FR2563130A1 - METHOD FOR MANUFACTURING CONTINUOUS CASTING SHELL WITH WEAR-RESISTANT LAYER - Google Patents

Abstract

A.PROCESS OF MANUFACTURING A CONTINUOUS CASTING SHELL WITH WEAR RESISTANT LAYER. B. CHARACTERIZED IN THAT A WEAR RESISTANT LAYER IS PRODUCED BY ACTING A LASER RAY. C. THE INVENTION RELATES TO A PROCESS FOR MANUFACTURING A CONTINUOUS CAST SHELL WITH A WEAR-RESISTANT LAYER.

Description

Method of manufacturing a continuous casting shell

  with a wear-resistant layer ".

  The present invention relates to the manufacture

  cation of a shell of copper-based materials for continuous steel casting installations, provided with

  of a wear-resistant layer on the surfaces of

  mace limiting the cavity of the shell.

  For the continuous casting of high melting metals, such as for example iron and steel, it is used, in known manner, continuous casting shells, which are made of copper-based materials because of the high-thermal conductivity of these materials. Depending on the purpose of use, one-piece shells should be distinguished from shells made of several pieces; they are made of shells of a single piece, they are made from tubes cast or pressed without welding, or also from sheets or

  welded bar; or when asked for shellfish

  the several pieces, they are made from

  molded parts, forming the cavity of the shell,

tight together in a frame.

All these types of construction of

  The coils have this in common that, as a result of the

  tart heat passage in the area of the bath level, the rillette casting or the slab quickly solidifies to the outer zone located opposite the wall of the

  shell; he is forming. as a result, a thin envelope.

  which unfolds from the wall of the shell and is again

  calf pressed against it by the melt which

  continues to flow. The conditions of irreversible cooling

  resulting quills on the perimeter of the casting stream

  and the length of the casting cause mechanical tensions.

  in the casing of the casting, which may

  hot cracks and breaks.

  When shellfish are used

  continuous casting in copper-based materials.

  these are besides subject in their cavity. because of the friction of the solidified casting shell and slag particles infiltrating between the jet of

  casting and the cavity of the shell, to a considerable wear

  corn. The resulting change in shape of the wall

  inside the shell shortens the life of the

  possible shells in a decisive way. A

  disadvantage is. moreover, in that certain

  determined steel grades absorb copper, which

  drag an intercrystalline diffusion and thus the fra-

fear of steel.

  In order to avoid these difficulties, he

  already proposed, therefore, to apply

  wear-resistant surfaces on the inner surfaces of the shells which are in contact with the melt, or also to provide inserts of low thermal conductivity in the area of the bath level relative to the material of the body of the bath. shell (DE-OS 19 57 332). Coatings must increase resistance

  abrasion of the shell and thus its duration of use.

  while the inserts offer the possibility of adjusting the heat transfer according to the height

of the shell.

  For example, it has already been applied.

  electrolytically on the surface of the shell

  which is in contact with the melt,

  chromium or nickel. Despite its high hardness, chromium, for example, has the disadvantage

  it is possible to apply only relatively

  thin, about 250 Pm, because sinai this

  layer is cracked due to differences in

  expansion of the shell material and applied material, as well as its low adhesion. The thin electrolytically applied layers, usually 60 to 150 μm, have the additional disadvantage of

  to be able to break easily because of the low

  resistance of the carrier base layer of copper-based material in case of mechanical forces caused by

hard objects.

  Nickel or nickel alloys, for example with cobalt or iron, behave more favorably here than chromium; it is also possible to apply on flat or slightly shaped plates. layers up to a few millimeters thick. The hardness of such layers is however

  low compared to chromium; in addition, the thick-

  layer thickness likely to be obtained in the case of rectangular or square shells - para. example in the

  case of shell tubes for the manufacture of

  This is limited, because of the unfavorable penetration power of the electrolyte, to about 150 to 200 μm, because otherwise the inner contour and the dimensional accuracy

  of the shell would change unacceptably.

  In addition to the electrolytic or chemical coating process, in particular using

  nickel, with phosphorus dispersions. boron or incorpo-

  of hard materials, for example silicon carbide, it has been proposed, in addition, to use thermal spraying methods, such as flame projection of

  metallic threads, powder flame projection, pu-lv

  plasma or plasma spray by explo-

  if we. As coating materials, were then used molybdenum, aluminum bronzes, brasses

  manganese and nickel-chromium-based hard metals

  boron-silicon-iron-carbon. The adherence of these layers applied by spraying or spraying processes, however, has proved insufficient; in addition, such projected or sprayed layers are more or less porous, they

  micro-fissures and are heterogeneous and aniso-

  tropes. As to obtain a possible improvement of the adhesion strength between the material of the shell and the layer applied by a preheating of the shell,

  this is excluded because it would then produce a softening

  cold-formed shell and, in the case of

  orerts, that is to say without covering protective gas.

  in addition unacceptable oxidation of the forming walls

of the shell.

