US2540242A - Apparatus for casting metal strips - Google Patents

Description

Feb. 6, 1951 J. B. BRENNAN APPARATUS FOR CASTING METAL STRIPS Filed May 26, 1947 ATTORNEYS fabrication to article form, such as a press or brake.

4 Patented Feb. 6, 1,1951

UNlTED' s'r rss msasrus i -oi: cssrmo snirsnsm Joseph 1:. a iii-mum. Ohio Application May as, 1947, No. 150,441

is cum. zz-iss) This invention relates to apparatus for casting f apparatus also is adapted to practice the method metal in' strip form, especially to casting long,

thin strips of alloy metal particularly suited for a bearing, in

whereas the properties of the bearings are ordi-- narily improved if more lead is present. Now

only thick sections or billets of alloy metal can be cast, and they require a great deal of subsequent reduction or rolling which causes undesirable lead segregation. This is also true of other alloy strip wherein different melting point metals are incorporated in the same melt for casting. alloys ultimately to be processed to strip form.

The general object of this invention is to avoid and overcome the foregoing and other disadvantages of present apparatus for producing alloy strip and to provide novel alloy strip forming apparatus characterized by its rapid freezing of molten metal in strip form.

Another object of the invention is to reduce the segregation of the lower melting point metal inthe production of thin alloy metal strip.

Another object of the invention is to eliminate transfer of molten metal from a container therefor to a mold and to provide a metal mixing container also adapted to form part of a die.

A further object of the invention is to cast a metal alloy in strip form and tosolidify such alloy rapidly when the liquid alloy is cast or molded to the desired shape.

Another object of the invention is to provide a practical, positive, uncomplicated die for easting alloy metal in strip form without obJection-' able segregation of the components thereof.

Another object of the invention is to provide an apparatus for forming a thin metal strip consisting of two layers of different metals.

Other objects of the invention are to provide difierent width coiled metal strips for use in defining a die cavity, to provide a die for casting measured quantities of metal therein, and to provide means for maintaining a pressure on the metal as it is cast.

The foregoing and other objects and advantages of the invention will be made apparent as the specification proceeds.

Attention is directed to the accompanying drawing, wherein:

Fig. 1 is a vertical section through apparatus embodying the principles of the invention, which of the invention; and

Fig. 2 is a bottom plan on line 2-2 of Fig. 1. Referring more in detail to the drawing, a suitable container I0, usually metal, is shown as being mounted on a base I I and provided for use 'in preparing liquid metal alloys to be processed in accordance with the principles of my invention. The container III has heating means ordinarily associated with it, in this instance, a helically positioned conduit I2 is formed in its base and connects to a suitable supply of heating fluid. In all events, the container l0 has an annular chamber l3 and is adapted to receive material therein and to heatsuch material to render or retain it fluid.

As a salient feature of my invention, Iam able to use the container'lll as one half of a forming die and avoid transfer of molten metal from the container to a separate die or mold for solidification. Avoiding such metal transfer obviously avoids the metal flow and delay, with consequent metal segregation, as occurs with prior casting procedure. To achieve this. result, I provide a novel mold or die section generally indicated at I which includes a die holder I5 that has an annular flange i6 extending therefrom designed so as to engage snugly with the chamber l3 of the container It to deflne therewith a die cavity. The die holder, II is positioned by conventional means (not shown) for movement to and from engagement with the container I'll. In order to form a long thin metal strip in the die, a helical cavity I1 is provided therein.- This cavity i1 is formed by means of tightly coiling together'a relatively wide metal strip. l8 and a relatively narow metal strip is with the upper (as shown) edges of the strips being aligned. The strips l8 and I9 are tightly wound on an arbor 2" in the position shown in Fig. 1, being retained in such shape by a band placed therearound or by in- 'sertion into the die holderl5. The strips l8 and I! may be secured in the die holder in any desired manner even to being retained therein by magnetic means, or by mechanical means, or combinations thereof. In all events, the coiled strips l8 and I9 tightly fill the die holder bethat it is exactly sufficient to flll the cavity I1.

