WO2022234793A1 - 骨格部材 - Google Patents
骨格部材 Download PDFInfo
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- WO2022234793A1 WO2022234793A1 PCT/JP2022/018966 JP2022018966W WO2022234793A1 WO 2022234793 A1 WO2022234793 A1 WO 2022234793A1 JP 2022018966 W JP2022018966 W JP 2022018966W WO 2022234793 A1 WO2022234793 A1 WO 2022234793A1
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- Prior art keywords
- flat portion
- standard deviation
- hardness
- cross
- section
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- 229910000831 Steel Inorganic materials 0.000 claims abstract description 42
- 239000010959 steel Substances 0.000 claims abstract description 42
- 239000002344 surface layer Substances 0.000 claims abstract description 27
- 238000009826 distribution Methods 0.000 claims abstract description 22
- 238000010521 absorption reaction Methods 0.000 description 37
- 239000010960 cold rolled steel Substances 0.000 description 16
- 238000005452 bending Methods 0.000 description 11
- 238000002474 experimental method Methods 0.000 description 10
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- 238000005261 decarburization Methods 0.000 description 4
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- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 238000007545 Vickers hardness test Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
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- 238000005498 polishing Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
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Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D21/00—Understructures, i.e. chassis frame on which a vehicle body may be mounted
- B62D21/15—Understructures, i.e. chassis frame on which a vehicle body may be mounted having impact absorbing means, e.g. a frame designed to permanently or temporarily change shape or dimension upon impact with another body
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
- C21D7/10—Modifying the physical properties of iron or steel by deformation by cold working of the whole cross-section, e.g. of concrete reinforcing bars
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D29/00—Superstructures, understructures, or sub-units thereof, characterised by the material thereof
- B62D29/007—Superstructures, understructures, or sub-units thereof, characterised by the material thereof predominantly of special steel or specially treated steel, e.g. stainless steel or locally surface hardened steel
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
- B21C37/15—Making tubes of special shape; Making tube fittings
- B21C37/155—Making tubes with non circular section
-
- 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
-
- 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
- B21D47/00—Making rigid structural elements or units, e.g. honeycomb structures
- B21D47/01—Making rigid structural elements or units, e.g. honeycomb structures beams or pillars
-
- 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
- B21D53/00—Making other particular articles
- B21D53/88—Making other particular articles other parts for vehicles, e.g. cowlings, mudguards
-
- 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
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/76—Adjusting the composition of the atmosphere
-
- 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
- C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
- C21D3/02—Extraction of non-metals
- C21D3/04—Decarburising
Definitions
- the present invention relates to a frame member having excellent energy absorption efficiency.
- This application claims priority based on Japanese Patent Application No. 2021-078462 filed in Japan on May 6, 2021, the content of which is incorporated herein.
- a hollow member made by processing a steel plate into a predetermined closed cross-sectional shape is used as a frame member of an automobile.
- Such a frame member is required to achieve weight reduction and exhibit sufficient strength and energy absorption performance when an input load is applied in the axial direction due to a collision.
- a method mainly used to achieve weight reduction is to reduce the weight by thinning the members by increasing the strength and energy absorption performance of the steel plate. Therefore, in recent years, cold-rolled steel sheets having a tensile strength of 980 MPa or more are sometimes used as materials for frame members.
- Patent Document 1 discloses a collision-resisting reinforcing member for a vehicle made of a molded thin plate for the purpose of improving buckling resistance, and includes a main body portion and a bent portion integrated with the main body portion.
- the main body is provided with a concave bead extending in the width direction center of the main body along the longitudinal direction thereof, and the distance between the concave bead and the bent portion is defined as the effective width.
- a vehicle crash reinforcement is disclosed in which a concave bead is provided to satisfy a specified range for c'.
- the present invention has been made in view of the above problems, and an object of the present invention is to provide a frame member with excellent energy absorption efficiency.
- a first aspect of the present invention is a skeletal member formed by cold press forming a steel plate, wherein the skeletal member has a closed cross-sectional portion whose cross section perpendicular to the longitudinal direction is a closed cross section.
- the closed cross-section portion has at least one flat portion that is a portion having a radius of curvature larger than the maximum outer dimension in the cross section, and among the at least one flat portion, the effective width is calculated from Karman's effective width formula
- a flat portion having a width having a maximum ratio to the effective width is defined as a reference flat portion
- the Vickers hardness of the plate thickness central portion of the reference flat portion is 300 Hv or more
- the width of the reference flat portion is the effective width.
- a standard that is 2.0 times or less than the width and is obtained by dividing the standard deviation of the hardness frequency distribution in the surface layer portion of the reference flat portion by the standard deviation of the hardness frequency distribution in the thickness center portion of the reference flat portion A skeleton member having a deviation ratio greater than 1.0.
- the closed cross-sectional portion may be present at 50% or more of the total length of the skeleton member in the longitudinal direction.
- the skeletal member includes a first skeletal member extending in the longitudinal direction and a and a second skeletal member to be joined, wherein the closed cross-section portion may include the first skeletal member and the second skeletal member.
- the standard deviation ratio may be greater than 1.20.
- FIG. 1 is a perspective view showing a skeleton member 10 according to one embodiment of the invention
- FIG. FIG. 3 is a cross-sectional view taken along a cutting line A1-A1 in FIG. 2
- 4 is a graph showing the relationship between the hardness standard deviation ratio and the VDA bending angle ratio in a VDA bending test for cold-rolled steel sheets having a tensile strength of 980 MPa or more.
