JP5402562B2 - Hot press molded product, manufacturing apparatus and manufacturing method thereof - Google Patents

Description

  The present invention relates to a hot press-formed product, an apparatus for manufacturing the same, and a manufacturing method thereof. Specifically, the steel sheet is heated in a hot state of 600 ° C. or higher by heating with a temperature rising furnace or the like and quenched. The present invention relates to a hot press-formed product manufacturing apparatus and method capable of manufacturing a high-strength press-formed product, and a hot press-formed product.

  In recent years, structural members for automobiles are required to be both thin and strong from the viewpoint of global environmental problems and collision safety performance. In order to satisfy these conflicting requirements, the application of high-strength steel sheets is expanding. However, as one of the problems when using a high-strength steel sheet, there are molding defects such as wrinkles and springbacks, which is an obstacle to expanding the application of high-strength steel sheets. As a technique for solving these problems, a hot press for producing a high-strength molded product by press-molding a steel plate (blank) heated to a high temperature of 700 ° C. or higher and then quenching in the mold or outside the mold. A molding method is known.

  Hot press forming is easy to suppress or eliminate forming defects because it is formed in a high temperature range where the tensile strength of the steel sheet decreases, and to achieve high strength by quenching after forming. An ultra-high strength product having a strength of, for example, 1500 MPa class can also be manufactured.

  In recent years, hot press molding has been put into practical use as a method for increasing the strength in order to reduce the weight of reinforcing members such as bumper reinforcements for automobiles and door impact beams. In hot press molding, a press-molded product with high strength and good dimensional accuracy can be obtained, but because of the low ductility and toughness of the material after molding, breakage occurs early from the end surface of the press-molded product during impact deformation. In some cases, sufficient absorbed energy cannot be obtained.

  Patent Document 1 discloses an invention relating to a method of quenching a pressed part in which a recess is provided so that a heated steel plate does not contact the surface of a die and a punch, and the quenching hardness is partially reduced. In the present invention, the hardness of a molded product is partially reduced by changing the cooling rate for each part of the molded product.

  In Patent Document 2, an open flange portion inclined by about 15 to 20 ° is bent at the end portion of the sheet metal material, and the formed open flange portion is directly installed in the axial direction of the sheet metal material and increased only in the sheet thickness direction. An invention relating to a local thickness increasing method for forming a thick part by making it thick is disclosed.

JP 2003-328031 A Japanese Patent Laid-Open No. 7-155883

  However, sufficient performance cannot always be obtained based on the invention disclosed in Patent Document 1. In addition, in order to carry out the present invention, a mold having a complicated structure is required, and the hardness distribution of the molded product may vary as the temperature of the mold increases during mass production. Are also susceptible to variations.

  In addition, in order to increase the strength of the end part of the molded product, a device design aspect such as providing a flange at the end part has been devised, but the factor that obstructs the weight reduction required for automobile components Therefore, it is not desirable.

  Since the invention disclosed in Patent Document 2 inevitably causes a folding defect because the inclined flange portion is installed in the axial direction as described in Paragraphs 0012 and 0017 of Patent Document 2, It is necessary to remove this folding defect from the press-formed product. However, since the hardness of the hot press-formed product after molding is extremely high, it is not easy to remove the folding defect from the hot press-formed product. For this reason, it is difficult to manufacture a hot press-formed product by the invention disclosed in Patent Document 2.

  The object of the present invention is to produce a hot press-molded product with increased energy absorption at the time of impact deformation while taking advantage of hot press molding that achieves both high strength and high dimensional accuracy. An object is to provide an apparatus and method for producing a hot press-formed product, and a hot press-formed product.

  The inventors of the present invention have made extensive studies in order to achieve such an object, paying attention to the end face properties and end face shapes of hot press-molded products after hot press forming, and variously changing the end face properties and end face shapes. A three-point bending crush test was performed using the press-formed product, and the influence on the crack resistance of the end face was investigated. As a result, (a) the end face is smoothed by pressing the end face of the material from the direction substantially perpendicular to the end face during the hot press forming, and the crack resistance and absorbed energy of the end face are greatly increased. ) Obtaining the knowledge that the energy absorption of the hot press-molded product is further increased by increasing the thickness of the end by pressing the end face, and the present invention has been completed.

