JP4253845B2 - Magnesium alloy wire, method for producing the same, and magnesium alloy molded body - Google Patents

Description

  The present invention relates to a magnesium alloy material excellent in forgeability, a method for producing the material, and a magnesium alloy molded body obtained by forging the material. In particular, the present invention relates to a magnesium alloy material having a large diameter and excellent forging processability at a relatively low temperature.

  Magnesium alloys are lighter than aluminum and have a higher specific strength and specific rigidity than steel and aluminum, and have been widely used for bodies of various electrical products in addition to aircraft parts and automobile parts. Further, as described in Patent Document 1, a magnesium alloy wire excellent in mechanical properties has been obtained by drawing out an extruded material made of a magnesium alloy.

JP2003-293069

  Since the magnesium alloy wire obtained by drawing is excellent in mechanical properties as described in Patent Document 1, plastic processing such as spring processing can be performed. However, the wire described in Patent Document 1 has a small diameter of about 6 mm or less, and a magnesium alloy wire having a large diameter of 8 mm or more, particularly 10 mm or more has not been studied. As a result of investigations by the present inventors, when a conventional wire drawing condition is applied as it is to obtain a large-diameter wire having a diameter of 8 mm or more, the obtained wire has a plastic workability such as forging into a thin wire. The knowledge that it fell compared was acquired.

  Therefore, a main object of the present invention is to provide a magnesium alloy material excellent in forgeability and a method for producing the material. Moreover, the other object of this invention is to provide the magnesium alloy molded object which consists of said magnesium alloy raw material.

  The material of the present invention achieves the above object by specifying the orientation. That is, the magnesium alloy material of the present invention is a magnesium alloy material containing Al: 0.01-12% by mass with the balance being Mg and impurities, and the X-ray diffraction peak height in the longitudinal section axis direction of this material. The ratio (shown in the following formula 1) satisfies 0.2 or more and 0.6 or less.

The magnesium alloy material can be obtained by the following manufacturing method. That is, the manufacturing method of the magnesium alloy material of the present invention includes the following steps.
A step of preparing a magnesium alloy base material containing Al: 0.01-12% by mass and the balance being Mg and impurities.
2 The process of drawing the base material using a wire drawing die with an approach angle of 6 ° to 12 °
3 A process of heat-treating the drawn material at 300 ° C or higher and 450 ° C or lower

  In a thin wire having a diameter of less than 8 mm, the entire cross section of the wire is processed almost uniformly during drawing. On the other hand, when a thick wire, in particular, a thick wire having a diameter of 8 mm or more is obtained using a die having the same specifications as the die used for the thin wire, the texture is different from that of the thin wire. Specifically, since the surface layer portion is relatively easily processed and the center portion is difficult to be processed, in a large-diameter wire, the orientation with the (0002) plane parallel to the axial direction of the wire on the surface layer side is increased. In the X-ray diffraction in the longitudinal cross-sectional axis direction of the wire, the peak height ratio shown in the above formula 1 tends to increase. In this way, the wire obtained from the high orientation is deteriorated in forgeability. Therefore, in the magnesium alloy material of the present invention, by specifying the orientation, an improvement in plastic workability such as forging workability is realized particularly in a large-diameter wire. In addition, in order to control to the above specific orientation, the manufacturing method of the magnesium alloy material of the present invention specifies that the wire is drawn using a wire drawing die having a specific die angle, and that the heat treatment is performed at a specific temperature condition after the drawing. . The present invention will be described in detail below.

  The magnesium alloy material of the present invention is manufactured using a magnesium alloy containing Al. In addition to Al, a magnesium alloy containing one or more elements selected from Mn: 0.1 to 2.0%, Zn: 0.1 to 7.0%, and Si: 0.01 to 5.0% by mass% may be applied. That is, as the magnesium alloy used for the material of the present invention, either a magnesium alloy for casting or a magnesium alloy for drawing can be used. Specifically, for example, an AZ system, an AM system, an AS system or the like in the ASTM symbol can be used. In the AZ system, for example, AZ10, AZ21, AZ31, AZ61, AZ80, and AZ91 can be mentioned. Examples of AM systems include AM60 and AM100. In the AS system, for example, AS21, AS41 and the like can be mentioned. Those containing one or more elements selected from Y: 0.01-3.0%, Sr: 0.1-3.0%, Ca: 0.01-5.0% by mass% in addition to these AZ, AM, and AS alloys May be used. By adding these elements, a material having a better balance between strength and toughness can be obtained. The impurities include Fe, Cu, Ni and the like, and the content thereof is preferably 0.01% by mass or less.

