US20160010171A1 - Hot press molding and manufacturing method therefor - Google Patents

Hot press molding and manufacturing method therefor Download PDF

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Publication number
US20160010171A1
US20160010171A1 US14/650,712 US201414650712A US2016010171A1 US 20160010171 A1 US20160010171 A1 US 20160010171A1 US 201414650712 A US201414650712 A US 201414650712A US 2016010171 A1 US2016010171 A1 US 2016010171A1
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Prior art keywords
molding
area
less
region
molded article
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US14/650,712
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Junya Naitou
Toshio Murakami
Shushi Ikeda
Keisuke Okita
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Kobe Steel Ltd
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Kobe Steel Ltd
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Assigned to KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.) reassignment KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.) ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: IKEDA, SHUSHI, MURAKAMI, TOSHIO, NAITOU, JUNYA, OKITA, KEISUKE
Publication of US20160010171A1 publication Critical patent/US20160010171A1/en
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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
    • 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
    • C21D8/0294—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a localised treatment
    • 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
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/02—Stamping using rigid devices or tools
    • B21D22/022—Stamping using rigid devices or tools by heating the blank or stamping associated with heat treatment
    • 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
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • B21D22/208—Deep-drawing by heating the blank or deep-drawing associated with 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
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C21D2211/008—Martensite
    • 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
    • C21D2221/00—Treating localised areas of an article

Definitions

  • the present invention relates to a hot press molded article which is used for a structural member of an automobile component and whose strength and ductility can be adjusted according to different regions in the molded article and to the method for producing such a hot press molded article. More specifically, the present invention relates to a hot press molded article exhibiting strength and ductility according to different regions in such a manner that when a pre-heated steel plate (blank) is molded into a predetermined shape, thermal treatment is applied at the same time as shaping, and also relates to the useful method for producing such a hot press molded article.
  • blade pre-heated steel plate
  • the following hot press molding method has been employed for component production.
  • a steel plate is heated to a predetermined temperature (e.g., a temperature at which an austenite phase is exhibited) to lower strength (i.e., to facilitate molding)
  • molding is, for shaping, performed using a die having a lower temperature (e.g., a room temperature) than that of the thin steel plate.
  • rapid-cooling thermal treatment quenching is performed using a temperature difference between the die and the steel plate, thereby ensuring strength after molding.
  • the above-described hot press molding method since molding is performed in a low-strength state, springback is small (favorable shape fixability is obtained).
  • a material containing, e.g., alloy elements of Mn and B and exhibiting favorable hardenability is used, a 1500 MPa class strength in terms of tensile strength can be obtained by rapid cooling.
  • the above-described hot press molding method is, in addition to hot pressing, called as various names such as hot forming, hot stamping, a hot stamp method, and die quenching.
  • FIG. 1 is a schematic view illustrating a die structure for performing hot press molding (hereinafter sometimes represented by “hot stamping”) as described above.
  • a reference numeral “ 1 ” denotes a punch
  • a reference numeral “ 2 ” denotes a die
  • a reference numeral “ 3 ” denotes a blank holder
  • a reference numeral “ 4 ” denotes a steel plate (blank)
  • reference characters “BHF” denote wrinkle pressing force
  • reference characters “rp” denote a punch shoulder radius
  • reference characters “rd” denote a die shoulder radius
  • reference characters “CL” denote a clearance between the punch and the die.
  • the punch 1 and the die 2 are formed respectively therein passages 1 a , 2 a through which a corresponding one of cooling media 5 a , 6 a (e.g., water) is able to pass. Configuration is made such that the cooling media 5 a , 6 a pass through these passages to cool the punch 1 and the die 2 .
  • cooling media 5 a , 6 a e.g., water
  • molding begins in such a state that the steel plate (blank) 4 is heated to a single-phase temperature range of an Acs transformation point or higher and then, is softened. That is, in the state in which the steel plate 4 in a high-temperature state is interposed between each pair of the die 2 and the blank holder 3 , the punch 1 pushes the steel plate 4 (in the direction indicated by an arrow A) into a hole of the dies 2 (the space between the dies 2 , 2 in FIG. 1 ). While the outer diameter of the steel plate 4 is being reduced, the steel plate 4 is molded into a shape corresponding to the outer shape of the punch 1 .
  • the punch 1 and the dies 2 are cooled in parallel with molding to draw heat from the steel plate 4 to the die (the punch 1 and the dies 2 ), and are further held and cooled at a lower dead point in molding (the point at which a punch tip end is positioned innermost: the state illustrated in FIG. 1 ) to quench the raw material (the steel plate 4 ).
