WO2017137656A1 - Method of manufacturing an iron product and use of an iron material in a cylinder head - Google Patents

Method of manufacturing an iron product and use of an iron material in a cylinder head Download PDF

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Publication number
WO2017137656A1
WO2017137656A1 PCT/FI2017/050034 FI2017050034W WO2017137656A1 WO 2017137656 A1 WO2017137656 A1 WO 2017137656A1 FI 2017050034 W FI2017050034 W FI 2017050034W WO 2017137656 A1 WO2017137656 A1 WO 2017137656A1
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WO
WIPO (PCT)
Prior art keywords
base material
iron
cylinder head
partially
manufacturing
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Ceased
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PCT/FI2017/050034
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French (fr)
Inventor
Jarkko Laine
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Wartsila Finland Oy
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Wartsila Finland Oy
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Classifications

    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/185—Hardening; Quenching with or without subsequent tempering from an intercritical temperature
    • 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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • C21D1/20—Isothermal quenching, e.g. bainitic hardening
    • 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
    • C21D1/34—Methods of heating
    • C21D1/44—Methods of heating in heat-treatment baths
    • C21D1/46—Salt baths

Definitions

  • the present invention relates to method of manufacturing an iron product, and its use in a cylinder head of an internal combustion engine.
  • Cast irons like steels, are basically alloys of iron and carbon. Gray cast iron is the oldest of the cast irons and the carbon in it exists in the form of graphite flakes. The main factor favouring the wide spread use of gray iron is its low cost. Even though the tensile properties of gray iron are inferior, it pos- sesses high compression strength coupled with excellent damping capacity.
  • VG iron vermicular graphite cast irons
  • graphite is present in a worm-like, tubby form with rounded edges in the matrix.
  • This material is also popularly known as compacted graphite cast iron or as CG iron.
  • Cast iron with vermicular graphite falls between cast iron with lamellar graphite and cast iron with spheroidal graphite not only in terms of its microstructure formation but in terms of its mechanical and physical properties as well.
  • Vermicular graphite irons have certain advantages over the older members of the cast iron family viz. gray, ductile and malleable irons.
  • the tolerable content of sulphur in VG iron is much higher than in ductile iron.
  • the tempera- ture range in which the reaction material is effective is very wide in VG iron as compared to SG iron.
  • the graphite is in the form of spherical nodules (hence the name Spheroidal Graphite) rather than flakes as in Grey cast iron.
  • CN102409220 A there is disclosed a vermicular cast iron and a preparation method thereof.
  • the high-strength vermicular cast iron consists of the following components in percentage by weight: 3.4-3.8 percent of C, 2.1 -2.6 percent of Si, 0.2-0.6 percent of Cu, 0.2-0.5 percent of Mo, 0.2-0.8 percent of Mn, 0.02-0.04 percent of Sn, 0.004-0.032 percent of Sb and the balance of iron and inevitable impurities.
  • the microscopic structure of the vermicular cast iron consists of a substrate and vermicular graphite, and the vermicular rate surpasses 85 percent.
  • the vermicular cast iron can be prepared into vermicular cast iron with excellent comprehensive performance by preserving heat at the temperature 900-950 °C for 1.5-3 hours, preserving heat in a saline solution at the temperature 320-360 °C for 1.5-3 hours and performing air cooling.
  • the ma- trix phase consists of austenite and bainite.
  • US2485760 discloses a cast ferrous alloy having a microstructure containing substantially spheroidal particles of uncombined carbon dispersed in a ferrous matrix.
  • An object of the invention is to provide a method of manufacturing an iron product which results in a material in which the mechanical and thermal properties are considerably improved compared to the prior art solutions, particularly in a view of use as a cylinder head of an internal combustion piston engine.
  • vermicular cast iron is used as a base material in the method.
  • the vermicular cast iron is standardized in EN 16079 or similar. At least 80% of graphite particles are in the vermicular form.
