EP0931844B1 - Cobalt-free maraging steel - Google Patents

Cobalt-free maraging steel Download PDF

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Publication number
EP0931844B1
EP0931844B1 EP98403247A EP98403247A EP0931844B1 EP 0931844 B1 EP0931844 B1 EP 0931844B1 EP 98403247 A EP98403247 A EP 98403247A EP 98403247 A EP98403247 A EP 98403247A EP 0931844 B1 EP0931844 B1 EP 0931844B1
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Prior art keywords
cobalt
maraging steel
steel according
free
mpa
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EP98403247A
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German (de)
French (fr)
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EP0931844A1 (en
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James Davidson
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Aperam Stainless Precision SAS
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Imphy Ugine Precision SA
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    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling

Definitions

  • the present invention relates to a cobalt-free maraging steel having a high yield strength and good ductility in the aged state after work hardening cold.
  • Maraging steels are self-hardening steels likely to acquire by air cooling a soft martensitic structure which can be considerably hardened by an aging heat treatment causing formation of intermetallic precipitates.
  • these steels contain 10% to 30% of nickel intended to allow a martensitic structure to be obtained by air cooling, low carbon to get martensite soft and additives intended to allow hardening by formation of intermetallic precipitates.
  • Additions intended to obtain precipitation hardening include titanium, aluminum and molybdenum whose effects are significantly enhanced by the presence of cobalt. We can also add niobium to fix the carbon and thus soften the non-aged martensitic structure.
  • the object of the present invention is to provide a maraging steel having the properties listed above, especially when used as thin cold rolled strips.
  • the subject of the invention is a cobalt-free maraging steel whose chemical composition comprises, by weight: 18% ⁇ Ni ⁇ 23% 4.5% ⁇ Mo ⁇ 8% 1% ⁇ Ti ⁇ 2% 0% ⁇ Al ⁇ 0.3% C ⁇ 0.01% the remainder being iron and impurities; the chemical composition satisfying, in addition, the following conditions: 23 ⁇ Ni + Mo ⁇ 27% and: Ni + 3 x Mo + 20 x Ti +10 x Al ⁇ 60%
  • This steel has a yield strength Re greater than or equal to 1900 MPa and a elongation greater than or equal to 6.5% in the aged state after cold work hardening, the work hardening rate being between 0% and 50%, and preferably between 10% and 45%.
  • Maraging steel contains from 18% to 23%, and preferably more than 19% nickel, on the other hand from 4.5% to 8%, and preferably more than 5%, from molybdenum, the sum of the nickel and molybdenum contents being between 23% and 27%, and preferably between 24% and 26%, so as to have a martensitic transformation start temperature which is neither too high nor too high low, and to obtain a sufficient hardening effect of the molybdenum.
  • the steel also contains from 1% to 2%, and preferably less than 1.6% of titanium, as well as 0% to 0.3% aluminum, in order to obtain a hardening effect by precipitation while limiting the risk of defect during hot rolling.
  • the carbon content is limited to a maximum of 0.01% to obtain a Martensite sufficiently soft before aging.
  • the rest of the composition is consisting of iron and impurities resulting from the production.
  • This steel is produced, then poured and hot rolled in accordance with the state of art. In addition, it can be cold rolled, for example to obtain a strip of less than 1.5 mm thick.
  • cold rolling can be performed in several stages separated by annealing at a temperature greater than or equal to 800 ° C.
  • the last cold rolling step corresponds to a work hardening rate of between 0% and 50%, and preferably between 10% and 45%, and better still, less than 35%. In this case, after aging between 450 ° C and 510 ° C, the elastic limit Re obtained is higher at 1900 MPa and the elongation at break A% is greater than 6.5%.
  • castings 1 to 7 were produced in accordance with the invention, and by way of comparison, casting A in accordance with the prior art.
  • these flows we have fabricated cold rolled strips with variable work hardening rates during the last cold rolling step, which is preceded by annealing parade at 1020 ° C. These strips were then hardened by aging at 480 ° C. for 4 hours, then the mechanical characteristics were measured by a test of traction.

Description

La présente invention concerne un acier maraging sans cobalt ayant une limite d'élasticité élevée et une bonne ductilité à l'état vieilli après écrouissage à froid.The present invention relates to a cobalt-free maraging steel having a high yield strength and good ductility in the aged state after work hardening cold.

