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WO2017021330A1 - Segments de piston en acier coulé nitrurable et procédé de production - Google Patents

Segments de piston en acier coulé nitrurable et procédé de production Download PDF

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Publication number
WO2017021330A1
WO2017021330A1 PCT/EP2016/068223 EP2016068223W WO2017021330A1 WO 2017021330 A1 WO2017021330 A1 WO 2017021330A1 EP 2016068223 W EP2016068223 W EP 2016068223W WO 2017021330 A1 WO2017021330 A1 WO 2017021330A1
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WO
WIPO (PCT)
Prior art keywords
cast
carbides
piston rings
steels
rings
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.)
Ceased
Application number
PCT/EP2016/068223
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English (en)
Other versions
WO2017021330A8 (fr
Inventor
Eduardo ALBERTIN
Mario BOCCALINI JR.
Moysés LEITE DE LIMA
Gisela MARQUES ARAUJO
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Mahle International GmbH
Original Assignee
Mahle International GmbH
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Filing date
Publication date
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Publication of WO2017021330A1 publication Critical patent/WO2017021330A1/fr
Publication of WO2017021330A8 publication Critical patent/WO2017021330A8/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D15/00—Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor
    • B22D15/02—Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor of cylinders, pistons, bearing shells or like thin-walled objects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D25/00—Special casting characterised by the nature of the product
    • B22D25/02—Special casting characterised by the nature of the product by its peculiarity of shape; of works of art
    • 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
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/36—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases using ionised gases, e.g. ionitriding
    • C23C8/38—Treatment of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
    • C23C8/42—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions only one element being applied
    • C23C8/48—Nitriding
    • C23C8/50—Nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/80—After-treatment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F5/00—Piston rings, e.g. associated with piston crown
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J9/00—Piston-rings, e.g. non-metallic piston-rings, seats therefor; Ring sealings of similar construction
    • 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
    • C21D2211/004—Dispersions; Precipitations