The present invention is provided with a die and a punch that are arranged to be relatively movable in the press forming direction, and a groove comprising a bottom portion and two side walls continuous to the bottom portion by quenching a heated steel plate simultaneously with press forming. An apparatus for manufacturing a hot press-formed product for producing a molded product having a cross-sectional shape, and is further disposed so as to be relatively movable in the press-molding direction with respect to the punch and facing the die, It is provided with an end face pressing die for manufacturing a molded product by pressing an end surface of a portion serving as a side wall in an intermediate product formed to have a groove-shaped cross-sectional shape by press molding in the press molding direction . It is a manufacturing apparatus of a hot press-formed product.

  In the apparatus for manufacturing a hot press-formed product according to the present invention, it is desirable that the end face pressing die be disposed on a base that supports punch operating means for urging the punch in the press forming direction. It is desirable to use a spring or a gas cushion as the punch actuating means.

  In the apparatus for manufacturing a hot press-formed product according to the present invention, it is desirable that the end face pressing die is attached to an end face pressing die actuating means that is disposed on the punch so as to expand and contract in the press forming direction.

  In the apparatus for manufacturing a hot press-formed product according to these inventions, the side wall constituting the molding surface of the die is formed from the bottom portion of the die toward the opening side, and the first slope portion. A second inclined portion formed so as to be continuous with the first inclined portion and having an inclination angle θ2 smaller than the inclined angle θ1 of the first inclined portion, and the second inclined portion while being continuous with the second inclined portion. It is desirable to have an escape portion formed to recede from the extension line.

  Here, it is desirable that the inclination angle θ1 of the first inclined portion is 0 degree or more and 20 degrees or less and the inclination angle θ2 of the second inclination part is 0 degree or more. More desirably, the inclination angle θ1 is not less than 2 degrees and not more than 10 degrees, and the inclination angle θ2 is less than the inclination angle θ1 and not more than 2 degrees. More desirably, the inclination angle θ2 is substantially parallel to the press molding direction.

  In addition, when performing the thickness increase processing of the end portion of the molded product according to the present invention, there is a shape defect at the end portion in the longitudinal direction of the molded product due to plastic flow of the material generated in the longitudinal direction of the molded product perpendicular to the pressing direction of the end portion. In order to prevent the occurrence, it is desirable that a stopper (for example, a rigid block) for preventing the material from protruding due to plastic flow is attached to the end face of the mold corresponding to the end in the longitudinal direction of the molded product.

From another point of view, the present invention is a method for producing a hot press-formed product, which is obtained by quenching a heated steel plate simultaneously with press forming to obtain a formed product having a groove-shaped cross section. The first step of press-forming into an intermediate product having a groove-like cross-sectional shape composed of a bottom and two side walls continuous with the bottom, and the side wall of the intermediate product while constraining the intermediate product with a die and a punch And a second step of manufacturing a molded product by pressing the end face toward the press molding direction in press molding .

  In the method of manufacturing a hot press molded product according to the present invention, the first step includes a pre-process for bending a steel plate to obtain a first intermediate product having a groove-shaped cross section, and a side wall of the first intermediate product. It is desirable to include a post-process for obtaining an intermediate product having bent-shaped side walls by bending the material.

From yet another aspect, the present invention provides a first inclined portion that is manufactured by hot press forming of a steel sheet, has a bottom portion and an inclination angle θ1 that is continuous with the bottom portion and has a tilt angle θ1 with respect to a press forming direction in hot press forming, and Having an end including the end face of the side wall and having a groove-like cross-sectional shape composed of two dog-shaped side walls composed of a second inclined portion having an inclination angle θ2 with respect to the press molding direction ; and The end face is a hot press-molded product characterized by having a surface property smoothed by a pressing process from a substantially orthogonal direction to the end face . In this hot press-formed product, it is desirable that the thickness of the end portion of the side wall is thicker than the thickness of the other side wall other than the end portion, and for example, it is exemplified as a member constituting an impact absorbing member of an automobile.

