JP2003260531A - Method for manufacturing strong structural member, and strong structural member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a strong structural member which can manufacture a strong structural member without the need to provide a number of welding equipment, can simplify the behavior of springback at the time of press molding and, at the same time, can ensure the accuracy of a component in a short time. <P>SOLUTION: A tapered hollow tube 1, which has been integrally formed from a steel sheet S having strain aging properties, is subjected to contracting for reducing the taper, by spinning or swaging, to provide a strain gradient from one end 2a (1a) located on a smaller-diameter side of the hollow tube 2 (1) toward the other end 2b (1b) located on a larger-diameter side. Thereafter, this hollow tube 2 is molded into a component shape followed by heat treatment to manufacture a strong structural member 4 having a strength gradient from one end 4a toward the other end 4b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a strong structural member used as a structural member of an automobile, for example, for absorbing impact energy at the time of collision and softening the impact, and a strong structural member. It is a thing.

[0002]

In the above-described strength structural member, the blank material used as the material is conveniently formed by joining plate materials having different plate thicknesses and strengths by laser welding or seam welding. In order to give a finer plate thickness distribution and strength distribution to this blank material, it is necessary to increase the number of plates to be welded. That is, in order to form one blank material that is press-molded in the subsequent process, many plate materials must be welded, and accordingly, a lot of welding equipment is required. there were.

Further, in the case where the blank material formed by joining the plate materials having different plate thicknesses and strengths is subjected to the press working, compared with the case where the press working is performed on one plate material, the spring back is performed. Behavior becomes complicated, and especially when using a plate material with high strength or a light alloy with a low Young's modulus, larger springback occurs, so it is difficult to secure component accuracy in a short time. Therefore, it has been a conventional problem to solve these problems.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to manufacture a strong structural member without requiring a lot of welding equipment. It is an object of the present invention to provide a method for manufacturing a strength structural member and a strength structural member that have a simple springback behavior and can secure component accuracy in a short time.

[0005]

According to a first aspect of the present invention, there is provided a method for manufacturing a strength structural member by spinning or swaging a tapered hollow tube integrally formed from a steel plate having strain aging. After performing shrinkage tube molding to reduce the taper and giving a strain gradient from one end located on the small diameter side of the hollow tube to the other end located on the large diameter side, this hollow tube is formed into a part shape. After molding, heat treatment is performed, and the structure is characterized in that a strength structural member having a strength gradient from the one end to the other end is manufactured. The configuration is a means for solving the above-mentioned conventional problems.

In the method of manufacturing a strength structural member according to claim 2 of the present invention, the diameter of one end located on the small diameter side in a tapered hollow tube integrally formed from a steel sheet having strain aging. And while reducing the taper due to spinning or swaging while maintaining the plate thickness, the plate thickness is gradually increased from one end located on the small diameter side of the hollow pipe to the other end located on the large diameter side. Of the hollow tube is formed, and then the hollow tube is formed into a shape of a part and then heat-treated to have a thickness gradient and a strength gradient from the one end to the other end. The present invention is characterized in that it is configured to manufacture a strength structural member, and the structure of the method for manufacturing the strength structural member is used as means for solving the above-mentioned conventional problems.

In the method for manufacturing a strength structural member according to claim 3 of the present invention, the contraction rate of the other end portion on the large diameter side is 8 to 8.
25%, and in the method for manufacturing a strength structural member according to claim 4 of the present invention, the shrinkage rate at one end on the small diameter side is set to 0 to 2%.

In the method for manufacturing a strength structural member according to claim 5 of the present invention, the equivalent strain at one end on the small diameter side is 0.035 or less, and the equivalent strain at the other end on the large diameter side is 0. In the method for manufacturing a strength structural member according to claim 6 of the present invention, the plate thickness increase rate with respect to the plate thickness before contraction molding at the other end on the large diameter side is 5 or more.
% And above.

On the other hand, the invention according to claim 7 of the present invention is
A hollow strength structural material integrally formed from a steel sheet having strain aging is characterized in that a strength gradient is provided from one end to the other end. The configuration is a means for solving the above-mentioned conventional problems.

According to the eighth aspect of the present invention, the strength structural member has a plate thickness gradient in which the plate thickness gradually increases from one end to the other end.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for manufacturing a strength structural member according to the present invention, a tapered hollow tube is formed by a strain aging type steel plate having an increased tensile strength, and the hollow tube is formed by spinning or swaging. Strain distribution and plate thickness distribution are given in the longitudinal direction of the hollow tube by reducing the taper to reduce the taper, and then the hollow tube having this strain distribution is formed into a part shape and then heat treatment is performed. This makes it possible to provide a strength gradient and a plate thickness distribution from one end on the small diameter side to the other end on the large diameter side.

