EP0717116B1 - Process for producing a work piece of machine construction steel and work piece produced by this process - Google Patents

Process for producing a work piece of machine construction steel and work piece produced by this process Download PDF

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Publication number
EP0717116B1
EP0717116B1 EP95402754A EP95402754A EP0717116B1 EP 0717116 B1 EP0717116 B1 EP 0717116B1 EP 95402754 A EP95402754 A EP 95402754A EP 95402754 A EP95402754 A EP 95402754A EP 0717116 B1 EP0717116 B1 EP 0717116B1
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Prior art keywords
heating
treatment
work piece
steel
blank
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German (de)
French (fr)
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EP0717116A1 (en
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Jacques Bellus
Claude Pichard
Pierre Jolly
Daniel Forest
Daniel Robat
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Ascometal SA
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Ascometal SA
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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
    • C21D1/18—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
    • 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
    • C21D1/06—Surface 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite

Definitions

  • the invention relates to thermomechanical treatments of rooms with high characteristics of microalloyed steel, such as forging, welding and treatments surface heat.
  • Microalloyed steels having the composition 0.05% ⁇ C ⁇ 0.5%; 1% ⁇ Mn ⁇ 2%; 0.05% ⁇ If ⁇ 1.5%; 0.1% ⁇ Cr ⁇ 1%; 0% ⁇ Mo ⁇ 0.5%; 0 ⁇ V ⁇ 0.30%; 0 ⁇ B ⁇ 0.010%; 0 ⁇ Ti ⁇ 0.030%, 0 ⁇ Nb ⁇ 0.1, the rest being iron, unavoidable impurities resulting from the development, are used in particular for manufacture forgings with high characteristics. These pieces should, for example, have a breaking strength between 900 and 1200 MPa and a good shock resistance.
  • This type of metallurgy is well suited to forging and other treatments which are practiced at high temperatures (above 1000 ° C for example), to which the austenitization of the part is complete.
  • this metallurgy poses problem when the part is subjected locally or entirely to temperatures of lower heating, between 500 and 900 ° C. This is particularly the case when the forging treatment aims to shape only one end of a steel bar, and where the heating action is therefore limited to this end.
  • the region of the bar which is not not directly heated but near the area to be forged is, in fact, brought to a lower temperature, but high enough to impose transformations metallurgical to this region.
  • a similar phenomenon occurs when the part undergoes welding, nitriding treatment or surface heat treatment, such as than laser quenching, or induction quenching: the subsurface layers of the piece are affected by treatment in a way that may be undesirable.
  • the problem is that the portions of these parts that have undergone such reheating between 500 and 900 ° C have a softening detrimental to the good mechanical strength of the part, especially its fatigue behavior.
  • An explanation of this phenomenon softening is that for these relatively low heating temperatures, the hardening effect of interphase precipitation is eliminated, and the hardenability is greatly reduced due to the very small grain size. The result is that the room therefore no longer has in its entire volume properties that are both high and homogeneous.
  • the object of the invention is to propose a method of manufacturing parts made of microalloyed steel with high mechanical characteristics allowing to overcome this softening problem, whatever the local heating conditions of the parts in question.
  • DE-A-1 225 217 or US-A-5 041 167 describe methods for manufacturing parts made of microalloyed steel in a bainitic structure subjected to nitriding or forging treatments.
  • the invention relates to a process for manufacturing a piece of mechanical steel, whereby a steel blank is submitted microalloy comprising, in weight percentages, 0.05% ⁇ C ⁇ 0.5%; 1% ⁇ Mn ⁇ 2%; 0.05% ⁇ Si ⁇ 1.5%; 0.1% ⁇ Cr ⁇ 1%; 0% ⁇ Mo ⁇ 0.5%; 0 ⁇ V ⁇ 0.30%, 0 ⁇ B ⁇ 0.010%; 0 ⁇ Ti ⁇ 0.030%, 0 ⁇ Nb ⁇ 0.1%, to treatment thermal or thermomechanical, as defined in claim 1.
  • the invention also relates to a structural steel part. mechanical manufactured by this process.
  • the invention consists in starting from a steel blank of microalloyed mechanical construction having a bainitic structure to produce a room to which heating is to be applied which, whether undergoing or desired, will at least locally its temperature between 500 and 900 ° C. Starting from such a draft which has both the specified composition and a bainitic structure, one does not obtain not, for the portions of the blank thus heated, the undesirable softening which one observes when the blank has a ferrito-pearlitic structure.
  • the conditions for cooling the bar in the hot rolling led, as is known, to the establishment of a structure ferrito-pearlitic.
  • an induction heating is carried out central part 2, for example with a view to subsequent forging.
  • a homogeneous temperature of about 1200 ° C.
  • this central part 2 which is directly influenced by the heating means, there is a decrease in the temperature of room 1 as one moves away from the central part 2, up to a temperature close to the ambient temperature of 20 ° C.
  • portions 3, 3 ′ of part 1 a temperature between the temperatures conventionally known as Ac3 and Ac1 of the shade constituting bar 1.
  • these temperatures are respectively 790 and 740 ° C.
  • the portions 3, 3 'concerned each extend over a length of approximately 30 mm. This evolution of the temperature along the bar 1 is translated by the curve 4 of the figure unique.
  • the heating action which, according to the invention, we want to prevent from leading localized or generalized softening of the part structure, may be various natures and exercised for different purposes.
  • the invention can also concern surface heat treatments such as laser quenching, induction quenching, electron beam bombardment and treatments of nitriding. Heating can also be a consequence of a welding operation.
  • the cooling of the part must be done at a speed not too weak, i.e. at least 500 ° C / hour, so as to preserve the structure bainitique previously obtained, in order to avoid possible softening.
  • the invention makes it possible to widen the range of shades which can be used for the manufacture of high-quality mechanical steel parts and homogeneous. It avoids having to resort to subsequent heat treatments to restore the mechanical properties which would have been affected by a softening of the structure as described, which saves time for manufacturing the part and for its manufacturing cost.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Articles (AREA)
  • Forging (AREA)
  • Gripping Jigs, Holding Jigs, And Positioning Jigs (AREA)
  • Gears, Cams (AREA)
  • Golf Clubs (AREA)
  • Coating With Molten Metal (AREA)

