JP2012122102A - Magnesium alloy sheet material improved in cold formability and strength, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a magnesium alloy sheet material having cold formability equal to that of an aluminum alloy and exhibiting excellent strength; a method for producing the magnesium alloy sheet material; and a member of the magnesium alloy sheet material.SOLUTION: This easily formable magnesium alloy sheet material having an Erichsen value of 7.0 or more and an yield stress in a TD direction of 90 MPa or more is produced by rolling an alloy at a sample surface temperature of 150°C to 450°C or below and then annealing the alloy. In the alloy, an additive amount of Zn is restricted in 2.61-6.20 mass%, 0.01-0.9 mass% of Ca is added or Ca and Sr are added so that the total amount of Ca and Sr is 0.01-1.5 mass% while a Ca concentration is restricted in 0.01-0.9 mass%, and, if required, 0.01-0.7 mass% of Zr and/or Mn is added. The member of the easily formable magnesium alloy sheet material is also produced. Thus, an inexpensive magnesium alloy can be positively applied to the press molding of home electric appliances, such as a digital camera, a notebook personal computer and a PDA.

Description

  The present invention relates to an easily formable magnesium alloy sheet having excellent room temperature formability and strength, a method for producing the same, a press-molded body produced using the easily formable magnesium alloy sheet, and a member thereof. Is an aluminum alloy (corresponding to 5000 series or 6000 series) at room temperature (30 ° C.) by rolling and annealing a rolled magnesium alloy material to which an appropriate amount of Zn, Ca, Sr, Zr, Mn is added under predetermined conditions. The present invention relates to a magnesium alloy sheet, a manufacturing method thereof, a press-molded body thereof, and a member thereof, which are capable of imparting formability comparable to that of a) and further capable of imparting excellent strength (yield stress). The present invention provides a new technology and a new product relating to a magnesium alloy member and a housing that can be used in a wide range of fields such as space / aviation materials / electronic device materials, automobile members, and the like.

Magnesium has the lowest density (= 1.7 g / cm ³ ) among practical structural metal materials, has easy recyclability unique to metal materials, and has abundant resources. It is attracting attention as a material.

  The plastic working process, especially press forming of plate materials, is an important means for producing precision molded products and large molded products while maintaining a high yield. In addition, high strength and high toughness are achieved simultaneously with forming. This kind of process can be said to be an effective means of expanding demand. When producing a compact from a magnesium alloy sheet by press molding, a thin and high specific strength compact can be produced by an inexpensive process. Can be predicted.

  It is known that dislocation motility, which is the basis of plastic deformation of metals, is affected by the ratio of slip plane spacing / interatomic distance. Therefore, in the case of a close-packed hexagonal magnesium alloy, the ratio of the a-axis length to the c-axis length (c / a ratio) is large (c / a = 1.6236). There is a big difference in motility.

  Therefore, the critical decomposition shear stress (CRSS) of the non-bottom slip of the magnesium alloy is very large at room temperature as compared with other slip systems, and the room temperature formability is inevitably low. Furthermore, since a texture is formed in the magnesium alloy plate material in which the (0002) plane is oriented parallel to the plate surface, distortion in the plate thickness direction during plastic deformation cannot be expected. This contributes to lowering the moldability.

  The room temperature formability (Ericsen value) of aluminum alloys currently used in a wide range of fields is higher than that of the above magnesium alloys, and is 8.3 (5083-O material) and 6000 series alloys. If it is, it is 11.0 (1100-O material) if it is 9.2 (6061-T4 material) and 1000 series alloy (Non-patent Document 1). On the other hand, the room temperature formability (Ericsen value) of conventional commercial magnesium alloys is at most 2.0 to 5.0 (Non-patent Document 2).

  Therefore, regarding the magnesium alloy, it is necessary to provide room temperature formability (the Erichsen value at room temperature is at least 7.0 or higher) equivalent to the aluminum alloy sheet in order to anticipate significant demand for the magnesium alloy sheet in the future. In this technical field, it is strongly demanded to develop a manufacturing technology for a new magnesium alloy sheet having excellent easy formability and its product.

  As a technique for press-molding a magnesium alloy having poor formability at room temperature, use of a magnesium alloy sheet having a controlled texture can be mentioned. In recent years, a technique for repeatedly bending a magnesium alloy sheet has been proposed as a technique for modifying the texture of the magnesium alloy.

  This method is mainly intended for general-purpose magnesium alloys (Mg—Al—Zn—Mn alloys), and its room temperature formability is improved to an aluminum alloy level (Ericsen value: 6.5 or more) (patent document). 1). However, this method has a problem that it is necessary to repeatedly perform bending in the rolling process, and the existing rolling equipment cannot be used directly.

  In recent years, as another technique for modifying the texture of a magnesium alloy, the present inventors have used a general-purpose magnesium alloy (Mg—Al—Zn—Mn alloy) at a predetermined sample temperature, that is, 490 ° C. to 566 ° C. Developed a technique to heat up to ℃ for a short time, preferably less than 5 minutes, perform hot rolling at a rolling rate of 5% or more, preferably 5 to 50%, and anneal after rolling. (Patent Document 2).

  In addition, the inventors of the present invention rolled a sample heated to a temperature range from a temperature lower than the solidus temperature to 50 ° C. to the solidus temperature with respect to the general-purpose magnesium alloy one or more times, and then heated A method of carrying out finish rolling at 150 to 300 ° C. and annealing after rolling has been developed (Patent Document 3).

