EP0738783B1 - Stainless austenitic steel suitable for the manufacture of wires - Google Patents

Stainless austenitic steel suitable for the manufacture of wires Download PDF

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Publication number
EP0738783B1
EP0738783B1 EP96400736A EP96400736A EP0738783B1 EP 0738783 B1 EP0738783 B1 EP 0738783B1 EP 96400736 A EP96400736 A EP 96400736A EP 96400736 A EP96400736 A EP 96400736A EP 0738783 B1 EP0738783 B1 EP 0738783B1
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inclusions
steel
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composition
mgo
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EP0738783A1 (en
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Frédéric Descaves
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Ugitech SA
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Ugine Savoie Imphy 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel

Definitions

  • the present invention relates to an austenitic stainless steel for the elaboration in particular of thread, having an inclusive cleanliness suitable for use in the field of wire drawing of diameter less than 0.3 mm and in the area of production of submitted parts to fatigue.
  • stainless steels we mean iron alloys containing minus 10.5% chromium. Other elements enter into the composition steels to modify their structure and properties.
  • Austenitic stainless steels have a composition determined. The austenitic structure is ensured after transformation, by a heat treatment of the hyper quenching type.
  • gamma-genes favor the appearance of austenite phase of metallographic structure of cubic type with faces centered.
  • these elements are carbon, nitrogen, manganese, copper, nickel.
  • stainless steels may, in the liquid state, contain in solution, due to the production processes, oxygen and sulfur contents of less than 100.10 -4 %. During the cooling of the steel in liquid or solid state, the solubility of the oxygen and sulfur elements decreases and the energy of formation of the oxides or sulphides is reached.
  • the object of the invention is to produce a stainless steel austenitic with selected inclusiveness, steel capable of be used in particular in the field of wire drawing with a diameter less than 0.3 mm and in the area of production of parts subject to tired.
  • Figures 1 and 2 respectively present an image of a example of slightly distorted, thick inclusion and an image of an example of inclusions contained in a steel according to the invention.
  • the steel according to the invention contains in its weight composition less than 200. 10 -3 % of carbon, less than 200.10 -3 % of nitrogen, from 0.3% to 4% of manganese, from 14% to 23% chromium, 5% to 17% nickel, 0.3% to 2% silicon, less than 10.10 -3 % sulfur, 50.10 -4 % to 120.10 -4 % total oxygen, 0, 1.10 -4 % to 20.10 -4 % aluminum, less than 2.10 -4 % magnesium, from 0.1.10 -4 % to 5.10 -4 % calcium, less than 5.10 -3 % titanium.
  • Carbon, nitrogen, chromium, nickel, manganese, silicon are the usual elements for obtaining a stainless steel austenitic.
  • the manganese, chromium, sulfur contents in proportion are chosen to generate deformable sulfides of good composition determined.
  • composition intervals of the silicon and manganese elements ensure according to the invention, the presence of inclusions of the silicate type, rich in SiO 2 and containing a non-negligible amount of MnO.
  • Mobybdenum can be added to the composition of steel austenitic stainless steel to improve corrosion resistance.
  • Copper can also be added to the composition of steel according to the invention because it improves the cold deformation properties and this fact stabilizes the austenite.
  • the copper content is limited to 3% to avoid difficulties of hot transformation because the copper lowers appreciably the upper limit of steel reheating temperature before rolling.
  • the intervals in total oxygen, aluminum and calcium make it possible, according to the invention, to obtain inclusions of the manganese silicate type containing a non-zero fraction of Al 2 O 3 and CaO.
  • the aluminum and calcium contents are greater than 0.1 ⁇ 10 -4 % so that the inclusions sought contain more than 1% of CaO and more than 3% of Al 2 O 3 .
  • the values of the total oxygen contents are according to the invention between 50 ppm and 120 ppm.
  • oxygen fixes the elements magnesium, calcium, aluminum and does not form the inclusion of oxides rich in SiO 2 and MnO.
  • the calcium content is less than 5.10 -4 % so that the desired inclusions do not contain more than 30% CaO.
  • the aluminum content is less than 20.10 -4 % to avoid that the desired inclusions contain more than 25% of Al 2 O 3 , which also promotes crystallization.
  • the invention relates to an austenitic stainless steel containing inclusions of chosen composition obtained voluntarily, the composition being related to the overall composition of the steel, so that the physical properties of these inclusions favor their deformation during hot processing of steel.
  • austenitic stainless steel contains inclusions of determined composition which have their softening point close to the rolling temperature of the steel and such that the appearance of crystals harder than steel at the temperature of rolling as in particular the defined compounds, SiO 2 , in the form of tridymite, christobalite, quartz; 3CaO-SiO 2 ; CaO; MgO; Cr 2 O 3 ; anorthite, mullite, gehlenite, corundum, spinel of the Al 2 O 3 -MgO or Al 2 O 3 -Cr 2 O 3 -MnO-MgO type; CaO-Al 2 O 3 ; CaO-6Al 2 O 3 ; CaO-2Al 2 O 3 , TiO 2 is inhibited.
  • the steel mainly contains inclusions of oxide of composition such as these form a vitreous mixture or amorphous during all the successive operations of shaping steel.
  • the viscosity of the inclusions chosen is sufficient for the growth of crystallized oxide particles in inclusions resulting from the invention is totally inhibited from the fact that, in a inclusion of oxide, short-range diffusion is weak and Convective displacements are very limited.
  • These inclusions remained glassy in the temperature range of hot steel treatments also have a lower hardness and modulus of elasticity than crystallized inclusions of corresponding composition. So the inclusions can be further deformed, crushed and elongated, when for example, wire drawing and the concentration of stresses neighborhood of the inclusions is greatly reduced, which attenuates important the risk of appearance, for example, of fatigue cracks or wire drawing breaks.
  • austenitic stainless steel contains inclusions of oxides of defined composition such as their viscosity in the temperature range of hot rolling steel is not too high. Therefore, the flow constraint of inclusion is clearly lower than that of steel under hot rolling conditions whose temperatures are generally between 800 ° C and 1350 ° C.
  • oxide inclusions deform at the same time as steel during hot rolling and therefore after rolling, these inclusions are perfectly elongated, and very thin, which allows to avoid any problem of breakage during, for example, an operation of wire drawing.
  • SiO 2 content is less than 40%, the viscosity of the oxide inclusions is too low and the growth mechanism of oxide crystals is not inhibited. If SiO 2 is greater than 60%, very hard harmful particles of silica are formed in the form of trydimite or christobalite or quartz.
  • the MnO content between 5% and 50% makes it possible to greatly lower the softening point of the mixture of oxides containing in particular SiO 2 , CaO, Al 2 O 3 , and promotes the creation of inclusions which remain in a state vitreous under the rolling conditions of the steel according to the invention.
  • crystals of MnO-Al 2 O 3 or of mullite are formed.
  • the CaO content is greater than 30%, crystals of CaO-SiO 2 or (Ca, Mn) O-SiO 2 are formed .
  • crystals of MgO are formed; 2MgO-SiO 2 ; MgO-SiO 2 ; Al 2 O 3 -MgO, which are extremely hard phases.
  • Al 2 O 3 is less than 3%, wollastonite crystals are formed and when Al 2 O 3 is greater than 25%, crystals of mullite, anorthite, corundum and spinels, especially of Al 2 type, appear O 3 -MgO or Al 2 O 3 -Cr 2 O 3 -MgO-MnO or alternatively of aluminates of the CaO-6Al 2 O 3 or CaO-2Al 2 O 3 or CaO-Al 2 O 3 type , or of gehlenite .
  • Oxides and sulfides inclusions are generally considered harmful with regard to the properties of use in the in the field of fine wire drawing and in the field of fatigue resistance, in particular, in bending and / or in torsion. It is usual to characterize the concentration of oxide and sulphide inclusions by observation a long polished cut of rolling on a wire rod rolled to hot diameter between 5 and 10 mm. We call cleanliness inclusionary the result of this characterization carried out according to different standards based on end use.
  • a form factor which is the ratio of length to thickness.
  • the shape is generally very high, i.e. up to 10 or 20 and therefore, the thickness of the inclusion is extremely small.
  • an inclusion which does not deform or undergoes a weak deformation is characterized by a low form factor, say of the order of 1, therefore, the thickness of the inclusion remains high and of the same order of magnitude as the size of the original product inclusion raw casting. Consequently, in the following description, we retain as a simple and effective characterization criterion with regard to properties of use of the laminated wire, the thickness of each inclusion observed on the wire the mine.
  • Figures 1 and 2 show respectively on a polished section of laminated wire with a diameter of 5.5 mm, an example of very thick inclusion and little distorted and an example of fine and very well deformed inclusions contained in the steel according to the invention.
  • Figure 1 shows a mixed inclusion called two-phase, consisting of a central crystalline non-deformable part of the Al 2 O 3 -MgO type, denoted AlMg in the figure, and two end portions, denoted in the figure SiAlMg, consisting of a slightly deformable phase rich in SiO 2 , Al 2 O 3 and MgO.
  • This inclusion has a thickness of 11 micrometers, a length of 40 micrometers and is particularly harmful for wire drawing applications or for producing parts subjected to fatigue.
  • Figure 2 shows four examples of inclusions less than 2 micrometers of thickness, of variable length, such as those contained in the steel according to the invention.
  • the inclusion characteristics are defined by counting the number of inclusions with a thickness equal to or greater than a given dimension for a sample surface of 1000 mm 2 .
  • Tables 1 and 2 below show steels showing the influence of the composition of the steel and of the composition of the oxide inclusions on the number of inclusions of given thickness.
  • STEEL AT B VS D E F G %VS 0.093 0.065 0.067 0.093 0.060 0.055 0.083 %NOT 0.030 0.045 0.045 0.026 0.041 0.056 0.040 %Yes 1.81 0.49 0.54 1.75 0.48 0.56 0.75 % Mn 1.32 0.26 0.30 1.25 0.58 0.53 1.08 % Cr 17.65 18.46 18.32 17.60 18.27 18.24 17.95 %Or 7.85 8.49 8.47 7.75 8.61 8.57 8.30 % Mo 0.71 0.10 0.17 0.73 0.24 0.28 0.33 % Cu 0.22 0.32 0.33 0.15 0.48 0.51 0.25 Ot ppm 25 40 48 28 129 138 65 Al ppm 43 10 8 26 25 13 18 Ca ppm 9 13 2 1 54 11 2 Mg ppm 1 1 1 3 2 1 1 Ti ppm
  • Table 1 presents compositions of steels considered of insufficient quality and Table 2 presents steel compositions according to the invention having remarkable inclusiveness.
  • the inclusion characteristics are materialized by the presence on a sampled surface of 1000 mm 2 of less than 5 inclusions of oxides with a thickness of more than 10 ⁇ m.
  • the sulfide inclusions are, in number, less than 10 having a thickness of more than 5 ⁇ m, for an area of 1000 mm 2 .
  • Steel A has a low total oxygen content and a high aluminum content.
  • the inclusions seen in the steel are poor in SiO 2 and MnO, very rich in Al 2 O 3 and MgO, of crystalline spin type Al 2 O 3 -MgO.
  • Steel B has a low total oxygen content and a high calcium content. Despite an acceptable aluminum content, the inclusions observed contain too much Al 2 O 3 and this is reflected, on the hot-rolled wire, by the presence of thick inclusions.
  • Steel D like steel C, has a low total oxygen content but a high content of aluminum and magnesium. On the steel, inclusions rich in SiO 2 and MgO are observed, inclusions which are not sufficiently deformable.
  • Steel E has a high sulfur content which causes the appearance of numerous, slightly deformed sulfides. In addition, it has a high content of oxygen, aluminum, calcium. This leads to the appearance of inclusions containing little SiO 2 , a lot of CaO, and very little MnO. These inclusions are not very deformable and numerous. Steel F also has high sulfur and oxygen contents, but the aluminum and calcium contents are quite low. In this steel, the inclusions are rich in SiO 2 and Cr 2 O 3 , which leads to the appearance of very hard Cr 2 O 3 crystals and viscous SiO 2 phases.
  • Steel G has a high sulfur content, which results in the appearance of numerous sulfides.
  • the other contents of the composition are within acceptable ranges and inclusions of oxides obtained are of a vitreous nature, on a wire and deformable as in the steel according to the invention.

