JP2018192584A - Production method of magnesium base material and production method of magnesium member - Google Patents

Abstract

To provide a magnesium base material having excellent metallic sheen and a production method of the same.SOLUTION: Provided is a magnesium base material having a flat surface part or a curved surface part, where the arithmetic average roughness Ra of a surface at the flat surface part or the curved surface part is 0.035 μm or less and an average particle diameter is 5.0 μm or less in a surface region from the surface to 200 μm in a depth direction. The magnesium base material can be suitably produced by a production method of a magnesium base material, comprising: a molding step A of molding magnesium and obtaining a magnesium molded body having a flat surface part or a curved surface part and a polishing step B of polishing the surface of the magnesium molded body by jetting an abrasive and making it collide with the magnesium molded body. The abrasive has a gel wich forms a core and abrasive grains supported at least on the surface of the gel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnesium base material, a magnesium member, and a method for producing the same.

  Magnesium base materials using magnesium and magnesium alloys (hereinafter sometimes referred to as “magnesium-based metals”) and members thereof are lightweight and have high specific strength, and thus have been conventionally used in aircraft, railway vehicles, automobiles, etc. It is applied to a wide range of applications such as parts for transportation equipment, household appliances such as TVs and refrigerators, casings for portable equipment such as notebook personal computers and cameras, architectural interior members, medical equipment and leisure goods.

On the other hand, in general, the metallic luster inherent to magnesium-based metals depends on the surface condition of the magnesium molded body obtained by molding the magnesium-based metal, and the surface is oxidized or roughened so that the luster is fully exhibited. Can not. Further, burrs and the like are generated in the molding process of the magnesium molded body.
Therefore, a magnesium molded body obtained by molding magnesium or a magnesium alloy is usually subjected to manual polishing or buffing in order to remove surface oxide film or burrs generated in the molding process or to smooth the surface. A polishing process such as mechanical polishing or electrochemical polishing such as electrolytic polishing is performed (for example, Patent Documents 1 and 2).

Japanese Patent Laying-Open No. 2015-25181 JP 2001-49493 A

  There is a demand for a magnesium base material (member) for various uses to have a more luxurious appearance by exhibiting the metallic luster of magnesium or a magnesium alloy. In order to exhibit metallic luster, a polishing process or the like may be performed. However, when conventional polishing (mechanical polishing or the like) as disclosed in Patent Documents 1 and 2 is performed on the magnesium molded body, a rough portion is likely to occur due to deep scratches or the like. Furthermore, in order to make it a base material and a member, when it has a complicated shape, there is a part where polishing itself is difficult. In order to smooth the rough portion and the unpolished portion, it is considered that the surface of the magnesium molded body is deeply dissolved by electrochemical polishing after mechanical polishing or the like.

  On the other hand, the magnesium molded body has fewer defects on its surface, and as it progresses into the interior, the number of defects (internal defects) tends to increase, and the grain size of the crystal grains tends to increase, and the strength tends to vary. . For this reason, even if electrochemical polishing or the like is performed to deeply dissolve the surface of the magnesium molded body, sufficient smoothness cannot be obtained due to exposure of internal defects. And when the internal defect is exposed, the surface becomes rough, so that the metallic luster of the magnesium-based metal cannot be exhibited. Moreover, there is a possibility that the durability of the magnesium base material itself may be reduced due to a decrease in the area with few structural defects near the surface.

  Under these circumstances, in order to achieve excellent metallic luster for magnesium base materials and members that have been subjected to surface treatment of magnesium molded bodies, what kind of state should these magnesium base materials and members be? I wasn't sure enough. Under such circumstances, an object of the present invention is to provide a magnesium substrate having an excellent metallic luster and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventor has found that the following inventions meet the above object, and have reached the present invention.

