Technical field
[0001]The present invention relates to a hat member having impact resistance.
BACKGROUND
[0002]Structural member used as a reinforcing member of the vehicle, high strength and light weight are required. Furthermore, the structural member, and impact resistance, deformation amount of inhibition often sought by the impact. Therefore, one structural member, which may comprise both impact sites and energy absorption site. Therefore, there is a case to vary the intensity distribution of the structural member partly.
[0003]For example, International Publication No. 2013/137454 (Patent Document 1), without applying the welding method has a region corresponding to the impact site and energy absorption site in a single molded article, according to each region Te, hot press molded product is disclosed which can achieve a balance of high strength and elongation.
[0004]Further, Japanese Patent 2011-173166 (Patent Document 2), composite pressing device is disclosed for facilitating separate formation of the high strength portion and a low strength portion in one of the press-molded product.
[0005]
　Patent No. 5894081 Publication, B-pillar for a vehicle is disclosed. The B pillar is provided with a central flange, two web portions, and a section of the hat shape including two side flanges. Section of the hat shape from a flat plate of boron steel is hot forming and cured. Section of the hat shape has a breaking strength of greater than 1400 MPa. In the curing step, part of the side flanges is not fully cured, has a breaking strength of less than 1100 MPa.
CITATION
Patent Document
[0006]
Patent Document 1: International Publication 2013/137454 Patent
Patent Document 2: JP 2011-173166 Patent Publication
Patent Document 3: Japanese Patent No. 5894081
Summary of the Invention
Problems that the Invention is to Solve
[0007]
　The above prior art is a technique to separately form the intensity in one member. However, for the intensity distribution in the member in order to obtain a sufficient impact-absorbing ability, there is room for further study.
[0008]
　The present application discloses a hat member having an intensity distribution can absorb impact energy efficiently.
Means for Solving the Problems
[0009]
　Hat member in one aspect of the present invention includes a top wall, and two first ridge at each end of said top wall, from one end adjacent said first edge line, an angle formed between the top surface portion It comprises two side walls extending to the other end in the direction of 90 ~ 135 °. Central hardness Dc defined by the hardness of the lower of the two hardness of the intermediate position in the direction perpendicular to each of the top surface of the side wall is at least 300 HV. Each of said two side walls has a softening unit, and a strength transition portion adjacent to the softened portion. The softened portion is provided in a range of up to short of the intermediate position from the other end. Hardness Dn of the softened portion is at least 8% lower than the center hardness Dc (Dc-Dn ≧ 0.08Dc). Said intensity transition is adjacent to the softened portion, wherein a range of more than 0.5mm toward said one end from the softened portion, the other end side than the middle position between the one and the end the other end It is provided to. Hardness Dt of the intensity transition transitions 8% to 1% range lower than the central hardness Dc (0.92Dc ≦ Dt ≦ 0.99Dc). The hat member further comprises two second edges respectively adjacent to said other end of said two side walls, extending from said two second ridge away from each other, at least 8% hardness than the central hardness and a lower two flanges.
[0010]
　Note that the front of the middle position, means any position between the other end and an intermediate position. Before the intermediate position does not include the other end and an intermediate position.
The invention's effect
[0011]
　According to the present disclosure can provide a hat member having an intensity distribution can absorb impact energy efficiently.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
It is a cross-sectional view in a plane perpendicular to the longitudinal direction of the hat member in FIG 1A] present embodiment.
Hat member 1 shown in FIG. 1B] FIG. 1A is a side view from the x-direction.
It is a graph showing an example of the intensity distribution in FIG. 2 the side wall.
It is a sectional view showing a modified example of the cross-sectional shape of FIG. 3 hat member.
It is a cross-sectional view showing another modified example of the cross-sectional shape of FIG. 4 hat member.
Is a side view showing an example of FIG. 5A] curved structural member.
Is a side view showing an example of FIG. 5B] curved structural member.
Is a side view showing an example of FIG. 5C] curved structural member.
Is a side view showing an example of FIG. 5D] curved structural member.
6 is a diagram showing an example of the structure member disposed on the vehicle.
It is a diagram showing a configuration of an analysis model in FIG. 7 simulation.
8 is a diagram showing a mesh hat member in the analysis model shown in FIG.
9 is a graph showing the SS curve of the material of the hat member of the analysis model.
It is a diagram for explaining FIG. 10 simulation set with the intensity distribution.
11 is a diagram showing a deformation state upon collapse of the hat member in the simulation.
It is a graph showing FIG. 12 the simulation results the relationship between the displacement amount and the reaction force at the time of crushing showing.
13 is a perspective view of a molded article was produced as Example.
14 is a diagram for explaining a plurality of molded articles each intensity distribution.
[FIG. 15A] is a diagram illustrating a configuration example of a press-forming devices.
[FIG. 15B] is a diagram illustrating a configuration example of a press-forming devices.
[FIG. 16A] is a diagram illustrating a configuration example of a press-forming devices.
[FIG. 16B] is a diagram illustrating a configuration example of a press-forming devices.
Is a top view of a model part in FIG. 17 the center pillar.
18 is a sectional view of A-A line shown in FIG. 17.
19 is a graph showing a speed pattern of triplicate punch.
Is a graph showing FIG. 20 hardness distribution of the model components.
DESCRIPTION OF THE INVENTION
[0013]
　For example, structural members such as used in the bodywork, it is required a high strength and lightweight. Higher strength of the structural member, toughness tends to decrease. Therefore, high-strength structural members will tend to fracture prematurely in stress multiaxiality high deformation field. That is, the strength of the structural member is high, in the secondary deformation such as collision, easily brittle fracture. As a result, structural members having increased strength, it may not be possible to achieve the desired impact resistance.
[0014]
　For example, the structural members of the steel, it is possible to increase the toughness by a heat treatment tempering. In general, increasing the toughness of the structural members, the strength is lowered. As a result, it decreases the maximum load during crushing of the structural member. While increasing the toughness of the structural member, for suppressing the decrease in the maximum load, the inventors under various conditions were carried back portion grilled structural member. As a result, in certain conditions, it was found to be both an improvement in maximum load in toughness and crushing of the structural member.
[0015]
　Therefore, the inventors have studied in more detail. More specifically, in order to improve the maximum load at the time of crushing deformation of the hat member, it focused on deformation mode of the side wall. By causing the strength of the side wall partially changed, an attempt was made to control the deformation mode of the side wall. Result of trial and error, by providing the intensity transition to the side wall, has been found to be able to control the deformation mode to improve the maximum load. Based on this finding, and conceived the structural member of the following embodiments.
[0016]
　Hat member in an embodiment of the present invention includes a top wall, and two first ridge at each end of said top wall, from one end adjacent said first edge line, an angle formed between the top surface portion 90 in the direction of ~ 135 ° with two side walls extending to the other end. Central hardness Dc defined by the hardness of the lower of the two hardness of the intermediate position in the direction perpendicular to each of the top surface of the side wall is at least 300 HV. Each of said two side walls has a softening unit, and a strength transition portion adjacent to the softened portion. The softened portion is provided in a range of up to short of the intermediate position from the other end. Hardness Dn of the softened portion is at least 8% lower than the center hardness Dc (Dc-Dn ≧ 0.08Dc). Said intensity transition is adjacent to the softened portion, wherein a range of more than 0.5mm toward said one end from the softened portion, the other end side than the middle position between the one and the end the other end It is provided to. Hardness Dt of the intensity transition transitions 8% to 1% range lower than the central hardness Dc (0.92Dc ≦ Dt ≦ 0.99Dc). The hat member further includes two second edges respectively adjacent to said other end of said two side walls, and a flange extending in a direction away from each other from the two second ridgeline.
