Apparatus and method for producing a strip using a rapid solidification technology, and a metallic strip

Abstract

A method for producing a strip using a rapid solidification technology is provided. A melt is poured onto a moving outer surface of a rotating casting wheel, the melt is solidified on the outer surface and a strip is formed. A gaseous jet is directed at the moving outer surface and the outer surface of the casting wheel is worked with the jet. The jet comprises CO.sub.2 and at least part of this CO.sub.2 strikes the moving outer surface of the casting wheel in a solid state.

Claims

1. A method for producing a strip using a rapid solidification technology, said method comprising: pouring a melt onto a moving outer surface of a rotating casting wheel, the melt being solidified on the outer surface and a strip being produced, wherein the melt comprises Fe.sub.100-a-b-w-x-y-z T.sub.a M.sub.b S.sub.iw B.sub.x P.sub.y C.sub.z (in at %), T denoting one or more of the elements in the group consisting of Co, Ni, Cu, Cr and V, and M denoting one or more of the elements in the group consisting of Nb, Mo and Ta, where 0≤a≤70 0≤b≤9 0≤w≤18 5≤x≤20 0≤y≤7 0≤z≤2, and, if present, up to 1 at % impurities, directing a gaseous jet onto the moving outer surface and working the outer surface of the casting wheel with the jet, the jet containing CO.sub.2, at least part of this CO.sub.2 being in solid state and striking the moving outer surface of the casting wheel in the solid state, wherein the gaseous jet strikes the outer surface of the casting wheel as the melt is cast onto the outer surface of the rotating casting wheel.

2. A method according to claim 1, wherein the casting wheel moves in a direction of rotation and the gaseous jet strikes the outer surface of the casting wheel at a first position which, when viewed in the direction of rotation, is arranged upstream of a second position at which the melt strikes the outer surface, this first position being arranged downstream of a point at which the strip detaches from the casting wheel when viewed in the direction of rotation, wherein one or more jet nozzles are provided through which the jet is directed onto the outer surface of the casting wheel.

3. A method according to claim 2, wherein the outer surface is further formed or worked using a material-removing process with a surface-working means at a third position, when viewed in the direction of rotation, this third position being arranged upstream of the first position at which the gaseous jet strikes the outer surface of the casting wheel, but downstream of the point at which the strip detaches from the casting wheel, wherein the surface-working means comprises: a rolling device, forming the outer surface of the casting wheel, that is pressed against the outer surface of the casting wheel as the casting wheel rotates, and/or a polishing device, removing material from the outer surface of the casting wheel, that is pressed against the outer surface of the casting wheel as the casting wheel rotates, and/or one or more brushes, removing material from and/or cleaning the outer surface of the casting wheel, that are pressed against the outer surface of the casting wheel as the casting wheel rotates, and wherein the surface-working means is pressed against the outer surface of the casting wheel such that it continuously smoothens the outer surface of the casting wheel as the melt is cast onto the outer surface of the casting wheel.

4. A method according to claim 3, wherein before the melt is poured onto the outer surface of the casting wheel, the gaseous jet strikes the moving outer surface of the casting wheel and the surface-working means is pressed against the moving-outer surface of the rotating casting wheel.

5. A method according to claim 3, wherein two or more surface-working means are used, when viewed in the direction of rotation, their positions being arranged upstream of the first position at which the gaseous jet strikes the outer surface of the casting wheel, but downstream of the point at which the strip detaches from the casting wheel.

6. A method according to claim 5, wherein an additional gaseous jet strikes the surface of the rotating casting wheel downstream of the polishing device and/or one or more brushes and upstream of the rolling device, wherein the additional gaseous jet comprises CO.sub.2 and at least part of this CO.sub.2 strikes the moving outer surface of the casting wheel in a solid state.

7. A method according to claim 1, wherein a CO.sub.2 source comprising dry ice particles is provided, and these dry ice particles are accelerated onto the outer surface to form the gaseous jet, and wherein the dry ice particles have an average particle size of 0.1 mm to 10 mm.

8. A method according to claim 7, wherein the gaseous jet further comprises particles of a further material, wherein the particles of a further material have an average diameter of 10 μm to 1 mm.

9. A method according to claim 8, wherein the particles are ceramic beads and/or glass beads.

10. A method according to claim 1, wherein a CO.sub.2 source comprising liquid CO.sub.2 is provided, out of which particles crystallise in order to form CO.sub.2 snow that strikes the outer surface of the casting wheel as a gaseous CO.sub.2 snow-containing jet, and wherein the particles of CO.sub.2 snow have an average particle size of 0.1 μm to 100 μm.

