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

Definitions

• the treatment medium has been a silicon-free magnesium master alloy, such for example, a Ni-Mg (nickel-magnesium) or Cu-Mg (copper-magnesium).
• a silicon-free magnesium master alloy such for example, a Ni-Mg (nickel-magnesium) or Cu-Mg (copper-magnesium).
• the nickel or copper which has thus been introduced produces no ferritization but instead favors the pearlite formation. Consequently, these known magnesium containing silicon-free master alloys should not be used for the production of ductile cast irons which are to possess a ferritic basic structure.
• Fe- Mg master alloys in the form of compressed material, as treatment additives for cast iron with spheroidal graphite.
• Fe-Mg master alloys have not been reliable, and the formation of spherolites has often been imperfect.
• an unfavorable shape and a small number of spherolites lowers the mechanical characteristics of the castings made from cast iron having such spherolitic graphite.
• a further drawback of these specifically master alloys having light weights reside in their handling because these alloys do not, of themselves, become submerged in the basic ferrous melt, but float upon the surface, and thus impair the magnesium (Mg) yield. When used in an immersion process, the treatment costs become substantially increased.
• the invention provides a process for producing a ductile cast iron which can be used to form a casting having improved plastic-deformation behavior and improved notch-impact toughness values.
• the process includes the step of adding to an initial melt at least metallic cobalt and magnesium in common and simultaneously, in quantities that lead to residual magnesium contents of 0.01 to 0.08% by weight, and to cobalt contents of 0.1 to 1.5% by weight, in the casting.
• the treatment process of the invention also has the same advantages as nickel-magnesium or the copper-magnesium treatments, particularly with respect to the simple manipulation required for introduction into the melt.
• the magnesium may be replaced, in part, by at least one other of the elements known to promote a formation of spherolitic graphite, such for example as calcium, yttrium and/or rare earthmetals, for example, cerium, lanthanum, etc.
• spherolitic graphite such for example as calcium, yttrium and/or rare earthmetals, for example, cerium, lanthanum, etc.
• magnesium is insoluble in its solid state in cobalt, it is not possible, because of the alloying behavior of these two elements, to smelt a actual magnesium-cobalt master alloy.
• the addition of the treatment medium to the molten ferrous based materials can, however, be accomplished advantageously by adding compressed and/ or sintered formed items, briquettes or compressed items, that contain in finely comminuted form at least cobalt and magnesium, and are except for impurities, free of silicon.
• Porous cobalt-carrying substances impregnated with magnesium can also be added to the molten metal.
• formed items, produced from comminuted or pulverized cobalt and mag nesium by the aid of binding mediums, such for example, as lime milk or cement, that do not influence the quality of the melt can be used to introduce the cobalt and magnesium.
• a ductile cast iron treated with a cobalt-magnesium additive is in the production of a casting that upon solidification displays an aligned dendritic crystalline growth, such for example, as a thin-walled sand casting, a continuous-length casting or a casting made in permanent molds producing a relatively great shrinkage effect, e.g. a casting made in a chill-mold.
• the invention is also applicable to a cast iron with spheroidal graphite having a maximum silicon content of 2.1% by weight, a maximum phosphorous content of 0.05% by weight, and a maximum magnanese content of 0.1% by weight, for making castings having a preponderant ferritic basic structure and that at room temperature and at lower temperatures down to -40 C. display an improved plastic deformation behavior. It is hereby possible to tolerate in the ferritic basic structure, depending on the required plastic deformability, a pearlite proportion going up to about 20% as viewed at the surface of the microstructure under a 100-times optical enlargement.
• the magnesium-cobalt treatment of the invention also allows a casting, apart from special cases, to be used in the cast state without further time-consuming and expensive heat-treatments.
• EXAMPLE 1 In a high-frequency induction crucible furnace of suitable size, lined with masses of compressed magnesite, about 11 kilograms (kg.) of magnetic iron scrap was melted down and carburized with 0.5 kilogram (kg) of graphite.
• the basic melt was treated with a cobalt-magnesium additive medium at a temperature of 1480 C., or C.