  • a molding method can be performed to obtain a 1500 MPa class molded article with favorable dimension accuracy.
  • a forming load can be reduced as compared to the case of molding a component of the same strength class as the above-described molded article in a cold state, the capacity of a pressing machine can be smaller.
  • Steel plates containing 22MnB5 steel as a raw material have been known as widely-used current steel plates for hot stamping. These steel plates have a tensile strength of 1500 MPa and an elongation of about 6-8%, and have been applied to shock-resistant members (members least deforming and rupturing in collision). Moreover, further development has been made to increase a C content and increase strength (1500 MPa or higher, a 1800 MPa class) with 22MnB5 steel being used as a base material.
  • components such as B pillars (center pillars), rear side members, and front side members may sometimes have both functions of a shock-resistant area and an energy-absorbing area, considering compatibility (the function of also protecting a collision partner in collision with a small-sized vehicle) in lateral collision or rear collision.
  • the following method has been mainly employed: super-high tensile steel having a high strength of a 980 MPa class and high tensile steel having an elongation of a 440 MPa class are, for example, laser-welded (form a tailor welded blank (TWB)) to press-mold the TWB in a cold state.
  • TWB tailor welded blank
  • Non-Patent Document 1 proposes the method for laser-welding (forming a tailor welded blank (TWB)) 22MnB5 steel for hot stamping and a material whose strength is not increased by quenching in a die and then, performing hot stamping. Different portions are formed in a component such that a tensile strength is 1500 MPa (an elongation of 6-8%) on a high-strength side (a shock-resistant area side) and that the tensile strength is 440 MPa (an elongation of 12% or higher) on a low-strength side (an energy-absorbing area side). From a similar point of view, the technique as described in Non-Patent Document 2 has been also proposed.
  • TWB tailor welded blank
  • Non-Patent Documents 1 and 2 on the energy-absorbing area side, the tensile strength is 600 MPa or lower, and the elongation is about 12-18%. It is required to perform laser-welding (form the tailor welded blank (TWB)) in advance, leading to an increase in the number of steps and an increase in a cost. Moreover, an energy-absorbing area which intrinsically does not need to be quenched is heated, and therefore, these techniques are not preferable considering heat consumption.
  • Non-Patent Documents 3 and 4 have been also proposed as the technique of forming portions different from each other in strength in a component.
  • the portions different from each other in strength are formed in such a manner that a temperature difference (distribution) is given to a blank in a heating furnace. Since 22MnB5 steel is used as a base material, poor robustness of the post-quenching strength against heating in a two-phase temperature range is exhibited due to addition of boron. Moreover, it is difficult to control the strength on the energy-absorbing area side, and only an elongation of about 15% can be obtained.
  • Non-Patent Document 4 the portions different from each other in strength are formed in such a manner that a cooling rate is changed in a die (by heating part of the die with a heater or using materials different from each other in coefficient of thermal conductivity). Since 22MnB5 steel is used as a base material, it is not rational in terms of controlling (die cooling control) such that 22MnB5 steel intrinsically having favorable hardenability is not quenched.
  • the present invention has been made in view of the foregoing situation, and is intended to provide hot press molded articles having, without application of welding, at least regions corresponding respectively to a shock-resistant area and an energy-absorbing area in a single molded article and exhibiting a high-level balance between high strength and elongation according to each region and to provide the useful method for producing such a hot press molded article.
  • the hot press molded article of the present invention capable of accomplishing the above-described objective is a hot press molded article formed by hot press molding of a thin steel plate, which includes a first molding region exhibiting a metal structure which contains 80-97 area % of martensite and 3-20 area % of retained austenite and which has a residual structure at 5 area % or less; and a second molding region exhibiting a metal structure which contains 70-97 area % of bainitic ferrite, 27 area % or less of martensite, and 3-20 area % of retained austenite and which has a residual structure at 5 area % or less.
  • the chemical component composition thereof is not limited.
  • examples of the chemical component composition include a chemical component composition in which the first and second molding regions have an identical chemical component composition, and steel of each component region contains, in units of mass %, 0.15-0.3% of C, 0.5-3% of Si, 0.5-2% of Mn, 0.05% or less of P, 0.05% or less of S, 0.01-0.1% of Al, 0.01-1% of Cr, 0.0002-0.01% of B, [N] ⁇ 4-0.1% of Ti, and 0.001-0.01% of N, where 0% is not inclusive for the P and the S and [N] denotes an N content in units of %, and the steel of each component region has a residual consisting of iron and an inevitable impurity.
  • the steel further contains, as other element, (a) one or more selected from a group consisting of Cu, Ni, and Mo in a total amount of 1% or less, where 0% is not inclusive, and that the steel further contains, as other element, (b) at least one of V or Nb in a total amount of 0.1% or less, where 0% is not inclusive.
