JP3856687B2 - Manufacturing method of pipe-shaped impact reinforcement - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a pipe-shaped collision reinforcing material.
[0002]
[Prior art and problems to be solved by the invention]
Inserting a pipe-shaped collision reinforcing material into the center pillar or door of the vehicle is an extremely effective measure for ensuring the strength of the vehicle and improving the collision safety. For this reason, bending work is applied to the high-tensile steel pipe material or the ultra-high-strength steel pipe material after quenching to give a curved shape that is convenient for mounting inside the center pillar and inside the door, and this is used to reinforce the pipe-like collision. There are attempts to use it as a material.
[0003]
However, pipes made of hard materials such as high-strength steel should be bent to fit the installation space due to the effect of springback even if they are bent cold by a bender or press. However, there is a drawback that bending accuracy is extremely low. In order to increase the accuracy of the bending process while accepting the springback, there is a method of increasing the number of processes by setting the bending process in multiple stages, but this does not meet the manufacturing cost. In addition, when mere quenching is performed after bending, there is a problem that the product is likely to be distorted, and the shape of the final product is not stable even when an accurate shape is given during bending.
[0004]
The present invention has been made in view of such circumstances. An object of the present invention is to provide a method for producing a pipe-shaped impact reinforcement capable of simultaneously producing an accurate bending shape and quenching a metal pipe material and capable of producing a pipe-shaped collision reinforcement with a small number of steps. Is to provide.
[0005]
[Means for Solving the Problems]
The invention of claim 1 makes welding so that the upper inner wall and the lower inner wall at each end of the metal pipe material extending straightly are in contact with each other and the gap between the upper and lower inner walls in contact with each other is completely filled. a sealing step of sealing the space of the interior of the metal pipe by sealing both ends of the metal pipe member, a heating process of the internal heat the enclosed space of metal pipe material, which is the heating A pipe-shaped collision characterized by comprising a pressing process for imparting a desired bending shape to a metal pipe material by pressing using a press mold relatively cooler than the metal pipe material It is a manufacturing method of a reinforcing material.
[0006]
The invention of claim 2 By crushing both ends of the metal pipe material extending straight or the vicinity thereof and welding the crushed portion, the both ends of the metal pipe material or the vicinity thereof are sealed and the inside of the metal pipe material A sealing process for forming a sealed space, a heating process for heating the metal pipe material in which the inside is sealed, and a press at a relatively lower temperature than the metal pipe material for the heated metal pipe material. It is a manufacturing method of the pipe-shaped impact reinforcement characterized by including the press process which provides a desired bending shape by giving a press work using a type | mold.
[0007]
According to the method of claim 1 or 2, in the sealing step, by sealing both ends of the metal pipe material extending straight or in the vicinity thereof, the metal is contained in the state where the air is confined in the metal pipe material. The inside of the pipe material is made into a sealed space (in addition, the gas confined inside can be changed to an inert gas by performing the sealing step in an inert gas atmosphere such as nitrogen). By heating the metal pipe material in the subsequent heating step, the gas pressure of air or the like confined in the metal pipe material is increased, and the metal pipe material is softened. In the subsequent pressing step, the metal pipe material softened by heating is pressed using a press die corresponding to the desired bending shape, whereby the desired bending shape is imparted to the metal pipe material all at once. This press work is hot forming, and the metal pipe material undergoes plastic deformation during pressing, so there is almost no rebound (ie spring back) when the product is removed from the press die after pressing, and the metal pipe material has the desired bending shape. Can be accurately given. Further, at the time of pressing, the shape of the pipe material is maintained by a high gas pressure inside the metal pipe material, so that a large shape collapse does not occur despite the press on the softened hollow body (metal pipe material). Further, in this pressing process, a press mold having a temperature lower than that of the heated metal pipe material is used. Therefore, the metal pipe material is quenched at the same time as the bending shape is imparted by the press, and the pressed product (pipe shape) The strength of the impact reinforcement is dramatically improved compared to before pressing. As described above, according to the method of the present invention, a desired bending shape can be imparted to the metal pipe material with high dimensional accuracy by a single press work, and a high strength can be imparted by simultaneous quenching.
