JP6497150B2 - Hot press mold, hot press apparatus, and hot press molded product manufacturing method - Google Patents

Description

  The present invention relates to a hot press die, a hot press apparatus, and a method for manufacturing a hot press molded product, specifically, a top plate, a ridge line continuous with the top plate, and a vertical wall continuous with the ridge line. The present invention relates to a technique for suppressing cracks in a vertical wall in the case of manufacturing a hot press-formed product having a cross section having a cross section (for example, a hat cross section or a groove cross section).

  In recent years, in order to reduce the weight of automobiles, it has been promoted to increase the strength of steel materials and reduce the weight used. In thin steel plates widely used in automobiles, press formability decreases with increasing strength, making it difficult to manufacture complex shapes. Specifically, in a high-strength blank, the ductility is reduced and breakage occurs at a portion with a high degree of processing, or the spring back and wall warp are increased, resulting in deterioration of the dimensional accuracy of the press-formed product. For this reason, it is not easy to produce a press-formed product having a desired shape by performing cold press forming on a blank made of a steel plate having high strength, particularly a tensile strength of 780 MPa or more. According to roll forming rather than press forming, it is possible to process a high-strength steel sheet, but only parts having a uniform cross section in the longitudinal direction can be produced.

  On the other hand, Patent Document 1 discloses a method called hot press forming in which a blank made of a heated steel plate is pressed, and Patent Document 2 discloses a method in which a blank is pre-formed into a predetermined shape at room temperature. There has been disclosed a hot press forming method (pre-press quench method) that simultaneously achieves high strength and formability of a steel sheet by heating to an austenite region and quenching in a press mold.

  In hot press forming, since the steel plate at the time of forming has high temperature, softness, and high ductility, it is possible to manufacture a press-formed product having a complicated shape with good dimensional accuracy. Furthermore, by increasing the strength of the steel sheet by martensitic transformation, the steel sheet is heated in the austenite region and rapidly cooled (quenched) in a press mold.

  Thus, although hot press forming has greatly increased the degree of freedom in forming high-strength steel sheets, cracking may occur during press forming even when hot press forming is performed.

  FIG. 8A is a perspective view showing the hot press-formed product 1 in which such a crack occurs, and FIG. 8B shows a half section of the press-forming device 3 of the hot press-formed product 1. It is explanatory drawing shown. FIG. 9A is a perspective view showing a hot press-formed product 2 that causes similar cracks, and FIG. 9B is a half section of the press-forming device 4 of the hot press-formed product 2. FIG. 9C is an explanatory view showing a cross section corresponding to the cross section AA ′ in FIG. 9A in the press forming apparatus 4 before the start of press forming. In addition, the two straight lines in FIG. 9A and FIG. 9C indicate that the positions indicated by each are corresponding positions before and after press forming.

  As shown in FIG. 8 (b), hot press molding by drawing is performed on the blank 8 using the punch 5, die 6 and blank holder 7 of the press molding apparatus 3, and as shown in FIG. 8 (a). For example, a cross section (for example, a hat cross section or a groove) having a top plate 1a, two ridge lines 1b and 1b continuous to the top plate 1a, and two vertical walls 1c and 1c continuous to the two ridge lines 1b and 1b, respectively. In the case of manufacturing a hot press-formed product 1 having a curved portion 1d having a curved ridge line 1b that protrudes outward from the top plate 1a in a plan view in the pressing direction and has a curved section) In the vertical wall 1c continuous with the top plate 1a of the portion 1d, cracks are likely to occur during hot press molding.

  Further, as shown in FIGS. 9B and 9C, hot press molding by bending is performed on the blank 8 using the punch 5 and the die 6 of the press molding apparatus 3, and FIG. As shown, for example, a cross section (for example, a cross-section (for example, two vertical walls 2c, 2c continuous to two ridge lines 2b, 2b) and two ridge lines 2b, 2b continuous to the top plate 2a (for example, When manufacturing a hot press-formed product 2 having a hat cross section or a groove type cross section and having a step 2e in the pressing direction (a direction perpendicular to the top plate 2a) on the top plate 2a, the top plate near the step 2e Cracks are likely to occur during hot pressing in the vertical wall 2c that continues to 2a (particularly the top plate 2a present at a low position with the step 2e as a boundary).