  • the characteristics of the hot press molded article are further improved.
  • the method of the present invention is the method for producing the above-described hot press molded article by forming a thin steel plate so as to divide the thin steel plate into a plurality of regions including at least first and second molding regions, which includes after the thin steel plate is heated to a temperature of an Acs transformation point or higher and 1000° C.
  • the conditions therefor are properly controlled according to each region of the molded article. This can adjust the metal structure of each region while a proper amount of retained austenite is present. Moreover, the hot press molded article can be achieved, which has a higher intrinsic ductility (residual ductility) as compared to a conventional case of using 22MnB5 steel. Further, combination of thermal treatment conditions and a pre-molded steel plate can properly control the strength and the elongation according to each region.
  • FIG. 1 is a schematic view illustrating a die configuration for performing hot press molding.
  • FIG. 2 is a schematic view illustrating a die used in an example.
  • FIGS. 3( a ) and 3 ( b ) are schematic views illustrating the shape of a press molded article formed in the example.
  • the inventor(s) of the present invention has conducted study from various angles in order to realize a hot press molded article which when a thin steel plate is heated to a predetermined temperature to produce a molded article by hot press molding, exhibits strength corresponding to the demand characteristics of each of different regions and exhibits favorable ductility (elongation) after molding.
  • the present invention has been accomplished based on the following findings.
  • a heating temperature and the conditions for each molding region in molding are properly controlled, and the structure of each molding region is adjusted so as to contain 3-20 area % of retained austenite. This realizes a hot press molded article exhibiting a strength-elongation balance according to each molding region.
  • High-strength martensite is used for a main structure of a first molding region, thereby ensuring a high strength in a particular region of the hot press molded article. From this point of view, it is necessary that the area fraction of the martensite is 80 area % or greater. However, when such a fraction exceeds 97 area %, the area fraction of retained austenite (a retained austenite fraction) is insufficient, and ductility (residual ductility) is lowered.
  • the lower limit of the martensite fraction is preferably 83 area % or greater (more preferably 85 area % or greater), and the upper limit of the martensite fraction is preferably 95 area % or less (more preferably 93 area % or less).
  • the retained austenite has the effect of transforming into the martensite during plastic deformation to increase a work hardening rate (transformation-induced plasticity) and improving the ductility of the molded article.
  • the retained austenite fraction is 3 area % or greater.
  • a greater retained austenite fraction results in better ductility.
  • the retained austenite which can be ensured is limited, and the upper limit thereof is about 20 area %.
  • the lower limit of the retained austenite fraction is preferably 5 area % or greater (more preferably 7 area % or greater).
  • ferrite, pearlite, bainite, etc. may be contained as a residual structure. These structures are softer than the martensite, and less contribute to the strength as compared to other structures. For this reason, these structures are preferably contained in the minimum possible amount. Note that these structures can be contained up to 5 area %.
  • the residual structure is more preferably 3 area % or less, and much more preferably 0 area %.
  • a portion e.g., a shock-resistant area of an automobile component
  • the strength a tensile strength TS
  • the elongation a total elongation EL
  • the lower limit of the bainitic ferrite fraction is preferably 75 area % or greater (more preferably 80 area % or greater), and the upper limit of the bainitic ferrite fraction is preferably 95 area % or less (more preferably 90 area % or less).
  • the high-strength martensite can be partially contained to increase the strength of the hot press molded article. However, a greater amount of martensite results in a lower ductility (a lower residual ductility). From this point of view, it is necessary that the area fraction of the martensite (the martensite fraction) is 27 area % or less.
  • the lower limit of the martensite fraction is preferably 5 area % or greater (more preferably 10 area % or greater), and the upper limit of the martensite fraction is preferably 20 area % or less (more preferably 15 area % or less).
  • the retained austenite fraction is 3 area % or greater and 20 area % or less.
  • the preferable lower limit of the retained austenite fraction is similar to that of the first molding region.
  • ferrite, pearlite, bainite, etc. may be contained as a residual structure. These structures are softer than the martensite, and less contribute to the strength as compared to other structures. For this reason, these structures are preferably contained in the minimum possible amount. Note that these structures can be contained up to 5 area %.
  • the residual structure is more preferably 3 area % or less, and much more preferably 0 area %.
  • the structures of the second molding region are formed as described above, a portion (e.g., an energy-absorbing area of the automobile component) where the strength (the tensile strength TS) is 1100 MPa or greater and the elongation (the total elongation EL) is 15% or greater can be formed.