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Abstract

Austenitic stainless steel consists of wt.%:- max. 0.2 C; max 0.2 N; 0.3-4 Mn; 14-23 Cr; 5-17 Ni; 0.3-2 Si; max 0.1 S; 0.005-0.012 O; 0.00001-0.002 Al. max 0.0002 Mg; 0.00001-0.0005 Ca; max 0.005 Ti. Inside the steel area oxide inclusions as follows:- 40-60 SiO2; 5-50 MnO; 1-30 CaO; 0.1-20 MgO; 3-25 Al2O3; 0.1-10 Cr2O3.

Description

La présente invention concerne un acier inoxydable austénitique pour l'élaboration notamment de fil, ayant une propreté inclusionnaire adaptée pour une utilisation dans le domaine du tréfilage de fil de diamètre inférieur à 0,3 mm et dans le domaine de la réalisation de pièces soumises à la fatigue.The present invention relates to an austenitic stainless steel for the elaboration in particular of thread, having an inclusive cleanliness suitable for use in the field of wire drawing of diameter less than 0.3 mm and in the area of production of submitted parts to fatigue.

On désigne par aciers inoxydables, les alliages de fer contenant au moins 10,5% de chrome. D'autres éléments entrent dans la composition des aciers afin de modifier leur structure et leurs propriétés.By stainless steels, we mean iron alloys containing minus 10.5% chromium. Other elements enter into the composition steels to modify their structure and properties.

Les aciers inoxydables austénitiques ont une composition déterminée. La structure austénitique est assurée après transformation, par un traitement thermique de type hypertrempe.Austenitic stainless steels have a composition determined. The austenitic structure is ensured after transformation, by a heat treatment of the hyper quenching type.

Du point de vue métallurgique, il est connu que certains éléments d'alliage entrant dans la composition des aciers favorisent l'apparition de la phase ferrite de structure métallographique de type cubique centré. Ces éléments sont dit alpha-gènes. Parmi ceux-ci figurent le chrome, le molybdène, le silicium.From a metallurgical point of view, it is known that certain elements alloy used in the composition of steels favor the appearance of ferrite phase of metallographic structure of centered cubic type. These elements are said to be alpha-genes. Among these are chromium, molybdenum, silicon.

D'autres éléments dits gamma-gènes favorisent l'apparition de la phase austénite de structure métallographique de type cubique à faces centrées. Parmi ces éléments figurent le carbone, l'azote, le manganèse, le cuivre, le nickel.Other elements known as gamma-genes favor the appearance of austenite phase of metallographic structure of cubic type with faces centered. Among these elements are carbon, nitrogen, manganese, copper, nickel.

Dans le domaine par exemple du tréfilage, il est connu que pour obtenir un fil de diamètre inférieur à 0,3 mm, dit fin, l'acier inoxydable utilisé ne doit pas comporter d'inclusions dont la taille génère la casse de fil lors du tréfilage.In the field for example of wire drawing, it is known that for obtain a wire of diameter less than 0.3 mm, said fine, stainless steel used must not include inclusions whose size generates the case of wire during drawing.

Dans l'élaboration des aciers inoxydables austénitiques, comme pour tous les autres aciers élaborés avec des moyens conventionnels et économiquement adaptés à la production de masse, la présence d'inclusions de type sulfures ou oxydes est systématique et irrémédiable. En effet, les aciers inoxydables peuvent, à l'état liquide, contenir en solution, du fait des procédés d'élaboration, des teneurs en oxygène et en soufre inférieures à 100.10-4%. Au cours du refroidissement de l'acier à l'état liquide ou solide, la solubilité des éléments oxygène et soufre diminue et l'énergie de formation des oxydes ou des sulfures est atteinte. On assiste alors à l'apparition d'inclusions formées d'une part, de composés de type oxydes contenant des atomes d'oxygène et des éléments d'alliage avides de réagir avec l'oxygène tels que calcium, magnésium, aluminium, silicium, manganèse, chrome, et d'autre part, de composés de type sulfures contenant des atomes de soufre et des éléments d'alliage avides de réagir avec le soufre tels que manganèse, chrome, calcium, magnésium. Il peut apparaítre également des inclusions qui sont des composés mixtes de type oxysulfure.In the production of austenitic stainless steels, as for all other steels produced with conventional means and economically suitable for mass production, the presence of inclusions of the sulphide or oxide type is systematic and irremediable. In fact, stainless steels may, in the liquid state, contain in solution, due to the production processes, oxygen and sulfur contents of less than 100.10 -4 %. During the cooling of the steel in liquid or solid state, the solubility of the oxygen and sulfur elements decreases and the energy of formation of the oxides or sulphides is reached. We then witness the appearance of inclusions formed on the one hand, of oxide type compounds containing oxygen atoms and alloying elements eager to react with oxygen such as calcium, magnesium, aluminum, silicon, manganese, chromium, and on the other hand, sulfide-like compounds containing sulfur atoms and alloying elements eager to react with sulfur such as manganese, chromium, calcium, magnesium. There may also appear inclusions which are mixed compounds of the oxysulfide type.

