TW201302334A - Magnesium alloy material and method of manufacturing the same - Google Patents

Abstract

Provided is a magnesium alloy which is thick and exhibits excellent corrosion resistance and excellent surface-deterioration resistance, and a production method for the same. A magnesium (Mg) alloy (typically a magnesium alloy plate) having a plate-shaped section having a thickness of at least 1.5mm, wherein, if the region as far as 1/4 of the thickness, in the thickness direction, from the surface of the plate-shaped section is the surface region, and the remaining section is the inner-section region, the ratio (OF/Oc) of the base surface peak ratio (OF) of the surface region to the base surface peak ratio (Oc) (orientation joint of the (002) surface) of the inner-section region satisfies 1.5F/Oc.; In this magnesium alloy, the surface of the plate-shaped section is formed by means of an aggregate structure in which the (002) surface, which is the base surface of the Mg alloy crystals, is strongly oriented in comparison with the inner-section, and the alloy exhibits excellent corrosion resistance because the grain size in the surface region is typically smaller than that in the inner-section region, and due to the excellent surface deterioration resistance a molded product having excellent surface quality can be obtained by carrying out press working. A plate-shaped Mg alloy can be obtained by rolling, for a plurality of passes, a twin-roll continuous cast material, with the rolling reduction for all the passes being 25% or less.

Description

Magnesium alloy material and manufacturing method thereof

The present invention relates to a magnesium alloy material suitable for various parts such as a conveyor or a bicycle part of an automobile or a railway vehicle, an airplane, or the like, a housing of an electric/electrical machine, and other structural members, and a constituent material of the member, and Its manufacturing method. In particular, it is a magnesium alloy material which is excellent in wall thickness, corrosion resistance, and texture roughness resistance.

Bicycle parts such as automobile parts, railway vehicle parts, frame, etc., such as a mobile phone or a notebook type personal computer such as a mobile phone or a notebook computer, such as a housing, a rim cover, or a paddle shifting paddle shift A magnesium alloy which is lightweight, and has excellent specific strength and specific rigidity is being reviewed. A member made of a magnesium alloy is mainly used as a casting material (ASTM-size AZ91 alloy) by a die casting method or a thixoforming method. In recent years, press-formed materials which are pressed by a magnesium alloy for stretching represented by the ASTM specification AZ31 alloy have been gradually used. Patent Document 1 discloses that a continuous casting material made of various magnesium alloys such as AZ91 alloy is produced by a two-roll casting method, and the continuous casting material is rolled, and the obtained rolled sheet is applied. Press processing.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2006/003899

In the past, attention has been paid to the lightweightness of the magnesium alloy, and the material of the plastic working material such as a press-worked material has been reviewed as a relatively thin plate having a thickness of 1 mm or less. However, with the expansion of the use range of the magnesium alloy, not only the thin plate as described above but also the thickness of the specific strength and the specific rigidity, specifically, a thick plate having a thickness of 1.5 mm or more is also expected to be developed. In the past, materials such as magnesium alloy sheets having such a thick thickness, methods for producing the same, and plastic working materials such as press-worked materials produced using the sheets have not been sufficiently reviewed.

A magnesium alloy sheet having a wall thickness can be obtained by a die casting method or a thixoforming method. When a cast material such as a die-casting material is used, in addition to internal defects such as pores, the elemental component may become highly concentrated locally or the crystal grains may be randomly aligned, and the composition or the structure may become uneven. . Therefore, the corrosion resistance of a cast material such as a die-cast material is inferior to those of a plasticizer which is applied to a rolled material or the like. Further, a cast material such as a die-cast material is inferior in plastic workability due to the above internal defects and the like, and cannot be referred to as a material suitable for plastic working.

Here, an object of the present invention is to provide a magnesium alloy material which is excellent in wall thickness, corrosion resistance and texture roughness resistance, or a wall thickness magnesium alloy material which has been subjected to plastic working. Further, another object of the present invention is to provide a magnesium alloy material which is excellent in corrosion resistance and texture roughness resistance. Gold material manufacturing method.

Compared with die-casting materials or thixoforming materials, magnesium alloy materials which have been subjected to plastic working such as rolling and rolling (primary processing) can reduce the defects during casting, or the crystals are fined, so even the same composition, strength or Mechanical properties such as hardness and toughness, corrosion resistance, and plastic workability are excellent. In addition, the magnesium alloy material obtained by subjecting the magnesium alloy material subjected to the above-described primary processing to plastic working (secondary processing) such as press working is also excellent in the above mechanical properties or corrosion resistance. In particular, when a continuous casting material produced by a continuous casting method such as a two-roll casting method is used as a material for a primary processing material, segregation or coarse crystal precipitation of the continuous casting material is compared with a die casting material or the like. It is small and has excellent plastic workability. Here, the team of the present invention applies rolling to various conditions for continuous casting materials to produce a wall thickness magnesium alloy sheet having a thickness of 1.5 mm or more. As a result, it has been found that, in addition to the wall thickness and excellent corrosion resistance, the magnesium alloy sheet produced under specific conditions has a small unevenness on the surface of the obtained plastic working material when subjected to plastic working such as press working or bending. It has a smooth surface (representatively glossy and has a perfect surface) and is excellent in texture roughness. The present invention is based on the above-mentioned insights.

