JP2005145168A - Method of manufacturing vehicle skeleton member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a vehicle skeleton member capable of rather easily applying finishing processes such as trimming and piercing processes to semi-finished products after shaping and quenching processes. <P>SOLUTION: Shaping and quenching are simultaneously performed for a sheet metal member by pressing the sheet metal material in a hot state by heating by using a relatively low temperature press die (die quench step). In the die quench step, cut-in grooves (16, 17, and 18) are simultaneously formed along predicted lines for trimming and piercing in the sheet metal material by the press die. Then, a vehicle skeleton member (for example, a roof side rail inner panel 10) as a final product can be provided by applying the trimming process or the piercing process to the semi-finished products provided by the die quenching along the cut-in grooves (16, 17, and 18). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a vehicle frame member.

  For example, vehicle frames such as various pillars and roof side rails for constructing passenger cabin space for passenger cars are required to have high strength and further weight reduction to ensure safety during a collision. In order to satisfy such contradictory requirements (improvement of strength and weight reduction), for example, a molded product obtained by press-forming an ERW steel pipe into a predetermined shape is heated to a temperature of 900 ° C. or higher by high-frequency induction heating, and then quenched with water. A processing method (so-called induction hardening) is performed as a method for manufacturing automobile door reinforcement (see Patent Document 1). According to Patent Document 1, when a post-mechanical cutting is necessary for the reinforcing material after induction hardening, the steel pipe material has high strength and is difficult to cut by a press. It is said that fusing using a laser or a laser or mechanical cutting with a grindstone is employed.

  By the way, even in the case of a vehicle skeleton member that is generally invisible to the human eye, for example, a skeleton member that forms a door opening, such as a roof side rail, requires high processing accuracy (ie, outer trim accuracy) on the end surface of the member. Therefore, it may be necessary to perform finishing such as trimming even after the strength is increased by quenching. However, in the case of fusing using plasma or laser, the processing time is long and the equipment cost is high. Mechanical cutting with a grindstone also takes a long time. Another possible method is to divide the trim processing into multiple press cutting processes and gradually increase the processing accuracy. However, a cutting press with a different cutting edge is prepared for each process. There is a problem in that it is difficult to maintain and manage the cutting edge due to the fact that the object to be processed is very hard, and an increase in processing cost is inevitable.

Japanese Patent No. 2837567 (particularly paragraph 0051)

  It is an object of the present invention to manufacture a vehicle frame member that can be subjected to finishing such as trimming (bordering) or piercing (drilling) relatively easily on an intermediate product after shaping and quenching. It is to provide a method.

  According to the first aspect of the present invention, a heating step of heating a metal plate material to a predetermined high temperature, and a metal plate material in a high temperature state by the heating are pressed against a metal plate material by using a relatively low temperature press die. In the method for manufacturing a vehicle frame member, comprising: a die quenching step for performing shape imparting and quenching simultaneously; and a finishing step for trimming or piercing the intermediate product obtained by the die quenching. A vehicle frame member characterized in that a cutting groove along a predetermined line of trim or piercing is simultaneously formed on the metal plate material by a mold, and in the finishing step, trimming or piercing is performed along the cutting groove. It is a manufacturing method.

  According to the method of claim 1, the cut groove along the planned line of trim or piercing is simultaneously formed on the metal plate material when the shape is given and quenched on the metal plate material in a high temperature state by heating. The Since the strength and hardness of a metal plate in a high temperature state is significantly lower than before heating, it is not possible to simultaneously form a cut groove along the planned line of trim or piercing on the metal plate using a die quench press die. Easy. In addition, the strength and hardness of the intermediate product (pre-formed product) are dramatically increased compared to the original strength and hardness of the metal plate material as a starting material due to the quenching effect of the relatively low temperature press mold, but the incision in the intermediate product The thickness of the groove portion is thinner than the thickness of the other portions (that is, the original plate thickness of the metal plate material). For this reason, in the finishing process, the shearing force when trimming or piercing is performed along the cut grooves given to the intermediate product is performed by trimming or piercing the portion corresponding to the original plate thickness of the metal plate material. It is surely reduced than the shearing force when applied. Therefore, according to this method, it is possible to relatively easily trim and pierce the intermediate product after shaping and quenching.