Il est connu le brevet EP-A-0 567 365 concernant un acier austénitique contenant notamment du cuivre et du calcium associé à de l'oxygène dans un rapport Ca/O élevé pour former des oxydes malléables. Ces oxydes ont des compositions qui se situent sur le diagramme Al2 O3 - Si O2 - Ca O, dans la zone du point triple anorthite, gehlénite et pseudo-wollastonite. Dans ce document qui concerne un acier à usinabilité améliorée, les oxydes sont introduits en nombre, volontairement.It is known from patent EP-A-0 567 365 concerning an austenitic steel containing in particular copper and calcium associated with oxygen in a high Ca / O ratio to form malleable oxides. These oxides have compositions which are located on the Al 2 O 3 - Si O 2 - Ca O diagram, in the region of the triple point anorthite, gehlenite and pseudo-wollastonite. In this document, which relates to a steel with improved machinability, the oxides are introduced in number, voluntarily.

Il est possible de réduire la quantité d'oxygène contenu dans l'acier inoxydable en utilisant des réducteurs puissants tels que magnésium, aluminium, calcium, titane ou une combinaison de plusieurs d'entre eux mais ces réducteurs conduisent tous à la création d'inclusions riches en MgO, Al2O3, CaO ou TiO2 qui sont sous la forme de réfractaires cristallisés, durs et indéformables dans les conditions de laminage de l'acier inoxydable. La présence de ces inclusions génère des incidents par exemple de tréfilage et des casses de fatigue sur les produits élaborés avec l'acier inoxydable.It is possible to reduce the quantity of oxygen contained in stainless steel by using powerful reducers such as magnesium, aluminum, calcium, titanium or a combination of several of them, but these reducers all lead to the creation of inclusions. rich in MgO, Al 2 O 3 , CaO or TiO 2 which are in the form of crystallized refractories, hard and undeformable under the rolling conditions of stainless steel. The presence of these inclusions generates incidents for example of wire drawing and fatigue breaks on products made with stainless steel.

L'invention a pour but la réalisation d'un acier inoxydable austénitique ayant une propreté inclusionnaire sélectionnée, acier pouvant être utilisé notamment dans le domaine du tréfilage en diamètre inférieur à 0,3 mm et dans le domaine de la réalisation de pièces soumises à la fatigue.The object of the invention is to produce a stainless steel austenitic with selected inclusiveness, steel capable of be used in particular in the field of wire drawing with a diameter less than 0.3 mm and in the area of production of parts subject to tired.

L'invention a pour objet un acier inoxydable austénitique qui se caractérise par la composition pondérale suivante:

  • carbone ≤ 200. 10-3%
  • azote ≤ 200. 10 -3%
  • 0,3% ≤ manganèse ≤ 4%,
  • 14% ≤ chrome ≤ 23%
  • 5% ≤ nickel ≤ 17%,
  • 0,3% ≤ silicium ≤ 2%,
  • soufre ≤ 10.10-3%,
  • 50.10-4% ≤ oxygène total ≤ 120.10-4%,
  • 0,1.10-4% ≤ aluminium ≤ 20.10-4%
  • magnésium ≤ 2.10-4%
  • 0,1.10-4 % ≤ calcium ≤ 5.10-4%
  • titane ≤ 5.10-3%
  • éventuellement molybdène < 3%, cuivre < 3%
  • des impuretés inhérentes à la fabrication, reste fer
et dans lequel des inclusions d'oxydes ont, sous forme de mélange vitreux, les proportions pondérales suivantes:
  • 40% ≤ SiO2 ≤ 60%
  • 5% ≤ MnO ≤ 50%
  • 1% ≤ CaO ≤30%
  • 0,1% ≤ MgO ≤ 20%
  • 3% ≤ Al2O3 ≤ 25%
  • 0,1% ≤ Cr2O3 ≤10%
The subject of the invention is an austenitic stainless steel which is characterized by the following weight composition:
  • carbon ≤ 200. 10 -3 %
  • nitrogen ≤ 200. 10 -3 %
  • 0.3% ≤ manganese ≤ 4%,
  • 14% ≤ chromium ≤ 23%
  • 5% ≤ nickel ≤ 17%,
  • 0.3% ≤ silicon ≤ 2%,
  • sulfur ≤ 10.10-3%,
  • 50.10 -4 % ≤ total oxygen ≤ 120.10 -4 %,
  • 0.1.10 -4 % ≤ aluminum ≤ 20.10 -4 %
  • magnesium ≤ 2.10 -4 %
  • 0.1.10 -4 % ≤ calcium ≤ 5.10 -4 %
  • titanium ≤ 5.10 -3 %
  • possibly molybdenum <3%, copper <3%
  • impurities inherent in manufacturing, iron remains
and in which oxide inclusions have the following weight proportions in the form of a glassy mixture:
  • 40% ≤ SiO 2 ≤ 60%
  • 5% ≤ MnO ≤ 50%
  • 1% ≤ CaO ≤30%
  • 0.1% ≤ MgO ≤ 20%
  • 3% ≤ Al 2 O 3 ≤ 25%
  • 0.1% ≤ Cr 2 O 3 ≤10%

Les autres caractéristiques de l'invention sont:

  • La composition de l'acier comprend moins de 5.10-3 % de soufre.
  • La composition de l'acier comprend en outre moins de 3% de molybdène.
  • La composition de l'acier comprend en outre moins de 3% de cuivre.
  • L'acier contient en nombre, après laminage à chaud en fil de diamètre supérieur à 5 mm, moins de 5 inclusions d'oxyde de plus de 10 µm d'épaisseur pour une surface de 1000 mm2
  • L'acier contient en nombre, après laminage à chaud en fil de diamètre supérieur à 5 mm, moins de 10 inclusions de sulfure de plus de 5 µm d'épaisseur pour une surface de 1000 mm2
The other characteristics of the invention are:
  • The composition of the steel includes less than 5.10-3% sulfur.
  • The composition of the steel further comprises less than 3% molybdenum.
  • The composition of the steel further comprises less than 3% copper.
  • The steel contains in number, after hot rolling in wire of diameter greater than 5 mm, less than 5 oxide inclusions of more than 10 µm thick for a surface of 1000 mm 2
  • The steel contains in number, after hot rolling in wire of diameter greater than 5 mm, less than 10 sulphide inclusions of more than 5 µm thickness for a surface of 1000 mm 2

La description qui suit et les figures annexées, le tout donné à titre d'exemple non limitatif fera bien comprendre l'invention.The following description and the attached figures, all given as non-limiting example will make the invention well understood.

Les figures 1 et 2 présentent respectivement une image d'un exemple d'inclusion peu déformée, épaisse et une image d'un exemple d'inclusions contenues dans un acier selon l'invention.Figures 1 and 2 respectively present an image of a example of slightly distorted, thick inclusion and an image of an example of inclusions contained in a steel according to the invention.

L'acier selon l'invention contient dans sa composition pondérale moins de 200. 10-3% de carbone, moins de 200.10 -3% d'azote, de 0,3% à 4% de manganèse, de 14% à 23% de chrome, de 5% à 17% de nickel, de 0,3% à 2% de silicium, moins de 10.10-3% de soufre, de 50.10-4% à 120.10-4% d'oxygène total, de 0,1.10-4% à 20.10-4% d'aluminium, moins de 2.10-4% de magnésium, de 0,1.10-4 % à 5.10-4% de calcium, moins de 5.10-3% de titane .The steel according to the invention contains in its weight composition less than 200. 10 -3 % of carbon, less than 200.10 -3 % of nitrogen, from 0.3% to 4% of manganese, from 14% to 23% chromium, 5% to 17% nickel, 0.3% to 2% silicon, less than 10.10 -3 % sulfur, 50.10 -4 % to 120.10 -4 % total oxygen, 0, 1.10 -4 % to 20.10 -4 % aluminum, less than 2.10 -4 % magnesium, from 0.1.10 -4 % to 5.10 -4 % calcium, less than 5.10 -3 % titanium.