That is, the present invention relates to the following inventions.
<1> A magnesium substrate having a flat surface portion or a curved surface portion,
The arithmetic average roughness Ra of the surface of the flat surface portion or the curved surface portion is 0.035 μm or less,
The magnesium base material whose average particle diameter of (alpha) phase is 5.0 micrometers or less in the surface area | region to 200 micrometers in the depth direction from the surface.
<2> The magnesium substrate according to <1>, which has an opening and / or an uneven portion.
<3> The magnesium substrate according to <1> or <2>, wherein the maximum height roughness Rz of the surface of the flat surface portion or the curved surface portion is 0.20 μm or less.
<4> A magnesium member having a protective film on the magnesium substrate according to any one of <1> to <3>.
<5> A forming step A for forming a magnesium-based metal to obtain a magnesium molded body having a flat surface portion or a curved surface portion;
A polishing step of polishing the surface of the flat surface portion or the curved surface portion of the magnesium molded body so as to have an arithmetic average roughness Ra of 0.035 μm or less by injecting and colliding an abrasive with the magnesium molded body. B and
A method for producing a magnesium substrate, wherein the abrasive is an abrasive having a core gel, water, and at least abrasive grains carried on the surface of the gel.
<6> The method for producing a magnesium substrate according to <5>, wherein the water content of the abrasive is 15% by mass or more and 20% by mass or less.
<7> The method for producing a magnesium substrate according to <5> or <6>, wherein the size of the abrasive grains is 1 μm or less in diameter.
<8> The method for producing a magnesium substrate according to any one of <5> to <7>, wherein the gel is gelatin.

  ADVANTAGE OF THE INVENTION According to this invention, the magnesium base material and member which have the outstanding metal luster, and its manufacturing method are provided.

It is a figure which shows the surface roughness curve of the plane part surface of the magnesium base material (1) obtained in Example 1. FIG. It is a figure which shows the surface roughness curve of the plane part surface of the magnesium molded object (1 ') (before grinding | polishing) of Example 1. FIG. It is a figure which shows the surface roughness curve of the plane part surface of the magnesium base material (2) obtained by the comparative example 1. FIG. It is a figure which shows the surface roughness curve of the plane part surface of the magnesium base material (3) obtained by the comparative example 2. FIG. 2 is a digital microscope image of a surface region of a flat portion of a magnesium substrate (1) obtained in Example 1. FIG.

  DESCRIPTION OF EMBODIMENTS Embodiments of the present invention will be described in detail below. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention will be described below unless the gist thereof is changed. It is not limited to the contents.

1. Magnesium base material of the present invention The present invention is a magnesium base material having a flat surface portion or a curved surface portion, the arithmetic average roughness Ra of the surface of the flat surface portion or the curved surface portion is 0.035 μm or less, and from the surface to the depth direction In addition, the present invention relates to a magnesium substrate (hereinafter, sometimes referred to as “magnesium substrate of the present invention”) having an α phase average particle size of 5.0 μm or less in a surface region of up to 200 μm. The magnesium substrate of the present invention has excellent metallic luster as a substrate using a magnesium-based metal.

  The present invention also provides a molding step A for forming a magnesium-based metal to obtain a magnesium molded body having a flat surface portion or a curved surface portion, and by injecting and colliding an abrasive with the magnesium molded body, thereby forming the magnesium molded body. And a polishing step B for polishing the surface of the substrate, wherein the abrasive is a polishing material having a core gel, water, and at least abrasive grains carried on the surface of the gel. Hereinafter, it may be described as “a method for producing a magnesium substrate of the present invention”. According to the method for producing a magnesium substrate of the present invention, a magnesium substrate having excellent metallic luster can be produced stably.

  The magnesium substrate of the present invention is obtained by polishing a magnesium molded body and having a predetermined roughness and a predetermined crystal grain size. The magnesium molded body forming the magnesium base is molded from magnesium and a magnesium alloy (magnesium-based metal). Magnesium-based metals that serve as raw materials for magnesium compacts include, for example, Mg, Mg—Al alloys (AM), Mg—Zn alloys (Z), Mg—Al—Zn alloys (AZ), and Mg—Zn. -Zr alloy (ZK), Mg-Cu-Zn alloy (ZC), Mg-RE-Zr alloy (EZ), Mg-Zr-Re-Ag alloy (QE), Mg-Y -RE alloys (WE), Mg-Al-Si alloys (AS), Mg-Al-RE alloys (AE) and Mg-Mn alloys (M) for casting magnesium alloys (for die casting) , Including thixomolds) and magnesium alloys for rolling (rolled plate, extruded bar, extruded profile), alloys obtained by adding Ca to these alloys (AZX, AMX, etc.), and the like. Specifically, magnesium alloys such as AZ91D or AM60B, AZ31B, and AZX911 can be used.

