US2943007A - Method for casting and working grain oriented ingots - Google Patents

Description

United States Patent O METHOD FR CASTING AND WORKING GRAIN ORIENTED INGOTS Filed Aug. 26, 1957, Ser. No. 680,360

6 Claims. (Cl. 148-2) This invention relates yto -so magnetic materials and more particularly to improved grain oriented ingots or castings composed of iron and soft magnetic alloys of iron and silicon, iron and aluminum and iron and molybdenum constituting cast intermediatesbr blanks lfrom which polycrystalline metal sheet material may be prepared by rolling and appropriate heat treatment to have a high percentage of its `grains oriented as cube texture, to a method of preparing such cast intermediates or blanks and to a method of preparing cube texture sheet material therefrom.

As pointed out in a co-pending application for Umted States Letters Patent, Ser. No. 610,909 led September 20, 195 6, Walter and Hibbard, of which one of the present applicants is a joint inventor and which is Vassigned to the assignee of this application and tiled concurrently with application Ser. No. 610,907 tiled September 20, 1956, now abandoned, of which this application is a continuation-impart, polycrystalline, magnetically soft sheet .metal having a high proportion of .the grams thereof singly oriented with respect to the rolling direction and .the plane of the sheet -has lfor some years past been utilized as a saturable core material in electrical and electronic apparatus. These previously known oriented sheet materials have usually been composed principally of iron with about or less silicon and have had .the body centered cubic lattice Iform at ternperatures below several hundred degrees centrigrade. The preferred orientation of .these previously known sheet materials has been characterized by a high proportion of their grains having their body-centered cubic lattice Vforms oriented such that the so-called (110) planes there- Aof lie substantially in planes parallel to the -plane of the sheet with four of .the unit cube edges being substantially parallel to the rolling direction of ,the sheet. This particular orientation is usually designated as the (110) 1001] orientation.

As will be readily recognized by those skilled in lthe metallurgical arts, the numerical notation of the (110) crystallographic plane previously used is the accepted idescription of a plane in the unit cube containing diagonally opposite cube edges according to Ithe Miller Crystallographic Index System. Similar numerical designations of crystal structure and rdirections used hereinater will be set `for-th in accordance with the same index system, a more complete discussion of which may b e found, for example, in Structure of Metals by C. S.l Barrett, McGraw-Hill Book Company, Inc., New York, 2nd edition, 1952, pages 1 25.

Sheet metals having this (110) [001] orientation may be otherwise described as an elongated polycrystalline body of sheet `metal having the body-centered cubic lattice form produced by conventional rolling procedures in which a majority of the grains of the sheet have their crystal structure so related to the direction of rolling and the plane of the sheet .that the body-centered unit cube lattices thereof are standing on edge with respect to the plane of the sheet and each yunit cube has two 2,943,007 y Patented June 28, 1960 c ICC 5 as singly oriented and which additionally discloses that since the direction of easiest magnetization in these materials is lalong .the cube edges of the unit cube lattice form, these previously known singly oriented sheet materials have had less desirable magnetic properties lin the transverse to rolling direction compared to the same propenties in the rolling direction.

In the previously referenced patent application, it isv disclosed that polycrystalline, rolled, bodycentered cubic, soft magnetic sheet material having improved magnetic properties may be prepared fby properly rolling and heat treating a grain oriented cast intermediate or blank. 'Ihe improved polycrystalline sheet material so produced is. characterized as having a majority of the grains of the sheet oriented in a cube texture. This cube texture may be described as an [001] orientation. Stated other-wise, la high proportion of the grains of such cube texture material have their crystal lattices oriented so that 4two opposite faces of .the unit cube are parallel to the rolling plane of the sheet, two other opposite cube faces .are perpendicular to .the rolling plane and parallel to the rolling Adirection and the two remaining cube faces are perpendicular to the rolling plane and perpendicular to the rolling direction. Sheet materials consisting essentially of iron, iron and up to about 5% silicon, iron and up to about 8% aluminum, and iron and up -to about 5 molybdenum, having this orientation have been Vfound tol have greatly improved magnetic properties, particularlyV in the transverse to rol-ling direction, compared to previously known polycrystalline oriented Vsheet materialsl of comparable compositions. It was found, however, that in order to realize .these'beneiicial resu-lts in a final sheet metal product that the grain oriented casting -then employed must be rolled in either one or the other of two relatively restricted modes. y

