GB1577779A - Method of and apparatus for converting molten metals into solidified products - Google Patents

Abstract

From a casting apparatus, a metal melt flows to a cooled rotating drum (9) and solidifies to give a thin metal strip (10) which is stripped off and divided in a flying shear (12) into sections which are laid one upon the other on a table (20) by means of supports (14). After each section is laid down, the workpiece to be produced is moved backwards and forwards and pressed between a pair (22, 23) of rollers, whereupon the finished workpiece is pushed off the table (20) at the side. This makes it possible to produce in any thickness workpieces which were hitherto produced by laying one upon the other individual strips produced in separate casting apparatuses, and a considerable reduction in the costs and space requirement is thereby achieved. <IMAGE>

Description

(54) METHOD OF, AND APPARATUS FOR, CONVERTING MOLTEN METALS INTO SOLIDIFIED PRODUCTS (71) 1, ERIK ALLAN OLSSON, a subject of Sweden, residing at Rotfluhstrasse 15, CH-8702 Zollikon/ZH, Switzerland, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to metal processing and more particularly to a method of and an apparatus for converting molten metal into a semi-finished product for conversion into a finished product.

In the usual process of casting molten metal, and particularly steel for the production of solid sections to be subsequently converted into finished products, such as, for example, the process of continuous casting, the molten metal is charged into an open-ended mould where the molten metal next to the cold mould walls solidifies to a skin which at first rapidly thickens as initial solidification proceeds.

However, the rate of solidification progressively decreases as the solidification toward the centre of the casting increases.

The solidification time, "T", of a billet, depending on whether it is round, square or rectangular can be roughly approximated as proportional to the square of the diameter or thickness of the billet and, is usually expressed by the formula T=kD2 where k is a factor depending on cooling conditions and D is the diameter or thickness from one surface to the other.

It is, of course, well known that when molten metal particularly steel, solidifies rapidly, the casting has a fine grain structure and the quick solidification prevents or minimises segregation of some elements, such as, for example, the alloying elements in steel. On the other hand slower solidification leads to larger or coarser and less desirable grain structure with accompanying rejection by the crystals as they form of some of the alloying elements, as well as "impurities", (which, in the case of steel may include S, P, As, Zn, Sn, etc.) and their resulting concentration in the area of the casting last to solidify. As a result, the outer portion of the casting, often referred to as "the chill zone layer" is superior from the standpoint of its fine grain structure, and also because it most nearly corresponds to the composition of the melt from which it was produced. To more nearly approach a uniformity of section across a conventionally cast ingot, from either a mould or continuous casting, heat-treating, rolling and forging operations are necessary which would not be necessary if a chill zone composition and structure prevailed across the entire section of the ingot.

A method has been proposed wherein several continuously formed thin strands are continuously brought together in face-toface contact at a temperature desirably above a usual hot rolling temperature but at which liquid metal is not visible. When light pressure less than that required for deforming the solidified metal is applied to the strands which are in face-to-face contact, fusing or welding at the contacting surfaces occurs by intercrystalline diffusion which takes place under these conditions.

This may be referred to as "flowless welding" or "pressure welding".

Thus, when forming a billet for example of diameter D according to this method of combining several individual layers or strands, the solidification time, being based on the thickness of the individual layers, is accelerated, so that the formula, instead of being expressed as T=kD2 will be expressed as (I))2 T=K (S) where S designates the number of layers and K is a factor depending on the cooling conditions. In pressing together a number of strands to effect welding, there is, at least in most cases, a reduction in thickness of the order of no more than about 2V so that to secure the dimension D this reduction of thickness must be taken into consideration in determining the dimension D of the finished casting. In other words, a ton of thin metal solidifying in separate layers from a molten condition solidifies much more rapidly than a ton of metal cast as a single casting into a billet or slab of the dimension D.

With perhaps two or three separate layers or strands being combined into a semifinished product, the formation of each separate layer using separate casting rolls for each layer is commercially practical, even with a separate pressure roll means for each additional layer over two, but with perhaps four, five or even ten or more layers being combined into a single slab or billet, the complication and space requirements for a plant having a separate casting unit for each layer together with pressure roll passes for each layer above two layers, and the investment involved in such a plant rapidly offsets the economy and advantages of the process of my earlier application.

According to one aspect of this invention there is provided a method of converting molten metal into a semi-finished product for subsequent conversion into a finished product comprising the steps of forming a thin layer of metal on a primary casting unit having a single moving chill surface on which molten metal from a molten metal source congeals, cutting or severing said layer into sections and delivering said sections of said thin layer of metal to an assembly unit, assembling a plurality of said thin sections of metal in said assembly unit into bodies of predetermined thickness by placing such sections in face-to-face relation with each section at a temperature at which each section will pressure weld to the contacting surface of an adjacent such section, and effecting pressure welding to form a semi-finished product.

According to a further aspect of this invention there is provided an apparatus for converting molten metal into a semifinished product for subsequent conversion into a finished product comprising a primary casting unit comprising a single moving chill surface and means for retaining a pool of molten metal against said chill surface whereby a thin continuous layer of rapidly congealed metal is formed and removed by the chill surface away from the pool means for removing the thin layer of metal so formed by the chill surface and delivering said layer to an assembly unit and means for cutting or severing said layer, prior to its delivery to said assembly unit, into sections, said assembly unit comprising assembly means for placing a series of said sections in face-to-face relation and a common consolidating means for applying pressure to effect pressure welding of said sections into a unitary body and means for removing the bodies so formed after pressure welding has been completed.

The invention also relates to semifinished products made by such a method.

A preferred embodiment of the present invention comprises a method of and apparatus for converting molten metal, especially steel, into a finished product where the molten metal is cast into thin layers by contacting a moving chill surface with molten metal against which surface a thin layer of the metal solidifies.

Conveniently the metal is cast as a continuous wide flat strip that is cut into lengths or strips. Advantageously, the lengths or strips are delivered to a single layering or stacking unit where they are fused together with a common means for pressure welding them progressively as successive layers are placed against a layer previously positioned by the unit. There may, in some cases, be optionally employed two casting units, but the layers from both units will be combined and fused in a common pressure welding unit.

The grain structure and composition of a thin layer cast in the manner herein disclosed is determined at the time a chilled layer forms on a moving chill surface and the combining of several layers into a common product, such as a billet or slab, slowing down the rate of heat transfer from the thicker product, is of little, if any, consequence at this time.

In the following description, the term "strand" is used to designate the emerging casting, whether continuously or intermittently produced on a cold surface moving in contact with a body of molten metal. The resulting solidified layer or strand is thereafter stripped from the moving cold or chill surface and is desirably about 3 mm thick and has the fine grain structure and uniform composition, for all practical purposes, of the melt from which it is formed. Such a layer or strand is often referred to as being of chill zone thickness.

The term "strip" is used, unless otherwise indicated, to designate division by slitting the strand longitudinally, and the terms "piece" or "pieces" or "lengths" designate individual pieces formed by cutting a strand or strip crosswise. The output of a complete unit, whatever the shape or size, is generally designated "product", "unitary product" or "semi-finished product".

Where several strands are being simultaneously cast and combined as in prior proposed apparatus, a higher rate of production can be achieved than with the herein disclosed improvement, assuming dimensions to be the same, because several strands are being simultaneously produced and combined into a semi-finished product.

However, the improvement herein disclosed will nevertheless result in a rate of conversion of liquid metal into a billet or slab faster than the same tonnage could be converted by conventional continuous or semi-continuous casting. This results from the increase in solidification speed with decreased thickness of the solidifying product.