  The invention of claim 2 is directed to a metal plate material by pressing the metal plate material in a high temperature state by the heating using a relatively low temperature press die, and heating the metal plate material to a predetermined high temperature. In the method for manufacturing a vehicle frame member, comprising: a die quenching step for performing shape imparting and quenching simultaneously; and a finishing step for trimming or piercing the intermediate product obtained by the die quenching. A step in the plate thickness direction along the planned line of trim or piercing is simultaneously formed on the metal plate material by a mold, and in the finishing step, trim processing or piercing is performed along the step in the plate thickness direction. This is a method for manufacturing a vehicle skeleton member.

  According to the method of claim 2, a step in the plate thickness direction along a predetermined line of trim or piercing is applied to the metal plate material in accordance with the shape imparting and quenching to the metal plate material in a high temperature state by heating. Are simultaneously molded. Since the strength and hardness of a metal plate in a high temperature state is significantly lower than before heating, a step in the plate thickness direction along the planned line of trim or piercing is simultaneously applied to the metal plate using a die quench press die. It is easy to mold. In addition, due to the quenching effect of the relatively low temperature press die, the strength and hardness of the intermediate product (pre-molded product) are dramatically increased compared to the original strength and hardness of the metal plate material as the starting material. The thickness of the step portion in the thickness direction is thinner than the thickness of the other portion (that is, the original plate thickness of the metal plate material). For this reason, in the finishing process, the shearing force when trimming or piercing is performed along the step in the plate thickness direction given to the intermediate product is trimmed to the portion corresponding to the original plate thickness of the metal plate material. Or it is reliably reduced rather than the shear force at the time of piercing. Therefore, according to this method, it is possible to relatively easily trim and pierce the intermediate product after shaping and quenching.

  According to a third aspect of the present invention, in the method for manufacturing a vehicle frame member according to the first or second aspect, in the finishing step, another press die having a cutting edge portion along a predetermined line of trim or piercing is used. Trimming or piercing is performed.

  According to the method of claim 3, by using another press die having a cutting edge portion along the planned line of trim or piercing, the cut groove or the step in the plate thickness direction along the planned line of trim or piercing is formed. Trimming or piercing is performed on a pre-applied intermediate product, so trimming or piercing can be completed with a single press operation, and processing time can be shortened. Moreover, since the press die with a cutting edge can be prepared at a relatively low cost, the equipment cost will not increase.

(Additional remark) The further preferable aspect and additional component of this invention are enumerated below.
A. In Claims 1-3, the “predetermined high temperature” in the heating step is a temperature of 850 ° C. to 1050 ° C., and the “metal plate in a high temperature state” in the die quench step is a high temperature of 850 ° C. or higher. The metal plate is in a state.

  B. In Claims 1-3, the said metal plate material is 0.18-0.25 wt% carbon (C), 0.15-0.35 wt% silicon (Si), 1.15-1.40 wt% manganese. (Mn), 0.15-0.25 wt% chromium (Cr), 0.01-0.03 wt% titanium (Ti) and 0.0005-0.0025 wt% boron (B) And a high-tensile steel plate having a thickness of 1.0 to 3.2 mm and a tensile strength of 500 to 600 MPa.

  In the case of (b) or (b) described above, the strength and hardness of the intermediate product are dramatically increased by the quenching effect by die quenching, so the necessity of the present invention is very high.

  According to the vehicle frame member manufacturing method described in each claim, trimming and piercing can be relatively easily performed on the intermediate product after shaping and quenching. Therefore, the vehicle frame member indispensable for finishing such as trimming and piercing can be reliably manufactured while significantly reducing the time, facility cost and manufacturing cost required for the processing.

  The present invention is applied to the manufacture of various vehicle skeleton members that construct passenger cabin spaces such as shown in FIG. Examples of the vehicle skeleton member include a roof side rail 1, a roof reinforcement 2, a door reinforcement 3, an A pillar 4 and a B pillar 5. Of these, the roof side rail 1 is generally configured by overlapping a roof side rail inner panel disposed on the indoor side and a roof side rail outer panel disposed on the outdoor side. The edge portions of the inner and outer panels are portions that define the upper edge 1a of the opening of each of the front and rear doors, and are provided with resin or rubber door opening trims. End face accuracy) is required. Hereinafter, a specific example of a method for manufacturing the roof side rail inner panel 10 will be described with reference to the drawings.

