KR20110054605A

KR20110054605A - Method for reforming surface of mold

Info

Publication number: KR20110054605A
Application number: KR1020090111320A
Authority: KR
Inventors: 여인웅
Original assignee: 현대자동차주식회사
Priority date: 2009-11-18
Filing date: 2009-11-18
Publication date: 2011-05-25

Abstract

PURPOSE: A method of reforming a surface for a mold is provided to dramatically enhance the compactability of parts since frictional force is minimized when a part, such as a high-tension steel sheet, is shaped. CONSTITUTION: A method of reforming a surface for a mold is as follows. A texturing pattern consisting of a plurality of holes is formed on a surface for a mold using laser. The holes are formed at the same intervals. The holes are formed with 40~80μm diameter and 40~80μm depth and the distance between two holes is 0.1~0.4mm. The diameter from entrance to the middle point of the whole depth of each hole is the same.

Description

Method for reforming surface of mold

The present invention relates to a surface modification method for a mold, and more particularly, to a surface modification method that can be applied to a forming tool, including a press mold, to improve the moldability of the mold.

Increasingly, the demand for weight reduction of automobiles for energy efficiency of vehicles (cars) is increasing due to the demand for reducing greenhouse gas (CO _2, etc.) due to global warming.

In other words, the application rate of automotive body high tensile steel sheet is increasing all over the world, which has been developed 590MPa class high strength high strength steel sheet for automobile body at home and abroad, theoretically 10 ~ 15 It is a figure that can significantly reduce weight (fuel efficiency: 2 ~ 4% compared to the present).

In order to be applied to the car body, steel sheet formability must be secured at the material side or special molding technology must be secured at the process side, so that the steel sheet can be applied to the car body. have.

Therefore, various measures to improve the moldability of automobile body molds have been made. As a conventional technique, most of the molds have been subjected to low friction coating on the surface of the mold or changed to a shape that is easily molded by design. .

However, in the case of the conventional low friction coating, there is a problem in the high cost and applicability according to the mold shape, and in the case of the design shape change, there is a problem of limiting the degree of freedom of the shape of the automobile vehicle. I'm not getting results.

The present invention has been made in view of the above, and using a laser on the surface of various forming tools, including a press mold for automobile body fabrication, using a laser to form a texturing pattern consisting of minute holes of 40 ~ 80㎛ diameter The purpose of the present invention is to provide a surface modification method for a mold, which minimizes the friction generated during molding using a mold and significantly improves the formability.

The present invention for achieving the above object is to form a texturing pattern consisting of a plurality of circular holes having an equal interval using a laser on the surface for forming the mold, to improve the low friction characteristics of the mold It provides a surface modification method for a mold, characterized in that.

In particular, the circular hole is formed with a diameter of 40 ~ 80㎛, 20 ~ 50㎛ depth, characterized in that the spacing between each hole is formed of 0.1 ~ 0.4mm.

Preferably, it is characterized in that the processing to be the same diameter from the entrance to the middle point of the entire depth of each circular hole.

Through the above problem solving means, the present invention provides the following effects.

According to the present invention, by processing a texturing pattern consisting of a fine hole of 40 ~ 80㎛ diameter by using a laser on the forming surface of the forming tool and other forming tools, when forming parts such as high-tensile steel sheet using a mold By minimizing the friction, the moldability of the part can be significantly improved.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The present invention focuses on forming a fine circular hole texturing pattern on the surface of a forming tool such as a punch or a die that comes into contact with a panel to be formed when forming a panel component such as a high tensile strength steel sheet using a press die. The texturing pattern can minimize the friction with the panel object to be molded and at the same time increase the molding pressure, thereby greatly improving the moldability of the panel part.

To this end, in the present invention, a Pico / Femto-class laser is used to form a texturing pattern on the functional surface of the press mold and various forming tools, that is, the surface in contact with the panel object to be formed. This is because post-processing can be minimized.

Thus, in order to maximize the low friction characteristics of the mold using the laser to process a texturing pattern consisting of a circular hole having a diameter of 40 ~ 80㎛ on the functional surface of the mold, the depth is formed to 20 ~ 50㎛, each The gap between the holes is to be formed 0.1 ~ 0.4mm (see micrograph of Figure 1).