As disclosed in the previously referenced application, molten metal .consisting principally of iron is cast into an ingot consisting essentially of a plurality of elongated columnar grains` whose longitudinal axes are substan-A tially parallel to each other. The improved magnetic sheet material previously referred to may then be prepared by appropriately rolling and heat Vtreating suchv an ingot` or a portion thereof. In order tol produce the desired cube text-ure in the inished sheet or stripmaterial,w

it has been founddesirable to coniinethe majority. of-

the rolling passes by which the material is worked to a direction in which the longitudinal axes of the. elongated columnar grains of the casting are maintained substan. tially perpendicular to an imaginary line lying between the working rolls which is substantially mutually parallel to the axis of rotation of each of the rolls. Asimore particularly disclosed in thepreviously referenced application, this direction of the longitudinal axes of the columnar grains inthe casting may be selected from oneor the other of twogeneral relationships of the direction with respect to the working or rolling plane and the rolling direction. For' example, the direction in the casting most nearly parallel to all the longitudinal axes of the velongated columnar grains thereof, must bemarntained substantially parallel to the rolling planeY and 'to the rolling direction during a majority of the reducing rolling passes andthe longitudinal axes of Aav majority of the elongated grains should not deviate'more than about 20 degrees from this-parallelism. In the' other preferred alternative relationship, the direction' in;

the casting most nearly parallel to all longitudinal Vaxes of the elongated columnar grains thereof must bie'n'iain-F and to the rolling direction during a majority of the Y reducing rolling passes, and the longitudinal axes of a majority of the elongated grains should not deviatemore than about :degrees from this perpendicular relationship. lt has been found that if the reduction of the casting to sheet ymetal by rolling is accomplished by maintaining the direction in the casting most nearly parallel to theV longitudinal axes of the columnar grains substantially parallel to the rolling plane and substantially perpendicular to the rolling direction during a majority of the reducing rolling passes, the resulting annealed sheet metal does not'have the well-developed cube texture characteristic of materials produced bythe otherV twopreviously disclosed modes ,ofV working and consequently does not have the desirable magnetic properties of the materials produced by lthese other two modes of rolling. Y

In'such grain `oriented castings, it has been found that the body-centered Vcubic latticesof each of the elongated columnar grainsrare similarly oriented with respect tothe longitudinal axis of each elongated grain lin that certain cube faces of the lattices in each grain are arf ranged substantially perpendicular to the longitudinal axis of that elongated grain. However, with respect to different elongated grains which have -their longitudinal axes substantially parallel, the cube facesV of one grains lattice which are substantially Vparallel to that grainls longitudinal axis are only occasionally parallel to corresponding cube faces 'in other elongated grains.

'.Itrwould be desirable to improve the orientation of the; elongated Vcolumnar grains in the previously de- VVscribed ingots so that a greater number of the grains thereof would have their axes more nearly parallel and thereby reduce the average or net angular deviation of these axes from either oflthe above noted preferred rolling relationships so that the nished polycrystalline sheet material produced therefrom would havera greater proportion of itsconstituent grains oriented in the cube texture. Furthermore, yet further improvements in the cube texture Vof such'v sheet or strip material may be achieved if the Ycubic lattices of the elongated grains of suchcastings are oriented with respect to each other so. that not only are the cube lfaces which arel substantially pegpendicular to the longitudinal grain axis in Vone Ygrain substantially parallel to corresponding cube faces in substantially all other grains, but the other cube `faces which are substantially parallelY to the longitudinal axisriof *one elongated grain- `are substantially parallel.

to corresponding cube faces in substantially every other elongated grain inthe casting. Additionally,.by using VYsueltan improved grain oriented casting, greater exfibility in rolling limi-tations may be achieved.; Forex-V ample, vsuch Van ingot may be rolled lto form sheetmetal Y Y having welldeveloped cube texture by .cross-rolling,y

i.e., by" maintaining the direction in the casting most nearly parallel to all the longitudinal axes-of the elongated columnar g-rains subs-tantially parallel'to the rolling plane and-'substantially'perpendicular*to the rolling direction duringl Va majority of the reducing rolling passes. 1

Accordingly, it is a principal; object of our invention to prov-ide an oriented cast intermediate or blank having an, improved, more regula-r, as-cast macrostructure.