  2 and 3B show the final finished state of the roof side rail inner panel 10. A roof side rail inner panel 10 as a final product includes a long main body 11, a flange-like upper joint 12 and a lower joint that are joined to a roof side rail outer panel (not shown) on the upper and lower sides of the main body 11. A long metal panel member having a portion 13 and a plurality of lightening holes 14 arranged in series at the center of the main body 11 and having an uneven cross-sectional shape as shown in FIG. It is. The roof side rail inner panel 10 having such a shape is manufactured through a plurality of processes as described below.

  First, a very long and flat rectangular metal plate is prepared as a starting material. The metal plate material was developed as a high-tensile steel plate for die quenching (hereinafter referred to as “high-strength steel plate A”), 0.18 to 0.25 wt% carbon (C), 0.15 to 0 .35 wt% silicon (Si), 1.15 to 1.40 wt% manganese (Mn), 0.15 to 0.25 wt% chromium (Cr), 0.01 to 0.03 wt% titanium (Ti) , 0.0005 to 0.0025 wt% of boron (B), 0.03 wt% or less of phosphorus (P), 0.01 wt% or less of sulfur (S), etc. . The weight percent range of each additive element is the quality control range itself in the high-tensile steel plate A. The high-tensile steel plate A has a melting point of about 1300 to 1400 ° C. and exhibits a tensile strength of 500 to 600 MPa in a plate thickness range of 1.0 to 3.2 mm. In this embodiment, a high-tensile steel plate A having a plate thickness t1 = 1.6 mm and a tensile strength of 590 MPa was used.

  Next, a long high-strength steel plate A (plate thickness: 1.6 mm, tensile strength: 590 MPa) is sealed in a heating device, and a target temperature within a range of 850 ° C. to 1050 ° C. (900 ° C. in this embodiment). Heated. In the present embodiment, an electric furnace is used as a heating device, and the inside of the electric furnace is an inert gas atmosphere (for example, a nitrogen gas atmosphere). The temperature is gradually raised from room temperature to reach the target temperature, and the target temperature is set for a little time. Held. The target heating temperature of the high-tensile steel plate A is preferably in the range of 850 ° C to 1050 ° C. When the heating temperature is lower than 850 ° C., the strength improvement by die quenching is insufficient. On the other hand, when the heating temperature exceeds 1050 ° C., not only does the strength increase due to die quenching corresponding to that increase, but the heating temperature is too high, which promotes the coarsening of the metal crystal and links the crystal structure. On the other hand, it becomes rough and rather the strength tends to decrease. In addition, the tensile strength of the high-tensile steel plate A heated to 900 ° C. is reduced to about 100 MPa.

  Subsequently, the long high-tensile steel plate A heated to the target temperature was conveyed at high speed from the heating device to the forming press machine, and immediately subjected to die quenching by the press machine. That is, the time until the high-tensile steel sheet A is taken out of the heating device, set in the press and started to be pressed is within 5 seconds so that the temperature of the high-tensile steel sheet A immediately before pressing does not fall below 850 ° C. . On the other hand, the temperature of the fixed mold and the movable mold constituting the molding press was kept at room temperature (for example, 20 to 30 ° C.). This is intended to ensure that a suitable temperature difference is ensured between the high-tensile steel plate A in a high temperature state and a normal temperature press die, and that quenching is effectively performed during pressing. In this embodiment, the press pressure is set to about 5,000 MPa, and the time required for one pressing process until the movable mold moves from the top dead center position to the bottom dead center position and returns to the top dead center position is 5 seconds. Within. By this die quenching, an intermediate product (pre-formed product of the roof side rail inner panel 10) as shown in FIG. 3A was obtained.

  One of the fixed die and the movable die of the molding press used for die quenching (in this embodiment, the movable die) is provided with cut grooves (16, 17, 18) for the high-tensile steel plate A during pressing. A linear or annular protrusion (or a group of protrusions) for forming is provided. For this reason, as shown in the cross-sectional view of FIG. 3A, the upper side portion, the main body portion, and the lower side portion of the intermediate product are provided with cut grooves (16, 17, 18) simultaneously with the die quench. Since the strength and hardness of the high-strength steel plate A in a high temperature state are significantly lower than before heating, the simultaneous formation of the cut grooves is easy.