The magnesium alloy material of the present invention is made of a magnesium alloy and has a plate-like portion having a thickness of 1.5 mm or more, and the plate-like portion satisfies the following alignment.

[Orientation]

From the surface of the plate-like portion toward the thickness direction, a region up to 1/4 of the thickness is used as the surface region, and the remaining portion is used as the inner region, and the (002) plane and the (100) plane of the surface region are ( The peak intensities of the X-ray diffraction of the 101, (102), (110), and (103) planes are I _F (002), I _F (100), I _F (101), and I _F (102, respectively). ), I _F (110) and I _F (103), the (002) plane, the (100) plane, the (101) plane, the (102) plane, the (110) plane, and the (103) plane of the inner region The peak intensity of the ray diffraction is taken as I _C (002), I _C (100), I _C (101), I _C (102), I _C (110), and I _C (103), respectively. 002) Orientation of the face: I _F (002) / {I _F (100) + I _F (002) + I _F (101) + I _F (102) + I _F (110) + I _F (103)} As the bottom peak ratio O _F , and the orientation of the (002) plane of the above inner region: I _C (002) / {I _C (100) + I _C (002) + I _C (101) + I _C (102 _{) + I C (110) +} I C (103)} as the bottom surface of the peak ratio O _C, with respect to the bottom surface of the peaks of the inner area than the bottom of the peak of the surface area O _c ratio ratio O _F of: O _F / O _c is 1.05 < O _F / O _c .

The above magnesium alloy material of the present invention can be produced by, for example, the following production method of the present invention. The method for producing a magnesium alloy material according to the present invention relates to a method for producing a magnesium alloy material by rolling a material made of a magnesium alloy, and has the following preparation steps and a rolling step.

Preparation step: a step of preparing a plate-shaped material for casting the molten magnesium alloy by a two-roll casting method.

Rolling step: a step of producing a plate-shaped magnesium alloy material having a thickness of 1.5 mm or more by applying a rolling of a plurality of rolling passes to the above material.

In the rolling step, the reduction ratio of each of the above-mentioned rolling passes is set to 25% or less.

Yet, so-called rolling reduction (%) refers to {(the thickness of the cast material before rolling t _b - thickness of the material roll delay t _a) thickness of the front / and rolling material of t _b} × 100.

According to the above-described production method of the present invention, it is possible to favorably apply rolling of a plurality of rolling passes by using a defect or a crystal precipitate which is a starting point of cracking or the like, segregation to be small, or a substantially continuous casting material which is not present as a material. . Further, the rolling reduction ratio of each of the rolling passes is relatively small, and by rolling through a plurality of rolling passes, the surface portion of the rolled material is sufficiently plastically processed by rolling as compared with the inside. That is, by repeating rolling with a relatively small reduction ratio, the surface structure of the rolled material can be made different from the internal structure. Therefore, according to the manufacturing method of the present invention, a magnesium alloy material composed of a structure constituting a surface region and a structure constituting the inner region can be obtained (representatively, a rolled plate (a type of magnesium alloy material of the present invention) state)). More specifically, since the structure constituting the surface region is sufficiently plastically processed by rolling, the crystal bottom surface of the magnesium alloy is mainly arranged in parallel with the rolling direction (the traveling direction of the material to be rolled). The aggregate structure (the c-axis of the crystal is a collective structure arranged in a direction perpendicular to the rolling direction) constitutes a structure of the inner region, and the bottom surface is a structure in which the surface region is more randomly arranged.

When the magnesium alloy material of the present invention is a rolled sheet to which the above specific rolling has been applied (that is, the entire magnesium alloy material of the present invention is formed of a plate-like portion) When the state is as described above, the microstructure of the surface region is a collective structure having a specific orientation; more specifically, the (002) plane of the crystal bottom surface of the magnesium alloy is a strong alignment assembly, and the inner region is It is composed of a tissue having a smaller orientation in the (002) plane than the surface region. The (002) plane is a collective structure of strong alignment, and is one of the indexes indicating that deformation is sufficiently accompanied by plastic working in plastic working such as rolling. When the processing such as rolling is performed more sufficiently, the crystal grain size of the magnesium alloy tends to be finer, and the entire area of the crystal grain boundary is increased by the miniaturization. As a result, since the ratio of the presence of the impurity element to the crystal grain boundary is relatively lowered, the magnesium alloy material of the present invention having the above specific structure is excellent in corrosion resistance. In particular, the surface area exposed to the external atmosphere is a finer structure than the inside, and the corrosion resistance is more excellent. Therefore, the magnesium alloy material of the present invention has a wall thickness and is excellent in corrosion resistance. Further, the magnesium alloy material is composed of a structure in which the surface portion and the interior are different as described above, and has a mechanical property in which the surface portion and the interior are different (hardness or strength, impact resistance, toughness, etc.). Characteristics, corrosion resistance, vibration damping, etc.). With such a difference in characteristics, the magnesium alloy material of the present invention is expected to be utilized for various members and materials of such members. Further, since the degree of alignment of the bottom surface ((002) plane) of the inner region of the magnesium alloy material of the present invention is small (the assembly degree of the aggregate structure is small), since the plastic workability such as press working or bending processing is good, It can be used for materials for plastic working such as press working or bending. Then, since the surface region is composed of a fine crystal structure, even if plastic processing such as press processing is applied, it is not easy to form large unevenness on the surface of the material, and a plasticized material having a smooth surface can be obtained. (One form of the magnesium alloy material of the present invention). Therefore, the magnesium alloy material of the present invention is excellent in texture roughness. Moreover, the obtained plastic working material also has excellent surface properties.

