KR20210077933A - Method for trimming ultra high-tensile steel molding products - Google Patents

Abstract

Disclosed is a method for cutting an ultra-high-tensile steel molded product. According to an embodiment of the present invention, the cutting method comprises the steps of: forming a thin plate product having a tensile strength of 1.2 Gpa or more; locally heating in the form of a dash line along a line to be cut of the thin plate product; cooling the dash-line-shaped heating line locally heated; and trimming the line to be cut using a mechanical cutter that applies an external force to the line to be cut.

Description

Cutting method of ultra-high-strength steel molded products {METHOD FOR TRIMMING ULTRA HIGH-TENSILE STEEL MOLDING PRODUCTS}

The present invention relates to a method for cutting ultra-high-strength steel molded products, and more particularly, to a method for cutting molded products that saves energy and improves efficiency during mechanical cutting or trimming of ultra-high-strength steel molded products.

Recently, the use of ultra-high-strength steel is increasing in the automobile industry. However, ultra-high tensile steel is easy to crack after forming and has a large springback, so there are many difficulties in application diffusion. Accordingly, many studies have been conducted to reduce cracks and springback of ultra-high-strength steel. A typical method is the warm forming method, which is formed by raising the temperature of the material. However, a lot of heating energy is consumed in order to increase the temperature of the entire material during warm forming. In addition, in the case of producing a product through thin plate molding, since the part where plastic deformation actually occurs is limited, heating the entire material is likely to cause unnecessary energy consumption. When molding is performed by heating only the part where plastic deformation occurs during thin plate molding, energy can be saved compared to the method of molding by raising the temperature of the entire material. As an existing invention of molding technology using local heating, there is an invention for springback and improvement of moldability by using a laser or near-infrared heating device. However, since it is heated and warm-formed within the molding process, a decrease in productivity due to heating time is inevitable, and it is difficult to maintain a constant quality because the local heating part is rapidly cooled while handling the material. (Reference invention: Korean Patent No. 10-1276142, 10-1354149, 10-1484907) Therefore, a method and apparatus for cold forming rather than warm forming in order to secure a constant quality without reducing productivity by not heating in the forming process has been developed

However, after forming ultra-high-strength steel, the edges of the molded product must be trimmed for final finishing of the molded product. However, during mechanical trimming, the cutting edge wear of the trimming knife is extreme and the cutting edge is frequently damaged, which increases the production cost of mechanical trimming, In this case, laser trimming is applied. In laser trimming, since the trimming is performed along the edge of the molded product, the trimming time is lengthened, resulting in a very low productivity.

Korean Patent No. 1276142 (published on June 18, 2013) Korea Registered Patent No. 1354149 (2014.01.27 Announcement) Korea Patent No. 1484907 (Announcement on Jan. 21, 2015)

Embodiments of the present invention are intended to provide a cutting method of a molded product capable of improving efficiency and reducing heating energy when cutting or trimming an ultra-high-strength steel molded product.

According to one aspect of the present invention, the step of forming a thin plate product having a tensile strength of 1.2 Gpa or more, the step of locally heating in the form of a dash line along the line to be cut of the thin plate product, the locally heated dotted line A method of cutting ultra-high-strength steel molded products comprising the steps of cooling the heating line of the form and trimming the line to be cut using a mechanical cutter that applies an external force to the line to be cut may be provided.

The thin plate product includes at least one of AHSS (Advanced High Strength Steel) steel and TRIP (Transformation Induced Plasticity Steel) steel.

The heating device for heating the line to be cut includes a heater that emits a heat source, and a reflector that collects the heat sources of the heater and collects them in a straight line.

When the thin plate product has a tensile strength of 1.2 Gpa, the ratio of the total length of the heating line to the total length of the line to be cut may satisfy 40% to 60%.

When the thin plate product has a tensile strength of 1.5 Gpa, the ratio of the total length of the heating line to the total length of the line to be cut may satisfy 60% to 80%.

The mechanical cutter includes a punching machine.

The sheet product may be manufactured by cold forming.

