US20250188577A1 - Iron casting and method of manufacturing it - Google Patents

Iron casting and method of manufacturing it Download PDF

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US20250188577A1
US20250188577A1 US18/846,783 US202318846783A US2025188577A1 US 20250188577 A1 US20250188577 A1 US 20250188577A1 US 202318846783 A US202318846783 A US 202318846783A US 2025188577 A1 US2025188577 A1 US 2025188577A1
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cooling
heat treatment
mass
holding
practical example
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Takuo Umetani
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Hinode Ltd
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Hinode Ltd
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/84—Controlled slow cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D5/00—Heat treatments of cast-iron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/007—Heat treatment of ferrous alloys containing Co
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2201/00—Treatment for obtaining particular effects
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/04—Cast-iron alloys containing spheroidal graphite

Definitions

  • the present invention relates to an iron casting and a method of manufacturing it.
  • Patent Literature 1 describes providing a method that is capable of readily manufacturing a cast-iron material that has a good casting property and/or workability, similarly to a general cast-iron material, and has a more excellent low thermal expansion property. Furthermore, the abstract of Patent Literature 1 describes holding a casting that is obtained by casting and has a cast-iron composition that contains 2.5 mass % or less of carbon and 25 mass % or more and 40 mass % or less of nickel in proportion thereof, at a temperature of 550° C. or higher and 700° C.
  • an annealing process that is composed of natural cooling such as furnace cooling to at least 200° C., then holding a casting that is thus provided by such a annealing process, at a temperature of 600° C. or higher and 1150° C. or lower for 1.5 hours or more, and subsequently executing a solution treatment that is composed of rapid cooling such as fan air cooling, water cooling, or oil cooling, so as to manufacture a low thermal expansion cast-iron material with a coefficient of thermal expansion within a temperature range of 50° C. or higher and 200° C. or lower that is 4 ⁇ 10 ⁇ 6 /° C. or less.
  • a method according to an aspect of the present invention is a method of manufacturing an iron casting by executing a heat treatment for a heat treatment object that is provided by using and casting an austenite-type material for casting.
  • the material for casting includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0 mass % or more and 8.0 mass % or less of Co, 0 mass % or more and 3.0 mass % or less of Mn, 0 mass % or more and 0.2 mass % or less of Mg, and a balance that is Fe and an inevitable element(s).
  • the heat treatment includes a first holding step of holding the heat treatment object at a first holding temperature of 850° C. or higher and 1250° C. or lower, and a first cooling step of cooling the heat treatment object to a first cooling end temperature of ⁇ 150° C. or higher and 150° C. or lower after the first holding step.
  • the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  • a heat treatment object is held at a first holding temperature (850° C. or higher and 1250° C. or lower) and for a first holding time (0.25 hours or more and 100 hours or less).
  • a first cooling step after a first holding step a heat treatment object is cooled to a first cooling end temperature ( ⁇ 150° C. or higher and 150° C. or lower).
  • the first cooling step includes cooling the heat treatment object at a first cooling rate of 0.01° C./min or higher and 300° C./min or lower.
  • the first cooling rate is 0.01° C./min or higher and 20° C./min or lower.
  • the first holding time is 2.5 hours or more and 25 hours or less.
  • the first cooling end temperature is 0° C. or higher and 100° C. or lower.
  • the first cooling step includes a primary cooling step of cooling the heat treatment object at a primary cooling rate, and a secondary cooling step of cooling the heat treatment object at a secondary cooling rate that is higher than the primary cooling rate after the primary cooling step
  • the primary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or higher and 950° C. or lower
  • the secondary cooling step includes cooling the heat treatment object to the first cooling end temperature
  • a first cooling step after a first holding step includes a primary cooling step of cooling a heat treatment object at a primary cooling rate, and a secondary cooling step of cooling such a heat treatment object at a secondary cooling rate that is higher than such a primary cooling rate after such a primary cooling step.
  • a primary cooling step a heat treatment object is cooled to a primary cooling end temperature (250° C. or higher and 950° C. or lower) at a primary cooling rate.
  • a heat treatment object is cooled to a first cooling end temperature ( ⁇ 150° C. or higher and 150° C. or lower) at a secondary cooling rate that is higher than a primary cooling rate.
  • the primary cooling rate is 0.01° C./min or higher and 20° C./min or lower
  • the secondary cooling rate is 1° C./min or higher and 40000° C./min or lower.
  • the secondary cooling rate is 100° C./min or higher and 40000° C./min or lower.
  • the first holding time is 2.5 hours or more and 25 hours or less.
  • the primary cooling end temperature is 450° C. or higher and 850° C. or lower.
  • the first cooling end temperature is 0° C. or higher and 100° C. or lower.
  • the heat treatment may further include a second holding step of holding the heat treatment object at a second holding temperature of 250° C. or higher and 950° C. or lower after the first cooling step, and a second cooling step of cooling the heat treatment object to a second cooling end temperature of ⁇ 150° C. or higher and 150° C. or lower after the second holding step, wherein the second holding step includes holding the heat treatment object for a second holding time of 0.25 hours or more and 25 hours or less.
  • the first cooling step includes cooling the heat treatment object at a first cooling rate of 0.01° C./min or higher and 300° C./min or lower.
  • the first cooling rate is 1° C./min or higher and 50° C./min or lower.
  • the second cooling step includes cooling the heat treatment object at a second cooling rate of 1° C./min or higher and 40000° C./min or lower.
  • the second cooling rate is 100° C./min or higher and 10000° C./min or lower.
  • the first holding time is 2.5 hours or more and 25 hours or less.
  • the first cooling end temperature is 0° C. or higher and 100° C. or lower.
  • the second holding temperature is 550° C. or higher and 950° C. or lower.
  • the second cooling end temperature is 0° C. or higher and 50° C. or lower.
  • a content of Co in the material for casting is 0.1 mass % or more and 8.0 mass % or less.
  • a content of Mn in the material for casting is 0.01 mass % or more and 3.0 mass % or less.
  • a content of Mg in the material for casting is 0.01 mass % or more and 0.2 mass % or less.
  • a method according to another aspect of the present invention is a method of manufacturing an iron casting by executing a heat treatment for a heat treatment object that is provided by using and casting an austenite-type material for casting.
  • the heat treatment includes a first holding step of holding the heat treatment object at a first holding temperature of 850° C. or higher and 1250° C. or lower, and a first cooling step of cooling the heat treatment object to a first cooling end temperature of ⁇ 150° C. or higher and 150° C. or lower after the first holding step.
