US2970075A

US2970075A - Cast intermediate or blank and method of preparation

Info

Publication number: US2970075A
Application number: US767059A
Authority: US
Inventors: Herbert E Grenoble
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1958-10-13
Filing date: 1958-10-13
Publication date: 1961-01-31
Anticipated expiration: 1978-01-31

Description

Jan. 31, 1961 H. E. GRENOBLE 2,970,075

CAST INTERMEDIATE OR BLANK AND METHOD OF PREPARATION Filed Oct. 15, 1958 2 Sheets-Sheet 1 f F fg.

a l \uq 2 We i d /n ventor Herbert E Grenob/e,

by p 4 M Hts Attorney.

Jan. 31, 1961 H. E. GRENOBLE 2,970,075

CAST INTERMEDIATE OR BLANK AND METHOD OF PREPARATION Filed Oct. 13, 1958 2 She ets-Sheet 2 Fig. 7,

In vemor Herberf E. Grenob/e,

His Attorney.

United States PatentO F CAST INTERMEDIATE OR BLANK AND METHOD OF PREPARATION Herbert E. Grenoble, Amsterdam, N.Y., assignor to General Electric Company, a corporation of New York Filed Oct. 13, 1958, Ser. No. 767,059

'6 Claims. (Cl. 148-110) This invention relates to sof magnetic materials and more particularly to improved grain oriented ingots or castings which are intended to be worked by rolling or ."forging, composed of iron and soft magnetic alloys of iron and silicon, iron and aluminum, and iron and molyb- =denum, constituting cast intermediates or blanks from which polycrystalline sheet material may be prepared by :rolling and appropriate heat treatment to have a high percentage of its grains oriented as cube texture, and to a .method of preparing such cast intermediates or blanks.

This application is a containuation-in-part of applicant's -co-pending application, Serial No. 610,908, now abanwdoned, filed September 20, 1956, and assigned to the same .assignee as the present application.

As disclosed in a co-pending application for Letters :apparatus. These previously known oriented sheet ma- :terials have usually been composed principally or iron :and up to about silicon and have had the body-centered cubic lattice form at temperatures below several hundred degrees centigrade. The preferred orientation of thesepreviously known sheet materials has been characterized by a high proportion of their grains having their body-centered cubic lattice forms orientedsuch that the so-called (110) planes thereof 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) [001] orientation.

-As will be readily recognized by those skilled in the metallurgical arts, the numerical notation of the (110) crystallographic plane previously used is the accepted description of a plane in the unit cube containing diagonally opposite cube edges according to the Miller crystallographic index system. Similar numerical designations of crystal structure and directions used hereinafter will be set forth in accordance with the same index system, a

.more complete discussion of which may be found, for example, in Structure of Metals, by C. S. Barrett, Mc- Graw-HillBook Company, Inc., New York, 2nd edition, 1952, pages 1 to 25.

.Sheet metals having this (110) [001] orientation may be :otherwise described as an elongated polycrystalline body of sheet metal having the body-centered cubielattice -form produced by conventional rolling procedures in which a high proportion of thegrains of the sheet have their crystal structure so related to the direction of rolling in the plane of the sheet that the body-centeredunit cube lattices thereof are standing on edge with respect to the plane of the sheet and each unit cube has two cubefaces perpendicular to the rolling direction and the plane of the tially parallel to each other.

sheet. This orientationis more completely described in the previously mentioned co-pending application wherein such materials are described as singly oriented and which additionally discloses that since the direction of easiest magnetization in these materials is along the cube edges of the unit cube:lattice form, thesepreviously known singly oriented sheet materials have had less desirable magnetic properties in the transverse to rolling direction compared to the same properties in the rolling direction.

In the previously referenced patent application .of Walter and Hibbard, it is disclosed that polycrystalline, rolled, b0dy-centered, cubic, soft magnetic sheet material having improved magnetic properties may be prepared by properly rolling and heat treating a grain oriented cast intermediate or blank. The improved polycrystalline sheet materialso 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 the [001] orientation. Stated otherwise, a high proportion of the grains of such cube texture material are so oriented that two 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 andparallel to the rolling direction and the two remaining faces are perpendicular to the rollingplane and per pendicular 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 found to havegreatly improved magnetic properties, particularly in the transverse to rolling direction, compared to ,previously knownpolycrystalline oriented sheet materials ofcomparable compositions, it was-,found,-.how ever, thatin order to realize these beneficial results in ,a final sheet metal product, the grain oriented casting then employed must be rolled in either one or the other .of-two relatively restricted modes.