A vfurther objectof our invention is the provision of a mediate Vor 'blank may be prepared.

rA yet furtherobject ofrour invention is the provision of Ya method whereby such an improved cast intermediate Y or blank may bereduc'edY by rolling and heat treatmentV to Vformsheet material having a well-developed cube tex- 4 Y Briefly stated, in accordance with one aspect of our invention, we provide an improved polycrystalline grain oriented casting constituting an intermediate or blank 4for subsequent rolling operations, the grain structure of which is principally composed of Velongated columnar grains whose longitudinal axes are nearly parallel to each other, the casting being composedprincipally of iron and having the body-centered cubic lattice form at temperatures below several hundred degrees centigrade, the casting being further characterized by the crystallographic orientation of eachiv individual, elongated, columnar ascast grain being substantially identically oriented with respect to every other individual elongated columnar asc'ast grain in the casting, a Ymethod vfor producing such a casting by pouring molten metal to be cast upon a grain oriented seed of similar chemical composition and by causing the molten metal to solidify in a temperature Vcontrolled manner upon such seed, and a method for Yrolling and heat treating such a casting to produce sheet of Fig. l taken along line 2 2 thereof;

Fig. 3 is a vertical sectional view otj aV casting apparatus including an ingot cast therein, illustrating one embodiment 4of our invention; Y

Fig. 4 is an enlarged viewof a portion of the ingot shown in Fig. 3;'and Y Fig. 5 is a sectional view of the portion of the ingot illustrated in Pig. 4 taken along line 5 5.

VAs disclosed in the previously referenced application, the cast intermediates or blanks `disclosed therein may be prepared according to one aspect of that invention by casting molten metal consisting principally of iron into an elongated tubular mold having preheated sidewalls and a cooled bottom, The superheat and the latent heatV ofthe molten metal is substantially all ex,-

Atracted` lthrough the cooled bottom of the mold `in a continuous manner'during'solidiiication of the molten metal oausingY the solidilicatiou to initiate and progress from the cooled bottom of the Vmold toward the top of the easrting. In this manner a casting is produced consisting essentially `of a plurality of elongated columnar grains Whose longitudinal axes are substantially parallel and VWhich extend .in la direction substantially parallel to the matically shown in perspective in Fig. l with parts broken away for greater clarity and with the grain structure of a portion of the lcasting schematically indicated. While the portion' 10 of the singly oriented casting has been shown asa generally rectangular prismic lbodyyit Vwill be appreciated that this particular form has been arbitrarily selected ,onlyV for purposes of illustration. As may lne-seen t method whereby Vsuch anV improved oriented cast inter- Yin the figure, the grain structureV of this casting is composedrof elongated'colurnnar grains whosellongitudinal axes Vextend in a generally vertical direction as shown.

Y. If a slab 11 is preparedfrorn portion 1i) by cuttingV along lines, 12 and 1s and along lines r4 and 15 and .the slab Y sectioned Yalong Ya plane 2-'2,"for. example, jthe grain structure ofthesectioned Yslab l1 will appearas'shown in Figure 2. Y,