  Furthermore, the present inventors used a general sample magnesium alloy (Mg—Al—Zn—Mn alloy) added with a trace amount, that is, 0.01 to 0.5 mass% of calcium, at a predetermined sample temperature, that is, A technique has been developed in which the temperature is raised to 450 to 566 ° C., hot rolling with a rolling rate of 5% or more is performed, and annealing is performed after rolling (Patent Document 4).

  Any of the rolled materials produced by the above method exhibits room temperature formability comparable to that of an aluminum alloy. However, in this method, it is necessary to heat the sample to 450 ° C. or higher at the time of rolling, and there are problems regarding ignition of the sample and oxidation of the sample, which is a problem in practical use.

  On the other hand, regarding a magnesium alloy having a composition different from that of a general-purpose magnesium alloy, the present inventors have prepared a magnesium alloy to which a specified amount of light rare earth element, Zn, Mn, Zr is added, or a specified amount of Ca, Zn, Al, We are developing a technique in which Mn and Zr-added magnesium alloys are hot and warm rolled under specific conditions and annealed under specific conditions.

  In the (0002) plane texture of the plate produced by this method, a pole tilted by about 35 degrees appears in the plate width direction (TD direction), and the formability (Erichsen value of 8.0 or more) similar to that of an aluminum alloy is exhibited. (Patent Document 5).

  However, since the (0002) plane texture of the rolled material obtained by this method has a pole inclined about 35 ° in the TD direction, it is difficult to deform in the rolling direction (RD direction), but in the TD direction. Therefore, it is easy to deform and the strength in TD direction (yield stress) is low, which is a problem for practical use.

  Conventionally, as a means for producing a magnesium alloy sheet having room temperature formability comparable to that of an aluminum alloy, a technique of repeatedly bending, a technique of rolling a general-purpose magnesium alloy (Mg—Al—Zn—Mn alloy) at a high temperature, Various methods such as a method of hot working a magnesium alloy to which a specific element is added in a small amount have been proposed. However, in any of the methods, 1) using an existing rolling mill, 2) at a rolling temperature at which it is not necessary to worry about ignition or oxidation of the sample, and 3) high cold formability and strength (yield stress) on the rolled material At the same time, it is difficult to satisfy the requirements simultaneously, which has been a problem for the practical application of magnesium alloy sheet.

Japanese Patent Laid-Open No. 2005-29885 JP 2010-133005 A JP 2010-202897 A Japanese Patent Application No. 2010-044795 JP 2010-013725 A

Aluminum Handbook (4th edition), Light Metal Association (published by Light Metal Association, Tokyo, 1989), p. 98 Y. Chino, H .; Iwasaki and M.I. Mabuchi: Mater. Sci. Eng. A, Vol. 466 (2007), p. 90

  In such a situation, the present inventors are a technique that uses an existing rolling mill in view of the above-described conventional technology, and heats a sample above 450 ° C. where ignition and oxidation are a concern. Developed a technology that is not necessary and that imparts excellent room temperature formability (Erichsen value of 7.0 or more) and strength (yield stress in the TD direction is 90 MPa or more) to the manufactured plate material. As a result of intensive research and development with the goal of doing, as a result of rolling a magnesium alloy with a specific amount of Zn, Ca (or Ca and Sr) and, if necessary, Zr, Mn, under suitable conditions, Furthermore, by using an appropriate heat treatment, a magnesium alloy sheet with excellent room temperature formability and strength (yield stress) was successfully produced by rolling at a sample temperature of 450 ° C or less using an existing rolling mill. And the present invention This has led to the formation.

  An object of the present invention is to provide an easily formable magnesium alloy sheet having excellent room temperature formability and strength (yield stress) and a method for producing the same. The present invention also provides a magnesium alloy press-molded body having a complex shape by molding the easily moldable magnesium alloy, and the magnesium alloy press-molded body that can be produced at room temperature. It aims at providing the manufacturing method of a body, and its product.

The present invention for solving the above technical problems is composed of the following technical means.
(1) By mass%, containing 2.61 to 6.20% Zn, 0.01 to 0.9% Ca, optionally containing one or more of Sr, Zr, Mn, the balance However, the Mg alloy composed of Mg and inevitable impurities is heated to a sample surface temperature of 150 to 450 ° C., subjected to rolling at a rolling rate of at least 5%, and annealed after rolling. Manufacturing method of magnesium alloy sheet.
(2) The method for producing an easily formable magnesium alloy sheet according to (1) above, containing Sr so that the total amount of Ca and Sr is 0.01 to 1.5% by mass%.
(3) The method for producing an easily formable magnesium alloy sheet according to (1) or (2), wherein an Mg alloy to which 0.01 to 0.7% of Zr and / or Mn is added in mass% is used.
(4) The method for producing an easily formable magnesium alloy sheet according to any one of (1) to (3), wherein the Mg alloy is heated to a sample surface temperature of 150 to 420 ° C.
(5) By mass%, containing 2.61 to 6.20% Zn, containing 0.01 to 0.9% Ca, optionally containing one or more of Sr, Zr, Mn, An easily formable magnesium alloy sheet material in which the balance is a Mg alloy rolled material composed of Mg and inevitable impurities, and the Erichsen value at room temperature is at least 7.0 or more.
(6) The easily formable magnesium alloy sheet according to (5), containing Sr so that the total amount of Ca and Sr is 0.01 to 1.5% by mass%.
(7) The easily formable magnesium alloy sheet according to (5) or (6), which is an Mg alloy added with 0.01 to 0.7% of Zr and / or Mn in mass%.
(8) The easily formable magnesium alloy sheet according to any one of (5) to (7), having a pole in the sheet width direction of the (0002) plane texture as measured by the XRD method (Schulz reflection method) .
(9) In the quasi-static room temperature tensile test in which tensile deformation is performed in parallel with the plate width direction, the 0.2% yield strength obtained is 90 MPa or more, and any of (5) to (8) The easily formable magnesium alloy sheet described.
(10) A magnesium alloy press-molded body comprising the easily-formable magnesium alloy sheet material according to any one of (5) to (9).
(11) A magnesium alloy member comprising the magnesium alloy press-molded body as described in (10) above.