As disclosed in the application previously referred to, 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- The :improved magnetic sheet materialpreviously referred to may then be prepared by appropriatelyrolling .and heat treating such an ingot ora portion thereof. In order to produce theadesired cube texture in a finished sheet or strip material, it

has been found desirable to confine the majority of the rolling passes by which the material is worked to a direction in which the longitudinal axes of ,the elongated columnargrains of the casting are maintained substantially perpendicular to animaginary linellying between the working rolls, which is-substantially mutually parallel to the axis of rotation of .each of the rolls. As more particularlydisclosed in the previously referenced application, this direction of the longitudinal axes of thecolumnar grainsin the casting may be selected from one or the other of two general relationships of the direction with respect to the Working plane and the rolling direction. For example, the direction in the casting most nearly parallel to all the longitudinal axes of the clangated colurnnar grains thereof must be maintained substantiallyparallel to the rolling plane andto the rolling direction during a majority of the reducing rollingpasses and thelongitudinal axes of a majority of the elongated grains should not deviate more than about'20.;fr0m this parallelism. in another .describedrelationship, the ;direc :tion in .the casting most nearly parallel to all longitudiand to the rolling direction during a majority of the reducing rolling passes and the longitudinal a'xes of a niaiority of the elongated grains should not deviate more than about 20 from this perpendicular relationship.

In such grain oriented castings, it has been found that the body-centered cubic lattices of each of the elongated columnar grains are similarly oriented with respect to the longitudinal axis of each elongated grain in that certain cube faces of the lattices in each grain are arranged 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 faces of one grains lattice which are substantially parallel to that grains longitudinal axis are only occasionally parallel to corresponding cube faces in other elongated grains.

It would be desirable to improve the orientation of the elongated columnar grains in the previously described ingots so that a great 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 of the above noted rolling relationships so that the finished polycrystalline sheet material produced therefrom would have a greater proportion of its constituent grains oriented in the cube texture. Additionally, by using such an improved grain oriented ingot, greater flexibility in rolling limitations may be achieved. Furthermore, improvements in the cube texture of such sheet or strip material may be achieved if the cubic lattices of the elongated grains of such castings are oriented with respect to each other so that not only are the cube faces which are substantially perpendicular to the longitudinal grain axes substantially parallel to each other, but the other cube faces which are substantially parallel to the longitudinal axis of one elongated grain are substantially parallel to corresponding cube faces in substantially every other elongated grain in the casting.

Accordingly, it is a principal object of my invention to provide an oriented cast intermediate or blank having an improved, more regular, as-cast macrostructure.

A yet further object of my invention is the provision of a method whereby such an improved oriented cast intermediate or blank may be prepared.

Other and specifically different objects of my invention will become apparent during the course of the detailed disclosure and description which follows.

Briefly stated, in accordance with one aspect of my invention, I provide an improved polycrystalline, grain oriented, casting constituting an intermediate or blank for subsequent rolling operations, the grain structures of which is principally composed of elongated, columnar grains whose longitudinal axes are nearly parallel to each other, the casting being composed principally 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 each individual, elongated, columnar, ascast grain being substantially identically oriented with respect to every other individual elongated columnar ascast grain in the casting, and the method for producing such a casting by pouring molten metal to be cast upon a grain oriented seed of similar chemical composition and by causing a molten metal to solidify in a temperature controlled manner upon such seed, my invention being particularly characterized by forming such seed from a plurality of polycrystalline oriented bodies particularly arranged with respect to the structure of the ingot mold.

My invention will be better understood from the following description taken in connection with the accompanying drawings and its scope fully pointed out in the appended claims.

With particular reference to the drawings,

Fig. 1 is a semi-schematic view in perspective of a seed-slab element according to one embodiment of my invention;

Fig. 2 is a plan view with parts broken away of casting apparatus including a seed-slab constructed of elements shown in Fig. 1;

Fig. 3 is a vertical sectional elevation with parts broken away of a casting apparatus of Fig. 2;

Fig. 4 is a semi-schematic view in perspective of a seed-slab element according to another embodiment of my invention;

Fig. 5 is a plan View with parts broken away of casting apparatus including a seed-slab constructed of elements shown in Fig. 4;

Fig. 6 is a vertical sectional elevation with parts broken away of a casting apparatus of Fig. 5;

Fig. 7 is an enlarged vertical sectional view of a portion of the apparatus shown in Fig. 6 after a casting op eration;

Fig. 8 is a semi-schematic plan view of a section of a casting made according to my invention taken along line 8-8 of Fig. 7; and,

Fig. 9 is a semi-schematic view in perspective of a seed-slab element according to another embodiment of my invention.

As 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 heat of the molten metal is substantially all extracted through the cooled bottom of the mold in a continuous manner during solidification of the molten metal,

causing the solidification to initiate and progress from the cooled bottom of the mold toward the top of the casting. In this manner, a casting is produced consisting essentially of a plurality of elongated columnar grains whose longitudinal axes are substantially parallel and which extend in a direction substantially parallel to the direction of solidification of the ingot. This type of casting may be referred to as a singly oriented casting in order to more clearly distinguish from a doubly oriented casting of my present invention, the distinguishing structural characteristics of which will be subsequently disclosed.