[0008]
The temperature of the press die may be “relatively lower than the heated metal pipe material”, but the temperature difference between the temperature of the metal pipe material in the heated state immediately before pressing and the temperature of the press die is Needless to say, the larger the value, the higher the quenching effect. Therefore, the temperature of the press die is preferably room temperature or room temperature (for example, 25 ° C.) or lower. Moreover, it is preferable to provide a forced cooling mechanism so that the press mold | type installed in the continuous production line can always maintain the state of "relatively lower temperature than the heated metal pipe material".
[0009]
In particular, according to the method of claim 2, since both ends of the metal pipe material or the vicinity thereof are crushed and then welded to the crushed portion, the airtightness of the metal pipe is improved, and the inside of the metal pipe is reliably secured. It is possible to make a sealed space. In addition, the shape when crushing both ends of the metal pipe material or the vicinity thereof may be any of “flat”, “curved”, or other shapes.
[0010]
According to a third aspect of the present invention, in the method of manufacturing a pipe-shaped collision reinforcing material according to the first or second aspect, in the heating step, the temperature of the metal pipe material is set to 850 ° C. or higher and lower than the melting point of the metal pipe material. While heating, in the said press process, said press processing is given with respect to the metal pipe material in a heating state of 850 degreeC or more, It is characterized by the above-mentioned .
[0011]
According to the third aspect, by applying the above pressing to the metal pipe material in a heated state of 850 ° C. or higher, it is possible to effectively achieve a desired curved shape and simultaneous quenching. In addition, when the temperature of the metal pipe material at the time of press is less than 850 degreeC, there exists a possibility that the hardening effect by a relatively low-temperature press type | mold may be small and sufficient intensity | strength improvement cannot be aimed at. Further, the metal pipe material is only elastically deformed by the press work, and there is a possibility that a spring back is generated. The reason why the heating temperature of the metal pipe material in the heating process is kept below the melting point is to avoid the deformation of the metal pipe material due to the temperature.
[0012]
Invention of Claim 4 is the manufacturing method of the pipe-shaped collision reinforcement material as described in any one of Claims 1-3. WHEREIN: When the said metal pipe material extended straight consists of high-tensile steel, the said heating process Then, while heating a metal pipe material to the temperature of 850 degreeC or more and 1050 degrees C or less, said press process is given with respect to the metal pipe material in a heating state of 850 degreeC or more in the said press process.
[0013]
According to the fourth aspect, by applying the above pressing to the metal pipe material in a heated state of 850 ° C. or higher, it is possible to effectively achieve a desired curved shape and simultaneous quenching. In addition, when the temperature of the metal pipe material at the time of press is less than 850 degreeC, there exists a possibility that the hardening effect by a relatively low-temperature press type | mold may be small and sufficient intensity | strength improvement cannot be aimed at. Further, the metal pipe material is only elastically deformed by the press work, and there is a possibility that a spring back is generated. The reason why the heating temperature of the metal pipe material in the heating process was kept below 1050 ° C is that when high-tensile steel is heated above 1050 ° C, the coarsening of the metal crystals is promoted and the bonding of the crystal structure becomes coarser, and the strength is improved. This is because there is a risk that it will not be possible.
[0014]
The high-strength steel referred to in claim 4 includes 0.18 to 0.25 wt% carbon, 0.15 to 0.35 wt% silicon, and 1.15 to 1.40 wt% as components other than iron. It is preferably an iron-based material containing at least manganese, 0.15-0.25 wt% chromium, and 0.01-0.03 wt% titanium. More preferably, it is a high-tensile steel having a melting point of 1300 to 1400 ° C.
[0015]
Invention of Claim 5 is a manufacturing method of the pipe-shaped collision reinforcement material as described in any one of Claims 1-4. WHEREIN: In the said sealing process, the predetermined amount of liquid was put into the inside of the said metal pipe material. The inside of the metal pipe material is sealed in a state .
