WO2008098910A1 - Procédé de production de composants par formage superplastique d'un élément tôle d'acier thermorégulé - Google Patents

Procédé de production de composants par formage superplastique d'un élément tôle d'acier thermorégulé Download PDF

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Publication number
WO2008098910A1
WO2008098910A1 PCT/EP2008/051632 EP2008051632W WO2008098910A1 WO 2008098910 A1 WO2008098910 A1 WO 2008098910A1 EP 2008051632 W EP2008051632 W EP 2008051632W WO 2008098910 A1 WO2008098910 A1 WO 2008098910A1
Authority
WO
WIPO (PCT)
Prior art keywords
steel
deformation
steel sheet
heated
sheet part
Prior art date
Application number
PCT/EP2008/051632
Other languages
German (de)
English (en)
Inventor
Harald Hofmann
Andreas Offergeld
Sascha Sikora
Original Assignee
Thyssenkrupp Steel Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thyssenkrupp Steel Ag filed Critical Thyssenkrupp Steel Ag
Publication of WO2008098910A1 publication Critical patent/WO2008098910A1/fr

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Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
    • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
    • B21D26/053—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure characterised by the material of the blanks
    • B21D26/055—Blanks having super-plastic properties
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
    • 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
    • C21D2201/00—Treatment for obtaining particular effects
    • C21D2201/02—Superplasticity
    • 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
    • C21D2201/00—Treatment for obtaining particular effects
    • C21D2201/05—Grain orientation

