JP2015025168A - Magnesium alloy coil material and production method of magnesium alloy coil material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnesium alloy coil material capable of forming a plastic working member excellent in morphological stability, and a production method of the magnesium alloy coil material.SOLUTION: Magnesium alloy coil material is formed by spirally winding plate material composed of magnesium alloy. Over the entire length of the plate material, variation in residual stress is within 20 MPa. A production method of the magnesium alloy coil material comprises the steps of: preparing material coil formed by spirally winding material plate which is composed of magnesium alloy and has been subjected to rolling; unwinding the material coil, traveling the material plate, and continuously performing heat treatment at 150°C or more and 300°C or less in a state where tensile stress of more than 5 MPa and 25 MPa or less is applied to the material plate; and spirally winding the plate material which is composed of magnesium alloy and has been subjected to the heat treatment.

Description

  The present invention relates to a magnesium alloy coil material in which a plate material made of a magnesium alloy is wound in a spiral shape, and a method for manufacturing the same. In particular, the present invention relates to a magnesium alloy coil material capable of forming a plastic working member having excellent shape stability after plastic working such as press working, and a manufacturing method thereof.

  A magnesium alloy that is lightweight and excellent in specific strength and specific rigidity has been used as a constituent material of various members such as a casing of a portable electric / electronic device such as a mobile phone and a notebook personal computer, and an automobile part.

  Magnesium alloys are lightweight among metals, have high specific strength, have excellent shock absorption properties, and have excellent corrosion resistance due to the addition of various elements to active magnesium. It is preferable for the constituent material of the member. As a specific magnesium alloy, for example, an Mg-Al alloy containing Al, more specifically, an AZ31 alloy defined as an alloy for extension in the ASTM standard, an AZ91 alloy defined as an alloy for casting, etc. There is.

  However, since the magnesium alloy has a hexagonal crystal structure (hcp structure), it is generally inferior in plastic workability at a low temperature such as room temperature, and thus is processed at a certain high temperature. In particular, a magnesium alloy having a high content of additive elements is inferior in plastic workability to a magnesium alloy having a low content of additive elements, and thus heating is required for processing. Patent document 1 is disclosing that the magnesium alloy coil material which is excellent in plastic workability is obtained by performing rolling by performing specific temperature control to the raw material which consists of AZ91 alloy. This magnesium alloy coil material has a structure in which processing strain exists, and is excellent in plastic workability by causing dynamic recrystallization during plastic processing such as press processing.

JP 2011-131274 A

  It is desired to develop a magnesium alloy coil material capable of forming a plastic working member having excellent shape stability after plastic working.

  When manufacturing a magnesium alloy member (plastic working member) by performing plastic working such as press working, if a continuous long plate or a wide plate having a wider width is used as a material, the length becomes a predetermined length. Compared with the case of using a cut sheet plate, it is expected that the yield can be reduced and the productivity can be improved. Therefore, it can be said that a magnesium alloy coil material obtained by winding a long plate or a wider plate can contribute to mass production of a magnesium alloy member (plastic working member). Moreover, if it is a raw material which can shape | mold the plastic processing member which is excellent in dimensional accuracy and shape accuracy, a defective product can be reduced and productivity can be improved.

  As described above, by making the temperature somewhat high (typically 200 ° C. or higher), the plastic workability can be improved and the plastic work member can be manufactured satisfactorily. However, as a result of investigations by the present inventors, it has been found that, when performing plastic working such as press working, when the material is heated, deformation such as warping may locally occur in the material. Specifically, when a sheet piece that has been unwound and cut to a predetermined length is heated, the edge of the sheet piece may be warped. If the material is partially deformed in this way, the material may not be accurately placed at a predetermined position on the mold provided in a device that performs plastic processing such as press work, or the material may be misaligned in the mold. I do not. For this reason, it cannot be accurately processed into a predetermined shape, the shape and dimensions of the molded body obtained after plastic processing are not stable and vary, and the defect rate increases. As a result, the productivity of the plastic working member is reduced.

  Then, one of the objectives of this invention is providing the magnesium alloy coil material which can shape | mold the plastic working member excellent in shape stability. Another object of the present invention is to provide a method for producing a magnesium alloy coil material capable of producing a magnesium alloy coil material capable of forming a plastic working member having excellent shape stability.

The magnesium alloy coil material of the present invention is a magnesium alloy coil material formed by winding a plate material made of a magnesium alloy in a spiral shape,
The variation in residual stress is within 20 MPa over the entire length of the plate material.

The manufacturing method of the magnesium alloy coil material of the present invention includes the following preparation process, heat treatment process, and winding process.
Preparation step A step of preparing a material coil material made of a magnesium alloy and rolled up in a spiral shape.
Heat treatment step: A step of continuously performing a heat treatment at 150 ° C. or more and 300 ° C. or less in a state where the material coil material is rewound and the material plate is run and a tensile stress of 5 MPa to 25 MPa is applied to the material plate.
Winding process The process which winds up the board | plate material which consists of a magnesium alloy in which the said heat processing was performed in the shape of a spiral.

  The magnesium alloy coil material of the present invention can form a plastic working member having excellent shape stability. The method for producing a magnesium alloy coil material of the present invention can produce a magnesium alloy coil material capable of forming a plastic working member having excellent shape stability.

It is explanatory drawing explaining the manufacturing method of the magnesium alloy coil material which concerns on embodiment.

[Description of Embodiment of the Present Invention]
As a result of studying measures for reducing local deformation that occurs during heating for performing the above-mentioned warm plastic working, preferably measures for substantially eliminating the above, It was found that a material that causes a large deformation has a large variation in residual stress when viewed over the entire length of the coil material. Moreover, in order to reduce the dispersion | variation in this residual stress, the knowledge that it was preferable to heat-process separately on a raw material on specific conditions before performing the heating for the above-mentioned warm plastic working was acquired. The present invention is based on the above findings. First, the contents of the embodiment of the present invention will be listed and described.

