JP2011179075A - Magnesium alloy sheet material having improved cold-formability and in-plane anisotropy, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a magnesium alloy sheet material having formability at ordinary temperature equal to that of an aluminum alloy; the magnesium alloy sheet material; and a member thereof. <P>SOLUTION: The method for manufacturing the easily formable magnesium alloy sheet material includes the steps of: preparing an alloy which is obtained by adding a small amount of (0.01-0.5 mass%) calcium to a commercial magnesium alloy (Mg-Al-Zn-Mn-based alloy); raising the temperature of the sample surface of the alloy to a predetermined temperature (450-566°C); hot-rolling the alloy at a rolling rate in the range of 5% or more; and annealing the alloy after the rolling. Thereby obtained magnesium alloy sheet material shows formability at ordinary temperature equal to that of an aluminum alloy (at least 7.0 or more by an Erichsen value) and shows such a superior in-plane anisotropy (the difference between a Lankford value obtained on the condition that a rolling direction and a tensile direction form 0° and a Lankford value obtained on the condition that a rolling direction and a tensile direction form 90° is less than 1.0 (absolute value)). The member of the magnesium alloy sheet is also disclosed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing an easily formable magnesium alloy, an easily formable magnesium alloy press-formed body, and an easily formable magnesium alloy member, and more specifically, magnesium to which appropriate amounts of Al, Zn, Mn, and Ca are added. The rolled alloy material is heated to a predetermined sample surface temperature (450 to 566 ° C.), hot-rolled, and then annealed, and at room temperature (30 ° C.), an aluminum alloy (5000 series or 6000). The present invention relates to a magnesium alloy plate material, a manufacturing method thereof, a press-formed body thereof, and a member thereof, which can provide formability comparable to that of a system and can further reduce in-plane anisotropy of the plate material. 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. It can be said that this is an effective means of expanding demand. When a molded body can be produced from a magnesium alloy sheet by press molding, a thin-walled and high specific strength molded body can be produced by an inexpensive process, and many demands such as home appliance housings 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 mobility.

  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 in which the (0002) plane is oriented parallel to the plate surface is formed in the magnesium alloy plate material, distortion in the plate thickness direction during plastic deformation cannot be expected, which is the normal temperature forming It contributes to lowering the sex.

  The room temperature formability (Erichsen value) of aluminum alloys currently used in a wide range of fields is higher than that of the above magnesium alloys, and it is 8.3 (5083-O material) and 6000 series alloys when they are 5000 series alloys. 9.2 (6061-T4 material), and 11.0 (1100-O material) for a 1000 series alloy (Non-patent Document 1). On the other hand, the room temperature formability (Ericsen value) of 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 more) corresponding to the aluminum alloy sheet in order to anticipate significant demand for the magnesium alloy sheet in the future. In this technical field, there is a strong demand for the development of new magnesium alloy sheet manufacturing technology and products having excellent easy formability.

  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, the present inventors have developed a magnesium alloy to which a specified amount of light rare earth elements, Zn, Mn, and Zr are added or a magnesium alloy to which specified amounts of Ca, Zn, Al, Mn, and Zr are added under specific conditions. When hot and warm rolled and annealed under specific conditions, poles inclined about 35 degrees in the plate width direction (TD direction) appear in the (0002) plane texture of the plate material, and the formability is remarkably improved (Erichsen) Value 8.0 or more) (Patent Document 1).

  Utilizing the present invention, it is possible to produce a magnesium alloy plate having room temperature formability comparable to that of an aluminum alloy, and positively applying the magnesium alloy to press-molded products of home appliances such as digital cameras, notebook computers, and PDAs. Is possible. On the other hand, in order to produce this alloy, it is necessary to use an expensive element such as a light rare earth element, and the product cost is higher than that of a commercial magnesium alloy (Mg—Al—Zn—Mn alloy).

  As a means for producing a magnesium alloy sheet having room temperature formability equivalent to that of an aluminum alloy, a method of hot working a magnesium alloy to which a specified amount of rare earth element or the like is added, a method of repeatedly bending, a commercial magnesium alloy (Mg-Al -Zn-Mn-based alloys) have been proposed in various ways, such as rolling after raising the temperature in a short time, but all methods improve formability, but the sample has in-plane anisotropy. There is a problem that anisotropy that cannot be ignored in formability and mechanical properties occurs.

