KR20200064661A - Selective heating system and cold forming method using the same - Google Patents

Abstract

According to the present invention, disclosed are a local heat treatment system and a cold forming method using the same, which locally heat a plastically deformed portion through an external heat source and then cool the same to adjust physical properties, thereby improving moldability. According to one aspect of the present invention, the local heat treatment system comprises: a heating device which locally heats only a plastic deformation-occurring portion of a blank material to a constant temperature; a moving device moving the heating device to a position of a local heating area of the blank material; and a control device controlling the heating device and the moving device.

Description

Local heat treatment system and cold forming method using the same{Selective heating system and cold forming method using the same}

The present invention relates to a local heat treatment system and a cold forming method using the same, and more particularly, to a local heat treatment system capable of improving the formability of an ultra-high-strength steel sheet and minimizing the springback phenomenon and a cold forming method using the same.

In general, in order to improve the fuel efficiency of automobiles, the weight reduction of automobiles is effective, and thus, the use of high-tensile steel, a material having a high specific strength, has recently increased. The strength of these high-tensile steel sheets is improving, and in recent years, ultra-high-tensile strengths with tensile strength of 1 GPa or more have been developed.

Since this ultra-high-strength steel sheet has high strength, it is not easy to press-form, so the forming load is large, the mold wear is large, and seizing is likely to occur. In addition, ductility is low and cracks are likely to occur when tensile stress acts during molding.

Accordingly, methods have been developed to improve moldability by heating the entire molding material in order to improve the moldability of the ultra-high-strength steel sheet, which is a difficult-to-form material, and reduce the springback phenomenon. As an example, a method of improving moldability by heating the entire material, such as a warm forming process, has been applied. However, in the method of heating the entire hard-forming material, there is a problem in that unnecessary energy loss occurs by heating an area in which molding does not occur.

Due to the above-mentioned problems, a method of locally heating and forming only a portion requiring plastic deformation through a laser or a near infrared heating device has been proposed and used. However, since the material is heated in the warm forming process and then warmed, the productivity due to the heating time decreases, and the local heating part is rapidly cooled while handling the material, and thus there is a problem that it is difficult to maintain a constant quality.

Accordingly, there is an increasing demand for a method and apparatus for cold forming rather than warm forming in order to secure a certain quality without deteriorating productivity due to not heating in the forming process.

The local heat treatment system and the cold forming method using the same according to an embodiment of the present invention can improve the formability by controlling the physical properties by locally heating and cooling the part that is plastically deformed through an external heat source.

In addition, the local heat treatment system and the cold forming method using the same according to an embodiment of the present invention can reduce the springback by cold forming a material with controlled physical properties and improve productivity.

According to an aspect of the present invention, the heating device for heating only a portion of the plastic material generated plastic deformation locally to a constant temperature; A moving device for moving the heating device to a position of a local heating area of the blank material; And a control device controlling the heating device and the moving device.

In addition, the heating device, the housing coupled to the mobile device; A heat source coupled to the housing to emit near infrared rays; And a reflector provided in the housing to reflect near-infrared rays generated from the heat source and converge into a local heating region.

In addition, the moving device, a rotary joint coupled to the heating device; And a plurality of moving members coupled to the rotating joint to move the heating device in a three-axis (x, y, z) direction.

In addition, the plurality of moving members, the first moving member coupled to the rotary joint to transfer the heating device in the direction in which the blank material is provided; A second moving member coupled to the first moving member to convey the first moving member in a vertical direction; And a third moving member coupled to the second moving member and transferring the second moving member in a horizontal direction.

In addition, the moving device and the heating device are provided as one sub-assembly, and the sub-assembly is provided in plural so as to be locally heated on one side and the other side of the blank material, and each sub-assembly is the control device. Can be controlled independently.

In addition, the control device may control the moving device and the heating device by setting a local heating position, a heating temperature, and a heating time in consideration of strain and stress according to a molding shape during the molding process of the blank material.