Embodiments of the present invention can reduce the trimming load during mechanical trimming to reduce the wear of the cutting edge of the trimming knife, and it is possible to reduce the heating energy due to the local heating of the line to be cut.

1 is a flowchart showing a method for cutting a molded product according to an embodiment of the present invention.
2 shows a heating device according to an embodiment of the present invention.
3 is a diagram illustrating a process of performing local heating using a heating device according to an embodiment of the present invention.
4 is a graph showing the trimming load according to the length ratio of the heating line of Table 1.
5 is a diagram for defining a heating rate according to an embodiment of the present invention.
6 is a graph showing the trimming load according to the length ratio of the heating line of Table 2.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments introduced below are provided as examples in order to sufficiently convey the spirit of the present invention to those of ordinary skill in the art to which the present invention pertains. The present invention is not limited to the embodiments described below and may be embodied in other forms. In order to clearly explain the present invention, parts irrelevant to the description are omitted from the drawings, and in the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals refer to like elements throughout.

1 is a flowchart showing a method of cutting a molded product according to an embodiment of the present invention, FIG. 2 is a heating device according to an embodiment of the present invention, and FIG. 3 is a heating device according to an embodiment of the present invention It shows the process of performing local heating using.

1 to 3, the cutting method of the ultra-high tensile steel molded product according to an embodiment of the present invention comprises the steps (a) of forming a thin plate product 10 having a tensile strength of 1.2 Gpa or more, and the thin plate product 10 A step (b) of locally heating the heating line 30 in the form of a dash line along the line to be cut 20 of the step (b), a step (c) of cooling the locally heated heating line 30, and the scheduled cutting It includes a step (d) of trimming the line to be cut 20 using a mechanical cutter 40 applying an external force to the line 20 and a step (e) of producing the trimmed final product 50 .

The thin plate product 10 formed in step (a) of forming the thin plate product 10 is an ultra-high tensile steel with a tensile strength of 1.2 Gpa or more, and is a dual phase steel (DP steel) known as AHSS (Advanced High Strength Steel). , transformation induced plasticity steel (TRIP steel), complex phase steel (CP steel), and the like. The thin plate product 10 may be manufactured through cold press forming.

As an example, the molded thin plate product 10 extends downward from both ends of the first surface 11 and the first surface 11 to form a finished upper plate after bending the plate material through press molding by an upper mold and a lower mold. It may include a pair of second surfaces 12 forming a pair, and a pair of third surfaces 13 forming a wing plate extending in the horizontal direction from the pair of second surfaces 12, respectively.

On the pair of third faces 13 , a line to be cut 20 for cutting at a position adjacent to the edge of the third face 13 for final finishing of the final thin plate product 10 may be defined along the longitudinal direction. .

The local heating step (b) is a step of performing local heating along the line to be cut 20 of the molded sheet product 10 .

In the local heating step (b), the heating line 30 is formed in the form of a dash line by heating at a predetermined interval along the line to be cut 20 using the heating device 60 .

Referring to FIGS. 2 and 3 , the heating device 60 collects the heat source of the heater 61 , which emits a heat source to enable local linear heating with respect to the line to be cut 20 , and the heat source of the heater 61 in a straight line. It may include a reflective plate 62 that reflects the shape.

The heater 61 includes a rod-shaped heating lamp having a length corresponding to the dotted line, and the reflector 62 is an oval or oval surrounding the heater 61 to linearly condense the heat source emitted from the heater 61 . It may include a parabolic reflector. The reflecting plate 62 may be appropriately selected according to the molding characteristics and shape of the thin plate product 10 .

The cooling step (c) is a step of cooling the heating line 30 in the form of a dotted line locally heated by the heating device 60 .

Physical properties of the area of the heating line 30 formed along the line to be cut 20 through a heat treatment for cooling after local heating with respect to the line to be cut 20 is controlled. That is, the heating line 30 cooled after heating has low strength and soft tissue.

The trimming step (d) is a step of cutting the line to be cut 20 using the mechanical cutter 40 to produce a final molded product.

The mechanical cutter 40 may include a punch machine. By applying an external force to the line to be cut 20 in a state where the heat-treated thin plate product is placed on the die of the punch machine, the line to be cut 20 is cut, and the final product production (e) is completed.