In Fig, 2 a portion of such a slab section is shown in which the several irregularareas represent individual columnar grainsfofY the casting sectioned approximately perpendicular to the longitudinal axes of the several elongated grains. As previously stated, the materials with which our invention is concerned, have the bodycentered cubic lattice form at temperatures below several hundred degrees centigrade. Upon examination of these individual grains in representative castings by means of X-ray diraction techniques, it was found that these individual elongated columnar grains were similarly oriented with respect to their crystal structure, i.e., that the cubic lattice form of each elongated grain was oriented so that certain of the (100) crystallographic planes, which correspond to the planes of the cube faces, are substantially perpendicular to the longitudinal axis of each grain. It was also found, however, that the planes corresponding to the unit cube faces of the crystal lattices of each grain which were necessarily substantially parallel to the longitudinal axis of that grain were only occasionally parallel to similar crystal planes in the other elongated grains. This may be better understood by reference to Fig. 2 in which the previously described grains are schematically illustrated in cross section with respect to the longitudinal axes of said grains and the cube faces schematically shown by the small squares in each grain area indicate the described crystallographic orientation of .each grain. lt will therefore be seen that each grain in Fig. 2 has its crystal structure oriented so that certain of the crystal planes corresponding to unit cube faces are substantially parallel to the plane ofthe paper which is substantially perpendicular to the longitudinal axis of each grain. Further, it will be noted in this illustration that only two of the illustrated grains 16 and 17 are substantially identically oriented in all respects, that is, all the planes corresponding to unit cube faces in grain 16 are substantially parallel to corresponding unit cube faces in grain 17. While for purposes of illustration, two grains out of seven are shown having this parallel orientation, no particular significance should be attached to this ratio since no particular ratio has been found or established for this type of parallelism,rhowever, it should be noted that this parallel orientation is found only among a minority of the grains in any particular section of such a casting.

According to one aspect of our invention, however, such a slab may be advantageously utilized to produce a casting consisting essentially of a plurality of elongated grains having a high degree of parallelism. Stated otherwise, such a casting consists essentially of a plurality of elongated columnar grains, the longitudinal axes of substantially all of such columnar grains being substantially parallel to each other and the orientation of the-lattice form of each such grain having certain crystallographic planes corresponding to unit cube faces perpendicular to the longitudinal axis of the grain, the remaining unit cube faces being. substantially parallel 4to corresponding cube faces in substantially every other such grain in the casting. Castings made according to our invention having this gross grain structure, may be referred to as being doubly oriented.

More specifically, according to our invention, a casting apparatus similar to that disclosed in the previously referenced application may be used to produce a singly oriented casting as also set forth in said application. A slab 11 as shown in Figs. l and 2 is cut therefrom.

The casting apparatus previously referred to may then be reassembled as it was for casting the single oriented casting. Referring toFig. 3, this apparatus is schematically illustrated therein and consists of a tubular mold 20 of a refractory material such as fused A1203, for example, having openends. The ,interior of the mold 20 may have any desired cross-sectional configuration such as circular or rectangular or the like. The bottom end of the mold vity is closed by the upper surface of a heat extraction rmember, 21 which is preferably constructed of a material having good heat exchange properties such as copper, for example. Member 21 is provided with means for permitting a cooling medium to be circulated in heat exchangeA relationship for the extraction of heat fromA said member. As shown, this may be accomplished, for example, by making heat extraction member 21 in the form of a hollow body and providing pipes 22 and 23 for circulation of a cooling medium such as cold water therethrough.

The tubular mold 20 and the heat extraction member 21 are assembled together as illustrated in Fig. 3 and cooling water is circulated through said member 21 by means of pipes 22 and 23. The interior of the mold cavity is heated to a temperature of about 1400 C. by any convenient means such as, for example, a removable electrical resistance heater while the upper surface of member 21 is maintained at about room temperature or about 20 C. by means ofthe coolant. Slab 11, which s of suicient size and configuration to readily lie liatly in the bottom of mold 20 may be preheated if desired to about l300 C. When the mold sidewalls have been. preheated to about l400 C., the hea-ting means is removed, the preheated slab 11 placed in the bottom.of the mold 20 upon surface 21 with a surface presented` to the mold cavity consisting of columnar grains sec- Y tioned substantially parallel to their longitudinal axes. Molten metal of substantially the same composition asv slab 11 is poured into the moldcovering slab 11 and substantially fillingl the mold cavityY before the preheated slab can be cooled to any substantial degree by' the heat extraction member 21. Coolant is circulated through member 21 untilthe casting solidies. During solidification substantially all the superheat and the late utheatfrom molten metal .is continuously extracted through the slab V11 bythe heat extraction member 21 and only aj small amount of the total heat of the metal is lost through the mold sidewalls and to the atmosphere at the top of the mold. In this manner the heat extraction s substantially entirely unidirectional toward the member 21 and during solidiiica-tion a temperature gradient is main'- tained in the metal from top to bottom. V Y

