JP5376508B2 - High strength magnesium alloy sheet having excellent cold formability and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnesium alloy sheet material having superior cold-forming characteristics, and to provide a manufacturing method therefor. <P>SOLUTION: The sheet material of the magnesium alloy is made from a wrought magnesium alloy which includes, by mass%, 5.0-9.5% aluminum, 0.2-2.0% zinc, 0.05-1.0% manganese and the balance magnesium with unavoidable impurities. The method for manufacturing the magnesium alloy sheet material to be press-formed includes: rolling the sheet material of the magnesium alloy at a high temperature in a range from a temperature 70&deg;C lower than the solidus temperature to the solidus temperature, once or a plurality of times as finish rolling. The magnesium alloy material to be press-formed produced by the method is also disclosed. Thus provided high-strength magnesium alloy sheet material has the superior cold-forming characteristics. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  TECHNICAL FIELD The present invention relates to a magnesium alloy plate material for press molding having high strength and excellent cold formability, and a method for producing the same, and more specifically, a high strength, high aluminum content AZ-based magnesium alloy plate material. A method for producing a magnesium alloy plate material for press forming, which can produce a magnesium alloy press-formed body having a complex shape at room temperature by performing high temperature rolling and randomizing the texture, and the press The present invention relates to a magnesium alloy sheet for forming. The present invention is a high-aluminum-content AZ-based magnesium alloy in which dynamic recrystallization is likely to occur. By performing high temperature rolling, fine crystal grains of several to tens of μm are obtained by dynamic recrystallization. It provides a magnesium alloy sheet that can weaken the structure and greatly improve cold formability, and can be used in a wide range of fields such as automobiles, electronic equipment, space and aviation. It provides new technologies and new products related to magnesium alloy sheet with excellent cold formability.

  Magnesium alloys have the lowest density, high specific strength, excellent vibration damping ability, and dent resistance characteristics among practical metal materials, and have many advantages in applications to transportation equipment. ing. However, in the normal constant-speed rolling method, the hexagonal c-plane which is a slip plane is strongly crystallized so as to be parallel to the rolling plane, and deformation in the plate thickness direction becomes extremely difficult. The room temperature Erichsen value of the magnesium alloy rolled material is 3 to 5, and the cold formability is extremely poor, which hinders application as a plate material. Moreover, the normal AZ31B rolled material (annealed material) has a defect that the tensile strength is 250 to 260 MPa and the strength is insufficient. It is expected that a further lightening effect can be obtained by increasing the strength.

  The formability of the magnesium alloy sheet can be improved by randomizing the texture or by inclining the hexagonal c-plane from the rolled surface. Recently, it has been reported that the AZ31B magnesium alloy has a bottom texture weakened by high-temperature rolling at 450 ° C. and has improved cold stretch formability, but the room temperature Erichsen value is 4.7. The range (3-5) of the room temperature Erichsen value of the rolled alloy material is not exceeded (Non-patent Document 1).

  Compared with the AZ31B alloy, the AZ61 and AZ80 alloys containing more aluminum have higher strength, and the aging treatment after forming can further improve the proof stress and the strength, and also the surface treatment property. It is an excellent material that exhibits better corrosion resistance. However, since the AZ61 alloy and the AZ80 alloy may be inferior in ductility compared with the AZ31B alloy, the AZ61 alloy and the AZ80 alloy have hardly been applied as rolling materials until now. At present, such a high aluminum content AZ-based magnesium alloy is at a level at which a thin plate can be produced, and research and development aimed at high formability have not yet been developed. The room temperature Erichsen value of the rolled alloy material is about 3 (Non-patent Document 2).

  When the amount of aluminum in the AZ-based magnesium alloy increases, the stacking fault energy decreases, dynamic recrystallization is promoted during hot working, and a structure having finer crystal grains can be formed at the same working temperature. It has been reported (Non-Patent Document 3). However, the effect of rolling temperature on the formability of AZ-based magnesium alloys with a high aluminum content is unclear, and AZ-based magnesium alloys have a rolling temperature of up to 450 ° C. even at normal rough rolling temperatures. However, no high temperature rolling at a high temperature of about 500 ° C. has been reported yet. As described above, since the magnesium alloy plate material having both high strength and easy formability has not been obtained in the prior art, in this technical field, a magnesium alloy having such high strength and easy formability. There was a strong demand to develop board materials.

