Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/003—Apparatus
  • C23C2/0034—Details related to elements immersed in bath
  • C23C2/00342—Moving elements, e.g. pumps or mixers
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/003—Apparatus
  • C23C2/0036—Crucibles

Definitions

• the present invention relates to a method for feeding supplementary metal in solid, preferably granular and/or particulate state to a bath of molten metal, said supple ⁇ mentary metal being supplied from a store down through a feed pipe which is inserted in the bath and has an inlet positioned on a level below the bath surface, at the same time as molten metal from the bath is sucked into the pipe inlet so as to be mixed with the supplementary metal which the supplementary metal passing through said feed pipe is is being molten while passing through said feed pipe.
• the invention also relates to a device for carrying out the method. Background of the invention
• a molten plating or coating metal such as zinc (hot-dip galvanising), tin (hot-dip tinning), lead, aluminium or different types of alloys.
• a molten plating or coating metal such as zinc (hot-dip galvanising), tin (hot-dip tinning), lead, aluminium or different types of alloys.
• the metal bath surface Owing to the high temperature in this context, the metal bath surface is oxidised by the oxygen in the air.
• the oxide contaminates the surface of the coating metal and must be removed in a scumming operation in which the oxide or the so-called ash is accumulated at one end of the bath and ladled out in accumulated state. Varying amounts of the coating metal accompany the ash and represent a waste which unfavourably increases the cost of the process.
• a certain amount of different kinds of impurities always collect on the bottom of the kettle, and there may also be a so-called bottom protection metal, e.g. lead, which serves to protect the cattle from being attacked. It is therefore important, especially when admixing supple ⁇ mentary metal, not to provide agitation of the bottom layer so that foreign substances enter the bath working area intended for immersion of objects, and thus to ensure that the metal in this area is kept pure.
• bottom protection metal e.g. lead
• oxide is supplied to and/or formed in the melt. This oxide must be given an opportunity of being separated in a quiet zone outside the working area above the outgoing flow of metal and at a safe distance from the inlet zone surrounding the upper part of the mixer. These oxides and other light impurities are accumulated on the surface of the metal bath. These substances must be prevented from mixing with the metal bath so as to avoid that defects are formed on the finished products.
• NO 1,357,111 and US 3,741,754 disclose devices for feeding supplementary metal to a melt. These devices resemble each other in many respects and therefore also suffer from largely the same drawbacks and deficiencies.
• the metal flow as formed is directed down ⁇ wards and cannot be directed in a different direction. This causes a flow of metal directed towards the bottom, which will carry along the impurities on the bottom, possibly also bottom protection metal, which will contaminate and deteriorate the pure melt in the working zone.
• the devices according to the above patent specifications do not allow separation of the added oxides in a quiet zone at a safe distance from the inlet zone.
• the Nor ⁇ wegian device is designed such that the contaminating material on the metal surface in the kettle, in the form of, inter alia, oxides, is not prevented from being carried along into the mixing zone where it is mixed in and contaminates the melt.
• the present invention aims at eliminating the above- mentioned drawbacks and, to this end, relates to a method for feeding supplementary metal to a bath of molten metal, said method being characterised in that the metal flow is caused to flow not only downwards via a pipe section which in known manner is substantially vertical, but also a distance in the horizontal direction via a substantially horizontal pipe section, before being allowed to flow into the metal bath.
• the invention also relates to a device for feeding supplementary metal to a bath of molten metal.
• a kettle 1 contains a bath of molten coating metal 2, e.g. zink, tin, lead, aluminium or an optional alloy.
• a storage container 3 is intended for storing a supplementary metal 4 in solid, preferably granular and/or particulate state.
• a discharge member 5 for example in the form of a screw, which can be driven at constant or variable speed by means of a suitable drive mechanism 6.
• the container 3 can be supported by a frame (not shown) which can be put on the floor beside the kettle 1.
• the inventive device which is designated 8 in its entirety, comprises a feed pipe which in the embodiment shown is composed of a substantially vertical pipe section 9 and, extending from the lower part thereof, a sub ⁇ stantially horizontal section 10.
• the upper portion of the vertical pipe section 9 is formed with an inlet 11.
• the outlet of the horizontal pipe section 10 is designated 12.
• a collar 13 of greater diameter or width than the pipe. The upper end of the collar is positioned consider- ably higher than the pipe inlet 11, while the lower end of the collar suitably extends a distance below the inlet 11.
