JP6536624B2 - Method of manufacturing hot press-formed product - Google Patents

Description

  The present invention relates to a method of manufacturing a hot press-formed product, and more particularly, to a method of manufacturing a hot press-formed product which manufactures a hot press-formed product having portions with different sheet thicknesses.

In recent years, along with the improvement of environmental performance due to the improvement of the fuel efficiency of the car, in response to the sophistication of the demand for the collision performance for the safety improvement of the driver and the passenger at the time of a collision It is progressing. In addition, with the increasing demand for driving performance such as steering stability of a car, the rigidity of the vehicle body has also been greatly improved.
Until now, high strength and rigidity of the car body have been realized by increasing the strength and thickness of materials for structural parts for automobiles, but if replacing the material of the whole parts, the weight increase and cost increase of the car body In order to reduce the weight and cost of the vehicle body, various improvements have been made.

In Patent Document 1, a plate material having a high material strength or a plate material having a large thickness is applied to a portion where strength and rigidity are required, and end faces of two or more dissimilar plate materials having different material strength and plate thickness are butted. The technique which aims at weight reduction of a press-formed article is disclosed by press-forming the blank material (tailored blank) formed by joining.
Further, in Patent Document 2, a bent portion which is partially bent is formed in a flat plate-shaped blank to form a preformed body, and in the thickening step, the bent portion is pressed to crush it into a flat plate shape. There is disclosed a method of manufacturing a press-formed product which achieves weight reduction while securing strength or rigidity partially by press-forming the thickened preformed body.
Further, Patent Document 3 discloses a method of forming a thin-walled portion having a small thickness by partially forming a plate-like blank material by stretching and extending it into a cross-sectional waveform to manufacture a differential-thickness plate material.

JP 2005-152975 A JP, 2010-12062, A JP 2005-59045 A

  However, in the technique disclosed in Patent Document 1, since the blank material (tailed blank) is obtained by joining end faces of two or more kinds of plate members to be joined, a high degree of abutment accuracy is required for the joining. Since the time required for wire welding by a laser welding machine or the like is long and the productivity is poor, it is difficult to suppress the manufacturing cost.

Further, according to the technology disclosed in Patent Document 2, up to 25% or less of the circumferential change rate of the thickening portion can be formed by a single thickening step, but the circumferential change rate is If it exceeds 25%, the bending portion is buckled and folds occur when the thickness is increased in the step of increasing the thickness, so it was necessary to suppress the circumferential change rate per step to be two steps or three steps or more .
That is, in patent document 2, in order to form a thickness increase part newly with respect to the plate | board thickness of a blank, in order to process the thickness increase part with a high circumferential change rate (thickness increase rate), the number of processes increases, There is a problem that leads to an increase in mold cost. In addition, since the forming load becomes excessive in the process of increasing the thickness, and the press is required to have an excessive ability, there is also a problem that the cost of equipment increases.
Furthermore, the thickness-increasing portion, which is a portion subjected to a large processing strain, has a problem that the hardness is not sufficiently increased by quenching by die cooling in hot press forming, and the strength varies depending on the portion.

  Further, the technique disclosed in Patent Document 3 includes a second pressing apparatus having a pressing surface with a cross-sectional waveform, and after forming a blank material into a cross-sectional waveform, the second pressing apparatus includes a pressing surface with a flat cross-sectional shape. Is a method of returning to a flat plate shape by the pressing device of In this method, both ends of the blank are held by the blank holder, and the center portion of the blank is stretched and formed into a cross-sectional waveform, so that only the two ends are thick and only the center is thin. The method applicable to the case of manufacturing of steel sheet, where thick and thin portions of the plate thickness targeted by the present invention are alternately arranged, and the plate thickness of the central thick portion holds the plate thickness of the blank material It was difficult to do.

  The present invention has been made to solve the problems as described above, and has a configuration reverse to that of Patent Document 2, and a plurality of thick portions are newly formed by newly forming thin portions in a thick blank. It is an object of the present invention to provide a method of manufacturing a hot press-formed product capable of forming a light-weight and high-strength hot press-formed product with different thickness continuously and alternately. I assume.