  Starting from this state of the art,

  the invention in order to find a possibility of applying

  durably, on the forming surfaces of

  bowling pins, layers of good quality

tants to wear.

  The invention relates, for this purpose, to a method for achieving this objective, which is essentially characterized in that the resistant layer

  wear is produced by causing a laser beam to act.

  The high energy density of the laser beam leads to a progressive melting of the material of the layer and also of the surface of the shell located in

  the area of the boundary surface. This results in a metal-

  between the copper-based shell materials and the layer materials. This results in a mechanically strong and durable notching of the adjacent metal layers; a burst of the resistant layer

  wear is avoided even after a long period of use.

  tion. The progressive heating, so narrowly limited and

  performed in the short term excludes a softening

  the shell formed cold; As a further particular advantage, it follows that the layers applied, or subjected to an improvement treatment after their application, are practically free from cracks.

and pores.

  As an embodiment of the invention

  It has been found advantageous to first apply, with adhesion to the forming surfaces of the shell, a layer of metal, or metal-containing, and then to bond metallurcally, by melting, by causing a reaction to occur.

  laser beam, this layer with the copper-based material

  of the shell. The treatment of the adherent metal layer that. for example can be a layer of nickel or chromium applied electrolytically, by laser beam, can be performed on the entire surface of the shell cavity, but this laser beam treatment

  may also be limited to areas of the particular shell

  exposed to mechanical forces.

  For example, it can often already suffice

  not to metallurgically bond, with the material of the shell, the metal layer, or metal-containing, wear-resistant, only in the area subjected to the forces

  highest mechanical forces under the effect of the jet of the

  continuous. more or less in the lower part of the shell. A bursting of the nickel or

  applied chromium, even in this zone, is thus

  me; an improvement treatment of the layer concerning the exemption of cracks and pores is operated at the same time. Another avaricious possibility of producing wear-resistant layers by means of laser beams consists, according to one embodiment of the invention. to apply first. on the forming surfaces of the shell, a metal layer, or metal-containing, and then to add by alloying the material of this layer, by causing the laser beam to act, additives increasing the wear resistance. For example,

  the nickel layer mentioned, applied electronically

  lytic, can be used for the formation of alloys, by alloying, by means of the laser beam, powders of suitable alloys, such as tungsten carbide (WC), chromium (Cr), silicon (Si), iron ( Fe), cobalt (Co) and

others, alone or in mixture.

  The method according to the invention allows

  to apply without difficulty wear-resistant

  thickness of up to a few mm, dura-

and of excellent quality.

  In this respect, it has furthermore proved advantageous, according to another embodiment of the invention, to apply the wear-resistant layer, by means of the laser beam, by application welding on the forming surfaces of the shell. The materials which are suitable for this procedure are virtually all those known in the spraying or spraying technique; for example, it can be used, for example, up to 90% by weight of tungsten carbide (WC) with cobalt base (Co). tungsten carbide with nickel base (Ni), tungsten carbide with nickel-cobalt-chromium base, self-flowing materials

  nickel-based alloys with chromium, boron, silicon, iron and

  bone, as well as with tungsten carbide additions

  up to 75% by weight, as well as stellites.

  It is then advantageously proceeded as follows: the material to be welded, is deposited in the form of metal powder, or powder containing metal, just in front of the point of impact of the laser beam on

  the forming surfaces of the shell, - with the provisions

  usual feedstocks for example in the plasma technique - then it is subjected to fusion. Thanks to the simultaneous melting of the area close to the surface -limite of the walls of the shell, it is obtained a bond by impeccable metal diffusion with the copper-based material

  from the wall of the shell. Such application welds

  are virtually free of pores; even when bending tests are carried out, there can no longer be any separation between the coating and the material

basic.

  Another possibility of realizing

  of the invention consists in applying the material

  wear resistant. for example, by the method of

  jection or conventional spraying on the forming surfaces of the shell and to operate only after its gradual fusion with a laser beam; it is then only during this subsequent fusion that the metallic link between the layer, applied in any way, is realized.

  and the base material of the shell.