A yschematicrepresentation of a vertical cross-section of an ingot 25 produced in this manner is shown in. the mold in Fig. 3 after solidilication is completed. The seed slab 11 is shown at the bottom of the ingot 25,the location of the former upper surface of such seed slab being shown bydashed line 14. As shown, vthe bulk of the ingot above the seed slab 11 is composed of a relatively few large columnar grains extending from the seed'` slab to a zone 26 at the top of the ingot which is cornpn'sed of relatively small equiaxed grains ofrconventionalv In thefinterest of clarity these-V equiaxed grains have not been shown in detail since they; are quite conventional in configuration and in practice,v

size and configuration.

are removed along with the pipe 27 by shearing or the.` like from the ingot as scrap.

Upon vX-ray examination of the long columnar grains formed between zone 26 and the slab 11 and comprising the bulk of the casting, it will be found that they-have their origin in grains of the seed slab 11 which are oriented so as to have a cube face almost nearly parallel to the face of the slab which was exposed to the molten metal and therefore .the crystal orientation of these grain bears a substantially parallel relationship to each other. 'I'he grains which grow upon soliditication from the surface of the seed slab `11 under these conditions assume amd continue their growth with substantially the same orientation as the parent grain provided the molten metal poured upon the seed slab 11 melts or tends to melt 'the surface of the seed slab with which it is yin contact before solidifieation begins. The grains which grow from seed grains having a less favorable orientation do not'attain the size of grains which grow from seed grains such as 16 amd 17, for example, and tend to be pinched off, as shown. Y

In Fig. 4, an enlarged view of the seed slab 11 and metal cast thereon is shown. For purposes of illustration, theseed slab portion shown in Fig. 2 has been reproduced f of molten-.metal which has solidiiied under the temperature gradient caused by the unidirectional extraction o f Y heattherefrom by member 21. Grainsy 16'V and 1.7' haveY substantially the same crystal orientation as grain 16, Yand 17 from which they grewand grow to the ultimate exclusionV Vof less favorably .oriented grains adjacentY to or surroundingA them and form the larger.v columnar grains, shown in Fig. 3. These larger grains, such as 16 andlf,

Vfor. example,Y have substantially completely parallel orientation Yas shown in'rFig. 5, a section taken alongS--S offFig.j4. Obviously all the larger columnar grains QQllSti/tuting the bodyV of castingssuch as castingv 2,5 are similarly oriented and therefore cush* av casting may be saidV to Vbe doubly oriented. Y v In practice, zone 26 and the seedslabn 1l and the short,

' misoriented grains adjacent the seed slab may be removedas; scrap leaving a doubly oriented castintermediate or blank which may then be reduced to cube texture softxnagnetic sheet material by appropriate rolling and heat treatment. The polycrystallinesheet material so produced fromA the Vdoubly oriented cast intermediate made` accordingA to our invention has a higher proportion of, theirA grains oriented in the desired cube texture and the limited directional relationships required Vfor processing of the singly oriented cast intermediates are materially increased makingthe production of suchcube texture sheetn laterialVv substantially easier.

Y Mere.- specicall'y, and by Way Of example, anI alloy composedof about 3% silicon, about 0.04% carborn'and thebalance substantially alliron Wa's'melted'and cast; into a tubular mold of fused A1203 supported uponaV Water,

y Vcooled copper block constituting the bottom closure thereof, as shown, for. example in Fig, 3 at 20` and 21f respectively. It should be noted howeventhat themolten alloy was pouredV directly upont'ne coppervvv bottom, andy that. in this casting operation noseedslab V11 wasgused.

