Method for producing steel sheet part and production plant
By heating locally on the stamping end face of the steel plate component, residual stress is reduced, and the problem of delayed fracture of high-strength steel plate components is solved, thereby realizing the overall strength of the component and the prevention of delayed fracture.
Patent Information
- Application Number
- CN202411468383.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-10-10
- Filing Date
- 2024-10-21
- Publication Date
- 2025-04-25
AI Technical Summary
When using high-strength steel plates to make steel plate parts, delayed fractures are prone to occur, especially when there is high residual stress on the stamping end surface.
By heating locally on the stamping end face of the steel plate component, high-frequency AC power supply is heated using a heating electrode (such as a coil) directly opposite the stamping end face, reducing residual stress to prevent delayed fracture.
This method can effectively reduce residual stress of steel plate components, prevent delayed fracture, and maintain the overall strength of the components.
Smart Images
Figure CN119876540A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a method for manufacturing a steel sheet component and a manufacturing apparatus. Background Art
[0002] Reducing the weight of a vehicle is an important challenge to increase the cruising range in the case of a BEV (Battery Electric Vehicle) and to improve fuel efficiency in the case of a conventional vehicle and thereby reduce CO2 emissions. Therefore, studies have been conducted to integrate multiple parts into one component by using a high-strength steel sheet and to reduce the wall thickness of such a component. Summary of the invention
[0003] One of the problems that occurs when using high-strength steel sheets is delayed fracture. Delayed fracture is a phenomenon in which a metal material that has been subjected to a constant tensile load suddenly fails after a certain period of time has passed.
[0004] It is known that such delayed fracture occurs due to the synergistic effect of the combination of corrosive environment and material and tensile stress. In sheet metal parts, delayed fracture may occur in the stamped end face due to high residual stress remaining in the stamped end face, thus posing a major obstacle to the increased use of high-strength steel sheets. Therefore, in conventional sheet metal parts, for parts with a high risk of delayed fracture, only one of the following methods can be selected, namely, avoiding the use of high-strength steel sheets, avoiding corrosive environments, and adopting a structure without residual stress.
[0005] In the method disclosed in Japanese Patent No. 7207283, there is disclosed a technique for improving flange ductility by clamping the edge end surface of a steel sheet with electrodes, feeding current therethrough, and thereby heating a region near the edge of the steel sheet.
[0006] However, in order to stabilize the heating range, regular maintenance of the electrodes is required, which increases the cost of the electrodes and requires a large number of processes for maintenance and quality control. In addition, since this technology uses a structure in which the unheated part is sandwiched between the upper and lower electrodes, the unheated surface can be in the vertical direction. In addition, when the unheated surface, etc. has a complex shape, it cannot be heated in some cases. In addition, according to Japanese Patent No. 7207283, induction heating is also possible. However, in this case, the heating coils are arranged above and below the working plane (the electrodes are arranged opposite to each other). This method is inefficient because the heating range is wide, and it is impossible to perform local heating, in which only the area near the edge is accurately heated.
[0007] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a method for manufacturing a steel plate component, etc., which can simultaneously maintain the overall strength of the component and prevent the occurrence of delayed fracture.
[0008] The method for manufacturing a steel plate component according to one aspect of the present disclosure is characterized in that the steel plate component is locally heated by a heating electrode disposed on one side of the steel plate component and spaced apart from and directly opposite to a stamping portion of the steel plate.
[0009] A manufacturing apparatus for a steel plate component according to one aspect of the present disclosure includes:
[0010] High frequency AC (alternating current) power supply;
[0011] a coil connected to the high frequency AC power source; and
[0012] A mounting base on which the steel plate is mounted, wherein
[0013] The mounting base is configured so that when the steel plate is mounted thereon, the processed portion of the steel plate is directly opposed to the coil, and
[0014] The manufacturing apparatus is configured to perform the above-mentioned manufacturing method.
[0015] According to the present disclosure, it is possible to provide a method, an apparatus (system), and the like for manufacturing a steel plate component, which are capable of simultaneously maintaining the overall strength of the component and preventing the occurrence of delayed fracture.
[0016] The above and other objects, features and advantages of the present disclosure will be more fully understood from the detailed description and accompanying drawings given below. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 is a schematic perspective view for explaining a method for manufacturing a steel plate component according to the present disclosure;
[0018] Figure 2 1 is a diagram for explaining each step in the method for manufacturing a steel plate component according to the embodiment.
