US3035911A - Cast iron - Google Patents

Cast iron Download PDF

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Publication number
US3035911A
US3035911A US46278A US4627860A US3035911A US 3035911 A US3035911 A US 3035911A US 46278 A US46278 A US 46278A US 4627860 A US4627860 A US 4627860A US 3035911 A US3035911 A US 3035911A
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US
United States
Prior art keywords
melt
carbide
magnesium
carbides
nodular
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Expired - Lifetime
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US46278A
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English (en)
Inventor
Harry H Kessler
William H Moore
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Individual
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Individual
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Publication date
Priority to DENDAT1251779D priority Critical patent/DE1251779B/de
Application filed by Individual filed Critical Individual
Priority to US46278A priority patent/US3035911A/en
Priority to GB44609/60A priority patent/GB912869A/en
Priority to CH147661A priority patent/CH396060A/de
Priority to ES0264813A priority patent/ES264813A1/es
Priority to BE600151A priority patent/BE600151A/fr
Priority to FI56461A priority patent/FI40015C/fi
Priority to DK312561AA priority patent/DK113607B/da
Application granted granted Critical
Publication of US3035911A publication Critical patent/US3035911A/en
Anticipated expiration legal-status Critical
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    • 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
    • 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
    • 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

Definitions

  • the cast iron may be hypoeutectic or hypereutectic in composition, but is one in which the uncombined carbon appears in the nodular or spheroidal form. This form of carbon is produced by the presence of carbide metastabilizing agents in the melt.
  • the present invention is directed to an improved process of making cast iron with conventional carbide metastabilizing agents such as magnesium and cerium.
  • carbide metastabilizing agents such as magnesium and cerium.
  • alloys of these materials may be readily used.
  • the process comprises adding a special agent after the carbide metastabilizing agent or nodule impelling agent has been incorporated into the melt.
  • magnesium will be used as the example of such an agent.
  • Magnesium when present in cast iron in excess amounts, detracts from the ductility of the as-cast material by the formation of excessive quantities of carbides. Most commercial castings containing more than 0.04% magnesium have to be annealed in order to provide complete freedom from carbides. Magnesium also combines very readily with the oxygen in the air with the formation of oxide dross. This dross leads to well-known casting defects when it becomes entrained in the metal. The amount of dross produced is in direct relation to the amount of magnesium in the iron.
  • Magnesium in the cast iron in amounts in excess of .G4% also has a serious effect on the soundness of the castings. This is probably because the vapor pressure of magnesium tends to prevent complete solidification of the crystal dendrites. In commercial practice those skilled in the art generally always try to keep the magnesium content to the barest minimum necessary for nodularity. This is the range of about .04%. Unfortunately, this practice does not allow for the fading effect due to loss of magnesium effect, and does not insure full modularity in slower cooling heavy casting sections.
  • Another object of the invention is to produce a melt wherein all the carbides are metastable by adding sufficient carbide metastabilizing agents to produce stable carbides and then rendering the stable carbides metastable by adding the carbide destabilizing agent of the present invention.
  • a still further object is to provide a means of removing excess carbide metastabilizing agents from the melt so as to provide uniform and dependable results.
  • nodular cast iron may be produced by adding certain agents to the melt. Because of the Whitening effect of these agents, the second step of conventional procedures is to add a graphitizing agent to the melt. This normally consists ice of ferro silicon or other silicon alloys which have a powerful graphitizing efiect. In many cases, certain fluxes are also added to the melt as a final step in order to remove dross, dirt, and other contaminants which may be present.
  • the present invention differs from the well-known method of producing cast irons having nodular and spherulitic forms of graphite, in that a special agent is used which produces a carbide destabilizing efiect by reducing the efiective carbide metastabilizing agent content in the melt, usually to a value of below that normally required for modularity.
  • This destabilizing efiect renders graphitization of the melt more positive, and reduces the danger due to the presence of excess stabilizers in the melt.
  • the basis of this invention is to add sumcient carbide metastabilizing agents to arrive at a condition in the melt which includes a substantial quantity of stable carbides. These stable carbides are then destabilized by the addition of the agents of this invention to the point where they may be graphitized by conventional means so as to provide a final structure with the graphite fully in the nodular form.
  • the diagram represented by the drawing is only intended to establish a basis of principle. It cannot be taken too specifically, because the line of demarcation of the various zones may vary from melt to melt or according to the specific type of metastabilizing agent used.