11. A method according to claim 10, wherein the particles of CO.sub.2 snow are accelerated onto the outer surface of the casting wheel with no additional carrier gas.

12. A method according to claim 10, wherein the particles of CO.sub.2 snow are accelerated onto the outer surface of the casting wheel with a carrier gas, and pressure of the carrier gas is adjustable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments are explained below with reference to the drawings.

(2) FIG. 1 shows a schematic representation of an apparatus for producing a metallic strip using a rapid solidification technology according to a first embodiment.

(3) FIG. 2 shows a schematic representation of a CO.sub.2-containing jet for working a surface.

(4) FIG. 3 shows a schematic representation of an apparatus for producing a metallic strip using a rapid solidification technology according to a second embodiment.

DETAILED DESCRIPTION

(5) FIG. 1 shows a schematic representation of apparatus 10 for producing a metallic strip 11 using a rapid solidification technology according to a first embodiment.

(6) The apparatus 10 has a rotating casting wheel 12 with an outer surface 13 onto which a melt 14 is cast. The casting wheel 12 can also be described as a heat sink and in the apparatus shown rotates about an axis 15 in a direction of rotation indicated by the arrow 16. The melt 14 solidifies on the outer surface 13 of the casting wheel 12 and the metal strip 11 is formed. The solidification rate of the melt 14 is typically very high and the melt 14 therefore solidifies as an amorphous strip 11.

(7) The apparatus 10 also has means 17 for directing a CO.sub.2-containing jet 18 onto the outer surface 13 of the casting wheel 12. The jet 18 comprises CO.sub.2. At least part of the CO.sub.2 strikes the moving outer surface 13 of the casting wheel 12 in a solid state such that the outer surface 13 of the casting wheel 12 is worked and/or cleaned by the jet 18. FIG. 1 shows solid particles 19 of CO.sub.2. These solid particles 19 may be either prefabricated dry ice particles or formed from liquid CO.sub.2 immediately upstream of the outer surface 13.

(8) The jet 18 strikes the outer surface 13 of the casting wheel 12 at a first position 20 that is arranged, when viewed in the direction of rotation 16, upstream of a second position 21 at which the melt 14 strikes the outer surface 13. When viewed in the direction of rotation, this first position 20 is arranged downstream of the point 22 at which the strip 11 detaches from the casting wheel 12. As a result, once the strip 11 has detached from the outer surface 13, the outer surface 13 is worked and cleaned by the CO.sub.2 jet 18 before the melt 14 strikes this region of the outer surface 13 again.

(9) The melt 14 and so the strip 11 may have different compositions. In one embodiment the melt 14 comprises: Fe.sub.100-a-b-w-x-y-z T.sub.a M.sub.b S.sub.iw B.sub.x P.sub.y C.sub.z (in at %), T denoting one or more elements in the group consisting of Co, Ni, Cu, Cr and V, and M denoting one or more of the elements in the group consisting of Nb, Mo and Ta, where

(10) 0≤a≤70

(11) 0≤b≤9

(12) 0≤w≤18

(13) 5≤x≤20

(14) 0≤y≤7

(15) 0≤z≤2.

(16) The melt may also contain up to 1 at % impurities.

(17) In one embodiment the means 17 for directing a CO.sub.2-containing jet 18 onto the outer surface 13 of the casting wheel 12 comprises a jet device 23 with one or more nozzles 24. The width of the jet nozzle 24 can be adjusted to the width of the metal strip 11 to be produced such that the jet 18 covers the complete casting track. However, the jet gun 23 can also be moved axially over the casting wheel 12 so that its spray jet travels over the casting track at certain points. The blasting device directs a jet of CO.sub.2 in a solid state onto the outer surface and so blasts it.

(18) In some embodiments the apparatus 10 also has one or more additional surface-working means 25. These further surface-working means 25 can work the outer surface 13 using a forming process, e.g. rolling, or using a material-removing process, e.g. polishing. In the embodiment shown in FIG. 1 a brush is provided as the surface-working means 25.

