US3674576A - Alloy cast iron - Google Patents

Alloy cast iron Download PDF

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Publication number
US3674576A
US3674576A US869440A US3674576DA US3674576A US 3674576 A US3674576 A US 3674576A US 869440 A US869440 A US 869440A US 3674576D A US3674576D A US 3674576DA US 3674576 A US3674576 A US 3674576A
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Prior art keywords
alloy
nickel
amount
heat
cast iron
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Expired - Lifetime
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US869440A
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English (en)
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Charles Robert Van-Der Ben
Joseph Albert Pope
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Mirrlees Blackstone Ltd
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Mirrlees Blackstone Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/06—Cast-iron alloys containing chromium
    • C22C37/08—Cast-iron alloys containing chromium with nickel

Definitions

  • a heat-treated alloy cast iron consisting essentially of to of a nickel equivalent component consisting of a metal selected from the group consisting of nickel, nickel equivalent metals and mixtures thereof, at least about 8% of said alloy being nickel, said nickel equivalent metals being present in an amount not over about 8% of said alloy and being selected from the group consisting of copper and manganese, the amount of copper not exceeding about 3% of said alloy, the amount of manganese, when present as an intended alloy addition, not exceeding about 2% of said alloy, the balance of the alloy consisting essentially of iron and carbon, and any manganese present as an incidental constituent, up to 1% of said alloy, not being included in said nickel equivalent metal amount, the presence of chromium being limited to a residual amount not exceeding about 0.07% of said alloy, all percentages being by weight, said alloy having been cast into an unstable austenitic structure which may contain martensite, then heat-treated to transform said austenitic cast iron into a baino-mar
  • This invention concerns an alloy cast iron, more particularly it concerns the heat treatment of a particular alloy to obtain highly desirable properties.
  • the invention is the result of a metallurgical research program carried out with a view to producing a machinable alloy cast iron having axceptionaly high strength and shock resistance and having structural stability over prolonged periods at temperatures of up to 500 C., and suitable for the construction of components of internal combustion engines or similar machinery, subject to high mechanical and thermal stresses and shock.
  • Normal plain (unalloyed) pearlitic grades of engineering irons are prone to structural breakdown on prolonged heating at temperatures in the range of 400450 C. and are subject to sharply falling mechanical properties at temperatures above about 450 C. on short time heating and have poor creep resistance at such temperatures.
  • alloyed pearlitic irons have rather better properties, depending upon the amounts and combination of alloying elements employed and the general composition balance but do not give the marked stability sought, this also applies to S.G. Iron.
  • Many special alloy irons have been developed for specific applications (e.g. resistance to heat, corrosion, scale, wear, etc. and other properties such as magnetic, electrical, etc.) but these do not give the combination of properties desired.
  • an alloy cast iron consists essentially of a component equivalent to from 10 to 15% of nickel and consisting of a metal taken from the class consisting of nickel, nickel equivalent metals and mixtures thereof, at least about 8% of such metal being nickel, the nickel equivalent metals being present in an amount not over about 8% and being taken from the class consisting of copper and manganese, the amount of copper (if present) not exceeding about 3%, the amount of maganese (if present as an intended alloy addition) not exceeding about 2% the balance consisting essentially of iron and carbon, any manganese present as in incidental constituent (up to 1%) not being included in said nickel equivalent, the presence of chromium being limited to a residual amount not exceeding about 0.07%, all percentages being by weight, characterised in that the alloy is heat treated from an as cast unstable austenite (which, subject to casting sections may contain some martensite) to form a product having a structure lying in the zone hereinafter defined.
  • nickel equivalent we mean both here and throughout the specification and claims that percentage of one of the alloying elements other than nickel which is equivalent in its effect to 1% of nickel in producing an austenitic as cast structure.
  • 1% of manganese and 10% of nickel together have a nickel equivalent percentage of 13, since manganese is approximately three times as effective as nickel in poducing an austenitic as cast structure.
  • 1% of copper and 10% of nickel together have a nickel equivalent percentage of 11 since copper is approximately equivalent to nickel in producing an austenitic as cast structure, providing that the nickel content is not less than approximately 3 times the copper content.
  • an alloy embodying the invention is formed by the casting of a fairly critical composition followed by a fairly critical heat treatment.