Definitions

  • the invention relates to a method for producing a component by deforming a tempered steel sheet part.
  • Modern steels are basically able to meet these requirements.
  • a wide range of steel grades is available whose properties are adapted to the tasks in practice.
  • sheets of these steels in a manner known per se, which are then deformed into the respective component, for example, molded parts for large-scale production can be produced Body and support structures of vehicles are produced inexpensively.
  • Deformation temperatures that are typically above the Ac 3 transformation temperature.
  • the hot forming can be combined with a hardening process. By means of such thermoforming, elaborately designed components of extreme strength can be produced.
  • JP 2006104526 A An example of this procedure is given in JP 2006104526 A.
  • sheets are made from a boron-alloyed steel, first, then to an above the Ac 3 temperature, typically in the range of 850 - 950 0 C are preheated, lying temperature.
  • the subsequent cooling in the pressing tool starting from this temperature range, a martensitic structure is produced in the component which is press-formed from the respective sheet metal blank and ensures the desired high strengths.
  • a favorable feature of this combination of hot working and hardening is that sheet metal parts heated to more than the Ac 3 temperature can be formed at significantly reduced forming forces and achieve a particularly high level of strength after shaping. Practical experience shows, however, that the possibilities of shaping these components are often still so limited due to the process that they do not meet future requirements.
  • a maximum deformability of metals is when they are in the so-called "superplastic" state. In this state, which can also be set with steels, metallic bodies can be stretched many times their initial length without causing breakage. In the article published in MAX PLANCK RESEARCH, 3/2004, pp.
  • the object of the invention was to provide a method that allows the production of components made of steel sheets with minimal limitation of the shaping and procedurally reduced effort.
  • a sheet steel part is processed, which is in the solidified state with a structure whose grains are predominantly a directed, d. H. have a shape deviating from the spherical shape with pronounced length orientation and are more than 10 ⁇ m in the rolling direction.
  • the sheet steel part thus obtained is heated for its superplastic deformation according to the invention to a temperature at which in the steel sheet of the Recrystallization at least begins or is already running. According to the invention, the deformation of the thus tempered sheet is then terminated within a period of time within which the unstable microstructure is present, that is, the recrystallization of the steel has not yet been completed.
  • the invention is based on the recognition that steels show a superplastic behavior in the limited period in which they have an unstable structure as a result of incipient or expiring recrystallization. This allows to deform them far beyond the extent to which deformation at lower or higher temperatures is possible without material breakage.
  • the time window in which the superplastic behavior used according to the invention occurs is sufficiently long in conventional steels already available in practice in order to be able to perform a deformation.
  • the invention thus provides a possibility to produce components with complex, complicated shape, by conventional cold forming of steels of the corresponding Property classes can not be represented.
  • the more complex geometries of components made of high strength steels made possible by the invention allow significant weight savings in the automotive industry, particularly in the automotive industry, which make an important contribution to reducing energy consumption and exhaust emissions.
  • the freedom of design opened up by the invention makes it possible to integrate a multitude of functions even in components produced from high-strength steels, so that overall only a smaller number of production steps is required for the production of the respective component and, consequently, a significant reduction in the value Manufacturing costs can be achieved.
  • the steel sheet part processed according to the invention can have a structure which can be significantly coarser and more anisotropic than the structure of such steel sheets which are provided in the prior art for the use of structural superplasticity.
  • the method according to the invention allows the steel sheet parts to be further processed directly in the state solidified after cold rolling. An energy-intensive final annealing of the Kaltband.es is not required. Practical experiments have shown in this context that the inventively used "instability superplasticity" even then occurs safely even if the average, measured in the longitudinal direction of the grains grain size of the grains of the structure of the sheet steel part is at least 20 ⁇ ra.
  • the grains of a steel sheet processed according to the invention have an elongate shape, as set, for example, by the forming forces exerted during cold rolling of a steel sheet.
  • the grain size of the structure according to the invention which amounts to more than 10 ⁇ m in the rolling direction of a steel sheet part processed according to the invention, is determined in a customary manner.
  • Suitable for this purpose is any experimental apparatus which allows the sample to be heated sufficiently quickly and precisely to the required temperature and to exert tensile forces in order to determine the extensibility of the material under investigation at the respectively set temperature.
  • Such test devices are currently available, for example, under the name “Gleeble system” from Dynamic Systems Inc., Poestenkill, NY, USA.
  • An essential advantage of the invention is that the respective steel sheet part is fed in the solidified state to the deformation according to the invention.
  • the parameters of the deformation can be easily chosen so that the component is in a recrystallized state at the end of the deformation.
  • a direct cooling carried out in the tool to a temperature below the recrystallization temperature also comes into consideration, so that a further warm forging step can follow.
  • the method according to the invention is suitable for heating the sheet steel part as a flat blank cut from a steel strip in the hard-rolling state to the deformation temperature set according to the invention and then deforming it in accordance with the invention.
  • the sheet steel part is, for example, separated from a steel strip previously obtained by cold rolling and fed without further cold deformation of the inventive transformation.
  • This procedure saves the otherwise required for the processing of cold strip annealing.
  • a particular advantage of the invention in this context is that it allows, according to the superplastic deformation according to the invention, a renewed cold deformation of the component obtained after superplastic forming.
  • the component brought back into a work-hardened state in this way can then be deformed again in accordance with the invention.
  • a heating device for heating the steel sheet part
  • the rapid, homogeneous heating of the sheet steel part allows.
  • particularly suitable devices heat the steel sheet with the help electric current, which is either passed directly through the respective sheet metal part (conductive heating) or generates an electromagnetic field, which in turn induces an electric current in the sheet steel part ⁇ inductive heating).
  • the electrical resistance caused by the steel component itself contrary to the directly induced or indirectly induced current, causes it to be heated to the desired temperature.
  • the advantageous for carrying out the invention high deformation rates can be achieved by means of commercially available hydraulic or mechanical presses.
  • these presses may indeed be suitable (accumulator presses, eccentric presses) to accomplish the desired high forming speeds.
  • the deformation forces required for the deformation according to the invention compared to a conventionally carried out deformation are significantly reduced, so that the time required for the generation of the forming force and thus the cost of purchase and operation of the presses is minimized accordingly.
  • the invention allows, for example, not only to process sheet metal parts made of high-strength and high-strength steels, but also those which consist of soft steels, tempered steels or multiphase steels.
  • components produced according to the invention have an optimized combination of strength and ductility. This makes them particularly suitable for the production of such components, which as crashrelevante components on the one hand ensure sufficient rigidity, but at the same time should be able to safely convert, for example, in an accident occurring kinetic energy in deformation energy.
  • FIG. 1 shows a sample rod according to the invention carried out superplastic expansion by 30 mm.
  • FIG. 2 shows a second sample rod after a superplastic expansion of 30 mm performed according to the invention
  • FIG. 3 shows a third sample rod after an elongation of 30 mm carried out in the warm, recrystallized state
  • FIGS. 1-3 shows the geometry of the sample rods shown in FIGS. 1-3 in the undeformed state
  • Diag. 1 the maximum achievable tensile strength of tensile specimens made of a steel A are prepared, applied over the respectively set temperature;
  • Diag. 2 the maximum achievable in tensile tests elongation of sample rods, which are made of a steel B, applied over the set temperature in each case;
  • Diag. 3 the maximum achievable in tensile tests elongation of sample rods, which are made of a steel C, applied over the set temperature.
  • the sample shown in Fig. 1 has an optimal uniform elongation due to the superplastic deformation portion.
  • the conventional sample is, as shown in Fig. 3, broken after the formation of a strong single constriction in its central part before the elongation of 30 mm has been reached.
  • samples were produced from three commercially available, cold-rolled steel sheets A, B, C, which had the shape shown in FIG. 4. With these samples tensile tests were carried out in a Gleehle apparatus in which the samples were clamped in a drawing device and heated in the clamped state at heating rates of more than 500 K / s to the respective deformation temperature TW.
  • the composition of steels A, B, C is shown in Table 1.
  • the steel A marketed under the name H300B has a high bake hardening potential.
  • Steel B is a microalloyed steel available under the designation H320LA.
  • Steel C is an IF steel and is sold under the name DX53D.
  • the texture grains of each of the samples obtained from the steels A, B, C had a pronounced elongated shape due to the foregoing cold rolling.
  • the respective "mean grain size" of the grains measured in the rolling direction is given in Table 2 for the samples consisting of steels A, B and C.
  • the optimal temperature window in the range from 750 ° C. to 850 ° C. and the optimum time window used for the heating and forming in the range from 2 to ⁇ 20 s for a deformation according to the invention is optimum.
  • the samples obtained from the hard-rolled micro-alloyed steel B are at temperatures of 700 - 880 0 C was tested.
  • a temperature window 800-850 0 C a significant increase in the maximum achievable stretching .DELTA.L up to twice the attainable elongation in .DELTA.L recrystallized structural state (hot tensile test).
  • the results obtained for the 2 s holding time are in Diag. 2 illustrated by white filled circles.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Fluid Mechanics (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)