  • the strength the tensile strength TS
  • the elongation the total elongation EL
  • the molded article of the present invention includes at least the first and second molding regions, but does not necessarily include only two molding regions.
  • the molded article of the present invention may further include a third or fourth molding region. These molding regions can be formed according to a production method described later.
  • a thin steel plate (having the same chemical component composition as that of the molded article) may be formed so as to be divided into a plurality of regions including at least the first and second molding regions.
  • the above-described thin steel plate may be heated to a temperature of an Acs transformation point or higher and 1000° C. or lower. Then, for at least the first and second molding regions, cooling at an average cooling rate of 20° C./sec or higher and molding may begin by pressing of the first and second molding regions together with the die.
  • molding may be terminated at equal to or lower than a temperature (hereinafter sometimes referred to as “Ms point—50° C.”) lower than a martensite transformation start temperature by 50° C.
  • Ms point—50° C. a temperature
  • Bs point—100° C. a temperature lower than a bainite transformation start temperature by 100° C. and equal to or higher than the martensite transformation start temperature (the Ms point)
  • molding may be terminated after a lapse of a stay time of 10 seconds or longer within the above-described temperature range.
  • the phrase of “molding is terminated” basically means the state at a lower dead point in molding (the point at which a punch tip end is positioned innermost: the state illustrated in FIG. 1 ). However, when the die needs to be cooled to a predetermined temperature in such a state, the phrase of “molding is terminated” also means the state until the die is detached after the die is maintained cooled.
  • the steel plate is divided into at least two molding regions (e.g., a high-strength region and a low-strength region), and the production conditions are controlled according to each region.
  • the molded article exhibiting the strength-ductility balance according to each region can be obtained.
  • the production conditions for forming each region will be described.
  • the heating temperature In order to properly adjust the structures of the hot press molded article, it is necessary to control the heating temperature within a predetermined range. By proper control of the heating temperature, a predetermined amount of retained austenite can be ensured at a subsequent cooling step. Meanwhile, the first molding region can transform into the structure mainly containing the martensite. As a result, the final hot press molded article can be formed with desired structures. If the heating temperature of the thin steel plate is lower than the Ac 3 transformation point, a sufficient amount of austenite cannot be obtained in heating, and a predetermined amount of retained austenite cannot be ensured at the final structure (the structures of the molded article).
  • the heating temperature of the thin steel plate exceeds 1000° C.
  • the particle size of the austenite increases in heating, and the martensite transformation start temperature (the Ms point) and a martensite transformation end temperature (an Mf point) increase.
  • the heating temperature is preferably (Acs transformation point+50° C.) or higher and 950° C. or lower.
  • first steel plate region a steel plate region corresponding to the first molding region of the molded article. It is necessary that an average cooling rate of 20° C./sec or higher is ensured at the die in molding and that molding is terminated at a temperature of (Ms point—50° C.) or lower.
  • the average cooling rate in molding and the molding end temperature need to be properly controlled.
  • the average cooling rate in molding is 20° C./sec or higher, and the molding end temperature is (Ms point—50° C.) or lower.
  • the average cooling rate in molding is preferably 30° C./sec or higher (more preferably 40° C./sec or higher).
  • the molding end temperature in the first steel plate region is cooled to a room temperature at the above-described average cooling rate, molding may be terminated.
  • cooling two-step cooling
  • the average cooling rate in a second cooling step is preferably 10° C./sec or lower (more preferably 5° C./sec or lower).
  • the heating temperature of a steel plate region (hereinafter sometimes referred to as a “second steel plate region”) corresponding to the second molding region within a predetermined range.
  • a predetermined amount of retained austenite can be ensured at a subsequent cooling step.
  • the second molding region can transform into the structure mainly containing the bainitic ferrite. As a result, the final hot press molded article can be formed with desired structures.
  • the heating temperature of the thin steel plate is lower than the Acs transformation point, a sufficient amount of austenite cannot be obtained in heating, and a predetermined amount of retained austenite cannot be ensured at the final structure (the structures of the molded article).
  • the heating temperature of the thin steel plate exceeds 1000° C., the state similar to that of the first steel plate region is brought about (the preferable temperature range is also similar to that of the first steel plate region).
  • Cooling is temporarily stopped within the above-described temperature range (the cooling rate change temperature), and such a state stays for 10 seconds or longer within the above-described temperature range (i.e., a temperature range of (Bs point—100° C.) or lower and the martensite transformation start temperature Ms point or higher).
  • bainite transformation proceeds in supercooled austenite so that the structure mainly containing the bainitic ferrite can be formed.
