GB2225740A

GB2225740A - Continuous casting of alloys containing immiscible components, for manufacture of slide elements for bearings

Info

Publication number: GB2225740A
Application number: GB8926025A
Authority: GB
Inventors: Erich Hodes; Robert Mergen
Original assignee: GLYCO METALL WERKE
Current assignee: GLYCO METALL WERKE
Priority date: 1988-11-19
Filing date: 1989-11-17
Publication date: 1990-06-13
Anticipated expiration: 2009-11-17
Also published as: DE3938234A1; GB2225740B; DE3938234C2; AT398784B; GB8926025D0; ATA264489A

Description

A METHOD AND A DEVICE FOR THE MANUFACTURE OF LAMINAR MATERIAL FOR SLIDE

ELEMENTS The invention relates to a method for the manufacture of a laminar material for slide elements having an overlay which is applied on a backing and is of at least one alloy in the form of a metallurgical twocomponent or multi-component system with a miscibility gap (monotectic). The invention also relates to a device for carrying out the method.

Alloys in the form of metalurgical twocomponent or multi-component systems with a miscibility gap (monotectic) which are also called dispersion alloys, consist in general of metallic - specific weight. The components of very different heavy componen-.s, such as Pb in A!-7b dispers-lon alloys have a strong tendency to segregation, i.e. during solidification of the alloy separate initially, according to the equilibrium diagram, -ion than mixed crystals of a different concentrat during the later stage of cooling so that mixed crystals from the melt are not homogeneous. The manufacture of A1Pb materials for plain bearings i terrestrial conditions using casting techniques is therefore made impossible, e.g. by the miscibility gap existing in the A1Pb system. The fine distribution of lead in an Al-matrix which is needed for use in a plain bearing material, is not achieved.

For the manufacture of functional layers of such dispersion alloys is known, for instance from DE-OS 31 37 745, the manufacture of metal powders by atomization of a melt and its sintering on a backing. The method provides, however, a very non-homogeneous structure so that the results considerably fluctuate 2 - when tested in a machine for the testing of bearings. It was found, in addition, that, due to the inner notch effect, the pores which are still present in the sintered layer cause cracking when the slide element is exposed to alternating loading.

Prom DE-AS 15 08 856 is known a method which requires the-use of continuous casting for aluminium alloys with a high content of lead. According to this method a homogenous one-phase melt of an alluminiumlead alloy containing 20 to 50% of lead is cast onto a backing to directly produce a composite backing material. This method results, " the A1Pb overlay however, in a faulty bond o-IL (functional layer) with steel. Moreoever, in spite of cooling will.-. water, separation takes place already in the mould, i.e. the temperature gradient between the temperature of the homogenous melt and the mould temperature is too small, so that setting of the thermodynamic equilibrium cannot be prevented. The result is an overlay with a homegenous, segregated structure; a tribiologically non- usable sandwich of two layers is produced which has, in addition, the disadvantage of a poor bond with the backing.

From DE-PS 21 30 421 and DE-OS 22 41 628 are known methods for the manufacture of a composite metal strip in which molten aluminium leaves through an opening in the bottom of a melting crucible and molten lead is guided in a thin thread-like stream through the molten aluminium also in an opening in the bottom of the melting crucible. The melt mixture of eg aluminium and lead, which is formed in the opening in the bottom of the melting crucible, is then by gas jets vibrated and mixed and blown onto the upper surface of a substrate which travels along. A functional layer produced in this way is not very non-homogenous while the lead particles have, due to their much greater density, the tendency to strongly segregate and coagulate during the flow of the agitated stream of melt mixture onto the surface of the substrate.

In a method known from DE-AS 22 63 268 a melt mixture of lead and aluminium is by means of a rotor made as a syphon laterally spun off in the form of fine particles, and segregated on an impact wall where the material solidifies in the form of scales (splat cooling). However, due to its scale-shaped (leaf-shaped) structure this material can be processed to a material capable of coating neither by extrusion nor by powder roiling. During the US4 production of form-pieces _nS pressure antemperature (by means of isostatic presses) segregation takes place which results in extensive non- homogenity and consequently unusability of AlPb bearings manufactured by this method.

In DE-CS 17 75 322 is described a plain bearing or material for its manufacture which consists of Al-alloys (eg dispersion alloys based on AlPb or AlSn) in which the Al material, which is later plated on steel serving as backing, is manufactured by a powder rolling method. The Al bearing material made in this way, has due to the compaction by the powder rolling and the following rolling and plating operation a line arrangement of the soft minority phase (eg Pb). However, such a line structure has for plain bearing exposed to alternating loading the considerable disadvantage that permanent cracks are formed in the lines due to inner notch effect.

In PCT WO 87/04377 is described a method by means of which a 1-5 mm thick AlPb strip is made - 4 which is then plated onto steel serving as a backing material. The fine lead distribution described in that specification is, however, not obtained in practice because by the rolling plating the lead is distributed in lines and is no longer in globular form even during subsequent heat treatment. It was found, in addition, that segregation takes place in strips which are thicker than 0.5mm.