  The magnesium substrate of the present invention has a flat surface portion or a curved surface portion. When there is a flat surface portion or a curved surface portion, when it has an appropriate surface property, it becomes a main portion having excellent glossiness. On the other hand, when the surface texture is not appropriate, no gloss is produced. In the present invention, the region satisfying the predetermined surface roughness and crystal grain size may be a portion (glossy portion) that needs to be glossy depending on the shape or use of the magnesium base material (member). That's fine.

  As for the magnesium base material of this invention, arithmetic mean roughness Ra of the surface of a plane part or a curved-surface part is 0.035 micrometer or less. The present inventors have found that the arithmetic average roughness Ra needs to achieve this range in order to exhibit excellent gloss as a magnesium base material. In order to make the metallic luster more excellent, the arithmetic average roughness Ra is preferably 0.030 μm or less.

  In addition, when there is a locally rough point on the surface of the magnesium base material of the present invention, deterioration tends to occur from that point. In addition, if there are local rough spots, gloss may be poor when visually recognized. Therefore, the maximum height roughness Rz of the flat surface portion or curved surface portion of the magnesium base material of the present invention is preferably 0.30 μm or less, more preferably 0.20 μm or less, and further preferably 0.15 μm or less.

  The arithmetic average roughness Ra and the maximum height roughness Rz are preferably managed together, and more preferably, the arithmetic average roughness Ra is 0.035 μm or less, and the maximum height roughness Rz is It is 0.20 μm or less. More preferably, the arithmetic average roughness Ra is 0.030 μm or less, and the maximum height roughness Rz is 0.15 μm or less.

  In the present application, “arithmetic mean roughness (Ra)” and “maximum height roughness (Rz)” are values measured by a method based on “JIS B 0601-2013 surface roughness—definition and indication”. . Specific measurement methods will be described later in Examples.

Further, the magnesium base material of the present invention has an average particle diameter of α phase (average) in a surface region (hereinafter sometimes simply referred to as “surface region”) from the surface of the base material to 200 μm in the depth direction. Crystal grain size) is 5.0 μm or less. By having such an average particle diameter, it is possible to reduce poor gloss caused by large crystal grains in the surface region of the magnesium base material. In addition, if a large amount of the crystal grain size is mixed in the surface region, the abrasiveness changes depending on the crystal grain size, and it is difficult to achieve the arithmetic average roughness Ra and the maximum height roughness Rz described above. Or there may be an increase in the area where preferable Ra and Rz are not achieved. In addition, the smaller the crystal grain size, the higher the strength of the metallographic structure due to the crystal grain size can be expected. May decrease. Furthermore, since the region where the crystal grain size is large is large on the inner layer side of the magnesium molded body, it is in a state where polishing or the like is excessive, and there is a possibility that the substrate dimension changes or the like occurs.
In order to show excellent gloss, strength, etc., this average particle size is preferably 4.0 μm or less.

  In the present application, “average grain size (average crystal grain size)” means an arbitrary cross section of a magnesium base material having a depth of 200 μm × width of 300 μm from the surface of the base material using a digital microscope. In the region, the crystal grain diameters of 20 arbitrary α-phase crystal grains are measured and averaged. When the crystal grains were not spherical, the average value was obtained with the maximum diameter of the crystal grains as the crystal grain diameter.

  There is no restriction | limiting in particular about the magnitude | size and shape of the magnesium base material of this invention, According to the objective, it can select. For example, the overall shape may be a plate shape, a rod shape, a tubular shape, or the like. In addition to these, in consideration of the shape as a housing or the like according to the use of the magnesium base material (member), the one formed into the shape can be targeted.