Scripta Materialia, (2008), Vol. 60 (2009) pp. 447-450 Press technology, Vol. 46 (2008) p. 56-61 Scripta Materialia, Vol. 56 (2008) pp. 237-240

  Under such circumstances, the present inventors have developed a magnesium alloy sheet for press forming that has high strength and excellent cold formability with a magnesium alloy for drawing in view of the above prior art. As a result of earnest research as a target, high-aluminum content AZ-based magnesium alloy sheet material is subjected to high-temperature rolling in a temperature range from 70 ° C. lower than the solidus temperature to the solidus temperature, It has been found that the intended purpose can be achieved by randomizing the texture, and the present invention has been completed. SUMMARY OF THE INVENTION An object of the present invention is to provide a magnesium alloy sheet for press forming, which is a wrought magnesium alloy and has excellent cold formability, and a method for producing the same. Another object of the present invention is to provide a magnesium alloy sheet for press forming having high strength and excellent easy formability, and a method for producing the same.

The present invention for solving the above-described problems comprises the following technical means.
(1) 5.0 to 9.5 mass% of aluminum, and zinc 0.2 to 2.0% by weight, and 0.05 to 1.0 mass% of manganese, and the balance of magnesium and unavoidable impurities To a magnesium alloy plate made of the above-mentioned, the roll circumferential speed ratio of the upper and lower rolls is at least 1.3, or rolling is performed by combining the constant speed rolling and the different circumferential speed rolling, and the solidus temperature A method for producing a magnesium alloy sheet for press forming, characterized in that high temperature rolling is performed in a temperature range from a temperature lower by 70 ° C. to a solidus temperature, and final rolling or rolling is performed once.
( 2 ) Rolling by combining the previous stage rolling at a temperature lower than the high temperature final rolling and the final rolling in a temperature range from 70 ° C. lower than the higher temperature solidus temperature to the solidus temperature , The manufacturing method of the magnesium alloy plate material for press forming as described in (1 ) .
( 3 ) The manufacturing method of the magnesium alloy plate material for press forming as described in said (1) which performs high temperature rolling in the range from 450 degreeC to 530 degreeC.
( 4 ) A magnesium alloy sheet for extension produced by the method described in (1) above, wherein 6.9 to 8.2 % by mass of aluminum; 5 to 0.6 mass% zinc; The room temperature elixir value measured according to JIS Z2247 and JIS B7729 is composed of a magnesium alloy composed of 21 to 0.25 % by mass of manganese and the balance of magnesium and inevitable impurities. A magnesium alloy sheet for press forming, characterized in that
( 5 ) The magnesium alloy sheet for press forming according to ( 4 ), which exhibits a tensile strength of at least 300 MPa and a room temperature Erichsen value of at least 5.3.
( 6 ) The pole of the (0002) pole figure is inclined at least 5 ° in the rolling direction, the maximum strength of the bottom texture is 5.0 at most, and the crystal grain size is 5 μm to 20 μm, 4 ) or the magnesium alloy sheet according to ( 5 ).
( 7 ) The magnesium alloy sheet according to ( 4 ) or ( 5 ), wherein the maximum strength of the bottom texture of the (0002) pole figure is 5.0 at most and the crystal grain size is 5 μm to 20 μm.
( 8 ) The magnesium alloy sheet according to ( 4 ) or ( 5 ), wherein the Rankford value (r value) is reduced to 1.41 at most as an average r value with respect to the alloy sheet before rolling. .
( 9 ) The magnesium alloy sheet according to ( 4 ) or ( 5 ), wherein the work hardening index (n value) is improved to at least 0.29 as an average n value with respect to the alloy sheet before rolling. .

Next, the present invention will be described in more detail.
The present invention is a magnifying magnesium alloy of 5.0 to 9.5 mass% aluminum, 0.2 to 2.0 mass% zinc, and 0.05 to 1.0 mass%. On the magnesium alloy plate made of manganese and the balance magnesium and inevitable impurities , roll speed ratio of the upper and lower rolls is at least 1.3, or constant speed rolling and the different speed rolling Is characterized by performing high temperature rolling in a temperature range from a temperature lower by 70 ° C. than the solidus temperature to the solidus temperature and rolling in one final roll or multiple times. is there. In order to obtain better cold formability, it is preferable to perform rolling at a higher temperature within a temperature range that does not exceed the solidus temperature.