This disadvantage is avoided by DE-PS 37 30 862.9-16 in that, while using a melt spin method similar to that described in WO 87/04377, claims an AlPb foil which is at the most 0.5 mm thick and has a very fine globular distribution o-L lead which is applied, while avoiding rolling operations, by ultrasound welding, soldering or gluing onto a backing.

It was found, however, that the ultrasound welding is an expensive and by no means reliable method of connection, while soldering and gluing are not suitable for the manufacture of semifinished material for the production of plain bearings by the strip method.

The aim of the invention is therefore to provide a method and a device for the manufacture of a laminar material for slide elements having an overlay which is applied onto a backing and is composed of at least one alloy in the form of a metallurgical two-component or multi-component system with a miscibility gap (monotectic), while a globular fine distribution of the dispersed metal components (the minority phase) in a quasi-amorphous metallic matrix should be obtained in the overlay.

This aim is achieved by a method having the features claimed in claim 1, or by the device having the features claimed in claim 22. Preferred t embodiments are the subject of dependent claims. Such a laminar material is obtained by a method in which the overlay is continuously cast from the alloy and immediately after casting is subjected in a continuous run to a cooling with a sufficiently high solidifcation rate to restrict growth of particles of the immiscible metallurgical components to dimensions not exceeding 1 p, preferably in the range of 0.01 to 1 lim. A uniform globular distribution of the dispersed metal component (minority phase) in the matrix of the melt is frozen by the high cooling rate. Segregation, which appears in alloys of this kind is reduced to a minimum.

A laminar material is produced in this way, the overlay (functional layer) of which has much improved properties due to the quasi-amorphous state of the material of its matrix and due to the substantially uniform globular distribution of the minority phase. The strength of the functional layer is thus considerably increased. In spite of the extremely high strength, also the ductility and toughness of the functional layer are improved.

The alloy or alloys are preferably made in a melt-metallurgical. way and are kept during that period, and also during their holding in readiness for casting at a temperature above the segregation temperature corresponding to the system and to the composition.

A particularly advantageous possibility of achieving within the framework of the invention a fine globular and, as far as possible, uniform distribution of the minority phase in the matrix consists in that nucleants adapted to the relevant alloy type, P, B, Ti, Si, borides, nitrides and/or oxides are added to the alloy or alloys to be cast in 1 6 an amount between 0.1 and 3.5% by weight. It is possible to achieve in this way that very quickly a large number of finest particles of the minority phase are formed which prevent each other from growing so that even with the high cooling rate achievable in practice a very fine globular distribution of the matrix which solidifies during cooling is achieved. In a method according to the invention systems with lead as a minority phase can be processed, for instance Al.Db, FePb, CuPb, MnPb, NiPb and possibly also CrPb and CoPb. In addition also similar systems with tin, bismuth or antimony as a minority phase, such as Al9n, AlBi, AlSb, CrSn. Also PbZn may be use,"'. The invention offers two basic possibil 'L " 4- El S:

(a) The dispersion alloy is cast in the form of a thin layer or a film onto a substrate - conti 7erably is cast forming a backing, preff -nuously -rate. The above mentioned onto a strip -sha-ped subst provisions according to the invention are used during fast cooling in order to this casting and subsequent 7 the minority achieve a fine globular distribution o-L phase in the metal matrix. The overlay can be cast in one or several stages. In multi-stage casting, initially the first thin film is cast and immediately afterwards quickly and effectively cooled. After the first cast film a second film solidification oL is cast thereon which is also caused to quickly solidify. The building-up of such an overlay can be performed in several stages. The individual cast films can have a different thickness. Also the composition of the alloy of the films can be different. By using different alloys and/or different cooling conditions it is possible to form within the overlay thin layers of different structure.

(b) Another possibility for the forming of an overlay is to first cast the overlay in the form of a strip or of a foil independently of the backing and to apply it after cooling by a method of joining, eg with the help of a laser beam, continuously onto the backing.

The method according to the invention can also be used without modifications for the mnaufacture of plain bearings composed of three materials. This may be achieved with both the basic working possibilities in that the overlay is cast directly onto a travelling strip. If the overlay is intended to be cast independently of the backing and subsequently attached thereto, a pre-coated strip can for also be used in this case as a backing inat the cast overlay foil.

In a method according to the invention such strips can have a steel backing and an intermediate layer consisting of the following alloys:

- copper-lead alloys, eg Pb 9 to 25%, Sn 1 - 11%, Fe, Ni, Mn smaller than/equal to 0.7%, the rest being Cu; - copper-aluminium alloys, eg Al 5 to 8%, the rest being Cu; - aluminium-tin alloys, eg Cu 0.5 to 1.5%, Sn 5 to 23%, Ni 0.5 to 1.5%, the rest being Al; - aluminium-nickel alloys, eg Ni 1 to 5%, Mn 0.5 to 2%, Cu smaller than/equal to 1%, the rest being Al; - aluminium-zinc alloys, eg Zn 4 to 6%, Si 0.5 to 3%, Cu up to 2%, Mg up to 1%, the rest being Al.