  (1) The magnesium alloy coil material according to the embodiment is obtained by winding a plate material made of a magnesium alloy in a spiral shape, and variation in residual stress is within 20 MPa over the entire length of the plate material. The variation of the residual stress over the entire length of the plate material is measured as follows.

  The magnesium alloy coil material is rewound, a sample plate material is cut out for each predetermined length, and a plurality of sample plate materials are prepared. The predetermined length is the total length of the coil material × 0.1 to 100 m. For example, when the total length of the coil material is 10 m, the predetermined length is 1 m or more. For example, when the total length of the coil material is more than 1000 m (more than 1 km), it is set to 100 m. The number of sample plates is 5 or more, preferably 8 or more. The length of one sample plate is set to a size at which the residual stress can be measured by at least X-ray diffraction. Then, on one surface of each sample plate, the residual stress is measured at one or more arbitrary points in the longitudinal direction, which is the center position in the width direction. One surface for measuring the residual stress in each sample plate material is a surface arranged outside when being wound, that is, a surface (surface) on the outer peripheral side of the winding. Regarding the measured residual stress (residual stress of 5 points or more in total), the difference between the maximum value and the minimum value is defined as the variation of the residual stress.

  The magnesium alloy coil material according to the embodiment is in a uniform state with a sufficiently small variation in residual stress over the entire length. Therefore, in performing plastic working such as press working on the magnesium alloy coil material according to the embodiment, even when the sheet material cut to an appropriate length is heated to a predetermined temperature, local deformation such as warpage is unlikely to occur. Or substantially does not occur. Moreover, even if there is unevenness in the heating for this plastic working, deformation hardly occurs. Therefore, in the magnesium alloy coil material according to the embodiment, even when a plate material (including a cut material) constituting the coil material is heated for plastic processing, the magnesium alloy coil material is positioned at an appropriate position of the molding die for plastic processing. In addition to being able to arrange with high precision, it is difficult to shift the arrangement position, and plastic working can be performed stably. Therefore, by using the magnesium alloy coil material according to the embodiment as the raw material of the plastic working member, the plastic working member having excellent dimensional accuracy and shape accuracy can be continuously and stably formed. From this, the magnesium alloy coil material according to the embodiment can contribute to mass production of a high-quality plastic working member excellent in dimensional accuracy and shape accuracy, that is, a plastic working member excellent in shape stability. Further, since the magnesium alloy coil material according to the embodiment has a uniform residual stress, the plate material can be uniformly stretched when plastic working is performed, and is excellent in plastic workability.

  (2) The magnesium alloy coil material according to the embodiment includes a form in which the residual stress of the plate material is in the range of −25 MPa to +25 MPa. -(Minus) means compressive residual stress, and + (plus) means tensile residual stress.

  In the above-mentioned form, since the residual stress (absolute value) of the plate material itself is small, when it is heated during the warm plastic working as described above, local deformation is less likely to occur and the plastic workability is excellent. Moreover, the said form can contribute to the mass production of the plastic processing member excellent in shape stability.

  (3) The magnesium alloy coil material according to the embodiment includes a form in which the magnesium alloy is an Mg-Al alloy containing Al.

  Mg-Al based alloy containing Al as an additive element is excellent in mechanical properties such as strength and hardness (rigidity) and corrosion resistance. Therefore, by using the magnesium alloy coil material of the above form as a material, mechanical properties and It is possible to manufacture plastic working members and plate materials having excellent corrosion resistance.

  (4) The magnesium alloy coil material according to the embodiment includes a form in which the average crystal grain size of the magnesium alloy is 10 μm or less.

  The said form is excellent in plastic workability because a board | plate material is comprised with a fine crystal structure.

The magnesium alloy coil material according to the above-described embodiment is obtained by, for example, a method for manufacturing a magnesium alloy coil material according to the following embodiment.
(5) The manufacturing method of the magnesium alloy coil material which concerns on embodiment is equipped with the following preparatory processes, a heat treatment process, and a winding process.
Preparation step A step of preparing a material coil material made of a magnesium alloy and rolled up in a spiral shape.
Heat treatment step A step of continuously performing a heat treatment at 150 ° C. or more and 300 ° C. or less in a state in which the material coil material is rewound and the material plate is run and a tensile stress of 5 MPa to 25 MPa is applied to the material plate.
Winding process The process which winds up the board | plate material which consists of a magnesium alloy to which the said heat processing was performed in the shape of a spiral.

  A material plate made of a magnesium alloy that has been subjected to plastic working such as rolling such as warm rolling has residual stress as described above. By performing the heat treatment accompanied by the application of the specific tensile stress on the material plate having the residual stress, the manufacturing method of the magnesium alloy coil material according to the embodiment provides a plate material made of a magnesium alloy obtained after the specific heat treatment ( The residual stress of the heat treatment plate can be reduced. And the manufacturing method of the magnesium alloy coil material which concerns on embodiment is the state which applied specific low tensile stress with respect to the continuous raw material board (in short, a long board), and a specific warm. Since the material plate is held in the region, the residual stress of the material plate can be reduced, preferably substantially eliminated, without substantially changing the plate thickness before and after the heat treatment. That is, the manufacturing method of the magnesium alloy coil material according to the embodiment can manufacture a heat-treated plate that substantially maintains the plate thickness adjusted by rolling such as warm rolling. The obtained plate material (heat-treated plate) is a plastically processed member that is hardly deformed or is substantially free of deformation even when heated during warm plastic processing as described above, and has excellent shape stability. Can be molded. Therefore, the manufacturing method of the magnesium alloy coil material according to the embodiment can manufacture a magnesium alloy coil material capable of manufacturing a highly accurate and high-quality plastic working member with high productivity. In particular, in the magnesium alloy coil material manufacturing method according to the embodiment, in the form in which the magnesium alloy is an Mg-Al alloy containing Al, a magnesium alloy coil material excellent in mechanical properties and corrosion resistance can be manufactured.