  When rolled at a high temperature, the rolled texture is weakened along with dynamic recrystallization due to the activity of non-bottom sliding and grain boundary sliding, and cold formability can be improved. In addition, the magnesium alloy constituting the magnesium alloy sheet of the present invention contains more aluminum than, for example, AZ31 alloy, so it has high strength and further improves proof stress and strength by aging treatment after forming. Is possible.

  In order to obtain more excellent cold formability, different peripheral speed rolling is preferable to constant speed rolling. Different peripheral speed rolling is performed by using rolls with different peripheral speeds, so that the position of the neutral point is shifted and the friction force direction is reversed in the region sandwiched between them, so the entire thickness direction of the material In addition, it is possible to introduce a shear strain and thereby to control the texture.

In the examples described later, a commercially available AZ61 (Mg-6.9% Al-0.5% Zn-0.21% Mn, weight ratio) magnesium alloy extruded plate having a thickness of 5 mm or a commercially available AZ80 (Mg) having a thickness of 5 mm is used. -8.2% Al-0.6% Zn-0.25% Mn, weight ratio) Although a magnesium alloy extruded plate was used as a test material, the test material is not limited to these. In the present invention, an AZ-based magnesium alloy containing 5.0 to 9.5% by mass of aluminum, 0.2 to 2.0% by mass of zinc, and 0.05 to 1.0% by mass of manganese, If it is an AZ-based magnesium alloy containing 5.0 to 9.0 mass% aluminum, 0.5 to 1.5 mass% zinc, and 0.05 to 1.0 mass% manganese, the test Can be used as a material. A combination of different peripheral speed rolling and constant speed rolling can also be used.

  For the magnesium alloy plate, for example, the different peripheral speed ratio, the rolling reduction, the roll temperature, and the material heating temperature are set to predetermined conditions, and the magnesium alloy plate is manufactured by performing final rolling once or multiple times. . When rolling a plurality of times, the magnesium alloy sheet may be heated to a target heating temperature in a heating furnace for each rolling pass, and intermediate annealing may not be performed.

  For the different peripheral speed rolling, for example, a gear type different peripheral speed rolling mill in which a heater is built in a roll is used. The peripheral speed on the high-speed roll side and the peripheral speed on the low-speed roll side are set to appropriate conditions. Further, the direction of different peripheral speed rolling is set so that the shear introduction direction is constant. High temperature rolling is performed in a range from 450 ° C to 530 ° C.

  Next, the magnesium alloy sheet will be described. In the present invention, the magnesium alloy sheet is observed with an optical microscope, but the optical microscope is observed with a cross section parallel to the rolling direction. The crystal grain size is measured by a cutting method. The texture is evaluated by measuring a rolled surface cut by about half the plate thickness by X-ray diffraction using a Schulz reflection method (α = 15 ° to 90 °). In order to evaluate the cold stretch formability, a room temperature Eriksen test is performed. The Eriksen test is performed in accordance with JIS Z2247 and JIS B7729.

  The blank shape is 50 mm (thickness 1 mm), the molding speed is 5 mm / min, and the wrinkle holding force is 10 kN. Graphite grease is used as the lubricant.

In the tensile test, a tensile test piece having a parallel part length of 12 mm, a width of 3.5 mm, and a thickness of 1 mm was cut out from three directions of 0 °, 45 ° and 90 ° with respect to the rolling direction, and a strain gauge was attached. A tensile test is performed at an initial strain rate of 2 mm / min, and an average value of mechanical property values (= (X _{0 °} + 2X _{45 °} + X _{90 °} ) / 4) is obtained from the results in three tensile directions. .

  In the magnesium alloy sheet of the present invention, the room temperature Erichsen value is improved as the rolling temperature is increased. For example, the room temperature Erichsen value of the AZ61 alloy sheet manufactured at a rolling temperature of 520 ° C. is 7.0, which is excellent in cold Extensive formability is shown. The maximum strength of the bottom texture of the magnesium alloy sheet for press forming of the present invention is 5.0 or less, for example, from 5.6 to 3.7, the crystal grain size is 5 μm to 20 μm, and (0002) The pole is inclined in the 5-10 ° rolling direction. The randomization of texture is thought to be due to the activity of non-bottom sliding and grain boundary sliding during high temperature rolling.