More specifically, for example, one end portion on the small diameter side has low strength, and the strength is increased toward the other end portion on the large diameter side which is contracted, or the plate is added to the strength in addition to the strength. It is possible to form a hollow tube whose thickness is increased toward the other end on the large diameter side, and thereby it is integrally formed from a steel plate having strain aging without welding many plate materials. It is possible to give the plate pressure distribution and strength distribution to the member.

Although it is possible to give a strain distribution in the longitudinal direction of the hollow tube by the above spinning, a larger strain is given to a portion having a large cross section of the hollow tube in which the size of the cross section changes, It is difficult to increase the plate thickness due to the nature of the spinning process. Therefore, in the method of manufacturing a strength structural member according to the present invention, the hollow tube used as a material is tapered, and a portion having a small cross section is not drawn, and a portion having a large cross section is contracted to have a large cross section. Large strain and thickening are formed in the part.

When a steel sheet having almost no strain aging is used as the steel sheet to be used, the yield strength increases due to work hardening, but the strength cannot be expected to increase significantly. Therefore, for example, a material having a strain aging property that increases not only the proof stress but also the strength is used, and at a temperature of 170 ° C., which is a typical heat treatment in the baking and painting process of automobiles,
By performing the heat treatment for a minute, it becomes possible to give greater yield strength and greater strength to a portion to which a large strain is applied, and therefore, it is possible to weld materials having different plate thicknesses and different strength levels without welding. It is possible to give a strength gradient and further a plate thickness distribution to one hollow tube integrally formed from a steel plate having strain aging.

In this manner, a tapered hollow tube is subjected to spinning to form a large shrink tube at a portion having a large cross section, and a steel sheet used for the hollow tube is subjected to a proof stress and a strength in a baking process of an automobile or the like. By using a steel plate having an increased strength, a strength structural member having a strength gradient in the longitudinal direction can be obtained.

[0016]

According to the method of manufacturing a strength structural member according to the present invention, since it has the above-mentioned structure, the strength gradient is increased from one end to the other end without using a lot of welding equipment. In addition to being able to manufacture a strong structural member having, it is possible to simplify the behavior of springback at the time of press molding and to ensure the accuracy of parts in a short time. Very good effect.

Since the strength structural member according to the present invention has the above-mentioned structure, the welding equipment can be almost unnecessary, and the behavior of the spring back at the time of press molding can be simplified and the parts can be easily manufactured. This has an extremely excellent effect of ensuring accuracy in a short time.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

[Embodiment 1] FIG. 1 shows a manufacturing process according to an embodiment of a method for manufacturing a strength structural member according to the present invention.

In the method of manufacturing a strength structural member according to this embodiment, first, as shown in FIG.
A steel plate S having a strain aging property of 60 MPa and a plate thickness of 1.8 mm is rolled into a tapered tubular shape having a length of 500 mm, and the edges of the steel plate S are joined by seam welding to obtain one of the smaller diameter sides. The diameter at the end 1a is 100 m
m, the diameter at the other end 1b on the large diameter side is 150 mm
The tapered hollow tube 1 is formed.

Next, as shown in FIG. 1 (b), by spinning the hollow tube 1 using spinning rollers R, R, as shown in FIG. 1 (c), the small diameter side The tapered hollow tube 2 has a diameter of 100 mm at one end 2a and a diameter of 120 mm at the other end 2b on the large diameter side.

At this time, the plate thickness of the hollow tube 2 was 1.8 mm over the entire length. Further, although the total length of the hollow tube 2 is longer than that of the hollow tube 1, compared with the length of the steel plate S as a raw material, the contracted tube ratio to the total length, that is, the diameter of each portion and the corresponding It was possible to mold such that the ratio of the diameter of each part before the contraction was linearly changed as shown in the graph of FIG.

The shrinkage rate at this time can be set to exceed 30%, but the tapered hollow tube 2 having the strain distribution is further subjected to a forming process in a later step. Therefore, it is desirable to keep the shrinkage rate at 25% or less. Further, when the strain-aged steel sheet S is used, the increase in strength after the bake hardening treatment is most effective when the shrinkage ratio is 8% or more.

Therefore, in the case of a strength structural member that is preferentially deformed from the front end (the small diameter side end on the left side in the figure) like the front side member of an automobile, the rear end (the right side in the figure on the right side) in which the deformation is desired to be suppressed most. The contraction rate of the large diameter end) is 8%
Between 25% and 25% is desirable. Expressed as equivalent strain, a strength increase after bake hardening treatment is effective when it is 0.09 or more.