[0017]
　In the above configuration, the two side walls extends in a direction from 90 to 135 degrees relative to the top surface. That is, the angle formed by the direction perpendicular to the side walls and top wall are made within 45 degrees. In each side wall, toward the first ridgeline that contacts the second ridge in contact with the flange on the top wall, until the middle position of the side wall, and a softening unit, the intensity transition portion is disposed adjacent to order. Here, the center hardness of the intermediate position of the side walls and above 300 HV, is set the hardness of the softened portion of at least 8% than the center hardness low. Intensity of the intensity transition transitions between 8% lower hardness than the center hardness up to 1% lower hardness than the center hardness. The intensity transition is provided in a range of more than 0.5mm in a direction towards the one end from the softened portion. That is, the width from the end closer to the first edge line of intensity transition to an end closer to the second edge line (i.e., the end in contact with the softened portion) is 0.5mm or more. Thus, by providing the softening part and an intensity transition, as compared with the case where the maximum load when a load is applied in the direction perpendicular to the top wall is not provided softened part and an intensity transition, it improves. Therefore, hat member having an intensity distribution can absorb impact energy efficiently can be provided.
[0018]
　In the above arrangement, when collapse of the structural member when a load is applied in the direction perpendicular to the top wall, the near intensity transition can be a deformation mode for preferentially deformed. In this case, further, the plastic strain is distributed so that not too concentrated in a narrow range by the vicinity intensity transition. That is, by providing the strength transition portion, while controlling the deformation mode, the effect of dispersing the plastic strain is obtained. As a result, the maximum load during crushing is estimated to be improved.
[0019]
　In the above configuration that the width from the end closer to the first edge line of the intensity transition to an end closer to the second ridge is less than 5 times the average thickness of the intensity transition It is preferred. Thus, by the intensity transition can be drawn more effective control and plastic strain distribution of deformation modes.
[0020]
　In the above structure, the width Lt from the end closer to the first edge line of the intensity transition to an end closer to the second ridge is preferably set to 1mm or more, be 3mm or more more preferable. Thus, by the intensity transition, control and certainty of the effect of plastic strain distribution of deformation mode is increased. From the same viewpoint, the width Lt from the end closer to the first edge line of the intensity transition to an end closer to the second ridge, than 0.5 times the average thickness t of the intensity transition big (Lt> 0.5 t) is preferably, and more preferable to be 1.0 or more (Lt ≧ 1.0 t), still preferably a 3.0 or higher (Lt ≧ 3.0t).
[0021]
　In the above structure, the rate of change of hardness in the direction toward the one end from the other end in the intensity transition, it is preferable that the 3 ~ 100HV / mm. It becomes the hardness change rate is easily broken by concentration of strain intensity transition exceeds 100 HV / mm, hardness change ratio is for a 3HV / mm less than the fully deformed intensity transition does not enter .
[0022]
　In each of the two side walls, the hardness of a portion other than the softened part and an intensity transition portion including an intermediate position may be the same hardness as the center hardness. That is, in each of the two side walls, a portion other than the softened part and an intensity transition, the portion including the middle position, the hardness may be high-strength portion of the above 300 HV. Or between the intermediate position and the first edge line, the softening of at least 8% lower hardness than the center hardness may be provided.
[0023]
　The hardness of the two flanges may be at least 8% lower than the center hardness. For example, the softening unit may be formed in a region from the flange to reach the front of the middle position of the through the second ridge and the side wall. In this case, the softening unit may be formed on the entire flange may be formed on a part of the flange.
[0024]
　Structural members of a closed cross section comprising a said hat member, and a closing plate to be bonded to the flange of the hat member are also included in embodiments of the present invention.
[0025]
　The hat member may be curved to be convex on the top surface side. Further, the vehicle body structure, a center pillar (B-pillar) and reinforcement or bumpers and reinforcement thereof containing the hat member are also included in embodiments of the present invention.
[0026]
　In the present invention, HV is a unit of Vickers hardness. Hardness of the hat member in the present invention is the Vickers hardness measured at Z2244 test method JIS. Incidentally, the Vickers hardness, can be converted to tensile strength or yield strength. Further, in the present invention, hardness is intended to mean a Vickers hardness.
[0027]
　The method of manufacturing the hat member is also one embodiment of the present invention. Method for producing a hat member in an embodiment of the present invention is a method for producing the hat member by press-forming using a punch and a die blank. In this manufacturing method, by heating the blank to above 900 ° C., for soaking or 1 minute at 900 ° C. or higher. Wherein when the temperature of the blank is 600 ° C. or higher 800 ° C. or less in contact with the die shoulder of the die, the die shoulder and the plate pressing surface of the punch (face) and was Surechigawa a forming said first ridge by . Wherein when the temperature of the blank is 300 ° C. or higher 700 ° C. or less in contact with half the height of the vertical wall of the die, and a plate holding surface of the half the height of the vertical wall of the die the punch to Surechigawa.
[0028]
　For example, when the temperature of the blank is 600 ~ 800 ° C. was Surechigawa a plate pressing surface of the die shoulder and the punch in, then, lowering the relative velocity between the die and the punch, down the temperature of the blank 300 ~ 700 ° C. and it is possible to Surechigawa height half position and the pressing surface of the punch of the vertical wall of the die when it becomes. Alternatively, when the temperature of the blank is 600 ~ 800 ° C. was Surechigawa a plate pressing surface of the die shoulder and the punch in, then leave away the punch and die, again Surechigawa the plate pressing face of the die shoulder and the punch so, it is possible to make pass each other and half the vertical wall height and the plate pressing surface of the punch of the die when it cools down in the blank to 300 ~ 700 ° C..
[0029]
　Blank, also called sheet material i.e. the material plate. Blanks, for example, steel. The manufacturing method includes the steps of heating soaking more than one minute blank above 900 ° C., a step of forming start temperature of said first ridge forming said first ridge at 600 ° C. or higher 800 ° C. or less and a step of forming start temperature of the second ridge is formed at 300 ° C. or higher 700 ° C. or less. Thus, the hat member with two of the vertical wall containing the softening unit and the intensity transition can be efficiently produced.
[0030]
　In the above manufacturing method, in the state in which the plate-shaped blank between the punch and the die, is moved in a direction to approach the punch against the die. Die has a recess. Punch reciprocates outside and during the time of the recess of the die. In this configuration, the distance in the stroke direction of the punch from the position of the plate pressing surface of the punch in the molding bottom dead center of the recess of the die to the edge or the die shoulder of the recess of the die to the height of the vertical wall of the die. Plate pressing surface of the punch, a plane that is at most protruding position in the stroke direction at the time of molding bottom dead center of the face of the punch. Plate pressing face of the die, and a plane that is at most protruding position in the stroke direction at the time of molding bottom dead center of the face of the die.
[0031]
　Method for producing a hat member in another embodiment of the present invention is a method for producing the hat member by press-forming using a punch and a die blank. In this manufacturing method, by heating the blank to above 900 ° C., for soaking or 1 minute at 900 ° C. or higher. Said die by Surechigawa the shoulder and the plate pressing surface of the punch and molding the first edge line, so Surechigawa the plate pressing surface of the punch height half the vertical walls of the die molding a second ridgeline.
[0032]
　In the above manufacturing method, since half the height of the vertical wall and the plate pressing surface of the punch of the die pass each other, to the plate pressing surface of the punch reaches the molding bottom dead center, the said die the average relative speed V2 of the punch, the die shoulder and the plate pressing surface of the punch of the die and the punch when passing each other relative speed V1, desirable that a less than 1 in 20 minutes.
[0033]
　In this case, at least a part of between half the height of the die shoulder to the molding bottom dead center, it is possible to reduce the speed of the punch. Thus, it is possible to generate a hardness difference between the center position of the vertical wall of the hat member molded to the other end. Therefore, the hat member having a strength transition and the softening unit, can be efficiently produced.
[0034]
　For example, the forming speed V1 of the first ridge, the average extrusion rate V2 is the following relationship from the molding bottom dead center to the forming bottom dead center than half the position in the height of the hat member (1) it may be shaped to meet.