Taking as an example, if 1 metre wide and 150 mm thick steel slabs are being made by fusing together 3 mm thick layers, this layer thickness of 3 mm will be achieved in approximately 1 second. Using a travelling belt conveyor as a chilling wall which, over a length of 1 metre is brought into contact with liquid steel, the belt speed can be 1 metre per second for withdrawing said 3 mm thick solidified layer. This corresponds to a production of approximately 1400 kg. per minute. To achieve this figure by conventional continuous casting in one strand, a rather sophisticated and expensive continuous casting machine would be required, considering that it would take about 6 minutes to get the section completely solidified at a minimum withdrawing speed of 1.24 metres per minute from an interior liquid pool of at least 7.5 metre length.

During this time the strand has to be properly cooled and supported over this length. On the other hand one embodiment of this invention requires a rather short travelling belt or a rotating drum, a shear for cutting the layer or strand to desired lengths after leaving the belt, and means for stacking them one upon another along with means for pressing the stacked lengths as they are progressively added onto the top of a previous layer or layers. An even higher production rate can be obtained if the strand as cast is kept thinner while the length over which the belt is in contact with the liquid steel is again only 1 metre.

Theoretically, a 1 mm thick layer would enable a withdrawal speed of approximately 540 meters per minute (due to the increase of solidification rate with decreased thickness) corresponding to approximately 4 tons per minute. This productivity is hardly achievable using present continuously casting techniques where a liquid pool of approximately 21 metres would be required and a casting speed of approximately 3.5 metres per minute would be necessary. If the width of the layer or strand were to be split longitudinally into 100 mm wide strips to be fused together into 100 mm sq. billets, an output of the order of about 54 metre billets per minute would be theoretically achieved.

In order that the invention may be more readily understood and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows schematically a longitudinal section through an apparatus in accordance with this invention for forming slabs of metal and which may be used in carrying out a method in accordance with the invention; Figure 2 is a schematic top plan view of the apparatus shown in Figure 1; Figure 3 represents a transverse vertical section in the plane of line Ill-Ill of Figure 2; Figure 3A is a schematic representation of a means for moving a bed-plate of the apparatus shown in Figures 1, 2 and 3, in timed relation to the placing of a length of metal on it or on a previously deposited length of metal; Figure 4 illustrates schematically a side view of an alternative apparatus in accordance with the invention, for forming blooms or billets of metal from a series of narrow strips cut from a wide cast layer of metal and which may be used for carrying out a method in accordance with the invention; Figure 5 is a top plan view of the apparatus shown in Figure 4; Figure 6 is a schematic side view of an apparatus in accordance with the invention forming single blooms or billets from a series of narrow strips cut from a wide cast layer of metal and which may be used for carrying out a method in accordance with the invention; Figure 7 illustrates schematically an apparatus similar to that shown in Figure 6 but in which there are two metal casting and slitting units the second of which is indicated in broken lines alongside the first; Figure 8 is a side view and Figure 9 is a top plan view of another apparatus for forming slabs of metal in which successive pieces cut from a continuous strand of metal are delivered vertically onto a space between opposed pressure plates to be welded together on closing of the pressure plates; Figure 10 is a schematic illustration of an apparatus for forming slabs of metal wherein successive pieces cut from a con tinuous strand of metal are delivered alternately onto a reciprocating support at either side of the roll pass of a reversing pressure roll; Figure 11 illustrates schematically a modified form of the apparatus shown in Figure 10; Figure 12 is a schematic view represent ing a longitudinal vertical section through another embodiment of an apparatus for the production of flat slabs of metal; Figure 13 is a schematic top plan view of the apparatus shown in Figure 12; Figure 14 is a staggered transverse vertical section taken on line XIV-XlV of Figure 13; and Figure 15 is a schematic diagram illustrating the conversion of molten metal to a finished product by a process utilising the apparatus shown in Figures 12 to 14.

Referring to Figures 1, 2 and 3, a casting ladle 2 has a discharge tube 3 that extends into an intermediate container 4 in which molten metal is normally maintained at a depth sufficient to immerse the discharge end of the tube 3. A flow control valve is indicated in the tube 3 at 5. For assuring that the molten metal in the container 4 will in operation of the apparatus immerse the lower end of the tube 3, the container 4 has an internal weir 6. Under normal operating conditions molten metal flows over the weir 6 which also serves to assure floatation and removal of slag from the metal. From the outflow side of the weir, the metal flows through a connecting passage 7 of generally U-shape into a vessel 8.

By means of a continuously moving endless cooling wall, here constituted by the surface of an internally cooled rotatable drum 9 dipping into the vessel 8 and rotating at a uniform speed, a thin continuous layer of solidifying metal is deposited on the drum and withdrawn by the drum from the vessel.

This layer, designated 10, is stripped from the upper surface of the drum at or close to the temperature where it is substantially entirely solidified and moved horizontally between levelling rolls 11. After emerging from the levelling rolls, the layer of metal 10 is sheared by a flying shear 12 into pieces of uniform length. A limit switch 13, which may include an electric eye circuit of a known construction, is arranged to actuate the shear 12. At the time of shearing, the piece of metal to be sheared will have moved over supporting means 14, comprising parallel support plates 19 one of which is suspended at each side of the machine by links 15 hung from respective rock-shafts 16. Various mechanisms of known construction, schematically indicated at 17, operate these shafts in unison to move the plates 19 apart to drop each still intensely hot successive length of sheared metal onto a movable receiving bed.

The very thin hot layer as removed from the drum is extremely weak and flexible and must be supported in some way both before and after shearing to avoid damage. Conventional supporting and transferring means would require cooling to avoid destruction or the sticking of the cast metal layer, or lengths, thereto. This would result in the undesirable removal of heat from the metal that would later need to be replenished, adding to the cost of equipping and operating the machine. It is contemplated that in an apparatus in accordance with the invention the supporting, guiding and transport of the layers may be accomplished by generating alternating electromagnetic fields which would provide a repelling force to levitate the metal and which might additionally supply heat to the moving metal.

To this end there are provided supporting plates indicated at 18 and 19, the latter comprising part of the movable supporting means 14 as discussed above, within which are water-cooled tubes charged with alternating electric current of a frequency and strength, which, according to well-established formula, will generate a field for the purpose both of repelling the metal clear of the plates 18, 19 and inductively generating heat in the metal. The force imparted to the metal from the drum 9 and levelling roll 11 will normally be sufficient to carry the leading end of the layer to the limit switch means 13 to actuate the shear, but, when particularly long pieces of metal are to be sheared from the advancing layer, the coils may be energised in a manner to progressively urge the metal in the direction of the limit switch 13 thereby to supplement the force supplied by the drum 9 and rolls 11. Means for the generation of such travelling magnetic fields are well known.

As above explained, the piece of metal to be severed by the operation of the flying shear will already be supported over the plates 19 and thus the limit switch 13 may also be utilised to actuate the mechanism 17 to move the plates 19 apart to allow the severed pieces of metal to drop between them. Various means to trigger the operation of the mechanism 17 to open and close the plates 19 following the operation of the shear are well known in automatic furnace and other door-operating mechanisms.

Below the supporting means 14 there is a layering or stacking unit comprising a bedplate 20 having a fluid pressure cylinder and piston means 21 of a length and stroke respectively to move the bed-plate a full back and forward stroke which is at least twice as great as the length of the pieces being sheared from the continuously cast layer. The operation of the piston is so timed that the bedplate is positioned to receive each piece as it drops from the support to lie flat on the bed-plate or directly on top of the piece last dropped if one or more pieces have previously been dropped in starting or forming a stack.