  Further, since the (0002) plane texture of the rolled material obtained by the present invention has a pole tilted by about 35 ° in the TD direction, it is easily deformed in the TD direction, but is relatively in the rolling direction (RD direction). Hard to deform. Therefore, eliminating the anisotropy of formability and mechanical properties has become an issue for practical use.

  As another method for modifying the texture of the magnesium alloy, a method of repeatedly bending the magnesium alloy sheet has been proposed. This method can be applied to a commercial magnesium alloy (Mg—Al—Zn—Mn alloy), and the room temperature formability of the commercial magnesium alloy can be improved to the level of an aluminum alloy (Ericsen value: 6.5 or more). (Patent Document 2). However, in the (0002) plane texture of the rolled material produced according to the present invention, since a pole inclined by about 45 ° appears in the RD direction, it is easily deformed in the RD direction, but hardly deformed in the TD direction. Therefore, as in Patent Document 1, eliminating the anisotropy of formability and mechanical properties is a problem for practical application.

  In recent years, the inventors have made commercial magnesium alloys (Mg—Al—Zn—Mn based alloys) up to a predetermined sample temperature (490 ° C. to 566 ° C.) as another method for modifying the texture of magnesium alloys. A method was developed in which the temperature was raised in a short time (less than 8 minutes: preferably less than 5 minutes), hot rolling was performed at a rolling rate of 5% or more, preferably 5 to 50%, and annealing was performed after rolling (patent) Reference 3). The (0002) plane texture of the rolled material produced according to the present invention is almost the same as that of a known magnesium alloy, and the formability and mechanical characteristics are different from those of the above inventions (Patent Documents 1 and 2). There is little nature.

  On the other hand, anisotropy also exists in the (0002) plane texture of a known rolled magnesium alloy material, indicating a texture in which the (0002) plane is inclined in the RD direction rather than the TD direction. Therefore, anisotropy also exists in the formability and mechanical properties of known magnesium alloy sheet materials, and it is a problem to eliminate the anisotropy.

Japanese Patent Application No. 2008-292848 Japanese Patent Laid-Open No. 2005-29885 Japanese Patent Application No. 2009-114038 JP 2000-104129 A Japanese Unexamined Patent Publication No. 2000-109963 JP 2006-257478 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 S. R. Agnew et al. : Acta Mater. , Vol. 49 (2001), p. 4277

  Under such circumstances, the present inventors, in view of the above-mentioned prior art, do not cause significant anisotropy in formability and mechanical properties, and commercial magnesium alloys (Mg—Al—Zn—Mn series). As a result of intensive research aimed at imparting room-temperature formability (erichsen value of 7.0 or more) equivalent to that of aluminum alloys to alloys), a small amount of calcium (0.01 to 0.5 mass) was added to commercial magnesium alloys. %) Is heated to a sample surface temperature of 450 to 566 ° C., then hot-rolled at a total rolling rate of 5% or more, and annealed after hot rolling, so that the room temperature formability is the same as that of an aluminum alloy. The present invention was completed by successfully producing a magnesium alloy rolled material having a low anisotropy.

  The present invention uses a material very close to the composition of a commercial magnesium alloy (Mg—Al—Zn—Mn alloy) to produce a plate material that exhibits excellent room temperature formability and in-plane anisotropy. It is intended to provide. Another object of the present invention is to provide a magnesium alloy sheet having formability and in-plane anisotropy superior to known magnesium alloy rolled materials. Another object of the present invention is to provide a production method for producing a magnesium alloy press-formed body and a magnesium alloy member having a complex shape at room temperature by forming the magnesium alloy sheet material. Furthermore, this invention aims at providing the magnesium alloy board | plate material produced by the said method, the magnesium alloy press-molding body, and the magnesium alloy member.

