JP2017160542A - Magnesium alloy casting material, magnesium alloy cast coil material, wrought magnesium alloy material, magnesium alloy member, magnesium alloy joint material, and method for producing magnesium alloy casting material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnesium alloy casting material having excellent flame retardancy and workability, and a magnesium alloy cast coil material, a wrought magnesium alloy material, a magnesium alloy member, a magnesium alloy joint material, and a method for producing a magnesium alloy casting material.SOLUTION: A magnesium alloy casting material comprises a magnesium alloy comprising Al, where the magnesium alloy comprises Al of 2 mass% or more and 11 mass% or less, and Ca of 0.1 mass% or more and 10 mass% or less, with the DAS of less than 4.5 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to various members made of a magnesium alloy (hereinafter sometimes referred to as an Mg alloy), in particular, an Mg alloy cast material and an Mg alloy cast coil suitable for a material of an Mg alloy member subjected to plastic working such as press working. The present invention relates to a material, a Mg alloy wrought material, a Mg alloy bonding material, a method for producing a Mg alloy cast material, and a Mg alloy member. In particular, the present invention relates to an Mg alloy cast material and an Mg alloy wrought material that are excellent in flame retardancy and workability.

  Magnesium alloy is the lightest alloy among structural metals and is excellent in various aspects such as resource amount, recyclability, shock absorption, and dent resistance. Therefore, in recent years, a magnesium alloy 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 or a notebook personal computer, an automobile part, and a railway vehicle part.

  The products made of magnesium alloys are mainly cast materials by die casting or thixomolding. Patent Document 1 discloses that a magnesium alloy plate excellent in press workability can be obtained by rolling a cast plate manufactured by a continuous casting method.

International Publication No. 2006/003899

  Magnesium alloys are very active and flammable. In order to increase the flame retardancy of the magnesium alloy, as described in Patent Document 1, addition of Ca is effective. However, when Ca is added, the workability decreases. Specifically, if the cast material is subjected to wrench processing such as rolling, or plastic processing such as press processing is applied to the wrought material that has been wrought, cracking is likely to occur. This leads to a decrease in productivity.

  Therefore, in order to manufacture a wrought material such as a rolled material and a plastic material such as a press-worked material with high productivity, it is desired that the cast material itself as the material is excellent in workability.

  Accordingly, one of the objects of the present invention is to provide a magnesium alloy cast material that is excellent in flame retardancy and excellent in workability. Another object of the present invention is to provide a method for producing a magnesium alloy cast material capable of producing a magnesium alloy cast material excellent in both flame retardancy and workability.

  Another object of the present invention is to provide a magnesium alloy wrought material excellent in both flame retardancy and workability, and a magnesium alloy cast coil material suitable for the material of the wrought material.

  Another object of the present invention is to provide a magnesium alloy member excellent in both flame retardancy and mechanical properties, and a magnesium alloy bonding material suitable for the material of the magnesium alloy member.

  The inventors of the present invention cast a magnesium alloy under various conditions for adding a relatively large amount of Ca in order to improve flame retardancy, and for a magnesium alloy in which Al is also added to improve mechanical properties such as strength and corrosion resistance. A material was prepared. As a result, it is possible to obtain a cast material that is excellent in stretch workability such as rolling, even if it is a magnesium alloy containing Ca by using a continuous casting method and quenching rapidly by cooling at the time of casting. In addition, the present inventors have found that a wrought material having excellent plastic workability such as press working can be obtained by using this cast material as a raw material. Moreover, when the structure of the cast material excellent in stretch workability was examined, it had a specific cast structure. The present invention is based on the above findings.

  The magnesium alloy cast material of the present invention is a cast material made of a magnesium alloy containing Al. The magnesium alloy contains Al in an amount of 2 to 11% by mass and Ca in an amount of 0.1 to 10% by mass. To do. The cast material has a DAS (dendrite arm spacing) of less than 4.5 μm.

The said casting material of this invention can be manufactured with the following this invention manufacturing method. The method for producing a magnesium alloy cast material of the present invention is a method for producing a cast material made of a magnesium alloy containing Al, and includes the following preparation process and casting process.
Preparation step: A step of preparing a magnesium alloy melt containing Al in an amount of 2% by mass to 11% by mass and Ca in an amount of 0.1% by mass to 10% by mass.
Casting step: A step of producing a cast material by continuously casting the molten metal with a twin roll continuous casting machine having a pair of casting rolls.
And the cooling rate at the time of the said casting shall be 650 degrees C / sec or more.

  As the Ca content increases, the liquidus temperature and solidus temperature of the alloy decrease, and the molten alloy becomes difficult to solidify, and the time until complete solidification increases. That is, it is considered that the Mg alloy melt containing a relatively large amount of Ca, particularly 0.1% by mass or more, tends to be long in an unsolidified state, and as a result, the DAS becomes large and the workability is lowered. In the production method of the present invention, the DAS can be made very small by greatly increasing the cooling rate, and the cast material of the present invention having a DAS of less than 4.5 μm can be produced. Since the DAS is sufficiently small, the cast material of the present invention is less prone to cracking when subjected to extension processing such as rolling, and is excellent in workability, and also contains Ca in a specific range, thus being flame retardant. Also excellent.

As one form of the manufacturing method of the present invention, when the gap between the pair of casting rolls is g _r and the gap between the nozzle openings for discharging the molten metal toward the casting roll is g _n , g _n <g _r The form which adjusts at least one of the gap between the said casting rolls and the space | interval of the opening part of the said nozzle so that it may become may be mentioned.

  The present inventors have found that it is preferable to cool the molten metal with a casting roll as quickly as possible in order to increase the cooling rate. In the above embodiment, the gap between the nozzle openings is smaller than the gap between the casting rolls, and the nozzle openings can be brought closer to the casting roll, or the thickness of the nozzle body can be increased to increase the heat insulation. it can. Therefore, since the high temperature state molten metal can contact a casting roll, the said form can fully increase the cooling rate at the time of casting, and can manufacture the casting material whose DAS is small enough.

  As one form of the manufacturing method of the present invention, in the preparation step, a Ca-containing molten metal containing a predetermined amount of Ca is produced, and then the remaining Ca is added to produce the molten magnesium alloy. A form is mentioned.

  The inventors of the present invention have found that it is preferable to mix Ca in multiple stages when producing a cast material containing Ca in the above specific range. Since the said form can mix Ca uniformly by adding Ca further to Ca containing molten metal, it can suppress uneven distribution of Ca. Therefore, the said form can prevent effectively generation | occurrence | production of the malfunction that the location where Ca is unevenly distributed and there exists a location which is hard to solidify, a location where a DAS is large is formed locally, and as a result workability falls.

  As one form of the cast material of the present invention, there is a form in which the magnesium alloy contains a first intermetallic compound containing Al and Ca, and the maximum diameter of the first intermetallic compound is 5 μm or less.

  Although the flame retardance is enhanced as the Ca content increases, a coarse intermetallic compound is likely to be formed in the cast material due to difficulty in solidification as described above. Here, the Mg alloy containing Al as an additive element has high strength and excellent corrosion resistance. However, in an Mg alloy containing both Al and Ca in the above range, an intermetallic compound containing Al and Ca is likely to be crystallized as coarse particles. A coarse intermetallic compound tends to be a starting point of cracking when the cast material is subjected to a stretching process such as rolling, and causes a decrease in the workability of the cast material. If the coarse intermetallic compound is to be made finer by the load during the stretching process such as rolling, an excessive load is applied to the stretching apparatus and the material is processed unevenly. Also, if the coarse intermetallic compound remains in the wrought material, the coarse intermetallic compound becomes a starting point of cracking when the wrought material is subjected to plastic working such as press working, and the workability of the wrought material is reduced. Incurs a decline. In the above-mentioned form, since the intermetallic compound containing Al and Ca is sufficiently small, it is difficult to become a starting point of cracking and is excellent in workability of the drawing process. Moreover, although the intermetallic compound containing Al and Ca in the cast material remains in the expanded material obtained by subjecting the cast material of the present invention to the extension processing (present invention expanded material), the intermetallic compound is Since the particles are very fine as described above, they are unlikely to become a starting point of cracking when the wrought material is subjected to plastic working such as press working, and this wrought material is also excellent in workability. The cast material having the above-described form in which the intermetallic compound is finely crystallized can be produced by the production method of the present invention in which the cooling rate during the continuous casting described above is extremely increased.

  As one form of the cast material of the present invention, the magnesium alloy contains a first intermetallic compound containing Al and Ca, the absolute value of the difference between the maximum diameter of the DAS and the first intermetallic compound is 2.5. The form which is below μm can be mentioned.

  Since the cast material of the present invention has a small DAS, it can be said that the above-mentioned form with the small difference is also a small intermetallic compound containing Al and Ca, and this intermetallic compound is about the same size as the DAS. . Moreover, since the said difference is small, it can be said that the said form is a uniform structure | tissue in which the fine intermetallic compound existed similarly in the fine cast structure. Since it is such a fine and uniform structure, the above-described form is less likely to cause cracking of the intermetallic compound and is more excellent in workability.

  As one form of the cast material of the present invention, the magnesium alloy contains a first intermetallic compound containing Al and Ca, and the maximum diameter of the first intermetallic compound containing DAS and the Al and Ca. The form whose sum is 5 micrometers or less is mentioned.

