Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
  • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
  • B21D26/021—Deforming sheet bodies
  • B21D26/029—Closing or sealing means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
  • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
  • B21D26/021—Deforming sheet bodies
  • B21D26/031—Mould construction
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D25/00—Superstructure or monocoque structure sub-units; Parts or details thereof not otherwise provided for
  • B62D25/20—Floors or bottom sub-units

Definitions

• This disclosure relates to a structural member and a manufacturing method thereof. This disclosure also relates to a mold, and more specifically, to a mold for manufacturing a structural member.
• Patent Document 1 discloses a rear module for a vehicle body.
• the rear module in Patent Document 1 includes left and right rear rails.
• Each rear rail includes a front section, a rear section, and a transition region connecting the front and rear sections.
• Each rear rail is formed, for example, from a tailor welded blank or a tailor rolled blank. Therefore, in Patent Document 1, the front and rear sections of the rear rail are integrated from the blank stage onwards.
• Patent Document 2 discloses a technology for integrating the front and rear sections of a rear rail from the blank stage.
• the objective of this disclosure is to provide a method for manufacturing structural members that can be productively molded into structural members as integrated components with hollow cross sections.
• the method for manufacturing a structural member according to the present disclosure comprises the steps of preparing a material and molding the material using a first mold and a second mold.
• the material includes a first blank and a second blank.
• the first blank has a through hole.
• the second blank is overlapped and joined to the first blank.
• the first mold includes a molding surface and a flange surface.
• the flange surface is arranged around the molding surface. A protrusion is formed on the flange surface.
• the molding step includes the steps of clamping the material between the flange surface and the second mold with the protrusion inserted into the through hole, creating a gap between the first blank and the second blank using the protrusion, and injecting a fluid into the gap through the protrusion, causing the fluid to expand the material within the hollow space formed by the molding surface and the second mold.
• the manufacturing method for structural members disclosed herein makes it possible to efficiently mold structural members as integrated components with hollow cross sections.
• FIG. 1A is a perspective view showing a schematic configuration of a structural member according to a first embodiment.
• FIG. 1B is an exploded perspective view of the structural member shown in FIG. 1A.
• FIG. 2 is a perspective view showing a schematic configuration of the mold according to the first embodiment.
• FIG. 3 is a cross-sectional view of the mold shown in FIG. 2 taken along line III-III.
• FIG. 4 is a diagram showing an example of a mold different from that shown in FIG.
• FIG. 5A is a schematic view for explaining the method for manufacturing a structural member according to the first embodiment.
• FIG. 5B is a schematic view for explaining the method for manufacturing a structural member according to the first embodiment.
• FIG. 5C is a schematic view for explaining the manufacturing method of the structural member according to the first embodiment.
• FIG. 5A is a schematic view showing a schematic configuration of a structural member according to a first embodiment.
• FIG. 1B is an exploded perspective view of the structural member shown in FIG. 1A
• FIG. 5D is a schematic view for explaining the manufacturing method of the structural member according to the first embodiment.
• FIG. 5E is a schematic view for explaining the manufacturing method of the structural member according to the first embodiment.
• FIG. 6 is a partial cross-sectional view of the structural member shown in FIG.
• FIG. 7 is a perspective view showing a schematic configuration of a structural member according to the second embodiment.
• FIG. 8A is a schematic view for explaining a manufacturing method of a structural member according to the second embodiment.
• FIG. 8B is a schematic view for explaining the manufacturing method of the structural member according to the second embodiment.
• FIG. 8C is a schematic view for explaining the method for manufacturing a structural member according to the second embodiment.
• FIG. 8D is a schematic diagram for explaining the method for manufacturing a structural member according to the second embodiment.
• FIG. 9 is a perspective view showing a schematic configuration of a structural member according to the third embodiment.
• FIG. 10A is a schematic view for explaining a manufacturing method of a structural member according to the third embodiment.
• FIG. 10B is a schematic diagram for explaining the manufacturing method of a structural member according to the third embodiment.
• FIG. 10C is a schematic view for explaining the manufacturing method of a structural member according to the third embodiment.
• FIG. 10D is a schematic diagram for explaining the manufacturing method of a structural member according to the third embodiment.
• FIG. 11 is a perspective view showing a schematic configuration of a structural member according to the fourth embodiment.
• FIG. 12A is a schematic view for explaining a manufacturing method of a structural member according to the fourth embodiment.
• FIG. 12B is a schematic diagram for explaining the manufacturing method of a structural member according to the fourth embodiment.
• FIG. 12C is a schematic view for explaining the manufacturing method of a structural member according to the fourth embodiment.
• FIG. 12D is a schematic view for explaining the manufacturing method of a structural member according to the fourth embodiment.
• FIG. 13 is a perspective view showing another example of a structural member.
• the molding step includes a step of clamping the material between the flange surface and the second mold with the protrusion inserted into the through hole, creating a gap between the first blank and the second blank using the protrusion, and a step of injecting a fluid into the gap through the protrusion, causing the fluid to expand the material in the hollow space formed by the molding surface and the second mold (first configuration).
• a mold according to a third configuration is used to manufacture a structural component from a material including a first blank and a second blank stacked together.
• This mold includes a first mold and a second mold.
• the first mold includes a first flange surface on which a protrusion is formed in addition to a first molding surface. Therefore, when the first and second molds are closed with the protrusion inserted into the through hole of the first blank and the material is clamped between the first and second flange surfaces, the protrusion lifts the second blank toward the second mold, creating a gap between the first and second blanks. By injecting a fluid into this gap through a flow path opening into the protrusion in the first mold, the fluid can expand the material within the hollow space formed by the first and second molding surfaces.
• a second seal portion is provided on at least one of the first flange surface of the first mold and the second flange surface of the second mold.
• the second seal portion is provided so as to surround the first seal portion.
• the structural member according to the sixth configuration may be a subframe for a vehicle body.
• the member main body includes a pair of side frames and a cross member.
• the cross member connects the side frames together.
• the curved portion is provided, for example, at the connection between each of the side frames and the cross member (ninth configuration).
• the structural member according to the sixth configuration may be a floor module for a vehicle body.
• the member body includes a cross member.
• the curved portion may be provided at the longitudinal end of the cross member (tenth configuration).
• Fig. 1A is a perspective view showing a schematic configuration of a structural member 10 according to this embodiment.
• Fig. 1B is an exploded perspective view of the structural member 10.
• the structural member 10 is used, for example, in the body of an automobile or the like.
• the structural member 10 is a rear module for the body.
• the structural member 10 is provided at the rear and lower part of the body of the automobile or the like.
• the first member 11 and second member 12 are arranged one above the other when the structural member 10 is assembled to the vehicle body.