V2 / V1 <0.05 (1)
[0035]
　The height of the vertical wall of the die shoulder corresponds to the height of the vertical wall of the hat member to be produced. Therefore, at a height of half the vertical wall of the die shoulder, corresponding to the center position of the vertical wall of the hat member.
[0036]
　Method for producing a hat member in another embodiment of the present invention is a method for producing the hat member by press-forming using a punch and a die blank. In this manufacturing method, by heating the blank to above 900 ° C., for soaking or 1 minute at 900 ° C. or higher. The die shoulder and the plate pressing surface of the punch by Surechigawa the (face) and molding the first ridge, and a plate holding surface of the half the height of the vertical wall of the die the punch Surechigawa not forming the second ridgeline to.
[0037]
　In this manufacturing method, the surface of the punch at a position opposite to the plate pressing surface of the die, or thermal conductivity 0.3 (W / m · K) or less of the heat insulating material provided on the plate pressing surface of the die it may be. In this case, the period from half the height of the vertical wall and the plate pressing surface of the punch of the die pass each other, to the plate pressing surface of the punch reaches the molding bottom dead center, the blank the it may be contacted with a heat insulating material. Furthermore, the average from half the height of the vertical wall and the plate pressing surface of the punch of the die is passing each other, to the plate pressing surface of the punch reaches the molding bottom dead center, of the die and the punch the relative speed V2 is the die shoulder and the plate pressing surface of the punch of the die and the punch when passing each other relative speed V1, may be 1 or less 1 or 2 minutes of the 20 minutes.
[0038]
　In this case, at least a part of between half the height of the die shoulder to the molding bottom dead center, blank contacting the heat insulating material, and the speed of the punch can be reduced. Thus, it is possible to generate a hardness difference between the center position of the vertical wall of the hat member molded to the other end. Therefore, the hat member having a strength transition and the softening unit, can be efficiently produced.
[0039]
　For example, the plate pressing surface of the die or the punch (face), a contact portion for contact with the blank during the press molding, thermal conductivity 0.3 (W / m · K) was composed of the following heat insulating material it may be. In this case, the the forming speed V1 the average forming speed V2 may be shaped to satisfy the following formula (2).
0.05 ≦ V2 / V1 ≦ 0.5 ( 2)
[0040]
　Method for producing a hat member in another embodiment of the present invention is a method for producing the hat member by press-forming using a punch and a die blank. In this manufacturing method, by heating the blank to above 900 ° C., for soaking or 1 minute at 900 ° C. or higher. The die shoulder and the plate pressing surface of the punch by Surechigawa the (face) and molding the first ridge, and a plate holding surface of the half the height of the vertical wall of the die the punch Surechigawa not forming the second ridgeline to.
[0041]
　In the above production method, the period from half the height of the vertical wall and the plate pressing surface of the punch of the die pass each other, to the plate pressing surface of the punch reaches the molding bottom dead center, the blank the surface of the punch 300 ° C. or higher in a position opposite to the plate pressing surface of the die or may be contacted with the plate pressing surface of the die above 300 ° C.. In this case, since the plate holding surface of the vertical wall of height between the half position the punch of the die pass each other, the plate pressing surface of the punch until it reaches the molding bottom dead center, the die and of the punch the average relative velocity V2, the the die shoulder and the plate pressing surface of the punch relative velocity V1 of the die and the punch when passing each other, it may be less than one-half of one or more of the 20 minutes.
[0042]
　In this case, at least a part of between half the height of the die shoulder to the molding bottom dead center, blank contacting the 300 ° C. or more plates pressing face, and the speed of the punch can be reduced. Thus, it is possible to generate a hardness difference between the center position of the vertical wall of the hat member molded to the other end. Therefore, the hat member having a strength transition and the softening unit, can be efficiently produced.
[0043]
　For example, may be heated contact portion for contact with the blank during press molding 300 ° C. or higher in the plate pressing surface of the punch or die. In this case, the the forming speed V1 the average extrusion rate V2 may be shaped to satisfy the above expression (2).
[0044]
　[Embodiment]
　FIG. 1A is a sectional view perpendicular to the longitudinal direction of the hat member in the present embodiment. Figure 1B is a side view from a direction parallel (x-direction) perpendicular and top wall of the hat member 1 in the longitudinal direction shown in FIG. 1A. Figure 1A shows a cross-section of the hat member 1 along the line A-A in FIG. 1B.
[0045]
　Hat member 1 has a top wall 13, and two first edge line 113 at the ends of the top wall 13, two first ridge 113 and two side walls 11 extending respectively in the two side walls 11 top wall 13 and comprises two second edges 114 at the opposite end, the two flanges 14 extending so away from each other from the two second ridge 114.
[0046]
　The angle theta formed by the top wall 13 and side walls 11, a 90 ° ≦ θ ≦ 135 °. One end of the side wall 11 is adjacent to the first ridge 113. The other end of the side wall 11 is adjacent to the second ridge 114. The first ridge 113 and the second ridge 114 are all extending in the longitudinal direction of the hat member 1. In the example shown in FIG. 1, the first ridge 113 and the second ridge 114 are parallel to each other, it may not be parallel to each other.
[0047]
　Each boundary portion between the top wall 13 of the two side walls 11, a bending portion (R) 5 is formed. That is, the end portion including the one end of the side wall 11 has a rounded curved shape. Thus, the surface of the shoulder portion of the hat member in the boundary between the side wall 11 and top wall 13 is made a curved surface. The curved portion (R) 5 is as being part of the side wall 11, side walls 11, the height H in a direction perpendicular to the top wall 13 is determined. That is, the curved portion (R) 5 top wall 13 side end of the R boundary of (R stoppage) 5b, and one end of the side wall 11. The first ridge 113 is adjacent to one end i.e. R boundary 5b of the side wall 11.
[0048]
　Respectively of the two side walls 11, the boundary portion between each of the two flanges 14, the curved portion (R) 6 is formed. That is, the end portion including the other end of the side wall 11 has a rounded curved shape. Thus, the surface of the shoulder portion of the hat member in the boundary between the side wall 11 and the flange 14 is a curved surface. The curved portion (R) 6 as a part of the side wall 11, side walls 11, the height H in a direction perpendicular to the top wall 13 is determined. That is, the curved portion (R) 6 flange 14 side end of the R boundary of (R stoppage) 6b, and the other end of the side wall 11. The second ridge 114 is adjacent to the other end of the side wall 11.
[0049]
　Central hardness Dc defined by the lower hardness of the hardness of each intermediate position 11c of the two side walls 11 in a direction perpendicular to the top wall 13 (z-direction) is not less than 300 HV. In other words, hardness at an intermediate position 11c of the two side walls 11 is greater than or equal to 300 HV.
[0050]
　Each two side walls 11, a softening unit L, the intensity transition portion T is provided. Softening unit L is provided in a range from the other end of the side wall 11 (R boundary 6b) to just before the intermediate position 11c. In the example shown in FIG. 1A, a softening unit L is provided in the bending portion 6 and the flange 14. Hardness Dn softening unit L is at least 8% lower than the center hardness Dc (Dc-Dn ≧ 0.08Dc).
[0051]
　Intensity transition T is adjacent to the softened portion L. Intensity transition T is a one end extent of more than 0.5mm toward the toward the (R boundary 5b) of the side wall 11 from the softening unit L, one end (5b) and the other end of the side wall 11 of (6b) from the intermediate position 11c between provided on the other end (6b) side. Specifically, the end Tu closer to the first edge line 113 of the intensity transition T, the width Lt between the end Td closer to the second ridge 114 is greater than or equal to 0.5 mm. The end Tu closer to the first ridge 113 of these intensity transitions, ends Td closer to the second ridge 114 are both between the intermediate position 11c and the other end of the side wall (6b) To position.
[0052]
　Hardness of intensity transition T is 8 to 1% range lower than the center hardness. That is, the hardness of the intensity transition T is 8% from the central lower hardness hardness, transitions between up to 1% lower than the center hardness.