  Moreover, the shape which has an opening part or / and an uneven | corrugated | grooved part may be sufficient as the magnesium base material of this invention. When these portions (openings or / and uneven portions) are provided, the degree of freedom in shape design as the base material (member) is improved. Here, the concavo-convex part can be assumed to be a visible concavo-convex part, and this “visible” means an concavo-convex part having a height of 1 mm or more in an arbitrary cross section.

  Moreover, durability can further be improved by forming a protective film on the surface of the magnesium base material of this invention. Examples of the protective film include a transparent chemical conversion film and a coating film, and a conventionally known method can be used as a protective film forming method. Since the magnesium base material of the present invention has a high surface smoothness, a protective film can be formed uniformly. Therefore, the magnesium base material is more suitable as a base material for forming a protective film than conventional magnesium base materials. In this application, the magnesium base material which has this protective film is called a magnesium member.

  The magnesium base material (member) of this invention can be used for various uses. For example, parts for transportation equipment such as airplanes, railway cars, automobiles, household appliances such as TVs and refrigerators, casings for portable equipment such as notebook personal computers and cameras, architectural interior members, medical equipment, golf and fishing gear It can be used as a magnesium member for applications such as leisure goods.

2. The manufacturing method of a magnesium base material Moreover, this invention relates to the manufacturing method of the magnesium base material of this invention as mentioned above. By this method for producing a magnesium substrate of the present invention, a magnesium substrate having a structure with high smoothness can be produced while maintaining a region with few surface structural defects. This makes it easy to obtain a magnesium substrate having an excellent metallic luster. Moreover, the manufacturing method of this invention is a method suitable for manufacture of the magnesium base material (member) of this invention mentioned above.

[Magnesium forming step A]
The manufacturing method of the magnesium base material of this invention has the formation process A which shape | molds magnesium or a magnesium alloy, and obtains the magnesium molded object which has a plane part or a curved surface part. In this forming step A, magnesium or a magnesium alloy (magnesium-based metal) is heated to an appropriate forming temperature as the magnesium-based metal and formed into a shape according to the use of the base material.

The forming method is not particularly limited, and can be formed by a known thixomold method, die casting method, rolling, or the like.
In particular, the thixomold method is preferably used because it is easy to produce a magnesium molded body having excellent dimensional accuracy and excellent mechanical properties and surface characteristics. A magnesium molded body formed by the thixomold method is easy to obtain a metallic luster by polishing.

  There is no restriction | limiting in particular about the magnitude | size and shape of a magnesium molded object, According to the use of a magnesium base material and a member, it can design suitably. Specifically, a design based on the amount of polishing and the like may be used as a base shape for making the shape and shape of the magnesium base material as described above.

  Moreover, it is preferable to shape | mold a magnesium molded object so that the average particle diameter of (alpha) phase may be 5.0 micrometers or less in a surface area | region. In the polishing step B described later, since the smoothness of the surface can be improved without deeply polishing the surface of the magnesium molded body, the average particle diameter of the α phase in the surface region of the magnesium molded body If it is 5.0 micrometers or less, the average particle diameter of (alpha) phase will be maintained also in the surface area | region of the magnesium base material obtained.

  In particular, the magnesium molded body of the present invention preferably further has a shape having an opening or an uneven portion. In the manufacturing method of the present invention, in the polishing step B described later, gel is used as the core of the abrasive, and the gel is deformed and polished along the shape. It is. Therefore, the magnesium substrate having a shape having an opening or a visually concavo-convex portion manufactured by the manufacturing method of the present invention can have an excellent metallic luster as a whole.

[Polishing process B]
The polishing step B is a step of polishing the surface of the magnesium molded body by injecting and colliding the abrasive with the magnesium molded body molded in the molding process A. Further, as the abrasive, an abrasive having gel as a core, water, and at least abrasive grains carried on the surface of the gel is used.