[0016]
According to the method of claim 5, the liquid sealed in the metal pipe material is vaporized during heating to increase the internal pressure, contributing to the maintenance of the pipe shape during hot pressing. In particular, it is possible to freely control the internal pressure of the pipe material in the heating process and the pressing process by adjusting the amount of liquid put into the metal pipe material.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is embodied in a method for manufacturing a reinforcement for a vehicle door frame, which is a kind of collision reinforcing material, will be described with reference to the drawings.
[0018]
(Contained space for metal pipe materials)
As shown in FIG. 1 (A), the starting material is a straight pipe member 10 having a circular cross section that is cut into a required length (in FIG. 1, the pipe material has a single thickness). Simplified display with a line.) The pipe material 10 is made of an iron-based material (referred to as “steel material A”) classified as high-tensile steel. In the steel material A, the quality control ranges of additive elements other than iron are carbon: 0.18 to 0.25 wt% (weight percent), silicon: 0.15 to 0.35 wt%, and manganese: 1.15 to 1, respectively. .40 wt%, chromium: 0.15 to 0.25 wt%, and titanium: 0.01 to 0.03 wt%. The melting point of the steel material A is approximately 1300 to 1400 ° C.
[0019]
As shown in FIG. 1 (B), both ends 11 and 11 of the metal pipe material 10 are pressed by a press machine (not shown) to flatten each end. Each of the flattened end portions 11 is constructed by bringing the upper inner wall and the lower inner wall that originally formed the circular inner peripheral wall into contact with each other and integrating them into a flat plate shape. However, with this degree of press work, sealing (or ensuring airtightness) of the end 11 of the metal pipe material does not occur. Therefore, as shown in FIG. 1C, seam welding (a kind of resistance welding) is performed on a part (W) of each flattened end portion 11 so as to cross the flat plate shape. As a result, the minute gap between the upper inner wall and the lower inner wall that are in contact with each other is completely filled, and the inside of the metal pipe member 10 is closed.
[0020]
(Heating and pressing metal pipe materials)
Subsequently, as shown in FIG. 1 (D), the metal pipe member 10 with the inside made into a sealed space was transferred to a heating device and heated to a predetermined target temperature (900 ° C. in the present embodiment). In the present embodiment, an electric heating furnace is used as a heating device, and the inside of the electric heating furnace is set to an inert gas atmosphere (for example, a nitrogen gas atmosphere). The temperature was maintained. Due to the heating to 900 ° C. (1173 K), the pressure of the air sealed in the metal pipe member 10 reaches about four times the normal temperature pressure (ie, atmospheric pressure).
[0021]
Next, the metal pipe material 10 heated to the target temperature was conveyed at high speed from the heating device between the fixed die 21 and the movable die 22 (see FIG. 2E) of the shaping press machine, and immediately subjected to press working. That is, the time until the metal pipe material 10 is taken out of the heating device, set in the shaping press and the pressing operation is started is within 5 seconds, so that the temperature of the metal pipe material 10 immediately before pressing does not fall below 850 ° C. Considered.
[0022]
As shown in FIG. 2 (E), the press machine for shaping is composed of a fixed die 21 and a movable die 22, and a shaping chamber 23 corresponding to the desired bending shape of the pipe material is obtained by matching the dies 21 and 22. Built. Cooling water passages 24 and 25 are secured inside the fixed mold 21 and the movable mold 22 so that both molds 21 and 22 can be forcibly cooled. This gives a corresponding temperature difference between the metal pipe material 10 in the high temperature state and the cold press dies 21 and 22, and when the metal pipe material 10 in the high temperature state contacts the cold press dies 21 and 22, It is intended that effective quenching is performed simultaneously with the provision of a desired curved shape.
[0023]
The pressing of the metal pipe material 10 in the press dies 21 and 22 is held for about 10 to 20 seconds, and after the stabilization of the shape of the metal pipe material 10 and the completion of quenching are expected, the movable die 22 is separated from the fixed die 21. The product was taken out (see FIG. 2F). The temperature of the product immediately after taking out from the press dies 21 and 22 was around 250 ° C., but after that, the product was allowed to cool naturally for several minutes, and reached a room temperature.