Definitions

  • the present invention relates to rings of cast nitridable steels for pistons of internal combustion engines.
  • the present invention proposes the obtainment of piston rings of nitridable steels utilising processes of casting with alloys having relatively high contents of nitrogen, comprising the composition of the alloy and the process of manufacture .
  • the process of manufacture of the rings from cast iron may be summarised in the following stages: (1) melting of the alloy and correction of composition; (2) pouring into sand moulds or centrifuging; (3) heat treatment of the rings obtained; (4) machining to define the final dimensions; (5) surface treatments such as nitridation or coatings to obtain a surface having high hardness.
  • a relevant technical aspect linked to the process of obtainment of rings by mechanical shaping of drawn stainless steel wires is the presence of microcracks flowing from decohesion between carbides and matrix caused by the cumulative cross-sectional reductions in the stages of rolling and drawing, notably in the regions of the microstructure wherein there is agglomeration of carbides.
  • the document US 20120090462 ( ⁇ Nitratable steel piston rings and steel cylindrical sleeves , and casting method for the production thereof ) describes an alloy and possible casting processes for the production of piston rings of nitridable steels.
  • the principal elements in the composition of the alloy proposed are: silicon (Si) with contents from 2 to 10 % by weight, chromium (Cr) with contents between 4 and 20 % by weight, and nickel (Ni) between 2 and 12 % by weight.
  • Si silicon
  • Cr chromium
  • Ni nickel
  • microstructure of the material obtained according to the description in the document US 20120090462 presents coarse eutectic carbides formed during solidification ( Figure 1). Coarse carbides facilitate the nucleation and propagation of cracks in the steels. The presence of these carbides in the final microstructure of the rings greatly restricts the employment thereof in conditions of high structural stress by virtue of the fact that it diminishes the fatigue strength occasioned by the initiation and propagation of cracks.
  • FIG. 1 shows the microstructure of a material obtained according to the description of the example of embodiment of the document US 20120090462 in the as-cast state and subsequent to tempering (final stage of the development of the microstructure) . It may be observed that the coarse eutectic carbides precipitated in a continuous manner in the interdendritic regions are not altered through the application of the cycles of heat treatment, including the tempering.
  • FIG. 1 obtained by means of the use of the thermodynamic modelling software ThermoCalc, presents the sequence of solidification of the material having a composition described in the document US 20120090462 and shows that the eutectic carbide is of the M 7 C 3 type.
  • the thermodynamic analysis indicates that the M 7 C 3 carbides are stable in the band of temperatures of heat treatments described in this document. This stability of the M 7 C 3 carbides is not observed in similar alloys having low contents of silicon (contents of up to 1 %) .
  • Figure 3 shows the microstructure of a material obtained according to the description of the example of embodiment of the document US 20120090462 in the tempered state, subsequent to Villela and Murakami differential chemical attacks. These chemical attacks permit differentiating the carbides of the M 7 C 3 and M2 3 C 6 types, wherein the carbides of the M 7 C 3 type are light in colour and those of the M2 3 C 6 type present colouration. It may be observed in Figure 3 that the eutectic carbides are of the M 7 C 3 type (carbides light in colour) and, consequently, have not undergone transformation. It is also noted that these carbides do not undergo significant alteration of morphology in relation to the as-cast state.
  • Figure 1 presents a micrograph showing the microstructure (a) in the as-cast state and (b) subsequent to tempering at 600 °C of the material produced according to the description of the example of embodiment of the document US 20120090462.
  • Figure 2 shows the graph of the development of the fractions of phases as a function of the temperature during the solidification of the material having a composition described in the document US 20120090462.
  • Figure 3 presents a micrograph showing the microstructure subsequent to tempering at 600 °C of a material produced according to the description of the example of embodiment of the document US 20120090462, subsequent to Villela and Murakami chemical attack.
  • Figure 4 presents a micrograph showing the microstructure of the material obtained in the example of embodiment of the present invention in the as-cast state.
  • Figure 5 presents a micrograph showing the microstructure of the material obtained in the example of embodiment of the present invention subsequent to the heat treatment at 1040 °C and quenching in still air .
  • Figure 6 presents a micrograph showing the microstructure subsequent to tempering at 600 °C of a material produced according to the description of the example of embodiment of the present invention, subsequent to Villela and Murakami chemical attack.
  • Figure 7 shows a graph of the development of hardness of the material obtained in the example of embodiment of the present invention in the different stages of the process of manufacture.
  • the stainless steels contemporaneously utilised for piston rings present in the microstructure thereof eutectic carbides formed during the stage of solidification of the alloys.
  • These eutectic carbides are relatively large and continuous and act as stress concentrators, as revealed by Tanaka et al (Tanaka, S., Yamamura, K. and Oohori, M., Excellent Stainless Bearing Steel (ESI). Motion & Control. May 2000. Vol. No. 8, pp. 23 - 26), and sites for nucleation and propagation of cracks.
  • Tanaka et al Tanaka, S., Yamamura, K. and Oohori, M., Excellent Stainless Bearing Steel (ESI). Motion & Control. May 2000. Vol. No. 8, pp. 23 - 26
  • ESI Excellent Stainless Bearing Steel
  • the present invention describes an alloy and the process for the obtainment of cast parts suitable for use in components of internal combustion engines, preferentially piston rings of nitridable steels having a relatively high content of N and having low contents of Si.