  Although it is difficult to obtain sufficient strength with magnesium alone, preferable strength can be obtained by including the above-mentioned additive elements. Moreover, the magnesium alloy raw material excellent in plastic workability, such as a forging process, can be obtained by manufacturing by such a manufacturing method using such a magnesium alloy.

The magnesium material of the present invention is a linear or rod-shaped wire (wire). The cross-sectional shape may be circular or non-circular, for example, an ellipse, rectangle, or polygonal variant. To make the cross-sectional shape of the material of the present invention non-circular, it can be easily handled by changing the shape of the die. The material of the present invention has a diameter of 8 mm (cross-sectional area of 50.2 mm ² (corresponding to a cross-sectional area of 8 mm in diameter)) or more, particularly 10 mm (cross-sectional area of 78.5 mm ² ) or more by controlling the orientation by the above manufacturing method. Although it is a diameter, it can be set as the material excellent in forgeability.

  In addition, the magnesium material of the present invention does not increase the specific orientation in order to improve plastic workability such as forging. Specifically, the ratio of X-ray diffraction peak heights in the longitudinal cross-sectional axis direction of the material (see Formula 1) is set to 0.2 or more and 0.6 or less. 0.5 or less is more preferable. As the peak height ratio is closer to 0.2, the crystal directions are hardly aligned, that is, exhibit random orientation and better forgeability. If the peak height ratio is more than 0.6, the crystal directions are too aligned, that is, the orientation is strong and the forgeability is poor. In addition, the ratio of the peak height is obtained by cutting the material in the longitudinal direction, performing X-ray diffraction in the axial direction of the material in the cross section, measuring the peak intensity (peak height) of each surface (crystal surface), It is obtained by calculating the obtained peak intensity. X-ray diffraction may be performed over the entire cross section.

  Such a magnesium alloy material of the present invention can be obtained by subjecting a base material made of a magnesium alloy containing a specific amount of Al to a specific drawing process and a specific heat treatment after the drawing. Examples of the base material to be used include an extruded material obtained by extruding a cast material, and a rolled material obtained by rolling the cast material. Solution treatment may be performed before extrusion or rolling. Examples of the solution treatment conditions include a temperature: 380 to 420 ° C. and a holding time: 2 to 20 hours. Such a base material is drawn using a wire drawing die. The solution treatment may be performed before drawing, and the conditions include, for example, temperature: 380 to 420 ° C., holding time: 1 to 10 hours.

  In carrying out the above drawing, in particular, the present invention uses a wire drawing die having an approach angle of 6 ° to 12 °. Conventionally, as the wire drawing dies, those having an approach angle of about 16 ° are often used, and the present inventors also used a conventional wire drawing die with an approach angle of 16 ° to obtain the material of the present invention. It has been found that the obtained drawn material is likely to have high orientation with the (0002) plane parallel to the axial direction of the wire on the surface side. And the knowledge that such drawn material with high surface orientation was inferior in plastic workability was also obtained. Therefore, the inventors of the present invention made various drawing materials by changing the die angle in various ways, and found that an approach angle of 6 ° to 12 ° was preferable. When the approach angle is less than 6 °, the contact area between the die hole and the base material is increased, so that the drawing force is increased, and there is a possibility of disconnection in the middle of drawing, which is not preferable. When the approach angle is over 12 °, drawing can be performed without disconnection, but as described above, the orientation that the (0002) plane is parallel to the axial direction of the wire on the surface side of the drawn material becomes strong. . A more preferred approach angle is 8 ° to 12 °.