The present invention for solving the above technical problems is composed of the following technical means.
(1) In mass%, Al: 2.5 to 7.2%, Zn: more than 0 to 2.0% or less, Mn: more than 0 to 1.0% or less, Ca: 0.01 to 0.5% The sample surface temperature of the Mg alloy rolled plate containing Mg and the inevitable impurities is heated to 450 to 566 ° C., and then hot-rolled at a total rolling rate of 5% or more, and annealed after hot rolling. A process for producing an easily formable magnesium alloy sheet, characterized in that
(2) By mass%, Al: 2.5-7.2%, Zn: 0.4-2.0%, Mn: 0.01-1.0%, Ca: 0.01-0.5% The method for producing an easily formable magnesium alloy sheet according to (1), wherein the sample surface temperature of the Mg alloy rolled sheet containing Mg and inevitable impurities is contained and heated to 450 to 566 ° C.
(3) The easy-formable magnesium according to (1) or (2), wherein the sample surface temperature of the rolled plate is set to less than 300 ° C. and annealing is performed in a range of less than 30% of the total rolling rate before annealing. A method for producing an alloy sheet.
(4) By mass%, Al: 2.5 to 7.2%, Zn: more than 0 to 2.0% or less, Mn: more than 0 to 1.0% or less, Ca: 0.01 to 0.5% An easily formable magnesium alloy sheet comprising a rolled Mg alloy comprising Mg and inevitable impurities, and having an Erichsen value of at least 7.0 or more.
(5) By mass%, Al: 2.5-7.2%, Zn: 0.4-2.0%, Mn: 0.01-1.0%, Ca: 0.01-0.5% The formable magnesium alloy sheet according to (4) above, which is a Mg alloy rolled sheet containing Mg and inevitable impurities.
(6) The index value of in-plane anisotropy (the difference between the Rankford value obtained when the rolling direction and the tensile direction are 0 ° and the Rankford value obtained when the rolling direction and the tensile direction are 90 °) is 1. The easily formable magnesium alloy sheet according to (4) or (5), which is less than 0.0 (absolute value).
(7) A magnesium alloy press-molded body comprising the molded body of the easily formable magnesium alloy sheet according to any one of (4) to (6).
(8) A magnesium alloy member comprising the magnesium alloy press-molded product according to (7).

Next, the present invention will be described in more detail.
In the present invention, Al: 2.5 to 7.2%, Zn: more than 0 to 2.0% (or Zn: 0.4 to 2.0%), Mn: more than 0 to 1. A predetermined sample of a magnesium alloy sheet containing 0% or less (or Mn: 0.01 to 1.0%), Ca: 0.01 to 0.5%, and the balance being composed of Mg and inevitable impurities The temperature is raised to a surface temperature (450 ° C. to 566 ° C.), hot rolling is performed at a rolling rate of 5% or more, and annealing is performed after hot rolling.

  Further, the present invention is, in mass%, Al: 2.5 to 7.2%, Zn: more than 0 to 2.0% (or Zn: 0.4 to 2.0%), Mn: more than 0 to 1.0% or less (or Mn: 0.01 to 1.0%), Ca: 0.01 to 0.5%, the balance is made of a magnesium alloy sheet having a composition consisting of Mg and inevitable impurities, It exhibits a room temperature formability of at least 7.0 or more in terms of Erichsen value.

  In the present invention, the mass% is Al: 2.5 to 7.2%, Zn: more than 0 to 2.0%, or Zn: 0.4 to 2.0%, Mn: more than 0 to 1. 0.0% or less, or Mn: 0.01 to 1.0%, Ca: 0.01 to 0.5%, the balance is made of a magnesium alloy sheet having a composition consisting of Mg and inevitable impurities, and in-plane Anisotropy index value (the difference between the Rankford value (r value) obtained when the rolling direction and the tensile direction are 0 ° and the r value obtained when the rolling direction and the tensile direction are 90 °) is 1.0. It is less than (absolute value).

  Furthermore, the present invention is a molded body of a readily moldable magnesium alloy sheet produced by the above production method, the magnesium alloy press-molded body exhibiting the Erichsen value and the in-plane anisotropy, and the magnesium It is characterized by a magnesium alloy member made of an alloy press-formed body.

  In the previous researches, the present inventors used a magnesium alloy as a means for producing a press-formed body of a commercial magnesium alloy (Mg—Al—Zn—Mn alloy) at room temperature (30 ° C.). The temperature of sample temperature (490 degreeC-566 degreeC) was heated in a short time (less than 8 minutes), the hot rolling of the rolling rate of 5% or more was performed, and the method of annealing after rolling was invented (patent document 3).