(1) The method for producing a hot press-formed product according to the present invention is to form a blank made of a steel plate into a hot press-formed product having a target shape at a temperature range of Ac3 transformation point to 1000 ° C. A preforming step of forming a blank into a preformed body in which a plurality of thick portions and a plurality of thin portions alternate with each other, and the preformed body formed in the preforming step is a hot press of the target shape And a main forming step of hot press forming the formed article, wherein the preforming step stretches and forms the blank, the outer periphery of the blank is held by a die and a blank holder, and the thickness of the blank is further reduced. The thickness of the portion held by the partial pad is set by pressing the portion corresponding to the thin portion with the partial pad and projecting the portion corresponding to the thin portion in the blank with a plurality of punches. It is characterized in that while maintaining the thickness equal to the plate thickness, the portion overhanged by the punch is thinned, and is formed into a preform in which a plurality of thick portions and a plurality of thin portions are alternately continued.

(2) In the thing of said (1), the said preforming process clamps the said blank outer periphery with the said die | dye and the said blank holder so that the edge part of the said blank may protrude, and the protruding edge part of the said blank is Having an ironing process which thins a portion which is ironed by the ironing punch while maintaining a plate thickness of a portion held by the die and the blank holder equal to a plate thickness of the blank by sieving with the ironing punch. It is a feature.

(3) In the above (1) or (2), the preforming step is characterized in that the thickness of the thin portion is reduced by 10% or more with respect to the thickness of the blank. It is.

(4) In the above (1) to (3), in the preforming step, the blank is heated to a temperature range of Ac3 transformation point to 1000 ° C., or 400 ° C. to 700 ° C. It is characterized in that it is molded into the above-mentioned preformed body in the following temperature range.

(5) In the thing of said (4), the said main-forming process reheats the said preforming body, It is characterized by hot-press-forming in the temperature range of Ac3 transformation point or more and 1000 degrees C or less. It is.

  In the present invention, a blank made of a steel plate is formed into a hot press-formed product of a target shape in a temperature range of Ac3 transformation point to 1000 ° C., and the blank is formed of a plurality of thick portions and a plurality of thin portions. A preforming step of forming a preformed body in which parts alternate with each other, and a main forming step of hot press forming the preformed body formed in the preforming step into a hot press-formed product of the target shape And the preforming step stretches and forms the blank, holding the outer periphery of the blank between a die and a blank holder, and pressing a portion corresponding to the thick portion in the blank with a partial pad. The portion corresponding to the thin portion in the blank is extended with a plurality of punches to maintain the plate thickness of the portion pressed by the partial pad equal to the plate thickness of the blank. A thin-walled portion can be formed into a thin preform, and can be formed into a preform in which a plurality of thick portions and a plurality of thin portions alternately continue, and a high strength and lightweight hot press-formed product is manufactured with a low forming load can do.

It is an explanatory view explaining a manufacturing method of a hot press molded article concerning this embodiment (a): An explanatory view of a preforming process, (b): Cross section of a preform, (c-1): Sectional drawing of a plate-shaped partial difference thickness part, (c-2): The perspective view of a plate-shaped partial difference thickness part). It is a figure which shows the partial difference thickness parts of the hat cross-sectional shape which is another example of the hot press molded object made into shaping object in the manufacturing method of the hot press molded product concerning this invention ((a): sectional view, b): perspective view). It is explanatory drawing explaining the other aspect of the manufacturing method of the hot press molded product which concerns on this Embodiment (a): Explanatory drawing of a preforming process, (b): Sectional drawing of a preform, (c -1): A cross-sectional view of a plate-like partially-differential-thickness part, (c-2): a perspective view of a plate-like partially-differential-thickness part). It is a figure which shows the partial difference thickness part of hat cross-sectional shape which is another example of the hot press molded object made into shaping object in the other aspect of the manufacturing method of the hot press molded product concerning this invention ((a): Cross sectional view, (b): perspective view).

  In the method of manufacturing a hot press-formed product according to the embodiment of the present invention, the thick plural thick portions 5a and the plate thickness as shown in an example in FIGS. 1 (c-1) and (c-2). The partial differential thickness component 5 having a plurality of thin thin portions 5b of the present invention is formed by hot press forming a plate-like blank 1 made of a steel plate at a temperature range of Ac3 transformation point to 1000.degree. C. as shown in FIG. Forming a blank 1 into a preform 3 in which a plurality of thick portions 3a and a plurality of thin portions 3b are alternately continuous, and forming the preform 3 into a partially-differential thickness component 5 of a target shape. And a main forming step of hot press forming.