According to another aspect of the present invention, as a method of cold forming using the local heat treatment system, (a) when a blank material is introduced into the local heat treatment system, the heating device is positioned to be located in the local heating region, which is a region of plastic deformation. Operating the; (b) when the heating device is located in the local heating region, heating a portion of the plastic deformation-generating portion of the blank material through a heating device to a predetermined temperature and cooling to locally control the physical properties of the material; And (c) cold-forming after transferring the blank material having controlled physical properties to a mold.

In addition, in step (a), the control device of the local heat treatment system sets the local heating position, heating temperature, and heating time in consideration of the strain and stress according to the shape to be formed during the molding process of the blank material to set the moving device. And a heating device.

The local heat treatment system and the cold forming method using the same according to an embodiment of the present invention have an effect of improving the moldability of the material by selectively heating the material locally using an external heat source and then cooling it to control physical properties.

In addition, it is possible to minimize the wear of the mold during cold forming by reducing the molding load as the physical properties are controlled by locally heating only the portion where plastic deformation occurs, and there is an effect of minimizing the springback phenomenon after cold forming.

In addition, as compared to the existing hot forming, it is possible to reduce energy costs, and also has an effect of improving productivity and quality.

In addition, by incorporating artificial intelligence (AI) and sensing technology, it is possible to easily and quickly process the material locally, thereby improving productivity, and to conveniently apply even with complicated molding shapes. There is.

The present invention will be specifically described by the following drawings, but these drawings represent preferred embodiments of the present invention and should not be construed as limiting the technical idea of the present invention only to the drawings.
1 is a view schematically showing a local heat treatment system according to an embodiment of the present invention.
2 is a view showing a state in which the local heat treatment system according to an embodiment of the present invention is operated.
3 is a perspective view specifically showing a moving device of the local heat treatment system shown in FIG. 2.
4 is a view showing a heating device provided in the local heat treatment system according to an embodiment of the present invention.
5 is a view showing a state of irradiating a heat source according to the shape of the reflector provided in the heating device shown in FIG. 4.
FIG. 6 is a view taken to compare a state in which the physical properties are adjusted by the local heat treatment system according to an embodiment of the present invention in a state of V bending molding and a state in which a conventional material is subjected to V bending molding.
7 is a view for comparing a state in which asymmetric molding of a material having physical properties controlled by a local heat treatment system and a conventional material according to an embodiment of the present invention.
8 is a view showing a comparison of a state in which a physical component is adjusted by a local heat treatment system according to an embodiment of the present invention, and a state in which a conventional component is molded.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are presented to sufficiently convey the spirit of the present invention to those of ordinary skill in the art. The present invention is not limited only to the embodiments presented herein, but may be embodied in other forms. In order to clarify the present invention, the drawings may omit the illustration of parts irrelevant to the description, and the size of components may be exaggerated to help understanding.

1 is a view schematically showing a local heat treatment system according to an embodiment of the present invention, FIG. 2 is a view showing a state in which the local heat treatment system according to an embodiment of the present invention is operated, FIG. 3 is in FIG. 2 It is a perspective view specifically showing a moving device of the illustrated local heat treatment system, and FIG. 4 is a view showing a heating apparatus provided in the local heat treatment system according to an embodiment of the present invention, and FIG. 5 is a heating apparatus shown in FIG. 4 It is a figure which shows the state which irradiates the heat source according to the shape of the provided reflector.

1 to 5, the local heat treatment system 1 according to an aspect of the present invention includes a heating device 100 and a heating device 100 that locally heats only the plastic deformation occurrence portion of the blank material 10 It includes a moving device 200 for moving to the location of the local heating area of the blank material 10, and a heating device 100 and a control device 300 for controlling the moving device 200.

Here, the blank material 10 is an ultra-high-strength steel material that is cut and provided to have a certain length in order to form a product through cold forming according to the present invention, and is a hard-forming material having a tensile strength of 1 GPa or more. Since the area where the actual plastic deformation occurs in the process of producing the blank material 10 as a product is local, the formability of the blank material 10 is improved by applying heat only to the area where the plastic deformation occurs using a separate external heat source. Can be improved. In other words, in order to improve the moldability of the material, it is important to focus the location where heat is applied only to the local area where plastic deformation of the blank material 10 occurs.