  According to the present invention, end face cracking during a collision is suppressed, it is possible to obtain a high collision performance, it is possible to improve the collision energy absorption performance of the hot press-formed product, and as a result, the safety improvement of the automobile and Fuel consumption can be improved by reducing the weight of the vehicle body.

  Further, according to the present invention, a hot press-formed product having high collision characteristics can be easily obtained, and productivity can be improved.

FIG. 1 is a schematic view of the shape of a hot press-formed product obtained by the present invention, FIG. 1 (a) is a perspective view, and FIG. 1 (b) is a cross-sectional view. FIG. 2 (a) is a schematic view schematically showing the structure of the apparatus for producing a hot press-formed product according to the present invention, and FIG. 2 (b) shows another hot press-formed product according to the present invention. It is a schematic diagram showing the structure of a manufacturing apparatus typically. FIG. 3 is a schematic diagram showing the shape of a part of the side wall constituting the molding surface of the die. FIG. 4 is an explanatory view schematically showing an escape portion formed on the die. 5 (a) to 5 (e) show a method of manufacturing a hot press-formed product over time using the hot press-formed product manufacturing apparatus shown in FIGS. 2 (a), 3 and 4. It is a schematic diagram shown. 6 (a) to 6 (e) show a method of manufacturing a hot press-formed product over time using the hot press-formed product manufacturing apparatus shown in FIG. 2 (b), FIG. 3 and FIG. It is a schematic diagram shown. Fig.7 (a)-FIG.7 (c) are explanatory drawings which show the various modifications of the hot press molded product manufactured by this invention. FIG. 8 is a two-side view showing the dimensional specifications of the channel-shaped member. FIG. 9 is an explanatory diagram showing the point of a three-point bending test for evaluating the cracking property of the end face and the amount of absorbed energy. FIG. 10 is a graph showing the relationship between the impactor stroke obtained by the three-point bending test and the load or the amount of absorbed energy for the present invention example 1 and the comparative example.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of the shape of a preferred example of a hot press-formed product 1 manufactured by the apparatus or method for manufacturing a hot press-formed product according to the present invention. FIG. 1 (a) is a perspective view, FIG. 1 (b) is a sectional view.

  As shown in FIGS. 1A and 1B, the hot press-formed product 1 includes a bottom portion 2 and two side walls 3 continuous on both sides of the bottom portion 2. The side wall 3 includes a first inclined portion 4 having an inclination angle θ1 that is the same as an inclination angle θ1 of the die 11 described later, and a second inclined portion 5 having the same inclination angle θ2 as the inclination angle θ2 of the die 11. It has a cross-sectional shape bent into a dogleg shape. The tilt angles θ1 and θ2 of the die 11 are both angles with respect to the moving direction (press direction) of the die 11.

  The side wall angle θ1 is 0 degree or more and the upper limit is not particularly limited, but is usually 20 degrees or less, and the inclination angle θ1 is 2 degrees or more and 10 degrees or less from the viewpoint of moldability to form a dogleg-shaped cross section with high accuracy. It is desirable to be. On the other hand, the inclination angle θ2 is desirably 0 degree or more, desirably less than the inclination angle θ1 and not more than 2 degrees. Since the end surface 3a of the side wall 3 has a smooth and excellent surface property, the crack resistance of the end surface 3a at the time of collision is improved, and the amount of absorbed energy at the time of collision deformation is increased. The end portion including the end surface 3a of the side wall 3 is desirably thicker than other portions other than the end portion.

FIG. 2A is a schematic diagram schematically showing the structure of the manufacturing apparatus 10 according to the present invention, and FIG. 2B schematically shows the structure of another manufacturing apparatus 10-1 according to the present invention. FIG.
2A includes a die 11, a punch 12, a pad 13, a base 14, an end face pressing die 15, a spring 16, and a spring 17.

  The die 11 and the pad 13 constitute an upper die 18, and the end face pressing die 15 and the punch 12 constitute a lower die 19. The upper mold 18 is provided so as to be movable up and down with respect to the lower mold 19 by a drive mechanism (not shown). The manufacturing apparatus 10 includes a pad 13 and a spring 16 that hold the punch bottom in advance, but the pad 13 and the spring 16 are not necessarily used.