In practicing my invention, I provide a generally planar grain oriented seed-slab upon which molten metal is cast, said metal assuming the grain orientation of the slab upon solidification. In addition, I provide means for the extraction of substantially all of the superheat and latent heat of the molten metal through the seedslab during solidification of the molten metal whereby the solidification processes of the molten metal progress from the surface of the seed-slab in a substantially unidirectional manner. During solidification of the ingot, elongated columnar grains are formed which extend from the seed-slab having their longitudinal axes substantially parallel to the direction of heat extraction, or in a direction substantially perpendicular to the general plane of the slab. Each of these elongated columnar grains comprising the cast ingot of body-centered cubic material produced according to my invention has its crystal lattice form oriented such that all the unit cube faces in said grain are substantially parallel to corresponding unit cube faces in substantially every other elongated grain in the casting. Furthermore, I provide means whereby, according to my invention, the grain orientation of such as-cast ingots is readily and accurately related to one or more substantially planar sides of the ingot, constituting one or more faces adapted to be worked as by rolling.

As previously pointed out, singly oriented polycrystalline sheet metal consisting of, for example, up to about 5% silicon, balance substantially all iron is well known and is commercially available. The single orientation of this material is widely known as cube-on-edge crystal orientation and there is only one direction of preferred magnetization. I This material is conventionally produced by rolling and heat treating this material to ppm- 16 T5 produce sheet metal in which :a majority -'of the-rgrains thereof are oriented with their cube lattices arranged with respect to the plane of the sheet and the direction of rolling as illustrated, for example, in .Fig. 1. :In this figure, a portion of such rolled sheet metal has superimposed thereon a schematic representation of-a unit cubic lattice .11, showing the relationship of the cube faces and directions of the body-centeredcubic space lattices of a majority of the grains of this polycrystalline material to the rolling plane orthe plane of the sheet and to the direction in which it was rolled. While the unit cube 11 has been schematically shown as a solid body for purposes of this disclosure, it will be understood that the actual tunit cube lattices are submicroscopic in size and are individually formed of nine spaced atoms, one located at each of the eight corners of the cube and the nineth-atomlocated at the geometrical-center of the cube.

The relationship shown in Fig. 1 illustrates the single orientation of these .commercial materials previously referred to, in which .a majority of the grains of the material have their crysetal lattices arranged so that a (110) plane, for example, the plane including opposite edges 12 and .13 of cube 11, is substantially parallel to the plane of the sheet 10 and two opposite cube faces, for example, cube faces 14 and .15, are substantially perpendicular to the plane of the sheet 10 and to the-direction in which the sheet metal was rolled'during its fabrication. Since in the subject soft magnetic alloys, the crystallographic direction of easiest magnetization is in the directions parallel to the unit cube edges, these prior grain oriented sheet materials have had their optimum magnetic properties in the plane of the sheet parallel to the rolling direction. However, in the transverse to rolling direction, or90 to the rolling directiomin the plane of the sheet the .same magnetic properties have been substantially poorer.

.As more particularly disclosed in the previously reference application, it has been found that sheet materialsof such soft magnetic alloys having cube texture may be prepared by particularly rolling and appropriately heat treating grain oriented polycrystalline castings or ingots. The grain orientation of the ingots may be briefly described as one in which substantially all the grains in the ingot are elongated columnar grains which are so positioned in the ingot that the longitudinal axes of these grains are substantially parallel to each other and to a single direction in the ingot. These oriented ingots may be prepared by casting molten metal into a mold and controlling the solidification thereof by providing means whereby substantially all the superheat and the latent heat of the metal is extracted in one direction.

may be accomplished for example, by using a vertically arranged tubular mold, preheating the sidewalls thereof just prior to pouring the molten metal therein and providing cooling means for the bottom. Heat is extracted from the solidifying metal through the cooled mold bottom more rapidly than through the mold sides so that solidification begins at the bottom and progresses upwardly in the mold as a plurality of elongated columnar grains having their longitudinal axes substantially parallel and substantially perpendicular to the cooled heat extraction surface constituting the mold bottom whereby the direction of growth of these elongated grains and their longitudinal axes are substantially parallel to the directionof heat flow during solidification.