  • the base material is subjected to heat treatment where the base material is maintained at a temperature between 738-1 154°C during a predetermined period of time, such that the microstructure of the base material is partially austenized. Subsequently, the base material is quenched to the temperature of 240-450°C, to get a final matrix, which is partially pearlitic-ferritic or per- ferritic.
  • the basic matrix of the vermicular cast iron before the heat treatment is ferritic.
  • the basic matrix of the vermicular cast iron before the heat treatment is ferritic-perlitic.
  • the basic matrix of the vermicular cast iron before the heat treatment is perlitic-ferritic.
  • the base material is partially austenized by maintaining the base material at 738-1 154°C from 0.2 to 3 hours.
  • the base material is partially austenized such that its micro-structure is partially austenized, while a portion of the microstructure remains in ferrite structure.
  • the base material is at least partially austenized such that its micro-structure is 20-80% austenized.
  • the base material is quenched to a salt bath temperature of 240-450°C.
  • the base material is quenched to a salt bath temperature of 240-450°C and held at the temperature during a predetermined time to provide austempering of the base material.
  • a base material for the cylinder head material which contains at least 80 wt% of graphite
  • the base material is subjected to heat treatment where the base material is maintained at a temperature between 738-1 154°C during a predetermined period of time, such that the microstructure of the base material is partially aus- tenized, subsequently, the base material is quenched to a temperature of 240- 450°C, to get a final matrix, which is at least partially pearlitic-ferritic or perferritic, and the cylinder head is formed from the base material.
  • Invention relates also to use of an iron material manufactured according to the invention in a cylinder head of an internal combustion engine for improving thermal properties of the cylinder head.
  • the invention relates to use of an iron material comprising vermicular cast iron containing at least 80 wt% of graphite and having a matrix, which is at least partially pearlitic-ferritic or perferritic, in a cylinder head of an internal combustion engine for improving thermal properties of the cylinder head.
  • Ferritic steels contain less than 0.10% carbon and are magnetic.
  • Pearl- ite is a two-phased, lamellar (or layered) structure composed of alternating lay- ers of ferrite (88 wt%) and cementite (12 wt%) in the matrix.
  • Austenization means heating of the iron of iron based metal such that its microstructure changes from ferritic to austenitic
  • FIG. 1 illustrates a time-temperature transformation diagram according to an embodiment of the invention. Detailed Description of Drawings
  • Figure 1 depicts schematically a time-temperature transformation diagram which describes the method of manufacturing an iron product according to an embodiment of the invention.
  • a vermicular iron is used as a base material.
  • the vermicular cast iron according to the invention contains at least 80 wt% of graphite.
  • the base material is subjected to heat treatment comprising several phases 20, 22, 24, 26, 28.
  • the first phase of the method is heating 20 the base material to a temperature between 738-1 154°C.
  • the base material is maintained 22 at the temperature between 738-1 154°C during a predetermined time ti.
  • the predetermined time ti is 0,2 to 3 hours and depends on the specific application.
  • the microstructure of the base material is partially austenized.
  • the base material is quenched 24 to a temperature of 240-450°C.
  • the base material is maintained 26 at the temperature of 240- 450°C during a predetermined time t.2 to provide austempering process.
  • a final matrix is provided, which is at least partially pearlitic-ferritic or perferritic.
  • the base material may be cooled to room temperature 28.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

Invention relates to method of manufacturing an iron product wherein vermicular cast iron is used as a base material which contains at least 80 wt% of graphite,the base material is maintained (22) at a temperature between 738-1154°C during a predetermined period of time, such that the microstructure of the base material is partially austenized, subsequently, the base material is quenched (24) to a temperature of 240-450°C, to get a final matrix, which is at least partially pearlitic-ferritic or perferritic. Invention relates also to use of an iron material manufactured according to the invention in a cylinder head of an internal combustion engine for improving thermal properties of the cylinder head.

