EP0806996B1 - A method of manufacturing cast products which are cast in a single-piece having controlled variations of compacted graphite iron and grey cast iron - Google Patents

A method of manufacturing cast products which are cast in a single-piece having controlled variations of compacted graphite iron and grey cast iron Download PDF

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Publication number
EP0806996B1
EP0806996B1 EP96902525A EP96902525A EP0806996B1 EP 0806996 B1 EP0806996 B1 EP 0806996B1 EP 96902525 A EP96902525 A EP 96902525A EP 96902525 A EP96902525 A EP 96902525A EP 0806996 B1 EP0806996 B1 EP 0806996B1
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EP
European Patent Office
Prior art keywords
cast iron
iron
graphite
molten cast
cast
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP96902525A
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German (de)
English (en)
French (fr)
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EP0806996A1 (en
Inventor
Steve Dawson
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SinterCast AB
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SinterCast AB
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Publication date
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D2/00—Arrangement of indicating or measuring devices, e.g. for temperature or viscosity of the fused mass
    • 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 present invention relates to a method of manufacturing cast products which are cast as a one-piece objects having controlled inhomogeneous graphite structure.
  • the products can be cast in a manner to obtain a grey cast iron having a flaky graphite structure in certain parts thereof, and a vermicular graphite structure in other parts thereof, therewith imparting to the cast product different properties in different parts of said product.
  • the background art comprises WO-A1-93/20969, WO-A1-89/04224, US-A-4 667 725, US-A-5 316 068, DE-A-43 08 614, SE-B-469 712, SE-B-444 817 and JP-A-6/106 331.
  • Compacted graphite iron or cast iron having a vermicular graphite structure, when viewed on a two-dimensional section, is an intermediate form between grey cast iron having a flaky graphite structure and ductile iron having a nodular graphite structure.
  • Compacted graphite cast iron possesses desirable and unique properties, which include good mechanical and physical properties and good machinability, which makes the material highly suitable for a number of components in mechanical devices. This includes machine constructions that are manufactured in large numbers, chiefly engines and, for instance, brake discs and hydraulic pumps of all sorts.
  • Compacted graphite iron will thus contain graphite that, during solidification, has precipitated in the form of vermicular graphite and is defined according to ISO/R 945-1975(E) as "Form III"- graphite or "Type IV”-graphite in accordance with ASTM A 247.
  • the graphite form was first described in England (1948) and has since been used for the manufacture of special components on a small scale. The reason for this small scale of manufacture is because it has not been possible to control properties and composition of the iron melts with sufficient accuracy to guarantee the composition and graphite structure of the cast product with sufficient reproducibility.
  • the properties of compacted graphite iron lie somewhere between the properties of grey iron and ductile iron.
  • the elastic modulus of compacted graphite iron is from 30-40% higher than the elastic modulus of grey iron, which means that the elastic modulus of compacted graphite iron is almost the same as that of ductile iron.
  • Compacted graphite cast iron has a ductility which is higher than that of grey iron, often more than ten times higher than that of grey iron, and has a much higher tensile strength, in the order of twice the tensile strength of grey iron.
  • the fatigue strength of compacted graphite iron is 100% higher than that of grey iron, and essentially the same as that of ductile iron.
  • the thermal conductivity of compacted graphite iron is of the same order of magnitude as that of grey iron, and 30-50% higher than that of ductile iron.
  • the machinability and castability of compacted graphite iron is also similar to grey iron.
  • One of these temperature sensors is placed in the centre of the melt in the sample vessel while the other sensor is placed in the melt in the proximity of the vessel wall.
  • T* w undercooling of the melt at the vessel wall
  • rec w recalescence at the vessel wall
  • ⁇ T+ positive difference between the temperature at the vessel wall and at the vessel centre
  • dT/d ⁇ constant equivalent growth temperatures
  • the structure modifying additives normally consist of magnesium optionally together with rare earth metals, particularly cerium or mischmetal.
  • WO-A-93/20969 discloses a method of manufacturing cast iron products, where some parts of the products have a compacted graphite structure and other parts of said products have a nodular graphite structure.
  • JP-A-6/106 331 relates to a process for producing ductile iron engine blocks for improved strength and stiffness and, by placing a reactive coating on the sand cores which form the cylinder bore walls, the active magnesium in the melt adjacent to the wall of the iron is reduced thus providing elongated graphite flakes and hence, good thermal conductivity and machinability in the bore walls.
  • the reactive coating applied to the surface of the cylinder cores can only reduce the magnesium to a certain amount. Therefore, reproducible results are difficult to obtain when the magnesium content of the iron to be poured into the moulds is constant. Variations in the magnesium content, which are common, are directly manifested as variations in the graphite structure in the bore walls.
  • the initial overtreatment with magnesium also results in a restricted ability to produce thick layers of flake graphite adjacent to the reactive core surfaces.
  • the magnesium content of the iron changes from its bulk concentration value to a sufficiently lower level near the wall which allows flake formation.
  • the thickness of the flake layer can be rather small. This is particularly important when it is realised that up to 3 mm of the surface iron may be removed as machining stock and thus, much of the flake graphite can be lost.