[Details of the embodiment of the present invention]
Hereinafter, the magnesium alloy coil material according to the embodiment and the manufacturing method of the magnesium alloy coil material according to the embodiment will be described in more detail. In addition, this invention is not limited to these illustrations, is shown by the claim, and is intended that all the changes within the meaning and range equivalent to the claim are included. For example, in the test examples described later, coil material specifications (material, thickness, length, width, etc.), manufacturing conditions (rolling conditions (rolling temperature, rolling reduction, etc.), heat treatment conditions (heating temperature, stress, etc.)), etc. Can be changed as appropriate.

(Magnesium alloy coil material)
The magnesium alloy coil material of the embodiment is a long plate material composed of magnesium alloys of various compositions containing various additive elements in Mg (50% by mass or more of Mg and additive elements, the remainder being inevitable impurities). Is wound and wound in multiple layers.

Composition The additive elements of the magnesium alloy include, for example, Al, Zn, Mn, Si, Be, Ca, Sr, Y, Cu, Ag, Sn, Li, Zr, Ce, Ni, Au, and rare earth elements (Y, Ce) 1 or more elements selected from (except for). In particular, an Mg-Al alloy containing Al is preferable because of its excellent corrosion resistance and mechanical properties. Examples of the Al content include 0.1% by mass or more, and the more the Al content, the better the corrosion resistance and mechanical properties. If the Al content exceeds 12% by mass, the plastic workability is deteriorated, so that it is preferably 12% by mass or less, and more preferably 11% by mass or less.

  Examples of the content of each element other than Al include 0.01% by mass to 10% by mass, and further 0.1% by mass to 5% by mass. In particular, a total of at least one element selected from Si, Sn, Y, Ce, Ca and rare earth elements (excluding Y and Ce) is 0.001% by mass or more, preferably a total of 0.1% by mass or more and 5% by mass. % Or less of the magnesium alloy is excellent in heat resistance and flame retardancy. Examples of the impurities in the magnesium alloy include Fe.

  A more specific composition of the Mg—Al-based alloy is, for example, an AZ-based alloy (Mg—Al—Zn-based alloy according to the ASTM standard, containing 0.2 to 1.5% by mass of Zn. For example, AZ31 Alloy, AZ61 alloy, AZ80 alloy, AZ91 alloy, etc.), AM alloy (Mg—Al—Mn alloy, containing 0.05 mass% or more, and further 0.15 mass% or more and 0.5 mass% or less) For example, AM60, AM100, etc.), AS alloys (Mg—Al—Si alloys, containing Si by 0.2 mass% or more and 6.0 mass% or less, eg, AS41, etc.), AX alloys (Mg -Al-Ca-based alloy containing 0.1% by mass or more of Ca, 0.2% by mass or more and 6.0% by mass or less, and further 4.0% by mass or less), AZX-based alloy (Mg-Al -Zn-Ca alloy.Zn The content of Ca is the same as that of AZ-based alloys and AX-based alloys.), AJ-based alloys (Mg—Al—Sr-based alloys; those containing 0.2 to 7.0 mass% Sr), and the like. Can be mentioned. In addition, Mg-Al-RE alloys (RE is a rare earth element and contains RE in an amount of 0.001% by mass or more, preferably 0.1% by mass or more and 5% by mass or less).

  Among Mg-Al based alloys, alloys containing Al in excess of 7.2% by mass, particularly Al in the range of 8.3% to 9.5% by mass, and Zn in the range of 0.5% to 1.5% by mass The Mg—Al based alloy, typically the AZ91 alloy, the AZX911 alloy, and the magnesium alloy containing Al and Zn corresponding to the AZ91 alloy are further excellent in corrosion resistance and mechanical properties.

-Thickness The thickness of the plate material constituting the magnesium alloy coil material of the embodiment can be selected as appropriate. When this coil material is used as a material for a plastic working member, the thickness of the plastic working member substantially maintains the thickness of the plate material constituting the coil material. It is possible to reduce the thickness and size of the member. Therefore, the thickness of a board | plate material is 2.5 mm or less, Furthermore, 2 mm or less, Especially 1.5 mm or less is mentioned. The lower limit of the thickness of the plate material is 0.1 mm. In particular, a form in which the thickness of the plate material is 0.3 mm to 1.2 mm is mentioned. As will be described later, such a thin plate can be easily manufactured by rolling.

-Width and length The width | variety and length of the said board | plate material can be selected suitably. For example, when a coil material composed of a long plate having a length of 50 m or more, further 100 m or more, 1000 m or more (1 km or more) is used as a material for the above-mentioned plastic working member, the above material is continuously supplied to the plastic working device. It is possible to mass-produce plastic processed members. For example, a coil material composed of a wide plate having a width of 100 mm or more, further 200 mm or more, particularly 1000 mm or more (1 m or more) is used as a material for the above-mentioned plastic working member, and is a small component such as a portable device component. It is possible to manufacture plastic working members of various sizes up to large ones such as parts of transportation equipment. The winding diameter (inner diameter) of the magnesium alloy coil material of the embodiment can also be selected as appropriate.

  Alternatively, the magnesium alloy coil material of the embodiment can have a large weight of 100 kg or more, and further 1000 kg or more. Although this coil material is dependent on the width | variety and thickness of a board | plate material, it becomes a coil material comprised from the elongate board whose length is 200 m or more, and also 1000 m or more, so that thickness is thin (for example, 1 mm or less). When such a coil material is used as a material for the above-mentioned plastic working member, it is possible to produce plastic working members of various sizes as described above, or to contribute to mass production of the plastic working member.

-Form The said board | plate material can take a various form with a manufacturing process. Typically, a heat treatment material that has been subjected to a specific heat treatment described later after undergoing a rolling step described later is given. In addition, after rolling, before the heat treatment described later, a form with excellent flatness and surface properties that have been subjected to correction processing and polishing described later, or a form excellent in surface properties, or after heat treatment described later, correction processing, polishing, chemical conversion treatment, Anti-corrosion treatment such as anodizing treatment, surface decoration processing (cutting processing such as diamond cut and hairline, etching, shot blasting, etc.), painting, etc., that is, correction materials, abrasives, anti-corrosion treatment materials, surface treatment materials And coating materials.