Le carbone, l'azote, le chrome, le nickel, le manganèse, le silicium sont les éléments habituels permettant l'obtention d'un acier inoxydable austénitique. Carbon, nitrogen, chromium, nickel, manganese, silicon are the usual elements for obtaining a stainless steel austenitic.

Les teneurs en manganèse, chrome, soufre, en proportion sont choisies pour générer des sulfures déformables de composition bien déterminée.The manganese, chromium, sulfur contents in proportion are chosen to generate deformable sulfides of good composition determined.

Les intervalles de composition des éléments en silicium et manganèse, en proportion, assurent selon l'invention, la présence d'inclusions de type silicate, riches en SiO2 et contenant une quantité non négligeable de MnO.The composition intervals of the silicon and manganese elements, in proportion, ensure according to the invention, the presence of inclusions of the silicate type, rich in SiO 2 and containing a non-negligible amount of MnO.

Le mobybdène peut être ajouté à la composition de l'acier inoxydable austénitique pour améliorer la tenue en corrosion.Mobybdenum can be added to the composition of steel austenitic stainless steel to improve corrosion resistance.

Le cuivre peut être également ajouté à la composition de l'acier selon l'invention car il améliore les propriétés de déformation à froid et de ce fait, stabilise l'austénite. Cependant le teneur en cuivre est limitée à 3% pour éviter des difficultés de transformation à chaud car le cuivre abaisse sensiblement la limite supérieure de température de réchauffage de l'acier avant laminage.Copper can also be added to the composition of steel according to the invention because it improves the cold deformation properties and this fact stabilizes the austenite. However the copper content is limited to 3% to avoid difficulties of hot transformation because the copper lowers appreciably the upper limit of steel reheating temperature before rolling.

Les intervalles en oxygène total, aluminium et calcium permettent, selon l'invention, d'obtenir des inclusions de type silicate de manganèse contenant une fraction non nulle de Al2O3 et de CaO. Notamment, les teneurs en aluminium et en calcium sont supérieures à 0,1.10-4% pour que les inclusions recherchées contiennent plus de 1 % de CaO et plus de 3% de Al2O3.The intervals in total oxygen, aluminum and calcium make it possible, according to the invention, to obtain inclusions of the manganese silicate type containing a non-zero fraction of Al 2 O 3 and CaO. In particular, the aluminum and calcium contents are greater than 0.1 × 10 -4 % so that the inclusions sought contain more than 1% of CaO and more than 3% of Al 2 O 3 .

Les valeurs des teneurs en oxygène total sont selon l'invention comprises entre 50 ppm et 120 ppm.The values of the total oxygen contents are according to the invention between 50 ppm and 120 ppm.

Pour une teneur en oxygène total inférieure à 50 ppm, l'oxygène fixe les éléments magnésium, calcium, aluminium et ne forme pas d'inclusion d'oxydes riches en SiO2 et MnO.For a total oxygen content of less than 50 ppm, oxygen fixes the elements magnesium, calcium, aluminum and does not form the inclusion of oxides rich in SiO 2 and MnO.

Pour une teneur en oxygène total supérieure à 120 ppm, il y aura dans la composition des oxydes plus de 10% de Cr2O3, ce qui favorise la cristallisation, ce que l'on cherche à éviter.For a total oxygen content greater than 120 ppm, there will be in the composition of the oxides more than 10% of Cr 2 O 3 , which promotes crystallization, which one seeks to avoid.

La teneur en calcium est inférieure à 5. 10-4% de façon que les inclusions recherchées ne contiennent pas plus de 30% de CaO.The calcium content is less than 5.10 -4 % so that the desired inclusions do not contain more than 30% CaO.

La teneur en aluminium est inférieure à 20.10-4% pour éviter que les inclusions recherchées contiennent plus de 25% de Al2O3, ce qui favorise également la cristallisation.The aluminum content is less than 20.10 -4 % to avoid that the desired inclusions contain more than 25% of Al 2 O 3 , which also promotes crystallization.

Il est concevable, après avoir réalisé selon un procédé conventionnel et économique, un acier contenant des inclusions de type oxyde et sulfure, de le raffiner pour faire disparaítre ces inclusions en utilisant des procédés de refusion lents et peu rentables économiquement tels que les procédés de refusion sous vide (Vacuum Argon Remelting) ou de refusion sous laitier ( Electro Slag Remelting ).It is conceivable, after having carried out according to a conventional process and economical, a steel containing oxide and sulphide inclusions, to refine it to remove these inclusions using methods slow and economically unprofitable remelters such as processes Vacuum Argon Remelting or slag remelting (Electro Slag Remelting).

Ces procédés de refusion ne permettent d'éliminer que partiellement, par décantation dans la flaque de liquide, les inclusions déjà présentes sans modifier leur nature et leur composition.These reflow processes only partially eliminate, by decantation in the puddle of liquid, the inclusions already present without modify their nature and composition.

L'invention concerne un acier inoxydable austénitique contenant des inclusions de composition choisie obtenue volontairement, la composition étant en relation avec la composition globale de l'acier, de telle sorte que les propriétés physiques de ces inclusions favorisent leur déformation lors de la transformation à chaud de l'acier.The invention relates to an austenitic stainless steel containing inclusions of chosen composition obtained voluntarily, the composition being related to the overall composition of the steel, so that the physical properties of these inclusions favor their deformation during hot processing of steel.

Selon l'invention, l'acier inoxydable austénitique contient des inclusions de composition déterminée qui ont leur point de ramollissement proche de la température de laminage de l'acier et telles que l'apparition de cristaux plus durs que l'acier à la température de laminage comme notamment les composées définis , SiO2, sous forme de tridymite, christobalite, quartz; 3CaO-SiO2; CaO; MgO; Cr2O3; anorthite, mullite, gehlenite, corindon, spinelle du type Al2O3-MgO ou Al2O3-Cr2O3-MnO-MgO; CaO-Al2O3; CaO-6Al2O3; CaO-2Al2O3,TiO2 est inhibée.According to the invention, austenitic stainless steel contains inclusions of determined composition which have their softening point close to the rolling temperature of the steel and such that the appearance of crystals harder than steel at the temperature of rolling as in particular the defined compounds, SiO 2 , in the form of tridymite, christobalite, quartz; 3CaO-SiO 2 ; CaO; MgO; Cr 2 O 3 ; anorthite, mullite, gehlenite, corundum, spinel of the Al 2 O 3 -MgO or Al 2 O 3 -Cr 2 O 3 -MnO-MgO type; CaO-Al 2 O 3 ; CaO-6Al 2 O 3 ; CaO-2Al 2 O 3 , TiO 2 is inhibited.

Selon l'invention, l'acier contient principalement des inclusions d'oxyde de composition telle que celles-ci forment un mélange vitreux ou amorphe pendant toutes les opérations successives de mise en forme de l'acier. La viscosité des inclusions choisies est suffisante pour que la croissance des particules cristallisées d'oxydes dans les inclusions résultantes de l'invention soit totalement inhibée du fait que, dans une inclusion d'oxyde, la diffusion à courte distance est faible et les déplacements convectifs sont très limités. Ces inclusions restées vitreuses dans le domaine de température des traitements à chaud de l'acier présentent également une dureté et un module d'élasticité plus faibles que des inclusions cristallisées de composition correspondante. Ainsi les inclusions peuvent être encore déformées, écrasées et allongées, lors d'opération par exemple, de tréfilage et la concentration de contraintes au voisinage des l'inclusions est fortement diminuée, ce qui atténue de façon importante le risque d'apparition, par exemple, de fissures de fatigue ou des casses au tréfilage.According to the invention, the steel mainly contains inclusions of oxide of composition such as these form a vitreous mixture or amorphous during all the successive operations of shaping steel. The viscosity of the inclusions chosen is sufficient for the growth of crystallized oxide particles in inclusions resulting from the invention is totally inhibited from the fact that, in a inclusion of oxide, short-range diffusion is weak and Convective displacements are very limited. These inclusions remained glassy in the temperature range of hot steel treatments also have a lower hardness and modulus of elasticity than crystallized inclusions of corresponding composition. So the inclusions can be further deformed, crushed and elongated, when for example, wire drawing and the concentration of stresses neighborhood of the inclusions is greatly reduced, which attenuates important the risk of appearance, for example, of fatigue cracks or wire drawing breaks.