[0053]
　By providing such a softening unit L and the intensity transition T, the maximum load when a load is applied in a direction perpendicular (z direction) in the top surface portion 13, compared with the case without the softening part and an intensity transition it is possible to improve Te. In the example shown in Figure 1B, the width in the perpendicular direction (z-direction) on the top surface 13 of the intensity transition T is constant in the longitudinal direction (y-direction) of the hat member. Not limited thereto, the width in the perpendicular direction (z-direction) on the top surface 13 of the intensity transition T may be changed in the longitudinal direction (y-direction) of the hat member. In that case, the end Tu of the intensity transition T, the width Lt between the end Td is the average value in the longitudinal direction (y direction) of the portion where the intensity transition of hat member 1 is present.
[0054]
　Further, in the example shown in FIG. 1B, the intensity transition portion T is formed over the entire longitudinal direction of the hat member 1 (y direction), it may be the strength transition portion T is provided on a part of the length . In that case, for example, the longitudinal dimension of intensity transition T is preferably equal to or greater than the height H of the side wall. Thus, it is possible to increase the certainty of the effect of improving the maximum load of the.
[0055]
　Arrangement range of the intensity transition portion T in the longitudinal direction of the hat member 1 is not particularly limited, describing an arrangement example below. It is preferable to dispose the intensity transition portion T in a region including the center in the longitudinal direction of the hat member 1. Thus, a portion locally deformed due to the vertical direction of the impact load to the top wall is assumed, it is possible to arrange the intensity transition T. Also, hat member 1, two support portions longitudinally spaced, which may be supported on another member. In a region including the longitudinal center of the two support portions of the hat member 1, it is preferable to dispose the intensity transition T. Thus, a portion locally deformed due to the vertical direction of the impact load to the top wall is assumed, it is possible to arrange the intensity transition T.
[0056]
　Also, hat member 1 in the longitudinal direction, it may be curved to be convex top wall 13 side. In this case, when the top wall 13 has placed a hat member 1 so that the upper horizontal plane, the side wall 11 of the portion top wall 13 is the highest, it is preferable to arrange the intensity transition T. Thus, a portion locally deformed due to the vertical direction of the impact load to the top wall against the top wall is envisaged, it is possible to arrange the intensity transition T. Alternatively, the closing plate may be joined to a pair of flanges 14 of the hat member 1. In this configuration, the hat member 1 in the longitudinal direction, may be curved to be convex closing plate side. In this case, when the closing plate is placed a hat member 1 so that the upper horizontal plane, the side wall 11 of the portion closing plate is the highest, it is preferable to arrange the intensity transition T. This makes it possible to local deformation due to the vertical direction of the impact load to the closing plate for closing plate in a portion contemplated to place an intensity transition T.
[0057]
　As an example, the hat member 1, a bumper reinforcement or, if used as a center pillar (B-pillar), may be arranged intensity transition portion T in a region containing the longitudinal center of the bumper reinforce, or the center pillar.
[0058]
　Further, the softening unit L may be formed over the entire longitudinal direction of the hat member 1 (y direction), it may be formed on a part of the length. For example, the longitudinal dimension of the softened portion L is preferably equal to or greater than the height H of the side wall. Thus, it is possible to increase the certainty of the effect of improving the maximum load of the.
[0059]
　Arrangement range of the softening unit L in the longitudinal direction of the hat member 1 is not particularly limited. For example, in the longitudinal direction of the hat member 1, it may be arranged softened portion L at a position overlapping the intensity transition T.
[0060]
　Figure 2 is a graph showing an example of the intensity distribution in the side wall 11. In the example shown in FIG. 2, the central hardness Dc is the hardness in the intermediate position 11c of the side wall 11 is more than 300HV (Dc ≧ 300HV). And hardness Dn softening unit L, the difference Derutadi3 the center hardness Dc of the side wall 11 is more 0.08Dc (ΔD3 = Dc-Dn ≧ 0.08Dc). That is, the maximum hardness of the softened portion L is 0.92Dc. In the example shown in FIG. 2, the flange 14 and the curved portion 6 it is also included in the softened portion L. In some of the softened portion L, to the extent that does not affect the material properties may include a region where the hardness exceeds 0.92Dc.
[0061]
　In between intermediate positions 11c of the side wall 11 from the second ridge 114, the hardness of the side wall 11, the closer the second ridge 114 in the intermediate position 11c, is high.
[0062]
　Between the intermediate position 11c of the softened portion L and the side wall 11, there is intensity transition T. Hardness Dt of intensity transition T is toward the softened portion L at the intermediate position 11c, a transition from Dd to Du. That is, the hardness Dt of intensity transition T transitions in the range of Dd ≦ Dt ≦ Du. Hardness Dd is, 0.08Dc lower than the central hardness Dc. That is, the difference between the minimum hardness Dd and the center hardness Dc intensity transition T .DELTA.D2 is 0.08Dc (ΔD2 = Dc-Dd = 0.08Dc). Maximum hardness Du intensity transition T is, 5HV lower than the center hardness Dc. That is, the difference .DELTA.D1 between hardness Du and the central hardness Dc is 0.01Dc (ΔD1 = Dc-Du = 0.01Dc).
[0063]
　In the example shown in FIG. 2, the side walls 11, the position of 8% from the center hardness Dc low hardness, the end closer to the second edge line 114 of the boundary or intensity transition portion T of the softening portion L and the intensity transition T the Td. Further, in the side wall 11, the position of the 1% lower hardness than the center hardness Dc is a strength transition portion T, the first ridge 113 of the boundary or intensity transition portion T of the region including the intermediate position 11c (non-softened portion) the end Tu closer.
[0064]
　In the example shown in FIG. 2, the hardness of the intensity transition T is higher the closer to the middle position 11c. That is, the hardness of the intensity transition T is toward the softened portion L at the intermediate position 11c, monotonically increasing. Incidentally, the transition of the hardness in the intensity transition T may be any tendency to monotonically increase the overall strength transition T. Some of intensity transition T, the closer to the middle position 11c, area or the hardness is low, region or hardness no change in hardness may include certain regions by position.
[0065]
　Width Lt of the side wall 11 from the end Td closer to the second ridge 114 of the intensity transition portion T to the end Tu closer to the first ridge 113 is 0.5mm or more (Lt ≧ 0.5mm) . Thus, when the applied vertical load on the top wall 13, strain intensity transition portion T can be prevented too concentrated. The width Lt, for example, it is preferably not more than 5 times the average thickness t of the intensity transition T (Lt ≦ 5t). Thus, when the applied vertical load on the top wall 13, to concentrate the deformation to the intensity transition, it is possible to obtain the preferred deformation mode. The width Lt is across Tu intensity transition portion T in a line projected onto the surface of the side wall 11 perpendicular direction of the line to the top wall 13, the distance between the Td.
[0066]
　The rate of change of hardness in the intensity transition (Du-Dd) / Lt, for example, preferably set to 3 ~ 100HV / mm (3 [HV / mm] ≦ (Du-Dd) / Lt ≦ 100 [HV / mm ]). It becomes the hardness change rate is easily broken by concentration of strain intensity transition exceeds 100 HV / mm, hardness change ratio is for a 3HV / mm less than the fully deformed intensity transition does not enter .
[0067]
　In the example shown in FIG. 2, between the intermediate position 11c and the first ridge 113 of the side wall 11, the hardness is greater than or equal to the high-strength portion 300 HV. In contrast, from the first ridge 113 in the intermediate position 11c of the side wall 11, the range up before the intermediate position 11c, even if the hardness is provided a second softened portion low 8% or more from the center hardness good.
[0068]
　Incidentally, the distribution of intensity and strength of the flange 14 is not particularly limited. This is because the strength of the flange 14 is because not have a particularly large impact on the performance of the hat member 1.