The diameter of the circular hole is 40 ~ 80㎛, the depth is 20 ~ 50㎛, and the interval between each hole is formed in 0.1 ~ 0.4mm reason is to maintain the appropriate level range to minimize the frictional force with the panel parts to be molded In addition, the press pressure for the panel object to be molded is intended to work smoothly.

At this time, it is preferable to process the same diameter of 40 ~ 80㎛ from the inlet to the middle point of the total depth of each circular hole, the reason is that if the depth is too low to 40㎛ or less, the frictional force reducing effect is lowered, 80㎛ or more This is because the circular state of the circular hole can be easily deformed by the press pressure.

Hereinafter, the effects of the present invention through Examples and Comparative Examples will be described.

Example

The Pico / Femto laser is used to process a texturing pattern consisting of a circular hole with a diameter of 70 μm on the surface of the die and punch, which are the functional surfaces of the press die, with a depth of 40 μm, and the spacing between each hole is 0.3 It was formed in mm, was processed to 70㎛ from the inlet to the middle point of the total depth of each circular hole.

At this time, carburizing heat treatment was performed on the functional surface of the mold, and the surface roughness was maintained at 0.1.

Comparative Examples 1-2

In Comparative Example 1, the surface of the die and punch, which are the functional surfaces of the press die, was not subjected to separate surface modification. Comparative Example 2 performed the carburizing heat treatment on the functional surface of the mold and the surface roughness was 0.1. CrN coating was performed using physical vapor deposition (PVD) while maintaining.

Test Example

For reference, as shown in FIG. 3, the press includes a die on which a part to be molded is placed, a punch for pressing and molding a part to be molded on the die, and a punch and a die while simultaneously holding the punch and the die. It comprises a blank holder for guiding.

That is, in the configuration of the press apparatus, the lower die 10 having the shape of the lower surface of the product panel is mounted on the bolster 13, and the cushion pin 15 is attached to the bolster 13 along the outside of the die 10. The blank holder 17 is mounted therethrough, and an upper punch 11 having an upper surface shape of the component panel to be molded is mounted on the upper slider (not shown) at the upper portion of the lower die 10.

Accordingly, the molding target part panel 20 is disposed between the lower die 10 and the blanking member 17. The upper punch 11 is pushed down to press the panel 20. Processing.

At this time, the blank holder 17 which is in contact with the edge portion of the upper punch (11) not only suppresses the wrinkles of the panel 20, but also controls the inflow of the material during molding to prevent bursting of the corners of the material, etc. It plays a role, and it is a part that has an absolute influence on the quality of the finished product panel.

Therefore, the molding pressure of the blank holder is the main item for evaluating low friction and molding quality.

Therefore, in order to evaluate the low friction properties and thus formability of the Examples and Comparative Examples 1 and 2, the molding pressure of the blank holder, which is one of the press molds, was measured. The results are shown in FIG. .

As shown in Figure 2, the maximum blankholder pressure of the blank holder (maximum blankholder pressure) compared to the surface modification used in the mold according to the conventional comparative example, the formability when the surface modification method according to the embodiment of the present invention is applied It can be seen that about 15% improvement.

That is, the maximum molding pressure of the blank holder is increased because the frictional force between the die, which is the functional surface of the press, and the modified surface of the punch is reduced from the panel surface to be formed, and thus the surface modification method according to the embodiment of the present invention is applied. In this case, the moldability can be expected to be improved by about 15%.

1 is a micrograph showing the surface of the simple mold surface-modified by the surface modification method for the mold of the present invention,

Figure 2 is a graph of the moldability test results of the press to which the method according to the surface modification method and the comparative example according to the embodiment of the present invention,

3 is a schematic diagram illustrating a configuration of a press and an operation thereof.

10: die 11: punch

13: bolster 15: cushion pin

17: blank holder 20: panel

Claims

A surface modification method for a mold, characterized in that to form a texturing pattern consisting of a plurality of circular holes having equal intervals on the surface for forming the mold to improve the low friction characteristics of the mold.

The method according to claim 1,

The circular hole is formed with a diameter of 40 ~ 80㎛, 20 ~ 50㎛ depth, the surface modification method for a mold, characterized in that the spacing between each hole is formed in 0.1 ~ 0.4mm.

The method according to claim 1 or 2,

Surface modification method for a mold, characterized in that for processing so that the same diameter from the entrance to the middle point of the total depth of each circular hole.