  Another embodiment of the invention

  vention, to obtain a wear-resistant layer on

  the forming surfaces of the shell, consists of incor-

  poring in metal surfaces, by means of

  by laser beam, materials that increase the resistance

  wear resistance, that is to say, bodies resistant to

  wear. For this purpose, it is possible to proceed to

  corporation of wear-resistant bodies, such as

  bures, nitrides and the like, in the metal layer, OL chrome nickel, applied for example electrolytically, and inserting them mechanically into this layer during melting by means of the laser beam. This incorporation of wear-resistant bodies can, however,

  also be carried out directly in the

  of the shell forming surfaces, so that the wear-resistant layer is formed by particles of solid material incorporated into the shell.

  Copper-based material of the shell.

  Continuous casting shells are known and referred to as self-lubricating (German Patent 29 30 572), having a blend plating layer as a forming surface of a solid lubricant,

  such as graphite and one or more of the following

  chrome, nickel or cobalt. The role of this layer

  mixing veneer is to create, without additional lubricant

  a very low coefficient of friction at

  high temperature, so as to reduce the resistance to

  abrasion for the continuous casting stream.

  The invention offers another possibility.

  advantageous flexibility of implementation. By means of the laser it is indeed possible to introduce at the same time, into the wear-resistant layer, solid lubricants, such as, for example, boron nitride (BN), chromium nitride (CrN), and also chromium carbide (CrC), tungsten carbide (WC) or molybdenum disulfide (MoS2) or

tungsten bisulfide (WS2).

  As already indicated. the adherent metal layer may be electrolytically applied to the forming surfaces of the shell, especially in the form of a nickel or pure chromium layer. This layer can then be metallurgically bonded. by means of the laser beam. with the shell wall: it can also be used for alloying with alloy-added material components or for use as a metal base matrix for incorporation

of wear-resistant bodies.

  The metal layer, or containing metal. may also be applied by plasma spraying, flame projection or flame shock projection (explosion spraying); it is good, in this respect, to refer to known devices. These processes make it possible to treat sputtering layers, for example based on tungsten carbide, chromium carbide, titanium carbide, or else aluminum oxide or chromium oxide, these compounds being used pure or with alloy additives, such as cobalt, nickel, chromium,

molybdenum among others.

  Another possibility of launching

  of the invention is that of applying the

  of metal, or containing metal, by

  plosion. The treatment with the laser beam for

  different goals are then achieved.

  According to the requirements laid down, it is possible to use, for the invention, the different materials or combinations of materials. It is thus possible to use advantageously, as a base for the metal layer, a nickel-chromium-cobalt alloy, but also this

  which is referred to as multiple cobalt-based alloys

  chromite stellite) which have proved advantageous for the purposes of the invention. The metal-containing layer may also be constituted by a metal base matrix with incorporated wear-resistant bodies, such as

  carbides or nitrides; it can, however, also

  contain oxides of metals, for example chromium oxide, titanium oxide or aluminum oxide, alone or in

mixed.

  The wear-resistant layer, or also the protective layer against wear, on the surfaces

  forming of the shell, constituted according to the inventio-

  is provided at least in the base area of the shell.

  This is the zone which, when the installation is working, is

  exposed to the greatest efforts of wear.

  On the basis of the proposal

  known (DE-OS 19 57 332) to provide insertions in the area of the bath level, so as to obtain a lower thermal conductivity of the shell or a higher wall temperature, the invention provides other advantages . According to the method of the invention, it becomes, indeed. possible, for example, by providing a rectangular or wedge-shaped groove in the zone of the level of the bath of a plate shell, to perform, using a laser beam, the filling of this throat

  with an appropriate metal powder and the fusion of this

  in the throat area. There is no longer any

  slits between the wall of the throat of the co-

  keel and the insertion introduced, since this insertion is practically integrated metallurgically in the wall of the shell, thanks to the metallic place of

  areas close to the boundary surface between them.

  The invention will be better understood using

  of the description below and the accompanying drawings

  experiencing exemplary embodiments of the invention.

  Figures 1 to 6 of these drawings

  trents of shell insertions walls, which can be individual plates, but also tube-shaped seamless insertions or insertions

welded of any shape.