Les aciers maraging sont des aciers autotrempants susceptibles d'acquérir par refroidissement à l'air une structure martensitique douce qui peut être considérablement durcie par un traitement thermique de vieillissement engendrant la formation de précipités intermétalliques. Pour l'essentiel, ces aciers contiennent de 10 % à 30 % de nickel destiné à permettre d'obtenir une structure martensitique par refroidissement à l'air, une faible teneur en carbone pour obtenir une martensite douce et des éléments d'addition destinés à permettre un durcissement par formation de précipités intermétalliques. Les éléments d'addition destinés à obtenir le durcissement par précipitation sont notamment le titane, l'aluminium et le molybdène dont les effets sont sensiblement renforcés par la présence de cobalt. On peut également ajouter du niobium afin de fixer le carbone et ainsi adoucir la structure martensitique non vieillie.Maraging steels are self-hardening steels likely to acquire by air cooling a soft martensitic structure which can be considerably hardened by an aging heat treatment causing formation of intermetallic precipitates. Essentially, these steels contain 10% to 30% of nickel intended to allow a martensitic structure to be obtained by air cooling, low carbon to get martensite soft and additives intended to allow hardening by formation of intermetallic precipitates. Additions intended to obtain precipitation hardening include titanium, aluminum and molybdenum whose effects are significantly enhanced by the presence of cobalt. We can also add niobium to fix the carbon and thus soften the non-aged martensitic structure.

La principale difficulté à laquelle se heurtent les concepteurs de ces aciers est l'obtention simultanée d'une très haute limite d'élasticité et d'une bonne ductilité. Dans un premier temps, la bonne ductilité a été obtenue par une addition simultanée de plusieurs % de cobalt et de molybdène. Cependant, le cobalt est un élément d'alliage coûteux et dont les conditions d'approvisionnement ne sont pas fiables. Afin de se dégager de la contrainte imposée par le cobalt, on a mis au point des aciers maraging sans cobalt (c'est à dire sans les additions massives citées ci-dessus) contenant de 17 % à 26 % de nickel, de 0,2 % à 4 % de molybdène, de 1 % à 2,5 % de titane, moins de 1 % d'aluminium, éventuellement du niobium, le reste étant du fer et des impuretés résultant de l'élaboration. Ces aciers sont décrits notamment dans le brevet GB 1 355 475 et dans le brevet US 4,443,254. Ils permettent d'obtenir sur du métal homogénéisé à haute température puis refroidi et vieilli une résistance à la traction élevée (de l'ordre de 1800 MPa) et une ductilité satisfaisante.The main difficulty faced by the designers of these steels is the simultaneous obtaining of a very high yield strength and good ductility. First, good ductility was obtained by simultaneous addition of several% of cobalt and molybdenum. However, cobalt is an element of expensive alloy and whose supply conditions are not reliable. To to break free from the stress imposed by cobalt, we have developed steels cobalt-free maraging (i.e. without the massive additions listed above) containing 17% to 26% nickel, 0.2% to 4% molybdenum, 1% to 2.5% titanium, less than 1% aluminum, possibly niobium, the rest being iron and impurities resulting from processing. These steels are described in particular in GB patent 1,355,475 and in US patent 4,443,254. They provide on metal homogenized at high temperature then cooled and aged resistance high tensile (of the order of 1800 MPa) and satisfactory ductility.

Cependant, pour certaines applications, il est souhaitable de pouvoir obtenir une limite d'élasticité supérieure à 1900 MPa avec un allongement à rupture supérieur à 6,5 % sur du métal vieilli directement après laminage à froid. C'est le cas, notamment, lorsque l'acier maraging est utilisé sous forme de bandes minces destinées à fabriquer des pièces d'horlogerie ou des courroies.However, for certain applications, it is desirable to be able to obtain a yield strength greater than 1900 MPa with an elongation at break greater than 6.5% on aged metal directly after cold rolling. It's the case, in particular, when maraging steel is used in the form of thin strips intended for manufacturing timepieces or belts.

Le but de la présente invention est de proposer un acier maraging ayant les propriétés indiquées ci-dessus, en particulier lorsqu'il est utilisé sous forme de bandes minces laminées à froid.The object of the present invention is to provide a maraging steel having the properties listed above, especially when used as thin cold rolled strips.