[0019] Figure 3 shows diagrams and photographs for explaining an evaluation method of a hydrochloric acid immersion test according to an embodiment;
[0020] Figure 4 A diagram and a photograph for explaining evaluation results in a hydrochloric acid immersion test on a cutout portion not subjected to local heating according to a comparative example are shown;
[0021] Figure 5 A photograph for explaining an evaluation result in a hydrochloric acid immersion test on a cutout portion where local heating is performed according to one embodiment is shown;
[0022] Figure 6 Shown is a diagram for illustrating the Figure 2Figures and graphs showing the temperature distribution in the circumferential direction of the stamping end after local heating;
[0023] Figure 7 Shown is a diagram for illustrating the Figure 2 The diagram and graph of the temperature distribution in the vertical direction of the end surface of the stamping end after local heating are shown;
[0024] Figure 8 is a diagram for explaining an example of a portion to be subjected to local heating according to an embodiment;
[0025] Fig. 9 is a diagram for explaining another example of a portion to be subjected to local heating according to an embodiment; and
[0026] Fig.10 is a diagram for explaining an example of an apparatus (system) for local heating using a laser beam according to another embodiment; and
[0027] Fig.11 It is a plan view for explaining the shape of the punch end and the coil. DETAILED DESCRIPTION
[0028] The following will refer to Figure 1 An overview of a method for manufacturing a steel sheet component according to the present disclosure is described.
[0029] A method is provided in which the residual stress is reduced by locally heating the punching end portion 20 of a high-strength steel sheet that initially has a high residual stress, thereby preventing the occurrence of delayed fracture.
[0030] Therefore, the method for manufacturing a steel plate component according to the present disclosure is characterized in that the processed portion of the steel plate (e.g., the punch end portion 20) is locally heated by a heating electrode (e.g., a coil) that is spaced apart from and directly opposite to the processed portion. In this specification, the expression "directly opposite" means that, for example, the processed portion of the steel plate (e.g., the punch end portion 20) and the heating electrode (e.g., the coil) can be arranged substantially or approximately parallel to each other, with a distance of 10 millimeters (mm) or less therebetween and do not contact each other. Figure 1 As shown, the processed portion of the steel plate (e.g., the punch end 20) protrudes toward the heating electrode (e.g., the coil) and extends in a cylindrical shape. In other words, the protruding top end (punching end face) and the heating electrode (e.g., the coil) can be arranged in a non-contact state and are approximately parallel to each other within 10 mm.
[0031] More specifically, the stamped end 20 of a high-strength steel sheet having a tensile strength grade of 780 MPa or more can be heated at 500 to 830° C. for a short period of time of 10 seconds or less. In this way, residual stress can be reduced and delayed fracture can be prevented from occurring. In this process, high-frequency induction heating is preferably used to locally heat the stamped end 20 for a short period of time. The number of turns of the coil can be set arbitrarily, but a coil having at least two turns is preferably overlapped with the stamped end 20 (for example, placed above or below the stamped end 20), such as Figure 1 Furthermore, by disposing the coil 10 directly opposite to the punching end 20 , the punching end 20 can be heated intensively, and deformation of the panel 2 can be minimized.
[0032] Although residual stress can be reduced and delayed fracture can be prevented even when the length of heating is 10 seconds or longer, the heat-affected portion (of the panel 2) spreads over a wide area due to heat transfer and may reduce the strength of the component. Therefore, it is preferable to complete the heating in as short a period of time as possible.
[0033] First embodiment
[0034] Embodiments according to the present disclosure will be described below with reference to the accompanying drawings.
[0035] Figure 2 It is a diagram for explaining each step (installation, heating, and removal) in a method for manufacturing a steel plate component.
[0036] Four L-shaped mounting bases 11 are provided at or near the center of the upper surface of the rectangular base portion 12, and the long narrow steel plate member 2 is mounted on the mounting bases 11. Further, on the upper surface of the rectangular base portion 12, two coils 10 are provided at both ends on the diagonal line of the base portion 12. An AC (alternating current) power source 15 that generates a high-frequency induced electromotive force by feeding an AC current through the coil 10 (i.e., each coil 10) is connected to the coil 10.
[0037] Punched ends 20 are provided on both ends of the long narrow steel plate member 2. Each punched end 20 is obtained by forming a hole in a raw material and performing a process for stretching (or forming) the edge of the hole into a cylindrical shape. This process is also called deburring.