The interior side Walls of the mold were heated-toal tern:V Y

perature of about 1200"V to 1400" C. justprior-to plll'ngi :a.1,1d,\byjvirtueV of, the water-cooling, the. temperature'of;

Y Y the copper-bottomwas maintainedat about 20g' C. during` thev rcasting,and'- solidivicationV ofthe ingot. Theingotiwa'ssectioned from top to bottom and found tol be Vsubstantially .completely comprised of elongatedcpolurnnark-grains,`

. having theirJ axes extending substantially.paralleletoth longitudinal axis'of the ingot or stated otherwise, substantially perpendicular to the copperV bottom, with a relativelysmall'zone of equiaxed grains adjacentftheupper: portion Vof the ingot whichv includeda: smallpip e.'Y

The equiaxed graiuzonefandpipe were-,removedrand af rectangular pris'mfshaped-1 slabA Was removed from onehalfV of Vthe sectionedingot to form a body similar to body` 11 of Fig. 1, which was thentrimmed to: a; dimension and conliguration compatible with the'moldllto forml a;

i YCganl supported upon .theWater-cooled copperme'mber 21 Within the'lowerendof a. tubular-fusedY A1203 .mold/f Zilwitblface I4 presented to thenioldV cavity, .-thejnterior'- Vside Walls Vof the. mold being-heatedgto aboutl200 to 1400" C., just'p'rior Yto casting. A molten alloyfcomposedn 1. andffoundlrto be principally` composed of. elongated,coeV

lumnalrV grains 25 extending upwardlyrorn the seedislab llfandhaving a relatively.l small equiaxedzone. 26 .con,

taining afpipe 27 substantially as illustrated' npFigY 3 A; rectangularprismic slab'0.'300"incl1"thick' was pref.

i Voffabout 3 percent silicon, l04 percent carbon, andthe.'

balance substantially all iron. was cast thereinto,all as'` paredtrom said sectione'dingot inrwhichaa direction substantially parallel to the longitudinal axes ofV all the elongatedcolumnar grains was substantially parallel tothe slab faces andthe portions containing Vthe equiaxed grains and pipe and the seed was removed; The slab Was Vthen divided approximately into two substantially equal-sized' portions each 0.300 inch thick by cutting along ai plane perpendicular to the slab faces and the longitudinal axes of .the columnar grains. lThese Vsubstantially identical salbs and the sheet material rolled therefromwill be hereinafter designated as A. and B for convenience.

PothY slabs A and B were heated to about l000 C'. and reduced in 8 rolling passes tok 0.083 inch `thick sheetmetal without reheating; The hot-rolled stripsV werereduced at a temperature of about 400 C. to abouts0.025Y inch tliicl; sheet or strip inra plurality of rolllingpasses` This strip or sheet material was then annealed by heating in a dry liydrogenratmosphere to a temperature of' 1000"v C., held'for 4 hours and' permitted to'rapidly coolf in the hydrogen. atmosphere.

rIfhe strips were then cold-reduced by unidirectional rolling to 0.0.12 inch thick in a plurality of rolling passes. Torque test specimens comprising vcircular disks l inch in diameter were stamped from the stripsY and annealed in dry hydrogen by heating at about 100g' C. per-hour to 1200J VC., held at that temperature for 5 minutes and slowly cooled, i.e. at about 100 C. per hour.

All thev rolling was unidirectional, the A slab beingy reduced by a rolling schedule during which the direction inthe slab substantiallyparallel to the longitudinal axes of the columnar grains was maintained substantially'par-y allel to the rolling planeand substantially perpendicular to the rolling-direction, while the same` directionin slab B was maintained substantially parallel to both the rolling ingots rolled- With the longitudinal axes ofthe columnar grains maintained substantially parallelv to the'rolling. piane and perpendicular tothe rolling directionduring rolling (ie. vcross-rolled) exhibited an average torque of;

67,000er'gs/cc., and apeak ratio of about 0.71 for 86 samples. This material has about 54%` cube texture.

