WO2012026591A1 - Procédé pour le traitement thermique d'un matériau de structure et matériau de structure traité thermiquement - Google Patents

Procédé pour le traitement thermique d'un matériau de structure et matériau de structure traité thermiquement Download PDF

Info

Publication number
WO2012026591A1
WO2012026591A1 PCT/JP2011/069324 JP2011069324W WO2012026591A1 WO 2012026591 A1 WO2012026591 A1 WO 2012026591A1 JP 2011069324 W JP2011069324 W JP 2011069324W WO 2012026591 A1 WO2012026591 A1 WO 2012026591A1
Authority
WO
WIPO (PCT)
Prior art keywords
structural material
rate
heat treatment
stress
volume fraction
Prior art date
Application number
PCT/JP2011/069324
Other languages
English (en)
Japanese (ja)
Inventor
卓也 桑山
鈴木　規之
康信 宮崎
川崎　薫
繁 米村
Original Assignee
新日本製鐵株式会社
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 新日本製鐵株式会社 filed Critical 新日本製鐵株式会社
Priority to EP11820051.8A priority Critical patent/EP2610355B1/fr
Priority to CN201180041017.6A priority patent/CN103069021B/zh
Priority to JP2012513793A priority patent/JP5130498B2/ja
Publication of WO2012026591A1 publication Critical patent/WO2012026591A1/fr

Links

Images

Classifications

    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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
    • C21D1/06—Surface hardening
    • C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
    • 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
    • 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