(19) This surface-working means 25 is arranged at a third position 26 on the casting wheel 12, wherein when viewed in the direction of rotation 16 this third position 26 is arranged upstream of the first position 20 at which the jet 18 comprising solid CO.sub.2 19 strikes the outer surface 13, but downstream of the point 22 at which the strip 11 detaches from the casting wheel 12. As a result, once the strip 11 has detached the outer surface 13 is first worked with the surface-working means 25 in order to remove large particles 29 from the outer surfaces 13, then worked with the CO.sub.2-containing jet 18 in order to remove residues 27, and only then is the melt 14 cast onto the outer surface 13 against. This sequence makes it possible for the CO.sub.2-containing jet 18 to remove residues 27 from the material-removing processes carried out on the outer surface 13, e.g. particles of the casting wheel itself, polishing agents, etc., or residues from forming processes carried out on the outer surface 13, e.g. lubricant.

(20) For example, the surface-working means 25 may be a rolling device that is pressed against the outer surface 13 of the rotating casting wheel 12 as the outer surface 13 of the casting wheel 12 moves and/or a grinding device that is pressed against the outer surface 13 of the rotating casting wheel 12 as the outer surface 13 of the casting wheel 12 moves and/or a polishing device that is pressed against the outer surface 13 of the rotating casting wheel 12 as the outer surface 13 of the casting wheel 12 moves, and/or have one or more brushes 28 that are pressed against the outer surface 13 of the rotating casting wheel 12 as the outer surface 13 of the casting wheel 12 moves.

(21) If material-removing and forming working methods are used in one apparatus 10, the outer surface 13 may first be worked using the material-removing working method, then using the forming working method and then using the CO.sub.2-containing jet 18.

(22) The casting-wheel surface 13 has good thermal conductivity and so causes the very rapid solidification of the melt 14 applied to it, thereby creating a strip 11 that has particular mechanical, physical and/or magnetic properties due to its specific structure and/or composition. The outer surface 13 of the casting wheel 12 may be made of copper or a copper-based alloy.

(23) According to the invention, the casting wheel 12 is worked and cleaned using solid CO.sub.2 during strip production. With a CO.sub.2-containing jet in which at least part of the CO.sub.2 is in a solid state, particles can be removed from the casting track and adhering oils and other layers on the casting track that impar wetting can also be removed, whereby its own residues, i.e. the CO.sub.2 gas created by sublimation, even having an advantageous effect on the production of many amorphous alloys.

(24) In one embodiment the casting wheel 12 is worked by dry ice jets during strip production. The blasting of the casting-wheel surface 13 with dry ice is carried out during the casting process, between a polishing station and the molten metal droplet, for example. This dry ice blasting removes impurities on the casting track that impair wetting as well as residues from the polishing process such as copper dust from the casting wheel material, abrasive grains, organic impurities, oils, etc.

(25) FIG. 2 shows a schematic representation of the working of the outer surface 13 of the casting wheel 12 with CO.sub.2 snow jets. In CO.sub.2 snow blasting, liquid CO.sub.2 30 from a pressurised cylinder is sprayed onto the surface 13 to be treated via a nozzle system. The expansion of the pressurised liquid CO.sub.2 30 creates small, highly dispersed ice crystals 31 or CO.sub.2 snow that strikes the surface 13 with high kinetic energy, as illustrated in FIG. 2. In this arrangement, the nozzle system may comprise single-substance (CO.sub.2 only) or dual-substance nozzles (i.e. with the addition of compressed air). The CO.sub.2 particles 31 in the jet 18 sublime both before and after the jet 18 strikes the outer surface 13 so that the residues 27 and other particles 29 are carried across the outer surface 13 and removed from the outer surface 13.

(26) The sublimation of the dry ice particles 19 or the snow 31 on the casting-wheel surface 13 creates a CO.sub.2-containing atmosphere upstream of the molten metal droplet, which is very advantageous for the wetting of ferrous molten metals and the reduction of air pocket size on the underside of the strip. It also directly cools the surface 13 of the casting track, which is advantageous for the rapid solidification of the molten metal 14 on the casting wheel 12.

(27) The residues 27 and particles 29 can be removed by the jet comprising solid CO.sub.2 by the effect of pulse transmission, the creation of mechanical stresses due to the abrupt differences in temperature, a solvent effect created by the change of aggregation state when the jet strikes the surface, and sublimation pulsed washing that takes place with sublimation due to the great increase in volume, e.g. a 600× to 800× increase in volume.