It-has been found that the body-centered cubic lattices of these elongated grains have a common crystallographic characteristic in that in each elongated grain certain (100) planes or cube faces are arranged substantially perpendicularly to the longitudinal grain axis. Therefore, in an ingot consisting essentially of a plurality of elongatedacolumnar grains, all of whose longitudinal axes are Substantially, parallelv to each other, the atoms: in one such grain which form planes corresponding tO'TtWO of the cube faces are substantially parallel to thecorresponding planes of atoms in all of-the other eloii 'gated grains in the ingot. However, the atoms forming planes corresponding to the-other four unit cube faces in such a grain are only occasionally substantially parallel to corresponding planes of atoms in a few of the other elongated grains of the ingot. I have discovered that a very high degree of parallelism between all the cube face planes of substantially all the grains in such a polycrystalline casting which has been found to be desirable may be achieved in the following manner.

Broadly, according to one embodiment of my invention, I provide a highly oriented seed-slab made up of a plurality of cube-on-edge grain oriented strips assembled in a manner that a majority of the-unit cube faces of the strips are substantially commonly aligned with two unit cube faces generally perpendicular to the side walls of a mold into which molten metal is cast. The seed slab is adapted to be placed in heat exchangerelationship with molten metal poured into said mold whereby the major portion of the superheat and latent heat of said molten metal is extracted by said slab during solidification by cooling means in heat exchange rela: tionship with said slab.

More particularly and with regard to the embodiment of my invention shown in Figs. 1 to 3 inclusive, I pro vide a composite laminated body 20 comprising a plurality of strips of cube-on-edge single oriented poly.- crystalline commercial silicon-iron sheet metal, as shown by strip 10 in Fig. 1. As illustrated, these strips are rectangular in shape and have their shortest surface dimension A disposed transversely or from the rolling direction of the sheet in the plane of the sheet, their thickness B corresponds to the thickness of the sheet and their longest surface dimension C parallel to therolling direction of the sheet. It will be understood that in this material the majority, and preferably 70% or more, of the grains comprising said strips 10 are oriented as schematically illustrated by unit cube 11 in Fig. 1. A number of these strips preferably have a somewhat larger A dimension than the remainder and may, for convenience, be referred to by the reference numeral 10' since they are otherwise identical in all respects with strips 10. These strips 10 and 10' are laminated or stacked together in face-to-face relationship to form a substantially rectangular slab with one substantially planar face 21 formed by one of the C edges of each of the strips, the strips having their rectangular faces inclined at an angle of about 45 to said planar face 21 as shown in Fig. 3. Additionally wider strips 10' are interspersed with strips 10 and project beyond the strips 10.

The composite body 20 is formed of a sufficient number of strips, 10 and 10 of thickness B and length C which may be secured together by tack welding, for example, so that slab 20 may be shaped by machining or the like to closely fit into a tubular mold 22 which is preferably rectangular in cross section. Preferably the slab 20 constitutes the bottom of the mold as shown and the upper portions of the wider strips 10' extend above the narrower strips Ill into the mold cavity 23 as shown in Fig. 3. The lengthwise dimensions C of

stripsv

10 and 10 extend transversely across the mold cavity 23 at; the bottom thereof and are parallel to a pair of opposed; parallel

straight walls

24 and 25 and perpendicular to a pair of opposed parallel

straight walls

26 and 27 con stituting the sidewalls of tubular mold 2 and the width wise dimension A of said strips 10 and 10 are inclined; at an angle of about 45 to the mold walls 24 and 25.v

It will be appreciated that the oriented grains of strips. 10 and 10' are thereby oriented with respect to the mold. walls and the mold cavity such that a pair of parallel" unit cube faces of the space lattices of all these oriented, grains are substantially perpendicular to the four mold-J.

walls, 24, 25, 26 and 27, another pair of parallel unit cube facesare substantially perpendicular to mold walls. 24 and 25 andsubstantially parallelto mold walls 26and.-.

'7 27, and the remaining pair of unit cube faces are substantially parallel to

mold walls

24 and 25 and substantially perpendicular to

mold walls

26 and 27.

As assembled for casting, the bottom of mold 22 containing slab 20 is supported upon a heat exchanger 30 which may conveniently comprise a hollow body having an upper substantially planar portion 31 which is coextensive and in good heat exchange relationship with surface 21 of slab 20. The interior of hollow body 30 is provided with means for extracting heat from slab 20 such as a cooling media such as cold water circulated therethrough by means of appropriate conduits, 32 and 33, which provide communication with the interior of body 30 for the cooling media.