As one of the magnesium alloy materials of the present invention, for example, when the average crystal grain size of the surface region is taken as D _F and the average crystal grain size of the inner region is taken as D _c , the average crystal grain size relative to the surface region is crystal ratio of the average area of the inner diameter D _F of the D _c: D _c / D _F to satisfy 1.5 <D _c / D _F of patterns.

With the above type, the crystal grain size of the inner region is larger than that of the surface region, in other words, since the crystal grain size of the surface region is sufficiently smaller than the inner region, as described above, the crystal grain boundary becomes long and the corrosion resistance is improved. Excellent. In addition, in the above-described form, the surface region is composed of a fine crystal structure, and the plastic workability is excellent, and the texture roughness is excellent, and the crystal grain size in the inner region is larger than the surface region. Therefore, the heat resistance is also excellent.

As one of the magnesium alloy materials of the present invention, the Vickers hardness (Hv) of the surface region is taken as H _F and the Vickers hardness (Hv) of the inner region is taken as H _c with respect to the surface region. Vickers ratio of the inner area of the Vickers hardness H _F H _c of hardness: H _c / H _F to satisfy H _c / H _F <0.85 of patterns.

According to the above type, the Vickers hardness of the inner region is smaller than the surface region, in other words, since the Vickers hardness of the surface region is sufficiently larger than the inner region, the abrasion resistance is excellent.

The magnesium alloy material of the present invention can be made by using various elements as additive elements. A magnesium alloy (residual part Mg and impurities). In particular, an alloy having a high concentration of the additive element, specifically a magnesium alloy having a total content of 5.0% by mass or more, may vary depending on the type of the added element, but mechanical properties such as strength and hardness, corrosion resistance, and difficulty Various properties such as flammability and heat resistance are excellent.

Specific additive elements are exemplified by Al, Zn, Mn, Si, Be, Ca, Sr, Y, Cu, Ag, Sn, Li, Zr, Ce, Ni, Au, and rare earth elements (except Y, Ce). At least one element selected. As the impurities, for example, Fe or the like is exemplified.

In particular, the Mg-Al alloy containing Al is excellent in corrosion resistance and mechanical properties such as strength and hardness. Therefore, as one of the magnesium alloy materials of the present invention, the above-mentioned magnesium alloy is in a form containing Al in an amount of 5.0% by mass or more and 12% by mass or less as an additive element. The more the content of Al is, the higher the above effect tends to be, and it is preferably 7% by mass or more, and more preferably 7.3 % by mass or more. However, when the content of Al exceeds 12% by mass, the plastic workability is lowered, so the upper limit is preferably 12% by mass, and more preferably 11% by mass. In particular, it contains a form of Al 8.3% by mass to 9.5% by mass, and is excellent in strength and corrosion resistance. The content of each element other than Al is, for example, 0.01% by mass or more and 10% by mass or less, preferably 0.1% by mass or more and 5% by mass or less.

A more specific composition of the Mg-Al alloy is, for example, an AZ alloy of the ASTM specification (Mg-Al-Zn alloy, Zn: 0.2% by mass to 1.5% by mass, for example, AZ31 alloy, AZ61 alloy, AZ91 alloy) Etc.), AM-based alloy (Mg-Al-Mn alloy, Mn: 0.15 mass% to 0.5 mass) %), AS-based alloy (Mg-Al-Si alloy, Si: 0.01% by mass to 20% by mass), Mg-Al-RE (rare earth element) alloy, AX alloy (Mg-Al-Ca system) Alloy, Ca: 0.2% by mass to 6.0% by mass), AJ-based alloy (Mg-Al-Sr-based alloy, Sr: 0.2% by mass to 7.0% by mass), and the like. An Al-containing 3% by mass to 9.5% by mass of Al is used as the alloy, and a Mg-Al-Zn-based alloy containing 0.5% by mass to 1.5% by mass of Zn is used, and for example, an AZ91 alloy is used.