  Hereinafter, a method of manufacturing a hot press-formed product according to the present embodiment will be described based on FIG. In the following description, the hot press-formed product to be formed is a flat plate-like partial difference thickness component 5 as shown in FIGS. 1 (c-1) and (c-2), The method for producing a hot press-formed product according to the present invention may be directed to forming a partially-differential-thickness part 7 having a hat cross-sectional shape as shown in FIG. It may be a three-dimensional shape in which the cross-sectional shape is not constant and changes, and the shape is not particularly limited.

<Preforming process>
In the pre-forming step, as shown in FIG. 1 (a), the blank 1 is pre-formed 3 (FIG. 1 (b) using a mold 10 provided with a punch 11, a die 13, a partial pad 15, and a blank holder 17. ))). In FIG. 1A, the plurality of punches 11 and the plurality of partial pads 15 are alternately and continuously arranged.

In the preforming step, first, the blank 1 is heated to a temperature range above the Ac3 transformation point.
Then, the heated blank 1 is placed between the punch 11 and the die 13, and the portion A (see FIG. 1A) corresponding to the thick portion 3 a of the preform 3 in the blank 1 is The upper surface side is held by the partial pad 15 while being supported by 13. Further, the outer periphery of the blank 1 is clamped by the die 13 and the blank holder 17. That is, the outer periphery of the blank 1 is held between the die 13 and the blank holder 17, and the portion other than the outer periphery of the blank 1 is held by the partial pad 15.

  The blank 1 is moved by moving the plurality of punches 11 relatively to the die 13 with the part A held down by the partial pad 15 and the blank holder 17 in a temperature range of Ac3 transformation point to 1000 ° C. B is stretched out, and the preform 3 is stretched out.

At this time, the material flow from the part A to the part B in the molding process is suppressed by molding the part B with the punch 11 while holding the part A with a sufficient load by the partial pad 15 and the blank holder 17. The thickness of the portion B decreases while maintaining the thickness.
Therefore, in the preformed body 3, a plurality of thick portions 3a in which the thickness of the blank 1 is maintained and a plurality of thin portions 3b reduced in thickness by thinning are alternately and continuously formed.

The average plate thickness of the thin-walled portion 3b of the preform 3 preformed in the preforming step decreases with the line length of the thin-walled portion 3b overhanged by the punch 11, so the shape and relative movement of the punch 11 The thickness of the part B can be adjusted.
In the present embodiment, in the preforming step, it is preferable to reduce the average plate thickness of the thin portion 3 b of the preform 3 by 10% or more with respect to the plate thickness of the blank 1.

  Further, as shown in FIG. 1A, when the cross section of the punch 11 in the forming direction is parabolic, the forming surface of the punch 11 abuts uniformly on the blank 1 and the thin portion 3b in the blank 1 It is preferable because it can be stretch formed so as to reduce the plate thickness of the corresponding portion more uniformly.

  Furthermore, in the preforming step, the correspondence between the portion where the blank 1 is held by the partial pad 15 and the thick portion 5a of the partially difference-thick component 5 corresponding to the portion is, for example, the preforming step and the preformed body 3 It can be obtained in advance by performing a CAE analysis or the like in the case of developing the partial difference thickness part 5.

<Main forming process>
In this forming step, the preformed body 3 stretched and formed in the preforming step is formed into a partially-differential-thickness part 5 as shown in FIGS. 1 (c-1) and (c-2).

  When the temperature of the preform 3 falls below the above temperature range, in the main forming step, the preform 3 is reheated and hot pressed in a temperature range of not less than the Ac3 transformation point and not more than 1000 ° C. When the temperature of the body 3 is maintained in the temperature range of the Ac3 transformation point to 1000 ° C., in the main forming step, the preformed body 3 can be hot press-formed as it is without reheating.

  However, if a large working strain is imparted when the blank 1 is hot-drawn and shaped in the preforming step, the hardness increase due to the coarsening of crystal grains of the preformed body 3 or the like depending on the condition of quenching in the main forming step. In such a case, in this case, in the main forming step, the preform 3 may be reheated to be hot pressed and cooled in the temperature range of not less than the Ac3 transformation point and not more than 1000 ° C. desirable.