(28) The use of the cleaning method also achieves the secondary cooling of the casting track. During casting, depending on the temperature of the molten metal being cast and once the primary cooling has been carried out and adjusted, the casting wheel, which is normally fitted with a water cooling system beneath the surface (referred to here as primary cooling), has a surface temperature of approx. 100° C.-500° C. on the casting track. With primary water cooling during continuous casting, lower surface temperatures are very difficult, not to say impossible, to achieve with large strip widths or larger formed metal strip thicknesses. By using cold dry ice at −80° C. directly on the surface of the casting track it is possible to further reduce the surface temperature of the casting track resulting from the primary cooling during casting, which can be very advantageous for some alloys. Dry ice can also be used to cool the metal strip produced directly.

(29) The only residue remaining after the cleaning process is an increased CO.sub.2 content in the surrounding atmosphere, which can actually be used to improve the quality of the amorphous metal strip to be produced. An improvement in quality due to the increased CO.sub.2 content can be achieved by the use of dry ice in the cleaning process.

(30) FIG. 3 shows a schematic representation of apparatus 10′ according to a second embodiment. The apparatus 10′ also has an exhaust system 40 for removing CO.sub.2 gas. This makes it possible to ensure that the atmosphere in the proximity of the apparatus meets the applicable environmental and industrial safety standards.

(31) The apparatus 10′ also has an extraction system 41 for removing the material detached from the outer surface of the casting wheel in order to prevent this detached material from landing on the outer surface again.

(32) In addition to the brush 28 that forms the surface-working means 25, the apparatus 10′ also has a rolling device as the second surface-working means 25 that forms the outer surface 13 of the casting wheel 12. When viewed in the direction of rotation 16, the rolling device is arranged downstream of the brush 28 and upstream of the CO.sub.2-containing jet 18. FIG. 3 also shows a winder 43, which continuously takes up the solidified metal strip.

(33) During casting, the casting-wheel surface is subject to very high mechanical and physical loads. For example, the local application of a very hot molten metallic mass (approx. 900 . . . 1500° C.) in the regions close to the surface results in high temperature peaks and extreme temperature gradients. During further cooling, the strip shrinks both longitudinally and transversely. High shear stresses occur between the strip and the heat sink surface, resulting in relative movements, and the strip either tears off the surface spontaneously or is torn off it by force at the detachment point.

(34) These processes are repeated thousands and even some tens of thousands of times during a casting process and so constantly change the surface of the cooling drum. This causes signs of wear caused by thermal and mechanical stresses, such as material fatigue, surface roughness and pitting, which can in turn have negative repercussions on the rapidly solidified strip to be produced.

(35) The efficiency of this production process is therefore very heavily dependent on mastering wear processes. Much can be done in advance to reduce the occurrence of these undesired side effects by selecting the appropriate material, production process and surface-working method, but they cannot be entirely excluded. According to the invention, the outer surface of the casting wheel is therefore worked with a CO.sub.2-containing jet, the jet comprising CO.sub.2 in a solid state such that particles of solid CO.sub.2 strike the outer surface at a specific speed.

(36) In addition to preventive measures, it is also possible to use directly acting processes that counter wear mechanisms during the production process. Known processes of this type are, in particular, abrasive processes such as brushing, grinding, polishing, etc. However, these processes can result in significant undesirable side effects (e.g. dust formation, residues, impurities, etc.) and ultimately cause wetting defects and tears.

(37) There are also other external influences that affect the production process. One significant factor in this context is surface contamination by residues, deposits and/or the formation of condensation resulting from the environment and the processes used. They impair wetting in the molten metal and so adversely affect cooling, geometry and the properties of the strip produced. The main causes can be volatile alloy components (B, C, Sn, etc.), volatile components of fireproof materials (resins, etc.), debris from the wiper, for example, and residues from surface wear and the finished strip.

(38) A highly effective cleaning process is thus carried out close to the casting nozzle, reliably removing any impurities whilst not itself having any adverse effect on the casting process.

