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
  • C21C1/10—Making spheroidal graphite cast-iron
  • C21C1/105—Nodularising additive agents
• • 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
• • 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
  • C21C1/10—Making spheroidal graphite cast-iron
• • 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

• This invention relates to an alloy for the treatment of spheroidal-graphite cast irons.
• the conventional two-stage treatment often produces unsatisfactory results.
• it has to be completed by a heat treatment of the solid metal, namely by annealing above the Ac point.
• annealing gives rise to surface faults which, in turn, produce such tensions, especially in the case of castings having zones of highly variable thickness, that permanent deformations occur.
• the use of the alloy, according to the invention thus affords a number of advantages. It simplifies the handling of and reduces the losses of heat from the liquid pig iron. The losses of magnesium are reduced, thus allowing substantial quantities of this nodularizing element to be saved and much tighter control of its final content. It is known that magnesium stabilizes carbides thereby increasing the fragile/ductile transition temperature of the cast iron with the result that its content has to be adjusted to the minimum compatible with effective nodularization. On the other hand, it is no longer necessary to adjust the silicon content of the cast iron by the addition of expensive silicon-based alloys after it has been nodularized with magnesium. This is because, by virtue of the novel additional alloys, it is possible to adjust the silicon content in the blast furnace or in the cupola furnace by means of less expensive starting materials.
• the additive alloy of the present invention is of the Fe-Si-Mg type and contains the Ba-N couple, the nitrogen being introduced, for example, by bubbling.
• the composition is as follows:
• the alloy is further characterized by a ratio by weight of MgzBa of 1 part by weight Mg to l-3 parts by weight Ba.
• the various constituents of the alloy of the invention are balanced to produce not only a ferrite matrix, but also a uniformity in the size of the spheroids precipitated and a level of resistance to the formation of troublesome elements (especially carbide formers) which is reflected in the tolerance, during manufacture of the cast iron, of a recycling rate (introduction of scrap and returns) which can reach 50% and higher.
• the alloy of this invention is characterized by the following:
• quantity of alloy to be used is such that the magnesium is usually present in a quantity of from 0.08 to 0.3% of the weight of the cast iron to be treated.
• cast irons can be nodularized with additive alloys of the Fe-Si-Mg-Ca-N type in which some of the nitrogen is present in the form of a suspension of calcium cyanarnide.
• A treatment with an alloy according to the invention
• B- substantially identical treatment except that the alloy contains Ca instead of Ba and then a quantity, equivalent to approximately 0.8% of the weight of the cast iron obtained, of an inoculating alloy which is a ferrosilicon with a silicon content of 75%.
• the three comparative treatments with alloys A, B and C are carried out on the same basic cast iron made in an induction furnace. Three batches of 600' kg. each are removed from the furnace for each of the treatments described.
• the temperature of the cast iron during treatments A, B and C is between 1480 C. and 1520 C.
• the castings and the control specimens are produced at the end of ladle casting
• the period of time elapsing between the treatment and casting of the specimens under examination was between 10 and 15 minutes.
• Tables 1 and 2 give the results obtained from micrographic structural examinations and from mechanical tests on the crude cast metal.
• Liquid cast iron is made in an acid cupola from a batch comprising 50% of new cast iron and 50% of scrap castings, being subsequently desulphurized with CaC by known methods.
• the cast iron is then transferred to a holding-type induction furnace. Passage through this holding furnace enables the silicon content of the cast iron to be adjusted before treatment A and B so as to obtain, after treatment, a cast iron having a composition comparable to that of a cast iron which has been subjected to treatment of type C.
• Treatments A and B comprise introducing, in sandwich" form, into the cast iron to be treated, a quantity of approximately 1.8% by weight of this cast iron of an alloy containing for treatment A:
• Treatment C comprises introducing in sandwich form into the cast iron to be treated, first a quantity equivalent to about 1.8% by weight of this cast iron of a nodularizing Fe-Si-Mg alloy with 8.10% Mg content containing:
• EXAMPLE 1 2.250 kg. of a master alloy, representing the practice of this invention, containing, in addition to iron and the usual impurities, 48.2% by weight silicon, 9.1% by weight magnesium, 4.75% by weight barium and 0.4% by weight nitrogen, is introduced by means of a known type of plunger into a ladle containing 75 kg. of cast iron, containing carbon and silicon, maintained at a temperature of 1480" C.
• the resulting cast iron has the following composition:
• the castings and the control specimens show a precipitation of perfectly spheroidal graphite. No carbide is present in the castings, even in the thin zones.
• the matrix has a ferrite content.
• EXAMPLE 2 4 kg. of a master alloy of this invention containing, in addition to iron and the usual impurities, 47.4% silicon, 5.02% magnesium, 2.70% barium, 0.4% calcium and 0.30% nitrogen, are introduced by means of a plunger into a ladle containing 75 kg. cast iron at a temperature of 1510 C.
• the cast iron has the following composition:
• the castings show a precipitation of perfectly spheroidal graphite. No carbide is present in the castings, even in the thin areas.
• the matrix has a ferrite content of 85 to 90%.
• EXAMPLE 3 13.2 kg. of a master alloy, containing 49.4% by weight Si, 8.8% Mg, 4.85% Ba, 0.32% Ca, 0.46% N, the remainder to 100% consisting of iron and impurities, are introduced by the so-called sandwich technique into a ladle containing 600 kg. of a cast iron prepared in an arc furnace from a batch comprising 40% of scrap iron and 60% of scrap castings at a temperature of 1480 C. (In the sandwich technique, the mother alloy is initially placed at the bottom of a treatment ladle, covered with scrap iron and then the cast iron to be treated is poured into the ladle.)
• the cast iron contains 3.55% C, 2.70% Si and 0.058% Mg.
• EXAMPLE 4 600 kg. of cast iron having a temperature of 1480" C. are treated by the sandwich technique with 25 kg. of a master alloy of the invention, containing 43.2% Si, 3.6% Mg, 15% Ba, 0.19% N, the remainder to 100% consisting of iron and impurities.
• Casting is finished 12 minutes after the treatment.
• All the castings obtained consist of spheroidal graphite cast iron. Examination reveals a carbide-free ferrite structure in the crude cast state.
• the average composition is as follows:
• the method for treatment to produce spheroidal graphite cast irons comprising introducing into the Cast iron while in the molten state an alloy additive consisting essentially of 4055% by weight Si, 3-15% by weight Mg, 1.48.6% by Weight Ba, nitrogen in an amount to provide a weight ratio of Ba: N within the range of 5-50, the remainder being iron plus impurities.

