WO2013002534A1

WO2013002534A1 - Method for molding a magnesium plate having high strength due to a local softening process using quick heating and high strength magnesium plate component molded thereby

Info

Publication number: WO2013002534A1
Application number: PCT/KR2012/005036
Authority: WO
Inventors: 김수호; 이영선; 박찬희
Original assignee: 한국기계연구원; 오창석
Priority date: 2011-06-27
Filing date: 2012-06-26
Publication date: 2013-01-03
Also published as: KR20130001511A

Abstract

The present invention relates to a method for molding a magnesium plate having high strength due to a local softening process using quick heating, and to a high-strength magnesium plate molded thereby. More particularly, the present invention relates to the method for molding the magnesium plate through the local softening process, the method comprising: a local softening step (step 1) of performing a heat treatment on only a portion which requires molding within a high-strength magnesium plate so as to locally improve elongation; and a molding step (step 2) of molding the magnesium plate which is locally softened in step 1. The present invention also relates to the magnesium plate molded using the molding method. According to the present invention, the method for molding the magnesium plate through the local softening process and the high-strength magnesium plate molded by the method enable local heating to be selectively performed on only a portion which requires molding so as to improve elongation. The portion which does not require processing and thus has to maintain a high strength is not heated or is only minimally heated so as to enable the portion which does not require processing to maintain the initial mechanical characteristics that the portion has before the molding is performed.

Description

【Specification】

[Name of invention]

Forming process of high strength magnet sheet by local softening process by rapid heating and high strength magnet sheet forming part molded by this

Technical Field

The present invention relates to a molding process of a high strength magnesium sheet through a local softening process and a high strength magnesium sheet molded part molded by the same.

Background Art

Recently, the government's policy and R & D direction has been promoted to address the social demand for efficient use of energy resources and reducing environmental pollution. In particular, regulations to reduce environmental pollution caused by carbon dioxide and various exhaust gases, which are the main causes of global warming, have been enacted in stages, and research and development are being actively conducted for efficient use of limited energy resources. Among them, to reduce environmental pollution and improve the efficiency of energy resource utilization, lightweight technology is applied to various transportation equipment to replace existing steel materials. In order to achieve this purpose, magnesium, which has a specific gravity less than 1/4 of iron and high specific strength, is attracting attention as the most powerful lightweight material. On the other hand, compared with the production process of magnesium casting material, which is technically mature, the manufacturing technology of magnesium plate parts using the firing process is very weak in technical foundation, and recently, R & D is started in the world. Edo is in the early stages of technology development. Therefore, in order to revitalize the domestic parts and materials industry and to apply magnesium plate parts that can create high added value, it is urgently needed to develop a variety of magnet plate forming processes and parts manufacturing technology. Magnesium material with Hexagonal Close Packed (HCP) has very poor formability at room temperature, so it can be used for stamping, press forging, In general metal plate forming process such as deep drawing, it is impossible to manufacture the plate molded products through all the hot forming process must be applied. However, molding in high silver causes a decrease in strength of the material after molding, and therefore, there is an urgent need for development of molding methods at low or normal temperatures to maintain the strength of raw materials. Therefore, the inventors of the present invention have studied the method of improving the formability while maintaining the overall strength of the molded parts of the magnet material at the same level as the strength before molding, and do not perform the final annealing after rolling in the manufacture of the plate material. By locally rapid heating only the portion of the magnesium plate raw material (H-temper) having strength to improve the elongation, the strength of the portion that does not require molding or requires a small amount of molding is maintained or Magnesium plate forming process was developed, which can be locally molded without deterioration, and completed the present invention.

[Detailed Description of the Invention]

[Technical problem]

SUMMARY OF THE INVENTION An object of the present invention is to provide a molding method of a high strength magnesium sheet through a local softening process by rapid heating and a high strength magnet sheet molded part molded by the molding.

Technical Solution

In order to achieve the above object, in the present invention, the local banquet step (step 1) to locally increase the elongation by rapid heat treatment only the part that needs to be molded into a high strength magnesium sheet Oi-temper; And ^'

Provided is a magnesium plate forming method through a local softening process comprising the step (step 2) of forming a locally softened magnesium plate in step 1.