  • the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  • the first cooling step includes a primary cooling step of cooling the heat treatment object at a primary cooling rate, and a secondary cooling step of cooling the heat treatment object at a secondary cooling rate that is higher than the primary cooling rate after the primary cooling step
  • the primary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or higher and 950° C. or lower
  • the secondary cooling step includes cooling the heat treatment object to the first cooling end temperature
  • the heat treatment may further include a second holding step of holding the heat treatment object at a second holding temperature of 250° C. or higher and 950° C. or lower after the first cooling step, and a second cooling step of cooling the heat treatment object to a second cooling end temperature of ⁇ 150° C. or higher and 150° C. or lower after the second holding step, wherein the second holding step includes holding the heat treatment object for a second holding time of 0.25 hours or more and 25 hours or less.
  • An iron casting according to an aspect of the present invention is an iron casting that is manufactured by using the method according to an aspect of the present invention or the method according to another aspect of the present invention.
  • FIG. 1 is a diagram that illustrates an example of an image that is observed by a microscope, for a microstructure of a heat treatment object that is provided by using and casting an austenite-type material for casting.
  • FIG. 2 is a diagram that illustrates a region that is occupied by graphite, in an image as illustrated in FIG. 1 .
  • FIG. 3 is a diagram that illustrates a region that is occupied by an intermetallic compound that is based on iron (Fe), in an image as illustrated in FIG. 1 .
  • FIG. 4 is a diagram that illustrates a region that is occupied by an austenite phase, in an image as illustrated in FIG. 1 .
  • an iron casting according to an embodiment of the present invention by executing a predetermined heat treatment as described later for a heat treatment object that is provided by using and casting an austenite-type material for casting.
  • An “austenite-type material for casting” means a material where a major tissue of a parent phase (an iron-based tissue that excludes graphite) of a casted heat treatment object at an ordinary temperature is an austenite phase. For example, a proportion of an austenite phase that occupies a parent phase of a heat treatment object is 50% or greater.
  • a proportion of an austenite phase that occupies a parent phase of a heat treatment object is preferably 70% or greater, is more preferably 80% or greater, is more preferably 85% or greater, is more preferably 90% or greater, and is more preferably 95% or greater.
  • FIG. 1 is a diagram that illustrates an example of an image that is observed by a microscope, for a microstructure of a heat treatment object that is provided by using and casting an austenite-type material for casting.
  • FIG. 2 is a diagram that illustrates a region that is occupied by graphite, in an image as illustrated in FIG. 1 .
  • FIG. 3 is a diagram that illustrates a region that is occupied by an intermetallic compound that is based on iron (Fe), in an image as illustrated in FIG. 1 .
  • FIG. 4 is a diagram that illustrates a region that is occupied by an austenite phase, in an image as illustrated in FIG. 1 .
  • a surface area of a parent phase of a heat treatment object by eliminating “a surface area of a region that is occupied by graphite” as illustrated in FIG. 2 from “a surface area of a whole microstructure of a heat treatment object” as illustrated in FIG. 1 . It is possible to calculate “a surface area of an austenite phase” by eliminating “a surface area of a region that is occupied by an intermetallic compound that is based on iron (Fe)” as illustrated in FIG. 3 from “a surface area of a parent phase of a heat treatment object” that is calculated as described above.
  • a proportion of an austenite phase that occupies a parent phase of a heat treatment object by dividing “a surface area of an austenite phase (see FIG. 4 )” that is calculated as described above by “a surface area of a parent phase of a heat treatment object”.
  • a number of a pixel(s) (a pixel number) of a region that corresponds to each of surface areas as illustrated in FIG. 1 to FIG. 4 is calculated by using a general-purpose image processing software, and as a result, a proportion of an austenite phase that occupies a parent phase of a heat treatment object is 84.6% (about 85%).
  • a proportion of an austenite phase that occupies a parent phase of a heat treatment object is 100%.
  • casting includes casting that is executed by various types of casting methods such as a sand mold casting method, a metallic mold casting method, a die-casting method, and a lost-wax casting method.
  • a “mass %” of an element means a percentage of a mass of an element in a mass of an austenite-type material for casting.
  • a notation of “X mass % or more and Y mass % or less of an element” means that a mass % of an element is X % or more and Y % or less.
  • a notation of “0 mass % or more and Y mass % or less of an element” means that such an element is not included or a mass % of such an element is Y % or less.
  • a “balance” means a component(s) other than a listed element(s), components that compose an austenite-type material for casting.
  • a first mode of an austenite-type material for casting (that will be referred to as “the present material” below) includes 26.0 mass % or more and 50.0 mass % or less of Ni and a balance that is Fe and an inevitable element(s).
  • a first mode of the present material may be referred to as “a first mode of the present material (a Ni—Fe composition)” below.
  • a first mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni.
  • a content of Ni is 26.0 mass % or more and 50.0 mass % or less, so that Ni is segregated around graphite. That is, Ni is concentrated in a region around graphite so as to stabilize an austenite.
  • a lower limit of a content of Ni is 26.0 mass %, so that it is possible to stabilize an austenite so as to reduce or prevent generation of a martensite. Hence, it is possible to reduce or prevent degradation of ductility of an iron casting and improve a cutting property of an iron casting.
  • an upper limit of a content of Ni is 50.0 mass %, so that it is possible to reduce or prevent an increase of a coefficient of linear expansion. The same also applies to a mode(s) of the present material as described below.
  • a balance in a first mode of the present material is Fe and an inevitable element(s).
  • an inevitable element(s) that is/are included in a balance for example, elements such as P (phosphorus), S (sulfur), Cu (copper), Al (aluminum), Cr (chromium), Mo (molybdenum), V (vanadium) Ti (titanium), and Zn (zinc) are provided.
  • a content of an inevitable element(s) is preferably 10.0 mass % or less in total, is more preferably 5.0 mass % or less in total, is more preferably 3.0 mass % or less in total, and is more preferably 1.0 mass % or less in total.
  • a mode(s) of the present material as described below.
  • a lower limit of a content of Ni is preferably 26.5 mass %, is more preferably 27.0 mass %, is more preferably 27.5 mass %, is more preferably 28.0 mass %, is more preferably 28.5 mass %, is more preferably 29.0 mass %, is more preferably 29.5 mass %, is more preferably 30.0 mass %, is more preferably 30.5 mass %, is more preferably 31.0 mass %, is more preferably 31.5 mass %, and is more preferably 32.0 mass %.