  • the wedge test is well known to those skilled in the art; however, the following explanation of the same will be given.
  • the Wedge test comprises the pouring of a casting of a predetermined length and of wedge in cross section with an acute angle of approximately 20 to 30 degrees.
  • the wedges may be of several sizes, namely, one-half inch base with approximately 28.5 acute angle, threefourths inch base with approximately 26.75 acute angle, one inch base with approximately 25 acute angle, and two inch base with approximately 23.5 acute angle.
  • the wedge casting is poured and cooled, it is broken in two so that the carbide balance may be observed.
  • the acute angle portion has a whitish appearance While the remaining base portion has a grayish-white appearance.
  • the carbon In the white portion, the carbon is generally in combined form, and in the grayish-white portion the carbon is generally in graphite form.
  • the white portion is unmachinable.
  • the width across the face of the wedge at the zone of demarcation between the white and grayish-white portions is an indication of the effect obtained by the carbide metastabilizer.
  • the knife edge of the wedge test piece cools quickly while the heavy section cools much more slowly, and the result is a varying texture in the casting, from the knife edge to the center, and often a shrink spot in the center.
  • the wedge-shaped casting has an acute angle, defining a knife edge, ranging from approximately 20 to 30 degrees.
  • the zone of instability with respect to carbides that is the zone of unstable carbides or graphite, shown as extending from line A to line B, would be represented by a wedge value ranging from zero to a just mottled condition.
  • the zone of carbide metastability extending from line B to line C on the diagram would be represented by a wedge value ranging from mottled to 1 times white. Passing from the line C to line B, the carbides become increasingly stable and at some point represented by line D there are relatively few unstable carbides in the melt. This would be represented by a wedge value of about 2 times white.
  • the line B would be represented by an amount of magnesium very close to .04%.
  • the line C would be represented by an amount of magnesium very close to .06%.
  • the line D would be represented by an amount of magnesium very close to -.09% It should be emphasized here that this magnesium content represents the total magnesium content of the melt which is the sum of that magnesium which is combined with other elements and that magnesium which may exist as free magnesium. Without limiting this invention to exact theory, it is thought that it is only the magnesium which is free in the meltthat is capable of producing the metastable condition in the melt. A very small quantity of free magnesium will produce this metastable condition. In conventional magnesium treated nodular irons, a fading effect often occurs.
  • carbides remain unstable, this is because the addition is used up by combining with the sulphur, oxygen, and other melt impurities. When these impurities have been used up, the passage through the zone of metastability com mences and proceeds at an extremely rapid rate. In terms of wedge values, the addition causes the metal to pass from the mottled to the several times white condition at an extremely rapid rate. Because this condition of carbide metastability occurs so quickly, it is diflicult to stop completely at the required point for producing a nodular form of graphite by subsequent graphitization. Further increasing additions will cause only a slow approach to the condition where the carbides are all stable.
  • the resultant casting will contain nothing but flake graphite. If graphitization additions are conducted from the point M, the resultant casting will contain the nodular form of graphite. If it is conducted from the point N, the final casting will contain some stable carbides, a considerable amount of flake graphite, and some poor nodular graphite.
  • a carbide destabilizing addition as taught in this invention, is made from the point N prior to or simultaneously with a graphitization addition, it quickly brings the melt down to a condition represented by the point 0.
  • the first parts of this requirement can be accomplished by using materials that tend to produce gas, which may neutralize or remove elements such as magnesium.
  • materials that tend to produce gas which may neutralize or remove elements such as magnesium.
  • sodium, potassium, calcium, or lithium carbonates or cyanides or cyanamides are effective in this regard.
  • the same eflect may be obtained by injection of carbon dioxide or nitrogen gas into the melt.
  • the second part of the requirement for a carbide destabilizing agent is best accomplished by elements such as calcium, sodium, potassium, and zirconium which are in themselves metastabilizing in nature.
  • the third part of the requirement is accomplished by using graphitizers such as silicon, and aluminum.
  • the wedge value was 5/32. After the castings had been poured, a second test bar was cast from the metal remaining in the ladle, this was found to contain 030% magnesium.
  • test bars were checked for structure and propertiesthey showed all graphite to be in the nodular form and to be very small in nature, with a matrix consisting of approximately 50% pearlite and 50% ferite.
  • the properties of the first bar were 82,000 pounds per square inch tensile with 10.5% elongation and the second bar was 81,500 pounds per square inch with a 10.0% elongation.
  • the approximate time elapsing between the casting of the first test bar and the second test bar was ten minutes.
