KR101232221B1 - The method for preparing of Al-Mg-Mn alloy strip using twin roll cast and Al-Mg-Mn alloy strip - Google Patents

Abstract

The present invention relates to a method for producing a magnesium alloy cast using a double roll casting method and a magnesium alloy cast prepared according to this, more specifically, to prepare an aluminum-manganese mother alloy by mixing the aluminum ingot and manganese element (step 1) ; Mixing the magnesium ingot and the additive to prepare a magnesium-additive mother alloy (step 2); Preparing an molten alloy by adding the aluminum-manganese master alloy and the magnesium-addition master alloy prepared in Steps 1 and 2 to molten magnesium (Step 3); And a method of preparing magnesium alloy slabs using the twin roll casting method (step 4), the method comprising the steps of preparing the alloy slats using the molten alloy prepared in step 3 by using a twin roll casting method and the yield stress and the maximum tensile strength produced by the above method. It relates to a magnesium alloy cast alloy with improved mechanical properties, including.

Description

The method for preparing of Al-Mg-Mn alloy strip using twin roll cast and Al-Mg-Mn alloy strip}

The present invention relates to a method for producing a magnesium alloy cast using a twin roll casting method and a magnesium alloy cast prepared accordingly.

Magnesium alloy is excellent in low density, high strength and rigidity, and castability and machinability, and can be usefully used for light weight structure. Therefore, the use of magnesium alloys as a lightweight structural component is rapidly increasing, and high pressure die casting parts are mainly cast using near net-shape die-casting technology. However, process magnesium alloys are often expensive and difficult to cast at room temperature as compared to those cast by traditional methods. In addition, workable magnesium alloys generally have better mechanical properties than cast alloys, but still lack competition in the workmanship of magnesium, particularly plates, required to fabricate a variety of lightweight metals. Therefore, processing cost and moldability improvement are calculated | required.

In recent years, the twin roll casting method has the advantage of manufacturing a rolled product of thin sheet in one step process, and it is possible to economically manufacture a magnesium alloy sheet for processing from the melt by consisting of continuous cast steel casting and direct hot rolling. In addition, the twin roll casting method has an even distribution in the particle size of the formed non-metallic inclusions and the like, and maintains uniformity in the microstructure. In order to improve the strength and formability of the working magnesium alloy, the working magnesium alloy should have a uniform microstructure (particle size and shape) and a low anisotropy structure (crystal orientation distribution). High cooling rates facilitate dispersion strengthening upon solidification by alloying components with limited solubility in Mg alloys and facilitate solid solution strengthening, which is commonly used in ingot casting because it forms large intermetallic particles at low cooling rates. I never do that. Therefore, dispersion strengthening and solid solution strengthening is given - can be used for ssangrol casting with a relatively high cooling rate of 10 ³ k / s-speed solid for 10 ^second. Korean Patent Laid-Open Publication No. 10-2007-0087137 discloses a method for producing an Al-Mg-based aluminum alloy plate having a plate thickness of 0.5 to 3 mm cast and cold rolled by a twin roll continuous casting method. In addition, the Republic of Korea Patent No. 0711793 describes a casting roll of a twin-roll thin plate casting machine and a method for manufacturing a cast piece manufactured using the same. U.S. Patent Publication No. 2003/0196733 contains Fe 0.15-1.5%, Mn 0.35-1.9% and additionally Si <0.8%, Mg <0.2%, Cu <0.2%, Cr <0.2%, Zn <0.2% A method for producing an aluminum alloy slab is described, and U.S. Patent No. 6193818 contains Si 0.5-13%, Mg 0-2%, Cu 0-2%, Mn 0-1%, Fe 0-2% And casting an aluminum alloy having a thickness of 1.5-5 mm.

Therefore, the inventors of the present invention while studying a magnesium alloy plate produced by twin roll casting method, to add a Al to strengthen the solid solution and to add a Mn to cause the dispersion of the Al-Mn mixture to exhibit a uniform microstructure, Mixing to develop a magnesium alloy plate with improved mechanical properties, to complete the present invention.

An object of the present invention is to provide a method for producing a magnesium alloy cast using a twin roll casting method.

It is another object of the present invention to provide a magnesium alloy cast with improved yield strength and maximum tensile strength produced using a twin roll casting method.