A different embodiment of my invention is illustrated in Figs. 4 to 6 inclusive. In this embodiment, a seedslab 38 is prepared by assembling a plurality of

strips

40 and 40 cut from singly oriented commercial siliconiron sheet material, as more particularly shown in Fig. 4. As illustrated these strips 40 are rectangular in shape and each have their shortest surface dimension A disposed parallel to the direction in which the sheet metal was rolled, their thickness B corresponds to the thickness of the sheet and their longest surface dimension C disposed transversely to or 90 from, the rolling direction of the sheet in the plane of the sheet. As before, it will be understood that the majority, and preferably 70% or more, of the grains comprising said strips 40 and 40' are oriented as schematically illustrated by unit cube 41 in Fig. 4 in which a (110) plane or, otherwise stated, a plane containing diagonally opposite cube edges 42 and 43, is substantially parallel to the plane of the sheet and a pair of opposite cube faces 44 and 45 are perpendicular to both the plane of the sheet and the rolling direction thereof. Strips 40 and 40' are identical in all respects except that preferably the width A of strips 40' is greater than the width A of strips 40.

These strips 40 and 40' are stacked together in a faceto-face relationship to form a substantially rectangular slab having a planar face 39 formed by one of the C edges of each of the strips, the strips having their rectangular faces extending vertically from planar face 39. The wider strips 40' are interspersed with and project beyond strips 40.

The composite body 33 is formed of a suflicient number of strips 40 and 40' of thickness B and length C which may be secured together by tack welding, for example, so that slab 38 may be shaped by machining or the like to the desired final size and shape. Slab 38 is preferably contoured to form the bottom closure of the rectangular mold 45 and the upper surface of slab 38 may be formed to receive and support the lower mold sidewall portions of mold 45 thereupon as illustrated. In this embodiment of my invention, the upper edges of the narrower strips 40 determine the plane of contact between the mold sidewalls and the slab 38, it being understood that the upper edge portions of strips 40' are reduced to the same height as strips 40 in these areas or zones of slab 38 which are in contact with the mold as shown, for example, at 46 in Fig. 5. The extending portions of strips 40' which remain unreduced project above the upper edges of the narrower strips 40 in the mold cavity 50. 1

- The lengthwise dimension C of strips 40 and 40' extend across the mold cavity in an angular relationship to the sidewalls. For example, as shown in'Fig. 5, the lengthwise dimensions C of the

strips

40 and 40 are inclined at an angle of about 45 to the substantially planar

straight sidewalls

51, 52, 53 and 54 which define the mold cavity 50 of mold 45. In this relationship, it will be apparent that the oriented grains of

strips

40 and 40 are oriented with respect to the mold walls and the mold cavities such that one pair of parallel unit cube faces of the space lattices of all these oriented grains is substantially perpendicular to the four mold walls 51,

'8 52, 53 and 54, another pair of parallel unit cube faces is substantially perpendicular to

mold walls

52 and 54 and parallel to

mold walls

51 and 53, and the remaining pair of unit cube faces is substantially parallel to

mold walls

52 and 54 and perpendicular to mold

Walls

51 and 53.

As assembled for casting, the bottom of mold cavity 50 is supported upon slab 38 as shown in Fig. 6, thereby forming an open top container to receive molten metal. Cooling means are provided for the extraction of heat from slab 38 such as, for example, the cooling liquid conduit 60 supplying a cooling media to a plurality of jets of nozzles 61 which are adapted to direct the coolant against surface 39 of slab 38. In either of the exemplary embodiments illustrated, it should be noted that while rectangular cross-sectioned mold cavities have been illustrated, other cross-sectional mold cavity configurations may be employed if desired. However, in order to realize the greatest benefits from my invention, it is desirable that the mold have at least one substantially planar straight sidewall so that the grain orientation of the seed-slab may be related thereto and therefore the resulting grain orientation of the resulting ingot may readily be determined in order that the most effective rolling or forging be accomplished thereon. It is additionally preferable for greater convenience and more effective working in which such ingots are to be reduced to sheet or strip-like materials solely by rolling, to provide the ingot mold with a pair of substantially parallel straight planar opposed sidewalls to form an ingot having a pair of substantially parallel straight planar opposed working faces which are substantially parallel to unit cube faces in the seed-slab and in the as-cast elongated grains comprising the ingot which have the same grain orientation as the oriented grains of the seed-slab.

In the practice of one aspect of my invention, and as a specific example thereof, a rectangular cross-section mold 22 and seed-slab 20, for example, are assembled and supported upon the heat exchanger 30 as illustrated in Fig. 3. Seed-slab 20 is composed of strips of an alloy consisting essentially of about 3% silicon and the balance substantially all iron, which are oriented and located with respect to the sidewalls of the mold 22 and the mold cavity 23 as shown in Fig. 3, said strips being prepared from commercial grain oriented silicon-iron polycrystalline sheet metal, having a majority and preferably at least 70% of its grains oriented with respect to the rolling direction and plane as illustrated in Fig. 1 and as previously described.