-Structure Although the said board | plate material is typically manufactured by performing specific heat processing after rolling, it can be set as the form comprised from the fine crystal structure by passing through the rolling process. For example, the crystal grain size of the magnesium alloy constituting the plate material may satisfy an average of 10 μm or less. As the crystal grain size is smaller, the plastic workability tends to be improved, and the average crystal grain size can satisfy 6 μm or less, and more preferably 4 μm or less.

Mechanical properties The plate material is excellent in mechanical properties as compared with a cast plate having the same composition, for example, by being subjected to rolling (at least one pass is warm rolling) as described later. For example, in a plate material made of a magnesium alloy containing Al in excess of 7.2% by mass such as AZ91 alloy, the tensile strength is 280 MPa to 450 MPa, the 0.2% proof stress is 230 MPa to 350 MPa, and the elongation at break is 1% or more. The form which satisfy | fills 15% or less is mentioned.

-Residual stress And the said board | plate material has the dispersion | variation in a residual stress small over the full length. Specifically, the difference between the aforementioned maximum value of residual stress and the minimum value of residual stress is within 20 MPa. That is, when the residual stresses at arbitrary positions in the longitudinal direction of the plate material are compared for the plate material constituting the coil material, the difference is small. Because the residual stress variation is small and the residual stress is uniform over the entire length, there are places where the residual stress differs locally even when the plate is heated. As described above, it is possible to form a highly accurate plastic working member having excellent shape stability. Since the smaller the variation in the residual stress, the more local deformation can be prevented, the variation in the residual stress is preferably within 15 MPa, more preferably within 10 MPa, and ideally there is no variation. Details of the residual stress measurement conditions will be described later.

  Further, the smaller the residual stress (absolute value) itself of the plate material, the less likely the above-mentioned local deformation occurs. Specifically, the residual stress of the plate material preferably satisfies the range of −25 MPa to +25 MPa, and more preferably the range of −15 MPa to +15 MPa. In addition, the board | plate material located in the inner peripheral side of a coil (plate material of the part with a small coil | winding diameter of a coil) may have a tensile stress rather than the board | plate material located in an outer peripheral side. However, when the residual stress range (over 0 to +25 MPa) is satisfied, local deformation hardly occurs.

  Regarding the plate material constituting the coil, when the residual stress at an arbitrary position in the width direction of the plate material is compared, the difference is preferably small, that is, the variation is small. Further, it is preferable that the residual stress (absolute value) at an arbitrary position in the width direction of the plate material satisfies the above range because local deformation hardly occurs. Further, in the plate material constituting the coil, it is preferable that the residual stress is substantially equal for the outer peripheral surface (front surface) of the winding and the inner peripheral surface (back surface) of the winding. However, the residual stresses on the front and back surfaces may differ depending on the winding diameter of the coil. Also in this case, when the residual stress (absolute value) on both the front and back surfaces satisfies the above range, local deformation hardly occurs.

(Manufacturing method of coil material)
-Preparation process In the manufacturing method of the magnesium alloy coil material of embodiment, first, the raw material coil material which is a raw material board which consists of magnesium alloys of desired composition, and is wound up in the shape of a spiral is prepared. This material coil material has been subjected to rolling, and preferably has been subjected to warm rolling for one pass or more. Such a coil material is a rolled coil material that has been rolled, a straightened coil material that has been straightened after rolling, a polished coil material that has been ground after rolling, and both straightened and ground after rolling. Coil material and the like.

  The rolled coil material is typically obtained by rolling a cast material made of a magnesium alloy (including one or more passes of warm rolling). As the casting material, for example, an ingot manufactured with a mold having a desired shape can be used. When a cast coil material obtained by winding a long cast plate made of a magnesium alloy by a continuous casting method such as a twin roll casting method is used as a cast material, a long rolled coil material can be easily manufactured.

  A heat treatment such as a solution treatment can be performed on the material before the rolling process. Although the solution treatment conditions depend on the composition, for example, the heating temperature is 350 ° C. or higher and 420 ° C. or lower, and the holding time is 1 hour or longer and 40 hours or shorter. By this heat treatment, precipitates that can be the starting point of cracking can be dissolved to improve mechanical properties and rollability. As the content of additive elements such as Al increases, more precipitates tend to precipitate, so it is preferable to increase the holding time.

  The rolling material (such as the above cast material or solution treated material subjected to solution treatment) is rolled for one pass or more. By rolling, a raw material plate having a desired thickness can be obtained, and a structure in which casting defects (internal defects) such as nests are small, small, or substantially absent can be obtained. Moreover, the improvement of the intensity | strength by work hardening, etc. can be expected by rolling. Furthermore, the crystal grains can be refined by rolling.

  When performing warm rolling, the condition is that the temperature of the material immediately before being supplied to the rolling roll to be rolled is 150 ° C. or higher and 400 ° C. or lower (preferably 350 ° C. or lower, more preferably 300 ° C. or lower, particularly 280 ° C. or lower). The rolling reduction per pass is 5% or more and 40% or less. By setting the specific temperature range as described above, (i) even a material plate made of a high-concentration alloy with a high content of additive elements can improve plastic workability and reduce edge cracking. A rolled sheet can be obtained. (Ii) The rolling reduction per pass can be increased (for example, about 10% or more and about 30% or less), and the productivity of the coil material can be improved. (Iii) Deterioration of surface properties due to seizure or the like. (Iv) It is possible to suppress the thermal deterioration of the rolling roll. Moreover, when not only a raw material but a rolling roll is heated, it is easy to suppress the temperature fall of a raw material or to reduce the crack of an edge part more (refer patent document 1). In addition, warm rolling can be performed using known rolling conditions. When performing rolling with a small rolling reduction, such as finish rolling, cold rolling can be performed.