  Many inventions have been proposed so far to prevent cracks in press-formed products. Patent Document 3 discloses a method of manufacturing a cold press-formed product of a cross-section hat-shaped member curved in a plan view with a line of sight orthogonal to the top plate, and Patent Document 4 discloses a cross-section hat by hot press molding. In forming a mold member, a method is disclosed in which an arc-shaped separate punch is built in a die (punch) and the separate punch is operated at a molding bottom dead center. There has been disclosed a hot press forming method by drawing which improves formability by cooling a specific portion of the material using a cooling catalyst.

British Patent Publication No. 1490535 Japanese Patent Laid-Open No. 10-96031 International Publication No. 2014-106932 Pamphlet Japanese Patent Laying-Open No. 2015-20175 JP 2014-208374 A

  However, when the manufacturing method disclosed in Patent Document 3 is applied to hot press molding, cracks may occur in the punch shoulder.

  With the method disclosed in Patent Document 4, it is not possible to suppress vertical wall cracks that occur before reaching the bottom dead center. Further, in order to operate the separate punch, it is necessary to separately provide an operation device for the separate punch, and the cost of the apparatus cannot be denied.

  Furthermore, although Patent Document 5 definitely defines a method for suppressing cracks in the vertical wall, this method inevitably increases the cost of the apparatus.

  As described above, the conventional technique cannot suppress the cracking of the vertical wall due to the elongation strain generated in the vertical wall at the time of hot press forming described with reference to FIGS. 8 and 9 without increasing the manufacturing cost.

  In many cases, cracking of a blank in hot press molding is caused by a local temperature drop of the blank caused by contact between the blank and a die (punch, die). The temperature drop part in contact with the mold in the blank is harder and more difficult to deform than the non-temperature drop part (high temperature part) that is not in contact with the mold in the blank. Will do.

  As a result of intensive studies to solve the above problems based on such premise, the present inventors have obtained knowledge AK listed below and completed the present invention.

  (A) FIG. 10A is a contour based on numerical analysis of the plate thickness reduction rate at the bottom dead center in the hot press-formed product 1 hot press-formed by the press forming apparatus 3 shown in FIG. 8B. FIG. 10B is a diagram showing the temperature of each part at a position 10 mm above the bottom dead center of molding in the hot press-molded product 1 that is hot press-molded by the press molding apparatus 3 shown in FIG. 8B. It is a contour figure by numerical analysis. The numbers in FIG. 10A indicate the plate thickness reduction rate in the indicated area.

As shown in FIG. 10 (a), the vertical wall 1c on the outer peripheral side of the curved portion 1d, which is likely to be cracked in hot press molding,
(I) It is a part to which tension is applied not only in the pressing direction but also in the direction orthogonal to the pressing direction during molding;
(Ii) It is a part that is kept at a high temperature because it does not come into contact with the molds 5 and 6, and (iii) It is a part that is sandwiched between the die shoulder R part and the punch shoulder R part of the mold that the blank 8 contacts. There is a feature.

  (B) From these features (i) to (iii), the vertical wall 1c on the outer peripheral side of the curved portion 1d is easily strained during molding, so that the plate thickness is greatly reduced and cracking is likely to occur. For this reason, in order to suppress the crack of the vertical wall 1c, the local concentration of the strain is alleviated by enlarging the region of the non-temperature drop portion (high temperature portion) of the vertical wall 1c on the outer peripheral side of the curved portion 1d. It is effective.

  (C) Two ridge lines 1b and 1b continuous to the top plate 1a and two vertical walls 1c and 1c respectively continuous to the two ridge lines 1b and 1b are arranged on the top plate 1a on the outside of the top plate 1a in a plan view in the pressing direction. When it has the curved part 1d provided with the ridge line 1b that protrudes and curves, the concentration of strain on the vertical wall 1c on the outer peripheral side of the curved part 1d occurs remarkably. This is because if the ridge line 1b is bent, the flow of the blank during press molding becomes non-uniform.