A molten charge of alloy is prepared for casting into the mold, preferably but not necessarily consisting essentially of about 3% silicon, about 0.05% or less carbon and the balance substantially all iron. It should be noted here that the composition of the molten metal and that of the seed-slab do not have to be exactly the same. For the purposes of my invention, the geometrical characteristics and dimensions of the crystal lattice of the seed-slab and the solid which forms upon freezing of molten metal must be very similar in order that the crystal lattice orientation of the grains of the seed-slab may be propagated in the cast structure of the ingot, but completely identical compositions thereof is not required. For example, the carbon content of the metal comprising the seed-slab is of the order of 0.005% or less, while it may be desirable to have about 0.02 to 0.05% carbon in the as-cast ingot. Further, silicon-iron seed-slabs according to my invention containing up to about 5% silicon may be employed in conjunction with molten siliconiron alloys containing up to about 5% silicon, molybdenum-iron alloys containing up to about 5% molybdenum, and aluminum-iron alloys containing up to about 8% aluminum, to produce the desired oriented castings.

It will also be apparent that seed-slabs may be made from oriented sheet material composed of molybdenumiron and aluminum-iron alloys. As pointed out in the 9; previously, referenced, co-pending application, the maintenance of a substantially unidirectional extraction of heat from the moltenmetal in the mold during solidifica tion isnecessary to preventtheformation of undesirable equiaxed grams in the ingot. The provision of the heat exchanger 30 is effective toextract a considerable amount of this heat, but it is desirable to augment its eiiect during solidification. This may be; effectively accomplished by preheating the mold sidewalls to a temperature of the order of 1400 C, just prior to castingby means of an electric resistance furnace inserted in the mold cavity or, by any other suitable means, It is generally desirable, that the mold sidewalls be of a thermal insulating mate: rial. The molten metal is poured into the mold 23 and. after a very brief interval, the circulation of coolant through heat exchanger 30' is begun. The short delay. in extracting heat from the seed-slab is desirable to prevent undesired heat extraction from themold walls prior. to casting and to insure that themolten metal Will melt. back the upper layers of; the seed to facilitate oriented. grain growth on solidification.

The melt back of the upper layers of-the seed may be retarded by the formation ofanoxide film of substantial thickness on the surface of the seed presented to the mold cavityduring the heatingof the. mold sidewalls. It may therefore be desirable to providethe upper surface of theseed-slab with a fluxingcoating prior to the heating. step, For example, a coating of an aqueous solution composed of fromabout 60 ,to 75% by weight water and thebalance-substantially, all potassium silicate in which silica is present in the ratio of-from about,3.3 to 4.0- m o1 s of S tol mol of K 0 may be brushed on the surfaceand permitted to dry. The application of this coating may be repeated several times to buildup the thickness of the dry coating. As the temperature of the mold sidewalls is increasedto .above 1400 C., the coating thus applied'melts and acting as a fiux dissolves the iron andsilicon oxide film. This molten flux containing the dissolved oxides is then washed from the surface by the molten metal during the pouring operation and the thus cleaned surface layers ofthe seed are readily melted back. Any known fiuxing agent capable of dissolving iron and silicon oxidefilmunder these conditions may obviously be employedin place of the potassium silicate.

After; the melt back has stopped, the molten metal beginsto solidify under the influence of the substan tially unidirectional'temperature gradient introduced by theheat exchanger 30. The metal solidifies as a plurality of elongated columnar grains extending upwardly from theseed-slab and a large schematic view is shown in Fig, 7 of a portion of such an ingot including the: portion ofthe mold 'wall'22'anda portion of the seed slahZjl. The preferred orientation of

strips

10 and 10 of the seed-slab is indicated by the small squares 65' shown in the strips which corresponds to a unit cube face in theplane of the paper. The degree of melt back of the seed-slab is indicatedby-the dashed line 66 and those portions of strips 10 and 10' which melted during thernelt back of the slab is shown by the portions of the strips in brokenlines. The employment ofthe wider strips 10 interspersed with narrower strips llLis effective to increase the surface of the seed-slab contacted by the molten metal and thereby promotes the melt back of the seed. It should be noted that the pro vision of wider strips 10' and in a case of the embodiment of my inventionillustrated in Figs. 4 to 6, strips 40, is not essential to the practice of my invention but merely an optional detail thereof. The portions of three elongated

columnar grains

67, 68 and 69, representative of the elongated columnar grains of the ingot which have formed by solidification of the melt upon the seed havetheir body-centered cubic space lattices arranged so that the crystallographic planes thereof are substantially parallel to the corresponding crystallographic planes in the oriented grains of the seed slab. This is h mat a ly. ndica ed in ig-17 y e large q aresflli;

f.- ansvers s ct on o sueh n ingot is takentalongz aplane indicatedby ine. 818, for example, and viewed in the direction of the arrows, it will be found that the elongated, columnar grains oftheingOt. as shown in Fig.

re o or euted hatsthei cry t la ti es are, substantially parallel and have unit cube faces. thereof arranged;

rolling such an ingot, the planar surfaces71, and 73,.fon

example, are. admirably adapted to being worked by rolling andthe high degree of parallel. grain orientationv between the. several as-cast grains constituting the grain: oriented ingot produces a; high degree ofthe desired pres ferretl orientation or; cube texture of the finished sheet; metal.

