US2244367A - Making composite metal articles - Google Patents

Description

June 3, 1941. R. E. KINKEAD MAKING COMPOSITE METAL ARTICLES 3 Sheets-Sheet 1 Filed June 10, 1959 g g E 2 I INVENTIOIIQI.

BY @411! g/rl/Gl ids ATTORNEYS.

June 3, 1941. R. E. KINKEAD MAKING COMPOSITE? METAL ARTICLES Filed June 10, 1939 3 Sheets-Sheet 2 INVENTOR. '4 19 @4244 3 41,} 11544.4

QM, 4.2244,, M ds ATTORNEYS.

June 3, 1941.

R. E. KINKEAD v MAKING COMPOSITE METAL ARTICLES Filed Jgne 10, 1939 3 Sheets-Sheet 3 5 m i My INVENTOR. 9%! di /m4: 4, Qua, 026;!

' ATTORNEYS.

Patented June 3, 1941 FFICE MAKING COMPOSITE METAL narrows Robert Emerson Kinkead, Cleveland, Ohio Application June 10, 1939, Serial No. 278 ,517

'7 Claims. (01. 22-201) This invention relates to composite metallic articles, and particularly composite ingots, comprising at least two dissimilar metals or alloys.

Composite metallic articles are desirable for various reasons, as to provide articles embodying the properties of different metals or alloys, or to provide in simplerand inexpensive fashion the properties of a relatively expensive metal or one that is difiicult to fabricate. All of the procedures proposed for such a purpose have been open to more or less serious disadvantages. For instance, although in some instances two metals can be welded by rolling them together in the form of plates or slabs, many metals can not be welded in that Way. Thus, it has been found to be practically impossible to completely weld the chromium irons and steels or austenitic Cr-Ni alloys to plain carbon steels in that manner. However, the more noble metals such, for example, as the chromium irons and steels, are particularly desirable for many purposes but because of their large content of alloying elements and because of fabricating difliculties articles consisting of them are quite expensive. It would be desirable, accordingly, to provide articles composed of a body of relatively cheap metal, such as mild steel, faced with a relatively thin layer of such a more noble metal.

Probably the main reason why metals such' as the chromium iron alloys can not be welded satisfactorily by simple rolling of plates of them in contact with plates of plain carbon steel is that oxidation of the surfaces during heating or rolling prevents welding. For that reason it has been proposed to cast one metal, say mild steel, about preformed inserts of the other metal, say stainless steel. Such procedures are ineffective unless the insert is carefully cleaned and is completely enclosed by cast metal because, a weld is not produced in such a casting and in the subsequent working operations oxidation occurs if the insert is exposed at its ends or sides. Also, in the preferred practice two insert plates are used which are separated by a weld-preventing material, but according to some proposals the two plates must be welded around their edges. All such procedures are therefore tedious and involve considerable labor costs in cleaning and otherwise preparing the inserts and in arranging them in molds to be wholly surrounded by cast metal.

It has been proposed also to make such articles by direct casting operations. They can not be made by casting the two metals freely into molds because the extensive or complete intermixing which inevitably occurs destroys the essential character of both metals.

For this reason it has been proposed to cast one of the two metals in a mold, permit it is solidify, and then cast the other metal against it. This procedure has not achievedcommercial success because'it does notproduce a satisfactory weld between the two metals. Again, it has been proposed to cast the metals on opposite sides of a partition member which is withdrawn progressively as the metals are cast or directly after they have been cast. Such procedures likewise haye-proigad to be incapable of producing the desired composite article consisting, essentially, of two integrally welded distinct bodies, because the identity of the two metals is more or less destroyed through turbulent intermixing or diffusion. 6

It is among the objects of this invention to provide a simple and easily practiced method of making composite metallic articles composed of dissimilar metals,- which involves direct casting of the metals, avoids or reduces the difliculties and disadvantages of prior art procedures, and is applicable generally to such ends.

A further object is to provide composite articles that are satisfactorily welded as cast, and may be used as castings or rolled or wrought otherwise to other shapes.

- Other objects will description.