  In addition, as drawing conditions, the heating rate to the processing temperature: 1 ° C./sec to 100 ° C./sec, the processing temperature: 50 ° C. to 200 ° C. (more preferably 150 ° C. to 200 ° C.), the processing degree: drawing processing 1 10% or more per rotation (1 pass), linear speed: 1 m / min or more, cooling rate after drawing: 0.1 ° C./sec or more. If the processing temperature is less than 50 ° C, the wire may be broken during drawing, and the higher the processing temperature, the better the drawing processability. However, if it exceeds 200 ° C, the strength may be reduced. When the cooling rate is less than 0.1 ° C./sec, the growth of crystal grains is promoted, which is not preferable. An example of the cooling means is blast, and the speed can be adjusted by the wind speed, the air volume, and the like.

  The drawing process may be performed in only one pass, but can be performed in multiple stages using a plurality of wire drawing dies. If the degree of processing in one drawing process is 10% or more in terms of the cross-sectional reduction rate, a material having excellent strength can be obtained. A more preferable cross-sectional reduction rate per pass is 15% or more. However, since the actual processing cannot be performed if the processing degree becomes too large, the upper limit of the cross-section reduction rate per pass is about 30% or less. The total degree of processing is preferably 15% or more in terms of the cross-sectional reduction rate. A more preferable total cross-sectional reduction rate is 25% or more.

  And while performing drawing using the said specific die, in order to adjust the orientation of the obtained drawing material, the heat processing of 300 to 450 degreeC is performed to a drawing material. The holding time is preferably 5 minutes or more, and if it is too long, it promotes the growth of crystal grains, and is preferably 60 minutes or less. The orientation can be sufficiently controlled with a holding time of about 15 minutes. If the heat treatment temperature is less than 300 ° C., the peak height ratio cannot be 0.6 or less. Since the ratio of the peak height can be reduced as the heat treatment temperature is higher, it is particularly preferably 350 ° C. or higher. However, if it exceeds 450 ° C., the material may melt or burn, which is not preferable. Therefore, in the present invention, the upper limit of the heat treatment temperature is set to 450 ° C. or less. In addition, as the temperature rises, the growth of crystal grains is promoted as described above, so that the grown crystal grains may become a starting point of cracking or the like during plastic working, and there is a tendency to reduce forging workability. . Therefore, it is more preferable to set it to 400 ° C. or lower. When performing multi-pass drawing, the heat treatment may be performed for each pass, the heat treatment may be performed for several passes, or the heat treatment may be performed only after the completion of all passes. Heat treatment is performed at least after all passes.

  The production method of the present invention can also be used when producing a thin wire having a diameter of less than 8 mm, but is suitable for producing a wire having a diameter of 8 mm or more, and particularly a diameter of 10 mm or more. .

  The magnesium alloy material of the present invention, which is controlled to have a specific orientation by performing a drawing process using the specific wire drawing die and a specific heat treatment after drawing, is excellent in plastic workability such as forging. In particular, it is excellent in forging processability at a relatively low temperature of 200 ° C. or less, and sufficient plastic working can be performed even by heating at about 150 ° C.

  Further, the magnesium alloy molded body of the present invention subjected to the forging process is lightweight and excellent in strength and rigidity, and can be used, for example, for bicycle parts such as a bicycle crank and other automobile parts. .

  As described above, according to the magnesium alloy material of the present invention, it is possible to achieve a specific effect that plastic processing such as forging can be performed even though it is a material having a large diameter. Moreover, a relatively low temperature forging process can be performed. Furthermore, according to the method for producing a magnesium alloy material of the present invention, the magnesium alloy material having excellent forgeability can be produced with high productivity. And the magnesium alloy molded object which gave the forge process to this invention magnesium alloy raw material can be utilized suitably as a material of the various field | areas calculated | required that it is lightweight and high intensity | strength.