  Since the cast material of the present invention has a small DAS, it can be said that the above-mentioned form having a small sum also has a sufficiently small intermetallic compound containing Al and Ca. Therefore, the above form can be said to be a uniform structure in which a very fine intermetallic compound is present in a fine cast structure. Since it is such a fine and uniform structure, the above-described form is less likely to cause cracking of the intermetallic compound and is more excellent in workability. When the sum is small and the above-described difference is small, the workability is further improved.

  As one form of the cast material of the present invention, the magnesium alloy contains a first intermetallic compound containing Al and Ca, and a second intermetallic compound containing Al and Mg. The form which provides the location where both the intermetallic compounds of an intermetallic compound and said 2nd intermetallic compound exist adjacently is mentioned. Moreover, this invention extended material is obtained by performing the extending | stretching process, such as rolling, using the cast material of the said form as a raw material. The magnesium alloy wrought material of the present invention is a wrought material composed of a magnesium alloy containing Al in an amount of 2% by mass to 11% by mass and Ca in an amount of 0.1% by mass to 10% by mass. And a first intermetallic compound containing Al and Ca, and a second intermetallic compound containing Al and Mg. The wrought material includes a particle group in which particles of both intermetallic compounds of the first intermetallic compound and the second intermetallic compound are adjacent to each other.

  When the present inventors investigated, the casting material obtained by continuously casting Mg alloy containing Ca and Al in the above specific range at the above specific cooling rate is a state where the above-mentioned intermetallic compounds are adjacent to each other. Thus, crystallization occurred between the arms of the dendrite structure, and it was found that the intermetallic compound has a structure in a network form. In addition, when the cast material having this structure is subjected to a stretching process such as rolling, the obtained stretched material (the present stretched material) is also a fine particle group in which the particles of the two intermetallic compounds are adjacent to each other. The knowledge that it has the structure | tissue which exists in a dispersion | distribution was acquired. Furthermore, it has been found that the wrought material having a structure in which the fine particle groups are dispersed is not easily cracked and has excellent workability when subjected to plastic working such as press working. Therefore, the cast material having the above-described form is excellent in the workability of the extending process such as rolling, and the expanded material is excellent in the workability of plastic working such as press working. The above-mentioned wrought material of the present invention is excellent in workability of plastic working such as press working, and also has excellent flame retardancy by containing Ca in a specific range.

  As one form of the cast material of the present invention, there may be mentioned a form in which the magnesium alloy contains a first intermetallic compound containing Al and Ca, and the average particle size of the intermetallic compound is 2 μm or less.

  The said form is that the average particle diameter of the intermetallic compound containing Al and Ca is small, and it can be said that all the intermetallic compounds which exist in the said Mg alloy are fine. Therefore, the said form does not become the starting point of a crack of the said intermetallic compound, and is excellent by workability. In particular, in the above embodiment, when the maximum diameter of the intermetallic compound is 5 μm or less, it is further difficult to break and the workability is further improved. The wrought material (one form of the wrought material of the present invention) obtained by performing a wrought process such as rolling on the cast material also has a maximum diameter of an intermetallic compound containing Al and Ca of 5 μm or less, and The average particle size is 2 μm or less. This wrought material is also excellent in workability of plastic working such as press working because the intermetallic compounds are all fine and hardly start a crack. In addition, since the wrought material has a structure in which fine and uniform intermetallic compounds are dispersed, the strength can be improved by dispersion strengthening. A plastic working material subjected to plastic working such as press working using the stretched material as a raw material also has excellent strength, impact resistance, and rigidity by maintaining the above-described dispersion strengthened structure.

  As one form of the cast material of the present invention or the stretched material of the present invention, in the magnesium alloy cast material or the magnesium alloy stretched material, Al present in the surface region and the central region in the thickness direction of the cast material or the stretched material; Examples include a form in which the first intermetallic compound containing Ca is fine and has a uniform size. The surface layer region is a region up to 20% of the thickness of the cast material or the wrought material in the thickness direction from the surface of the cast material or the wrought material. The central region is a region up to 10% of the thickness of the cast material or the stretched material from the center in the thickness direction of the cast material or the stretched material toward the surface side. And as for the said cast material or the said wrought material, the maximum diameter of the 1st intermetallic compound containing the said Al and Ca in each area | region of the said surface layer area | region and the said center area | region is 5 micrometers or less, and an average particle diameter is Further, the difference between the average particle size in the surface layer region and the average particle size in the central region is within 20%.

  In the above embodiment, since the difference in the size of the intermetallic compound existing in the surface region and the central region is small, the size of the intermetallic compound is uniform over the entire cast material or the entire stretched material. It can be said that the target is fine. Therefore, the said form does not produce a crack etc. easily at the time of plastic processing, such as extension processing, such as rolling, and press processing, and is excellent in workability.

  As one form of the cast material of the present invention or the expanded material of the present invention, the magnesium alloy contains at least one of a second intermetallic compound containing Al and Mg and a third intermetallic compound containing Al and Mn. An example in which the average particle size of at least one of the second intermetallic compound and the third intermetallic compound is 2 μm or less is included.

  The cast material of the present invention and the expanded material of the present invention contain not only the above-described intermetallic compound containing Al and Ca, but also an intermetallic compound containing Al and Mg as in the above form, and Al and Mn. There may be a form containing an intermetallic compound. In the cast material of the present invention, the above-mentioned intermetallic compounds are all small and uniform by increasing the cooling rate at the time of continuous casting and quenching as described above, and these intermetallic compounds are unlikely to become the starting point of cracking. . Therefore, the cast material of the above form is excellent in the stretch workability such as rolling. Further, the wrought material of the present invention obtained using this cast material as a raw material also has the above-mentioned intermetallic compounds small and uniform in the same manner as the raw material (the cast material of the above form). Therefore, the wrought material of the above form is excellent in plastic workability such as press working.

  As one form of the cast material of the present invention or the expanded material of the present invention, the magnesium alloy further includes Zn, Mn, Si, Sr, Y, Cu, Ag, Ce, Sn, Li, Zr, Be, Ni, Au and Examples include a form in which at least one element selected from rare earth elements (excluding Y and Ce) is contained in a total of 7.3% by mass or more with Al, and the balance is Mg and impurities.

  The said form is excellent in various characteristics, such as intensity | strength, plastic deformation resistance, corrosion resistance, and heat resistance, by containing various elements.

  The cast material of the present invention can take various shapes. For example, the magnesium alloy cast coil material of the present invention obtained by winding a plate-like material having a length of 100 m or more made of the cast material of the present invention.

  Since the cast material of the present invention is manufactured by continuous casting as described above, a long plate material of 100 m or more can be easily manufactured, and the coil material of the present invention can be obtained by winding up the plate material. When the coil material of the present invention is used as a material for an extension process such as rolling, the material can be continuously supplied to an extension processing apparatus, which can contribute to an improvement in the productivity of the extension material. A rolled coil material can be manufactured by winding up the obtained stretched material. And, when this stretched coil material is used as a material for plastic working such as press working, since the material can be continuously supplied to the plastic working device, the plastic working material (one form of the magnesium alloy member of the present invention) It can contribute to the improvement of productivity.

  As one aspect of the present invention, the absolute value of the difference between the maximum diameter of the first intermetallic compound containing Al and Ca and the maximum diameter of the second intermetallic compound containing Al and Mg is The form which is 2 micrometers below is mentioned.

  Since the difference between the two intermetallic compounds between the first intermetallic compound and the second intermetallic compound is small, the variation in the size of these two intermetallic compounds is small, and the uniform structure I can say that. Therefore, the said form is more excellent in workability than the said intermetallic compound being a starting point of a crack.

  As one form of the wrought material of the present invention, there is a form in which the ignition temperature of the magnesium alloy wrought material is 600 ° C. or higher and the tensile strength is 300 MPa or higher.

  In addition to being excellent in workability as described above, the above form is excellent in heat resistance because the ignition temperature is sufficiently high, and high in strength because the tensile strength is sufficiently high. Therefore, the said form is a member of the various field | areas where heat resistance and high intensity | strength are desired, Comprising: It can utilize suitably for the raw material of the member in which plastic processing, such as press work, is given.

  The magnesium alloy member of the present invention made of the above-described expanded material of the present invention is proposed. The magnesium alloy member of the present invention is obtained by subjecting the above-mentioned expanded material of the present invention to press working at a heating temperature of room temperature to 500 ° C.

  As described above, the wrought material of the present invention is excellent in workability, so that the press working can be performed well and the magnesium alloy member of the present invention can be manufactured with high productivity. In the case of performing press working with a complicated shape and a high degree of processing, the plastic workability can be improved as the heating temperature is increased, and the molding can be performed with high accuracy. In addition, since the wrought material of the present invention has a high ignition temperature and high strength as described above, the magnesium alloy member of the present invention made from the wrought material of the present invention also has a high ignition temperature and high strength.

  A magnesium alloy bonding material of the present invention is proposed in which a plurality of the above-mentioned expanded materials of the present invention are prepared and bonded to form a large material. The magnesium alloy bonding material of the present invention includes a plurality of the above-described expanded materials of the present invention and a bonding region in which the expanded materials of the present invention are bonded together by friction stir welding.

