EP1704948B1 - Wear resistant pipe of tubular shape and casting process for manufacture thereof - Google Patents

Wear resistant pipe of tubular shape and casting process for manufacture thereof Download PDF

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Publication number
EP1704948B1
EP1704948B1 EP06111618A EP06111618A EP1704948B1 EP 1704948 B1 EP1704948 B1 EP 1704948B1 EP 06111618 A EP06111618 A EP 06111618A EP 06111618 A EP06111618 A EP 06111618A EP 1704948 B1 EP1704948 B1 EP 1704948B1
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EP
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Prior art keywords
wall
casting
metal
less
wearing part
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EP06111618A
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German (de)
French (fr)
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EP1704948A1 (en
Inventor
Christian Novagraaf Technologies Carbonnier
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Nouvelle Des Fonderies De Treveray Ste
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Nouvelle Des Fonderies De Treveray Ste
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D19/00—Casting in, on, or around objects which form part of the product
    • B22D19/16—Casting in, on, or around objects which form part of the product for making compound objects cast of two or more different metals, e.g. for making rolls for rolling mills
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D19/00—Casting in, on, or around objects which form part of the product
    • B22D19/08—Casting in, on, or around objects which form part of the product for building-up linings or coverings, e.g. of anti-frictional metal

Definitions

  • the present invention relates to a generally tubular metal wear part, the inner surface of which has a high abrasion resistance, and to a process for the casting of such a wear part.
  • a wear part can be in particular a pipe element in a transport facility of loaded and abrasive fluids, such as for example the pipes for transporting materials in underwater dredging operations.
  • the invention is particularly directed to pipe elements such as elbows, T-joints or Y, etc. It can also be applied to the production of other parts, such as, for example, pump bodies or other elements that may be subject to strong internal abrasion.
  • the dimensions of such parts may be, for example, and in no way limiting, more than 200 mm in diameter, and in the case of dredging of about 700 to 1200 mm in diameter or even more, with wall thicknesses of several tens to a few hundred millimeters.
  • the weight of such parts can commonly exceed several tons.
  • the wear parts must only have a very good abrasion resistance, but also a mechanical strength and particularly a high impact resistance. Indeed, in the effluent pumped during dredging operations, can be found not only abrasive materials, but also of relatively large dimensions and masses.
  • the non-rectilinear parts of the pipes are particularly subject to abrasion, but also to the resulting shocks impacts of stones or similar heavy and aggressive materials.
  • To ensure good resistance to abrasion use is conventionally made of cast iron, or a hard steel with a high carbon content, of the order of 1% for example. But such hard and abrasion-resistant materials are generally brittle, and therefore do not withstand, or at least withstand, shocks or other mechanical stresses likely to be exerted on the parts considered. It is therefore also known to ensure this additional mechanical strength by surrounding an inner piece of cast iron or the like by a steel piece which may have poorer abrasion resistance characteristics, but a better mechanical strength.
  • This steel piece is also used for fixing the part on the other pipe elements, for example by carrying at its ends assembly flanges.
  • a bend the manufacture of such a composite part can be currently performed in different ways. After molding a cast iron bend, a welded steel low carbon steel shell is placed around it, this shell constituting an external protection for the cast iron bend and ensuring its holding even in case of strong mechanical stresses on the elbow or violent shocks produced inside the elbow.
  • the steel shell can be lined around the elbow, or made in two half-shells assembled together on both sides of the elbow.
  • the solution currently used is to place around the cast iron elbow, for example cast iron GX 260 CrMoNi 20.2.1 which is an alloy cast with high wear resistance, a larger steel elbow, reserving a space between them and, if this space is planned large enough, fill this space with poured concrete.
  • Such a solution poses implementation problems, by the need to manufacture the two elbows separately, then to keep them precisely in place relative to each other during casting of the concrete, to avoid possible spacing reductions that may prevent proper concrete filling, etc.
  • the concrete itself does not provide mechanical strength, and in case, following a strong wear of the internal elbow, it would be pierced, it also does not ensure good resistance to abrasion.
  • the document JP 10099960 describes a bend intended to withstand wear, comprising a wall 10 to 30 mm thick obtained by casting cast iron around a thin stainless steel bend, of the order of 1 mm, at a temperature and in such a way that a metallurgical interaction occurs between the steel and the cast iron, hardening elements of the stainless steel diffusing into the cast iron to form a surface layer of improved hardness. It is therefore rather a molded surface treatment of the cast iron to increase its hardness.
  • methods of producing "bi-metallic" metal pipes that is to say having an outer layer made of a metal having certain characteristics and an inner layer of another metal having different characteristics, are also known. adapted to the intended use.
  • centrifugal casting Such pipes are made by centrifugal casting, this method can not be used for the manufacture of parts that are not revolution, such as bends or other connecting parts covered by the invention.
  • the centrifugal casting process used for bi-material parts generates a property gradient in the thickness of the wall formed, and, in the case of the applications referred to here, would lead to a gradual reduction of the hardness of the layer. internally at the interface between the two metals from the inside. In use, the more wear would be pronounced, the less the metal would be resistant to abrasion, which is obviously not desirable.
  • the present invention aims to solve the problems mentioned above and is particularly aimed at providing a wear part optimally having high abrasion resistance inside and a high mechanical resistance to the outside.
  • the subject of the invention is a molded metal wear part, in particular by sand molding, of generally tubular shape, such as a pipe element, the internal surface of which has a resistance to high abrasion, characterized in that it comprises an inner wall with a thickness greater than or equal to 20 mm, a first abrasion-resistant metal, of hardness greater than or equal to 56 HRC, and an outer wall made of a second metal resistant to mechanical stresses and shocks, the two walls being in intimate contact, without bond or metallurgical interaction, at the interface between said walls, said intimate contact resulting from the casting of the second molten metal around the wall internal prefabricated.
  • the first metal of the inner wall is chosen from: steels and white cast iron alloyed with chromium.
  • the first metal of the inner wall is chosen from: steels and white cast iron alloyed with chromium.
  • the second metal of the outer wall is a low carbon steel, typically having a higher ultimate tensile strength Rm or equal to 500 MPa, an elongation at break A greater than or equal to 22%, and a KV resilience greater than or equal to 40 joules, ensuring good mechanical strength, in particular the shocks likely to be caused during the use of the channeling element, typically a bend. Thanks to the invention, a bi-material part is obtained which has an optimum and constant resistance to abrasion over the entire thickness of the inner wall, which will also be called “shielding" thereafter.
  • the concrete did not durably ensure proper maintenance of such damaged shielding elements, especially because of the heterogeneity of the materials, and unavoidable bad contacts that result between shielding steel or cast iron and concrete, leaving local free spaces at the interface, or the shielding is not supported and all the more sensitive to shocks.
  • the low carbon steel casing of the invention in close contact with the shield, not only provides improved mechanical strength, but also acts as a kind of vibration damper when shielding is subjected to shocks likely to generate such vibrations because of the hardness of the said shielding.
  • the softening heat treatment is intended to reduce the hardness of the shielding, to facilitate the subsequent casting of the steel of the envelope without causing deterioration of the shielding when in contact with the molten steel of the envelope, it is to say so as to limit the effects of thermal shock occurring at this time.
  • This further treatment prepares the shield for the subsequent hardening treatment, which is aimed specifically at giving the shield a greater hardness once the casing has been poured.
  • This second heat treatment of course also has a curing effect on the envelope, but which remains limited and without being really detrimental to its mechanical characteristics required.
  • the softening heat treatment is typically a pearlitization annealing treatment, the effects of which are to reduce hardness, typically to less than 340HB, and to improve ductility, to reduce the tendency for internal stress crack generation due to expansion differentials important.
  • the final curing heat treatment is typically a quenching treatment, followed by a flashback, to provide the shield with adequate hardness, typically at least 56 HRC at all points of the shield.
  • the manufacture of the elbow according to the invention is carried out according to the following process.
  • the shielding 1 is made by casting in traditional sand molding of an alloy of Z100CD 6.1 type, as specified above.
  • the cast shield is then conventionally deburred and then subjected to a softening treatment, by a pearlitisation annealing, for example with a hold at 900 ° C. for 5 hours, followed by slow cooling in the oven.
  • the aim is to give the shield, and throughout its thickness, greater ductility, which results in a drop in hardness to a value less than 340HB, or even more preferably 230 HB.
  • the hardness of the shielding is then controlled, and the treatment renewed if necessary.
  • a mold 10 is prepared, with the imprint of the envelope 2 desired.
  • the shielding prepared as above is placed in the position as shown in the figures by a core 11 placed inside the shield 1 and resting with its projecting ends 12 in the sand of the mold 10. , in known manner in molding with the use of cores.
  • supports 13 made of steel of the same nature as the steel of the casing 2 are arranged in the space 2 'existing between the cavity of the casing made in the mold and the shield 1, for example three supports below the shield and two above as shown figure 1 , to complete the centering and support of the shield before casting the envelope.
  • These supports 13 are integrated in the casing 2 during casting thereof.
  • the low-carbon steel for example of the G8Mn3 type, having a composition as indicated beforehand, is cast in the mold and around the shield so that the cast steel fills the mold by coming into good contact with the mold. shielding, but without causing it to melt.
  • the shielding is not preheated, or only slightly, for example at about 100 ° C, by simply blowing hot air to dry the mold before casting the envelope 2. It is not It is conceivable to preheat the shield more strongly, without the risk of destroying the mold, the resin of which resists only for a short time at temperatures of the order of 200 ° C. or more, which also implies that the casting is carried out rapidly.
  • a relaxation income is achieved by holding at 180 ° C for 4 hours, for example.
  • the hardness and magnetoscopic control operations are then carried out to check the internal health of the bi-material wall of the elbow and the absence of any cracks or other internal defects, and the required machining is then carried out, in particular on the flanges.
  • the invention is not limited to the examples described above of parts and method of production.
  • the invention can be applied to other parts than elbows, in particular T- or Y-branches, for example, or even other parts constituting driving elements that must internally resist abrasion.
  • the compositions of the alloys used are not limiting and should be understood to include alloys having characteristics similar to those of the alloys indicated.
  • the parameters of the process may also be adapted, according to conventional knowledge of casting and heat treatment, insofar as the parameters chosen make it possible to obtain the desired effects in accordance with the indications set out above.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Heat Treatment Of Articles (AREA)
  • Polishing Bodies And Polishing Tools (AREA)
  • Rigid Pipes And Flexible Pipes (AREA)
  • Laminated Bodies (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)