Next, the present invention will be described in more detail.
The present invention is an easily moldable magnesium that has excellent formability at ordinary temperature (30 ° C.), an excellent Erichsen value of 7.0 or higher, and a tensile yield stress in the TD direction of 90 MPa or higher. A method for producing an alloy sheet, wherein the total amount of Zn is 2.61 to 6.20 mass% (hereinafter, mass% is described as mass%), and the total amount of Ca is 0.01 to 0.00. 9 mass%, or 0.01 to 0.9 mass% of Ca, and 0.01 to 1.5 mass% of Ca and Sr as a total amount, and if necessary, Zr and / or A magnesium alloy plate material containing 0.01 to 0.7 mass% of Mn and the balance being composed of Mg and inevitable impurities is heated to a sample temperature of 150 to 450 ° C., more preferably 150 to 420 ° C. On Rolling ratio of 5% or more of the rolling performed, after rolling, is characterized in that to perform annealing.

  In the present invention, the total amount of Zn is 2.61 to 6.20 mass%, the total amount of Ca is 0.01 to 0.9 mass%, or Ca is 0.01 to 0.9 mass%. In addition, Ca and Sr are contained in a total amount of 0.01 to 1.5 mass%, and if necessary, Zr and / or Mn is contained in an amount of 0.01 to 0.7 mass%, and the balance is A magnesium alloy sheet having a composition comprising Mg and inevitable impurities, having a pole in the TD direction of the (0002) plane texture as measured by XRD method (Schulz reflection method), and having an Erichsen value of at least 7. It exhibits a room temperature formability of 0 or more, and further exhibits a yield stress (0.2% yield strength) of 90 MPa or more in a room temperature tensile test in the TD direction.

  Furthermore, the present invention is a molded body of a readily moldable magnesium alloy sheet produced by the above-described manufacturing method, the magnesium alloy press-molded body exhibiting the Erichsen value and the yield stress, and the magnesium alloy. It has characteristics in terms of magnesium alloy members made of a press-formed body.

  In the previous studies, the inventors have made a slight amount of an alloy obtained by adding a small amount of light rare earth elements (Ce, La, Nd, Pr, Y, etc.) to an Mg—Zn alloy, or an Mg—Zn alloy. It was clarified that when the alloy containing Ca was subjected to hot rolling and further subjected to heat treatment, excellent room temperature formability with an Erichsen value of 8.0 or more was exhibited.

  (1) and (2) in FIG. 1 show that an Mg-1.5 mass% Zn alloy sample and an Mg-1.5 mass% Zn-0.1 mass% Ca alloy sample are measured at a sample temperature of 450 ° C. per pass. It is the result of the (0002) plane texture and the room temperature Eriksen test after annealing of a sample rolled at a reduction rate of 20% / pass and a thickness of 5 mm to 1 mm.

  1 (1) and (2) correspond to [Comparative Example 1] and [Comparative Example 2] described later. In FIG. 1 (1), a texture specific to the general-purpose magnesium alloy rolled material is observed. That is, the peak of the (0002) plane appears at a position parallel to the ND direction (vertical direction).

  On the other hand, in FIG. 1 (2), a pole on the (0002) plane appears in the vicinity of about 35 ° rotation from the ND direction to the TD direction. Mg-1.5mass% Zn-0.1mass% Ca alloy rolled material showing a texture with a spread in the TD direction has a random texture than general-purpose magnesium alloys, and room temperature formability is significantly improved. To do.

  The texture in which the poles of the (0002) plane appear in the vicinity of about 35 ° rotated in the TD direction is the same as the texture obtained when rolling an HCP metal (Zr or αTi) with a low c / a ratio. is there. Therefore, the formation of a specific texture appearing in the Mg-1.5 mass% Zn-0.1 mass% Ca alloy rolled material is based on the specific conditions of the alloy to which Zn and a specific element (light rare earth element or calcium) are added. Then, when rolling is performed, the same effect as when the c / a ratio is lowered (such as activation of non-bottom slip) is exhibited, and this is the result of affecting the texture formation. Can be considered.

  The rolled material produced in the previous research described above exhibits excellent room temperature formability, but has a (0002) plane pole at a position inclined about 35 ° in the TD direction, and therefore deforms in the TD direction. Although it is easy, there is a defect that it is difficult to deform in the RD direction. Here, Table 1 below shows room temperature tensile properties of various Mg alloys. (1) and (2) of Table 1 are the results of the Mg-1.5 mass% Zn alloy and the Mg-1.5 mass% Zn-0.1 mass% Ca alloy. These are the results of the same samples as (1) and (2) in FIG. 1 or [Comparative Example 1] and [Comparative Example 2], respectively.

  Paying attention to the results of the Mg-1.5 mass% Zn-0.1 mass% Ca alloy rolled material, when tensile deformation is applied in the direction of 0 ° with respect to the RD direction, the Mg-1.5 mass% Zn alloy However, the yield stress when tensile deformation is applied in the 45 ° and 90 ° directions with respect to the rolling direction is significantly lower than that of the Mg-1.5 mass% Zn alloy. The cause of the decrease in yield stress is due to the inclination of the (0002) plane pole in the TD direction. Improving such anisotropy of mechanical properties, that is, suppressing a decrease in yield stress in the TD direction is a problem in putting the magnesium alloy rolled material into practical use.