In order to achieve the above object, the present invention comprises the steps of preparing an aluminum-manganese master alloy by mixing the aluminum ingot and manganese element (step 1); Mixing the magnesium ingot and the additive to prepare a magnesium-additive mother alloy (step 2); Preparing an molten alloy by adding the aluminum-manganese master alloy and the magnesium-addition master alloy prepared in Steps 1 and 2 to molten magnesium (Step 3); And it provides a method for producing a magnesium alloy cast using a twin roll casting method comprising the step (step 4) of producing an alloy cast using the molten alloy prepared in step 3 using a twin roll casting method.

In addition, the present invention provides a magnesium-aluminum-manganese alloy slab with improved yield stress and maximum tensile strength using the twin roll casting method.

Magnesium-aluminum-manganese alloy cast using the twin roll casting method according to the present invention, aluminum is added to strengthen the solid solution, manganese is added to promote dispersion strengthening, and has an improved microstructure than the ingot cast slab manufactured by the conventional method , Yield stress, maximum tensile strength and elongation also have improved values, so it can be useful as a lightweight structural material.

1 is an optical microscope (OM) photograph of an end portion of an alloy slab of Example 1 according to the present invention;
FIG. 2 is an optical microscope (OM) photograph and energy dispersive spectroscopy (EDS) analysis of the alloy cast of Example 1 according to the present invention;
3 shows the results of scanning electron micrograph and energy dispersive spectroscopy (EDS) of Comparative Example 1;
4 is an optical micrograph after the rolling process of Example 1 and Comparative Example 1 alloy cast according to the present invention;
5 is an optical micrograph after the heat treatment of the alloy specimens of Example 1 and Comparative Example 1;
6 is an optical micrograph of an end portion of an alloy slab of Example 3 according to the present invention;
7 is an optical microscope photograph of Example 3 alloy slab and Comparative Example 3 alloy slab according to the present invention;
8 is an optical microscope photograph after the rolling process of Example 3 and Comparative Example 3 alloy cast according to the present invention;
9 is an optical microscope photograph after heat treatment of the alloy cast of Example 3 and Comparative Example 3;
10 is a stress-strain graph of a magnesium-aluminum-manganese-calcium alloy slab (Example 2) produced by a twin roll casting method according to the present invention (Comparative Example 2);
11 is a stress-strain graph of a magnesium-aluminum-manganese-calcium alloy slab prepared by the twin roll casting method (Example 4) and an alloy slab prepared by the ingot casting method (Comparative Example 4); And
12 is a graph showing yield stress, ultimate tensile stress and elongation of Examples 2, 4 and 6 and Comparative Examples 2, 4 and 6 according to the present invention.

Mixing the aluminum ingot and manganese element to produce an aluminum-manganese master alloy (step 1);

Mixing the magnesium ingot and the additive to prepare a magnesium-additive mother alloy (step 2);

Preparing an molten alloy by adding the aluminum-manganese master alloy and the magnesium-addition master alloy prepared in Steps 1 and 2 to molten magnesium (Step 3); And

A method of manufacturing a magnesium alloy cast using the twin roll casting method comprising the step (step 4) of manufacturing an alloy cast using the molten alloy prepared in step 3 by a twin roll casting method.

Hereinafter, the present invention will be described in detail step by step.

First, in the method of manufacturing a magnesium alloy cast using the twin roll casting method according to the present invention, step 1 is a step of producing an aluminum-manganese mother alloy by mixing the aluminum ingot and manganese element.

The content of aluminum and manganese in step 1 is preferably 2.5 to 3.5% by weight, 0.2 to 1.5% by weight based on the magnesium alloy cast. If the aluminum content is less than 2.5% by weight, there is a problem that the strength is lowered. If the content of aluminum is more than 3.5% by weight, precipitation phases such as Mg ₁₇ Al ₁₂ and Al ₈ Mn ₅ , which are not good for corrosiveness and weaken solid solution strengthening, are present. There is a problem formed. In addition, when the content of manganese is less than 0.2% by weight, there is a problem in that the dispersed precipitated phase is less, and when it exceeds 1.5% by weight, the dispersed precipitated phase is excessively coarse to reduce the ductility.

Next, in the method of producing a magnesium alloy cast using a twin roll casting method according to the present invention, step 2 is a step of preparing a magnesium-additive mother alloy by mixing the magnesium ingot and the additive.

