Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C37/00—Cast-iron alloys
  • C22C37/10—Cast-iron alloys containing aluminium or silicon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D19/00—Casting in, on, or around objects which form part of the product
  • B22D19/14—Casting in, on, or around objects which form part of the product the objects being filamentary or particulate in form
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
  • B22D27/20—Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor
• • 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
  • C21C1/08—Manufacture of 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
• • 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
  • C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
  • C22C29/18—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on silicides
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0242—Making ferrous alloys by powder metallurgy using the impregnating technique
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
  • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
  • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
• • 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 an inoculant alloy for treating cast-iron.
• Cast-iron is a well-known iron-carbon alloy widely used for manufacturing mechanical parts. Cast-iron is obtained by mixing the constituents of the alloy in the liquid state at a temperature comprised between 1320 and 1450° C. before casting in a mold and by cooling the obtained alloy.
• carbon When cooling, carbon may adopt several physicochemical structures depending on several parameters.
• White cast-iron has the characteristic of being hard and brittle, which is not desirable for some applications.
• gray cast-iron If carbon appears in the form of graphite, the resulting cast-iron is called gray cast-iron. Gray cast-iron is softer and may be worked.
• the liquid cast-iron undergoes an inoculation treatment aiming to introduce in the cast-iron graphitizing components or graphitization supports commonly called germs which will promote, when the cast-iron is cooling in the mold, the apparition of graphite rather than iron carbide.
• the components of an inoculant hence consist of elements which promote the formation of graphite and the decomposition of iron carbide during the solidification of the cast-iron.
• examples may include carbon, silicon, calcium, aluminum.
• an inoculant may be designed so as to fulfill other functions and comprise to this end other components having a particular effect.
• the cast-iron may also undergo prior or subsequent additional treatments.
• the formed graphite is spheroidal, vermicular or lamellar.
• Either graphitic form may be obtained preferably by a particular treatment of the cast-iron by means of specific components.
• spheroidal graphite may be promoted by a treatment called nodularizer treatment mainly aiming to provide the cast-iron with an enough quantity of magnesium so that graphite can grow so as to form round particles (spheroids or nodules).
• nodularizer components are generally added in the form of a specific alloy (nodularizer alloy) prior to the inoculant treatment of the cast-iron during a particular treatment.
• the nodularizer alloy allows essentially to influence the shape of the graphite nodules, whereas the inoculant product aims to increase the number of these nodules and homogenize the graphitic structures.
• These treatments may be performed at once or in several times and at different moments during manufacturing the cast-iron.
• inoculants are conventionally manufactured from a ferrosilicon alloy such as FeSi 45 , FeSi 65 or FeSi 75 while adjusting the chemistry according to the aimed composition of the inoculant. It may also consist of mixtures of several alloys.
• the inoculation efficiency of the cast-iron part also depends on its thickness (or on the solidification rate).
• cooling will be slower (2 to 4 hours) and will promote the formation of graphite.
• parts having areas with different thicknesses may have physicochemical structures which differ from one area to another, which is not desirable.
• the formation of degenerated graphite and/or chunky graphite may reduce the mechanical properties of the cast-iron.
• the smelter generally proceeds to the addition of pure Antimony in the liquid metal.
• the addition of pure Antimony in the liquid metal raises accuracy problems because the rate of introduction is very low (in the order of 10 to 30 g per tonne of liquid cast-iron).
• the addition efficiency of pure Antimony is comprised between 50 and 80% and the effective introduced quantity is hence difficult to control.
• degraded graphite may be formed in the structure.
• the smelter should further associate Rare Earths (abbreviated as RE) in order to achieve a maximum improvement of the form of the graphite.
• RE Rare Earths
• the part will have a spiky type graphite defect.
• the graphite defect will rather be of the chunky type, which essentially happens when the used raw materials are relatively pure.
• the introduction of pure antimony in the liquid cast-iron causes its vaporization and thus results in a strong gassing. It has been measured that, with the addition of pure antimony, the threshold of release of antimony in the working environment is higher than 0.5 mg/m 3 , which is the exposition limit value (ELV set by the regulations). Hence, the operators must work with a respirator for protection from N95-type particles or higher.
