EP4153791A1 - Procédé pour le traitement d'un acier à haute résistance avancé - Google Patents

Procédé pour le traitement d'un acier à haute résistance avancé

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Publication number
EP4153791A1
EP4153791A1 EP21809887.9A EP21809887A EP4153791A1 EP 4153791 A1 EP4153791 A1 EP 4153791A1 EP 21809887 A EP21809887 A EP 21809887A EP 4153791 A1 EP4153791 A1 EP 4153791A1
Authority
EP
European Patent Office
Prior art keywords
temperature
steel material
amount
steel
component
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21809887.9A
Other languages
German (de)
English (en)
Other versions
EP4153791A4 (fr
Inventor
Timothy W. Skszek
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Magna International Inc
Original Assignee
Magna International Inc
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 Magna International Inc filed Critical Magna International Inc
Publication of EP4153791A1 publication Critical patent/EP4153791A1/fr
Publication of EP4153791A4 publication Critical patent/EP4153791A4/fr
Pending legal-status Critical Current

Links

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
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/673—Quenching devices for die quenching
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
    • 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
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • 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
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • C—CHEMISTRY; METALLURGY
    • 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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • 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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Definitions

  • the present invention relates to processing steel, a method of manufacturing a component formed of steel, and components formed of steel, such as energy absorbing components for vehicle applications.
  • Energy absorbing components such as structural components for vehicle applications, are oftentimes formed of steel. Energy absorption is the product of strength and ductility, and manufacturability requires good formability and weldability. Thus, the energy absorbing components formed of steel preferably have a good combination of strength, ductility, weldability, and formability.
  • a traditional process of forming a component from boron steel includes heating a sheet formed of the boron steel to a defined elevated temperature and for a time period that enables the formation of a face-centered cubic crystallographic phase referred to as austenite. The austenitic steel sheet is then transferred to a temperature-controlled steel die.
  • a hydraulic press forms the component and achieves a desired profile. The hydraulic press applies the force required to form the desired profile and controls the rate of heat transfer, to achieve the desired cooling rate.
  • the cooling rate and alloy composition of the boron steel causes a phase transformation of the low strength austenite to either a high strength martensite phase or pearlitic microstructure.
  • the critical cooling rate is based on the alloy composition.
  • the combination of alloy composition and cooling rates imposed by conventional hot stamp processing of boron steel does not result in retained austenite.
  • GEN3 steels are a commercially available series of advanced high strength steel (AHSS) which have a high strength and ductility, which is associated with the bainitic microstructure.
  • AHSS advanced high strength steel
  • the components formed of the GEN3 steels are formed at room temperature.
  • the hot stamped boron steel exhibits a higher energy absorption characteristic than the GEN 3 steel.
  • the forming tonnage required to form the boron steel at an elevated temperature is lower than that required for the GEN3 steel at room temperature.
  • the cost of a boron steel sheet is less than a GEN3 steel sheet.
  • post-formed hot stamped boron steel has a relatively low ductility, which limits commercial applications to crash-formed strength-based bending applications, which do not include flange design features.
  • the flange design features increase design efficiency and facilitate attachment to other components.
  • the post-formed strength and ductility characteristics of components formed of the hot stamped boron steel necessitate the use of lasers to trim the stamped components.
  • the processing and manufacturing costs of the hot stamped boron steel components are high due to the capital costs, operating costs, and floor space allocation associated with blank preheat furnaces, hydraulic presses, and laser trim equipment typically used to manufacture the components.
  • the manufacturing and processing costs are greater than those associated with the GEN3 steels, due to the increased capital and operating cost associated with inline solution heat treat of the boron steel sheet prior to the forming operation, use a hydraulic press capable of stopping at the bottom to achieve the required transformation cooling rate, and the laser-based trim processes required to trim the stamped components formed of the boron steel.
  • the post-formed microstructure of the conventional hot stamped boron steel typically includes martensite, but does not include retained austenite.