At this time, the additive of step 2 may be calcium, cerium and lanthanum, or yttrium.

In the case of preparing a master alloy of magnesium-calcium, the content of calcium is preferably 0.10-1.0% by weight based on the magnesium alloy cast. If the calcium content is less than 0.10% by weight, there is no effect on the high temperature resistance and corrosion resistance of the magnesium alloy, and when the calcium content exceeds 1.0% by weight, there is a problem in that the master alloy is burned and oxidized in the melting process.

In the case of manufacturing the magnesium-cerium-lanthanum master alloy, the content of cerium and lanthanum is preferably 0.05 to 0.5% by weight and 0.05 to 0.5% by weight based on the magnesium alloy slab, respectively. If the content of cerium and lanthanum is less than 0.05% by weight, there is a problem in that a uniform and fine crystal structure is not generated because the microstructure and structure of the magnesium alloy are not changed, and the sum of the content of cerium and lanthanum exceeds 1.0% by weight. In this case, there is a problem in that the grain refining effect is reduced.

When producing a magnesium-yttrium master alloy, the content of yttrium is preferably 0.1 to 1.0 wt% based on the magnesium alloy slab. If the yttrium refining effect is relatively insignificant than that of adding cerium-lanthanum, and the yttrium content is less than 0.1 wt%, the effect of grain refinement or solid solution strengthening is not great. There is a problem in that crack propagation is promoted.

Next, in the method of manufacturing a magnesium alloy cast using the twin roll casting method according to the present invention, step 3 is an alloy by adding the aluminum-manganese master alloy and magnesium-additive master alloy prepared in Step 1 and Step 2 to the molten magnesium It is a step of preparing a molten metal.

At this time, the molten alloy is preferably maintained for 20 to 40 minutes at 700-800 ℃. If the temperature is less than 700 ℃, there is a problem of low fluidity of the molten metal, if the temperature exceeds 800 ℃ there is a problem that the gas content due to overheating increases. In addition, if the time is less than 20 minutes, there is a problem that the dispersion is reduced by the complete solid solution of the alloying elements, if more than 40 minutes there is a problem that excessive energy is consumed in terms of energy efficiency.

Next, in the method for producing a magnesium alloy cast using a twin roll casting method according to the present invention, step 4 is a step of producing an alloy cast using a double roll casting method of the molten alloy prepared in step 3.

For a twin roll casting process, molten metal, which is molten metal, flows into a casting tundish under a cooling slab, whereupon the molten metal is moved to a rotating roller surface. The molten metal solidified rapidly in contact with the cooled roller and rolled between the upper and lower rollers.

At this time, it is preferable that the roll speed in the twin roll casting process is 3 to 3.5 rpm, and the interval between rolls is 3.0 to 4.0 mm. If the roll speed is less than 3 rpm, there is a problem that the liquid-liquid interface is located in front of the roll, if the roll speed exceeds 3.5 rpm, there is a problem that the solid-liquid interface is located behind the roll. Moreover, when the space | interval between rolls is less than 3.0 mm, there exists a problem that productivity falls, and when it exceeds 4.0 mm, there exists a problem that a solidification rate becomes slow and a structure becomes coarse.

In addition, in the method of manufacturing a magnesium alloy cast using a twin roll casting method according to the present invention, the alloy slab prepared in step 4 is heat-treated and warm-rolled 1 to 7 times using a two-roller mill. It may further comprise the step of post-heat treatment.

Prior to the warm rolling, the magnesium-aluminum-manganese-calcium alloy slabs prepared by the twin roll casting method are preheated and passed through a twin roller mill to perform a warm rolling process. The twin roller mill is heated to 200-300 ° C., and the speed of the twin roller mill is variable depending on the roller mill function, but in the present invention, it is preferable to perform at 3.0-4.0 rpm. Warm rolling is preferably carried out until a reduction of about 86% is made over 1 to 7 times in order to reduce the thickness of the slabs, and the alloy slabs are reheated between the points passing through the twin roller mills.

At this time, it is preferable to heat-treat the alloy cast for 20-40 minutes at 300-400 ℃ before performing the warm rolling. The electrothermal treatment is a process for completely dissolving and dispersing an alloying element. When the electrothermal treatment is less than 300 ° C., there is a problem that the alloying element is not dissolved, is precipitated on the crystal of the alloy slab, and is not evenly dispersed on the alloy slab. If it exceeds 400 ℃ there is a problem in that the alloy element is burned and energy is consumed in excess in terms of energy efficiency.