  Therefore, as a result of earnest research and development, the present inventors express the above-mentioned rolled material by dissolving Zn at a high concentration in magnesium as a means for simultaneously imparting high room temperature formability and excellent strength. We focused on actively using solid solution strengthening.

  As a result of trying detailed and systematic experiments, the present inventors limited the amount of Zn added to 2.61 to 6.20 mass%, and limited the element to be added in a small amount to Ca (or Ca and Sr). Above, a predetermined concentration of Ca (or Ca and Sr) is added, and if necessary, an alloy sample added with a predetermined concentration of Zr and / or Mn is rolled at a sample surface temperature of 150 to 450 ° C. and annealed. When it did, it discovered that the outstanding normal temperature moldability and the outstanding intensity | strength (yield stress) were expressed simultaneously.

  Here, (3) in FIG. 1 shows the (0002) plane texture and the Erichsen test result after annealing of a sample obtained by rolling an Mg-3.0 mass% Zn-0.1 mass% Ca alloy at 350 ° C. (3) in FIG. 1 corresponds to [Example 2] described later. The (0002) plane texture of (3) in FIG. 1 has a (0002) plane pole in the vicinity of about 35 ° rotation from the ND direction to the TD direction, as in (2) of FIG. Since it shows a texture having a spread in the TD direction, excellent room temperature formability (Ericsen value: 8.1) similar to that of an aluminum alloy is exhibited.

  The Mg-3.0 mass% Zn-0.1 mass% Ca alloy rolled material [(3) in FIG. 1] showed a unique texture as described above, because a small amount of Ca was added to the Mg-Zn alloy. By adding, the same effect as when the c / a ratio is lowered (activation of non-bottom slip) is manifested, which can be considered to have affected the material deformation mechanism during rolling. .

  The present inventors have further found that when Sr is additionally added in addition to Ca, excellent room temperature formability is exhibited in the same manner or relatively when Ca is added alone. (4) in FIG. 1 shows (0002) texture and Erichsen after annealing of a sample obtained by rolling an Mg-3.0 mass% Zn-0.1 mass% Ca-0.1 mass% Sr alloy at 350 ° C. It is a result of a test.

  (4) in FIG. 1 corresponds to [Embodiment 8] described later. As shown in FIG. 1 (4), an alloy added with 0.1 mass% of Sr exhibits a better room temperature formability than an alloy without adding Sr [(3) of FIG. 1]. In addition, from (3) of FIG. 1 and (4) of FIG. 1, the change of the bottom texture accompanying the presence or absence of Sr addition cannot be confirmed. Therefore, the reason why the room temperature formability is improved by adding Sr is that relatively fine crystal grains are obtained by adding Sr.

  (3) in Table 1 is a result of a room temperature tensile test of a sample obtained by rolling an Mg-3.0 mass% Zn-0.1 mass% Ca alloy at 350 ° C. The sample of (3) in Table 1 corresponds to the sample of (3) in FIG. 1 ([Example 1]). The sample of (3) in Table 1 shows a higher yield stress (0.2% proof stress) than the sample of (2) in Table 1, and even when 90 ° tensile deformation is applied to the rolling direction. The yield stress is 94 MPa.

  The reason why the Mg-3.0 mass% Zn-0.1 mass% Ca alloy rolled material ((3) in Table 1) exhibits a relatively high yield stress is that it is expressed by adding a high concentration of zinc. Examples include solution hardening. That is, it is considered that a single-range ordered lattice was formed in the matrix (magnesium) by adding a high concentration of zinc, and remarkable material hardening occurred. The material curing by the formation of the single range ordered lattice is manifested even when Sr is added, as shown in the examples described later.

  The Zn addition amount was limited to 2.61 to 6.20 mass%, and the element to be added in a small amount was limited to Ca (or Ca and Sr), and then a predetermined concentration of Ca (or Ca and Sr) was added. Even if the Mg alloy is rolled under the same conditions as (2) in FIG. 1 ([Comparative Example 2]), an excellent rolled material cannot be produced.

  Here, the appearance after rolling of various Mg alloy rolled materials is shown together in FIG. (1) in FIG. 2 is a sample that was rolled after heating the sample surface of the Mg-3.0 mass% Zn alloy sample to 350 ° C., and (2) is an Mg-3.0 mass% Zn alloy sample. The sample surface was heated to 400 ° C. and then rolled, (3) after heating the sample surface of the Mg-3.0 mass% Zn—0.1Ca alloy sample to 480 ° C. This is a rolled sample.

  (4) in FIG. 2 is a sample in which the sample surface of the Mg-3.0 mass% Zn-0.1Ca alloy sample was heated to 300 ° C. and then rolled, and (5) is Mg-3. The sample surface of the 0 mass% Zn-0.1Ca alloy sample was heated to 350 ° C. and then rolled. (6) is the sample surface of the Mg-3.0 mass% Zn-0.1Ca alloy sample. The sample was rolled after heating to 400 ° C.

  Except for (3) in FIG. 2 above, rolling was performed from a thickness of 5 mm to 1 mm at a total rolling rate of 80% (20% rolling rate per pass). (1), (2), (3), (4), (5), and (6) in FIG. 2 are respectively shown as [Comparative Example 3], [Comparative Example 4], [Comparative Example 5], This corresponds to [Example 1], [Example 2], and [Example 3].