Advantageous Effects

Forming method of high strength magnet plate through the local softening process by rapid heating according to the present invention and the high strength magnesium plate molded parts formed by this to selectively localize only the parts that need to be molded to increase the elongation and thereby improve the formability In this case, the part which does not need to be processed or the processing amount is small and maintains high strength is not heated or only minimally heated, so the magnesium plate before molding Has the effect of maintaining the initial mechanical properties. In addition, by forming simultaneously with the local heating, there is an additional effect of improving the mechanical properties of the molding part by utilizing the dynamic recrystallization phenomena generated in the high-strength magnesium plate microstructure by the action of heat and deformation. The high-strength magnesium plate according to the present invention can be molded into the desired part shape because the site where the heating is not maintained maintains the mechanical properties of the raw material and the site where the heating is locally improves the formability. Magnesium sheet molding parts maintain the excellent mechanical properties of the initial high strength magnesium sheet. Therefore, by applying the magnet plate molded parts according to the present invention to the transport equipment, while maintaining a high mechanical strength and exhibits the maximum weight loss effect, it is possible to save energy through the fuel economy of the transport equipment.

[Brief Description of Drawings]

1 is a photograph showing specimen deformation before and after molding;

2 is a graph measuring the Vickers hardness value change after the test piece is deformed;

3 is a photograph observing the microstructure after the specimen is deformed.

[Best form for implementation of the invention]

Hereinafter, the present invention will be described in detail. The present invention

Localized softening step of locally increasing the elongation by heat-treating only the portion of the high-strength magnet plate (H-temper) molding process (step 1); And

Provided is a method for forming a magnet plate through a local softening process comprising the step of forming a locally softened magnesium plate in step 1 (step 2). Hereinafter, the present invention will be described in detail step by step. In the molding process of the magnet plate according to the present invention, step 1 is a local softening step step of rapidly heat-treating a high-strength magnet plate, (H-temper) to a portion requiring molding processing to locally increase the calculation rate. . In the existing magnesium sheet forming process, the entire sheet is heated and molded to form a part that does not require molding or requires a small amount of molding. Accordingly, the entire sheet is annealed and softened. There is a problem that the mechanical properties are reduced, that is, the high strength properties of the raw material before molding. However, in the molding process according to the present invention, by heating only the portion that needs to be molded of the magnesium plate raw material, while maintaining the mechanical properties of the portion that does not need to be formed at the same time to increase the elongation of the portion that needs to be formed to improve the formability Can be. The rapid heating heat treatment of the first stage may be performed by heating using a heat source such as a high frequency wave, a laser, and a halogen lamp. Preferably, the heat treatment may be performed through a silver forming mold in which a heating element is inserted only in the molding part. Can be.

At this time, the rapid heat treatment for the local softening is preferably carried out at a temperature of 150 to 400 ^° C. When the rapid heat treatment is performed at less than 150 ^° C, there is a problem that a desired level of formability cannot be obtained. When the rapid heat treatment is performed at a temperature exceeding 400 ^° C, moldability is increased but mechanical properties are excessively degraded. there is a problem. The rapid heat treatment is performed within 1 to 120 seconds, which is suitable for the plate forming process in a continuous process (In-line). The longer the rapid heat treatment is performed, the more delayed the molding process of the magnesium plate is, and thus the productivity decreases. However, in the molding process according to the present invention, by locally softening the magnesium sheet through rapid heat treatment, it is possible to produce the product through a continuous process and improve productivity. In the molding method of the magnesium plate according to the present invention, step 2 is a step of forming the locally softened magnesium plate in step 1. The molding process of step 2 is to be processed through a plastic deformation process, such as clamping, press forging, etc. according to the field and the degree of processing to apply the plate material, there is no particular limitation. ^{"Washing-forming} group in step 2 may be carried out at a temperature not higher than room temperature to 400 ^° C, and most preferably is carried out at room temperature. The molding of step 2 is performed at a temperature in the above range, thereby maintaining the mechanical properties while simultaneously forming the magnet plate. In addition, by utilizing the dynamic material crystal phenomenon generated by the combined effect of heat and deformation in the above temperature range can be obtained an additional effect of improving the mechanical properties of the molded part. Accordingly, the magnesium plate formed by the present invention is characterized by excellent strength. The molding process of the magnesium sheet according to the present invention may be performed simultaneously by the local softening by the rapid heat treatment of step 1 and the molding of the step 2 by a mold including a heating element, thereby continuous Productivity is improved by the process. At this time, the heat source of the mold may be a high frequency, a laser, a halogen lamp, but is not particularly limited thereto. In addition, the present invention provides a molded magnesium molded part through the molding process. Magnesium and magnesium alloy plates having a dense hexagonal lattice (HCP) crystal structure are plate materials using conventional plastic working processes applied to carbon steel having a body centered cubic (BCC) crystal structure and aluminum alloy having a face centered cubic (FCC) crystal structure. Molding is difficult This is because of the low symmetry characteristic of the dense hexagonal crystal structure and the large anisotropy of the rolled sheet, which is caused by the preferential arrangement of the dense surface parallel to the rolling direction during the rolling process. In order to solve the formation of the magnet plate and the difficulty, it is inevitable to form or process at a high temperature where the non-dense surface slip system is activated to improve the formability, and accordingly, the mechanical strength of the raw material is degraded by forming at a high temperature. .