Abstract

Micro-alloyed steel consists of (in wt%): 0.05-0.5 C; 1-2 Mn; 0.05-1.55 Si; 0.1-1 Cr; 0-0.5 Mo; 0-0.3 V; 0-0.01 B; 0-0.03 Ti; and 0-0.1Nb. It has a bainitic structure. A blank of the steel is subjected to surface heat treatment by laser beam, induction heating or electron bombardment, followed by quenching. The heat affected zones are heated to 500-900 degrees C and cooled at a rate of above 500 degrees C/hr..

Description

L'invention concerne les traitements thermomécaniques des pièces à hautes caractéristiques en acier microallié, tels que le forgeage, le soudage et les traitements thermiques superficiels.The invention relates to thermomechanical treatments of rooms with high characteristics of microalloyed steel, such as forging, welding and treatments surface heat.

Les aciers microalliés ayant la composition (les pourcentages sont des pourcentages pondéraux) 0,05 %≤ C ≤ 0,5 %; 1 % ≤ Mn ≤ 2 %; 0,05 %≤ Si ≤ 1,5 %; 0,1 % ≤ Cr ≤ 1 %; 0%≤Mo≤0,5%; 0 ≤ V ≤ 0,30 %; 0 ≤ B ≤ 0,010 %; 0 ≤ Ti ≤ 0,030 %, 0 ≤ Nb ≤ 0,1, le reste étant du fer, des impuretés inévitables résultant de l'élaboration, sont utilisés notamment pour fabriquer des pièces forgées à hautes caractéristiques. Ces pièces doivent, par exemple, présenter une résistance à la rupture comprise entre 900 et 1200 MPa et une bonne tenue aux chocs. Ces aciers sont classiquement utilisés avec une structure ferrito-perlitique qui résulte naturellement d'un durcissement secondaire au cours du refroidissement qu'ils ont subi lors de leur dernière mise en forme. Ils peuvent aussi être utilisés, avec la même structure ferrito-perlitique, pour d'autres applications nécessitant divers traitements thermiques ou thermomécaniques.Microalloyed steels having the composition (the percentages are weight percentages) 0.05% ≤ C ≤ 0.5%; 1% ≤ Mn ≤ 2%; 0.05% ≤ If ≤ 1.5%; 0.1% ≤ Cr ≤ 1%; 0% ≤Mo≤0.5%; 0 ≤ V ≤ 0.30%; 0 ≤ B ≤ 0.010%; 0 ≤ Ti ≤ 0.030%, 0 ≤ Nb ≤ 0.1, the rest being iron, unavoidable impurities resulting from the development, are used in particular for manufacture forgings with high characteristics. These pieces should, for example, have a breaking strength between 900 and 1200 MPa and a good shock resistance. These steels are conventionally used with a ferrito-pearlitic structure which naturally results from secondary hardening during cooling they underwent during their last shaping. They can also be used, with the same ferrito-pearlitic structure, for other applications requiring various thermal or thermomechanical treatments.