• such an inoculant for thin parts comprises in particular a ferrosilicon-based inoculant alloy and comprising between 0.005 and 3% by weight of Rare Earths, in particular Lanthanum, as well as between 0.005 and 3% by weight of bismuth, lead or antimony with a Rare Earths/(Bismuth+Lead+Antimony) ratio comprised between 0.9 and 2.2; bismuth being particularly preferred, the descriptions of these documents covering only but bismuth.
• the document WO2006/068487A1 describes an inoculant comprising a phase-modifying component (inoculant function) associated with an agent for modifying the structure of the graphite which may consist of antimony.
• this structure-modifying agent is used in mixture with the inoculant compound (ferrosilicon) and not in an allied form.
• antimony is clearly referred to as being a perlite promoter, which phase is not desirable in general, as above-mentioned.
• the used quantity of antimony is comprised between 3 and 15%, which corresponds to a significant quantity probably at the origin of the formed perlite proportion.
• JP2200718A describes an inoculant which consists of a mixture of ferrosilicon, antimony, calcium silicide and rare earths. Antimony is not used in an allied form.
• JP57067146A describes a ferrosilicon-based alloy comprising between 5 and 50% by weight of antimony and up to 10% of rare earths. Besides the high proportion of antimony, this alloy is used as a perlite inhibitor, and not as an inoculant.
• the present invention aims an inoculant alloy for treating thick ferrosilicon-based cast-iron parts, containing between 0.005 and 3% by weight of rare earths, characterized in that it also contains between 0.2 and 2% by weight of antimony.
• antimony when allied to rare earths in a ferrosilicon-based alloy according to the claimed proportions, would allow an effective inoculation, and with the spheroids stabilized, of thick parts without the above-mentioned drawbacks of pure antimony.
• the introduction of antimony in the form of an alloy allows achieving a high efficiency of use of antimony, in the order of 97 to 99%.
• the effective introduced quantity is known much more precisely.
• an alloy according to the invention allows limiting the gassing of antimony between 0.1 and 0.2 mg/m 3 and the use of a respirator mask is no longer necessary.
• the antimony/rare earths association significantly lengthens the antimony decay time. Hence, the produced effect lasts longer in the complete foundry process. It will be noted that the antimony decay time is even longer than the bismuth decay time in the inoculant alloys for thin parts.
• the alloy according to the present application upon ladle or furnace addition, may thereby allow replacing and even suppressing an additional jet or late inoculation.
• the alloy according to the present application also allows particularly limiting greatly and even avoiding the formation of chunky or spiky type graphite defects, but also improving the form of graphite by ensuring a nodularity greater than 95% while bringing the spheroids closer to the perfect sphere.
• the alloy according to the present application allows thus ensuring a homogeneous ferrite/perlite matrix across the different thicknesses of the manufactured part, which improves in particular the conditions of a subsequent machining of the part.
• the ratio Antimony to Rare Earths will be higher than 1.4, preferably higher than 1.6, and lower than 2.5, preferably lower than 2.
• the inoculant alloy also comprises magnesium. It will then be a nodularizer with an additional inoculant effect.
• antimony allows achieving a better efficiency of the magnesium introduced in the cast-iron.
• the inoculant alloy does not contain magnesium.
• the ratio rare earths to antimony is comprised between 0.9 and 2.2.
• the proportion by weight of Antimony is higher than 0.3%, preferably higher than 0.5%, still preferably higher than 0.8%.
• the proportion by weight of antimony is lower than 1.5%, preferably lower than 1.3%.
• the rare earths comprise Lanthanum, preferably only but Lanthanum.
• the proportion by weight of rare earths is higher than 0.2%, preferably higher than 0.3%.
• the proportion by weight of rare earths is lower than 1.2%, preferably lower than 1%.
• the present invention also relates to the use of the inoculant according to the invention.
• said inoculant is introduced in the form of a powder.
• said inoculant is introduced in the form of a solid insert placed in a casting mold.
• the use of the inoculant according to the invention aims to manufacture cast-iron parts having portions with thicknesses larger than 6 mm, preferably portions with thicknesses larger than 20 mm, and still more preferably portions with thicknesses larger than 50 mm.