  The cut grooves 16 and 17 respectively provided on the upper side and the lower side of the intermediate product extend linearly along a planned line of trim processing (border processing) in the finishing process described later. That is, the upper side cut groove 16 is located at the boundary between the upper joint 12 and the remaining material 12a in the final product (that is, excess burr material to be cut, the same applies hereinafter), and the lower side cut groove 17 is formed in the final product. It is located at the boundary between the lower joint 13 and the remaining material 13a. Further, the cut groove 18 provided in the main body of the intermediate product extends in a closed ring shape along a planned line for piercing (drilling) in a finishing process described later. That is, the cut groove 18 of the main body is located at the boundary between the main body 11 and the remaining material 14a (that is, the surplus material that fills the lightening holes 14) in the final product.

  As shown in FIG. 4, the cut groove 18 of the main body has a wedge shape in cross section, and the cut depth d is about 1.0 mm. Accordingly, the remaining thickness t2 at the deepest portion of the cut groove 18 is about 0.6 mm with respect to the thickness t1 of the main body (thickness t1 of the high-tensile steel plate A = 1.6 mm). This remaining thickness t2 of about 0.6 mm has a problem that the pre-formed product with the remaining material is undesirably deformed when the pre-formed product with the remaining material (intermediate product) is taken out from the press machine, that is, the next finishing process is hindered. It is the thickness which can avoid producing the excessive deformation | transformation to come. The cut depth d and the remaining thickness t2 in the cut grooves 16 and 17 on the upper side and the lower side are also set to substantially the same values as the cut groove 18.

  The temperature of the intermediate product immediately after taking out from the press machine is 100 to 200 ° C., but after that, it is naturally cooled and reaches near normal temperature. In addition, when taking out from the press machine, the spring back of the intermediate product (a phenomenon in which the product shape partially returns after removing the mold) was hardly seen. Further, due to the quenching effect on the high-tensile steel sheet A, the tensile strength of the main body of the intermediate product was improved to about 1470 MPa.

  Finally, trimming along the cut grooves 16 and 17 and piercing along the cut grooves 18 were performed on the intermediate product of FIG. In this embodiment, by performing a finishing process using a second press die for finishing having a plurality of cutting edge portions along the planned trimming line and the planned piercing line, all remaining materials 12a, 13a and 14a were separated at a time, and trimming and piercing were completed simultaneously with a one-time press operation. Thus, the roof side rail inner panel 10 as a final product as shown in FIGS. 2 and 3B was finished.

  As described above, according to the present embodiment, the strength and hardness of the intermediate product jumps compared to the original strength and hardness of the high-strength steel sheet A as the starting material by die quenching that simultaneously performs shaping (shape imparting) and quenching. However, at the time of die quenching, the cut grooves 16 to 18 as described above are simultaneously formed with respect to the intermediate product, and the remaining thickness t2 of each cut groove portion is clearly thinner than the thickness t1 of the other portions. . Therefore, the shearing force when trimming and piercing is performed along the cut grooves 16 to 18 given to the intermediate product using the second press machine is performed on the portion of the thickness t1 by trimming or piercing. It is surely reduced than the shearing force when processing. Therefore, according to this embodiment, it is possible to relatively easily trim and pierce the intermediate product after shaping and quenching.

  Further, according to the present embodiment, the trim processing and the piercing processing for the intermediate product can be completed by a one-time press operation by the second press die for finishing processing, so that the processing time can be greatly shortened. For the second press die with a cutting edge portion, the cost for producing the die is relatively low, and the equipment cost is not increased. Furthermore, since the roof side rail inner panel 10 as the final product obtained in the present embodiment is excellent in dimensional accuracy without springback, the end surface accuracy of the portion defining the upper edge 1a of the door opening is high. .