The invention will be described with reference to the accompanying drawings in which Fig. 1 is a vertical sectional view through a mold prepared for casting in accordance with one embodiment of the invention, taken on line 1-1 of .Fig. 2; Fig. 2 is a plan view of the mold shown in Fig. 1, the flask being omitted for clarity; Fig. 3 a view similar to Fig. 1 showing the condition within the mold just prior to withdrawal of the partition member; Fig. 4 a view similar to Fig. 3 showing the condition within the mold immediately after withdrawal of thepartition member; Fig. 5 a vertical sectional view through the solidified ingot produced in accordance with the practice of the invention and taken generally in the plane of Fig. 1; Figs. 6 and '7 views similar to Fig. 2 showing other embodiments of partition members; Fig. 8 a detail of the lower portion of a partition member in accordance with the preferred embodiment of the invention; Fig. 9 a vertical sectional view through a mold during the process of casting in accordance with another emappear from the following bodiment of the invention, taken on line IX-IK,

Fig. 9: and Fig. 11 a view similar Fig. 2 of another'modiflcation. In accordance with this invention composite castings are made from dissimilar metals by casting them into a mold on opposite sides of a partition having refractory surfaces exposed to the metals, permitting the metals to solidify to a definite extent defined hereinafter, and then withdrawing the partition member.

The invention is predicated largely upon my discovery that the disadvantages of prior casting procedures of this type are overcome by retaining the partition separating the metals until at least one of them has solidified to an extent such that turbulent mixing of the metals is avoided when the partition member is withdrawn,

and then withdrawing the partition before both metals have solidified completely.

Most suitably, however, the partition is withdrawn before either metal has solidified completely. Thus one of the metals, usually that which constitutes the minor section of the casting where, as is usual in composite articles, there are major and minor sections, is permitted or caused to solidify to an extent such that it has become highly viscous, or mushy, and is about to freeze completely, in the vicinity of the partition member. At that moment and before complete solidification in that region has occurred, the partition member is withdrawn to permit the two metals to come into contact with one another. The casting is then allowed or caused to solidify completely.

In this manner the two metals become mixed with one another in the plane of the partition member before either has frozen completely and thus while they are in condition to form a perfect and satisfactory weld with one another. However, turbulent mixing of the two, metals is avoided in the practice of the invention, the mixing being confined to the region of the partition because one of the metals has solidified almost to it before they are permitted to come into contact. Hence the resultant casting consists essentially of two distinct bodies of the dissimilar metals which are thoroughly welded by intermixing or diffusion in an intermediate relatively narrow region extending lengthwise of the casting.

The castings produced in this manner may be used in that form if desired, as in the caseof rolls or a large variety of other articles, or it may take the form of an ingot to be worked to produce articles of desired shape.

The invention thus provides a method of making composite metallic articles from dissimilar metals and alloys, and it is of general applicability thereto although it is particularly adapted to the manufacture of composite ferrous metal articles. The metals may comprise, for example, low and high carbon steels, but it is especially advantageous for the production of articles comprising a major portion, or body, of relatively cheap steel, such as mild steel, and a minor portion, or facing, of relatively expensive ferrous metal, such as any of the chromium irons and steels which have been diflicultly applicable in the manufacture of articles of this type.

The partitions used in the practice of the invention are, of course, to be refractory with respect to the cast metals. They may consist, for example, of refractory ceramic material which is not attacked by the molten metals. Necessarily the partitions must be strong, particularly to be withdrawn at the proper time, and to avoid the yet danger which may attend disintegration or breaking of ceramic partitions it is preferred to use metallic partition members provided with surfaces which are refractory with respect to the cast metals. For example, sheet iron or steel may be coated with graphite, silica, or other materiab which effectively provide the partition Dunbawith refractory surfaces. :0- what has been said it will be realized avoidance of premature or delayed withdrawal of the partition. Under carefully controlled casting conditions it may be feasible to apply time schedules for that purpose. However, in most instances the variables are such that the time elapsed after pouring is not a suitable guide by which to determine when to remove the partition. Thus, the solidification rate will depend on a number of factors such as the temperature of the metals when poured, the temperature of the mold, the mass of the mold and of the casting, the section of the mold and its wall thickness, the ambient temperature, and the rate of air movement around the molds, and variation of any one or more of these factors may cause considerablevariation in the freezing rate. I have found, however, that the proper time for removal of the partition can be determined readily by probing the metals, or one of them, as with a wood rod of small diameter.