  (D) FIG.10 (c) is a contour figure by the numerical analysis of the plate | board thickness reduction | decrease rate in the shaping | molding bottom dead center in the hot press-molded product 10 hot-press-molded with the press molding apparatus which concerns on this invention mentioned later. FIG. 10 (d) is a contour diagram based on numerical analysis of the temperature of each part at a position 10mm above the bottom dead center of molding in the hot press molded product 10 that is hot press molded by the press molding apparatus according to the present invention. is there. The numbers in FIG. 10C indicate the plate thickness reduction rate in the indicated area.

  As can be understood from a comparison of FIGS. 10C and 10D with FIGS. 10A and 10D, the hot press-formed product 10 is manufactured by hot press forming. At that time, a punch having an inner pad attached to the top of the punch is used. Specifically, a portion of the blank that is formed into the curved portion 10d of the top plate 10a in a plan view in the press direction is used as the top of the punch. The region of the non-temperature-decreasing portion (high-temperature portion) of the vertical wall 1c on the outer peripheral side of the curved portion 10d is expanded by performing hot press molding using a punch and a die supported by an inner pad that is freely installed and removed. This can alleviate local concentration of strain and suppress the reduction rate of the plate thickness, so that the occurrence of cracks in the vertical wall 10c on the outer peripheral side of the curved portion 10d can be effectively eliminated.

  (E) The knowledge of (A) to (D) above is based on the fact that there is only one ridgeline on the top plate, that is, from an annular ridgeline such as a circle, an ellipse, or a polygon in plan view in the press direction relative to the blank. The present invention can also be applied when the formed top plate is hot press-molded.

  (F) FIG. 5 (a) shows the bottom die of molding in the hot press-molded product 2 having the step 2e on the top plate 2a, which is hot press-molded by the press molding device 4 shown in FIGS. 9 (b) and 9 (c). FIG. 5B is a contour diagram by numerical analysis of the plate thickness reduction rate at a point, and FIG. 5B is a step on the top plate 2a that is hot press-formed by the press-forming device 4 shown in FIGS. 9B and 9C. It is the contour figure by the numerical analysis of each part temperature in the position 4 mm above the bottom dead center of shaping | molding in the hot press molded product 2 with 2e. Here, the level | step difference 2e is a boundary part from which the shaping | molding height of the top plate 2a changes.

As shown in FIG. 5A, the top plate 2a in the vicinity of the step 2e (top plate 2a existing at a low position with the step 2e as a boundary, particularly the punch side at the boundary of the step 2e, which is easily cracked in hot press molding. In the vertical wall 2c continuing to the convex portion), similarly to the curved portion 1d shown in FIGS. 10 (a) and 10 (d),
(I) It is a part to which tension is applied not only in the pressing direction but also in the direction orthogonal to the pressing direction during molding;
(Ii) It is a part that is kept at a high temperature because it does not come into contact with the molds 5 and 6; It is characterized by being a part.

  (G) From these characteristics (i) to (iii), since the vertical wall 2c of the stepped portion 2e of the top plate 2a concentrates strain at the time of molding, the plate thickness is greatly reduced and cracking is likely to occur. The reason for this will be described in more detail.

  Fig.6 (a) is explanatory drawing which shows the shape of the blank 20 in the shaping | molding bottom dead center 20mm upper position at the time of shape | molding the hot press molded product 14 with the press molding apparatus 12 which concerns on this invention, FIG. (b) is explanatory drawing which shows the cross section of the press molding apparatus 12 at this time.