Hereinafter, trimming performance evaluation using local heat treatment according to an embodiment of the present invention will be described.

[Table 1] is a table showing the results of the existing method for 1.2 Gpa high-strength steel and the results of this example, and FIG. 4 is a graph showing the trimming load according to the length ratio of the heating line in Table 1.

Example
/comparative example heating rate
(%) energy saving rate
(%) weight
(N/mm) load reduction ratio
(%) Comparative Example 1 0 % 100% 1032.2 - Example 1 20% 80% 1002.3 2.9% Example 2 40% 60% 991.7 3.9% Example 3 60% 40% 923.3 10.5% Example 4 80% 20% 849.8 17.7% Example 5 100% 0 % 761.5 26.3%

Here, the heating ratio (%) is defined as the ratio of the total length of the locally heated heating line to the total length of the line to be cut.

For example, when the length of the entire line to be cut 20 is L as shown in FIG. 5, and the length of the locally heated heating line (H) among the total length of the line to be cut is H1 and H2, respectively, the heating ratio is Equation 1 is the same.

Heating ratio = (H1+H2)/L X 100 [Equation 1]

As seen in [Table 1] and FIG. 4, it can be seen that the trimming load decreases as the heating ratio increases, and it can be seen that the reduction ratio of the trimming load is 10% or more when the heating ratio is 60% compared to the conventional method It can be seen that trimming load of 1 kN/mm or less is possible even at a heating rate of 40%.

[Table 2] is a table showing the results of the existing method for 1.5Gpa high-strength steel and the results of this embodiment, and FIG. 6 is a graph showing the trimming load according to the length ratio of the heating line in Table 2.

Example
/comparative example heating rate
(%) energy saving rate
(%) weight
(N/mm) load reduction ratio
(%) Comparative Example 2 0 % 100% 1233.4 Example 6 20% 80% 1196.9 2.9% Example 7 40% 60% 1160.4 5.9% Example 8 60% 40% 1057.1 14.3% Example 9 80% 20% 989.0 19.8% Example 10 100% 0 % 948.2 23.1%

As seen in [Table 2] and FIG. 6, it can be seen that the trimming load decreases as the heating ratio increases, and it can be seen that the reduction ratio of the trimming load is 10% or more when the heating ratio is 60% compared to the conventional method It can be seen that trimming load of 1 kN/mm or less is possible even at a heating rate of 80%.

In the above, specific embodiments have been shown and described. However, it is not limited to the above-described embodiment, and those of ordinary skill in the art to which the invention pertains will be able to make various changes without departing from the spirit of the invention described in the claims below.

10: thin plate product, 20: line to be cut,
30: heating line, 40: mechanical cutter,
50: final product, 60: heating device.

Claims (7)

Forming a thin plate product having a tensile strength of 1.2 Gpa or more;
local heating in the form of a dash line along the line to be cut of the thin plate product;
cooling the locally heated dotted line heating line; and
The cutting method of ultra-high-strength steel molded products including; trimming the line to be cut using a mechanical cutter that applies an external force to the line to be cut. According to claim 1,
The thin plate product is AHSS (Advanced High Strength Steel) steel, TRIP (Transformation Induced Plasticity Steel) cutting method of the ultra-high-strength steel molded product comprising at least one of steel. According to claim 1,
The heating device for heating the line to be cut is a cutting method of ultra-high-strength steel molded products including a heater that emits a heat source, and a reflector that collects the heat sources of the heater and collects them in a straight line. According to claim 1,
When the thin plate product has a tensile strength of 1.2 Gpa, a ratio of the total length of the heating line to the total length of the line to be cut is 40% to 60%. According to claim 1,
When the thin plate product has a tensile strength of 1.5Gpa, the ratio of the total length of the heating line to the total length of the line to be cut is 60% to 80% of the ultra-high-strength steel molded product cutting method. According to claim 1,
The mechanical cutter is a cutting method of ultra-high-strength steel molded products including a punching machine. According to claim 1,
The thin plate product is a cutting method of ultra-high-strength steel products produced by cold forming.

Images