Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
  • B22D41/50—Pouring-nozzles
  • B22D41/52—Manufacturing or repairing thereof
  • B22D41/54—Manufacturing or repairing thereof characterised by the materials used therefor

Definitions

• the present invention relates to a nozzle for casting ultra low carbon steel.
• an ultra low carbon steel has been proposed which contains less than 15 ppm carbon.
• a need has arisen for a casting nozzle suitable for casting ultra low carbon steels by the continuous casting process.
• alumina-graphite nozzles which are used for casting conventional, carbon-containing steels, are used for casting ultra-low carbon steels. carbon pickup becomes apparent either as the nozzle is worn away by the molten steel or through decarburization of the nozzle itself.
• conventional alumina-graphite nozzles are not suitable for use with ultra low carbon steels.
• Fused silica nozzles do not contain carbon. However, these nozzles are susceptible to wear, especially by high manganese steel.
• a casting nozzle formed of a material comprising 70 to 98 weight % of a refractory material other than carbon or graphite, and 2 to 30 weight % of boron nitride.
• the refractory material is selected from sintered or electrically fused magnesium, non-stabilized or semi-stabilized zirconia, alpha-alumina, beta-alumina, mullite, sillimanite, clay materials, fused silica, Si 3 N 4 , B 4 C and SiC.
• an inorganic bonding agent is mixed with the composition, e.g in an amount of from 5 to 20 weight % of the composition.
• an inorganic bonding agent e.g. clay (e.g. bentonite), waterglass, aluminium phosphate etc.
• the nozzle of the present invention is made by moulding the present composition followed by sintering in a reducing atmosphere.
• boron nitride If more than 30% boron nitride is used, then the nozzle is easily oxidized to B 2 0 3 and wear of the nozzle is increased. If less than 2% boron nitride is used, the desirable characteristics of boron nitride, i.e. chemical inertness and high thermal conductivity are not shown and thermal shock spalling is increased.
• compositions and bonding agents mentioned above are added with an appropriate amount of water and kneaded in a kneader for 40 minutes.
• the mixtures are dried in a drying furnace at 80°C for 12 hours so that the residual water content goes down to 1% to 3%, and thereafter crushed by a crusher to particles smaller than lmm.
• Rubber molds are filled with the thus prepared materials and molded under a molding pressure of 1,000 kg/cm 2 in order to form immersion nozzles of predetermined shapes.
• the molding products are then sintered in a tunnel furnace whose ceiling temperature is 1250°C, and manufactured into predetermined shapes.
• An immersion nozzle according to Composition 1 was compared with the conventional nozzle of Composition A When using each nozzle four times with a 250 short ton (227 tonne) ladle for 240 minutes, the wear of the present nozzle was 0.021 mm/minute while the wear of the conventional nozzle A was 0.022 mm/minute. As for the pickup of carbon, the present nozzle showed no carbon pick up while the conventional nozzle showed a carbon pick up of 11 ppm by wt.
• An immersion nozzle according to Composition 2 was compared with the conventinal nozzle of composition B.
• the wear of the present nozzle was 0.015 mm/minute while the wear of the conventional nozzle be was 0.020 mm/minute.
• the pickup of carbon the present nozzle had a carbon pick up of only 1 ppm by wt while the conventional nozzle B had a carbon pickup of 10 ppm by wt.
• a long nozzle according to the Composition 3 was used between a ladle and a tundish six times with a 280 short ton (254 tonne) ladle for 300 minutes.
• the wear was 0.023 mm/minute and there was no carbon pickup.
• An immersion nozzle according to Composition 4 was compared with the conventional nozzle of compositon A.
• the wear of the nozzle of Composition 4 was 0.023 mm/minute and the wear of the conventional nozzle of Composition A was 0.022 mm.minute.
• the pickup of carbon the nozzle of Composition 4 showed no carbon pickup while the conventional nozzle of Composition A had a carbon pickup of 11 ppm by wt.
• An immersion nozzle according to Composition 5 was compared with the Comparative Example.
• the wear of the nozzle of the Comparative Example was so substantial that the nozzle broke off for the third time while the nozzle of Composition 5 was capable of casting five times for 250 minutes.
• the wear thereof was 0.020 mm/minute and the carbon pickup was 2 ppm by wt.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Ceramic Products (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Continuous Casting (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=13983078

Family Applications (1)

Country Status (4)

Cited By (2)

Family Cites Families (2)

• 1983
  • 1983-05-19 JP JP58089880A patent/JPS59232959A/ja active Pending
• 1984
  • 1984-03-28 KR KR1019840001617A patent/KR840009231A/ko not_active Abandoned
  • 1984-04-27 EP EP84302838A patent/EP0126560A3/de not_active Withdrawn
  • 1984-05-10 AU AU27875/84A patent/AU2787584A/en not_active Abandoned

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