  • an upper limit of a content of Ni is preferably 45.0 mass %, is more preferably 42.0 mass %, is more preferably 41.0 mass %, is more preferably 40.0 mass %, is more preferably 39.5 mass %, is more preferably 39.0 mass %, is more preferably 38.5 mass %, is more preferably 38.0 mass %, is more preferably 37.5 mass %, and is more preferably 37.0 mass %.
  • the same also applies to a mode(s) of the present material as described below.
  • a second mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, and a balance that is Fe and an inevitable element(s).
  • a second mode of the present material may be referred to as “a second mode of the present material (a Ni—C—Fe composition)” below.
  • a second mode of the present material includes 0.1 mass % or more and 3.5 mass % or less of C.
  • a lower limit of a content of C is 0.1 mass %, so that it is possible to lower a liquidus line temperature of the present material. Hence, it is possible to improve fluidity of the present material.
  • a lower limit of a content of C is 0.1 mass %, so that it is possible to increase an amount of crystallized or an amount of precipitated graphite. Hence, it is possible to improve a cutting property of an iron casting.
  • an upper limit of a content of C is 3.5 mass %, so that it is possible to reduce or prevent graphite floatation (carbon floatation).
  • an upper limit of a content of C is 3.5 mass % and an upper limit of a content of Ni that acts as a graphitization acceleration element is 50.0 mass %, so that it is possible to reduce or prevent excessive graphitization of C.
  • the same also applies to a mode(s) of the present material as described below.
  • a lower limit of a content of C is preferably 0.15 mass %, is more preferably 0.2 mass %, is more preferably 0.4 mass %, is more preferably 0.7 mass %, is more preferably 1.0 mass %, is more preferably 1.25 mass %, is more preferably 1.5 mass %, and is more preferably 1.75 mass %.
  • a lower limit of a content of C is 0.7 mass %, so as to strengthen a tendency of graphite that is crystallized at a time of solidification to form a eutectic structure, so that it is possible to increase an amount of expanded graphite and reduce or prevent generation of a shrinkage cavity.
  • an upper limit of a content of C is preferably 3.3 mass %, is more preferably 3.1 mass %, is more preferably 3.0 mass %, is more preferably 2.95 mass %, is more preferably 2.9 mass %, is more preferably 2.85 mass %, is more preferably 2.8 mass %, is more preferably 2.75 mass %, is more preferably 2.7 mass %, is more preferably 2.65 mass %, is more preferably 2.6 mass %, is more preferably 2.55 mass %, and is more preferably 2.5 mass %.
  • the same also applies to a mode(s) of the present material as described below.
  • a third mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, and a balance that is Fe and an inevitable element(s).
  • a third mode of the present material may be referred to as “a third mode of the present material (a Ni—C—Si—Fe composition)” below.
  • a third mode of the present material includes 0.1 mass % or more and 3.5 mass % or less of Si.
  • a content of Ni is 26.0 mass % or more and 50.0 mass % or less and a content of Si is 0.1 mass % or more and 3.5 mass % or less, so that Ni is segregated around graphite, and as a result, Si is segregated in a finally solidified part. That is, Ni is concentrated in a region around graphite so as to stabilize an austenite and Si is concentrated in a finally solidified part that is a residual liquid side.
  • a lower limit of a content of Si is 0.1 mass %, so that a liquidus line temperature of the present material is readily lowered.
  • a lower limit of a content of Si is 0.1 mass %, so that it is possible to increase a proportion of a content of Si relative to a content of C. Hence, it is possible to reduce or prevent formation of a CO gas. Therefore, it is possible to reduce a gas defect that is generated on a surface of an iron casting.
  • an upper limit of a content of Si is 3.5 mass %, so that it is possible to reduce an amount of Si that is dissolved in Fe (an iron base). Hence, it is possible to reduce or prevent an increase of a coefficient of linear expansion.
  • an upper limit of a content of Si that acts as a graphitization acceleration element is 3.5 mass %, so that it is possible to reduce or prevent excessive graphitization of C. Hence, it is possible to reduce or prevent generation of chunky graphite. Therefore, it is possible to improve elongation of an iron casting. The same also applies to a mode(s) of the present material as described below.
  • a lower limit of a content of Si is preferably 0.25 mass %, is more preferably 0.5 mass %, is more preferably 0.75 mass %, is more preferably 1.0 mass %, is more preferably 1.2 mass %, is more preferably 1.3 mass %, and is more preferably 1.4 mass %.
  • an upper limit of a content of Si is preferably 3.3 mass %, is more preferably 3.1 mass %, is more preferably 2.9 mass %, is more preferably 2.7 mass %, is more preferably 2.5 mass %, is more preferably 2.3 mass %, and is more preferably 2.1 mass %.
  • the same also applies to a mode(s) of the present material as described below.
  • a fourth mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0.1 mass % or more and 8.0 mass % or less of Co, and a balance that is Fe and an inevitable element(s).
  • a fourth mode of the present material may be referred to as “a fourth mode of the present material (a Ni—C—Si—Co—Fe composition)” below.
  • a fourth mode of the present material includes 0.1 mass % or more and 8.0 mass % or less of Co.
  • a content of Co is 0.1 mass % or more and 8.0 mass % or less, so that it is possible to further reduce a coefficient of linear expansion by a synergistic effect with Ni.
  • a lower limit of a content of Co is 0.1 mass %, so that it is possible to reduce a local minimum value of a coefficient of linear expansion by a synergistic effect with Ni.
  • an upper limit of a content of Co is 8.0 mass %, so that it is possible to reduce or prevent increasing of a coefficient of linear expansion after indicating a local minimum value thereof with excessive addition of Co. The same also applies to a mode(s) of the present material as described below.
  • a lower limit of a content of Co is preferably 0.5 mass %, is more preferably 1.0 mass %, is more preferably 1.5 mass %, is more preferably 2.0 mass %, is more preferably 2.5 mass %, is more preferably 3.0 mass %, is more preferably 3.5 mass %, and is more preferably 4.0 mass %.
  • an upper limit of a content of Co is preferably 7.5 mass %, is more preferably 7.0 mass %, is more preferably 6.5 mass %, is more preferably 6.25 mass %, and is more preferably 6.0 mass %.