  Randomizing the texture results in a decrease in the Rankford value (r value) and an increase in the work hardening index (n value). The r value of the magnesium alloy sheet for press forming of the present invention decreases from 1.71 to 1.33, the n value increases from 0.26 to 0.31, and the magnesium alloy sheet for press forming of the present invention A small r value and a large n value are shown.

  The decrease in the r value means that the deformation in the thickness direction of the plate material is facilitated, and the increase in the n value leads to an improvement in the uniform deformation ability until the occurrence of local contraction. The magnesium alloy sheet for press forming is considered to be the cause of the excellent stretch formability. Similarly, randomizing the texture improves deep drawability and bendability.

  The increase in the room temperature Erichsen value as the rolling temperature rises is considered to be related to the weakening of the bottom texture by high temperature rolling. Even if it is rolled at a lower temperature in the previous stage, a magnesium alloy sheet material exhibiting excellent cold formability can be produced by performing one high temperature rolling.

  In the different peripheral speed rolling, the pole of the bottom texture of the magnesium alloy can be inclined in the rolling direction, whereby the cold formability can be improved as compared with the constant speed rolled material. Further, it is known that the cold formability is improved with a decrease in the maximum strength of the bottom texture [Iwanaga et al. , JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 155-156 (2004) 1313]. Therefore, in order to improve cold formability, it is important to tilt or randomize the bottom texture of the magnesium alloy.

  As the rolling reduction per time increases, the bottom texture becomes random, and by increasing to 20% or more, a weak bottom texture having a pole gradient is obtained. As the rolling temperature rises, the texture becomes random, and the formability improves accordingly. In the AZ61 alloy, the room temperature Erichsen value is increased from 4.7 to 7.0 only by increasing the rolling temperature from 430 ° C. to 520 ° C. The reason for the randomization of the texture is thought to be due to the activity of non-bottom sliding and grain boundary sliding during high temperature rolling. However, the effect of improving formability by such high temperature rolling is relatively weak in the AZ31B alloy.

  In the present invention, it is important to perform high-temperature rolling with an AZ-based magnesium alloy having a high aluminum content in which dynamic recrystallization is likely to occur. As a result, fine crystal grains of several to several tens of μm are obtained by dynamic recrystallization, and the rolling texture becomes weak as the rolling temperature rises. As a result, the tensile strength is 250-260 MPa, the room temperature Erichsen value is 3- Compared with a normal AZ31B alloy rolled material showing 5, a magnesium alloy sheet material having a tensile strength of 300 MPa and a room temperature Erichsen value of 7.0 and high strength and excellent cold formability can be produced.

  The high temperature rolling of the present invention can be applied not only to the AZ61 alloy but also to the AZ80 alloy and magnesium alloys equivalent to them, and the room temperature Erichsen value is 4.5 to 5 only by increasing the rolling temperature from 430 ° C to 490 ° C. .6. Moreover, even if it is rolled at a lower temperature in the previous stage, the cold formability can be remarkably improved if the high temperature rolling is performed at the last time.

The present invention has the following effects.
(1) In the method for producing a magnesium alloy sheet for press forming according to the present invention, a high aluminum content AZ-based magnesium alloy in which dynamic recrystallization is likely to occur. Fine crystal grains of more than a dozen μm are obtained, the rolling texture becomes weak, and the cold formability can be greatly improved.
(2) The present invention makes it possible to manufacture a thin-walled complex shape part by press molding a magnesium alloy sheet material having high strength and excellent cold formability, and can greatly contribute to weight reduction of an applied product.
(3) In general, in high temperature rolling, cracking hardly occurs even at a large rolling reduction, so that production efficiency can be increased.
(4) By using the high-strength magnesium alloy sheet of the present invention, a further lightening effect can be obtained, and since it contains a lot of aluminum, the strength can be further improved by aging treatment after molding. .
(5) Since much aluminum is contained, better corrosion resistance can be obtained.
(6) Due to sufficient dynamic recrystallization during high-temperature rolling, there is little residual strain in the material, so that excellent cold formability can be obtained even without annealing after rolling, and production costs are reduced. Bring.