Having reference now to the drawings, Fig. 1 shows a mold prepared for the bottom casting of an ingot in accordance with the invention. It comprises a tubular mold member i of rectangular section resting upon sand 2 rammed in a flask t which rests upon a base member 4. Mounted within the mold is a partition member 5 which divides the mold into chambers 8 and 1 which are fed respectively by gates I and 9 formed in the flask to receive risers, not shown;

The mold shown in Figs. 1 and 2 is adapted to the making of an ingot from which to roll articles comprising a body of relatively cheap metal faced with more noble or with relatively expensive metal, say mild steel faced with stable surface chromium steel. For economy the facing is generally as thin as possible, and accordingly chamber 8, which is to receive the cheaper metal,

, e. g., mild steel, occupies the major portion of the mold opening, while chamber 1 is of relatively small size and receives the facing metal, e. g., chromium steel. As an example, but not by way of limitation, with a mold having an 18 x 18 inch opening, partition I might be spaced 3 inches from the right-hand wall ofthe mold as seen in Figs. 1 and 2.

The partitions are prepared by carefullyfreeing their surfaces from dirt, scale and the like, and then applying a graphite or the like wash to provide a thin refractory surface coating 50. In the drawings this coating is shown of exaggerated thickness for clarity of illustration. The partition is then positioned in the mold. In the preferred practice of the invention the partition member is so mounted within the mold as to permit it to expand transversely of the mold to avoid undue buckling during casting. In the embodiment shown in Figs. '1 and 2 the mold is recessed as indicated at I 0, Fig. 2, to provide chambers for receiving sand. Partition 5 is supported in the mold and sand H is then rammed into the chambers, care being taken to maintaining the proper positioning of the partition member. The sand is then baked, as by playing a flame over it, after which it may be given a graphite an important feature of the invention is wash, and after being'dried out and preheated the mold is ready for casting. As seen from Fig. 2, partition is of such width that it extends only partway through the sand cores ll so that it may expand transversely of the mold during casting to avoid buckling. Also, this mounting of the edges of the diaphragm in sand permits its ready removal from the mold at the proper time and prevents its being frozen into the metal as it solidifies from the faces of the mold inwardly. For the latter reason the use of cores II within the mold itself is, desirable to retard the differential rate of cooling around these two corners of the mold.

The mold being prepared as shown in Figs. 1 and 2, the two metals are then poured through gates 8 and 9, as by pouring mild steel 12 (Fig. 3) into chamber 6 and stainless steel I3 (Fig. 3) into chamber '1. Most'suitably the two metals are poured simultaneously and at rates such as to maintain them at the same level on opposite sides of the partition. If the pourin rates are such that one of the metals becomes higher than the other, the partition member may be stressed and distorted. Of course, gates 8 and! must be of such length and the risers so disposed as to permit the two ladles to be brought up to the mold and poured at the same time.

After the mold has been filled with metals l2 and i3 solidification is permitted or caused to ensue. If the partition were withdrawn at once the two metals, being completely liquid, or substantially so, would become thoroughly intermixed. In the practice of the invention at least one of the metals, generally that occupying the lesser portion of the mold, 13 in the embodiment being described, is permitted to solidify to an extent such that when the partition is withdrawn mold at the proper time.

Although the invention is not restricted to the use ofpartition members of any specific thickness, I have found that for'many purposes they should be as thin as consistent with avoidance of destruction by the cast metal. Satisfactory results have been had with molds of the size stated. above with iron sheet about inch thick, although the partition members may in some instances be of inch sheet metal.

Inasmuch as the partition member may tend to be solidified at its lower end while the casting is solidifying to theproper point, it is preferred to provide it with a line of weakness adjacent its lower end so that if it does tend to stick it will break along the line of weakness when it is to be the two metals will become diffused in a narrowly restricted zone, i. e., only in the zone of the partition member. Most suitably it is Permitted or caused to freeze in such manner that the metal against and immediately adjacent the partition 'has become viscous, or mushy, and is about to solidify completely. At this time the partition is withdrawn to permit mixing of molten metal from the opposite side with the residual liquid or viscous metal.

