JP6354955B2 - Method for producing press-formed product having hat-shaped cross-sectional shape - Google Patents

Description

The present invention relates to a method for producing a press-molded article having a hat-shaped cross-sectional shape such as automobile parts.

  In the manufacture of a press-molded product having a hat-shaped cross-sectional shape such as an automobile part, that is, press molding, if the final molded product is molded by a single molding, cracks and wrinkles may appear. In order to prevent this, conventional preforms with a relatively shallow hat cross-sectional shape are formed by drawing, and the remaining vertical wall is formed by bending or foaming (drawing without wrinkles) in subsequent processes. By doing so, a method of forming a final molded product is known (see Non-Patent Document 1).

  In addition, as a technology for reducing the spring back in the R (fillet) portion between the top plate portion and the vertical wall portion, conventionally, there is a countermeasure technology by devising the shape of the shoulder portion of the mold for molding the R portion. It is known (see, for example, Patent Document 1).

  On the other hand, as a countermeasure technique for warping of the vertical wall portion, conventionally, when the molded product is press-molded, the surface is partially pressed in the plate thickness direction to form a number of local R portions. There is known a countermeasure technique for alleviating the unevenness of the stress inside and outside (see, for example, Patent Documents 2 and 3).

Mazda Corporation Shinji Tamaru, Akira Sakai, Makoto Morisawa (Type Engineer Workshop (2013/06/18), Type Technology 2013) Monthly Issue 2013 Volume 28 No. 12, Special Feature “Die Technology Workshop 2013 in Kitakami” Lecture Collection <Press Processing> (A-5)

JP 2012-232329 A Japanese Patent No. 3745202 Japanese Patent No. 3750421

  However, in the above conventional technique, each R part formed in the first process cannot be flattened in the next process and cannot cope with a shape defect caused by a local R shape, and a hat-shaped cross-section press There is a problem that a springback occurs in a part or the whole of the vertical wall portion of the molded product, and so-called opening occurs. This is a problem in terms of securing rigidity, collision resistance, visibility, etc. in automobile parts.

  For this reason, an object of this invention is to suppress the opening of the vertical wall part by the springback which appears in the final molded product after bending molding or foam molding.

  The present inventor who researched the above-mentioned problems has confirmed that the change in the angle of the punch shoulder in a press-molded product such as a hat shape is substantially proportional to the radius R of the die shoulder by a test with a simple model described below. Elucidated. In this simple model test, a sample S having a material plate thickness: 1.4 mm, a material strength: 1180 MPa class steel plate (tensile strength 1250 MPa), and a sample size: width 40 mm × length 100 mm was used.

  In the simple model test, as shown in FIG. 1, two samples S arranged symmetrically with respect to the punch 1 are sandwiched between a blank holder 2 and a die 3, and the punch 1 is lifted to raise two samples. A bending test in which the central portion in the longitudinal direction of S is bent along the shoulders of the radius R of the left and right dies 3 is carried out with various radii R being set. The change Δθ was determined.

  Thus, as shown in FIG. 2, it was found that the radius R (mm) of the shoulder portion of the die 3 and the angle change amount Δθ (°) due to the springback of each sample S are substantially proportional. .

The method for producing a press-formed product having the hat-shaped cross-sectional shape of the present invention, which has advantageously solved the above-mentioned problems based on the above knowledge of the present inventors,
In the preforming step, part or all of the vertical wall portion of the hat-shaped cross-sectional shape of the final molded product is pre-molded, and the upper part is stepped in order from the top to the portion that becomes the vertical wall portion of the hat-shaped cross-sectional shape of the final molded product A step shape in which the step portion, the rising portion, and the step bottom portion are connected via the R portion ,
In the subsequent molding step, the step shape provided by the preforming is extended and flattened in the vertical direction to form a vertical wall portion having a hat-shaped cross-sectional shape of the final molded product.

Further, the preform for molding a preliminary molding step in the method of manufacturing the press molded article,
Part or all of the vertical wall portion of the hat-shaped cross-sectional shape of the final molded product is preformed, and a step shape is provided in the portion that becomes the vertical wall portion of the hat-shaped cross-sectional shape of the final molded product. It is a feature.

  According to the method for producing a press-formed product having a hat-shaped cross-sectional shape according to the present invention, a hat-shaped final product is formed in a preforming process by foam forming (drawing without wrinkle press) or normal drawing with wrinkle press. Preliminarily mold part or all of the vertical wall part of the cross-sectional shape, and form a preformed part by providing a step shape in the part that becomes the vertical wall part, then in the molding process by subsequent foam molding or normal drawing The step shape of the preform is extended and substantially flattened to form a vertical wall portion with a hat-shaped cross section of the final product, so that the radius of each R portion forming the step shape and the R portion are adjacent to each other. By appropriately selecting and combining the length of the flat portion to be performed, it is possible to suppress the opening of the vertical wall portion of the final molded product due to the spring back.