Selon l'invention, l'acier inoxydable austénitique contient des inclusions d'oxydes de composition définie telle que leur viscosité dans le domaine des températures de laminage à chaud de l'acier ne soit pas trop élevée. De ce fait, la contrainte d'écoulement de l'inclusion est nettement plus faible que celle de l'acier dans les conditions de laminage à chaud dont les températures sont généralement comprises entre 800 °C et 1350°C. Ainsi les inclusions d'oxydes se déforment en même temps que l'acier lors du laminage à chaud et donc après laminage, ces inclusions sont parfaitement allongées, et d'épaisseur très faible ce qui permet d'éviter tout problème de casse lors, par exemple, d'une opération de tréfilage.According to the invention, austenitic stainless steel contains inclusions of oxides of defined composition such as their viscosity in the temperature range of hot rolling steel is not too high. Therefore, the flow constraint of inclusion is clearly lower than that of steel under hot rolling conditions whose temperatures are generally between 800 ° C and 1350 ° C. Thus the oxide inclusions deform at the same time as steel during hot rolling and therefore after rolling, these inclusions are perfectly elongated, and very thin, which allows to avoid any problem of breakage during, for example, an operation of wire drawing.

Les inclusions décrites ci-dessus sont selon l'invention, réalisées avec les moyens d'élaboration classiques et très productifs d'une aciérie électrique pour aciers inoxydables tels que four électrique, convertisseur AOD ou VOD, métallurgie en poche et coulée continue.The inclusions described above are according to the invention, carried out with the classic and very productive means of production of a steelworks electric for stainless steels such as electric oven, converter AOD or VOD, pocket metallurgy and continuous casting.

Avec les procédés classiques d'élaboration et de coulée, décrits précédemment, la distribution en taille des inclusions sur le produit brut de coulée est relativement indépendante de la composition de celles-ci. Donc, avant laminage à chaud, on retrouve dans les aciers les même tailles et la même distribution d'inclusions.With the classic processes of elaboration and casting, described previously, the size distribution of inclusions on the gross product of casting is relatively independent of their composition. Therefore, before hot rolling, the same sizes are found in steels and the same distribution of inclusions.

Les inclusions d'oxydes ci dessous présentant les propriétés favorables décrites sont selon l'invention composées d'un mélange vitreux de SiO2, MnO, CaO, Al2O3, MgO et Cr2O3,, et éventuellement, de trace de FeO et ou de TiO2, dans les proportions pondérales suivantes:

  • 40% ≤ SiO2 ≤ 60%
  • 5% ≤ MnO ≤ 50%
  • 1 % ≤ CaO ≤ 30%
  • 0,1% ≤ MgO ≤ 20%
  • 3% ≤ Al2O3 ≤ 25%
  • 0,1% ≤ Cr2O3 ≤ 10%
The oxide inclusions below having the favorable properties described are according to the invention composed of a vitreous mixture of SiO 2 , MnO, CaO, Al 2 O 3 , MgO and Cr 2 O 3 , and, optionally, trace of FeO and or of TiO 2 , in the following weight proportions:
  • 40% ≤ SiO 2 ≤ 60%
  • 5% ≤ MnO ≤ 50%
  • 1% ≤ CaO ≤ 30%
  • 0.1% ≤ MgO ≤ 20%
  • 3% ≤ Al 2 O 3 ≤ 25%
  • 0.1% ≤ Cr 2 O 3 ≤ 10%

Si la teneur en SiO2 est inférieure à 40%, la viscosité des inclusions d'oxydes est trop faible et le mécanisme de croissance de cristaux d'oxyde n'est pas inhibé. Si SiO2 est supérieur à 60%, il se forme des particules nocives très dures de silice sous forme de trydimite ou de christobalite ou de quartz.If the SiO 2 content is less than 40%, the viscosity of the oxide inclusions is too low and the growth mechanism of oxide crystals is not inhibited. If SiO 2 is greater than 60%, very hard harmful particles of silica are formed in the form of trydimite or christobalite or quartz.

La teneur en MnO, comprise entre 5% et 50% permet d'abaisser fortement le point de ramollissement du mélange d'oxydes contenant notamment SiO2, CaO, Al2O3, et favorise la création d'inclusions qui restent dans un état vitreux dans les conditions de laminage de l'acier selon l'invention. The MnO content, between 5% and 50% makes it possible to greatly lower the softening point of the mixture of oxides containing in particular SiO 2 , CaO, Al 2 O 3 , and promotes the creation of inclusions which remain in a state vitreous under the rolling conditions of the steel according to the invention.

Pour une teneur en CaO inférieure à 1%, il se forme des cristaux de MnO-Al2O3 ou de mullite. Lorsque la teneur en CaO est supérieure à 30%, il se forme alors, des cristaux de CaO-SiO2 ou (Ca,Mn)O-SiO2.
Pour une teneur en MgO supérieur à 20%, il se forme des cristaux de MgO; 2MgO-SiO2; MgO-SiO2; Al2O3-MgO, qui sont des phases extrêmement dures.For a CaO content of less than 1%, crystals of MnO-Al 2 O 3 or of mullite are formed. When the CaO content is greater than 30%, crystals of CaO-SiO 2 or (Ca, Mn) O-SiO 2 are formed .
For an MgO content greater than 20%, crystals of MgO are formed; 2MgO-SiO 2 ; MgO-SiO 2 ; Al 2 O 3 -MgO, which are extremely hard phases.

Si Al2O3 est inférieur à 3%, il se forme des cristaux de wollastonite et lorsque Al2O3 est supérieur à 25%, apparaissent des cristaux de mullite, d'anorthite, de corindon, de spinelles notamment de type Al2O3-MgO ou Al2O3-Cr2O3-MgO-MnO ou bien encore d'aluminates du type CaO-6Al2O3 ou CaO-2Al2O3 ou CaO-Al2O3, ou de gehlenite.If Al 2 O 3 is less than 3%, wollastonite crystals are formed and when Al 2 O 3 is greater than 25%, crystals of mullite, anorthite, corundum and spinels, especially of Al 2 type, appear O 3 -MgO or Al 2 O 3 -Cr 2 O 3 -MgO-MnO or alternatively of aluminates of the CaO-6Al 2 O 3 or CaO-2Al 2 O 3 or CaO-Al 2 O 3 type , or of gehlenite .

Avec plus de 10% de Cr2O3 apparaissant également des cristaux durs de Cr2O3 ou Al2O3-Cr2O3-MgO-MnO, CaO-Cr2O3, MgO-Cr2O3.
Selon une forme de l'invention la teneur en soufre doit être inférieure à 0,010% pour obtenir des inclusions de sulfure d'épaisseur ne dépassant pas 5 µm sur produit laminé . En effet, les inclusions de type sulfure de manganèse et de chrome sont parfaitement déformables dans les conditions suivantes:

  • 5% < Cr < 30%
  • 30% < Mn < 60 %
  • 35 % <S< 45%
    • With more than 10% of Cr 2 O 3 also appearing hard crystals of Cr 2 O 3 or Al 2 O 3 -Cr 2 O 3 -MgO-MnO, CaO-Cr 2 O 3 , MgO-Cr 2 O 3 .
    According to one form of the invention, the sulfur content must be less than 0.010% in order to obtain sulphide inclusions of thickness not exceeding 5 μm on the rolled product. In fact, inclusions of the manganese sulfide and chromium type are perfectly deformable under the following conditions:
  • 5% <Cr <30%
  • 30% <Mn <60%
  • 35% <S <45%

    • Les inclusions de type oxydes et sulfures sont généralement considérées comme néfastes vis à vis des propriétés d'emploi dans le domaine du tréfilage en fil fin et dans le domaine de la tenue en fatigue, notamment, en flexion et/ou en torsion. Il est usuel de caractériser la concentration en inclusions de type oxyde et sulfure par l'observation d'une coupe polie en sens long de laminage sur un fil machine laminé à chaud de diamètre compris entre 5 et 10 mm. On appelle propreté inclusionnaire le résultat de cette caractérisation réalisée selon différentes normes en fonction de l'utilisation finale.Oxides and sulfides inclusions are generally considered harmful with regard to the properties of use in the in the field of fine wire drawing and in the field of fatigue resistance, in particular, in bending and / or in torsion. It is usual to characterize the concentration of oxide and sulphide inclusions by observation a long polished cut of rolling on a wire rod rolled to hot diameter between 5 and 10 mm. We call cleanliness inclusionary the result of this characterization carried out according to different standards based on end use.