  When performing the warm rolling, various heating means can be used for heating the above-described material. For example, as described in Patent Document 1, a rolling line having an atmospheric furnace such as a heat box can be used. The heating time can be appropriately set according to the weight, size (width, thickness), number of turns, and the like of the coil.

  When a lubricant is used for rolling, the friction between the material and the rolling roll can be reduced and rolling can be performed satisfactorily.

  Preferably, one or more passes of warm rolling are performed. When performing a plurality of passes in the rolling step, all passes can be made warm, or some of the passes can be made hot or at room temperature. In any case, residual stress exists in the magnesium alloy after rolling (rolled sheet) by performing plastic working such as rolling on the magnesium alloy. In particular, when at least one pass of rolling is warm rolling, that is, when rolling is performed in a state in which the rolling material is heated, the edge portion in the width direction of the rolling material is liable to decrease in temperature, The central part tends to be hot. This variation in temperature inevitably causes a variation in the degree of reduction, so that a variation in residual stress can occur in the rolled material. However, in the manufacturing method of the magnesium alloy coil material of the embodiment, variation in residual stress can be reduced by performing heat treatment under a specific condition to be described later after rolling (not immediately after).

  By rolling a plurality of passes, the thickness of the rolled plate is further reduced, or the crystal grain size of the structure constituting the rolled plate is reduced (for example, the average crystal grain size is 10 μm or less, preferably 5 μm or less). can do. In the manufacturing method of the magnesium alloy coil material of the embodiment, by performing a specific heat treatment after rolling, crystal grains recrystallized by this heat treatment can grow to some extent. However, if crystal grains are made fine to some extent in the rolling process, excessive crystal growth can be prevented in the heat treatment after rolling, and the fine crystal structure (for example, the average crystal grain size is 10 μm or less) is satisfied as described above. A magnesium alloy coil material can be manufactured. Coarse crystal grains serve as starting points for cracks and cause a decrease in plastic workability. Therefore, when the crystal structure is fine to some extent as described above, it is possible to suppress a decrease in plastic workability. The number of passes, the rolling reduction of each pass, and the total rolling reduction can be appropriately selected so that a rolled plate having a desired thickness or a rolled plate having crystal grains of a desired size can be obtained. For example, the rolling reduction per pass is about 10% to 40%, and the total rolling reduction is about 75% to 85%. In addition, when performing multi-pass rolling, as described in Patent Document 1, a rolling line including a pair of reels and a rolling roller disposed between the reels is constructed, and the reels are rotated for each pass. If reverse rolling is performed with the direction reversed, rolling can be performed efficiently.

  The rolled coil material which is one form of a raw material coil material is obtained by finally winding up the rolled sheet in which the said rolling was performed in the shape of a spiral. If this winding is also warm, the occurrence of cracks during winding can be suppressed and winding can be performed easily.

  In addition, the rolling coil material described above can be further corrected and polished. For the correction, a roller leveler (see Patent Document 1) in which a plurality of rollers are arranged in a staggered manner, and a material can be repeatedly bent by passing the material between the rollers can be suitably used. In particular, when warm correction is performed in a state where the material is heated to 100 ° C. or higher and 300 ° C. or lower, cracks and the like are unlikely to occur. When cold straightening is performed in a state where the material is at room temperature or higher and lower than 100 ° C., thermal deterioration of parts of the straightening device can be reduced. It is difficult to sufficiently reduce the residual stress in the material only by correction. On the other hand, after corrective processing (warm processing, cold processing), as will be described later, by performing a specific heat treatment in which a specific low stress is applied to the material plate, the residual stress varies. The flatness can be maintained while reducing the above. That is, the manufacturing method of the magnesium alloy coil material according to the embodiment can manufacture a heat treatment material that is excellent in flatness without impairing flatness when the material plate is an orthodontic material.

  The correction and polishing can be performed after a specific heat treatment described later. In this case, correction processing can be performed using heat remaining in the material after a specific heat treatment described later. In addition, if the above-described anticorrosion treatment (anodizing treatment, chemical conversion treatment, etc.), painting, surface decoration processing, etc. are performed after a specific heat treatment described later, it is possible to improve the corrosion resistance, the decorativeness, and the metal texture it can.

-Heat treatment process The raw material coil material obtained through the rolling process including the above-mentioned warm rolling has residual stress due to plastic working such as rolling as described above, and the residual stress may vary. In the manufacturing method of the magnesium alloy coil material of the embodiment, the material coil material is subjected to heat treatment for the purpose of correcting (reducing) the variation in the residual stress. In particular, this heat treatment is performed in a state where a material plate on which the material coil material has been rewound is run and a state where a specific stress is applied. This stress is a tensile stress.

  Typically, as shown in FIG. 1, the material coil material 100 is attached to a reel 200, and the material plate 10 made of magnesium alloy is sequentially fed out, and is sequentially wound around another reel 210. That is, the material plate 10 and the plate material 11 can be run by passing the material plate 10 and the heat-treated plate material 11 between the reels 200 and 210. The traveling speed can be adjusted by adjusting the rotational speeds of both reels 200 and 210. By providing the heating means 20 on the travel lines of the material plate 10 and the plate material 11, the material plate 10 can be heated.

  Residual stress can be released by setting the heating temperature during this heat treatment to 150 ° C. or higher. The higher the heating temperature, the easier it is to reduce the residual stress (absolute value), and 200 ° C. or higher is more preferable. However, as the heating temperature is higher, the material plate 10 is more easily deformed, and the specific stress is applied in the manufacturing method of the magnesium alloy coil material of the embodiment, so that the thickness of the plate material 11 after the heat treatment decreases. There is a fear. Further, as the heating temperature is higher, crystal grains and precipitates grow, and there are coarse grains that become the starting point of cracking during plastic processing, which may lead to a decrease in plastic workability. Therefore, the heating temperature is 300 ° C. or less, and more preferably 250 ° C. or less.