[0069]
　Figure 3 is a sectional view showing a modification of the cross-sectional shape of the hat member 1. Hat member 1 shown in FIG. 3 has two side walls 11 having different shapes. Two side walls 11, an angle θ1 with respect to top wall 13, .theta.2 and the height HR, HL are different from each other. Therefore, the position in the height direction of the two flanges 14 are different. Thus, if the cross section of the hat member 1 is asymmetrical, two side walls 11, respectively the height H1, H2 are defined separately.
[0070]
　In the example shown in FIG. 3, the side wall 11 of one of the two side walls 11 and 12, has a step. Thus, even if there is a step on the side wall 11, from one end in contact with the first ridge 113, the height dimension to the other end in contact with the second ridge 114, and the height H1 of the side wall 11 . That is, in the height direction, a dimension of up to the highest position from the lowest position of the side wall 11, and the height H1 of the side wall 11. The side wall 11, the same applies to the case where there are irregularities or pores. The height direction is the direction perpendicular to the top wall 13.
[0071]
　Although not shown, at least one surface of the top wall 13, side walls 11, and flanges 14 may be curved rather than planar. In other words, top wall 13, at least one of the side walls 11, and flanges 14 may be curved.
[0072]
　Figure 4 is a sectional view showing a modification of the cross-sectional shape of the hat member 1. Hat member 1 shown in FIG. 4, top wall 13 includes the inclined portion 13a at both ends, and 13c, the inclined portion 13a, a central portion 13b between the 13c. Inclined portions 13a, 13c, respectively, in contact with the first ridge 113, has an inclined surface. The inclined surface of the inclined portion 13a, 13c is enough to go to the inside of the top wall 13 is inclined so that the lower. In other words, top wall 13 has a recess. In this case, the direction perpendicular to the central portion 13b of the top wall 13, a direction perpendicular to the top wall 13, the height H1, H2 of the side wall 11 is defined. Further, the angle between the surface and the side wall 11 of the central portion 13b of the top wall 13, the angle between the top wall 13 and side walls 11. In the example shown in FIG. 4, the curved portion 5 between the top wall 13 and side walls 11 is slightly bulging outward.
[0073]
　In the example shown in FIGS. 1A and 1B, the hat member 1 is formed to extend linearly in the longitudinal direction. In contrast, the hat member 1 may be curved. For example, the hat member 1 may be a curved shape so as to be convex on the top surface 13 side. That is, the outer surface of the top wall 13 may be curved hat member 10 so as to project.
[0074]
　FIGS. 5A ~ 5D are side views showing an example of a hat member 1 which is curved in the longitudinal direction. In the example shown in FIGS. 5A ~ FIG 5D, hat member 1 is curved to be convex top wall 13 side. 5A, the hat member 1 is curved at a constant curvature throughout the longitudinal direction. In Figure 5B and 5C, longitudinal curvature according to the position of (the extending direction of the first two lines) of the closed section structural member of the hat member 1 is changed. In FIG. 5D, hat member 1 is curved at a part of the length. In the example shown in FIGS. 5A and FIG. 5D, hat member 1 is curved so as to be symmetrical as viewed from a direction perpendicular to the side wall 11 (x-direction). 5B, the hat member 1 of FIG. 5C, and 5D includes a curved a portion (a curved portion) and a portion extending in a straight line (straight line portion). In the example shown in FIG. 5C, the curved portion is disposed on both longitudinal sides of the straight portion. That is, the straight line portion is arranged between the curved portion. In the example shown in FIG. 5D, the linear portions are arranged on both longitudinal sides of the curved portion.
[0075]
　By thus curving the hat member 1, it is possible to improve impact resistance against an impact in the direction opposite to the convex direction of the bending. For example, structural members formed by supporting both ends of the bonding the closing plate a curved hat member 1 structural member, with respect to the direction of the impact faces the convex direction of the bending, with a high impact resistance. Note that as the top surface 13 is concave, may also be curved hat member 1.
[0076]
　Application Example of the vehicle]
　structural member formed by joining closing plate to the flange 14 of the hat member 1, for example, may be used as a structural member for a vehicle. In this case, the structural members, may be attached to a vehicle while supporting the two connecting portions longitudinally spaced. Structural member comprising a hat member 1 is, for example, the vehicle body is used as a structural member of a bumper or vehicle door. Therefore, the vehicle body comprising a structural member comprising a hat member 1, also a bumper or vehicle door, are included in embodiments of the present invention.
[0077]
　When installing a structural member comprising a hat member 1 to the vehicle, it is often longitudinal structural member is located a structural member so that along the contour of the vehicle. That is, as the impact in the case of a vehicle collision is perpendicular to the longitudinal direction of the structural member, the structural member is often attached to the vehicle. Further, on the outside of the top wall 13 is a vehicle, so closing plate is positioned inside the vehicle, there is the structural member is attached to the vehicle. Thus, in the event of an impact from the outside of the vehicle structural member, the degree to which structural member protrudes to the inside of the vehicle is reduced. Sometimes reverse the closing plate is arranged on the outside of the vehicle. Sometimes closing plate is arranged on the outside of the vehicle, in the event of an impact from the outside of the vehicle structural member, the degree to which structural member protrudes to the inside of the vehicle is reduced.
[0078]
　Structural member comprising a hat member 1, as described above, may be curved. In this case, the structural member is attached to the vehicle so as to be convex toward the outside of the vehicle. Thus, in the event of an impact from the outside of the vehicle, it can be more difficult to break the structural member.
[0079]
　Structural member comprising a hat member 1 may be a structural member constituting the vehicle body, a part of the bumper or the vehicle door. For example, it is possible to use A-pillar, B-pillar, side sill, locker, roof rails, floor members, the structural member comprising a member constituting a vehicle body such as a front side member of hat member 1. Alternatively, it attached to the body such as door impact beams or bumper reinforcement, it is also possible to use a structural member comprising a hat member 1 to member to protect the equipment and passenger in the vehicle from impact from the outside.
[0080]
　Figure 6 is a diagram showing an example of the structure member disposed on the vehicle of monocoque construction. In the example shown in FIG. 6, A-pillar 15, B-pillar 16, the rocker 17, roof rail 18, the bumper reinforcement 19, a front side member 20, the door impact beam 21, the floor members 22, and the structural member for the rear side member 23 in the vehicle used as. At least one of these vehicle structural member can be composed of a structural member containing the above hat member.
[0081]
　[Production Process]
　hat member 1 may form a whole with the same material. Hat member 1 is formed, for example, a steel plate. The manufacturing process of the hat member 10, includes the step of fabricating a hat member 1 having a softening unit L and the intensity transition T. The manufacturing process of the hat member 1, provide strength difference to the material includes the step of forming a low-intensity region. The step of curving the hat member 1 may be included in the manufacturing process. When bending the hat member 1, for example, press bending, tensile bending, bending compression, bending rolls, push-through bending or eccentric plug bending or the like of the bending method is used.
[0082]
　The manufacturing process of the hat member 1 includes a step of forming the softened part and an intensity transition in the material. A method of forming a softened part and an intensity transition is not particularly limited, for example, a steel sheet by roll forming and deforming the cross hat, laser or by the method of high frequency heating or the like, locally heating the material, hardening by performing, it is possible to produce a hat member 1 comprising a cured region. In this case, the area is not performed hardening becomes relatively low strength softening part and an intensity transition. Further, after the strengthening entire hat member 1 performs thermal refining, it is also possible to form the softened part and an intensity transition performed partially annealed.
[0083]
　Alternatively, it is also possible to manufacture the hat member 1 using a hot press (hot stamping) technology. In the step of hot pressing, by varying the conditions of the heating or cooling partially in the same material, it is possible to form the softening region and intensity transition region in the material. For example, by using a steel sheet, the steel is heated above the temperature (Ac3 temperature) as the austenite single-phase region, performing quenching while performing molding using a mold. At this time, by attaching a difference in cooling rate, quench is roughly hard martensitic structure, mildly unit is a mixed-phase structure or bainite structure of soft ferrite and pearlite. Thus, it is possible to mildly unit, the softened region and intensity transition region. Further, after the entire member was high-strength portion of the martensitic structure by hot pressing, it may be formed softened part and an intensity transition partially tempered.