Embodiments of the present invention will be described below.
(Test Example 1)
AZ31 equivalent alloy (Al: 3.0% by mass, Zn: 0.77%, including Mn: 0.65%, the balance being Mg and impurities), AZ61 equivalent alloy (Al: 6.4% by mass, Zn: 0.76%, Mn: Prepare AZ91 equivalent alloy (Al: 9.0%, Zn: 0.7%, Mn: 0.32% in mass%, balance is Mg and impurities) Casting, solution treatment (400 ° C. × 4 hours), and rolling were sequentially performed to obtain a bar with a diameter of 25 mm. The obtained bar was subjected to a solution treatment at 400 ° C. for 2 hours and then drawn at 150 to 200 ° C. to obtain a drawn material having a diameter of 20 mm. Drawing is performed using a wire drawing die with the approach angle shown in Table 1. Temperature increase rate to the processing temperature: 20 ° C / sec, processing degree per pass: 14-18% (total processing degree: 36% ), Linear velocity: 3 m / min, cooling rate after drawing: about 1 ° C./sec.

  The obtained drawn material was heat-treated at the temperature (AN temperature) shown in Table 1 (holding time: 15 minutes), the obtained heat-treated material was cut in the longitudinal direction, and an X-ray diffraction analyzer (XRD) was used. Then, the peak intensity (peak height) of each surface was measured by X-ray diffraction in the axial direction of the longitudinal section (entire surface), and the ratio of peak heights shown in the following formula 2 was evaluated. The results are shown in Table 1.

  Further, the obtained material having a diameter of 20 mm was cut into a length of 40 mm, and an upsetting test in the axial direction (upsetting test temperature: 150 ° C.) was performed. This test is based on “Cold Upsetting Test Method for Metallic Materials (Provisional Standard)” described in “Forging” (Edited by Japan Society for Technology of Plasticity, Corona Publishing August 1995, pages 155-156). Accordingly, when compressing the test piece with the pressure plate, the test piece was heated to 150 ° C., the strain rate was 0.5 / sec, and the maximum upsetting rate up to 50% was evaluated. The results are shown in Table 1.

  As shown in Table 1, a magnesium alloy material (sample Nos. 6-9, 16-19, 26) that was heat-treated at 300 ° C to 450 ° C on a drawn material using a wire drawing die having an approach angle of 6 ° to 12 °. -29,32-35), the ratio of the peak height shown in Formula 2 is 0.2 or more and 0.6 or less. And it turns out that each raw material which satisfy | fills ratio of these peak heights 0.2-0.6 is excellent in forge processability. In particular, among these materials, materials subjected to heat treatment at 400 ° C. or lower were more excellent in forgeability.

  On the other hand, even if the approach angle of the wire drawing dies is 11 °, the material not subjected to heat treatment (Sample No.1, 11, 21), or the material less than 300 ° C even if heat treated, The ratio of peak height is large and forging processability is inferior. On the other hand, even when heat treatment is performed at 350 ° C, the material with a large wire die approach angle (sample No. 36, 37) has an orientation in which the (0002) plane is parallel to the axial direction of the wire on the surface side. The peak height ratio is increased and the forging processability is deteriorated. In addition, the material with a small approach angle (Sample No. 31) was broken due to increased friction during drawing. Furthermore, the obtained drawn material was heat-treated at a temperature of 480 ° C., but a part of the drawn material was melted or burned, and the peak height ratio evaluation and upsetting test can be performed. No possible sample was obtained.

(Test Example 2)
AZ31 equivalent alloy material, AZ61 equivalent alloy material, AZ91 equivalent alloy material used in Test Example 1 above, 0.1% by mass of Y, 0.5% by mass of Sr, AM60 equivalent alloy (% by mass) Al: 6.1%, Mn: 0.44% included, balance is Mg and impurities), AS41 equivalent alloy (mass% is Al: 4.2%, Si: 1.0%, Mn: 0.40%, balance is Mg and impurities) Prepared under the same conditions as in Test Example 1 above, melt casting → solution treatment → rolling process (diameter φ25 mm) → solution treatment → drawing process (using wire drawing die with an approach angle of 11 °) A drawn material with a diameter of 20 mm was obtained. The obtained drawn material was heat-treated at 350 ° C. for 15 minutes, and the peak height ratio shown in Formula 2 was obtained in the same manner as in Test Example 1 for the obtained heat-treated material. As a result, the peak height ratio was 0.25 to 0.46, and all the samples satisfied 0.2 to 0.6.