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)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9054061

Family Applications (1)

Country Status (15)

Cited By (6)

• 1970
  • 1970-04-16 FR FR7013757A patent/FR2087003A5/fr not_active Expired
• 1971
  • 1971-03-04 US US00121178A patent/US3717456A/en not_active Expired - Lifetime
  • 1971-04-12 IL IL36594A patent/IL36594A/en unknown
  • 1971-04-13 NO NO01358/71A patent/NO127201B/no unknown
  • 1971-04-13 LU LU62982D patent/LU62982A1/xx unknown
  • 1971-04-13 BE BE765645A patent/BE765645A/xx not_active IP Right Cessation
  • 1971-04-13 ES ES390133A patent/ES390133A1/es not_active Expired
  • 1971-04-13 NL NLAANVRAGE7104866,A patent/NL169347C/xx active
  • 1971-04-14 CA CA110341A patent/CA935670A/en not_active Expired
  • 1971-04-14 ZA ZA712390A patent/ZA712390B/xx unknown
  • 1971-04-14 SE SE7104815A patent/SE380291B/xx unknown
  • 1971-04-14 CH CH532271A patent/CH522737A/fr not_active IP Right Cessation
  • 1971-04-15 AT AT319771A patent/AT312646B/de not_active IP Right Cessation
  • 1971-04-16 BR BR2266/71A patent/BR7102266D0/pt unknown
  • 1971-04-19 GB GB1289925D patent/GB1289925A/en not_active Expired

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