• the inoculant according to the invention will be typically used in the context of an inoculation of a cast-iron bath. It may also be used for pre-conditioning said cast-iron as well as a nodularizer, if appropriate.
• composition of an inoculant alloy according to the invention may for example comprise:
• Inoculant alloy-composition 1 Quantity Element (% by weight) Si 45-80 Ca 0.5-4 Al 0.5-3 Sb 0.2-2 Rare Earths 0.2-3 (including Lanthanum) Iron Balance
• the inoculant may also comprise additional elements which bring particular effects depending on the required properties. More particularly, this may be the case in the context of an iron-cast pre-conditioning treatment.
• the inoculant alloy thus may have the following composition:
• Inoculant alloy-composition 2 Quantity Element (% by weight) Si 45-80 Ca 0.5-8 Al 0.5-3 Sb 0.2-2 Rare Earths 0.2-3 (including Lanthanum) Ba 2-15 Mn 2-6 Zr 2-6 Iron Balance
• An inoculation treatment will typically consist in adding from 0.05 (preferably at least 0.1%) to 0.8% by weight of the inoculant to the cast-iron bath, in particular under the following conditions given as examples:
• the grain size distribution of the inoculant according to the invention may be adapted depending on its methods of addition.
• Examples may include:
• the inoculant alloy may also be successfully added as an inoculant before filling the casting mold or during a ladle or late inoculation, after having adjusted the chemistry of the alloy (in particular Ba between 1.5 and 5% by weight and Ca between 0.5 and 2% by weight).
• composition of the alloy will also comprise magnesium.
• composition of such a nodularizer alloy with an inoculant function may be as follows:
• Nodularizer alloy with inoculant effect-composition 3 Quantity Element (% by weight) Si 30-60 Ca 0.2-5 Al 0.2-3 Sb 0.1-2 Rare Earths 0.1-3 (including Lanthanum) Mg 3-12 Iron Balance
• the grain size distribution of the nodularizer (in particular with an inoculant function) according to the invention will be adapted depending on the size of the treatment ladles. For example, for ladles with 100 to 500 kg of cast-iron, preference will be given to a grain size distribution comprised between about 0.4 and about 2 mm, and even up to 7 mm. For ladles with 500 to 1000 kg of cast-iron, preference will be given to a grain size distribution comprised between about 2 and about 7 mm, or between about 10 and about 30 mm. For ladles with more than 1000 kg of cast-iron, preference will be given to a grain size distribution comprised between about 10 and about 30 mm.
• liquid cast-iron has been treated by adding, in the induction furnace, pure antimony in a proportion of 30 g of antimony per tonne of liquid cast-iron.
• the cast-iron has undergone a nodularizer treatment by means of a FeSiMg type nodularizer alloy comprising a third of a FeSiMg alloy comprising 2% of rare earths and two thirds of a FeSiMg alloy free of rare earths.
• the cast-iron has undergone an inoculation treatment by addition, in the casting basin, of 0.1% by weight of a FeSiMnZr alloy and 0.1% of a FeSiAl alloy, the inoculant alloys being added in the form of an inoculant insert in the mold.
• the step of addition of pure antimony has been suppressed and the nodularizer treatment has been simplified by using only but a FeSiMg nodularizer alloy which does not contain rare earths.
• the foundry A treated with an inoculant according to the present application, has shown an increase of the tensile elongation on test samples for a EN-GJS-400-15 grade.
• liquid cast-iron has been treated by adding, in the induction furnace, pure antimony in a proportion of 20 g of antimony per tonne of liquid cast-iron.
• the cast-iron has undergone a nodularizer treatment by means of a FeSiMg type nodularizer alloy comprising 1% by weight of rare earths and introduced in the cast iron in the form of a cored wire.
• the cast-iron has undergone an inoculation treatment by addition, in the casting basin, of 0.15% by weight of a FeSiBiRE alloy.
• the step of addition of pure antimony has been suppressed and the nodularizer treatment has been simplified by using only but a nodularizer alloy FeSiMg which does not contain rare earths (also introduced in the form of a cored wire).