  In the method for producing a press-formed product having a hat-shaped cross-sectional shape according to the present invention, the step shape is preferably set as follows. That is, as shown in FIG. 3, the radius R1 [mm] of the R portion between the stepped portion 12 and the stepped portion 13 in the step shape 11 provided in the preform 10, and the flat portion length L1 [mm] of the stepped portion 13. ], Radius R2 [mm] of the R portion between the step portion 13 and the rising portion 14, the flat portion length L2 [mm] of the rising portion 14, and the radius of the R portion between the rising portion 14 and the step lower portion 15 For R3 [mm], the following relationship is established.

[Equation 1]
R1 + R3 = α × R2 (provided that 0.9 ≦ α ≦ 1.0) (1)
L1 × R1 = β × L2 × R3 (where 1.0 ≦ β ≦ 1.3) (2)

  By setting the dimensions as described above based on the proportional relationship between the radius of each R portion and the return angle after bending, the spring back of each R portion of the preformed product 10 is adjusted according to the equation (1). The vertical wall portion 17 of the final press-molded product 16 as shown in FIG. 4 obtained by extending and flattening the step shape 11 from the upper step 12 to the lower step 15 provided in the molded product 10 becomes substantially vertical (2 ) To adjust the protruding amount of the step portion 13 from the step upper portion 12 of the preformed product 10 and the return amount of the rising portion 14 from the step portion 13, and the vertical wall portion 17 of the final press-formed product 16, Since the portion corresponding to the step lower portion 15 (indicated by the same reference numeral as in FIG. 3) inwardly from the portion corresponding to the step upper portion 12 (indicated by the same reference numeral as in FIG. 3) is suppressed, The opening amount X of the vertical wall portion 17 is equal to or less than a predetermined amount ( It can be suppressed to 1.5% or less) of the height of Ebatatekabe portion. In addition, the dimension shown to FIG.3, 4 is an illustration, and this invention is not limited to this.

Also, it is shown in FIG. 5 (a), the R portion between the bending angle .theta.1, stepped portion 13 and the rising portion 14 of the R portion between the stepped upper 12 and the stepped portion 13 of the preliminary formed shape bending angle θ2 Further, the bending angle θ3 of the R portion between the rising portion 14 and the stepped lower portion 15, that is, the bending angle θn [°] (where n = 1 to 3) is preferable from the viewpoint of suppressing the shape variation at the time of preforming. Is 90 ° ≦ θn ≦ 100 °.

Further, for the R part of the die and the punch at the time of preforming, the radius R preferably satisfies the following condition with respect to the plate thickness tmm in any R part in order to prevent cracking at the time of molding.
2t ≦ R

  Furthermore, when preforming is carried out by so-called shallow drawing, in which the punch width is the same or larger than the drawing depth of the punch, if the radius of the R part of the die and punch is made too large, it becomes impossible to form by shallow drawing. Therefore, the radius R is preferably made as small as possible within the range that satisfies the above conditions in any R portion.

  The present invention can be applied not only to a cold-rolled material but also to various plating materials, and can also be applied to a steel plate of 590 MPa class or higher where springback is a problem. Furthermore, the range of the thickness of the material to be applied is not particularly specified.

It is sectional drawing which shows the structure of the bending die which this inventor used for the simple model test. It is a relationship diagram which shows the relationship between the radius R of the die shoulder part calculated | required by the said simple model test, and angle variation | change_quantity (DELTA) (theta) by springback. It is sectional drawing which shows the cross-sectional shape of the preform in one Embodiment of the manufacturing method of the press-molded product which has a hat-shaped cross-sectional shape of this invention. It is sectional drawing which shows the cross-sectional shape of the half part of the final press molded product in the manufacturing method of the press molded product which has a hat-shaped cross-sectional shape of the said embodiment. (A) And (b) is explanatory drawing which expands and shows two types of shape examples of the vertical wall part of the final press-formed product shown in FIG.