Definitions

  • the present invention relates to a heat treatment method for a structural material and a heat treated structural material.
  • a tubular press-formed product having a polygonal cross section is often used as a structural material for automobiles and the like.
  • a structural material is roughly used for two purposes.
  • One is a structural material that constitutes, for example, an engine compartment, a trunk room, and the like, and is a structural material that acts to crush and absorb impact energy when an automobile or the like collides.
  • the other is a structural material that constitutes, for example, a cabin or the like, and is a structural material that can be prevented from being deformed from the viewpoint of securing a living space for a passenger even when an automobile or the like collides.
  • the laser heat treatment means that an untreated structural material is irradiated with a laser beam having a high energy density to locally heat the structural material to a temperature equal to or higher than the transformation temperature or the melting point, and then quench hardening is performed by a self-cooling action. Means to do.
  • Patent Document 1 discloses a technique for increasing the strength of a press-formed product by performing local heat treatment on the press-formed product with a laser. Specifically, in Patent Document 1, after cold forming a steel sheet, a laser beam is rapidly heated to a predetermined temperature or higher in a stripe shape or a lattice shape, and then cooled to strengthen the cold-formed press-formed product. is doing. By adopting such a method, the occurrence of distortion after heat treatment is suppressed as compared with the case where the entire press-formed product is uniformly heat-treated. In particular, in the technique disclosed in Patent Document 1, laser heat treatment is performed in the form of stripes in the longitudinal direction on the outer surface of the press-molded product or in a grid pattern on the entire outer surface of the press-molded product.
  • Patent Document 2 discloses that a local heat treatment is performed on the press-formed product for the purpose of increasing the strength of the press-formed product while suppressing the occurrence of distortion.
  • heat treatment is performed on a portion where the strength of the press-formed product is required, for example, a high stress portion analyzed by a vehicle crash test, a finite element method, or the like.
  • laser heat treatment is performed in a stripe shape or a lattice shape so as to extend over the entire length in the longitudinal direction of the press-formed product.
  • Patent Document 3 discloses a method of performing laser heat treatment after controlling the components contained in the steel plate to be subjected to laser heat treatment to a specific component, whereby the laser heat treatment was performed while maintaining the workability of the steel plate. Increase the strength of the location. Also in the method disclosed in Patent Document 3, laser heat treatment is performed on a portion where the strength needs to be increased. Specifically, the laser heat treatment is performed in a linear shape extending over the entire length in the longitudinal direction of the press-formed product. Is going.
  • Patent Document 4 discloses a method of performing a laser heat treatment linearly along the load direction of a compressive load on the outer peripheral surface of a press-formed product for the purpose of increasing the impact energy absorption capability of the press-formed product. According to such a method, since the laser heat treatment is performed in the same direction as the input direction of the impact load, the resistance to deformation can be increased and the crushing mode can be made regular. In particular, in the technique disclosed in Patent Document 4, laser heat treatment is continuously performed over the entire length in the longitudinal direction of the press-formed product along the direction of the compression load.
  • laser heat treatment is performed on a portion of the outer surface of the press-formed product that requires strength. Specifically, the laser heat treatment is performed in a linear shape continuously extending over the entire length in the longitudinal direction of the press-formed product, or the laser heat treatment is performed in a lattice shape or the like over the entire outer surface of the press-formed product.
  • FIG. 1 shows the axial compressive stress ⁇ x and compressive strain ⁇ x (longitudinal length of the cylindrical structural material when the cylindrical structural material receives a compressive load in the axial direction (x direction).
  • the relationship with the amount of deformation in the longitudinal direction) is schematically shown.
  • ⁇ 1 , ⁇ 2, and ⁇ 3 in the figure indicate peak stresses, and a region indicated by diagonal lines W indicates the amount of energy absorbed by the structural material.
  • ⁇ 1 indicates the initial peak stress.
  • structural materials used in automobiles and the like include a structural material that absorbs impact energy in the event of a collision (hereinafter referred to as “impact absorbing structural material”), and its deformation is suppressed in the event of a collision.
  • structural materials hereinafter referred to as “structural materials for suppressing deformation”.
  • structural materials for suppressing deformation in the structural material for absorbing shock, it is necessary to make the absorbed energy amount W as large as possible and to make the initial peak stress ⁇ 1 relatively small.
  • the structural material for suppressing deformation in the structural material for suppressing deformation, it is necessary to make the initial peak stress ⁇ 1 as large as possible. This is because if the initial peak stress ⁇ 1 is increased, the structural material is less likely to buckle even when a large stress is applied to the structural material. Therefore, it is necessary to perform laser heat treatment on the deformation-suppressing structural material so that the initial peak stress ⁇ 1 becomes large.
  • the object of the present invention is to sufficiently improve the deformation suppressing ability by locally curing the structural material by performing a heat treatment on an untreated structural material. It is to provide a structural material.
  • the inventors of the present invention have a region (location or amount) for performing heat treatment on the untreated structural material, The relationship between the ability to suppress deformation of structural materials, especially the initial peak stress, was investigated.
  • a heat treatment method for a structural material according to one aspect of the present invention includes a bent portion that extends in one direction of the structural material and is bent in a direction perpendicular to the one direction.
  • An effective width e of the bent portion is determined; and an area including the bent portion whose distance from the bent portion in a direction perpendicular to the one direction is within the effective width e is defined as an effective width region.
  • the value of the hardening rate f M may be a value when it is zero.
  • the work hardening coefficient E h calculated based on the change ratio to be equal to or greater than the predetermined value, it determines the range of the hardening rate f M May be.
  • the predetermined value may be a work hardening coefficient E h when the hardening rate f M is 1.
  • the difference of .DELTA..sigma h between flow stress when the curing rate f M and the flow stress when the curing rate f M is 1 is 0
  • the difference between the yield stress when the curing rate f M is 1 and the yield stress when the curing rate f M is 0 is defined as ⁇ Y
  • the rate of change is defined as b
  • the curing rate f The range of M may be f M-min or more and less than 1 represented by the following formula (1).
  • the range of the curing rate f M may be f M-max or less represented by the following formula (2).
  • the equal boundary hardening rate f M and the rate of change of flow stress sigma h determined in f M-max the rate of change with respect to the curing rate f M it may determine the extent of the curing rate f M on the basis of the f M-max.
  • the range of the hardening rate f M may determine the range satisfying the following formula (3).
  • the range of the curing rate f M may be determined to be f M-min that satisfies the following formula (4) and less than 1.
  • the difference between the flow stress when the curing rate f M is 1 and the flow stress when the cure rate f M is 0 is defined as ⁇ h. when, as the difference between the change rate this .DELTA..sigma h is equal to or less than a predetermined value, it may determine the extent of the curing ratio f M.
  • the region cured by the heat treatment is represented by the following formula: It may be a region equal to or higher than the Vickers hardness calculated by (5) and (6).
  • the heat treatment may be performed by a laser.
  • one pass of the heat treatment may be continuously performed over the entire length in the one direction.
  • the heat-treated structural material according to one aspect of the present invention is a structural material including a bent portion that extends in one direction of the structural material and is bent in a direction perpendicular to the one direction.
  • a region including the bent portion whose distance from the bent portion in a direction perpendicular to the one direction is within the effective width e is defined as an effective width region, and a ratio of the effective width region occupied by a region cured by heat treatment the when defined as hardening rate f M, the curing rate f M is less than 1, and, in the range of curing rate f M which is determined based on the rate of change of the yield stress sigma Y for hardening rate f M included.
  • the value of the hardening rate f M may be a value when it is zero.
  • the range of the hardening rate f M is the rate of change work hardening coefficient E h calculated based on are determined to be equal to or greater than the predetermined value Range may be used.
  • the predetermined value may be a work hardening coefficient E h when the hardening rate f M is 1.
  • the difference between the flow stress when the curing rate f M is 1 and the flow stress when the curing rate f M is 0 is ⁇ h
  • the difference between the yield stress when the curing rate f M is 1 and the yield stress when the curing rate f M is 0 is defined as ⁇ Y
  • the rate of change is defined as b
  • the curing rate f The range of M may be f M-min or more represented by the following formula (7).
  • the range of the curing rate f M may be f M-max or less represented by the following formula (8).
  • each flow stress may be defined as a proof stress when 5% plastic strain occurs.
  • the width dimension perpendicular to the one direction is w
  • the yield stress when the hardening rate f M is 0 is ⁇ Y0
  • the one direction of the structural material When the stress at each position in the width direction perpendicular to the one direction when the stress that gives the maximum stress of ⁇ Y0 toward the one direction is defined as ⁇ x , the effective width e May be defined by the following formula (9).
  • the effective width e may be defined by the following formula (10).
  • the effective width e may be defined by the following formula (11).
  • the region cured by the heat treatment is represented by the following formula: The area
  • the heat treatment may be performed by a laser.
  • the structure material is locally hardened.