In addition, when the heating temperature of the twin roller mill is less than 200 ℃, there is a problem that the rolling bonds due to crack generation increases, and when it exceeds 300 ℃, there is a problem that the roller surface sintering and roller equipment management is difficult.

In addition, after performing the warm rolling process, the alloy slab is preferably heated for 3-7 minutes at 300-400 ℃. If the heating temperature is less than 300 ℃, there is a problem that the rolling bond is increased by the crack generation, when the heating temperature is higher than 400 ℃ there is a problem that the surface state of the plate material is not good. In addition, the warm rolling is preferably performed 1 to 7 times, more preferably to be carried out 7 times, and if more than 7 times, work hardening occurs, so that sufficient intermediate annealing treatment is performed to soften it. There is a problem that needs to be done.

In addition, the post-heat treatment is preferably carried out at 300-400 ℃ for 50-70 minutes. If the heat treatment is less than 300 ℃, there is a problem that does not sufficiently remove the internal stress, if the heat treatment exceeds 400 ℃ there is a problem that the surface oxidation is increased and excess energy is consumed.

In addition, the present invention provides a magnesium alloy cast with improved mechanical properties, including yield stress and maximum tensile strength produced by the twin roll casting method.

Magnesium alloy cast steel according to the present invention has an improved microstructure, and has improved values in yield stress, maximum tensile strength and elongation, it can be useful as a lightweight structural material (see Experimental Example 5).

Hereinafter, the present invention will be described in more detail by way of examples. It should be noted, however, that the following examples are illustrative of the invention and are not intended to limit the scope of the invention.

Example 1 Preparation of Magnesium-Aluminum-Manganese-Calcium Alloy Cast Iron Using Twin Roll Casting Method 1

A horizontal twin roll casting machine with a water cooling system was used to produce magnesium alloy slabs. Copper alloy twin rollers with a diameter of 300 nm were used in horizontal twin roll casting machines. Pure magnesium and aluminum ingots were used to produce the alloy. Manganese and calcium elements were added in the form of Al-10% by weight, Mn and Mg-30% by weight, alloying elements of Ca, SF ₆ as a protective gas to protect the molten alloy And CO ₂ were used. Alloying elements of Al, Al-Mn, and Mg-Ca master alloys were added to the molten magnesium at 750 ° C., and the molten metal was held at 750 ° C. for 30 minutes to completely dissolve and disperse the alloy elements. For twin roll casting, the molten metal was allowed to flow into the casting tundish under the cooling slop, after which the molten metal was moved to the rotating roller surface. The molten metal solidified rapidly in contact with the cooled roller and rolled between the upper and lower rollers. The rolling speed is 3-3.25 rpm and the roller spacing is 3 mm. A magnesium-aluminum-manganese-calcium alloy slab (Al: 3.27 wt%, Mn: 0.52 wt%, Ca: 0.12 wt%, Mg: bal.) Having a thickness of 4 mm, a width of 180 mm, and a length of 10 m was prepared.

Example 2 Preparation of Magnesium-Aluminum-Manganese-Calcium Alloy Cast Steel Using Twin Roll Casting Method 2

Magnesium-aluminum-manganese alloy slabs were prepared in the same manner as in Example 1, except that the heat-treated, warm-rolled and post-heated treatments were carried out to produce an equiaxed and fine grained magnesium alloy plate. It was. Magnesium-aluminum-manganese-calcium alloy slabs prepared by twin roll casting were reheated at 350 ° C. for 30 minutes before warm rolling, and passed through a roller mill having a roller diameter of 200 mm. The roller was heated to 250 ° C. and operated at 3.5 rpm. Between each passing point the alloy was reheated at 350 ° C. for 5 minutes. Warm rolling was performed until the slab thickness was reduced by about 86% over seven times to reduce the thickness of the slab from 4.0 mm to 0.56 mm, and the heat treatment was carried out at 350 ° C. for 60 minutes to carry out the magnesium-aluminum-manganese-calcium alloy cast. Was prepared.