The condition of the metal within the mold at the time when the partition is withdrawn is indicatedin Fig. 3, which shows the greater portion 33a of metal i3 completely frozen with a small amount l3b, in contact with the partition memher, just about to freeze. On the other side of the partition a portion iZa of metal I! has solidified but the major portion iZb is yet liquid. In accordance with the invention the partition memher is withdrawn at this time, before portion l3b freezes completely, to permit intermixing of liquid metal 92b with residue i3b at the region previously occupied by the partition member. Inasmuch as the metals freeze inwardly from gthe walls and upwardly and downwardly from, respectively, the bottom and top, this condition can be determined readily by probing as described above.

The condition of the ingot at the moment after removal of partition 5 is indicated schematically in Fig. 4, which shows a narrow band it extending lengthwise and crosswise of the ingot which consists of a mixture'of liquid metal portion l2b and residue 13b. Upon solidification this will form a perfect weld between the two metals which, as shown in Fig. 5, solidify to form a major portion I20 and a minor portion liic each withdrawn. In the use of sheet metal members this may be accomplished by providing notches I6, Fig. 8, extending into the partition member from opposite sides adjacent its lower end. To prevent the metal from washing through the partition member at the notched region'during casting, the notches may be filled with cement H or other suitable refractory material. Should the partition member become frozen at the bottom it will break in the line of notches l6 when pulled upwardly by the crane, thus leaving the lower portion I8 embedded in the metal. This is not objectionable, however, because this will normally be in a croppage region.

The invention is not restricted to the use of rectangular section molds, to partitions extending across the mold, as shown in Figs. 1 to 3, or to their being mounted in the sand cores ll. As

. shown in Figs. 6 and 7, the partition member may comprise an I-section l9 or a simple sheet 20 extending across the mold but supported wholly within its normal opening. These partition members are of less-width than the mold, say inch, to permit their expansion within the mold during casting. To maintain them in place and to permit their ready withdrawal it is preferred to arrange them in the mold and then ram sand 2! around their ends as shown in Figs. 6 and 7,

say to a thickness of about inch. The sand is then baked to prepare the mold for casting.

Similarly, the invention is not restricted to bottom casting. Figs. 9 and 10 show it applied to top pouring as Well as to the production of forms other than that described hereinabove, namely, to

the production of ingots for the manufactureof seamless tubing. In this embodiment mold la is provided with a partition 5a in the form of a metallic tube having its surfaces provided with a refractory coating 50a. The relatively cheap metal 22 is poured inside of the tubular partition, while the relatively expensive surfacing metal 23 is poured around the outside of the partition member. The practice in connection with this and other possible embodiments of the invention is as described above, namely, pouring the two metals at rates such that their levels are substantially the same on opposite sides of,-the partie tion member, permitting at least one of the metals to solidify to an extent such that the two metals will be mixed only in a narrow zone corresponding to the region occupied by the partition, and then withdrawing the partition and then permitting solidification to be completed.

Various other modifications from the embodi- 5 ments shown and described are, of course, permissible. For example, the invention is not restricted to making composite articles from only two metals, or of only two layers, but, is applicable, for example, to making articles comprising 19 a body of one metal faced on opposite sides with layers of another or of two other metals. Also, it will be understood that in some instances the partition may be removed when both metals are solidified to an extent such that each is liquid,

or not fully solid, only in the region of the partition.

As indicated above, welding may be efiected by permitting one metal to solidify as long as the other is yet liquid at the partition when it is 20 Likewise, the invention is not restricted to the molds shown in the drawings but rather is applicable to any mold satisfactory to the end in view. Fig. 11 shows the application of the invention to, for example, split molds, and shows also a modification desirable in the production of quite thin layers of one metal. The mold lb consists of two halves 25 held together in any suitable way, as by clamps 26. It is prepared for the practice of the invention by mounting a partition memher 2'! as described hereinabove to separate the mold opening into two chambers to receive a body metal and a facing metal. Suitably the ends of the partition are mounted in sand cores 2'8 formed in recesses in the mold, as shown.

Where the partition is mounted close to one wall, as in Fig. 11, to form a quite thin layer of one metal, there may be a tendency for that metal to wash the refractory surface from the partition during pouring, with likelihood of welding of the metal to the partition or of cutting through it. This may be avoided by forming a recess 29 longitudinally of the mold on that side of the partition, and by pouring the metal into the recess. Thus, whether top or bottom poured,

the axis of pouring may suitably be as indicated at X in recess 29. Recess 29 may be provided with a refractory liner 30. Of course, the other metal is also poured at a point well removed from the partition, as at X in chamber Ii.