In addition, at least one element selected from the group consisting of Y, Ce, Ca, Si, Sn, and a rare earth element (excluding Y and Ce) is 0.001% by mass or more, and preferably 0.1% by mass or more and 5% by mass or less in total. Further, the residual magnesium alloy formed of Mg and impurities is excellent in heat resistance and flame retardancy. When the rare earth element is contained, the total content is preferably 0.1% by mass or more. In particular, when Y is contained, the content is preferably 0.5% by mass or more.

The magnesium alloy material of the present invention is excellent in wall thickness, corrosion resistance and texture roughness. The method for producing a magnesium alloy material of the present invention is a magnesium alloy material which is excellent in wall thickness, corrosion resistance and texture roughness resistance.

[Best form of implementing the invention]

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

[Magnesium alloy material] (composition)

The magnesium alloy material of the present invention is composed of 50% by mass or more of Mg and a representative of the above-mentioned additive elements.

(type)

The plate-like portion of the magnesium alloy material of the present invention has a pair of parallel faces, and the interval between the two faces (the distance between the faces) is substantially uniform, that is, the thickness is a uniform portion. The magnesium alloy material of the present invention may have a plate-like portion as part of it, and other portions may allow processing by cutting, etc., with the hub or the like being joined, having a groove type, and a table. The back surface has a shape of a through hole, and the like, and the portion has a shape in which the thickness is different.

A representative form of the magnesium alloy material of the present invention having the above-described plate-like portion is, for example, a plate-like form (magnesium alloy plate). The shape (planar shape) of the magnesium alloy sheet may be various shapes such as a rectangular shape and a circular shape. Further, the magnesium alloy sheet may be any type of a coil material obtained by winding a continuous long strip material or a short strip material having a specified length and a shape of ‧ The magnesium alloy sheet can also be in various forms by the manufacturing steps. For example, a calendered sheet, a rolled sheet, a heat-treated or straightened heat-treated sheet or a straightening sheet described later, a milled or coated polished sheet or a coated sheet for the above-mentioned rolled sheet or heat-treated sheet, and a straightened sheet Wait.

In the magnesium alloy material of the present invention, for example, the magnesium alloy sheet is subjected to plastic working (secondary processing) such as press working such as bending or deep drawing, and the plastic working is performed on a part. have Part of the processed material of the plastic working portion (only at least a portion has the above-mentioned plate-like portion). The molded body has, for example, a case having a top plate portion (bottom portion) and a side wall portion formed by the periphery of the top plate portion, or a frame-like body and a top plate portion having a circular plate shape and a side wall portion being rounded. A cylindrical covered cylindrical body or the like. At least the top plate portion is equivalent to a plate portion. The type of magnesium alloy material can be selected depending on the intended use.

(thickness)

The magnesium alloy material of the present invention is one of the features in which the thickness of the plate-like portion is 1.5 mm or more. This thickness can be selected from any value of 1.5 mm or more depending on the intended use and the like. However, in order to set the above-mentioned plate-shaped portion to be thick, the material to be cast is also required to be thick. When the cast material is thickened, as described above, the rolling property is lowered due to defects or the like. Therefore, when the thickness is 10 mm or less, particularly 5 mm or less, it is preferable to produce a rolled plate having a thickness (a type of the magnesium alloy material of the present invention) with good productivity.

When the magnesium alloy material of the present invention is the above-mentioned molded body or the above-mentioned partially processed material, it is deformed into a small portion (typically a plate-like portion) by plastic working, and is substantially maintained as the above-mentioned magnesium alloy sheet as a material for plastic working. Tissue or mechanical properties.

(organization) <Orientation>

In the magnesium alloy material of the present invention, at least the surface region of the plate-like portion is composed of a structure having an aggregate structure having a bottom surface as described above, and the inner region is composed of an organization having a smaller degree of alignment with the bottom surface. Set as one of the features. Since the surface region exposed to the external atmosphere is composed of a structure in which the (002) plane is strongly aligned, the corrosion resistance is excellent as described above. Further, when the difference in the degree of alignment between the surface region and the inner region is larger, the corrosion resistance, the surface hardness, and the texture roughness are expected to be improved. However, when the difference in the degree of alignment becomes too large, it is difficult to uniformly apply plastic working such as press working, and therefore the ratio of the bottom surface peak ratio O _F /O _c preferably satisfies O _F /O _c ≦1.2.

<Average crystal grain size>

A representative form of the magnesium alloy material of the present invention is exemplified by the fact that the crystal grain size of the inner region is larger than the surface region. In this form, the inner region is excellent in heat resistance, and the surface region having a relatively small crystal grain size has high corrosion resistance or high hardness as described above. In particular, since the surface region is a relatively fine structure, it has high hardness, is excellent in abrasion resistance, is not easily damaged, and is excellent in surface properties. Therefore, the magnesium alloy material of the present invention is expected to be suitably used for a structural material or the like which requires durability. When the difference in average crystal grain size is larger between the surface region and the inner region, corrosion resistance, texture roughness, and surface hardness can be expected to be improved. However, when the difference in the average crystal grain size is large, it is difficult to uniformly apply plastic working such as press working, so the ratio of the average crystal grain size: D _c /D _{F is} preferably D _c /D _F ≦2.0. .