  • a stay time in this state is preferably 50 seconds or longer (more preferably 100 seconds or longer). If the stay time is too long, the austenite begins decomposing, and the retained austenite fraction cannot be ensured. For this reason, the stay time is preferably 1000 seconds or shorter (more preferably 800 seconds or shorter).
  • the stay step may be any of an isothermal holding step, a monotonic cooling step, or a re-heating step.
  • the stay step as described above may be added after molding is terminated, or the holding step may be added within the above-described temperature range in the middle of termination of molding. After molding is terminated as described above, cooling may be performed to the room temperature by cold heat radiation at a proper cooling rate.
  • Control of the average cooling rate in molding can be achieved by a unit such as (a) a unit for controlling the temperature of the die (the cooling media illustrated in FIG. 1 ) and (b) a unit for controlling the coefficient of thermal conductivity of the die (the same applies to cooling in the later-described method).
  • the cooling conditions in molding vary according to each steel plate region.
  • the control units such as the units (a) and (b) may be provided separately in a single die, and cooling control may be performed corresponding to each steel plate region in the single die.
  • the method for producing the hot press molded article according to the present invention is applicable not only to the case (the direct method) of producing a hot press molded article in a simple shape as illustrated in FIG. 1 , but also to the case of producing a molded article in a relatively-complicated shape.
  • the method (called an “indirect method”) for performing cold press molding as a preceding process of hot press molding can be employed.
  • a portion which is difficult to be molded is pre-molded into an approximate shape by cold working, and the other portion is hot-press-molded.
  • the first and second recessed-raised portions are formed by cold press molding, and then, the third recessed-raised portion is formed by hot press molding.
  • the present invention is intended for a hot press molded article made of a high-strength steel plate.
  • the steel grade of such a steel plate may include steel grades of high-strength steel plates with typical chemical component compositions, C, Si, Mn, P, S, Al, Cr, B, Ti, and N are preferably adjusted to suitable ranged. From this point of view, the preferable ranges of these chemical components and the reasons for limiting these ranges are as follows.
  • the lower limit of the C content is more preferably 0.18% or greater (much more preferably 0.20% or greater), and the upper limit of the C content is more preferably 0.27% or less (much more preferably 0.25% or less).
  • Si produces the effect of forming the retained austenite in quenching. Moreover, Si also produces the effect of increasing, by solid solution strengthening, the strength without lowering the ductility much. If a Si content is less than 0.5%, a predetermined amount of retained autstenite cannot be ensured, and favorable ductility cannot be obtained. On the other hand, if the Si content becomes excess and exceeds 3%, the degree of solid solution strengthening becomes too high, and the ductility is significantly lowered.
  • the lower limit of the Si content is more preferably 1.15% or greater (much more preferably 1.20% or greater), and the upper limit of the Si content is more preferably 2.7% or less (much more preferably 2.5% or less).
  • Mn is a useful element in reduction of formation of ferrite and pearlite during primary cooling. Moreover, Mn is also a useful element in micronizing the structure unit of the bainitic ferrite by lowering (Bs point—100° C.), or in enhancement of the strength of the bainitic ferrite by increasing a dislocation density in the bainitic ferrite. Further, Mn is also a useful element in stabilizing the austenite to increase the amount of retained austenite. In order to produce these effects, Mn is preferably contained at 0.5% or greater. Only considering characteristics, a great Mn content is preferable. However, since the cost for alloy addition increases, the Mn content is preferably 2% or less.
  • the Mn content exceeds 2%, considering productivity.
  • the lower limit of the Mn content is more preferably 0.7% or greater (much more preferably 0.9% or greater), and the upper limit of the Mn content is more preferably 1.8% or less (much more preferably 1.6% or less).
  • the P content is preferably 0.05% or less (0% is not inclusive).
  • the upper limit of the P content is more preferably 0.045% or less (much more preferably 0.040% or less).
  • the S content is preferably 0.05% or less (0% is not inclusive).
  • the upper limit of the S content is more preferably 0.045% or less (much more preferably 0.040% or less).
  • Al is useful as a deoxidizing element, and is also useful in ductility improvement because Al fixes, as AlN, solid liquid N present in steel.
  • an Al content is preferably 0.01% or greater. However, if the Al content becomes excess and exceeds 0.1%, Al 2 O 3 is excessively generated, and the ductility is lowered. Note that the lower limit of the Al content is more preferably 0.013% or greater (much more preferably 0.015% or greater), and the upper limit of the Al content is more preferably 0.08% or less (much more preferably 0.06% or less).
  • Cr has the effect of reducing ferrite transformation and pearlite transformation.
  • Cr is an element preventing formation of ferrite and pearlite during cooling and contributing to ensuring the retained austenite.