  Specific heating means 20 includes, for example, a plurality of heating rolls. In this embodiment, a plurality of heating rolls are arranged in parallel in the travel direction of the material plate 10, and the material plate 10 is heated to a predetermined temperature by bringing the material plate 10 into contact with these heating rolls. Examples of the heating roll include those equipped with a structure capable of heating the material plate 10 such as a built-in heating means such as a heater and a built-in circulation mechanism through which a heated fluid is circulated. Examples of the material of the heating roll include steel having excellent heat resistance. The plurality of heating rolls are in contact with the front and back surfaces of the material plate 10 so that the front and back surfaces can be heated, so that the front side of the material plate 10 (upper side in FIG. 1) and the back side of the material plate 10 (lower side in FIG. 1). It is preferable to arrange them on both sides. However, the plurality of heating rolls are in the traveling direction of the material plate 10 so that the thickness of the heated material plate 10 is not changed (not thinned) by being sandwiched between the heating rolls arranged on the front and back surfaces of the material plate 10. It arrange | positions in the position shifted along, for example, arrange | positions in zigzag form.

  The length of the heating roll in the axial direction can be selected according to the width of the material plate 10. The diameter of the heating roll and the number of heating rolls can also be selected as appropriate. The greater the number of arrangements, the longer the holding time. In addition, a constant temperature bath capable of keeping the temperature of the material plate 10 by covering the location where the heating roll is disposed in the traveling material plate 10 can be provided.

  Alternatively, the heating means 20 may be a heating furnace capable of heating the material plate 10 to a predetermined temperature. In this embodiment, the material plate 10 traveling through the heating furnace is passed and the material plate 10 is heated to a predetermined temperature. The heating furnace can be an atmosphere furnace (such as one that can circulate hot air at a predetermined temperature or one that can be equipped with a heating means such as a heater and can maintain an atmosphere at a predetermined temperature), a resistance heating furnace (such as energizing a material plate) And an induction heating furnace (which heats the material plate by electromagnetic induction by supplying high frequency power). The heating furnace does not substantially bend the material plate 10 during heating, and it is easy to obtain the magnesium alloy coil material 1 made of a plate material having excellent flatness.

  The specifications of the heating furnace (the current value that can be energized, the volume of the atmosphere furnace, the length of the furnace along the travel direction of the material plate, etc.) are determined depending on the traveling speed, the thickness of the material plate 10 and the like. It may be selected so that it can be held at a predetermined temperature for a desired time. The atmosphere in the atmosphere furnace may be air, but a non-oxygen-containing atmosphere such as argon or nitrogen is preferable because oxidation of the material plate 10 can be prevented. If it is an atmospheric atmosphere, the construction of the equipment is easy.

  Or it can be set as the heating means provided with both the above-mentioned several heating roll and heating furnace.

  Various methods can be used to adjust the tensile stress applied to the blank 10 during the heat treatment. For example, a method of adjusting the rotational speeds of both reels 200 and 210 can be mentioned. This form does not require any additional adjustment equipment. Or the method of adjusting the tension | tensile_strength provided to the raw material board 10 by arrange | positioning a pinch roll etc. suitably and clamping at least one of the raw material board 10 and the board | plate material 11 is mentioned. Alternatively, a tension adjusting device such as a dancer device may be provided separately. In any case, it is preferable to adjust the stress while attaching the tension measuring device 30 to at least one of the material plate 10 and the plate material 11 and confirming the tension applied to the material plate 10.

  If the tensile stress applied to the material plate 10 during heat treatment is too large, the plate thickness is reduced or, in the worst case, the material is broken, so that it is 25 MPa or less. If the tensile stress to be applied is too small, the residual stress of the material plate 10 cannot be sufficiently reduced. In the range where the tensile stress is more than 5 MPa and not more than 25 MPa, it is preferable to increase the applied tensile stress as the thickness of the material plate increases. Further, when the temperature during the heat treatment is high (for example, 250 ° C. or more and 300 ° C. or less), even if the tensile stress applied within the above range is reduced (for example, more than 5 MPa and 10 MPa or less), the material plate 10 remains. Stress can be reduced sufficiently. A more preferable value of the tensile stress to be applied is 10 MPa or more and 20 MPa or less, and further 15 MPa or less. The residual stress of the plate 11 varies depending on the above heat treatment conditions. For example, the higher the heating temperature in the range of 150 ° C. or higher and 300 ° C. or lower, or the greater the tensile stress applied in the range of 5 MPa or higher and 25 MPa or lower, the smaller the variation or absolute value.

-Winding process While applying the above-mentioned low stress, the reel 11 is used to wind the plate material 11 that has been subjected to the heat treatment for heating the material plate 10 by the heating means 20 described above. A magnesium alloy coil material 1 is obtained in which a plate material 11 having a small variation in residual stress is wound up in a spiral shape. If the temperature of the plate material immediately before winding is 200 ° C. or less, preferably 100 ° C. or less, the plate material is less likely to be curled and the coil material 1 having excellent flatness can be easily obtained. The low temperature may be achieved, for example, by adjusting the traveling speed of the material plate 10 and naturally cooling, or may be achieved using forced cooling means such as blast or water cooling means.

  In the manufacturing method of the magnesium alloy coil material of the embodiment, the heat treatment is performed in a state where the raw material plates are spread in a single sheet, not in a multi-layered state. Easy to control. Therefore, the obtained coil material has a uniform crystal grain size over the entire length (small variation in grain size), or precipitation caused by warm rolling in a composition with a high content of additive elements. An object (mainly intermetallic compound) is re-dissolved to form a structure in which precipitates are small over the entire length (precipitates are fine and variation is small). Therefore, the magnesium alloy coil material having a uniform structure over the entire length can be manufactured by the method for manufacturing the magnesium alloy coil material of the embodiment.

[Test Example 1]
A magnesium alloy coil material made of a magnesium alloy was produced, and a plastic working member was produced using the coil material as a raw material, and the shape stability was evaluated.