By this polishing step B, the glossiness of the magnesium base material after the polishing step is improved. In the production method of the present invention, in the polishing step B, the gel is softened by the heat generated when the abrasive contacts the molded magnesium molded body by using the gel as the core of the abrasive. Since polishing can be performed along the shape, it is considered that the surface can be finished with high smoothness without being deeply polished.
Further, since the impact generated when the abrasive and the magnesium molded body come into contact with each other can be absorbed by the gel, it is considered that the surface of the magnesium molded body is not easily damaged.

Further, by adopting such a manufacturing method, there is little variation in the smoothness between the areas subjected to the polishing step regardless of the shape and size of the magnesium substrate, and the area where the magnesium substrate polishing process is performed A magnesium base material having excellent smoothness as a whole can be obtained.
Moreover, the oxide film which may exist on the surface of the molded body can be efficiently removed.

  In addition, magnesium dust generated by polishing magnesium-based metals is more likely to ignite than stainless steel and iron, and dry polishing of magnesium may be dangerous. Depending on the property, the polishing waste is adsorbed and the scattering of the polishing waste is suppressed, so that the risk of ignition and the like is remarkably reduced. Since dry polishing can also suppress oxidation of the magnesium compact due to moisture, the polishing step B is preferably dry polishing.

  The polishing conditions in the polishing step B are appropriately determined depending on the abrasive injection method, injection speed, etc., but polishing so that the arithmetic average roughness Ra of the surface of the magnesium substrate is 0.035 μm or less. Is preferred. By doing in this way, the obtained magnesium base material is excellent in metallic luster.

  Further, in the polishing step B, it is preferable to polish so that the maximum height roughness Rz is 0.30 μm or less.

Moreover, it is preferable to manage both the arithmetic average roughness Ra and the maximum height roughness Rz, the arithmetic average roughness Ra is 0.035 μm or less, and the maximum height roughness Rz is 0.20 μm or less. It is more preferable to polish so that the arithmetic average roughness Ra is 0.030 μm or less and the maximum height roughness Rz is 0.15 μm or less.
By doing in this way, the magnesium base material which has the outstanding metal luster can be obtained more reproducibly.

(Abrasive)
The abrasive used in the production method of the present invention (hereinafter sometimes simply referred to as “abrasive” or “abrasive used in the present invention”) is a core gel, water, and at least the gel. Abrasive grains carried on the surface. The abrasive used in the present invention has a function of physically polishing the surface of the magnesium molded body by colliding with the molded magnesium molded body.

  The shape of the abrasive used in the present invention is not particularly limited, and may be a spherical shape, an oval shape, or a shape in which a part of these shapes is flattened.

  The size of the abrasive used in the present invention is substantially equal to the size of the gel serving as a nucleus. The size of the abrasive used in the present invention is appropriately determined depending on the size of the abrasive grains, the shape and structure of the magnesium molded body, and the like. The smaller the size of the abrasive, the more detailed it can be polished. On the other hand, the larger the abrasive, the higher the polishing speed and the shorter the polishing time.

On the other hand, if the abrasive is too small, the amount of abrasive particles carried on the surface is small and cannot be sufficiently polished, or the impact when the abrasive contacts the surface of the magnesium molded body can be sufficiently mitigated. The surface may become rough. On the other hand, if the abrasive is too large, the abrasive does not reach the details depending on the shape of the magnesium molded body, making it difficult to polish and removing the oxide film. For this reason, although depending on the shape of the magnesium molded body, the size of the abrasive is usually 0.1 to 5.0 mm in diameter.
When the abrasive is in a shape other than spherical, the longest diameter of the abrasive is taken as the diameter. The size of the abrasive is a value obtained by averaging the diameters of 100 arbitrary abrasives.

The size of the abrasive is appropriately selected depending on the shape of the magnesium molded body. In the flat molded body and the flat portion of the molded body, an abrasive having a diameter of 0.3 to 3.0 mm is used. Preferably, a diameter of 0.5 to 2.0 mm is used.
In addition, when the magnesium molded body has a fine structure portion, the size of the abrasive is preferably 0.1 to 1.0 mm in diameter for polishing the fine structure portion, and 0.1 to 0. More preferably, it is 5 mm.