  • Cr is preferably contained at 0.01% or greater. Even if Cr is excessively contained at greater than 1%, a cost increases. Moreover, since Cr significantly increases the strength of the austenite, a hot rolling load increases, and it is difficult to produce a steel plate. For this reason, it is not preferable that a Cr content exceeds 1%, considering the productivity.
  • the lower limit of the Cr content is more preferably 0.02% or greater (much more preferably 0.05% or greater), and the upper limit of the Cr content is more preferably 0.8% or less (much more preferably 0.5% or less).
  • B has the effect of increasing the hardenability and reducing ferrite transformation and pearlite transformation.
  • B is an element preventing formation of ferrite and pearlite during primary cooling after heating and contributing to ensuring the bainitic ferrite and the retained austenite.
  • B is preferably contained at 0.0002% or greater. If B is excessively contained, at greater than 0.01%, the effect thereof is saturated.
  • the lower limit of a B content is more preferably 0.0003% or greater (much more preferably 0.0005% or greater), and the upper limit of the B content is more preferably 0.008% or less (much more preferably 0.005% or less).
  • Ti produces the effect of improving the hardenability by fixing N and maintaining B at a solid solution state.
  • Ti is preferably contained at at least equal to or greater than four times as great as an N content [N]. However, if a Ti content becomes excessive and exceeds 0.1%, a great amount of TiC is formed. In addition, the strength increases due to precipitation strengthening, but the ductility is lowered.
  • the lower limit of the Ti content is more preferably 0.05% or greater (much more preferably 0.06% or greater), and the upper limit of the Ti content is more preferably 0.09% or less (much more preferably 0.08% or less).
  • N is an element capable of reducing a hardenability improvement effect by fixing B as BN
  • N is preferably reduced as much as possible.
  • the lower limit of the N content is preferably 0.001%. If the N content becomes excessive, coarse TiN particles are formed, and such TiN functions as a starting point for destruction to lower the ductility.
  • the upper limit of the N content is preferably 0.01%.
  • the upper limit of the N content is more preferably 0.008% or less (much more preferably 0.006% or less).
  • the basic chemical components in the press molded article of the present invention are as described above.
  • the residual substantially consists of iron can means, in addition to iron, not only a slight amount of components (e.g., Mg, Ca, Sr, Ba, REM such as La, and carbide-forming elements such as Zr, Hf, Ta, W, and Mo) not inhibiting the characteristics of the steel material of the present invention, but also inevitable impurities (e.g., O and H) other than P and S.
  • the press molded article of the present invention it is useful for the press molded article of the present invention to further contain, as necessary, (a) one or more selected from the group consisting of Cu, Ni, and Mo in the total amount of 1% or less (0% is not inclusive) and (b) at least one of V or Nb in the total amount of 0.1% or less (0% is not inclusive), for example.
  • the characteristics of the hot press molded article are further improved.
  • the preferable ranges of these contained elements and the reasons for limiting these ranges are as follows.
  • Cu, Ni, and Mo reduce ferrite transformation and pearlite transformation, Cu, Ni, and Mo effectively function to prevent formation of ferrite and pearlite during primary cooling and to ensure the retained austenite.
  • Cu, Ni, and Mo are preferably contained at the total amount of 0.01% or greater. Only considering characteristics, a great content is preferable. However, since the cost for alloy addition increases, the total amount is preferably 1% or less. Moreover, since Cu, Ni, and Mo have the effect of significantly increasing the strength of the austenite, a hot rolling load increases, and it is difficult to produce a steel plate. For this reason, it is preferable that the total amount is 1% or less, considering the productivity.
  • the lower limit of the total content of these elements is more preferably 0.05% or greater (much more preferably 0.06% or greater), and the upper limit of the total content of these elements is more preferably 0.9% or less (much more preferably 0.8% or less).
  • V and Nb have the effect of forming fine carbide particles and micronizing a structure by a pinning effect.
  • at least one of V or Nb is preferably contained at the total amount of 0.001% or greater.
  • the total content is preferably 0.1% or less.
  • the lower limit of the total content of these elements is more preferably 0.005% or greater (much more preferably 0.008% or greater), and the upper limit of the total content of these elements is more preferably 0.08% or less (much more preferably 0.06% or less).
  • the press molding conditions can be properly adjusted to control the characteristics, such as the strength and the elongation, of the molded article according to each molding region.
  • the hot press molded article can be obtained with a high ductility (a high residual ductility).
  • the present invention is also applicable to a portion (e.g., a member requiring both of shock resistance and energy absorption reduction) that has been difficult to apply in a conventional hot press molded article, and is significantly useful in enlargement of the scope of application of the hot press molded article.