It has been found that a laminar material of steel/intermediate layer with a cast-on or by other joining method attached functional layer may be produced in this way reliably and continuously, preferably with the desired thickness of the functional layer.

In order to increase the strength of the matrix materials and wear resistance, also other elements may be added to the melts. It has been found that approximately I to 4% by weight of Si, 0.2 to 1% by weight of Mg and 0.1 to 1.5% by weight of Co may be added to an AlPb dispersion alloy to obtain a wear resistant functional layer. In order to improve the corrosion resistance of the minority phase lead, it is recommended to further add 0.5 to 3% by weight of tin. To alloys based on copper, such as CuPb22, are usually added 0.5 to 2% by weight of Sn and 0.2 to 19 by weight of Fe.

In order to improve the bonding strength between the overlay and the intermediate layer a bonding layer or a diffusion barrier is provided between the overlay and the intermediate layer, eg of Ni, Zn, Fe, Co (particularly with alloys based on copper), and also NiSn, CuZn, Co, CuSn (particularly for aluminium alloys). I A device is preferably used for carrying out the method, which is provided with a crucible for the melting and/or holding in readiness for casting of an alloy in the form of a metal twocomponent or multi- component system with a miscibility gap, with casting means situated downstream of the crucible and serving for the casting of a strip from the alloy, and further with means for the receiving of the cast strip and for its guiding from the point of casting, and also with cooling means for the cast alloy strip which has left the casting point. According to the invention, the casting means should be made for the formation of a film-shaped or foil-shaped thin strip either independently of, or cast onto, a substrate, and the 1 9 - cooling means should have a forced-cooled receiving surface for the cast foil or a forced-cooled support surface for the substrate to receive the cast material, and also very effective cooling units directed onto the free surface of the cast foil or of the cast film.

In particularly advantageous embodiments the device has strongly forcedcooled rollers, particularly a strongly forced-cooled roller for receiving the cast foil, or carrier for the substrate receiving the casting. In another embodiment of a device according to the invention a flat guiding or transport path may be provided, which may be cooled. Transversely to this guiding or transport path is 4 arranged a casting flow dev.ce for the melted alloy, -he guiding path or above the distance of which above IV 4 a substrate positioned on the guidlng path, may be adjustable. An overlay composed of several layers may be particularly advantageously cast onto a substrate with such a casting flow device. For this purpose several casting flow devices spaced apart in the direction of transport are arranged, and between these casting flow devices and behind the last one of these devices are provided cooling units acting on the free surface of the cast film or on the free surface of the cast foil.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

Figure I is a much enlarged partial section of a laminar material comprising a cast-on overlay of a dispersion alloy; Figure 2 is a much enlarged partial section of a laminar material according to another embodiment; Figure 3 is a diagrammatic representation of a first embodiment of a manufacturing device; Figure 4 is a diagrammatic representation of a second embodiment of a manufacturing device; Figure 5 is a diagrammatic representation for a third embodiment of a manufacturing device; Figure 6 is a diagrammatic representation of a fourth embodiment of a manufacturing device; Figure 7 is a diagrammatic representation of a fifth embodiment of a manufacturing device, and Figure 8 is a much enlarged partial section of a laminar material which was made in a device according to Figure 7 and has a welded-on overlay of a dispersion alloy.

Figure 1 shows a much enlarged partial section of a laminar material 10 comprising cast-on overlay 13 of a dispersion alloy A1Pb8Si4SnCu, an intermediate layer 12 of AlZn5SiCuPbMg and backing 11 of steel. The overlay (functional layer) 13 contains a quasi-amorphous aluminium matrix in which are g16bular finely distributed lead particles of which only the largest lead particles 14 are visible in the representation in Figure 1, the dimensions of which are of the order of 10-2 ym. A large number of the lead particles are smaller and not visible in the enlargement chosen for Figure 1. The large number of lead particles is caused, among others, in that a nucleant, adapted to the alloy type, was added to the dispersion alloy, eg P, B, Ti, Si, boride, nitride or oxide in the amount of, for instance, 2% by weight. In this way a very large number of very fine lead particles was produced in the dispersion alloy, which, however, have during casting and cooling of the overlay 13 hindered each other from growth, so that by fast cooling or 1 4 chilling with a cooling rate of the order of 102 to 106 K/s. The large number of lead particles which were kept so small that their dimensions were below 10-2 pm. The segregation of the lead particles could be strongly reduced both in the case of large lead particles 14 and also invisible small lead particles by very fast cooling or chilling of the cast-on overlay 13. Crystallisation of alluminium, hitherto typical for alluminium, was considerably reduced in the alluminium matrix of the overlay 13 by the influence of crystallisation inhibitors (glass formers) for which, for instance Si, B, P, Fe, Co or Ti can be used either individually or in a mixture in a proportion of 0.2 to 256 by weight, and by a very fast cooling of the cast-on overlay 13.