Immediately after each piece is receivea on the top of the stack on the bed-plate then in progress, or being laid on the bed-plate in the initial stage of making a stack, the piston operates to move the bed-plate 20 toward the right as viewed in Figure 2 between a pair of rolls 22 and 23, the upper roll of the pair 22 being arranged to move or be moved upward as the height of the stack of pieces of metal supported by the bed-plate 20 increases but to exert a predetermined light pressure on the top of the newly placed piece as the bed-plate 20 reciprocates between the rolls 22, 23.

In Figure 3A there is schematically illustrated one simple type of means for controlling the movement of the bed-plate 20 in timed relation to the dropping of the pieces of hot metal onto it. When the support plates 19 are positioned to support a piece of the advancing layer of metal a switch 24 is closed to energise a solenoid 25 which operates a four-way valve 26 to admit fluid pressure to the left end of the cylinder of the cylinder-piston unit 21 and to release pressure in the opposite end of said cylinder to move the bedplate 20 from the left limit of its travel as shown in Figure 3A. At the same time as switch 24 is closed, a switch 27 is opened, but, as soon as the plates 19 move in a manner to release a sheared piece of metal the switch 24 is opened and the switch 27 is closed, whereupon a solenoid 28 is energised to reverse the four-way valve 26 and return and the bed-plate 20 through the rolls 22 and 23.

There is a floating type of switch indicated at 30 for de-energising both solenoids 25, 28 when the bed-plate 20 is at the retracted or right end of its travel when the stack of pieces of metal reaches a predetermined height. This provides a pause in the operation of the piston means 21 to enable the stack to be pushed sideways from the bed-plate for subsequent removal from the casting unit, as shown in Figure 2 and as indicated by the arrows in Figure 3. A pusher such as, for example, the pusher mechanism to be described hereinafter may be used.

The right end of the bed-plate 20, as shown in Figure 1, has an elevated end portion 20a that slopes at 20b to the flat level of the main area of the bed-plate. This elevated level is between the rolls 22 and 23 at the extended or left limit of the travel of the base plate as here illustrated so as to lower the upper roll 22 onto the accumulating stack with each pass of the base plate toward the right or retracted position.

The broken lines, designated 31, indicate an enclosure beginning forwardly of the vessel 8 and extending past the rear of the roller table over which the base plate moves, the enclosure having side walls and a bottom wall so that a controlled, inert atmosphere, that is, a non-oxidising atmosphere, may be maintained around the enclosed apparatus, and so that, to a considerable extent, heat loss is retarded. At the discharge end of the machine, that is the right end as shown in Figures 1 and 2, there is a liquid seal 32 comprising a liquid-filled vessel into which the edge of the enclosure 31 dips. The stacked and rolled metal product after being pushed sideways from the bed-plate 20 enters this vessel 32 and is subsequently removed, as indicated by the curved dotted arrow 33. The molten metal between the vessel 4 and the vessel 8 constitutes a trap to prevent air entering the enclosure at the point where the molten metal is introduced into the enclosure.

In the operation of this apparatus, a continuous layer of metal, typically about 3 mm in thickness, i.e. of chill zone thickness, is formed, cut into uniform lengths, and these are stacked in the manner described to form a slab or billet of the required thickness. Each piece, after the first one, is placed on the hot piece beneath it and because of its high temperature and clean surface, and because of the elimination or substantial elimination of air from the enclosure and the resultant prevention of any appreciable oxidation of the metal, a fusion welding of the metal between the contacting surfaces occurs under application of appropriate pressure.

The approriate pressure depends upon the physical properties of the layers. It must be sufficient immediately to cause intimate contact to be established between the confronting surfaces. When slabs or billets are being formed from metal with poor plastic properties, it may be preferable not to apply welding pressure until the metal has reached a temperature where it can stand a relatively high pressure without rupturing.

In such a case two or more bed-plates arranged for alternate operation may be used. In the case of other grades of metal, e.g., low carbon steel, which quickly reach good plasticity (hot working properties), relatively high pressure can be applied immediately since the material quickly becomes stiff. Absolute parameters for particular grades of carbon and alloy steels may have to be determined according to the size and shape of the product, the composition of the metal, the manner of applying pressure, as by rolls or by a press, oscillating plates or the like.

Taking as an example of this operation, 150 mm thick slabs with a length of 3 meters will be made by fusing together at least 50 pieces cut from the continuously formed strip which are each 3 mm thick as they leave the solidfying apparatus. With the watercooled drum 9 operating at a speed of 1 meter per second and with the piston and cylinder unit 21 making a full back-andfourth stroke within 3 seconds a slab will be completed about every 150 seconds.

However, a certain degree of height reduction, due to the pressure to which the hot metal is subjected, must be taken into consideration so that some additional pieces or layers will be needed for achieving the desired thickness of 150 mm of the finished piece. However, since the reduction of thickness results in a corresponding extension of the length, the pieces or lengths can be cut slightly shorter. Thus, the stroke cycle of the piston may be somewhat shorter and the production rate per unit of time remains the same. That is, the finished weight per time unit is the same or approximately the same.

Figures 4 and 5 show an apparatus for simultaneously forming blooms or billets of narrow width from a wide cast layer of metal. As shown in Figures 4 and 5, four billets or integrated bodies of progressively narrower width are formed from a single wide strand of metal emerging from a casting unit.

While a rotatable drum as illustrated in Figures 1 to 3 could be used to form the thin continuously cast layer, Figures 4 and 5 show an alternative arrangement which utilises a continuously moving heat-resistant belt 35. The upper reach of the belt 35 travels upwardly in the direction of the arrow from a molten metal vessel 35a to a roll 36, where the belt passes around the roll 36, to form a discharge end and then passes downwardly to and around a roll 37. The vessel 35a is of upwardly decreasing depth and the upper reach of the belt, as here shown, moves along under the molten metal vessel 35a, forming a chill bottom wall for the pool of molten metal. By this means a thin layer of metal rapidly forms on the belt.

This layer of metal cools before it reaches the roll 36 to a temperature at which the metal may be stripped from the belt and slit longitudinally by slitter 38 into parallel strips, here designated S', S2, S3 and S4.

While the strips might be the same width, or various combinations of widths, as here illustrated S' is the widest and the other strips are progressively narrower, S4 being the narrowest.

The parallel strips then are sheared by a flying or rotating shear 39 into pieces of uniform length.

Below the casting unit where the strips are formed and cut to length, there is a roller table 40 with plates 41 between spaced rollers 42. These plates retard radiant heat loss from the strips and may have resistance or induction heating means incorporated therein to heat the strips.

About midway between the ends of the roller table 40 there is a pair of pressure rolls 43 and 44, the upper one, 43, being vertically movable (in a manner corresponding to that of roll 22 in Figure 1) to apply appropriate pressure to the stacks of metal strips passing between them. There is a reversible drive indicated at 45 for driving one or both of these rolls. Guides 46 are positioned for directing and confining the sheared strips of metal into spaced parallel channels adjacent the bight of the rolls 43 and 44 and other guides 47 along the roll table maintain such parallelism.

In order to direct the strips which leave the shear 39 in close side-by-side relation into spaced parallel paths, the casting unit is positioned at an angle to the roller table and the emerging strips are looped downwardly from the shear to a guide roller means 48 about a radius of curvature which is progressively larger for the successive strips S1 to S4. By reason of this, each successive strip from S' to S4 travels through a longer loop, although each strip travels round its loop in the same period of time, and undesirable distortion of the strips is avoided.

In Figures 4 and 5, the parallel stacks being formed are indicated as B, and each stack extends from one side of the rolls 43 and 44. In operation, the stacks B travel to the right as shown in Figures 4 and 5, there being a limit switch 50 at the right end of the roller table which will be engaged by the end of at least one of the billets formed from the stacks B (or other product being formed) to reverse the rolls 43, 44 when the trailing ends of the billets have cleared these rolls and reverse the travel of the billet back into the bight of the rolls 43, 44.