Example 3 Preparation of Magnesium-Aluminum-Manganese-Cerium-Lanthanum Alloy Cast Steel Using Twin Roll Casting Method 1

Manganese element, cerium element and lanthanum element were added in the form of Al-10 wt%, Mn and Mg-30 wt%, alloy elements of cerium and lanthanum, and alloys of Al, Al-Mn, and Mg-Ce-La master alloys. Except for adding the element to the molten magnesium, magnesium-aluminum-manganese-cerium-lanthanum alloy cast (Al: 3.16% by weight, Mn: 0.50% by weight, Ce: 0.06% by weight) in the same manner as in Example 1 La 0.10 wt%, Mg: bal.) Was prepared.

Example 4 Preparation of Magnesium-Aluminum-Manganese-Cerium-Lanthanum Alloy Cast Steel Using Twin Roll Casting Method 2

In order to manufacture a magnesium alloy plate for processing the alloy cast slab prepared in Example 3 is equiaxed and has a fine grain structure, the same electrothermal treatment, warm rolling and post-heat treatment process as in Example 2 were carried out. Manganese-cerium-lanthanum alloy slabs were prepared.

Example 5 Preparation of Magnesium-Aluminum-Manganese-Yttrium Alloy Cast Iron by Twin Roll Casting Method 1

Manganese element and yttrium element were added in the form of Al-10 wt%, Mn and Mg-30 wt%, yttrium alloy elements, and alloy elements of Al, Al-Mn and Mg-Y master alloys were added to the molten magnesium. A magnesium-aluminum-manganese-yttrium alloy slab (Al: 2.75 wt%, Mn: 0.26 wt%, Y: 0.32 wt%, Mg: bal.) Was prepared in the same manner as in Example 1.

Example 6 Preparation of Magnesium-Aluminum-Manganese-Yttrium Alloy Cast Iron by Twin Roll Casting Method 2

In order to manufacture a magnesium alloy sheet for processing the alloy cast slab prepared in Example 5 having an equiaxed and fine grain structure, the same electrothermal treatment, warm rolling and post-heat treatment process as in Example 2 were performed. Manganese-yttrium alloy slabs were prepared.

Comparative Example 1 Preparation of Magnesium-Aluminum-Manganese-Calcium Alloy Cast Steel Using Ingot Casting Method 1

The molten alloy prepared in Example 1 was injected into a metal mold having a size of 180 mm × 160 mm × 25 mm at 720 ° C. to cast magnesium-aluminum-manganese-calcium alloy slab (Al: 3.37 wt%, Mn: 0.59 wt%, Ca: 0.14 wt%, Mg: bal.) Was prepared.

Comparative Example 2 Preparation of Magnesium-Aluminium-Manganese-Calcium Alloy Cast Using Ingot Casting Method 2

Magnesium-aluminum-manganese-calcium alloy slabs were manufactured by performing the same heat treatment, warm rolling, and post-heat treatment processes as those of Example 2 on the alloy slabs prepared in Comparative Example 1.

Comparative Example 3 Preparation of Magnesium-Aluminum-Manganese-Cerium-Lanthanum Alloy Cast Using Ingot Casting Method 1

The molten alloy prepared in Example 3 was injected into a metal mold having a size of 180 mm × 160 mm × 25 mm at 720 ° C. to cast magnesium-aluminum-manganese-cerium-lanthanum alloy slab (Al: 3.30 wt%, Mn: 0.70 wt) %, Ce: 0.07 wt%, La: 0.11 wt%, Mg: bal.) Was prepared.

Comparative Example 4 Preparation of Magnesium-Aluminum-Manganese-Cerium-Lanthanum Alloy Cast Using Ingot Casting Method 2

Magnesium-aluminum-manganese-cerium-lanthanum alloy slabs were prepared by performing the same heat treatment, warm rolling, and postheat treatment processes as those of Example 2 on the alloy slabs prepared in Comparative Example 3.

Comparative Example 5 Preparation of Magnesium-Aluminum-Manganese-Yttrium Alloy Cast by Using Ingot Casting Method 1

The molten alloy prepared in Example 5 was injected into a metal mold having a size of 180 mm × 160 mm × 25 mm at 720 ° C. to cast magnesium-aluminum-manganese-yttrium alloy slab (Al: 3.30 wt%, Mn: 0.70 wt%, Y: 0.45 wt%, Mg: bal.) Was prepared.