The intermediate layer 12 shows, in contrast to the overlay 13, a typical structure for cast-on alluminium alloys.

The embodiment shown in Figure 2 is a laminar material 10 with a backing 11 of steel and an overlay 13 as a functional layer of aluminium/lead dispersion alloy AM10Si7SnCu, ie with a lead content of 10% by weight and a content of silicon of 76 by weight which in this case acts both as a nucleant for the minority phase lead and also as a crystallisation inhibitor in aluminium. As is apparent from Figure 2 in the quasiamorphous aluminium matrix of the functional layer 13 are present dispersed lead particles 15 in globular fine distribution while again only the larger lead particles with dimensions of about 10-2 ym are visible. The silicon is mostly dissolved in the quasi-amorphous aluminium matrix as a glass former and in a smaller part taken over into the minority 3.5 phase lead as a nucleant. Tin is taken into the lead substantially for protection against corrosion.

The intermediate layer 16 consists in this embodiment of a dispersion alloy CuPb22Sn and has in the illustrated example a distribution of the lead particles 17 typical for this dispersion alloy.

One embodiment of a device for carrying out the method for the manufacture of the above described. laminar material having an overlay 13 of alloys with a miscibility gap is shown in Figures 3 and 4 in two variants.

The alloy or dispersion alloy is melted and put into a crucible 21 which has at its lower end an outlet 22 for a fine stream 23 of the melt. As indicated by the arrow 24, gas under pressure is forced into the crucible 21 from above, this gas being of a type which is inert towards the melt and which dissolves in the melt as little as possible. The crucible 21 is in the illustrated example surrounded by an induction coil 25 by means of which the melt is kept at a predetermined temperature at which it is sufficiently liquid, so that it can be pressed through the outlet 22 and form a thin stream 23. For the processing of a dispersion alloy the crucible 21 can be additionally provided with agitators or vibrators which permanently intensively mix the melt mixture of the dispersion alloy and keep the components of the mixture in fine distribution. These mixers or vibrators were, for the sake of simplicity, not illustrated in Figures 3 and 4.

The backing 11 is in the form of a metal strip 40 unwound from a reel and guided on a strongly forced-cooled cylinder 26. Before the metal strip 40 reaches the cylinder 26, it passes through a device 41 for the cleaning and de-oxidisation of its surface, for instance a brushing device, to ensure that the surface of the metal strip 40 to be coated is free from oxides. For further preparation for the casting-on the metal strip 40 passes through a tempering device 43 to ensure immediate bonding of the cast-on alloy with the surface of the metal strip 40. In order to keep this set state up to the casting-on, the metal strip 40 is guided up to the outlet 22 of the crucible 21 in a protective gas, as is indicated by a cover 42 delimiting the protective gas atmosphere. In the illustrated example, also the casting itself and the the subsequent cooling take place within this cover 42.

The thin strip-shaped or planar stream 23 of a molten alloy or molten mixture of a dispersion alloy pressed downwards from the crucible 21 meet, in the embodiment shown in Figure 3, the surface of the metal strip 40 at an accute angle. The angle 4 is so chosen that the stream 23 is distributed on the surface of the metal strip 40 immediately in the form a thin film 20 without splashing. The cooling is provided first by the cylinder 26. In order to intensively cool also the free coated surface of the laminar material 10, it is arranged in the embodiment according to Figure 3 that jets 28 of cool gas or cool liquid from a nozzle arrangement 27 are directed onto the layer 20. The laminar material 10 is separated from the cylinder 26 by a strip remover 29.

The cooling rate of the layer 20 on the cooled cylinder 26 obtained by the cooling jets 28 is from above 102 K/S up to about 10 K/s. Correspondingly a true alloy which forms the film 20 is kept in a quasi- amorphous state, particularly when a crystallisation inhibitor (glass former), has been added to the alloy. If a dispersion alloy with a miscibility.gap of its components is processed, a film 20 results in which the component of the dispersion alloy forming the matrix is in a quasiamorphous state, while the component (minority phase) dispersed in this matrix is globular and finely distributed in the-matrix.

In a method according to Figure 4 the melt mixture of a dispersion alloy is put into a crucible 21 in which it is put under pressure by a gaseous medium as shown by the arrow 24. From the outlet 22 at the lower end of the crucible 21 flows the melt or a melt mixture in a stream 23 into a gap 30 between the metal strip 40 guided over a roller 31 and an opposite roller 32. Both the rollers 31 and' 32 are strongly forced-cooled. The width of the gap 30 between the rollers is adjusted according to the desired thickness of the layer 20 to be produced. As is apparent from Figure 4, the melt or melt mixture is slightly accumulated upstream of the gap 30 without any delay worth mentioning being caused at this point in the transfer of the melt or melt mixture from the outlet 22 of the crucible 21 into the gap 30. The two rollers 31 and 32 therefore do not exert any pressure worth mentioning onto the laminar material being formed, but have only a certain polishing affect on the surface of the created layer 20. This small accumulation of material at the gap results in a distribution of the melt or of the melt mixture in the axial direction of the rollers 31 and 32, so that even strips may be produced the width of which is greater than that in the embodiment according to Figure 3. In order to make the axial distribution of the melt or melt mixture along the gap 30 easier, the crucible 21 is inclined at an angle e so that the melt or melt mixture, onto which pressure acts in the crucible 21, may be injected directly into the gap 30.