  One of the principles of the present invention is that the sample surface temperature is set to 490 ° C. or more, and the activity of the column surface <a> slip or the conical surface <c + a> slip (non-bottom slip) is activated and (0002) ) It is to suppress the activity of {10-12} <10-11> twins that promote the formation of plane texture. Another important principle is to suppress the abnormal grain growth during heating by significantly shortening the heating time of the sample.

  The (0002) plane texture of the rolled material produced according to the present invention has almost the same shape as a known magnesium alloy, but the relative strength is significantly lower than that of the known magnesium alloy. Therefore, high cold formability is exhibited in a state where the anisotropy of formability and mechanical properties is small.

  It should be noted that weak crown anisotropy also exists in the (0002) plane texture of a known rolled magnesium alloy material, indicating a texture in which the (0002) plane is inclined in the RD direction relative to the TD direction. Therefore, anisotropy exists in the formability and mechanical properties of known magnesium alloys, and there is a problem to eliminate the anisotropy.

  Therefore, the present inventors add a trace amount of an additive element to the commercial magnesium alloy as a means of simultaneously imparting high room temperature formability and anisotropy to the commercial magnesium alloy (Mg—Al—Zn—Mn alloy). Inspired by the method, I tried detailed and systematic experiments. As a result, an alloy obtained by adding a trace amount of calcium (0.01 to 0.5% by mass) to the composition of a commercial magnesium alloy is hot-rolled at a sample surface temperature of 450 to 566 ° C. and annealed. It was found that the texture was modified and excellent room temperature formability and in-plane anisotropy were developed at the same time.

  As one of the results of the present invention, FIG. 1 [Example 1] shows an Mg-3.0 mass% Al-1.0 mass% Zn-0.5 mass% Mn alloy (AZ31) described in the examples described later. The (0002) plane texture and Erichsen test result of a sample obtained by rolling an alloy (AZ31 + 0.1Ca alloy) with 0.1 mass% Ca added to the alloy) at a sample surface temperature of 470 ° C. are shown.

  FIG. 1 [Comparative Example 1] shows the (0002) plane texture and Erichsen test result of a sample obtained by rolling an AZ31 alloy at a sample surface temperature of 450 ° C. FIG. 1 [Comparative Example 2] shows the AZ31 alloy on the sample surface. The (0002) plane texture and the Erichsen test result of a sample rolled at a temperature of 525 ° C. are shown. Details of the sample manufacturing method will be described in Examples.

  The (0002) plane texture of the AZ31 alloy produced in Comparative Example 1 (sample surface temperature 450 ° C.) has a pole parallel to the sample vertical direction (ND axis), and the pole extends and distributes in the RD direction. Further, although the (0002) plane texture of the AZ31 alloy produced in Comparative Example 2 (sample surface temperature 525 ° C.) is similar to Comparative Example 1, the strength of the pole is halved compared with Comparative Example 1. Comparative Example 2 having a remarkably low degree of bottom surface orientation exhibits superior room temperature formability (Ericsen value: 8.8) as compared with Comparative Example 1.

  The (0002) plane texture of the AZ31 alloy produced in Example 1 (sample surface temperature 470 ° C.) shows a distribution similar to Comparative Example 1 and Comparative Example 2, but compared with Comparative Example 1 and Comparative Example 2. It can be confirmed that the pole distribution extends in the TD direction. Moreover, Example 1 shows the intensity | strength of the pole similar to the comparative example 2, and shows the normal temperature moldability (Ericsen value: 8.0) which can be compared with the comparative example 2.

  As shown in FIG. 1, the sample of Example 1 in which the poles on the (0002) plane are expanded and distributed in the TD direction as compared with the known magnesium alloy has similar formability and mechanical properties in the RD direction and the TD direction. And its in-plane anisotropy is reduced.

  The texture unique to commercial magnesium alloys in which the (0002) plane is oriented parallel to the plate surface is such that the main deformation mode during hot working is the bottom surface <a> slip or {10-12} <10−. 11> It is predicted by numerical calculation that it is formed when twins are formed (Non-patent Document 3).