A cet effet, l'invention a pour objet un acier maraging sans cobalt dont la composition chimique comprend, en poids : 18 % ≤ Ni ≤ 23 % 4,5 % ≤ Mo ≤ 8 % 1 % ≤ Ti ≤ 2 % 0 % ≤ Al ≤ 0,3 % C ≤ 0,01 % le reste étant du fer et des impuretés ; la composition chimique satisfaisant, en outre, les conditions suivantes : 23 ≤ Ni + Mo ≤ 27 % et: Ni + 3 x Mo + 20 x Ti +10 x Al ≥ 60% To this end, the subject of the invention is a cobalt-free maraging steel whose chemical composition comprises, by weight: 18% ≤ Ni ≤ 23% 4.5% ≤ Mo ≤ 8% 1% ≤ Ti ≤ 2% 0% ≤ Al ≤ 0.3% C ≤ 0.01% the remainder being iron and impurities; the chemical composition satisfying, in addition, the following conditions: 23 ≤ Ni + Mo ≤ 27% and: Ni + 3 x Mo + 20 x Ti +10 x Al ≥ 60%

Cet acier a une limite d'élasticité Re supérieure ou égale à 1900 MPa et un allongement supérieur ou égal à 6,5 % à l'état vieilli après écrouissage à froid, le taux d'écrouissage étant compris entre 0% et 50 %, et de préférence entre 10 % et 45 %.This steel has a yield strength Re greater than or equal to 1900 MPa and a elongation greater than or equal to 6.5% in the aged state after cold work hardening, the work hardening rate being between 0% and 50%, and preferably between 10% and 45%.

L'invention va maintenant être décrite plus en détails et illustrée par des exemples.The invention will now be described in more detail and illustrated by examples.

L'acier maraging contient d'une part de 18 % à 23 %, et de préférence plus de 19 % de nickel, d'autre part de 4,5 % à 8 % , et de préférence plus de 5 %, de molybdène, la somme des teneurs en nickel et en molybdène étant comprise entre 23 % et 27 %, et de préférence entre 24 % et 26 %, de façon a avoir une température de début de transformation martensitique qui ne soit ni trop haute ni trop basse, et pour obtenir un effet durcissant suffisant du molybdène.Maraging steel contains from 18% to 23%, and preferably more than 19% nickel, on the other hand from 4.5% to 8%, and preferably more than 5%, from molybdenum, the sum of the nickel and molybdenum contents being between 23% and 27%, and preferably between 24% and 26%, so as to have a martensitic transformation start temperature which is neither too high nor too high low, and to obtain a sufficient hardening effect of the molybdenum.

L'acier contient également de 1 % à 2 %, et de préférence moins de 1,6 % de titane, ainsi que de 0 % à 0,3 % d'aluminium, afin d'obtenir un effet de durcissement par précipitation tout en limitant les risques de défaut lors du laminage à chaud. The steel also contains from 1% to 2%, and preferably less than 1.6% of titanium, as well as 0% to 0.3% aluminum, in order to obtain a hardening effect by precipitation while limiting the risk of defect during hot rolling.

La teneur en carbone est limitée à 0,01 % au maximum pour obtenir une martensite suffisamment douce avant vieillissement. Le reste de la composition est constitué de fer et d'impuretés résultant de l'élaboration.The carbon content is limited to a maximum of 0.01% to obtain a Martensite sufficiently soft before aging. The rest of the composition is consisting of iron and impurities resulting from the production.

Cet acier est élaboré puis coulé et laminé à chaud conformément à l'état de l'art. En outre il peut être laminé à froid, par exemple pour obtenir une bande de moins de 1,5 mm d'épaisseur. Lorsqu'il est laminé à froid, selon l'épaisseur du produit de départ et l'épaisseur finale visée, le laminage à froid peut être exécuté en plusieurs étapes séparées par des recuits à une température supérieure ou égale à 800 °C. On peut, notamment, prévoir que la dernière étape de laminage à froid corresponde à un taux d'écrouissage compris entre 0 % et 50 %, et de préférence entre 10 % et 45 %, et mieux encore, inférieur à 35 %. Dans ce cas, après vieillissement entre 450 °C et 510 °C, la limite d'élasticité Re obtenue est supérieure à 1900 MPa et l'allongement à rupture A % est supérieur à 6,5 %.This steel is produced, then poured and hot rolled in accordance with the state of art. In addition, it can be cold rolled, for example to obtain a strip of less than 1.5 mm thick. When cold rolled, depending on the thickness of the starting material and target final thickness, cold rolling can be performed in several stages separated by annealing at a temperature greater than or equal to 800 ° C. One can, in particular, provide that the last cold rolling step corresponds to a work hardening rate of between 0% and 50%, and preferably between 10% and 45%, and better still, less than 35%. In this case, after aging between 450 ° C and 510 ° C, the elastic limit Re obtained is higher at 1900 MPa and the elongation at break A% is greater than 6.5%.