  From the above, by the method of manufacturing a hot press-formed product according to the present invention, it is possible to manufacture a partially-differential-thickness part having a difference in plate thickness having a thin portion and a thick portion by hot press forming. In the thick part where thickness is required, the strength is satisfied by maintaining the thickness of the blank, while in the thin part where thickness reduction is possible in the partial thickness difference parts, the weight is reduced by reducing the thickness compared to the blank. Can be achieved.

In the above description, the preforming step is to stretch out the blank 1 by hot forming, but in the preforming step according to the present invention, the blank 1 is to stretch out by cold without heating the blank 1. Alternatively, the blank 1 may be heated and stretched and formed in the warm temperature range of 400 ° C. to 700 ° C.
Then, when the blank 1 is stretched out cold or warm in the preforming step, the preform 3 is reheated and hot press-formed at a temperature range of Ac3 transformation point to 1000 ° C. or less.

  As described above, the preforming step according to the present invention can be performed in any temperature range of cold, warm at 400 ° C. to 700 ° C., or hot at Ac 3 transformation point to 1000 ° C. If there is a large thickness reduction rate to reduce the thickness of the portion B of the blank 1 to be reduced relative to the blank 1 or if the area of the portion B is large, the blank 1 is heated to warm it, more preferably It may be formed by hot extrusion.

  In particular, when the preforming step is performed hot, the portion A corresponding to the thick portion 3a of the blank 1 is pressed by the partial pad 15 and the blank holder 17 so that the portion A is cooled by the partial pad 15 and hardened. It is considered that the material inflow to the portion B which is overhanged by the punch 11 can be further prevented in the process of overhang molding, and the overhang formability can be further improved.

  Moreover, although the said description used the strip-shaped thing along the longitudinal direction of the partial difference thickness part 5 as the partial pad 15, the manufacturing method of the hot press-formed product which concerns on this invention is a part The shape of the pad is not limited to that described above, and may be, for example, an island-like or ring-like partial pad.

  In the above description, in the pre-forming step, as shown in FIG. 1, the outer periphery including the end of the blank 1 is held between the die 13 and the blank holder 17 and a portion corresponding to the thin portion 3b is formed by extension. In the preforming step according to the present invention, as shown in FIG. 3 (a), the mold is provided with a punch 11, a die 13, a partial pad 15, a blank holder 17 and an ironing punch 21 as shown in FIG. 20 may be used to form a preform 23 (see FIG. 3B) having a thick portion 23c and a thin portion 23d in addition to the thick portion 23a and the thin portion 23b.

  In this case, the blank 1 heated to a temperature range above the Ac3 transformation point is placed between the punch 11 and the die 13, and the end of the blank 1 (the part D in FIG. 3A) protrudes. The outer periphery (the part C in FIG. 3A) is held by the die 13 and the blank holder 17. Then, in a state where the portion C is held between the die 13 and the blank holder 17 in the temperature range of the Ac3 transformation point to 1000 ° C., the ironing punch 21 is relatively moved to the die 13 side to hold the end of the blank 1 It is processed by ironing.

  As a result, the thickness of the portion C held between the die 13 and the blank holder 17 is maintained equal to the thickness of the blank 1, and the end of the blank 1 which has been ironed by the ironing punch 21 is thinned. The preformed body 23 in which the thick portions 23a and 23c and the thin portions 23b and 23d are alternately and continuously formed is formed. Then, in the subsequent main forming step, the preformed body 23 can be formed into a partially-differential-thickness part 25 as shown in FIGS. 3 (c-1) and 3 (c-2).

  At this time, it is preferable that the average plate thickness of the thin portions 23 d be reduced by 10% or more with respect to the plate thickness of the blank 1, as in the thin portions 23 b thinned by the punch 11.