• the additive medium had previously been prepared, by a powder-metallurgical technique, from a mixture of 76% powdered cobalt (99.56% Co content, grain size 40 microns tm.]), 4% cesium (Ce) powder of a similar grain size, and 20% magnesium (Mg) powder (99.8% Mg, grain size 100 MIL), the form of compressed tablets which had been cold-pressed with a pressure of 3.5 metric tons per square centimeters (cm?).
• the quantity of treatment medium added amounted to 1% of the weight of the melt.
• the additive was introduced through immersion, by means of a graphite bell, in the molten metal.
• the treatment proceeded smoothly, and without any special light effects.
• the treated melt was inoculated with 0.3% Fe-Si (75%), and was then cast into specimens for testing (Specimen Y-block size 2 in per ASTM A536 67) the casting being done in dry slightly preheated sand molds.
• EXAMPLE 2 A ferrous based melt, smelted as described above and whose silicon content amounted to approximately 1.7% by weight, was treated with a treatment medium made by cold-compression from cobalt, magnesium and aluminum in the following proportions: 60% cobalt; 20% magnesium; 20% aluminum. The treatment temperature of Example 1 was retained.
• EXAMPLE 3 For the continuous casting of horizontal bars (35 to 43 mm. diameter) from ferrous material with spheroidal graphite having a preponderatingly ferritic basic structure, it is necessary periodically to re-treat the basic melt, pretreated with various kinds of Mg master alloys, in heat retaining containers with Mg-containing additives, for the purpose of compensating the fading-away effect of the initial magnesium (Mg) treatment.
• the quantity of iron present in each case in the heatretaining container of the continuous-casting machine is, at intervals of about 1 hour given an addtion of 400 to 800 kg. of pretreated liquid metal.
• the treatment is carried out by the immersion process, with 3.4 kg. of Mg-Co additive at intervals of 10 to 15 minutes.
• the treatment temperature is 1340 C.
• the continuous-casting produced in this way has the following measured final values: Yield strength: 38 to 45 kg./mm. Tensile strength: 43 to 65 kg./mm. Elongation in 2 in.: 17% to 21%; BHN: kg./mm.
• microstructure showed across the entire cross-section a very uniform and preponderant ferritic solidification, with perfectly-formed small spherolites.
• Mg-Co additives By using Mg-Co additives a definite high degree of uniformity of the structure occured, and. the separating-out of eutectic cementite was suppressed, while slag and dross inclusions were diminished.
• the invention is obviously not limited to the above described examples. It is, of course, also easily possible to increase the already very good mechanical characteristics of the castings obtained in their cast state by heat treatment.
• a process for the production of cast iron with spheroidal graphite comprising the step of adding at least metallic cobalt and metallic magnesium in common and simultaneously to a melt with the cobalt and magnesium being added in quantities to produce a residual cobalt content of from 0.1% to 1.5 by weight and a residual magnesium content of from 0.01% to 0.08% by weight.
• a process as set forth in claim 1 which further comprises the step of adding at least one element from the group consisting of spherolite forming elements to the melt in common and simultaneously with the cobalt and magnesium.
• a process as set forth in claim 2 which further comprises the step of simultaneously adding aluminum in a quantity of up to 3 by weight of the melt with the cobalt and magnesium.
• a process as set forth in claim 1 which further comprises the step of simultaneously adding aluminum in a quantity of up to 3 by weight of the melt with the cobalt and magnesium.
• a process for the production of cast iron with spheroidal graphite consisting of the step of adding metallic cobalt and metallic magnesium in common and simultaneously to a ferrous melt, said cobalt being added in an amount by weight greater than the amount of added magnesium.

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• 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)
• Manufacture And Refinement Of Metals (AREA)

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Publications (1)

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• 1969
  • 1969-12-30 CH CH1937869A patent/CH521443A/de not_active IP Right Cessation
• 1970
  • 1970-01-14 DE DE19702001495 patent/DE2001495A1/de active Pending
  • 1970-01-21 NL NL7000859A patent/NL7000859A/xx unknown
  • 1970-10-15 AT AT930770A patent/AT312023B/de not_active IP Right Cessation
  • 1970-11-30 US US93802A patent/US3689255A/en not_active Expired - Lifetime
  • 1970-12-03 CA CA099731A patent/CA934992A/en not_active Expired
  • 1970-12-10 GB GB1289627D patent/GB1289627A/en not_active Expired
  • 1970-12-29 FR FR7047091A patent/FR2072125B1/fr not_active Expired

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