[0038] When the long narrow steel plate member 2 is mounted on the four L-shaped mounting bases 11, the two stamped ends 20 at both ends of the steel plate member 2 are positioned directly opposite to the coil 10, respectively, and are approximately parallel to the coil 10. A positioning mechanism (e.g., Figure 2The pin hole 23 in the steel sheet component 2 and the pin 13 in the base portion 12 as shown are arranged so that the steel sheet component 2 is directly opposite to the coil 10 in a substantially parallel manner. The axes of the two coils 10 may be perpendicular to the upper surface of the base portion 12. They are aligned so that the outermost portions of the coils 10 partially overlap with the stamped end portions 20 (for example, placed above or below the stamped end portions 20), respectively. In this way, heating of the panel 2 is suppressed, and the stamped end portions 20 are locally heated. The diameter of the coil (i.e., each coil) is slightly larger than the diameter of the stamped end portion 20 (i.e., each stamped end portion 20). The coil may be a coiled copper tube (or a copper coil). As Fig.11 As shown, the coil diameter CD can be at most equal to or shorter than the sum of the diameter PED of the stamped end and the length corresponding to the tube diameter PD of the two tubes P forming the coil. In this way, the stamped end can be prevented from being widely heated to the area outside the stamped end, thereby more appropriately heating the stamped end locally. In addition, the input end S and the output end E of the coil are arranged on one radius (one side) of the coil extending from the center O of the coil along the diameter L of the coil. In this way, more uniform heating can be achieved by arranging the turns of the coil approximately uniformly over the entire stamped end. As a result, delayed fracture can be prevented. The coil 10 can be, for example, a coil having two or more turns for the stamped end 20 in order to ensure a sufficient magnetic field for rapid heating. The only turn of the coil is not connected to each other at its folded portion (that is, the input end S and the output end E are not connected to each other). The magnetic field propagates only in this discontinuous portion, so that the current density does not increase. As a result, the temperature rise at this portion becomes lower, so that a temperature change occurs as a whole. Therefore, uniform heating can be achieved by using a coil having two or more turns. As a result, delayed fracture in this discontinuous portion can be prevented. As Figure 1 and Figure 2 As shown, a coil having at least two turns overlaps the punching end 20 (ie, each punching end 20). Thereafter, the AC power source 15 is turned on, and AC current is fed through each coil 10. As a result, a high-frequency induced electromotive force is generated, and the punching ends 20 at both ends of the steel plate part 2 are locally heated.
[0039] After the punched end 20 is heated for a short period of time (e.g., 10 seconds or less) by using the above-mentioned manufacturing apparatus (local heating apparatus) for steel sheet components, the AC power source 15 is turned off and the steel sheet component 2 is removed. The punched end 20 of the steel sheet component 2 is uniformly heated (the details of which will be described later).
[0040] According to the first embodiment, since the deformation of the high-strength steel sheet (which would otherwise be caused by the heating process, etc.) is eliminated by using high-frequency induction heating, delayed fracture can be prevented from occurring. Local heating is performed at 500 to 830°C for a short period of time of 10 seconds or less. By locally heating the stamping end with a coil directly opposite to the stamping end face, softening of the entire component can be prevented and the strength of the component can be maintained. Thermal deformation of the panel can be suppressed by the arrangement of the coil, wherein the coil is directly opposite to the stamping end face. In any step after the stamping step or before the spraying step, the above reference Figure 2 The heating of the stamping end surface. Note that in other embodiments, the local heating step may be performed during the stamping step (ie, included in the stamping step).
[0041] Will refer to Figures 3 to 5 A hydrochloric acid immersion test performed on a fabricated steel sheet component is described.
[0042] A high-strength steel plate was prepared, which was cut into a rectangular shape in which bolt holes 35 were formed at both ends by a drill. A cutout of R5 was formed at the center of the high-strength steel plate by a stamping process, and its edge was bent at a bending angle of 90 degrees so that the end became R6. After that, stress was applied to the apex of this bend (hereinafter also referred to as the bending apex) by tightening the bolt, and a hydrochloric acid immersion test (PH3, 100H) was performed.
[0043] Figure 3 A process for evaluating delayed fracture in bending is shown. 1) A blank 30 having a rectangular shape (C110mm x L30mm) is prepared. A notch 31 of R5 is formed by punching at the center of the blank in the longitudinal direction. 2) A V-shaped bend 32 (end R6, bend angle 90°) is formed near the notch 31 of the blank 30. 3) The stress occurring at the bend apex 34 is adjusted by tightening a bolt 33 inserted into a bolt hole 35. 4) A hydrochloric acid immersion test (PH3, 100H) is performed to evaluate delayed fracture in bending.
[0044] When the end face is heated according to this embodiment, local heating is performed which becomes part of the cutout 31 when the blank is manufactured.