Ce type de métallurgie est bien adapté aux forgeages et autres traitements qui sont pratiqués à des températures élevées (supérieures à 1000 °C par exemple), pour lesquelles l'austénitisation de la pièce est complète. En revanche, cette métallurgie pose problème lorsque la pièce est soumise localement ou en totalité à des températures de chauffage inférieures, entre 500 et 900 °C. C'est le cas, en particulier, lorsque le traitement de forge vise à ne mettre en forme qu'une extrémité d'une barre d'acier, et où l'action de chauffage est donc limitée à cette extrémité. La région de la barre qui n'est pas chauffée directement mais avoisine la zone à forger est, de fait, portée à une température inférieure, mais suffisamment élevée pour imposer des transformations métallurgiques à cette région. Un phénomène similaire se produit lorsque la pièce subit un soudage, un traitement de nitruration ou un traitement thermique superficiel, tel qu'une trempe laser, ou une trempe par induction: les couches subsurfaciques de la pièce sont affectées par le traitement d'une manière qui peut être indésirable. Le problème est que les portions de ces pièces qui ont subi un tel réchauffage entre 500 et 900 °C présentent un adoucissement préjudiciable à la bonne tenue mécanique de la pièce, notamment à son comportement en fatigue. Une explication de ce phénomène d'adoucissement est que, pour ces températures de chauffage relativement faibles, l'effet durcissant des précipitations interphases est annihilé, et que la trempabilité est fortement diminuée du fait de la très faible taille des grains. Le résultat est que la pièce n'a donc plus dans la totalité de son volume des propriétés à la fois élevées et homogènes.This type of metallurgy is well suited to forging and other treatments which are practiced at high temperatures (above 1000 ° C for example), to which the austenitization of the part is complete. On the other hand, this metallurgy poses problem when the part is subjected locally or entirely to temperatures of lower heating, between 500 and 900 ° C. This is particularly the case when the forging treatment aims to shape only one end of a steel bar, and where the heating action is therefore limited to this end. The region of the bar which is not not directly heated but near the area to be forged is, in fact, brought to a lower temperature, but high enough to impose transformations metallurgical to this region. A similar phenomenon occurs when the part undergoes welding, nitriding treatment or surface heat treatment, such as than laser quenching, or induction quenching: the subsurface layers of the piece are affected by treatment in a way that may be undesirable. The problem is that the portions of these parts that have undergone such reheating between 500 and 900 ° C have a softening detrimental to the good mechanical strength of the part, especially its fatigue behavior. An explanation of this phenomenon softening is that for these relatively low heating temperatures, the hardening effect of interphase precipitation is eliminated, and the hardenability is greatly reduced due to the very small grain size. The result is that the room therefore no longer has in its entire volume properties that are both high and homogeneous.

On a jusqu'ici remédié à ce problème en recourant à des nuances au chrome-molybdène trempées-revenues, ou à des aciers peu alliés ayant subi un traitement de normalisation. Mais ces solutions limitent la gamme de nuances utilisables. De plus, lorsqu'un traitement thermique de restauration des propriétés mécaniques est nécessaire, il induit généralement des déformations inacceptables de la pièce qui nécessiteront un redressage de celle-ci. Cela augmente sensiblement les durées et les coûts de fabrication des pièces.This problem has so far been remedied by using chromium-molybdenum grades quenched or quenched, or to low alloy steels which have undergone a treatment of standardization. However, these solutions limit the range of shades that can be used. Moreover, when a heat treatment to restore mechanical properties is necessary, it generally induces unacceptable deformations of the part which will require a straightening of it. This significantly increases the durations and parts manufacturing costs.