    Pour une inclusion observée, sur coupe polie de fil laminé, on mesure sa longueur et son épaisseur, puis on définit un facteur de forme qui est le rapport de la longueur sur l'épaisseur. Pour une inclusion qui s'est très bien déformée au cours des opérations de laminage, le facteur de forme est en général très élevé, c'est à dire pouvant atteindre 10 ou 20 et en conséquence, l'épaisseur de l'inclusion est extrêmement faible. Au contraire, une inclusion qui ne se déforme pas ou subit une faible déformation est caractérisée par un facteur de forme peu élevé, c'est à dire de l'ordre de 1, donc, l'épaisseur de l'inclusion reste élevée et du même ordre de grandeur que la taille de l'inclusion originelle sur produit brut de coulée. En conséquence, dans la suite de la description, on retient comme critère de caractérisation simple et efficace vis à vis des propriétés d'emploi du fil laminé, l'épaisseur de chaque inclusion observée sur le fil laminé.For an observed inclusion, on a polished section of laminated wire, we measure its length and thickness, then define a form factor which is the ratio of length to thickness. For an inclusion that deformed very well during rolling operations, the shape is generally very high, i.e. up to 10 or 20 and therefore, the thickness of the inclusion is extremely small. At on the contrary, an inclusion which does not deform or undergoes a weak deformation is characterized by a low form factor, say of the order of 1, therefore, the thickness of the inclusion remains high and of the same order of magnitude as the size of the original product inclusion raw casting. Consequently, in the following description, we retain as a simple and effective characterization criterion with regard to properties of use of the laminated wire, the thickness of each inclusion observed on the wire the mine.

    Les figures 1 et 2 présentent respectivement sur une coupe polie de fil laminé de diamètre 5,5 mm, un exemple d'inclusion très épaisse et peu déformée et un exemple d'inclusions fines et très bien déformées contenues dans l'acier selon l'invention.Figures 1 and 2 show respectively on a polished section of laminated wire with a diameter of 5.5 mm, an example of very thick inclusion and little distorted and an example of fine and very well deformed inclusions contained in the steel according to the invention.

    La figure 1 montre une inclusion mixte dite biphasée, constituée d'une partie centrale cristallisée indéformable de type Al2O3-MgO, notée AlMg sur la figure, et de deux parties d'extrémité, notée sur la figure SiAlMg, constituées d'une phase peu déformable riche en SiO2, Al2O3 et MgO. Cette inclusion présente une épaisseur de 11 micromètres, une longueur de 40 micromètres et est particulièrement nocive pour des applications de tréfilage ou de réalisation de pièces soumises à la fatigue.Figure 1 shows a mixed inclusion called two-phase, consisting of a central crystalline non-deformable part of the Al 2 O 3 -MgO type, denoted AlMg in the figure, and two end portions, denoted in the figure SiAlMg, consisting of a slightly deformable phase rich in SiO 2 , Al 2 O 3 and MgO. This inclusion has a thickness of 11 micrometers, a length of 40 micrometers and is particularly harmful for wire drawing applications or for producing parts subjected to fatigue.

    La figure 2 présente quatre exemples d'inclusions de moins de 2 micromètres d'épaisseur, de longueur variable, telles que celles contenues dans l'acier selon l'invention.Figure 2 shows four examples of inclusions less than 2 micrometers of thickness, of variable length, such as those contained in the steel according to the invention.

    Ces dernières inclusions ne présentent pas de nocivité vis à vis des applications de tréfilage fin en fil de diamètre inférieur à 0,3 mm ou de pièce soumises à la fatigue telles que des ressorts, renfort de pneumatique.These latter inclusions are not harmful to fine wire drawing applications with a diameter of less than 0.3 mm or part subject to fatigue such as springs, reinforcement pneumatic.

    Les caractéristiques inclusionnaires sont définies par le comptage du nombre d'inclusions d'une épaisseur égale ou supérieure à une cote donnée pour une surface d'échantillon de 1000 mm2.The inclusion characteristics are defined by counting the number of inclusions with a thickness equal to or greater than a given dimension for a sample surface of 1000 mm 2 .

    Les tableaux 1 et 2 suivants présentent des aciers montrant l'influence de la composition de l'acier et de la composition des inclusions d'oxydes sur le nombre d'inclusions d'épaisseur donnée. ACIER A B C D E F G %C 0,093 0,065 0,067 0,093 0,060 0,055 0,083 %N 0,030 0,045 0,045 0,026 0,041 0,056 0,040 %Si 1,81 0,49 0,54 1,75 0,48 0,56 0,75 %Mn 1,32 0,26 0,30 1,25 0,58 0,53 1,08 %Cr 17,65 18,46 18,32 17,60 18,27 18,24 17,95 %Ni 7,85 8,49 8,47 7,75 8,61 8,57 8,30 %Mo 0,71 0,10 0,17 0,73 0,24 0,28 0,33 %Cu 0,22 0,32 0,33 0,15 0,48 0,51 0,25 Ot ppm 25 40 48 28 129 138 65 Al ppm 43 10 8 26 25 13 18 Ca ppm 9 13 2 1 54 11 2 Mg ppm 1 1 1 3 2 1 1 Ti ppm 28 32 45 62 56 36 39 S ppm 31 25 46 40 279 286 126 nature des inclusions %SiO2 4 36 39 48 39 61 42 %CaO 3 24 16 2 36 2 13 %MnO 1 2 8 6 1 20 22 %Al2O3 69 33 25 2 20 2 15 %MgO 21 2 4 40 2 1 3 %Cr2O3 2 3 8 2 2 14 5 Cotation inclusionnaire sur fil machine laminé à chaud de diamètre 5.5mm ACIER A B C D E F G Cotation nombre de sulfures épaisseur. > 5µm par 1000mm2 0 0 0 0 71 98 17,6 cotation nombre d'oxydes épaisseur. > 10µm par 1000mm2 13,9 8 6 6,1 39 19 3,5 ACIER H I J K L M N O %C 0,069 0,088 0,079 0,079 0,075 0,078 0,081 0,099 %N 0,045 0,030 0,035 0,039 0,048 0,058 0,056 0,034 %Si 0,51 1,71 0,78 0,83 0,69 0,63 0,66 0,68 %Mn 0,32 1,29 1,05 0,96 0,74 0,70 0,72 0,85 %Cr 18,39 17,75 17,80 17,60 18,52 18,52 18,50 17,65 %Ni 8,40 7,85 8,36 8,24 8,86 8,87 8,85 7,82 %Mo 0,17 0,69 0,29 0,17 0,15 0,17 0,15 0,32 %Cu 0,34 0,21 0,28 0,21 0,34 0,36 0,35 0,25 Ot ppm 52 51 70 65 53 71 50 95 Al ppm 9 19 17 16 12 9 11 9 Ca ppm 5 1 2 2 2 2 2 2 Mg ppm 1 1 1 1 1 1 1 1 Ti ppm 35 15 22 23 30 18 25 23 S ppm 8 37 35 31 50 35 37 30 nature des inclusions %SiO2 45 54 45 46 47 49 48 50 %CaO 15 2 11 2 17 1 14 4 %MnO 10 14 25 42 8 38 11 30 %Al2O3 22 7 12 5 24 3 18 7 %MgO 1 18 2 0,1 2 1 3 1 %Cr2O3 7 4 5 5 2 8 3 8 Cotation inclusionnaire sur fil machine laminé à chaud de diamètre 5.5mm ACIER H I J K L M N O Cotation nombre de sulfures épaisseur. > 5µm par 1000mm2 0 0 0 0 0 0 0 0 cotation nombre d'oxydes épaisseur. > 10µm par 1000mm2 3,5 2,4 2,6 3,1 1,2 0 1,2 0,5 Tables 1 and 2 below show steels showing the influence of the composition of the steel and of the composition of the oxide inclusions on the number of inclusions of given thickness. STEEL AT B VS D E F G %VS 0.093 0.065 0.067 0.093 0.060 0.055 0.083 %NOT 0.030 0.045 0.045 0.026 0.041 0.056 0.040 %Yes 1.81 0.49 0.54 1.75 0.48 0.56 0.75 % Mn 1.32 0.26 0.30 1.25 0.58 0.53 1.08 % Cr 17.65 18.46 18.32 17.60 18.27 18.24 17.95 %Or 7.85 8.49 8.47 7.75 8.61 8.57 8.30 % Mo 0.71 0.10 0.17 0.73 0.24 0.28 0.33 % Cu 0.22 0.32 0.33 0.15 0.48 0.51 0.25 Ot ppm 25 40 48 28 129 138 65 Al ppm 43 10 8 26 25 13 18 Ca ppm 9 13 2 1 54 11 2 Mg ppm 1 1 1 3 2 1 1 Ti ppm 28 32 45 62 56 36 39 S ppm 31 25 46 40 279 286 126 nature of inclusions % SiO2 4 36 39 48 39 61 42 % CaO 3 24 16 2 36 2 13 % MnO 1 2 8 6 1 20 22 % Al2O3 69 33 25 2 20 2 15 % MgO 21 2 4 40 2 1 3 % Cr2O3 2 3 8 2 2 14 5 Inclusive quotation on hot rolled wire rod 5.5mm diameter STEEL AT B VS D E F G Rating number of thickness sulfides. > 5µm per 1000mm2 0 0 0 0 71 98 17.6 rating number of oxides thickness. > 10µm per 1000mm2 13.9 8 6 6.1 39 19 3.5 STEEL H I J K L M NOT O %VS 0.069 0.088 0.079 0.079 0.075 0.078 0.081 0.099 %NOT 0.045 0.030 0.035 0.039 0.048 0.058 0.056 0.034 %Yes 0.51 1.71 0.78 0.83 0.69 0.63 0.66 0.68 % Mn 0.32 1.29 1.05 0.96 0.74 0.70 0.72 0.85 % Cr 18.39 17.75 17.80 17.60 18.52 18.52 18.50 17.65 %Or 8.40 7.85 8.36 8.24 8.86 8.87 8.85 7.82 % Mo 0.17 0.69 0.29 0.17 0.15 0.17 0.15 0.32 % Cu 0.34 0.21 0.28 0.21 0.34 0.36 0.35 0.25 Ot ppm 52 51 70 65 53 71 50 95 Al ppm 9 19 17 16 12 9 11 9 Ca ppm 5 1 2 2 2 2 2 2 Mg ppm 1 1 1 1 1 1 1 1 Ti ppm 35 15 22 23 30 18 25 23 S ppm 8 37 35 31 50 35 37 30 nature of inclusions % SiO2 45 54 45 46 47 49 48 50 % CaO 15 2 11 2 17 1 14 4 % MnO 10 14 25 42 8 38 11 30 % Al2O3 22 7 12 5 24 3 18 7 % MgO 1 18 2 0.1 2 1 3 1 % Cr2O3 7 4 5 5 2 8 3 8 Inclusive quotation on hot rolled wire rod 5.5mm diameter STEEL H I J K L M NOT O Rating number of thickness sulfides. > 5µm per 1000mm2 0 0 0 0 0 0 0 0 rating number of oxides thickness. > 10µm per 1000mm2 3.5 2.4 2.6 3.1 1.2 0 1.2 0.5