Abstract

The tubular component, e.g. part of a pipe, has an inner wall (1) at least 20 mm thick of an abrasion resistant metal, and an outer wall (2) of a second metal that is resistant to mechanical stresses and shocks. The inner and outer walls, made from chrome and low carbon steels respectively, are in intimate contact but without bonding or metallurgical interaction, produced by casting the outer wall round the prefabricated inner one, which is subjected to thermal treatment to reduce its hardness.

Description

La présente invention concerne une pièce d'usure métallique de forme généralement tubulaire, dont la surface interne présente une résistance à l'abrasion élevée, et un procédé de fabrication par coulée d'une telle pièce d'usure.
Une telle pièce d'usure peut être notamment un élément de canalisation dans une installation de transport de fluides chargés et abrasifs, tels que par exemple des canalisations de transport des matériaux dans des opérations de dragage sous-marin. L'invention vise particulièrement des éléments de canalisation tels que coudes, dérivations en T ou Y, etc. Elle peut aussi s'appliquer à la réalisation d'autres pièces, telles que par exemple des corps de pompes ou autres éléments susceptibles d'être soumis à une forte abrasion interne. Les dimensions de telles pièces peuvent être par exemple, et de manière nullement limitative, de plus de 200 mm de diamètre, et dans le cas du dragage d'environ 700 à 1200 mm de diamètre ou même plus, avec des épaisseurs de paroi de plusieurs dizaines à quelques centaines de millimètres. Le poids de telles pièces peut couramment dépasser plusieurs tonnes.
Dans le domaine visé par l'invention, les pièces d'usure doivent dont seulement avoir une très bonne résistance à l'abrasion, mais également une résistance mécanique et particulièrement une résistance aux chocs importante. En effet, dans les effluents pompés lors des opérations de dragage, peuvent se trouver des matériaux non seulement abrasifs, mais également de dimensions et masses relativement importantes. Les parties non rectilignes des canalisations sont particulièrement soumises à l'abrasion, mais aussi aux chocs résultants des impacts des pierres ou matériaux similaires lourds et agressifs.
Pour assurer une bonne résistance à l'abrasion, on utilise classiquement de la fonte, ou un acier dur à teneur en carbone élevée, de l'ordre de 1% par exemple. Mais de tels matériaux durs et résistants à l'abrasion sont généralement cassants, et donc ne résistent pas, ou au moins résistent mal, aux chocs ou autres contraintes mécaniques susceptibles de s'exercer sur les pièces considérées. Il est donc également connu d'assurer cette résistance mécanique complémentaire en entourant une pièce interne en fonte ou similaire par une pièce en acier qui peut avoir de moins bonnes caractéristiques de résistance à l'abrasion, mais une meilleure résistance mécanique. Cette pièce en acier sert par ailleurs à la fixation de la pièce sur les autres éléments de canalisation, par exemple en portant à ses extrémités des brides d'assemblage.
En prenant comme exemple un coude, la fabrication d'une telle pièce composite peut être actuellement réalisée de différentes façons. Après avoir fabriqué par moulage un coude en fonte, on place autour de celui ci une coquille en acier mécano-soudée en acier à bas carbone, cette enveloppe constituant une protection externe pour le coude en fonte, et assurant sa tenue même en cas de fortes contraintes mécaniques sur le coude ou de chocs violents produits à l'intérieur du coude. La coquille en acier peut être chemisée autour du coude, ou réalisée en deux demi-coquilles assemblées entre elles de part et d'autre du coude. Mais du fait des grandes dimensions des pièces et des dispersions dimensionnelles résultant des opérations de coulée du coude en fonte et de fabrication des coquilles, il n'est pas possible d'obtenir à des coûts raisonnables des coquilles s'adaptant précisément sur le coude en fonte.
La solution actuellement utilisée est de placer autour du coude en fonte, par exemple en fonte GX 260 CrMoNi 20.2.1 qui est une fonte alliée à forte résistance à l'usure, un coude en acier de plus grande dimension, en réservant un espace entre eux, puis, si cet espace est prévu suffisamment grand, de combler cet espace par un béton coulé. Une telle solution pose cependant des problèmes de mise en oeuvre, par la nécessité de fabriquer les deux coudes séparément, puis de les maintenir précisément en place l'un par rapport à l'autre lors de la coulée du béton, pour éviter d'éventuelles réductions d'espacement susceptible d'empêcher un remplissage correct en béton, etc. De plus, le béton n'assure pas par lui-même de résistance mécanique, et au cas où, suite à une forte usure du coude interne, celui-ci viendrait à être percé, il n'assure pas non plus de bonne résistance à l'abrasion. Tout ceci conduit à sur-dimensionner inutilement les pièces en augmentant l'épaisseur globale de la paroi.
Une autre méthode de fabrication connue consiste à placer à l'intérieur d'une pièce en acier mécaniquement résistant des plaquettes de revêtement en matériau résistant à l'abrasion, en les maintenant par exemple par vissage à partir de l'extérieur. Cette solution est également compliquée et coûteuse.
Dans le domaine des pièces bi-matériaux, il a déjà été proposé, par exemple par le document JP 02133161 , de couler de la fonte autour d'un coude préformé en acier inoxydable. Une telle réalisation, outre ses dimensions très sensiblement plus petites que les pièces visées par l'invention, vise à fournir une plus grande résistance à l'oxydation par les gaz d'échappement, mais nullement une résistance à l'abrasion par des corps solides et abrasifs passant dans le coude, l'acier inoxydable ne présentant pas de caractéristiques anti-abrasion suffisantes.The present invention relates to a generally tubular metal wear part, the inner surface of which has a high abrasion resistance, and to a process for the casting of such a wear part.
Such a wear part can be in particular a pipe element in a transport facility of loaded and abrasive fluids, such as for example the pipes for transporting materials in underwater dredging operations. The invention is particularly directed to pipe elements such as elbows, T-joints or Y, etc. It can also be applied to the production of other parts, such as, for example, pump bodies or other elements that may be subject to strong internal abrasion. The dimensions of such parts may be, for example, and in no way limiting, more than 200 mm in diameter, and in the case of dredging of about 700 to 1200 mm in diameter or even more, with wall thicknesses of several tens to a few hundred millimeters. The weight of such parts can commonly exceed several tons.