  Hereinafter, an embodiment of a method for producing a press-formed product having a hat-shaped cross-sectional shape according to the present invention will be described in detail by way of examples. In this example, the applied material is a 1180 MPa class high-strength steel plate (Yp: 320 MPa, TS: 1250 MPa, El: 11%), with a plate thickness of 1.4 mm, the sample size is 50 mm wide × 500 mm long, The center of the sample in the longitudinal direction is arranged so as to correspond to the center of the punch. First, as shown in FIG. 3 in the preforming step, the step shape follows the upper part of the vertical wall part of the hat-shaped cross section and the lower end part of the upper part. Then, as shown in FIG. 4, a final press-formed product having a hat-shaped cross-sectional shape was drawn from the preform. In both the pre-forming step and the main forming step, the clearance between the punch and the die was 1.25 mm, and the punch width between the left and right vertical wall portions of the hat-shaped cross-section was 50 mm.

  The opening amount of the final molded product indicated by the length X in FIG. 4 is 1.5 mm (1.5% of the length 100 mm of the vertical wall portion 16), and the opening amount is equal to or less than the predetermined amount. The case was evaluated as the production method of the example of the present invention. Further, as shown in an enlarged view in FIG. 5 for the vertical wall portion 16 shown in FIG. 4, when the dimension a corresponding to L1 × R1 exceeds 1.3 times the dimension b corresponding to L2 × R3 (a / b> 1.3) is evaluated as a comparative example because the bulging portion remaining when the step shape of the preform is extended and flattened becomes too large, and the dimension a corresponding to L1 × R1 is L2 × R3. When the dimension b is smaller than the dimension b corresponding to (a−b <0) or R2 is too small relative to R1 + R3 and the dimension a is smaller than the dimension c (ac−0), the vertical wall portion 16 is punched. It was evaluated as a comparative example. These led to the conditions of the above formulas (1) and (2).

  Table 1 below shows the manufacturing methods of Examples and Comparative Examples evaluated according to the above criteria, and the opening amount and properties of the vertical wall portion of the final press-formed product as a result.

  As is clear from the above results, according to the manufacturing method of the press-formed product of this example and the preformed product formed by the manufacturing method, a hat-shaped cross-sectional shape from a steel material having a thickness of 1.4 mm and a 1180 MPa class high-strength steel plate Even when producing a press-formed product having a thickness, the amount of opening of the final press-formed product can be suppressed to 1.5 mm or less, and excessive bulging of the vertical wall portion and biting into the punch can be prevented. .

Thus , according to the method for producing a press-formed product of the present invention, in the preforming step, a part or all of the vertical wall portion of the hat-shaped cross-sectional shape of the final molded product is pre-molded and the portion that becomes the vertical wall portion is added The preform is formed by providing a step shape in which the upper part, the step part, the rising part, and the lower part are connected via the R part in order, and in the subsequent molding process, the step shape of the preform is formed. Is vertically flattened to form a vertical wall portion having a hat-shaped cross-sectional shape of the final molded product. Therefore, the radius of each R portion forming the step shape and the length of the flat portion adjacent to the R portion By appropriately selecting and combining them, it is possible to suppress the opening of the vertical wall portion of the final molded product due to the spring back.

DESCRIPTION OF SYMBOLS 1 Punch 2 Blank holder 3 Die 10 Preliminary product 11 Step shape 12 Step upper part 13 Step part 14 Rising part 15 Step lower part 16 Final press molding product 17 Vertical wall part S Sample X Opening amount

Claims (3)

In the preforming step, part or all of the vertical wall portion of the hat-shaped cross-sectional shape of the final molded product is pre-molded, and the upper part is stepped in order from the top to the portion that becomes the vertical wall portion of the hat-shaped cross-sectional shape of the final molded product A step shape in which the step portion, the rising portion, and the step bottom portion are connected via the R portion,
In the subsequent molding step, the step shape provided by the preforming is extended and flattened in the vertical direction to form a vertical wall portion of the hat-shaped cross-sectional shape of the final molded product. A method for producing a press-formed product. In the step shape, a radius R1 of the R portion between the stepped portion and the stepped portion, a flat portion length L1 of the stepped portion, a radius R2 of the R portion between the stepped portion and the rising portion, 2. The hat-shaped cross-sectional shape according to claim 1, wherein the following relation is established for the flat portion length L <b> 2 of the rising portion and the radius R <b> 3 of the R portion between the rising portion and the lower step portion. The manufacturing method of the press-formed product which has this.
R1 + R3 = α × R2 (provided that 0.9 ≦ α ≦ 1.0) (1)
L1 × R1 = β × L2 × R3 (where 1.0 ≦ β ≦ 1.3) (2) The method for producing a press-formed product having a hat-shaped cross-sectional shape according to claim 1 or 2, wherein the applied material of the preform formed in the preforming step is a steel plate of 590 MPa class or higher.

Images