  • the boron steel components lack a post forming work hardening response associated with the transformation of retained austenite in the post-formed matrix.
  • the quenched and partitioned GEN3 steels comprised of a combination of bainite and retained austenite, have improved formability and ductility relative to martensitic hot stamped steel enabling the ability to form flange features to increase the design efficiency of the component.
  • the quenched and partitioned GEN3 steels also have the advantage of reduced processing costs, relative to the hot stamped boron steel.
  • the reduced processing costs are typically associated with processing at room temperature, reduced cycle time related to the use of a higher speed mechanical press, avoidance of dwell time associated with transformation cooling, and feasible secondary operations (restrike, trim, flange and pierce) which are performed in-line to the forming operation.
  • the post-formed dimensional repeatability of the GEN3 steel stamped components is low relative to the hot stamped boron steel and other high strength steel alloys stamped at room temperature.
  • the reduced dimensional repeatability is related to spring back.
  • the post-formed total energy absorption characteristics of the GEN3 steel is lower relative to boron steel.
  • the strength of the GEN3 steel during the forming operation is high relative to the hot stamped boron steel, which limits the size (area) or number of GEN3 steel parts formed for a given press tonnage. Increased press tonnage is required relative to the hot stamped boron steel.
  • bainitic GEN3 steel does not exhibit a work hardening characteristic due to the lack of retained austenite after the forming operation.
  • a commercially available series of GEN3 steel is an austenitic advanced high strength steel (AHSS) referred to as austenitic GEN3 TRIP steel.
  • AHSS austenitic advanced high strength steel
  • TRIP steels leverage the strength and ductility associated with the transformation to austenite to martensite (known as the TRIP effect) to enhance formability and strength characteristics, as a result of strain imposed during the forming process.
  • One aspect of the invention provides a method for processing steel material, such as material used to form an energy absorbing component for a vehicle.
  • the method comprises heating a steel material to a temperature above an upper critical temperature (Ac3) of the steel material.
  • the steel material has a microstructure which includes ferrite and bainite, and the heating step includes converting a portion of the ferrite and bainite to austenite.
  • the method further includes forming the steel material into a component after the steel material is heated to the temperature above the upper critical temperature (Ac3) of the steel material.
  • the steel material is cooled during the forming step, and a portion of the austenite transforms to martensite and bainite during the forming step.
  • the steel material includes iron in an amount of 91.95 to 98.55 wt. %, carbon in an amount of 0.15 to 0.3 wt. %, manganese in an amount of 1.5 to 2.5 wt. %, silicon in an amount of 0.6 to 1.6 wt. %, chromium in an amount of 0.55 to 0.65 wt. %, copper in an amount of 0.0 to 1.0 wt. %, nickel in an amount of 0.0 to 1.0 wt. % and aluminum in an amount of 0.0 to 1.0 wt. %, based on the total weight of the steel material.
  • the steel material also includes bainite and martensite. BRIEF DESCRIPTION OF THE DRAWINGS
  • Figure 1 illustrates an energy absorbing component formed of a steel material according to an example embodiment
  • Figure 2 illustrates a quench and partition process wherein a steel material is heated above the Ac3 temperature of the steel material, die quenched in a heated die to a temperature between the M s and Mf temperature of the steel material, and then heated to an elevated temperature to increase energy absorption.
  • Figure 3 illustrates a quench and temper process wherein a steel material is heated above the Ac3 temperature of the steel material, die quenched in a steel die to a temperature below the M s and Mf temperatures of the steel material, and reheated to an elevated temperature to increase energy absorption.
  • Figure 4 is a table showing ultimate tensile strength (TS), yield strength
  • Figure 5 is a graph of phase distribution and temperature for a steel material according to an example embodiment.
  • AHSS advanced high strength steel
  • the example embodiments are only provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and/or well-known technologies are not described in detail.
  • the method includes processing of the advanced high strength steel (AHSS) referred to as bainitic GEN3 steel.
  • Bainitic GEN3 steel typically comprises iron in an amount of 91.95 to 98.55 wt. %, carbon in an amount of 0.15 to 0.3 wt. %, manganese in an amount of 1.5 to 2.5 wt. %, silicon in an amount of 0.6 tol.6 wt. %, chromium in an amount of 0.55 to 0.65 wt. %, copper in an amount of 0.0 to 1.0 wt. %, nickel in an amount of 0.0 to 1.0 wt. % and aluminum in an amount of 0.0 to 1.0 wt.
  • AHSS advanced high strength steel