  • a content of Co is preferably 4.0 mass % or more and 5.5 mass % or less. Furthermore, in a case where a lower limit of a content of Ni is 28.5 mass %, a content of Co is preferably 5.0 mass % or more and 8.0 mass % or less. An upper limit and a lower limit of a content of Co is thus provided, so that a coefficient of linear expansion is reduced more readily by a synergistic effect with Ni. The same also applies to a mode(s) of the present material as described below.
  • a fifth mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0.1 mass % or more and 8.0 mass % or less of Co, 0.01 mass % or more and 3.0 mass % or less of Mn, and a balance that is Fe and an inevitable element(s).
  • a fifth mode of the present material may be referred to as “a fifth mode of the present material (a Ni—C—Si—Co—Mn—Fe composition)” below.
  • a fifth mode of the present material includes 0.01 mass % or more and 3.0 mass % or less of Mn.
  • a content of Mn is 0.01 mass % or more and 3.0 mass % or less, so that it is possible to stabilize an austenite so as to reduce or prevent generation of a martensite by a synergistic effect with Ni. Therefore, it is possible to improve a cutting property of an iron casting.
  • a lower limit of a content of Mn is 0.01 mass %, so that it is possible to stabilize an austenite even at an ordinary temperature.
  • an upper limit of a content of Mn is 3.0 mass %, so that it is possible to reduce an amount of Mn that is dissolved in Fe (an iron base). Hence, it is possible to reduce or prevent an increase of a coefficient of linear expansion.
  • a lower limit of a content of Mn is preferably 0.05 mass %, is more preferably 0.07 mass %, is more preferably 0.08 mass %, is more preferably 0.09 mass %, and is more preferably 0.1 mass %.
  • an upper limit of a content of Mn is preferably 2.5 mass %, is more preferably 2.0 mass %, is more preferably 1.5 mass %, is more preferably 1.0 mass %, is more preferably 0.85 mass %, and is more preferably 0.7 mass %.
  • the same also applies to a mode(s) of the present material as described below.
  • a sixth mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0.1 mass % or more and 8.0 mass % or less of Co, 0.01 mass % or more and 0.2 mass % or less of Mg, and a balance that is Fe and an inevitable element(s).
  • a sixth mode of the present material may be referred to as “a sixth mode of the present material (a Ni—C—Si—Co—Mg—Fe composition)” below.
  • a sixth mode of the present material includes 0.01 mass % or more and 0.2 mass % or less of Mg.
  • a content of Mg is 0.01 mass % or more and 0.2 mass % or less, so that it is possible to enhance a spheroidizing action of graphite and segregate Mg in a finally solidified part.
  • a lower limit of a content of Mg is 0.01 mass %, so that it is possible to enhance a spheroidizing action of graphite.
  • an upper limit of a content of Mg is 0.2 mass %, so that it is possible to reduce or prevent generation of an oxide or a sulfide of Mg. Hence, it is possible to reduce or prevent degradation of fluidity of the present material. Moreover, it is possible to reduce a cast defect of an iron casting.
  • a lower limit of a content of Mg is preferably 0.02 mass %, is more preferably 0.03 mass %, and is more preferably 0.04 mass %. Furthermore, an upper limit of a content of Mg is preferably 0.15 mass %, is more preferably 0.1 mass %, and is more preferably 0.08 mass %. The same also applies to a mode(s) of the present material as described below.
  • a seventh mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0.1 mass % or more and 8.0 mass % or less of Co, 0.01 mass % or more and 3.0 mass % or less of Mn, 0.01 mass % or more and 0.2 mass % or less of Mg, and a balance that is Fe and an inevitable element(s).
  • a seventh mode of the present material may be referred to as “a seventh mode of the present material (a Ni—C—Si—Co—Mn—Mg—Fe composition)” below.
  • An eighth mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0.01 mass % or more and 3.0 mass % or less of Mn, and a balance that is Fe and an inevitable element(s).
  • An eighth mode of the present material may be referred to as “an eighth mode of the present material (a Ni—C—Si—Mn—Fe composition)” below.
  • a ninth mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0.01 mass % or more and 3.0 mass % or less of Mn, 0.01 mass % or more and 0.2 mass % or less of Mg, and a balance that is Fe and an inevitable element(s).
  • a ninth mode of the present material may be referred to as “a ninth mode of the present material (a Ni—C—Si—Mn—Mg—Fe composition)” below.
  • a tenth mode of the present material includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0.01 mass % or more and 0.2 mass % or less of Mg, and a balance that is Fe and an inevitable element(s).
  • a tenth mode of the present material may be referred to as “a tenth mode of the present material (a Ni—C—Si—Mg—Fe composition)” below.
  • a first mode of a heat treatment that is executed for a heat treatment object that is provided by using and casting the present material includes a first holding step of holding a heat treatment object at a first holding temperature of 850° C. or higher and 1250° C. or lower and a first cooling step of cooling such a heat treatment object to a first cooling end temperature of ⁇ 150° C. or higher and 150° C. or lower after such a first holding step.
  • a first holding step includes holding a heat treatment object at a first holding time of 0.25 hours or more and 100 hours or less.
  • a first mode of the present heat treatment may include another heat treatment step before and/or after at least one of a first holding step and a first cooling step.
  • a first mode of the present heat treatment in a case where another heat treatment step is not included before and/or after at least one step as described above, only a first holding step and a first cooling step are executed in order for a heat treatment object that is provided by using and casting the present material, so that it is possible to prevent acting of unexpected heat affection on such a heat treatment object. Therefore, it is possible to reduce a coefficient of linear expansion of an iron casting more reliably.
  • a heat treatment object is held at a first holding temperature (850° C. or higher and 1250° C. or lower) and for a first holding time (0.25 hours or more and 100 hours or less). Then, at a first cooling step after a first holding step, a heat treatment object is cooled to a first cooling end temperature ( ⁇ 150° C. or higher and 150° C. or lower).
  • a first holding step it is possible to reduce solidification segregation of a solute element in a heat treatment object and reduce a relative difference between crystal orientations inside respective crystal grains that compose an austenite phase (a crystal orientation difference). Thereby, it is possible to adjust arrangement of a crystal lattice in an austenite phase. As a result, it is possible to reduce a coefficient of linear expansion of an iron casting.
  • a first cooling step includes cooling a heat treatment object at a first cooling rate of 0.01° C./min or higher and 300° C./min or lower.
  • a first cooling rate is preferably 0.01° C./min or higher and 20° C./min or lower.
  • a first holding time is preferably 2.5 hours or more and 25 hours or less.