  • US-A-5 316 068 also begins with a ductile iron base material, but the graphite transition mechanism is changed from reactive cores to high speed spinning of the moulds during solidification to promote grey iron in the outer region and compacted graphite iron in the central bore areas. Not only does this technique seem physically awkward, but it is also plagued by the same problems as outlined in the discussion concerning JP-A-6/106 331, which stem from a ductile starting point.
  • DE-A-43 08 614 relates to a method for producing a cast iron product where parts of the product contain flaky grey iron and other areas contain compacted graphite iron. Parts of the mould are covered by oxygen or sulphur emitting substances in order to reduce the active magnesium content of the part of the melt that is adjacent to the covered mould wall.
  • DE-A-43 08 614 does not disclose anything about how to control the composition of the melt in order to make the casting method reproducible. It has already been mentioned in this application that it is difficult to cast compacted graphite iron in a reproducible manner, and it must be considered to be extremely difficult to use the method according to DE-A-43 08 614 in order to reproducibly cast an inhomogenous graphite structure without having the possibility of controlling the composition of the melt. Moreover, when using said method, it is usual to use an excess of magnesium or similar metals. Hence, up to now, it has not been possible to cast an inhomogenous graphite structure consisting of parts containing flaky grey iron and parts containing compacted graphite iron.
  • the present invention it is possible to reliably reproduce a compacted graphite iron of optimal solidification potential so that single castings can be consistently generated with a preferred mixture of compacted graphite particles and flake-type graphite.
  • a compacted graphite base iron By beginning with a compacted graphite base iron, the thickness of grey flake iron which can be produced by a given reactive coating is increased, and simultaneously, the internal stress and strain gradients are lessened because the mechanical and physical properties of grey iron and vermicular iron are more similar than those of grey iron and ductile iron. The castability and machinability of the finished components will also be markedly better.
  • the method according to SE-B-469 712 allows a precise determination of the proximity of the treated iron to the rapid transition between compacted and flake graphite.
  • By strategically altering the distance between the measuring point of the thermocouple and the reactive wall coating in the sample or by altering the reactivity of the coating placed on the inner wall of the vessel it is possible to accurately produce a compacted graphite base iron which is rather close to the left hand edge of the stable vermicular plateau (point A in Figure 1) and is therefore prone to producing considerable amounts of grey flake iron when poured into moulds containing cores and mould sand which are coated with reactive coatings.
  • the following example relates to a cylinder head, but the method according to the invention can also be used in the casting of engine blocks, where, for example, the cylinder bore and water jacket cores can contain grey iron, while the bulk head, top deck, pan rail and crank case areas contain higher strength compacted graphite iron, or brake discs where, for example, the outer flange contains lamellar iron with high thermal conductivity and the inner hub contains compacted graphite iron to provide higher strength.
  • ⁇ max ⁇ T Eo ⁇ 2(1- ⁇ )
  • the thermal expansion and Poisson's ratio of vermicular iron and grey iron are essentially equal. Therefore, the only means of minimizing the thermal stresses which accumulate at the hot-face and ultimately lead to crack formation between the valve ports, is to minimize the parameters ⁇ T and Eo, where ⁇ T is inversely related to thermal conductivity.
  • the objective therefore is to have a material with high thermal conductivity and low elastic modulus at the hot-face which can only be satisfied by grey cast irons.
  • the bulk material of the cylinder head and the outer peripheral regions are made from a material with higher strength, stiffness, and ductility.
  • the present invention is particularly useful in existing cylinder head designs where it is not possible to re-design the head because it must continue to fit an existing engine.
  • many designs are canidates for conversion to a stronger material, and compacted graphite iron is ideal for this.
  • the head is prone to failure due to thermal loading, the lower thermal conductivity and higher elastic modulus of compacted graphite iron compared to grey iron will actually increase the thermal load and may result in a shorter service life.
  • the only possible way to reduce the ⁇ T term in equation (1) would then be to reduce the thickness of the flame deck.
  • the present invention is an ideal solution in these cases since the introduction of grey iron flakes in the flame deck provides the necessary thermal conductivity and lower elastic modulus to withstand the thermal loading, while the compacted graphite iron provides the necessary strength, stiffness and ductility to withstand the mechanical loading, without sacrificing machinability or castability behaviours.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Mold Materials And Core Materials (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Investigating And Analyzing Materials By Characteristic Methods (AREA)
EP96902525A 1995-02-07 1996-01-04 A method of manufacturing cast products which are cast in a single-piece having controlled variations of compacted graphite iron and grey cast iron Expired - Lifetime EP0806996B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9500432A SE504136C2 (sv) 1995-02-07 1995-02-07 Förfarande för framställning av gjutgods som är gjutna i ett enda stycke där vissa delar innehåller kompaktgrafitjärn och andra grått gjutjärn
SE9500432 1995-02-07
PCT/SE1996/000003 WO1996024451A1 (en) 1995-02-07 1996-01-04 A method of manufacturing cast products which are cast in a single-piece having controlled variations of compacted graphite iron and grey cast iron