Comparative Example 6 Preparation of Magnesium-Aluminum-Manganese-Yttrium Alloy Cast Iron by Ingot Casting Method 2

The alloy cast slab prepared in Comparative Example 3 was subjected to the same heat treatment, warm rolling, and post-heat treatment process as in Example 2, to prepare a magnesium-aluminum-manganese-yttrium alloy cast.

The chemical composition, the number of warm rolling and the heat treatment conditions of Examples 1 to 6 and Comparative Examples 1 to 6 are shown in Table 1 above.

Yes Al
(weight%) Mn
(weight%) Ca
(weight%) Ce
(weight%) La
(weight%) Y
(weight%) Mg
(weight%) Casting method Heat treatment, hot rolling and post heat treatment
The presence or absence Example 1 3.27 0.52 0.12 Honey. Double Roll Casting X Example 2 3.27 0.52 0.12 Honey. Double Roll Casting O Example 3 3.16 0.50 0.06 0.10 Honey. Double Roll Casting X Example 4 3.16 0.50 0.06 0.10 Honey. Double Roll Casting O Example 5 2.75 0.26 0.32 Honey. Double Roll Casting X Example 6 2.75 0.26 0.32 Honey. Double Roll Casting O Comparative Example 1 3.37 0.59 0.14 Honey. Ingot casting X Comparative Example 2 3.37 0.59 0.14 Honey. Ingot casting O Comparative Example 3 3.30 0.70 0.07 0.11 Honey. Ingot casting X Comparative Example 4 3.30 0.70 0.07 0.11 Honey. Ingot casting O Comparative Example 5 2.89 0.34 0.45 Honey. Ingot casting X Comparative Example 6 2.89 0.34 0.45 Honey. Ingot casting O

Experimental Example 1 Analysis of Microstructure of Magnesium Alloy Cast

To investigate the microstructure of the magnesium-aluminum-manganese-calcium alloy slab according to the present invention, an optical microscope (OM) and energy dispersive spectroscopy (EDS) analysis were performed, and the results are shown in FIGS. 1, 2, and 3.

1 is an optical micrograph of an end portion of an alloy cast of Example 1 according to the present invention, it can be seen that the alloy structure of Example 1 is different from the surface to the center of the microstructure. Columnar dendrite was observed on the surface, and it can be seen that it is oriented at 45-80 ° along the casting roll direction (see FIG. 1 (a)), which indicates directional solidification (solidification) during the twin roll casting process. This is due to the combination of and high temperature deformation. It can be seen from Figure 1 (b) that the columnar isotropic transition occurred in the middle thickness portion. No distinct macro-segregation was found in the alloy cast of Example 1 above.

In addition, Figure 2 (a) is a close-up photographed by an optical micrograph of the alloy cast steel of Example 1 according to the present invention, the alloy cast steel of Example 1 can be seen that there are small primary particles dispersed in the dendritic interface. . The average size of the dispersed particles was about 1 μm. 3A is a scanning electron micrograph of Comparative Example 1, and it can be seen that acicular phases exist along grain boundaries or inside grain boundaries, as well as large polygons and relatively small round particles. Therefore, it can be seen that Example 1 alloy slab according to the present invention is composed of particles of a smaller size compared to Comparative Example 1 alloy slab.

2 (b) and 3 (b) show the results of energy dispersive spectroscopy, most of the dispersed primary particles are mainly composed of Al and Mn, the dispersed primary particles Al ₈ Mn ₅ and the needle-shaped phases shown in Comparative Example 1 were (AlMg) ₂ Ca phases. The energy dispersive spectroscopic analysis shows that the average composition of Al and Mn elements in the α-Mg matrix of Example 1 is higher than that of Comparative Example 1, which means that the twin roll casting process has a faster solidification rate than the conventional ingot casting process. It can be seen that fine primary particles are dispersed and high solubility of Al and Mn elements in the α-Mg matrix.

Experimental Example 2 Analysis of Microstructure after Warm Rolling Process and Heat Treatment of Magnesium Alloy Cast

In order to determine the microstructure after the warm rolling process and heat treatment of the magnesium-aluminum-manganese-calcium alloy cast according to the present invention, an optical microscope (OM) was used, and the results are shown in Table 2 and FIGS. 4 and 5.

