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
  • C21C7/064—Dephosphorising; Desulfurising
  • C21C7/0645—Agents used for dephosphorising or desulfurising
• • 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
  • C21C1/00—Refining of pig-iron; Cast iron
  • C21C1/02—Dephosphorising or desulfurising
  • C21C1/025—Agents used for dephosphorising or desulfurising

Definitions

• the present invention relates to desulfurizing agents for pig iron and steel melts based on a calcium carbide containing calcium oxide and to processes for their production.
• carbide for desulfurizing metal melts, in particular those carbide which, in addition to calcium oxide (hereinafter referred to briefly as lime), also contains fluorspar.
• additives in the form of a mixture consisting of lime and fluorspar are added to the melt of a relatively high-percentage carbide, the grain size of the additives being less than 20 mm, preferably 0.5 to 10 mm, and their adhesion and Crystal water content should be less than 5% by weight, preferably less than 0.5% by weight.
• carbide which has 20 to 55% by weight CaC 2 and a high CaO content of more than 45 to 80% by weight, is better suited for the desulfurization of pig iron and steel melts, especially when it is in has been produced in a certain way, and that the relatively expensive fluorspar as an additive can also be dispensed with.
• the desulfurizing agent according to the invention is obtained by entering finely divided calcium oxide in an existing and customarily produced calcium carbide melt, which already has a calcium oxide content of up to 45% by weight, in an excess of 3 to 15% by weight, based on that in the end product desired amount.
• the mixture obtained is then solidified to temperatures of 350 to 450 ° C. and pre-crushed to grain size smaller than 150 mm at these temperatures.
• the inevitably occurring grain fraction smaller than 4 mm is then separated from the remaining product and the latter is crushed to exclude moisture by breaking and grinding to grain sizes smaller than 10 mm.
• the calcium oxide which is introduced into the melt, is preheated to temperatures up to 2000 ° C., preferably up to 1100 ° C., and introduced hot into the melt at these temperatures, it is possible to determine the CaO content in the carbide to increase to 80% by weight, the higher the preheating chosen, the higher the desired proportion of additionally dissolved calcium oxide should be between 45 and 80% by weight. This enables use in low-carbon pig iron and steel melts and also increases the desulfurization yield based on calcium carbide.
• a calcium carbide melt is preferably used, which contains between 20 and 45% by weight of CaO.
• the portions smaller than 4 mm which have been screened off after the preliminary crushing essentially consist of CaaO and can be returned to the process as finely divided calcium oxide, where they, together with fresh CaO, serve as the starting product.
• the lime-coke mixture in the Möller is adjusted to a weight ratio of 100:40, which corresponds to a carbide with a CaO content of approx. 40% by weight.
• CaO with a grain size of 3 to 8 mm and a Ca (OR) 2 and CaCO 3 content of less than 1% by weight each is injected into the jet of the molten carbide which has been tapped from the furnace into a crucible at such a rate and in such a rate Amounts entered that, until the crucible is filled, there is a total CaC 2: CaO weight ratio of 43:57, which corresponds to an excess of 14% by weight CaO, based on the CaO content of 50% by weight desired in the end product. It is then cooled until the average temperature of the solidified carbide block is approximately 400 ° C. and the block has broken down to sizes smaller than 150 mm.
• the fractions less than 4 mm obtained during the preliminary crushing essentially contain the CaO used in excess, while the remaining product with grain sizes larger than 4 mm represents an intensive mixture of 50% by weight CaC 2 and 50% by weight CaO, which is then applied in the usual way Grain sizes smaller than 10 mm are ground.
• the screened grain fraction smaller than 4 mm is used together with fresh lime as a starting product.
• Example 2 The procedure is as in Example 1, with the changes that the CaO is preheated to a temperature of about 1100 ° C. and the amount of CaO is increased so that a total Cau content of 62.5 Gev % results, which corresponds to an excess of 4% by weight, based on the desired content of 60% by weight of CaO in the finished end product.
• 1800 kg of the product worked up and ground according to the invention are used to desulfurize 300,000 kg of a molten steel having a sulfur content of 0.02% by weight at 1650 ° C.
• the sulfur content of the melt is reduced to less than 0.005% by weight.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Heat Treatment Of Steel (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

Country Status (9)

Cited By (2)

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Citations (1)

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• 1979
  • 1979-05-14 DE DE19792919324 patent/DE2919324A1/de not_active Withdrawn
• 1980
  • 1980-04-14 AT AT80101985T patent/ATE4227T1/de not_active IP Right Cessation
  • 1980-04-14 DE DE8080101985T patent/DE3064206D1/de not_active Expired
  • 1980-04-14 EP EP80101985A patent/EP0019087B1/fr not_active Expired
  • 1980-04-21 CA CA000350241A patent/CA1141964A/fr not_active Expired
  • 1980-05-09 US US06/148,565 patent/US4323392A/en not_active Expired - Lifetime
  • 1980-05-13 ZA ZA00802836A patent/ZA802836B/xx unknown
  • 1980-05-13 JP JP6234480A patent/JPS55158212A/ja active Granted
  • 1980-05-13 NO NO801420A patent/NO153108C/no unknown
  • 1980-05-14 ES ES491528A patent/ES491528A0/es active Granted

Patent Citations (1)

Non-Patent Citations (4)

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