  • the molded article of the present invention has a higher residual ductility as compared to that of a molded article whose structure is adjusted by typical annealing performed after cold press molding.
  • a steel material having a chemical component composition shown in Table 1 below was vacuum-fused, thereby forming an experimental slab. Then, after hot rolling was performed, the slab was cooled and rolled up. Further, cold rolling was performed, thereby forming a thin steel plate. Note that an AC3 transformation point, an Ms point, and (Bs point—100° C.) as shown in Table 1 were obtained using Expressions (1)-(3) described below (e.g., see “The Physical Metallurgy of Steels,” Maruzen Co., Ltd., 1985).
  • Ms point (° C.) 550 ⁇ 361 ⁇ [C] ⁇ 39 ⁇ [Mn] ⁇ 10 ⁇ [Cu] ⁇ 17 ⁇ [Ni] ⁇ 20 ⁇ [Cr] ⁇ 5 ⁇ [Mo]+30 ⁇ [Al] (2)
  • [C], [Si], [Mn], [P], [Al], [Ti], [V], [Cr], [Mo], [Cu], and [Ni] represent the contents (mass %) of C, Si, Mn, P, Al, Ti, V, Cr, Mo, Cu, and Ni, respectively. If an element(s) shown as each term in Expressions (1)-(3) is not contained, calculation is made without taking such an element(s) into consideration.
  • press molding was performed using a bending die having a hat channel shape (a HAT shape) illustrated in FIG. 2 .
  • a reference numeral “ 10 ” denotes an upper die (equivalent to the punch 1 illustrated in FIG. 1 )
  • a reference numeral “ 11 ” denotes a lower die (equivalent to the die 2 illustrated in FIG. 1 ).
  • a pad 12 is provided, and is configured such that press molding is performed with a steel plate 4 being interposed between the pad 12 and the upper 11 while pressure (pad pressure) is being applied (at a pad pressure of 9800 N).
  • the heating temperature and the average cooling rate in each steel plate region are shown in Table 2 below (the molding end temperature (a die-detaching temperature) was 200° C. in any of the regions).
  • the steel plate size in molding and cooling was 220 mm ⁇ 500 mm (a plate thickness of 1.4 mm) (the area ratio between the first steel plate region and the second steel plate region was 1:1).
  • the shape of a molded press molded article is illustrated in FIGS. 3( a ) and 3 ( b ) ( FIG. 3( a ) is a perspective view, and FIG. 3( b ) is a view schematically illustrating the cross section).
  • FIG. 3( a ) is a perspective view
  • FIG. 3( b ) is a view schematically illustrating the cross section).
  • a reference numeral “ 15 ” denotes the first steel plate region (corresponding to the first molding region of the molded article), and a reference numeral “ 16 ” denotes the second steel plate region (corresponding to the second molding region of the molded article).
  • “Average Cooling Rate 1 ” of the first steel plate region as shown in Table 2 is an average cooling rate from the heating temperature to (Ms point—50° C.) or lower (the molding end temperature)
  • “Average Cooling Rate 2 ” of the first steel plate region is an average cooling rate from the molding end temperature to 200° C. or lower.
  • a tensile strength (TS) and an elongation (a total elongation EL) were measured in the following manner, and metal structures (the fraction of each structure) were observed in the following manner.
  • evaluation was made as “successful” when (a) in the first region, the tensile strength (TS) satisfies 1500 MPa or greater and the elongation (the total elongation EL) satisfies 10% or greater and (b) in the second region, the tensile strength (TS) satisfies 1100 MPa or greater and the elongation (the total elongation EL) satisfies 15% or greater.
  • a retained austenite fraction (an area ratio) in the steel plate was measured in such a manner that after the steel plate was ground to the quarter of the thickness of the steel plate, chemical polishing was performed, and then, X-ray diffractometry was performed (e.g., ISJJ Int., Vol. 33, 1933, No. 7, P. 776).
  • the area ratio of the martensite was measured as follows. The steel plate was subjected to Repera corrosion. Then, the area ratio of a white contrast as the mixed structure of the as-quenched martensite and the retained austenite was measured by SEM observation. The retained austenite fraction obtained by X-ray diffractometry was subtracted from the area ratio of the white contrast, thereby measuring the as-quenched martensite fraction.
  • Test Nos. 2 and 4 were examples satisfying the requirements defined in the present invention, and the results show that in each of Test Nos. 2 and 4, the molded article exhibiting high performance, i.e., a high strength-ductility balance, in each region was obtained.