Description

METHOD OF MANUFACTURING AN IRON PRODUCT AND USE OF AN IRON MATERIAL IN A CYLINDER HEAD
Technical field [001 ] The present invention relates to method of manufacturing an iron product, and its use in a cylinder head of an internal combustion engine.
Background art
[002] Materials used in internal combustion piston engines are subjected to considerable mechanical and/or thermal stresses. It is known to use cast irons as a base material in engine components.
[003] Cast irons, like steels, are basically alloys of iron and carbon. Gray cast iron is the oldest of the cast irons and the carbon in it exists in the form of graphite flakes. The main factor favouring the wide spread use of gray iron is its low cost. Even though the tensile properties of gray iron are inferior, it pos- sesses high compression strength coupled with excellent damping capacity.
[004] In vermicular graphite cast irons, i.e. VG iron, graphite is present in a worm-like, tubby form with rounded edges in the matrix. This material is also popularly known as compacted graphite cast iron or as CG iron. Cast iron with vermicular graphite falls between cast iron with lamellar graphite and cast iron with spheroidal graphite not only in terms of its microstructure formation but in terms of its mechanical and physical properties as well.
[005] Vermicular graphite irons have certain advantages over the older members of the cast iron family viz. gray, ductile and malleable irons. The tolerable content of sulphur in VG iron is much higher than in ductile iron. The tempera- ture range in which the reaction material is effective is very wide in VG iron as compared to SG iron. In SG iron the graphite is in the form of spherical nodules (hence the name Spheroidal Graphite) rather than flakes as in Grey cast iron.
[006] In CN102409220 A there is disclosed a vermicular cast iron and a preparation method thereof. The high-strength vermicular cast iron consists of the following components in percentage by weight: 3.4-3.8 percent of C, 2.1 -2.6 percent of Si, 0.2-0.6 percent of Cu, 0.2-0.5 percent of Mo, 0.2-0.8 percent of Mn, 0.02-0.04 percent of Sn, 0.004-0.032 percent of Sb and the balance of iron and inevitable impurities. The microscopic structure of the vermicular cast iron consists of a substrate and vermicular graphite, and the vermicular rate surpasses 85 percent. The vermicular cast iron can be prepared into vermicular cast iron with excellent comprehensive performance by preserving heat at the temperature 900-950 °C for 1.5-3 hours, preserving heat in a saline solution at the temperature 320-360 °C for 1.5-3 hours and performing air cooling. The ma- trix phase consists of austenite and bainite.
[007] US2485760 discloses a cast ferrous alloy having a microstructure containing substantially spheroidal particles of uncombined carbon dispersed in a ferrous matrix.
[008] An object of the invention is to provide a method of manufacturing an iron product which results in a material in which the mechanical and thermal properties are considerably improved compared to the prior art solutions, particularly in a view of use as a cylinder head of an internal combustion piston engine.
Disclosure of the Invention [009] The objects of the invention can be met substantially as is disclosed in the independent claims and in the other claims describing more details of different embodiments of the invention.
[0010] According to an embodiment of the invention vermicular cast iron is used as a base material in the method. The vermicular cast iron is standardized in EN 16079 or similar. At least 80% of graphite particles are in the vermicular form.
[001 1 ] In the method the base material is subjected to heat treatment where the base material is maintained at a temperature between 738-1 154°C during a predetermined period of time, such that the microstructure of the base material is partially austenized. Subsequently, the base material is quenched to the temperature of 240-450°C, to get a final matrix, which is partially pearlitic-ferritic or per- ferritic.
[0012] This provides a novel cast iron for use in cylinder head of an internal com- bustion piston engine which performance is considerably improved.
[0013] According to an embodiment of the invention the basic matrix of the vermicular cast iron before the heat treatment is ferritic.