  In general, when a magnesium alloy is heated to 250 ° C. or more, the activity of non-bottom sliding is activated and the rolling characteristics thereof are remarkably improved. As shown in (1) and (2) of FIG. 2, for the Mg-3.0 mass% Zn alloy sample, the sample temperature is increased from 350 ° C. to 400 ° C. to produce a rolled material free from ear cracks. Can do. This tendency also appears in an Mg—Zn—Ca alloy having a low zinc concentration (Mg1.5 mass% Zn—0.1 mass% Ca alloy [Comparative Example 2]).

  On the other hand, when the Zn concentration of the Mg—Zn—Ca alloy (Mg—Zn—Ca—Sr alloy) is set to 2.61% by mass or more, rolling characteristics different from the above appear. As shown in (4) and (5) of FIG. 2, when the rolling temperature of the alloy sample is 300 ° C. to 350 ° C., rolling without cracks by increasing the sample temperature from 300 ° C. to 350 ° C. A material can be produced.

  On the other hand, as shown in FIG. 2 (6), when the sample surface temperature of the alloy sample is set to 400 ° C. or higher, the rolling characteristics deteriorate, and an edge crack occurs at the end of the sample. Furthermore, when the sample surface temperature is set to a high temperature exceeding 450 ° C., destruction occurs only by applying a slight reduction.

  For example, when an alloy sample is rolled at a sample surface temperature of 480 ° C., the plate material is destroyed only by applying 20% reduction [(3) in FIG. 2]. As described above, the rolling characteristics of the Mg—Zn—Ca alloy (Mg—Zn—Ca—Sr alloy) to which high-concentration zinc is added show temperature dependence opposite to that of the known magnesium alloy.

The reason why the Mg—Zn—Ca alloy (Mg—Zn—Ca—Sr alloy) added with high concentration of zinc exhibits unique rolling characteristics (inverse temperature dependence of rolling characteristics) is currently under investigation. However, one of the presumed reasons is the melting point of the precipitated intermetallic compound. The melting point of the intermetallic compound of the Ca—Zn alloy is relatively low, and Ca ₃ Zn and Ca ₇ Zn ₄ are melted at 380 to 420 ° C. Therefore, when a high concentration of Zn is added, an intermetallic compound having a low melting point is excessively precipitated, and it can be presumed that apparent rolling characteristics (reverse temperature dependence of rolling characteristics) are manifested.

  As a result, in order to roll a Mg-Zn-Ca alloy containing a high concentration of zinc, the sample surface temperature during rolling is set to 150 to 450 ° C, more preferably 150 to 420 ° C. Need to do. As a result, it is possible to produce high-performance magnesium alloy sheets with excellent room temperature formability and strength (yield stress) even when rolling at rolling temperatures that do not require concern about sample ignition and sample oxidation. is there.

  From the above knowledge, the Zn addition amount is limited to 2.61 to 6.20 mass%, and the element to be added in a small amount is limited to Ca (or Ca + Sr), and then a predetermined concentration of Ca (or Ca + Sr) is added. By adding an alloy sample to which a predetermined concentration of Zr and / or Mn is added, if necessary, rolling at a sample surface temperature of 150 to 450 ° C., more preferably 150 to 420 ° C., and annealing, A high-performance magnesium alloy sheet was created that exhibits excellent room temperature formability with an Erichsen value of 7.0 or higher and excellent strength (yield stress in the TD direction of 90 MPa or higher) at the same time.

  Explaining the reasons for limiting the components and production conditions of the magnesium alloy sheet of the present invention, the magnesium alloy applied to the production method of the present invention is Zn: 2.61-6.20 mass%, Ca: 0.01-0. 9 mass% is contained, and the balance has a component composition consisting of Mg and inevitable impurities, or contains 2.61 to 6.20 mass% Zn, 0.01 to 0.9 mass% Ca, and , Sr is contained so that the total amount of Ca and Sr becomes 0.01 to 1.5 mass%, and the balance has a component composition consisting of Mg and inevitable impurities. Moreover, it has a component composition which added 0.01-0.7 mass% of Zr and / or Mn as needed.

  The Zn content is preferably added in the range of 2.61 to 6.20 mass% in order to achieve significant solid solution hardening. In addition, since addition of 2.61 mass% or more of Zn may cause precipitation of a Ca—Zn-based intermetallic compound having a relatively low melting point, it is necessary to perform rolling at a sample temperature of 450 ° C. or less. In addition, when the addition amount of Zn exceeds 6.20 mass%, a fine precipitation layer is formed, and the strength of the plate material is remarkably improved. However, since the room temperature formability is remarkably deteriorated, zinc addition exceeding 6.20 mass% is Should be avoided.

The Ca content is preferably added in the range of 0.01 to 0.9 mass%, and if it is less than 0.01 mass%, no significant change appears in the texture formation. On the other hand, if calcium exceeding 0.9 mass% is added, coarse intermetallic compounds such as Mg ₂ Ca are precipitated in the grains and at the grain boundaries, which adversely affects hot workability and room temperature formability. It is.

When Sr is additionally added in addition to Ca, superior strength and formability are exhibited in the same manner as when Ca is added alone or when Ca is added alone. When Ca and Sr are added simultaneously, in order to cause significant texture deformation while suppressing precipitation of coarse intermetallic compounds such as Mg ₂ Ca, the Ca content is set to 0.01 to 0.9 mass. It is desirable to limit the total amount of Ca and Sr to 0.01 to 1.5 mass%.