'The'term "metal as used in the specification and claims includes, of course, both pure, or commercially pure, metals, and also metallic alloys. The invention is not restricted to ferrous alloys. For example, ferrous alloys may be provided with layers or coatings of copper, nickel and other non-ferrous metals and their alloys, as well as to other metallic composite articles.

According to the provisioiis of the patent statutes, I have explained the principle and method of practicing my invention and have illustrated and described what I now consider'to represent its best embodiment. However, I'desire to have it understood that, within the scope of the appended claimsythe invention may be practiced otherwise than as specifically illustrated and described.

Iclaim: -1. That method of making a composite casting from dissimilar metals which comprises pouring said metals into a mold on opposite sides of a partition having refractory surfaces, cilfecting partial solidification of said metals in said mold, and withdrawing said partition before either-metal has solidified completely but after solidificationofatleastonehasprosressedto an extent such as to avoid turbulent mixing of the metals and thereby effecting welding'of said metals into a composite structure by inter-mixing of the two metals along a relatively narrow zone lengthwise of the casting.

2. That method of making a composite casting from dissimilar metals comprising a major, or body, portion of relatively cheap metal and a minor, or facing, portion of relatively expensive metal, which comprises pouring said metals into a mold on opposite sides of a partition having refractory surfaces and dividing it into said por-' tions, effecting partial solidification of said metals, and withdrawing said partition before either metal has solidified completely but after solidification of said minor portion has progreased to an extent such as to avoid turbulent mixing of the metals and thereby electing welding of said metals into a compositestructure by intermixing of the two metals along a relatively narrow none lengthwise-of the casting.

3. A process according to claim 2, said cheap metal being mild steel, and said expensive metal being stable surface chromium ferrous base alloy.

4. That method of making a composite casting from dissimilar metals which comprises pouring said metals into a mold on opposite sides of a partition having refractory surfaces and at a rate such that the level of the metals is substantially the same on opposite sides of the partition, effecting partial solidification of said metals in said mold, and then withdrawing said partition before either metal has solidified completely but after solidification has progressed to an extent such as to avoid turbulent mixing of the metals and thereby eil'ecting welding of said metals into a composite structure by intermixing of the two metals along a relatively narrow zone lengthwise of the casting.

5. That method of making a composite casting from dissimilar metals which comprises pouring said metals into a mold on opposite sides of a partition having refractory surfaces and free to expand transversely of the mold while maintaining the level of the metals substantially the same, causing said metals to partially solidify in said mold, then withdrawing said partition before either metal has solidified completely but when at least one of them has become highly viscous, or mushy, and is about to solidify completely in the vicinity of said partition, and thereby effecting intermixing of said metals along a relatively narrow band extending lengthwise of,the casting, and then completing solidification of said metals. g

6. That method of making a composite casting from dissimilar metals which comprises providing a mold with a removably positioned transverse partition member having refractory surfaces for contact with said metals, having its vertical edges covered with granular refractory and free to expand transversely of the mold, and having a line of weakness adjacent its bottom end, pouring said metals into said mold, effecting partial solidification of said metals in said mold, then withdrawing said partition before either metal has solidified completely but after solidification of at least one of said metals has progressed to an extent such that it is highly viscous, or mushy, and is about to solidify completely in the vicinity of said partition, and thereby efiecting intermixing of said metals along a relatively narrow band extending lengthwise of the casting, and then completing solidification of said metals.

'7. That method of making a composite casting of a major, or body, portion of plain carbon steel and a minor, or facing, portion of chromium ferrous base alloy, which comprises providing a mold with a removably positioned transverse partition member separating the mold into said portions, said member having refractorysurtaces for contact with said metals and being free to expand transversely of the mold, pouring said metals into said mold at rates such that their levels are substantially the same, effecting partial solidification of said metals in said mold, withdrawing said partition before either metal has solidified completely but after solidification of said chromium alloy has progressed to an extent such as to avoid turbulent mixing of the metals, and completing solidification and thereby efl'ecting'welding 0! said metals into a composite structure by intermixing of the two metals along a relatively narrow zone lengthwise of the casting.

ROBERT EMERSON KINKEAD.

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