- FIG. 11 is a perspective view showing a skeleton member 20 according to a modified example
- FIG. 6 is a cross-sectional view taken along a cutting line A2-A2 in FIG. 5
- 1 is a perspective view showing an automobile frame 100 as an example to which structural members are applied
- FIG. It is a schematic diagram for demonstrating the cross-sectional shape of the square tube material used in an Example. It is the graph which plotted the relationship between effective width ratio and energy absorption efficiency about an experimental example.
- the present inventors diligently studied the structure of a frame member that can exhibit excellent energy absorption efficiency.
- elastic buckling may occur at the flat portion at the initial stage of deformation.
- the necessary yield strength may not be obtained, and excellent energy absorption efficiency may not be exhibited.
- Longitudinal direction means the material axial direction of the skeleton member, that is, the direction in which the axis extends.
- a “flat portion” means a linear portion in a cross section perpendicular to the longitudinal direction of the frame member, specifically, a portion having a radius of curvature larger than the maximum outer dimension of the cross section. The maximum external dimension means the length of a straight line that maximizes the distance between the ends of any two points on the cross section.
- a “corner portion” means a non-linear portion of a cross section perpendicular to the longitudinal direction of a frame member, excluding a flat portion.
- “Width” means the line length along the circumferential direction of the closed section, and "width of the flat portion” means line length between one end and the other end of the flat portion.
- the “effective width” is the effective width W e obtained from the following equation (1) based on Karman's effective width theory, ie, Karman's effective width formula. here, ⁇ y : Yield stress of flat part (MPa) E: Young's modulus of flat part (MPa) t: Plate thickness of flat portion (mm) ⁇ : Poisson's ratio of the flat site.
- general physical property values may be used for the above-mentioned Young's modulus and Poisson's ratio at the flat portion.
- the "effective width ratio” is the ratio of the width W of the flat portion to the effective width We, and is a value calculated by W /We. It can be said that the smaller the value of the effective width ratio, the less elastic buckling occurs in the cross-sectional shape.
- a “reference flat portion” means a flat portion having the largest effective width ratio among flat portions in a closed cross section at an arbitrary position in the longitudinal direction.
- “Surface layer” refers to the depth position where the distance from the surface of the steel sheet in the thickness direction is 1% of the thickness of the steel sheet, and the distance from the surface of the steel sheet in the thickness direction to the thickness of the steel sheet. It means the area between the depth position which is 5%.
- the “thickness center” means a depth position where the separation distance in the thickness direction of the steel sheet from the surface of the steel sheet is 3/8 of the thickness.
- the “surface of the steel plate” used as a reference for the depth position means the surface of the base steel plate. For example, if the steel plate is plated or painted, or if rust is formed, the surface of the steel sheet without plating, painting and rust is used as the reference for the depth position. When a surface layer coating such as plating, painting, or rust is formed on the surface of the base steel sheet, the boundary between the surface layer coating and the surface of the base steel sheet can be easily identified by various known means.
- the “energy absorption amount” is an energy absorption amount calculated from the relationship between the impactor reaction force (load) and the stroke when the frame member is deformed into a bellows shape. As shown in Fig. 1, the impactor reaction force (load) and stroke were measured by arranging the frame members so that the longitudinal direction is in the vertical direction, and with the lower end side completely restrained, the impactor is moved from the upper end in the direction of the white arrow. It can be obtained by colliding with a flat impactor. "Energy absorption efficiency” is the energy absorption amount per cross-sectional area (thickness x cross-sectional line length) of the frame member.
- the cross-sectional area (plate It is the energy absorption amount per (thickness x cross-sectional line length).
- FIG. 2 is a perspective view of the skeleton member 10.
- FIG. The skeleton member 10 is a hollow tubular member extending in the longitudinal direction.
- FIG. 3 is a cross-sectional view taken along line A1-A1 in FIG.
- the frame member 10 has four flat portions 11 and four corner portions C forming a substantially rectangular closed cross section.
- the closed cross-sectional portion includes a first flat portion 11a, a second flat portion 11b connected to the first flat portion 11a through the corner portion C, and a corner portion C to the second flat portion 11b through the corner portion C.
- a continuous third flat portion 11c and a fourth flat portion 11d continuous with the third flat portion 11c through the corner portion C are provided, and the fourth flat portion 11d is continuous with the first flat portion through the corner portion C. It is formed by
- All four corner sites C have the same radius of curvature r.
- the curvature radius r should be 140 mm or less.
- the radii of curvature of the four corner portions C do not have to be the same, and may be different from each other.
- the upper limit of the radius of curvature is not particularly defined, a portion with a radius of curvature larger than the maximum outer dimension of the cross section is regarded as a separate flat portion rather than a corner portion, or a part of an adjacent flat portion, so the corner portion It can be said that the upper limit of the radius of curvature of C is substantially "less than the maximum outer dimension of the cross section".
- the reference flat portion is defined as the flat portion having the maximum effective width ratio among the flat portions in the closed section.
- the first flat portion 11a, the second flat portion 11b, the third flat portion 11c, and the fourth flat portion 11d all have the same yield stress ⁇ y , Young's modulus E, plate thickness t, and Poisson's ratio ⁇ . ing. Therefore, the effective width ratio calculated as width W/effective width We for each flat portion 11 is determined depending only on the width W of each flat portion 11 . For this reason, in the present embodiment, the first flat portion 11a and the third flat portion 11c having the largest width W among the closed cross-sectional portions are set as reference flat portions.
- the width WS of the reference flat portion is set to 2.0 times or less of the effective width W e .
- the width W S of the reference flat portion is preferably 0.1 times or more the effective width W e .
- the plate thickness at the reference flat portion is preferably 4.2 mm or less.
- the plate thickness of the reference flat portion is preferably 0.4 mm or more.
