Classifications

• • 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
  • B22D11/111—Treating the molten metal by using protecting powders

Definitions

• the invention relates to a casting powder for the continuous casting of steel on the basis of silicate slags following analysis values as well as impurities due to raw materials.
• casting powder is generally introduced into the continuous casting mold in order to protect the liquid steel flowing into the mold by means of an immersion tube against reoxidation, to dissolve the ascending oxidic inclusions and to produce a well-lubricated lubricating film between the solidifying steel strand and the mold.
• Mixtures of finely ground, oxidic and carbonate raw materials are mostly used for this purpose. These mixtures may also contain a few percent of graphite to prevent the powder particles from prematurely sintering or melting into lumps when heated (see U.S. Patent 3,964,916).
• the mixed continuous casting powders are very uncomfortable to handle, because they are very dusty when they are poured into the mold.
• the powders mentioned in practice there is a common defect: the powders form more or less large lumps on the surface of the bath before a melted slag layer is formed. These lumps attach to the edge of the mold and form the dreaded cinder lines, which create impressions in the surface of the steel strand. The defects on the strand surface have to be removed at great cost either by flaming or grinding.
• the invention is therefore based on the object of providing a casting powder which does not cause the dreaded slag cords to occur and therefore the strand surface has a high degree of freedom from defects.
• a casting powder on the basis of introduction described silicate slag which is characterized in that it is pre-melted and foamed, and his mm to a grain size up to 5 milled and sieved particulate by means of an adhesive with a layer of 1, 5 to 15 % By weight of carbon black and / or graphite are coated.
• slag composition within the specified limits depends in individual cases on the special casting conditions, the particular type of continuous casting machine used and the steel melts used which are cast on the continuous casting machine.
• the powders according to the invention can be produced as follows:
• a slag of the desired composition is smelted in an electric furnace, for example.
• the superheated melt is then foamed by pouring it into water to a bulk density of 0.5 to 1.4 kg / l, preferably 0.8 to 1.2 kg / l.
• the resulting granulate is dried and ground to the desired grain size and sieved until a particle size of at least 95% by weight of the particles within 0.05 to 5 mm, preferably at least 98% by weight of the particles within 0.1 to 2 mm, with a remainder of at most 5% by weight or at most 2% by weight of fine dust.
• the premelted, ground and sieved slag is then coated, for example in a mixer, with 1.5 to 15% by weight, preferably 2 to 6% by weight, carbon black and / or graphite with the aid of an adhesive.
• Organic and inorganic adhesives can be used, adhesives based on polyvinyl acetate or polyvinyl alcohol in aqueous or alcoholic solution or as a suspension having proven particularly useful. Depending on the adhesive used, about 0.3 to 3% by weight, based on the weight of the slag, is generally required, depending on the amounts of carbon used. With the preferred amount of 2 to 6% by weight of carbon black and / or graphite as carbon component for the coating, for example, smaller amounts of about 0.4 to 1% by weight of adhesive are sufficient.
• the casting powder according to the invention When using the casting powder according to the invention, the otherwise very unpleasant development of smoke when introducing conventional continuous casting powder is avoided. When the powders are melted in the mold, there are no malodorous gases, such as those which often occur with other conventional casting powders, and are a nuisance to the operating personnel. Another great advantage of the casting powder according to the invention is that it does not dust when poured into the mold.
• silicate granules which had been foamed to a bulk density of about 1 kg / l, were sieved to a grain size of 0.1 to 1.5 mm and coated with 4% carbon black with the aid of 0.6% by weight of 10% aqueous polyvinyl alcohol.
• This continuous casting powder thus produced was used in the casting of the steel mentioned above. 493 t of steel were cast.
• the casting powder consumption was 200 kg, corresponding to a consumption of 0.4 kg / t poured steel.
• the slabs produced using the continuous casting powder according to the invention had an excellent surface quality, which was only rated good and very good according to the usual criteria.
• the surfaces of the slabs were particularly free from edge cracks and surface cracks. Except for the sprue, no pores or inclusions were found in the surface of the slab, as are otherwise very common when casting this high-aluminum steel.
• the spreading was increased significantly due to the excellent block surface compared to the usual quality level.
• a steel was cast with the following analysis: 0.08% C, 0.5% Si, 1.5% Mn and 1% Cr.
• the slag was foamed to a bulk density of 0.9 kg / l, ground to a grain size of 0.1-2 mm and with the aid of 0.8% by weight of 10% strength aqueous polyvinyl alcohol with 6% by weight of carbon black and Graphite coated in equal parts, based on the weight of the silicate slag.
• a steel was cast with the following analysis: 0.6% C, 0.3% Si and 0.6% Mn.
• the slag was at a bulk density of 1.3 kg / l. foamed, ground to a grain size of 0.1-1.5 mm and coated with the aid of 2.5% by weight of 10% aqueous polyvinyl alcohol with 12% by weight of a mixture of carbon black and graphite in equal parts.
• the billets produced in this way had a much better surface than those obtained with the mixed continuous casting powders, which was expressed in that the grinding loss in the billets produced with the powder according to the invention was only about 4%, while when using the mixed powders which are usually used a grinding loss of about 7 - 8% is expected.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

Family

ID=6069797

Family Applications (1)

Country Status (6)

Cited By (11)

Families Citing this family (19)

Family Cites Families (16)

• 1979
  • 1979-05-02 DE DE19792917763 patent/DE2917763A1/de not_active Withdrawn
  • 1979-09-10 US US06/074,223 patent/US4248631A/en not_active Expired - Lifetime
• 1980
  • 1980-03-27 JP JP3828880A patent/JPS55148715A/ja active Granted
  • 1980-04-28 CA CA000350782A patent/CA1146760A/fr not_active Expired
  • 1980-04-30 AT AT80102344T patent/ATE3251T1/de not_active IP Right Cessation
  • 1980-04-30 EP EP80102344A patent/EP0018633B1/fr not_active Expired
  • 1980-04-30 DE DE8080102344T patent/DE3063061D1/de not_active Expired

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