US2203679A - Method of and apparatus for making bimetallic strip - Google Patents

Description

June 11., 1940. EDWARDS 2,203,679

METHOD OF AND APPARATUS FOR MAKING BIME'IALLIC STRIP Filed Dc. 16, 1938 2 Sheets-Sheet 1 III I M /24 I2 9 3i 1, a V -a lu 'H l n M. 2

| 1 Fl 6 s 6 F INVENTOR. GEORGE EDWARDS @4 BY ATTORNE June 11., 1940. G. EDWARDS A 2,203,679

METHOD OF AND APPARATUS FOR MAKING BIMETALLIC STRIP Filed Dec. 1.6, 1938 2 Sheets-Sheet 2 '1 Ill/11111,

INVENTOR. GEORGE EDWARDS ATTORNEYJ,

Patented June 11, 1910' METHOD OF AND APPARATUS FOR MAKING BIMETALLIC STRIP George Edwards, Cleveland, Ohio, assignor to The Cleveland Graphite Bronze Company,

Cleveland, Ohio, a corporation of Ohio Application December 16,1938, Serial No. 246,127 6 Claims. (Cl. 22-57.2)

' This invention relates, as indicated, to methods of and apparatus for making bimetallic or composite strip, but has reference more particularly to methods and apparatus for the application of one metal in molten condition onto a strip strip, while it may be of any width desired, may 5 of a second metal of higher melting point. The be taken, for illustration, at 5 inches. It is deinvention is particularly directed to the problem signed to put a coating of plastic bronze onto of applying metal such as a copper alloy having the steel which, when finished, will be .020, .030 a high melting point to steel strips of such widths or .050 in thickness. To secure this thickness of m as three and one-half inches and greater, while material on the finished strip it is necessary 10 controlling the thickness of the coating alloy, atu y to produce an initial thicknes te securing a true and uniform bond or weld bethan the finished thickness. The maximum tween the two metals, and preventing undue conthickness may be Set at which, When tamination of the molten metal from remaining chined down, will be .060.

1. in contact with other metals during the opera- The ppli i n o a c a f this hickness tion, I requires the pouring of onlyabout 10 pounds of The problem which we have solved by the presmetal per minute, which is approximately one ent invention is obviously far removed from that ce f molten metal De inch of length of e of applying a thin coating of such low melting st p o which it s po The p o l m Which point metals as tin, zinc, or alloys of the same th s s ua p e ts i t t o p u a e 20 to rods, wires and strips, since in such operations t eme y s al S e f metal which W011ld pwhich have been commercially practical for some esen e Ounce of metal p inch of length years the molten metal can either be confined by 0f the p. a Causing s molten metal to a chamber on the strip, or the strip, rod or the spread laterally the full Width of the strip in the like can be drawn through a bath of the molten t me interval during which each portion of the 25 metal. strip is beneath the stream of poured metal. The

The nature of the problem and the manner in p l m is greatly mp i y the v ry which the control of the aforesaid factors and d s of V sc y of the metal which'are in conditions is best exercised will probably be best turn affected by many different conditions in the understood by a description thereof with referapparatus. 30

, ence to actual working conditions, as illustrated, This problem has been solved in the present for example, in the accompanying drawing method by pouring the necessarily small stream 7 wherein: of molten metal onto the strip from a height very Fig. 1 is a longitudinal cross-sectional viewof t y above the s ce of e s ip so that the pouring box showing the strip moving there will be no spattering of metal, causing a 5 through the box and having molten bronze or D 01 metal to form on the strip Which s sufbrass applied to the upper surface thereof; ficient depth, that is, head, to cause the metal Fig. 2 is a plan view of the pouring box, with to flow transversely of the strip to the edges the cover removed; thereof in order to completely coat the strip Fig, 3 is a cross-sectional view, taken on the and the Same time move the strip lengthline 3-3 of Fig. 1; wise under the poured stream to remove Fig. 4 is a cross-sectional view, taken on th each increment of the strip from beneath the line 4-4 of Fig. 1; stream with a coating of metal. In effect, the Fig, 5 is a, cross-sectional view of apparatus process consists of establishing a pool of molten which may be employed for tilting the pouring metal on the strip of suflicient height to insure 45 box; j spreading of the metal laterally across the strip Fig 6 is an elevation f the base and carriage and maintaining this pool at the predetermined of the tilting apparatus; height or head by adding molten metal approxi- Fig. 7 is a fragmentary cross-sectional View, mately as rapidly to the pool as such metal is taken on the line of Fig and removed from the pool by the forward movement 50 Fig. 8 is a fragmentary cross-sectional view, of the Striptaken on t line H of 1 6 It is possible, however, with very narrow strips In order t explain clearly th nature of th or with heavy streams of molten metal to secure present, invention and the dificulties which are spreading of the metal all the way across the 55 overcome by theme of the present method, it

should be stated that a normal operation in which plastic bronze, for example, is poured onto the steel strip involves the movement of the strip at the rate of, say, 15 feet per minute. The

strip without the formation of any substantial pool. For example, a strip-1" in width can .be coated from the stream without forming any substantial pool, as the metal will spread and flow over such a narrow width even when not under the influence of any substantial head in the form of a pool. It has been found that a pool is, however, necessary where the width of the strip is approximately twenty or more times the thickness of the coating applied to the molten strip, 'even in cases of narrow strips the application is improved by following the above formula.