The loops between the shear 39 and the bight of the rolls 43, 44 must, for products of substantial length, be nearly as long as the finished products, and the rolls 43, 44 must operate faster than the rate at which strips emerge from the shear so that when one set of strips are entirely deposited on the roll Figures 1 and 2, a trap will also usually be provided in the molten inlet, indicated at 55.

There will also be provided looping guides for directing the strips S' to S4 into their proper positions between the pressure rolls 43, 44, but for clarity of illustration they have not been shown. Since such guides will remove heat from the length or pieces of metal passing therethrough, electromagnets energised from an alternating current source and generally of the type illustrated in Figure 1, will be associated with the guides to provide heat to the metal pieces and relieve, to some extent. the contact pressure of the metal pieces with the guides and the resultant loss of heat.

In Figure 6 there is shown a casting unit of the endless belt type, as shown in Figures 4 and 5, with an upwardly inclined endless belt 60 of the type illustrated in those figures, and a vessel 61 for holding a body of molten metal at a uniform depth from a supply inlet (not shown) but similar to that shown in Figure 5 and also Figure 7, to be hereinafter described. The molten metal is contained above the upper reach of the endless belt 60, which forms a constantly moving chill bottom wall for the pool of metal retained by the vessel 61, as previously explained, on which a thin layer of molten metal is continuously congealed.

This continuously formed layer is stripped from the upper reach of the belt 60 at its upper end and passed between a slitting roll means 62 that divides the continuously formed layexlongitudinally into a plurality of continuous parallel strips S9 of equal width, which then pass between guiding rolls 63. As in the embodiment shown in Figure 5, the casting unit is angularly disposed with reference to the longitudinal axis of the means to which the strips are to be delivered.

The means for receiving the strips comprises a pair of pressure rolls 64 with a guide means 65 in advance of the bight of these rolls of a width to receive, with only a working clearance, the strips S9, but of a depth to permit all of the strips, one upon the other, to enter the pass between rolls 64.

At the emerging side of these rolls there is a guide means 66 similar to 65 but reversed thereto. Other guides are provided, as indicated at 67, and elsewhere if needed.

There is a second pair of upper and lower rolls 68 which are flanged to provide a pass between them, and between 67 and 68 is another pair of grooved rolls 69 which rotate about vertical axes. They bear against the sides of the fused bundle of strips emerging from between the rolls 64.

The stacking of the several strips S9 is effected in the manner described with reference to Figures 5 and 6, by having the parallel strips emerging from the rolls 63, each travelling through successively larger loops (from the right side, as shown in Figure 6) while effecting a 1800 twist in such manner that the strip S9 at the left side of the series, as here illustrated, becomes the lower-most strip to enter the pass between pressure rolls 64, and each strip thereafter from left to right is guided in succession onto the strip beneath, forming a stack or bundle of strips, all at a temperature where they may be pressed and fuse-welded or pressurewelded as before described, and at a temperature as explained where welding under relatively light or appropriate pressure (as hereinbefore defined) will take place. By looping the parallel strips in the manner described, the strips are easily brought to a position where they will come together without destructively twisting or bending the metal.

The product of the process described with reference to the apparatus shown in Figure 6 may be cut into billets of uniform length, or of varying length by a flying shear indicated at 70. The hot continuously formed product could then be delivered, for example, to a rod of bar mill and reduced to a rod or bar of a desired length or into bars which subsequently would be cut to length.

Referring to Figure 7 which is a modified top view of Figure 6 wherein corresponding parts are designated by corresponding reference characters, all the strips, S9, are of equal width and, in place of guiding rolls at 63, there is a rotary shear 63A with staggered cutters for progressively severing each of the emerging strips S9 into strips of uniform length so that while the loops may be progressively larger in diameter from one side of the unit toward the other, the lengths of all the strips will be equal, or approximately so, and they will stack or bundle one upon another with both the leading and trailing ends of all the strips being approximately square with and vertically aligned with the corresponding ends of the other strips.

Another difference between the structures shown in Figures 6 and 7 is that Figure 7 illustrates in dotted lines a second casting, slitting, and cut-off unit 71 ahead of the first. With this arrangement, one bundle of strips may be assembled and integrated and then the other unit may operate to add additional pieces where the product to be produced is of a dimension, either in width or thickness, or both, too great to be produced from a single casting unit. Also, instead of using the two casting units in succession, both may operate at the same time and the pieces from one unit be interleaved with those of the other to form an integrated billet.

In Figure 7 a flying shear 70 is also indicated, to be used as in Figure 6, when desired. The finished billets may be discharged sideways as shown in Figure 3 but without it being necessary to reverse the direction of travel of the billets.

Alternatively the billets may be discharged endwise from the enclosure. As in the preceding figures, an enclosure around the entire casting and product-forming unit is indicated by chain lines, this enclosure being designated 73 so that a non-oxidising atmosphere may be maintained therein. The metal inlet to the casting unit, which, as previously explained, also constitutes a trap or seal, is designated 74. It will be appreciated that the apparatus of Figures 6 and 7 may be so adapted that either may operate in the same way as the other.

The arrangements shown schematically in Figures 8 and 9 are designated primarily for the production of slabs of a relatively short length. As in the other embodiments of the invention, the product is formed by progressively combining layers of metal, one on another, and pressure-welding each layer in turn to the next preceding one until a product of the required thickness has been produced.

In these Figures, 8 and 9, the casting unit is shown as comprising an endless belt 80 of the type previously described. From the discharge end 81 of the endless belt, the continuously formed layer, at a temperature above a temperature where it still has insufficient plasticity for normal hot rolling, is deflected downwardly into the space between two confronting refractory blocks 83, 84. The lower or left one of these blocks, as here shown, designated 83, is secured to a metal supporting structure 82. The upper or right one of these blocks 84 is carried on a metal supporting structure 85. The refractory block 83 and its support 82 is hinged at 86 to swing in a vertical arc from one upright position where it is steeply inclined with respect to a vertical plane to a horizontal position, a fluid pressure cylinder and piston unit 87 being provided to effect this pivoting movement.

The opposite refractory block 84 and its support, 85, is supported to move toward and away from the block 83. Fluid pressure cylinder and piston elements 88 are provided for moving the block 84 toward and away from the other one.

The blocks 83, 84 in the position shown in Figure 8 are located so that the descending layer of metal from the end of the casting machine enters the space between the two blocks with the inclination of the block 83 being such that some support is provided for the layer of hot metal as it moves down to prevent it from buckling or collapsing.

When the leading end of the layer of metal has almost reached a supporting ledge 86 at the lower end of the block 83, a flying shear 89 will sever the descending layer of metal.

When there is more than one sheared length of metal between the two pressure blocks, the pressure block 84 will be operated to press each added length of metal against the face of the preceding one.

The refractory blocks 83 and 84 are heated to retard the loss of heat from the metal pieces so that pressure-welding of the successive pieces is rapidly and effectively initiated. When the slab or billet being formed has reached the required thickness, the lower block 83 is swung down to the horizontal position indicated by dotted lines. When this position has been reached, a pusher 90 (see Figure 9) is operated by fluid pressure means 91 to slide the freshly formed product or slab 92 onto a roller table 93. The slab 92 is transported by the roller table to a reversing roll stand 74, here indicated as a three-high stand so arranged that the slab may be alternately passed through the upper pass in one direction and the lower pass in the other direction. The roll stand 74 is sometimes referred to as a ".jumping mill". This rolls the hot slab to assure complete unity of the several layers and compact it to the required thickness for subsequent processing into a finished product. Although not shown, the slab could pass directly from the roll stand 74 to an adjacent rolling mill to be further rolled, perhaps to finished dimensions without reheating.