In the field of the invention, the wear parts must only have a very good abrasion resistance, but also a mechanical strength and particularly a high impact resistance. Indeed, in the effluent pumped during dredging operations, can be found not only abrasive materials, but also of relatively large dimensions and masses. The non-rectilinear parts of the pipes are particularly subject to abrasion, but also to the resulting shocks impacts of stones or similar heavy and aggressive materials.
To ensure good resistance to abrasion, use is conventionally made of cast iron, or a hard steel with a high carbon content, of the order of 1% for example. But such hard and abrasion-resistant materials are generally brittle, and therefore do not withstand, or at least withstand, shocks or other mechanical stresses likely to be exerted on the parts considered. It is therefore also known to ensure this additional mechanical strength by surrounding an inner piece of cast iron or the like by a steel piece which may have poorer abrasion resistance characteristics, but a better mechanical strength. This steel piece is also used for fixing the part on the other pipe elements, for example by carrying at its ends assembly flanges.
Taking as an example a bend, the manufacture of such a composite part can be currently performed in different ways. After molding a cast iron bend, a welded steel low carbon steel shell is placed around it, this shell constituting an external protection for the cast iron bend and ensuring its holding even in case of strong mechanical stresses on the elbow or violent shocks produced inside the elbow. The steel shell can be lined around the elbow, or made in two half-shells assembled together on both sides of the elbow. However, because of the large dimensions of the parts and the dimensional dispersions resulting from cast iron elbow casting and shell-making operations, it is not possible to obtain at a reasonable cost shells that fit precisely on the elbow. melting.
The solution currently used is to place around the cast iron elbow, for example cast iron GX 260 CrMoNi 20.2.1 which is an alloy cast with high wear resistance, a larger steel elbow, reserving a space between them and, if this space is planned large enough, fill this space with poured concrete. Such a solution, however, poses implementation problems, by the need to manufacture the two elbows separately, then to keep them precisely in place relative to each other during casting of the concrete, to avoid possible spacing reductions that may prevent proper concrete filling, etc. In addition, the concrete itself does not provide mechanical strength, and in case, following a strong wear of the internal elbow, it would be pierced, it also does not ensure good resistance to abrasion. All this leads to unnecessarily oversize the parts by increasing the overall thickness of the wall.
Another known method of manufacture is to place inside inserts of abrasion-resistant material inside a mechanically resistant steel part, for example by screwing them from the outside. This solution is also complicated and expensive.
In the field of bi-material parts, it has already been proposed, for example by the document JP 02133161 , cast iron around a preformed stainless steel elbow. Such an embodiment, in addition to its dimensions substantially smaller than the parts targeted by the invention, aims to provide greater resistance to oxidation by the exhaust gas, but in no way a resistance to abrasion by solid bodies and abrasives passing through the elbow, the stainless steel not having sufficient anti-abrasion characteristics.

Le document JP 10099960 décrit quant à lui un coude destiné à résister à l'usure, comportant une paroi de 10 à 30 mm d'épaisseur obtenue par coulée de fonte autour d'un coude en acier inoxydable de faible épaisseur, de l'ordre de 1 mm, à une température et de manière telle que se produise une interaction métallurgique entre l'acier et la fonte, des éléments durcisseurs de l'acier inoxydable diffusant dans la fonte pour former une couche de surface de dureté améliorée. Il s'agit donc ici plutôt d'un traitement de surface en moule de la fonte coulée pour accroître sa dureté.
Par ailleurs, on connaît aussi des méthodes de réalisation de tuyaux métalliques "bi-métalliques", c'est à dire comportant une couche externe faite d'un métal présentant certaines caractéristiques et une couche interne d'un autre métal présentant des caractéristiques différentes, adaptées à l'usage projeté. De tels tuyaux sont réalisés par coulée centrifuge, ce procédé ne pouvant pas être utilisé pour la fabrication de pièces qui ne sont pas de révolution, telles que les coudes ou autres pièces de raccordement visées par l'invention. De plus, le procédé de coulée centrifuge utilisée pour des pièces bi-matériaux génère un gradient de propriété dans l'épaisseur de la paroi formée, et, dans le cas des applications visées ici, conduirait à une réduction progressive de la dureté de la couche interne au niveau de l'interface entre les deux métaux à partir de l'intérieur. En cours d'utilisation, plus l'usure serait prononcée, moins le métal serait résistant à l'abrasion, ce qui n'est évidemment pas souhaitable.The document JP 10099960 describes a bend intended to withstand wear, comprising a wall 10 to 30 mm thick obtained by casting cast iron around a thin stainless steel bend, of the order of 1 mm, at a temperature and in such a way that a metallurgical interaction occurs between the steel and the cast iron, hardening elements of the stainless steel diffusing into the cast iron to form a surface layer of improved hardness. It is therefore rather a molded surface treatment of the cast iron to increase its hardness.
Furthermore, methods of producing "bi-metallic" metal pipes, that is to say having an outer layer made of a metal having certain characteristics and an inner layer of another metal having different characteristics, are also known. adapted to the intended use. Such pipes are made by centrifugal casting, this method can not be used for the manufacture of parts that are not revolution, such as bends or other connecting parts covered by the invention. In addition, the centrifugal casting process used for bi-material parts generates a property gradient in the thickness of the wall formed, and, in the case of the applications referred to here, would lead to a gradual reduction of the hardness of the layer. internally at the interface between the two metals from the inside. In use, the more wear would be pronounced, the less the metal would be resistant to abrasion, which is obviously not desirable.