  An elastic spring 17 is disposed as a punch actuating means between the punch 12 and the fixed base 14, and the punch 12 is pressed against the base 14 in the press molding direction by the spring force generated by the spring 17. It is urged and moved in the vertical direction in FIG.

  The end face pressing die 15 is fixed to the base 14 below the bottom of the punch 12 and directly below the pressing direction of the die R portion 20 of the die 11. The end face pressing die 15 presses the end face of the workpiece 21 formed into a groove-shaped cross section by the upper mold 18 and the punch 12 in the vicinity of the press bottom dead center.

  The stroke amount S1 of the punch 12 due to the contraction of the spring 17 needs to be adjusted according to the pressing amount of the end surface of the workpiece 21, but when the end surface pressing die 15 presses the end surface of the workpiece 21, In order to suppress the buckling of the side wall of the workpiece 21, it is desirable to set it to 20 mm or less. In addition, since it is necessary to perform a stroke for lowering the punch 21 in the vicinity of the bottom dead center of molding after the stroke of the pad 13 is completed, the initial back pressure (initial reaction force) of the spring 17 is set higher than the final pressure of the pad 13. It is desirable to do. Further, it is desirable that the punch 12 and the base 14 have a bottom-out structure at the bottom dead center.

In this embodiment, the spring 17 is exemplified as the punch actuating means. However, a gas cushion in which a gas is sealed between the punch 12 and the base 14 may be used.
The manufacturing apparatus 10-1 shown in FIG. 2B includes a die 11, a punch 12, a pad 13, an end face pressing die 15, a spring 16, and an end face pressing die operating mechanism 22.

  The die 11 and the pad 13 constitute an upper die 18, and the end face pressing die 15 and the punch 12 constitute a lower die 19. The upper mold 18 is provided so as to be movable up and down with respect to the lower mold 19 by a drive mechanism (not shown).

  The end face pressing die 15 is provided below the bottom of the punch 12 and directly below the pressing direction of the die R portion 20 of the die 11, and an end face pressing die operating mechanism 22 is disposed between the end pressing die 15 and the punch 12. . The end face pressing die operating mechanism 22 is disposed so as to be expandable and contractable in the press molding direction. The end surface pressing die 15 can be pushed up in the press molding direction by the operation of the end surface pressing die operating mechanism 22. The punch 12 is fixedly provided.

  The stroke amount S2 of the end face pressing die 15 due to the pushing up of the end face pressing die operating mechanism 22 needs to be adjusted according to the pressing amount of the end face of the workpiece 21, but the end face of the workpiece 21 is moved by the end face pressing die 15. In order to suppress buckling of the side wall of the workpiece 21 during pressing, it is desirable that the thickness be 20 mm or less. The end face pressing die operating mechanism 22 may be driven by hydraulic pressure, air pressure or gas pressure, or may be a cam mechanism.

  In either of the manufacturing apparatus 10 shown in FIG. 2A or the manufacturing apparatus 10-1 shown in FIG. 2B, the end face pressing die 15 is formed by press molding so as to have a groove-like cross-sectional shape. In the intermediate product, the end surface 3a of the portion that becomes the side wall 3 of the hot press-formed product 1 is pressed toward the direction in which the portion that becomes the bottom 2 of the hot press-formed product 1 exists in the intermediate product. This is for manufacturing the molded article 1.

FIG. 3 is a schematic diagram showing the shape of a part of the side wall 11 a constituting the molding surface of the die 11.
The side wall 11a constituting the molding surface of the die 11 is continuous with the first inclined portion 23 formed to have an inclination angle θ1 from the bottom of the die toward the opening side, and the first inclined portion 23. The second inclined portion 24 formed to have an inclination angle θ2 smaller than the inclination angle θ1 of the first inclined portion 23, and an extension line of the second inclined portion 24 that is continuous with the second inclined portion 24 And an escape portion 25 formed to be further retracted.

  It is desirable that the inclination angle θ1 of the first inclined portion is 0 degree or more and 20 degrees or less, and the inclination angle θ2 of the second inclination part is 0 degree or more. More desirably, the inclination angle θ1 is not less than 2 degrees and not more than 10 degrees, and the inclination angle θ2 is less than the inclination angle θ1 and not more than 2 degrees. More desirably, the inclination angle θ2 is substantially parallel to the press molding direction.

