Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C35/00—Master alloys for iron or steel
  • C22C35/005—Master alloys for iron or steel based on iron, e.g. ferro-alloys
• • 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
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/08—Making cast-iron alloys

Definitions

• the present invention relates to a ferrosilicon based inoculant for the manufacture of cast iron with lamellar, compacted or spheriodal graphite and to a method for production of the inoculant.
• Cast iron is typically produced in a cupola or induction furnaces, and generally has about 2 to 4 percent carbon.
• the carbon is intimately mixed in with the iron and the form which the carbon takes in the solidified cast iron is very important to the characteristics of the cast iron. If the carbon takes the form of iron carbide, then the cast iron is referred to as white cast iron and has the physical characteristics of being hard and brittle which in certain applications is undesirable. If the carbon takes the form of graphite, the cast iron is soft and machinable and is referred to as gray cast iron.
• Graphite may occur in cast iron in the lamellar, compacted or spheroidal forms and variations thereof.
• the spheroidal form produces the highest strength and most ductile form of cast iron.
• the form that the graphite takes as well as the amount of graphite versus iron carbide. can be controlled with certain additives that promote the formation of graphite during the solidification of cast iron. These additives are referred to as inoculants and their addition to the cast iron as inoculation.
• inoculants additives that promote the formation of graphite during the solidification of cast iron.
• inoculants additives that promote the formation of graphite during the solidification of cast iron.
• iron carbide suppressants It is thought that calcium and certain other elements suppress the formation of iron carbide and promote the formation of graphite. A majority of inoculants contain calcium. The addition of these iron carbide suppressants is usually facilitated by the addition of a ferrosilicon alloy and probably the most widely used ferrosilicon alloys are the high silicon alloy containing 75 to 80 % silicon and the low silicon alloy containing 45 to 50 % silicon.
• the supression of carbide formation is associated by the nucleating properties of the inoculant.
• nucleating properties it is understood the number of nuclei formed by an inoculant. A high number of nuclei formed improve the inoculation effectiveness and improves the carbide supression. Further a high nucleation rate may also give better resistance to fading of the inoculating effect during prolonged holding time of the molten iron after inoculation.
• the present invention relates to an inoculant for the manufacture of cast iron with lamellar, compacted or spheroidal graphite wherein said inoculant comprises between 40 and 80 % by weight of silicon, between 0.5 and 10 % by weight of calcium and/or strontium and/or barium, less than 4 % by weight of aluminium, 0 - 10 % by weight of manganese and/or titanium and/or zirconium, between 0.5 and 10 % by weight of oxygen in the form of one or more metal oxides, the balance being iron.
• the inoculant is in the form of a solid mixture of a ferrosilicon based alloy and the metal oxide.
• the inoculant is in the form of a ferrosilicon based alloy containing the metal oxide.
• the inoculant according to the present invention preferably comprises 0.5 to 5 % by weight of manganese and/or titanium and/or zirconium.
• the metal oxide is selected among FeO, Fe2 ⁇ 3, Fe3 ⁇ 4, Si ⁇ 2, MnO, MgO, AI2O3, Ti ⁇ 2 and CaSi ⁇ 2.
• the oxygen content of the inoculant is preferably between 1 and 6 9. by weight.
• the inoculant according to the present invention increases the number of nuclei formed when the inoculant is added to cast iron, thus obtaining an improved supression of iron carbide formation using the same amount of inoculant as with conventional inoculants, or obtaining the same iron carbide suppression using less inoculant than when using conventional inoculants.
• the present invention relates to a method for producing an inoculant for the manufacture of cast iron with lamellar, compacted or spheroidal graphite, comprising providing a base alloy comprising 40 to 80 % by weight of silicon, 0.5 to 10 % by weight of calcium and/or strontium and/or barium, 0 - 10 % by weight of manganese and/or titanium and/or zirconium, less than 4 % by weight of aluminium, the balance being iron, and adding 0.5 to 10 °I ⁇ by weight of oxygen in the form of one or more metal oxides to the base alloy.
• the metal oxides are mixed with the base alloy by mechanical mixing of solid base alloy particles and solid metal oxide particles.
• the mechanical mixing can be carried out in any conventional mixing apparatus which gives a substantially homogeneous mixing, such as for example a rotating drum.
• the metal oxides are supplied to a melt of the base alloy whereafter the melt is solidified.
• the metal oxides are preferably added to the stream of molten base alloy when pouring the alloy into casting moulds.
• the metal oxides may be added in the casting moulds before pouring molten base alloy into the moulds.
• the four inoculants A through D produced in example 1 were used for inoculation of a cast iron containing 3.7 % by weight of carbon, 2.4 % by weight of silicon, 0.1 % by weight of manganese 0.025 % by weight of phosphorus, 0.005 % sulphur and 0.050 % by weight of magnesium.
• two tests were made using a conventional base inoculant containing 75 % ferrosilicon, 1 % by weight of calcium, 1 % by weight of barium and 1 % by weight of aluminium.
• inoculant was added to the cast iron melts. After casting nodule densities in 5 mm sections of the castings were determined. The results are shown in table 2.
• Heat No. 1 and 2 refer to tests with the conventional inoculant, while heat No. 3 - 6 in table 2 refer to tests with inoculants A through D according to table 1 in example 1.
• Table 2 Table 2
• the inoculants according to the present invention give an increased nodule density compared to the conventional inoculant of up to about 70 %.
• the four inoculants E through H produced in sample 3 were used for inoculation of a cast iron containing 3.7 % by weight of carbon, 2.4 % by weight of silicon, 0.1 % by weight of manganese, 0.025 % by weight of phosphorus, 0.005 % sulphur and 0.050 % by weight of magnesium.
• a conventional base inoculant containing 75 % ferrosilicon, 1 % by weight of calcium, 1 % by weight of barium and 1 % by weight of aluminium.
• inoculant was added to the cast iron melt. After casting nodule densities in 5 mm sections of the casting were determined. The results are shown in table 4.
• Heat No. 1 refer to the test with the conventional inoculant
• heat No. 2 - 5 in table 4 refer to tests with inoculants E through H according to table 3 in example 3.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Soft Magnetic Materials (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

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Cited By (27)

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Citations (2)

• 1994
  • 1994-03-09 NO NO940819A patent/NO179079C/no not_active IP Right Cessation
• 1995
  • 1995-02-13 WO PCT/NO1995/000029 patent/WO1995024508A1/en active Application Filing

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