- the frame member 10 is formed by forming a cold-rolled steel plate having a tensile strength of 980 MPa or more into a predetermined shape by press forming, and then joining the end faces.
- the skeleton member 10 thus formed has a tensile strength of 980 MPa or more.
- the Vickers hardness of the plate thickness central portion of the reference flat portion of the skeleton member 10 is 300 gf (2 .9 N), it becomes 300 Hv or more.
- the hardness of the central portion of the plate thickness at the reference flat portion is specified to be 300 Hv or more in terms of Vickers hardness, because the deformability is enhanced on the premise of high strength and excellent energy absorption efficiency is exhibited.
- the upper limit of the hardness at the central portion of the sheet thickness is not particularly defined, the Vickers hardness may be 900 Hv or less.
- the method for measuring the hardness at the center of the plate thickness is as follows.
- a sample having a cross section perpendicular to the plate surface is taken from the frame member, the cross section is prepared as a measurement surface, and the measurement surface is subjected to a hardness test.
- the size of the measurement surface may be about 10 mm ⁇ 10 mm, depending on the measuring device.
- the preparation method of the measurement surface is carried out according to JIS Z 2244:2009. After polishing the surface to be measured using silicon carbide paper of #600 to #1500, the surface to be measured is mirror-finished using a liquid prepared by dispersing diamond powder with a particle size of 1 ⁇ m to 6 ⁇ m in diluted liquid such as alcohol or pure water. Finish.
- a hardness test is implemented by the method of JISZ2244:2009. Using a micro Vickers hardness tester, 30 points are measured at 3/8 positions of the plate thickness of the sample with a load of 300 gf at intervals of 3 times or more of the indentation, and their average value is the hardness at the center of the plate thickness. do.
- elastic buckling can be suppressed when the width W S of the reference flat portion is 2.0 times or less the effective width W e .
- high-strength materials such as cold-rolled steel sheets with a tensile strength of 980 MPa or more, even if elastic buckling can be suppressed by controlling the effective width We, if the bending performance is insufficient, the axial direction Due to the fact that breakage occurs in the middle of the bellows deformation due to the load of , excellent energy absorption efficiency cannot be obtained.
- the standard deviation of the hardness frequency distribution at the plate thickness central portion and the standard deviation of the hardness frequency distribution at the surface layer portion at the reference flat portion are substantially the same, and the hardness standard deviation ratio is 1.0.
- the skeletal member 10 according to the present embodiment by appropriately controlling the ratio of the standard deviation of the hardness frequency distribution at the central portion of the thickness of the reference flat portion to the standard deviation of the hardness frequency distribution at the surface layer portion, , which improves bending performance. Therefore, even if a high-strength material is used, breakage during bellows deformation can be suppressed, making it possible to exhibit energy absorption efficiency that is significantly superior to that of the prior art.
- the hardness is a value obtained by dividing the standard deviation of the hardness frequency distribution in the surface layer portion by the standard deviation of the hardness frequency distribution in the central portion of the plate thickness.
- the height standard deviation ratio is controlled to be greater than 1.0.
- FIG. 4 is a graph showing the results of a VDA bending test using 1470 MPa class, 1180 MPa class, and 980 MPa class cold-rolled steel sheets with a thickness of 1.6 mm.
- the hardness standard deviation ratio is preferably greater than 1.05, more preferably greater than 1.20. Even if the hardness standard deviation ratio is greater than 3.0, the effect of improving bendability is saturated. Therefore, the hardness standard deviation ratio is preferably 3.0 or less.
- the hardness frequency distribution at the plate thickness central portion and the hardness frequency distribution at the surface layer portion are obtained by a Vickers hardness test.
- a sample having a cross section perpendicular to the plate surface is taken from the frame member, the cross section is prepared as a measurement surface, and the measurement surface is subjected to a hardness test.
- the size of the measurement surface may be about 10 mm ⁇ 10 mm, depending on the measuring device.
- the preparation method of the measurement surface is carried out according to JIS Z 2244:2009. After polishing the surface to be measured using silicon carbide paper of #600 to #1500, the surface to be measured is mirror-finished using a liquid prepared by dispersing diamond powder with a particle size of 1 ⁇ m to 6 ⁇ m in diluted liquid such as alcohol or pure water. Finish.
- a hardness test is performed on the measurement surface thus mirror-finished by the method described in JIS Z 2244:2009.
- the hardness of the surface layer is measured using a micro Vickers hardness tester. Under a load of 300 gf, 30 points are measured at intervals of 3 times or more of the indentation to obtain the hardness frequency distribution in the surface layer. Similarly, at a depth position of 3/8 of the plate thickness, a load of 300 gf is applied, and 30 points are measured at an interval of three times or more of the indentation to obtain the hardness frequency distribution at the center of the plate thickness.
- the hardness frequency distribution at the surface layer is the hardness frequency distribution at the thickness center. and the hardness standard deviation ratio is 1.0.
- the metal structure of only the surface layer portion and its vicinity is modified, the hardness standard deviation ratio becomes a value different from 1.0.
- the metal structure of the surface layer is close to a two-phase structure by modifying the metal structure of only the surface layer and its vicinity.
- the hardness standard deviation ratio can be controlled by adjusting the maximum heating temperature and holding time during the decarburization annealing of the steel sheet, which are known techniques.
- the conditions for decarburization annealing are as follows: in a moist atmosphere containing hydrogen, nitrogen or oxygen, the decarburization annealing temperature (maximum temperature of the steel sheet) is 700 to 950 ° C., and the residence time in the temperature range of 700 to 950 ° C. is 5. Seconds to 1200 seconds are preferred.
- the hardness standard deviation ratio can be made larger than 1.20.