  Further, the limit upsetting rate (150 ° C., strain rate: 0.5 / sec, maximum limit upsetting rate: 50%) was evaluated on the obtained heat treated material under the same conditions as in Test Example 1. As a result, it was confirmed that each sample had a limit upsetting rate of 40% and showed good forgeability.

(Test Example 3)
AZ31 equivalent alloy (Al: 3.1% by mass, Zn: 0.75%, Mn: 0.67% included, the balance being Mg and impurities), AZ61 equivalent alloy (Al by mass: Al: 6.4%, Zn: 0.77%, Mn: Extruded material (diameter: 25 mm in diameter including 0.28%, balance Mg and impurities), AZ91 equivalent alloy (mass% Al: 9.1%, Zn: 0.70%, Mn: 0.55%, balance Mg and impurities) A rod-like body) was prepared, and the extruded material was drawn at 150 to 200 ° C. without subjecting the extruded material to a solution treatment to obtain a drawn material having a diameter of 20 mm. Drawing is performed using a wire drawing die with an approach angle of 11 °, the rate of temperature rise to the processing temperature: 20 ° C / sec, the processing rate per pass: 14-18% (total processing rate: 36%) The drawing speed was 3 m / min, and the cooling rate after drawing was about 1 ° C./sec.

  The obtained drawn material was heat-treated at 400 ° C. for 15 minutes, and the peak height ratio shown in Formula 2 was obtained for the obtained heat-treated material in the same manner as in Test Example 1. As a result, AZ31 equivalent alloy material: 0.40, AZ61 equivalent alloy material: 0.36, AZ91 equivalent alloy material: 0.25, and the peak height ratio satisfied 0.2 to 0.6.

  Further, the limit upsetting rate (150 ° C., strain rate: 0.5 / sec, maximum limit upsetting rate: 50%) was evaluated on the obtained heat treated material under the same conditions as in Test Example 1. As a result, it was confirmed that each sample had a limit upsetting rate of 40% and showed good forgeability.

  From the above test, it was confirmed that in the case of a magnesium alloy material having a large diameter of 8 mm or more, it is possible to obtain a material excellent in forgeability by specifying the approach angle of the wire drawing die and the heat treatment temperature.

  The magnesium alloy material of the present invention is suitable as a forging material. In particular, it is excellent in forging workability at a relatively low temperature of 200 ° C. or less. Moreover, the manufacturing method of this invention magnesium alloy raw material is suitable for manufacture of the raw material which is excellent in the said forge workability. The molded product of the present invention obtained by subjecting this material to forging can be used for, for example, bicycle parts such as a bicycle crank and various automobile parts.

Claims (6)

A magnesium alloy wire containing Al: 0.01-12% and Mn : 0.1-2.0% by mass, the balance being Mg and inevitable impurities,
When X-ray diffraction in the axial direction of the wire is performed in the longitudinal section of this wire, the ratio of the X-ray diffraction peak height satisfies the following formula:
A magnesium alloy wire characterized by having a wire diameter of 10 mm or more.

2. The magnesium alloy wire according to claim 1, further comprising one or more elements selected from Zn : 0.1 to 7.0% and Si: 0.01 to 5.0% by mass%. A step of preparing a magnesium alloy base material containing Al: 0.01-12% and Mn : 0.1-2.0% by mass%, with the balance being Mg and inevitable impurities;
Using a wire drawing die with an approach angle of 6 ° or more and 12 ° or less, a step of pulling out the base material,
A process of performing heat treatment on the drawn material at 300 ° C. or higher and 450 ° C. or lower,
According to these steps, when performing X-ray diffraction in the axial direction of the wire in the longitudinal section of the wire , a magnesium alloy wire is produced in which the ratio of X-ray diffraction peak heights satisfies the following formula: A manufacturing method of a wire.

4. The method for producing a magnesium alloy wire according to claim 3, further comprising using a base material containing at least one element selected from Zn : 0.1 to 7.0% and Si: 0.01 to 5.0% by mass%. Method for producing a magnesium alloy wire according to claim 3 or 4, characterized in that diameter to produce a more magnesium alloy wire 8 mm.   3. A magnesium alloy molded body produced by subjecting the magnesium alloy wire according to claim 1 or 2 to forging.