  As a result of investigations by the present inventors, a joint material obtained by joining plate-like expanded materials of the present invention by friction stir welding does not break in the joining region even when subjected to plastic working such as press working. They obtained knowledge that they can be treated in the same way as a uniform material that does not have a bonding region. By joining a plurality of the wrought materials of the present invention by friction stir welding, they can be made into an arbitrary size or an arbitrary planar shape. The inventive bonding material is a material of a large plastic work material or a plastic material of a desired shape. It can utilize suitably for the raw material of a processed material.

  The magnesium alloy cast material, cast coil material, wrought material, and bonding material of the present invention are excellent in both flame retardancy and workability. The magnesium alloy member of the present invention is excellent in flame retardancy and high strength. The manufacturing method of this invention magnesium alloy casting material can manufacture this invention casting material.

Fig. 1 (A) is a micrograph (5000 times) of the cast material of sample No. 1-22, and Fig. 1 (B) is a micrograph (5000 times) of the stretched material of sample No. 1-22. . 2 is a composition mapping image by FE-EPMA of the cast material of sample No. 1-22, FIG. 2 (A) shows the Ca concentration distribution, and FIG. 2 (B) shows the Al concentration distribution. 3A is a micrograph (5000 times) of the cast material of sample No. 100, and FIG. 3B is a micrograph (5000 times) of the stretched material of sample No. 100. FIG. 4 is an explanatory view illustrating the relationship between the gap of the casting roll and the interval between the openings of the nozzle.

Hereinafter, the present invention will be described in more detail.
[composition]
Magnesium alloy cast material, cast coil material, wrought material (including the case of a material constituting the bonding material), magnesium alloy constituting the magnesium alloy member, both Ca and Al as essential additive elements, The balance consists of Mg (50% by mass or more) and impurities.

  By containing at least 0.1% by mass of Ca, it has excellent flame retardancy and can improve the ignition temperature. The higher the Ca content, the higher the ignition temperature. In view of flame retardancy, 0.5% by mass or more, preferably 1% by mass or more is preferable. However, if Ca is too much, workability is lowered, so the upper limit is made 10 mass%. In consideration of workability, the Ca content is more preferably 3% by mass or less.

  A magnesium alloy containing 2% by mass or more of Al is excellent in strength and corrosion resistance. The higher the Al content, the more excellent the strength and corrosion resistance of the magnesium alloy. Therefore, considering the strength and corrosion resistance, it is preferably 2.5% by mass or more, and more preferably 4.5% by mass or more. However, if there is too much Al, workability will be reduced, so the upper limit of the Al content is 11% by mass. An Mg-Al alloy having an Al content of 7.3% by mass or more, particularly 8.3% by mass to 9.5% by mass is preferable because of excellent mechanical properties such as strength and hardness, corrosion resistance, and plastic workability.

  Additive elements other than Ca and Al are selected from Zn, Mn, Si, Sr, Y, Cu, Ag, Ce, Sn, Li, Zr, Be, Ni, Au, and rare earth elements (excluding Y and Ce) One or more elements are listed. When these elements are contained, the content of each element is 0.01 mass% or more and 10 mass% or less, preferably 0.1 mass% or more and 5 mass% or less. The total content of additive elements other than Ca and Al and Al is preferably 7.3% by mass or more. By including the above additive elements in addition to Al, depending on the type of element, various mechanical properties such as strength, hardness, toughness, impact resistance, and dent resistance, vibration damping, corrosion resistance, heat resistance, etc. The characteristics can be improved. Among the above additive elements, one or more elements selected from Si, Sn, Y, Ce and rare earth elements (excluding Y and Ce) are in total 0.001% by mass or more, preferably in total 0.1% by mass or more and 5% by mass or less When it contains, heat resistance and a flame retardance can be improved more. When the rare earth element is contained, the total content is preferably 0.1% by mass or more, and particularly when Y is contained, the content is preferably 0.5% by mass or more. Examples of the impurity include Fe.

  More specific compositions of Mg-Al alloys include, for example, AZ alloys (Mg-Al-Zn alloys, Zn: 0.2% to 1.5% by mass), AM alloys (Mg-Al-Mn) according to ASTM standards. Alloy, Mn: 0.15 mass% to 0.5 mass%), Mg-Al-RE alloy (RE: rare earth element), AJ alloy (Mg-Al-Sr alloy, Sr: 0.2 mass% to 7.0 mass%) Etc. In particular, a Mg-Al alloy containing 8.3 mass% to 9.5 mass% Al and 0.5 mass% to 1.5 mass% Zn, typically AZ91 alloy, is preferable because of its excellent corrosion resistance and mechanical properties. .

[DAS]
The cast material of the present invention has a very small DAS of less than 4.5 μm. By increasing (accelerating) the cooling rate at the time of casting, the DAS can be further reduced, and a cast material having a DAS of 4 μm or less and further 3 μm or less can be obtained. The smaller the DAS, the better the workability, and there is no particular lower limit. The method for measuring DAS will be described later.

[Al-Ca intermetallic compound]
(Casting material, Casting coil material)
In a typical structure of the cast material of the present invention (including a plate material constituting a cast coil material), an intermetallic compound containing Al and Ca (for example, Al ₂ Ca) exists, and the intermetallic compound is present. It is fine. The intermetallic compound containing Al and Ca is mainly a crystallized product, and the size generated at the time of casting is substantially maintained in the processes after casting or becomes finer by processing. In the production method of the present invention, the maximum diameter of the intermetallic compound containing Al and Ca can be reduced to 5 μm or less by rapidly cooling the casting at a specific cooling rate. By increasing the cooling rate during casting, the maximum diameter can be further reduced, and the maximum diameter can be 3 μm or less, further 1.5 μm or less. Depending on the Ca content and the like, the intermetallic compound having the maximum diameter of 1 μm or less can be in a very fine form. The finer the intermetallic compound, the harder it becomes to be the starting point of cracking, and there is no particular lower limit on the maximum diameter. The measuring method of the said intermetallic compound and the maximum diameter of an intermetallic compound mentioned later, an average particle diameter, etc. is mentioned later.

  In the typical structure of the cast material of the present invention, the intermetallic compounds containing Al and Ca are all fine and uniform in size. Specifically, the average particle size of the intermetallic compound is 2 μm or less. Since this form has a fine and uniform structure in which a fine and uniform intermetallic compound exists in a fine cast structure with a small DAS, coarse intermetallic particles are locally present. Thus, the problem that the coarse particles are the starting point of cracking hardly occurs and the processability is excellent. Depending on casting conditions, composition, etc., a cast material having an average particle size of the intermetallic compound of 1.5 μm or less, and further 1.0 μm or less can be obtained.

  In the typical structure of the cast material of the present invention, the variation in the intermetallic compound containing Al and Ca is small or substantially uniform throughout the entire thickness direction of the cast material, and has a uniform size. That's it. Specifically, the maximum diameter and average particle size of the intermetallic compound are small in both the surface layer region and the central region described above, and the difference in average particle size between the two regions is small (within 20%). Depending on the casting conditions, composition, etc., it is possible to obtain a cast material in which the difference in average particle size between the two regions is 15% or less.

(Spread)
The intermetallic compound containing Al and Ca present in the cast material of the present invention is fine as described above, and is rolled without applying an excessive load when the cast material is subjected to extension processing such as rolling. Can be done. Therefore, the size of the intermetallic compound present in the obtained wrought material is substantially maintained as the size of the cast material, or is further reduced by the wrench processing. Therefore, in a typical structure of the wrought material of the present invention, an intermetallic compound containing Al and Ca (for example, Al ₂ Ca) is present, and the intermetallic compound is fine. For example, a form in which the maximum diameter of the intermetallic compound satisfies 5 μm or less, further 3.0 μm or less, especially 1.5 μm or less, or an average particle diameter of 2 μm or less, further 1 μm or less, particularly 0.5 μm or less can be mentioned. Further, in both the surface layer region and the central region described above, the maximum diameter and the average particle size of the intermetallic compound are small, and the difference between the average particle sizes of the two regions is 20% or less, and further, 15% or less can do.

(Bonding material)
In the present invention bonding material prepared by joining a plurality of the present invention stretched material, the portion excluding the bonding region is the structure of the present invention stretched material (for example, the maximum diameter of the intermetallic compound containing Al and Ca: 5 μm Hereinafter, the average particle size: 2 μm or less and the difference in average particle size between the surface layer region and the central region: within 20% are substantially maintained.

(Magnesium alloy member)
In the magnesium alloy member of the present invention in which the present invention expanded material or the present invention bonding material is subjected to plastic working such as press working, a place where the plastic working is not substantially performed (typically a flat place) or processing When plastic working is performed at a low degree, the structure of the wrought material of the present invention (for example, the maximum diameter of intermetallic compounds including Al and Ca: 5 μm or less, average particle diameter: 2 μm or less, surface layer region and center The difference in the average particle diameter from the region: within 20%) is substantially maintained.