- At least one surface layer portion of the skeleton member 10 may satisfy the above condition of the hardness standard deviation ratio. However, it is preferable that the surface layer portions on both sides of the skeleton member 10 satisfy the condition of the hardness standard deviation ratio.
- the frame member 10 As described above, according to the frame member 10 according to the present embodiment, elastic buckling is suppressed by controlling the width WS of the reference flat portion, and the bellows is formed by controlling the hardness standard deviation ratio. Breakage during deformation can be suppressed. Therefore, the energy absorption efficiency can be remarkably improved while having a sufficient Vickers hardness of 300 Hv or more at the plate thickness central portion of the reference flat portion.
- the skeleton member 10 described above is composed of a single member, but may be composed of a plurality of members.
- FIG. 5 is a perspective view showing a skeleton member 20 according to a modification
- FIG. 6 is a cross-sectional view taken along section line A2-A2 in FIG.
- the skeletal member 20 includes a longitudinally extending first skeletal member 20A and a longitudinally extending second skeletal member 20B joined to the first skeletal member 20A.
- a closed cross section is formed by the first skeleton member 20A and the second skeleton member 20B.
- the first skeleton member 20A is a member having an open cross section in which a cross section perpendicular to the longitudinal direction has a substantially hat-shaped shape by cold press forming a steel plate having a thickness of 1.2 mm.
- the cross-section perpendicular to the longitudinal direction of the first skeleton member 20A has five flat portions 21 and four corner portions C.
- the cross section perpendicular to the longitudinal direction of the first skeleton member 20A includes a first flat portion 21a, a second flat portion 21b connected to the first flat portion 21a via a corner portion C, and a second flat portion 21b.
- the second skeleton member 20B is a member having an open cross-section in which a cross section perpendicular to the longitudinal direction has a substantially hat-shaped shape by cold press forming a steel plate having a thickness of 0.8 mm.
- the cross-section perpendicular to the longitudinal direction of the second skeleton member 20B has five flat portions 23 and four corner portions C.
- the cross section perpendicular to the longitudinal direction of the second skeleton member 20B includes a first flat portion 23a, a second flat portion 23b connected to the first flat portion 23a via a corner portion C, and a second flat portion 23b.
- the first flat portion 21a and the fifth flat portion 21e of the first skeleton member 20A and the first flat portion 23a and the fifth flat portion 23e of the second skeleton member 20B are respectively joined by spot welding.
- the skeleton member 20 has a closed cross section in a cross section perpendicular to the longitudinal direction.
- the reference flat portion is defined as the flat portion having the maximum effective width ratio among the flat portions in the closed section.
- the flat portion 21 of the first skeleton member 20A and the flat portion 23 of the second skeleton member 20B both have the same yield stress ⁇ y , Young's modulus E, and Poisson's ratio ⁇ . Therefore, the effective width ratio calculated as width W/effective width We for each flat portion 21, 23 is determined depending on the width W and plate thickness t of each flat portion 21, 23.
- FIG. In this closed cross section, both the third flat portion 21c of the first skeleton member 20A and the third flat portion 23c of the second skeleton member 20B are flat portions having the largest width among all the flat portions. .
- the third flat portion 23c of the second skeleton member 20B is smaller than the plate thickness of the third flat portion 21c of the first skeleton member 20A, the third flat portion 23c of the second skeleton member 20B has the largest effective width ratio. Therefore, the third flat portion 23c of the second skeleton member 20B is the reference flat portion.
- the third flat portion 23c of the second skeleton member 20B which is the reference flat portion, has a Vickers hardness of 300 Hv or more at the center of the plate thickness, and a width W s of the effective width W e .
- Excellent energy absorption efficiency can be exhibited by controlling the ratio to 2.0 times or less and the standard deviation ratio to a value greater than 1.0.
- the skeleton member 10 has a substantially rectangular cross-sectional shape in which the opposing sides have the same width
- the four flat portions 11 may have a substantially square cross-sectional shape with the same width. good.
- the number of flat portions 11 is not particularly limited, and at least one is sufficient.
- the skeleton member 10 has a uniform cross-sectional shape over the entire length, but the cross-sectional shape may not be uniform over the entire length. It is sufficient that the closed cross-section having the minimum cross-sectional area (thickness x cross-sectional line length) is the above-described closed cross-sectional portion, and it is sufficient that it exists in a part of the entire length in the longitudinal direction. However, the above-mentioned closed cross-section portion preferably exists in 50% or more of the total length in the longitudinal direction, and more preferably 80% or more.
- FIG. 7 is a diagram showing an automobile frame 100 as an example to which the frame members 10 and 20 are applied.
- frame members 10 and 20 are structural members of an automobile body, including a front side member 101, a rear side member 103, a side sill 105, an A pillar 107, a B pillar 109, a roof rail 111, a floor cloth 113, and a roof. It can be applied to cloth 115 and underlining force 117 .
- Steel plate A and steel plate B which are 1470 MPa class cold-rolled steel plates with a plate thickness of 1.6 mm
- steel plate C which is a 1180 MPa class cold-rolled steel plate with a plate thickness of 1.6 mm
- steel plate D which is a 980 MPa class cold-rolled steel plate with a plate thickness of 1.6 mm.
- Steel sheets B, steel sheets C, and steel sheets D were decarburized and annealed at a decarburization annealing temperature (maximum attainable temperature of the steel sheet) of 700 to 900°C in a moist atmosphere containing a mixture of hydrogen and nitrogen.
- steel plates A, B, C, and D were cold press-formed, and their end faces were welded to obtain rectangular cylindrical members each having a height of 300 mm.
- Steel plate A has the same metallographic structure at the thickness center and at the surface layer. and the hardness standard deviation ratio was 1.0.