2 is a structural photograph of an AZ61 magnesium alloy sheet produced in Example 1. (A) is a plate made at each rolling temperature of 430 ° C., (b) is 460 ° C., (c) is 490 ° C., and (d) is 520 ° C. 2 is a (0002) pole figure of an AZ61 magnesium alloy sheet produced in Example 1. FIG. (A) is a plate made at each rolling temperature of 430 ° C., (b) is 460 ° C., (c) is 490 ° C., and (d) is 520 ° C. The pole figure is obtained by measuring the center part of the plate thickness and performing internal standardization, and the upward direction of the pole figure is the rolling direction. It is a figure which shows the room temperature Eriksen test result of the AZ61 magnesium alloy board | plate material produced in Example 1. FIG. (A) is a plate made at each rolling temperature of 430 ° C., (b) is 460 ° C., (c) is 490 ° C., and (d) is 520 ° C.

  EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by the following Examples.

  In this example, a commercially available AZ61 (Mg-6.9% Al-0.5% Zn-0.21% Mn, weight ratio) magnesium alloy extruded plate having a thickness of 5 mm was used as a test material, and press molding was performed. An attempt was made to produce a magnesium alloy sheet.

  Next, with respect to the magnesium alloy plate, intermediate annealing is not performed, a different peripheral speed ratio of 1.36, a rolling reduction of 33% for one pass (total of 4 passes), a roll temperature of 300 ° C., and a material heating temperature of 430 ° C. and 460 ° C. Rolling was performed at 490 ° C. and 520 ° C. to produce a magnesium alloy plate having a plate thickness of 1.0 mm. Since the solidus temperature of AZ61 is 525 ° C, rolling at a temperature of 520 ° C or higher was not performed.

  For each rolling pass, the magnesium alloy plate was heated to a target heating temperature in a heating furnace. The time required for one heating was within 10 minutes. For the different speed rolling, a gear type different speed rolling mill with a built-in heater was used. The peripheral speed on the high speed roll side was 13.6 m / min, and the peripheral speed on the low speed roll side was 10 m / min. Moreover, the direction of different peripheral speed rolling was set so that the shear introduction direction was constant.

  An optical microscope observation was performed on the material (F material) with the magnesium alloy sheet rolled. The optical microscope observation was performed with a cross section parallel to the rolling direction. The crystal grain size was measured by a cutting method. In order to evaluate the texture, the rolled surface cut by about half the plate thickness was measured by X-ray diffraction using the Schulz reflection method (α = 15 ° to 90 °). In order to evaluate the cold stretch formability, a room temperature Erichsen test was performed. The Eriksen test was conducted according to JIS Z2247 and JIS B7729.

The blank shape was φ50 mm (thickness 1 mm), the molding speed was 5 mm / min, and the wrinkle pressing force was 10 kN. Graphite grease was used as the lubricant. In the tensile test, a tensile test piece having a parallel part length of 12 mm, a width of 3.5 mm, and a thickness of 1 mm was cut out from three directions of 0 °, 45 ° and 90 ° with respect to the rolling direction, and a strain gauge was used. Mounting was performed at an initial strain rate of 2 mm / min. The Rankford value (r value) was measured after applying 9% plastic strain to the tensile specimen. The work hardening index (n value) was determined in the strain range of 4% to 14% in the uniform elongation region. Further, an average value of mechanical property values (= (X _{0 °} + 2X _{45 °} + X _{90 °} ) / 4) was obtained from the results in the three tensile directions.

  FIG. 1 shows a photograph of F material of a magnesium alloy sheet for press forming of the present invention produced at rolling temperatures of 430 ° C., 460 ° C., 490 ° C. and 520 ° C. Since the rolling temperature is high, it can be seen that sufficient dynamic recrystallization has occurred, resulting in equiaxed crystal grains. The crystal grain sizes are 7.4, 7.8, 9.2, and 11.5 μm, respectively, and increase as the rolling temperature rises. 13.4 μm).

  FIG. 2 shows the measurement results of the texture. In the measurement result of FIG. 2, the (0002) pole is inclined in the 5 ° to 10 ° rolling direction due to the introduction of shear deformation by different peripheral speed rolling. As the rolling temperature increased, the bottom texture decreased from 460 ° C., and the maximum strength decreased from 5.6 to 3.7. The reason for the randomization of the texture is thought to be due to the activity of non-bottom sliding and grain boundary sliding during high temperature rolling.