  In the abrasive used in the present invention, the gel serving as the nucleus develops elasticity by absorbing the solution (water), so that the solution is absorbed and used. The elastic modulus of the abrasive can be adjusted as appropriate by adjusting the amount of the solution to be absorbed, and may be adjusted and used within a range that does not damage the magnesium compact excessively by abrasive grains when it collides with the magnesium compact. .

  The solution used at this time is generally water. The water includes a mixed solution containing water.

The water content of the abrasive is substantially the water content of the gel.
If the water content of the abrasive is too high, the adhesive of the abrasive will increase, and the adhesiveness to the magnesium molded body will increase, so that the polishing power may be impaired, and the surface of the magnesium molded body will be easily oxidized. It is difficult to remove the oxide film. On the other hand, if the water content of the abrasive is too low, the abrasive is not soft enough to easily reduce the impact when it collides with the magnesium molded body, and the surface is easily roughened.

Therefore, the moisture content of the abrasive is preferably 20% by mass or less with respect to the mass of the abrasive. Moreover, it is preferable that the lower limit of the moisture content of the abrasive is 15% by mass or more. In addition, when the solution used is a mixed solution containing water, the moisture content means the amount of the mixed solution contained in the abrasive.
The moisture content of the abrasive can be measured with, for example, an electric resistance type moisture ticker (for example, Sato Keiki Seisakusho SK-940A).

  The gel is a core part of the abrasive used in the present invention, and has a role of mitigating impact at the time of collision between the abrasive and the magnesium molded body and preventing the magnesium molded body from being damaged excessively by the abrasive grains. .

  Examples of the gel include gelatin, pectin, and agar. Preferred is gelatin.

  The size of the gel is substantially the same as the size of the abrasive.

  As described above, the gel absorbs moisture and exhibits viscoelasticity, whereby the abrasive grains can be easily carried on the surface of the gel.

The abrasive has a role of removing impurities such as an oxide film from the surface of the magnesium molded body, polishing the surface of the magnesium molded body, and smoothing.
The abrasive grains only need to be supported on at least the surface of the gel, and may be present not only on the surface of the gel but also inside the gel. Moreover, as long as the abrasive grain carried | supported on the surface of the gel protrudes from the surface of a gel in the range which can grind the surface of a magnesium molded object, a part of abrasive grain may exist in the inside of a gel.

  Examples of the abrasive grains include diamond, carbon silicon, alumina, or a mixture of two or more of these, and diamond is preferred.

  The size of the abrasive grains may be appropriately selected depending on the size of the abrasive and the shape and structure of the magnesium molded body, but is preferably 1 μm or less, and more preferably 0.25 μm or less. When the abrasive grains are too small, the polishing efficiency is lowered, and when the abrasive grains are too large, it is difficult to smoothly polish the surface of the magnesium molded body.

  The combination of the gel and the abrasive can be appropriately selected depending on the purpose, but the preferred combination is that the gel is gelatin and the abrasive is diamond.

  What is necessary is just to determine suitably the ratio of a gel and an abrasive grain according to the magnitude | size and shape of a magnesium molded object, and the intended purpose of a magnesium molded object.

(Method of spraying abrasive)
A method for injecting the abrasive is not particularly limited, and examples thereof include a method using compressed air and a method using centrifugal force of an impeller, and a method using centrifugal force of an impeller is preferable.

  As an apparatus which can inject | pour abrasives using the centrifugal force by an impeller and can grind | polish, the Aero wrap made from Yamato towers is mentioned, for example.

The size of the abrasive to be selected, the injection speed of the abrasive, the injection amount, and the like are appropriately selected depending on the size and shape of the magnesium molded body.
For example, when the magnesium compact is thin, the impact when the abrasive collides with the magnesium compact can be mitigated by reducing the injection amount of the abrasive.

  The polishing time may be appropriately selected in consideration of the size of the abrasive to be selected, the injection speed of the abrasive, and the injection amount. For example, the polishing time may be 1 minute, 3 minutes, 5 minutes, or 10 minutes.