  As shown in FIGS. 6A and 6B, when there is a step in the portion 8a formed on the top plate 2a of the blank 8, the portion 8a located on the convex side 5a of the punch 5 is punched at the initial stage of molding. 5 is constrained and molded before the portion 8b located on the concave side 5b. For this reason, when molding progresses and the portion 8b located on the concave side 5b of the punch 5 is molded, the portion 8a located on the convex side 5a of the punch 5 is constrained, so the amount of inflow of material is small. Insufficient cracks are likely to occur in the portion formed in the vertical wall 2c that is continuous with the portion 8b. In particular, in the hot press forming, the blank 8 is restrained more than in the cold press forming because the region of the non-temperature reduced portion (high temperature portion) of the portion formed on the vertical wall 2c in the blank 8 at the time of forming becomes smaller. And the crack is more likely to occur in the portion formed in the vertical wall 2c that is continuous with the portion 8b.

  (H) For this reason, in order to suppress the crack in the vertical wall 2e in the hot press-formed product 2 having the step 2e on the top plate 2a, the non-temperature drop of the vertical wall 2c continuous to the step 2e in the top plate 2a It is effective to alleviate local concentration of strain by enlarging the region of the part (high temperature part).

  Fig.7 (a) is explanatory drawing which shows the shape of the blank 20 in the shaping | molding bottom dead center 20mm upper position at the time of shape | molding the hot press molded product 14 with the press molding apparatus 12 which concerns on this invention mentioned later. FIG. 7B is an explanatory view showing a cross section of the press molding apparatus 12 at this time.

  As shown in FIG. 7B, the punch 16 having the inner pad 21 mounted on the top of the punch is used, specifically, the blank 20 is formed on the top plate 14 a of the hot press-formed product 14. A portion 20a located on the convex side 16a of the punch 16 in the blank 20 is formed by supporting the vicinity of the portion to be formed in the step 14e by the inner pad 21 and performing hot press molding using the punch 16 and the die 18. And the part 20b located in the concave side 16b of the punch 16 will be shape | molded substantially simultaneously, and the restraint of the blank 20 at the time of shaping | molding of the part 20b will become small.

  (I) FIG.5 (c) is a contour figure by numerical analysis of the plate | board thickness reduction | decrease rate in the shaping | molding bottom dead center in the hot press-molded product 14 hot-press-molded by the press molding apparatus based on this invention mentioned later. FIG. 5D is a contour diagram by numerical analysis of the temperature of each part at a position 4 mm above the bottom dead center in the hot press-formed product 14 that is hot press-formed by the press forming apparatus according to the present invention. is there.

  As understood from comparing FIGS. 5 (c) and 5 (d) with FIGS. 5 (a) and 5 (b), the hot press having a step 14e on the top plate 14a by hot press forming. When the molded product 14 is manufactured, a punch having an inner pad attached to the top of the punch is used. Specifically, the blank 14 is formed on the top plate 14a on the lower side with the step 14e as a boundary. The portion to be formed on the vertical wall 14c in the vicinity of the step 14e in the blank 20 is supported by an inner pad that is detachably attached to the top of the punch and is subjected to hot press molding using a punch and a die. Since the region of the non-temperature drop part (high temperature part) can be enlarged, thereby reducing the local concentration of strain and suppressing the reduction of the plate thickness, the occurrence of cracks in the vertical wall 14c in the vicinity of the step 14e. The can be effectively resolved.

  (J) Thus, by using the inner pad 21, the restraint of the blank 20 at the time of shaping | molding of the part 20b becomes small, and the non-temperature fall part (high temperature part) of the part shape | molded in the vertical wall 14c in the blank 20 ) Is enlarged, the moldability is greatly improved, and cracks in the vertical wall 14c in the vicinity 14d of the step 14e are suppressed. That is, when hot press molding is performed on the blank 20 to produce a hot press molded product 14 having a step in the pressing direction (height of the molded product 14) on the top plate 14 a having a hat-shaped section or a groove-shaped section. By using the inner pad 21, it is possible to effectively suppress the occurrence of cracks in the vertical wall 14 c that continues to the top plate 14 a having a low height with the step 14 e as a boundary.