[Relationship between DAS and Al-Ca intermetallic compound]
As described above, the DAS is small, and the intermetallic compound containing Al and Ca is also small, so in the typical structure of the cast material of the present invention (including the plate-like material constituting the cast coil material), the DAS and the above The difference from the intermetallic compound is also small (absolute value is 2.5 μm or less). That is, this structure can be said to be a structure in which the above-mentioned intermetallic compound having a fine and uniform size and the same size as DAS is dispersed in a fine cast structure with a small DAS. By having such a specific fine and dispersed structure, the intermetallic compound is less likely to be a starting point of cracking, and is excellent in workability. Depending on casting conditions, composition, etc., a casting material having an absolute value of the difference of 2 μm or less can be obtained.

  As described above, the DAS is small, and the intermetallic compound containing Al and Ca is also small, so in the typical structure of the cast material of the present invention (including the plate-like material constituting the cast coil material), the DAS and the above The sum with the intermetallic compound is also small (5 μm or less). Since the sum is small, both DAS and the intermetallic compound are sufficiently small, and processability is excellent. Depending on the casting conditions and composition, the sum is 5 μm or less, further 4 μm or less, particularly 3.5 μm or less, or the absolute value of the above difference is 2.5 μm or less, and the sum is 5 μm or less. It can be a cast material that fills.

[Al-Mg intermetallic compound]
(Casting material, Casting coil material)
Since the cast material of the present invention (including the plate material constituting the cast coil material) contains Al, in a typical structure of the cast material, an intermetallic compound containing Al and Mg (for example, Al ₁₂ Mg ₁₇ ) exists mainly adjacent to an intermetallic compound containing Al and Ca. As a result of investigations by the present inventors, it was found that an intermetallic compound containing Al and Ca tends to form a crystalline phase preferentially over an intermetallic compound containing Al and Mg. Therefore, in the present invention, it is proposed that the size of an intermetallic compound containing Al and Ca, which easily becomes a hindrance to workability, is set within a specific range together with DAS.

  As mentioned above, the cooling rate during casting is set to a specific size and rapidly cooled, so that an intermetallic compound containing Al and Mg can also be made fine, for example, the average particle size can be 2 μm or less. it can. In this case, since both the intermetallic compound containing Al and Mg and the above-described intermetallic compound containing Al and Ca are fine, even if these two types of intermetallic compounds exist adjacently, Each intermetallic compound is unlikely to become a starting point of cracking, and workability is hardly hindered.

(Spread)
The present expanded material obtained by subjecting the present cast material, which contains the two types of intermetallic compounds to be adjacent to each other, also has particles adjacent to the two types of intermetallic compounds, It has a unique organization. The fact that the wrought material has a structure in which the two types of intermetallic compounds are present adjacent to each other is one of the indicators indicating that the two types of intermetallic compounds were also present in the cast material. Become.

  Intermetallic compounds containing Al and Mg are mainly precipitates, although there are crystallized substances. Although the precipitate may grow due to the thermal history of the manufacturing process after casting, if it is fine when present in the cast material, it is likely to be present in a fine state in the wrought material. For example, a wrought material having an average particle diameter of an intermetallic compound containing Al and Mg of 2 μm or less can be obtained. In addition, the intermetallic compound containing Al and Mg can be made finer due to the load during the stretching process, and the average particle size of the intermetallic compound is 1 μm or less, and further, the expanded material is 0.5 μm or less. be able to.

  When the intermetallic compound containing Al and Mg is fine, since the intermetallic compound containing Al and Ca is fine as described above, these two types of intermetallic compounds have a uniform size. Can be wrought material. For example, a wrought material in which the difference (absolute value) of the maximum diameters of the two types of intermetallic compounds is 2 μm or less and, depending on manufacturing conditions, can be further 1.5 μm or less, and is unlikely to become a starting point of cracking.

[Al-Mn intermetallic compound]
The cast material of the present invention (including the plate material constituting the cast coil material), depending on the composition, further contains another intermetallic compound, that is, a form containing three or more types of intermetallic compounds. Can be. For example, when the additive element further contains Mn, a form containing an intermetallic compound containing Al and Mn (for example, MnAl ₄ etc.) can be mentioned. As described above, the cooling rate at the time of casting is set to a specific size for rapid cooling, so the intermetallic compound containing Al and Mn is also fine, and for example, the average particle size satisfies 2 μm or less. Therefore, this intermetallic compound itself is also unlikely to become a starting point of cracking.

  The wrought material of the present invention obtained using a cast material containing an intermetallic compound containing Al and Mn as a raw material can also be in a form in which the intermetallic compound is present. Since intermetallic compounds containing Al and Mn are also mainly crystallized products, they may grow due to the thermal history of the manufacturing process after casting. It is easy to make it fine even during drawing. For example, a wrought material in which the average particle size of the intermetallic compound containing Al and Mn is 2 μm or less can be obtained. In addition, as described above, the intermetallic compound containing Al and Mn can be made finer due to the load during the stretching process, and the average particle size of the intermetallic compound is 0.5 μm or less, further 0.3 μm or less. Can be wrought material.

  In the bonding material of the present invention using an expanded material in which an intermetallic compound containing Al and Mg or an intermetallic compound containing Al and Mn is present, the press work is substantially performed in a portion other than the bonding region, or in the magnesium alloy member of the present invention. The part which is not applied to the surface substantially maintains the same structure as the wrought material, and therefore has a structure in which the intermetallic compound having a fine and uniform size exists as described above.

[Characteristic]
The present cast material, cast coil material, wrought material, bonding material, and magnesium alloy member (hereinafter sometimes collectively referred to as the present invention material) contain a specific amount of Ca, all of which have an ignition temperature. high. The higher the Ca content, the higher the ignition temperature, for example, 600 ° C or higher, and further 650 ° C or higher.

  The material of the present invention is continuously cast, and in addition to using this continuous cast material as a material, it also has excellent mechanical properties by containing a specific amount of Al, for example, tensile strength Is big. In particular, the wrought material of the present invention obtained by subjecting a continuous cast material to a drawing process has a higher tensile strength and can have a form satisfying, for example, 300 MPa or more, depending on the composition.

[shape]
(Casting material, Casting coil material)
A typical shape of the cast material of the present invention is a plate-like material having a rectangular plane. By appropriately cutting after continuous casting, it is possible to obtain a cast sheet material having a relatively short length, or without cutting, for example, a long material having a length of 10 m or more, further 50 m or more, particularly 100 m or more. The cast coil material of the present invention is obtained by winding the long material.

  When the thickness of the cast material of the present invention is 10 mm or less, more preferably 7 mm or less, particularly 5 mm or less, it is easy to rapidly cool at a uniform rate in the thickness direction, and DAS and intermetallic compounds can be made sufficiently small. Moreover, in the case of a cast coil material, it is easy to wind up because the thickness of a plate-shaped material is 10 mm or less.

  The width of the cast material of the present invention can be appropriately selected. Since a wide expanded material can be easily manufactured by using a bonding material as described above, a material having a small width may be used. When the width of the cast material of the present invention is about 100 mm to 300 mm, it is expected to be easy to manufacture.

(Spread)
A typical shape of the wrought material of the present invention is a plate-like material having a rectangular plane. When the above-mentioned cast sheet material is used as a raw material, a relatively short stretched sheet material is obtained. When a cast coil material is used as a raw material, a stretched coil material or a stretched sheet material is obtained by appropriate cutting. . Moreover, it can be set as the wrought material of a desired planar shape by stamping etc. to a desired shape.

  When the thickness of the wrought material of the present invention is 5 mm or less, further 3 mm or less, particularly 1 mm or less, a thin and light plastic work material (typically, a press work material) can be produced. Moreover, by making it thin in this way, it is easy to join by friction stir welding, and it can contribute to the improvement of productivity of a joining material.

  The width of the wrought material of the present invention can be appropriately selected. A plurality of wrought materials having a small width are prepared, and a wrought material having a wide width (for example, 1000 mm or more, further 2000 mm or more) can be obtained by friction stir welding.

(Magnesium alloy member)
The magnesium alloy member of the present invention is a plastically processed material that is at least partially pressed, and can take various shapes depending on the processing form.

[Production method]
(Preparation process)
First, Al is contained in an amount of 2% by mass to 11% by mass and Ca is contained in an amount of 0.1% by mass to 10% by mass. Prepare a magnesium alloy melt containing the remaining amount of Mg and impurities. Typically, a melt having a desired composition can be produced by dissolving a desired additive element in a base melt obtained by dissolving an ingot having a base composition. In particular, when producing a cast material containing Ca in a specific range as in the present invention, a desired amount of Ca is not dissolved at once in the base molten metal, but is dissolved in multiple stages. Then, a desired amount of Ca can be uniformly mixed, and uneven distribution of Ca can be prevented. As a result, the molten metal can be cooled rapidly and DAS and intermetallic compounds can be made sufficiently small.

  Specifically, a Ca-containing molten metal containing a predetermined amount of a part of Ca is prepared, and the remaining Ca is further added to the molten metal to prepare a molten metal containing a desired amount of Ca. The Ca-containing molten metal is prepared, for example, as an ingot of a base composition, for example, by preparing and melting one containing 1% by mass to 90% by mass of Ca of a predetermined amount, or does not contain Ca as an ingot of a base composition It may be prepared by preparing a product (the Ca content in the ingot is measured in advance) and dissolving Ca simultaneously so as to obtain a desired amount when the ingot is dissolved. By using the Ca-containing molten metal, combustion of the molten metal can be prevented when impurities are removed from the molten metal or when components are adjusted, and the effect of reducing the formation of oxides is also achieved. Further, by mixing Ca in multiple stages, there are effects such as (1) easy accurate component adjustment and (2) stable quality. When the remainder of Ca is mixed with the Ca-containing molten metal, it may be mixed at once, but may be further divided into multiple stages. It is easy to adjust the component more accurately by mixing the remaining Ca with the Ca-containing molten metal in a plurality of times. In this case, the mixing amount of Ca at each time may be equal or different.