  • the composition of the steel material comprises iron in an amount of 96.03 wt. %, carbon in an amount of 0.22 wt. %, manganese in an amount of 2.35 wt. %, silicon in an amount of 0.6 wt. %, and aluminum in an amount of 0.8 wt. %, based on the total weight of the steel.
  • the microstructure of the steel includes bainite, typically in an amount of at least 75 vol. %, based on the total volume of the steel material.
  • the remainder of the steel material includes ferrite.
  • the process begins with a blank formed of the steel material, which is typically in the form of a sheet. The following example embodiments will refer to the steel sheet, however, the steel material could comprise other shapes.
  • the bainitic steel material is heated to a temperature above the upper critical temperature (Ac3) of the steel material.
  • the Ac3 temperature is defined at the temperate at which the ferrite and bainite phases of the steel material transform to austenite. Thus, during the heating step, a portion of the ferrite and bainite transform to austenite.
  • the temperature above the Ac3 temperature ranges from 850° C to 900° C.
  • the Ac3 temperature for the bainitic GEN3 steel disclosed above is 850 °C.
  • the Ac3 temperature varies by composition, and Ac3 kinetics are slow. Heating above the Ac3 temperature reduces the time required to achieve a microstructure which is 100% austenite.
  • the specific fraction of ferrite, bainite and austenite in the steel material after the heating step is dependent on a phase equilibrium at temperature for the specific composition of the steel material.
  • the fraction of ferrite, bainite and austenite in the steel sheet is also dependent on the temperature history of the steel sheet prior to forming and the specific composition of the steel material.
  • the steel sheet which was previously heat treated to a temperature above the Ac3 temperature, typically 850° C to 900° C, is formed into a component 10 having a desired shape.
  • the forming step is preferably conducted in a temperature controlled steel die using a forming press, preferably a mechanical press.
  • the method also includes cooling the steel material during and possibly after the forming step.
  • the temperature of the steel die ranges from 100° C to 360° C while forming the steel material into the desired shape.
  • the temperature of the steel material itself during the forming step ranges from 900° C to a temperature ranging between 100° C to 360° C.
  • a high fraction percentage of the austenite is transformed to martensite and bainite during the forming process, as a result of the rate of heat transfer imposed by the forming process.
  • the transformation of the austenite to a combination of bainite and/or martensite during the forming step reduces the forming tonnage required, improves formability, reduces dimensional variance by improving dimensional repeatability associated with spring back, and increases the strength of the formed component 10.
  • An example of the component 10 is shown in Figure 1. According to this example, the component 10 is a B-pillar between a passenger and driver door of a vehicle.
  • the method preferably includes cooling the steel material and/or shaped component in the die, for example by quenching.
  • the steel material and/or component is cooled to a temperature below the M s temperature.
  • the method preferably includes heating or tempering the component to a temperature above the Ms temperature in the die.
  • the M s temperature is the temperature at which the formation of martensite in the steel material begins
  • the Mf temperature is the temperature at which the formation of martensite in the steel material finishes.
  • Regulating the temperature of the die during and after the forming step controls the amount of martensite, bainite, and retained austenite in the component and thus is able to tailor the energy absorption, weldability, and/or deformation characteristics in specific regions of the component.
  • the cooling step typically includes forming retained austenite in the component.
  • the retained austenite is maintained in a matrix of bainite and martensite. For example, greater than 0 and up to 15 volume % of the austenite present in the steel material prior to the forming step may be retained in the matrix of bainite and martensite after the cooling step.
  • the percentage of retained austenite in the post-formed steel sheet is dependent on the temperature of the form die, cooling rate, strain imposed during the forming process and the specific steel composition.
  • the amount of retained austenite present in the component after forming is the result of diffusion-related transformation kinetics relative to the martensite start temperature (M s ) and martensite finish (M s ) temperature range.
  • the M s temperature for the steel composition disclosed above is approximately 350° C to 360° C and the Mf temperature is approximately 135° C to 145° C.
  • the percentage of retained austenite in the component ranges from 0% to 15% based on stability of the austenite during cooling determined by the cooling rate below the M s temperature.
  • Austenite stability and the relative percentage of bainite versus martensite present in the formed component is determined by the cooling rate below the Ms temperature which is influenced by the temperature of the steel die used to form the component.