  • the quantity of M 7 C 3 eutectic carbides is reduced to fractions of less than 2.0 % by weight through the substitution of part of the C by N and, furthermore, these eutectic carbides are transformed into M2 3 C 6 carbides during the stage of heat treatment.
  • This transformation is accompanied by an alteration in the morphology of the carbides, reducing the maximum size thereof and their continuity in the microstructure of the material.
  • This microstructural alteration of the material of the present invention is due to the chemical composition (low contents of Si and relatively high contents of N) , and appropriate heat treatments .
  • Table 1 shows the limits of composition for the material of the present invention.
  • the raw materials utilised in the process of the present invention may be scrap of low alloy steels, recycled production, and ferroalloys, not being limited to these materials.
  • the melting of the material for preparation of the alloy is realised preferentially in induction furnaces.
  • the furnace utilised for the preparation and melting of the alloy may have atmosphere and pressure control, it not being, however, strictly necessary.
  • the pouring of the alloy into the moulds must be realised at temperatures of between 1500 °C and 1650 °C.
  • the parts are removed from the moulds and the system of casting channels, should it exist, is removed, separating the rings or tubes.
  • the rings or tubes are annealed at temperatures of between 600 °C and 800 °C.
  • This stage of heat treatment there occurs the transformation of the M 7 C 3 eutectic carbides formed in the solidification of the material into M2 3 C 6 .
  • This transformation is accompanied by alteration in the morphology of the carbides, there being a reduction in sizes and in continuity of the eutectic structure.
  • This alteration in the morphology leads to an improvement in the fatigue strength of the material, being an important property for application in piston rings.
  • the parts pass through an initial machining.
  • heat treatments are carried out on the parts, having the objective of obtaining microstructures and properties appropriate for the rings.
  • the heat treatments consist in heating the parts at temperatures of between 1000 °C and 1100 °C (austenitisation) and quenching in air (forced or still) or in oil. These heat treatments may be realised in furnaces without a controlled atmosphere, but preferentially having a controlled atmosphere to prevent alterations in composition of the surfaces of the parts.
  • the parts must pass through a stage of tempering at temperatures of between 500 °C and 700 °C.
  • the present invention presents cast rings of nitridable steels having low contents of silicon and high contents of nitrogen, having the following principal characteristics: they are appropriate for common casting processes, they do not present microstructural characteristics detrimental to the mechanical properties of the piston rings, such as coarse eutectic carbides typical of the cast stainless steels having high silicon content, and they do not present microcracks or decohesion between carbide and matrix, typical of the mechanically shaped stainless steels. These characteristics, in addition to representing an economic benefit, signify a greater capacity of resistance to breakage during manufacture and greater fatigue strength of the rings subjected to high loading.
  • a charge containing low alloy steel, recycled production, and ferroalloys containing elements of alloys of the composition was melted in an induction furnace without a chamber for pressure control. To prevent the excessive oxidation of the molten metal there was utilised an injection of argon onto the surface of the bath. Subsequent to the complete melting of the charge and verification of temperature, the molten metal was poured at 1530 °C into a mould of sand-resin. During the pouring samples were taken for analysis of chemical composition, the result whereof is shown in Table 2.
  • a tube was cast having internal and external diameters of dimensions proximate to those of a piston ring. Following cooling, the tube was cleaned and passed through an annealing stage at 750 °C. Subsequently, initial machining and cutting of the tube into rings was carried out. Then the rings were subjected to a heat treatment with heating to 1040 °C and cooling in still air, and to a tempering treatment at 600 °C. Finally the rings were nitrided employing gas nitridation.
  • Figure 4 shows the structure of the material obtained in the as-cast state and Figure 5 shows the structure of the material following the heat treatment of quenching and tempering.
  • Figure 4 coarse and continuous eutectic carbides formed in the interdendritic region may be observed, however through the chemical composition and the thermal treatments utilised in the present invention these eutectic carbides formed during solidification (M 7 C 3 type) are transformed into carbides of the M2 3 C 6 type during the stage of heat treatment. This transformation is accompanied by an alteration in the morphology of the carbides, reducing the maximum size of the carbides in the microstructure of the material.
  • FIG. 6 shows the microstructure of a material obtained in the present invention following tempering and being passed through Villela and Murakami chemical attack. It may be observed in Figure 6 that the carbides in the interdendritic region are of the M2 3 C 6 type (region with colouration) and do not present continuity, substantiating the aforedescribed transformation .
  • the M2 3 C 6 carbides have a hardness lower than the M 7 C 3 carbides, as revealed by Li, Yefei, et al (Li, Yefei, et al .
  • This characteristic of the M2 3 C 6 carbides renders the material obtained tougher than the materials of the state of the art possessing M 7 C 3 carbides .
  • Figure 7 shows the development of the hardness of the material obtained during the process of manufacture.
  • this stage is fundamental for the determination of the properties of the material, taking into account the microstructural alterations with transformations of the carbides as aforedescribed .
  • the quenching increases the hardness of the material with the formation of martensite.
  • the resulting hardness of the material obtained subsequent to tempering is 600 HV, being substantially greater than the result of 420 HV found in the state of the art