Meanwhile, it is more efficient to use the near-infrared heat source as an external heat source than other processes when bending the blank material 10. In addition, it is preferable to use a linear heat source because the bending molding is mostly linear.

Therefore, in the present invention, the heating apparatus 100 is used as an external heat source, but the temperature of the local area where plastic deformation occurs is increased by using a linear near-infrared heater to improve the bending property of the hard-forming material to form the material into a precise shape. Make it possible.

More specifically, as shown in FIG. 4, the heating device 100 includes a heat source 110 and a reflector 120. The heat source 110 may be provided as a lamp generating near infrared rays.

The heat source 110 is an electromagnetic wave having a wavelength of 700 to 1300 nm and is generated outside the red visible light. Since the heat source 110 is 90% or more radiant heat, it can be called high efficiency (efficiency 85% to 90%). Since the heat source 110 is near infrared, it does not burn air, so it can be used indoors as non-toxic, smokeless, odorless, and noiseless. The heat source 110 is very convenient to use because it only takes about 0.1 seconds to reach the maximum output.

The reflector 120 serves to reflect near infrared rays generated from a heat source and condense the local heating region. The reflector 120 may adjust a region in which near-infrared rays are irradiated linearly according to a shape. For example, the reflector 120 in an oval shape is illustrated in FIG. 5A, and the parabolic reflector 120 is illustrated in FIG. 5B. In the case of the oval reflector 120, the near infrared rays generated from the heat source 110 are reflected and condensed into one place, and the blank material 10 is linearly irradiated. In addition, in the case of the parabolic reflector 120, the near infrared rays generated from the heat source 110 are parallelized to irradiate the blank material 10 in a predetermined area. That is, according to the plastic deformation region of the blank material 10, a suitable reflector 120 may be applied to locally heat. In addition, various shapes of reflectors exist, so that each characteristic may be used differently. Therefore, the shape of the reflector 120 may be modified according to the purpose and used.

As described above, since the heating apparatus 100 using near infrared rays only needs to use the heat source 110 and the reflector 120, it is possible to locally heat the blank material 10 in one direction.

Meanwhile, the heating device 100 may further include a housing 130. The housing 130 serves to protect the heat source 110 and the reflector 120 from external impacts and prevent energy loss through heat insulation. The housing 130 is provided so that the heat source 110 and the reflector 120 are coupled, and has a partially open shape so that near infrared rays generated from the heat source 110 are irradiated in one direction through the reflector 120. In addition, the housing 130 may be combined with a moving device 200 to be described later.

The moving device 200 is coupled to the heating device 100 and serves to move the heating device 100 to the surface of the blank material 10 in the plastically deformed region. The moving device 200 includes a rotating joint 213 coupled to the heating device 100 and a plurality of moving members 210, 220, and 230 that move the heating device 100 in a three-axis direction.

The rotary joint 213 is coupled to the housing 130 of the heating device 100 and is provided to adjust the angle of the heating device 100. That is, the rotating joint 213 serves to smoothly converge near infrared rays to the blank surface 10 of the local heating region by adjusting the angle of the heating device 100. Since the structure of the rotating joint 213 is a well-known and well-known technique, detailed description thereof will be omitted.

The plurality of moving members 210, 220, and 230, the first moving member 210, the second moving member 220 to move the heating device 100 in the three-axis direction, that is, the x, y, z-axis direction It may be configured as a third moving member 230. For example, as illustrated in FIG. 3, the third moving member 230 is provided to move in the x-axis direction, the second moving member 220 is provided to move in the y-axis direction, and the first moving member 210 may be provided to move in the z-axis direction.

The first moving member 210 is coupled to the rotating joint 213 and is provided to transport the heating device 100 in the direction in which the blank material 100 is provided, that is, in the z-axis direction. The first moving member 210 may be provided to have a configuration of a hydraulic or pneumatic cylinder to move in one direction.

The second moving member 220 is coupled to the first moving member 210 and is provided to transport the first moving member 210 in the vertical direction, that is, in the y-axis direction. At this time, since the first moving member 210 is coupled to the heating device 100, the heating device 100 is moved together when the first moving member 210 is moved. The second moving member 220 may be provided to have a configuration of a hydraulic or pneumatic cylinder to move in one direction.