  In order to reduce the formation of oxides, the above-mentioned dissolution is performed in an atmosphere with a low oxygen concentration (5% by volume or less), or an atmosphere that does not substantially contain oxygen, for example, an inert gas atmosphere such as nitrogen or argon, a carbon dioxide atmosphere It is preferable to carry out in a mixed atmosphere of an inert gas and carbon dioxide.

(Casting process)
In the manufacturing method of the present invention, a continuous casting method capable of rapid solidification is used. Further, since the cast material of the present invention is typically a plate-like material, a twin roll casting method or a twin belt casting method suitable for casting of the plate-like material is used as a continuous casting method. In particular, the twin roll casting method, which has a pair of casting rolls as a movable mold, is excellent in rigidity and thermal conductivity, can be rapidly solidified by using a mold having a large heat capacity, can easily increase the cooling rate, and is segregated. Therefore, it is preferable because it can form a cast material having a high strength and a high hardness as compared with conventional die casting materials and thixo mold materials.

The production method of the present invention is characterized in that the cooling rate during casting is 650 ° C./second or more. The higher the cooling rate, the more easily the growth can be achieved by suppressing the growth of DAS and various intermetallic compounds. Accordingly, the cooling rate is 1000 ° C./second or more, more preferably 1500 ° C./second or more, particularly 2000 ° C./second or more, and there is no particular upper limit, but the mass production system uses about 1000 ° C./second to 5000 ° C./second. Easy to do. For example, for the AZ alloy, the cooling rate is determined by using the following equation that holds in a general Mg—Al—Zn alloy. Using test pieces with various compositions and specifications (thickness, width, etc.), obtain the relationship between DAS: d and cooling rate: V in advance, create correlation data, and refer to this correlation data. If the cooling rate is adjusted to achieve the desired DAS, the workability is excellent.
When d is DAS (μm) and the cooling rate (° C./sec) is V, d = 35.5 × V ^−0.31 .
For magnesium alloys with compositions other than AZ alloys, α and β are constants depending on the composition (alloy type), and d ′ is DAS (μm), and d ′ = α × ^V′−β The cooling rate: V ′ may be obtained by

  In order to set the cooling rate within the specific range, for example, the temperature of the casting roll is lowered, the peripheral speed of the casting roll is lowered, or the roll load is increased. In other words, the heat discharged from the nozzle is increased by increasing the heat removal capacity of the casting roll itself, increasing the contact time between the molten metal and the casting roll, or allowing the molten metal to sufficiently contact the casting roll. To be sufficiently cooled.

In particular, as shown in FIG. 4, a pair of casting between rolls 100 Gap: discharging the molten metal towards the (portion between the pair of casting rolls 100 closest spacing gap position p _g) g _r, the casting rolls 100 to when the distance between the opening 220 of the nozzle 200 and g _n, such that the g _n <g _r, increasing the cooling rate adjusting at least one of the spacing g _n and gap g _r of the casting roll 100 of the nozzle 200 Easy to (fast).

4 as shown in (A), (if the overall thickness of the nozzle 200 is thick) when the interval between the outer surfaces of the pair of the nozzle body 210 constituting the nozzle 200 is large, so as to satisfy g _n <g _r By adjusting the interval g _{n of the} nozzles 200, the thickness of the nozzle body 210 can be increased. Therefore, since the heat insulation of the nozzle body 210 can be improved, the molten metal discharged from the opening 220 of the nozzle 200 is maintained at a high temperature up to the vicinity of the casting roll 100 and is cooled by contacting the casting roll 100. Therefore, since the temperature of the molten metal at the gap position p _g can be increased, the cooling rate can be increased. The nozzle body 210 can be made of a known material.

Alternatively, as shown in FIG. 4B, when the distance between the outer surfaces of the pair of nozzle bodies 210 constituting the nozzle 200 is narrow (when the overall thickness of the nozzle 200 is thin), the gap position p _{g of the} casting roll 100 The nozzle 200 itself can be arranged close to the nozzle. Therefore, since the molten metal discharged from the opening 220 of the nozzle 200 has a short distance until it contacts the casting roll 100, it immediately contacts the casting roll 100 and is cooled. Therefore, since the temperature of the molten metal at the gap position p _g can be increased, the cooling rate can be increased.

Specific examples of the gap g _n between the nozzles 200 include g _n = 0.8 × g _{r to} 0.95 × g _r . Since the gap between the casting rolls is a factor that determines the thickness of the cast material, there is a limit to the adjustment, but the interval between the nozzles is relatively easy to change.

  The cast material discharged from the casting roll can be cut into an appropriate length to produce a cast sheet material, and the cast coil material can be produced by winding the long material without cutting. When winding the long material, the inner diameter (winding diameter) of the coil is small by winding the cast material to 150 ° C or higher by heating or keeping the part immediately before winding. Can be wound without cracking.

(Solution process)
When manufacturing the wrought product of the present invention by subjecting the cast material of the present invention to a rolling process such as rolling, if a solution treatment is performed before the stretching process, the composition is homogenized or an element such as Al is fixed. It is preferable because it can be dissolved. Solution treatment depends on the type and content of the additive element, but holding temperature: 350 ° C or higher, especially holding temperature: 380 ° C to 420 ° C, holding time: 60 minutes to 2400 minutes (1 hour to 40 hours) It is preferable that The holding time is preferably increased as the content of additive elements such as Al increases. In the cooling process from the above holding time, if the cooling rate is increased by using forced cooling such as water cooling or blast (preferably 1 ° C / min or more, more preferably 50 ° C / min or more), coarse precipitates This is preferable because precipitation of (typically intermetallic compounds) can be suppressed.

(Stretching process)
In performing the extension processing such as rolling, extrusion, forging and the like to the cast material of the present invention and the above-mentioned solution-treated material, workability can be improved by heating the raw materials (including those in the middle of rolling). At least once (1 pass) is warm working. In particular, since the cast material of the present invention is inferior in workability due to containing Ca, it is preferable to perform warm processing multiple times (multiple passes). However, if the heating temperature of the material is too high, it will cause excessive growth and precipitation of precipitates, seizure of the material, and the mechanical properties of the wrought material obtained by coarsening the crystal grains of the material. The characteristics are degraded. Therefore, the heating temperature of the raw material in the warm extension processing is preferably 400 ° C. or lower, and more preferably 350 ° C. or lower. In particular, processing with a heating temperature of the material exceeding 300 ° C and processing at 300 ° C or less should be combined to minimize the processing above 300 ° C (preferably, after the solution treatment, the material will exceed 300 ° C. It is preferable that the total time of the retention time is 6 hours or less, more preferably about 1 hour). In the processing at 300 ° C. or lower, it is more preferable that the heating temperature of the material is 100 ° C. or higher and 280 ° C. or lower.

  In the case of rolling, for example, rolling, by applying multi-pass rolling, it is possible to achieve a desired plate thickness and reduce the average crystal grain size of the material (for example, 30 μm or less, further 20 μm or less, especially 10 μm or less, Preferably, the plastic workability such as rolling or pressing is improved. For the rolling, known conditions can be used. For example, when not only a raw material but a rolling roll is heated, workability can be improved more. In rolling with a small rolling reduction such as finish rolling, the rolling may be performed cold. Conditions such as number of rolling passes, degree of processing per pass, total degree of processing, heat treatment after rolling or after rolling, which will be described later, have a desired thickness and desired properties (such as tensile strength). Material) can be selected as appropriate. The width of the rolled material can also be selected as appropriate. A wide width can be produced and cut as appropriate to obtain a desired width, or a wide width material can be obtained by joining by friction stir welding. It is good also as a material.

  When performing multi-pass rolling, intermediate heat treatment may be performed between passes. By performing the intermediate heat treatment, it is possible to remove or reduce strain, residual stress, texture, and the like introduced into the material to be processed by rolling up to the heat treatment. As a result, inadvertent cracking, distortion, and deformation can be prevented by rolling after the heat treatment, and rolling can be performed more smoothly. The holding temperature of the intermediate heat treatment is preferably 350 ° C. or lower, more preferably 300 ° C. or lower, and particularly preferably 250 ° C. or higher and 280 ° C. or lower. This is preferable because growth of the precipitates and coarsening of crystal grains can be prevented. Examples of the retention time include 20 minutes to 60 minutes.

(Processing / processing after stencil processing)
The wrought material can be subjected to a final heat treatment (final annealing) for the purpose of removing strain introduced by processing. Alternatively, when the wrought material is a rolled material, it can be straightened without being subjected to final heat treatment. When plastic processing such as press processing is performed on the straightened material that has been subjected to straightening processing, dynamic recrystallization occurs during the plastic working, and thus the plastic workability is excellent. The straightening process includes warm straightening performed by heating the rolled material to 100 ° C to 300 ° C, preferably 150 ° C to 280 ° C. For warm correction, a heating furnace that can heat the rolled material, and a roll in which a plurality of rolls are arranged in a staggered manner facing each other in order to continuously bend (strain) the heated rolled material A roll leveler device comprising a portion can be suitably used. The rolled material is introduced into the heating furnace by the roll leveler device and is sent to the roll part while being heated. Each time the rolled material passes between the upper and lower rolls of the roll part, the rolls are sequentially bent.