[0084]
　As an example, a manufacturing process of the hat member may include a step of molding a steel plate, a step of quenching the steel sheet molding, and a step of the steel sheet quenching the hat shape partially tempered.
[0085]
　In the forming step, for example, a steel plate, by press molding while heat treatment above Ac3 point of at least one, and top wall, and two first ridge at each end of the top wall, a first from one end adjacent to the ridge, and two side walls an angle formed between the top surface portion extends to the other end in the direction of 90 ~ 135 °, and two second edges adjacent to the two other ends of the two side walls It is formed into a hat shape having two flanges extending from two second edges away from each other.
[0086]
　The quenching step, the central hardness defined by the lower hardness of the two side walls hardness of each intermediate position in the direction perpendicular to the top wall to quenching the molded steel plate so that the above 300 HV.
[0087]
　The tempering step, softened portion ranging from the other end of the two side walls of the steel plate quenching the hat-shaped to front intermediate position, and, adjacent to the softened portion, toward the one end from the softened portion 0.5mm a range above, while the intensity transition portion on the other end side than the position of the intermediate between the end and the other end, at least once, then heated to 200 ° C. or higher, at least the hardness of the softened portion from the center hardness 8 % lower, the hardness of the intensity transition 8% to 1% range lower than the center hardness.
[0088]
　The manufacturing method of the hat member 1 is not limited to the above example. For example, by using a tailored blank, it may form a hat member 1. As another example, more than 980 MPa (more preferably, more than 1180 MPa) to the molded article of the hat shape of the high strength steel sheet having a tensile strength of the tempering by laser major focused diameter, the other end of the side wall also be carried out in a range of intermediate positions, it is possible to obtain a hat member 1. Using other known methods, it may form a hat member 1 having a softening part and an intensity transition.
Example
[0089]
　[Simulation]
　In this example, the analysis of the deformation of the structural member when colliding the indenter hat member in the simulation. Figure 7 is a diagram showing the configuration of an analysis model in the simulation. In this simulation, top wall 130, a hat member 10 having a side wall 110 and flange 140, and analyzed the deformation behavior when a force is applied to compress in a direction perpendicular to the top wall 130. The size and shape of the hat member 10 in the analysis model is shown in Figure 7.
[0090]
　Figure 8 shows the mesh of the hat member 10 in the analysis model shown in FIG. Mesh shown in FIG. 8 is a configuration in which a mesh size is superimposed five layers mesh 0.28 mm. Element type, and a plane strain element (CPE8 [8 nodes, secondary elements). The number of nodes is, and 6607, the number of elements, was 1940. Young's modulus of the hat member 10, and 2.0594E + 5 [N / mm ^ 2], Poisson's ratio, 0.3 - was []. SS curve materials were used as shown in the graph of FIG. The characteristics of the low-strength material in the graph of FIG 9, is applied to the softened portion, the characteristics of high strength material in the graph of FIG. 9, was applied to the high-strength portion. The intensity transitions, apply multiple SS curve that gradually changes from the characteristics of high strength material and the characteristics of the low-strength material in the graph of FIG. 9, the material properties in the intensity transition is so gradual transition .
[0091]
　Using an analysis model of FIG. 7 and FIG. 8, by changing the intensity distribution of the side wall 110, a simulation was performed. Figure 10 is a diagram for explaining an intensity distribution set in the simulation. Two intensity distribution pattern V shown in FIG. 10, a simulation was performed in P. In the intensity distribution pattern V, there are softened portion L and the intensity transition T between the ends of the intermediate position 110c and the flange 140 of the side wall 110, a portion between the intensity transitions T and the top wall 130, high-strength portion it is. In the intensity distribution pattern P, a between the intermediate position 110c and the flange 140 of the side wall 110, between the top surface portion 130 and the intermediate position 110c, there is a softening unit L and the intensity transition T. Two intensity distribution pattern V, in each P, we analyzed by changing the width of intensity transition T. Specifically, the width of intensity transition T, is changed stepwise between 0.5 times to 6.0 times the average thickness of the intensity transition T, was analyzed at each stage.
[0092]
　The intensity of the other intensity manner shown in FIG. 10, the entire over high strength style intensity distribution and uniform intensity distribution of the N of the hat member 10, a uniform intensity distribution is softened throughout the hat member 10 distribution pattern a, the even intensity distribution patterns F which is softened only flange 140, were analyzed.
[0093]
　Figure 11 is a diagram showing a deformed state when the hat member 10 collapse in the simulation. Comparative Example 1 is the case of the intensity distribution pattern = N (uniformly high strength), Comparative Example 2 is the case of the intensity distribution pattern = F (flange only softening). Example 1 is the intensity distribution pattern is V, the width Lt of intensity transition portion, is 1.0 times the average thickness t of the intensity transition (1.0 t). Example 4, the intensity distribution pattern is P, the width Lt of intensity transition portion, is 1.0 times the average thickness t of the intensity transition (1.0 t).
[0094]
　As shown in FIG. 11, and if the intensity distribution pattern is V, the P, the intensity distribution pattern is N, in the case of F, the deformation behavior That member deformation mode different. Therefore, if the intensity distribution pattern is V, the P, that, in case of providing a softening unit and intensity transition in the side wall 110, the maximum load is larger.
[0095]
　Figure 12 is a graph showing the relationship between the displacement amount and the reaction force at the time of crushing the simulation results indicate. As shown in FIG. 12, the conditions of Comparative Examples 1 and 2 and Examples 1 and 4 are the same as FIG. 11. From the results shown in FIG. 12, in Examples 1, 4 of the case in which the softened portion and intensity transition to the side wall 110, as compared with Comparative Examples 1 and 2, the load collateral amount increases, the reaction force increases there.
[0096]
　Table 1 is a table showing the conditions and results of Comparative Examples 1-7 and Examples 1-6 in the simulation. In Table 1, the intensity distribution, the intensity transition portion of the side wall, the starting position of the intensity transition, and the length to the average thickness of the intensity transition is a condition of the simulation. In Table 1, the maximum load at the time of compression, maximum load stroke, strain surface maximum plastic at maximum load, bending crack whether is the result of the simulation. Intensity distribution shows the above intensity distribution pattern V, P, N, A, one of F. Starting position of the intensity transition portion, the distance from the end of the nearest side wall to the intensity transition portion of the side wall to the intensity transition, the side walls of a line obtained by projecting the line perpendicular to the surface of the sidewall length (top wall of the side wall It is shown whereas divided by the length) from the end to the other end of the (length of the distance / sidewalls from end to intensity transition). If this value is 0.5, indicating an intermediate position 110c of the side wall. The length to the thickness of intensity transition portion, the length of the intensity transition (the length between both ends of the intensity transitions of a line obtained by projecting the line perpendicular to the top wall to the surface of the side wall), the average of the intensity transition It is indicated by thick divided by value (the average thickness of the intensity transition portion length / strength transition). More superficial maximum plastic strain values ​​at maximum load is large, it can ensure load is too large crack occurs. The presence or absence of bending cracks, are determined to crack when the surface layer up to plastic strain> 0.5 at maximum load.
[0097]
[Table 1]

[0098]
　The results shown in Table 1, the case in which the intensity transition in the side wall (in the case of the intensity distribution = V or P), the case without the intensity transition (intensity distribution = N, A, F) as compared to, the maximum load is larger. The length of the intensity transition portion is greater than 0.5, if less than 6.0, the maximum load is larger.