• the first member 11 includes a member body 111 and a flange 112.
• the second member 12 includes a member body 121 and a flange 122.
• the member body 111 of the first member 11 has a convex shape on the side opposite the second member 12.
• the member body 111 includes a pair of side frames 111a and a cross member 111b.
• the member body 111 includes one cross member 111b.
• the member body 111 may include multiple cross members 111b.
• the side frame 111a and the cross member 111b each have a hollow shape.
• the side frame 111a and the cross member 111b each have a hollow rectangular shape.
• Each side frame 111a extends in the fore-and-aft direction of the vehicle body when the structural member 10 is assembled to the vehicle body.
• the cross member 111b extends in the left-and-right direction of the vehicle body when the structural member 10 is assembled to the vehicle body.
• the cross member 111b extends from one side frame 111a to the other side frame 111a, connecting the side frames 111a together.
• the member body 111 has at least one curved portion 111c.
• the curved portion 111c is a portion of the member body 111 that is curved in a plan view of the structural member 10. More specifically, when the structural member 10 is viewed from the first member 11 side, the curved portion 111c is curved concavely inward or convexly outward of the member body 111. In this embodiment, the curved portion 111c is provided at the connection between each side frame 111a and the cross member 111b. In other words, the curved portion 111c is a corner portion between each side frame 111a and the cross member 111b.
• the curved portion 111c extends with a radius of curvature of, for example, 10 mm or more and 100 mm or less.
• the flange 112 is provided contiguous with the member body 111.
• the flange 112 is provided at the end of the member body 111 so as to surround the member body 111.
• the flange 112 is provided contiguous with each of the side frame 111a and the cross member 111b.
• the first member 11 forms a hollow cross section together with the second member 12 by joining the flange 112 to the second member 12.
• a hollow space is formed between the member body 111 of the first member 11 and the member body 121 of the second member 12.
• the member body 121 of the second member 12 has a convex shape on the side opposite the first member 11.
• the member body 121 includes a pair of side frames 121a and a cross member 121b.
• the member body 121 includes one cross member 121b.
• the member body 121 may include multiple cross members 121b.
• the side frame 121a and the cross member 121b each have a hollow shape.
• the side frame 121a and the cross member 121b each have a hollow rectangular shape.
• Each side frame 121a extends in the fore-and-aft direction of the vehicle body when the structural member 10 is assembled to the vehicle body.
• the cross member 121b extends in the left-and-right direction of the vehicle body when the structural member 10 is assembled to the vehicle body.
• the cross member 121b extends from one side frame 121a to the other side frame 121a, connecting the side frames 121a together.
• the side frame 121a of the second member 12 is positioned to face the side frame 111a of the first member 11.
• the side frames 111a, 121a have convex shapes on opposite sides.
• the cross member 121b of the second member 12 is also positioned to face the cross member 121b of the first member 11.
• the cross members 111b, 121b have convex shapes on opposite sides.
• the member body 121 has at least one curved portion 121c.
• the curved portion 121c is a portion of the member body 121 that is curved in a plan view of the structural member 10. More specifically, when the structural member 10 is viewed from the second member 12 side, the curved portion 121c is curved concavely inward or convexly outward of the member body 121. In this embodiment, the curved portion 121c is provided at the connection between each side frame 121a and the cross member 121b. In other words, the curved portion 121c is a corner portion between each side frame 121a and the cross member 121b.
• the curved portion 121c extends with a radius of curvature of, for example, 10 mm or more and 100 mm or less.
• the flange 122 is provided contiguous with the member body 121.
• the flange 122 is provided at the end of the member body 121 so as to surround the member body 121.
• the flange 122 is provided contiguous with each of the side frames 121a and the cross member 121b.
• the flange 122 of the second member 12 is joined to the flange 112 of the first member 11.
• the flanges 112, 122 are typically joined to each other by welding.
• the flanges 112, 122 are joined intermittently, for example, by spot welding.
• the flanges 112, 122 may also be joined by continuous welding, for example, laser welding.
• [Mold] 2 is a perspective view showing a schematic configuration of a mold 20 according to this embodiment.
• the structural member 10 (FIGS. 1A and 1B) can be manufactured using the mold 20.
• the mold 20 comprises a first mold 21 and a second mold 22.
• the first mold 21 and the second mold 22 are a pair of molds.
• the first mold 21 and the second mold 22 are attached to a press device or the like so that they can approach each other.
• the direction in which the first mold 21 and the second mold 22 approach each other will be referred to as the processing direction D.
• the processing direction D is, for example, the vertical direction.
• the first mold 21 is a mold used primarily to mold the first member 11 (FIGS. 1A and 1B).
• the first mold 21 includes a molding surface 211 and a flange surface 212.
• the molding surface 211 and the flange surface 212 are provided on the surface of the first mold 21 that faces the second mold 22 in the processing direction D.
• the molding surface 211 has a shape corresponding to the member body 111 ( Figures 1A and 1B) of the first member 11.
• the molding surface 211 includes a pair of side frame molding portions 211a and at least one cross member molding portion 211b.
• the side frame molding portion 211a is a portion of the molding surface 211 configured to mold the side frame 111a ( Figure 1B).
• the cross member molding portion 211b is a portion of the molding surface 211 configured to mold the cross member 111b ( Figure 1B).
• the flange surface 212 is arranged around the molding surface 211.
• the flange surface 212 is provided on the first mold 21 so as to surround the entire periphery of the molding surface 211 when viewed along the processing direction D.
• At least one protrusion 213 is formed on the flange surface 212.
• the protrusion 213 protrudes from the flange surface 212 toward the second mold 22.
• multiple protrusions 213 are formed on the flange surface 212.
• the protrusions 213 are positioned near the side frame molding portion 211a of the molding surface 211.
• Each of the protrusions 213 has, for example, a circular shape when viewed along the processing direction D. However, when viewed along the processing direction D, the protrusions 213 may also have a polygonal shape such as a triangular or rectangular shape. If the protrusions 213 have a shape other than a circle, the protrusions 213 may be formed so that they are wider on the side closer to the molding surface 211.
• the first mold 21 further includes a flow path 214 for the fluid.
• the flow path 214 is formed within the first mold 21.
• the flow path 214 opens to each of the protrusions 213.
• the flow path 214 is connected to a fluid supply source (not shown) provided outside the first mold 21.
• the first mold 21 is provided with multiple flow paths 214 corresponding to the multiple protrusions 213.
• Each of the flow paths 214 can open to the side of the first mold 21.
• the multiple flow paths 214 may be combined into a single system within the first mold 21 and then open to the back surface of the first mold 21, etc.
• the second mold 22 is a mold primarily used to mold the second member 12 ( Figures 1A and 1B). In this embodiment, the second mold 22 is positioned above the first mold 21.