  In addition, it is desirable that the length L1 of the second inclined portion 24 be in the range of 5 mm or more and 30 mm or less from the end portion with a length L1 of 2 mm or more and 20 mm or less. If the length L1 of the second inclined portion 24 is too small, the bending of the character on the side wall 11a is uncertain and the end face is not sufficiently pressed. Conversely, if it is too large, the bending of the character is accelerated. As a result, the time from bending to pressing becomes longer, the temperature tends to decrease due to heat removal from the punch 12 side, and the yield stress increases, so that buckling is likely to occur.

FIG. 4 is an explanatory view schematically showing the relief portion 25 formed on the die 11.
In FIG. 4, the width L2 of the relief portion 25 is preferably not less than the plate thickness and not more than three times the plate thickness. If the width L2 is too small, sufficient thickness increase processing cannot be obtained, and there is a concern that galling may occur in the mold. On the other hand, if the width L2 is too large, buckling is likely to occur during pressure deformation.

  In the example shown in FIGS. 2 to 4, bending is performed using the pad 13 by a single-action press, but this molding can be performed even with a double-action press. In addition, it is not always required to bend, but when drawing by adding a blank holder, the temperature of the end face that is planned to be pressed at the end of molding by holding the workpiece by the blank holder and the die Since it decreases and the yield stress increases, problems such as buckling may occur in subsequent pressing.

Next, the 1st example of the method of manufacturing the hot press-formed product 1 using the manufacturing apparatus 10 shown to Fig.2 (a) is demonstrated.
5 (a) to 5 (e) are schematic views showing a method of manufacturing the hot press-formed product 1 with the use of the manufacturing apparatus 10 shown in FIGS. 2 (a), 3 and 4. is there. 5A to 5E show a half cross section of the manufacturing apparatus 10.

  First, the workpiece 21 shown in FIG. 5A is heated at a predetermined temperature, for example, general hot press molding, by a heating device such as an atmospheric furnace, an electric heating device, an induction heating device, or a steam heating device. Heat to a temperature of 900 ° C. In addition, a heating device may be provided in the mold apparatus, and the workpiece 21 may be heated on the mold.

  Next, as shown in FIG. 5 (a), the heated workpiece 21 is transported to the molds 18 and 19, positioned, and as the upper mold 18 constituted by the die 11 and the pad 13 descends, The upper surface portion of the punch 12 is pressed by the pad 13 through the workpiece 21.

  Next, as shown in FIG. 5 (b), as the upper die 18 is lowered, the portion forming the vertical wall portion of the workpiece 21 is formed to wrap around the punch shoulder portion 12a. At this time, since the workpiece 21 is bent starting from the punch shoulder 12a, the end 21a of the workpiece 21 is not in contact with the molds 18 and 19, and the high temperature is maintained.

  Next, as the molding proceeds, as shown in FIG. 5C, the entire portion of the workpiece 21 forming the vertical wall portion is sandwiched between the die 11 and the punch 12, and the molds 18, 19 The cooling by is started. Even in this state, the end 21a of the workpiece 21 is prevented from coming into contact with the mold by the relief portion 25 provided in the die R portion 20, and the high temperature is maintained.

  Next, as shown in FIG. 5 (d), when molding approaches the bottom dead center, the workpiece is processed by the R portion of the second inclined portion 24 provided in the vicinity of the die R portion 20 of the upper mold 18. The vicinity of the end 21a of the material 21 is bent. In this way, an intermediate product having a groove-like cross-sectional shape is formed by press molding using the die 11 and the punch 12.

  After that, as shown in FIG. 5 (e), the workpiece 21 that is an intermediate product starts the stroke of the punch 12 while being constrained by the die 11 and the punch 12, and the end 21a of the workpiece 21 is the end face. Pressed against the pressing die 15. As a result, a hot press-formed product 1 having a cross-sectional shape bent in a dogleg shape as shown in FIGS. 1A and 1B is obtained. In order to perform molding at a higher temperature, immediately after the end of the workpiece 21 is bent by the R portion of the second inclined portion 24 in the step shown in FIG. It is desirable to perform end face pressing in the process shown in FIG.

