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
  • C21C7/076—Use of slags or fluxes as treating agents
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• scum When aluminumkilled steel is being continuously cast, nonmetallic particles accumulate atop the molten steel in the mold. This accumulation of non-metallics on the surface of steel is termed scum.
• the scum usually consists of macroscopic alumina particles on liquid steel. Frozen steel on the top surface of molten metal, with or without entrapped nonmetallics, is known as skull. Often skimmings from the mold surface are essentially steel with only a few macroscopic particles of alumina. There are a few clusters of alumina within the metal in the skull but the original surface skull layer consists of fine alumina particles in steel and this dispersion approaches a cermet in form. Fine oxides dispersed in metal are termed cermet.
• the surface (cermet) layer As soon as the surface layer of steel in the mold becomes sufficiently saturated with M particles to form the cermet layer, the surface (cermet) layer is stabilized, the viscosity is greatly increased, and, as heat is dissipated to the water-cooled copper mold above the surface of the liquid, the thin crust of metal freezes. Once frozen, the thickness of the cnist increases because heat continues to be dissipated from the surface. It is at this stage that the scum, as well as the metal crust, may become entrapped in the skin of the slab to form a breakout or an internal defect in the steel.
• One method of casting in which the formation of mold scum is controlled is teeming with a special submerged nozzle and, while casting, covering the steel with a low-melting mixture of lime, fluorides and bora tes to combine with the alumina particles. How ever, some of this mixture usually becomes entrapped beneath the skin of the slab and, when rolled, the product usually shows seams. This condition is also intolerable.
• I prevent alumina particles from forming a stable cermet layer in the mold by continuously feeding a small amount of calcium carbide to the molten steel in the tundish.
• I add from oneeighth to 2 pounds of calcium carbide per ton of steel teemed into the tundish. The addition is preferably made at the point where the stream enters the molten metal pool in the tundish.
• the calcium carbide is pulled under the surface and moved turbulently throughout the tundish where it reacts with alumina in the steel. Calcium oxidizes to form calcium oxide, which unites with the alumina particles to form a calcium aluminate.
• the calcium carbide can be added to the mold at a position adjacent to that at which the metal stream enters the mold. It can alternatively be added in the tundish above the tundish nozzle or the molten metal stream feeding the mold. Additions at these positions will cause the calcium ions to deoxidize the steel and to flux alumina particles that may be in the steel at either position or which forms in the steel because of the aluminum content and the oxygen content of the steel.
• My usual calcium carbide addition is from oneeighth to two-thirds pounds per ton of steel, but a larger addition is required when the steel is highly oxidized or where the tundish stream is ragged or excessively turbulent. Then up to two pounds of calcium carbide per ton of steel may be added. When more than one-fourth pound of calcium carbide per ton is to be added, it is desirable to have a lower than normal carbon content in the ladle.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Treatment Of Steel In Its Molten State (AREA)

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Citations (1)

• 0
  • BE BE787920D patent/BE787920A/xx unknown
• 1971
  • 1971-08-26 US US00175331A patent/US3718173A/en not_active Expired - Lifetime
• 1972
  • 1972-08-22 ZA ZA725774A patent/ZA725774B/xx unknown
  • 1972-08-23 AU AU45875/72A patent/AU4587572A/en not_active Expired
  • 1972-08-23 NL NL7211506A patent/NL7211506A/xx unknown
  • 1972-08-24 FR FR7230160A patent/FR2150485A1/fr not_active Withdrawn
  • 1972-08-25 BR BR005843/72A patent/BR7205843D0/pt unknown
  • 1972-08-25 AR AR243746A patent/AR193289A1/es active
  • 1972-08-25 IT IT69746/72A patent/IT965131B/it active
  • 1972-08-25 DE DE2241876A patent/DE2241876A1/de active Pending
  • 1972-08-26 JP JP47085780A patent/JPS4831133A/ja active Pending

Patent Citations (1)

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