  • the value of the elastic-plastic buckling stress ⁇ p, Cr corresponding to the initial peak stress ⁇ 1 of bending can be obtained, and the volume fraction of the hardened region in the effective width region that maximizes the elastic-plastic buckling stress ⁇ p, Cr The rate can be presented properly.
  • an appropriate deformation suppression guideline can be given.
  • the volume fraction of the hardened region in the effective width is appropriately presented from the characteristic value of the test piece without evaluating the structure. be able to.
  • the volume fraction of the hardened region in the effective width can be appropriately presented with as few evaluation pieces as possible.
  • FIG. 1 It is the figure which showed typically the relationship between the compressive stress and compressive strain of an axial direction when a cylindrical structural material receives the compressive load in the axial direction.
  • FIG. 1 It is a perspective view which shows an example of the structural material to which the heat processing method of the structural material which concerns on one Embodiment of this invention is applied.
  • FIG. It is a cross-sectional view of the structural material shown in FIG.
  • FIG. is a cross-sectional view of the structural material of another example.
  • the volume fraction of the hardened zone in the heat treatment method of a structural material according to the present embodiment is a flow chart illustrating an example of a method of determining the range (hardening rate) f M.
  • the volume fraction of the hardened zone in the heat treatment method of a structural material according to the present embodiment is a flow chart illustrating an example of a method of determining the range (hardening rate) f M.
  • the volume fraction of the hardened zone in the heat treatment method of a structural material according to the present embodiment is a flow chart illustrating an example of a method of determining the range (hardening rate) f M.
  • the heat processing method of the structural material which concerns on one Embodiment of this invention is demonstrated.
  • the heat treatment is performed on the structural material including a bent portion that extends in one direction of the structural material and is bent in a direction perpendicular to the extending direction.
  • the distance in the direction perpendicular to the extending direction of the bent portion is within the effective width, which corresponds to a predetermined ratio (that is, effective rate) of the region in the structural material including the bent portion (that is, the effective width region).
  • Part is cured.
  • the rate of change of yield stress (yield strength) with respect to the proportion of the effective width region that is cured by heat treatment ie, the rate of cure
  • the rate of cure varies depending on the rate of cure
  • the amount of change (change) Is greater than the amount of change (the degree of change) in the rate of change of the flow stress relative to the cure rate. Therefore, the work hardening rate of the effective width region necessary for increasing the initial peak stress (deformation suppressing ability) of the structural material is affected by the rate of change of the yield stress with respect to the hardening rate.
  • the heat treatment cost is reduced by performing heat treatment on the effective width region that mainly bears the load applied to the structural material so as to satisfy the range of the hardening rate determined based on the rate of change of the yield stress with respect to the hardening rate. While being reduced, the ability to suppress deformation of the structural material can be increased.
  • the flow stress is a stress generated at the time when the elastic limit is exceeded and the fluid deformation is shifted and after that time.
  • a hardening rate may be described as a volume fraction.
  • the effective width for the bent portion is determined (S2), and the yield stress with respect to the hardening rate.
  • a curing rate range is determined based on the change rate (S3), and heat treatment is performed on the effective width region of the structural material so as to satisfy the curing rate range (S4).
  • the effective width can be determined from the definition formula of the effective width of Expression (14) described later or various expressions derived from this definition expression.
  • the range of the curing rate can be determined using the rate of change of yield stress with respect to at least one curing rate.
  • the range of the curing rate can be determined based on the curing rate when the change rate of the yield stress with respect to the curing rate satisfies a predetermined condition.
  • FIG. 2 is a perspective view showing an example of a structural material to which the structural material heat treatment method according to this embodiment is applied.
  • 3 is a cross-sectional view of the structural material in a cross section perpendicular to the longitudinal direction of the structural material shown in FIG.
  • the structural member 10 includes a flat plate portion 11 (11a to 11e) extending in the longitudinal direction and a plurality of bent portions 12 (12a to 12d) extending in the longitudinal direction between the flat portions 11. ). That is, as shown in FIG. 3, the structural member 10 includes five flat portions 11a to 11e and four bent portions 12a to 12d provided between the flat portions 11a to 11e.
  • the structural material 10 is used for a part of a frame of a vehicle such as an automobile, for example, and is particularly used in a place where it is necessary to suppress the deformation when the automobile collides. Therefore, for example, taking an automobile frame as an example, the structural member 10 is preferably used for a frame constituting a cabin or the like.
  • the structural material 10 when the structural material 10 is used for a part of a frame of a vehicle such as an automobile, the structural material 10 is welded to another flat structural material 20 as shown by a one-dot chain line in FIGS. Are used. For this reason, of the five flat portions 11a to 11e of the structural material 10, the flat portions 11a and 11e provided at both edges of the structural material 10 are formed in a flange shape. When the structural material 10 is welded to another structural material 20, the flat portions 11 a and 11 e are welded to the other structural material 20.
  • the structural member 10 includes five flat portions 11a to 11e and four bent portions 12a to 12d provided between the flat portions 11a to 11e.
  • the structural material has any shape as long as it has at least one bent portion that extends in one direction (for example, the longitudinal direction) and is bent in a direction perpendicular to the extending direction.
  • it may have a cross-sectional shape as shown in FIGS. 4A to 4C.
  • the structural member 10 ′ includes four flat portions 11 and three bent portions 12 provided between the flat portions 11, and among these, the cross-sectional shape is located on both edges.
  • the flat portion 11 that functions serves as a flange for connecting the structural member 10 ′ to another flat plate-shaped structural member (not shown).
  • the structural member 10 '' includes five flat portions 11 and four bent portions 12 provided between the flat portions 11, and among these, the cross-sectional shape is on both edges.
  • the positioned flat portion 11 functions as a flange for connecting the structural member 10 '' with another flat plate-shaped structural member (not shown).
  • the structural member 10 ′ ′′ includes four flat portions 11 and four bent portions 12 provided between the flat portions 11 so that the cross-sectional shape thereof is a quadrangle. To do.
  • the structural material 10 does not necessarily extend linearly in the longitudinal direction, and may be curved or bent as shown in FIG. 5, for example.
  • a direction along the curve and the bend is referred to as a longitudinal direction. Therefore, in the example shown in FIG. 5, the alternate long and short dash line Z in the figure indicates the longitudinal direction of the structural material 10.
  • the flat portion means a portion of the structural material whose cross section is a straight line (strip shape).
  • a bending part means the part of the linear structural material formed by the intersection of the extension direction of two flat parts adjacent in the cross section of a structural material.
  • a heat treatment (here, laser heat treatment is performed as an example) is performed on a specific portion of the untreated structural material 10 formed into the shape as described above.
  • a laser heat treatment apparatus such as a carbonic acid laser, a YAG laser, or a fiber laser is used.
  • the depth in the plate thickness direction of the region to be hardened by laser heat treatment is hardened to a depth of at least 10% of the plate thickness from the laser light irradiation surface. Further, it is desirable to control the depth in the plate thickness direction of the region to be hardened by laser heat treatment to be less than 90% of the plate thickness from the laser light irradiation surface.
  • the stress acting on the thin plate is non-uniformly distributed in the cross-section (plate width direction) of the thin plate perpendicular to the direction in which the compressive load is applied.
  • the longitudinal direction (x direction) applied to the cross section a stress sigma x of) are distributed as shown in Figure 6B.
  • FIG. 6A shows a thin plate having a width w as shown in FIG. 6A and the thin plate is deformed out of plane by elastic buckling.
  • This effective width e can be expressed by the following equation (16) using the elastic modulus E, Poisson's ratio ⁇ , and thickness t of the thin plate, particularly when the yield stress ⁇ Y0 of the thin plate is uniformly distributed.
  • the effective width e can be expressed as in the following formula (17).
  • the effective width e represented by the above formulas (16) and (17) is a theoretical value, and it has been proved that the experimental result and the yield phenomenon differ greatly depending on the conditions when this theoretical value is used. Therefore, considering the experimental result, the effective width e is defined as in the following formulas (18A) and (19), for example.
  • ⁇ is a slenderness factor, and is determined as Equation (20) when the yield stress ⁇ Y0 of the thin plate is uniformly distributed in the portion of the effective width e.
  • k means a flat plate buckling coefficient.
  • the effective width e there are various definitions other than the above formula (18A) as in the following formula (18B). In the heat treatment method for a structural material according to the present embodiment, these various types are defined. Any of the definitions may be used. Also, the stress distribution in the thin plate width direction (that is, the stress distribution shown in FIG. 6B) when the thin plate is buckled by receiving a compressive load is calculated by numerical analysis (for example, numerical integration such as the finite element method). The effective width e that satisfies the above equation (14) may be calculated from the stress distribution thus calculated.
  • the region mainly responsible for the compressive load in each flat portion 11 extends from the bent portion 12 in the width direction (that is, the structural material 10 This is a region whose distance in the direction perpendicular to the longitudinal direction is within the effective width e.
  • a region that is, a region including a bent portion whose distance in the width direction from a certain bent portion is within the effective width e is referred to as an effective width region.