When deformation occurs, it is not preferable to apply an unnecessarily large strain to the front end portion which is to be deformed most preferentially because of the characteristic of using the strain hardening material. By keeping the equivalent strain amount to 0.035 or less,
A large increase in strength can be suppressed. Further, the shrinkage rate of the front end portion is preferably 0% to 2%.

Then, the initial hydraulic pressure is set to 1 by a hydraulic forming die.
The hollow tube 2 is controlled to 0 MPa while controlling the subsequent increase in hydraulic pressure to 20 MPa or less so that the hollow tube 2 is not expanded by hydraulic pressure.
1 (e), a hollow rectangular tube 3 having a component shape was obtained, that is, one end 3 was formed.
The cross section of a has a small square shape of 60 mm × 90 mm, and the cross section of the other end 3 b is 80 mm × 100.
A rectangular hollow tube 3 having a large mm shape was obtained.

Then, as shown in FIG. 1 (f), the hollow rectangular tube 3 was heat-treated in an oven at 170 ° C. for 20 minutes. In the strength structural member 4 thus manufactured, the Vickers hardness of one end 4a (left end in the drawing) is Hv = 200, and the Vickers hardness of the other end 4b (right end in the drawing) is Hv = 250. Therefore, the strength structural member 4 has a strength distribution over the entire length, and thus the strength structural member 4 having a strength gradient from one end 4a to the other end 4b is manufactured by the method for manufacturing a strength structural member according to this embodiment. It has been proved that can be manufactured.

[Embodiment 2] FIG. 2 shows a manufacturing process according to another embodiment of the method for manufacturing a strength structural member according to the present invention.

In the method of manufacturing a strength structural member according to this embodiment, first, as shown in FIG.
A steel plate S having a strain aging property of 60 MPa and a plate thickness of 1.8 mm is rolled into a tapered tubular shape, and the edges of the steel plate S are joined by seam welding, whereby one end 21a on the small diameter side is joined. A tapered hollow tube 21 having a diameter of 100 mm and a diameter of 125 mm at the other end 21b on the large diameter side is formed.

Next, as shown in FIG. 2 (b), by spinning the hollow tube 21 using spinning rollers R, R, as shown in FIG. 2 (c), on the small diameter side. From one end 22a to the other end 22b on the large diameter side
400mm in length with a constant diameter of 100mm
The straight hollow tube 22 of FIG.

At this time, one end 22a of the hollow tube 22 is
And the plate thickness at the other end 22b is 2.0 mm.
It was molded to have a size of mm. Further, although the entire length of the hollow tube 22 is extended, compared with the length of the steel plate S as a material, the plate thickness distribution with respect to the entire length changes linearly as shown in the graph of FIG. Could be molded as.

Then, the initial hydraulic pressure is set to 1 by a hydraulic forming die.
The pressure is set to 0 MPa, and the hollow pipe 22 is press-molded while controlling the subsequent increase in hydraulic pressure to 20 MPa or less so that the hollow pipe 22 is not expanded by hydraulic pressure, and as shown in FIG.
A hollow square tube 23 having a component shape was obtained, that is, a hollow square tube 2 having a rectangular cross section of 75 mm × 75 mm.
Got 3.

Then, as shown in FIG. 2F, the hollow rectangular tube 23 was heat-treated in an oven at 170 ° C. for 20 minutes. Strength structural member 2 manufactured in this manner
4, the Vickers hardness of one end 24a (left end in the drawing) is Hv = 200, and the Vickers hardness of the other end 24b (right end in the drawing) is Hv = 250.
Has strength distribution and plate thickness distribution over the entire length,
From this, it can be demonstrated that the method for manufacturing a strength structural member according to this example can manufacture a strength structural member 24 having a strength gradient and a plate thickness gradient from one end 24a to the other end 24b. It was

[Embodiment 3] FIG. 3 shows a manufacturing process according to still another embodiment of the method for manufacturing a strength structural member according to the present invention.

In the method of manufacturing a strength structural member according to this embodiment, first, as shown in FIG.
A steel plate S having a strain aging property of 60 MPa and a plate thickness of 1.8 mm is rounded to form a taper tube having a length of 500 mm, and the edges of the steel plate S are joined by seam welding. The diameter at the end 31a is 100
mm, the diameter at the other end 31b on the large diameter side is 150
A mm-shaped tapered hollow tube 31 is formed.