(39) In the rapid solidification technology (melt spinning) required for the production of amorphous strips, a glass-forming metal alloy is melted in a crucible that is typically made substantially of an oxidic ceramic (e.g. aluminium oxide) and/or graphite. Depending on the reactivity of the melt, the melting process may take place in air, in a vacuum or in an inert gas such as argon. Once the alloy has been melted down to temperatures well above the liquidus point, the melt is transported to a casting tundish and injected through a casting nozzle, which generally has a slit-shaped outlet opening, onto a rotating wheel made of a copper alloy. To this end, the casting nozzle is brought very close to the surface of the rotating copper drum and sits at a distance of approx. 50-500 μm from it during the casting process. The melt passes through the nozzle outlet and strikes the moving copper surface, where it solidifies at cooling rates of approx. 10.sup.4 K/min to 10.sup.6 K/s. The rotational movement of the drum carries the solidified melt away from the cooling drum as a continuous strip band, detaches it from the cooling drum and winds it onto a winding device as a continuous band strip. As a general rule, the maximum possible length of the strip band is limited by the holding capacity of the crucible, which can range from a few kilogrammes to several tonnes depending on the size of the apparatus. When operating with a plurality of crucibles in parallel, it is even possible to achieve an almost continuous supply of molten metal to the casting tundish. The scale of apparatus in which commercially available amorphous strips are economically manufactured typically has crucible sizes of greater than 100 kg. Given a strip cross section with a strip width of approx. 100 mm and a strip thickness of approx. 0.018, 100 kg of the alloy VITROPERM 500 results in a strip length of approx. 8 km. In an industrial process, a full crucible therefore produces a length of tens of kilometres and, if the casting process involves the regular refilling of a tundish in a continuous casting method, in a significantly greater number of kilometres.

(40) The wear on the casting-wheel surface during the uninterrupted casting process results in increased surface roughness of the wheel surface and, in turn, in the formation of cavities or uneven structures that both transport process gas beneath the molten metal droplet and cause larger gas bubbles in the contact region between the molten metal droplet and the casting wheel. When the molten metal solidifies, these gas bubbles are frozen in the amorphous strip and can lead to hole-like defects, particularly in thin strips. This wheel roughness is also carried through to the surface of the strip that is produced on it such that the strips produced on it also show increased roughness.

(41) In order to minimise wear on the casting wheel it is desirable to select a high-strength casting-wheel material. In the metallurgical copper materials generally used, the properties of strength and heat conductivity tend to act in opposite directions. A copper material with maximum possible heat conductivity will always have a lower strength than more highly alloyed copper materials. Higher alloyed copper materials are generally stronger but are associated with lower conductivity. However, the production of amorphous metal strips requires the use of casting-wheel materials with relatively high thermal conductivities in order to achieve sufficiently high cooling rates during strip production. If the cooling rates are not sufficiently high, the strips become brittle or partially brittle, form undesirable crystalline structures, e.g. a level of surface crystallinity, and so cannot be wound continuously in the casting process or tear off during winding, resulting in undesirably low productivity in strip production. It is desirable to use casting-wheel materials with a thermal conductivity of greater than 200 W/mK. However, such materials have a hardness of less than 250 HV (HV30)

(42) In order to be able to use these relatively soft and highly thermally conductive materials in the casting of amorphous strips in the long term it is also necessary to ensure that the contact surface between the molten metal/strip and the casting wheel, i.e. between the casting track and the casting-wheel surface, is worked evenly during strip production and to keep the roughness of the wheel surface at a constant and uniformly low level. This can be achieved by material-removing processes such as polishing or polishing the drum or by means of brushes.

(43) Rotating metal brushes can be used to remove residues on the casting drum that impair wetting. However, these rotating brushes may leave residues in the form of detached brushes that can result in local defects on the strip and to frequent tears in the strip during strip production.

(44) The use of even coarser brushes leads to tears in the thin strip on the casting wheel. Although the invention describes a vacuum source designed to reliably aspirate any removed items and dust, the extraction of dust on fast rotating casting wheels has not proved reliably practicable. There are always some minute dust residues left adhering to the casting wheel, resulting in imperfections in the strip.

(45) The polishing of the casting wheel using emery paper or a rotating polishing substrate can also be used as the surface-working process. However, a polishing material of this type produces a small amount of dust that can result in defects in the strip.

(46) Non-abrasive forming processes such as the rolling of the casting drum should be advantageous. Although forming processes have the advantage that they leave no polishing material residues on the casting drum, the fast-rotating tools used for surface forming at the pivot and bearing points are lubricated and minute particles of the lubricant reach the wheel surface where they can impair wetting and so result in the formation of holes in the strip.

(47) It cannot be excluded that working residues (dust, brush hairs, polish residues, grease, oil, organic material) are carried into the molten metal droplet, where they may cause imperfections. None of the prior art teach how such working residues can be removed, i.e. how either solid particles such as abrasive dust, polishing material grains and brush hairs or adhering organic residues of oils or polishing agents can be reliably removed.