  • This effective width area (effective width area 15 in FIGS. 2 and 3) is indicated by hatching in FIG. 2, and is filled in FIG.
  • an untreated structural material (a bent portion of the structural material) having at least one bent portion as shown in the bent portion 12 (12a to 12d) in FIG.
  • the effective width is determined for.
  • heat treatment here, laser heat treatment is taken as an example
  • the proportion of the effective width region occupied by the region where the laser heat treatment is performed will be described.
  • FIG. 7 shows a true stress-true plastic strain diagram of a steel sheet having a tensile strength of 440 MPa.
  • the work hardening coefficient E h is expressed by the following formula (21).
  • ⁇ p represents the strain (plastic strain) after the yield of the steel sheet
  • ⁇ h represents the stress when the plastic strain is ⁇ p .
  • ⁇ h is described as the stress when the plastic strain ⁇ p is 1%. As shown in these figures, ⁇ h may be determined from the stress when the plastic strain ⁇ p is 1%.
  • Elastic-plastic buckling phenomenon such steel have been proposed are theoretical formula representing the elastic-plastic buckling stress sigma p, Cr as a function of work hardening coefficient E h, elastoplastic buckling stress sigma p, Cr Is represented, for example, by the following formula (22).
  • w is the width of the steel plate
  • t is the thickness of the steel plate
  • k is a coefficient corresponding to the plate shape and the like.
  • the elastoplastic buckling stress ⁇ p, Cr increases in proportion to the work hardening coefficient E h .
  • the initial peak stress ⁇ 1 shown in FIG. 1 is considered to have the same tendency as the elastoplastic buckling stress ⁇ p, Cr , the initial peak stress ⁇ 1 is also proportional to the work hardening coefficient E h. Will increase.
  • the said Formula (22) represents the elastic-plastic buckling stress (sigma) p, Cr in the steel plate as shown to FIG. 6A, and the elastic-plastic seat regarding the structural material which has a polygonal cross section as shown in FIG. It does not represent the bending stress ⁇ p , Cr .
  • the elastic-plastic buckling stress ⁇ p, Cr increases in proportion to the work hardening coefficient E h . Accordingly, it is considered that the initial peak stress ⁇ 1 increases in proportion to the work hardening coefficient E h also in the cylindrical shell.
  • FIG. 8 shows a true stress-true strain diagram of an untreated steel sheet having a tensile strength of 440 MPa class and a material heat-treated (quenched) on the whole steel sheet having a tensile strength of 440 MPa class.
  • the solid line in FIG. 8 shows the true stress-true strain diagram of the untreated steel sheet, and the broken line shows the true stress-true strain diagram of the steel sheet after heat treatment.
  • the work hardening coefficient E h0 of the untreated steel sheet is It can be expressed as in equation (24) (see FIG. 9A).
  • ⁇ Y0 is the yield stress of the untreated steel plate
  • ⁇ Y0 is the true strain of the untreated steel plate when the yield stress is reached
  • ⁇ h0 is a predetermined true strain greater than ⁇ Y0
  • ⁇ h0 Indicates the stress (corresponding to the flow stress described later) of the untreated steel plate when the true strain is ⁇ h0 .
  • the work hardening coefficient E hM of the steel plate after the heat treatment can be expressed as the following formula (25) (see FIG. 9B).
  • ⁇ YM is the yield stress of the steel plate after heat treatment
  • ⁇ YM is the true strain of the steel plate after heat treatment when the yield stress is reached
  • ⁇ hM is a predetermined true strain greater than ⁇ YM
  • ⁇ hM Indicates the stress (corresponding to the flow stress described later) of the steel sheet after the heat treatment when the true strain is ⁇ hM .
  • the initial peak stress ⁇ 1 is larger between the untreated steel sheet and the steel sheet that has been heat-treated as a whole.
  • the ratio of heat-treating the steel sheet that is, the ratio of the region hardened to a predetermined hardness or higher by the heat treatment (hereinafter referred to as “cured region”) with respect to the entire steel plate.
  • the present inventors have determined that the volume fraction f M and the work hardening coefficient of the steel sheet after partial hardening when the volume fraction (hardening ratio) f M of the hardening region with respect to the entire steel sheet is changed from 0 to 100%.
  • the following findings were obtained.
  • the obtained knowledge will be described in detail.
  • the proof stress ⁇ h of the steel sheet when a plastic strain of 5% occurs can be approximated by a straight line with respect to the volume fraction f M. This is because when a certain degree of finite plastic strain is applied to the entire steel sheet, the plastic strain acts almost equally in both the hardened area and the non-hardened area (the area of the steel sheet other than the hardened area, ie, the untreated area). It is to do.
  • yield strength sigma h after the plastic strain 5% impart to the volume fraction f M of the hardened region can be expressed as the following equation (26) as a function of the volume fraction f M.
  • the yield strength of the steel plate is achieved.
  • the relationship between ⁇ h and the volume fraction f M of the hardened region can be expressed sufficiently accurately.
  • the yield stress ⁇ Y is approximated by a quadratic function of the volume fraction f M of the hardening region
  • the yield stress ⁇ Y ( ⁇ Y (f M )) is expressed as a function of the volume fraction f M as follows. It can be expressed as equation (29).
  • equation (29) a, b, and c are constants.
  • the constant b in the equation (29) is expressed by the following equation (30) Can do. That is, the constant b can be approximated by the change gradient of yield stress ⁇ Y (f M) with respect to the volume fraction f M when the volume fraction f M of the hardened zone is zero.
  • the work hardening coefficient E h is a function of the volume fraction f M of the hardening region, that is, the following equation (31) ).
  • the plastic strain ⁇ p is 0.05
  • the yield stress ⁇ YM of the hardened region is 794 MPa
  • the yield stress ⁇ Y0 of the non-hardened region is 301 MPa
  • the yield strength ⁇ hM of the hardened region when the plastic strain ⁇ p is applied Assuming that the proof stress ⁇ h0 of the uncured region when applying the plastic strain ⁇ p is 447 MPa and b is 350 MPa, ⁇ h (f M ) calculated by the equation (26) and ⁇ calculated by the equation (29) Y (f M ) can be expressed as shown in FIG. At this time, the work hardening coefficient E h (f M ) calculated by the equation (31) can be expressed as shown in FIG.
  • the yield stress ⁇ Y is approximated by a quadratic function of the volume fraction f M of the hardened region (a function convex downward when the volume fraction f M is in the range of 0 to 1).
  • the work hardening coefficient E h (f M ) can also be expressed as a quadratic function of the volume fraction f M of the hardened region (a function convex upward when the volume fraction f M is in the range of 0 to 1). . Therefore, as can be seen from FIG. 12, the work hardening coefficient E h (f M ) becomes maximum at a specific volume fraction f M-max .
  • volume fraction f M of the hardened area may work hardening coefficient E h (f M) is higher than the work hardening coefficient when the volume fraction f M of the hardened zone is 1 (100%) Exists.
  • work hardening coefficient E h is the volume fraction f M of the hardened regions is 1 (100%)
  • work hardening coefficient E h (f M 1) or more.
  • the initial peak stress when the volume fraction f M of the cured region is f M-min ⁇ 1 is 1 (100%) when the volume fraction f M of the cured region is 1 (100%). In some cases (that is, when the entire effective width is heat-treated), the initial peak stress is exceeded.
  • laser heat treatment is used as the heat treatment for locally hardening a part of the steel sheet.
  • the larger the treatment area the greater the amount of energy consumed, thus increasing the manufacturing cost.
  • it is preferable that the region where the laser heat treatment is performed is as narrow as possible.
  • the work hardening coefficient E h is obtained when the volume fraction f M of the hardened region is 1 (100%).
  • the minimum volume fraction f M-min is expressed by the following equation (32).
  • the minimum volume fraction f M-min is 53.3%.
  • the constants b and ⁇ h are 0 ⁇ b ⁇ 2 ⁇ Y ⁇ h and ⁇ Y ⁇ h ⁇ 2 ⁇ . It is necessary to satisfy Y.
  • the work hardening coefficient E h (f M ) that is, the initial peak stress becomes maximum at a specific volume fraction f M-max .
  • the volume fraction f M of the cured region is set to the volume fraction when the work hardening coefficient E h (f M ) is maximized. It is preferable to control to a rate f M-max or less.
  • the steel sheet peak stress (structural member) from the viewpoint of maximizing the volume fraction f M of the hardened region, the work hardening coefficient E h (f M) the volume fraction of the time that maximizes f M- It is preferable to control to max . Therefore, even if the volume fraction f M of the hardening region is controlled to the volume fraction f M-max (hereinafter referred to as “maximum volume fraction”) when the work hardening coefficient E h (f M ) becomes maximum. Good.
  • the maximum volume fraction f M-max is expressed by the following equation (33).
  • the maximum volume fraction f M-max is 76.6%.
  • the constants b and ⁇ h are 0 ⁇ b ⁇ h and 0 ⁇ b ⁇ Y It is necessary to satisfy.
  • the relationship between the volume fraction f M and the initial peak stress or work hardening coefficient E h of the hardened region described above a relationship obtained for steel sheets, for example, structural materials having a shape as shown in FIG. 2 It is not the relationship obtained for 10.
  • the region that mainly bears the compressive load is the effective width region 15, and each effective width region 15 is regarded as a steel plate having a width of 2 ⁇ e. be able to. Therefore, the volume fraction f M of the hardened region in such an effective width region, that is, the ratio of the effective width region to the region where the hardening process (for example, laser heat treatment) is performed is set by the method described above. Can do.
  • the volume fraction f M of the cured region in each effective width region 15 is not less than f M-min represented by the above equation (32) and not more than f M-max represented by the above equation (33).
  • laser heat treatment is performed.
  • the yield strength of the heat treatment region (hardened region) at the time of applying the predetermined strain the yield strength of the untreated region (non-hardened region) at the time of the given strain, the yield stress of the heat treated region (hardened region), and the untreated region ( It shows the yield stress in the non-hardened region.
  • ⁇ hM , ⁇ h0 , ⁇ YM and ⁇ Y0 are parameters related to a material (ste).
  • the volume fraction f M of the hardened areas in the effective width region 15 by setting in this manner, while reducing the area to be laser heat treatment, it is possible to increase the initial peak stress of the structural member 10.
  • the volume fraction f M of the hardened areas in the effective width region 15 is controlled below f M-min or more and f M-max, the volume fraction f M of the hardened zone, as described above May be controlled to f M-min or more and 1 (100%) or less or less than 1.