• the second mold 22 includes a molding surface 221 and a flange surface 222. The molding surface 221 and the flange surface 222 are provided on the surface of the second mold 22 that faces the first mold 21 in the processing direction D.
• the molding surface 221 has a shape corresponding to the member body 121 ( Figures 1A and 1B) of the second member 12. That is, the molding surface 221 includes a pair of side frame molding portions 221a and at least one cross member molding portion 221b.
• the side frame molding portion 221a is a portion of the molding surface 221 configured to mold the side frame 121a ( Figure 1B).
• the cross member molding portion 221b is a portion of the molding surface 221 configured to mold the cross member 121b ( Figure 1B).
• the molding surface 221 of the second mold 22 forms a hollow space together with the molding surface 211 of the first mold 21. Therefore, when the mold 20 is in use, the molding surfaces 211, 221 face each other in the processing direction D. Furthermore, one or both of the molding surface 211 of the first mold 21 and the molding surface 221 of the second mold 22 have a concave shape in at least a portion. In this embodiment, the molding surfaces 211, 221 have concave shapes on opposite sides. That is, in the first mold 21, the molding surface 211 is formed so as to be concave relative to the flange surface 212. In the second mold 22, the molding surface 221 is formed so as to be concave relative to the flange surface 222.
• the flange surface 222 is arranged around the molding surface 221.
• the flange surface 222 is provided on the second mold 22 so as to surround the entire periphery of the molding surface 221 when viewed along the processing direction D.
• the mold 20 further includes convex seal portions 23, 24.
• the seal portions 23, 24 are provided on the flange surface 212 of the first mold 21 and the flange surface 222 of the second mold 22, respectively.
• the seal portion 23 is provided so as to substantially surround the molding surface 211.
• the seal portion 23 also surrounds each of the protrusions 213. It is preferable that the seal portion 23 surrounds the entire molding surface 211 without interruption. However, for example, at a position away from each of the protrusions 213, part of the seal portion 23 may be interrupted.
• the seal portion 23 may be interrupted, for example, within a range of 30 mm or less.
• the seal portion 24 is provided so as to substantially surround the seal portion 23.
• the flange surface 212 is provided with a double seal portion 23, 24.
• the seal portion 24 may surround the entire circumference of the seal portion 23 without interruption, but, for example, at a position away from each protrusion 213, a portion of the seal portion 24 may be interrupted.
• the seal portion 24 may be interrupted within a range of, for example, 150 mm or less.
• the seal portion 23 is provided so as to substantially surround the molding surface 221.
• the seal portion 23 of the second mold 22 is provided so as to face the seal portion 23 of the first mold 21 in the processing direction D, and has a shape corresponding to the seal portion 23 of the first mold 21.
• the seal portion 23 surrounds the molding surface 221 without interruption all around.
• the seal portion 23 may be interrupted, for example, within a range of 30 mm or less.
• the seal portion 24 is arranged so as to substantially surround the seal portion 23.
• the flange surface 222 is provided with a double seal portion 23, 24.
• the seal portion 24 of the second mold 22 is arranged so as to face the seal portion 24 of the first mold 21 in the processing direction D, and has a shape corresponding to the seal portion 24 of the first mold 21.
• the seal portion 24 may surround the seal portion 23 without interruption all around, or may be interrupted within a range of, for example, 150 mm or less.
• Figure 3 is a cross-sectional view of the mold 20 shown in Figure 2 taken along line III-III.
• Figure 3 shows one of the protrusions 213 provided on the first mold 21 of the mold 20 and its vicinity.
• the protrusion 213 includes a tip surface 213a and a side surface 213b.
• the tip surface 213a is the surface of the protrusion 213 that is located furthest from the flange surface 212 in the machining direction D.
• the tip surface 213a is a flat surface that is substantially perpendicular to the machining direction D.
• the side surface 213b connects the tip surface 213a to the flange surface 212.
• the side surface 213b is inclined with respect to the processing direction D so that the width of the protrusion 213 is greater at the base end and smaller at the tip end.
• Figure 4 is a diagram showing another example of the protrusion 213.
• the side surface 213b of the protrusion 213 is an inclined surface that is inclined overall with respect to the processing direction D, but in the example of Figure 4, a step is provided on the side surface 213b at the base end side of the protrusion 213.
• the portion 213c of the side surface 213b adjacent to the flange surface 212 is substantially parallel to the processing direction D. Therefore, the width of the protrusion 213 is substantially constant at the portion 213c of the side surface 213b adjacent to the flange surface 212.
• the other portions of the side surface 213b may be inclined with respect to the processing direction D, as in Figure 3.
• the flow path 214 preferably opens to the side surface 213b of the protrusion 213.
• the flow path 214 can open in the portion of the side surface 213b of the protrusion 213 that is closer to the molding surface 211.
• the flow path 214 preferably opens in the protrusion 213 at a position closer to the tip of the protrusion 213 than to the flange surface 212.
• the portion of the flow path 214 that passes through the protrusion 213 is substantially parallel to the processing direction D. However, at least the portion of the flow path 214 that passes through the protrusion 213 may be inclined with respect to the processing direction D.
• the flow path 214 can be inclined with respect to the processing direction D so as to intersect with the side surface 213b of the protrusion 213.
• at least the portion of the flow path 214 that passes through the protrusion 213 may be inclined, for example, at an angle greater than 0° and less than 60° with respect to the processing direction D.
• a recess 222a is formed in the flange surface 222 of the second mold 22 near the protrusion 213.
• the recess 222a extends from the portion of the flange surface 222 facing the tip surface 213a of the protrusion 213 to the molding surface 221.
• the recess 222a has a concave shape relative to the rest of the flange surface 222.
• the seal portions 23, 24 of the first mold 21 and the second mold 22 preferably have a shape that allows for surface contact with the mating mold or its seal portions 23, 24.
• each of the seal portions 23, 24 can have, for example, a substantially rectangular cross section.
• the width W of each of the seal portions 23, 24 may be 1.0 mm or more, and is preferably 2.0 mm or more.
• the width W is preferably 5.0 mm or less, and more preferably 3.0 mm or less.
• the height H of each of the seal portions 23, 24 is, for example, 0.2 mm or more.
• the height H may be 0.5 mm or less.
• the inner seal portion 23 is made of, for example, metal.
• the seal portion 23 may be formed integrally with the first mold 21 or the second mold 22.
• the outer seal portion 24 may be made of metal, but may also be made of an elastic material such as resin.
• the seal portion 24 may also be a resin gasket such as an O-ring.
• the first mold 21 and the second mold 22 each have a groove formed therein for arranging the seal portion 24.
• the method for manufacturing the structural member 10 using the mold 20 includes a preparation step and a molding step.