  Although the die 20 shown in FIG. 3A performs the ironing process by the ironing punch 21 in the same process as the stretch forming by the punch 11, in the pre-forming process, the ironing process is a separate process from the stretch forming It may be performed by

  In addition, when a large working strain is imparted when the end portion of the blank 1 is hot ironed, depending on the condition of hardening in the main forming step, the hardness increase is not caused by the coarsening of the crystal grains of the preformed body 23 or the like. In such a case, in this case, in the main forming step, it is preferable to reheat the preform 23 and hot press form in the temperature range of the Ac3 transformation point to 1000 ° C. and rapidly cool it. .

However, even when ironing in the preforming step, the blank 1 is cold-formed without heating, or the blank 1 is heated and shaped in the warm temperature range of 400 ° C. to 700 ° C. It may be something.
Then, when blank 1 is formed cold or warm in the preforming step, the preformed body 23 is reheated in the main forming step and hot press-formed in a temperature range of Ac3 transformation point to 1000 ° C. Is preferred.

  As described above, the preforming step of performing stretch forming and ironing may be performed in any temperature range of cold, warm at 400 ° C. to 700 ° C., or hot at Ac 3 transformation point to 1000 ° C. Although it is possible, the thickness of the portions B and D (see FIG. 3 (a)) in the blank 1 to be reduced with respect to the blank 1 is large. In the case of a large size, the blank 1 may be heated and hot-rolled, more preferably hot-rolled and ironed.

  Since the experiment for confirming the effect of the method for manufacturing a hot press-formed product according to the present invention was performed, the results will be described below.

  In Example 1, a hot press-formed product to be formed in the present invention is a flat plate having thick portions 5a and thin portions 5b as shown in FIGS. 1 (c-1) and (c-2). Partially differential thickness part 5 or partial difference thick part 7 of hat cross section having thick part 7a and thin part 7b as shown in FIG. 2 and forming blank 1 made of steel plate as shown in FIG. 1 And a preforming step of obtaining a preform 3 in which a plurality of thick portions 3a and a plurality of thin portions 3b are alternately continued, and heating the preform 3 to 900 ° C., which is in the range of Ac 3 transformation point to 1000 ° C. Partially differential thickness parts 5 or 7 were manufactured by the main forming step of hot press forming.

Here, in Example 1, a steel plate with a thickness of 2.0 mm and a material strength of 1490 MPa class after quenching is used as the blank 1 and the preforming step is a hot temperature which is a temperature range of Ac3 transformation point to 1000 ° C. or less of the blank 1 The extrusion molding was performed.
In the preforming step, the average thickness of the plurality of thin portions 3b thinned by the plurality of punches 11 is maintained while maintaining the thickness of the thick portion 3a pressed by the partial pad 15 at 2.0 mm of the thickness of the blank 1. The preformed body 3 having a diameter of 1.0 to 1.8 mm was preformed. In the case where the preform 3 having a thickness of about 1.8 mm at the thin portion 3 b is preformed by stretch forming, it may be performed cold.

  In Example 1, partial thickness difference parts 5 or 7 manufactured by the method for manufacturing a hot press-formed product according to the present invention are Inventive Example 1, and thick parts 5a and 7a in partial thickness difference parts 5 and 7; The plate thicknesses of the thin portions 5 b and 7 b were measured, and the plate thickness ratio thereof (= (plate thickness in thick portion) / (plate thickness in thin portion)) was determined.

  In addition, in Example 1, as Comparative Example 1, a preforming step of stretch forming with a punch in a state where only the outer peripheral portion of the blank 1 is restrained by the die 13 and the blank holder 17 without using the partial pad 15, and the preformed body Partially thick parts were manufactured by the main forming step of hot press forming. And the board thickness in the thick part and thin part of this partial difference thickness part was measured like the example of an invention, and these board thickness ratio was calculated.

  In the partially-differential-thickness parts according to the comparative example, the thin-walled portion corresponds to a portion overhanged by the punch in the preforming step, and the thick-walled portion corresponds to the outer periphery of the blank restrained by the die and the blank holder in the preforming step. .

  In both of the partially difference-thickened parts 5 and 7 according to the invention example 1, the plate thickness in the thick portion 5a or 7a is maintained at 2.0 mm which is the plate thickness of the blank 1 and is overhang-formed in the preforming step. Since it is hot-press molded using the preformed body 3 whose average plate thickness of the thin portion 3b is 1.0 to 1.8 mm, the plate thickness ratio of the thin portion 5b and the thick portion 5a, and the thin portion Partial thickness difference parts 5 or 7 in which the thickness ratio of 7b and thick part 7a is 1.1 to 2.0 could be manufactured.