  The addition of Mn and Zr is effective for strengthening the material because the crystal grain size of the magnesium alloy sheet is made fine. On the other hand, when Mn and Zr are added in a certain amount or more, coarse Mn and Zr phases or Mn and Zr-based intermetallic compound phases are formed inside, and the formability and ductility of the material deteriorate. Therefore, the addition amount of Mn and Zr should be set to 0.01 to 0.7 mass%.

  As described above, when rolling an alloy sample, when the sample surface temperature is set to 150 to 450 ° C., and more preferably 150 to 420 ° C., and rolling is performed, a rolled material with no ear cracks can be produced. . Note that the sample heating time before rolling does not have a significant effect on the texture formation of commercial magnesium alloy sheets with a small amount of Ca (or Ca and Sr) added, so the sample heating time should be set arbitrarily. Can do.

  In order to build the target texture in the sample, it is necessary to impart sufficient plastic deformation to the plate during hot rolling. Specifically, it is desirable to perform a reduction of 5% or more at least at a predetermined sample temperature in the entire rolling process.

  Since high-density dislocations are accumulated inside the sample after hot rolling, it is desirable to perform heat treatment (complete annealing) before forming the plate material at room temperature. Specifically, it is desirable to subject to press molding after being subjected to heat treatment at 300 to 450 ° C. for 10 minutes or longer.

  The magnesium alloy sheet produced by making full use of the above inventive elements exhibits formability (Erichsen value of at least 7.0 or more) corresponding to an aluminum alloy at room temperature (30 ° C.). Here, the Erichsen value was adopted as an index representing the formability of the magnesium alloy sheet. The Eriksen test refers to a test according to JIS B7729 and JIS Z2274.

The magnesium alloy sheet produced by making full use of the above inventive elements exhibits a relatively high strength (yield stress). Here, as an index value indicating high strength (yield stress), 0.2% yield strength obtained by a quasi-static room temperature tensile test is adopted, and the rolling direction and the tensile direction are obtained under the condition of 90 °, 0.2 % Proof stress was defined as yield stress and used as an index value. The quasi-static tensile test refers to a tensile test having an initial strain rate of 10 ⁻⁴ to 10 ⁻¹ (s ⁻¹ ) when performing the tensile test.

The present invention has the following effects.
(1) The Zn addition amount is limited to 2.61 to 6.20 mass%, the element to be added in a small amount is limited to Ca (or Ca and Sr), and the Ca concentration is set to 0.01 to 0. .9 mass% (or a total amount of Ca and Sr of 0.01 to 0.15 mass%) is added, and if necessary, an alloy to which Zr and / or Mn is added in an amount of 0.01 to 0.7 mass%, A magnesium alloy sheet having excellent room temperature formability and strength can be produced by rolling at a sample surface temperature of 150 to 450 ° C., more preferably 150 to 420 ° C., and annealing.
(2) Using the present invention, a magnesium alloy sheet having excellent room temperature formability and strength can be produced by rolling at a sample surface temperature of 150 to 450 ° C., more preferably 150 to 420 ° C. The rolling can be performed without concern about the ignition of the sample, and the rolling can be performed without concern about the oxidation of the sample surface.
(3) The obtained plate material exhibits excellent room temperature formability (Erichsen value of 7.0 or more), and further has an excellent strength (yield stress of 90 MPa or more obtained when the rolling direction and the tensile direction are 90 °). And a magnesium alloy plate material applicable to a wide range of uses.
(4) By using the present invention, it is possible to produce a plate material exhibiting excellent room temperature formability and excellent strength using an existing rolling apparatus, and it is possible to produce a plate material at low cost.
(5) A magnesium alloy press-molded body can be produced and provided by forming the magnesium alloy sheet material at room temperature.
(6) A magnesium alloy member such as a casing made of the magnesium alloy press-formed body can be produced and provided.

The (0002) plane texture of the rolled magnesium alloy and the results of the Erichsen test are shown. In the figure, (1) is a sample obtained by rolling an Mg-1.5 mass% Zn alloy after holding it in a muffle furnace at 450 ° C. for 20 minutes. In (2), the Mg-1.5 mass% Zn-0.1 mass% Ca alloy is rolled after being held in a muffle furnace at 450 ° C. for 20 minutes. (3) is a sample which was rolled after heating the sample surface of the Mg-3.0 mass% Zn-0.1 mass% Ca alloy sample to 350 ° C. (4) is a sample obtained by rolling the sample surface of the Mg-3.0 mass% Zn-0.1 mass% Ca-0.1 mass% Sr alloy sample to 350 ° C. and then rolling it. The total rolling rate of any sample is 80% (rolling rate 20% per pass), and is rolled from 5 mm to 1 mm in thickness. After rolling, it is subjected to annealing at 350 ° C. (90 minutes). It is a thing. FIG. 2 shows the appearance of the magnesium alloy rolled material. In the figure, (1) is a sample that was rolled after the sample surface of the Mg-3.0 mass% Zn alloy sample was heated to 350 ° C. (2) is a sample obtained by rolling the sample surface of the Mg-3.0 mass% Zn alloy sample to 400 ° C. and then rolling it. (3) is a sample obtained by rolling the sample surface of the Mg-3.0 mass% Zn-0.1Ca alloy sample to 480 ° C. and then rolling it at a rolling rate of 20% once. The sample broke. (4) is a sample that was rolled after the sample surface of the Mg-3.0 mass% Zn-0.1Ca alloy sample was heated to 300 ° C. (5) is a sample obtained by rolling the sample surface of the Mg-3.0 mass% Zn-0.1Ca alloy sample to 350 ° C. and then rolling it. (6) is a sample obtained by rolling the sample surface of the Mg-3.0 mass% Zn-0.1Ca alloy sample to 400 ° C. and then rolling it. Samples other than the above (3) were rolled from 5 mm to 1 mm in thickness at a total rolling rate of 80% (rolling rate per pass of 20%).