(Modification) The embodiment of the present invention may be modified as follows.
In the above embodiment, as shown in FIG. 4, the cross-sectional shape of the cut groove 18 and the like is a wedge shaped isosceles triangle, but instead, as shown in FIGS. 5 (A) and 5 (B), the cut is made. The cross-sectional shape of the groove G may be a right triangle shaped wedge. Moreover, as shown to FIG. 5 (C) and (D), the notch groove G may be formed in both the front side and back side of a metal plate material.

  In the above-described embodiment, the cut grooves 16 to 18 along the planned line of the trim or the piercing are simultaneously formed on the metal plate material at the time of die quench by the forming press machine, but instead of such a cut groove, for example, FIG. As shown to A) and (B), you may form simultaneously the level | step difference S along the planned line of a trim or a piercing with respect to a metal plate material. Each level difference S on the front side and the back side of the metal plate material is a result of partial shearing of the metal plate material when pressed by a press, resulting in the metal plate material being displaced in the direction of the plate thickness t1. The thickness t2 is thinner than the original plate thickness t1 of the metal plate material. Such a step S also contributes to a reduction in shearing force in trimming or piercing of an intermediate product using the second press die for finishing.

  In the above embodiment, the temperatures of the fixed mold and the movable mold constituting the molding press are set to room temperature, but the fixed mold and the movable mold are kept at a temperature lower than the normal temperature by using a cooling means (for example, a water-cooled pipe). You may do it. By actively cooling in this way, the temperature difference between the high-tensile high-strength steel sheet A and the press die is increased, and the quenching effect at the time of die quenching can be enhanced as compared with the above embodiment.

  (Definition) In this specification, the “vehicle frame member” refers to the original vehicle frame member represented by the roof side rail 1, the roof reinforcement 2, the door reinforcement 3, the A pillar 4, the B pillar 5, and the like. In addition to this, a member similar to a vehicle skeleton member such as a vehicle collision reinforcement represented by a bumper reinforcement, a door beam or the like is also included.

The perspective view which shows the outline of the vehicle frame | skeleton which builds the passenger room space of a passenger car. The front view of a roof side rail inner panel (final product). 2A and 2B are cross-sectional views taken along the line XX of FIG. 2, wherein FIG. 2A is a cross-sectional view of an intermediate product obtained by die quenching a metal plate, and FIG. 2B is a trim process and a piercing process performed on the intermediate product. The cross-sectional view of the final product obtained by giving. The figure which expands and shows the part enclosed with the round broken line of FIG. 3 (A). (A)-(D) are the figures which show the variation of the notch groove G along the planned line of a trim or piercing. (A) And (B) is a figure which shows the variation of the level | step difference S to the plate | board thickness direction along the planned line of trim or piercing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Roof side rail inner panel (vehicle frame member), 16, 17 ... Cut groove for trim processing, 18 ... Cut groove for piercing, G ... Cut groove, S ... Step in thickness direction, t1 ... Plate Thickness, t2 ... remaining thickness.

Claims (3)

A heating step of heating the metal plate to a predetermined high temperature;
A die quench step of simultaneously performing shape imparting and quenching on the metal plate material by pressing the metal plate material in a high temperature state by using a relatively low-temperature press die;
In the manufacturing method of the vehicle frame member comprising a finishing step of trimming or piercing the intermediate product obtained by the die quench,
In the die quenching step, a cut groove along a predetermined line of trim or piercing is simultaneously formed on the metal plate material by the press die, and in the finishing step, trimming or piercing is performed along the cut groove. A method for manufacturing a vehicle skeleton member characterized by A heating step of heating the metal plate to a predetermined high temperature;
A die quench step of simultaneously performing shape imparting and quenching on the metal plate material by pressing the metal plate material in a high temperature state by using a relatively low-temperature press die;
In the manufacturing method of the vehicle frame member comprising a finishing step of trimming or piercing the intermediate product obtained by the die quench,
In the die quenching step, a step in the plate thickness direction along the planned line of trim or piercing is simultaneously formed on the metal plate material by the press die, and in the finishing step, along the step in the plate thickness direction. A method for manufacturing a vehicle frame member, wherein trimming or piercing is performed.   3. The vehicle skeleton member according to claim 1, wherein in the finishing step, trimming or piercing is performed using another press die having a cutting edge portion along a predetermined line of trim or piercing. Manufacturing method.

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