KR20050065935A - Hot rolling method for mg alloy sheet - Google Patents

Abstract

The present invention relates to a hot rolling method of a magnesium sheet, which is hot rolled by hot rolling the magnesium sheet to 200-225 ° C. and increasing the edge temperature by 20-30 ° C.

This invention has the effect of producing a magnesium plate having an excellent microstructure without the edge crack of the plate.

Description

Hot Rolling Method of Magnesium Sheet {HOT ROLLING METHOD FOR Mg ALLOY SHEET}

The present invention relates to the rolling of magnesium (Mg) sheet, and more particularly, to a hot rolling method capable of obtaining a good magnesium sheet having a finer structure without edge cracking in hot rolling of the magnesium sheet.

Magnesium alloy is the lowest density metal among commercial structural alloys and has a density of 1.74 g / cc. This is about two thirds of aluminum and about one fifth of iron. In addition, magnesium alloy has excellent machinability, high vibration damping ability, excellent absorption against vibration and shock, and excellent electromagnetic shielding properties. In recent years, the use is rapidly expanding to parts such as computers, cameras, mobile phones, etc., because it is possible to form a thin plate due to light weight, excellent recyclability, electromagnetic shielding and high specific strength.

Most parts of Mg materials have been produced by die casting, but in recent years, a lot of researches have been conducted on the development of plate materials, and the production of parts by molding of plate materials is gradually increasing.

However, magnesium has a dense hexagonal lattice (HCP) structure with a small slip system, which is essential for plastic deformation. Therefore, most of the rolling is performed during the production of the sheet in hot or hot, and finally cold rolling is performed for surface properties.

However, if the rolling temperature is high during hot rolling, the rolling is easy, but mechanical properties are inferior due to surface oxidation and coarsening of grains. And when the rolling temperature is low, the mechanical properties are excellent and there is no oxidation problem, but there is a disadvantage that a lot of cracks occur at the edge of the plate during rolling.

The present invention is to solve the problems of the prior art as described above, it is an object of the present invention to provide a method of hot rolling that can produce a magnesium plate material having excellent mechanical properties without edge cracking.

The present invention for achieving the above object provides a method for hot rolling by increasing the hot rolling temperature of the magnesium sheet to 200 ~ 225 ℃ and the temperature of the edge 20 ~ 30 ℃.

In the rolling of a magnesium sheet, when the rolling temperature is high, dynamic recrystallization easily occurs during rolling, and grains grow rapidly during heating, and thus a fine structure cannot be obtained. In addition, when the rolling temperature is low, edge cracking occurs badly and a normal plate cannot be obtained.

Therefore, in the present invention, in order to prevent edge cracking while obtaining a microstructure, the overall rolling temperature is rolled at a temperature at which the microstructure is obtained, but the rolling is performed by raising the temperature of the edge portion to an appropriate degree.

Hereinafter, the present invention will be described through examples.

(Example)

Table 1 shows the results of rolling by adjusting the overall rolling temperature and the edge rolling temperature. The rolling reduction per pass was 30% and the size of the rolled sheet was approximately 100 mm × 100 mm × 3 mm.

At the rolling temperature of 175 ° C. or less, edge cracking occurred regardless of edge heating. At the rolling temperature of 250 ° C. or higher, edge cracking did not occur, but dynamic recrystallization occurred severely, and a fine grain was not obtained.

In addition, when the temperature variation of the edge was lowered below 10 ° C., the effect of edge heating could not be obtained. When the temperature of the edge was increased above 40 ° C., the edges were relatively easily elongated to generate waves in the plate.

<Table 1> Edge cracking pattern according to rolling condition

The results of the above examples are experimental results. Before the rolling test, the heating of the plate was performed by means of a hot plate, which was tested by placing a hot plate at each of the center and the edge of the plate. The central hot plate set temperature and the edge temperature means the edge heating hot plate set temperature.

Mg plate was tested based on set temperature because thermocouple welding was not good and accurate temperature measurement was difficult.

As described above, when rolling is performed by the method of the present invention, there is an effect of obtaining an excellent magnesium sheet having a fine structure without edge cracking.

1 is a photograph showing a state where edge cracking occurs in a hot-rolled magnesium sheet according to the prior art;

Figure 2 is a photograph showing an example of a plate having excellent microstructure without edge cracking by rolling under the conditions of the present invention.

Claims (1)

Magnesium plate hot rolling method in hot rolling of a magnesium plate material, hot rolling temperature is 200-225 degreeC and edge temperature is raised 20-30 degreeC.