• the cast-iron B2 has achieved results in compliance with the requirements.
• liquid cast-iron has been treated by adding, in the induction furnace, pure antimony in a proportion of 25 g of antimony per tonne of liquid cast-iron.
• the cast-iron has undergone a nodularizer treatment by means of a FeSiMg type nodularizer alloy comprising 6.7% by weight of magnesium as well as 1.2% of calcium and 0.98% of rare earths.
• the cast-iron has undergone a late inoculation treatment by addition of 0.12% by weight of a FeSiMnZrBa alloy having a grain size distribution comprised between 0.2 and 5 mm.
• a nodularizer alloy with an inoculant function according to the above-mentioned composition 3 has been used.
• the nodularizer treatment has been performed by means of a FeSiMg type alloy according to the composition 3 of the present application and comprising 6.4% by weight of magnesium as well as 1.3% of calcium, 0.6% of antimony and 1.2% of rare earths.
• a complementary inoculation has been performed according to a late inoculation method with 0.09% of a FeSiAlCa alloy and 0.009% of a FeSiMnZrBa alloy.
• liquid cast-iron has been treated by adding, in the induction furnace, pure antimony in a proportion of 30 g of antimony per tonne of liquid cast-iron.
• the cast-iron has undergone a nodularizer treatment by means of a FeSiMg type nodularizer alloy comprising 9.1% by weight of magnesium as well as 1.4% of calcium and 1.1% of rare earths.
• the cast-iron has undergone an inoculation treatment by addition of a 10 kg insert per tonne of cast-iron of a FeSiMnZr inoculant alloy.
• the nodularizer treatment has been performed by means of a same alloy as the reference, namely by using a FeSiMg type nodularizer alloy comprising 9.1% by weight of magnesium as well as 1.4% of calcium and 1.1% of rare earths.
• the cast-iron D allows preparing a cast-iron EN-GJS-400-18-LT grade, used in particular in the wind power field.
• the use of the inoculant according to the application has allowed significantly increasing the impact resistance.
• the liquid cast-iron has undergone a nodularizer treatment by means of a FeSiMg type nodularizer alloy comprising 9.1% by weight of Magnesium as well as 0.8% of Bismuth and 0.7% of rare earths.
• the cast-iron has undergone an inoculation treatment according to a late inoculation method by addition of 0.18% of a FeSiMnZr alloy having a grain size distribution comprised between 0.2 and 5 mm.
• a nodularizer alloy according to the above-mentioned composition 3 has been used.
• the used alloy is a FeSiMg type alloy comprising 9.1% of magnesium as well as 0.75% of antimony and 0.5% of rare earths.
• the cast-iron has undergone an additional inoculation treatment according to a late inoculation method by addition of 0.17% of a FeSiMnZr alloy having a grain size distribution comprised between 0.2 and 5 mm.
• the foundry reference (F1) and the test (F2) using an inoculant alloy according to the application have been realized in accordance with the example 4 and the foundry D by inoculating massive parts.
• the foundry F2 has allowed for a significant economy by reducing by 31.5% the doses of antimony to be added.
• the foundry reference (G1) and the test (G2) using an inoculant alloy according to the application have been realized in accordance with the example 4 and the foundry D by inoculating massive parts.
• the antimony release is significantly limited and much lower than the regulatory threshold 0.5 mg/m 3 .
• the work conditions are thereby improved.
• liquid cast-iron has been treated by adding, in the induction furnace, pure antimony in a proportion of 15 g of antimony per tonne of liquid cast-iron.
• the cast-iron has undergone a nodularizer treatment by means of nodularizer cored wire (13 mm diameter, 32% of Mg, 1.2% of RE, 230 g/m of powder).
• the cast-iron has undergone a late inoculation treatment by addition, to the casting jet, of 0.15% by weight of a FeSiMnZr alloy.
• the cast-iron H2 Upon the impact resistance results, the cast-iron H2 has achieved results in compliance with the requirements.

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• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
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• 2012
  • 2012-11-14 FR FR1260817A patent/FR2997962B1/fr active Active
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