  As the rolling temperature increased, the tensile strength slightly decreased from 313 MPa, but even a rolled material produced at a rolling temperature of 520 ° C. shows a high strength of 300 MPa. The work hardening index (n value) increases from 0.26 to 0.31, and the Rankford value (r value) decreases from 1.71 to 1.33.

  FIG. 3 shows the room temperature Erichsen value. As shown in FIG. 3, the room temperature Erichsen values are 4.7, 5.3, 6.0, and 7.0 in the order of increasing rolling temperature. The value could be improved by about 1.5 times. It is considered that the main cause of the improvement of the stretch formability is a decrease in r value and an increase in n value due to randomization of the texture. As described above, the magnesium alloy sheet for press molding of the present invention produced at a rolling temperature of 520 ° C. has a tensile strength of 300 MPa and a room temperature Erichsen value of 7.0, and exhibits high strength and easy moldability.

  Next, a commercially available AZ31B (Mg-3% Al-1% Zn-0.4% Mn, weight ratio) magnesium alloy extruded plate having a thickness of 5 mm was used as a test material, and intermediate annealing was performed in the same manner as described above. Without rolling, rolling was performed under the conditions of a different peripheral speed ratio of 1.36, a reduction rate of 33% for one pass (total of 4 passes), a roll temperature of 300 ° C., and a material heating temperature of 520 ° C. A magnesium alloy plate of 0.0 mm was manufactured.

  The comparative material 1 had a crystal grain size of 12.6 μm, a maximum texture of the bottom texture of 5.1, a room temperature Erichsen value of 4.7, and a tensile strength of 246 MPa. Compared to the comparative material 1, the AZ61 alloy sheet produced under the same conditions, that is, the magnesium alloy sheet for press forming of the present invention, shows a smaller crystal grain size and a weaker bottom texture. It is considered that there is a possibility of recrystallization, and as a result, it is considered that the magnesium alloy sheet for press molding of the present invention showed higher strength and easier moldability than the AZ31B alloy of Comparative Material 1.

  In this example, a commercially available AZ80 (Mg-8.2% Al-0.6% Zn-0.25% Mn, weight ratio) magnesium alloy extruded plate having a thickness of 5 mm was used as a test material. In the same manner as in Example 1, the intermediate annealing is not performed, the different peripheral speed ratio is 1.36, the rolling reduction ratio of 33% for one pass (4 passes in total), the roll temperature is 300 ° C., and the material heating temperature is 430 ° C. and 490 ° C., respectively. Rolling was performed under conditions to produce a magnesium alloy plate having a plate thickness of 1.0 mm.

  Since the solidus temperature of AZ80 is 490 ° C., rolling at a temperature of 490 ° C. or higher was not performed. The room temperature Eriksen test was conducted in the same manner as in Example 1. The room temperature Erichsen values of the plate materials produced at the rolling temperatures of 430 ° C. and 490 ° C. were 4.5 and 5.6, respectively. As the rolling temperature increased, the maximum strength of the bottom texture decreased from 5.7 to 4.4. Along with this, the r value decreased from 1.68 to 1.41, and the n value improved from 0.26 to 0.29. This improvement in stretch formability is considered to be due to randomization of the texture. Moreover, the pole of the (0002) pole figure is inclined about 13 ° in the rolling direction.

  The room temperature Erichsen value of the AZ80 alloy sheet produced at 490 ° C. was 5.6, which was higher than that of a normal AZ31B alloy rolled material having a room temperature Erichsen value of 3 to 5. The present invention can also be applied to a high-strength AZ80 alloy, and the tensile strength of the AZ80 alloy sheet produced at 490 ° C. is 324 MPa, which is higher than that of the AZ61 alloy of Example 1. Yes. Moreover, the tensile strength of the AZ80 alloy sheet was further improved from 324 MPa to 348 MPa by aging treatment at 175 ° C. for 18 hours.

  In this example, the same AZ61 magnesium alloy extruded plate as in Example 1 was used as a test material. Different peripheral speed ratio 1.36, 1 pass 33% rolling reduction (total 3 passes), roll temperature 300 ° C, material heating temperature 370 ° C, different peripheral speed rolling, thickness 5mm to 1.5mm Then, different peripheral speed rolling was performed in one pass at a rolling reduction of 33% under the conditions of different peripheral speed ratio 1.36, roll temperature 300 ° C. and material heating temperature 520 ° C. A 0 mm magnesium alloy plate was produced. In the final rolling, the AZ61 alloy sheet produced at the same rolling temperature of 370 ° C. was used as the comparative material 2.