The third moving member 230 is coupled to the second moving member 220 and is provided to transport the second moving member 220 in the horizontal direction, that is, in the x-axis direction. At this time, since the second moving member 220 is coupled to the first moving member 210, the first moving member 210 is moved together when the second moving member 220 is moved. The third moving member 230 may be provided to have a coupling structure of a rack pinion gear that receives the rotational force of the motor 232 and converts it into a linear motion.

On the other hand, the first and second moving members 210 and 220 are shown as having a cylinder structure, and the third moving member 230 is shown as having a gear coupling structure for converting rotational motion into linear motion. However, the present invention is not limited thereto, and any shape may be used as long as the heating device 100 can be moved in a three-axis direction.

The local heat treatment system 1 according to an aspect of the present invention comprises the moving device 200 and the heating device 100 as one sub-assembly, and the sub-assembly is one side and the other side of the blank material 10. It can be provided in a plurality so as to be locally heated at each required position. The plurality of sub-assemblies can be independently controlled by the control device 300.

The control device 300 may control the heating device 100 and the mobile device 200, respectively, and independently control a plurality of sub-assemblies, as described above. The control device 300 is combined with artificial intelligence (AI) and sensing technology to control each sub-assembly more efficiently. For example, before the local heating of the blank material 10, the strain and stress are measured during the molding process, which is the molding characteristic of the molding target material, and the local heating position, heating temperature, heating time, etc. are taken into account in consideration of the molding shape and the processing time. To be optimized. That is, the mobile device 200 and the heating device 100 can be controlled by setting a local heating position, a heating temperature, and a heating time on the basis of measurement data obtained by measuring a molding object. Accordingly, when the blank material 10 is located by the local heat treatment system 1, the moving device 200 operates to move the heating device 100 to the optimized point quickly and easily, and the heating device 100 is heated. Is heated over time and at a constant temperature. Therefore, even if the object to be molded has a complicated molding shape, it can be conveniently applied, and can be applied to various shapes.

Then, a method of cold forming the blank material 10 using the above-described local heat treatment system 1 will be described with reference to FIGS. 1 to 5.

The cold forming method of the present invention is largely a process of locally heating and cooling the plastic deformation-producing portion of the blank material 10 through the local heat treatment system 1, and the locally heated blank material 10 as a mold. And positioning and molding.

Specifically, as shown in FIG. 1, when the blank material 10 flows into the local heat treatment system 1, the moving device 200 is positioned so that the heating device 100 is located in the local heating area, which is a region where plastic deformation occurs. It works. That is, as illustrated in FIG. 2, when the heating apparatus 100 is located in the local heating region, the plastic deformation occurrence region of the blank material 10 is heated to a constant temperature through the heating apparatus 100. The locally heated blank material 10 is subjected to a cooling step, and the physical properties of the material are locally adjusted to provide a cold forming process. That is, by adjusting the physical properties of the blank material 10 in advance before the cold forming process, it is possible to reduce the molding process time compared to the process of heating the material in the existing warm forming process and then performing warm forming.

Meanwhile, the heating device 100 and the moving device 200 may be controlled to locally heat the blank material 10 by the control device 300. The control device 300 independently controls the heating device 100 and the mobile device 200 provided in plural. The mobile device 200 and the heating device are set by setting the local heating position, heating temperature, and heating time in consideration of the strain and stress according to the shape formed during the molding process of the blank material 10 through the control device 300. 100) can be controlled.

For example, the control device 300 is combined with artificial intelligence (AI) and sensing technology to control each heating device 100 and the mobile device 200 more efficiently. That is, before the local heating of the blank material 10, strain and stress are measured during the molding process, which is a molding characteristic of the molding target material, and the local heating position, heating temperature, and heating time are optimized in consideration of the molding shape and the processing time. do. Accordingly, the mobile device 200 and the heating device 100 may be controlled by setting a local heating position, a heating temperature, and a heating time on the basis of measurement data obtained by measuring the molding object. Therefore, when the blank material 10 is located by the local heat treatment system 1, the moving device 200 operates to quickly and easily move the heating device 100 to an optimized point, and the heating device 100 is heated. Is heated over time and at a constant temperature.