Publications (2)

Publication Number Publication Date
EP0806996A1 EP0806996A1 (en) 1997-11-19
EP0806996B1 true EP0806996B1 (en) 1999-08-18

Family

ID=20397113

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96902525A Expired - Lifetime EP0806996B1 (en) 1995-02-07 1996-01-04 A method of manufacturing cast products which are cast in a single-piece having controlled variations of compacted graphite iron and grey cast iron

Country Status (11)

Country Link
EP (1) EP0806996B1 (zh)
KR (1) KR100417049B1 (zh)
CN (1) CN1173837A (zh)
AU (1) AU4680596A (zh)
CA (1) CA2211804A1 (zh)
CZ (1) CZ243097A3 (zh)
DE (1) DE69603830T2 (zh)
RU (1) RU2153004C2 (zh)
SE (1) SE504136C2 (zh)
WO (1) WO1996024451A1 (zh)
ZA (1) ZA96262B (zh)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6021581A (en) * 1998-06-22 2000-02-08 Voith Sulzer Paper Technology North America, Inc. Method of drying a paper web in a paper-making machine at speeds greater than 6000 feet per minute
DE19942780A1 (de) * 1999-09-08 2001-03-15 Bruehl Eisenwerk Zylinderkopf für eine Kolbenbrennkraftmaschine
JP4076438B2 (ja) * 2002-12-27 2008-04-16 株式会社キリウ ねずみ鋳鉄における黒鉛組織の評価方法および評価システム
DE10342582B4 (de) * 2003-05-06 2010-09-16 Halberg-Guss Gmbh Herstellen eines Gradientenwerkstücks durch Schichtgießen
US8726974B2 (en) 2010-01-29 2014-05-20 Caterpillar Inc. In-situ graphite shape control for iron castings
US10054140B2 (en) 2016-02-12 2018-08-21 Crystaphase Products, Inc. Use of treating elements to facilitate flow in vessels
CN109115672B (zh) * 2018-11-06 2021-01-01 苏交科集团股份有限公司 一种沥青路面再生封层材料渗透性能评价方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE501003C2 (sv) * 1990-10-15 1994-10-17 Sintercast Ab Förfarande för framställning av segjärn
SE470092B (sv) * 1992-04-09 1993-11-08 Sintercast Ltd Förfarande för framställning av gjutgods med homogen grafitstruktur
DE4308614A1 (de) * 1993-03-18 1994-09-22 Fritz Winter Eisengieserei Ohg Verfahren zur Herstellung von Werkstücken aus Gußeisen und danach hergestellte hohle Gußstücke

Also Published As

Publication number Publication date
KR100417049B1 (ko) 2004-03-18
DE69603830T2 (de) 2000-03-09
WO1996024451A1 (en) 1996-08-15
CA2211804A1 (en) 1996-08-15
CN1173837A (zh) 1998-02-18
SE9500432D0 (sv) 1995-02-07
ZA96262B (en) 1996-08-01
SE504136C2 (sv) 1996-11-18
DE69603830D1 (de) 1999-09-23
SE9500432L (sv) 1996-08-08
EP0806996A1 (en) 1997-11-19
RU2153004C2 (ru) 2000-07-20
KR19980702029A (ko) 1998-07-15
CZ243097A3 (cs) 1998-07-15
AU4680596A (en) 1996-08-27

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