    Le tableau 1 présente des compositions d'aciers considérées de qualité insuffisante et le tableau 2 présente des compositions d'acier selon l'invention ayant une propreté inclusionnaire remarquable.Table 1 presents compositions of steels considered of insufficient quality and Table 2 presents steel compositions according to the invention having remarkable inclusiveness.

    Les caractéristiques inclusionnaires sont matérialisées par le fait de la présence sur une surface échantillonnée de 1000 mm2 de moins de 5 inclusions d'oxydes d'épaisseur de plus de 10 µm. Les inclusions de sulfure sont, en nombre, moins de 10 ayant une épaisseur de plus de 5 µm, pour une surface de 1000 mm2.The inclusion characteristics are materialized by the presence on a sampled surface of 1000 mm 2 of less than 5 inclusions of oxides with a thickness of more than 10 μm. The sulfide inclusions are, in number, less than 10 having a thickness of more than 5 μm, for an area of 1000 mm 2 .

    L'acier A a une faible teneur en oxygène total et une forte teneur en aluminium. De ce fait, les inclusions vues dans l'acier sont pauvres en SiO2 et en MnO, très riches en Al2O3 et MgO, de type spinelle Al2O3-MgO cristallisées. Cela se traduit par la présence, dans le fil laminé à chaud, de nombreuses inclusions d'épaisseur supérieures à 10 µm, c'est à dire environ 14 inclusions pour 1000 mm2.Steel A has a low total oxygen content and a high aluminum content. As a result, the inclusions seen in the steel are poor in SiO 2 and MnO, very rich in Al 2 O 3 and MgO, of crystalline spin type Al 2 O 3 -MgO. This results in the presence, in the hot rolled wire, of numerous inclusions of thickness greater than 10 μm, that is to say approximately 14 inclusions per 1000 mm 2 .

    L'acier B a une faible teneur en oxygène total et une forte teneur en calcium. Malgré une teneur en aluminium acceptable, les inclusions observées contiennent trop d'Al2O3 et cela se traduit, sur le fil laminé à chaud, par la présence d'inclusions épaisses.Steel B has a low total oxygen content and a high calcium content. Despite an acceptable aluminum content, the inclusions observed contain too much Al 2 O 3 and this is reflected, on the hot-rolled wire, by the presence of thick inclusions.

    L'acier C a une teneur en oxygène assez faible alors que les autres éléments tels que l'aluminium, le calcium, le magnésium sont dans des teneurs acceptables. Cela conduit à observer des inclusions qui contiennent insuffisamment de SiO2. On remarque par ailleurs, que la quantité d'Al2O3 est de l'ordre de 25%. Les inclusions observées ne sont pas parfaitement déformables dans les conditions de laminage et on observe sur le fil laminé un nombre encore conséquent d'inclusions peu déformées.Steel C has a fairly low oxygen content while the other elements such as aluminum, calcium, magnesium are in acceptable contents. This leads to the observation of inclusions which contain insufficient SiO 2 . Note also that the amount of Al 2 O 3 is of the order of 25%. The inclusions observed are not perfectly deformable under the rolling conditions and a still substantial number of slightly deformed inclusions are observed on the rolled wire.

    L'acier D a, comme l'acier C, une faible teneur en oxygène total mais une forte teneur en aluminium et en magnésium. On observe sur l'acier des inclusions riches en SiO2 et MgO, inclusions qui ne sont pas suffisamment déformables.Steel D, like steel C, has a low total oxygen content but a high content of aluminum and magnesium. On the steel, inclusions rich in SiO 2 and MgO are observed, inclusions which are not sufficiently deformable.

    L'acier E présente une forte teneur en soufre qui provoque l'apparition de très nombreux sulfures peu déformés. De plus, il a une forte teneur en oxygène, en aluminium, en calcium. Cela entraíne l'apparition d'inclusions contenant peu de SiO2, beaucoup de CaO, et très peu de MnO. Ces inclusions sont peu déformables et nombreuses.
    L'acier F présente également de fortes teneurs en soufre et en oxygène mais les teneurs en aluminium et en calcium sont assez basses. Dans cet acier, les inclusions sont riches en SiO2 et en Cr2O3, ce qui conduit à l'apparition de cristaux de Cr2O3 très durs et de phases SiO2 visqueuses.    Steel E has a high sulfur content which causes the appearance of numerous, slightly deformed sulfides. In addition, it has a high content of oxygen, aluminum, calcium. This leads to the appearance of inclusions containing little SiO 2 , a lot of CaO, and very little MnO. These inclusions are not very deformable and numerous.
    Steel F also has high sulfur and oxygen contents, but the aluminum and calcium contents are quite low. In this steel, the inclusions are rich in SiO 2 and Cr 2 O 3 , which leads to the appearance of very hard Cr 2 O 3 crystals and viscous SiO 2 phases.

    L'acier G a une teneur en soufre élevée, ce qui se traduit par l'apparition de sulfures nombreux. Par ailleurs, les autres teneurs de la composition sont dans des intervalles acceptables et les inclusions d'oxydes obtenues sont d'une nature vitreuse, sur fil et déformables comme dans l'acier selon l'invention.Steel G has a high sulfur content, which results in the appearance of numerous sulfides. In addition, the other contents of the composition are within acceptable ranges and inclusions of oxides obtained are of a vitreous nature, on a wire and deformable as in the steel according to the invention.

    Dans les exemples du tableau 2 selon l'invention, lorsque la teneur en aluminium est inférieure à 15.10-4% et lorsque la teneur en calcium est inférieure à 4.10-4%, il est constaté une diminution très nette du nombre des inclusions grossières d'oxydes d'épaisseur supérieure à 10µm.In the examples of Table 2 according to the invention, when the aluminum content is less than 15.10 -4 % and when the calcium content is less than 4.10 -4 %, a very marked reduction in the number of coarse inclusions is observed. '' oxides thicker than 10µm.