Meanwhile, the blank material 10 introduced into the local heat treatment system 1 may be fixed at a certain position through a separate holder (not shown). That is, the blank material 10 may be supported so as not to interfere with a portion heated by the holder through the heating device 100.

The blank material 10 locally heated through the local heat treatment system 1 is cooled to be provided in a controlled state of material properties.

Subsequently, the blank material 10 with controlled physical properties is molded to have a desired shape through cold forming. That is, the blank material 10 transferred to a mold (not shown) is pressed by a punch (not shown) and plastically deformed.

Hereinafter, the present invention will be described in more detail through Examples 1 to 6 and Comparative Examples 1 to 3.

Example 1

The blank material was prepared from an ultra-high tensile steel having a tensile strength of 1.5 GPa, and the plastically deformed portion was locally heated to 550° C. and then V-bended.

Example 2

The blank material was prepared from an ultra-high tensile steel having a tensile strength of 1.5 GPa, and the plastically deformed portion was locally heated to 850° C. and then V-bended.

Example 3

The blank material was prepared with an ultra-high tensile steel having a tensile strength of 1.5 GPa, and the plastically deformed portion was locally heated to 950° C. and then V-bended.

Example 4

The blank material was prepared from ultra-high tensile steel having a tensile strength of 1.2 GPa, and the plastically deformed portion was asymmetrically molded after local heating at 400°C.

Example 5

The blank material was prepared from ultra-high tensile steel having a tensile strength of 1.2 GPa, and the plastically deformed portion was asymmetrically molded after local heating at 800°C.

Example 6

The blank material was prepared from an ultra-high tensile steel having a tensile strength of 1.5 GPa, and the plastically deformed portion was locally heated to 800° C. and then a real part was molded.

Comparative Example 1

The blank material was prepared from an ultra-high tensile steel having a tensile strength of 1.5 GPa and V-bended without local heating.

Comparative Example 2

The blank material was prepared from ultra-high tensile steel having a tensile strength of 1.2 GPa, and was asymmetrically molded without local heating.

Comparative Example 3

The blank material was prepared from an ultra-high tensile steel having a tensile strength of 1.5 GPa, and a real component was molded without local heating.

Steel Example/Comparative Example Forming method Local heating Molding result 1.5GPa ultra-high tensile steel Example 1 V bending molding 550℃ No crack Example 2 V bending molding 850℃ No crack Example 3 V bending molding 950℃ No crack 1.2GPa ultra-high tensile steel Example 4 Asymmetric molding 400℃ Springback 15° Example 5 Asymmetric molding 800℃ Springback 7° 1.5GPa ultra-high tensile steel Example 6 Real part molding 800℃ No crack 1.5GPa ultra-high tensile steel Comparative Example 1 V bending molding - Cracking 1.2GPa ultra-high tensile steel Comparative Example 2 Asymmetric molding - Springback 25° 1.5GPa ultra-high tensile steel Comparative Example 3 Real part molding - Cracking

As can be seen from the molding results in [Table 1], cracking did not occur as a result of molding after local heating, and the springback phenomenon was significantly reduced. The results of experiments of these examples and comparative examples are shown in FIGS. 6 to 9.

FIG. 6 is a view taken to compare a state in which the material is controlled by the local heat treatment system according to an embodiment of the present invention, in a state of V bending molding and a state in which a material of V is conventionally subjected to V bending molding.

FIG. 6(a) shows the state of V bending molding through Comparative Example 1, and FIG. 6(b) shows the state of V bending molding through Examples 1 to 3. That is, as shown, in Comparative Example 1, it can be confirmed that cracks were generated in the plastically deformed portion. On the other hand, in the case of Examples 1 to 3 of the present invention, since the part to be plastically deformed is locally heated to control the physical properties, cracks are not generated and are smoothly formed.

7 is a view for comparing a material in which the physical properties are adjusted by the local heat treatment system according to an embodiment of the present invention and an asymmetrically molded state of a conventional material.