Still, rolling is performed as described above to produce a thickness of 1.5 mm or more. When the plate-shaped magnesium alloy material having a thick wall has a uniform particle diameter in the entire region across the thickness direction, and the fine particle diameter is set as a limit, the average crystal of the surface region and the inner region in the magnesium alloy material of the present invention The particle diameter may be 3.5 μm or more. However, when the crystal grain size is small, the plastic workability is excellent, and the average crystal grain size of the surface region and the inner region of the plate-like portion is preferably 20 μm or less, and particularly preferably 10 μm or less. The average crystal grain size changes depending on the reduction ratio of the rolling step or the heating temperature of the material, and when the reduction ratio is larger, the lower the heating temperature, the smaller the tendency becomes.

(mechanical characteristics)

Since the magnesium alloy material of the present invention is subjected to rolling, it is excellent in mechanical properties such as strength, hardness, toughness, and the like as compared with a cast material such as a die-cast material. For example, as described above, the Vickers hardness of the surface region is higher than that of the inner region. Between the surface area and the inner area, if the difference in Vickers hardness is larger, the surface hardness is relatively higher. However, if the difference in Vickers hardness is too large (to excessively increase the surface hardness), conversely, the ratio of Vickers hardness (Hv): H _c /H _{F is} preferably 0.7 由于 due to the loss of press workability. H _c /H _F . Although the absolute value of the Vickers hardness varies depending on the rolling reduction rate or the rolling temperature of the material, the larger the content of the additive element, the larger the tendency. When the magnesium alloy material of the present invention is a plastic working material (molded body) or a partially processed material, the hardness tends to be improved by work hardening.

(other components)

When at least a part of the surface of the magnesium alloy material of the present invention is subjected to an anti-corrosion treatment such as phosphating or anodizing, and the anti-corrosion layer is provided, the corrosion resistance is further improved. Further, when at least a part of the surface of the magnesium alloy material of the present invention is coated and set to have a coating layer, the designability or commercial value can be improved.

〔Production method〕

Hereinafter, each step of the above-described production method of the present invention will be described in more detail.

(preparation step) <casting>

In the manufacturing method of the present invention, the starting material is a continuous casting material. Since the continuous casting method can be rapidly cooled and solidified, even when the content of the additive element is large, segregation, oxides, and the like can be reduced, and generation of coarse crystal precipitates such as more than 10 μm which may become the starting point of cracking can be suppressed. Therefore, a cast material excellent in plastic workability such as rolling can be obtained. Further, the continuous casting method is a casting material in which a long strip shape can be continuously produced, and the long strip material obtained by the continuous casting method can be used as a material for rolling. When the material is in the form of a strip, it is possible to manufacture a long strip of rolled material. The continuous casting method includes a double roll method, a double belt method, a belt type method, and the like, but in the manufacture of a plate-shaped casting material, a double roll method or a double belt method is particularly suitable as a double roll method, particularly It is preferable to use a continuous casting material produced by the casting method described in Patent Document 1. The thickness, width and length of the cast material can be adapted Locally selected to obtain the desired rolling material (rolled sheet). When the thickness of the cast material is too large, since segregation is likely to occur, it is preferably 10 mm or less, and particularly preferably 5 mm or less. When the obtained continuous casting material is set to a long strip shape and is wound into a cylindrical shape and set as a coil material, it is easy to carry it to the next step. When the part before the coiling of the cast material is heated to a state of about 100 ° C to 200 ° C to be wound up, the content of the additive element such as the AZ91 alloy is high, and even if it is an alloy which is likely to be broken, it becomes It is easy to bend, and even if the winding diameter is small, the winding can be performed without cracking or the like. The obtained continuous casting material may be set as a material for rolling, which is a sheet material that has been cut into an appropriate length. In this case, a rolled material (rolled sheet) of a specified length can be obtained.

<Solution>

When the casting material is subjected to a solution treatment before the rolling is applied, the composition of the casting material is homogenized, or the element such as Al is sufficiently solid-solved to improve the toughness. The conditions of the solution treatment include, for example, a heating temperature of 350 ° C or higher, particularly 380 ° C or higher and 420 ° C or lower, and a holding time of 1 hour or longer and 40 hours or shorter. In the case of a Mg-Al alloy, when the content of Al is larger, it is preferred to extend the holding time. Further, after the lapse of the holding time, in the cooling step by the heating temperature, forced cooling such as water cooling or air blowing or the like is performed, and when the cooling rate is accelerated (preferably 50 ° C/min or more), coarse precipitates can be suppressed. Precipitate.