The apparatus illustrated in Figs. 5 and 6 may be: employed in thesamemanner as;disclosed for the appa-, ratus for-Fig. -v 2, and. 3 and theresulting ingot, except for the zone constituting the nnmelted portions of the seed-slab 38 is, structurally, indistinguishable from the ingot produced. by the apparatus of Figs. 2 and 3.

While certain specific embodiments of my invention have been particularly. set forth, it will be obvious to those skilled in.the artthat certain variations may. be. made thereon; For, example, the relationship between ingot mold 23 and seed-slab 20 could equally well be used with ingotmold 50, and slab 38, or the relationship between ingot mold 50'and slab 38 could equally well' be used withingot mold 23'and slab 2%. Additionally, the heat exchangers illustrated in Figs. 3 and 6 could be interchanged, withoutmaterially affecting the as-cast structure. of; the ingots produced or other functionally equivalent heatexchange means could-be substituted for those shown.

The final. annealed soft magnetic sheet metal which is fabricated by working ingots having the improved as-cast grain orientation manufactured according to my invention has a strong cube texture as previously described. This. grain orientation has been schematically indicated in Fig. 9 in which a portion of a larger body of sheet metal. having this orientation is shown as a strip having, for example, its shortest dimension A disposed transversely or about 90 to the rolling direction of the sheet, its thickness B corresponding to the thickness of-the sheet and its longest dimension C dis posed in parallel relationship to the rolling direction. The cube texture orientation of this material is schematically illustrated by cube 81 in which one pair off parallel cube faces-82 and 83 are substantially parallel to the plane of the sheet 80, another pair of parallel cube faces 84 and 85: are substantially perpendicular to the plane of the-sheet, or the rolling plane, and substantially parallel to the rolling direction, and the remaining pair of parallel cube-faces 86 and 87 are substantially perpendicular to the rolling direction at the plane of the sheet. It will be understood that the majority ofthe grains comprising this cube texture material will be Oriented so that their crystallographic crystal lattices will be comprised of atoms constituting cube face planes which are substantially parallel to correspondingcube. faces of cube-81, It is apparent that sheet material having this cube-texture orientation may be fabricated into seed-slabs similar tothose previously disclosed;

fabricated from singly oriented sheet material, if desired, in the practice of my invention. material is used, strips such as strip 89 may be cut from a cube texture sheet material as shown or obviously, may equally well be cut with the longest dimension C perpendicular or transverse to the rolling direction. Such strips may then be formed into a seed-slab by stacking them in a face-to-face relationship and securing them together to form a substantially rectangular prism one face of which has an area equal to C nB where n is equal to the number of strips. In view of the symmetry If such cube texture of the cube texture orientation with respect to the rolling direction and rolling plane of these strips the seedslab made in this manner may be arranged at the bottom of the rectangular or square mold so that the previously referenced seed-slab face is adapted to be contacted by molten metal in the casting operation with A dimension substantially parallel to the direction the heat extraction and the seed dimensions of the slab either parallel or perpendicular to one of the sidewall faces of the rectangular mold.

Alternatively, rectangular pieces of sheet metal each having substantially the dimensional and geometrical configuration of the bottom of the mold cavity may be cut from this material and stacked to form a seed-slab of which the upper surface comprises a single piece each piece having an edge out substantially parallel to the rolling direction which is adapted to be disposed parallel to one of the sidewall faces of the mold.

From the foregoing it may be seen and in every case I provide a grain-oriented seed-slab fabricated from grain-oriented body centered .cubic polycrystalline sheet material in which a majority of the grains have their crystal lattices particularly oriented with respect to each other so that such seed-slab may be arranged with a tubular mold so as to constitute the bottom thereof, the seed-slab presenting a substantially planar face to the mold cavity for contact with molten metal to be poured therein and means adapted to cause a major part of the heat of the molten metal to be extracted through the seed-slab in substantially a unidirectional manner, the grain orientation of the seed-slab being such that one cube face of the crystal lattices of a majority of the grains are substantially parallel to the face of the seed-slab exposed to contact with the molten metal and substantially perpendicular to the direction of the heat flow during the heat extraction. Further, the oriented grains of the seed-slab are additionally characterized by having all their corresponding cube faces arranged substantially parallel and at least one cube face in each such oriented grain substantially parallel or perpendicular to a substantially straight planar sidewall of the mold.

Other variations too numerous to catalogue would readily occur to those skilled in the art. Therefore, I do not intend my invention to belimited in any manner except as defined by the appended claims.