Also; since the slabs may be too hot to have attained the desired plasticity for processing in the rolling mill 74, the roller table 93 may be of a length to support several of the freshly formed slabs at each side of the roll stand until they have cooled to a suitable temperature. Also, there is a third roller table 95 alongside of table 93 so that after passage of the slab 92 through the mill, it may be moved sideways from table 93 to table 95 for further rolling, or to be carried to the discharge end (not shown) of the table 95, the several arrows in Figure 9 indicating various directions in which slabs may be moved relative to the roller tables 93, 95. An enclosure, as discussed above with reference to the preceding figures, would desirably surround the mill of Figures 8 and 9 so that the casting, forming and rolling operations may be performed in a non-oxidising atmosphere, but, for purposes of clarity, this enclosure has not been shown in these figures.

Figure 10 illustrates schematically an arrangement in which a continuous layer 100 of metal cast on a moving chill surface, as previously described but not shown in this figure, is cut by a flying shear 101 into pieces of uniform length. These pieces are delivered to a supporting and conveying table 102. The table 102 is pivoted at 103 near the shear for oscillation in a vertical arc, as indicated in the drawing. The oscillation of the table 102 is effected by an operating mechanism comprising a fluid pressure cylinder 104 with a piston rod 105.

There is a pair of reversibly rotatable pressure rolls, comprising an upper roll 106 and a lower roll 107, and the reversible driving means for these rolls may be of a known construction, and such means is not shown in the drawings.

There is a roller table 108 extending to each side of this pair of rolls 106, 107 on which lies a bed plate 109 that may be shuttled back and forth through the pass between the two pressure rolls, the reversing travel of the bed plate over the roll table from end to end being initiated by a fluid pressure cylinder and piston unit 110 at the left end of the roll table, and a similar unit 111 at the right.

The roller table 108 is supported for controlled vertical movement which will enable it to lower as the weight on the bedplate increases. The means for lowering or raising the roller table 108 comprises a series of dashpots or like fluid pressurecontrolled elements 112 located at various positions along the roller table frame. At a level which is normally fixed with respect to the upper roll 106 during the operation of the mill, there is an entrance guide 113 on the left side of said roll and on the opposite side there is an oppositely facing entrance guide 114.

At the free end of the pivoted table 102 there is a supporting plate section or table 115 spaced above the roll 106, and which, in effect, forms a continuation of table 102 when the free end of said table is in its upper-most position. Beyond section 115 there is another table section 116 of a length somewhat greater than the length of the pieces into which the continuously cast layers of metal are cut. Section 116 is pivoted at 117 between its ends to rock in a vertical arc so as to tilt from the position shown in full lines in Figure 10 to the position shown in dotted lines. In the latter position it forms an extension of table 115, but when tilted to the full-line position, its left end, as here shown, is flush with the inclined top surface of the roll pass entrance guide 114. There is a cylinder and piston unit 118 for rocking table 114 up and down.

When the table 102 is rocked about pivot 103 to the lower limit of its movement, its free end then forms, in effect, a continuation of the left roll pass entrance guide 113.

In operation of the apparatus of Figure 10, a length or piece of the continuous casting, upon leaving the shear, moves down conveying table 102. With the table 102 in its upper position, as shown in Figure 10, the cut piece will move over section 115, at which time section 116 would be in the dotted-line position to receive it. When the piece is entirely on the table section 116, that table will tilt to the full-line position, and the lead end of the piece of metal will pass from the right under the upper pressure roll 106 onto the bed-plate, which is then also just entering the roll pass from the right, and the piece will move through the roll pass being thereby pressure-welded to the last piece previously placed on the roll table. The lower roll 107 will exert pressure against the bed plate 108 which holds the cast layer or layers of metal up against the upper roll 106 at an appropriate pressure.

The machine may be controlled by any one of several well-known types of control systems so that the various steps of operation of the apparatus are coordinated.

In Figure 10, a partially formed billet or slab is shown on the bed-plate 109.

When the bed-plate 109 has reached the limit of its travel toward the left and has cleared or about cleared the pass between the pressure rolls 106 and 107, the cylinder and piston unit 110 will operate to start it back through the roll pass in the opposite direction. By this time the table 102 will have been lowered to direct the next piece sheared from the casting over the left entrance guide 113 to enter the roll pass and deposit the leading end of that piece on the then leading or right end of the bed-plate or the last previously deposited piece on the bed-plate. This cycle of operation is repeated until the required number of pieces have been integrated into a homogenous mass. Then the slab or billet will be pushed or otherwise removed from the bed-plate, as, for example, by pushing means (not shown), but in the same manner as previously described in other figures.

Sequencing relays and other well-known circuitry may control the operation although manual operation can be provided for. An enclosure 120, as in previous figures, is provided (indicated in broken lines) to keep a non-oxidising atmosphere therewithin to prevent scaling of the metal and assure a clean surface-to-surface contact of the successive pieces of metal forming a slab. The lower pressure roll 107 is yieldably supported by a cylinder and piston means 107' to apply the required appropriate pressure upwardly toward roll 106. The lower pressure roll 107 may, by means of the cylinder and piston means 107' be lowered as the thickness of the product builds up on the bed-plate. Similarly, the roll table 108 can lower as the lower roll 107 lowers.

In Figure 11 the construction is for the most part the same as in Figure 10, and the same reference numerals are used to designate corresponding parts in the two figures. The significant difference is the more simple switching arrangement for alternating the direction of travel of the successive pieces of metal through the pressure rolls. In this embodiment there is a guide 125 at the left side of the upper pressure roll 106 with an upwardly and rearwardly turned extension 126. A generally similar guide 127 at the right of this pressure roll 106 has an upwardly curved extension 128 that passes above the upper roll 106 and extends above the guide extension 126. In the space between the extensions 126 and 128 there is a fixed guide 129 having diverging branches 130 and 131 providing two passages, one of which, 133, extending in spaced relation to guide extension 126, provides a passage for directing the leading end of a severed piece of a cast layer under the upper pressure roll from the left and onto the bed-plate which is then moving toward the right. The upper branch 131 together with guide extension 128 provide a passage arranged to direct pieces above the upper roll and then downwardly under the upper pressure roller from the right toward the left and onto the bed-plate which is then moving toward the left. In this case the piece is turned over in relation to its original top and bottom surfaces. The pivoted table 102 in this case moves between the full-line position shown in Figure 11 where it confronts and is flush with the end of guide extension 126 and the end of fixed guide 129, as indicated in dotted lines, and back down to the full-line position to alternately feed the strips under the upper pressure roll from the left toward the right and then from the right toward left in synchronism with the travel of the bedplate, first from the left toward the right and then from the right toward the left. The movement of the bed-plate may, for example, be timed by the operation of the flying shear 101, as can also the raising and lowering of the conveying table, controls suitable for this purpose being well known.

In order to supply heat to the sheared pieces as they are alternately guided to one side of the upper pressure roll and then the other in the arrangement shown in either Figure 10 or Figure 11, conductors indicated by spaced dots in the drawings are arranged to be energised from the source of alternating current (not shown). The conductors are enclosed or contained in the pivoted table 102 and the several conveyor sections and guides, when energised serve to generate repulsion forces to reduce the contact between the successive pieces of metal and the tables and guides, and also to aid in effecting their travel, and, as previously described, inductively to heat the pieces to maintain them at a temperature where they can be pressure welded.