  One of the principles of the present invention is that the sample surface temperature is set to 450 ° C. or more, and the activity of the column surface <a> slip or the cone surface <c + a> slip (non-bottom slip) is activated, and during rolling (0002) The object is to suppress the activity of {10-12} <10-11> twins that promote the formation of the plane texture. Another principle of the present invention is to control the spread of the (0002) plane texture in the TD direction by adding a small amount of calcium.

  Agnew et al. Predicted by numerical analysis that the degree of activity of the column surface <a> slip during rolling is closely related to the spread of the (0002) plane texture of the rolled material in the TD direction. (Non-patent Document 3). Therefore, it can be considered that the addition of a small amount of calcium activated the activity of the column surface <a> slip during rolling, and as a result, an isotropic (0002) plane texture was developed.

  A magnesium alloy obtained by adding calcium to a commercial magnesium alloy (Mg—Al—Zn—Mn alloy) is recognized as a flame retardant magnesium alloy, and by adding calcium, the surface oxide of the molten magnesium is stably grown. It is an alloy that significantly suppresses ignition (Patent Documents 4 to 6). The present invention minimizes the amount of calcium added to a commercial magnesium alloy, and further, by rolling under specific conditions, excellent cold formability and in-plane that were not manifested in conventional flame retardant magnesium alloys It has succeeded in developing anisotropy.

  Based on the knowledge obtained from the above research and development, a commercial magnesium alloy (Mg—Al—Zn—Mn alloy) is heated to a predetermined sample temperature (450 ° C. to 566 ° C.), and the rolling rate is in the range of 5% or more. By performing hot rolling at an annealing temperature and annealing after hot rolling, excellent cold formability (Erichsen value: 7.0 or more) and excellent in-plane anisotropy (the rolling direction and the tensile direction are 0 °) The easy-formability magnesium alloy sheet material is characterized in that the difference between the r value obtained under the above conditions and the r value obtained when the rolling direction and the tensile direction are 90 ° is less than 1.0 (absolute value)) Succeeded in doing.

  The reasons for limiting the components and production conditions of the magnesium alloy sheet of the present invention will be described. The magnesium alloy applied to the production method of the present invention is, by weight%, Al: 2.5 to 7.2%, Zn: more than 0 to 2.0%, Mn: more than 0 to 1.0%, Ca: 0.01 to 0.5% is contained, and the balance has a composition composed of Mg and inevitable impurities. Further, the magnesium alloy applied to the production method of the present invention is more preferably by weight%, Al: 2.5 to 7.2%, Zn: 0.4 to 2.0%, Mn: 0.01 -1.0%, Ca: 0.01-0.5% is contained, and the remainder has a component composition consisting of Mg and inevitable impurities.

  The Al content is preferably added in the range of 2.5 to 7.2% in order to achieve sufficient castability and solid solution strengthening. In addition, when the addition amount of Al exceeds 7.2%, hot workability will fall. Further, when the added amount of Al is less than 2.5%, sufficient solid solution strengthening cannot be achieved.

  The Zn content may be added within a range of 2.0% or less. Zn, like Al, contributes to improvement of mechanical properties such as castability and strength. However, if the added amount of Zn exceeds 2.0%, castability deteriorates.

  The Mn content is preferably added within a range of 1.0% or less. When Mn is added to the Mg—Al—Zn-based alloy, an Al—Mn-based intermetallic compound precipitates in the grains and at the grain boundaries, and plays a role of suppressing abnormal grain growth during hot rolling. On the other hand, if the amount of Mn added exceeds 1.0%, the intermetallic compound becomes coarse, so excessive addition should be avoided.

The Ca content is preferably added within a range of 0.01 to 0.5%. If it is less than 0.01%, no significant change appears in the texture formation. On the other hand, when 0.5% or more of calcium is added, coarse intermetallic compounds such as Mg ₂ Ca and Al ₂ Ca are precipitated in the grains and at the grain boundaries, which adversely affects hot workability and room temperature formability. Should be avoided.

  In hot rolling, it is necessary to heat the sample surface temperature to 450 ° C. or higher at which the column surface <a> slip and the conical surface <c + a> slip are sufficiently active. On the other hand, when the sample surface temperature is heated to a solidus temperature (566 ° C.) or higher, the sample is dissolved, and therefore the sample surface temperature should be set to less than 566 ° C. In addition, since the sample heating time before rolling does not have a great influence on the texture formation and crystal grain formation of the commercial magnesium alloy sheet material to which a small amount of calcium is added, the temperature raising time can be arbitrarily set.

