-"the ingot until the ent re ingofiand sink head have become cooled and solidified fromthe bottom upwardly. I obtain a steel that i'ssuperi'or in its'respon'se to forgingand heat'treatment and the finished product of which is of av higher quality thanthat producedf'frorn, ingotsmade by, methods heretofore known'to-the art, ,atthe same time effecting a'saving by increasing the yield of sound product obtainable from the ingot.

. Iclaim as my invention The herein described method of producing sound steelingots by which the defective fportion of the ingot is reduced, which consists in dcoxidiz ing themolten metal in'the bath after the desired chemical analysis is ob tained,'transferring-the metal to a pouring or finishing treatment, then teemin the metal into a mold for the formation an ingot, pro ressivel accelerating by absorption the radiation o heat from the forming in ct from the bottom thereof towards the top or approximately 90% of the mass of molten metal and in substantially suspending the absorption of heat from the ingot at the up per portion thereof and positively retarding the radiation of heat therefrom for up proximately to of the upper portion of said forming ingot, to thus cause the upper portion of the mass to feed deoxidized molten metal to the forming in 0t to compensate for the shrinkage in the b0 while the metal is cooling an solidifying, and to thus cause the physically defective or porous portion of the ingot to be entirely confined within the u per 5% to 10% therefor.

In testimony w ereof, I have hereunto sub: scribed my name.

EMiL .GATHMANN.

(y of the ingot

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