Figures 12, 13 and 14 show a mill for producing slabs or plates of metal at a high rate of production. To this end, there is a reversing pressure roll stand 140, here illustrated as a 3-high stand of the type sometimes referred to as a "jump roll". In such a roll stand the pass in one direction is between the top and middle roll, as shown in the drawing, but between the middle and bottom roll in the opposite direction, means being provided for moving the rolls vertically to maintain the roll pass in both directions at the same level.

There is a roller table 141 at the left of the pressure roll stand 140 at a level to receive slab lengths of metal and to support the material being rolled, and a similar roller table 142 at the right of the pressure roll stand. There are two lines for producing slab length castings, one, designated generally at 143, being along one side of and parallel with the roller tables 141 and 142, and the other line, also parallel with the roller tables but on the opposite side of said roller tables, is designated generally as 144.

There is a continuous casting unit 145 at one end of each of said lines 143 and 144. They are here shown at the left end of the respective lines. They are illustrated as being belt type units of the type previously described. Each has a molten metal retaining vessel 146 with a molten metal supply inlet 147. At the discharge end of each continuous belt there is a flying shear 148 that cuts the respective continuous thin flat casting produced by the respective casting units 145 after they have been stripped from the belts, into slab length pieces 149, as best seen at the left end of line 143 in Figure 13. These pieces, as they are sheared, pass over a sectional receiving table 150 for line 143 and table 151 for line 144.

A sectional table 150 in line 143 is elevated above the level of the roller table 141 and is comprised of two fixed sections 150a and 150c and two transversely tiltable sections 150b and 150d. As best seen in Figure 14, the tiltable sections 150b and 150d are mounted on supports 155 arranged to rock or tilt sideways about a longitudinal axis 156 from the full-line horizontal position in Figure 14 to the tilted position shown in dotted lines. There is a movable stop 157 between sections 150b and 150c which, in the position shown in Figure 13, will block the movement of a severed length of metal 149 to retain it on the tilt section 150b but which, if moved out of blocking position, as shown in dotted lines, will enable a severed length of metal to pass along onto the second tilting section 150d.

By tilting one of the table sections 150b or 150d, a piece of metal supported thereon can be caused to slide onto an adjacent bedplate 160 on the roller tables 141 or 142 respectively, which is movable between the pressure rolls of the roll stand 140. The bedplate may then be moved along one or the other of the roller tables 141 or 142 to cause the piece of metal supported thereon to be rolled by the pressure rolls.

All of the sections of the table 150 are provided with multiphase alternating current windings designated in Figure 12 by the spaced, staggered, parallel lines. These windings may be energised to move a piece of metal 149 to the stop 157 if the piece is to be discharged onto a bed-plate 160 which is at that time entirely supported on table 141 to the left of roll stand 140, or if the stop 157 is withdrawn from its operating position, to move the piece to the end of the table 150, that is, to a position where it is centred on the tilt-table section 150d to be discharged sideways onto the bed-plate 160 which will then be positioned to the right of the pressure roll stand 140 and supported on the roller table 142. The alternating current windings may serve, as previously explained, also inductively to heat the successive pieces of metal as they are moved along over the table sections.

With the arrangement of tilting section 150b and 150d, selected lengths of thin cast flat metal can, for example, be alternately placed on the bed-plate 160 as it travels back and forth, first when the bed-plate is to the left of the pressure roll stand, and then to the right, and as each piece is placed on the one preceding, it is pressure-welded and integrated with the underlying piece.

The line 144 on the other side of the mill shown in Figures 12 to 14 arranged to operate somewhat differently from line 143, although it has a supporting table 165 for receiving sheared pieces of metal from its casting unit 145. The table 165, like table 150, is also at a level above the roller tables 141 and 142, but it is spaced laterally from these tables at a substantially greater distance than the sections of the sectional table 150 on the other side of the mill. The successive pieces of metal sheared from the continuous casting are moved along the table 165 from the casting unit by polyphase magnetic means (not shown) which are arranged similarly to the alternating current windings in the table 150 as above described. There is a stop 166 over table 165 similar to stop 157 on the other line. If the stop 166 is in the blocking position shown in full lines in Figure 13, the cast piece of metal will be stopped on the table 165 to the left of the pressure roll stand 140, but, if the stop is moved out of a position to block the travel of a cast piece or layer of metal, the piece will travel along the table to stop at the other side of the pressure roll stand 140.

As best seen in Figure 14, there is a transversely sloping lower platen 170 between the table 165 and the roller table 141. Above this platen 170 there is a vertically movable platen 171 which may be moved up and down by power cylinder units 172 on fixed parallel supporting rails 173, the upper platen 171 being movable in such a way that its lower face is parallel with the top surface of the transversely sloped lower platen 170. Alongside the portions of the table 165 adjacent the platens 170, 171 there are pushers 174 which operate simultaneously to push a sheared piece of metal transversely from the surface of the table 165 to the left of the stop 166, onto the platen 170. A second length or piece may then be pushed onto the first piece and the upper platen lowered to fuse or pressure weld the second piece over the first. This cycle may be repeated until an integrated slab of the desired thickness has been built up on the platen 170.

At the right end of the table 165 there is a similar press arrangement with a lower platen 170' and a vertically movable transversely inclined upper platen 171' powered by cylinders 172', also supported on the spaced rails 173. There are pusher means 174' which operate simultaneously to move successive pieces or lengths of metal that are delivered to the right end of table 165 to platen 170' to form an integrated stack of pieces.

The platens 170 and 170' and 171 and 171', respectively, of each of the two presses have electric heating means encased therein or otherwise arranged to assure optimum fusion of successive layers of metal, although by this means alone the layers of metal may not be as thoroughly fused as desired. There is a downwardly movable side plate 170a which extends along the lower edge of each of the lower platens 170, 170'. By selectively moving one or the other of these side plates down, the fused stack of plates thereon may slide onto roller table 141 or 142, as the case may be, and may be passed between the pressure rolls 140 one or more times to more completely effect the fusion welding of the several sheets or layers of metal in the stacks being processed. The slabs being formed from the stacks of metal sheets should at this time be of sufficient mass to retain enough heat to enable such consolidation to be performed effectively.

When this process is being effected the bedplate 160 is not required and may be run out of the way onto a roller table 180 indicated in dotted lines at the end of roller table 141 and the slab of metal thus formed may be run off onto a conveyor table 181, also indicated in dotted lines in Figure 13. At this time an end stop 182 at the left end of roll table 141 is lowered and an end stop 183 at the right end of roller table 142 is lowered to enable the finished slab to be removed.

An enclosure 190, indicated by broken lines, surrounds the mill so that a controlled non-oxidising atmosphere may be maintained around the mill during its operation. A seal is provided, such, for example, as that shown in Figure 3 but at the end of the roller table 142 through which the slabs are discharged endwise. However, some other sealed outlet for the discharge of the slabs to the atmosphere may be provided, as for example a "decompression" type of multiple door system of a type known and used in other industries.

Figure 15 is a block diagram illustrating the conversion of molten metal to an intermediate product and then to a finished product. In this diagram a ladle 200 receives molten metal which is to be cast and formed into slabs, blooms or billets by the casting unit and mill 201. The intermediate product, either blooms, billets or slabs 202, may pass directly to a rolling or finishing mill 203 and may be converted to a finished product, indicated by the coil 204. Alternately some or all of the intermediate product may be diverted in advance of the mill 203, as indicated in dotted lines, to be stored at 205.

The stored items may then be subsequently charged into a reheating furnace 206 and entered, as indicated by the dotted line 207, into the same or another finishing unit 203.