Abstract

Elément en tôle d'acier qui, à l'état solidifié dans lequel il a une structure de grains ayant en majorité une forme différente de la forme sphérique et une taille moyenne de grains > 10 μm, est chauffé à une température de formage (TW) à laquelle on trouve dans l'élément en tôle d'acier une microstructure instable consécutive à la recristallisation qui s'amorce ou se poursuit. Le formage de l'élément tôle d'acier chauffé à la température de recristallisation TW s'effectue sensiblement pendant l'opération de recristallisation. La température de formage est comprise, de préférence, entre 700 et 950 C. Le chauffage et le façonnage sont terminés au bout de 1 à 120 sec et la vitesse d'allongement est comprise entre 10-2 et 101 1/s.
PCT/EP2008/051632 2007-02-14 2008-02-12 Procédé de production de composants par formage superplastique d'un élément tôle d'acier thermorégulé WO2008098910A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102007007328.5 2007-02-14
DE102007007328A DE102007007328A1 (de) 2007-02-14 2007-02-14 Verfahren zum Herstellen von Bauteilen durch Verformen eines temperierten Stahlblechteils

Publications (1)

Publication Number Publication Date
WO2008098910A1 true WO2008098910A1 (fr) 2008-08-21

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DE (1) DE102007007328A1 (fr)
WO (1) WO2008098910A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2162533A1 (de) * 1970-12-16 1972-06-29 Republic Steel Corp Verfahren zum Überführen von Stahl in einen Zustand hoher Duktilität und zum Verformen dieses Stahls
EP1415735A1 (fr) * 2002-11-04 2004-05-06 General Motors Corporation Procédé de formage d'un article en tôle par déformation superplastique ou par déformation plastique rapide

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3519503A (en) 1967-12-22 1970-07-07 United Aircraft Corp Fabrication method for the high temperature alloys
EP1783234A3 (fr) 2002-09-26 2007-08-08 ThyssenKrupp Steel AG Procédé destiné à la fabrication de produits par le déformage à températures élevées
JP4975245B2 (ja) 2004-10-06 2012-07-11 新日本製鐵株式会社 高強度部品の製造方法
DE102005027258B4 (de) 2005-06-13 2013-01-31 Daimler Ag Hochkohlenstoffhaltiger Stahl mit Superplastizität

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2162533A1 (de) * 1970-12-16 1972-06-29 Republic Steel Corp Verfahren zum Überführen von Stahl in einen Zustand hoher Duktilität und zum Verformen dieses Stahls
EP1415735A1 (fr) * 2002-11-04 2004-05-06 General Motors Corporation Procédé de formage d'un article en tôle par déformation superplastique ou par déformation plastique rapide

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