  • a suitable melt was treated with a cerium alloy to a wedge value of 2% times white.
  • the carbide destabilizing addition reduced this wedge value to about A; of white.
  • the cerium content of the melt was reduced from .035 to 0.10% and the graphite was found to be substantially nodular in form.
  • the method of treating the melt with carbide metastabilizing agents prior to adding the carbide destabilizer of this invention is of no importance.
  • magnesium for example, may be added as pure magnesium or as any of the well-known alloys of magnesium. It may be added to the surface of the metal, or it may be added under the surface by plunging or by injection.
  • the essential part of the first step of this invention is to introduce sufiicient carbide metastabilizing agents to the melt to insure a completely nodular graphite.
  • this magnesium is reduced to a value of under 04% usually to about 030% or .035 but at times as high as .045
  • the magnesium content of the final melt before casting is substantially lower than that of the melt before the carbide destabilizing addition is made.
  • the amount of carbide destabilizer added to the melt does not appear to be critical. Where carbide metastabilizing additions have been heavy, it is wise to add a correspondingly heavy amount of carbide destabilizer. For instance, where the magnesium content of the melt is 08% or more, we prefer to use between 1 and 3% of the carbide destabilizer; where the magnesium content of the melt is of the order or" 04%, an addition of about /2% of carbide destabilizer appears to be effective.
  • the process of producing a cast iron from a melt comprising the steps of adding an amount of a carbide metastabilizing agent to the melt so as to provide a substantially over-saturated carbide-iron solution containing metastable and stable carbides, and adding an agent selected from the group consisting of the carbonates, cyanides, and cyanamides of sodium, potassium, calcium, and lithium; carbon dioxide gas; and nitrogen gas; to the melt to change said stable carbides to metastable carbides, and graphitizing the melt.
  • the process of producing a nodular cast iron from a melt comprising the steps of adding an amount of magnesium to the melt so as to provide a substantially oversaturated carbide iron solution containing metastable and stable carbides in the range of from one times to five times White, adding an agent to the melt to reduce the amount of magnesium in the melt so as to increase carbide metastability and provide a melt in the range of from mottled ,to one times white, and graphitizing the melt.
  • the process of producing a nodular cast iron from a melt comprising the steps of adding an amount of nodule impelling agent to the melt sons to provide a substantially oversaturated carbide iron solution containing metastable and stable carbides in the range of from one time to five times white, adding an agent to the melt to reduce the amount of nodule impelling agent in the melt so as to increase carbide metastability and provide a melt in the range of from mottled to one times white, and graphitizing the melt.
  • the process of producing a nodular cast iron from a metal comprising the steps of adding an amount of magnesium to the melt so as to provide a substantially oversaturated carbide iron solution containing metastable and stable carbides in the range of from one times to five times White, adding an agent to the melt to reduce the magnesium content of the melt substantially so as to increase carbide metastability in the melt and graphitizing the melt.
  • the process of producing a nodular cast iron from a melt comprisingthe steps of adding an amount of nodule impelling agent to the melt so as to provide a substantially oversaturated carbide iron solution containing metastable and stable carbides in the .range of from one times to five times White, adding an agent to the melt to reduce the nodule impelling agent content of the melt substantially so as to increase carbide metastability in the melt and graphitizing the melt.
  • the process of producing a cast iron from a melt comprising the steps of, adding an amount of magnesium to the melt so as to provide a substantially over-saturated carbide iron solution containing metastable and stable carbides, adding an agent to the melt to reduce the amount of magnesium in the melt and to change stable carbides to metastable carbides, and graphitizing the melt to change metastable carbides to the nodular form of graphite.
  • the process of producing a cast iron from a melt comprising the steps of, adding an amount of a nodule impelling agent to the melt so as to provide a substantially over-saturated carbide iron solution containing metastable and stable carbides, adding an agent to the melt to reduce the amount of nodule impelling agent in the melt and to change stable carbides to metastable carbides, and graphitizing the melt to change metastable carbides to the nodular form of graphite.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
US46278A 1960-07-29 1960-07-29 Cast iron Expired - Lifetime US3035911A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
DENDAT1251779D DE1251779B (en)) 1960-07-29
US46278A US3035911A (en) 1960-07-29 1960-07-29 Cast iron
GB44609/60A GB912869A (en) 1960-07-29 1960-12-29 Improvements in or relating to cast iron
CH147661A CH396060A (de) 1960-07-29 1961-02-08 Verfahren zur Herstellung von Gusseisen
ES0264813A ES264813A1 (es) 1960-07-29 1961-02-10 Proceso de producciën de hierro fundido
BE600151A BE600151A (fr) 1960-07-29 1961-02-13 Fonte améliorée
FI56461A FI40015C (fi) 1960-07-29 1961-03-27 Menetelmä valuraudan valmistamiseksi
DK312561AA DK113607B (da) 1960-07-29 1961-07-29 Fremgangsmåde til fremstilling af gråt jernstøbegods med kuglegrafit.