• the manufacturing method may further include a heating step.
• a blank 30 is prepared.
• the blank 30 includes a first blank 31 and a second blank 32.
• the first blank 31 is a blank corresponding to the first member 11 ( Figures 1A and 1B).
• the first blank 31 has at least one through hole 311.
• the through hole 311 is provided to correspond to the protrusion 213 ( Figure 2) of the first mold 21.
• the first mold 21 is provided with multiple protrusions 213, and therefore the first blank 31 also has multiple through holes 311 corresponding to these.
• the second blank 32 is a blank that corresponds to the second member 12 ( Figures 1A and 1B).
• the second blank 32 is overlapped and joined to the first blank 31.
• the second blank 32 is overlapped on the first blank 31 so as to block each of the through holes 311.
• the first blank 31 and the second blank 32 are joined at portions corresponding to the flanges 112, 122 ( Figures 1A and 1B) of the structural member 10.
• the first blank 31 and the second blank 32 are typically joined by welding.
• the first blank 31 and the second blank 32 are preferably joined at their outer peripheries by intermittent welding, such as spot welding.
• the first blank 31 and the second blank 32 may also be joined at their outer peripheries substantially over their entire peripheries by continuous welding, such as laser welding. However, no welds are provided in portions of the first blank 31 and the second blank 32 corresponding to the recess 222a ( Figure 3) of the second mold 22.
• the first blank 31 and the second blank 32 may each be formed from a single metal plate, or may include multiple metal plates (sub-blanks).
• the metal plate may be, for example, a steel plate. However, the metal plate may also be, for example, an aluminum alloy plate.
• first blank 31 and/or the second blank 32 When multiple metal plates are present in the first blank 31 and/or the second blank 32, these metal plates may differ in at least one of tensile strength and thickness.
• first blank 31 includes multiple metal plates
• the metal plates are typically joined to each other by welding.
• second blank 32 includes multiple metal plates
• the metal plates are typically joined to each other by welding.
• the metal plates are joined to each other by, for example, spot welding or laser welding.
• adjacent metal plates may be joined with their end faces butted together, or with their end faces overlapping.
• the heating step is performed before the forming step.
• the prepared material 30 is heated.
• the material 30 is heated, for example, in a heating furnace.
• the heating temperature of the material 30 is determined depending on the materials of the first blank 31 and the second blank 32.
• the material 30 is preferably heated to a temperature equal to or higher than the austenite transformation completion temperature (A c3 point) of the first blank 31 and the second blank 32.
• the material 30 is heated to, for example, 900°C or higher.
• the heating step does not necessarily have to be performed.
• the material 30 is molded using the first mold 21 and the second mold 22.
• the heating process is performed, the heated material 30 is molded by the first mold 21 and the second mold 22 in the molding process.
• the first mold 21 and the second mold 22 are separated in the processing direction D, and the raw material 30 is placed between them.
• the raw material 30 is placed so that each through-hole 311 in the first blank 31 corresponds to the protrusion 213 of the first mold 21.
• the first mold 21 is placed below the second mold 22, so the raw material 30 is placed on the first mold 21.
• the first mold 21 and the second mold 22 are brought relatively close to each other and closed. Specifically, with the protrusions 213 of the first mold 21 inserted into each through-hole 311 of the first blank 31, the material 30 is clamped between the flange surface 212 of the first mold 21 and the flange surface 222 of the second mold 22, and a gap is created between the first blank 31 and the second blank 32 by the protrusions 213.
• the protrusions 213 are inserted into the through-holes 311 of the first blank 31 and lift the second blank 32 from the inside of the material 30, creating a gap between the first blank 31 and the second blank 32.
• the tip surface 213a of the protrusion 213 is substantially flat, so the tip surface 213a of the protrusion 213 can come into surface contact with the second blank 32.
• the raw material 30 is first clamped between the tip surface 213a of the protrusion 213 and the recess 222a of the flange surface 222 of the second mold 22. This allows the raw material 30 to be positioned.
• the material 30 is sandwiched between the seal portion 23 of the first mold 21 and the seal portion 23 of the second mold. Furthermore, when the first mold 21 and the second mold 22 are closed, the seal portion 24 ( Figure 2) of the first mold 21 abuts against the seal portion 24 ( Figure 2) of the second mold. The material 30 is sandwiched more tightly at the position of the seal portion 23 than at other parts of the flange surfaces 212, 222.
• a fluid is injected from the protrusion 213 into the gap between the first blank 31 and the second blank 32.
• the fluid is supplied to the flow path 214 from a fluid supply source (not shown), passes through the flow path 214, and flows out from the protrusion 213. This fluid inflates the raw material 30 within the hollow space formed by the molding surface 211 of the first mold 21 and the molding surface 221 of the second mold 22.
• the first blank 31 of the material 30 is inflated by the fluid and then pressed against the molding surface 211 of the first mold 21.
• the second blank 32 of the material 30 is inflated by the fluid and then pressed against the molding surface 221 of the second mold 22.
• a structural member 10 ( Figures 1A and 1B) having hollow member bodies 111, 121 is molded.
• the fluid used to form the blank 30 is not particularly limited.
• the fluid may be a liquid such as water, or a gas such as nitrogen gas or compressed air.
• the fluid may be a high-pressure liquid or gas, for example, 10 MPa or higher.
• the temperature of the fluid may be determined appropriately depending on the material of the blank 30, and may be, for example, room temperature. If a heating step is performed, i.e., if forming is performed by hot stamping, the fluid may be heated.
• the first blank 31 and the second blank 32 are quenched by being brought into contact with the first mold 21 and the second mold 22, respectively, to remove heat.
• the structural member 10 ( Figures 1A and 1B) can be obtained.
• the outer periphery of the structural member 10 may be removed by laser cutting or the like. At least the portion of the structural member 10 where the through-hole 311 ( Figure 5E) is provided is typically removed after the molding process.
• Figure 6 is a partial cross-sectional view of the structural member 10 after the forming process.
• Figure 6 shows a cross-section (transverse cross-section) of the structural member 10 cut along the thickness direction of the first member 11 and the second member 12 at the positions of the curved portions 111c, 121c ( Figure 1B) of the member bodies 111, 121.
• the transverse cross-section of the structural member 10 in Figure 6 also includes the welded portion 13 joining the flange 112 of the first member 11 and the flange 122 of the second member 12.
• the member body 111 of the first member 11 includes a top plate 113 and a vertical wall 114.
• the vertical wall 114 connects the top plate 113 and the flange 112.
• the vertical wall 114 is curved concavely toward the inside of the member body 111 when the structural member 10 is viewed in plan.
• the member body 121 of the second member 12 also includes a top plate 123 and a vertical wall 124.