Le but de l'invention est de proposer une méthode de fabrication de pièces en acier microallié à hautes caractéristiques mécaniques permettant de s'affranchir de ce problème d'adoucissement, quelles que soient les conditions locales de chauffage des pièces en question.The object of the invention is to propose a method of manufacturing parts made of microalloyed steel with high mechanical characteristics allowing to overcome this softening problem, whatever the local heating conditions of the parts in question.

DE-A-1 225 217 ou US-A-5 041 167 décrivent des procédés de fabrication des pièces en acier microallié en structure bainitique soumis aux traitements de nitruration ou forgeage.DE-A-1 225 217 or US-A-5 041 167 describe methods for manufacturing parts made of microalloyed steel in a bainitic structure subjected to nitriding or forging treatments.

A cet effet, l'invention a pour objet un procédé de fabrication d'une pièce en acier de construction mécanique, selon lequel on soumet une ébauche en acier microallié comportant, en pourcentages pondéraux, 0,05 %≤ C ≤ 0,5 %; 1 %≤Mn≤2%; 0,05 %≤Si≤1,5%; 0,1 %≤Cr≤1 %; 0%≤Mo≤0,5%; 0 ≤V ≤0,30 %, 0 ≤B≤0,010 %; 0 ≤Ti ≤0,030 %, 0≤Nb ≤0,1 %, à un traitement thermique ou thermomécanique, comme il est défini dans la revendication 1.To this end, the invention relates to a process for manufacturing a piece of mechanical steel, whereby a steel blank is submitted microalloy comprising, in weight percentages, 0.05% ≤ C ≤ 0.5%; 1% ≤Mn≤2%; 0.05% ≤Si≤1.5%; 0.1% ≤Cr≤1%; 0% ≤Mo≤0.5%; 0 ≤V ≤0.30%, 0 ≤B≤0.010%; 0 ≤Ti ≤0.030%, 0≤Nb ≤0.1%, to treatment thermal or thermomechanical, as defined in claim 1.

L'invention a également pour objet une pièce en acier de construction mécanique fabriquée par ce procédé.The invention also relates to a structural steel part. mechanical manufactured by this process.

Comme on l'aura compris, l'invention consiste à partir d'une ébauche en acier de construction mécanique microallié ayant une structure bainitique pour réaliser une pièce à laquelle on doit appliquer un chauffage qui, de manière subie ou voulue, portera au moins localement sa température entre 500 et 900 °C. En partant d'une telle ébauche qui possède à la fois la composition spécifiée et une structure bainitique, on n'obtient pas, pour les portions de l'ébauche ainsi chauffées, l'adoucissement indésirable que l'on observe lorsque l'ébauche présente une structure ferrito-perlitique.As will be understood, the invention consists in starting from a steel blank of microalloyed mechanical construction having a bainitic structure to produce a room to which heating is to be applied which, whether undergoing or desired, will at least locally its temperature between 500 and 900 ° C. Starting from such a draft which has both the specified composition and a bainitic structure, one does not obtain not, for the portions of the blank thus heated, the undesirable softening which one observes when the blank has a ferrito-pearlitic structure.

L'invention sera mieux comprise à la lecture de la description qui suit, donnée en référence à la figure unique qui illustre un exemple de mise en oeuvre de l'invention.The invention will be better understood on reading the description which follows, given with reference to the single figure which illustrates an example of implementation of the invention.

Sur la figure unique, on a représenté une barre 1 dont une portion 2 est chauffée. Cette barre 1 a un diamètre de 40 mm et une longueur L de 800 mm environ. Elle est en un acier de construction dont la composition, exprimée en pourcentages pondéraux, est C = 0,35 %; Mn = 1,8 %; Si = 0,25 %; V = 0,12 %: Mo = 0,050 %; B ≤ 0,0005 %; Ti = 0,012 % le reste étant du fer et des impuretés résultant du processus d'élaboration habituel de ce type de nuances d'acier. Dans un des cas envisagés sur la figure unique, les conditions du refroidissement de la barre dans la chaude de laminage ont conduit, comme il est connu, à l'établissement d'une structure ferrito-perlitique. Dans l'autre cas envisagé, on a, selon l'une des caractéristiques de l'invention et comme l'homme du métier sait le réaliser à l'aide des diagrammes Temps-Températures-Transformation, obtenu une structure bainitique.In the single figure, there is shown a bar 1 of which a portion 2 is heated. This bar 1 has a diameter of 40 mm and a length L of about 800 mm. It is made of a structural steel whose composition, expressed in percentages by weight, is C = 0.35%; Mn = 1.8%; If = 0.25%; V = 0.12%: Mo = 0.050%; B ≤ 0.0005%; Ti = 0.012% the remainder being iron and impurities resulting from the usual development process for this type of steel grade. In one of the cases envisaged in the single figure, the conditions for cooling the bar in the hot rolling led, as is known, to the establishment of a structure ferrito-pearlitic. In the other case considered, we have, according to one of the characteristics of the invention and as a person skilled in the art knows how to realize it using Time-Temperatures-Transformation diagrams, obtained a bainitic structure.