  By means of a laser beam of 5 KW, for example, the forming surface of the shell wall 1

  according to Figure 1 has been provided with a coating 2 resistant

  aunt to wear, extending all the way up. In this

  Indeed, it was applied and melted on the shell wall.

  the 1, presenting itself as a CuAg plate, in front of the point of impact of the laser beam on this shell wall - using a suitable metering device - a material in powder form consisting of a mixture of% by weight of WC 21% by weight of Ni, 3.5% by weight of Cr, 0.5% by weight of B, 0.8% by weight of Si and 0.8% by weight of Fe; for this application and this merger, have operated. in synchronism, the dosing device and the

laser ray.

  With a working speed of approximately 0.3 to 0.6 cm 2 / sec, a wear-resistant layer with a thickness of 1.5 mm could thus be applied. An impeccable metal diffusion bond was obtained with the base material of the shell, with a hardness of the alloy layer of 1070 HV: the layer was practically free of pores. In this way, the operating phase of the "application of material by flame projection

  or plasma spraying "could be saved.

  The invention can also be applied

  advantageously in combination with protective layers

  electrolytic picks. This is how it is pos-

  for example, to deposit a layer of Ni of 0.7 mm, in order to prevent diffusions of copper, on all the internal surface of the shell, and then to constitute alloys on this surface - or only on the zone of this surface which is exposed to the greatest efforts of wear - by means of a laser raon, with the addition of

  alloy powders such as tungsten carbide, chromium, silicon

  : cium. iron, cobalt, among others, in an appropriate mixture.

  Figures 2 to 4 show another embodiment of the invention. In the zone of

  base of a shell 3, designated as a shell for

  For example, a recess 4 has been provided. Electrolytically, the entire plate formed by the shell, including the recess 4,

  chromium 5 approximately 80 μm thick. In order to increase

  the wear resistance in the base zone is then inserted into the recess 4, in addition, a mixture 3: in the form of a powder consisting for example of 60% by weight of tungsten carbide, 29% by weight, nickel, 2% by weight of boron, 2% by weight of silicon, 2% by weight of iron and 0.5% by weight of carbon, and this mixture is then melted by means of the laser beam, so that In this zone, a layer of hard metal 6 is formed. This process has the advantage that the chromium layer 5, which is also present in the zone 4, can be used for the formation of alloy for the layer 6. resistant to wear. It has thus been possible to obtain degrees of hardness of 1020 HV.

  As a variant of this embodiment example,

  In addition, hardness levels which can also be used with powder mixtures can be obtained by adding combinations of nickel-voresilicon-iron and carbon without tungsten carbide, or by using cobalt instead of nickel, or by a combination of nickel / cobalt. Similarly. it is also possible, following the implementation of the invention, not to start from a primary coating of chromium 5, but, for example, from a

  nickel coating, and to choose correspondingly

  te the alloy powder. Instead of tungsten carbide

  (WC), it is also possible to use

both TiC and Cr3C.

  The shell wall 7, made of copper-based materials, which is shown in FIG. 5, shows, in the zone of the bath level, an insertion S. of rectangular shape er. cross section. By filling with a mixture in the form of a powder, in particular a combination of Ni-Al with 3 to 5% by weight of Al, a groove prepared correspondingly in the wall of the shell, and then proceeding to the melting of this powder by means of a laser beam, a firmly durable anchoring could be obtained. The invention

  provides a solution to the problem of

  apply coatings, or inserts, firmly adhered

  relatively thick, without the risk of

  slots between the insert 8 and the shell wall adja-

  cente. This is especially true for areas of the

  shell in which a lower

  thermal conductivity or higher wall temperature of the shell. This goal is often

  case of casting of sensitive steels.

  Finally, Figure 6 shows a possible

  embodiment, according to which provision is made, in the zone of the bath level of the shell wall 9,

  wedge-shaped section 10 made of a conductive material

  relatively low thermal capacity. This insertion ecalement is embedded firmly in the wall of the cuckold, thanks to the fact that it was obtained, by fusion with

  O1 mnen of the laser beam, a link by diffusion with the sur-

  adjacent faces of the shell wall.

RE V E N D I C AT IO N S

1) Method of manufacturing a

  shell made of copper-based materials for installations

  continuous steel casting, provided with a wear-resistant layer on the limiting forming surfaces

  the cavity of the shell, characterized in that it is

  a wear-resistant layer by acting on a

laser ray.

  2) Process according to claim 1,

  characterized in that it is applied first with

  on the forming surfaces of the shell, a layer of metal, or containing metal, and then. in

  causing a laser beam to act, this layer by fusion.

  metallurgically is bonded with the material-based

copper of the shell.

