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
  • 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
  • C21C5/34—Blowing through the bath

Definitions

• the invention relates to a method which makes it possible to improve the operation of the nozzles, ensuring the injection of oxygen through the bottom of a converter, into a molten metal. This process is particularly useful for the manufacture of steel by refining cast iron.
• Gaseous oxygen is injected through the inner tube, while the annular space between the inner tube and the outer tube is used for the intake of a shielding gas.
• This generally consists of a hydrocarbon. It forms a protective sheath around the jet of oxygen in the contact zone between the refractory wall and the molten metal, and thanks to this protection the lively reaction which occurs with the molten metal is distant from the refractory wall . The delay thus imposed on the exothermic reaction of the oxygen and of the molten metal is sufficient to keep the refractory lining intact.
• the present invention therefore aims to improve the life of refractory linings and injection devices compared to what is already possible in the known process for refining a molten metal according to which oxygen is injected into the bath.
• molten metal at a level below that of the free surface thereof, in the form of a jet which is surrounded by an annular jet of protective gas injected simultaneously.
• the method according to the invention is characterized in that the relative speeds of the oxygen and of the protective gas on injection are chosen, so as to reduce as much as possible the mixing of the two jets by turbulence.
• the protective gas constituted for example by a hydrocarbon, plays an essential role in the process by its ability to repel oxygen.
• this protective gas By repressing the oxygen which tends to diffuse from the central jet in the annular sheath of protective gas, this protective gas has the effect of preventing the reaction of oxygen with the molten metal to take place at the interface between the refractory lining and the molten metal and at the interface between the molten metal and the injection nozzles.
• This discharge effect plays an important role in increasing the life of the nozzles and it has been found that there is every advantage in designing the nozzles so that there is as little turbulence as possible between the jet central oxygen and the annular gas jet protective.
• a ratio of between 0.5 and 1.5 between the speed of the jet of protective gas and the speed of the jet of oxygen While maintaining the speed ratio in this range, it can be advantageous, in particular in the case of a protective gas which poorly avoids mixing with oxygen, such as nitrogen, sulfur dioxide, water vapor, gas carbon dioxide or argon, to increase the overall amount of protective gas compared to that which may be sufficient in the case of a hydrocarbon.
• the invention is considered in particular in its application to the refining of cast iron in the manufacture of steel.
• This operation is carried out in a converter whose internal wall is constituted by a refractory lining.
• the converter contains molten iron.
• Gas injection nozzles pass through the bottom of the converter and open onto the internal surface of the refractory lining, according to any one of the arrangements which are described in more detail in US Patent 3,706,549.
• Each nozzle is formed from two tubes coaxial which ends with two con nozzles centric flush with the surface of the refractory lining.
• the two tubes are connected outside the converter to gas supply sources, so as to allow in operation to admit pure oxygen through the internal tube and to inject through the annular space between the inner tube and the outer tube a protective gas which is most often constituted by a hydrocarbon, but which can also be constituted by other gases such as nitrogen, sulfur dioxide, water vapor, carbon dioxide or argon.
• protective gas a relatively low endothermic gas, for example natural gas rather than propane .
• the proportion of the protective gas relative to the oxygen in the required flow rates is then relatively large. It can be further increased by using an inert gas such as nitrogen, the proportion of which is then 22 to 30% by volume relative to oxygen.
• an inert gas such as nitrogen, the proportion of which is then 22 to 30% by volume relative to oxygen.
• a relatively large internal tube diameter for example between 15 and 30 mm.
• a pressure of protective gas which is between 1/4 and 2/3 of the pressure of oxygen.
• the process can be used in the context of refining cast iron by injecting oxygen and natural gas through the bottom of the converter containing the molten bath under the following conditions:
• the invention is not limited to these particular conditions indicated by way of examples.
• the method according to the invention is not limited to the refining of cast iron. It can also be used with advantage for the treatment of other molten metals such as lead, tin, nickel, cobalt or copper.

Landscapes

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

Applications Claiming Priority (2)

Publications (1)

Family

ID=4115498

Family Applications (1)

Country Status (4)

Cited By (1)

Citations (2)

Family Cites Families (1)

• 1979
  • 1979-10-31 CA CA000338905A patent/CA1141168A/en not_active Expired
• 1980
  • 1980-10-31 EP EP80401550A patent/EP0028570A1/fr not_active Withdrawn
  • 1980-10-31 AU AU64024/80A patent/AU6402480A/en not_active Abandoned
  • 1980-10-31 JP JP15236880A patent/JPS5681612A/ja active Granted

Patent Citations (2)

Also Published As

Similar Documents

Legal Events