La présente invention a pour but de résoudre les problèmes évoqués ci-dessus et vise particulièrement à fournir une pièce d'usure présentant de manière optimale une grande résistance à l'abrasion à l'intérieur et une résistance mécanique élevée à l'extérieur.
Avec ces objectifs en vue, l'invention a pour objet une pièce d'usure métallique moulée, en particulier par moulage en sable, de forme généralement tubulaire, telle qu'un élément de canalisation, dont la surface interne présente une résistance à l'abrasion élevée, caractérisée en ce qu'elle comporte une paroi interne d'épaisseur supérieure ou égale à 20 mm, en un premier métal résistant à l'abrasion, de dureté supérieure ou égale à 56 HRC, et une paroi externe en un deuxième métal résistant aux contraintes mécaniques et aux chocs, les deux parois étant en contact intime, sans liaison ni interaction métallurgique, au niveau de l'interface entre les dites parois, le dit contact intime résultant de la coulée du deuxième métal en fusion autour de la paroi interne préfabriquée. Il est donc explicitement exclu de l'invention des pièces d'usures dont la paroi externe serait de faible épaisseur, ne permettant pas d'être réalisée par coulée en moule. Est de même exclu de l'invention des pièces d'usures dont la paroi interne serait d'une épaisseur trop faible pour assurer une durée de vie suffisante à la pièce en service et pour, lors de la fabrication, supporter sans déformations ou fusion la coulée du dit deuxième métal autour de la dite paroi. C'est pourquoi typiquement l'épaisseur de la paroi interne est supérieure ou égale à 20 mm.
Préférentiellement, le premier métal de la paroi interne est choisi parmi : les aciers et la fonte blanche alliée au chrome. On pourra par exemple utiliser un alliage de type Z100CD 6.1, présentant une dureté de plus de 56 HRc.
Préférentiellement aussi, le deuxième métal de la paroi externe est un acier bas carbone, ayant typiquement une résistance limite à la traction Rm supérieure ou égale à 500 MPa, un allongement à la rupture A supérieur ou égal à 22%, et une résilience KV supérieure ou égale à 40 joules, assurant une bonne résistance mécanique, en particulier aux chocs susceptibles d'être provoqués lors de l'utilisation de l'élément de canalisation, typiquement un coude.
Grâce à l'invention, on obtient une pièce bi-matériau qui présente une résistance à l'abrasion optimale et constante sur toute l'épaisseur de la paroi interne, que l'on appellera aussi "blindage" par la suite. Il a ainsi été constaté expérimentalement que, dans le cas d'un coude de canalisation d'une installation de dragage, le taux d'usure a été amélioré de 40 % par rapport aux coudes réalisés selon l'art antérieur. Un autre avantage est que, du fait de la liaison très étroite entre le blindage et la paroi extérieure, appelée aussi "enveloppe" par la suite, et s'il se produit une fissuration ou même une casse d'éléments du dit blindage suite à des chocs violents provoqués par les matériaux dragués transportés, ces éléments de blindage cassés ou fissurés restent en place, fermement maintenus par l'enveloppe. Comparativement, dans les coudes selon l'art antérieur avec béton entre le blindage et l'enveloppe mécano soudée, le béton n'assurait pas durablement un maintien correct de tels éléments de blindage abîmés, notamment du fait de l'hétérogénéité des matériaux, et des inévitables mauvais contacts qui en résultent entre blindage en acier ou fonte et béton, laissant localement des espaces libres à l'interface, ou le blindage n'est alors pas soutenu et d'autant plus sensible à des chocs.
Contrairement à cela, l'enveloppe en acier à bas carbone de l'invention, en contact étroit avec le blindage, assure non seulement une résistance mécanique améliorée, mais agit aussi comme une sorte d'amortisseur de vibrations lorsque blindage est soumis à des chocs susceptibles de générer de telles vibrations du fait de la dureté du dit blindage. On notera incidemment qu'il n'y a pas, sauf de manière très localisée et exceptionnelle, de liaison d'accrochage ou liaison métallurgique entre le blindage et l'enveloppe au niveau de leur interface, telle qu'une liaison de fusion ou diffusion entre les deux métaux. En conséquence, il y a une transition brusque des caractéristiques de dureté au niveau de l'interface et, de même que la dureté du blindage n'est pas sensiblement influencée ni variable dans son épaisseur, par la coulée de l'enveloppe autour de celui-ci, il y a aussi conservation des caractéristiques mécaniques de l'enveloppe de manière sensiblement homogène dans toute son épaisseur.The present invention aims to solve the problems mentioned above and is particularly aimed at providing a wear part optimally having high abrasion resistance inside and a high mechanical resistance to the outside.
With these objects in view, the subject of the invention is a molded metal wear part, in particular by sand molding, of generally tubular shape, such as a pipe element, the internal surface of which has a resistance to high abrasion, characterized in that it comprises an inner wall with a thickness greater than or equal to 20 mm, a first abrasion-resistant metal, of hardness greater than or equal to 56 HRC, and an outer wall made of a second metal resistant to mechanical stresses and shocks, the two walls being in intimate contact, without bond or metallurgical interaction, at the interface between said walls, said intimate contact resulting from the casting of the second molten metal around the wall internal prefabricated. It is therefore explicitly excluded from the invention wear parts whose outer wall is of small thickness, not to be achieved by casting in mold. Is also excluded from the invention wear parts whose internal wall would be too thin to ensure a sufficient service life of the part in service and, during manufacture, bear without deformation or melting the pouring said second metal around said wall. This is why typically the thickness of the inner wall is greater than or equal to 20 mm.
Preferably, the first metal of the inner wall is chosen from: steels and white cast iron alloyed with chromium. For example, it is possible to use an alloy of the Z100CD 6.1 type having a hardness of more than 56 HRc.
Preferably also, the second metal of the outer wall is a low carbon steel, typically having a higher ultimate tensile strength Rm or equal to 500 MPa, an elongation at break A greater than or equal to 22%, and a KV resilience greater than or equal to 40 joules, ensuring good mechanical strength, in particular the shocks likely to be caused during the use of the channeling element, typically a bend.
Thanks to the invention, a bi-material part is obtained which has an optimum and constant resistance to abrasion over the entire thickness of the inner wall, which will also be called "shielding" thereafter. It has thus been found experimentally that, in the case of a pipe bend of a dredging installation, the wear rate has been improved by 40% compared to bends made according to the prior art. Another advantage is that, because of the very close connection between the shield and the outer wall, also called "envelope" thereafter, and if there is a crack or even a breakage of elements of said shielding following violent shocks caused by transported dredged material, these broken or cracked shielding elements remain in place, firmly held by the envelope. Comparatively, in the elbows according to the prior art with concrete between the shielding and the welded envelope, the concrete did not durably ensure proper maintenance of such damaged shielding elements, especially because of the heterogeneity of the materials, and unavoidable bad contacts that result between shielding steel or cast iron and concrete, leaving local free spaces at the interface, or the shielding is not supported and all the more sensitive to shocks.
Contrary to this, the low carbon steel casing of the invention, in close contact with the shield, not only provides improved mechanical strength, but also acts as a kind of vibration damper when shielding is subjected to shocks likely to generate such vibrations because of the hardness of the said shielding. It will be noted incidentally that there is no, except in a very localized and exceptional manner, bonding connection or metallurgical bond between the shield and the envelope at their interface, such as a fusion bond or diffusion between the two metals. Consequently, there is an abrupt transition of the hardness characteristics at the interface and, just as the hardness of the shielding is not substantially influenced nor variable in its thickness, by the casting of the envelope around that here, there is also conservation of the mechanical characteristics of the envelope substantially homogeneously throughout its thickness.