  • the volume fraction f M of the hardened region in each effective width region 15 is greater than the work hardening coefficient when the work hardening coefficient E h of the effective width region 15 is hardened by laser heat treatment over the entire effective width region 15. It can be determined that the setting is made.
  • the volume fraction f M of the hardened areas in the effective width region 15 may be controlled to f M-max as described above.
  • the volume fraction f M based on the rate of change of the yield stress sigma Y for the volume fraction f M when the volume fraction f M of the hardened area is 0 (constant) b as shown in FIG. 17 determines the minimum value of (S311), the maximum value of the range of the volume fraction f M by determining (S312) that the 1 or less or less than 1, determining the range of the volume fraction f M of the hardened region it can.
  • an example of a method of determining the constant b to determine the range of the volume fraction f M of the hardened area above As a first method, a tensile test is performed on three samples in which the volume fraction f M of the hardened region of the steel sheet is 0, 1, and any value greater than 0 and less than 1 (for example, 0.5), The constants a, b, and c can be determined by obtaining the yield stress ⁇ Y of these samples and performing the least square method. Further, as a second method, a tensile test is performed on two samples in which the volume fraction f M of the hardened region of the steel sheet is 0 and an arbitrary value (for example, 0.1) sufficiently close to 0 exceeding 0.
  • the yield stress ⁇ Y of these samples can be obtained, and the rate of increase of the yield stress ⁇ Y with respect to the volume fraction f M of the hardened region can be determined as a constant b.
  • the method for determining the constant b with the minimum number of data (the number of data of the yield stress ⁇ Y ) as a simple method has been described, but the upper limit of the number of data is not particularly limited. As the number of data is large, the range of the volume fraction f M can be determined with higher accuracy.
  • the yield stress ⁇ Y and the proof stress ⁇ h are measured by performing a tensile test according to JIS Z2241 on a JIS No. 5 test piece (test piece) taken from a steel plate (no heat treatment and bending) used for the structural material. can do.
  • a test piece obtained by subjecting the above test piece to a predetermined heat treatment may be used.
  • the predetermined heat treatment is performed in the longitudinal direction of the test piece.
  • the above-described tensile test may be performed by performing laser heat treatment under corresponding conditions. In this case, pulling the volume fraction f M of the hardened region was measured after the test, may be determined corresponding relationship between the volume fraction f M and yield stress sigma YM and yield strength sigma hM.
  • the volume fraction f M of the hardened region of the can be determined by the following method. For example, the area of the hardened region in a cross section perpendicular to the longitudinal direction of the test piece is measured, and the volume of the hardened region is obtained by multiplying this area by the length (total distance) after laser heat treatment. it can be determined the volume fraction f M of the hardened region by dividing the total volume of the test piece.
  • the area of the hardened region may be determined from the quenched structure observed with an optical microscope for the cross section perpendicular to the longitudinal direction of the test piece, and determined by obtaining the Vickers hardness using a Vickers hardness meter as described later. You may do it.
  • the relationship between the yield strength sigma h of the steel sheet and the volume fraction f M of the hardened region was expressed by a linear function, and the yield stress of the steel sheet sigma Y It expressed in relation to a quadratic function of the volume fraction f M of the hardened zone, but it is not always necessary to use these functions.
  • the rate of change of the yield stress versus the volume fraction f M of the hardened area changes according to the volume fraction f M of the hardened region
  • the amount of change may be utilized larger than the variation of the rate of change of flow stress versus the volume fraction f M of the hardened zone (degree of change).
  • the relationship between the yield stress ⁇ Y of the steel sheet and the volume fraction f M of the hardening region is expressed by an arbitrary function ⁇ Y (f M ), and the rate of change of the yield stress with respect to at least one hardening rate (2 If the next function, it is possible to determine the range of the volume fraction f M of the hardened region by using the equivalent) to the above-described constant b.
  • ⁇ Y (f M ) can also be expressed by a function including the constant b described above.
  • the relationship between the proof stress ⁇ h of the steel sheet and the volume fraction f M of the hardened region may be expressed by an arbitrary function ⁇ h (f M ).
  • the maximum volume fraction f M-max can be determined so as to satisfy the following formula (36).
  • the maximum volume fraction (boundary hardening rate) f M-max is used, for example.
  • equation (37) may determine the range of the volume fraction f M of the hardened zone in any of a range of - (40).
  • the range of the volume fraction f M of the hardened zone as in the above formula (37) to (41), stable with excellent balance between improved deformation suppressing capability of reducing the structural material cost of the heat treatment Heat treatment can be performed.
  • the range of the volume fraction f M of the hardened region, the correction term, including the cost and heat treatment conditions and the like may be included as appropriate upper and lower limits.
  • the work hardening coefficient E h (volume fraction f M and work hardening coefficient E is based on the rate of change of the yield stress ⁇ Y with respect to the volume fraction f M of the hardening region. estimating or calculating the relationship between h) (S301), so the estimated or calculated work hardening coefficient E h is equal to or greater than a predetermined value may be determined the range of the volume fraction f M (S302) . For example, the difference between the work hardening coefficient E h when the volume fraction f M is 1 and the work hardening coefficient E h when the volume fraction f M is f M ⁇ max is ⁇ E h , 0 or more and 1 or less.
  • this predetermined value may be the work hardening coefficient E h when the volume fraction f M of the hardening region is 1.
  • another work hardening index including at least the yield stress ⁇ Y as a variable may be used.
  • the relationship between the yield strength ⁇ h of the steel sheet and the volume fraction f M of the hardened region is expressed by a linear function, and the relationship between the yield stress ⁇ Y of the steel plate and the volume fraction f M of the hardened region is expressed by a quadratic function. Then, it is possible to determine the range of the volume fraction f M of the most conveniently cured area. In this case, instead of the constant b, it can be determined the range of the volume fraction f M of the hardened region by using the constant a, the constant a as shown in the following formula (42) with a constant b Since it can be expressed (constant a is a dependent variable of constant b), the use of constant a is considered the same as the use of constant b.
  • a dependent variable that can be the rate of change of the yield stress sigma Y e.g., rate of change of the yield stress sigma Y volume fraction f M is for the volume fraction f M in the case of 1) to the volume fraction f M
  • the rate of change of the yield stress ⁇ Y with respect to the volume fraction f M is used. That is, as shown in the following equation (43) obtained by substituting the following equation (42) into the primary differential equation of the above equation (29), the change rate of the yield stress ⁇ Y at an arbitrary volume fraction f M is expressed as follows. Even if it uses, b which is the rate of change of the yield stress ⁇ Y when the volume fraction f M is 0 can be obtained. For example, even if the rate of change of the yield stress ⁇ Y when the volume fraction f M is 1 is defined as d as shown in the following formula (44), d is used from the following formula (45). b can be obtained.
  • f M first derivative is zero becomes like the volume fraction f M for, i.e., the volume fraction that satisfies the above formula (36) to (boundary hardening rate) f M determined the maximum volume fraction f M-max Also good.
  • the range of the volume fraction f M of the hardened zone for example, can be determined in the range that satisfies the above formula (37) to Formula (41).
  • the minimum volume fraction f M-min (other than 1) can be determined using the above equation (34).
  • the above - described ⁇ E h is determined from the minimum volume fraction f M-min and the maximum volume fraction f M-max determined by the equations (34) and (36), and processing is performed using the above-described improvement coefficient n.
  • hardening coefficient E h is the volume fraction f M is equal to or greater than the value obtained by adding the n ⁇ Delta] E h to work-hardening coefficient E h when it is 1, may determine the range of the volume fraction f M. That is, as shown in FIG. 18, determines the maximum volume fraction f M-max volume fraction f M based on the rate of change of the yield stress sigma Y for the volume fraction f M of the hardened region (S321), the volume the minimum value of the range of the fraction f M determined to a predetermined value smaller than the maximum volume fraction f M-max (S322), if determined the maximum value of the range of the volume fraction f M to 1 or less, or less than 1 Good (S323).
  • the maximum value of the range of the volume fraction f M determined to a predetermined value greater than the maximum volume fraction f M-max It is good (S324).
  • the same function for example, a linear function such as a quadratic function
  • the range may be divided into a plurality of ranges, and different functions may be used for each of these ranges.
  • the function within this range it is necessary to be able to differentiation upstairs by the volume fraction f M.
  • interpolation functions by various interpolation methods for example, spline interpolation
  • interpolation function is linear (line graph)
  • measured data for example, 5 points or more
  • the same function for example, a linear function such as a linear function
  • this range may be divided into a plurality of ranges, and different functions may be used for each of these ranges.
  • volume fraction f M of the hardened region with a small number of measurements as possible (number of tests prepared number and tensile strength of the test piece) has a yield strength sigma h of steel the relationship between the volume fraction f M of the hardened region was expressed by a linear function, it is preferred to express the relationship between the volume fraction f M of the yield stress sigma Y and curing area of the steel sheet by a quadratic function.
  • ⁇ h (f M ) is defined as a yield strength when a plastic strain of 5% occurs, but the plastic strain corresponding to the yield strength is not necessarily limited to 5%. If it is larger than 0%, it may not be 5%.
  • ⁇ h (f M ) can be defined as a yield strength when 1% plastic strain occurs.
  • ⁇ h (f M ) Represents the flow stress
  • ⁇ hM represents the flow stress in the hardened region
  • ⁇ h0 represents the flow stress in the non-hardened region (untreated structural material).