[0099]
　[Molded article]
　FIG 13 is a perspective view of a molded article was produced as Example. The molding conditions are as follows. As a molding material, after hardening strength, it was used 2.0GPa grade HS for steel sheet (thickness 1.6 mm). The heating of the first time, for complete solid solution for molding material of the carbide, after the molding material was heated for about 5 minutes isothermally held until 1050 ° C., the molding was put into a press die went. Thereafter, a material obtained by molding and quenched by cooling to room temperature by using a contact heat transfer by the mold. Thereafter, the second heating, a material obtained by molding, was heated to about 900 ° C., it was quenched in a mold heated while molding press decided immediately poured into a mold. Thereafter, a material obtained by molding, partially contacting the mold heated up to 400 ° C., and heating the material up to 379 ° C. using a heat transfer.
[0100]
　In the molded article having the shape shown in FIG. 13, what intensity distribution different from a plurality of prepared was subjected to a compression test. Figure 14 is a diagram for explaining the intensity distributions of the plurality of molded articles. Aspects of the intensity distribution was N, V, and three types of P. Intensity distribution N are as quenched, that is, the molded article intensity distribution without tempering. Intensity distribution V includes a flange 14, in which tempering a portion of the curved portion of the side wall 11 of the flange 14 side (die shoulder). Between the flange 14 end of the side wall 11 to an intermediate position, the softening part and the intensity transition portion is formed. Intensity distribution P includes a flange 14, baked and part of the curved portion of the side wall 11 of the flange 14 side (die shoulder), the curved portion of the top wall 13 of the side wall 11 and an inclined portion of the (punch shoulder) and the top wall 13 it is those that were returned. And between the flange 14 side of the end wall 11 to the intermediate position, between the end of the top wall 13 of the side wall 11 to an intermediate position, the softening part and the intensity transition portion is formed. The compression tests were compressed to moldings in a direction perpendicular to the top wall 13.
[0101]
　Table 2 is a table showing the conditions and results of Comparative Example 8 and Examples 7 and 8 in the molded article. Item in each column of Table 2 are the same as in Table 1. In the results shown in Table 2, tempered molded articles so that the softening part and the intensity transition portion is formed on the side wall, compared with the molded article without tempering, the maximum load is larger.
[0102]
[Table 2]

[0103]
　[Example of Manufacturing Method]
　An example of the hot stamping technology manufacturing method of the hat member 1 with be described. In this example, by press forming a blank in a mold die and the punch, producing a hat member 1. 15A and 15B are diagrams showing a configuration example of an apparatus for press-molding using a die and punch. In the example shown in FIGS. 15A and 15B, as a mold, die 31 and the punch 32 is used. Die 31 has a recess. Recess includes a bottom portion 32c, and the vertical wall 32b. Vertical wall 32b is adjacent to the bottom 32a. Surface of the vertical wall 32b is inclined with respect to the surface of the bottom 32c. Punch 32 reciprocates the middle and outside of the recess of the die 31. Arrow SY indicates the direction, that is the stroke direction of the reciprocating motion of the die 31. Figure 15B die 31 and the punch 32 shows a state in which the molding bottom dead center.
[0104]
　As shown in FIGS. 15A and 15B, at the time of press molding, a plate-shaped blank 1A is disposed between the die 31 and the punch 32. Die 31 is moved toward the punch 32. At this time, the plate pressing surface 31a of the punch 32 in a central portion of the blank 1A is in contact, the central portion of the blank 1A is pushed into the recess of the die 31. When the plate pressing surface 32a and the die shoulder 31ab of the punch 32 pass each other, the die shoulder 31ab and the blank 1A is in contact, the molding of the first ridge line is started. As shown in FIG. 15B, when the die 31 has reached the molding bottom dead center, in a state where the blank 1A is filled between the punch 32 and the die 31.
[0105]
　Plate pressing surface 31a of the punch 32 is the surface of the tip of the punch 32. That is, in a state where the punch 32 is in the molding bottom dead center, the surface of the most projecting portion in the stroke direction is a plate-pressing face 31a of the punch.
[0106]
　In hot pressing, the blank 1A is a heated state, it is press-formed by the die 31 and the punch 32. Heating of the blank 1A is, for example, may be electrical heating. Electrical heating, the blank 1A is an arrangement state between the die 31 and the punch 32 is carried out by energizing with a electrode blank 1A. Alternatively, the blank 1A from being heated in a heating furnace, is disposed between the die 31 and the punch 32, it may be pressed.
[0107]
　By controlling the relative speed of the heating temperature and the die 31 and the punch 32 of the blank 1A in press forming, it is possible to produce a hat member with a softening part and an intensity transition as described above.
[0108]
　As an example, heating the blank 1A, the blank 1A is held for more than one minute soaking at or above 900 ° C.. Thereafter, when the temperature of the blank 1A in contact with the die shoulder 31ab of 600 ° C. or higher 800 ° C. or less, by Surechigawa the plate pressing surface 32a of the die shoulder 31ab and the punch 32, forming the first ridge 113. Further, when the temperature of the blank 1A in contact with the position of the half height of the vertical wall 31b of the die 31 (W / 2) of 300 ° C. or higher 700 ° C. or less, and a plate pressing surface 32a of the die shoulder 31ab and the punch 32 Surechigawa allowed by molding the first edge line 113, thereby Surechigawa a plate pressing surface 32a of the position and the punch 32 of the half height of the vertical wall 31b of the die 31 (W / 2). Thus, the hat member with a softening unit L and the intensity transition portion T of the above can be produced by hot-play molding. In this case, the tempering step for forming the softened portion L and the intensity transition portion T is not necessary.
[0109]
　Incidentally, as shown in FIG. 15B, the height W of the vertical wall 31b of the die 31 is the distance in the stroke direction from a height of the plate pressing surface 32a of the punch 32 to the height of the die shoulder 31ab in the molding bottom dead center .
[0110]
　Further, in the hot press forming, half height of the vertical wall 31b of the die 31 (W / 2) positions and from the plate pressing surface 32a of the punch 32 pass each other in the plate pressing surface 32 forming the bottom dead punch 32 to reach the point, it may reduce the average relative speed V2 of the die 31 and the punch 32. Thus, it is possible between the central position 11c and the second ridge 114 of the vertical wall 11 of the hat member molded to form a softened portion L and the intensity transition T. For example, a relative speed V1 die and the punch when the pass each other and the plate pressing surface of the die shoulder and the punch, as in the relationship between the average relative speed V2 of the is the following formula (1), controls the speed of the punch 32 it is preferable to. Thus, it is possible to more efficiently form a softened portion L and the intensity transition T.
V2 / V1 <0.05 (1)
[0111]
　The above speed control, if the surface 32b of the punch 32 to the plate pressing surface 31a and facing the die 31 is not provided with the heat insulating material, i.e., the thermal conductivity of the die 31 and the punch 32 is 0.3 ( W / m · K) is an example of greater than.
[0112]
　At least one thermal conductivity of the surface 32b of the plate pressing surface 31a and an opposing punch 32 of the die 31 may be provided with a 0.3 (W / m · K) or less insulation. In this case, for example, as V1, relation of V2 becomes the following formula (2), it is preferable to control the speed of the punch 32. Thus, it is possible to more efficiently form a softened portion L and the intensity transition T.
0.05 ≦ V2 / V1 ≦ 0.5 ( 2)
[0113]
　Between the plate pressing surface 32a of the punch 32, from passing each other with the position of the half height of the vertical wall 31b of the die 31 (W / 2) until it reaches the bottom dead center, the blank 1A is, 300 ° C. or more dies 31 of the plate pressing surface 31a, or, for contacting the surface 32b of the plate pressing face 31a opposed to 300 ° C. over the punch 32 of the die 31, may control the temperature of the die 31 or the punch 32. In this case, for example, as V1, relation of V2 becomes the equation (2), it is preferable to control the speed of the punch 32. Thus, it is possible to more efficiently form a softened portion L and the intensity transition T. Incidentally, the plate pressing surface 31a of 300 ° C. or more dies 31, and the both surface 32b of the plate pressing face 31a opposed to 300 ° C. over the punch 32 of the die 31, the plate pressing surface 32a of the punch 32, die 31 during a period from half height of the vertical wall 31b and the position of (W / 2) pass each other until reaching the bottom dead center, it may be brought into contact with the blank 1A.