<rolling delay>

The above-mentioned cast material or solution-treated material is used as a material, and the material is subjected to rolling of a plurality of rolling passes. At least one rolling pass preferably contains warm rolling or hot rolling in which the material (cast material, solid solution treatment material, and processed material in the rolling process) is heated at 150 ° C or higher and 400 ° C or lower. By heating the material to the above temperature, even when the reduction ratio per one pass is increased, cracking or the like is less likely to occur during rolling, and when the temperature is higher, cracking or the like becomes smaller, by setting Below 400 ° C, the deterioration of the surface of the factor material or the thermal deterioration of the rolling roll can be suppressed. Therefore, the heating temperature is preferably 350 ° C or lower, more preferably 300 ° C or lower, and particularly preferably 150 ° C or higher and 280 ° C or lower. Not only the material but also the rolling rolls can be heated. The heating temperature of the rolling roll is, for example, 100 ° C to 250 ° C.

In particular, in the production method of the present invention, the total reduction ratio of each pass is set to 25% or less. The rolling reduction with a relatively low reduction ratio is applied by means of a plurality of rolling passes, in particular, a concentrated plastic working is applied to the surface portion of the material. The reduction ratio of each rolling pass can be appropriately selected within a range of 25% or less. However, when the temperature is too small, the number of rolling passes up to the desired thickness is increased, which is preferable because the productivity is lowered. It is 10% or more.

For each pass, conditions such as the heating temperature of the material, the temperature of the rolling rolls, and the reduction ratio can be changed. Therefore, the reduction ratio of each pass can be the same or different. Further, an intermediate heat treatment can be performed between the rolling passes. By performing the intermediate heat treatment, the deformation or residual stress introduced into the material until the heat treatment is reduced, and the rolling after the heat treatment can be easily applied. The conditions of the intermediate heat treatment, for example, the heating temperature: 150 ° C to 350 ° C (preferably 300 ° C or less, more preferably 250 ° C to 280 ° C), retention time: 0.5 hours to 3 hours). Further, after the rolling, the above conditions can also be used for the final heat treatment. On the other hand, when the above-described rolling is appropriately used, the frictional resistance of the rolling delay can be reduced, and the burning of the material can be prevented, and rolling can be easily performed.

In addition, in the case of rolling delay and cracking at the edge portion, the crack may not be advanced, and the edge portion of the cast material before rolling may be trimmed, or in the middle of the rolling step, after rolling, etc., for the sake of appropriateness The ground adjustment width can also be trimmed.

<Other processing> ≪grinding ≫

After the above rolling, grinding may be applied. By grinding, the lubricant used for the rolling delay or the damage or oxide film existing on the surface of the rolled material can be removed and reduced. When grinding is used, if the material is a long strip, the material can be easily subjected to continuous polishing, which is preferable. Further, in order to prevent scattering of the powder, the polishing is preferably wet.

≪ straightening

After the above rolling or after the above grinding, straightening can be applied. By applying straightening, flatness can be improved, and plastic working such as press working can be performed with high precision. In the case of straightening, it is suitable to use a plurality of rolls as a steel plate flattening device arranged in a zigzag shape. Further, the straightening can be carried out, for example, by heating the material to a temperature of from 100 ° C to 300 ° C, particularly from 150 ° C to 280 ° C (warm straightening).

Plastic processing

When the magnesium alloy material of the present invention is provided as a part of the processed material including the molded body or the plastic worked portion, the material (the rolled material, the abrasive, and the straightening material) which has been subjected to the rolling step can be provided. The production is carried out by at least a part of a manufacturing method of a plastic working step of plastic working such as press working. When the plastic working is performed in a temperature range of 200 ° C to 300 ° C, the plastic workability of the material can be improved, which is preferable. Further, after the plastic working after the plastic working, it is possible to remove the deformation or residual stress introduced by the plastic working and to improve the mechanical properties. The heat treatment conditions are, for example, heating temperature: 100 ° C to 300 ° C, and heating time: 5 minutes to 60 minutes.

≪Surface treatment≫

When the magnesium alloy material of the present invention is set to have the above-mentioned corrosion resist layer or coating layer, it may be provided by at least a part of the material which has been subjected to the rolling step or has been subjected to the above plastic working step. At least a portion of the material is subjected to a manufacturing method of an anti-corrosion treatment or a surface treatment step of coating. Alternatively, at least one of the above materials may be subjected to processing selected from at least one of hairline processing, diamond cutting, bead blasting, etching, and rotary cutting. By performing such surface treatment, corrosion resistance or mechanical protection function, or designability, metal texture, and commercial value can be improved.

The following are examples of experimental examples to illustrate specific embodiments of the invention.

[Test example]

A material made of a magnesium alloy having the following composition was rolled under various conditions to prepare a magnesium alloy sheet having a thickness of 1.5 mm or more, and the orientation, crystal grain size, and Vickers hardness were measured.

In this test, a magnesium alloy sheet formed of a magnesium alloy (Mg-9.0% by mass Al-0.6% by mass Zn) having a composition equivalent to the AZ91 alloy, and a magnesium alloy having a composition equivalent to the AZ31 alloy were produced ( A magnesium alloy sheet formed of Mg-3.1 mass% Al-0.7 mass% Zn).