Préférentiellement encore, la paroi interne est en un alliage ferreux comportant, en poids :

  • C : de 0,5 à 1,4 %
  • Si : moins de 0,8 %
  • Mn : moins de 1,1 %
  • Mo : de 0,8 à 1,4 %
  • Cr : de 5 à 8 %
  • V : moins de 1 %
et la paroi externe est en acier comportant, en poids :
  • C : moins de 0,2 %
  • Si : de 0,2 à 0,8 %
  • Mn : moins de 1,0 %
Preferentially, the inner wall is made of a ferrous alloy comprising, by weight:
  • C: 0.5 to 1.4%
  • If: less than 0.8%
  • Mn: less than 1.1%
  • Mo: 0.8 to 1.4%
  • Cr: 5 to 8%
  • V: less than 1%
and the outer wall is made of steel comprising, by weight:
  • C: less than 0.2%
  • If: 0.2 to 0.8%
  • Mn: less than 1.0%

L'invention a aussi pour objet un procédé de fabrication d'une pièce d'usure telle que définie ci-dessus, ce procédé étant caractérisé en ce que :

  • on réalise par coulée la paroi interne,
  • on soumet la dite première paroi à un traitement thermique d'adoucissement visant à réduire sa dureté
  • on place la dite première paroi ainsi traitée dans un moule préparé comportant une empreinte souhaitée pour l'enveloppe,
  • on coule le métal constitutif de la deuxième paroi dans le dit moule, de manière à enrober la première paroi,
  • et on soumet l'ensemble de la pièce bi-matériaux ainsi obtenue à un traitement thermique final de durcissement.
Selon une disposition particulière de l'invention, la première paroi est maintenue dans le moule utilisé pour la coulée de la deuxième paroi, par un noyau placé à l'intérieur de la dite première paroi et soutenu dans le moule par ses extrémités, et la première paroi est soutenue en complément par des supports en acier intégrés dans la deuxième paroi lors de la coulée de celle-ci.The invention also relates to a method of manufacturing a wear part as defined above, this method being characterized in that:
  • the inner wall is cast
  • said first wall is subjected to a softening heat treatment aimed at reducing its hardness
  • the so-called first wall thus treated is placed in a prepared mold having a desired impression for the envelope,
  • pouring the constituent metal of the second wall into said mold, so as to coat the first wall,
  • and subjecting the entire bi-material part thus obtained to a final heat treatment hardening.
According to a particular embodiment of the invention, the first wall is held in the mold used for casting the second wall, by a core placed inside said first wall and supported in the mold by its ends, and the first wall is supported in addition by steel supports integrated into the second wall during the casting thereof.

Le traitement thermique d'adoucissement vise à réduire la dureté du blindage, pour faciliter la coulée ultérieure de l'acier de l'enveloppe sans engendrer de détérioration du blindage lors du contact avec l'acier en fusion de l'enveloppe, c'est à dire de manière à limiter les effets du choc thermique survenant à ce moment. Ce traitement de plus prépare le blindage au traitement de durcissement ultérieur, lequel vise précisément à conférer à nouveau une plus grande dureté au blindage, une fois l'enveloppe coulée. Ce deuxième traitement thermique a bien sûr également un effet de durcissement sur l'enveloppe, mais qui reste limité et sans être réellement préjudiciable pour ses caractéristiques mécaniques requises.
Le traitement thermique d'adoucissement est typiquement un traitement de recuit de perlitisation, dont les effets sont de réduire la dureté, typiquement à moins de 340HB, et d'améliorer la ductilité, pour réduire la tendance à génération de fissuration par contraintes internes dues à des différentiels de dilatation importants.
Le traitement thermique final de durcissement est typiquement un traitement de trempe, suivi d'un revenu de détente, visant à conférer au blindage une dureté adéquate, typiquement de 56 HRC au moins en tous points du blindage.The softening heat treatment is intended to reduce the hardness of the shielding, to facilitate the subsequent casting of the steel of the envelope without causing deterioration of the shielding when in contact with the molten steel of the envelope, it is to say so as to limit the effects of thermal shock occurring at this time. This further treatment prepares the shield for the subsequent hardening treatment, which is aimed specifically at giving the shield a greater hardness once the casing has been poured. This second heat treatment of course also has a curing effect on the envelope, but which remains limited and without being really detrimental to its mechanical characteristics required.
The softening heat treatment is typically a pearlitization annealing treatment, the effects of which are to reduce hardness, typically to less than 340HB, and to improve ductility, to reduce the tendency for internal stress crack generation due to expansion differentials important.
The final curing heat treatment is typically a quenching treatment, followed by a flashback, to provide the shield with adequate hardness, typically at least 56 HRC at all points of the shield.

D'autres caractéristiques et avantages apparaîtront dans la description qui va être faite, uniquement à titre d'exemple, d'un coude bi-matériau conforme à l'invention et de son procédé& d'obtention.Other features and advantages will become apparent in the description which will be made, by way of example only, of a bi-material bend according to the invention and of its method of obtaining.