  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, at least the total rolling rate of hot rolling needs to be set to 5% or more.

  When rolling at a sample surface temperature of 450 ° C. or higher, surface oxidation occurs at a level that cannot be ignored. Therefore, it is better to have as few opportunities as possible to expose the sample surface to a high temperature. For example, when rolling is performed at a relatively low sample surface temperature (450 ° C. or less) to a predetermined thickness, and only the final rolling (reduction rate of 5% or more) is performed by raising the sample to a high temperature in a short time and rolling The chance of exposing the sample to a high temperature can be reduced, and a rolled material having excellent surface properties can be created.

  When precision rolling is performed to ensure the uniformity of the thickness of the rolled material, it is necessary to perform warm rolling or cold rolling in the final pass of rolling. In the final pass of rolling, the present inventors found that if the sample surface temperature was warm / cold rolling with a sample surface temperature of less than 300 ° C. and a total rolling rate of less than 30%, the texture of the rolled material did not change greatly and was excellent. It has been confirmed that moldability and in-plane anisotropy are maintained.

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

  The above-described magnesium alloy sheet produced by making full use of the 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 excellent in-plane anisotropy. Here, as an index value indicating the in-plane anisotropy, a Rankford value (r value) obtained by a room temperature tensile test is adopted, and the r value and the rolling direction obtained under the condition that the rolling direction and the tensile direction are 0 °. The absolute value of the difference between the r values obtained under the condition where the pulling direction is 90 ° was used as an index value.

The present invention has the following effects.
(1) An alloy obtained by adding a trace amount (0.01 to 0.5 mass%) of calcium to a commercial magnesium alloy (Mg—Al—Zn—Mn alloy) at a predetermined sample temperature (450 ° C. to 566 ° C.) To produce a magnesium alloy sheet having excellent room temperature formability and in-plane anisotropy by performing hot rolling in the range of 5% or more of the rolling rate and annealing after hot rolling. Can do.
(2) The obtained plate material exhibits excellent room temperature formability (Erichsen value of 7.0 or more), and further has excellent in-plane anisotropy (r value obtained under the condition that the rolling direction and the tensile direction are 0 °). And the difference in r value obtained under the condition that the rolling direction and the tensile direction are 90 ° are less than 1.0 (absolute value)). According to the present invention, a magnesium alloy plate material applicable to a wide range of applications is provided. Can be provided.
(3) By using the present invention, it is possible to produce a plate material having excellent room temperature formability and in-plane anisotropy by using an existing rolling device with an alloy having a composition very close to that of a commercial magnesium alloy. Yes, a plate material can be produced at low cost.
(4) A magnesium alloy press-molded body can be produced and provided by forming the magnesium alloy sheet material at room temperature.
(5) A magnesium alloy member such as a casing made of the magnesium alloy press-molded body can be produced and provided.

The (0002) plane texture of the magnesium alloy rolled material used in the examples and the results of the Erichsen test are shown. [Example 1], [Comparative Example 1], and [Comparative Example 2] are shown in Example 1. The (0002) plane texture and the Erichsen test results of the samples prepared in Comparative Example 1 and Comparative Example 2 are shown.

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

  AZ31 alloy (Mg-3.0 mass% Al-1.0 mass% Zn-0.5 mass% Mn), an alloy obtained by adding a specified amount of calcium to the AZ31 alloy (AZ31 + 0.1% Ca alloy, AZ31 + 0 .3% Ca alloy, AZ31 + 0.8% Ca alloy (mass%), AZ51 alloy (Mg-5.0 mass% Al-1.0 mass% Zn-0.5 mass% Mn), the AZ51 alloy, An alloy to which a specified amount of calcium was added (AZ51 + 0.1% Ca alloy (mass%)) was used as a test material.

The sample shape before rolling is 50 × 60 × 5.0 mm ³ . For rolling, a two-high rolling mill having a roll diameter of 152 mm and a roll width of 200 mm was used. Table 1 summarizes the rolling conditions of the samples. The sample surface was heated using a muffle furnace previously maintained at 275 to 555 ° C. Except for Example 2, the temperature of the muffle furnace was set 10-25 ° C. higher than the target sample surface temperature.