  • the method can further including heating or tempering the steel component after the cooling and forming steps.
  • the temperature of the steel component in the steel die is controlled and is kept at temperature between the M s and Mf temperatures of the steel material after the forming step, and then the steel component is heated to a temperature above the M s temperature for a defined period of time.
  • Figure 2 illustrates a quench and partition process wherein the steel material is heated above the Ac3 temperature, die quenched in a heated die to a temperature between the M s and Mf temperatures, which are specific to the steel material composition, and then heated to an elevated temperature to increase energy absorption.
  • the temperature of the steel component is controlled and kept at a temperature below the Mf temperature prior to heating the steel component to a temperature above the M s temperature for a defined period of time.
  • Figure 3 illustrates a quench and temper process wherein the steel material is heated above the Ac3 temperature, die quenched in a steel die to a temperature below the M s and Mf temperatures, which are specific to the steel material composition, and reheated to an elevated temperature to increase energy absorption.
  • the cooling and reheating steps are conducted to increase energy absorbing properties of the steel component.
  • Various other heating, tempering, quenching, partitioning, and/or austenitizing steps can be conducted on the steel component after the forming step to increase energy absorbing properties of the steel component.
  • the composition of the steel material of the finished component still includes iron in an amount of 91.95 to 98.55 wt. %, carbon in an amount of 0.15 to 0.3 wt. %, manganese in an amount of 1.5 to 2.5 wt. %, silicon in an amount of 0.6 to 1.6 wt. %, chromium in an amount of 0.55 to 0.65 wt. %, copper in an amount of 0.0 to 1.0 wt. %, nickel in an amount of 0.0 to 1.0 wt. % and aluminum in an amount of 0.0 to 1.0 wt. %, based on the total weight of the steel material.
  • the method includes heating the steel material to a temperature above the Ac3 temperature, preferably to a temperature of 900° C.
  • the steel material is then cooled during the forming process in a steel die, preferably controlled to a temperature of 100° C to 350° C.
  • the cooling rate of the steel material below the Ms temperature is greater than 10° C/second, preferably 50° C/second.
  • the formed component is then reheated to a temperature above the Ms temperature, preferably to a temperature range of 360° C to 400° C.
  • Figure 4 is a table showing the ultimate tensile strength (TS), yield strength
  • FIG. 5 includes a graph of phase distribution and temperature for a steel material according to an example embodiment.
  • the process can further include restriking, trimming, flanging, and/or piercing operations on the finished formed steel component. If the finished formed component is used in a vehicle application and includes a fraction percentage of retained austenite, then during a possible crash event the formed component is subjected to strain which transforms some of the retained austenite to martensite. The transformation of the retained austenite to martensite during the crash event increases strength and energy absorption characteristic of the component.
  • the process and finished component formed by the process described above provides numerous advantages.
  • the transformation of austenite to a combination of martensite, bainite and/or retained austenite addresses the need to improve dimensional repeatability, formability, forming tonnage requirements, and energy absorption characteristics, relative to GEN3 bainitic steel formed at room temperature.
  • the transformation of austenite to a combination of martensite, bainite and retained austenite also addresses the need to reduce manufacturing costs, enables use of a mechanical press, and increases design efficiency relative to hot stamped boron steel components.
  • the transformation of retained austenite to martensite during a strain event imposed during a crash addresses the need to improve energy absorption characteristics relative to GEN3 bainitic steel.
  • the steel component of the present disclosure also provides enhanced formability due to the presence of retained austenite and transformation of the austenite to martensite during the forming process.
  • the dimensional characteristics associated with the steel component are also enhanced due to the presence of the retained austenite and the transformation of the austenite to martensite during the forming process.
  • the post-formed energy absorption characteristics of the steel component are greater than GEN3 boron steel due to the transformation of a portion of austenite to martensite during the forming event and the transformation of the retained austenite to martensite during a crash event.
  • the cost associated with the manufacture of the steel component is less than boron steel due to reduced heating requirements and use of lower cost trimming methods.
  • the design efficiency of the steel component is greater than hot stamped boron steel due to the ability to form flange features.