Referring more particularly to Figs. 1 to 4 inclusive of the drawings, it will be seen that the pouring box comprises a center guide shoe or base plate I having laterally spaced ribs or flanges 2 onthe upper surface thereof. Mounted on the base plate i is the pouring box proper which comprises a casting having side walls I connected at one end by a back wall I, and at the other end by a front wall or bridgin piece 5. The side walls 3 are provided on their lower surfaces with ribs or flanges 6, which are spaced inwardlyfrom the ribs 2 to provide spaces for a purpose to be presently disclosed. The back wall 3 is transversely curved on its lower surface as at I, and is beveled as at 8, immediately in advance of said curved surface.

Mounted'on the side walls 3 of the pouring box is a pan 9, having a transversely curved bottom III which slopes rearwardly and downwardly when considered with reference to the direction of movement of the strip. This is further provided with an end wall or spreader plate II, which is disposed at an acute angle to the strip as the latter moves through the box. This plate ll extends crosswise of the space between the innersurfaces of the side walls of the box and the bottom It terminates short of such spreader plate, so as to leave a space through'which the molten metal flows onto the strip. In practice, the lower edge of the spreader plate H is about A, inch from the strip.

Mounted on the box is a cover I2 which has a circular opening through which the molten metal flows onto the bottom iii of the pan 9.

Associated with the pouring box is a front guide shoe l3 which is aligned with the center guide shoe l, and has mounted thereon a cover I4. A rear guide I5 is also provided which is aligned with the opening in the rear of the pouring box.

Before entering the pouring box, the strip 8 is provided at its edges with flanges F, which serve as means for laterally confining the flow of the applied molten metal. As the strip enters the pouring box, its forward end strikes the beveled surface 8 of the back wall 3 and the strip is thereby directed below the curved surface I of the back wall, and is transversely bowed so as to present a concave upper surface to the molten metal subsequently applied thereto. As the strip proceeds through the pouring box, the flanges F thereof move through the spaces between the ribs 2 and 6.

The object of this bowing or concaving the strip is to avoid uncontrolled buckling or warping of the strip which might otherwise occur, due to the high temperature to which the strip is heated even before it enters the pouring box.

As the concave strip proceeds through the pouring box,. molten' metal M which may be bronze or brass is poured upon the upper concaved surface thereof, and, due to such concavity of the strip, such molten metal will be thicker in the center than at itslateral edges.

asosmo This condition, moreover, is somewhat aggravated due to the surface tension of the metal, which pool of molten metal, indicated by the reference numeral P, is formed, and the excess metal at the center of the strip, which is due to the concavity of thestrip, will continuously flow rearwardly into this pool from the point at which the strip reassumes a horizontal position, that is, a point somewhat beyond the right end of Fig. i of the drawings. This rearward flow is primarily a flow due to gravity, and is such that the thickness of the molten metal layer at the point where the strip reassumes a horizontal position will be more or less uniform, that is, the thickness of such metal at the center of the strip will not vary materially from that of the edges of the strip. Moreover, the kinetic energy of such molten metal, as it flows rearwardly into the pool, tends to overcome its surface tension to some extent, thereby improving the distribution effect.

Since the flow of molten metal is constant and uniform in amount, the depth of the pool will depend on the angle of inclination of the strip,

and upon the speed of the strip. The speed of the strip is so controlled that the rear edge of the pool P is not permitted to come into contact with the back wall 3 of the pouring box. The pool doesnot normally come into contact with the front wall 5 of the pouring box, since the latter-does not extend downwardly sufllcient- 1y to contact the normal pool. The spreader plate ii is, of course, subject to corrosion due to the molten metal flowing thereover, but since this plate is part of a small casting which is readily removable from the pouring box, it can be replaced at a cost which is but a fraction of the cost of the entire pouring box. There is no appreciable contamination of the molten metal from the metal of the plate ll since the rate of corrosion of this plate is extremely low.

The extent to which the strip is inclined will vary in accordance with the viscosity of the metal which is applied to the strip, but in general, when working -with metals such as plastic bronze and brasses, the pouring box is tilted about 2 to the horizontal at the outset of the pouring operations. After the operations have proceeded for some time and the various temperatures have been more or less equalized, the angle of inclination may be reduced.