    Claims (6)

    1. Austenitic stainless steel for the production of wire that can be used in the field of wire drawing down to a diameter of less than 0.3 mm and in the field of the production of components subjected to fatigue, characterized by the following composition by weight:
      carbon ≤ 200×10-3%
      nitrogen ≤ 200×10-3%
      0.3% ≤ manganese ≤ 4%
      14% ≤ chromium ≤ 23%
      5% ≤ nickel ≤ 17%
      0.3% ≤ silicon ≤ 2%
      sulphur ≤ 10×10-3%
      50×10-4% ≤ total oxygen ≤ 120×10-4%
      0.1×10-4% ≤ aluminium ≤ 20×10-4%
      magnesium ≤ 2×10-4%
      0.1×10-4% ≤ calcium ≤ 5×10-4%
      titanium ≤ 5×10-3%
      optionally, molybdenum ≤ 3% and copper ≤ 3%
      impurities inherent in the manufacture, and
         the balance iron
      and in which steel oxide inclusions have, in the form of a vitreous mixture, the following proportions by weight:
      40% ≤ SiO2 ≤ 60%
      5% ≤ MnO ≤ 50%
      1% ≤ CaO ≤ 30%
      0.1% ≤ MgO ≤ 20%
      3% ≤ Al2O3 ≤ 25%
      0.1% ≤ Cr2O3 ≤ 10%.
    2. Steel according to Claim 1, characterized in that its composition includes less than 5×10-3% sulphur.
    3. Steel according to Claim 1, characterized in that its composition furthermore includes less than 3% molybdenum.
    4. Steel according to Claim 1, characterized in that its composition furthermore includes less than 3% copper.
    5. Steel according to Claim 1, characterized in that it contains, in terms of number, after hot rolling to a diameter of greater than 5 mm, less than 5 oxide inclusions of more than 10 µm in thickness over an area of 1000 mm2.
    6. Steel according to Claim 1, characterized in that it contains, in terms of number, after hot rolling to a diameter of greater than 5 mm, less than 10 sulphide inclusions of more than 5 µm in thickness over an area of 1000 mm2.
    EP96400736A 1995-04-21 1996-04-05 Stainless austenitic steel suitable for the manufacture of wires Revoked EP0738783B1 (en)

    Applications Claiming Priority (2)

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    FR9504782 1995-04-21
    FR9504782A FR2733252B1 (en) 1995-04-21 1995-04-21 AUSTENITIC STAINLESS STEEL FOR THE PREPARATION OF YARN IN PARTICULAR

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    EP0738783A1 EP0738783A1 (en) 1996-10-23
    EP0738783B1 true EP0738783B1 (en) 2000-03-08

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    EP (1) EP0738783B1 (en)
    JP (1) JPH08337852A (en)
    KR (1) KR960037853A (en)
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    Publication number Priority date Publication date Assignee Title
    FR2759709B1 (en) 1997-02-18 1999-03-19 Ugine Savoie Sa STAINLESS STEEL FOR THE PREPARATION OF TREWNED WIRE, ESPECIALLY OF PNEUMATIC REINFORCEMENT WIRE AND PROCESS FOR MAKING THE SAID WIRE
    FR2776306B1 (en) * 1998-03-18 2000-05-19 Ugine Savoie Sa AUSTENITIC STAINLESS STEEL FOR THE PREPARATION OF YARN IN PARTICULAR
    JP3504521B2 (en) * 1998-12-15 2004-03-08 株式会社神戸製鋼所 Spring steel with excellent fatigue properties
    FR2818290A1 (en) * 2000-12-15 2002-06-21 Ugine Savoie Imphy Stainless steel for shaping by severe working and notably by cold striking or drawing into small diameter wires, with a controlled composition for selection of the type and dimensions of its inclusions
    FR2818289B1 (en) * 2000-12-15 2003-08-08 Usinor STAINLESS STEEL FOR SEVERE SHAPING AND IN PARTICULAR DEEP DRAWING OF A SHEET
    JP2002206148A (en) * 2001-01-09 2002-07-26 Nisshin Steel Co Ltd Austenitic stainless steel sheet having low work cracking sensitivity and production method therefor
    JP2003041349A (en) * 2001-08-01 2003-02-13 Nisshin Steel Co Ltd Electrically resistive material
    JP4150054B2 (en) * 2006-06-21 2008-09-17 株式会社神戸製鋼所 FORGING STEEL, PROCESS FOR PRODUCING THE SAME AND FORGED PRODUCT
    US7985304B2 (en) 2007-04-19 2011-07-26 Ati Properties, Inc. Nickel-base alloys and articles made therefrom
    JP4673343B2 (en) * 2007-06-06 2011-04-20 日本冶金工業株式会社 Stainless steel sheet excellent in corrosion resistance, weldability and surface properties and method for producing the same
    KR20090066000A (en) * 2007-12-18 2009-06-23 주식회사 포스코 Austenitic stainless steel for the high vacuum or high purity gas tube application
    JP5853281B2 (en) * 2011-03-25 2016-02-09 日新製鋼株式会社 Austenitic stainless steel sheet with excellent surface gloss
    JP6491983B2 (en) * 2015-08-28 2019-03-27 新日鐵住金ステンレス株式会社 High strength and high ductility stainless steel wire for extra fine wire, High strength and high ductility stainless steel wire for extra fine wire
    JP7042057B2 (en) * 2017-10-25 2022-03-25 日鉄ステンレス株式会社 Stainless steel materials and welded structural members with excellent slag spot generation suppression ability and their manufacturing methods
    CN107760973B (en) * 2017-10-26 2019-04-02 江西省中蔚建设集团有限公司 A kind of processing method of austenitic stainless steel for building
    CN110791710A (en) * 2019-11-12 2020-02-14 江阴康瑞成型技术科技有限公司 Environment-friendly energy-saving austenite cold-heading stainless steel wire and production process thereof
    US20230099909A1 (en) * 2020-01-15 2023-03-30 Nippon Steel Stainless Steel Corporation Ferritic stainless steel

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    US3933480A (en) * 1972-09-18 1976-01-20 Republic Steel Corporation Method of making stainless steel having improved machinability
    JPS55122858A (en) * 1979-03-13 1980-09-20 Daido Steel Co Ltd High carbon high manganese steel with high machinability
    FR2456785A1 (en) * 1979-05-17 1980-12-12 Daido Steel Co Ltd DECOLLETING STEEL CONTAINING DETERMINED INCLUSIONS AND A PROCESS FOR THE PREPARATION THEREOF
    FR2690169B1 (en) * 1992-04-17 1994-09-23 Ugine Savoie Sa Austenitic stainless steel with high machinability and improved cold deformation.
    US5314549A (en) * 1993-03-08 1994-05-24 Nkk Corporation High strength and high toughness stainless steel sheet and method for producing thereof

    Also Published As

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    TR199600325A2 (en) 1996-11-21
    ATE190361T1 (en) 2000-03-15
    ES2145395T3 (en) 2000-07-01
    DK0738783T3 (en) 2000-07-31
    UA44716C2 (en) 2002-03-15
    GR3033479T3 (en) 2000-09-29
    CZ291422B6 (en) 2003-03-12
    RO116098B1 (en) 2000-10-30
    TW399100B (en) 2000-07-21
    CA2174567C (en) 2001-10-23
    EG21379A (en) 2001-09-30
    PL185044B1 (en) 2003-02-28
    DE69606902T2 (en) 2000-11-09
    CZ113996A3 (en) 1996-11-13
    EP0738783A1 (en) 1996-10-23
    FR2733252A1 (en) 1996-10-25
    CA2174567A1 (en) 1996-10-22
    RU2106425C1 (en) 1998-03-10
    NO961531D0 (en) 1996-04-18
    SI9600129A (en) 1996-10-31
    NO961531L (en) 1996-10-22
    IL117977A0 (en) 1996-08-04
    PT738783E (en) 2000-07-31
    FR2733252B1 (en) 1997-05-23
    NO312469B1 (en) 2002-05-13
    JPH08337852A (en) 1996-12-24
    IL117977A (en) 2000-11-21
    US5651937A (en) 1997-07-29
    DE69606902D1 (en) 2000-04-13
    KR960037853A (en) 1996-11-19

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