The materialirolledf'ro'm slab B'hadfan average torque of 109,600 ergs/cc., a peak ratiorof 0.75 and therefore was about 89% cube texture. l Y

From theforegoingzit Vis, apparent that a sharp cube texture isE obtainableV fromV aseeded columnar ingot when.

rolled withthe directongiriA theQin'got which is nearest tov parallel to the longitudinal columnar `grains maintained substantiallyk parallel to the rolling plane and perpendicular-to the rolling direction,- Whereas similarly rolling a; non-seeded columnar casting vproducesv stripA having` aV much poorerv texture. It should benoted that 'the1term5l substantially parallelrV and fsubstantially perpendicular. include. directions Vwithin 20 of absoluteflparallel': and

perpendicular! It' will also beappreciated by those` skilled in the-,art

' that the oriented seedvslabrnay b e-composedofian, alloyv or metal differingincompositionfromthemelt provided it has amelting point substantially the same'asthemeln, in Vorder to permit meltback, anda` lattice parameter.vv sim-ilario the moltenv metal fso that: orientednucleation and growth of grains havingvthe same orientationpas the-V grains of the seed mayibeaccomplished. Y

From the foregoing, it will .be-:apparentrto those skilled in therart that such seed slabsY having higher proportionsl of grains orientedivith respect toy the surface presentedtol fh? ,molten metal similar to grains 16Y and 17in Figs.

2 and 3 would be more desirable. Defined in a more general Way, the reduction of the casting into sheet metal in accordance with this invention Will be carried out by heating the casting to a temperature of from about 700 C. to about l100 C. and then rolling the heated casting to affect at least a 70% reduction in its thickness. It is then annealed in a hydrogen atmosphere for from 4 hours at about 1000 C. to about l/2 hour at about 1200 C., cooled and cold rolled (i.e, at room temperature) to a thickness reduction of at least 40%. The resulting cold rolled sheet metal is next annealed and recrystallized by heating to at least 1150 C. in a hydrogen atmosphere and finally slowly cooled in a hydrogen atmosphere.

In View of the foregoing disclosure, it will be apparent to those skilled in the metallurgical arts that We have invented a process whereby the grain orientation of cast ingots of body-centered cubic iron alloys such as alloys containing up to about 5% silicon, balance substantially all iron, up to about 5% molybdenum, balance substantially all iron, and up to about 8% aluminum, balance substantially all iron may be substantially improved.

What we claimed as new and desire to secure by Letters Patent of the United States is:

1. A method for preparing cube texture soft magnetic sheet metal comprising the steps of providing a casting consisting essentially of iron comprising a plurality of elongated columnar grains having their longitudinal axes extending substantially parallel to a rst single direction, a majority of said elongated grains having a unit cube face of their crystal lattices substantially parallel to said rst direction and substantially perpendicular to a single second direction which is substantially perpendicular to said first direction; reducing the casting into sheet metal by a plurality of rolling passes in the majority of which rolling passes the first direction is maintained substantially parallel to the rolling plane and substantially perpendicular to the rolling direction and the second direction is maintained substantially perpendicular to the rolling plane and to the rolling direction; and annealing the cold rolled sheet metal by heating to at least 1150" C. in a hydrogen atmosphere and slowly cooling the recrystallized sheet metal in the hydrogen atmosphere.

2. The method recited in claim l in which the casting is prepared by melting the metal to be cast, bringing the molten metal into contact with a surface of a non-molten body of metal having the body-centered cubic crystal lattice form, said non-molten body being comprised of a plurality of elongated columnar grains having their longitudinal axes extending substantially parallel to a single direction substantially parallel to said surface, maintaining said molten metal in contact with said surface for a period of time suihcient to melt a portion of said surface and ywithdrawing heat from the molten metal through the seed slab in a direction substantially perpendicular to the surface of the seed slab and thereby solidifying the molten metal on said surface to form an ingot.

3. The method recited in claim 2 in which the casting is prepared by pouring .said molten metal into an ingot mold and maintaining a temperature gradient along a single lateral direction of the ingot mold so that substantially all of the grains in the ingot grow during solidiication of the metal as elongated columnar grains having their longitudinal axes substantially parallel to the gradient and substantially perpendicular to the surface of the non-molten body of metal.