  On the other hand, in the partial difference thickness part according to Comparative Example 1, the thickness of the portion corresponding to the thick part in the blank of the portion using the partial pad 15 in Example 1 in the preforming step can not be maintained at 2.0 mm. The plate thickness of the thick part of thick parts produced a distribution in the range of 1.7 to 1.9 mm.

Also, as a conventional example, a steel plate of 1.0 mm thickness and 1490 MPa grade material strength is used as a blank according to the method shown in Patent Document 2, a pre-forming step forms a bending portion, and this bending portion is crushed into a flat plate shape An attempt was made to form a thickness-increasing part with a thickness of 2.0 mm as a target.
As a result, the thickness-increasing portion could be made into a flat plate shape up to 1.1 mm, but if it was attempted to increase the thickness more than this, the flexing portion would buckle and folding would occur, and the plate as in the present invention It was not possible to form a differential thickness part with a thickness of 1.0 mm to 2.0 mm.

  As described above, according to the method of manufacturing a hot press-formed product according to the present invention, the outer periphery of the blank is held between the die and the blank holder in the preforming step, and further, the plurality of punches The blank is stretched and formed, and while keeping the thickness of the portion pressed by the partial pad equal to the thickness of the blank, the portion stretched by the punch is thinned to form a plurality of thick portions and a plurality of thin portions A hot press-formed product having a thickness ratio of a thin part to a thick part of 1.1 to 2.0 by forming alternately continuous preforms and subjecting the preforms to hot press forming in the main forming step. It has been demonstrated that it can be manufactured.

In the second embodiment, as shown in FIGS. 3 (c-1) and 3 (c-2), flat-plate partially-differential-thickness parts 25 having thick portions 25a and 25c and thin portions 25b and 25d, or FIG. The partial difference thick part 27 having a hat cross-sectional shape having thick portions 27a and 27c and thin portions 27b and 27d as shown in FIG.
Then, a pre-forming step of forming a pre-formed body 23 in which a plurality of thick portions 23a or 23c and a plurality of thin portions 23b or 23d are alternately continued using a mold 20 shown in FIG. Partially differential thickness parts 25 or 27 were manufactured by the main forming step of heating and compacting the formed body 23 to 900 ° C., which is in the range of Ac 3 transformation point to 1000 ° C.

  In the second embodiment, as the invention example 2, the plate thickness of the blank 1 is about the thickness of the thick portion 23a held by the partial pad 15 and the thick portion 23c held by the die 13 and the blank holder 17 in the preforming step. The preform 23 is pre-formed to have an average plate thickness of 1.0 to 1.8 mm in the plurality of thin portions 23 b thinned by the plurality of punches 11 and the thin portions 23 d thinned by the ironing punch 21 while maintaining the thickness 2.0 mm. Molded. In the case where the preformed body 23 having a thickness of about 1.8 mm in the thin portions 23b and 23d is stretched and ironed, it may be performed cold.

  Further, in Example 2, as Comparative Example 2, in a state in which only the outer periphery of the blank 1 is restrained by the die 13 and the blank holder 17 without using the partial pad 15, the extrusion is performed by the punch 11 and the ironing is performed by the ironing punch 21 simultaneously. The partial thickness difference parts 25 or 27 were manufactured by the preforming step and the main forming step of hot pressing the preformed body.

  In the partially differential thickness parts 25 and 27 according to the invention example 2, the thickness at the thick portions 25a and 25c and the thick portions 27a and 27c is both maintained at 2.0 mm which is the thickness of the blank 1, Since the average thickness of the thin-walled part 23b overhang-formed in the forming step and the thin-walled part 23d ironed is a hot-press-formed using the preformed body 23 having a thickness of 1.0 to 1.8 mm, the thin-walled part Producing partial difference thickness parts 25 and 27 in which the thickness ratios of 25b and 25d to thick parts 25a and 25c and the thickness ratios of thin parts 27b and 27d to thick parts 27a and 27c are 1.1 to 2.0 It was possible.