Next, as shown in FIG. 3B, the hollow tube 31 is subjected to a spinning process by using spinning rollers R, R, and as shown in FIG. The tapered hollow tube 32 has a diameter of 100 mm at one end 32a and a diameter of 120 mm at the other end 32b on the large diameter side.

At this time, one end 32a of the hollow tube 32
And the plate thickness at the other end 32b is 2.0 mm.
It was molded to have a size of mm. Further, the plate thickness distribution of the entire length of the hollow tube 32 with respect to the length of the material could be molded so as to change linearly as shown in the graph of FIG.

Next, the initial hydraulic pressure is set to 1 by a hydraulic forming die.
As shown in FIG. 3 (e), the hollow pipe 32 is press-molded while controlling the hydraulic pressure to 20 MPa or less so that the hollow pipe 32 is not expanded by hydraulic pressure.
A hollow rectangular tube 33 having a component shape was obtained, that is, a cross section of one end 33a had a small square shape of 60 mm × 90 mm, and a cross section of the other end 33b had a large square of 80 mm × 100 mm. A hollow rectangular tube 33 having a shape was obtained.

Then, as shown in FIG. 3F, the hollow rectangular tube 33 was heat-treated in an oven at 170 ° C. for 20 minutes. Strength structural member 3 manufactured in this manner
4, the Vickers hardness of one end 34a (left end in the drawing) is Hv = 200, and the Vickers hardness of the other end 34b (right end in the drawing) is Hv = 255.
Has strength distribution and plate thickness distribution over the entire length,
From this, it can be demonstrated that it is possible to manufacture a strength structural member 34 having a strength gradient and a plate thickness gradient from one end 34a to the other end 34b by the method for manufacturing a strength structural member according to this example. It was

[Brief description of drawings]

FIG. 1 is a manufacturing process explanatory view (a) to (f) according to an embodiment of a method for manufacturing a strength structural member according to the present invention.

2A to 2F are manufacturing process explanatory diagrams according to another embodiment of the method for manufacturing a strength structural member according to the present invention.

FIG. 3 is manufacturing process explanatory diagrams (a) to (f) according to still another embodiment of the method for manufacturing a strength structural member according to the present invention.

[Explanation of symbols]

1, 21, 31 Tapered hollow tube 2, 22, 32 Hollow tube 2a, 22a, 32a after contracted tube One end 2b, 22b located on the small diameter side of the hollow tube after contracted tube , 32b One end 3,23,33 located on the large diameter side of the hollow tube after the contraction molding Hollow square tube 4,24,34 molded into a component shape Strength structural members 4a, 24a, 34a Strength structural member One end 4b, 24b, 34b The other end of the strength structural member

Claims (8)

[Claims] 1. A tapered hollow tube integrally formed from a steel plate having strain aging is subjected to a shrink tube forming for reducing a taper due to spinning or swaging,
After applying a strain gradient from one end located on the small diameter side of the hollow tube to the other end located on the large diameter side, heat treatment is subsequently performed after forming this hollow tube into a component shape. A method for manufacturing a strength structural member, comprising manufacturing a strength structural member having a strength gradient from the one end to the other end. 2. A taper hollow tube integrally formed of a steel plate having strain aging, which is formed by spinning or swaging while maintaining the diameter and plate thickness of one end located on the small diameter side. After reducing the diameter of the hollow pipe, the hollow pipe has a thickness gradient that gradually increases from one end located on the small diameter side to the other end located on the large diameter side. A strength structural member characterized by producing a strength structural member having a plate thickness gradient and a strength gradient from the one end to the other end by performing heat treatment after forming the pipe into a component shape. Manufacturing method. 3. The contraction rate of the other end on the large diameter side is 8 to 25.
%, The method for manufacturing a strong structural member according to claim 1 or 2. 4. The shrinkage ratio of one end on the small diameter side is 0 to 2%.
The method for manufacturing a strong structural member according to claim 3. 5. The equivalent strain of one end on the small diameter side is set to 0.
5. The method for manufacturing a strong structural member according to claim 1, wherein the strain is 035 or less and the equivalent strain of the other end on the large diameter side is 0.09 or more. 6. The method for manufacturing a strength structural member according to claim 5, wherein the plate thickness increase rate with respect to the plate thickness before contraction molding at the other end on the larger diameter side is 5% or more. 7. A strength structural member which is a hollow strength structural member formed integrally from a steel plate having strain aging, wherein a strength gradient is provided from one end to the other end. 8. The strength structural member according to claim 7, wherein the strength structural member has a plate thickness gradient in which the plate thickness gradually increases from one end to the other end.