Yes Average particle size (㎛) Average diameter (㎛) Example 2 ～ 7.8 -0.8 Comparative Example 2 -11.2 -6.5

4 is an optical micrograph after the rolling process of the alloy cast of Example 1 and Comparative Example 1 according to the present invention, Example 1 is fine and uniform particles having an average diameter of about 0.8 ㎛ after warm rolling Although it can be seen that the dispersion, Comparative Example 1 can be seen that the particles having an average diameter of about 6.5 ㎛ uniformly dispersed (see Table 2). In Comparative Example 1, relatively small particles of 1 to 3 μm tend to be arranged in a line, which means that large primary particles are broken during the warm rolling process. Therefore, it can be seen that the warm rolling process makes the primary particles more fine and uniformly dispersed.

In addition, Figure 5 is an optical micrograph after the heat treatment of the alloy slabs of Example 1 and Comparative Example 1, as shown in Figure 5 (a), Example 2 alloy slab according to the present invention that was subjected to warm rolling and heat treatment is static It was found that recrystallization occurred, uniform nucleation and crystal growth resulted in fine crystals and equiaxed microstructures. The grain size was about 7.8 μm. On the other hand, as shown in (b) of FIG. 5, the particle size of the alloy slab of Comparative Example 2, which was warm-rolled and heat-treated, was about 11.2 µm, and it was found that the particle size of the alloy slab of Example 2 was larger than that of the alloy slab, which was about 10 µm in diameter. Particles with dominantly appeared (see Table 2).

Experimental Example 3 Microstructure Analysis of Magnesium Alloy Cast 2

In order to determine the microstructure of the magnesium-aluminum-manganese-cerium-lanthanum alloy slab according to the present invention, an optical microscope (OM) was used, and the results are shown in FIGS. 6 and 7.

FIG. 6 is an optical micrograph of an end portion of an alloy slab of Example 3 according to the present invention, and in Example 3, the alloy slab has a microstructure from the surface (FIG. 6A) to the center (FIG. 6B). It can be seen that it is different. Columnar dendrite was observed oriented at 40-80 ° along the casting roll direction at the surface. This is due to the combination of directional solidification (solidification) and high temperature deformation during the twin roll casting process. No distinct macro-segregation was found in the alloy cast of Example 3 above. Example 3 The microstructure difference between the surface and the center of the alloy slab is due to different solidification rates along the thickness direction.

In addition, Figure 7 is an optical photomicrograph of the alloy slab of Example 3 and Comparative Example 3 in accordance with the present invention in close proximity, the alloy slab of Example 3 is found that the presence of small primary particles dispersed in the dendritic interface (See FIG. 7A). The average size of the dispersed particles was about 1 μm. Figure 7 (b) is an optical micrograph of Comparative Example 3, it can be seen that the acicular phases (acicular phases) as well as the large polygons, relatively small round particles are present along the grain boundaries or inside the grain boundaries. Therefore, it can be seen that the Example 3 alloy slab according to the present invention is composed of primary particles having a smaller size as compared with the Comparative Example 3 alloy slab.

Experimental Example 4 Analysis of Microstructure after Warm Rolling Process and Heat Treatment of Magnesium Alloy Cast 2

In order to investigate the microstructure after the warm rolling process and heat treatment of the magnesium-aluminum-manganese-cerium-lanthanum alloy cast according to the present invention, an optical microscope (OM) was analyzed and the results are shown in FIGS. 8 and 9.

Yes Average particle size (㎛) Average diameter (㎛) Example 4 ～ 8 -0.8 Comparative Example 4 -15 -6.5

8 is an optical micrograph after the rolling process of the alloy slabs of Example 3 and Comparative Example 3 according to the present invention, Example 3 is fine and uniformly dispersed particles having an average diameter of 1.0 ㎛ or less after warm rolling As can be seen, Comparative Example 3 shows that the particles having an average diameter of about 6.5 μm are non-uniformly dispersed. In Comparative Example 1, relatively small particles of 1 to 3 μm tend to be arranged in a line, which means that large primary particles are broken during the warm rolling process. Therefore, it can be seen that the warm rolling process makes the primary particles more fine and uniformly dispersed.