- steel sheets B, C, and D the metal structure of the surface layer is modified without modifying the metal structure of the central part of the plate thickness, thereby changing the hardness frequency distribution of the surface layer.
- the hardness standard deviation ratio of the surface layer portion to the plate thickness central portion at the reference flat portion of steel plate B is 2.37
- the hardness standard deviation ratio at the reference flat portion of steel plate C is 1.25
- the hardness standard deviation ratio of steel plate D is 1.25.
- the hardness standard deviation ratio at the site was 1.28.
- Table 1 shows the material properties at the flat portion after press molding.
- the section perpendicular to the longitudinal direction of the rectangular tubular member is designed to be a substantially square section in which the four flat portions have the same width. That is, in each rectangular tube member, all four flat portions are reference flat portions having the maximum effective width ratio. Based on these conditions, the width WS of the reference flat portion was set for each experimental example. The radius of curvature of each of the four corner portions C was designed to be 5 mm.
- FIG. 9 is a graph comparing the energy absorption efficiency with respect to the effective width ratio for the experimental results shown in Table 2.
- the energy absorption efficiency is not improved only by reducing the effective width ratio, but when the hardness standard deviation ratio is appropriately controlled as in the present application, the effective width ratio can be reduced. It can be seen that the energy absorption efficiency is remarkably improved at .
- Experiment No. 2C (1180 MPa class cold-rolled steel sheet) and Experiment No. In 2D (980 MPa class cold-rolled steel sheet), the hardness standard deviation ratio is properly controlled and the effective width ratio is also appropriate.
- experiment no. 2C experiment no. Since the strength class is lower than that of 2B (1470 MPa class cold-rolled steel sheet), the energy absorption efficiency is inferior, but no fracture or elastic buckling occurs. Therefore, Experiment No. 1, which is a comparative example in which the hardness standard deviation ratio is not properly controlled, It can be seen that although the strength class is lower than that of 2A (1470 MPa class cold rolled steel sheet), high energy absorption efficiency was exhibited.
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Abstract
Description
本願は、2021年5月6日に、日本に出願された特願2021-078462号に基づき優先権を主張し、その内容をここに援用する。
(1)本発明の第一の態様は、鋼板を冷間プレス成形することにより形成される骨格部材であって、前記骨格部材は、長手方向に垂直な断面が閉断面である閉断面部を有し、前記閉断面部は、当該断面における最大外形寸法よりも曲率半径が大きい部位である少なくとも1つの平坦部位を有し、前記少なくとも1つの平坦部位のうち、カルマンの有効幅式から求められる有効幅に対する割合が最大である幅を有する平坦部位を基準平坦部位と定義したとき、前記基準平坦部位における板厚中心部のビッカース硬度が300Hv以上であり、前記基準平坦部位の幅が、前記有効幅の2.0倍以下であり、前記基準平坦部位の表層部における硬さ頻度分布の標準偏差を、前記基準平坦部位の板厚中心部における硬さ頻度分布の標準偏差で割って求められる標準偏差比が1.0より大きい骨格部材である。