[0014] According to another embodiment of the invention the basic matrix of the vermicular cast iron before the heat treatment is ferritic-perlitic. [0015] According to still another embodiment of the invention the basic matrix of the vermicular cast iron before the heat treatment is perlitic-ferritic.
[0016] According to an embodiment of the invention the base material is partially austenized by maintaining the base material at 738-1 154°C from 0.2 to 3 hours.
[0017] According to an embodiment of the invention the base material is partially austenized such that its micro-structure is partially austenized, while a portion of the microstructure remains in ferrite structure. Advantageously the base material is at least partially austenized such that its micro-structure is 20-80% austenized.
[0018] According to an embodiment of the invention after austenizing process the base material is quenched to a salt bath temperature of 240-450°C. [0019] According to an embodiment of the invention after austenizing process the base material is quenched to a salt bath temperature of 240-450°C and held at the temperature during a predetermined time to provide austempering of the base material.
[0020] According to an embodiment of the invention in method of manufacturing a cylinder head for an internal combustion piston vermicular cast iron is used as a base material for the cylinder head material which contains at least 80 wt% of graphite, the base material is subjected to heat treatment where the base material is maintained at a temperature between 738-1 154°C during a predetermined period of time, such that the microstructure of the base material is partially aus- tenized, subsequently, the base material is quenched to a temperature of 240- 450°C, to get a final matrix, which is at least partially pearlitic-ferritic or perferritic, and the cylinder head is formed from the base material. [0021 ] Invention relates also to use of an iron material manufactured according to the invention in a cylinder head of an internal combustion engine for improving thermal properties of the cylinder head.
[0022] As a particular embodiment the invention relates to use of an iron material comprising vermicular cast iron containing at least 80 wt% of graphite and having a matrix, which is at least partially pearlitic-ferritic or perferritic, in a cylinder head of an internal combustion engine for improving thermal properties of the cylinder head.
[0023] Ferritic steels contain less than 0.10% carbon and are magnetic. Pearl- ite is a two-phased, lamellar (or layered) structure composed of alternating lay- ers of ferrite (88 wt%) and cementite (12 wt%) in the matrix. Austenization means heating of the iron of iron based metal such that its microstructure changes from ferritic to austenitic
[0024] The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims.
Brief Description of Drawings
[0025] In the following, the invention will be described with reference to the accompanying exemplary, schematic drawing, in which
Figure 1 illustrates a time-temperature transformation diagram according to an embodiment of the invention. Detailed Description of Drawings
[0026] Figure 1 depicts schematically a time-temperature transformation diagram which describes the method of manufacturing an iron product according to an embodiment of the invention.
[0027] In the method a vermicular iron is used as a base material. The vermicular cast iron according to the invention contains at least 80 wt% of graphite.
[0028] The base material is subjected to heat treatment comprising several phases 20, 22, 24, 26, 28. The first phase of the method is heating 20 the base material to a temperature between 738-1 154°C. The base material is maintained 22 at the temperature between 738-1 154°C during a predetermined time ti. The predetermined time ti is 0,2 to 3 hours and depends on the specific application. During the first phase 20, 22 the microstructure of the base material is partially austenized. [0029] In the next phase the base material is quenched 24 to a temperature of 240-450°C. The base material is maintained 26 at the temperature of 240- 450°C during a predetermined time t.2 to provide austempering process.
A final matrix is provided, which is at least partially pearlitic-ferritic or perferritic. After the process the base material may be cooled to room temperature 28. [0030] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the in- vention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such combination is technically feasible.