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

Abstract

L'invention concerne un procédé de fabrication d'un composant d'absorption d'énergie pour un véhicule. Le procédé inclut le chauffage d'un matériau d'acier GENS bainitique qui a une microstructure incluant de la ferrite et de la bainite à une température supérieure à la température Ac3 pour convertir une partie de la ferrite et de la bainite en austénite. Le procédé comprend en outre le formage pendant le refroidissement de l'ébauche en acier chauffé en un composant dans une matrice en acier à température régulée. Pendant l'étape de refroidissement, le matériau en acier est refroidi à une température inférieure à la température Ms pour former de l'austénite retenue. Une partie de l'austénite se transforme en martensite et en bainite pendant l'étape de formage et de refroidissement. Le procédé peut en outre inclure le chauffage du composant à une température supérieure à la température Ms après l'étape de formage et de refroidissement pour augmenter les caractéristiques d'absorption d'énergie. Pendant un accident, la contrainte imposée au composant convertit l'austénite retenue présente dans le composant en martensite.
EP21809887.9A 2020-05-18 2021-05-18 Procédé pour le traitement d'un acier à haute résistance avancé Pending EP4153791A4 (fr)

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US202063026230P 2020-05-18 2020-05-18
PCT/US2021/032936 WO2021236619A1 (fr) 2020-05-18 2021-05-18 Procédé pour le traitement d'un acier à haute résistance avancé

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CN1865481A (zh) * 2005-05-19 2006-11-22 宝钢集团上海梅山有限公司 一种贝氏体耐磨钢板制备工艺
EP1767659A1 (fr) * 2005-09-21 2007-03-28 ARCELOR France Procédé de fabrication d'une pièce en acier de microstructure multi-phasée
DE102008022399A1 (de) * 2008-05-06 2009-11-19 Thyssenkrupp Steel Ag Verfahren zum Herstellen eines Stahlformteils mit einem überwiegend ferritisch-bainitischen Gefüge
WO2012048841A1 (fr) * 2010-10-12 2012-04-19 Tata Steel Ijmuiden B.V. Procédé de formage à chaud d'un flan d'acier et pièce formée à chaud
WO2013154071A1 (fr) * 2012-04-10 2013-10-17 新日鐵住金株式会社 Tôle d'acier adaptée à être utilisée comme élément d'absorption d'impact, et son procédé de fabrication
CN102953004B (zh) * 2012-11-19 2015-03-04 宝山钢铁股份有限公司 一种高强度复相钢板及其制造方法
JP6003837B2 (ja) * 2013-07-25 2016-10-05 Ｊｆｅスチール株式会社 高強度プレス部品の製造方法
WO2019003449A1 (fr) * 2017-06-30 2019-01-03 Ｊｆｅスチール株式会社 Élément pressé à chaud et son procédé de fabrication, et tôle d'acier laminée à froid pour pressage à chaud
CN110872641A (zh) * 2018-09-03 2020-03-10 山东建筑大学 一种奥氏体逆正转变与亚温成形生产汽车安全件的方法

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US20230183828A1 (en) 2023-06-15
EP4153791A4 (fr) 2024-04-10
WO2021236619A1 (fr) 2021-11-25
CN115667568A (zh) 2023-01-31

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