  3) Process according to claim 2, characterized in that the adhering layer of metal, or metal-containing, by causing the laser beam to act with the copper-based material of the shell, is only metallurgically bonded in the zone which is exposed to the most important mechanical forces under the effect of

casting stream.

  4) Process according to one or the other

  Claims 1 and 2, characterized in that it is

  firstly with adherence to the forming surfaces of the shell, a layer of metal, or metal-containing, and then it is added by alloy to the material

  of this layer, by causing the laser beam to act; additions

  increasing wear resistance.

  50) Method according to claim 1, characterized in that the wear-resistant layer on the forming surfaces of the shell is applied to the

  means of the laser beam. welding ensuring this application

  tion. 6C) A method according to claim 5, characterized in that the welding product is applied in the form of a metal powder, or containing Cu metal, just in front of the point of impact of the laser beam. on the

  forming surfaces of the shell, and fixed by fusion.

  7) Process according to any one of

  Claims 1 and 2 to 6, characterized in that it is

  incorporated, by causing the laser beam to act, in the neighboring areas of the outside of the

  shell, materials increasing wear resistance.

  8) Process according to any one of

  Claims 2 and 3 to 7, characterized in that it is

  incorporated, by causing the laser beam to act, in the adhering layer of metal, or containing metal, materials

* increasing wear resistance.

  9) Process according to any one of

  Claims 1 and 2 to 8, characterized in that in the

  a wear-resistant layer produced under the action of a laser beam, solid lubricants are intimately introduced. 10) Method according to one orphanage of

  Claims 4 and 5 to 9, characterized in that it is

  operated, by means of a laser beam, the adjoncticn -par alloy

  and / or the incorporation of additives increasing the resistance

  this to wear, as well as the welding ensuring the application,

  in the area exposed to the greatest mechanical damage

  under the effect of the casting jet.

  11) Method according to any one of

  Claims 2 and 3 to 10, characterized in that the

  che metal. or containing metal, is appXicated by

electrolytic route.

  12) Method according to any one of

  Claims 2 and 3 to 10, characterized in that the

  che metal. or containing metal, is applied by flame plasma spraying or spray

shock to the flame.

  1.6 13) Process according to any one of

  Claims 2 and 3 to 10, characterized in that the

  metal, or containing metal, is applied by

explosion plating.

  14) Process according to any one of

  Claims 2 and 3 to 13, characterized in that nickel is used as a base for the metal layer

(Ni) or chromium (Cr).

   ) Process according to any one of

  2 and 3 to 14, characterized in that it is

  used, as a base for the metal layer, an alloy

  nickel (Ni) - chromium (Cr) - cobalt (Co).

  16) Process according to any one of

  Claims 2 and 3 to 15, characterized in that it is

  used as a base for the metal layer, alloys

  multiples based on cobalt (Co) -chrome (Cr) (stellites).

  - 17) Process according to any one of

  claims 2 and 3 to 16, characterized in that the

  metal-containing drum consists of a metal base matrix with incorporated wear-resistant bodies,

such as carbides or nitrides.

  18) Process according to any one of

  claims 2 and 3 to 17, characterized in that the

  containing metal contains metal oxides.

  19) Continuous casting shell

  by the method according to any one of the claims

  1 and 2 to 18, provided with a protective layer

  the wear on the inner forming surfaces of the shell wall, characterized in that the wear protection layer is metallurgically bonded, at least in part, to the shell wall after melting at least the area adjacent to the outer surface of the

wall of the shell.

   Shell according to claim 19, characterized in that at least the lower zone

2 5 6 3 1 3 0

  of the shell has a protective layer against

  wear metallurgically related to the wall of the co-

  keel. 21) Shell according to claim 20, characterized in that the protective layer against wear provided in the lower zone of the shell has a greater wall thickness than the one

in the remaining area.

  220) Shell according to claim 19, characterized in that it is provided in the region of the bath level, a wear protection layer having at the same time a thermal conductivity

scaled down.

  23) Shell according to claim 22, characterized in that the protective layer against wear with reduced thermal conductivity is arranged

  in the form of insertions in the bath level area.

  240) Shell according to claim 23, characterized in that the inserts consist of

  wedges or partial corners in trans-

  versale, with limiting surfaces presenting

  one on the other in the direction of the passage of the casting jet.

 ) Shell according to any one

  claims 19 and 20 to 24, characterized in that

  the solidified zone after fusion contains constituents of different alloys, by the nature and / or the quantity,

from those in the surrounding areas.