Pour le traitement de la barre 1, on réalise par induction un chauffage de sa partie centrale 2, par exemple en vue d'un forgeage ultérieur. On obtient ainsi dans l'épaisseur de la pièce 1 et sur toute la longueur de ladite partie centrale 2 une température homogène de 1200 °C environ. En dehors de cette partie centrale 2 qui subit directement l'influence des moyens de chauffage, on assiste à une décroissance de la température de la pièce 1 au fur et à mesure que l'on s'éloigne de la partie centrale 2, et ce jusqu'à une température proche de la température ambiante de 20 °C. C'est ainsi que, sur des portions 3, 3' de la pièce 1, s'établit une température comprise entre les températures dites classiquement Ac3 et Ac1 de la nuance constituant la barre 1. Dans l'exemple envisagé, ces températures sont respectivement de 790 et 740 °C, et les portions 3, 3' concernées s'étendent chacune sur une longueur d'environ 30 mm. Cette évolution de la température le long de la barre 1 est traduite par la courbe 4 de la figure unique.For the treatment of bar 1, an induction heating is carried out central part 2, for example with a view to subsequent forging. We thus obtain in the thickness of the part 1 and over the entire length of said central part 2 a homogeneous temperature of about 1200 ° C. Apart from this central part 2 which is directly influenced by the heating means, there is a decrease in the temperature of room 1 as one moves away from the central part 2, up to a temperature close to the ambient temperature of 20 ° C. It is as well as, on portions 3, 3 ′ of part 1, a temperature between the temperatures conventionally known as Ac3 and Ac1 of the shade constituting bar 1. In the example envisaged, these temperatures are respectively 790 and 740 ° C., and the portions 3, 3 'concerned each extend over a length of approximately 30 mm. This evolution of the temperature along the bar 1 is translated by the curve 4 of the figure unique.

Dans le cas de référence où la barre 1 a initialement une structure ferrito-perlitique, on observe dans des portions de la barre 1, qui couvrent notamment celles dont la température est comprise entre Ac3 et Ac1, un adoucissement de la structure. Il se traduit par une chute sensible de la dureté Vickers qui passe de 300 à 250 Hv environ. Cette chute de dureté, dont les raisons ont été données plus haut, est illustrée par la courbe 5 de la figure unique. Mais dans le cas de l'invention où on a conféré à la barre 1 une structure initiale bainitique dans la chaude de laminage,. on n'observe pas cet adoucissement localisé, comme le montre la courbe 6. Ainsi, les propriétés mécaniques qui auraient été affectées par un tel adoucissement demeurent homogènes sur toute la longueur de la pièce forgée. C'est notamment le cas de sa tenue en fatigue et de sa résistance aux chocs. In the reference case where the bar 1 initially has a ferrito-pearlitic structure, we observe in portions of bar 1, which cover in particular those whose temperature is between Ac3 and Ac1, a softening of the structure. he results in a significant drop in Vickers hardness from 300 to 250 Hv about. This drop in hardness, the reasons for which have been given above, is illustrated. by curve 5 of the single figure. But in the case of the invention where we have conferred on the bar 1 an initial bainitic structure in the hot rolling ,. we don't observe this localized softening, as shown in curve 6. Thus, the properties mechanical effects which would have been affected by such softening remain homogeneous along the entire length of the forged part. This is particularly the case with its fatigue resistance and its impact resistance.