[0045] Figure 4 There are shown diagrams and photographs for explaining evaluation results in a hydrochloric acid immersion test for a notched portion according to a comparative example to which local heating was not performed.
[0046] Figure 4 Each of the photos shown in the figure is an enlarged photo of the bending apex when the bolt is tightened to 4mm, 8mm, 12mm, 16mm, and 20mm. Figure 4As shown in the figure, when the tightening amount of the bolt is 4mm, 8mm or 12mm, no crack is formed at the bending apex. On the contrary, when the tightening amount of the bolt is 16mm or 20mm, a crack is formed at the bending apex.
[0047] Figure 5 There are shown photographs for explaining the evaluation results in the hydrochloric acid immersion test for the cutout portion subjected to local heating according to the first embodiment.
[0048] According to this embodiment, the cutout portion 31 is locally heated to each of 400° C., 600° C., and 800° C. and then naturally cooled.
[0049] When the tightening amount is 16mm or 20mm, the hydrochloric acid immersion test is carried out (under the condition that cracks occur without heating, such as Figure 4 as shown).
[0050] like Figure 5 As shown, when the tightening amount of the bolt is 16 mm, no cracks occur at the bending apex at any of 400°C, 600°C and 800°C. In contrast, when the tightening amount of the bolt is 20 mm, cracks that penetrate (i.e., extend through) the bending apex occur at 400°C. When the tightening amount of the bolt is 20 mm, cracks that do not penetrate the bending apex occur even at 600°C. When the tightening amount of the bolt is 20 mm, no cracks occur at the bending apex at 800°C. That is, when the tightening amount of the bolt is 20 mm, the cracks can be reduced (i.e., alleviated) by increasing the heating temperature of the local heating according to this embodiment, and the formation of cracks can be prevented at 800°C. As described above, by adopting the local heating according to this embodiment, delayed fracture can be prevented or suppressed. Note that the required temperature may vary depending on the material and residual stress conditions.
[0051] Will refer to Figure 6 and Figure 7 CAE (Computer Aided Engineering) analysis describing heating temperatures.
[0052] After feeding an AC current with a frequency of 240 kHz at a constant voltage of 200 V for 1 second, the temperature rise at the punch end was analyzed.
[0053] Figure 6 Shown is a diagram for illustrating the Figure 2 The diagram and graph show the temperature distribution in the circumferential direction of the punch end portion 20 after local heating. Figure 6 The figure shown in the upper part of shows the CAE analysis of the heating temperature when the stamping end is viewed from above. After the stamping end is heated for one second, the temperature rises to a maximum temperature of 450°C at and around the end surface. Figure 6As shown in the graph shown in the lower part of , the temperature at the central portion of the end face has a temperature distribution with a maximum value equal to or lower than 70°C even within one circumference of the end face portion, indicating that the temperature difference is small and stable. As described above, in the arrangement provided with the punch end portion 20, the punch end portion 20 can be heated approximately uniformly by locally heating the punch end portion 20 by high-frequency induction heating of the coil 10 so that it is directly opposed to the coil 10 approximately in parallel.
[0054] Figure 7 Shown is a diagram for illustrating the Figure 2 The temperature distribution in the vertical direction of the end surface of the stamping end 20 after local heating is shown in the figure and the curve diagram. Figure 7 The drawing shown in the upper part of shows a CAE analysis of the heating temperature when the punch end is viewed obliquely from above.
[0055] Repeat the temperature measurement by lowering the measuring point 0.5 mm at a time from the corner of the upper surface along the outer periphery of the end surface. Figure 7 As shown in the graph shown in the lower part of , the temperature of the remaining part returns to about 6 mm from the corner of the upper surface, so it is considered that the influence of heat is limited to the inside of the vertical flange part and the influence on the strength of the component is small. Therefore, by heating the deburring part, that is, the stamping end 20, by using local heating according to this embodiment, the overall strength of the component can be maintained and delayed fracture can be prevented.
[0056] Heating target part
[0057] The part to which the method according to the present disclosure is applied is a part made of a high-strength steel plate having a tensile strength grade of 780 MPa or more, and the part has been subjected to a large strain caused by stamping or bending. In addition, the method is mainly applied to a part to which a tensile stress is applied when the part is used and the part is expected to be used in a part where a large amount of ambient hydrogen exists, such as in a corrosive environment. Examples of specific target parts include the parts shown below.
[0058] Figure 8 A bushing press-fitting portion of an arm or the like is shown, which is an example of a portion to be heated.