  In addition, the rolled material, the heat-treated material subjected to the final heat treatment, and the straightening material may be polished. The polishing is preferably wet polishing in order to prevent scattering of the polishing powder. In particular, belt polishing can continuously polish a plate-like material, and is excellent in workability.

(Joining)
Prepare a plurality of the above-mentioned wrought materials of the present invention (typically rolled materials. In addition, the rolled materials may be subjected to the above-mentioned final heat treatment, correction, and polishing), and these wrought materials are prepared by friction stir welding. By joining, this invention joining material which has the joining area | region by friction stir welding is obtained.

  At the time of joining, edge processing is performed on the end surfaces of the materials to be joined so that the angle formed by the surface of the materials and the end surfaces becomes a right angle. By performing such edge processing, the end surfaces of the materials to be joined can be brought into contact with each other with high accuracy and can be joined well. The friction stir welding uses a joining probe that is made of a hard material such as tool steel or cemented carbide and has a small-diameter portion used for stirring and a large-diameter portion attached to the apparatus main body. In particular, when joining thin plate-like materials with a thickness of 3 mm or less, further 1 mm or less, the tip diameter of the small diameter part of the probe for bonding: 3 mm to 6 mm, the height of the small diameter part: the thickness of the plate material to be joined Probes such as 60% to 100%, the diameter on the small diameter part side in the large diameter part: 8 mm to 15 mm, and the angle between the tip surface and the side surface in the small diameter part and the large diameter part: 90 ° to 150 ° can be suitably used. Joining conditions are: probe rotation speed: 500 rpm to 5000 rpm, feed speed: 0.1 m / min to 1.0 m / min, pushing amount: 60% to 100% of the thickness of the plate to be joined, Angle: Angle between the probe feed direction and the center axis of the probe is 90 ° to 96 °, parallel direction of a pair of adjacent plate materials (perpendicular to the boundary line formed by contacting the plate materials) ) And the central axis of the probe is 90 °.

  When joining a plurality of materials, preparing a plurality of the above-mentioned joining probes and joining them at a plurality of locations at the same time shortens the joining time and excels in workability. When using a single joining probe, the equipment can be simplified. .

(Plastic processing)
The above stretched material of the present invention or the above bonded material of the present invention is prepared as a material, and a plastically worked material is obtained by subjecting these materials to plastic working such as pressing, bending, forging, and the like. When the press working is performed, the magnesium alloy member of the present invention is obtained. Even when plastic working is performed, the plastic workability can be improved by heating the raw material, but if it is too high, there is a problem such as seizure, so the heating temperature of the raw material is preferably 500 ° C. or lower. It may be room temperature depending on the degree of processing. In particular, when the heating temperature of the raw material is set to 200 ° C. to 300 ° C., the plastic workability of the raw material can be sufficiently improved and seizure can be easily prevented. Further heat treatment can be performed after the plastic working to remove strain and residual stress introduced by the plastic working and improve the mechanical characteristics. Examples of the heat treatment conditions include a heating temperature: 100 ° C. to 300 ° C. and a heating time: about 5 minutes to 60 minutes.

(Other processing / processing)
In addition, by applying anticorrosion treatment (anodic oxidation treatment, chemical conversion treatment), coating, etc. to the wrought material or plastic work material, it is possible to improve corrosion resistance, aesthetics, and commercial value. It is also possible to perform plastic working on the wrought material subjected to anticorrosion treatment.

Hereinafter, more specific embodiments of the present invention will be described.
[Test Example 1]
Cast materials made of magnesium alloys of various compositions were prepared and their metal structures were examined.

  A cast material containing a magnesium alloy with a composition equivalent to AZ91 alloy (Mg-9.0% Al-1.0% Zn-0.23% Mn (all mass%)) and containing Ca in the amount shown in Table 1. Produced. When the base alloy ingot is melted, the Ca-containing cast material also dissolves a part of the amount of Ca shown in Table 1 to produce a Ca-containing molten metal, and the remaining Ca is added to the obtained Ca-containing molten metal. Thus, a molten metal having a desired composition was prepared. For the cast material containing no Ca, a molten metal in which a base alloy ingot was melted was prepared.

Each prepared molten metal is continuously cast by a twin roll continuous casting machine to produce a cast material (thickness: 4.1mm to 4.2mm, width: 290mm), and this cast material is wound to produce a cast coil material. did. Table 1 shows the cooling rate during casting. The cooling rate was changed by adjusting the roll peripheral speed and the temperature of the casting roll. The slower the roll peripheral speed or the lower the temperature of the casting roll, the greater (faster) the cooling rate. Also, in this test, for any sample, when the gap between the casting rolls is g _r and the gap between the nozzle openings is g _n , the nozzle gap g _n is smaller than the gap g _r . The interval g _n was adjusted (here, g _n ≈0.9 g _r ).

Each of the obtained cast coil materials was rewound to prepare a test piece cut to an appropriate length. The cross section of each test piece (the cross section in the direction perpendicular to the longitudinal direction of the coil material) was observed and analyzed using SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy). SEM observation images (5000 times) are shown in FIGS. 1 (A) and 3 (A). As shown in FIG. 3 (A), it can be seen that in the cast material corresponding to the AZ91 alloy not containing Ca: sample No. 100, fine intermetallic compounds are dispersed throughout the entire structure. On the other hand, as shown in FIG. 1 (A), it can be seen that the cast material containing Ca: Sample No. 1-22 is connected in a network and an intermetallic compound is present. In addition, as shown in FIG. 1 (A), this mesh is formed by adjacent intermetallic compounds of different colors, specifically, whitish and grayish ones. I understand that X-ray diffraction of this cross section shows that it contains an intermetallic compound containing Al and Ca, such as Al ₂ Ca, and an intermetallic compound containing Al and Mg, such as Al ₁₂ Mg ₁₇ , that is, between different metals. The presence of the compound was confirmed. Further, it was confirmed that these intermetallic compounds were substantially crystallized between the arms of the dendrite structure.

  A cross section (transverse section) was taken as described above, this cross section was observed with an optical microscope (400 times), and DAS was measured using this observation image. Here, three cross sections are taken, one observation image is taken for each cross section, DAS is obtained from the three observation images, and the average is shown in Table 1.

  Take a cross-section (transverse cross section) as described above, perform composition mapping with FE-EPMA (Field Emission Electron Microanalyzer) of SEM observation image (5000 times) of this cross section, Ca concentration distribution and Al concentration distribution I investigated. FIG. 2 (A) shows the Ca concentration distribution, and FIG. 2 (B) shows the Al concentration distribution. When color mapping is performed with a commercially available EPMA device, the content of elements such as Ca and Al can be displayed in different colors. The observation magnification of the microscope can be selected as appropriate.

As shown in FIG. 2, it can be seen that Ca and Al are present in a high concentration between the arms of the dendrite structure, and that the high concentration portion of Ca and the high concentration portion of Al are substantially the same. Considering the above-mentioned X-ray diffraction results, the high-concentration portion of Ca and the high-concentration portion of Al are considered to be crystal phases of an intermetallic compound containing Al and Ca such as Al ₂ Ca. .

  For each test piece (cast material), the maximum diameter of the intermetallic compound containing Al and Ca, the difference between the maximum diameter of the intermetallic compound containing Al and Ca and DAS (absolute value), including Al and Ca The sum of the maximum intermetallic compound diameter and DAS, and the average particle diameter of intermetallic compounds containing Al and Ca were examined. The results are shown in Table 1. For the extraction of the intermetallic compound, a scanning electron microscope: SEM reflected electron image, energy dispersive X-ray spectroscopy: EDX can be used. From the area within the contour of each extracted intermetallic compound, the equivalent circle diameter of the intermetallic compound having an area equal to this area is obtained, and this equivalent circle diameter is defined as the particle diameter of the intermetallic compound. Here, for each test piece, take three cross-sections (transverse cross-section), take one observation image for each cross-section, of the intermetallic compound containing all Al and Ca present in the three observation images The particle diameter was determined, and the maximum value of the particle diameters in the three observation images was taken as the maximum diameter. As described above, the average particle size was obtained by calculating the particle size of an intermetallic compound containing all Al and Ca present in the three observed images. However, intermetallic compounds having a particle size of 0.05 μm or less were excluded because it was difficult to measure the particle size (this is the same in the test examples described later). Therefore, the substantial average particle diameter is smaller than the values shown in Table 1.

  In addition, in the cross section (cross section) of the test piece, take an observation image from both the surface layer region and the central region, the maximum diameter of the intermetallic compound containing Al and Ca in each region, the average particle size, The difference in average particle size was determined. The surface layer area is the area up to 20% of the thickness (4.1 mm to 4.2 mm) of the test piece in the thickness direction from the surface of the test piece, that is, the area from 0.82 mm to 0.84 mm in the thickness direction from the surface. The central region is a region up to ± 10% of the thickness of the test piece from the center in the thickness direction of the test piece toward the surface, that is, a region of 0.82 mm to 0.84 mm including the center in the thickness direction. To do. The maximum diameter and average particle diameter were determined in the same manner as described above. However, the observation image of the central region was taken from the region excluding the center line segregation part.