  A rolled coil material was prepared as a material. The rolled coil material was manufactured by using a rolling line provided with a rolling roll (a pair of opposed rolls) between a pair of reels. The following rolling material is attached to one feeding reel, one end of the rolled material is taken up by the other winding reel, and the rolling material can be run by rotating both reels. By passing, the material for rolling is rolled. A plurality of passes of warm rolling were performed under the following conditions (using reverse rolling), and finally rolled up to obtain a rolled coil material. The above heat box or the like can be suitably used for heating the rolling material.

(Rolling material)
Cast coil material produced by a twin roll casting method having the composition shown in Table 1 Thickness: 4.0 mm Length: 100 m
Solution treatment after casting: 400 ° C x 20 hours (rolling conditions)
Rolling temperature: 250 ° C
Plate thickness after rolling: 0.8mm
Total reduction rate: 80% (reduction rate of each pass: 10% / pass to 25% / pass)

  The obtained rolled coil material was straightened (here, a roller leveler device was used. Warm straightening with a material temperature of 200 ° C.), and tensile stress was applied under the processing conditions shown in Table 1. A sample having a heating temperature of 200 ° C. to 280 ° C. under the processing conditions shown in Table 1 means that the sample was heated at the time of applying the above-described tensile stress, and was subjected to a heat treatment accompanying the application of the tensile stress. The heating and the application of tensile stress are performed by rewinding the correction coil material (material coil material) wound around the reel for feeding, and winding the rewound correction plate (material plate) with the reel for winding. The material plate was hung between the two reels so that the material plate (and the plate material connected to the material plate) can travel between the two reels. The plate material subjected to the above treatment was wound up to produce a magnesium alloy coil material.

  Sample No. which is subjected to heat treatment accompanied by application of the tensile stress described above. 2-No. 4, no. 12-No. 14, no. 22-No. In 24, as a heating means, a heating furnace (here, a hot air circulating furnace) is prepared, arranged between the two reels (see FIG. 1), and the material plate is passed through the heating furnace, whereby the material plate Was heated for heat treatment.

  And sample no. 2-No. 4, no. 12-No. 14, no. 22-No. In No. 24, the above heat treatment was performed by adjusting the rotation speeds of both reels so that the tensile stress shown in Table 1 was applied to the material plate. On the other hand, the sample No. 1 in which the heating temperature under the processing conditions shown in Table 1 is room temperature. 1, No. 1 11, no. In No. 21, the rotation speeds of both reels were adjusted so that the tensile stress shown in Table 1 was applied to the material plate, and the reel was fed and wound, and the material plate was not heated.

The distribution of residual stress of the obtained magnesium alloy coil material (heat treatment material or stress applying material) was examined. Specifically, it investigated as follows. The coil material (500 m or more in length and 230 mm in width) was rewound, and a sheet piece having a length of 1 m was cut out every 50 m for the remainder obtained by cutting 5 m from both ends, and this sheet piece was used as a sample plate. Here, eight sheet pieces were prepared. The residual stress was measured for each sheet piece (here, the cut 1 m sheet piece was further cut into a short piece having a length of 300 mm). Here, the center position in the width direction on the surface of each sheet piece (the surface disposed on the outer periphery side in the wound state) is taken, and the residual stress is measured at any one point in the length direction at this center position. did. The residual stress was measured by the sin ² Ψ method using the following micro-part X-ray stress measurement apparatus with the (104) plane as the measurement plane. And the maximum value and the minimum value were extracted from the residual stress (absolute value) of a total of 8 points in the 8 sheet pieces, and the difference was defined as the variation in the total length. The results are shown in Table 1. In addition, Table 1 shows the maximum value among the total of 8 residual stresses measured in each sample. Regarding the maximum value shown in Table 1, a value with “minus” means a compressive residual stress, and a value without “minus” means a tensile residual stress.

Equipment used: Microscopic X-ray stress measurement device (MSF-SYSTEM, manufactured by Rigaku Corporation)
X-ray used: Cr-Kα (V filter)
Excitation conditions: 30 kV 20 mA
Measurement area: φ2mm (use collimator diameter)
Measurement method: sin ² Ψ method (parallel tilt method, with oscillation)
Ψ = 0 °, 10 °, 15 °, 20 °, 25 °, 30 °, 35 °, 40 °, 45 ° Measurement surface: Mg (104) surface Usage constant: Young's modulus = 45,000 MPa, Poisson's ratio = 0 .306
Measurement location: center of the surface of the sheet piece (center position in the width direction)
Measurement direction: Sheet strip rolling direction

  The obtained magnesium alloy coil material (heat treatment material or stress applying material) was cut into a predetermined length to prepare a test piece (rectangular sheet material) for plastic working. The test piece for plastic working was subjected to warm press working, and the state during processing and the state after processing were examined to evaluate the shape stability.

  In this test, a mold heated to 250 ° C. is prepared, a test piece for plastic working is placed on the mold and heated, and the rising state of the periphery due to warpage is confirmed. The distance between the surface of the mold and the test piece (the size of the gap due to lifting) was measured with a gap gauge, and it was examined whether the maximum value of this distance was greater than 10 mm or less than 10 mm. Here, 20 specimens for plastic working are prepared for each sample, the above-mentioned interval is measured, and the case where the interval of all 20 sheets is 10 mm or less is Good. Among the 20 sheets, the interval is more than 10 mm The case where there is is evaluated as B, and Table 1 shows the evaluation of the state during processing.

  Warm pressing was performed using the mold heated to 250 ° C. The state after processing of the obtained molded body (200 mm × 300 mm × depth 5 mm, inner angle R = 1 mm) was evaluated as follows. The flat part (200 mm × 300 mm surface) of the obtained molded body is placed on a surface plate, and the lift of the flat surface portion is measured with a gap gauge, and the gap between the surface plate and the flat surface portion is more than 1 mm or 1 mm. The following was investigated. Here, 20 molded bodies are prepared for each sample, and the above-mentioned lifting (gap) is measured. When all the 20 gaps are 1 mm or less, Good, and among 20 pieces, the gap is more than 1 mm. A case is evaluated as B, and Table 1 shows an evaluation of the state after processing.