[0114]
　16A and 16B are views showing a modification of the apparatus for press-molding using a die and punch. In the example shown in FIGS. 16A and 16B, the sheet holder 33 is attached to the die 31. Seat holder 33 includes an elastic member attached to the bottom 31c of the recess of the die 31, the push plate attached to the tip of the elastic member. Press plate is pressed against the blank 1A at the time of press molding.
[0115]
　Specifically, at the time of press molding, the central portion of the blank 1A has a plate holding surface 32a of the punch 32, with the push plate of the seat holder 33 in a state of being pressed from both. In this state, the punch 32 is inserted into the recess of the die 31.
[0116]
　Again, as shown in FIG. 16B, the height W of the vertical wall 31b of the die 31, the distance in the stroke direction from a height of the plate pressing surface 32a of the punch 32 to the height of the die shoulder 31ab in the molding bottom dead center to.
[0117]
　Speed control of Example
　was analyzed hot press forming of a model part of the center pillar shown in FIGS. 17 and 18. Figure 17 is a top view of the model part. Figure 18 is a cross-sectional view taken along line A-A shown in FIG. 17. Model part in cross section is hat-shaped. Forming height of the model part is 75 mm. Each pattern of three different punching speed to the die, analyzes the hot press forming was measured the hardness distribution in the cross section shown in FIG. 18. Figure 19 is a graph showing a speed pattern triplicate. In the graph shown in FIG. 19, the vertical axis, the stroke of the die during molding of the bottom dead center 0, the horizontal axis represents time. In case1, and molded by moving the die at a constant speed 40 mm / sec over the entire stroke. In case2, from the beginning of the stroke up to 30mm in front bottom dead center, at a speed of 50 mm / sec, from the bottom dead center before the 30mm to the bottom dead center, and molded over 15 seconds. The last of 30mm speed of Case2 is a 2mm / sec. In case3, from the beginning of the stroke up to 30mm in front bottom dead center, the last 30mm punch stroke at a speed of 40 mm / sec, and molded over 45 seconds. The last of 30mm speed of Case3 is a 0.66mm / sec.
[0118]
　Figure 20 is a graph showing the hardness distribution in the cross section shown in Case1 ~ Case3 model part of Figure 18 that was created in each condition. In case1, hardness from vertical wall toward the flange are made substantially constant. In Case3, hardness difference from the vertical wall toward the flange has occurred. That is, the softening part and an intensity transition portion is formed. Although not shown, even Case2, softened part and an intensity transition portion is formed. In this analysis, in the range of V1 / V2 <0.05, the softening part and an intensity transition portion is formed.
[0119]
　Having described an embodiment of the present invention, the above-described embodiment is merely an example for implementing the present invention. Accordingly, the present invention is not limited to the embodiments described above, it can be implemented by modifying the embodiment described above without departing from the scope and spirit thereof as appropriate.
DESCRIPTION OF SYMBOLS
[0120]
　1: hat member
　11: side wall
　13: top wall
　14: Flange
　L: Softening unit
　T: strength transition

The scope of the claims

[Requested item 1]And top wall,
　and two first ridge at each end of the top wall,
　extending from one end adjacent said first edge line, to the other end angle formed between the top wall in the direction of 90 ~ 135 ° a two side walls, the central hardness Dc defined by the lower hardness of the hardness of the intermediate position in the direction perpendicular to each of the top wall of the two side walls is at least 300 HV, said from said other end provided range up before the intermediate position, and at least 8% lower softening unit than the hardness Dn is the central hardness Dc, adjacent to the softened portion, a range of more than 0.5mm toward said one end from said softening unit a is provided at the other end from the intermediate position between the other hand the end the other end, 8% to 1% hardness Dt is from the central lower hardness range (0.92Dc ≦ Dt ≦ 0.99Dc) in the intensity transition transitioning To the two side walls,
　the two two second edges respectively adjacent to the other end of the side wall,
　said two second and two flanges extending away from each other from the edge line,
hat member with a.
[Requested item 2]
　Width from the end closer to the first edge line of the intensity transition to an end closer to the second ridge is less than 5 times the average thickness of the intensity transition, to claim 1 hat member described.
[Requested item 3]
　The blanks A method of manufacturing the described hat member to claim 1 by press forming using a punch and a die,
　heating the blank to above 900 ° C., soaking and at least 1 minute at 900 ° C. or higher ,
　wherein when the temperature of the blank is 600 ° C. or higher 800 ° C. or less in contact with the die shoulder of the die, molding the first edge line by Surechigawa the plate pressing surface of the punch and the die shoulder,
　the die said when the temperature of the blank is 300 ° C. or higher 700 ° C. or less in contact with half the height of the vertical wall, Surechigawa a plate pressing surface with half the height of the vertical wall of the die the punch thereby,
the production method of the hat member.
[Requested item 4]
　The blanks A method of manufacturing the described hat member to claim 1 by press forming using a punch and a die,
　heating the blank to above 900 ° C., soaking and at least 1 minute at 900 ° C. or higher ,
　the die by Surechigawa the shoulder and the plate pressing surface of the punch and molding the first edge line,
　so Surechigawa a plate pressing surface of the vertical wall of height between the half position the punch of the die molding the second ridgeline Te,
　since the plate holding surface of the vertical wall of height between the half position the punch of the die pass each other, the plate pressing surface of the punch until it reaches the molding bottom dead center , average relative speed V2 of the die and the punch, the die shoulder and the plate pressing surface of the punch of the die and the punch when passing each other relative speed V1, is less than one twentieth, of the hat member Production method.
[Requested item 5]
　The blanks A method of manufacturing the described hat member to claim 1 by press forming using a punch and a die,
　heating the blank to above 900 ° C., soaking and at least 1 minute at 900 ° C. or higher ,
　the die by Surechigawa the shoulder and the plate pressing surface of the punch and molding the first edge line,
　so Surechigawa a plate pressing surface of the vertical wall of height between the half position the punch of the die molding the second ridge Te,
　the surface of the punch at a position opposite to the plate pressing surface of the die, or, the thermal conductivity of 0.3 to a plate holding surface of the die (W / m · K) or less of insulation provided,
　from half the height of the vertical wall and the plate pressing surface of the punch of the die pass each other, until the plate pressing surface of the punch reaches the molding bottom dead center, the blank in contact with the heat insulating material,
　wherein a half the height of the vertical wall of the die punch After the plate pressing surface is passing each other of up to the plate pressing surface of the punch reaches the molding bottom dead center, the die and the average relative speed V2 of the punch, and the plate pressing surface of the die shoulder and the punch the die and the relative speed V1 of the punch, is less than half 1 or more 20 minutes, the production method of the hat member when passing each other.
[Requested item 6]
　The blanks A method of manufacturing the described hat member to claim 1 by press forming using a punch and a die,
　heating the blank to above 900 ° C., soaking and at least 1 minute at 900 ° C. or higher ,
　the die by Surechigawa the shoulder and the plate pressing surface of the punch and molding the first edge line,
　so Surechigawa a plate pressing surface of the vertical wall of height between the half position the punch of the die molding the second ridgeline Te,
　since the plate holding surface of the vertical wall of height between the half position the punch of the die pass each other, the plate pressing surface of the punch until it reaches the molding bottom dead center during the blank, the surface of the punch 300 ° C. or higher in a position opposite to the plate pressing surface of the die or, in contact with the plate pressing surface of the die above 300 ° C.,
　a high vertical walls of the die after passing each other is positioned a plate pressing surface of the punch half Up plate pressing surface of the punch reaches the molding bottom dead center, the die and the average relative speed V2 of the punch, said die shoulder and the plate pressing surface of the punch and the die when passing each other of the punch the relative speed V1, is 1 or less 1 or 2 minutes of the 20 minutes, the production method of the hat member.