(2)上記(1)に記載の骨格部材では、前記閉断面部が、前記骨格部材の前記長手方向の全長の50%以上に存在してもよい。
(3)上記(1)又は(2)に記載の骨格部材では、前記骨格部材は、前記長手方向に延在する第一骨格部材と、前記長手方向に延在するとともに前記第一骨格部材に接合される第二骨格部材と、を含み、前記閉断面部は、前記第一骨格部材と、前記第二骨格部材とを含んでもよい。
(4)上記(1)~(3)のいずれか一項に記載の骨格部材では、前記標準偏差比が1.20より大きくてもよい。
まず、優れたエネルギー吸収効率を発揮するためには、一定以上の耐力を有することが重要である。衝突により軸方向への入力荷重が加えられた際には、変形初期に平坦部位での弾性座屈が生じる場合がある。弾性座屈が発生すると、必要な耐力が得られず、優れたエネルギー吸収効率を発揮できない場合がある。
また、優れたエネルギー吸収効率を発揮するためには、衝突により軸方向への入力荷重が加えられた直後に、骨格部材が所望の変形モードでの折り畳み変形を実現することで衝撃エネルギーを効率的に吸収することも重要である。特に、軸方向の荷重による蛇腹変形の途中での破断(折り畳まれ部での破断)が発生すると、優れたエネルギー吸収効率を発揮できない場合がある。
従って、平坦部位において弾性座屈が発生しにくい断面設計とするとともに、破断しにくい高い曲げ性能を付与することができれば、優れたエネルギー吸収効率を発揮することが可能となると言える。
・薄肉化により部材の平坦部位での弾性座屈が発生し易くなるため必要な耐力を得ることが困難となる。
・高強度化により鋼板の曲げ性能が低下し、変形開始後の折り畳まれ部での破断が発生し易くなるため、衝撃エネルギーを効率的に吸収することが困難となる。
上記の問題点が、高強度鋼板の更なる高強度化及び薄肉化を妨げる要因となっていることに本発明者らは着目した。
本発明者らは更に検討を進めたことにより、基準平坦部位において、幅及び硬さ標準偏差比を適正な範囲に制御することにより、弾性座屈を抑制しながら軸方向の荷重による蛇腹変形の途中での破断を防止することができることを見出した。このような制御により、高強度鋼板を用いる場合において懸念される上記の問題点を解消し、優れたエネルギー吸収効率を発揮できることを見出し、本発明を完成させた。
なお、本明細書及び図面において、実質的に同一の機能構成を有する構成要素については、同一の符号を付することにより重複説明を省略する。
「長手方向」とは、骨格部材の材軸方向、すなわち、軸線が延びる方向を意味する。
「平坦部位」は、骨格部材の長手方向に垂直な断面において直線状の部位、具体的には、断面の最大外形寸法よりも曲率半径が大きい部位を意味する。最大外形寸法とは、当該断面における任意の二点の端部間距離が最大となる直線の長さを意味する。
「コーナ部位」は、骨格部材の長手方向に垂直な断面のうち、平坦部位を除いた非直線状の部位を意味する。
「有効幅」は、カルマンの有効幅理論に基づく以下の(1)式、すなわちカルマンの有効幅式から求められる有効幅Weである。
σy:平坦部位の降伏応力(MPa)
E:平坦部位のヤング率(MPa)
t:平坦部位の板厚(mm)
ν:平坦部位のポアソン比
である。
また、鋼板においては、上記平坦部位のヤング率や平坦部位のポアソン比は、一般的な物性値を用いれば良く、更に平坦部位の降伏応力を板厚中心部のビッカース硬度に置き換えることで、有効幅WeはWe=577t/√hの式から求めることもできる。
ここで、
t:平坦部位の板厚(mm)
h:平坦部位の板厚中心部のビッカース硬度(Hv)
である。(1)式にて有効幅Weを求めることが困難な場合には、上記式により求めることができる。
「有効幅比」とは、有効幅Weに対する平坦部位の幅Wの割合であり、W/Weで算出される値である。有効幅比の値が小さいほど、弾性座屈が生じにくい断面形状であると言える。
「基準平坦部位」は、長手方向の任意の位置での閉断面部における平坦部位のうち、有効幅比が最大である平坦部位を意味する。
「表層部」とは、鋼板の表面から板厚方向への離間距離が鋼板の板厚の1%である深さ位置と、鋼板の表面から板厚方向への離間距離が鋼板の板厚の5%である深さ位置との間の領域を意味する。
「板厚中心部」とは、鋼板の表面から鋼板の板厚方向への離間距離が板厚の3/8である深さ位置を意味する。
深さ位置の基準としている「鋼板の表面」とは、母材鋼板の表面を意味する。例えば、めっき又は塗装がされている場合や錆等が形成されている場合には、めっき、塗装および錆を除いた状態の鋼板の表面を深さ位置の基準とする。なお、母材鋼板の表面にめっき、塗装、錆等の表層被膜が形成される場合、当該表層被膜と母材鋼板の表面との境界は様々な公知の手段で容易に識別される。
「エネルギー吸収効率」は、骨格部材の断面積(板厚×断面線長)あたりのエネルギー吸収量である。骨格部材が長手方向に一様の断面を有していない場合は、部材長手方向に垂直な閉断面のうち、断面積(板厚×断面線長)が最小となる閉断面における断面積(板厚×断面線長)あたりのエネルギー吸収量である。
具体的には、この閉断面部は、第一平坦部位11aと、第一平坦部位11aにコーナ部位Cを介して連なる第二平坦部位11bと、第二平坦部位11bにコーナ部位Cを介して連なる第三平坦部位11cと、第三平坦部位11cにコーナ部位Cを介して連なる第四平坦部位11dと、を備えるとともに、第四平坦部位11dがコーナ部位Cを介して第一平坦部位に連なることにより形成されている。
第一平坦部位11a、第二平坦部位11b、第三平坦部位11c、及び第四平坦部位11dは、いずれも同一の降伏応力σy、ヤング率E、板厚t、及びポアソン比νを有している。
従って、それぞれの平坦部位11についての幅W/有効幅Weで算出される有効幅比は、それぞれの平坦部位11の幅Wのみに依存して決定される。
このため、本実施形態においては、閉断面部のうち幅Wが最も大きい第一平坦部位11aと第三平坦部位11cが基準平坦部位として設定される。
従って、基準平坦部位の幅WSは、有効幅Weの0.1倍以上であることが好ましい。
一方、基準平坦部位の板厚が0.4mm未満である場合、基準平坦部位における弾性座屈が生じやすくなるため、基準平坦部位の幅WSの設定範囲の制約が大きくなる。従って、基準平坦部位の板厚は0.4mm以上であることが好ましい。