A titre d'exemple on a réalisé les coulées 1 à 7 conformes à l'invention, et à titre de comparaison la coulée A conforme à l'art antérieur. Avec ces coulées on a fabriqué des bandes laminées à froid avec des taux d'écrouissage variables au cours de la dernière étape de laminage à froid, celle-ci étant précédée d'un recuit au défilé à 1020 °C. Ces bandes ont alors été durcies par vieillissement à 480 °C pendant 4 heures, puis on a mesuré les caractéristiques mécaniques par un essai de traction.By way of example, castings 1 to 7 were produced in accordance with the invention, and by way of comparison, casting A in accordance with the prior art. With these flows we have fabricated cold rolled strips with variable work hardening rates during the last cold rolling step, which is preceded by annealing parade at 1020 ° C. These strips were then hardened by aging at 480 ° C. for 4 hours, then the mechanical characteristics were measured by a test of traction.

Les compositions chimiques des aciers étaient, en % en poids : échantillon Ni Mo Ti Al C Fe 1 19,66 4,84 1,34 0,14 0,0021 bal. 2 19,30 5,07 1,42 0,1 0,0015 bal. 3 19,86 4,62 1,29 0,11 <0,001 bal. 4 20,28 5,06 1,24 0,11 <0,001 bal. 5 20,81 4,61 1,28 0,12 <0,001 bal. 6 18,86 6,58 1,23 0,13 0,0087 bal. 7 19,84 6,55 1,23 0,13 0,0015 bal. A comparaison 18,13 2,92 1,36 0,14 0,0031 bal. The chemical compositions of the steels were, in% by weight: sample Or MB Ti al VS Fe 1 19.66 4.84 1.34 0.14 0.0021 ball. 2 19,30 5.07 1.42 0.1 0.0015 ball. 3 19.86 4.62 1.29 0.11 <0.001 ball. 4 20.28 5.06 1.24 0.11 <0.001 ball. 5 20.81 4.61 1.28 0.12 <0.001 ball. 6 18.86 6.58 1.23 0.13 0.0087 ball. 7 19.84 6.55 1.23 0.13 0.0015 ball. By comparison 18.13 2.92 1.36 0.14 0.0031 ball.

Les résultats des essais mécaniques ont été les suivants : Echantillon 1 (invention) : écrouissage % 0 % 25 % 50 % 75 % Re (MPa) 1859,5 1934,5 2001,5 2138,5 A % 7,13 7,67% 7 % 3,54 % Echantillon 2 (invention) : écrouissage % 0 % 7,4 % 24,1 % 45,9 % 72,9 % Re (MPa) 1946 1979,1 % 2029,5 2120,2 2268 A % % 6,88 % 7,3 % 7,07 % 6,65 % 2,87 % Echantillon 3 (invention) : écrouissage % 0 % 5.4 % 22,7 % 48,2 % 74,6 % Re (MPa) 1887,4 1932,3 1912 1994,8 2127,5 A % 7,65 % 7,96 % 7,47 % 6,83 % 2,57 % Echantillon 4 (invention) : écrouissage % 0 % 3 % 19,2 % 44,6 % 71,2 % Re (MPa) 1840,6 1967,6 1967,6 2001,2 2198,2 % A % 9,48 % 10,08 % 8,85 % 8,24 % 7,79 % Echantillon 5 (invention): écrouissage % 0 % 4 % 22 % 48,4 % 74,5 % Re(MPa) 1852,1 1908,8 1970,7 2032,5 % 2197,2 % A % 8,99 % 8,17 % 7,39 % 5,59 % 3,32 % Echantillon 6 (invention): écrouissage % 0 % 8 % 25,2 % 49,8 % 74 % Re (MPa) 1956,3 2043,6 2097 2216,1 2318,6 A % 9,64 % 9,02 % 8,65 % 7,93 % 6,32 % Echantillon 7 (invention) : écrouissage % 0 % 8,8 % 23,5 % 48,8 % 74,3 % Re (MPa) 1696,7 1836,5 2012,5 2151,1 2336,7 A % 9,93 % 8,37 % 8,25 % 7,05 % 3,98 % Echantillon A (comparaison) : écrouissage % 0 % 25 % 50 % 75 % Re (MPa) 1724 1771 1861 1965,5 A % 9,3 % 8,94 % 10,16 % 6,1 % The results of the mechanical tests were as follows: Sample 1 (invention): work hardening% 0% 25% 50% 75% Re (MPa) 1859.5 1934.5 2001.5 2138.5 AT % 7.13 7.67% 7% 3.54% Sample 2 (invention): work hardening% 0% 7.4% 24.1% 45.9% 72.9% Re (MPa) 1946 1979.1% 2029.5 2120.2 2268 AT % % 6.88% 7.3% 7.07% 6.65% 2.87% Sample 3 (invention): work hardening% 0% 5.4% 22.7% 48.2% 74.6% Re (MPa) 1887.4 1932.3 1912 1994.8 2127.5 AT % 7.65% 7.96% 7.47% 6.83% 2.57% Sample 4 (invention): work hardening% 0% 3% 19.2% 44.6% 71.2% Re (MPa) 1840.6 1967.6 1967.6 2001.2 2,198.2% AT % 9.48% 10.08% 8.85% 8.24% 7.79% Sample 5 (invention): work hardening% 0% 4% 22% 48.4% 74.5% Re (MPa) 1852.1 1908.8 1970.7 2,032.5% 2,197.2% AT % 8.99% 8.17% 7.39% 5.59% 3.32% Sample 6 (invention): work hardening% 0% 8% 25.2% 49.8% 74% Re (MPa) 1956.3 2043.6 2097 2216.1 2318.6 AT % 9.64% 9.02% 8.65% 7.93% 6.32% Sample 7 (invention): work hardening% 0% 8.8% 23.5% 48.8% 74.3% Re (MPa) 1696.7 1836.5 2012.5 2151.1 2336.7 AT % 9.93% 8.37% 8.25% 7.05% 3.98% Sample A (comparison): work hardening% 0% 25% 50% 75% Re (MPa) 1724 1771 1861 1965.5 AT % 9.3% 8.94% 10.16% 6.1%