  • Test Nos. 1, 3, 5, and 6 were comparative examples not satisfying any of the requirements defined in the present invention, and any of the characteristics was lowered. That is, in Test No. 1, the stay time at (Bs—100° C.) to the Ms point was short in the second steel plate region, the fraction of the bainitic ferrite in the structure of the second region of the molded article was low, the fraction of the martensite in the structure of the second region of the molded article was high, and only a low elongation (a low total elongation EL) was obtained in the second region.
  • the press molded article of the present invention includes the first molding region exhibiting the metal structure which contains 80-97 area % of the martensite and 3-20 area % of the retained austenite and which has the residual structure at 5 area % or less; and the second molding region exhibiting the metal structure which contains 70-97 area % of the bainitic ferrite, 27 area % or less of the martensite, and 3-20 area % of the retained austenite and which has the residual structure at 5 area % or less.

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017137259A1 (fr) * 2016-02-09 2017-08-17 Schwartz Gmbh Procédé de traitement thermique et dispositif de traitement thermique
US20180361454A1 (en) * 2017-06-16 2018-12-20 Ford Global Technologies, Llc Method and apparatus for forming varied strength zones of a vehicle component
US11027522B2 (en) 2017-01-17 2021-06-08 Nippon Steel Corporation Steel sheet for hot stamping
US11103911B2 (en) 2015-12-09 2021-08-31 Arcelormittal Method for producing an automotive structural part comprising a lowerside sill and a lower front pillar
US11724338B2 (en) * 2020-11-24 2023-08-15 Hyundai Motor Company Hot-stamped article using a tailor welded blank method and a method of manufacturing the same

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016046593A1 (fr) * 2014-09-22 2016-03-31 Arcelormittal Élément de renfort pour un véhicule, procédé de production correspondant et ensemble porte
EP2998410A1 (fr) * 2014-09-22 2016-03-23 Autotech Engineering A.I.E. Procédé de traitement thermique au laser de pièces trempées sous presse
JP6428282B2 (ja) * 2015-01-15 2018-11-28 新日鐵住金株式会社 プレス成形品の製造方法
JP6589928B2 (ja) * 2017-04-13 2019-10-16 Ｊｆｅスチール株式会社 ホットプレス部材およびその製造方法
US20240044012A1 (en) 2021-04-08 2024-02-08 Nippon Steel Corporation Steel sheet for hot stamping and hot-stamped member
CN115255138B (zh) * 2022-08-12 2023-07-07 海盐恒欣宇模具有限责任公司 一种可微调模具冲头的冲压模具

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011179028A (ja) * 2010-02-26 2011-09-15 Sumitomo Metal Ind Ltd 成形品の製造方法
JP5327106B2 (ja) * 2010-03-09 2013-10-30 Ｊｆｅスチール株式会社 プレス部材およびその製造方法
EP2719786B1 (fr) * 2011-06-10 2016-09-14 Kabushiki Kaisha Kobe Seiko Sho Article moulé par pressage à chaud, procédé pour produire celui-ci, et tôle d'acier mince pour moulage à la presse à chaud
KR20140027451A (ko) * 2011-06-10 2014-03-06 가부시키가이샤 고베 세이코쇼 열간 프레스 성형품, 그 제조 방법 및 열간 프레스 성형용 박강판
CN102304612B (zh) * 2011-09-20 2013-07-17 山东建筑大学 超高强钢高温拼接淬火成形工艺及装置
JP5890710B2 (ja) * 2012-03-15 2016-03-22 株式会社神戸製鋼所 熱間プレス成形品およびその製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
English language machine translation of JP 2011179028 to Uematsu et al. Generated 1 September 2017. *

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US11103911B2 (en) 2015-12-09 2021-08-31 Arcelormittal Method for producing an automotive structural part comprising a lowerside sill and a lower front pillar
WO2017137259A1 (fr) * 2016-02-09 2017-08-17 Schwartz Gmbh Procédé de traitement thermique et dispositif de traitement thermique
US11230746B2 (en) 2016-02-09 2022-01-25 Schwartz Gmbh Heat treatment method and heat treatment apparatus
US11027522B2 (en) 2017-01-17 2021-06-08 Nippon Steel Corporation Steel sheet for hot stamping
US20180361454A1 (en) * 2017-06-16 2018-12-20 Ford Global Technologies, Llc Method and apparatus for forming varied strength zones of a vehicle component
US11141769B2 (en) * 2017-06-16 2021-10-12 Ford Global Technologies, Llc Method and apparatus for forming varied strength zones of a vehicle component
US11724338B2 (en) * 2020-11-24 2023-08-15 Hyundai Motor Company Hot-stamped article using a tailor welded blank method and a method of manufacturing the same

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