  (K) Thus, when hot-pressing into a hat-shaped or groove-shaped cross section, or when forming a convex portion having a top plate with respect to the blank by hot pressing, in the blank, near the punch shoulder R portion. If the part formed on the vertical wall is a part where cracking is a concern due to tension applied in a direction perpendicular to the press direction, the vicinity of the blank part is supported by the inner pad. However, by performing hot press molding, it is possible to avoid blank cracking at this site.

The present invention is listed below.
(1) In a hot press die comprising a punch top and a punch shoulder R portion continuous with the punch top, a predetermined amount protrudes from the punch top to the outside of the punch, and at the bottom dead center of molding A hot press die comprising an inner pad accommodated in a punch top.

  (2) The inner pad is a portion of the blank where the tension is applied in a direction perpendicular to the press direction at a portion formed on the vertical wall in the vicinity of the punch shoulder R portion (the punch that applies tension to the blank). The hot pressing die according to item 1, which is disposed in the portion).

  (3) The hot press die according to item (2), wherein the portion is a portion where an edge of the top of the punch projects and bends to the outside of the punch in a plan view in the press direction.

  (4) The hot press described in 2 above, wherein the portion is a lower portion (a lower portion of the punch) having a lower punch height with a stepped portion formed in the punch top portion in the punch height direction as a boundary. Mold.

  (5) A hot press apparatus comprising the hot press die described in any one of items 1 to 4.

  (6) By performing press molding on the heated blank using the punch and die that are the hot pressing molds described in any one of items 1 to 4, the top plate and the top A method of manufacturing a hot press-formed product having a cross section comprising a ridge line continuous with a plate and a vertical wall continuous with the ridge line, wherein the press molding is formed on the top plate in the heated blank. The hot pressing is performed by clamping the mold by bringing the punch relatively close to the die while supporting the portion by the inner pad arranged to protrude from the top of the punch by a predetermined amount. Manufacturing method of molded products.

  The “hot press-formed product” in the present invention is a large number of components of automobile bodies and automobile parts, such as a center pillar inner panel and a center pillar outer panel, a side sill inner panel and a side sill outer panel, an A pillar inner panel and an A pillar outer panel. A roof rail inner panel, a roof cross, a front side member and a rear side member, a subframe (suspension member), and the like are exemplified.

  In accordance with the present invention, the non-temperature-decreasing portion (high-temperature portion) of the portion formed on the vertical wall portion is enlarged by performing hot press molding using a punch and die having an inner pad that is mounted on the top of the punch freely. Thus, the occurrence of cracks in the vertical wall can be effectively eliminated. Specifically, the punch and die are brought into contact with the inner pad that is freely attached to the top of the punch at the place where the top plate protrudes to the outside in a plan view in the press direction and where the top plate has a step. By performing the hot press molding using the above, it is possible to eliminate the occurrence of cracks in the part molded on the vertical wall of the part.