The surface of the roller 32 is so made that practically no bonding with the melted alloy or one of the components of a dispersion alloy to be processed takes place. In order to keep the film 20, formed in the gap 30t on the surface of the metal - strip 40, the upper roller 32 is provided with a strip remover 33. In order to cool the free surface of the film 20 formed at the outlet of the gap 30, a cooling nozzle 34 is provided which directs a jet of -let of the cold gaseous or liquid medium onto the out gap 30.

The metal strip 40 is further coo,-ed by the colling roller 31 in order to cause additional cooling of the film 20 by the metal strip 40, or to avoid warming up of the film 20 by the metal strip 40.

Opposite to the cooling roller 31 is situated a third cooling roller 35 which is strongly forced-cooled to further cool the film 20 at its surface chilled by the roller 32 and the jet of a coolant emerging from the nozzle 34. Downstream of the third cooling roller 35 is provided a fourth cooling roller 36 which takes from the roller 31 the metal strip with the film 20. To achieve effective bearing of the film 20 onto the surface of the fourth cooling roller 36, a deflection roller 38, which is also cooled, is situated opposite the fourth cooling roller 36. The strip of laminar material 10 is removed from the fourth cooling roller 36 by a strip remover 39. As is apparent from Figure 4 a second cooling nozzle 34' is situated between the cooling rollers 35 and 36 and a third cooling nozzle 34'' is situated between the rollers 31 and 38. In contrast to the method according to Figure 3 a further intensification of the cooling process takes place in the embodiment according to Figure 4, so that the film 20, which changes into the overlay 13, is subjected to cooling rays of the order of between 103 Kls to 106 K/s. This enables the manufacture of layers 20 of greater thickness, for instance 0.5 mm, which may be so intensively chilled in their whole thickness that the amorphous state of the metallic material freezes during the cooling. The method according to Figure 4 finally enables the manufacture of wider strips, particularly when several crucibles 21 are arranged next to each other a-long the gap 30.

A strip of laminar material 10, produced by the method according to Figure 3 or Figure 4, is then wound onto a reel (not shown).

If a laminar material 10 with an intermediate layer 12 or 16 is to be produced, a metal strip 40 in the form of a laminate is supplied to the device according to Figure 3 or Figure 4 which has already been provided on the side to be coated with the metal of the intermediate layer.

In th e embodiments illustrated in Figures 5 and 6 the metal strip 40, representing the cast-on substrate, moves continuously at a speed v in the transport direction 44 indicated by an arrow on a guide and transport path 45, which may be forcedcooled. Above, and spaced from, the guide and transport path 45 is situated a casting flow device 46 which belongs to a casting device. The distance of the casting flow device 46 from the guide and transport path 45 is so adjusted that between the lower surface of the casting flow device 46, which 1 extends substantially parallel to the guide and transport path 45, and the upper surface of the metal strip 40, which is situated on the guide and transport path 45, corresponds to a preselected distance d which is such that the alloy melt is substantially prevented from outflowing due to its surface tension in the gap formed in this way as is apparent in the left-hand part of Figure 5. On the side were the metal strip 40 moves away from the casting flow device 46 a film 20 is formed by the adhesion of the alloy melt on the surface of the metal strip 40. The thicknessS of the film 20 is smaller than the distance d of the lower surface of the cas t4 Lng flow device 46 from the surface of the metal strip 40, but is reproduceable and calculable on the basis of the distance d, of the transport speed v of t1le metal strip 40, of a pressure which might be exerted on the melt, and of the volume flow rate of the melt which is influenced thereby, and also by the dimensions 11 and 12 of the casting flow device 46.

The film formed on the metal strip 4 on leaving the casting flow device 46 is very quickly cooled on the one hand by the cooled metal strip 40 and on the other hand by a cooling unit which may be directed onto the free surface of the film 20, for instance gas jets or liquid jets: the cooling rate may be for instance 102 to 104 K/s.