  • a first cooling end temperature is preferably 0° C. or higher and 100° C. or lower.
  • a lower limit of a first holding temperature is preferably 875° C., is more preferably 900° C., is more preferably 925° C., is more preferably 950° C., is more preferably 975° C., is more preferably 1000° C., and is more preferably 1025° C.
  • an upper limit of a first holding temperature is preferably 1225° C., is more preferably 1200° C., is more preferably 1175° C., is more preferably 1150° C., and is more preferably 1125° C. The same also applies to a mode(s) of the present heat treatment as described below.
  • a lower limit of a first holding time is preferably 0.5 hours, is more preferably 1.0 hours, is more preferably 1.5 hours, is more preferably 2.0 hours, is more preferably 2.5 hours, is more preferably 3.0 hours, is more preferably 3.5 hours, and is more preferably 4.0 hours.
  • an upper limit of a first holding time is preferably 90 hours, is more preferably 80 hours, is more preferably 70 hours, is more preferably 60 hours, is more preferably 50 hours, is more preferably 40 hours, is more preferably 30 hours, is more preferably 25 hours, is more preferably 20 hours, is more preferably 15 hours, and is more preferably 10 hours.
  • the same also applies to a mode(s) of the present heat treatment as described below.
  • a lower limit of a first cooling end temperature is preferably ⁇ 125° C., is more preferably ⁇ 100° C., is more preferably ⁇ 75° C., is more preferably ⁇ 50° C., is more preferably ⁇ 25° C., and is more preferably 0° C.
  • an upper limit of a first cooling end temperature is preferably 125° C., is more preferably 100° C., is more preferably 75° C., and is more preferably 50° C. The same also applies to a mode(s) of the present heat treatment as described below.
  • a lower limit of a first cooling rate is preferably 0.1° C./min, is more preferably 0.2° C./min, is more preferably 0.3° C./min, is more preferably 0.4° C./min, is more preferably 0.5° C./min, is more preferably 0.6° C./min, is more preferably 0.7° C./min, and is more preferably 0.75° C./min.
  • an upper limit of a first cooling rate is preferably 250° C./min, is more preferably 200° C./min, is more preferably 150° C./min, is more preferably 100° C./min, is more preferably 50° C./min, is more preferably 25° C./min, is more preferably 10° C./min, and is more preferably 5° C./min.
  • a second mode of the present heat treatment includes a first holding step of holding a heat treatment object at a first holding temperature of 850° C. or higher and 1250° C. or lower, and a first cooling step of cooling such a heat treatment object to a first cooling end temperature of ⁇ 150° C. or higher and 150° C. or lower after such a first holding step.
  • a first holding step includes holding a heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  • a first cooling step includes a primary cooling step of cooling a heat treatment object at a primary cooling rate, and a secondary cooling step of cooling such a heat treatment object at a secondary cooling rate that is higher than such a primary cooling rate after such a primary cooling step.
  • a primary cooling step includes cooling a heat treatment object to a primary cooling end temperature of 250° C. or higher and 950° C. or lower.
  • a secondary cooling step includes cooling a heat treatment object to a first cooling end temperature ( ⁇ 150° C. or higher and 150° C. or lower).
  • a second mode of the present heat treatment may include another heat treatment step before and/or after at least one of a first holding step and a first cooling step.
  • a first holding step and a first cooling step are executed in order for a heat treatment object that is provided by using and casting the present material, so that it is possible to prevent acting of unexpected heat affection on such a heat treatment object. Therefore, it is possible to reduce a coefficient of linear expansion of an iron casting more reliably.
  • a heat treatment object is held at a first holding temperature (850° C. or higher and 1250° C. or lower) and for a first holding time (0.25 hours or more and 100 hours or less). Then, at a first cooling step after a first holding step, a heat treatment object is cooled to a first cooling end temperature ( ⁇ 150° C. or higher and 150° C. or lower).
  • a first holding step it is possible to reduce solidification segregation of a solute element in a heat treatment object and reduce a relative difference between crystal orientations inside respective crystal grains that compose an austenite phase (a crystal orientation difference). Thereby, it is possible to adjust arrangement of a crystal lattice in an austenite phase. As a result, it is possible to reduce a coefficient of linear expansion of an iron casting.
  • a first cooling step after a first holding step includes a primary cooling step of cooling a heat treatment object at a primary cooling rate, and a secondary cooling step of cooling such a heat treatment object at a secondary cooling rate that is higher than such a primary cooling rate after such a primary cooling step.
  • a heat treatment object is cooled to a primary cooling end temperature (250° C. or higher and 950° C. or lower) at a primary cooling rate.
  • a primary cooling step it is possible to diffuse carbon in an austenite phase to a side of graphite therein. Hence, it is possible to reduce an amount of carbon that is dissolved in an austenite phase.
  • a heat treatment object is cooled to a first cooling end temperature ( ⁇ 150° C. or higher and 150° C. or lower) at a secondary cooling rate that is higher than a primary cooling rate.
  • a primary cooling rate is 0.01° C./min or higher and 20° C./min or lower and a secondary cooling rate is 1° C./min or higher and 40000° C./min or lower.
  • a secondary cooling rate is preferably 100° C./min or higher and 40000° C./min or lower.
  • a first holding time is preferably 2.5 hours or more and 25 hours or less.
  • a primary cooling end temperature is preferably 450° C. or higher and 850° C. or lower.
  • a first cooling end temperature is preferably 0° C. or higher and 100° C. or lower.
  • a lower limit of a primary cooling end temperature is preferably 275° C., is more preferably 300° C., is more preferably 325° C., is more preferably 350° C., is more preferably 375° C., is more preferably 400° C., is more preferably 425° C., is more preferably 450° C., is more preferably 475° C., is more preferably 500° C., is more preferably 525° C., is more preferably 550° C., is more preferably 575° C., and is more preferably 600° C.
  • an upper limit of a primary cooling end temperature is preferably 925° C., is more preferably 900° C., is more preferably 875° C., is more preferably 850° C., is more preferably 825° C., and is more preferably 800° C.
  • a lower limit of a primary cooling rate is preferably 0.1° C./min, is more preferably 0.5° C./min, is more preferably 0.75° C./min, is more preferably 1.0° C./min, is more preferably 1.25° C./min, is more preferably 1.5° C./min, and is more preferably 1.75° C./min.
  • an upper limit of a primary cooling rate is preferably 17.5° C./min, is more preferably 15.0° C./min, is more preferably 12.5° C./min, is more preferably 10.0° C./min, and is more preferably 7.5° C./min.