(48) In one embodiment dry ice blasting is used. Dry ice blasting is a compressed-air blasting process in which solid carbon dioxide at a temperature of approx. −79° C., so-called dry ice, is used as the blasting medium. The process is used in surface technology for cleaning and deburring.

(49) Dry ice is electrically non-conductive, chemically inert, non-toxic and non-combustible. In contrast to other blasting media, dry ice passes directly from a solid to a gaseous state at ambient pressure without liquifying, i.e. it sublimes.

(50) For cleaning, dry ice particles are blasted at a rate of 5000 litres of air per minute, for example, and strike the material to be cleaned at the speed of sound. This locally supercools and embrittles the layer to be removed. Subsequent dry ice particles penetrate the brittle fissures and sublime abruptly on impact. The carbon dioxide becomes gaseous, increasing its volume approx. 700× to 1000×, causing the debris or deposit to split off the surface.

(51) The advantages of this minimally abrasive process lies in the low level of damage or change to the surface to be cleaned and in the fact that no solid or liquid cleaning medium remains on the surface after working.

(52) Since dry ice is relatively soft, it does not damage the surfaces of the casting wheels. Dry ice blasting can be used to remove paint, rubber, oil, grease, silicon, wax bituminous coatings, releasing and binding agents and adhesives. In the use of dry ice blasting on the casting wheel according to the invention we also use the high kinetic energy of the blasted dry ice particles to remove solid polishing residues such as copper dust or solid abrasive residues or brush hairs from the casting track and so prevent these working resides from impacting the molten metal droplet.

(53) Compressed air at a pressure of 0.5 to 25 bar can be used as the carrier gas for the dry ice particles. In an alternative embodiment CO.sub.2 snow blasting is used. CO.sub.2 cleaning takes place during strip production.

(54) In a further embodiment the compressed air-dry ice mixture is added to a further blasting medium such as glass beads, corundum, nutshells or plastic granulate, for example. This achieves the same cleaning results as conventional abrasive blasting (sand blasting). Since dry ice is a soft blasting medium (2-3 Mohs), in some embodiments it is also possible to use the additional harder blasting media to remove stubborn impurities such as paint on steel, corrosion pitting in steel, patina on metals, etc.

(55) In a further embodiment CO.sub.2 snow blasting jets are used as the CO.sub.2-containing jet to reliably remove particulate and adhesive impurities without no adverse effect on the casting process.

(56) In CO.sub.2 snow blasting liquid CO.sub.2 from pressurised cylinders is sprayed via a nozzle system onto the surface to be treated. The expansion of the pressurised liquid CO.sub.2 creates small, highly dispersed ice crystals (snow) that strike the surface, as illustrated in FIG. 2. The nozzle system may comprise single-substance nozzles (CO.sub.2 only) or dual-substance nozzles (i.e. with the addition of compressed air).

(57) CO.sub.2 snow blasting is used for effective inline cleaning in melt spinning processes. CO.sub.2 snow blasting is the ideal process for the continuous cleaning of the surface of the cooling drum during the casting process. It can be used both on its own and in conjunction with a further wear-reduction process.

(58) The process is typically used on its own when wear mechanisms are of minor significance to ensure that the outer surface of the casting wheel is adequate throughout the casting process. Certain alloy systems (e.g. Cu-based alloys) cause only negligible signs of wear on the surface of the cooling drum. However, condensate deposits, strip residues and fine abrasion dust (for the wiper, for example) can lead to wetting defects that have a significant negative effect on strip quality and can lead to breaks. They can be removed using the blasting jet containing solid CO.sub.2.

(59) Snow blasting can also be used in conjunction with any other casting-wheel conditioning process. With forming processes (such as rolling) it offers an additional cleaning effect; with material-removing processes (such as brushing, polishing, polishing, etc.) it also helps remove any dust or other abrasive residues that may occur.

(60) If, in addition, the CO.sub.2 nozzles are arranged close to the casting nozzle, an air displacement effect means that it is also possible to positively influence wetting and the solidification rate in the region of the molten metal.

(61) As already described, CO.sub.2 snow blasting is a dry residue- and solvent-free process that requires no subsequent treatment of the worked surface. It can easily be adapted to existing processes and apparatus and adjusted to process parameters. If the relatively high air concentration limits are respected when it is used, it is can also be used in conjunction with electricity, molten metal, fire and water in complete safety.