本願においては、高強度化を前提に変形能を高めて優れたエネルギー吸収効率を発揮させるものであるため、基準平坦部位における板厚中心部の硬度はビッカース硬さで300Hv以上に規定する。
板厚中心部の硬度の上限は特に規定しないが、ビッカース硬さで900Hv以下としてもよい。
骨格部材から板面に垂直な断面を有する試料を採取し、当該断面を測定面として調製し、当該測定面を硬さ試験に供する。
測定面のサイズは、測定装置にもよるが、10mm×10mm程度で良い。
測定面の調製方法は、JIS Z 2244:2009に準じて実施する。#600から#1500の炭化珪素ペーパーを使用して測定面を研磨した後、粒度1μmから6μmのダイヤモンドパウダーをアルコール等の希釈液や純水に分散させた液体を使用して測定面を鏡面に仕上げる。硬さ試験は、JIS Z 2244:2009に記載の方法で実施する。マイクロビッカース硬さ試験機を用いて、試料の板厚の3/8位置に、荷重300gfで、圧痕の3倍以上の間隔で30点測定し、それらの平均値を板厚中心部の硬度とする。
しかしながら、本実施形態に係る骨格部材10においては、基準平坦部位における板厚中心部における硬さ頻度分布の標準偏差と表層部における硬さ頻度分布の標準偏差との比を適切に制御することによって、曲げ性能を高めている。
従って、高強度材を適用しても蛇腹変形の途中での破断を抑制し、従来と比べて格段に優れたエネルギー吸収効率を発揮することを可能としている。
具体的には、本実施形態に係る骨格部材10では、基準平坦部位において、表層部における硬さ頻度分布の標準偏差を板厚中心部における硬さ頻度分布の標準偏差で割った値である硬さ標準偏差比が、1.0より大きくなるように制御されている。
図4は、厚さ1.6mmの1470MPa級、1180MPa級、980MPa級の冷延鋼板を用いた場合のVDA曲げ試験の結果を示すグラフであり、各強度クラスの鋼板において、従来のように硬さ標準偏差比が1.0となる鋼板に対して、硬さ標準偏差比が1.0より大きい鋼板の場合、VDA曲げ試験における最大曲げ角(°)が高くなり、VDA角度比が高くなることがわかる。すなわち、硬さ標準偏差比が1.0より大きい場合に、軸方向の荷重により蛇腹変形の途中で破断が発生しにくくなり、優れたエネルギー吸収効率を発揮できる。
硬さ標準偏差比は、3.0より大きくても曲げ性を高める効果は飽和する。従って、硬さ標準偏差比は3.0以下であることが好ましい。
骨格部材から板面に垂直な断面を有する試料を採取し、当該断面を測定面として調製し、当該測定面を硬さ試験に供する。
測定面のサイズは、測定装置にもよるが、10mm×10mm程度で良い。
測定面の調製方法は、JIS Z 2244:2009に準じて実施する。#600から#1500の炭化珪素ペーパーを使用して測定面を研磨した後、粒度1μmから6μmのダイヤモンドパウダーをアルコール等の希釈液や純水に分散させた液体を使用して測定面を鏡面に仕上げる。
マイクロビッカース硬さ試験機を用いて、表層部における硬さを測定する。
荷重300gfで、圧痕の3倍以上の間隔で30点測定し、表層部における硬さ頻度分布を求める。
同様に、板厚の3/8の深さ位置においても、荷重300gfで、圧痕の3倍以上の間隔で30点測定し、板厚中心部における硬さ頻度分布を求める。
一方、表層部とその近傍のみの金属組織を改質した場合、硬さ標準偏差比は、1.0とは異なる値となる。
本実施形態に係る引張強度が980MPa以上の冷延鋼板で形成された骨格部材10では、表層部とその近傍のみの金属組織を改質することにより、表層部の金属組織が二相組織に近い組織となるため、表層部での硬度の分布、ばらつきが大きくなり、表層部と板厚中心部との硬さ標準偏差比を1.0より大きくすることができる。
具体的には、硬さ標準偏差比は、公知の技術である、鋼板の脱炭焼鈍時の最高加熱温度と保持時間とを調整することにより制御できる。脱炭焼鈍の条件は、水素、窒素または酸素を含有する湿潤雰囲気において、脱炭焼鈍温度(鋼板の最高到達温度)を700~950℃とし、700~950℃の温度域での滞留時間を5秒~1200秒とすることが好ましい。
また、この条件範囲内において焼鈍温度をより高い温度範囲と、滞留温度をより長い時間範囲に絞り込むことで、硬さ標準偏差比を1.20より大きくすることができる。
なお、硬さ標準偏差比の上記条件は、骨格部材10の少なくとも一方の表層部が満たせばよい。ただし、骨格部材10の両側の表層部が上記硬さ標準偏差比の条件を満たすことが好ましい。
従って、基準平坦部位の板厚中心部のビッカース硬さが300Hv以上という十分な硬さを有しながらも、エネルギー吸収効率を格段に向上させることができる。
本発明の属する技術の分野における通常の知識を有する者であれば、本願技術的思想の範疇内において、各種の変更例または修正例に想到し得ることは明らかであり、これらについても、当然に本発明の技術的範囲に属するものと了解される。
この骨格部材20は、長手方向に延在する第一骨格部材20Aと長手方向に延在するとともに第一骨格部材20Aに接合される第二骨格部材20Bを含む。そして、第一骨格部材20Aと第二骨格部材20Bにより閉断面部を形成している。
図6に示すように、第一骨格部材20Aの長手方向に垂直な断面部は、五つの平坦部位21と四つのコーナ部位Cとを備える。
具体的には、第一骨格部材20Aの長手方向に垂直な断面部は、第一平坦部位21aと、第一平坦部位21aにコーナ部位Cを介して連なる第二平坦部位21bと、第二平坦部位21bにコーナ部位Cを介して連なる第三平坦部位21cと、第三平坦部位21cにコーナ部位Cを介して連なる第四平坦部位21dと、第四平坦部位21dにコーナ部位Cを介して連なる第五平坦部位21eと、を備える。
図6に示すように、第二骨格部材20Bの長手方向に垂直な断面部は、五つの平坦部位23と四つのコーナ部位Cとを備える。
具体的には、第二骨格部材20Bの長手方向に垂直な断面部は、第一平坦部位23aと、第一平坦部位23aにコーナ部位Cを介して連なる第二平坦部位23bと、第二平坦部位23bにコーナ部位Cを介して連なる第三平坦部位23cと、第三平坦部位23cにコーナ部位Cを介して連なる第四平坦部位23dと、第四平坦部位23dにコーナ部位Cを介して連なる第五平坦部位23eと、を備える。
このように構成されていることにより、骨格部材20は、長手方向に垂直な断面が閉断面部を有する。
第一骨格部材20Aの平坦部位21と第二骨格部材20Bの平坦部位23は、いずれも同一の降伏応力σy、ヤング率E、及びポアソン比νを有している。従って、それぞれの平坦部位21,23についての幅W/有効幅Weで算出される有効幅比は、それぞれの平坦部位21,23の幅Wと板厚tに依存して決定される。