FIG. 1 is an explanatory view schematically showing a hot press apparatus according to the present invention and a press-formed product manufactured by them. FIG. 2 is an explanatory view schematically showing a hot press device according to the present invention and a press-formed product manufactured by the hot press device. FIG. 3 is an explanatory diagram showing a situation in which hot press molding is performed on a blank using a conventional hot press apparatus including a punch and a die. FIG. 4 is an explanatory view showing a situation in which hot press molding is performed on a blank using the hot press apparatus according to the present invention. FIG. 5 (a) is based on numerical analysis of the plate thickness reduction rate distribution at the bottom dead center of the press-formed product shown in FIG. 9 (a) manufactured by the conventional hot press forming method using no inner pad. FIG. 5 (b) is a contour diagram at a position 4mm above the molding bottom dead center of the press-molded product shown in FIG. 9 (a) manufactured by a conventional hot press molding method that does not use an inner pad. FIG. 5 (c) is a contour diagram by numerical analysis of the temperature of each part, and FIG. 5 (c) shows the bottom of the press-formed product shown in FIG. 2 (a) manufactured by the hot press forming method according to the present invention. FIG. 5 (d) is a contour diagram by numerical analysis of the plate thickness reduction rate distribution at the dead center, and FIG. 5 (d) is shown in FIG. 4 mm above the bottom dead center of the press-molded product It is a contour diagram in accordance with the numerical analysis of each part temperature at location. Fig.6 (a) is explanatory drawing which shows the shape of the blank in the shaping | molding bottom dead center 20mm upper position at the time of shape | molding a hot press molded product with the press molding apparatus which concerns on this invention, FIG.6 (b) It is explanatory drawing which shows the cross section of the press molding apparatus at this time. Fig.7 (a) is explanatory drawing which shows the shape of the blank in the shaping | molding bottom dead center 20mm upper position at the time of shape | molding a hot press molded product with the press molding apparatus which concerns on this invention mentioned later, FIG.7 (b) ) Is an explanatory view showing a cross section of the press molding apparatus at this time. Fig.8 (a) is a perspective view which shows the hot press molded product which produces a crack, FIG.8 (b) is explanatory drawing which shows the 1/2 cross section of the press molding apparatus of a hot press molded product. Fig.9 (a) is a perspective view which shows the hot press molded product which produces the same crack, FIG.9 (b) is explanatory drawing which shows the 1/2 cross section of the press molding apparatus of a hot press molded product. FIG. 9C is an explanatory view showing a cross section corresponding to the cross section AA ′ in FIG. 9A in the press molding apparatus before the start of press molding. FIG. 10 (a) is a contour diagram by numerical analysis of the plate thickness reduction rate at the bottom dead center in the hot press-formed product hot-pressed by the press-forming apparatus shown in FIG. ) Is a contour diagram by numerical analysis of the temperature of each part at a position 10 mm above the bottom dead center of the hot press-formed product that is hot press-formed by the press-forming apparatus shown in FIG. These are the contour figures by the numerical analysis of the plate | board thickness reduction | decrease rate in the shaping | molding bottom dead center in the hot press-molded goods hot-press-molded with the press molding apparatus based on this invention, FIG.10 (d) is this invention. It is a contour figure by the numerical analysis of each part temperature in the position 10 mm above the formation bottom dead center in the hot press-molded product hot-press-molded by the press molding apparatus which concerns on.

The present invention will be described with reference to the accompanying drawings.
1. Hot press apparatus 11, 12 according to the present invention
Fig.1 (a) is explanatory drawing which shows typically the press molded product 13 manufactured with the hot press apparatus 11 which concerns on this invention, FIG.1 (b) is the hot press apparatus 11 which concerns on this invention. It is explanatory drawing which shows. Moreover, Fig.2 (a) is explanatory drawing which shows typically the press molded product 14 manufactured with the hot press apparatus 12 which concerns on this invention, FIG.2 (b) is the hot press which concerns on this invention. FIG. 10 is an explanatory diagram showing the device 12.

  Hereinafter, the hot press apparatuses 11 and 12 will be described together with reference to FIGS. 1 (a) and 1 (b), FIG. 2 (a) and FIG. 2 (b).

  As shown in FIGS. 1B and 2B, the hot press apparatuses 11 and 12 include punches 15 and 16 that are hot press molds and dies 17 and 18, and are hot presses. The apparatus 11 further includes a blank holder 19.

  The hot press device 11 performs hot press forming by drawing on the blank 20 using the punch 15, the die 17, and the blank holder 19, so that the top plate 13a and the two ridge lines continuous to the top plate 13a 13b, 13b and a cross section (for example, a hat cross section or a groove-type cross section) provided with two vertical walls 13c, 13c continuous to the two ridge lines 13b, 13b, and the two ridge lines 13b, 13b and two vertical walls A hot press-formed product 13 having a curved portion 13d in which at least one ridge line 13b and the vertical wall 13c of 13c and 13c project and bend to the outside of the top plate 13a in a plan view in the press direction is manufactured.