However, the magnesium plate molded part according to the present invention selectively improves the moldability by heating only the portion that needs to be molded, and the portion that does not need to be heated does not heat to maintain the mechanical properties of the original magnesium plate. Molding is carried out. This solves the conventional problem that the mechanical properties are deteriorated by applying high temperature heat to the whole plate to process the magnesium plate, there is an effect that can improve the formability of the magnesium plate and maintain or improve the mechanical properties. Meanwhile, the magnesium plate molded part according to the present invention may be used as a vehicle body or an electronic product case of a transportation device. By using the magnesium plate molded part according to the present invention as a large-area part of the transport machine, it is possible to reduce the weight of the transport device, thereby improving fuel efficiency and energy saving effect. In addition, by applying to electronic products such as notebooks, it is possible to obtain a lightening effect of the electronic products and to improve the strength of the electronic case can be protected from the outer layer.

Correction Sheet (Rule 91) ISA / KR For example, large-area parts such as the roof of automobiles have changes in dimensions and shapes due to buckling caused by the difference in coefficient of thermal expansion in the post-painting heat treatment process. Yield strength above 200 MPa is required. Although it is difficult to maintain such a high yield strength value by the conventional method of heating the whole sheet to be processed, when applying the magnesium sheet formed by the present invention to the vehicle body, it is preferable to extend the elongation only at the edge portion of the sheet. By increasing and processing, it is possible to maintain the yield strength value to be applied to the car body and at the same time, to be processed in the desired shape, and to improve fuel efficiency and energy saving effect due to light weight due to the application of magnesium plate.

[Form for implementation of invention]

Hereinafter, the present invention will be described in detail through examples. However, it will ^'be limited by the following examples, it may make to the contents of the present invention to illustrate the invention.

Example 1 Local Molding of High Strength Magnesium Alloy Plate 1

Step 1: After processing a 1 mm thick H-Temper High Strength Magnesium Alloy (AZ31-H24) plate into 150 mm long and 15 mm wide specimens, the center of the specimen was heated to 40 ^° C / sec using an electrical resistance heating method. A local softening heat treatment was performed to heat up to 150 ^° C. at a heating rate and maintain the temperature for 60 seconds. At this time, the temperature was measured using a thermocouple spot-welded to the test specimen from left to right 40 mm from the center of heating. Step 2: In step 1, the locally softened magnesium sheet test specimen was uniaxially stretched at a crosshead speed of 3 mm / sec to form a high strength magnesium alloy sheet.

Example 2 Local Forming of High Strength Magnesium Alloy Plate 2

A high strength magnesium alloy plate was formed in the same manner as in Example 1 except that the center of the test piece was heated to 200 ^° C. in Step 1 of Example 1 to perform a local softening heat treatment.

Comparative Example 1

Correction Sheet (Rule 91) ISA / KR Without performing step 1 of Example 1, a high strength magnesium alloy sheet was formed by uniaxial stretching until breakage of the test piece occurred at room temperature.

Experimental Example _; 1> Elongation measurement of magnesium plate

In order to analyze the elongation of the high strength magnesium alloy sheet formed in Examples 1 and 2 and Comparative Example 1, the local elongation was measured from the change of position of the grid indicated on the test piece, and the results are shown in FIGS. wrote.