  • the flow stress is greater than the strain corresponding to the yield stress (that is, the plastic strain is greater than 0) and is less than the uniform elongation strain (for example, the maximum nominal strain).
  • the stress at is used. As a general evaluation, this flow stress is preferably 5%.
  • the structural material 10 is locally heated and cured by laser heat treatment.
  • local hardening of the structural material 10 is not necessarily performed by laser heat treatment, and may be performed by other heat treatment.
  • the hardness of the region hardened by the heat treatment is C for the carbon content of the structural material 10 as a steel material, Si for the silicon content, Mn for the manganese content, Ni for the nickel content, and Cr for the chromium content.
  • the molybdenum content is defined as Mo
  • the niobium content is defined as Nb
  • the vanadium content is defined as V
  • the hardness is preferably equal to or higher than the reference hardness (Vickers hardness) Hv calculated by the following formulas (45) and (46).
  • the laser heat treatment is performed on the effective width region 15 around the two bent portions 12b and 12c, and the effective width region 15 around the other two bent portions 12a and 12d.
  • No laser heat treatment is performed.
  • the laser heat treatment may be performed also on the effective width region around the other two bent portions, or the laser heat treatment is performed only on the effective width region 15 around one of the two bent portions 12b and 12c. May be performed.
  • the effective width region including at least one bent portion may be heat-treated at the volume fraction f M as described above.
  • the heat-treated structural material according to this embodiment includes at least one bent portion that extends in one direction of the structural material and is bent in a direction perpendicular to the one direction, as in the above-described embodiment. Yes. Therefore, the heat-treated structural material according to the present embodiment includes a structural material having a shape as shown in FIGS. Further, for the above-mentioned effective width region, the volume fraction f M of the above-described hardening region is less than 1, and the volume fraction determined based on the rate of change of the yield stress ⁇ Y with respect to the volume fraction f M f is included in the range of M.
  • the heat-treated structural material according to the present embodiment can exhibit a higher deformation suppressing ability than the conventional one while maintaining the lowest possible cost.
  • the scope of the volume fraction f M of the hardened region be determined based on the rate of change of the yield stress sigma Y for the volume fraction f M when the value of the volume fraction f M as described above is 0 Can do.
  • the scope of the volume fraction f M is a range in which the work hardening coefficient E h calculated based on the rate of change of the yield stress sigma Y for the volume fraction f M is determined to be equal to or greater than the predetermined value.
  • this predetermined value is preferably a value of work-hardening coefficient E h when the volume fraction f M is 1, greater than work hardening coefficient E h when the volume fraction f M is 1 More preferably it is a value.
  • the range of the volume fraction f M of the hardened zone (lower) is preferably at above formula (32) with minimum volume fraction f M-min or more represented.
  • the range of the volume fraction f M of the hardened zone (upper limit) is preferably at the maximum volume fraction f M-max or less represented by the above formula (33).
  • test pieces were sampled from the flat part of the structural material, and two test pieces were set so that the volume fractions f M of the cured regions of these test pieces were 0, 1, and 0.5, respectively.
  • a tensile test of these three specimens is performed to obtain the required mechanical strength, and the relationship between the yield stress ⁇ Y and the volume fraction f M is calculated by the least square method (30 ) Constant b may be determined.
  • the effective width e may be defined by the above formula (15), the above formula (17), the above formula (18B), or the following formula (47).
  • the finite element method may be used. Equation (47) is derived from Equations (18A) to (20) assuming that the flat plate buckling coefficient k is 4.
  • the cured region (the region cured by the heat treatment) can be obtained by the same method as in the above embodiment. That is, the hardened region can be determined as a region having a Vickers hardness or higher calculated by the above formulas (45) and (46).
  • the heat treatment is preferably performed by a laser. The history of heat treatment by this laser can be confirmed by observing the structure of the cross section of the structural material.
  • the thickness is 1.0 mm, the yield stress is 301 MPa, the tensile strength is 457 MPa, the elongation is 39%, the carbon content is 0.09%, the silicon content is 0.02%, and the manganese content is 1.24%.
  • Eleven JIS5 test pieces were collected from one 440 MPa class steel plate BP. Of these test pieces, ten test pieces were subjected to laser heat treatment in a plurality of passes so as to have a predetermined volume fraction in the longitudinal direction (tensile direction) of the test piece, and the hardening region with respect to the effective width region. Test pieces having a volume fraction of 0.1 to 1 (increments of 0.1) were prepared.
  • a carbon dioxide laser was used, the laser output was controlled to 5 kW, and the heat treatment speed was controlled to 12 m / min. Further, a tensile test was performed on these 11 test pieces to evaluate yield stress and tensile stress.
  • the effective width e was calculated using the above formulas (18A) to (20) (or the above formula (47)). As a result, 19.2 mm was obtained as the effective width e.
  • the plate buckling coefficient k which is a coefficient corresponding to the plate shape or the like, is 4, the plate width w is 60 mm, the plate thickness t is 1.0 mm, the yield stress ⁇ Y0 is 301 MPa, and the elasticity The rate E is 180 GPa.
  • an average value (60 mm) of the height (50 mm) and the top width (70 mm) of the structural material shown in FIG. 14 was used as a representative value.
  • the steel plate BP (FIG. 13A) was bent to produce an untreated structural material 10 having a shape as shown in FIG. 13B.
  • the untreated structural member 10 includes five flat portions arranged so that the cross section has a hat shape as shown in FIG. 14, and among these, the vertical cross section of each side including the three flat portions 11 at the center.
  • the side length was 50 mm, 70 mm, and 50 mm.
  • the other structural material 20 having a flat plate shape was spot-welded to the untreated structural material 10 thus produced, and a structural material assembly as shown in FIG. 13C was produced.
  • the spot welding S was performed at an interval of 30 mm in the longitudinal direction at the center in the width direction of the flat portion constituting the flange portion. Further, the distance from the longitudinal end portion (end portion on the impact applying side, hereinafter referred to as “impact application side end portion”) to the first spot welding was 15 mm.
  • the structural material assembly thus manufactured was subjected to a plurality of laser heat treatments in the longitudinal direction (tensile direction) of the test piece with a carbon dioxide laser.
  • the laser output was controlled to 5 kW, and the heat treatment speed was controlled to 12 m / min.
  • the laser output and the heat treatment rate in the laser heat treatment were controlled in the same manner in the following examples.
  • Test No. 1 laser heat treatment was performed over the entire region of 19.2 mm from the bent portion shown in black in FIG. 14, that is, over the entire effective width region. Therefore, in this case, the volume fraction of the hardened area with respect to the effective width area was 100%.
  • Vickers hardness was measured for the places where laser heat treatment was performed.
  • the Vickers hardness of the untreated structural material was 140, whereas the Vickers hardness after the laser heat treatment was 306, and it was confirmed that the hardened region was sufficiently quenched and hardened.
  • the structural material assembly is installed so that the longitudinal direction of the structural material assembly subjected to the laser heat treatment is aligned with the vertical direction, and the impact application side end portion is upward, and immediately above the structural material assembly.
  • An impact test was performed by dropping a 300 kg falling weight from a height of 2 m.
  • a load meter (load cell) was installed immediately below the structural material assembly, and the load history after the falling weight contacted the structural material assembly was measured.
  • the displacement history of the falling weight after the falling weight contacted the structural material assembly with the laser displacement meter (the time history of the falling weight of the falling weight after the falling weight contacted the structural material assembly) was also measured. .
  • a load-strain diagram was created based on the load history and displacement history thus measured.
  • the initial peak reaction force was calculated from this load-strain diagram, and the initial peak reaction force was calculated by dividing the initial peak reaction force by the cross-sectional area (340 mm 2 ) of the structural material assembly.
  • the initial peak reaction force at this time was 146.9 kN, and the initial peak stress was 432.0 MPa.
  • Test No. In No. 2, the above test no. In the same manner as in Example 1, an untreated structural material assembly was manufactured, and this structural material assembly was subjected to laser heat treatment. Laser heat treatment was performed so that the volume fraction of the hardened region with respect to the effective width region was 76.6%. At this time, the work hardening coefficient E h calculated by the above formula (31) using the above data was 4301.6 MPa (where ⁇ p 0.05).
  • the above test No. was applied to the structural material assembly thus subjected to the laser heat treatment.
  • the impact test was conducted in the same manner as in Example 1, and the initial peak reaction force and the initial peak stress were calculated based on the test results.
  • the initial peak reaction force at this time was 150.6 kN, and the initial peak stress was 443.0 MPa.
  • Test No. No. 3 the above test no.
  • an untreated structural material assembly was manufactured, and this structural material assembly was subjected to laser heat treatment.
  • Laser heat treatment was performed so that the volume fraction of the hardened region with respect to the effective width region was 53.3%.
  • the above test No. was applied to the structural material assembly thus subjected to the laser heat treatment.
  • the impact test was conducted in the same manner as in Example 1, and the initial peak reaction force and the initial peak stress were calculated based on the test results.
  • the initial peak reaction force at this time was 146.3 kN, and the initial peak stress was 430.1 MPa.
  • ⁇ Structure material with sufficiently improved ability to suppress deformation can be provided by performing heat treatment on an untreated structure material at an appropriate location to locally harden the structure material.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Body Structure For Vehicles (AREA)