  • the four alloys each have a combined nickel and nickel equivalent percentage lying in the range of from to Such combined percentages being 12.5, 10.7, 14.73 and 10.7 respectively, bearing in mind that the first 1% of manganese is ignored for the purpose of calculating the nickel equivalent percentage, since up to 1% of manganese is normally present in an alloy cast iron as an incidental constituent. In no case does the percentage of copper exceed 3 whilst the percentage of manganese (excluding the first 1%) does not exceed 2, and a programme of tests has shown that these limits must be approximately adhered to in order to achieve the desired product. Chromium if present should only be in residual amounts not exceeding about 0.07%.
  • the graph shows a plot of hardness against heat treatment time.
  • Curves A and B respectively show the eifect of isothermal heat treatment on the material, whence it will be seen that with the passage of time the structure transforms from an austenitic through a bainomartensitic state of maximum hardness.
  • the continuation of the heat treatment after the fully hardened condition is reached eventually produces a further change of structure marked by a crop in hardness, and we have discovered that this drop in hardness is accompanied by exceptional increases in toughness and thermal structural stability at temperatures up to 500 C. Whilst maintaining exceptionally high strength.
  • Iron No.s II and IV Heated to 900 C. and held for 2 hours Cooled to 800 C. and held for 24 hours Cooled to 700 C. and held for 24 hours 150 hrs. approx.
  • molybdenum may be included up to 1% by weight in the alloy for the purpose of increasing hot strength and creep resistance if required.
  • Additions of niobium of up to 1% by weight may be made to give rise to finely dispersed niobium carbide particles which appear to act in a similar manner to that of a precipitation hardening and strengthening phase, the form distribution and efiect being completely difiereut from the carbides produced by chromium, which by their massive form considerably increase hardness but also increase brittleness when present in quantity in a grey iron.
  • Alloys may be cast so that the carbon not in solution is in either spheriodal or flake condition.
  • a heat-treated alloy cast iron consisting essentially of 10 to 15% of a nickel equivalent component consisting of a metal selected from the group consisting of nickel, nickel equivalent metals and mixtures thereof, at least about 8% of said alloy being nickel, said nickel equivalent metals being present in an amount not over about 8% of said alloy and being selected from the group consisting of copper and manganese, the amount of copper not exceeding about 3% of said alloy, the amount of manganese, when present as an intended alloy addition, not exceeding about 2% of said alloy, the balance of the alloy consisting essentially of iron and carbon, and any manganese present as an incidental constituent, up to 1% of said alloy, not being included in said nickel equivalent metal amount, the presence of chromium being limited to a residual amount not exceeding about 0.07% of said alloy, all percentages being by weight, said alloy having been cast into an unstable austenitic structure which may contain martensite, then heat-treated to transform said austenitic cast iron into a baino-martensitic state of maximum hardness, said heat-
  • a heat treated alloy cast iron according to claim 1 wherein the heat treatment comprises the steps of heating the alloy composition to about 900 C. for homogenization thereof and subsequently cooling the alloy to a temperature of about 500 C. over a period of at least about 100 hours.
  • a heat treated alloy cast iron according to claim 1 wherein the heat treatment comprises the steps of heating the alloy composition to about 900 C. for homogenization thereof, cooling the alloy composition at a temperature in the range of 500-600 C, and alternately reheating and recooling the alloy composition, the cooling in each case being to a temperature in the range of 500-600 C. and the reheat temperature at each successive cycle being less than at the previous cycle.
  • a heat treated alloy cast iron according to claim 1 wherein the heat treatment comprises the steps of heating the alloy to a temperature of about 900 C., cooling the alloy composition to a temperature of about 500 C. and maintaining the alloy composition at a temperature of about 500 C. for at least about 300 hours.
  • a heat treated alloy cast iron according to claim 1 including niobium as an additive in an amount of up to 1% by weight.
  • a heat treated alloy cast iron according to claim 1 including molybdenum as an additive in an amount of up to 1% by weight.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Continuous Casting (AREA)
  • Heat Treatment Of Steel (AREA)
US869440A 1962-09-25 1969-10-02 Alloy cast iron Expired - Lifetime US3674576A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB36321/62A GB985874A (en) 1962-09-25 1962-09-25 An alloy cast iron

Publications (1)

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US3674576A true US3674576A (en) 1972-07-04

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US869440A Expired - Lifetime US3674576A (en) 1962-09-25 1969-10-02 Alloy cast iron

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US (1) US3674576A (de)
CH (1) CH501059A (de)
GB (1) GB985874A (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080206584A1 (en) * 2007-02-28 2008-08-28 Jaszarowski James K High strength gray cast iron

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080206584A1 (en) * 2007-02-28 2008-08-28 Jaszarowski James K High strength gray cast iron
US8333923B2 (en) 2007-02-28 2012-12-18 Caterpillar Inc. High strength gray cast iron

Also Published As

Publication number Publication date
GB985874A (en) 1965-03-10
CH501059A (de) 1970-12-31

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