Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/10—Supplying or treating molten metal
  • B22D11/11—Treating the molten metal

Definitions

• the invention relates to a method for producing steel with a Carbon content equal to / less than 0.9 percent by weight and an Si content of 0.15 - 1.0 percent by weight according to the preamble of claim 1.
• An essential quality feature of a steel is the degree of purity. It is significantly influenced by the oxygen dissolved in the steel, which should be equal to or less than 20 ppm in order to prevent oxidation with manganese and silicon.
• the process of so-called full sedation by adding aluminum has prevailed. Since aluminum has a high affinity for oxygen, such an addition releases the still dissolved oxygen and forms Al 2 O 3 partially mixed with MgO.
• the alumina particles are naturally small, but have a high melting point, so that they can cake together during continuous casting, particularly in the turbulent areas. This is called in English clogging ". Through this clogging effect increases the immersion spout, so that the flow rate changes constantly and there is a risk that larger particles are entrained, which leads to a corresponding contamination of the steel.
• One of the known remedial measures is the calcium treatment of the steel, which is disadvantageous due to the formation of liquid aluminates clogging ".
• Another remedial measure is the supply of argon to the stopper or slide of the distribution channel.
• Another possibility is to provide the immersion spout with a channel opening in the inlet area, or to arrange a flushing stone in the perforated brick, in order in this way to add argon All of the above measures make it more difficult for the alumina particles to cake together.
• a disadvantage of this treatment is the possible inclusion of argon bubbles, which do not weld during rolling. Usually the argon bubbles are mixed with alumina particles, so that this often leads to surface defects on the end products .
• DE 25 27 156 A1 describes a method for producing a molten steel for the continuous casting process in which one from a melting unit Retain the fresh slag containing FeO tapped into a ladle sulfur-containing initial melt by adding silicon and / or aluminum deoxidized, mixed with alloying elements and possibly a vacuum treatment is subjected.
• Step on the material produced by the continuous casting process typical errors such as segregation cracks, core segregations and accumulations of non-metallic inclusions.
• the segregating elements include in molten steel dissolved oxygen and sulfur. Avoiding the The aforementioned error can be achieved if the steel to be cast in the strand contains practically no dissolved oxygen and no sulfur.
• the Lowering sulfur can be done by adding calcium and lowering oxygen reach over silicon and especially aluminum.
• the deoxidized melt with calcium treatment agents post-treatment the amount of calcium carriers is greater than for the Desulfurization and / or toughness adjustment is required.
• the addition takes place in a lid with a ladle with silica-free, preferably made of dolomite with powdered lime, the 10-30 % silica-free and non-oxygen-releasing flux, e.g. B. fluorspar and / or Alumina are admixed, and the fine-grained in the steel melt at a depth of at least 2000 mm and approx. 300 mm above the pan base with a neutral carrier gas is blown.
• the object of the invention is to provide a method for producing steel with a carbon content equal to / less than 0.9 percent by weight and an Si content of 0.15-1.0 percent by weight, in which despite deoxidation only with silicon, carbon and manganese without the addition of aluminum, the degree of purity meets the requirements and the continuous casting is free of special measures clogging "can be performed.
• a silica-setting agent is added as a slag former during tapping and / or during ladle metallurgical treatment.
• the investigations have shown that this condition alone is not sufficient. In order for the specified deoxidation reaction to proceed quickly, an intensive rinsing treatment must be carried out.
• One way to do this is through intensive floor washing as part of a vacuum treatment, usually in a stationary degassing system (VD process).
• a vacuum of less than 100 millibars should preferably be set and the floor flushing should be carried out with a gas flow of at least 4 liters per minute and ton of steel.
• a neutral flux such as e.g. B. fluorspar up to 10 weight percent has an advantageous effect.
• the alumina content of the slag must be less than / equal to 10%, preferably ⁇ 5%, since with increasing Al 2 O 3 content there is a reduction-related increase in the Al content in the steel, which in turn leads to the casting problems mentioned at the beginning.
• the advantage of the proposed method can be seen in the fact that for all steel grades with carbon contents equal to / less than 0.9 weight percent and Si contents between 0.15 and 1.0 weight percent, which do not necessarily have to be treated with aluminum, an addition of Aluminum can be dispensed with for deoxidation.
• the proposed ladle metallurgical treatment makes this process possible.
• the sharp reduction in the number of alumina particles present in the steel greatly improves the casting behavior during continuous casting, so that the clogging "effect is avoided.
• casting performance is evened out and the degree of purity is improved.
• the deoxidation costs are considerably reduced by saving aluminum, which is considerably more expensive than silicon.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Heat Treatment Of Steel (AREA)

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Publications (2)

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Citations (5)

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• 1998
  • 1998-10-07 DE DE19847271A patent/DE19847271C1/de not_active Expired - Fee Related
• 1999
  • 1999-05-27 DE DE59904362T patent/DE59904362D1/de not_active Expired - Fee Related
  • 1999-05-27 AT AT99250167T patent/ATE233142T1/de not_active IP Right Cessation
  • 1999-05-27 EP EP99250167A patent/EP0992299B1/fr not_active Expired - Lifetime

Patent Citations (5)

Non-Patent Citations (2)

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