  Furthermore, the average particle diameter of the intermetallic compound containing Al and Mg was measured. The average particle size of the intermetallic compound was measured in the same manner as the average particle size of the intermetallic compound containing Al and Ca described above. The results are shown in Table 1.

  In addition, the above cast coil material is rewound and cut appropriately to produce a JIS 13B plate test piece (JIS Z 2201 (1998))), based on the metal material tensile test method of JIS Z 2241 (1998). Then, perform a tensile test (mark distance GL = 50mm, tensile speed: 5mm / min) along the casting direction at room temperature (about 20 ° C to 25 ° C), and measure tensile strength (MPa) and elongation (%) did. The results are shown in Table 1 (minimum value of n = 5).

  As shown in Table 1, it can be seen that, in producing a cast material containing Ca in a specific range, a cast material having a small DAS can be obtained by sufficiently increasing the cooling rate during casting. Further, it can be seen that the obtained cast material has a fine intermetallic compound containing Al and Ca, and its size variation is small. Furthermore, the variation in the size of the intermetallic compound containing Al and Ca over the thickness direction of the obtained cast material is small, and the difference or sum between the intermetallic compound containing Al and Ca and DAS is small. It can be seen that not only intermetallic compounds containing Al and Ca but also other intermetallic compounds (such as intermetallic compounds containing Al and Mg) are fine and have little variation. Therefore, it can be seen that the obtained cast material has a structure in which fine and uniform intermetallic compounds are dispersed in a fine cast structure. In addition, when the obtained cast material was investigated, the intermetallic compound containing Al and Mn also existed, and all were fine particles. When the maximum diameter of the intermetallic compound containing Al and Mn was examined in the same manner as described above, it was about 0.3 μm, and it was confirmed that the average particle diameter of the intermetallic compound was 0.3 μm or less.

[Test Example 2]
The ignition temperature of the cast material was examined.

  The ignition test was performed as follows. The above-described cast coil material was rewound and cut to an appropriate length to prepare a test piece (mass: 3 g, n = 3), and a stainless steel board was placed in a small melting furnace. A test piece was placed in Raise the ambient temperature in the melting furnace step by step, hold each temperature for 10 minutes, and check the condition of the test piece. The ambient temperature was confirmed by a thermocouple disposed in the melting furnace, and the temperature was changed by adjusting a heater built in the melting furnace. When confirmed at each temperature, the case where it was not burned was evaluated as “good”, and the case where it was burned was evaluated as “burned”. The results are shown in Table 2.

  As shown in Table 2, as the Ca content increases, it becomes difficult to burn, and it can be seen that the ignition temperature is 600 ° C. or higher, and further 650 ° C. or higher. Further, it can be seen that the sample containing Ca has an ignition temperature increased by 100 ° C. or more, and further 150 ° C. or more, compared with the sample not containing Ca, thereby improving the flame retardancy.

[Test Example 3]
The cast material produced in Test Example 1 was rolled to produce a wrought material (rolled material), and the metal structure was examined.

  Here, each cast coil material was subjected to a solution treatment: 405 ° C. × 17 hours (nitrogen atmosphere, oxygen concentration: 50 mass ppm or less, cooled by water cooling) to produce a solution coil material. The solution coil material was rewound and warm-rolled to produce a rolled plate having a thickness of 0.62 mm. Here, the rolled plate was wound up to obtain a rolled coil material. The warm rolling was performed in a plurality of passes at a working degree (rolling rate): 5% / pass to 40% / pass, a heating temperature of the material plate: 200 ° C. to 350 ° C., and a roll temperature: 100 ° C. to 250 ° C. The obtained rolled coil material was rewound and subjected to warm correction and polishing treatment in order to prepare a polishing plate (thickness: 0.6 mm). Warm correction was performed using the roll leveler apparatus described above (temperature: 300 ° C.). In the above polishing treatment, wet belt type polishing was performed using a # 600 polishing belt (polishing amount: 0.01 mm on each surface). These warm correction and polishing treatments may be omitted.

The obtained polishing plate was cut into an appropriate length to produce a test piece, and the cross section in the direction perpendicular to the rolling direction was observed and analyzed in this test piece using SEM-EDX. SEM observation images (5000 times) are shown in FIGS. 1 (B) and 3 (B). As shown in FIG. 1 (B) and FIG. 3 (B), it can be seen that the fine and round intermetallic compound is uniformly dispersed throughout the entire structure of each test piece. In particular, wrought material obtained using a cast material containing Ca: Sample No. 1-22 is an intermetallic compound with different colors as shown in FIG. It can be seen that particles of different types of intermetallic compounds, such as particles having a light gray color, are adjacently dispersed as a particle group. As a result of X-ray diffraction of this cross section, each intermetallic compound forming the particle group is composed of an intermetallic compound containing Al and Ca such as Al ₂ Ca and an intermetallic compound containing Al and Mg such as Al ₁₂ Mg _17. It was confirmed that. From this, it is considered that the above-mentioned particle group was formed by dividing the intermetallic compound that was connected in a mesh form in the cast material shown in FIG.

  For each test piece (polishing plate), the maximum diameter and average particle diameter of the intermetallic compound containing Al and Ca, the average particle diameter of the intermetallic compound containing Al and Mg, the difference in the maximum diameter of both intermetallic compounds ( (Absolute value), the maximum diameter and average particle diameter of the intermetallic compound containing Al and Ca in the surface layer region and the central region, and the difference in average particle size in both regions were examined. The results are shown in Table 3. Extraction of an intermetallic compound containing Al and Ca and an intermetallic compound containing Al and Mg is performed by image processing the SEM observation image, and each metal present in the observation image is the same as in Test Example 1. The equivalent circle diameter of the intermetallic compound is determined, and this equivalent circle diameter is defined as the particle diameter. And among the particle sizes of each intermetallic compound in the three observed images, the largest particle size is the maximum diameter of the intermetallic compound containing Al and Ca, the maximum diameter of the intermetallic compound containing Al and Mg, did. In addition, the average particle size of the intermetallic compound of each composition existing in the three observed images is the average particle size of the intermetallic compound containing Al and Ca, the average particle size of the intermetallic compound containing Al and Mg It was. The surface layer area is the area up to 20% of the thickness of the test piece (0.6 mm) in the thickness direction from the surface of each test piece, that is, the area from the surface to 0.12 mm in the thickness direction, and the central area is A region from the center in the thickness direction of the test piece toward the surface up to ± 10% of the thickness of the test piece, that is, a region of 0.12 mm including the center in the thickness direction. The maximum diameter and average particle diameter of the surface layer region and the central region are obtained by taking SEM observation images (5000 times) from the surface layer region and the central region, respectively, in the cross section, and applying image processing to the circle as described above. The equivalent diameter was obtained to calculate the particle diameter, and the maximum value and the average value of the three observation images in each region were used. Further, a combustion test was conducted in the same manner as in Test Example 2, and the ignition temperature was examined using the combustion temperature as the ignition temperature. The results are also shown in Table 3 (the lowest temperature among n = 3).

  In addition, the above polishing plate was appropriately cut to produce a plate-like test piece as in Test Example 1, and as in Test Example 1, a tensile test at room temperature (about 20 ° C. to 25 ° C.) (marking distance GL = The tensile strength (MPa) and the elongation (%) were measured (50 mm, tensile speed: 5 mm / min) (number of evaluations: both n = 5). The results are shown in Table 3 (minimum value of n = 5).

  As shown in Table 3, by using a casting material with a small DAS as a raw material, even if it is a magnesium alloy containing Ca in a specific range, it can be satisfactorily applied without cracking etc. I understand that I can do it. It can also be seen that the obtained wrought material has high strength and excellent flame retardancy, such as a tensile strength of 300 MPa or more and an ignition temperature of 600 ° C. or more. Therefore, from Test Examples 1 to 3, a continuous cast material composed of a magnesium alloy containing Ca in a specific range and having a small DAS is excellent in stretch workability such as rolling, and also excellent in flame retardancy. I understand.

  In addition, the obtained wrought material has an intermetallic compound containing Al and Ca and an intermetallic compound containing Al and Mg adjacent to each other, and these two intermetallic compounds are fine and have little variation. It can also be seen that there is little variation in the intermetallic compound containing Al and Ca across the thickness direction of the wrought material, and that the difference in size between the two intermetallic compounds is also small. When the obtained wrought material was examined, an intermetallic compound containing Al and Mn was also present, and the maximum diameter was about 0.3 μm like the cast material. Therefore, it can be said that the average particle size of the intermetallic compound is 0.3 μm or less for the wrought material.

[Test Example 4]
The wrought material (polishing plate) produced in Test Example 3 was warm-pressed to produce a magnesium alloy member.