On se reportera aux dessins annexés dans lesquels :

  • la figure 1 représente le coude, en coupe selon un plan axial montrant la structure bi-matériau de sa double paroi, le coude étant situé dans le moule de coulée de son enveloppe, dont le plan de joint est le dit plan axial,
  • la figure 2 est une vue en coupe selon la ligne II-II de la figure 1.
Reference is made to the accompanying drawings in which:
  • the figure 1 represents the elbow, in section along an axial plane showing the bi-material structure of its double wall, the elbow being located in the casting mold of its envelope, whose joint plane is said axial plane,
  • the figure 2 is a sectional view along line II-II of the figure 1 .

La pièce représentée figure 1 dans son moule 10, est un coude à 45°, par exemple de diamètre intérieur 700 mm, pour une canalisation utilisée lors d'une opération de dragage. L'épaisseur de sa paroi interne, ou blindage, 1 est typiquement de 35 mm ; celle de sa paroi externe, ou enveloppe, 2 est d'environ 30 mm, ces dimensions n'étant nullement limitatives. Par ailleurs, des brides de fixation 3 sont formées directement d'une pièce avec l'enveloppe 2, lors de la coulée en moule de l'enveloppe puis usinées par la suite.
Le blindage 1 est en un alliage ferreux très proche du Z100CD 6.1, ayant typiquement la composition, en poids, suivante :

  • C : de 0,9 à 1,2 %
  • Si : de 0,4 à 0,6 %
  • Mn : de 0,6 à 0,9 %
  • Mo : de 1,1 à 1,2 %
  • Cr : de 6,0 à 6,6 %
  • V : de 0,4 à 0,5 %
  • Al : moins de 0,1 %
The piece represented figure 1 in its mold 10, is a 45 ° elbow, for example of internal diameter 700 mm, for a pipe used during a dredging operation. The thickness of its inner wall, or shield, 1 is typically 35 mm; that of its outer wall, or envelope, 2 is about 30 mm, these dimensions being in no way limiting. Furthermore, fastening flanges 3 are formed directly in one piece with the casing 2, during the mold casting of the envelope and then machined thereafter.
The shield 1 is made of a ferrous alloy very close to the Z100CD 6.1, typically having the composition, by weight, as follows:
  • C: 0.9 to 1.2%
  • If: 0.4 to 0.6%
  • Mn: 0.6 to 0.9%
  • Mo: from 1.1 to 1.2%
  • Cr: 6.0 to 6.6%
  • V: 0.4 to 0.5%
  • Al: less than 0.1%

L'enveloppe 2 est en un acier à bas carbone de composition, en poids :

  • C : moins de 0,1 %
  • Si : moins de 0,5 %
  • Mn : moins de 0,9 %
  • S : moins de 0,01 %
  • P : moins de 0,02 %
et des traces d'autres éléments et impuretés inévitables.
L'enveloppe 2 enrobe le blindage 1 en étant directement à son contact, sans cependant fusion des matériaux des deux parois à l'interface. Un éventuel collage peut exister localement, résultant du procédé de fabrication qui va être décrit par la suite, mais un tel collage, s'il n'est pas nuisible en soi s'il reste limité, n'est nullement nécessaire ni recherché.The envelope 2 is made of a low carbon steel of composition, by weight:
  • C: less than 0.1%
  • If: less than 0.5%
  • Mn: less than 0.9%
  • S: less than 0.01%
  • P: less than 0.02%
and traces of other unavoidable elements and impurities.
The casing 2 surrounds the shield 1 while being directly in contact with it, without, however, fusing the materials of the two walls at the interface. A possible bonding may exist locally, resulting from the manufacturing process that will be described later, but such a bond, if not harmful in itself if it remains limited, is not necessary or sought.

La fabrication du coude selon l'invention est effectuée selon le processus suivant.The manufacture of the elbow according to the invention is carried out according to the following process.