As thus illustrated, the molten metal is c shown, for example, in Figure 13 where an initial pressure is applied in press 170, 171 or 170', 171' and final consolidation is effected in roll stand 140. Also it includes apparatus of the type shown in Figure 13 where a slitting roll, as 62 in Figure 7, could divide the strand lengthwise into two pieces, one of which would be moved over the top of the other, the pieces being initially pressed together in unit 170, 172 to then be discharged onto bed-plate 160 to await the discharge of a second pair the two pairs then being passed through rolls 140.

Alternatively a pair may first be fused together in press 170, 172 and then moved through rolls 140 to receive a second pair from press 170', 172' and then returned to the first position and thus alternated until a piece of the required thickness had been completed.

It may be further noted that the terms "billet" and "slab" as used herein to designate the composite body produced as herein described are not strictly limited to bodies intended to be converted to a finished product by reheating, but is intended primarily to indicate shape, as a billet primarily indicates a shape which is thicker and more nearly of square section while slab refers to a product the width of which is much greater than the thickness.

Each term, however, is used in the sense of a semi-finished product intended to be subsequently converted to a finished product by further working, hot or cold.

In addition, or in lieu of, the means herein illustrated for supplying heat to the pieces as they move between the casting unit and the pressure welding unit, torches, inductive heating means, etc. may be located at the bight where pressure rolls engage the layer or layers to supply heat locally to assure adequate pressure welding of the layers, but for clarity of illustration and in view of the small scale of the drawings, they have not been shown.

Typically, each cast layer in a billet or slab will be of the same thickness and this thickness will be in the range of perhaps 2 mm to about 5 mm., but may be thinner or slightly thicker.

It is also well known to metallurgists that, in processes such as this where intercrystalline diffusion takes place, time and temperature are significant variables, so that in some cases it may be desirable to retain the pressure welded product at elevated temperature in the non-oxidising atmosphere to take advantage of these factors before exposing the product to ambient temperature and atmosphere.

Reference is made to co-pending Application No. 7928215 (Serial No.

1577780) divided from the present application. This divisional application relates to a method of converting molten metal into a semi-finished product for subsequent conversion into a finished product comprising the steps of forming a thin strand of metal on a primary casting unit having a moving chill surface on which molten metal from a molten metal source congeals, delivering said thin strand of metal to an assembly unit, folding said thin strand back upon itself a plurality of times in said assembly unit to form a body of predetermined thickness by sequentially placing layers formed by said strand in faceto-face relation with each layer at a temperature where it will pressure weld to the contacting surface of an adjacent such layer, and effecting pressure welding to form a semi-finished product.

WHAT WE CLAIM IS: 1. A method of converting molten metal into a semi-finished product for subsequent conversion into a finished product comprising the steps of forming a thin layer of metal on a primary casting unit having a single moving chill surface on which molten metal from a molten metal source congeals, cutting or severing said layer into sections and delivering said sections of said thin layer of metal to an assembly unit, assembling a plurality of said thin sections of metal in said assembly unit into bodies or predetermined thickness by placing such sections in face-to-face relation with each section at a temperature at which each section will pressure weld to the contacting surface of an adjacent such section, and effecting pressure welding to form a semifinished product.

2. A method according to claim 1 wherein all said sections of metal which are assembled and pressure welded to form a single semi-finished product are formed on a single primary casting unit.

3. A method as claimed in claim I or claim 2 wherein the sections are discharged in succession from the primary casting unit and transported in succession to the assembly unit to be assembled in succession in the formation of each semi-finished product.

4. A method as claimed in any one of claims 1 to 3 further comprising the step of supplying heat to each section between its initial formation and its assembly into a semi-finished product.

5. A method as claimed in any one of claims 1 to 4 in which heat loss from each section is retarded and the metal is retained at a temperature below a melting temperature but at which it will pressure weld to the section against which it will be placed.

6. A method as claimed in claim 5 wherein the thin metal sections are removed

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (48)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   shown, for example, in Figure 13 where an initial pressure is applied in press 170, 171 or 170', 171' and final consolidation is effected in roll stand 140. Also it includes apparatus of the type shown in Figure 13 where a slitting roll, as 62 in Figure 7, could divide the strand lengthwise into two pieces, one of which would be moved over the top of the other, the pieces being initially pressed together in unit 170, 172 to then be discharged onto bed-plate 160 to await the discharge of a second pair the two pairs then being passed through rolls 140.

   Alternatively a pair may first be fused together in press 170, 172 and then moved through rolls 140 to receive a second pair from press 170', 172' and then returned to the first position and thus alternated until a piece of the required thickness had been completed.

   It may be further noted that the terms "billet" and "slab" as used herein to designate the composite body produced as herein described are not strictly limited to bodies intended to be converted to a finished product by reheating, but is intended primarily to indicate shape, as a billet primarily indicates a shape which is thicker and more nearly of square section while slab refers to a product the width of which is much greater than the thickness.

   Each term, however, is used in the sense of a semi-finished product intended to be subsequently converted to a finished product by further working, hot or cold.

   In addition, or in lieu of, the means herein illustrated for supplying heat to the pieces as they move between the casting unit and the pressure welding unit, torches, inductive heating means, etc. may be located at the bight where pressure rolls engage the layer or layers to supply heat locally to assure adequate pressure welding of the layers, but for clarity of illustration and in view of the small scale of the drawings, they have not been shown.

   Typically, each cast layer in a billet or slab will be of the same thickness and this thickness will be in the range of perhaps 2 mm to about 5 mm., but may be thinner or slightly thicker.

   It is also well known to metallurgists that, in processes such as this where intercrystalline diffusion takes place, time and temperature are significant variables, so that in some cases it may be desirable to retain the pressure welded product at elevated temperature in the non-oxidising atmosphere to take advantage of these factors before exposing the product to ambient temperature and atmosphere.

   Reference is made to co-pending Application No. 7928215 (Serial No.

   1577780) divided from the present application. This divisional application relates to a method of converting molten metal into a semi-finished product for subsequent conversion into a finished product comprising the steps of forming a thin strand of metal on a primary casting unit having a moving chill surface on which molten metal from a molten metal source congeals, delivering said thin strand of metal to an assembly unit, folding said thin strand back upon itself a plurality of times in said assembly unit to form a body of predetermined thickness by sequentially placing layers formed by said strand in faceto-face relation with each layer at a temperature where it will pressure weld to the contacting surface of an adjacent such layer, and effecting pressure welding to form a semi-finished product.

   WHAT WE CLAIM IS: 1. A method of converting molten metal into a semi-finished product for subsequent conversion into a finished product comprising the steps of forming a thin layer of metal on a primary casting unit having a single moving chill surface on which molten metal from a molten metal source congeals, cutting or severing said layer into sections and delivering said sections of said thin layer of metal to an assembly unit, assembling a plurality of said thin sections of metal in said assembly unit into bodies or predetermined thickness by placing such sections in face-to-face relation with each section at a temperature at which each section will pressure weld to the contacting surface of an adjacent such section, and effecting pressure welding to form a semifinished product.
2. 2. A method according to claim 1 wherein all said sections of metal which are assembled and pressure welded to form a single semi-finished product are formed on a single primary casting unit.
3. 3. A method as claimed in claim I or claim 2 wherein the sections are discharged in succession from the primary casting unit and transported in succession to the assembly unit to be assembled in succession in the formation of each semi-finished product.
4. 4. A method as claimed in any one of claims 1 to 3 further comprising the step of supplying heat to each section between its initial formation and its assembly into a semi-finished product.
5. 5. A method as claimed in any one of claims 1 to 4 in which heat loss from each section is retarded and the metal is retained at a temperature below a melting temperature but at which it will pressure weld to the section against which it will be placed.
6. 6. A method as claimed in claim 5 wherein the thin metal sections are removed