  After the sample was put into the muffle furnace, when the sample surface temperature measured by the thermocouple reached a predetermined value, the sample was taken out of the muffle furnace and immediately subjected to hot rolling. Except for Example 2, the sample heating time for all rolling passes is less than 5 minutes. The rolling rate per pass during rolling was 20%, and hot rolling was performed to a predetermined thickness. The direction of the sample for each rolling pass is the same. After rolling, annealing was performed at 350 ° C. for 90 minutes.

  For Comparative Example 2 and Example 1, in rolling from 5.0 mm to 1.6 mm in thickness, rolling is performed at a relatively low sample surface temperature, and in rolling from 1.6 mm to 1.0 mm in thickness, the sample surface Was heated to a high temperature (470 ° C. and 525 ° C.) and then rolled.

  For Example 2, after putting the sample into the muffle furnace, the sample was held in the furnace for 20 minutes, and then the sample was taken out of the muffle furnace and subjected to hot rolling. The sample surface temperature during rolling is substantially the same as the muffle furnace temperature.

  For Example 6, in rolling from a thickness of 5.0 mm to 1.3 mm, the sample surface was heated to a high temperature (470 ° C.) and then rolled. In a rolling from 1.3 mm to 1.0 mm, The muffle furnace was set to a low temperature (275 ° C.), and when the sample surface temperature reached 250 ° C., the muffle furnace was taken out from the muffle furnace and rolled.

  In order to evaluate the room temperature formability of the produced magnesium alloy sheet, an Erichsen test was performed. The Eriksen test conforms to JIS B7729 and JIS Z2247. The blank shape was set to 60 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 evaluate the in-plane anisotropy of the produced magnesium alloy sheet at room temperature, a tensile test was performed. The test piece has a parallel part length of 10 mm, a parallel part width of 5 mm, and a parallel part thickness of 1.0 mm. A tensile test piece having an angle between the rolling direction and the tensile direction of 0 ° and 90 ° was cut out from the rolled material, and a tensile test was performed.

  The crosshead speed was 1.0 mm / min. Measure the parallel part width and parallel part thickness before the tensile test with a length measuring microscope or micrometer, measure the parallel part width and parallel part thickness of the sample after applying a 7% nominal strain by the tensile test, and the width direction Strain and strain in the thickness direction were measured, and an r value (width direction strain / thickness direction strain) was derived.

  Table 2 summarizes the Erichsen value and r value of each sample.

  Comparative example 1 and comparative example 2 are AZ31 alloys which do not add calcium. When the sample surface temperature during rolling is 450 ° C. or lower, the Erichsen value is less than 7.0. On the other hand, when the sample surface temperature during rolling is set to 525 ° C., the Erichsen value is improved to 8.8, but the in-plane anisotropy index value is 1.0 or more.

  Comparative Example 3 is a result of rolling an alloy obtained by adding 0.1 mass% of calcium to AZ31 at a sample surface temperature of 420 ° C. When the sample surface temperature is low, the Erichsen value is less than 7.0.

  Comparative Example 4 is the result of rolling an alloy obtained by adding 0.1 mass% of calcium to the AZ51 alloy at a sample surface temperature of 420 ° C. When the sample surface temperature is low, the Erichsen value is less than 7.0.

  Comparative Example 5 is a result of rolling an alloy obtained by adding 0.8 mass% of calcium to an AZ31 alloy at a sample surface temperature of 480 ° C. An alloy to which calcium exceeding 0.5 mass% is added has an Erichsen value of less than 7.0 even when rolled at a high temperature.

  Example 1 and Example 2 are the results of rolling an alloy obtained by adding 0.1% by mass of calcium to an AZ31 alloy at a predetermined sample surface temperature. By setting the composition of the sample to an appropriate composition and rolling under an appropriate condition, a plate material having an Erichsen value of 7.0 or more and an in-plane anisotropy of less than 1.0 can be created.

  Examples 3 and 4 are the results of rolling an alloy obtained by adding 0.1 mass% of calcium to the AZ51 alloy at a predetermined sample surface temperature. By setting the composition of the sample to an appropriate composition and rolling under an appropriate condition, a plate material having an Erichsen value of 7.0 or more and an in-plane anisotropy of less than 1.0 can be created.