[0024]
Through the series of steps as described above, a pipe-like reinforcement 10 having a desired bending shape as shown in FIG. 2 (F) and FIG. 3 can be obtained. In addition, about the flat both ends 11 and 11 of the pipe-shaped reinforcement 10, it is also possible to utilize as the attachment interposition part (what is called a bracket) at the time of attaching the said reinforcement to a door frame.
[0025]
In addition, the preferable range of the target temperature at the time of the heating is a temperature at which the temperature when the press die is charged when the heated metal pipe material 10 is conveyed to the press dies 21 and 22 at a high speed becomes 850 ° C. or more and 1050 ° C. or less. When the temperature at the time of pressing the press die is less than 850 ° C., the temperature difference when pressing with the cold press die becomes small, and the strength improvement by quenching may be insufficient. On the other hand, if the temperature when the press mold is charged is higher than 1050 ° C., the strength may rather decrease (or the strength may tend to peak). The reason for this is that if the heating temperature in the heating device is set too high in order to increase the temperature at the time of charging the press die, the coarsening of the metal crystal is promoted in the heating stage, and the connection of the crystal structure becomes coarse instead. It is. In this way, the metal pipe material is pre-heated so that the temperature of the metal pipe material when the press die is charged is from 850 ° C. to the nearest temperature of the melting point of the metal pipe material, more preferably from 850 ° C. to 1050 ° C. Is preferred.
[0026]
According to the present embodiment, after sealing both ends of the metal pipe material 10 as a starting material, the metal pipe material whose inside is hermetically sealed is preheated, and the press die is cooled in a high temperature state. By adopting a method of using and pressing (hot stamp method), the following effects can be obtained.
[0027]
(A) When the high-temperature metal pipe material 10 is shaped by the press dies 21 and 22, the high internal pressure of the metal pipe material 10 facilitates maintaining the shape of the softened hollow metal pipe material. To do.
[0028]
(B) For the metal pipe member 10 that extends straight as a starting material, it is possible to simultaneously perform shaping with a gently curved shape and quenching. This makes it possible not only to improve the strength of the final product by quenching, but also to simplify the manufacturing process of the impact reinforcement and improve productivity.
[0029]
(C) Unlike conventional cold bending and cold pressing, there is no mold return due to springback even after the product is taken out of the press dies 21 and 22, and the shape stability of the final product is excellent. In addition, it is extremely easy to impart a “curve shape with a gentle curve”, which is difficult to impart with the conventional cold working method.
[0030]
(Modification) The embodiment of the present invention may be modified as follows.
In the above embodiment, laser welding may be used instead of seam welding in the process of FIG.
[0031]
In the above embodiment, both ends of the metal pipe material 10 are flattened in the step of FIG. 1B, but the processing method for sealing the end of the metal pipe material 10 is limited to this. It is not a thing. For example, as shown in FIGS. 4A and 4B, the end 11 of the metal pipe member 10 may be crushed so as to have a concave curved shape with a semicircular cross section. In this case, as shown in FIG. 4 (A), the semicircular arc-shaped edge portion is welded to ensure the airtightness inside the metal pipe material.
[0032]
Instead of crushing the end portion 11 of the metal pipe material 10, for example, as shown in FIG. 5, the end portion 11 may be drawn so that the tip end portion thereof is tapered. In this case, since it is unavoidable that a hole is left in the tapered tip portion, MIG welding or TIG welding is performed on the tip portion so as to close the hole at the tip portion, thereby ensuring airtightness inside the metal pipe material. become.
[0033]
In the above embodiment, as a result of the series of steps shown in FIGS. 1A to 1C, air corresponding to atmospheric pressure is sealed inside the metal pipe material 10, but the metal before the end 11 is sealed An appropriate amount of liquid (for example, water) may be placed in the pipe material 10, and both end portions 11 of the metal pipe material 10 may be sealed in that state. In this case, the liquid is vaporized by heating the metal pipe member 10, and an internal pressure of vapor pressure corresponding to the heating temperature is generated in the pipe. That is, it is possible to control the internal pressure during heating and hot pressing by adjusting the amount of liquid enclosed.