この閉断面部においては、第一骨格部材20Aの第三平坦部位21cと、第二骨格部材20Bの第三平坦部位23cが共に、すべての平坦部位の中で幅が最大である平坦部位である。しかし、第一骨格部材20Aの第三平坦部位21cの板厚よりも、第二骨格部材20Bの第三平坦部位23cの板厚の方が小さいため、第二骨格部材20Bの第三平坦部位23cの有効幅比が最も大きい。従って、第二骨格部材20Bの第三平坦部位23cが基準平坦部位である。
また、平坦部位11の数は特に限られるものではなく、少なくとも一つあればよい。
この図7を参照すると、骨格部材10,20は、自動車車体の構造部材のうち、フロントサイドメンバ101、リアサイドメンバ103、サイドシル105、Aピラー107、Bピラー109、ルーフレール111、フロアクロス113、ルーフクロス115、及びアンダーリンフォース117に適用することができる。
板厚1.6mmの1470MPa級冷延鋼板である鋼板A及び鋼板B、板厚1.6mmの1180MPa級冷延鋼板である鋼板C、板厚1.6mmの980MPa級冷延鋼板である鋼板Dを準備した。
鋼板B、鋼板C、及び鋼板Dでは、脱炭焼鈍時に、水素と窒素を混合した湿潤雰囲気において、脱炭焼鈍温度(鋼板の最高到達温度)を700~900℃とし、700~900℃の温度域での滞留時間を60~600秒とすることにより、表層部とその近傍のみの金属組織を改質させた。
鋼板Aは、板厚中心部と表層部で金属組織が同じであるため、基準平坦部位の板厚中心部における硬さ頻度分布の標準偏差と基準平坦部位の表層部における硬さ頻度分布の標準偏差とが等しく、硬さ標準偏差比は1.0となった。一方、鋼板B、鋼板C及び鋼板Dは、板厚中心部の金属組織は改質させずに表層部の金属組織を改質することで、表層部の硬さ頻度分布を変化させ、表層部の標準偏差を調整した。これによって、鋼板Bの基準平坦部位における板厚中心部に対する表層部の硬さ標準偏差比は2.37、鋼板Cの基準平坦部位における硬さ標準偏差比は1.25、鋼板Dの基準平坦部位における硬さ標準偏差比は1.28となった。
プレス成形後の平坦部位における材料特性を表1に示す。
実験No.1B、2B、3Bでは、硬さ標準偏差比が適切に制御され、且つ、有効幅比も適切であったため、1470MPa級冷延鋼板を用いながらも、蛇腹変形途中での破断及び弾性座屈が生じず、優れたエネルギー吸収効率を発揮することができた。
尚、図9は、表2に示す実験結果について、有効幅比に対するエネルギー吸収効率を比較したグラフである。このグラフに示す通り、有効幅比を小さくするだけではエネルギー吸収効率の向上は見られないが、本願のように硬さ標準偏差比を適切に制御した場合においては、有効幅比を小さくすることでエネルギー吸収効率が格段に向上することがわかる。
20A 第一骨格部材
20B 第二骨格部材
100 自動車骨格
Claims (4)
- 鋼板を冷間プレス成形することにより形成される骨格部材であって、
前記骨格部材は、長手方向に垂直な断面が閉断面である閉断面部を有し、
前記閉断面部は、当該断面における最大外形寸法よりも曲率半径が大きい部位である少なくとも1つの平坦部位を有し、
前記少なくとも1つの平坦部位のうち、カルマンの有効幅式から求められる有効幅に対する割合が最大である幅を有する平坦部位を基準平坦部位と定義したとき、
前記基準平坦部位における板厚中心部のビッカース硬度が300Hv以上であり、
前記基準平坦部位の幅が、前記有効幅の2.0倍以下であり、
前記基準平坦部位の表層部における硬さ頻度分布の標準偏差を、前記基準平坦部位の板厚中心部における硬さ頻度分布の標準偏差で割って求められる標準偏差比が1.0より大きい
ことを特徴とする骨格部材。 - 前記閉断面部が、前記骨格部材の前記長手方向の全長の50%以上に存在する
ことを特徴とする請求項1に記載の骨格部材。 - 前記骨格部材は、前記長手方向に延在する第一骨格部材と、前記長手方向に延在するとともに前記第一骨格部材に接合される第二骨格部材と、を含み、
前記閉断面部は、前記第一骨格部材と、前記第二骨格部材とを含む
ことを特徴とする請求項1又は2に記載の骨格部材。 - 前記標準偏差比が1.20より大きい
ことを特徴とする請求項1又は2に記載の骨格部材。
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Publication number | Priority date | Publication date | Assignee | Title |
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JPH05195149A (ja) * | 1992-01-21 | 1993-08-03 | Nkk Corp | 曲げ加工性及び衝撃特性の優れた超高強度冷延鋼板 |
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 |
JP2020153401A (ja) * | 2019-03-19 | 2020-09-24 | 日本製鉄株式会社 | 閉断面構造体 |
JP2021078462A (ja) | 2019-11-21 | 2021-05-27 | 日油株式会社 | 製パン用油脂組成物、製パン用穀粉生地、製パン用穀粉生地の製造方法 |
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Publication number | Priority date | Publication date | Assignee | Title |
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JPH05195149A (ja) * | 1992-01-21 | 1993-08-03 | Nkk Corp | 曲げ加工性及び衝撃特性の優れた超高強度冷延鋼板 |
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 |
JP2020153401A (ja) * | 2019-03-19 | 2020-09-24 | 日本製鉄株式会社 | 閉断面構造体 |
JP2021078462A (ja) | 2019-11-21 | 2021-05-27 | 日油株式会社 | 製パン用油脂組成物、製パン用穀粉生地、製パン用穀粉生地の製造方法 |
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