• the top plate 123 is positioned opposite the top plate 113 of the first member 11.
• the vertical wall 124 connects the top plate 123 to the flange 122.
• the vertical wall 124 is curved concavely toward the inside of the member body 121 when the structural member 10 is viewed in plan.
• the thickness reduction rate T1 is 30% or more.
• the thickness reduction rate T1 depends on the material of the member body 111, the forming height, etc., but is, for example, 50% or less, and preferably less than 45%.
• the thickness reduction rate T1 is the thickness reduction rate based on the thickness of the flange 112. In other words, when the thickness of the flange 112 is t0 and the thickness of the member body 111 at the curved portion 111c is t, the thickness reduction rate T1 [%] can be obtained by (t0 - t) / t0 x 100.
• the thickness t0 is, for example, the thickness of the flange 112 measured at a position 2.0 mm or more away from the weld 13 toward the free end of the flange 112.
• the thickness t0 is substantially equal to the thickness of the first blank 31 before forming.
• the plate thickness t is the minimum value of the plate thickness measured at five or more points at 1 mm intervals, starting from the corner between the flange 112 and the vertical wall 114 and extending along the vertical wall 114, on the cross section of the structural member 10 when cut at the bottom of the curved portion 111c.
• the thickness reduction rate T2 at the curved portion 121c ( Figure 1B) of the member body 121 is taken as the thickness reduction rate T2, it is 30% or more.
• the thickness reduction rate T2 depends on the material and forming height of the member body 121, but is, for example, 50% or less, and preferably less than 45%.
• the thickness reduction rate T2 is based on the thickness of the flange 122.
• the thickness reduction rate T2 can be obtained using the same measurement and calculation methods as the thickness reduction rate T1. That is, when the thickness of the flange 122 is t0 and the thickness at the curved portion 121c of the member body 121 is t, the thickness reduction rate T2 [%] can be obtained by (t0 - t) / t0 x 100.
• the thickness t0 is, for example, the thickness of the flange 122 measured at a position 2.0 mm or more away from the weld 13 toward the free end of the flange 122.
• the thickness t0 is substantially equal to the thickness of the second blank 32 before forming.
• the thickness t is the minimum value of the thickness measured at five or more points at 1 mm intervals along the vertical wall 124, starting from the corner between the flange 122 and the vertical wall 124, on a cross section of the structural member 10 when cut at the bottom of the curved portion 121c.
• the minimum Vickers hardness of the heat-affected zone of the weld 13 is 70% or more of the Vickers hardness of the non-welded portions of the first member 11 and the second member 12.
• the Vickers hardness is preferably 80% or more, and more preferably 90% or more, of the Vickers hardness of the first member 11 and the second member 12.
• the minimum Vickers hardness of the heat-affected zone is equal to or lower than the Vickers hardness of the non-welded portions.
• Vickers hardness can be measured using the Vickers hardness test specified in JIS Z 2244-1:2020. Specifically, a test specimen including the first and second members 11 and 12 and the weld 13 is first obtained from the structural member 10 by laser cutting or other methods at a position passing through the weld center of the weld 13. The test specimen is then embedded in resin so that the cross section passing through the weld center of the weld 13 is located on the surface, and the cross section is polished.
• Vickers hardness is measured at a position 1/4 of the plate thickness from the surface on the weld center side of the weld 13 to a position 12.0 mm outward from the weld center, in accordance with JIS Z 2244-1:2020, using a test force of 0.49 N and measurement intervals (pitch) of 0.1 to 0.2 mm, for example.
• the smallest value of the measured Vickers hardness is the minimum Vickers hardness of the heat-affected zone of the weld 13.
• the Vickers hardness is measured in accordance with JIS Z 2244-1:2020 at a position 15.0 mm or more away from the weld center of the welded portion 13 and at a position 1/4 of the plate thickness from the surface on the weld center side of the welded portion 13, using a test force of, for example, 0.49 N.
• This Vickers hardness is the Vickers hardness of the non-welded portions of the first member 11 and the second member 12.
• a first mold 21 and a second mold 22 are used to manufacture a structural member 10 from a raw material 30 including a first blank 31 and a second blank 32.
• At least one protrusion 213 is formed on a flange surface 212 of the first mold 21.
• the protrusion 213 lifts the second blank 32 toward the second mold 22.
• a gap is formed between the first blank 31 and the second blank 32.
• a fluid passage is formed simply by closing the first mold 21 and the second mold 22, so there is no need to perform separate pre-forming to ensure a fluid flow path. Therefore, using the first blank 31 and the second blank 32 joined together, a structural member 10 in which the first member 11 and the second member 12 are integrated can be molded with good productivity.
• the fluid used to form the structural member 10 is preferably a gas. That is, in the forming process, the structural member 10 is preferably gas blow molded. For example, if the structural member 10 is hydroformed, liquid remains inside the structural member 10 after forming, and therefore processing is required to drain the liquid from inside the structural member 10 after the forming process. On the other hand, if the structural member 10 is gas blow molded, post-processing of the fluid is not necessary. Therefore, by using a gas to form the structural member 10, the productivity of the structural member 10 can be improved.
• the clamping force between the first mold 21 and the second mold 22 can seal the outer peripheries of the overlapping first blank 31 and second blank 32. Therefore, the outer peripheries of the first blank 31 and second blank 32 do not need to be laser welded all around, as is the case with conventional sheet metal hydroforming technology.
• the first blank 31 and second blank 32 only need to be joined at multiple locations by spot welding, for example. In this case, the labor hours and costs required to manufacture the structural member 10 can be reduced compared to when full-periphery laser welding is performed. Therefore, a structural member 10 with a hollow cross section can be formed with greater productivity.
• the raw material 30 may be formed into the structural member 10 using hot stamping. That is, the raw material 30 may be subjected to a heating process before the forming process using the first mold 21 and the second mold 22.
• the HAZ softening can be reduced by heating to a high temperature of, for example, 900°C or higher in the heating process.
• HAZ softening occurs due to welding, and the minimum Vickers hardness of the HAZ is approximately 60% of the Vickers hardness of the non-welded portion.
• the minimum Vickers hardness of the HAZ of the welded portion 13 is 70% or more of the Vickers hardness of the non-welded portion of the first member 11 and the second member 12. This reduces the number of relatively low-strength portions in the structural member 10, thereby improving the crash resistance of the structural member 10.
• the structural member 10 When the structural member 10 is formed using hot stamping, it is preferable that the structural member 10 be gas blow-formed during the forming process. On the other hand, when the structural member 10 is hydroformed during the forming process, typically no heating step is performed, and the forming process is a cold forming step.
• a seal portion 23 is provided on each of the flange surface 212 of the first mold 21 and the flange surface 222 of the second mold 22.