L'ensemble de ces résultats montre d'une part, qu'avec un acier conforme à l'invention, il est possible d'obtenir à la fois une limite d'élasticité supérieure à 1900 MPa et un allongement supérieur à 6,5 % lorsque le traitement de vieillissement est effectué directement après un écrouissage à froid compris entre 0 % et 50 %, alors qu'avec l'acier selon l'art antérieur ce n'est pas possible.All of these results show on the one hand, that with a steel conforming to the invention, it is possible to obtain both an elastic limit greater than 1900 MPa and an elongation greater than 6.5% when the treatment of aging is carried out directly after cold work hardening between 0 % and 50%, whereas with steel according to the prior art this is not possible.

Claims (8)

  1. Cobalt-free maraging steel, characterized in that its chemical composition comprises, by weight: 18% ≤ Ni ≤ 23% 4.5% ≤ Mo ≤ 8% 1% ≤ Ti ≤ 2% 0% ≤ Al ≤ 0.3% C ≤ 0.01% the balance being iron and impurities and the chemical composition furthermore satisfying the following conditions: 23 ≤ Ni + Mo ≤ 27% and Ni + 3 x Mo + 20 x Ti + 10 x Al ≥ 60%.
  2. Cobalt-free maraging steel according to Claim 1, characterized in that: Mo ≥ 5%.
  3. Cobalt-free maraging steel according to Claim 1 or Claim 2, characterized in that: Ni ≥ 19%.
  4. Cobalt-free maraging steel according to any one of Claims 1 to 3, characterized in that: 24 ≤ Ni + Mo ≤ 26%.
  5. Cobalt-free maraging steel according to any one of Claims 1 to 4, characterized in that: Ti ≤ 1.6%.
  6. Cobalt-free maraging steel according to any one of Claims 1 to 5, characterized in that it has a yield strength Re ≥ 1900 MPa and an elongation ≥ 6.5% in the aged state after cold working, the reduction ratio being between 0% and 50%.
  7. Maraging steel according to Claim 6, characterized in that the reduction ratio is between 10% and 45%.
  8. Maraging steel according to Claim 7, characterized in that the reduction ratio is less than 35%.
EP98403247A 1998-01-23 1998-12-22 Cobalt-free maraging steel Expired - Lifetime EP0931844B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9800694A FR2774099B1 (en) 1998-01-23 1998-01-23 STEEL MARAGING WITHOUT COBALT
FR9800694 1998-01-23

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EP0931844B1 true EP0931844B1 (en) 2002-05-22

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US (1) US6080359A (en)
EP (1) EP0931844B1 (en)
JP (1) JPH11256278A (en)
DE (1) DE69805495T2 (en)
ES (1) ES2176934T3 (en)
FR (1) FR2774099B1 (en)

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US6080359A (en) 2000-06-27
DE69805495T2 (en) 2002-11-28
JPH11256278A (en) 1999-09-21
FR2774099A1 (en) 1999-07-30
EP0931844A1 (en) 1999-07-28
FR2774099B1 (en) 2000-02-25
ES2176934T3 (en) 2002-12-01
DE69805495D1 (en) 2002-06-27

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