  On the other hand, the hot press device 12 performs hot press forming by bending on the blank 20 using the punch 16 and the die 18 to thereby form the top plate 14a and the two ridge lines 14b and 14b continuous to the top plate 14a. And a cross-section (for example, a hat cross-section or a groove-type cross-section) having two vertical walls 14c, 14c continuous to the two ridgelines 14b, 14b, respectively, and the top plate 14a is in the height direction of the hot press-formed product 14 A hot press-formed product 14 having a step 14e in a direction (perpendicular to the top plate 14a) is manufactured. With the step 14e as a boundary, the top plate 14a is divided into the high portion and the low portion, and the height changes at the step 14e.

  For the punches 15 and 16, a hot pressing die according to the present invention is used. That is, the punches 15 and 16 include punch top portions 15a and 16a and two punch shoulder R portions 15b and 16b continuous to the punch top portions 15a and 16a.

  In the hot press apparatus 11, at least one of the two punch shoulder R portions 15b has a curved portion in plan view in the pressing direction. This curved portion is for molding the curved portion 13 d of the hot press-formed product 13. FIG. 1 shows a cross-section at the position of the curved portion of the punch 15.

  In the press-formed product 14 formed by the hot press device 12, the ridge line 14b formed by the two punch shoulder R portions 16b hits another vertical wall portion, and a step 14e is generated on the top plate 14a. FIG. 2B shows a cross section in the vicinity where the ridge line 14b formed by the punch shoulder R portion 16b hits another vertical wall portion, that is, at a low height portion of the top plate 14a with the step 14e as a boundary.

  The punches 15 and 16 are provided with inner pads 21 and 21 which are arranged so as to protrude from the punch tops 15a and 16a by a predetermined amount in FIGS. 1B and 2B. Inner pads 21 and 21 are part of the portion formed on top plate 13a and 14a of blank 20 (the portion formed on vertical walls 13c and 14c in the vicinity of punch shoulder R in blank 20 is orthogonal to the pressing direction. The vicinity of the portion where tension is applied in the direction to be applied) may be supported, but the remaining part (for example, all) excluding this part may also be supported.

  The punch tops 15a and 16a are provided with receiving holes 15c and 16c for receiving the inner pads 21 and 21, and the inner pads 21 and 21 are punched at the bottoms 15d and 16d of the receiving holes 15c and 16c. Appropriate pressurizing mechanisms such as springs 15e and 16e and gas cushions are provided in order to project a predetermined amount from the top portions 15a and 16a.

  The inner pads 21 and 21 are disposed at the positions shown in FIGS. 1B and 2B at the start of press molding, and as the dies 17 and 18 approach the punches 15 and 16 after the press molding starts. The dies 17 and 18 are urged to gradually move from the above positions toward the bottom portions 15d and 16d of the receiving holes 15c and 16c, and are completely accommodated in the punch top portions 15a and 16a at the bottom dead center of the forming to be punch top portions 15a. , 16a are arranged so as to form a part.

In addition, as shown in FIG. 1, it is preferable to use the die pad 17a supported by the die | dye 17 grade | etc., And to clamp the blank 20 with the die pad 17a and the inner pad 21. FIG. Also in FIG. 2B, it is desirable that there is a die pad as well (not shown).
The hot press apparatuses 11 and 12 according to the present invention are configured as described above.

2. Manufacturing Method According to the Present Invention In the present invention, as shown in FIGS. 1 (a), 1 (b), 2 (a), and 2 (b), hot blanks 20 and 20 are hot-pressed. By performing press molding using 11 and 12, hot press-molded products 13 and 14 are manufactured.

  FIG. 3 is an explanatory view showing a situation in which hot press molding is performed on the blank 20 using a conventional hot press device 30 including a punch 31 and a die 32, and FIG. 4 is a hot press device according to the present invention. It is explanatory drawing which shows the condition which performs hot press molding to the blank 20 using 11,12.

  As shown in FIG. 3, during the conventional hot press molding using the hot press apparatus 30, the first portion 20a of the blank 20 is cooled by contacting the die R portion 32a, and the second portion 20b. Is cooled by contact with the punch shoulder R portion 31a. For this reason, in the blank 20, the 3rd part (part shape | molded by the vertical wall in a press-molded product) 20c between the 1st part 20a and the 2nd part 20b is a non-temperature fall part ( Since the strain concentrates at the portion where the curved portion 13d or the step 14e is formed (that is, 14d), the plate thickness is greatly reduced and cracking is likely to occur.