• Each seal portion 23 is arranged to surround the hollow space formed by the molding surface 211 of the first mold 21 and the molding surface 221 of the second mold 22.
• the seal portion 23 can improve the liquid-tightness or air-tightness of the hollow space. Specifically, when the first mold 21 and the second mold 22 are closed, the seal portion 23 of the first mold 21 and the seal portion 23 of the second mold 22 firmly abut against and clamp the first blank 31 and the second blank 32, respectively. This makes it difficult for fluid to enter between the first mold 21 and the first blank 31, and between the second mold 22 and the second blank 32, and to leak around the hollow space. This allows for better molding of the structural member 10 using a fluid.
• a seal portion 24 is further provided on each of the flange surface 212 of the first mold 21 and the flange surface 222 of the second mold 22.
• Each seal portion 24 is arranged so as to surround the other seal portion 23.
• the seal portion 24 can further improve the liquid-tightness or air-tightness of the hollow space. In other words, when the first mold 21 and the second mold 22 are closed, the seal portion 24 can seal the periphery of the material 30 in the mold 20. This makes it less likely for fluid to leak outside the mold 20, and allows for even better molding of the structural member 10 using the fluid.
• the protrusion 213 provided on the first mold 21 may have a step on its side surface 213b. That is, a portion 213c of the side surface 213b of the protrusion 213 adjacent to the flange surface 212 of the first mold 21 may be substantially parallel to the processing direction D in a cross-sectional view. In this case, it is preferable that the size of this portion 213c is equal to or greater than the size of the through hole 311 of the first blank 31. As a result, when the protrusion 213 is inserted into the through hole 311 of the first blank 31, this portion 213c widens the through hole 311.
• the periphery of the through hole 311 comes into strong contact with the side surface 213b of the protrusion 213 along its entire circumference, making it less likely that a gap will form between the periphery of the through hole 311 and the protrusion 213.
• This makes it less likely that fluid from the protrusion 213 will enter between the first blank 31 and the first mold 21. Therefore, fluid is more reliably supplied between the first blank 31 and the second blank 32, allowing for better molding of the material 30.
• the flow path 214 formed in the first mold 21 preferably opens at a position near the tip of the protrusion 213. Furthermore, at least the portion of the flow path 214 that passes through the protrusion 213 is preferably inclined with respect to the processing direction D so as to intersect with the side surface 213b of the protrusion 213. This makes it difficult for fluid from the protrusion 213 to enter between the first blank 31 and the first mold 21, and makes it easier for fluid to be supplied between the first blank 31 and the second blank 32. This allows for better molding of the material 30 using a fluid.
• a structural member 10 having a hollow cross section is formed by inflating the raw material 30 with a fluid.
• a greater reduction in thickness can be tolerated than in conventional press molding.
• cracks, necking, etc. occur in the raw material 30 when the thickness reduction rate reaches 30, resulting in poor molding.
• cracks, necking, etc. are less likely to occur in the portion of the raw material 30 that is formed by the fluid, even if the thickness reduction rate is large.
• the thickness reduction rate T1 at the curved portion 111c of the first member 11, where thickness reduction is most likely to occur is 30% or more.
• the thickness reduction rate T2 at the curved portion 121c of the second member 12, where thickness reduction is most likely to occur is 30% or more. Even when the thickness reduction rates T1 and T2 are 30% or more, the member bodies 111 and 121 can be formed satisfactorily without cracks, necking, etc.
• FIG. 7 is a perspective view showing the schematic configuration of a structural member 10A according to this embodiment.
• the structural member 10A is a front module for a vehicle body.
• the structural member 10A is provided at the front and bottom of a vehicle body such as an automobile.
• the structural member 10A may also be a subframe for a vehicle body.
• the structural member 10A is provided at the front or rear and bottom of a vehicle body such as an automobile.
• the subframe can have a configuration generally similar to that of the front module.
• the side frames 111a of the first member 11 are connected at their longitudinal centers by a cross member 111b.
• the side frames 121a of the second member 12 are connected at their longitudinal centers by a cross member 121b.
• the side frames 111a of the first member 11 are connected at one longitudinal end by a cross member 111b.
• the side frames 121a of the second member 12 are connected at one longitudinal end by a cross member 121b.
• the structural member 10A according to this embodiment can also be manufactured using a manufacturing method similar to that of the first embodiment.
• Figures 8A to 8D are schematic diagrams illustrating the manufacturing method for the structural member 10A.
• a raw material 30 including a first blank 31 and a second blank 32 is also prepared.
• the basic configuration of the first blank 31 and the second blank 32 is as described in the first embodiment.
• the shape of the structural member 10A ( Figure 7) is different from that in the first embodiment, the first blank 31 and the second blank 32 have shapes different from the first blank 31 and the second blank 32 ( Figures 5A and 5B) used in the manufacturing method according to the first embodiment.
• the blank 30 is subjected to the same molding process as in the first embodiment.
• the blank 30 may be subjected to the molding process after the heating process described above.
• the protrusion 213 of the first mold 21 is inserted into the through hole 311 of the first blank 31, and the blank 30 is clamped between the flange surface 212 of the first mold 21 and the flange surface 222 of the second mold 22, and the protrusion 213 creates a gap between the first blank 31 and the second blank 32.
• a fluid is injected into the gap from the protrusion 213, and the fluid expands the blank 30 between the molding surface 211 of the first mold 21 and the molding surface 221 of the second mold 22.
• protrusions 213 are provided in the first mold 21 and the second mold 22 near the cross member molding portions 211b, 221b of the molding surfaces 211, 221.
• the material 30 expands due to the fluid supplied from the protrusions 213, and the first blank 31 and the second blank 32 are pressed against the first mold 21 and the second mold 22, respectively.
• the material 30 expands due to the fluid flowing from the cross member molding portions 211b, 221b side ( Figure 8C), and the first blank 31 and the second blank 32 are pressed against the first mold 21 and the second mold 22, respectively.
• the outer periphery of structural member 10A may be removed by laser cutting or the like. At least the portion of structural member 10A where through-hole 311 (Figure 8C) is provided is typically removed after the molding process.
• flanges 112, 122 are provided to surround the entire periphery of member bodies 111, 121.
• both end portions of cross members 111b, 121b, including through holes 311 may be removed after the molding process, thereby opening both longitudinal ends of cross members 111b, 121b.
• one longitudinal end of side frames 111a, 121a may be opened by removing the end portion of side frames 111a, 121a opposite cross members 111b, 121b after the molding process.
• Third Embodiment 9 is a perspective view showing a schematic configuration of a structural member 10B according to this embodiment.
• the structural member 10B is a front floor module for a vehicle body.