In addition, by adjusting the stroke amount S1 of the punch 12, the amount of increase in the thickness of the end 21a of the workpiece 21 can be adjusted.
Next, the 2nd example of the method of manufacturing the hot press-molded product 1 using the manufacturing apparatus 10-1 shown in FIG.2 (b) is demonstrated.

  FIGS. 6A to 6E are schematic views showing a method of manufacturing the hot press-formed product 1 using the manufacturing apparatus 10-1 shown in FIGS. 2B, 3 and 4 over time. FIG. 6A to 6E show a half cross-sectional structure of the manufacturing apparatus 10-1.

The heating of the workpiece 21 prior to the press molding is the same as described above, and is therefore omitted.
As shown in FIG. 6A, the heated workpiece 21 is conveyed and positioned on the dies 18 and 19, and the punch 12 is moved as the upper die 18 constituted by the die 11 and the pad 13 descends. The upper surface portion is pressed by the pad 13 through the workpiece 21.

  Next, as shown in FIG. 6B, as the upper die 18 is lowered, the portion to be the vertical wall portion of the workpiece 21 is formed to wrap around the punch shoulder portion 12a. Since the workpiece 21 is bent starting from the punch shoulder 12a, the end of the workpiece 21 does not contact the molds 18 and 19, and the high temperature is maintained.

  Next, as shown in FIG. 6 (c), as the molding progresses, the entire portion of the workpiece 21 that becomes the vertical wall portion is sandwiched between the die 11 and the punch 12, and the mold 18, Cooling by 19 is started. Even in this state, the end 21a of the workpiece 21 is prevented from coming into contact with the mold by the relief portion 25 of the die R portion 20, and the high temperature is maintained.

  Next, as shown in FIG. 6 (d), immediately before the bottom dead center of the molding, the R portion of the second inclined portion 24 provided in the vicinity of the die R portion 20 in the upper mold 18 causes the workpiece 21 to be processed. The vicinity of the end is bent. In this way, an intermediate product having a groove-like cross section is formed by press molding using the die 11 and the punch 12.

  Thereafter, as shown in FIG. 6 (e), after the upper die 18 reaches the bottom dead center of molding, the end surface pressing die 15 is pushed upward in the pressing direction by the end surface pressing die elevating mechanism 22, and the workpiece is an intermediate product. The material 21 is hot press-molded having a cross-sectional shape in which the end 21a of the workpiece 21 is pressed against the end face pressing die 5 while being constrained by the upper die and the punch, and is bent in a letter shape as shown in FIG. Product 1 is obtained.

  In order to perform molding at a higher temperature, immediately after the end 21a of the workpiece 21 is bent by the R portion of the second inclined portion 24 in the step shown in FIG. It is desirable to perform end face pressing in the step shown in e).

In addition, the thickness increase amount of the edge part 21a of the workpiece 21 can be adjusted by adjusting the stroke amount S2 of the end face pressing die lifting mechanism 22.
As described above, by using the dies 18 and 19 shown in FIG. 2A or FIG. 2B, the end 21a of the workpiece 21 is maintained at a high temperature without touching the dies until immediately before pressing. Therefore, it is possible to press the end 21a in a soft state at a high temperature while suppressing problems such as buckling.

This pressing process does not need to be performed on the entire end portion of the molded product, and may be performed at a location where the bending deformation of the component preferentially occurs at the time of collision.
The present invention is not limited to the manufacture of the hot press-formed product 1 having the shape shown in FIGS. 1 (a) and 1 (b). Fig.7 (a)-FIG.7 (c) are explanatory drawings which show the various modifications of the hot press molded product manufactured by this invention.

  A hot press-formed product 1-1 shown in FIG. 7A has a concave portion 6 or a convex portion 6 on the bottom 2. Moreover, the concave-shaped or convex-shaped part 6 in these bottom parts 2 may be continuously formed to the edge part of the hot press molded product 1-1 in the longitudinal direction, or is intermittent in the longitudinal direction. It may be formed.