  • a lower limit of a secondary cooling rate is preferably 2.5° C./min, is more preferably 5° C./min, is more preferably 7.5° C./min, is more preferably 10° C./min, is more preferably 50° C./min, is more preferably 100° C./min, is more preferably 200° C./min, is more preferably 300° C./min, is more preferably 400° C./min, is more preferably 500° C./min, and is more preferably 600° C./min.
  • an upper limit of a secondary cooling rate is preferably 37500° C./min, is more preferably 35000° C./min, is more preferably 32500° C./min, is more preferably 30000° C./min, is more preferably 27500° C./min, and is more preferably 25000° C./min.
  • a third mode of the present heat treatment includes a first holding step of holding a heat treatment object at a first holding temperature of 850° C. or higher and 1250° C. or lower, a first cooling step of cooling such a heat treatment object to a first cooling end temperature of ⁇ 150° C. or higher and 150° C. or lower after such a first holding step, a second holding step of holding such a heat treatment object at a second holding temperature of 250° C. or higher and 950° C. or lower after such a first cooling step, and a second cooling step of cooling such a heat treatment object to a second cooling end temperature of ⁇ 150° C. or higher and 150° C. or lower after such a second holding step.
  • a first holding step includes holding a heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  • a second holding step includes holding a heat treatment object for a second holding time of 0.25 hours or more and 25 hours or less.
  • a third mode of the present heat treatment may include another heat treatment step before and/or after at least one of a first holding step, a first cooling step, a second holding step, and a second cooling step.
  • a third mode of the present heat treatment in a case where another heat treatment step is not included before and/or after at least one step as described above, only a first holding step, a first cooling step, a second holding step, and a second cooling step are executed in order for a heat treatment object that is provided by using and casting the present material, so that it is possible to prevent acting of unexpected heat affection on such a heat treatment object. Therefore, it is possible to reduce a coefficient of linear expansion of an iron casting more reliably.
  • a heat treatment object is held at a first holding temperature (850° C. or higher and 1250° C. or lower) and for a first holding time (0.25 hours or more and 100 hours or less). Then, at a first cooling step after a first holding step, a heat treatment object is cooled to a first cooling end temperature ( ⁇ 150° C. or higher and 150° C. or lower).
  • a first holding step it is possible to reduce solidification segregation of a solute element in a heat treatment object and reduce a relative difference between crystal orientations inside respective crystal grains that compose an austenite phase (a crystal orientation difference). Thereby, it is possible to adjust arrangement of a crystal lattice in an austenite phase. As a result, it is possible to reduce a coefficient of linear expansion of an iron casting.
  • a heat treatment object is held at a second holding temperature (250° C. or higher and 950° C. or lower). Then, at a second cooling step after a second holding step, a heat treatment object is cooled to a second cooling end temperature ( ⁇ 150° C. or higher and 150° C. or lower).
  • a second cooling step an amount of a change of spontaneous volumetric magnetostriction with a temperature change at a Curie point or lower is readily increased.
  • a first cooling step preferably includes cooling a heat treatment object at a first cooling rate of 0.01° C./min or higher and 300° C./min or lower.
  • a first cooling rate is preferably 1° C./min or higher and 50° C./min or lower.
  • a second cooling step preferably includes cooling a heat treatment object at a second cooling rate of 1° C./min or higher and 40000° C./min or lower.
  • a second cooling rate is preferably 100° C./min or higher and 10000° C./min or lower.
  • a first holding time is preferably 2.5 hours or more and 25 hours or less.
  • a first cooling end temperature is preferably 0° C. or higher and 100° C. or lower.
  • a second holding temperature is preferably 550° C. or higher and 950° C. or lower.
  • a second cooling end temperature is preferably 0° C. or higher and 50° C. or lower.
  • a lower limit of a first cooling rate is preferably 1.0° C./min, is more preferably 5.0° C./min, is more preferably 7.5° C./min, is more preferably 10.0° C./min, is more preferably 12.0° C./min, and is more preferably 14.0° C./min.
  • an upper limit of a first cooling rate is preferably 250° C./min, is more preferably 200° C./min, is more preferably 150° C./min, is more preferably 100° C./min, is more preferably 75° C./min, is more preferably 50° C./min, is more preferably 45° C./min, and is more preferably 40° C./min.
  • a lower limit of a second holding temperature is preferably 275° C., is more preferably 300° C., is more preferably 325° C., is more preferably 350° C., is more preferably 375° C., is more preferably 400° C., is more preferably 425° C., is more preferably 450° C., is more preferably 475° C., is more preferably 500° C., is more preferably 525° C., is more preferably 550° C., is more preferably 575° C., and is more preferably 600° C.
  • an upper limit of a second holding temperature is preferably 925° C., is more preferably 900° C., is more preferably 875° C., is more preferably 850° C., is more preferably 825° C., and is more preferably 800° C.
  • a lower limit of a second holding time is preferably 0.3 hours, is more preferably 0.4 hours, is more preferably 0.5 hours, is more preferably 0.6 hours, is more preferably 0.7 hours, is more preferably 0.8 hours, is more preferably 0.9 hours, and is more preferably 1.0 hours.
  • an upper limit of a second holding time is preferably 20 hours, is more preferably 15 hours, is more preferably 10 hours, is more preferably 9 hours, is more preferably 8 hours, is more preferably 7 hours, is more preferably 6 hours, and is more preferably 5 hours.
  • a lower limit of a second cooling end temperature is preferably ⁇ 125° C., is more preferably ⁇ 100° C., is more preferably ⁇ 75° C., is more preferably ⁇ 50° C., is more preferably ⁇ 25° C., and is more preferably 0° C.
  • an upper limit of a second cooling end temperature is preferably 125° C., is more preferably 100° C., is more preferably 75° C., is more preferably 50° C., is more preferably 40° C., and is more preferably 30° C.
  • a lower limit of a second cooling rate is preferably 25° C./min, is more preferably 50° C./min, is more preferably 75° C./min, is more preferably 100° C./min, is more preferably 200° C./min, is more preferably 300° C./min, and is more preferably 400° C./min.
  • an upper limit of a second cooling rate is preferably 35000° C./min, is more preferably 30000° C./min, is more preferably 25000° C./min, is more preferably 20000° C./min, is more preferably 15000° C./min, is more preferably 10000° C./min, is more preferably 9000° C./min, is more preferably 8000° C./min, is more preferably 7000° C./min, and is more preferably 6000° C./min.