4. The method recited in claim l lirl which the casting is reduced into sheet metal by the steps comprising heating the casting to a temperature of from about 700 to about 1l00 C., rolling the heated casting to effect at least a reduction in thickness, annealing in a hydrogen atmosphere for from 4 hours at about 1000" C. to about one-half hour at about 12007 C., cooling the rolled, annealed metal, reducing the thicknes of the annealed metal at least 40 percent by cold rolling, annealing the cold rolled sheet metal by heating to at least 1150 C. in a hydrogen atmopshere and slowly cooling the recrystallzed sheet metal inthe hydrogen atmosphere.

5. A method for casting grain-oriented ingots of magnetic metal consisting essentially of iron comprising the steps of melting the metal to be cast, bringing the molten metal into contact with a surface of a non-molten body of metal consisting essentially of iron, said non-molten body being comprised of a plurality of elongated columnar grains having their longitudinal axes extending substantially parallel to a single direction substantially parallel to said surface, maintaining said molten metal in contact with said surface for a period of time sulcient to melt a portion of said surface and solidifying the molten metal on said surface to form an ingot.

6. A method for casting grain-oriented ingots comprising the steps of pouring a molten magnetic metal consisting essentially of iron upon a surface of a body of solid metal consisting essentially of iron, said body of solid metal being comprised of a plurality of elongated columnar grains having their longitudinal axes extending substantially parallel to a single direction substantially parallel to said surface, permitting the surface of said body to become molten and then causing the molten metal to solidify by extracting substantially' all the superheat and the latent heat of the molten metal through said body of solid metal.

References Cited in the le of this patent UNITED STATES PATENTS 1,793,672 Bridgman Feb. 24, 1931 1,961,399 Snook June 5, 1934 2,112,084 Frey et al. Mar. 22, 1938 2,113,537 Hiemenz Apr. 5, 1938 2,307,391 Cole et al. Jan. 5, 1943 'UNiTED STATES PATENT OFFICE ACERTIFICATE OF CORRECTION June 28, 1960 Patent No. 2,943,007

Johh L. Walter et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

the drawings.t name of inventor, i ad J. L. WALTER ET AL In the heading to OI "J, L. WALKER ET AL" re Signed and sealed this 20th day of December 1960.

(SEAL) Attest:

ROBERT C. WATSON KARL H. AXLINE Attest ing Officer. Commissioner of Patents

Claims (1)

1. A METHOD FOR PREPARING CUBE TEXTURE SOFT MAGNETIC SHEET METAL COMPRISING THE STEPS OF PROVIDING A CASTING CONSISTING ESSENTIALLY OF IRON COMPRISING A PLURALITY OF ELONGATED COLUMNAR GRAINS HAVING THEIR LONGITUDINAL AXES EXTENDING SUBSTANTIALLY PARALLEL TO A FIRST SINGLE DIRECTION, A MAJORITY OF SAID ELONGATED GRAINS HAVING A UNIT CUBE FACE OF THEIR CRYSTAL LATTICES SUBSTANTIALLY PARALLEL TO SAID FIRST DIRECTION AND SUBSTANTIALLY PERPENDICULAR TO A SINGLE SECOND DIRECTION WHICH IS SUBSTANTIALLY PERPENDICULAR TO SAID FIRST DIRECTION, REDUCING THE CASTING INTO SHEET METAL BY A PLURALITY OF ROLLING PASSES IN THE MAJORITY OF WHICH ROLLING PASSES THE FIRST DIRECTION IS MAINTAINED SUBSTANTIALLY PARALLEL TO THE ROLLING PLANE AND SUBSTANTIALLY PERPENDICULAR TO THE ROLLING DIRECTION AND THE SECOND DIRECTION IS MAINTAINED SUBSTANTIALLY PERPENDICULAR TO THE ROLLING PLANE AND TO THE ROLLING DIRECTION, AND ANNEALING THE COLD ROLLED SHEET METAL BY HEATING TO AT LEAST 1150*C. IN A HYDROGEN ATMOSPHERE AND SLOWLY COOLING THE RECRYSTALLIZED SHEET METAL IN THE HYDROGEN ATMOSPHERE.

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