The hot press-molded product 1-2 shown in FIG. 7B has a curved bottom 2 and the hot press-molded product 1-3 shown in FIG. 7C has a concave bottom 2. Is curved.
Moreover, the hot press-molded products manufactured by the present invention including the hot press-molded products 1, 1-1, 1-2 and 1-3 described above are the ratio of the width of the bottom and the length of the side wall (width / Length) is 0.5 or more and 10 or less. Here, the width of the bottom portion refers to the center in the circumferential direction of the R portion existing between one bottom portion and the side wall, and the center in the circumferential direction of the R portion existing between the other bottom portion and the side wall. It means the distance in the circumferential direction, and the length of the side wall means the distance in the circumferential direction between the center in the circumferential direction of the R portion existing between the bottom and the side wall and the end of the side wall.

Next, examples of the present invention will be described.
First, a channel-shaped member having a substantially U-shaped cross-section was manufactured for evaluation of end fracture. FIG. 8 is a two-side view showing the dimensional specifications of the channel-shaped member 30.

In this channel-shaped member 30, an outer member 31 and an inner member 32 are spot-bonded at intervals of 30 mm. The black circle mark in the right figure of FIG. 8 shows the spot welding position.
At this time, the inner member 32 is manufactured by cold forming a 440 MPa class high strength steel plate having a thickness of 1.2 mm by press brake bending.

  The outer member 31 is manufactured according to the present invention. As a molding die for molding the outer member 31, the manufacturing apparatus 10 shown in FIG. At this time, as the spring 16 for supporting the pad 13, a plurality of gas springs having a stroke of 50 mm were arranged so that the initial load was 30 tons in total.

  A plurality of gas springs were arranged as the springs 17 supporting the punch 12 so that the initial load was 100 tons in total. The stroke amount of the spring 17 was appropriately adjusted according to the pressing amount of the end portion.

  The die 11, the punch 12, the pad 13, and the end face pressing die 15, etc., were all made of SKD61 quenching and tempering materials at the parts that contact the material during molding. The roughness of the upper surface contacting the material of the end face pressing die 15 was finished so that the maximum height Rz was 5.0 μm or less.

This mold was attached to a 700-ton hydraulic press machine, and hot press molding was performed at a constant speed of 40 mm / sec.
The material of the outer member 31 has a chemical composition consisting of C: 0.21% by mass, Si: 0.25% by mass, Mn: 1.2% by mass, B: 0.0014% by mass, the balance Fe and impurities. And the steel plate for hot press whose plate | board thickness is 1.6 mm was used.

  Blanking of the portion that becomes the end 3a after molding was performed by shear cutting, and the shear clearance at that time was 10%. The blank size was 600 mm long and 170 mm wide.

  The outer member 31 was manufactured as described below. A gas heating furnace was used to heat the hot-press steel plate as the material of the outer member 31, and it was burned at an air-fuel ratio of 0.85 to adjust the furnace temperature to 900 ° C. The in-furnace time was 4 minutes. After the heating was completed, the hot press steel sheet was quickly taken out from the furnace, and molding was started at 800 ° C. or higher. Further, the molding was maintained for 15 seconds at the bottom dead center. The hardness of the hot press-formed product after quenching is about Hv 470 (corresponding to 1490 MPa).

The end pressing amount is 3 levels: 0.5 mm (invention example 1) for smoothing the end face, 2.0 mm (invention example 2) for end face smoothing and thickening, and no end face treatment (comparative example). It was.
FIG. 9 is an explanatory diagram showing the point of a three-point bending test for evaluating the cracking property of the end face and the amount of absorbed energy.

  As shown in FIG. 9, a rigid block 33 made of a material having a tensile strength of 590 MPa class is provided between the outer member 31 and the inner member 32 in order to easily cause breakage of the end portion. It inserted in the center part of 30 longitudinal directions (left-right direction in FIG. 9). The size of the rigid block 33 was 16 mm thick, 70 mm long, and 70 mm wide. The impactor 34 was lowered at a speed of 1 mm / sec.

  FIG. 10 shows the relationship between the impactor stroke obtained by the three-point bending test and the load or the amount of absorbed energy for the present invention example 1 (shown as “invention example 1” in the graph of FIG. 10) and the comparative example. It is a graph. In this example, the impactor stroke amount when the fracture occurred and the amount of energy absorbed until the fracture were evaluated. The test results are summarized in Table 1.