En premier lieu, le blindage 1 est réalisé par coulée en moulage sable traditionnel d'un alliage de type Z100CD 6.1, tel que précisé ci-dessus.
Le blindage coulé est ensuite classiquement ébarbé puis soumis à un traitement d'adoucissement, par un recuit de perlitisation, par exemple avec un maintien à 900°c pendant 5 heures, suivi d'un refroidissement lent dans le four. Le but visé est de conférer au blindage, et dans toute son épaisseur, une plus grande ductilité, qui se traduit par une baisse de dureté à une valeur inférieure à 340HB, ou même préférentiellement à 230 HB.
La dureté du blindage est alors contrôlée, et le traitement renouvelé si besoin.
Un moule 10 est préparé, avec l'empreinte de l'enveloppe 2 souhaitée. On y place le blindage préparé comme indiqué ci-dessus, en le maintenant en position comme on le voit sur les figures, par un noyau 11 placé à l'intérieur du blindage 1 et reposant par ses extrémités débordantes 12 dans le sable du moule 10, de manière connue en moulage avec utilisation de noyaux. De plus, des supports 13 en acier de même nature que l'acier de l'enveloppe 2 sont disposés dans l'espace 2' existant entre l'empreinte de l'enveloppe réalisée dans le moule et le blindage 1, par exemple trois supports en dessous du blindage et deux au-dessus comme illustré figure 1, pour compléter le centrage et le soutien du blindage avant la coulée de l'enveloppe. Ces supports 13 sont intégrés dans l'enveloppe 2 lors de la coulée de celle-ci.
On coule alors l'acier à bas carbone, par exemple de type G8Mn3, ayant une composition telle qu'indiqué préalablement, dans le moule et autour du blindage, de manière que l'acier coulé remplisse le moule en venant bien en contact avec le blindage, mais sans cependant provoquer de fusion de celui-ci. On notera que le blindage n'est pas préchauffé, ou seulement faiblement, par exemple à environ 100°C, par un simple soufflage d'air chaud visant à sécher le moule avant coulée de l'enveloppe 2. Il n'est pas en effet envisageable de préchauffer le blindage plus fortement, sans risque de détruire le moule dont la résine ne résiste que peu de temps à des températures de l'ordre de 200°C ou plus, ce qui implique par ailleurs d'effectuer la coulée rapidement.
Il résulte nécessairement de l'arrivée du métal en fusion dans l'espace 2' moule une certaine élévation de température du blindage 1, en particulier un échauffement plus élevé de la face extérieure du blindage que du côté intérieur jouxtant le noyau 11. Le choc thermique causé par le fort gradient de température qui peut alors s'établir dans le blindage pourrait alors provoquer dans celui-ci des fissurations rédhibitoires pour l'utilisation et la fiabilité ultérieure du coude. Le traitement de recuit préalable vise justement à éviter ces effets en donnant au blindage une meilleure ductilité, limitant ainsi les contraintes internes de dilatation différentielle dans l'épaisseur même du blindage, et évitant ainsi les risques de fissurations.
On notera par ailleurs que, même si le blindage n'était pas préalablement recuit ou l'était seulement partiellement, l'augmentation de température du blindage par l'arrivée de l'acier coulé à son contact, aurait aussi un effet de recuit, qui doit être nécessairement compensé par la trempe ultérieure qui sera indiquée par la suite. Mais cette sorte de "recuit" induit n'est pas non plus uniforme dans l'épaisseur du blindage et, sans recuit préalable, il en résulterait aussi une hétérogénéité de caractéristiques, et de dureté en particulier, dans l'épaisseur du blindage, avec en particulier un adoucissement plus marqué vers l'interface avec l'enveloppe. Un tel adoucissement serait susceptible de provoquer des inconvénients similaires à ceux rencontrés dans le cas de la coulée centrifuge évoquée au début de ce mémoire. Le recuit préalable permet de limiter cette tendance et évite de trop grandes variations de caractéristiques dans l'épaisseur du blindage.In the first place, the shielding 1 is made by casting in traditional sand molding of an alloy of Z100CD 6.1 type, as specified above.
The cast shield is then conventionally deburred and then subjected to a softening treatment, by a pearlitisation annealing, for example with a hold at 900 ° C. for 5 hours, followed by slow cooling in the oven. The aim is to give the shield, and throughout its thickness, greater ductility, which results in a drop in hardness to a value less than 340HB, or even more preferably 230 HB.
The hardness of the shielding is then controlled, and the treatment renewed if necessary.
A mold 10 is prepared, with the imprint of the envelope 2 desired. The shielding prepared as above is placed in the position as shown in the figures by a core 11 placed inside the shield 1 and resting with its projecting ends 12 in the sand of the mold 10. , in known manner in molding with the use of cores. In addition, supports 13 made of steel of the same nature as the steel of the casing 2 are arranged in the space 2 'existing between the cavity of the casing made in the mold and the shield 1, for example three supports below the shield and two above as shown figure 1 , to complete the centering and support of the shield before casting the envelope. These supports 13 are integrated in the casing 2 during casting thereof.
The low-carbon steel, for example of the G8Mn3 type, having a composition as indicated beforehand, is cast in the mold and around the shield so that the cast steel fills the mold by coming into good contact with the mold. shielding, but without causing it to melt. Note that the shielding is not preheated, or only slightly, for example at about 100 ° C, by simply blowing hot air to dry the mold before casting the envelope 2. It is not It is conceivable to preheat the shield more strongly, without the risk of destroying the mold, the resin of which resists only for a short time at temperatures of the order of 200 ° C. or more, which also implies that the casting is carried out rapidly.
It necessarily results from the arrival of the molten metal in the space 2 'mold a certain elevation of shielding temperature 1, in particular a higher heating of the outer face of the shield than the inner side adjacent to the core 11. The thermal shock caused by the strong temperature gradient which can then be established in the shielding could then cause in that crashes unacceptable for the use and subsequent reliability of the elbow. The prior annealing treatment aims to avoid these effects by giving the shielding a better ductility, thus limiting the internal stresses of differential expansion in the thickness of the shielding, and thus avoiding the risk of cracking.
Note also that, even if the shielding was not previously annealed or was only partially, the increase in temperature of the shielding by the arrival of the steel cast on contact, would also have an annealing effect, which must necessarily be compensated for by the subsequent tempering which will be indicated later. But this kind of induced "annealing" is also not uniform in the thickness of the shielding and, without prior annealing, it would also result in a heterogeneity of characteristics, and hardness in particular, in the thickness of the shielding, with in particular a softening more marked towards the interface with the envelope. Such softening would be likely to cause disadvantages similar to those encountered in the case of the centrifugal casting mentioned at the beginning of this paper. Pre-annealing limits this tendency and avoids excessive variations in characteristics in the thickness of the shield.

Après démoulage du coude bi-matériau obtenu et parachèvement, celui-ci est soumis à un traitement thermique de trempe à coeur comportant typiquement :

  • une montée en température jusqu'à 980°C et un maintien de 2 heures à cette température pour assurer l'homogénéité dans toute l'épaisseur de la double paroi, et en particulier dans l'épaisseur du blindage, jusqu'à l'interface avec l'enveloppe,
  • puis une trempe à l'eau, à l'huile ou polymère, en fonction des épaisseurs de paroi de la pièce considérée, et avec une sortie du bain lorsque la température de la pièce est de préférence inférieure à 170°C par exemple. L'objectif est que la trempe soit relativement sévère et complète dans l'épaisseur jusqu'à l'interface entre blindage et enveloppe, pour obtenir une dureté typiquement d'au moins 56HRC en tous points du blindage, avec une telle dureté jusqu'au coeur de l'épaisseur, pour que la résistance à l'usure du blindage, en cours d'utilisation, reste sensiblement constante, ou au moins sans réduction notable, lorsque l'épaisseur du blindage diminue, et cela jusqu'à l'interface avec l'enveloppe.
After demolding the bi-material elbow obtained and completion, it is subjected to a quenching heat treatment typically comprising:
  • a rise in temperature up to 980 ° C and a maintaining 2 hours at this temperature to ensure homogeneity throughout the thickness of the double wall, and in particular in the thickness of the shield, to the interface with the envelope,
  • then quenching with water, oil or polymer, depending on the wall thicknesses of the room in question, and with a bath outlet when the temperature of the room is preferably less than 170 ° C for example. The objective is that the quenching is relatively severe and complete in the thickness up to the interface between shielding and casing, to obtain a hardness typically of at least 56HRC in all points of the shielding, with such hardness up to heart of the thickness, so that the wear resistance of the shield, in use, remains substantially constant, or at least without significant reduction, when the thickness of the shield decreases, and that up to the interface with the envelope.

Optionnellement, un revenu de détente est réalisé, par un maintien à 180°C pendant 4 heures par exemple.
On procède ensuite aux opérations de contrôle de dureté, et de contrôle magnétoscopique pour vérifier la santé interne de la paroi bi-matériau du coude et l'absence d'éventuelles fissures ou autres défauts internes, et on effectue ensuite les usinages requis, notamment sur les brides.Optionally, a relaxation income is achieved by holding at 180 ° C for 4 hours, for example.
The hardness and magnetoscopic control operations are then carried out to check the internal health of the bi-material wall of the elbow and the absence of any cracks or other internal defects, and the required machining is then carried out, in particular on the flanges.

On notera que l'utilisation d'un acier bas carbone pour l'enveloppe, peu sensible à la trempe, permet de conférer au coude la résistance mécanique et aux chocs requise, et de conserver une bonne usinabilité des brides et des trous réalisés dans ces brides, même après la trempe à coeur effectuée sur le coude après coulée de l'enveloppe, cette trempe n'ayant pas ou peu d'effet sur l'enveloppe.It will be noted that the use of a low carbon steel for the casing, which is not very sensitive to quenching, makes it possible to give the elbow the required mechanical strength and shocks, and to retain good machinability of the flanges and holes made in these casings. flanges, even after hardening done on the elbow after casting of the casing, this quench having little or no effect on the casing.