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)

Abstract

La présente invention ("Segments de piston en acier coulé nitrurable et procédé de production") concerne un alliage et le procédé pour l'obtention de pièces coulées adaptées pour des segments de piston d'aciers nitrurables ayant une teneur relativement élevée en N et ayant de faibles teneurs en Si. Dans cette invention, la fraction de carbures eutectiques M7C3 est réduite à des fractions inférieures à 2,0 % en poids par l'intermédiaire de la substitution d'une partie de C par N et, en outre, ces carbures eutectiques sont transformés en carbures M23C6 pendant l'étape de traitement thermique. Cette transformation est accompagnée par une modification de la morphologie des carbures, réduisant la taille maximale de ceux-ci et la continuité de ceux-ci dans la microstructure du matériau. Cette modification microstructurale du matériau de la présente invention est due à la composition chimique (faibles teneurs en Si et teneurs relativement élevées en N) et des traitements thermiques appropriés. Les anneaux d'aciers coulés nitrurables ayant de faibles teneurs en Si et des teneurs élevées en azote obtenus dans la présente invention ont surmonté les limitations imposées par les procédés et/ou matériaux appartenant à l'état de l'art actuel, celles-ci étant : la limite de la charge à laquelle les anneaux de fonte peuvent être soumis, les limites dimensionnelles du processus de formation de câbles d'aciers inoxydables, et la formation de carbures macroscopiques dans les alliages proposés dans le document US 20120090462. Le tableau suivant présente les limites de composition pour le matériau.
PCT/EP2016/068223 2015-08-03 2016-07-29 Segments de piston en acier coulé nitrurable et procédé de production Ceased WO2017021330A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115896609A (zh) * 2022-07-06 2023-04-04 钢铁研究总院有限公司 一种高强度高塑性气阀钢及其制备方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19836360A1 (de) * 1997-08-11 1999-02-18 Hitachi Metals Ltd Kolbenringmaterial mit hervorragender Bearbeitbarkeit und Resistenz gegen Fressen sowie Kolbenring hieraus
EP1304393A1 (fr) * 2000-07-17 2003-04-23 Kabushiki Kaisha Riken Segment de piston presentant une resistance elevee a l'erosion, a la fissuration et a la fatigue, procede permettant de produire ce segment et combinaison segment de piston et bloc-cylindres
EP2011892A1 (fr) * 2006-04-20 2009-01-07 Hitachi Metals, Limited Matériau de segment de piston pour moteur à combustion interne
US20120090462A1 (en) 2009-03-26 2012-04-19 Federal-Mogul Burscheid Gmbh Nitratable steel piston rings and steel cylindrical sleeves, and casting method for the production thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19836360A1 (de) * 1997-08-11 1999-02-18 Hitachi Metals Ltd Kolbenringmaterial mit hervorragender Bearbeitbarkeit und Resistenz gegen Fressen sowie Kolbenring hieraus
EP1304393A1 (fr) * 2000-07-17 2003-04-23 Kabushiki Kaisha Riken Segment de piston presentant une resistance elevee a l'erosion, a la fissuration et a la fatigue, procede permettant de produire ce segment et combinaison segment de piston et bloc-cylindres
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