Classifications

• • 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
• • 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

• This invention relates to unique ferrous alloys possessing improved properties, and processes for preparing the same, and, more particularly, to cast iron containing small, but effective, amounts of an addition agent selected from Group III metals of the periodic table.
• ferrous metal containing carbon can be improved by forming the graphite in compacted, spheriodal, and nodular shapes.
• the metallic matrix is free of discontinuities, and possesses superior physical properties, particularly improved ductility.
• Gray iron has been made more ductile by addition to the molten iron containing graphite-yielding carbon, certain agents, such as cerium, magnesium, calcium, misch metal, and the other materials, in the elemental form, as alloys, as mixtures with inert substances, or as chemical compounds of the desired addition metal.
• Copending application Serial No. 789,468, filed December 15, 1958, now Patent No. 3,055,756, assigned to the same assignee discloses yttrium as an addition for producing nodular iron.
• Elemental yttrium addition to molten cast iron is remarkably quiet, compared, for example, with elemental magnesium; however, the heat of solution of yttrium is exothermic and there is noticeable activity in the bath when yttrium is added. Furthermore, elemental metals are expensive to produce, and are sometimes less effective as nodularizers because of their method of manufacture.
• the invention is concerned with addition to molten cast iron mix the hydride of a Group III metal of the periodic table having atomic numbers up to 71.
• the hydride of metals of Group III of the periodic table having atomic numbers up to 71 when added to a molten cast iron mix decompose to release the elemental metals which act as nodularizing agents, produce marked improvements in ductility of the cast product.
• the decomposition reaction is endothermic and offsets the simultaneous exothermic heat of solution, so that the addition is more quiet than obtained by elemental metals having high boiling points.
• the decomposition reaction is as follows:
• Group III metal hydrides within the above definition are not equally effective, available, or desirable, they include the light and heavy lanthanons, and yttrium. Special preference is given to yttrium.
• the micro-structure in one form of product of the invention is obtained in the as-cast condition, with spheroidal, compacted, or nodular graphite and substantially devoid of the flake form.
• the nodular, or spheroidal, form of carbon is obtained in any matrix which as-cast, without a nodularizing agent, possesses flake graphite, such as gray cast iron.
• the various matrix constituents and structure can be controlled by well known methods by regulating the ingredients with or without heat treatments to obtain, for instance, pearlite, ferrite, martensite, tempered martensite, acicular transformation product of austenite, or combinations of the foregoing.
• the addition of Group III metals also enhances what would otherwise be white iron, in another form of the invention. If heat treatments of the white iron are employed, beneficial results are obtainable which are attributable to the addition. Also, the presence of-Group III metals in white iron improves its physical characteristics, in some instances. In the production of malleable iron, the presence of the addition agents shortens the essential heat treatment, or annealing cycle.
• the amount of addition agent to be introduced to the bath will depend upon a number of conditions. If too large a quantity is retained in the product, iron carbide will result in the as-cast structure. Too small amounts of addition agent will fail to obtain the optimum nodularizing effect of the carbon.
• the temperature of the molten iron, the contemplated delay in casting after introduction of addition agent, the proportion of retained addition agent in the product, and the amount of retained addition agent desired will be factors to be considered. Amounts will, therefore, be such as to obtain in the cast metal retained addition agent in the proportions previously indicated.
• the molten bath was inoculated with approximately 0.5% silicon as ferr c-silicon and cast into a mold.
• the resulting casting possessed as-cast graphite in spheroidal compacted form.
• a further advantage of the invention is the release in situ of the elemental metal by the decomposition of the hydride in the molten bath. This controls the elemental metal, so that it is in a form effective for nodularizing which may not be the case if produced in elemental form by certain manufacturing techniques.
• Another advantage is the economic route for the preparation of certain metal hydrides which is less expensive, in certain instances, than preparation of elemental metal.
• the process for producing iron castings in which graphitic carbon is present in the nodular form and with substantially no separation of flake-like graphitic carbon which comprises the steps of preparing a bath of molten cast iron mix, introducing into said bath a small but effective amount of the hydride of a Group III metal having an endothermic heat of decomposition selected from the class consisting of lanthanons and yttrium, and thereafter casting metal from said bath to produce a casting containing a small but effective amount of addition agent and containing graphite in a compacted form.
• the process for producing iron castings in which graphitic carbon is present in the as-cast state as agglomerates of nodular form and with substantially no separation of flake-like graphitic carbon which comprises the steps of preparing a bath of molten cast iron mix, introducing into said bath the hydride of a Group III metal having an endothermic heat of decomposition selected from the class consisting of lanthanons and yttrium, in etTective amounts ranging from about 0.2% to about 0.8% by weight, and thereafter casting metal from said bath to produce a casting containing a small but effective amount of addition agent and containing graphite in acompacted form.

Landscapes

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

Priority Applications (3)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22588186

Family Applications (1)

Country Status (3)

Cited By (4)

Citations (2)

• 1961
  • 1961-12-29 US US163035A patent/US3146090A/en not_active Expired - Lifetime
• 1962
  • 1962-05-11 GB GB18192/62A patent/GB946642A/en not_active Expired
  • 1962-05-25 BE BE618107A patent/BE618107A/fr unknown

Patent Citations (2)

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