Using the magnesium alloy of each of the above compositions, a long cast sheet (thickness: 4.5 mm (4.50 mm to 4.51 mm) × width: 320 mm) was produced by a two-roll continuous casting method, and temporarily wound up to produce a cast coil material. Each of the cast coil materials was subjected to a solution treatment at 400 ° C for 24 hours. After the solid solution coil material which has been subjected to the solution treatment is rewinded, the rolling of the plurality of rolling passes is applied to the material using the rolling conditions as shown in Table 1, and the thickness is made 2.0 mm (2.00 mm to 2.01). Mm) or 1.5 mm rolled material (magnesium alloy sheet). Each rolling pass is set to warm rolling (heating temperature of the material: 250 ° C to 280 ° C, temperature of the rolling roll: 100 ° C to 250 ° C). The thickness of the cast material, the thickness of the processed material during the rolling, and the thickness of the obtained magnesium alloy sheet are 50 mm at the center portion in the width direction of the sheet to be measured and the distance between the edges in the width direction. A total of 3 points thick Degrees come as average.

[Orientation]

The obtained magnesium alloy sheets were subjected to X-ray diffraction to measure the ratio of the bottom surface peak ratio O _{F to} the surface area of the bottom surface peak ratio O _c of the inner region: O _F /O _c . The results are shown in Table 2. The bottom surface peak ratio O _{F of the} surface region is X-ray diffraction for the surface of each magnesium alloy plate; the bottom surface peak ratio O _{c of the} inner region is from the surface of each magnesium alloy plate toward the thickness direction, to 1/4 of the thickness The area (surface area) is chemically removed to expose the inside, and X-ray diffraction is performed on the exposed surface. Next, the peak intensities of the (002) plane, the (100) plane, the (101) plane, the (102) plane, the (110) plane, and the (103) plane of each region were measured, and the measurement results were used to obtain OFF _. /O _c .

Bottom peak ratio O _F :I _F (002)/{I _F (100)+I _F (002)+I _F (101)+I _F (102)+I _F (110)+I _F (103)}

Bottom peak ratio O _C :I _C (002)/{I _C (100)+I _C (002)+I _C (101)+I _C (102)+I _C (110)+I _C (103)}

[Average crystal grain size]

With respect to each of the obtained magnesium alloy sheets, the average crystal grain size (μm) of the inner region and the surface region was measured in accordance with "Microscopic test method for steel-crystal grain size JIS G 0551 (2005)". Here, for each magnesium alloy sheet, a section (cross section and longitudinal section) in the thickness direction is taken, and an optical microscope is used to observe (400 times) each section, respectively, for the surface area of each of the above sections (from The surface is oriented in the thickness direction, up to 1/4 of the thickness, and the internal region (the residual portion other than the surface region) takes three fields of view (the total number of fields in each region: 6), and each field of view To find the average crystal grain size. The average value (D _F ) of the average crystal grain size of the total of six fields of view in the surface area, and the average (D _C ) of the average crystal grain size of the total of six fields in the internal region are shown in Table 2. Further, the ratio of the average crystal grain size D _c of the inner region with respect to the average crystal grain size D _F of the surface region was also determined: D _c /D _F . The results are shown in Table 2.

[Vickers hardness]

The Vickers hardness (Hv) of the inner region and the surface region was measured for each of the obtained magnesium alloy sheets. The Vickers hardness and the average crystal grain size are measured in the same manner. For each magnesium alloy sheet, the cross section (cross section and longitudinal section) in the thickness direction is taken, and the Vickers hardness H _F of the surface region is the indenter pressure. The surface area of each of the above-mentioned cross sections was measured, and the Vickers hardness H _c of the inner region was measured by pressing the indenter into the inner region of each of the above-mentioned cross sections. The average value (H _F ) of the Vickers hardness of the above two sections of the surface region and the average value (H _C ) of the Vickers hardness of the above two sections of the inner region are as shown in Table 2. Further, the ratio of the Vickers hardness H _{c to} the inner region of the Vickers hardness H _F of the surface region is also obtained: H _c /H _F . The results are shown in Table 2.

[Corrosion test]

The corrosion resistance of each of the obtained magnesium alloy sheets was measured. Here, a test piece (having a thickness as a thickness) prepared in accordance with JIS Z 2371 (2000) was subjected to a salt spray test for 96 hours, and the amount of corrosion loss (mg/cm ² ) after the test was measured. The results are shown in Table 2.

As shown in Tables 1 and 2, the continuous casting material is rolled by a rolling pass of 25% or less per one pass through a plurality of passes, and is a wall thickness magnesium alloy having a thickness of 1.5 mm or more. In the plate (magnesium alloy material), it was found that the structure (bottom peak ratio) of the inner region in the thickness direction of the obtained wall thickness magnesium alloy sheet and the structure (bottom peak ratio) of the surface region were different. Further, it was found that the mechanical properties of the magnesium alloy sheet in the inner region and the mechanical properties of the surface region were different.