9 is an optical micrograph after heat treatment of the alloy slabs of Example 3 and Comparative Example 3, as shown in FIG. It was found that recrystallization occurred and uniform nucleation and crystal growth resulted in fine crystals and equiaxed microstructures. The grain size was about 8 μm. On the other hand, as shown in (b) of FIG. 9, the particle size of the alloy slab of Comparative Example 4, which was warm-rolled and heat-treated was about 15 ㎛, it can be seen that the larger than the particle size of the alloy slab of Example 2, 5-8 ㎛ Particles with diameter appeared mainly (see Table 3).

Experimental Example 5 Analysis of yield stress, maximum tensile strength and elongation of magnesium alloy cast

Yield stress, maximum tensile strength and elongation of the magnesium-aluminum-manganese-calcium alloy cast according to the present invention according to the present invention were analyzed, and the results are shown in Table 4 and FIGS. 10, 11, and 12.

Yes Yield Stress (YS, MPa) Tensile strength (UTS, MPa) Elongation (%) Example 2 237 300 24.8 Example 4 250 309 24.1 Example 6 262 315 21.8 Comparative Example 2 162 220 20.5 Comparative Example 4 170 232 25.4 Comparative Example 6 202 258 21.0

The magnesium-aluminum-manganese-calcium alloy slabs (Example 2) and the magnesium-aluminum-manganese-cerium-lanthanum alloy slabs (Example 4) prepared by the twin roll casting method according to the present invention are alloy slabs (comparatively prepared) It can be seen that yield stress, ultimate tensile stress, and similar elongation are higher than those of the alloy cast (Comparative Example 4) manufactured by Example 2) and the ingot casting method (see FIG. 12). .

The overall mechanical properties indicate that the alloy slabs produced by the twin roll casting method according to the present invention are improved over the alloy slabs produced by the ingot casting method, and are due to the particles and the grain strengthening effect by the finely dispersed particles and the small size crystals.

10 and 11 are magnesium-aluminum-manganese-calcium alloy slabs (Examples 2 and 4) prepared by the twin roll casting method according to the present invention and alloy slabs (Comparative Example 2, Comparative Example) prepared by the ingot casting method. By showing the stress-strain curve of 4), it can be seen that the alloy slabs produced by the twin roll casting method can withstand high stress.

Claims (14)

Mixing the aluminum ingot and manganese element at 2.5-3.5 wt% and 0.2-1.5 wt% based on the magnesium alloy slab, respectively, to prepare an aluminum-manganese master alloy (step 1);
Magnesium ingot and additives are mixed, wherein the additive is any one selected from the group consisting of calcium, cerium and lanthanum and yttrium,
The calcium is 0.10-1.0 wt% based on the magnesium alloy cast,
The cerium and lanthanum are 0.05-0.5% by weight and 0.05-0.5% by weight based on the magnesium alloy cast, respectively,
Preparing a magnesium-additive mother alloy by mixing the yttrium with the magnesium ingot and the additive, wherein the yttrium is 0.1 to 1.0 wt% based on the magnesium alloy cast (step 2);
Preparing an molten alloy by adding the aluminum-manganese master alloy and the magnesium-addition master alloy prepared in Steps 1 and 2 to molten magnesium (Step 3); And
Method of producing a magnesium alloy cast using a twin roll casting method comprising the step (step 4) of producing an alloy cast using the molten alloy prepared in step 3 using a twin roll casting method.
delete delete delete delete delete The method of claim 1, wherein the molten alloy of step 3 is maintained at 700-800 ° C for 20-40 minutes.
The method of claim 1, wherein the twin roll casting of step 4 has a roll speed of 3 to 3.5 rpm and an interval between rolls of 3.0 to 4.0 mm.
The method of claim 1, further comprising the step of heat-treating the alloy slab prepared in step 4 and the post-heat treatment 1-7 times warm rolling using a two-roller mill (two-roller mill). Method for producing magnesium alloy cast using the casting method.
10. The method of claim 9, wherein the electrothermal treatment is performed at 300-400 ° C for 20-40 minutes.
The method of claim 9, wherein the twin roller mill is heated to 200-300 ℃, the speed is 3.0-4.0 rpm manufacturing method of magnesium alloy cast using a twin roll casting method.
10. The method of claim 9, wherein the alloy cast is heated for 3 to 7 minutes at 300-400 ° C for every one warm rolling.
10. The method of claim 9, wherein the post-heat treatment is performed at 300-400 ° C. for 50-70 minutes.
Magnesium alloy slab prepared by the method of any one of claims 1 and 7 to 13.

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