In the manufacturing method of the present invention, the electrolytic polishing step C may be performed after the polishing step B. Since the magnesium substrate after the polishing step B is smooth and has few defects in the surface region, it can be uniformly electropolished in the electropolishing step C.
The method of electrolytic polishing is not particularly limited, and for example, a conventionally known method such as Japanese Patent Application Laid-Open No. 2001-49493 and Japanese Patent Application Laid-Open No. 2006-135898 can be implemented.

In the manufacturing method of the present invention, the protective film forming step D may be performed after the polishing step B. In addition, when performing the electrolytic polishing process C after the polishing process B, it is preferable to perform the protective film forming process D after the electrolytic polishing process C.
The protective film forming method can be appropriately selected from conventionally known methods according to the purpose.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to these.

[Example 1]
A magnesium alloy (AZ91D) was molded by a thixomold method to obtain a magnesium molded body (1 ′) having a length of 70 mm, a width of 40 mm, and a thickness of 2 mm. The magnesium molded body (1 ′) was processed so as to have a shape having an opening, a protrusion having a width of 2 mm, a height of 1 mm, and a depth of 30 mm, and a flat portion.
Next, the molded magnesium molded body (1 ′) was polished by using an aero lapping device (YT-300) manufactured by Yamashita Towers to obtain a magnesium substrate (1). The magnesium molded body (1 ′) was polished by changing the operating conditions of the abrasive and the apparatus to be used at the opening, the convex portion, and the flat portion. Each condition is shown below.

Opening Abrasive: A fine sample (# 20000, size 0.1-0.5 mm) manufactured by Yamashita Towers was used by adjusting the moisture content to 16.5%. The water content was measured with Sato Meters SK-940A.
Conveyor speed: 10rpm
Polishing time: 3 minutes

-Convex part and plane part Abrasive: A standard sample (# 20000, size 0.5-2.0 mm) made by Yamashita Towers was used by adjusting the water content to 16.5%. The water content was measured with Sato Meters SK-940A.
Conveyor speed: 30rpm
Polishing time: 3 minutes

[Comparative Example 1]
The same magnesium molded body (1 ′) as in Example 1 was used as the magnesium molded body. Using a # 2500 sandpaper, it was polished by hand for 3 minutes to obtain a magnesium substrate (2). In addition, since it was not able to grind | polish an opening part and a convex part by grinding | polishing by hand, only the plane part was grind | polished.

[Comparative Example 2]
The same magnesium molded body (1 ′) as in Example 1 was used as the magnesium molded body. Using a Picar metal polish (manufactured by Nippon Abrasive Industry Co., Ltd.), it was polished by hand for 3 minutes to obtain a magnesium substrate (3). In addition, since it was not able to grind | polish an opening part and a convex part by grinding | polishing by hand, only the plane part was grind | polished.

[Evaluation]
1. Surface roughness The obtained magnesium base material (1) surface roughness was measured using Surfcom 5000DX (cut-off value 0.25 mm) manufactured by Tokyo Seimitsu based on JIS B 0601-2013. The surface roughness was defined as an average value obtained by measuring five points in a 30 mm × 30 mm range of the flat portion. The results are shown in Table 1. Moreover, the surface roughness curve obtained by the measurement is shown in FIG.
For measurement, a stylus having a tip radius of 2 μmR was used, and the measurement speed was 0.3 mm / second, the cutoff value was 0.25 mm, and the measurement length was 1.25 mm.

  The surface roughness of the magnesium molded body (1 '), the magnesium substrate (2) and the magnesium substrate (3) was measured in the same manner. The results are shown in Table 1. Moreover, each surface roughness curve obtained by the measurement is shown in FIGS.

2. Average crystal grain size of α phase The obtained magnesium base material (1) was embedded in an epoxy resin (Specifix 20 made by Marumoto Struers), and the observation portion of the flat part was cut using a cutting machine. A cross section was cut out. After the cut section was polished by buffing (conditions), the cross section of the substrate was observed with a digital microscope (VHX-2000 manufactured by Keyence) at 1000 times. The results are shown in FIG. The average crystal grain size was obtained by measuring and averaging the grain sizes of any 20 α-phase crystal grains in a measurement region of 200 μm in the depth direction and 300 μm in the width direction from the substrate surface. The results are shown in Table 1.