L'action de chauffage dont, selon l'invention, on veut éviter qu'elle ne conduise à un adoucissement localisé ou généralisé de la structure de la pièce, peut être de diverses natures et exercée dans différents buts. Outre le forgeage, l'invention peut aussi concerner les traitements thermiques superficiels tels que la trempe laser, la trempe à induction, le bombardement par faisceau d'électrons et les traitements de nitruration. Le chauffage peut aussi être une conséquence d'une opération de soudage. Une fois le traitement effectué, le refroidissement de la pièce doit se faire à une vitesse pas trop faible, à savoir au moins 500 °C/heure, de manière conserver la structure bainitique précédemment obtenue, afin d'éviter un éventuel adoucissement.The heating action which, according to the invention, we want to prevent from leading localized or generalized softening of the part structure, may be various natures and exercised for different purposes. In addition to forging, the invention can also concern surface heat treatments such as laser quenching, induction quenching, electron beam bombardment and treatments of nitriding. Heating can also be a consequence of a welding operation. Once the treatment has been carried out, the cooling of the part must be done at a speed not too weak, i.e. at least 500 ° C / hour, so as to preserve the structure bainitique previously obtained, in order to avoid possible softening.

La liste des éléments entrant dans la composition de l'acier telle qu'elle a été spécifiée plus haut n'est, bien entendu, pas limitative.The list of elements entering into the composition of the steel as it was specified above is, of course, not limiting.

L'invention permet d'élargir la gamme de nuances utilisables pour la fabrication de pièces en acier de construction mécanique à caractéristiques élevées et homogènes. Elle évite d'avoir recours à des traitements thermiques ultérieurs pour restaurer les propriétés mécaniques qui auraient été affectées par un adoucissement de la structure tel qu'on l'a décrit, d'où un gain de temps pour la fabrication de la pièce et pour son coût de fabrication.The invention makes it possible to widen the range of shades which can be used for the manufacture of high-quality mechanical steel parts and homogeneous. It avoids having to resort to subsequent heat treatments to restore the mechanical properties which would have been affected by a softening of the structure as described, which saves time for manufacturing the part and for its manufacturing cost.

Claims (9)

  1. Method for producing a workpiece made of machine construction steel, according to which a blank made of microalloyed steel comprising, in percentages by weight,
    0.05% ≤ C ≤ 0.5%;   1% ≤ Mn ≤ 2%;   0.05% ≤ Si ≤ 1.5%;
    0.1% ≤ Cr ≤ 1%;   0% ≤ Mo ≤ 0.5%;   0 ≤ V ≤ 0.30%;
    0 ≤ B ≤ 0.010%;   0 ≤ Ti ≤ 0.030%;   0 ≤ Nb ≤ 0.1%;
    the remainder being of iron and unavoidable impurities, said blank having a bainitic structure, is subjected to a thermal or thermomechanical treatment, said treatment comprising a heating stage which imposes on a portion only of said blank a temperature between 500 and 900 °C, characterised in that said heating is followed by a cooling stage of said portion at a rate greater than 500 °C/hour, in such a manner as to preserve the bainitic structure and to avoid a possible softening in at least one part of the workpiece apart from the part of the workpiece which directly undergoes the influence of the heating means.
  2. Method according to claim 1, characterised in that said heating is carried out with a view to a forging.
  3. Method according to claim 1, characterised in that said heating is carried out during a nitriding treatment.
  4. Method according to claim 1, characterised in that said heating is a superficial thermal treatment.
  5. Method according to claim 4, characterised in that said thermal treatment is a laser hardening.
  6. Method according to claim 4, characterised in that said thermal treatment is an induction hardening.
  7. Method according to claim 4, characterised in that said thermal treatment is a bombardment by a beam of electrons.
  8. Method according to claim 1, characterised in that said heating results from a welding operation.
  9. Workpiece made of machine construction steel, characterised in that it is produced by the method according to one of the claims 1 to 8.
EP95402754A 1994-12-13 1995-12-07 Process for producing a work piece of machine construction steel and work piece produced by this process Expired - Lifetime EP0717116B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9414941 1994-12-13
FR9414941A FR2727981B1 (en) 1994-12-13 1994-12-13 METHOD FOR MANUFACTURING A PART OF MECHANICAL CONSTRUCTION STEEL AND A PART THUS MANUFACTURED

Publications (2)