   from the primary casting unit and transported to the assembly unit where they are stacked for pressure welding and wherein the thin sections are simultaneously inductively heated and are electromagnetically conveyed at least in part during their transport from the casting unit to the assembly unit.
7. 7. A method as claimed in claim 1 in which the thickness of the semi-finished product is selectively increased by additonally supplying sections of metal from a secondary casting unit and assembling said sections with those from the primary casting unit and consolidating the additional sections in the same body with the sections from the primary casting unit in a common pressure welding unit.
8. 8. A method as claimed in claim 1 in which the primary casting unit initially produces a thin, wide, flat continuous strand that is then severed into a plurality of separate sections which are then subsequently assembled.
9. 9. A method as claimed in claim 8 wherein the thin, wide, flat continuous strand is severed transversely of its length into separate sections.
10. 10. A method as claimed in claim 9, in which each section is at least the length of a single layer in the assembly forming the semi-finished product.
11. 11. A method as claimed in claim 8 in which the continuous strand is severed lengthwise into multiple sections which are subsequently layered one upon another to be pressure welded together to form a semifinished product.
12. 12. A method as claimed in claim 11 in which the continuous strand is severed lengthwise and crosswise into multiple sections of predetermined length and width, which are then simultaneously assembled into a unitary body of predetermined length and width, and are then pressure welded to each other to form a semi-finished product.
13. 13. A method as claimed in any one of the preceding claims in which said sections of metal are kept in a non-oxidising atmosphere at least until they have been pressure welded to form a semi-finished product.
14. 14. An apparatus for converting molten metal into a semi-finished product for subsequent conversion into a finished product comprising a primary casting unit comprising a single moving chill surface and means for retaining a pool of molten metal against said chill surface whereby a thin continuous layer of rapidly congealed metal is formed and removed by the chill surface away from the pool, means for removing the thin layer of metal so formed by the chill surface and delivering said layer to an assembly unit and means for cutting or severing said layer, prior to its delivery to said assembly unit, into sections, said assembly unit comprising assembly means for placing a series of said sections in factto-face relation and a common consolidating means for applying pressure to effect pressure welding of said sections into a unitary body and means for removing the bodies so formed after pressure welding has been completed.
15. 15. An apparatus as claimed in claim 14 in which the sections so delivered to the assembly unit comprise a succession of separate pieces of metal.
16. 16. An apparatus as claimed in claim 14 or claim 15 wherein the primary casting unit is a continuously operating unit in which molten metal is continuously solidified into a thin, wide casting.
17. 17. An apparatus as claimed in any one of claims 14, 15 or 16 wherein means is provided for maintaining the layers at a temperature at which pressure welding may be effected by the consolidating means between one such layer and an adjacent such layer.
18. 18. An apparatus as claimed in any one of claims 14 to 17 wherein the casting unit, removing and delivering means and the assembly unit are contained in a common enclosure in which a substantially nonoxidising environment is maintained.
19. 19. An apparatus as claimed in any one of claims 14 to 18 in which the means for cutting or severing the thin, wide continuous casting into sections severs the casting longitudinally into a plurality of strips, and the assembly unit is arranged to stack all of said plurality of strips in layered arrangement in a single operation.
20. 20. An apparatus as claimed in claim 19 wherein the means for cutting or severing the thin, wide casting into sections is arranged to produce strip sections of different width and uniform lengths and the assembly unit is arranged to stack all of the strips of the same width in successive layers to form bodies of a predetermined number of sections, said consolidating means being arranged simultaneously to consolidate the successive layers of the bodies of different widths, common means being provided for simultaneously discharging all of the bodies after they have accumulated a predetermined number of layers.
21. 21. An apparatus as claimed in claim 14 or any claim dependant thereon in which the assembly unit and the consolidating means comprises at least one pressure roll arranged to apply pressure to the layers which are being assembled and the assembly unit comprises a support for the layers which are being assembled, means being provided for effecting relative longitudinal reciprocable travel of said layers on said support relative to the pressure roll.
22. 22. An apparatus as claimed in any one of claims 14 to 21 wherein the primary casting unit comprises a continuously driven chill surface arranged constantly to contact the pool of metal and to remove therefrom a thin layer of metal congealed to its surface as a continuous layer.
23. 23. An apparatus as claimed in claim 22 wherein said cutting or severing means are adapted to divide the cast layer transversely of the direction of its travel into a succession of pieces of uniform length and stacking means is provided to layer said pieces into successive multilayered bodies of predetermined length and thickness, the consolidating means being arranged to pressure weld each piece after the first one to the preceding one as the stacking of the pieces is effected.
24. 24. An apparatus as claimed in claim 23 in which the stacking means comprises a reciprocable bed-plate.
25. 25. An apparatus as claimed in claim 24 in which the reciprocable bed-plate has a heat insulating insert on which the stack is layered.
26. 26. An apparatus as defined in any one of claims 23 to 25 in which the stacking means comprises also means for supplying heat to the successive pieces of metal sufficient to assure that each piece, when stacked and subjected to pressure welding, will be at a temperature below a melting temperature but at which it will pressure weld to the piece against which it will be stacked.
27. 27. An apparatus as claimed in claim 23 in which the stacking means and consolidating means are combined into a single apparatus having opposed platens, one of which is movable toward and away from the other.
28. 28. An apparatus according to any one of claims 14 to 23 wherein the said apparatus is adapted to place all the layers necessary to form a single semi-finished product in said assembly unit, all the layers being derived from said primary casting unit alone.
29. 29. A semi-finished product made by a method according to any one of claims 1 to 13.
30. 30 A method substantially as herein described with reference to Figures 1, 2, 3 and 3A of the accompanying drawings.
31. 31. A method substantially as herein described with reference to Figures 4 and 5 of the accompanying drawings.
32. 32. A method substantially as herein described with reference to Figure 6 of the accompanying drawings.
33. 33. A method substantially as herein described with reference to Figure 7 of the accompanying drawings.
34. 34. A method substantially as herein described with reference to Figures 8 and 9 of the accompanying drawings.
35. 35. A method substantially as herein described with reference to Figure 10 of the accompanying drawings.
36. 36. A method substantially as herein described with reference to Figure 11 of the accompanying drawings.
37. 37. A method substantially as herein described with reference to Figures 12, 13 and 14 of the accompanying drawings.
38. 38. A method substantially as herein described with reference to Figure 15 of the accompanying drawings.
39. 39. A semi-finished product made by a method according to any one of claims 30 to 38.
40. 40. An apparatus substantially as herein described with reference to and as illustrated in Figures 1, 2, 3 and 3A of the accompanying drawings.
41. 41. An apparatus substantially as herein described with reference to and as illustrated in Figures 4 and 5 of the accompanying drawings.
42. 42. An apparatus substantially as herein described with reference to and as illustrated in Figure 6 of the accompanying drawings.
43. 43. An apparatus substantially as herein described with reference to and as illustrated in Figure 7 of the accompanying drawings.
44. 44. An apparatus substantially as herein described with reference to and as illustrated in Figures 8 and 9 of the accompanying drawings.
45. 45. An apparatus substantially as herein described with reference to and as illustrated in Figure 10 of the accompanying drawings.
46. 46. An apparatus substantially as herein described with reference to and as illustrated in Figure 11 of the accompanying drawings.
47. 47. An apparatus substantially as herein described with reference to and as illustrated in Figures 12, 13 and 14 of the accompanying drawings.
48. 48. An apparatus substantially as herein described with reference to and as illustrated in Figure 15 of the accompanying drawings.