Abstract

L'invention porte sur un procédé pour le traitement thermique d'un matériau de structure doté d'une section pliée qui s'étend dans une direction dudit matériau de structure et qui est pliée dans une direction perpendiculaire à ladite direction. Ledit procédé : détermine la largeur effective (e) pour la section pliée ; définit une région de largeur effective comme étant la région, comprenant la section pliée, dans laquelle la distance à la section pliée, dans la direction perpendiculaire susmentionnée, est inférieure ou égale à la largeur effective (e) susmentionnée ; détermine un intervalle pour un pourcentage de durcissement (fM ), ledit pourcentage de durcissement (fM ) étant défini comme étant le pourcentage de la région de largeur effective durcie par traitement thermique, sur la base du taux auquel une limite apparente d'élasticité (σ Y ) change en fonction du pourcentage de durcissement (fM ) ; et traite thermiquement la région de largeur effective du matériau de structure de façon à ce que le pourcentage de durcissement (fM ) s'inscrive dans l'intervalle susmentionné.
PCT/JP2011/069324 2010-08-27 2011-08-26 Procédé pour le traitement thermique d'un matériau de structure et matériau de structure traité thermiquement WO2012026591A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP11820051.8A EP2610355B1 (fr) 2010-08-27 2011-08-26 Procédé pour le traitement thermique d'un matériau de structure et matériau de structure traité thermiquement
CN201180041017.6A CN103069021B (zh) 2010-08-27 2011-08-26 结构材料的热处理方法及经热处理的结构材料
JP2012513793A JP5130498B2 (ja) 2010-08-27 2011-08-26 構造材の熱処理方法及び熱処理された構造材