• annular gap 14 Between the collar 13 and the narrower pipe 9 there is formed an annular gap 14 through which the molten metal 2 can pass.
• the device 8 in its entirety is supported by a schematically illustrated holder 15 which in practice can in turn be supported by the same frame (not shown) as supports the container 3. It is schematically indicated at 16 that the holder and/or the device 8 are vertically adjustable relative to the kettle 1, which renders it possible to set the inlet 11 of the pipe 9 on an optional, desired level relative to the surface of the bath.
• the pipe 9 is set such that its inlet 11 is positioned on a level below the surface 17 of the bath of molten coating metal 2.
• the inlet of the pipe can be set on an optional level below the bath surface, the flow of molten metal through the pipe can also be varied.
• a mechanical type feeding means in this case in the form of a centri ⁇ fugal pump impeller 18 which, via a shaft 19, is connected to a suitable drive mechanism, for example a motor 20 and a transmission 21.
• the feeding means 18 may also be a screw, propeller or the like.
• the horizontal pipe section 10 is pivotable and adjustable in optional directions relative to the device as such.
• the flow of metal can then be directed such that the under ⁇ lying contaminated layer is not touched and the oxide which is possibly added to the melt, rises to the surface at a desired point and at a safe distance from the inlet of the mixer.
• Adjustability can conveniently be provided by a screw joint between the horizontal and vertical pipe sections, the screws being equidistantly spaced from each other along a circle.
• the direction of the pipe can readily be changed in that the screw holes of the vertical and horizontal pipe sections are matched in different ways.
• the invention is applied in the following manner. From the container 3, the screw 5 discharges an amount of supplementary metal which is fixed per unit of time and is allowed to fall via the chute 7 into the area of the inlet 11 of the pipe 9. At the same time, the centrifugal pump impeller 18 is rotated while providing a flow of molten metal which is sucked in via the inlet 11 and discharged through the outlet 12.
• the screw 5 discharges an amount of supplementary metal which is fixed per unit of time and is allowed to fall via the chute 7 into the area of the inlet 11 of the pipe 9.
• the centrifugal pump impeller 18 is rotated while providing a flow of molten metal which is sucked in via the inlet 11 and discharged through the outlet 12.
• the amounts of molten coating metal 2 entering the pipe 9 and solid supplementary metal 4 can be adapted to each other such that an energy content is produced in the pipe 9,10, which is sufficient to melt all the supplementary metal as it reaches the bath, at the latest.
• the amount of molten metal sucked in per unit of time should thus be at least 10 times larger than the amount of supplementary metal which is simultaneously fed into the pipe.
• the amount of molten metal can advantageously be 50- 100 times larger that the amount of supplementary metal.
• 1 kg supplementary metal can thus be supplied per second, at the same time as more than 50 kg molten coating metal is sucked into the pipe 9. While passing through the pipe 9,10, the granular or particlate supplementary metal is intensively mixed with the molten coating metal and is effectively molten therein, and the fact that the molten metal is sucked down in the pipe 9 by the feeding means 18 ensures that the supplementary metal is effectively mixed with the bath and does not remain on the surface thereof.
• the bath can be replenished periodically with the required amount of supplementary metal, and after each replenishment the device described above is removed from the bath.
• This can be carried out by e.g. a fork truck or the like which simply lifts and carries away the frame on which both the holder 3 and the device 8 are mounted.
• the invention is of course not limited to the embodiment described above and shown in the drawing.
• the inventive idea is in no way restricted to returning of metal obtained by scumming of the existing bath and treated, but can also be used to feed any solid material whatsoever, for example conventional substitute metal, to the bath of molten coating metal.
• the schematically illustrated holder 15 may consist of a parallel arm system whose arms are pivotable relative to the associated frame, for example by means of a double- acting hydraulic cylinder or a screw, the chute 7 also being movably pivotable relative to the container 3, thereby to accompany the device 8 in the vertical movements thereof relative to the frame.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Coating With Molten Metal (AREA)
• Manufacture And Refinement Of Metals (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20373681

Family Applications (1)

Country Status (4)

Family Cites Families (5)

• 1988
  • 1988-10-19 SE SE8803735A patent/SE462433B/sv not_active IP Right Cessation
• 1989
  • 1989-10-17 AU AU44184/89A patent/AU4418489A/en not_active Abandoned
  • 1989-10-17 WO PCT/SE1989/000571 patent/WO1990004660A1/en not_active Ceased
  • 1989-10-17 EP EP89911626A patent/EP0439486A1/de not_active Ceased

Non-Patent Citations (1)

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