FIG. 7(a) shows an asymmetric molded state through Comparative Example 2, and FIG. 7(b) shows an asymmetric molded state through Example 4. That is, as shown, in the case of Comparative Example 2, it can be confirmed that a springback phenomenon of 25° occurred after asymmetric molding. On the other hand, in the case of Example 5 of the present invention, the crack is not generated because the plastically deformed portion is locally heated to control the physical properties, and a springback phenomenon of 7° occurs. That is, it can be seen that the springback is significantly reduced compared to the prior art.

FIG. 8 is a view showing a comparison of a state in which a physical component having a physical property controlled by a local heat treatment system according to an embodiment of the present invention is molded with a conventional physical component.

Figure 8 (a) shows a state in which the actual parts are molded through Comparative Example 3, and Figure 8 (b) shows a state in which the actual parts are molded through Example 6. That is, as shown, in the case of Comparative Example 6, it can be confirmed that cracks and fractures occurred in the plastically deformed portion. On the other hand, in the case of Example 6 of the present invention, since the part to be plastically deformed is locally heated to control the physical properties, it is molded without cracking or breaking.

On the other hand, in Figure 8 (b), instead of heating the part where the real part is plastically deformed, the both ends, i.e., only the part where cracks and fractures occurred during plastic deformation, are locally heated and cooled to cool the physical properties. You can see the adjustment. This is determined by data values of strain and stress measured during the molding process in consideration of the molding characteristics of the molding material. Therefore, it is possible to prevent unnecessary heating of all parts to be plastically deformed, so that it is possible to more effectively reduce waste of energy and to improve productivity. In addition, it is possible to set an optimized heating position and provide a heating time and a heating temperature. That is, it is possible to provide a molded article with improved quality while providing a local heat treatment system (1) capable of improving moldability and minimizing the phenomenon of springback and a cold forming method.

As described above, although the present invention has been described by a limited number of embodiments and drawings, the present invention is not limited by this, and the technical idea of the present invention and the following will be described by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the equivalent scope of the claims to be described.

1: Local heat treatment system
100: heating device
110: heat source
120: reflector
200: moving device
300: control device

Claims (8)

A heating device that locally heats only the plastic deformation-producing portion of the blank material to a constant temperature;
A moving device for moving the heating device to a position of a local heating area of the blank material; And
Local control system comprising a; control device for controlling the heating device and the moving device. According to claim 1,
The heating device,
A housing coupled with the mobile device;
A heat source coupled to the housing to emit near infrared rays; And
A local heat treatment system provided with a reflector provided in the housing and reflecting near infrared rays generated from the heat source to collect light into a local heating region. According to claim 1,
The mobile device,
A rotating joint coupled with the heating device; And
A local heat treatment system comprising a; a plurality of moving members coupled to the rotating joint to move the heating device in a three-axis (x, y, z) direction. According to claim 3,
The plurality of moving members,
A first moving member coupled to the rotating joint and transferring the heating device in a direction in which a blank material is provided;
A second moving member coupled to the first moving member to convey the first moving member in a vertical direction; And
And a third moving member coupled to the second moving member to transfer the second moving member in a horizontal direction. According to claim 1,
The moving device and the heating device are provided as one sub-assembly,
The sub-assembly is provided in plural to be locally heated on one side and the other side of the blank material, respectively.
Each sub-assembly is a local heat treatment system controlled independently by the control device. According to claim 1,
The control device is a local heat treatment system that controls the moving device and the heating device by setting a local heating position, heating temperature, and heating time in consideration of strain and stress according to a molding shape during the molding process of the blank material. A method for cold forming using the local heat treatment system according to any one of claims 1 to 6,
(a) operating a moving device such that when the blank material is introduced into the local heat treatment system, the heating device is located in the local heating area, which is a plastic deformation generating site;
(b) when the heating device is located in the local heating region, heating a portion of the plastic deformation-generating portion of the blank material through a heating device to a predetermined temperature and cooling to locally control the material properties; And
(c) cold forming after transferring the blank material with controlled physical properties to a mold; and cold forming. The method of claim 7,
In step (a),
The control device of the local heat treatment system is a cold forming method of controlling the moving device and the heating device by setting the local heating position, heating temperature, and heating time in consideration of strain and stress according to the shape to be formed during the molding process of the blank material. .

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