  On the other hand, in the partial difference thickness part according to Comparative Example 2, the plate thickness of the portion corresponding to the thick part in the blank of the portion using the partial pad 15 in Example 2 in the preforming step can not be maintained at 2.0 mm. The plate thickness of the thick part of thick parts produced a distribution in the range of 1.7 to 1.9 mm.

  As described above, according to the method of manufacturing a hot press-formed product according to the present invention, the outer periphery of the blank is held between the die and the blank holder so that the end of the blank protrudes in the preforming step, and the protruding end of the blank is A plurality of thick parts are thinned by thinning the area which is ironed by the ironing punch while maintaining the plate thickness of the area held by the die and the blank holder equal to the plate thickness of the blank by ironing with the ironing punch. And a plurality of thin-walled portions alternately form a preformed body, and the preformed body is hot-press-formed in the main forming step, thereby both the stretch-formed thin-walled portion and the ironed thin-walled portion It has been demonstrated that a hot press-formed product having a thickness ratio of 1.1 to 2.0 with respect to the thick portion can be produced.

DESCRIPTION OF SYMBOLS 1 blank 3 preforming body 3a thick part 3b thin part 5 part difference thickness parts 5a thick part 5b thin part 7 part difference thick parts 7a thick part 7 b thin part 10 mold 11 punch 13 die 15 partial pad 17 blank holder Reference Signs List 20 mold 21 ironing punch 23 preformed body 23a thick portion 23b thin portion 23c thick portion 23d thin portion 25 partial difference thickness part 25a thick portion 25b thin portion 25c thick portion 25d thin portion 27 partial difference thickness part 27a thickness Thick part 27b Thin part 27c Thick part 27d Thin part

Claims (4)

A method of manufacturing a hot press-formed product, comprising forming a blank made of a steel plate into a hot press-formed product of a target shape in a temperature range of Ac3 transformation point to 1000 ° C.,
A preforming step of forming the blank into a preform in which a plurality of thick portions and a plurality of thin portions are alternately continued;
And a main forming step of hot press forming the preformed body formed in the preforming step into a hot press-formed product having the target shape,
The preforming step stretches and forms the blank, sandwiching the outer periphery of the blank with a die and a blank holder, and further pressing a portion corresponding to the thick portion in the blank with a partial pad, in the blank By extending the portion corresponding to the thin portion with a plurality of punches, while keeping the plate thickness of the portion pressed by the partial pad equal to the plate thickness of the blank, the portions which are extended by the punch are thinned and plural Forming a thick-walled portion and a plurality of thin-walled portions alternately into a continuous preform , and sandwiching the outer periphery of the blank between the die and the blank holder so that the end portion of the blank protrudes The thickness of the portion sandwiched between the die and the blank holder is determined by ironing the end with the punch. Method for producing a hot press molded product, which comprises thinning the site squeezed by the ironing punch while maintaining equal to the plate thickness. A method of manufacturing a hot press-formed product, comprising forming a blank made of a steel plate into a hot press-formed product of a target shape in a temperature range of Ac3 transformation point to 1000 ° C.,
A preforming step of forming the blank into a preform in which a plurality of thick portions and a plurality of thin portions are alternately continued;
And a main forming step of hot press forming the preformed body formed in the preforming step into a hot press-formed product having the target shape,
The preforming step stretches and forms the blank, sandwiching the outer periphery of the blank with a die and a blank holder, and further pressing a portion corresponding to the thick portion in the blank with a partial pad, in the blank By extending the portion corresponding to the thin portion with a plurality of punches, while keeping the plate thickness of the portion pressed by the partial pad equal to the plate thickness of the blank, the portions which are extended by the punch are thinned and plural The blank is heated to form a preformed body in which a thick portion and a plurality of thin portions continue alternately, and the blank is heated to a temperature range of Ac3 transformation point to 1000 ° C. or a temperature range of 400 ° C. to 700 ° C. A method for producing a hot press-formed product, characterized in that the preform is formed into the preform .   3. The method according to claim 2, wherein said main forming step reheats said preformed body to perform hot press forming at a temperature range of Ac3 transformation point to 1000 ° C., inclusive.   The hot press-formed product according to any one of claims 1 to 3, wherein in the pre-forming step, the thickness of the thin portion is reduced by 10% or more with respect to the thickness of the blank. Manufacturing method.

Images