  • An iron casting according to a first embodiment is an iron casting that is obtained by executing a second mode of the present heat treatment for a heat treatment object that is provided by using and casting a fifth mode (a Ni—C—Si—Co—Mn—Fe composition), a seventh mode (a Ni—C—Si—Co—Mn—Mg—Fe composition), an eighth mode (a Ni—C—Si—Mn—Fe composition), and a ninth mode (a Ni—C—Si—Mn—Mg—Fe composition) of the present material.
  • a second mode of the present heat treatment is executed, so that it is possible to reduce a coefficient of linear expansion of an iron casting, as described above.
  • a heat treatment object is casted by using an austenite-type material for casting where a content of Ni is 26.0 mass % or more, so that an Ms point (a temperature where transformation from an austenite to a martensite starts) is readily lowered. Therefore, an iron casting that reduces or prevents generation of a martensite is readily provided.
  • solidification segregation of a solute element in a heat treatment object are reduced, and as a result, it is possible to increase a concentration of Ni that is distributed in a finally solidified part in such a heat treatment object, at a low concentration.
  • An iron casting according to a second embodiment is an iron casting that is obtained by executing a third mode of the present heat treatment for a heat treatment object that is provided by using and casting a fifth mode (a Ni—C—Si—Co—Mn—Fe composition), a seventh mode (a Ni—C—Si—Co—Mn—Mg—Fe composition), and a ninth mode (a Ni—C—Si—Mn—Mg—Fe composition) of the present material.
  • a third mode of the present heat treatment is executed, so that it is possible to reduce a coefficient of linear expansion of an iron casting as described above.
  • An iron casting according to a third embodiment is an iron casting that is obtained by executing a first mode of the present heat treatment for a heat treatment object that is provided by using and casting a fifth mode (a Ni—C—Si—Co—Mn—Fe composition), a seventh mode (a Ni—C—Si—Co—Mn—Mg—Fe composition), and a ninth mode (a Ni—C—Si—Mn—Mg—Fe composition) of the present material.
  • a first mode of the present heat treatment is executed, so that it is possible to reduce a coefficient of linear expansion of an iron casting as described above.
  • an iron casting according to an embodiment as described above is suitable for a wide variety of applications where low thermal expansion (coefficient) is needed.
  • a component(s), etc., of a semiconductor manufacturing device, an electronic component manufacturing device, a machine tool, etc. is/are provided.
  • a use environment at about 20° C.
  • a spindle holder and a calibration gauge (a gauge block, etc.) of a dicer in association with a semiconductor manufacturing device, and a work stage and a wire holding member of a wire electrical discharge machine in association with a machine tool are provided.
  • a dry vacuum pump component(s) and a guard holder for a prober in association with a semiconductor manufacturing device are provided.
  • Table 1 illustrates compositions of practical examples in a first embodiment and compositions of comparative examples that correspond thereto.
  • Table 2 illustrates compositions of practical examples in a second embodiment and compositions of comparative examples that correspond thereto.
  • Table 3 illustrates compositions of practical examples in a third embodiment and compositions of comparative examples that correspond thereto.
  • a content (mass %) of C (carbon) is a value that is measured by using a material carbon/sulfur analyzer “EMIA-Expert” produced by HORIBA, Ltd. according to a combustion—infrared absorption method.
  • contents (mass %) of Si (silicon), Ni (nickel), Mg (magnesium), and Co (cobalt) are values that are measured by using an emission spectrophotometer “SPS3520UV” produced by Hitachi High-Tech Science Corporation according to an inductively coupled plasma emission spectrometric analysis method. Furthermore, contents (mass %) of other elements are values that are measured by using an emission spectrophotometer “PDA-8000” produced by SHIMADZU CORPORATION according to an emission spectrometric analysis method.
  • Table 4 illustrates heat treatment conditions and average coefficients of linear expansion of practical examples in a first embodiment, and heat treatment conditions and average coefficients of linear expansion of comparative examples that correspond thereto.
  • Table 5 illustrates heat treatment conditions and average coefficients of linear expansion of practical examples in a second embodiment, and heat treatment conditions and average coefficients of linear expansion of comparative examples that correspond thereto.
  • Table 6 illustrates heat treatment conditions and average coefficients of linear expansion of practical examples in a third embodiment, and heat treatment conditions and average coefficients of linear expansion of comparative examples that correspond thereto.
  • a holding temperature indicates a temperature where a heat treatment object is held in a heat treatment furnace (a heat treatment device). Additionally, a muffle furnace “QUICK TEMPER” produced by Tec Co., Ltd.
  • a holding time indicates a period of time when a heat treatment object is held in a state where an inside of a heat treatment furnace is provided at such a holding temperature.
  • a cooling method indicates a method of cooling a heat treatment object where furnace cooling is a method of cooling a heat treatment object gradually in a heat treatment furnace, natural cooling is a method of cooling a heat treatment object in air outside a heat treatment furnace, and rapid cooling is a method of dipping a heat treatment object in water, oil, a coolant that uses dry ice, liquid nitrogen, etc., so as to cool it rapidly.
  • a cooling end temperature indicates a temperature where cooling of a heat treatment object according to such a cooling method is ended.
  • a cooling end temperature in a case of furnace cooling is a surface temperature of a heat treatment object that is measured inside a heat treatment furnace by causing such a heat treatment object inside such a heat treatment furnace to contact a temperature measurement part of a thermocouple.
  • a cooling end temperature in cases of natural cooling and rapid cooling is a surface temperature of a heat treatment object that is measured outside a heat treatment furnace by causing such a heat treatment object outside such a heat treatment furnace to contact a temperature measurement part of a thermocouple.
  • a cooling rate (° C./min) or (° C./sec) indicates an amount of a change of a temperature with respect to a period of time from starting to ending of cooling of a heat treatment object.
  • an average coefficient of linear expansion ( ⁇ 10 ⁇ 6 /° C.) is a value that is measured for a test piece for measurement of a coefficient of linear expansion (a diameter of 6 mm and a length of 25 mm) that is sampled from an iron casting (a Y-shaped type-B specimen) after a predetermined heat treatment is applied to a heat treatment object where casting is executed by a sand mold casting method, according to an ASTM standard (ASTM E228-17) by using a thermal dilatometer “DIL 402 Expedis Supreme” produced by NETZSCH Japan K.K., and indicates average coefficients of linear expansion at respective temperatures (50° C., 100° C., and 150° C.) in Table 4 to Table 6 with respect to 20° C. as a reference thereof.