Table 1

As shown in Figure 1 and Table 1, the magnesium plate material uniaxially tensioned by Example 1 and Example 2 of the present invention was found to significantly improve the local elongation, that is, formability by deformation after local heating. It was confirmed that the magnet plate of Comparative Example 1, which was uniaxially stretched in a heated state, showed no increase in formability due to local heating, so that the AZ31 H-temper plate had a value in the elongation range of 15-20% which is typical. . Through this, it was confirmed that the molding process according to the present invention can improve the formability of the high strength magnesium sheet.

Experimental Example 2 Vickers Hardness Measurement

After the molding of the high-strength magnesium plate (H-temper) subjected to local heating by Examples 1 and 2 of the present invention was carried out, the V as hardness value was measured to a position 50 mm away from the local heating source, and the results are as follows. It is shown in Fig _'

As shown in Fig. 2, the magnesium sheet formed in Examples 1 and 2 was compared with the hardness value of the magnesium sheet (temper) which was completely annealed by the hardness of the molding portion by the combined action of the addition heat and the molding. It can be seen that it is very high. This is due to the dynamic recrystallization that occurs in the microstructure by the combined action of local heating and molding of high strength fine magnesium plate (H-teniper), and the mechanical properties of the molding site using the molding process according to the present invention are improved. It was confirmed that an additional effect of improvement could be obtained.

Correction Sheet (Rule 91) ISA / KR Experimental Example 3 Scanning Electron Microscope Analysis

According to the present invention, the microstructure of the high strength magnesium plate (AZ31 H-temper) subjected to local heating according to Example 1 was observed by scanning electron microscopy to analyze the microstructure, and the results are shown in FIG. 3.

By Example 1, the _"combined action of heating and molding, forming part of a high strength magnesium plate the local heating is performed by, as shown in Fig. 3 got widely up the dynamic recrystallization in grain boundaries and twin crystal interface, whereby It can be seen that the grain size is very small. In other words, by softening and forming by local heating according to the present invention, the grain refinement due to the same loading crystal phenomenon appears, thereby improving the moldability of the part requiring processing, and the mechanical properties of the molded part after molding are confirmed to be improved. It was.

Correction Sheet (Rule 91) ISA / KR

Claims

[Range of request]

[Claim 1]

Localized softening din-based by heat-treating only the portion of the high-strength magnet plate (H-temper) that needs to be processed to increase the elongation locally (step 1); And

Molding method of high-strength magnet sheet through the local softening process comprising the step (step 2) of forming a locally softened magnesium plate in step 1.

[Claim 2]

The method of claim 1, wherein the local softening of step 1 is carried out ^at a temperature of 150 to 400 ^° C molding process of the magnet plate material through a local softening process.

[Claim 3]

The method of claim U, wherein the local softening of step 1 is a rapid heat treatment is carried out for 1 to 120 seconds to form a continuous process (In-line) of the magnet plate material forming process through a local softening process.

[Claim 4]

The method of claim 1, wherein the heat treatment of the metal of step 1 is a magnet alloy sheet through a local softening process, characterized in that performed by any one heat source (Heating element) selected from the group consisting of high frequency, laser and halogen lamps. Forming Process of.

[Claim 5]

The method of claim 1, wherein the forming process of step 2 of the magnesium alloy sheet through a local softening process, characterized in that carried out at a temperature of room temperature to 400 ^° C.

Molding process.

[Claim 6]

The method of claim 1, wherein the forming process of step 2 is carried out through any one process selected from the group consisting of stamping, pressing forging and bending (bending) process. Forming Process of Magnesium Alloy Plate through Softening Process

[Claim 7]

In the U term, the local softening of step 1 and the forming process of step 2

Molding method of the magnet alloy plate material through a local softening process, characterized in that performed simultaneously by a mold containing a heat source (Heating element).

[Claim 8]

Magnesium alloy molded part molded by the molding method of any one of claims 1 to 7.

[Claim 9]

The method of claim 18, wherein the molded magnesium molded part is a magnesium molded part, characterized in that applied to large area parts of the transport equipment or electronics and electronic devices