  Example 5 is a result of rolling an alloy obtained by adding 0.3 mass% of calcium to an AZ31 alloy at a predetermined sample surface temperature. By setting the composition of the sample to an appropriate composition and rolling under an appropriate condition, a plate material having an Erichsen value of 7.0 or more and an in-plane anisotropy of less than 1.0 can be created.

  Example 6 is a result of rolling an alloy obtained by adding 0.1 mass% of calcium to an AZ31 alloy at a predetermined sample surface temperature. By setting the composition of the sample to an appropriate composition and rolling under appropriate conditions, a plate material that exhibits an Erichsen value of 7.0 or more and an in-plane anisotropy of less than 1.0 even when finish rolling is performed. Can be created.

  As described above in detail, the present invention relates to a magnesium alloy sheet material having improved cold formability and in-plane anisotropy and a method for producing the same, and according to the present invention, a commercial magnesium alloy (Mg—Al—Zn) is provided. -Mn-based alloy) is heated to a predetermined sample surface temperature (450 ° C. to 566 ° C.) by adding a trace amount (0.01 to 0.5 mass%) of calcium to a rolling rate of 5% or more. An easily formable magnesium alloy sheet can be produced by performing hot rolling in the range and annealing after rolling. The produced plate material exhibits room temperature formability similar to that of an aluminum alloy and exhibits excellent in-plane anisotropy. By using the present invention, it is possible to produce a magnesium alloy sheet having formability comparable to that of an aluminum alloy and excellent in-plane anisotropy at a low cost, and magnesium having improved anisotropy and formability at the same time. An alloy sheet can be produced. INDUSTRIAL APPLICABILITY The present invention is useful for providing an easily formable magnesium alloy sheet material that can be actively applied mainly to press-formed bodies of home appliances such as digital cameras, notebook computers, and PDAs.

Claims (8)

  In mass%, Al: 2.5 to 7.2%, Zn: more than 0 to 2.0% or less, Mn: more than 0 to 1.0% or less, Ca: 0.01 to 0.5%, Heat the sample surface temperature of the Mg alloy rolled sheet consisting of Mg and inevitable impurities to 450 to 566 ° C., then hot-roll at a total rolling rate of 5% or more, and perform annealing after hot rolling A process for producing an easily formable magnesium alloy sheet characterized by the following.   In mass%, Al: 2.5-7.2%, Zn: 0.4-2.0%, Mn: 0.01-1.0%, Ca: 0.01-0.5%, The manufacturing method of the easily moldable magnesium alloy sheet | seat material of Claim 1 which heats the sample surface temperature of the Mg alloy rolled sheet which a remainder consists of Mg and an unavoidable impurity to 450-566 degreeC.   The method for producing an easily formable magnesium alloy sheet according to claim 1 or 2, wherein the sample surface temperature of the rolled sheet is set to less than 300 ° C and the finish rolling is performed in a range of less than 30% of the total rolling ratio before annealing.   In mass%, Al: 2.5 to 7.2%, Zn: more than 0 to 2.0% or less, Mn: more than 0 to 1.0% or less, Ca: 0.01 to 0.5%, A readily formable magnesium alloy sheet characterized in that the balance is Mg alloy rolled material composed of Mg and inevitable impurities, and the Erichsen value is at least 7.0 or more.   In mass%, Al: 2.5-7.2%, Zn: 0.4-2.0%, Mn: 0.01-1.0%, Ca: 0.01-0.5%, The formable magnesium alloy sheet according to claim 4, wherein the balance is a Mg alloy rolled sheet made of Mg and inevitable impurities.   The index value of in-plane anisotropy (the difference between the Rankford value obtained when the rolling direction and the tensile direction are 0 ° and the Rankford value obtained when the rolling direction and the tensile direction are 90 °) is less than 1.0. The easily formable magnesium alloy sheet according to claim 4 or 5, which is (absolute value).   A magnesium alloy press-molded body comprising the molded body of the easily formable magnesium alloy sheet according to any one of claims 4 to 6.   A magnesium alloy member comprising the magnesium alloy press-formed product according to claim 7.