Il peut apparaître, suite à des effets de dilatation différentielle lors du refroidissement du coude après coulée de l'enveloppe, des fissurations extérieures dans la dite enveloppe. Du fait notamment de l'acier à bas carbone qui la constitue, il peut aisément y être remédié, sans nuire par ailleurs aux autres caractéristiques de la pièce, par des opérations de rechargement par soudage. On veillera simplement alors à ne pas faire monter le blindage localement à une température trop élevée, pour ne pas risquer d'en amoindrir la dureté au niveau de l'interface avec l'enveloppe à proximité de la zone de réparation.It can appear, following differential expansion effects during the cooling of the elbow after casting of the envelope, external cracks in said envelope. In particular because of the low carbon steel which constitutes it, it can easily be remedied, without otherwise affecting the other characteristics of the part, by welding reloading operations. Just be careful not to raise the shield locally at too high a temperature, so as not to risk reducing the hardness at the interface with the envelope near the repair area.

Les essais réalisés par les inventeurs ont permis de montrer des valeurs moyenne de résilience de 14 joules à 20°C, et des valeurs moyennes de dureté du blindage de l'ordre de 60,9 HRC.The tests carried out by the inventors made it possible to show average resilience values of 14 joules at 20 ° C., and average values of hardness of the shielding of the order of 60.9 HRC.

L'invention n'est pas limitée aux exemples décrits ci-dessus de pièces et de procédé de réalisation.
On pourra en particulier appliquer l'invention pour d'autres pièces que des coudes, en particulier des dérivations en T ou Y par exemple, ou même d'autres pièces constituant des éléments de conduite devant résister intérieurement à l'abrasion. Egalement, les compositions des alliages utilisés ne sont pas limitatives et doivent s'entendre comme englobant les alliages présentant des caractéristiques similaires à celles des alliages indiqués. Les paramètres du procédé pourront aussi être adaptés, selon les connaissances classiques en matière de coulée et traitement thermique, dans la mesure où les paramètres choisis permettent d'obtenir les effets recherchés conformément aux indications exposées ci-dessus.The invention is not limited to the examples described above of parts and method of production.
In particular, the invention can be applied to other parts than elbows, in particular T- or Y-branches, for example, or even other parts constituting driving elements that must internally resist abrasion. Also, the compositions of the alloys used are not limiting and should be understood to include alloys having characteristics similar to those of the alloys indicated. The parameters of the process may also be adapted, according to conventional knowledge of casting and heat treatment, insofar as the parameters chosen make it possible to obtain the desired effects in accordance with the indications set out above.

Claims (10)

  1. Cast metal wearing part of overall tubular shape, such as a pipework element, whereof the internal surface has a high abrasion resistance, characterised in that it comprises an inner wall (1) of thickness greater than or equal to 20 mm made of a first abrasion-resistant metal of hardness greater than or equal to 56 HRC and an outer wall (2) made of a second metal resistant to mechanical stresses and impacts, the two walls being in intimate contact but with no connection or metallurgical interaction at the interface between said walls, said intimate contact resulting from the casting of the molten second metal around the prefabricated inner wall (1).
  2. Wearing part according to Claim 1, characterised in that the first metal of the inner wall is chosen from amongst steels and white cast iron alloyed with chromium.
  3. Wearing part according to Claim 2, characterised in that the inner wall is made of a ferrous alloy comprising, by weight: C: 0.5 to 1.4% Si: less than 0.8% Mn: less than 1.1% Mo: 0.8 to 1.4% Cr: 5 to 8% V: less than 1%
  4. Wearing part according to Claim 1, characterised in that the outer wall is a low-carbon steel.
  5. Wearing part according to Claim 4, characterised in that the outer wall is made of steel comprising, by weight: C: less than 0.2% Si: 0.2 to 0.8% Mn: less than 1.0%
  6. Method of manufacturing a wearing part according to any one of Claims 1 to 5, characterised in that:
    - the inner wall (1) is produced by casting;
    - said wall is subjected to a softening heat treatment aimed at reducing its hardness;
    - said first wall thus treated is placed in a prepared mould comprising a desired impression for the casing;
    - the constituent metal of the casing (2) is poured into said mould, so as to coat the first wall;
    - and the whole of the bi-material component thus obtained is subjected to a final hardening heat treatment.
  7. Method according to Claim 6, characterised in that the softening heat treatment is a pearlitizing treatment.
  8. Method according to Claim 6, characterised in that the final hardening heat treatment is a core hardening treatment.
  9. Method according to Claim 6, characterised in that the hardening treatment is followed by stress-relieving.
  10. Method according to Claim 6, characterised in that the first wall (1) is held in the mould (10) used for the casting of the second wall by a core (11) placed inside said first wall and supported in the mould by its ends (12), and the first wall (1) is supported in addition by steel supports (13) integrated into the second wall (2) during the casting thereof.
EP06111618A 2005-03-24 2006-03-23 Wear resistant pipe of tubular shape and casting process for manufacture thereof Not-in-force EP1704948B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR0502917A FR2883496B1 (en) 2005-03-24 2005-03-24 METALLIC WEAR PIECE OF A GENERALLY TUBULAR SHAPE, AND METHOD OF MANUFACTURING BY CASTING SUCH A WEAR PIECE

Publications (2)

Publication Number Publication Date
EP1704948A1 EP1704948A1 (en) 2006-09-27
EP1704948B1 true EP1704948B1 (en) 2008-04-16

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP06111618A Not-in-force EP1704948B1 (en) 2005-03-24 2006-03-23 Wear resistant pipe of tubular shape and casting process for manufacture thereof

Country Status (4)

Country Link
EP (1) EP1704948B1 (en)
AT (1) ATE392282T1 (en)
DE (1) DE602006000921D1 (en)
FR (1) FR2883496B1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090095436A1 (en) * 2007-10-11 2009-04-16 Jean-Louis Pessin Composite Casting Method of Wear-Resistant Abrasive Fluid Handling Components
JP6201074B1 (en) * 2017-02-27 2017-09-20 株式会社木村鋳造所 Lining steel pipe, plant piping equipment using lining steel pipe, lining steel pipe inspection method, lining steel pipe installation method, and lining steel pipe manufacturing method

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3568723A (en) * 1967-06-23 1971-03-09 Du Pont Metal-ceramic composite structures
JPS59120357A (en) * 1982-12-28 1984-07-11 Mitsubishi Heavy Ind Ltd Casting method of wear resistant pipe
JPH02133161A (en) * 1988-11-10 1990-05-22 Kubota Ltd Production of stainless steel-lined special shaped cast iron pipe
JPH0741397B2 (en) * 1989-05-18 1995-05-10 株式会社クボタ Manufacturing method of stainless steel coated cast iron pipe
JPH1099960A (en) * 1996-09-30 1998-04-21 Hitachi Metals Ltd Complex casting member and production thereof

Also Published As

Publication number Publication date
EP1704948A1 (en) 2006-09-27
FR2883496B1 (en) 2008-10-24
DE602006000921D1 (en) 2008-05-29
ATE392282T1 (en) 2008-05-15
FR2883496A1 (en) 2006-09-29

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