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EP0717116A1 EP0717116A1 (en) 1996-06-19
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US (1) US5667605A (en)
EP (1) EP0717116B1 (en)
AT (1) ATE202151T1 (en)
BR (1) BR9505758A (en)
DE (1) DE69521276T2 (en)
DK (1) DK0717116T3 (en)
ES (1) ES2159614T3 (en)
FR (1) FR2727981B1 (en)
GR (1) GR3036386T3 (en)
MX (1) MX9505194A (en)
PT (1) PT717116E (en)

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CN103526117A (en) * 2012-07-03 2014-01-22 广西柳工机械股份有限公司 Non-quenched and tempered steel, engineering mechanical semiaxle manufactured by using same and manufacturing method of semiaxle

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US5906691A (en) * 1996-07-02 1999-05-25 The Timken Company Induction hardened microalloy steel having enhanced fatigue strength properties
US6823812B2 (en) * 2001-05-25 2004-11-30 Von Wolske James P. Trim tabs and surface drive propeller bite control
FR2848225B1 (en) * 2002-12-05 2006-06-09 Ascometal Sa STEEL FOR MECHANICAL CONSTRUCTION, METHOD FOR HOT SHAPING A PIECE OF THIS STEEL AND PIECE THUS OBTAINED
FR2848226B1 (en) * 2002-12-05 2006-06-09 Ascometal Sa STEEL FOR MECHANICAL CONSTRUCTION, METHOD FOR HOT SHAPING A PIECE OF THIS STEEL, AND PIECE THUS OBTAINED
US20050039830A1 (en) * 2003-08-19 2005-02-24 Mark Christofis Induction heat treatment method and coil and article treated thereby
MX2007002009A (en) * 2004-08-18 2007-04-23 Bishop Innovation Ltd Method of manufacturing a hardened forged steel component.
US20110277886A1 (en) 2010-02-20 2011-11-17 Nucor Corporation Nitriding of niobium steel and product made thereby
CN101899551B (en) * 2009-05-26 2011-11-16 宁波市鄞州商业精密铸造有限公司 Heat treatment technology of wear-resistant alloy cast steel
CN101899552B (en) * 2009-05-26 2012-01-18 宁波市鄞州商业精密铸造有限公司 Heat treatment equipment of antifriction alloy cast steel
CN101899553B (en) * 2009-05-26 2012-01-18 宁波市鄞州商业精密铸造有限公司 Heat treatment technology and device of wear-resistant alloy cast steel
CN102051455B (en) * 2009-11-04 2012-07-04 宁波市鄞州商业精密铸造有限公司 Heat-treatment process for low-temperature abrasion-resistant alloy cast steel
ES2391322B1 (en) * 2011-04-29 2013-10-14 Consejo Superior De Investigaciones Científicas (Csic) BAINÍTICO STEEL 38MnV6, PROCEDURE OF OBTAINING AND USE.
CN102433507B (en) * 2012-01-16 2013-12-25 江苏省沙钢钢铁研究院有限公司 Low yield ratio and high strength weldable steel plate and preparation technology thereof
FR2992328A1 (en) * 2012-06-26 2013-12-27 Peugeot Citroen Automobiles Sa Heat treating a steel part of a car, comprises performing isothermal treatment for bainite formation, where the isothermal treatment is carried out by a controlled induction heating, direct induction, and low frequency induction
CN103522016B (en) * 2013-10-17 2016-03-23 江苏星源电站冶金设备制造有限公司 The processing method of semi-autogenous mill middle cylinder body liner plate
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CN103526117A (en) * 2012-07-03 2014-01-22 广西柳工机械股份有限公司 Non-quenched and tempered steel, engineering mechanical semiaxle manufactured by using same and manufacturing method of semiaxle

Also Published As

Publication number Publication date
DE69521276D1 (en) 2001-07-19
BR9505758A (en) 1998-04-22
PT717116E (en) 2001-11-30
EP0717116A1 (en) 1996-06-19
DK0717116T3 (en) 2001-10-01
ES2159614T3 (en) 2001-10-16
FR2727981A1 (en) 1996-06-14
ATE202151T1 (en) 2001-06-15
DE69521276T2 (en) 2002-01-10
US5667605A (en) 1997-09-16
MX9505194A (en) 1997-05-31
GR3036386T3 (en) 2001-11-30
FR2727981B1 (en) 1997-01-10

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