  • a primary cooling end temperature for practical example 1-1 to practical example 1-30 is 950° C. or lower whereas a primary cooling end temperature for comparative example 1-1 is 1000° C.
  • each of an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower, an average coefficient of linear expansion at 20° C. or higher and 100° C. or lower, and an average coefficient of linear expansion at 20° C. or higher and 150° C. or lower, for practical example 1-1 to practical example 1-30 is reduced as compared with comparative example 1-1.
  • an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower is 3.51 ⁇ 10 ⁇ 6 /° C.
  • a primary cooling end temperature is 950° C. or lower (in particular, 900° C. or lower), so that it is possible to reduce thermal expansion of an iron casting.
  • a primary cooling end temperature for practical example 1-1 to practical example 1-30 is 250° C. or higher whereas a primary cooling end temperature for comparative example 1-2 is 200° C.
  • each of an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower, an average coefficient of linear expansion at 20° C. or higher and 100° C. or lower, and an average coefficient of linear expansion at 20° C. or higher and 150° C. or lower, for practical example 1-1 to practical example 1-30 is reduced as compared with comparative example 1-2.
  • an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower is 3.51 ⁇ 10 ⁇ 6 /° C.
  • a primary cooling end temperature is 250° C. or higher (in particular, 300° C. or higher), so that it is possible to reduce thermal expansion of an iron casting.
  • a second holding temperature for practical example 2-1 to practical example 2-26 is 950° C. or lower whereas a second holding temperature for comparative example 2-1 is 1000° C.
  • each of an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower, an average coefficient of linear expansion at 20° C. or higher and 100° C. or lower, and an average coefficient of linear expansion at 20° C. or higher and 150° C. or lower, for practical example 2-1 to practical example 2-26 is reduced as compared with comparative example 2-1.
  • an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower is 3.30 ⁇ 10 ⁇ 6 /° C.
  • a second holding temperature is 950° C. or lower (in particular, 900° C. or lower), so that it is possible to reduce thermal expansion of an iron casting.
  • a second holding temperature for practical example 2-1 to practical example 2-26 is 250° C. or higher whereas a second holding temperature for comparative example 2-2 is 200° C.
  • each of an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower, an average coefficient of linear expansion at 20° C. or higher and 100° C. or lower, and an average coefficient of linear expansion at 20° C. or higher and 150° C. or lower, for practical example 2-1 to practical example 2-26 is reduced as compared with comparative example 2-2.
  • an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower is 3.30 ⁇ 10 ⁇ 6 /° C.
  • a second holding temperature is 250° C. or higher (in particular, 300° C. or higher), so that it is possible to reduce thermal expansion of an iron casting.
  • a first holding temperature for practical example 3-1 to practical example 3-13 is 850° C. or higher whereas a first holding temperature for comparative example 3-1 is 800° C.
  • each of an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower, an average coefficient of linear expansion at 20° C. or higher and 100° C. or lower, and an average coefficient of linear expansion at 20° C. or higher and 150° C. or lower, for practical example 3-1 to practical example 3-13 is reduced as compared with comparative example 3-1.
  • an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower is 3.80 ⁇ 10 ⁇ 6 /° C.
  • a first holding temperature for practical example 3-1 to practical example 3-13 is 850° C. or higher whereas a first holding temperature for comparative example 3-2 is 800° C.
  • each of an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower and an average coefficient of linear expansion at 20° C. or higher and 100° C. or lower, for practical example 3-1 to practical example 3-13 is reduced as compared with comparative example 3-2.
  • an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower is 3.80 ⁇ 10 ⁇ 6 /° C. or less (3.89 ⁇ 10 ⁇ 6 /° C.
  • a first holding temperature is 850° C. or higher (in particular, 950° C. or higher), so that it is possible to reduce thermal expansion of an iron casting.
  • a first holding temperature for practical example 3-1 to practical example 3-13 is 1250° C. or lower whereas a first holding temperature for comparative example 3-3 is 1300° C.
  • each of an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower, an average coefficient of linear expansion at 20° C. or higher and 100° C. or lower, and an average coefficient of linear expansion at 20° C. or higher and 150° C. or lower, for practical example 3-1 to practical example 3-13 is reduced as compared with comparative example 3-3.
  • an average coefficient of linear expansion at 20° C. or higher and 50° C. or lower is 3.80 ⁇ 10 ⁇ 6 /° C.
  • a first holding temperature is 1250° C. or lower (in particular, 1200° C. or lower), so that it is possible to reduce thermal expansion of an iron casting.
  • a material for casting for practical example 3-9, comparative example 3-1, and comparative example 3-2 does not contain Co.
  • a first holding temperature for practical example 3-9 is 850° C. or higher and 1250° C. or lower
  • a first holding temperature for comparative example 3-1 is 800° C.
  • a first holding temperature for comparative example 3-3 is 1300° C.
  • an average coefficient of linear expansion at 20° C. or higher and 150° C. or lower for practical example 3-9 is reduced as compared with comparative example 3-1 and comparative example 3-3.
  • an average coefficient of linear expansion at 20° C. or higher and 150° C. or lower is 4.84 ⁇ 10 ⁇ 6 /° C. or less (5.58 ⁇ 10 ⁇ 6 /° C. for comparative example 3-1 and 5.67 ⁇ 10 ⁇ 6 /° C. for comparative example 3-3).
  • Co is not contained and a first holding temperature is 850° C. or higher and 1250° C. or lower, so that it is possible to reduce thermal expansion of an iron casting at a high temperature.
  • a material for casting for practical example 3-1 to practical example 3-8, practical example 3-10 to practical example 3-13, and comparative example 3-2 contains Co. Furthermore, as illustrated in Table 6, a first holding temperature for practical example 3-1 to practical example 3-8 and practical example 3-10 to practical example 3-13 is 850° C. or higher and 1250° C. or lower whereas a first holding temperature for comparative example 3-2 is 800° C. As illustrated in Table 6, as practical example 3-1 to practical example 3-8 and practical example 3-10 to practical example 3-13, and comparative example 3-2 are compared where any of them contains Co, an average coefficient of linear expansion at 20° C. or higher and 150° C.
  • a manufacturing method for an iron casting that includes executing a first heat treatment for a heat treatment object that is provided by using and casting an austenite-type material for casting, wherein

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