Thus, when the last metal, such as lead, is mixed with the metal in the chamber I: to produce a homogeneous alloy, the die holder is is rapidly brought down into engagement with the container I. and all of the metal in the chamber I3 is forced into the helical cavity l1. As soon as the die holder II is seated in the chamber It, the heating medium flowing through the conduit i2 is shut oil, if it has not previously been shut off, and cooling fluid is sprayed on the associated die holder and container by nozzles 2| which are connected to a conventional supply of a cooling medium. The foregoing procedure effects a rapid chilling action on the material in the mold cavity, which action maybe accelerated, if desired by flowing a coolant through the conduit II, or by forming cooling fins on the die holder and container, or by use of other cooling means. Hence segregation of the low melting metal of the alloy is avoided since the molten metal in the chamber I3 is stirred continuously until the die holder I5 is engaged therewith. Conventional vents (not shown) are formed for the mold cavity and they may comprise tiny grooves (not shown) in the narrow band I8 extending transversely thereof. The vent grooves in the band is should connect to other vents 23 which may be formed in the die holder l5 for leading any entrapped gases to the atmosphere. solidified alloy in the cavity I1 is ejected by knock out pins 22 slidably carried by the die holder for unitary action. Such pins 22 may eject the solidified metal and the strips l8 and I9 as a unit to be separated thereafter in any desired manner, or the pins 22 may pass through holes in the narrow strip I9 andeject only the solidified helical cell. In the latter case, it would be preferable to have the strips II and I9 integrally connected and suitably secured in the die holder. Usually the strips l8 and I! are not integrally bonded or fixed in position.

The helical cavity I! may be. for example, 2

inches deep, 1; inch wide (radially) and 500 or more feet in length when the die holder is about 36 inches in diameter. Practice of the invention has produced copper-lead alloys with uniform lead distribution, when up to 20% lead has been present, with no lead particle larger than .010".

The helical alloy strip produced can be finished in any desired manner, such as by cleaning, mechanically rolling, heat treating, etc., although it may be used in some instances without any further shaping or forming thereof.

Adhesion between the cast material and the strips l8 and I9 is avoided by coating them with a suitable lubricant, such as lampblack, powdered mica, graphite, or plumbago prior to each casting cycle. The extreme casting speedreduces the erosion of the apparatus to a minimum.

Pressurized strip casting can be achieved by my invention, if desired, so as to produce a line grain structure and increased tensile strength. For example, the cast metal can be subjected to any desired pressure as it is being cast if the material to be fabricated into bearings.

The container 10 can be made of any material adapted to stand the high temperatures to which the apparatus is subjected. A material known as Inconel or Inconelex, which is a high chromium nickel ferrous alloy, has been used to form the wide strip IS with excellent results. For bearing alloys, the strips, it and is can be made of ordinary cold rolled strip steel while any metal material of higher melting point than the cast material can be used, as a general rule. The narrow strips is can be made from heat resistant non-metallic material, such as asbestos, or fiberglass, or combinations thereof. The strips i8 and I! can be of the same thickness if desired, or of any desired thickness relation.

It is desirable. of course, to maintain an accurately controlled temperature, usually only a few degrees above the melting point of the material, on the metal in the chamber to facilitate the rapid solidification thereof. Usually the metal in the chamber is agitated in any conventional manner to becertain that the mixture isuniform in composition and temperature until is of minimum length as the metal is displaced from a normal level position in the chamber to a helical position in the die holder. This substantially equal casting flow results in an extremely uniform grain in the cast metal which has good characteristics and is free from segregation of non-alloying constituents.

In some instances, vacuum or suction creating means may be associated with the apparatus embodying the invention to facilitate and assist in the casting action and to aid in-filling the cavity. Such vacuum on the casting cavity may be established by connection of a vacuum generator to the vents 23 formed in the die holder i5.

In some instances, it may be desirable to use a briquet of carbon or other heat resisting material in place of the arbor 20 as a core for the helical strips [8 and is. As the coiled strips' l8 and I9 will spring out to the largest diameter possible and thus leave the center of the coiled strips void of. material, the core for the strips i8 and i9 could be positioned in the container Such a iii to extend up into the chamber i3. core for the strips I8 and l9.could even originally be formed on or integral withthe container Hi to position the molten metal in the chamber iii in annular form prior to engagement of the die holder and the container.