  Here, polishing plates cut to a predetermined length were prepared, and cylindrical deep drawing (punch shoulder R = 2.0 mm) was performed in a state where each polishing plate was heated to 250 ° C., and the degree of occurrence of cracks was examined. Specifically, when a blank diameter: φ100 mm, a drawing ratio of 2.0, and n = 10 were tested, all samples could be deep drawn without cracking. Therefore, from Test Examples 1 to 4, a wrought material made of a magnesium alloy containing Ca in a specific range and obtained from a continuously cast material having a small DAS is excellent in plastic workability such as press working. I understand.

[Test Example 5]
A plurality of wrought materials (polishing plates) prepared in Test Example 3 were prepared, joined by friction stir welding to produce a joining material, and this joining material was subjected to warm press working to produce a magnesium alloy member.

  Cut the peripheral edge of each polishing plate, and the accuracy of the cut surface is a standard number sequence with centerline average roughness Ra (JIS B 0601 (2001)): 6.3 μm or less (finished symbol with triangle display: ▽ 2 or more ), And the material (width: 210 mm, thickness: 0.6 mm) on which the edge was formed was joined by friction stir welding (probe tip diameter: 6 mm). The obtained bonding material was subjected to warm press processing (heating temperature of the material: 250 ° C.) to produce a cross-sectional casing (magnesium alloy member) having a bottom surface and side walls standing on the bottom surface ( 300mm x 300mm x 50mm).

  As a result, although a part of the joining region was also bent, it was possible to perform press working without causing cracks and fractures in the joining region. Therefore, it can be seen from Test Example 5 that the bonding material made of the wrought material is also excellent in plastic workability such as press working.

  In addition, this invention is not limited to embodiment mentioned above, It can change suitably in the range which does not deviate from the summary of this invention. For example, magnesium alloy composition (type of element contained, content), casting conditions (cooling rate, relationship between gap between casting rolls and gap between nozzle openings, etc.), rolling conditions (material temperature, roll temperature) Etc.) can be changed as appropriate.

  The magnesium alloy wrought material and the magnesium alloy bonding material of the present invention are members of various fields where characteristics such as high strength, high hardness, light weight, and impact resistance are desired, for example, vehicles such as automobiles, trains, airplanes, etc. Components of transport equipment such as airplanes (for example, bodies, frames, bumper parts, etc.), other components of various electrical and electronic equipment (cases, etc.), materials for various storage members such as bags and storage cases Can be suitably used. The magnesium alloy cast material of the present invention and the magnesium alloy cast coil material of the present invention are suitably used as the material of the magnesium alloy stretched material of the present invention, which is obtained by subjecting the cast material to a stretching process such as rolling, extrusion, and forging. be able to. The magnesium alloy member of the present invention can be suitably used for members in the various fields described above. The manufacturing method of the magnesium alloy casting material of the present invention can be suitably used for manufacturing the magnesium alloy casting material.

  100 Casting roll 200 Nozzle 210 Nozzle body 220 Opening

Claims (23)

A magnesium alloy casting material made of a magnesium alloy containing Al,
The magnesium alloy contains Al in an amount of 2% by mass to 11% by mass and Ca in an amount of 0.1% by mass to 10% by mass,
Magnesium alloy cast material characterized in that DAS is less than 4.5 μm. The magnesium alloy contains a first intermetallic compound containing Al and Ca,
2. The magnesium alloy casting according to claim 1, wherein the maximum diameter of the first intermetallic compound is 5 μm or less. The magnesium alloy contains a first intermetallic compound containing Al and Ca,
3. The magnesium alloy casting according to claim 1, wherein an absolute value of a difference between the DAS and the maximum diameter of the first intermetallic compound is 2.5 μm or less. The magnesium alloy contains a first intermetallic compound containing Al and Ca,
The magnesium alloy casting material according to any one of claims 1 to 3, wherein a sum of the maximum diameter of the first intermetallic compound containing DAS, the Al, and Ca is 5 µm or less. The magnesium alloy contains a first intermetallic compound containing Al and Ca, and a second intermetallic compound containing Al and Mg,
The magnesium according to any one of claims 1 to 4, further comprising a location where both intermetallic compounds of the first intermetallic compound and the second intermetallic compound are adjacent to each other. Alloy casting material.   6. The magnesium alloy casting material according to claim 2, wherein an average particle diameter of the first intermetallic compound containing Al and Ca is 2 μm or less.   In the magnesium alloy cast material, a region up to 20% of the thickness of the cast material in the thickness direction from the surface is defined as a surface layer region, and the cast material of the cast material is directed from the center in the thickness direction of the cast material toward the surface side. When the region up to 10% of the thickness is a central region, the maximum diameter of the first intermetallic compound containing Al and Ca in each of the surface layer region and the central region is 5 μm or less, and the average The particle size is 2 μm or less, and the difference between the average particle size in the surface layer region and the average particle size in the central region is within 20%. The magnesium alloy casting material according to any one of the above. The magnesium alloy contains at least one of a second intermetallic compound containing Al and Mg and a third intermetallic compound containing Al and Mn,
The magnesium according to any one of claims 2 to 7, wherein an average particle diameter of at least one of the second intermetallic compound and the third intermetallic compound is 2 µm or less. Alloy casting material.   The magnesium alloy is further at least one selected from Zn, Mn, Si, Sr, Y, Cu, Ag, Ce, Sn, Li, Zr, Be, Ni, Au and rare earth elements (excluding Y and Ce). 9. The magnesium alloy casting material according to claim 1, wherein the total amount of seed elements is 7.3% by mass or more with Al, and the balance is Mg and impurities.   A magnesium alloy cast coil material, comprising a plate-like material having a length of 100 m or more, made of the magnesium alloy cast material according to any one of claims 1 to 9. A method for producing a magnesium alloy casting material for producing a casting material comprising a magnesium alloy containing Al,
A preparation step of preparing a molten magnesium alloy containing Al in a range of 2 mass% to 11 mass% and Ca in a range of 0.1 mass% to 10 mass%;
A casting process for producing a cast material by continuously casting the molten metal by a twin roll continuous casting machine comprising a pair of casting rolls,
A method for producing a magnesium alloy cast material, wherein a cooling rate during casting is 650 ° C./second or more. When the pair of the gap between the casting rolls g _r, the distance between the opening of the nozzle for discharging the molten metal toward the casting rolls and g _n, such that g _n <g _r, between the casting rolls 12. The method for producing a magnesium alloy cast material according to claim 11, wherein at least one of the gap and the gap between the nozzle openings is adjusted. In the preparation step,
13. The magnesium alloy casting material according to claim 11 or 12, wherein a molten Ca-containing molten metal containing a predetermined amount of Ca is produced, and then the remaining Ca is added to produce the molten metal. Manufacturing method. A magnesium alloy wrought material composed of a magnesium alloy containing Al,
The magnesium alloy is
Al is contained in an amount of 2 to 11% by mass, and Ca is contained in an amount of 0.1 to 10% by mass.
Furthermore, containing a first intermetallic compound containing Al and Ca, and a second intermetallic compound containing Al and Mg,
A magnesium alloy wrought material characterized in that there is a particle group in which particles of both intermetallic compounds of the first intermetallic compound and the second intermetallic compound are adjacent to each other.   15. The magnesium alloy wrought material according to claim 14, wherein an absolute value of a difference between the maximum diameter of the first intermetallic compound and the maximum diameter of the second intermetallic compound is 2 μm or less.   16. The expanded magnesium alloy material according to claim 14, wherein the first intermetallic compound containing Al and Ca has a maximum diameter of 5 μm or less and an average particle diameter of 2 μm or less.   In the magnesium alloy wrought material, a region up to 20% of the thickness of the wrought material in the thickness direction from the surface is defined as a surface layer region, and the region from the center in the thickness direction of the wrought material toward the surface side. When the region up to 10% of the thickness of the wrought material is a central region, the maximum diameter of the first intermetallic compound containing Al and Ca in each of the surface layer region and the central region is 5 μm. The average particle size is 2 μm or less, and the difference between the average particle size in the surface region and the average particle size in the central region is 20% or less. The magnesium alloy wrought material according to any one of 14 to 16. The magnesium alloy contains at least one of a second intermetallic compound containing Al and Mg and a third intermetallic compound containing Al and Mn,
18. The magnesium according to claim 14, wherein an average particle diameter of at least one of the second intermetallic compound and the third intermetallic compound is 2 μm or less. Alloy wrought material.   The magnesium alloy wrought material according to any one of claims 14 to 18, wherein the magnesium alloy wrought material has an ignition temperature of 600 ° C or higher and a tensile strength of 300 MPa or higher.   The magnesium alloy is further at least one selected from Zn, Mn, Si, Sr, Y, Cu, Ag, Ce, Sn, Li, Zr, Be, Ni, Au and rare earth elements (excluding Y and Ce). The magnesium alloy wrought material according to any one of claims 14 to 19, wherein the total amount of seed elements is 7.3% by mass or more with Al, and the balance is Mg and impurities.   A magnesium alloy wrought material obtained by subjecting the magnesium alloy cast material according to any one of claims 1 to 9 to a wrought process.   A magnesium alloy member obtained by pressing the magnesium alloy wrought material according to any one of claims 14 to 21 at a heating temperature of room temperature to 500 ° C. A plurality of magnesium alloy wrought materials according to any one of claims 14 to 21,
A magnesium alloy joining material comprising: a joining region in which the magnesium alloy wrought materials are joined by friction stir welding.