[0059] In an arm such as a rear control arm, there is a press-fit portion 20a (an example of a processed portion made of a steel plate) used by press-fitting one bushing. Since such a portion is formed by hole expansion molding after a stamping process, a very high residual stress remains. In addition, since a tensile residual stress is applied by press-fitting of the components, delayed fracture may be caused (i.e., may occur). Therefore, the local heating method according to the present disclosure can also be applied to the bushing press-fit portion processed as described above.
[0060] Fig. 9 A bolt tightening portion of an exchange arm or the like is shown, which is an example of a heating target portion.
[0061] The exchange arm is usually fastened with bolts. In addition to the residual stress caused by the punching process of the tightening hole, due to the poor surface accuracy of the tightening surface in the bolt tightening part 20b (an example of a processed part made of a steel plate), tensile residual stress may occur during tightening, so that delayed fracture may be caused (i.e., may occur). Therefore, the local heating method according to the present disclosure can also be applied to the bolt tightening part processed as described above.
[0062] Note that, in general, residual stress may increase near the boundary between the shear surface and the fracture surface in the stamping end face. In which part of the stamping end face the boundary portion is formed depends on the material and the plate thickness. Local heating according to this embodiment is preferably performed near the boundary.
[0063] Fig.10 is a diagram for explaining an example of an apparatus for local heating by a laser beam according to another embodiment.
[0064] In the case of laser heating, similar effects to those of the above embodiment can also be obtained. For example, the laser source 40 is attached to the end of the arm of the six-axis robot 50. As described above, the laser source 40 can emit a laser beam while moving the laser beam in a circumferential direction along the punching end.
[0065] Note that the present disclosure is not limited to the above-described embodiments, and they can be modified appropriately without departing from the scope and spirit of the present disclosure.
[0066] From the disclosure thus described, it will be apparent that the embodiments of the present disclosure may be varied in many ways. Such variations should not be considered as departing from the spirit and scope of the present disclosure, and all such modifications obvious to those skilled in the art are intended to be included within the scope of the appended claims.
Claims
1. A method for manufacturing a steel sheet component, wherein: The steel plate component is locally heated by a heating electrode, which is disposed at one side of the steel plate component and is spaced apart from and directly opposed to a punching portion of the steel plate.
2. The method for manufacturing a steel sheet component according to claim 1, wherein: The steel plate is a high-strength steel plate having a tensile strength grade of 780 MPa or higher.
3. The method for manufacturing a steel sheet component according to claim 1, wherein: The steel plate is locally heated by high frequency induction for a short period of time of 10 seconds or less.
4. The method for manufacturing a steel sheet component according to claim 1, wherein: The heating temperature is 500 to 830°C.
5. The method for manufacturing a steel sheet component according to claim 1, wherein The processed portion of the steel plate is formed to protrude on one side of the steel plate by a stamping process, and The heating electrode is arranged to be directly opposite to the punching end surface, and the punching end surface is a top end formed as the processed portion protrudes.
6. The method for manufacturing a steel sheet component according to claim 1, wherein The processed portion of the steel plate is a bushing press-fitting portion formed by hole expansion molding after the stamping process, and The heating electrode is disposed directly opposite to the bushing press-fitting portion.
7. The method for manufacturing a steel sheet component according to claim 1, wherein The processed portion of the steel plate is a bolt tightening portion formed by a stamping process, and The heating electrode is disposed directly opposite to the bolt tightening portion.
8. The method for manufacturing a steel sheet component according to claim 1, wherein: The heating electrode is a coil larger than the punching portion, and the heating electrode has two or more turns with respect to the punching portion.
9. The method for manufacturing a steel sheet component according to claim 8, wherein: The outermost portion of the coil is disposed to be aligned with a punched end surface formed by a punching process.
10. The method for manufacturing a steel sheet component according to claim 8, wherein: The coil is a coiled tube coil, and a diameter of the coiled tube coil is equal to or smaller than the sum of a diameter of the punched end portion and a length corresponding to twice a tube diameter PD of the coiled tube coil.
11. The method for manufacturing a steel sheet component according to claim 8, wherein: The input and output of the coil are arranged on a radius of the coil from the center of the coil.
12. A manufacturing device for steel plate components, comprising: High frequency AC (alternating current) power supply; a coil connected to the high frequency AC power source; and A mounting base to which the steel plate component is mounted, wherein The mounting base is configured so that when the steel plate member is mounted on the mounting base, the processed portion of the steel plate is directly opposed to the coil, and The manufacturing apparatus is configured to carry out the method according to any one of claims 1 to 11.