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

, 1. An ingot mold for casting body-centered cubic alloys consisting of not less than 92 percent iron, up to percent silicon, up to 5 percent molybdenum and up to 8 percent aluminum comprising, side walls defining a mold cavity, and bottom means mounted in cooperating relationship with said side walls to close said mold cavity and adapt it to receive and contain a mass of molten metal, said bottom means comprising a plurality of cubeon-edge grain oriented strips assembled in a manner that a majority of the unit cube faces of said strips are substantially commonly aligned and have two unit cube faces generally perpendicular to said mold side walls.

2. An ingot mold for casting body-centered cubic alloys consisting of not less than 92 percent iron, up to 5 percent silicon, up to 5 percent molybdenum and up to 8 percent aluminum comprising, side walls including at least one planar side wall defining a mold cavity, and bottom means mounted in cooperating relationship with said side walls to close said mold cavity and adapt it to receive and contain a mass of molten metal, said bottom means comprising a plurality of cube-on-edge grain oriented strips assembled ina manner that a majority of the unit cube faces of said strips, are substantially commonly aligned and have two unit cube faces generally perpendicular to said mold side walls and two unit cube faces generally parallel to said planar side wall.

3. A method for producing a grain oriented casting of a body-centered cubic alloy consisting of not less than 92 percent iron, up to 5 percent silicon, up to 5 percent molybdenum and up to 8 percent aluminum comprising, providing a seed slab made of a plurality of cube-on-edge grain oriented strips assembled in a manner that a maiority of the strips are substantially commonly aligned, positioning the seed slab in the bottom of an ingot mold in "a manner that two unit cube faces of the metal composing the seed slab are generally perpendicular to the side walls of the mold, bringing amass of molten metal of a composition'corresponding to that of the seed slab into contact with the seed slab causing the surface thereof to melt, and thereafter extracting substantially all the superheat and latent heat from the mass of molten metal unidirectionally through the seed slab.

4. The method as defined in claim 3 wherein the surface of the seed slab exposed to the molten metal is coated with a flux consisting essentially of from 60 to weight percent water and the remainder substantially all potassium silicate, said silica being present in the ratio of from 3.3 to 4.0 mols of SiO to 1 mol K 0.

5. In an ingot mold for obtaining grain oriented castings of body-centered cubic alloys consisting of not less than 92 percent iron, up to 5 percent silicon, up to 5 percent molybdenum and up to 8 percent aluminum, having a bottom and vertically extending side walls; a seed slab constituting the bottom of the mold, said seed slab comprising a plurality of cube-on-edge grain oriented strips assembled in'a manner that a majority of the unit cube faces of said :strips' are substantially commonly aligned and have two unit cube faces generally perpendicular to the side walls of the mold. a

6. A seed slab for use in the bottom of an ingot mold to obtain grain oriented castings of body-centered cubic alloys consisting of not less than 92 percent iron. up to 5 percent silicon, up to 5 percent molybdenum and up to 8 percent aluminum comprising a plurality of first and second cube-on-edge grain oriented strips assembled in 2. directly integrated manner such that a majority of the unitcube faces of said strips are substantially commonly aligned and have two unit cube faces generally perpendicular to the side walls of the mold, said individual first strips being interspersed between said second strips and said first strips being of greater width than said second strips whereby said first strips extend above said second strips when positioned in said mold.

References Cited in the file of this patent U NlTED STATES PATENTS 1,793,672 a Bridgman Feb. 24, 1931 l,961,399 Snook June 5, 1934 2,053,162 Pfolzgrafi' Sept. .1, 1936 2,807,846 Sterick et al Oct. 1, 1957 2,874,427 'Sterick Feb. 24, 1959 'FOREIGN PATENTS 610,440 Great Britain oct. 15, 1958

Claims

3. A METHOD FOR PRODUCING A GRAIN ORIENTED CASTING OF A BODY-CENTERED CUBIC ALLOY CONSISTING OF NOT LESS THAN 92 PERCENT IRON, UP TO 5 PERCENT SILICON, UP TO 5 PERCENT MOLYBDENUM AND UP TO 8 PERCENT ALUMINUM COMPRISING, PROVIDING A SEED SLAB MADE OF A PLURALITY OF CUBE-ON-EDGE GRAIN ORIENTED STRIPS ASSEMBLED IN A MANNER THAT A MAJORITY OF THE STRIPS ARE SUBSTIANTIALLY COMMONLY ALIGNED, POSITIONING THE SEED SLAB IN THE BOTTOM OF AN INGOT MOLD IN A MANNER THAT TWO UNIT FACES OF THE METAL COMPOSING THE SEED SLAB ARE GENERALLY PERPENDICULAR TO THE