As is shown in Figure 6 the casting device provided with the casting flow device 46 is particularly suitable for multi-stage building-up of the overaly of two (or more) films 20a, 20b cast successively onto the substrate. The two-stage (or multi-stage) building-up of the overlay hasthe advantage that the very thin alloy films 20a, 20b could be correspondingly quickly cooled so that cooling grades of the order of 103 to 105 K/s may be achieved. Between the successive casting flow devices 46 and after the last one of these devices 46 may be provided cooling units which are always directed onto the free surface of the alloy film 20a, 20b which has just been freshly formed, this unit - being for instance in the form of nozzle arrangements 27 producing jets 28 of a coolant. In the embodiments shown in Figures 5 and 6 the casting flow device 46 extends transversely across the guide and transport path 45, substantially at right angles to the direction of transport 44. However, it is also possible to arrange the casting flow device or the casting flow devices inclined at an angle above the guide and transport path 45.

The arrangement in the embodiment according to Figure 6 is such that the films, formed for the coating of the substrate or metal strip 40, are of the same alloy and have the same thickness. One can, of course, expect a certain difference in the structure of the partial layers of the overlay, formed from the films 20a, 20b, because the lower partial layer is at least partly reheated by the casting-on of the second film 20b.

The devices in the embodiments shown in Figures 5 and 6 offer particularly advantageous possibilities of regulation. The defined thickness of the liquid film may be adjusted by regulation of the displacement speed of the solid metallic substrate. Also the cooling rate of the cast-on layer may be adjusted by the regulation of the displacement speed of the solid metallic substrate. The adjustment of the defined thickness of the liquid film can also be achieved by the change of geometry of the outlet of the alloy either by a change of the distance d between the lower surface of the casting flow device 46 and the upper surface of the metal strip 40 and also by the change of dimensions of the casting flow device. By the adjustment of the distance d between the lower side of the casting flow device 46 and the upper surface of the metal strip 40 can also be influenced and adjusted the cooling rate of the cast-on layer or of the cast-on film 20.

In Figure 7 is illustrated an embodiment in which first a foil 47, forming the overlay, is produced independently of the substrate or metal strip 40 and at"ter its cooling and solidification is joined by means of laser beams with the metal strip 40. In this device the alloy or the dispersion alloy are brought in molten state into a crucible 21 which has, at its lower end, an outlet 22 for a stream 23 of the melt. This melt stream 23 arrives directly onto the surface of a strongly forced-cooled cylinder 26 and forms there a foil 47 which is rapidly cooled by the cylinder 26 and brought below a nozzle arrangement 27 by which jets 28 of cold gas or cold liquid are directed onto the free surface of the foil 47. The thickness of the foil 47 may be determined by the rotational frequency of the cylinder 26 and by the expelling pressure built up inside the crucible 21 by an inert gas, as indicated by the arrow 24. The casting of the dispersion alloy or alloys onto the surface of the cylinder 26 takes place at an angle J which is so chosen that no parts of the melt splash when they come into contact with the surface of the cylinder 26. The surface of the cylinder 26 is so made that no bond is formed between the cast-on melt and the surface of the cylinder, but only intensive heat transfer is achieved.

The cooling rate of the foil 47 on the forced-cooled cylinder 26 and the additional cooling by the jets 28 from the opposite side is in the range of about 106 K/s and about 108 K/s up to about 109 K/s. Consequently, a true alloy, which forms the foil 47, is kept substantially in an amorphous state. If a dispersion alloy, the components of which have a miscibility gap, is used in the indicated manner to form a foil 47 a matrix is produced in this foil 47 in a substantially amorphous state while the component dispersed in this matrix is globular and exceptionally finely distributed. Foil 47 produced in this manner is transferred on a strongly forced-cooled roller 32. The foil 47 is separated from the roller 32 by a strip remover 33. Opposite to the roller 32 is situated an extensively forced-cooled roller 31 so that a gap 30 is formed into which are brought the foil 47 and a strip-shaped substrate bearing onto the roller 31, eg a metal strip 40. Into this gap 40 is directed a bundle 48 of laser beams at an angle cf. in such a way that the meeting surfaces of the foil 47 and of the metal strip 40 are heated. By light pressing together, without any significant reduction of thickness, the foil 47 and metal strip 40 are welded together along the heated surfaces. The strips joined in this way are further cooled between the roller 31 and a third cooling roller 35 situated opposite to the latter and are transferred to a fourth cooling roller 36. Opposite to the fourth cooling roller 36 is situated a deflection roller 38 which is also cooled. The strip 10 of laminar material is then separated from the cooling roller 36 by a strip remover 39. This device has also three cooling nozzles 34, 34'34'' arranged in a manner similar to that described in connection with Figure 4.

In contrast to the method described in connction with Figures 3 and 4 and also that described in connection with Figures 5 and 6 a certain warming of the surfaces welded together necessarily takes place. As a consequence some structure changes must be expected on the surfaces welded together as is apparent from Figure 8. Figure 8 shows the composition of the laminar material 10 which corresponds substantially to that shown in Figure 1 in that the laminar material is composed of a backing 11 of steel, an intermediate layer 12 of AlZn5SiCuPbMg and an overlay 13 of a dispersion alloy A1Pb8Si4SnCu. In contrast Uc the laminar material according to Figure 1, the laminar material shown in Figure 8 exhibits some coarsening in the structure of the intermediate layer 12 on the junction surface 49 with the overlay 13. In the overlay 13, namely in the region of the welded-on junction surface 49 with the intermediate layer 12, were formed somewhat larger lead particles 14 due to the heating needed for the welding. This coarsening of the structure and formation of somewhat larger lead particles 14 are quite acceptable in view of the fact that the overlay 13 is made as a foil and consequently enables much faster cooling of the foil forming the overlay 13 so that in the overlay 13 proper the aluminium matrix has much stronger amorphous properties than in the embodiment according to Figure 1. This difference is not visible in the magnification chosen for Figure 8.