• the structural member 10B is provided at the front portion of the floor of a vehicle body such as an automobile.
• the member body 121 of the second member 12 includes a pair of side frames 121a and a cross member 121b.
• the side frames 121a are connected at one longitudinal end by the cross member 121b.
• the member body 121 forms a hollow cross section together with the first member 11 by joining the flange 122 to the first member 11.
• the first member 11 includes a floor panel 115 and a floor tunnel 116.
• the first member 11 may include at least one cross member 111b ( Figures 1B and 7).
• the floor tunnel 116 When the structural member 10B is assembled to the vehicle body, the floor tunnel 116 is located in the left-right center of the floor panel 115 and extends in the front-to-rear direction.
• the floor tunnel 116 has a convex shape toward the second member 12 relative to the floor panel 115.
• the cross member 111b may be positioned to face the cross member 121b of the second member.
• the portions of the flange 122 of the second member 12 that are continuous with each side frame 121a are joined to the floor panel 115.
• the portions of the flange 122 of the second member 12 that are continuous with the cross member 121b are joined to the floor panel 115 and the floor tunnel 116.
• the structural member 10B according to this embodiment can be manufactured using the same manufacturing method as the manufacturing methods according to the other embodiments.
• Figures 10A to 10D are schematic diagrams illustrating the manufacturing method for the structural member 10B.
• a raw material 30 including a first blank 31 and a second blank 32 is prepared.
• the first blank 31 and the second blank 32 are overlapped and joined.
• the shapes of the first blank 31 and the second blank 32 are also different from each other.
• the blank 30 is subjected to the same molding process as in other embodiments.
• the blank 30 may be subjected to the molding process after the heating process described above.
• the protrusion 213 of the first mold 21 is inserted into the through hole 311 of the first blank 31, and the blank 30 is clamped between the flange surface 212 of the first mold 21 and the flange surface 222 of the second mold 22, and the protrusion 213 creates a gap between the first blank 31 and the second blank 32.
• a fluid is injected into the gap from the protrusion 213, and the fluid expands the blank 30 between the molding surface 211 of the first mold 21 and the molding surface 221 of the second mold 22.
• the first mold 21 and the second mold 22 have protrusions 213 provided near the cross member molding portions 211b, 221b of the molding surfaces 211, 221.
• the material 30 expands due to the fluid supplied from the protrusions 213, and the first blank 31 and the second blank 32 are pressed against the first mold 21 and the second mold 22, respectively.
• the first member 11 does not include a side frame
• the side frame molding portion 221a exists only in the second mold 22.
• the material 30 expands due to the fluid flowing from the cross member molding portions 211b, 221b side ( Figure 10C), and the first blank 31 and the second blank 32 are pressed against the first mold 21 and the second mold 22, respectively.
• the material 30 bulges mainly toward the second mold 22, and does not substantially bulge toward the first mold 21.
• the portion of the first blank 31 that does not overlap with the second blank 32 is clamped between the first mold 21 and the second mold 22, as in normal press molding, and is molded into a shape that conforms to the molding surfaces 211, 221.
• the outer periphery of structural member 10B ( Figure 9) may be removed by laser cutting or the like. At least the portion of structural member 10B where through-hole 311 ( Figure 10C) is provided is typically removed after the molding process.
• both ends of cross member 121b may be removed to open both longitudinal ends of cross member 121b.
• the left and right ends of floor panel 115, including through-hole 311, can also be removed.
• Fourth Embodiment 11 is a perspective view showing a schematic configuration of a structural member 10C according to this embodiment.
• the structural member 10C is a center or rear floor module for a vehicle body.
• the structural member 10C is provided in the center or rear part of the floor of a vehicle body such as an automobile.
• the structural member 10C includes multiple second members 12F, 12R.
• the second member 12F is positioned in front of the second member 12R on the vehicle body.
• Each of the second members 12F, 12R includes a cross member 121b as the member body 121.
• a curved portion 121c is provided at one or both longitudinal ends of the cross member 121b.
• the cross member 121b has wide portions at both longitudinal ends. The corners between these wide portions and other portions form the curved portions 121c.
• Flanges 122 are provided on both sides of the cross member 121b.
• the member bodies 121 of each of the second members 12F, 12R form a hollow cross section together with the first member 11.
• the first member 11 includes a floor panel 115 and a floor tunnel 116.
• the first member 11 may include at least one cross member 111b ( Figures 1B and 7).
• the first member 11 may also include multiple cross members 111b corresponding to the second members 12F, 12R.
• a raw material 30 is prepared that includes a first blank 31 and a plurality of second blanks 32F, 32R.
• the second blanks 32F, 32R are blanks that correspond to the second members 12F, 12R ( Figure 11), respectively.
• Through holes 311 are formed in the first blank 31 at positions that correspond to the second members 12F, 12R.
• the blank 30 is subjected to the same molding process as in other embodiments.
• the blank 30 may be subjected to the molding process after the heating process described above.
• the protrusion 213 of the first mold 21 is inserted into the through hole 311 of the first blank 31, and the blank 30 is clamped between the flange surface 212 of the first mold 21 and the flange surface 222 of the second mold 22, and the protrusion 213 creates a gap between the first blank 31 and the second blank 32. Fluid is then injected into the gap from the protrusion 213, and the fluid expands the blank 30 between the molding surface 211 of the first mold 21 and the molding surface 221 of the second mold 22.
• first blank 31 and the second blank 32F are pressed against the first mold 21 and the second mold 22, respectively, as shown in Figure 12C.
• first blank 31 and the second blank 32R are pressed against the first mold 21 and the second mold 22, respectively.
• the outer periphery of the structural member 10C ( Figure 11) may be removed by laser cutting or the like. At least the portion of the structural member 10C where the through holes 311 ( Figures 12C and 12D) are provided is typically removed after the molding process. For example, by removing both ends of the second members 12F, 12R, each cross member 121b may be opened at both longitudinal ends. At this time, the left and right ends of the floor panel 115, including the through holes 311, can also be removed at the same time.
• the plate thickness reduction rate T1 of the curved portion 111c and/or the plate thickness reduction rate T2 of the curved portion 121c have the same characteristics as in the first embodiment. Furthermore, in these embodiments, if a heating process is performed before the forming process, the minimum Vickers hardness value of the heat-affected zone of the weld 13 also has the same characteristics as in the first embodiment.
• the first blank 31 is formed from one or more metal plates (sub-blanks), just as in the first embodiment.
• the second blanks 32, 32F, and 32R are also each formed from one or more metal plates (sub-blanks), just as in the first embodiment.
• structural member 10 is a rear module of the vehicle body
• structural member 10A is a front module
• structural members 10B and 10C are floor modules.