  As shown in Table 1, sample No. 1 was subjected to heat treatment at a specific heating temperature in a state in which a tensile stress having a specific size was applied to a blank plate subjected to warm rolling. 2, no. 3, No. 12, no. 13, no. 22, no. It can be seen that all of Nos. 23 have small variations in residual stress over the entire length. Specifically, in any of these samples, the difference between the maximum value and the minimum value of the residual stress is within 20 MPa (here, less than 19 MPa, and further within 10 MPa). In addition, any of these samples has a small residual stress itself. Specifically, all of these samples satisfy the range of the maximum residual stress shown in Table 1 in the range of −25 MPa to +25 MPa. That is, it can be said that any of the total of 8 residual stresses measured for each sample satisfies the range of −25 MPa to +25 MPa. Furthermore, the sample No. subjected to the specific heat treatment described above was used. 2, no. 3, No. 12, no. 13, no. 22, no. It can be seen that No. 23 hardly undergoes deformation such as warping when heated during the warm plastic working. Therefore, it can be said that all of these samples maintain the flatness by the correction processing performed before the heat treatment. And sample no. 2, no. 3, No. 12, no. 13, no. 22, no. Each of the press-formed bodies (plastically processed members) obtained using the magnesium alloy coil material of No. 23 is formed with high accuracy with little or substantially no shape defect such as lifting, It can be seen that the shape stability is excellent.

  Thus, sample No. 2, no. 3, No. 12, no. 13, no. 22, no. The reason why the magnesium alloy coil material of No. 23 is capable of forming a plastic working member having excellent shape stability is that the residual stress is uniformly present over the entire length before the plastic working. This is thought to be because the local deformation (warping, etc.) due to the balance loss could be reduced.

  In addition, the sample No. subjected to the specific heat treatment described above was used. 2, no. 3, No. 12, no. 13, no. 22, no. The average crystal grain size of 23 coil materials was measured. The results are shown in Table 1. The measurement was performed based on “steel-crystal grain size microscopic test method JIS G 0551 (2005), cutting method using linear test line”. As shown in Table 1, these samples all have an average crystal grain size of 10 μm or less (here, all are 5 μm or less). All of these samples have a uniform crystal structure (recrystallized structure) over the entire length as described above by being heat-treated under uniform conditions over the entire length of the material plate. From this point, it is considered that the plastic workability was improved. Sample No. 2, no. 3, No. 12, no. 13, no. 22, no. For each of 23, an arbitrary one of the above-described eight sheet pieces was selected, and the variation in the residual stress in the width direction was examined. Specifically, with respect to the selected sheet piece, the residual stress of 5 to 10 points along the width direction so as to include the center position in the width direction in which the above-described residual stress is measured is measured according to the above-described conditions (the measurement direction is rolled). Direction). As a result, it was confirmed that the variation in the residual stress in the width direction was within 20 MPa.

  On the other hand, sample No. 1, No. 1 11, no. No. 21 has a large variation in residual stress, and the maximum value of the residual stress is also large, and it can be seen that deformation such as warping can occur when heating is performed during warm plastic working. On the other hand, Sample No. 2 was subjected to heat treatment in a state where a very low tensile stress was applied. 4, no. 14, no. 24 also has a large variation in residual stress, and the maximum value of the residual stress is also large. The reason for this is considered that the variation in residual stress could not be sufficiently improved because the tensile stress was too low. And sample no. 4, no. 14, no. It can be seen that No. 24 has a large variation in residual stress, and warping or the like may occur when heating is performed during warm plastic working.

  As described above, it was confirmed that the magnesium alloy coil material with small variation in residual stress over the entire length of the magnesium alloy plate can form a magnesium alloy member having excellent shape stability after plastic working. In addition, by applying a heat treatment in a state where a specific temperature and a specific tensile stress are applied in a state where the material coil material that has been rolled (preferably warm rolling of one pass or more) is rewound, the entire length is obtained. It was confirmed that a magnesium alloy coil material composed of a magnesium alloy plate with small variations in residual stress was obtained.

  The magnesium alloy coil material of the present invention can be suitably used as a material for plastic working members to which various plastic workings such as press working, bending, forging and upsetting are performed. In particular, the magnesium alloy coil material and the sheet material obtained by appropriately cutting the coil material are members that are desired to have characteristics such as light weight, thinness, high strength, and vibration damping properties, such as various electronic and electric devices (personal computers). (PC), tablet PCs, mobile phones such as smartphones and foldable mobile phones, digital cameras, etc.) exterior members such as housings and covers, components of transport equipment such as automobiles and aircraft, skeleton members, bags, various It can be suitably used for a material such as a protective case. The method for producing a magnesium alloy coil material of the present invention can be suitably used for producing a magnesium alloy coil material used as a material for a magnesium alloy member (plastic working member).

DESCRIPTION OF SYMBOLS 1 Magnesium alloy coil material 10 Material plate 11 Plate material 100 Material coil material 20 Heating means 30 Tension measuring device 200,210 Reel

Claims (5)

A magnesium alloy coil material obtained by winding a plate material made of a magnesium alloy in a spiral shape,
A magnesium alloy coil material in which variation in residual stress is within 20 MPa over the entire length of the plate material.   The magnesium alloy coil material according to claim 1, wherein a residual stress of the plate material is in a range of -25 MPa to +25 MPa.   The magnesium alloy coil material according to claim 1 or 2, wherein the magnesium alloy is an Mg-Al alloy containing Al.   The magnesium alloy coil material according to any one of claims 1 to 3, wherein an average crystal grain size of the magnesium alloy is 10 µm or less. A step of preparing a material coil material made of a magnesium alloy and rolled into a spiral shape;
Rewinding the material coil material and running the material plate, and continuously applying a heat treatment of 150 ° C. or more and 300 ° C. or less with a tensile stress of 5 MPa or more and 25 MPa or less applied to the material plate;
A method of manufacturing a magnesium alloy coil material, comprising: winding a plate material made of a magnesium alloy subjected to the heat treatment into a spiral shape.

Images