[0034]
-Metals other than high-tensile steel may be used as the material of the starting material (metal pipe material) used in the present invention.
[0035]
-The application object of this invention is not limited to the reinforcement for doors, You may apply to manufacture of the collision reinforcement for other vehicles (for example, bumper reinforcement and a center pillar member). As used herein, the term “collision reinforcement” refers to a member that is attached to each part of a vehicle in order to protect passengers in the vehicle in the event of a vehicle collision or other accident, and that independently exhibits a protective function. It does not matter whether the protective function is exhibited in cooperation with other members.
[0036]
【The invention's effect】
As described above in detail, according to the method for manufacturing a pipe-shaped collision reinforcing material described in each claim, it is possible to perform accurate bending shape formation and quenching on a metal pipe material at the same time, and to reduce the number of processes. Can be produced.
[Brief description of the drawings]
FIGS. 1A to 1D are diagrams showing an example of a manufacturing procedure of a pipe-shaped collision reinforcing material.
FIGS. 2E and 2F are diagrams illustrating an example of a manufacturing procedure of a pipe-shaped collision reinforcing material (continuation of FIG. 1).
FIG. 3 is a perspective view of a pipe-shaped collision reinforcing material made by the procedure of FIGS. 1 and 2;
4A is a perspective view showing a modified example of the end portion of the pipe-shaped collision reinforcing material, and FIG. 4B is an end view of the pipe-shaped collision reinforcing material according to the modified example.
FIG. 5 is a cross-sectional view showing a modified example of an end portion of a pipe-shaped collision reinforcing material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Metal pipe material, 11 ... End part, 13 ... Cover, 21 ... Fixed type (press type), 22 ... Movable type (press type), 23 ... Shaping chamber, 24, 25 ... Passage for cooling water (forced) Cooling mechanism), W ... welded portion at the end.

Claims (5)

Both ends of the metal pipe material are welded so that the upper inner wall and the lower inner wall at each end of the straightly extending metal pipe material are brought into mutual contact and the gap between the upper and lower inner walls that are in contact with each other is completely filled. a sealing step of sealing the space of the inside of the metal pipe material sealed sealed,
A heating step of heating the metal pipe material in which the inside is sealed space;
A pressing step of imparting a desired bending shape to the heated metal pipe material by pressing using a press mold having a temperature lower than that of the metal pipe material. A method for manufacturing a pipe-shaped collision reinforcing material. By crushing both ends of the metal pipe material extending straight or the vicinity thereof and welding the crushed portion, the both ends of the metal pipe material or the vicinity thereof are sealed and the inside of the metal pipe material A sealing process for creating a sealed space;
A heating step of heating the metal pipe material in which the inside is sealed space;
A pressing step of imparting a desired bending shape to the heated metal pipe material by pressing using a press mold having a temperature lower than that of the metal pipe material. A method of manufacturing a pipe-shaped collision reinforcing material. In the heating step, the metal pipe material is heated to a temperature of 850 ° C. or higher and lower than the melting point of the metal pipe material, and in the pressing step, the metal pipe material is heated to 850 ° C. or higher. 3. The method for producing a pipe-shaped collision reinforcing material according to claim 1, wherein pressing is performed . In the case where the straightly extending metal pipe material is made of high-tensile steel, in the heating step, the metal pipe material is heated to a temperature of 850 ° C. or higher and 1050 ° C. or lower, and in the pressing step, the heating state is 850 ° C. or higher. The method for producing a pipe-shaped collision reinforcing material according to any one of claims 1 to 3, wherein the press working is performed on the metal pipe material . The said sealing process WHEREIN: The inside of a metal pipe material is made into sealed space in the state which put the predetermined amount of liquid in the inside of the said metal pipe material , As described in any one of Claims 1-4 characterized by the above-mentioned. A method of manufacturing a pipe-shaped impact reinforcement.

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