  As shown in Table 1, in Example 1 of the present invention in which end face smoothing was performed compared to the comparative example without end face treatment, the amount of impactor stroke at the time of fracture increased, and as a result, high absorbed energy was obtained. Furthermore, in the present invention example 2 in which the end face thickness was increased by increasing the end pressing amount, a higher absorbed energy was obtained than in the present invention example 1.

1-1, 1-2, 1-3 Hot press-formed product 2 Bottom part 3 Side wall 3a End face 4 First inclined part 5 Second inclined part 6 Concave or convex shaped part 10, 10-1 Press molding Device 11 Die 11a Side wall 12 Punch 12a Punch shoulder 13 Pad 14 Base 15 End face pressing dies 16, 17 Spring 18 Upper mold 19 Lower mold 20 Die R section 21 Work material 22 End face pressing die operating mechanism 23 First inclination Part 24 second inclined part 25 relief part 30 channel-like member 31 outer member 32 inner member 33 rigid block 34 impactor

Claims (9)

A groove-like cross-sectional shape comprising a bottom and two side walls continuous to the bottom by quenching simultaneously with press forming on a heated steel plate, provided with a die and a punch that are relatively movable in the press-forming direction An apparatus for manufacturing a hot press-molded product for producing a molded product having:
It becomes the side wall in the intermediate product which is disposed so as to be relatively movable in the press molding direction with respect to the punch and is opposed to the die, and has the groove-like cross-sectional shape by the press molding. An apparatus for manufacturing a hot press-formed product, comprising: an end face pressing die for manufacturing the molded product by pressing an end surface of the portion toward the press molding direction .   2. The apparatus for manufacturing a hot press-formed product according to claim 1, wherein the end face pressing die is disposed on a base that supports punch operating means for urging the punch in the press forming direction.   The apparatus for manufacturing a hot press-formed product according to claim 1, wherein the end face pressing die is attached to an end face pressing die actuating means that is disposed on the punch so as to be expandable and contractable in the press forming direction.   The side wall constituting the molding surface of the die is formed from the bottom portion of the die toward the opening side, and is continuous with the first inclined portion and the inclined portion of the first inclined portion. A second inclined part formed so as to have an inclination angle smaller than the angle, and a relief part formed continuously with the second inclined part and receding from an extension line of the second inclined part. The apparatus for manufacturing a hot press-formed product according to any one of claims 1 to 3. A method of manufacturing a hot press-formed product, which is obtained by quenching a heated steel plate simultaneously with press forming to obtain a molded product having a groove-shaped cross section, wherein the steel plate is continuous with the bottom and the bottom by a die and a punch. A first step of press-molding into an intermediate product having a groove-like cross-sectional shape composed of two side walls;
A second step of manufacturing a molded product by pressing the end surface of the side wall of the intermediate product toward the press molding direction in the press molding while restraining the intermediate product by the die and the punch. A method for producing a hot press-molded product.   The first step includes a step of bending the steel plate to obtain a first intermediate product having a groove-shaped cross section, and a middle step of bending the side wall of the first intermediate product to have a letter-shaped side wall. The method for producing a hot press-formed product according to claim 5, comprising a post-process for obtaining a product. A steel plate is manufactured by hot press forming of a steel plate, and has a bottom portion , a first inclined portion that is continuous with the bottom portion and has an inclination angle θ1 with respect to a press forming direction in the hot press forming, and an end portion including an end surface of the side wall. And having a groove-like cross-sectional shape composed of two side-shaped side walls composed of a second inclined portion having an inclination angle θ2 with respect to the press molding direction , and the end surface is substantially in a direction orthogonal to the end surface A hot press-molded product characterized in that it has a surface property smoothed by pressing .   The hot press-formed product according to claim 7, wherein the thickness of the end portion including the end face of the side wall is thicker than the thickness of the side wall other than the end portion. The hot press according to claim 7 or 8, wherein the inclination angle θ1 is not less than 2 degrees and not more than 10 degrees, and the inclination angle θ2 is not less than 0 degrees and less than the inclination angle θ1 and not more than 2 degrees. Molding.

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