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

In the following examples and comparative examples, samples were prepared and evaluated by the test methods shown below. That is, after melting pure Mg using a high frequency furnace, Zn, Ca, Sr, Zr, and Mn were appropriately added to prepare an Mg alloy. The Mg alloy ingot (50 × 30 × 50 mm ³ ) was subjected to hot extrusion (extrusion temperature: 300 ° C., extrusion speed: 5 mm / min, extrusion ratio: 6), and extruded plate material (cross-sectional area: 50 × 5 mm ^2). ) Was produced. From the obtained extruded plate material, 60 mm × 50 mm × 5 mm test pieces were cut out, and these test pieces were subjected to rolling.

  During rolling, for [Comparative Example 1] and [Comparative Example 2] shown later, after holding the sample in a muffle furnace maintained at 450 ° C. for 20 minutes, the sample was rolled at a rolling speed of 5 m / min and 1 pass. It was subjected to rolling at a rolling reduction of 20%. By repeating this rolling, the rolling was performed from 5 mm to 1 mm in thickness. Finally, the obtained rolled material was subjected to a heat treatment at 350 ° C. for 90 minutes.

  For other samples, the sample was inserted into a muffle furnace set 20 ° C. higher than the target sample temperature, and when the sample reached a predetermined temperature, the sample was rolled at a rolling speed of 5 m / min. Min. Rolled at a rolling reduction of 20% per pass. Table 2 shows the sample surface temperature during rolling of each sample.

  By repeating this rolling, the rolling was performed from 5 mm to 1 mm in thickness. Finally, the obtained rolled material was subjected to a heat treatment at 350 ° C. for 90 minutes. The roll diameter was 152 mm and the roll temperature was 90 ° C. As a roll and sample lubricant, an ester-based hot rolling lubricant was used.

  In addition, regarding [Comparative Example 5] shown later, since the sample was destroyed in the first rolling, no further rolling was performed.

  In order to evaluate the room temperature formability of the produced magnesium alloy sheet, an Erichsen test was performed. The Eriksen test was conducted according to JIS B7729 and JIS Z2247. In addition, the shape of the blank was set to φ60 mm (thickness 1 mm) for the convenience of the plate material shape. The mold (sample) temperature was 30 ° C., the molding speed was 5 mm / min, and the wrinkle holding force was 10 kN. Graphite grease was used as the lubricant.

In order to investigate the strength (yield stress) of the produced magnesium alloy sheet, room temperature tensile properties were performed. The parallel part length of the test piece was 10 mm, the parallel part width was 5 mm, and the parallel part thickness was 1.0 mm. A tensile test piece having an angle between the rolling direction and the tensile direction of 90 ° was cut out from the rolled material, subjected to a tensile test, and 0.2% proof stress was measured to obtain a yield stress. The initial strain rate when carrying out the tensile test was 1.7 × 10 ⁻³ s ⁻¹ .

  The (0002) plane texture of the magnesium alloy sheet was measured by the XRD method (Schulz reflection method). At the time of measurement, a 20 mm × 20 mm × 1 mm plate was cut out from the rolled material, the RD-TD surface was chamfered to a thickness of 0.5 mm, and a sample subjected to surface polishing with # 4000 SiC abrasive paper was prepared. used. After the measurement data was normalized with random data (powder data), the presence or absence of a pole in the TD direction was confirmed.

  Table 2 below summarizes the results of the Erichsen value, tensile test, and texture measurement of each sample.

[Example 1] to [Example 6]
In Examples 1 to 6, an alloy sample in which the Zn addition amount was set to 2.61 to 6.20 mass% and the Ca addition amount was set to 0.01 to 0.9 mass%, the sample surface temperature was 150 to 450. Heated to 0 ° C. and rolled. When predetermined rolling was performed with the alloy composition defined in the claims, excellent room temperature formability and excellent strength were exhibited at the same time.

[Example 7] to [Example 19]
In Examples 7 to 19, the Zn addition amount is set to 2.61 to 6.20 mass%, Ca is contained to 0.01 to 0.9 mass%, and the total amount of Ca and Sr is 0.01 to 1%. An alloy sample containing Sr so as to be 0.5 mass% was heated to a sample surface temperature of 150 to 450 ° C. and rolled. When predetermined rolling was performed with the alloy composition defined in the claims, excellent room temperature formability and excellent strength were exhibited at the same time.

[Example 20] to [Example 21]
In Examples 20 to 21, the Zn addition amount is set to 2.61 to 6.20 mass%, Ca is contained to 0.01 to 0.9 mass%, and the total amount of Ca and Sr is 0.01 to 1%. An alloy sample containing Sr in an amount of 0.5 mass% and further containing Zr and / or Mn in an amount of 0.01 to 0.7 mass% was heated to a sample surface temperature of 150 to 450 ° C. and rolled. When predetermined rolling was performed with the alloy composition defined in the claims, excellent room temperature formability and excellent strength were exhibited at the same time.

[Comparative Example 1] and [Comparative Example 2]
In Comparative Examples 1 and 2, the Zn addition amount was set to less than 2.61 mass%. The (0002) plane texture of [Comparative Example 1] to which no Ca was added did not have a pole in the TD direction, and thus showed a low Erichsen value. Moreover, since the pole of the TD direction can be confirmed in the (0002) plane texture of [Comparative Example 2], excellent room temperature formability was exhibited. However, since the Zn concentration was low, the yield stress was low.