When the obtained magnesium alloy sheets are subjected to press working (heating temperature of the magnesium alloy sheets: 250 ° C to 270 ° C), all the samples can be subjected to press working. Further, as a result of measuring the structure of the flat portion of each of the obtained press-worked materials, the microstructure of each of the magnesium alloy sheets before the press working was substantially the same, and the same bottom-surface ratio or average crystal grain size was obtained. Further, in each of the obtained press-worked materials, the surface roughness Ra of the bent portion was measured. The results are shown in Table 2. The surface area and the inner area are samples having different structures. Specifically, the particle size of the inner area is sample No. B, C, E, F, H, I, K, and L composed of a large tissue. The surface roughness Ra is small, about 0.5 μm or less, and has a smooth surface.

As a result of the above test, a magnesium alloy material having a thick plate-like portion having a thickness of 1.5 mm or more, which has a structure in which the thickness of the plate-like portion is different in the thickness direction and is composed of a structure having a specific orientation, can be confirmed to be resistant. The texture roughness is excellent. Further, since the surface region is composed of a relatively fine structure, the magnesium alloy material is excellent in corrosion resistance.

Further, it is possible to appropriately change the present invention without departing from the gist of the present invention, but the above-described embodiment is not limited to the above configuration. example For example, the composition of the magnesium alloy, the thickness of the magnesium alloy material, the shape, the reduction ratio of each of the rolling passes in the rolling step, the number of rolling passes, and the like can be appropriately changed.

[Industry Utilization]

The magnesium alloy material of the present invention can be suitably used for automobile parts, railway vehicle parts, aircraft parts, bicycle parts, various electronic and electrical equipment parts, and the like, particularly in various fields requiring corrosion resistance or wear resistance, and A constituent material of a member, a bag, or the like. The method for producing a magnesium alloy material of the present invention is suitable for use in the production of the above-described magnesium alloy material of the present invention.

Claims (6)

A magnesium alloy material which is formed of a magnesium alloy and has a plate-like portion, wherein the thickness of the plate-like portion is 1.5 mm or more, and the plate-like portion satisfies the following alignment; [Orientation] from the plate The surface of the portion faces the thickness direction, and the region up to 1/4 of the thickness is used as the surface region, and the remaining portion is used as the inner region, and the (002) plane, the (100) plane, and the (101) plane of the surface region are formed. The peak intensities of the X-ray diffraction of the (102) plane, the (110) plane, and the (103) plane are I _F (002), I _F (100), I _F (101), I _F (102), I, respectively. _F (110) and I _F (103), X-ray diffraction of the (002) plane, (100) plane, (101) plane, (102) plane, (110) plane, and (103) plane of the inner region The peak intensities are I _C (002), I _C (100), I _C (101), I _C (102), I _C (110), and I _C (103), respectively, and the (002) plane of the aforementioned surface region The degree of alignment: I _F (002) / {I _F (100) + I _F (002) + I _F (101) + I _F (102) + I _F (110) + I _F (103)} as the bottom peak Ratio O _F , and the degree of alignment of the (002) plane of the aforementioned inner region: I _C (002) / {I _C (100) + I _C (002) + I _C (101) + I _C (102) + I _C (110) + I _C (103)} as the bottom peak ratio O _{In the case of C} , the ratio of the bottom surface peak ratio O _F of the surface area of the bottom surface peak ratio O _c of the inner region is: O _F /O _c is 1.05 < O _F /O _c . The magnesium alloy material according to the first aspect of the invention, wherein, when the average crystal grain size of the surface region is taken as D _F and the average crystal grain size of the inner region is taken as D _c , the average crystal crystallization is relative to the surface region. The ratio of the average crystal grain size D _c of the aforementioned inner region of the particle diameter D _F : D _c / D _F satisfies 1.5 < D _c / D _F . The magnesium alloy material according to claim 1, wherein the Vickers hardness (Hv) of the surface region is taken as H _F and the Vickers hardness (Hv) of the inner region is taken as H _c relative to the surface The ratio of the Vickers hardness H _c of the aforementioned inner region of the Vickers hardness H _F of the region: H _c /H _F is such that H _c /H _F <0.85 is satisfied. A magnesium alloy material according to claim 2, wherein the Vickers hardness (Hv) of the surface region is referred to as H _F and the Vickers hardness (Hv) of the inner region is taken as H _c relative to the surface The ratio of the Vickers hardness H _c of the aforementioned inner region of the Vickers hardness H _F of the region: H _c /H _F is such that H _c /H _F <0.85 is satisfied. The magnesium alloy material according to any one of the above-mentioned items, wherein the magnesium alloy-based additive element is contained in an amount of 5.0% by mass or more and 12% by mass or less or less. A method for producing a magnesium alloy material, which is characterized in that a magnesium alloy material is produced by rolling a material made of a magnesium alloy, and is characterized in that it has the following steps: preparing a step of preparing a molten magnesium alloy by double Roll-casting method for continuous casting of sheet-like material, and rolling step: applying a rolling pass of a plurality of rolling passes to the aforementioned material A plate-shaped magnesium alloy material having a thickness of 1.5 mm or more is formed; and the reduction ratio of each of the above-mentioned rolling passes is set to 25% or less.