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

Definitions

• This invention relates to an improvement in desulfurization agent for ferrous melts, e.g., pig iron, cast iron and steel melts, and to an improved desulfurization process.
• ferrous melts e.g., pig iron, cast iron and steel melts
• precipitated, carbon-containing calcium carbonate refers to a mixture consisting essentially of finely divided calcium carbonate and carbon such as that obtained in the preparation of a dicyandiamide product, in the course of which an aqueous calcium cyanamide' suspension is treated with carbon dioxide to precipitate the calcium carbonate in a very finely divided state intimately admixed with finely divided and co-precipitated carbon.
• This precipitate contains about 70 to 85% by weight calcium carbonate and about 8 to 12% carbon in addition to minor proportions of impurities, especially ferric oxide, aluminum oxide and silicon dioxide.
• the desulfurizing agent of the invention is added to a ferrous melt in an amount that depends upon the initial and desired final sulfur contents of the melt.
• ordinary initial sulfur contents of the order of about 0.04 to 0.06% by weight
• 1.3 kg. desulfurizing agent per ton of melt suffices to reduce the sulfur content by about 0.010%
• approximately 1.7 kg. per ton is required to obtain the same effect of reducing the sulfur content by about 0.01% at melt temperatures of the order of 1200 to 1400 C.
• the desulfurizing agent of the invention is that it is available in very finely divided form. It is, therefore, entirely practical to add it to the melt by blowing or by stirring it in, the latter being accomplished with a shaking pan or a mechanical stirring device. Basically, however, introduction of the desulfurizing agent may take place in a manner suitable to any other pulverulent material and can also take place in the furnace.
• the precipitated calcium carbonate has a structure which is particularly favorable for desulfurization due, perhaps, to increased intimate mixing and contact between the iron in the melt and the calcium carbide promoted by generation of carbon dioxide.
• the finely divided carbon contained in the precipitated carbonate compensates for the slight decarbonization that takes place with desulfurization and, at the same time, provides the reducing conditions required for desulfurization.
• the desulfurizing agent of the invention is positive in its desulfurizing function and is also more economical to use because the losses of iron into the slag are thereby reduced.
• the efficiency with which the calcium carbide component of the combination is consumed, as compared with the consumption of calcium carbide when used alone, is significantly greater.
• EXAMPLE 1 (Prior art) Charges of approximately 35 metric tons pig iron each were desulfurized at between 1260 and 1380 C. with a commercial grade of calcium carbide having a CaC content of approximately by weight introduced into the melt with predried air at 5 atmospheres pressure as carrier gas.
• the carbide had granule sizes of 0.3 to 0.7 mm. in Charges Nos. 1 to 9 and 0.06 to 0.08 mm. in Charges Nos. 10 to 15.
• the amounts of carbide charged, the sulfur contents of the melt before and after desulfurization, and the efliciency were:
• Example 2 The procedure in Example 1 was repeated, all conditions remaining the same except that the desulfurization agent used was a mixture of (A) 80% by weight of the same commercial grade calcium carbide having a CaC content of approximately 80%, and (B) 20% by weight precipitated calcium carbonate containing approximately 75% by weight CaCO 12% by weight carbon and the remainder Fe O A1 0 and SiO impurities.
• the carbide had granule sizes of 0.06 to 0.08 mm. and the precipitated carbonate had granule sizes of less than 0.06 mm.
• the desulfurization agent used was a mixture of (A) 80% by weight of the same commercial grade calcium carbide having a CaC content of approximately 80%, and (B) 20% by weight precipitated calcium carbonate containing approximately 75% by weight CaCO 12% by weight carbon and the remainder Fe O A1 0 and SiO impurities.
• the carbide had granule sizes of 0.06 to 0.08 mm. and the precipitated carbonate had granule sizes of less than
• a desulfurization agent for ferrous melts essentially consisting of from about to about 98% by weight calcium carbide and from about 2 to 40% by weight precipitated, carbon-containing calcium carbonate.
• a process for desulfurizing a sulfur-containing ferrous melt which comprises treating said melt with between about 1.3 and 1.7 kg. of a desulfurization agent per ton of iron melt per 0.01% desired reduction in sulfur content, said desulfurization agent consisting essentially of from about 60 to about 98% by weight calcium carbide and from about 2 to about 40% by weight precipitated, carbon-containing calcium carbonate.

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)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=5694942

Family Applications (1)

Country Status (9)

Cited By (30)

Families Citing this family (8)

• 1968
  • 1968-04-29 DE DE19681758250 patent/DE1758250B1/de active Pending
• 1969
  • 1969-03-11 SE SE03300/69A patent/SE341196B/xx unknown
  • 1969-03-12 CH CH375969A patent/CH514677A/de not_active IP Right Cessation
  • 1969-03-12 AT AT243369A patent/AT297768B/de not_active IP Right Cessation
  • 1969-03-27 BE BE730577D patent/BE730577A/xx not_active IP Right Cessation
  • 1969-03-27 FR FR6909166A patent/FR2007154A1/fr active Pending
  • 1969-04-18 LU LU58448D patent/LU58448A1/xx unknown
  • 1969-04-28 US US819997A patent/US3598573A/en not_active Expired - Lifetime
  • 1969-04-29 GB GB1226088D patent/GB1226088A/en not_active Expired

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