  The magnesium molded body (1 '), the magnesium base material (2) and the magnesium base material (3) were also evaluated in the same manner. The results are shown in Table 1.

  As shown in Table 1 and FIGS. 1 to 4, the magnesium base material (2) of Comparative Example 1 has almost the same arithmetic average roughness Ra and maximum height roughness Rz as the magnesium molded body (1 ′) before treatment. There wasn't. Moreover, the smoothness of the surface is falling by processing a magnesium base material (3). On the other hand, it turns out that the magnesium base material (1) of Example 1 has high smoothness compared with the magnesium molded object (1 ') before a process.

  The average crystal grain size of the magnesium substrate (1) was 5.0 μm. In Comparative Examples 1 and 2, the average crystal grain size was 5.0 μm. However, since Comparative Examples 1 and 2 have lower surface smoothness than Example 1, Comparative Examples 1 and 2 Further polishing is necessary to increase the smoothness of the surface. Therefore, in Comparative Examples 1 and 2, in order to obtain the same surface smoothness as in Example 1, it is considered that polishing is performed from the surface to a deeper region, and the average crystal grain size becomes large.

3. Evaluation of metallic luster When the obtained magnesium substrate (1), magnesium substrate (2), and magnesium substrate (3) were visually confirmed, the magnesium substrate (1) had openings and protrusions. Nevertheless, it had a metallic luster as a whole. On the other hand, the magnesium base material (2) and the magnesium base material (3) were partially scratched or whitened, and in particular, the openings, convex portions, and the vicinity thereof were whitish. This is presumably because the oxide film remained because the opening and the convex portion could not be polished.

  About the magnesium base material (1) which was favorable by visual evaluation, the glossiness was measured using the photometer. For comparison, the glossiness of the magnesium molded body (before treatment) was also measured. The glossiness was measured at five points using a gloss meter (GM-60Plus, manufactured by Konica Minolta) at a measurement angle of 60 °, and an average was obtained. The gloss of the magnesium molded body was 143.2 GU, the gloss of the magnesium substrate (1) was 562.6 GU, and it was confirmed that the magnesium substrate (1) had excellent gloss.

  The magnesium substrate of the present invention has an excellent metallic luster regardless of the shape and size. Therefore, it can adapt to various uses and is industrially useful.

Claims (8)

A magnesium substrate having a flat surface portion or a curved surface portion,
The arithmetic average roughness Ra of the surface of the flat surface portion or the curved surface portion is 0.035 μm or less,
The magnesium base material whose average particle diameter of (alpha) phase is 5.0 micrometers or less in the surface area | region to 200 micrometers in the depth direction from the surface.   The magnesium base material of Claim 1 which has an opening part and / or an uneven | corrugated | grooved part.   The magnesium base material according to claim 1 or 2, wherein a maximum height roughness Rz of the surface of the flat surface portion or the curved surface portion is 0.20 µm or less.   The magnesium member which has a protective film on the magnesium base material in any one of Claims 1-3. A molding step A for forming a magnesium-based metal to obtain a magnesium molded body having a flat surface portion or a curved surface portion, and
A polishing step of polishing the surface of the flat surface portion or the curved surface portion of the magnesium molded body so as to have an arithmetic average roughness Ra of 0.035 μm or less by injecting and colliding an abrasive with the magnesium molded body. B and
A method for producing a magnesium substrate, wherein the abrasive is an abrasive having a core gel, water, and at least abrasive grains carried on the surface of the gel.   The manufacturing method of the magnesium base material of Claim 5 whose water content of the said abrasive is 15 mass% or more and 20 mass% or less.   The method for producing a magnesium substrate according to claim 5 or 6, wherein the size of the abrasive grains is 1 µm or less in diameter.   The said gel is a manufacturing method of the magnesium base material in any one of Claims 5-7 which is gelatin.