22 -

Claims

CLAIMS,

A method for the manufacture of a laminar material for slide elements having an overlay which is applied onto a backing and is composed of at least one alloy in the form of a metallurgical two component or multi-component system with a miscibility gap (monotectic), in which the overlay is continuously cast from the alloy and immediately after casting is subjected in a continuous run to a cooling with a sufficiently high solidification rate to restrict growth of particles of the immiscible metallurgical components such that the particle dimensions are not greater than 1 lim.
2. A method according to Claim 1 wherein the particle dimensions are in the range of 0.01 to 1 m.
3. A method according to Claim 1 or 2 wherein the alloy or alloys are made in a melt-metallurgical way and are kept during that period and also during their holding in readiness for casting at a temperature above the segregation temperature corresponding to the system and to the composition.
4. A method according to any one of Claims 1 to 3 wherein nucleants adapted to the relevant alloy type, P, B, Ti, Si, borides, nitrides and oxides, individually or in combination, are added to the alloy or alloys to be cast in an amount between 0.1 and 3.5% by weight.
5. A method according to any one of Claims 1 to 4 wherein the setting of the desired thickness of the cast alloy layer is achieved by the metering of the stream of molten alloy issuing from a crucible
6. A method according to any one of Claims 1 to 5 wherein the cooling rate of the cast alloy layer is set by the metering of the stream of molten alloy issuing from a crucible.

t 1 1
7. A method according to any one of Claims 1 to 6 wherein a setting of the desired thickness of the cast alloy layer is achieved by the regulation of the speed of removal of the cast layer from the point of casting.
8. A method according to any one of Claims 1 to 7 wherein the following alloys with a miscibility gap are cast; AlPb, FePb, CuPb, MnPb, or NiPb, while the content of lead is greater than the eutectic composition affected by the system, and is up to 40% by mass.
9. A method according to any one of Claims 1 to 8 wherein the overlay is cast in the form of a strip independently of the backing and is, after cooling, by a joining method continuously applied onto the backing.
10. A method according to Claim 9 wherein laser beams are used in the joining method.
11. A method according to any one of Claims I to 10 wherein the alloy or alloys in the form of a metallurgical two-component or multi-component system is or are continuously cast as a liquid film with a defined layer thickness in one or more consecutive stages onto a solid metallic substrate forming the backing, and is or are immediately afterwards cooled at a high solidification rate together with the sub strate while being joined to the substrate.
12. A method according to Claim 11 wherein the substrate is strip-shaped.
13. A method according to Claim 11 or 12 wherein the defined thickness of the liquid film is set by regulation of the speed of advance of the solid, metallic substrate.
14. A method according to Claim 13 wherein the rate of cooling of the cast layer is set by regulation of the speed of advance of the solid, metallic substrate
15. A method according to any one of Claims 11 to 13 wherein th.e setting of the defined thickness of the liquid film is achieved by the change of geometry of the outflow point of the alloy.
16. A method according to any one of Claims 11 to 13 wherein the setting of the defined thickness of the liquid film is achieved by the setting of the distance between the outflow point of the alloy and the surface of the solid metallic substrate.
17. A method according to Claim 13 wherein the rate of cooling of the cast layer is controlled by the setting of the distance between the outflow point of the alloy and the surface of the substrate.
18. A method according to any one of Claims 13 to 17 wherein a total layer is built-up oil several discrete layers by repeated consecutive casting and intermediate cooling of the substrate.
19. A method according to Claim 18 wherein the total layer is built-up of individual layers of different thickness.
20. A method according to Claim 18 or 19 wherein the individual layers are cast of alloys of different composition.
21. A method according to any one of Claims 18 to 20 wherein the individual layers are caused to have different microstructure by varying the composition of the alloy and/or by varying the cooling conditions.
22. A method according to any one of Claims IS to 21 wherein before the casting the substrate is brought to a temperature chosen according to cooling parameters and according to adhesion formation.
23. A method according to any one of Claims 13 A to 22 wherein a strip is used for the substrate strip to be cast on, on which is, before the casting-on of the overlay, applied an intermediate layer having good sliding properties.
24. A method according to Claim 23 wherein the intermediate layer is made from the following alloys:

- copper-lead alloys, eg Pb 9 to 25%, Sn 1 to 11%, Fe, Ni, Mn smaller than/equal to 0.7%, the rest being Cu; - copper-aluminium alloys, eg Al 5 to 86, the rest being Cu; - aluminium-tin alloys, eg Cu 0.5 to 1.5%, Sn 5 to 23%y Ni 0.5 to 1.56, the rest being Al; - aluminium-nickel alloys, eg Ni 1 to 5%, Mn 0.5 to 2%, Cu smaller than/equal to 1%, the rest being Al; - aluminium-zinc alloys, eg Zn 4 to 6%, Si 0.5 to 3%, Cu up to 276, Mg up tp 16, the rest being Al.
25. A device for carrying out the method according to Claim 1 Provided with a crucible for the melting and/or holding in readiness for the casting of an alloy in the form of a metallurgical two component or multi-component system with a miscibility gap, with casting means situated downstream of the crucible and serving for the casting of a strip from the alloy, and with means for receiving the cast strip and for its guiding from the point of casting, and with cooling means for the cast alloy strip leaving the point of casting, wherein the casting means is made to form a film-shaped or foil shaped thin strip which is made either free of a substrate or is associated therewith, and the cooling means have a forced-cooled receiving surface for the cast foil or a forced-cooled support surface for the substrate to be cast-on, and also very effective i cooling units directed onto the free surface of cast foil or of the cast film.
26. A device according to Claim 25 wherein the casting means is an outlet from the crucible and a casting flow device, the forced-cooled receiving surface is a cylinder, the forced-cooled support surface is a cylinder, a roller and a guide and transport path, and the cooling units are a nozzle arrangement and cooling rollers.
27. A device according to Claim 25 or 26 wherein a cooled roller is arranged below the casting foil or carrier for means as a receiver for the cast the substrate to be cast on and is rotated at a rotational frequency corresponding to the desired speed of movement of the foil or film from the casting point.
28. A device according to Claim 27 wherein the rotational frequency of the roller is adjustable.
29. A device according to any one of Claims 25 to 28 wherein a nozzle arrangement for coolant is arranged in the region of the receiving surface for the foil or supporting surface for the substrate in the direction of transport downstream of the casting point.
30. A device according to any one of Claims 25 to 29 wherein a cooling roller is situated downstream of the casting point, the roller engaging the free surface of the foil or film and being positioned opposite to a receiving surface or a supporting surface.
31. A device according to any one of Claims 28 to 30 comprising a plurality of forced-cooled cooling rollers for transporting the foil or the cast-on substrate, the rollers being situated downstream of the casting point.

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32. A device according to Claim 31 comprising cooling nozzles directed onto the foil or the cast-on substrate, the nozzles being situated between the cooling rollers which are arranged one after another in the direction of transport.
33. A device according to Claim 25 wherein a strongly forced-cooled guide and transport path, which serves as a receiver for the cast foil or as a carrier for the cast-on substrate, is arranged below the casting means, the path being driven at an advance speed corresponding to the speed of movement of the foil or film from the casting point, the casting means including a cast flow device which extends transversely over the path and below which -ated on the path moves the path or the substrate situt V at a predetermined distance and speed.
34. A device according to Claim 33 wherein the distance and sneed of the path are adjustable.
35. A device according to Claim 33 or 34 comprising two or more casting flow devices arranged with a predetermined mutual spacing next to each other in the direction of transport of the guide and transport path 16.
A device according to Claim 35 wherein between adjacent casting flow devices and downstream of the last casting flow device are arranged cooling units acting on the free surface of the cast foil or film.
37. A device according to Claim 36 wherein the cooling units are cooling nozzles.
38. A device according to Claim 25 wherein the casting means is designed to form from the alloy a thin foil, and joining arrangement is situated downstream of the casting point and of a first cooling device, the joining arrangement serving for f 1 continuous firm joining together of the previously cooled alloy foil and of the substrate strip which are brought together in a joining gap into which the foil is guided over a first forced-cooled roller and the substrate strip over a second forced cooled roller.
39. A device.according to Claim 38 wherein the joining arrangement is means producing a bundle of laser beams directed into the said joining gap.
40. A device according to any one of Claims 25 to 39 wherein the delivery of the molten alloy to the casting point and the metering of its amount are performed by the controlled pressure of a protective gas which acts onto the surface of the melted alloy situated in the crucible.
41. A device according to any one of Claims 25 to 40 wherein the casting point is provided with means for supplying protective gas to and keeping it at the casting point.
42. A device according to any one of Claims 25 to 40 wherein those regions of the device where the casting and cooling of the alloy foil or alloy film are carried out are provided with means for supplying protective gas to and keeping it in these regions.
43. A method according to Claim 1 substantially as herein described with reference to the accompanying drawings.
44. A device according to Claim 25 constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, the accompanying drawings.

INiPRislmd 1990 atThe Patent Office, State House, 66r7l High Holborn. London WCIR 4TP Further copies maybe obtained from The Patent Office.

9-1Branch, St Mary Cray. Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray. Kent. Con. 1187 1