  The room temperature Erichsen value of the magnesium alloy sheet produced at the final rolling temperature of 520 ° C. is 6.7, which is more than double the room temperature Erichsen value 3.3 of Comparative Material 2, and all the 520 shown in Example 1 are shown. The plate material rolled at 0 ° C. was close to the room temperature Erichsen value of 7.0, and was high in tensile strength of 306 MPa. Compared with the comparative material 2, the maximum strength of the bottom texture decreases from 7.2 to 4.7, and accordingly, the r value decreases from 1.82 to 1.33, and the n value decreases from 0.23. Increased to 0.29. That is, even if it is rolled at a lower temperature in the previous stage, the cold formability can be remarkably improved if the high temperature rolling is performed at the last time.

  As described in detail above, the present invention relates to a magnesium alloy sheet having excellent cold formability and a method for producing the same, and in the method for producing a magnesium alloy sheet for press forming according to the present invention, by high-temperature rolling, The texture is weakened, and random texture and fine crystal grains of a few tens of μm are obtained. The different peripheral speed rolled material can maintain the slope of the bottom pole, and can achieve excellent cold formability. The present invention enables manufacturing of thin-walled complex shaped parts by press molding, and can greatly contribute to weight reduction of applied products. The present invention is useful for providing a magnesium alloy sheet having excellent cold formability. The present invention can be suitably applied to, for example, a press-molded body as a housing of home appliances such as a notebook computer, a digital camera, a mobile phone, a CD player, and a PDA, or an automobile body panel or covers.

Claims (9)

5.0 to 9.5 mass% of aluminum, magnesium consisting of zinc 0.2 to 2.0% by weight, and 0.05 to 1.0 mass% of manganese, and the balance of magnesium and unavoidable impurities The alloy plate material is subjected to different peripheral speed rolling at a roll peripheral speed ratio of at least 1.3 or a combination of constant speed rolling and the different peripheral speed rolling, and 70 ° C. from the solidus temperature. A method for producing a magnesium alloy sheet for press forming, characterized in that high temperature rolling is performed in a temperature range from a low temperature to a solidus temperature, and the final rolling or rolling is performed once. And rolling the previous step at a temperature lower than the high temperature of the final rolling, rolling in combination more final rolling in the temperature range from the high temperature of the solidus temperature than 70 ° C. lower temperature to the solidus temperature, in claim 1 The manufacturing method of the magnesium alloy sheet | seat for press forming of description.   The manufacturing method of the magnesium alloy sheet | seat for press molding of Claim 1 which performs high temperature rolling in the range from 450 degreeC to 530 degreeC. A magnesium alloy sheet for extension produced by the method according to claim 1, wherein 6.9 to 8.2 % by mass of aluminum; 5 to 0.6 mass% zinc; The room temperature elixir value measured according to JIS Z2247 and JIS B7729 is composed of a magnesium alloy composed of 21 to 0.25 % by mass of manganese and the balance of magnesium and inevitable impurities. A magnesium alloy sheet for press forming, characterized in that The magnesium alloy sheet for press forming according to claim 4 , which exhibits a tensile strength of at least 300 MPa and a room temperature Erichsen value of at least 5.3. (0002) pole of pole figure is at least 5 ° inclined to the rolling direction, the maximum intensity of the basal texture is a 5.0 even greater, the crystal grain size is 5Myuemu～20myuemu, claim 4 or 5 2. Magnesium alloy sheet described in 1. The magnesium alloy sheet according to claim 4 or 5 , wherein the maximum strength of the bottom texture of the (0002) pole figure is 5.0 at most and the crystal grain size is 5 to 20 µm. The magnesium alloy sheet according to claim 4 or 5 , wherein the Rankford value (r value) is reduced to 1.41 at most as an average r value with respect to the alloy sheet before rolling . The magnesium alloy sheet according to claim 4 or 5 , wherein the work hardening index (n value) is improved to at least 0.29 as an average n value with respect to the alloy sheet before rolling .