Claims

Claims
1 . Method of manufacturing an iron product, wherein method vermicular cast iron is used as a base material which contains at least 80 wt% of graphite, the base material is subjected to heat treatment where the base material is maintained (22) at a temperature between 738-1 154°C during a predetermined period of time, such that the microstructure of the base material is partially austenized, - subsequently, the base material is quenched (24) to a temperature of 240-450°C, to get a final matrix, which is at least partially pearl itic-ferritic or perferritic.
2. Method of manufacturing iron product according to claim 1 , characterized in that the basic matrix of the vermicular cast iron before the heat treatment is ferritic.
3. Method of manufacturing iron product according to claim 1 , characterized in that the basic matrix of the vermicular cast iron before the heat treatment is ferritic-perlitic.
4. Method of manufacturing iron product according to claim 1 , character- ized in that the basic matrix of the vermicular cast iron before the heat treatment is perl itic-ferritic.
5. Method of manufacturing iron product according to claim 1 , characterized in that the base material is at least partially austenized by maintaining (22) the base material at 738-1 154°C from 0,2 to 3 hours.
6. Method of manufacturing iron product according to claim 1 , characterized in that the base material is at least partially austenized such that its micro- structure is partially austenized, while a portion of the microstructure remains in ferrite structure.
7. Method of manufacturing iron product according to claim 1 or 6, characterized in that the base material is at least partially austenised such that its mi- crostructure is 20-80% austenized.
8. Method of manufacturing iron product according to claim 1 , character- ized in that after austenizing process the base material is quenched (24) to a salt bath temperature of 240-450°C and held (26) at the temperature during a predetermined time to provide austempering of the base material.
9. Method of manufacturing a cylinder head for an internal combustion piston engine by a method according to anyone of the preceding claims, wherein method vermicular cast iron is used as a base material for the cylinder head and after th base material is quenched to a temperature of 240-450°C, to get a final matrix, which is at least partially pearlitic-ferritic or perferritic, the cylinder head is formed from the base material.
10. Use of an iron material manufactured according anyone of the claims 1 - 8 in a cylinder head of an internal combustion engine for improving thermal properties of the cylinder head.
1 1 . Use of an iron material comprising vermicular cast iron containing at least 80 wt% of graphite and having a matrix, which is at least partially pearlitic- ferritic or perferritic, in a cylinder head of an internal combustion engine for im- proving thermal properties of the cylinder head.
PCT/FI2017/050034 2016-02-10 2017-01-24 Method of manufacturing an iron product and use of an iron material in a cylinder head Ceased WO2017137656A1 (en)

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FI20165096 2016-02-10
FI20165096 2016-02-10

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2485760A (en) 1947-03-22 1949-10-25 Int Nickel Co Cast ferrous alloy
US20090320971A1 (en) * 2006-07-03 2009-12-31 Zanardi Fonderie S.P.A. Method for manufacturing spheroidal cast iron mechanical components
CN102409220A (en) 2011-11-25 2012-04-11 西安工业大学 High strength and toughness vermicular graphite cast iron and its preparation method
DE102013017665A1 (en) * 2013-10-25 2015-04-30 Eisenwerk Brühl GmbH Engine block with improved properties

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2485760A (en) 1947-03-22 1949-10-25 Int Nickel Co Cast ferrous alloy
US20090320971A1 (en) * 2006-07-03 2009-12-31 Zanardi Fonderie S.P.A. Method for manufacturing spheroidal cast iron mechanical components
CN102409220A (en) 2011-11-25 2012-04-11 西安工业大学 High strength and toughness vermicular graphite cast iron and its preparation method
DE102013017665A1 (en) * 2013-10-25 2015-04-30 Eisenwerk Brühl GmbH Engine block with improved properties

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
B. T. SIM ET AL: "Influence of alloying additions on austempering kinetics of compacted graphite cast iron", MATERIALS SCIENCE AND TECHNOLOGY, vol. 14, no. 2, 1 February 1998 (1998-02-01), GB, pages 89 - 96, XP055356570, ISSN: 0267-0836, DOI: 10.1179/mst.1998.14.2.89 *
FRANCO ZANARDI ET AL: "A Contribution to New Material Standards for Ductile Irons and Austempered Ductile Irons", INTERNATIONAL JOURNAL OF METALCASTING, vol. 11, no. 1, 14 October 2016 (2016-10-14), pages 136 - 147, XP055356793, ISSN: 1939-5981, DOI: 10.1007/s40962-016-0095-6 *
JAW-MIN CHOU ET AL: "Affects of graphite morphology and matrix structure on mechanical properties of cast ions", JOURNAL OF MATERIALS SCIENCE, vol. 25, no. 4, 1 April 1990 (1990-04-01), Dordrecht, pages 1965 - 1972, XP055356634, ISSN: 0022-2461, DOI: 10.1007/BF01045750 *
S. KRUSE: "Should you add ADI, CGI, SiMO to your iron menu?", MODERN CASTING JULY 2006 AMERICAN FOUNDARY SOC. USA, vol. 96, no. 7, 1 July 2006 (2006-07-01), pages 33 - 36, XP009193799, ISSN: 0026-7562 *

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