  On the other hand, as shown in FIG. 4, in the present invention, hot press molding of the top plate 14 a on the top side having a low height with the curved portion 13 d and the step 14 e as a boundary is performed on the top plates 13 a and 14 a in the blank 20. By clamping the molds 15 and 16 relatively close to the dies 17 and 18 while supporting the parts to be molded by the inner pads 21 arranged to protrude from the punch tops 15a and 16a by a predetermined amount Sip. Done.

  The first portion 20a of the blank 20 is cooled by being in contact with the die-shaped R portions 17a and 18a, and the second portion 20b is in contact with the inner pad shoulder R portion 21a instead of the punch shoulder R portions 15a and 16a. It is cooled by.

  At this time, since the blank 20 is supported by the inner pad 21 at a position close to the dies 17 and 18 by a predetermined amount, the third portion 20a between the first portion 20a and the second portion 20b in the blank 20 is supported. The portion (the portion formed on the vertical wall in the press-molded product) 20c has a non-temperature-decreasing portion (high temperature portion) in a wider range than the conventional example shown in FIG. It is alleviated that the strain concentrates at the time of forming at 14e, thereby reducing the thickness reduction rate and eliminating the cracks.

  FIG. 5 (a) is a numerical analysis of the thickness reduction rate distribution at the bottom dead center of the press-formed product 2 shown in FIG. 9 (a) manufactured by a conventional hot press forming method without using an inner pad. FIG. 5 (b) shows a contour 4mm above the bottom dead center of the press-formed product 2 shown in FIG. 9 (a) manufactured by a conventional hot press forming method without using an inner pad. FIG. 5C is a contour diagram by numerical analysis of each part temperature at the position, and FIG. 5C is a press-formed product 14 shown in FIG. 2A manufactured by the hot press forming method according to the present invention using an inner pad. FIG. 5 (d) is a contour diagram by numerical analysis of the thickness reduction rate distribution at the bottom dead center of molding, and FIG. 5 (d) is a diagram of FIG. From the bottom dead center of the press-formed product 14 shown in FIG. It is a contour diagram in accordance with the numerical analysis of each part temperature at 4mm upper position.

  As understood from comparison between FIG. 5 (b) and FIG. 5 (d), in the present invention, the stepped portion of the press-formed product 14 is positioned at a position 4 mm above the bottom dead center of the molding, compared with the conventional example. The non-temperature reduction part (high temperature part) of the part shape | molded by the vertical wall 14c is expanded.

  For this reason, as shown in FIGS. 5 (a) and 5 (b), in the conventional example, the plate thickness reduction rate of the vertical wall 14c of the stepped portion of the press-formed product 14 reaches 28.9% indicating cracking. However, according to the present invention, the plate thickness reduction rate is suppressed to 18.6%, and it can be seen that the vertical wall 14c of the step portion does not crack.

13 Hot Press Molded Product 15 Hot Press Die 15a Punch Top 15b Punch Shoulder R 20 Blank 21 Inner Pad

Claims (3)

In a hot press die having a punch top and a punch shoulder R portion continuous to the punch top, a predetermined amount protrudes from the punch top to the outside of the punch, and at the bottom dead center of molding, With inner pads to be accommodated,
The inner pad is arranged at a location where a tension is applied in a direction perpendicular to the press direction in a portion of the blank that is formed on the vertical wall in the vicinity of the punch shoulder R portion,
The hot stamping die according to claim 1, wherein the portion is a lower portion having a low punch height with a step portion formed in the punch top portion in the punch height direction as a boundary. Hot pressing apparatus, characterized in that it comprises a hot press mold according to claim 1. The heated blanks, hot manufacturing method of a press-molded article which is characterized in that the press-molded with a hot press mold according to claim 1.