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2010-190741 2010-08-27
JP2010190741 2010-08-27

Publications (1)

Publication Number Publication Date
WO2012026591A1 true WO2012026591A1 (fr) 2012-03-01

Family

ID=45723580

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2011/069324 WO2012026591A1 (fr) 2010-08-27 2011-08-26 Procédé pour le traitement thermique d'un matériau de structure et matériau de structure traité thermiquement

Country Status (5)

Country Link
EP (1) EP2610355B1 (fr)
JP (1) JP5130498B2 (fr)
CN (1) CN103069021B (fr)
TW (1) TWI498765B (fr)
WO (1) WO2012026591A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107907409A (zh) * 2017-11-10 2018-04-13 中国地质大学（武汉） 一种确定岩石起裂应力的方法、设备及存储设备

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3867127B1 (fr) * 2018-10-15 2024-07-03 Autotech Engineering, S.L. Profil pour une poutre structurelle d'un véhicule

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07119892A (ja) * 1993-10-27 1995-05-12 Nissan Motor Co Ltd 強度部材
JP2004114912A (ja) * 2002-09-27 2004-04-15 Sumitomo Metal Ind Ltd 耐軸圧潰特性に優れた成形部材
JP2007062733A (ja) * 2006-10-18 2007-03-15 Kikuchi Co Ltd 車体用部品及びその高周波焼入れ方法
JP2009286351A (ja) * 2008-05-30 2009-12-10 Nippon Steel Corp 耐座屈性に優れた車両用耐衝突補強材及びその製造方法

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06246303A (ja) * 1993-03-01 1994-09-06 Aichi Steel Works Ltd アングル材及びチャンネル材の局部加熱式製造方法
JPH08183473A (ja) * 1994-12-28 1996-07-16 Nissan Motor Co Ltd 車両用強度部材
US6942262B2 (en) * 2001-09-27 2005-09-13 Shape Corporation Tubular energy management system for absorbing impact energy
JP2003335266A (ja) * 2002-05-17 2003-11-25 Nissan Motor Co Ltd 車体骨格フレームの補強構造
FR2849059B1 (fr) * 2002-12-23 2005-08-19 Peugeot Citroen Automobiles Sa Procede et dispositif de traitement thermique local d'une piece metallique et piece metallique obtenue par un tel procede.
US6820924B2 (en) * 2003-01-13 2004-11-23 Ford Global Technologies, Llc Method of improving impact absorbing and deformation control characteristics of vehicle components
JP4969827B2 (ja) * 2005-10-19 2012-07-04 富士重工業株式会社 車体前部構造
CN1834268B (zh) * 2006-02-27 2010-08-04 天津市特种设备监督检验技术研究院 球形容器局部热处理残余热应力控制方法
DE102007024797A1 (de) * 2007-05-26 2008-11-27 Linde + Wiemann Gmbh Kg Verfahren zur Herstellung eines Profilbauteils, Profilbauteil und Verwendung eines Profilbauteils

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07119892A (ja) * 1993-10-27 1995-05-12 Nissan Motor Co Ltd 強度部材
JP2004114912A (ja) * 2002-09-27 2004-04-15 Sumitomo Metal Ind Ltd 耐軸圧潰特性に優れた成形部材
JP2007062733A (ja) * 2006-10-18 2007-03-15 Kikuchi Co Ltd 車体用部品及びその高周波焼入れ方法
JP2009286351A (ja) * 2008-05-30 2009-12-10 Nippon Steel Corp 耐座屈性に優れた車両用耐衝突補強材及びその製造方法

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107907409A (zh) * 2017-11-10 2018-04-13 中国地质大学（武汉） 一种确定岩石起裂应力的方法、设备及存储设备

Also Published As

Publication number Publication date
EP2610355A4 (fr) 2017-08-30
CN103069021A (zh) 2013-04-24
EP2610355B1 (fr) 2021-11-10
JPWO2012026591A1 (ja) 2013-10-28
JP5130498B2 (ja) 2013-01-30
CN103069021B (zh) 2014-06-04
TW201220110A (en) 2012-05-16
TWI498765B (zh) 2015-09-01
EP2610355A1 (fr) 2013-07-03

Similar Documents

Publication Publication Date Title
DE102017108835B4 (de) Verfahren zur verstärkung von bereichen eines hochfesten stahls
US9452792B2 (en) Vehicle collision energy absorbing member excellent in energy absorbing performance and manufacturing method therefor
CN102893049B (zh) 冲击吸收部件
Bardelcik et al. The influence of martensite, bainite and ferrite on the as-quenched constitutive response of simultaneously quenched and deformed boron steel–Experiments and model
RU2625357C1 (ru) Горячештампованная толстолистовая сталь, формованное штампованием изделие и способ изготовления формованного штампованием изделия
EP3730388B1 (fr) Élément d'ossature
US20120144989A1 (en) High ballistic strength martensitic armour steel alloy
EP1980635B1 (fr) Feuille d'acier convenant parfaitement a un decoupage fin et son procede de production
CN1246161A (zh) 冲击能吸收特性和成形性良好的高强度钢板及其制造方法
EP2565288A1 (fr) Tôle d'acier à deux phases laminée à chaud à une excellente résistance dynamique, et son procédé de production
KR102628567B1 (ko) 오스테나이트계 twip 또는 trip/twip 강의 구성 요소를 제조하는 방법
EA022687B1 (ru) Термообработанный стальной материал, способ его получения и базовый стальной материал для него
JP2010236560A (ja) 衝撃吸収特性に優れた構造部材の製造方法
WO2017208762A1 (fr) Tôle d'acier à haute résistance et son procédé de production
KR20110127241A (ko) 특히 스프링 요소용의 조직 압연 스트립 강으로서의 마이크로 합금 탄소강
JP6424841B2 (ja) 成形部材の製造方法
JP5130498B2 (ja) 構造材の熱処理方法及び熱処理された構造材
JP2018095896A (ja) 高強度鋼板およびその製造方法
JP6762797B2 (ja) 高強度鋼板およびその製造方法
Zhang et al. Springback characteristics in U-channel forming of tailor rolled blank
JP6465040B2 (ja) 成形部材の製造方法
EP3924527A1 (fr) Procédé de fabrication d'une pièce en tôle d'acier
DE102016122596A1 (de) Ultrahochfester Federstahl
Taylor et al. TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation
JP2002020843A (ja) 衝突吸収性能に優れたオーステナイト系ステンレス鋼

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 201180041017.6

Country of ref document: CN

WWE Wipo information: entry into national phase

Ref document number: 2012513793

Country of ref document: JP

121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 11820051

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

WWE Wipo information: entry into national phase

Ref document number: 2011820051

Country of ref document: EP