[Comparative Example 3] and [Comparative Example 4]
In Comparative Examples 3 and 4, the Zn addition amount was set to 2.61 mass% or more, but Ca was not added. In any case, the 0.2% yield strength of the rolled material showed a high strength of 90 MPa or more. On the other hand, in the (0002) plane textures of [Comparative Example 3] and [Comparative Example 4], the pole in the TD direction did not appear, and therefore a low Erichsen value was shown.

[Comparative Example 5]
In Comparative Example 5, the amount of Zn added was set to 2.61 mass% or more, and an alloy sample added with 0.1 mass% of Ca was rolled at a temperature higher than the rolling temperature specified in the claims. When rolling was performed at a temperature exceeding 450 ° C., the sample was broken even if a slight reduction was applied, and a rolled material could not be produced.

[Comparative Example 6] and [Comparative Example 7]
In Comparative Examples 6 and 7, the Zn addition amount was set to 2.61 mass% or more, Ca was added by 0.9 mass% or more (1.0 mass%), and Sr was added in a predetermined amount (0.1 mass%). The samples were rolled at sample temperatures of 300 ° C and 350 ° C, respectively. In any sample, when rolling with a thickness of 5 mm to 1 mm was performed, severe ear cracks occurred, and a rolled material for sample evaluation could not be produced. As described above, when a higher concentration of Ca was added than the amount of Ca specified in the claims, severe ear cracks occurred in the sample during rolling, and it was difficult to perform rolling.

[Comparative Example 8]
In Comparative Example 8, the amount of Zn added was set to 2.61 mass% or more, and alloy samples added with 0.8 mass% Ca and 0.8 mass% Sr were each rolled at a sample temperature of 350 ° C. The (0002) plane texture of [Comparative Example 8] has a pole in the TD direction, but the Erichsen value of the rolled material showed a low value. Thus, when Ca and Sr are added at a higher concentration than the amount of Ca and Sr specified in the claims, a coarse intermetallic compound is formed inside the rolled material, and the room temperature formability is significantly deteriorated. I found out.

  As described above in detail, the present invention relates to a magnesium alloy sheet material having improved room temperature formability and strength and a method for producing the same, and according to the present invention, the amount of Zn added is 2.61 to 6.20 mass%. In addition, 0.01 to 0.9 mass% of Ca is added, or Ca and Sr are limited to 0.01 to 0.9 mass%, and the total amount of Ca and Sr is 0.01 to 1%. An alloy sample to which Zr and / or Mn of 0.01 to 0.7 mass% is added as required is added to a sample surface temperature of 150 to 450 ° C., more preferably 150 to 420. It is possible to provide a method for producing a readily formable magnesium alloy sheet material which is rolled at 0 ° C. and annealed, and a product thereof. The produced plate material exhibits room temperature formability (Erichsen value of 7.0 or higher) and excellent strength (yield stress in the TD direction of 90 MPa or higher) similar to that of an aluminum alloy. Utilizing the present invention, it is possible to produce a magnesium alloy plate material having excellent formability and excellent strength comparable to an aluminum alloy, without worrying about ignition and oxidation of the sample using an existing rolling mill, A magnesium alloy sheet having improved formability and strength can be produced. In addition, the present invention is useful for providing an easily formable magnesium alloy sheet material that can be positively applied mainly to press-formed bodies of home appliances such as digital cameras, notebook computers, and PDAs. is there.

Claims (11)

  In mass%, Zn is contained in 2.61 to 6.20%, Ca is contained in 0.01 to 0.9%, optionally containing one or more of Sr, Zr and Mn, and the balance is Mg And an Mg alloy comprising inevitable impurities, heated to a sample surface temperature of 150 to 450 ° C., subjected to rolling at a rolling rate of at least 5%, and annealed after rolling. Manufacturing method.   The manufacturing method of the easily moldable magnesium alloy plate material of Claim 1 which contains Sr so that the total amount of Ca and Sr may be 0.01 to 1.5% by mass%.   The manufacturing method of the easily moldable magnesium alloy plate material of Claim 1 or 2 using Mg alloy which added 0.01 to 0.7% of Zr and / or Mn by mass%.   The method for producing an easily formable magnesium alloy sheet according to any one of claims 1 to 3, wherein the Mg alloy is heated to a sample surface temperature of 150 to 420 ° C.   % By mass, containing 2.61 to 6.20% of Zn, 0.01 to 0.9% of Ca, optionally containing one or more of Sr, Zr, Mn, An easily formable magnesium alloy sheet material, which is a Mg alloy rolled material composed of Mg and inevitable impurities, and has an Erichsen value at room temperature of at least 7.0 or more.   The easily formable magnesium alloy sheet according to claim 5, which contains Sr so that the total amount of Ca and Sr is 0.01 to 1.5% by mass.   The easily formable magnesium alloy sheet according to claim 5 or 6, wherein the Mg alloy is a Mg alloy added with 0.01 to 0.7% of Zr and / or Mn in mass%.   The easily formable magnesium alloy sheet material according to any one of claims 5 to 7, which has a pole in the sheet width direction of the (0002) plane texture as measured by an XRD method (Schulz reflection method).   The easily formable magnesium according to any one of claims 5 to 8, wherein a 0.2% yield strength obtained in a quasi-static room temperature tensile test in which tensile deformation is performed in parallel to the sheet width direction is 90 MPa or more. Alloy plate material.   A magnesium alloy press-molded body comprising the readily-formable magnesium alloy sheet material molded body according to any one of claims 5 to 9.   A magnesium alloy member comprising the magnesium alloy press-formed product according to claim 10.