• the structural members manufactured using the manufacturing method of the present disclosure are not limited to structural members 10, 10A-10C illustrated in the above embodiments.
• the manufacturing method of the present disclosure can be applied to various structural members as long as they include a first member and a second member, and one of the first member and the second member forms a hollow cross section with the other of the first member and the second member.
• the hollow member body and the flange continuous with the member body may be provided on both the first member and the second member, as in the first and second embodiments, or may be provided on only one of the first member and the second member, as in the third and fourth embodiments.
• the manufacturing method disclosed herein can also be applied to a structural member 10D that includes a first member 11, which is a lid for a battery case, and multiple second members 12.
• the member body 121 of each of the second members 12 is a cross member.
• the first member 11 also serves as a floor panel for the vehicle body.
• the second members 12 are disposed on the first member 11 and each extend in the left-right direction of the vehicle body.
• the through holes 311 in the first blank 31 may be positioned according to the shape of the structural member to be formed.
• the through holes 311 are preferably provided in locations on the first blank 31 where relatively little material flows into the hollow space of the mold 20 during the forming process. For example, if the material 30 is rectangular and the first blank 31 and the second blank 32 are overlapped at the corners of the material 30, it is preferable to position the through holes 311 in the corners of the material 30. This allows the structural member to be formed while suppressing deformation of the through holes 311.
• the first mold 21, which includes one or more protrusions 213, is positioned below the second mold 22.
• the positional relationship between the first mold 21 and the second mold 22 is not limited to this.
• the first mold 21 may be positioned above the second mold 22, for example.
• the protrusions 213 are positioned above the material 30, and the material 30 is placed on the flange surface 222 of the second mold 22. Therefore, the material 30 can be stably positioned before the mold 20 is closed. Therefore, there is no need to provide a flat tip surface 213a on the protrusions 213 to position the material 30.
• both the first mold 21 and the second mold 22 are provided with seal portions 23, 24.
• first mold 21 or the second mold 22 may not be provided with seal portion 23 and/or seal portion 24, or neither the first mold 21 nor the second mold 22 may be provided with seal portions 23, 24.
• at least seal portion 23 be provided on both the first mold 21 and the second mold 22. More preferably, double seal portions 23, 24 are provided on both the first mold 21 and the second mold 22.
• each of the structural members 10, 10A-10C is formed using a material 30 including a first blank 31 and a second blank 32.
• a reinforcing plate may be affixed to at least one of the first blank 31 and the second blank 32.
• the reinforcing plate may be affixed to a portion of the structural member 10, 10A-10C where rigidity is required.
• a reinforcing plate may be affixed to the second blank 32 before molding at a position corresponding to the ridge of the floor tunnel 116. The reinforcing plate is joined to the first blank 31 from the side opposite the surface where the first blank 31 and the second blank 32 mate.
• the reinforcing plate may be joined to the second blank 32 from the side opposite the surface where the first blank 31 and the second blank 32 mate.
• the reinforcing plate is joined to at least one of the first blank 31 and the second blank 32 by welding, for example, spot welding or laser welding.
• the mold 20 was used to form the structural member 10, 10A-10C from a material 30 including a first blank 31 and a second blank 32 or 32F, 32R joined to the first blank 31.
• the mold 20 can also be used to form a material 30 in which the second blank 32 is superimposed on the first blank 31 but is not joined to the first blank 31.
• a forming test was conducted on the structural member 10 according to the first embodiment.
• the structural member 10 was formed using the manufacturing method (hydraulic blowing or gas blowing) described in the above embodiment, and the thickness reduction rate T2 at the curved portion 121c of the member body 121 of the upper member (second member) 12 was measured.
• industrial water mixed with a rust inhibitor was used as the forming fluid
• gas blowing compressed air was used as the forming fluid.
• no heating process was performed on the material, but for gas blowing, a heating process was performed on the material before the forming process.
• the second member 12 was formed using the conventional manufacturing methods of cold press forming and hot stamping, and the thickness reduction rate T2 at the curved portion 121c of the member body 121 was measured.
• Table 1 The test conditions and results are shown in Table 1.
• Table 1 shows the forming method, material and strength (tensile strength), forming height, thickness reduction rate T2, and forming evaluation for each example and comparative example.
• the thickness reduction rate T2 was calculated by obtaining the thickness t of the curved portion 121c of the member body 121 using the measurement method described in the above embodiment, and setting the thickness of the blank (steel plate) before forming, 1.2 mm, as t0.
• the forming height is the length along the processing direction D from the flange 122 to the top plate 123 of the second member 12.
• the plate thickness reduction rate T2 at the curved portion 121c of the member main body 121 was 34%, and cracks occurred at the curved portion 121c.
• Comparative Examples 3 and 4 a 1.5 GPa-class hot stamp material was used as the raw material, and the second member 12 was formed using only hot stamping.
• the forming height was relatively small, so the thickness reduction rate T2 at the curved portion 121c of the member main body 121 was less than 30%, and no forming defects occurred at the curved portion 121c.
• the forming height was relatively large, so the thickness reduction rate T2 was 30%, and necking occurred at the curved portion 121c.
• Comparative Examples 5 and 6 a 2.0 GPa-class hot stamp material was used as the raw material, and the second member 12 was formed solely by hot stamping.
• the forming height was relatively small, so no forming defects occurred at the curved portion 121c of the member main body 121.
• the forming height was relatively large, so necking occurred at the curved portion 121c.
• the plate thickness reduction rate T2 at the curved portion 121c was 26%
• Comparative Example 6 the plate thickness reduction rate T2 was 28%.
• Example 2 which used a steel plate with a tensile strength of 270 MPa, cracks occurred in the curved portion 121c when the thickness reduction rate T2 exceeded 50%
• Example 4 which used a steel plate with a tensile strength of 590 MPa, cracks occurred in the curved portion 121c when the thickness reduction rate T2 was 45%.
• Example 6 which used a 1.5 GPa-class hot-stamped material
• Example 8 which used a 2.0 GPa-class hot-stamped material. Therefore, with regard to the forming method, material, and forming height of this test, it was confirmed that forming defects are generally suppressed when the thickness reduction rate T2 is 50% or less, and no forming defects occur when the thickness reduction rate T2 is less than 45%.
• first member 111 member body 111a: side frame 111b: cross member 111c: curved portion 112: flange 12, 12F, 12R: second member 121: member body 121a: side frame 121b: cross member 121c: curved portion 122: flange 20: mold 21: first mold 211: (first) molding surface 212: (first) flange surface 213: protrusion 214: flow path 22: second mold 221: (second) molding surface 222: (second) flange surface 23: (first) seal portion 24: (second) seal portion 30: material 31: first blank 311: through hole 32, 32F, 32R: Second blank

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