Since the viscosity of metals decreases in gen eral as the temperature of the metals increase,

the inclination may also be said to be varied in consequently the pouring box and associated.

parts, a carriage 25 is provided which is mounted on rollers 26 journalled in a base 21. The carriage 25 is of substantially rectangular form, and is provided at the four corners thereof with screw jacks 28, upon which the furnace rests, and through suitable manipulation of which the furnace is tilted. The tilting may, however, be accomplished in other ways which will readily occur to those skilled in the art to which the invention relates.

It will be noted that since four screw jacks are provided, one at each corner of the furnace, that the furnace can be inclined transversely as well as longitudinally, and that the strip can accordingly be transversely inclined. This at times is desirable for the purpose of causing the pool of molten metal which is applied to the strip to spread toward the edges of the strip.

The surface tension, and consequently the viscosity, of the molten metal may be controlled to some extent by changes in the atmospheric conditions within the pouring box. This may be accomplished, for example, by increasing the hydrogen content of the non-oxidizing or reducing gas which is introduced into the pouring box through the conduit 23. Thus, when the metal becomes sluggish, the hydrogen content of the gas, which is essentially a mixture of nitrogen and hydrogen, may be increased from about 7% up to about Specific examples of the methods used for vari ous coating metals are given below. In these examples, steel strip having a thickness of from about .020" to about .135", and containing from about .04% to about carbon was employed.

(1) The strip, after being heated to a temperature of about 1850 F. in a non-oxidizing atmosphere, is passed through the pouring box in the mannerdescribed, and is coated with a bronze alloy containing from 55% to 65% copper and from 35% to 45% lead, the temperature of the coating metal being from about 2250 to 2350 F. The strip is inclined at an angle of about 2 degrees to the horizontal.

(2) The strip, after being heated as in example (1) is coated with a bronze alloy containing about 78% copper, 9% to 11% lead and 9% to 11% tin, the temperature of this coating metal being from about 2250 F. to about 2350 F. The angle of inclination of the strip is about 2 degrees.

(3) The strip, after being heated as in example (1) is coated with a brass containing about 60% copper and about 40% zinc, the temperature of the coating metal being about 1800 F.- The strip 'is inclined at an angle of about 2 degrees to the Other coating metals which have been employed are a bronze containing 6'! %-74% copper, 22%- 27% lead, 3%4% tin and 3% zinc, and another containing 83% copper, 7%-9% lead, 3.5%-4.5% tin and 4% zinc. For these the strip is inclined at an angle 0! about 2 degrees to the horizontal.

In each case, after the strip is coated, the strip is cooled and the coating solidified, which may be effected by any convenient method, such cooling being effected immediately after the strip emerges from the furnace. The cooling may also be effected by means of air.

It is to be understoodho'wever, that the invention is not in any way limited to the use of any particular base metal or coating metal, nor to any specified thickness of metal. The metliod is also applicable to the coating of metals such as invar, and to the use of other coating metals, such as aluminum and aluminum alloys. The product may be used for various purposes, such as, for example, bearings, bushings, thermostats, etc.

Other forms may be employed embodying the features of my invention instead of the one herein explained, change being made as regards the. means and the steps herein disclosed, provided the elements stated by any of the following claims or the equivalent of such stated elements be employed, whether produced by my preferred method or by others embodying steps equivalent to those stated in the following claims.

I therefore point out and distinctly claim as my invention:

l. The method of making a bimetallic strip which consists in continuously moving a metal strip in a direction inclined upwardly to the horizontal, pouring molten metal on said strip to form a pool lying intermediate the edges of the strip, and varying the inclination of the strip to cause spreading of the pool toward the edges of the strip. i

2. The method of making a bimetallic strip which consists in continuously moving a metal strip, pouring molten metal on said strip to form a pool lying intermediate the edges of the strip and inclining said strip transversely to cause spreading of the pool toward the edges of the strip. i

3. The method of making a bimetallic strip which consists in continuously moving a metal strip in a direction inclined upwardly to the horizontal, pouring molten metal on said strip to form a pool lying intermediate the edges of the strip, varying the inclination of the strip and inclining the'strip transversely to cause spreading of the pool toward the edges of the strip.

4. The method of making bimetallic strip which consists in continuously moving a metal strip through a pouring box having a rear wall. said pouring box being inclined upwardly in the direction of movement of the strip, applying molten metal to the upper surface of the inclined strip and controlling the forward movement of said strip so as to avoid contact of said molten metal with said rear wall of the pouring box.

5. Apparatus for making a bimetallic strip comprising a pouring box through which said strip is adapted to be passed, said box having an entrance and an exit'for said strip and means for elevating said exit relatively to said entrance whereby said strip will pass through the box at an upward inclination, and other means for elevating either side of the pouring box.

6. Apparatus for making bimetallic strip comprising a pouring box through which said strip is adapted to be passed, said box having an entrance and an exit for said strip, the exit being elevated relatively to said entrance whereby said strip will pass through the box at an upward inclination, and means for varying said inclination.

GEORGE EDWARDS.

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