The principles of the invention can be used to coat a metal strip on one side with a different metal. This action may be achieved by substituting two superimposed metal strips for the wider strip i8. Thu one surface of each strip would be exposed to the molten metal entering the die cavity. The surfaces of -the double thickness metal strip it, which are to bond to the cast metal, should be precleaned- A molten salt bath, for example potassium cyanate, is suitable for this cleaning action. Other preparatory steps, such as pretinning, or electroplating with copper or electroflashing with nickel facilitates bonding copper or silver bearing metals to steel strips in accordance with the invention.

The invention can be used in casting various metallic strips including alloys .of aluminum, tin, copper, or lead. However, any metal or thermoplastic material can be processed in accordance with the invention when one desires to produce a helical article.

The drawing shows electro-conductive coils l0 and 3| associated with the outer surfaces of the that an improved metal strip can be providedby the invention.

One complete embodiment of the invention has i been illustrated and described in detail herein. but it will be understood that the invention is not limited to the specific example set forth since modification may be resorted to within the scope of the appended claims.

I claim:

1. A casting mold, or die comprising two interwound helices of heat-resisting strip material of diiferent widths, having one edge of each strip in the same plane, the other edge of one strip protruding appreciably from the corresponding edge of the second strip to define a helical mold cavity therebetween, said strips being separable to facilitate removal of a casting therefrom.

2. In a casting mold or die, a cavity forming device consisting of two interwound'helices of thin wide strips of heat resisting material with one edge of each of the helices being exposed to a die chamber, one of said strips of material being wider than the other, said exposed edges being spaced axially of the mold from each other to expose a portion of one helix and define a helical cavity between adjacent surfaces thereof for forming a thin wide strip therein.

3. An article as in claim 2 wherein said strips are separate and said strip that is partially exposed is thinner than the other strip which determines the thickness of the die cavity.

4. In a matrix for forming thin-strip metal in long lengths, the combination of a matrixbody different widths in edge alignment wound into a spiral, one edge only of each tape comprising said spiral being in the same plane, opposite edges of each tape being in substantially different planes, both faces of the narrower tape being in facial contact with only a portion of the faces of the wider tape, the remaining portions of the faces of the wider tape defining a hollow helical groove in conjunction with the unaligned. edge of the narin the same plane as the other edge of the wider tape.

6. In a matrix for forming thin strip metal, a pair of thin flexible heat resistant tapes one of which is about several inches wider than the other, said narrower tape being approximately in. thick and with said wider tape being thinner than the other said tape, said tapes being helicomprising two thin metal tapes of substantially cally positioned in a unit in abutting face to face relationship to each other, said tapes being positioned with'one lateral section and edge of said wider tape protruding from said unit and defining a narrow relatively deep mold cavity therebetween,said strips being separable after a molding actionto facilitate removal of a cast strip therefrom.

7. In a matrix for forming thin strip metal, a pair'of thin flexible heat resistant tapes one of which is appreciably wider than the other, said narrower tapebeing thicker than the other said tape, each of said tapes being positioned in a plurality of helical convolutions with the convolutions of each tape forming alternate laminae in a unit in abutting face to face relation to each other, said tapes being positioned with one lateral section and edge of said wider tape protruding from said unit and defining a narrow relatively deep mold cavity therebetween, said strips being separable after a molding actionto facilitate removal of a cast strip therefrom.

8. In a matrix for forming thin strip metal, a pair of thin flexible metal tapes one of which is appreciably wider than the other, each of said tapes being positioned in a plurality of helical convolutions with the convolutions of each tape forming alternate laminae in a unit in abutting face to face relation to each other, said tapes being positioned with one lateral section and edge of said wider tape protruding from said unit and defining a narrow relatively deep mold cavity therebetween, said strips being separable after a molding action to facilitate removal of a cast strip therefrom.

9. In a matrix for forming thin strip metal, a pair of thin relatively wide flexible heat resistant tapes, said tapes being of different widths, said tapes being superimposed and being helically positioned in a unit in abutting face to face relationship to each other, said tapes being positioned with one lateral section and edge of one said tape protruding from said unit and defining a narrow relatively deep mold cavity therebetween.

10. A matrix as in claim 7 wherein said unit is positioned with'its longitudinal axis extending substantially vertically and with said cavity being open from the lower surface of the matrix, and vent means in said unit and communicating with the upper portion of said cavity.

JOSEPH B. BRENNAN.

nnrannncas CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Martin July 23, 1946

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