Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/072—Treatment with gases
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/30—Regulating or controlling the blowing
  • C21C5/35—Blowing from above and through the bath

Definitions

• the present invention relates to the gas treatment of a melt, particularly a metal melt, in a converter, and particularly pertains to a method of intensifying and making more effective the contact between gas and melt, and of achieving effective admixture of the gas with the melt.
• the invention also relates to an arrangement for carrying out such treatment.
• the gas is introduced to the melt through a plurality of nozzles disposed in a converter.
• the nozzles are con- nected, via a vaporizer, to a storage container which contains gas in a liquid state.
• the storage container normally consists of a pressurized container having a working pressure of 16 or 25 -bars. Because of pressure losses, the working pressure of 25 bars will give a maximum pressure of about 15 bars at the cold ends of the nozzles. In practice, this pressure is even lower, about 12 bars, because the process cannot be carried out with optimum values.
• the hydrostatic pressure in the converter in the locations of the nozzles can be about 4 bars, and hence the useful pressure-difference of the delivered gas flow is only about 8 bars.
• a pressure in the order of 8 bars will cause the gas delivered to the melt to bubble up towards the surface of said melt in the form of relatively large gas bubbles. Because of the low pressure, these bubbles will rise relatively close to the wall where the nozzle concerned is situated.
• the system operates with a two-phase system, a gas-phase in the form of discrete bubbles and a liquid phase in the form of separate, homogenous lumps of melt, these two phases remaining separate from one another.
• the present invention is based on the realization that gas could be better introduced into the melt and ad ⁇ mixed therewith if it were possible to deliver the gas at a much higher pressure, therewith providing a greater impulse and improved conditions for achieving a more effective process and of eliminating certain pro- blems associated with present-day techniques and render the process more positive.
• a method of the kind mentioned in the introductory paragraph of the description is particularly charac- terized in that, in accordance with the invention, the gas is delivered to the melt in the form of at least one high-pressure jet; and in that the pressure of the jet is so great as to achieve a finely divided mixture of gas or melt in a jet zone in said melt.
• the gas jet will preferably have a pressure within the range of 20-200 bars, preferably 70-130 bars.
• Figure l illustrates schematically an arrangement con ⁇ structed in accordance with known techniques.
• FIG. 2 is a corresponding arrangement which has been modified in accordance with the present invention.
• Figure 1 of the drawing illustrates schematically a converter 1 for manufacturing steel and containing a molten metal bath or melt 2.
• the converter can be tipped around an axis 3.
• a gas pipe 4 for instance operative to deliver oxygen gas for the purpose of decarburizing the metal melt 2, is connected to a plurality of nozzles 5 mounted on one side of the converter, of which nozzles only one is shown.
• the gas source used is a storage container 6 which contains gas in liquid state, said liquid gas being vaporized in a vaporizer 7 prior to being delivered to the nozzles 5.
• the pressure at the cold end of the nozzles 5 will be at most about 15 bars, and normally only about 12 bars. Furthermore, if the hydrostatic pressure at the nozzle locations is about 4 bars, the useful working pressure will only be about 8 bars. This will cause the gas to rise towards the surface of the melt in the form of relatively large, discrete gas bubbles, without causing appreciable turbulence in the melt.
• FIG 2 illustrates an arrangement which has been modified in accordance with the invention and in which a cryopump 9 is incorporated in the line between the storage container 6 and the vaporizer 7.
• a cryopump 9 is incorporated in the line between the storage container 6 and the vaporizer 7.
• a pressure of the aforesaid magnitude will result in the generation of a jet zone 10 in the melt 2, in which zone there is obtained an emulsion-like finely divided mixture of melt and gas, which provides a maximum con ⁇ tact surface area between said melt and gas, and also result in highly effective admixture of gas with melt as a result of the turbulence that ensues.
• This thorough admixture of gas with melt is achieved because the mixture, which moves forwards at high speed in the jet zone 10, will entrain surrounding melt 2 therewith.
• each nozzle When using a plurality of such nozzles, for instance three nozzles, each nozzle will produce a mixing effect at a deeper depth into the melt than the nozzles of the Figure 1 embodiment, and therewith, when seen in total, a much more effective mixture of the gas with the melt and more effective contact between said gas and said melt.
• the use of a pressure-elevating cryopump in accordance with the invention also means that the arrangement between the pump and the converter need only include pipes and nozzles of small dimensions, which, among other things, renders the high-pressure system accord ⁇ ing to the invention more beneficial from the aspect of cost.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Carbon Steel Or Casting Steel Manufacturing (AREA)
• Manufacture And Refinement Of Metals (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20376091

Family Applications (1)

Country Status (7)

Families Citing this family (2)

Citations (1)

Family Cites Families (5)

• 1989
  • 1989-05-29 SE SE8901915A patent/SE463876B/sv not_active IP Right Cessation
• 1990
  • 1990-05-22 BR BR909007404A patent/BR9007404A/pt not_active Application Discontinuation
  • 1990-05-22 EP EP90909210A patent/EP0474759A1/en not_active Withdrawn
  • 1990-05-22 JP JP2508697A patent/JPH04505480A/ja active Pending
  • 1990-05-22 WO PCT/SE1990/000339 patent/WO1990015160A1/en not_active Application Discontinuation
  • 1990-05-22 US US07/776,351 patent/US5211743A/en not_active Expired - Fee Related
• 1991
  • 1991-11-28 FI FI915606A patent/FI915606A0/fi not_active Application Discontinuation

Patent Citations (1)

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