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Application Number Priority Date Filing Date Title
US46278A US3035911A (en) 1960-07-29 1960-07-29 Cast iron

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US3035911A true US3035911A (en) 1962-05-22

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BE (1) BE600151A (en))
CH (1) CH396060A (en))
DE (1) DE1251779B (en))
DK (1) DK113607B (en))
ES (1) ES264813A1 (en))
FI (1) FI40015C (en))
GB (1) GB912869A (en))

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8203733A (nl) * 1979-10-24 1984-04-16 Moore William H Werkwijze ter bereiding van gietijzer.

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1683087A (en) * 1927-08-27 1928-09-04 Meehanite Metal Corp Cast iron and method of making same
US2038639A (en) * 1933-07-26 1936-04-28 Union Carbide & Carbon Corp Method of producing castings
US2527037A (en) * 1949-01-17 1950-10-24 Smalley Oliver Method of producing nodular cast iron
US2747990A (en) * 1953-05-25 1956-05-29 British Cast Iron Res Ass Process of producing grey cast iron
US2821473A (en) * 1956-08-01 1958-01-28 Meehanite Metal Corp Method of making nodular cast iron

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1683087A (en) * 1927-08-27 1928-09-04 Meehanite Metal Corp Cast iron and method of making same
US2038639A (en) * 1933-07-26 1936-04-28 Union Carbide & Carbon Corp Method of producing castings
US2527037A (en) * 1949-01-17 1950-10-24 Smalley Oliver Method of producing nodular cast iron
US2747990A (en) * 1953-05-25 1956-05-29 British Cast Iron Res Ass Process of producing grey cast iron
US2821473A (en) * 1956-08-01 1958-01-28 Meehanite Metal Corp Method of making nodular cast iron

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8203733A (nl) * 1979-10-24 1984-04-16 Moore William H Werkwijze ter bereiding van gietijzer.

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FI40015B (en)) 1968-05-31
CH396060A (de) 1965-07-31
FI40015C (fi) 1968-09-10
DK113607B (da) 1969-04-08
BE600151A (fr) 1961-05-29
DE1251779B (en))
ES264813A1 (es) 1961-07-01
GB912869A (en) 1962-12-12

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