JP3735101B2 - Magnesium-based alloy pipe manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a pipe made of a magnesium-based alloy. In particular, the present invention relates to a production method capable of producing a magnesium-based alloy pipe excellent in strength and ductility with high productivity.

  Magnesium-based alloys are lighter than aluminum and have a higher specific strength and specific rigidity than steel and aluminum, and are widely used in the body of various electrical products as well as aircraft parts and automobile parts. In particular, conventionally, it is often used for a press-formed product, and as a method for producing the plate material for press, a method by rolling is known (for example, see Patent Document 1 and Patent Document 2).

JP 2001-200349 A (refer to claims) Japanese Unexamined Patent Publication No. Hei 6-93944 (see claims)

  Magnesium-based alloys are excellent in various properties as described above, and are desired to be used not only as plate materials but also as pipe materials. However, since Mg and its alloys have a close-packed hexagonal lattice structure, ductility is poor and plastic workability is extremely poor. Therefore, it is difficult to obtain a pipe of Mg and its alloy having high strength and excellent toughness, and an optimum method has not been known. In particular, it was very difficult to manufacture with high productivity.

  Although the magnesium-based alloy pipe can be obtained by hot extrusion, the strength is low, and it is difficult to use the obtained pipe as a structural material. For example, a pipe obtained by this hot extrusion does not have an excellent strength as compared with a pipe made of an aluminum alloy. Therefore, a production method capable of obtaining a high-strength magnesium-based alloy pipe has been demanded.

  Accordingly, a main object of the present invention is to provide a method for producing a magnesium-based alloy pipe, which can obtain a magnesium-based alloy pipe excellent in strength and ductility with high productivity.

  The present invention aims to improve productivity by performing drawing at room temperature. And as a 1st method, in order to implement | achieve drawing processing at room temperature, this invention prescribes | regulates performing heat processing during a manufacturing process.

  Specifically, the heat treatment is performed after the staking process and before the drawing process. That is, the manufacturing method of the magnesium-based alloy pipe of the present invention includes a mouth-forming step of performing a mouth-forming process on a tip portion of a base material pipe made of a magnesium-based alloy, a heat treatment step of performing a heat treatment on the mouthed base-material pipe, A drawing step of drawing a base material pipe that has been heat-treated. The heat treatment step includes a step of heating at least a tip portion of the base material tube to 200 ° C. or higher and lower than 450 ° C., and a step of cooling after the heating. The drawing process is performed without heating after the heat treatment step.

  Alternatively, heat treatment is performed after the first pass, and then the second pass is performed. That is, in the manufacturing method of the magnesium-based alloy pipe of the present invention, the extruded material made of the magnesium-based alloy is drawn at a room temperature with a cross-section reduction rate of 15% or less, and the drawing is performed following the first drawing step. It is characterized by comprising an intermediate heat treatment step for heat-treating the first drawn tube and a second drawing step for drawing the obtained drawn tube at room temperature following the intermediate heat treatment step.

  As a second method, the present invention provides that surface treatment is performed before drawing. That is, the method for producing a magnesium-based alloy pipe according to the present invention includes a surface treatment process for roughening a surface of a base material pipe made of a magnesium-based alloy, and a drawing process for performing a drawing process on the base material pipe subjected to the surface treatment. It is characterized by comprising.

  Moreover, this invention aims at the improvement of productivity by performing a drawing process with a big processing degree. And this invention prescribes | regulates drawing | extracting warmly, in order to implement | achieve the drawing process with a big processing degree.

  That is, the manufacturing method of the magnesium-based alloy pipe of the present invention includes a drawing step of drawing a base material pipe made of a magnesium-based alloy. The drawing process includes an intermediate heat treatment step in which a plurality of passes are performed in a warm stage in multiple stages and heat treatment is performed on a drawn tube drawn every two passes.

  As a result of various studies by the present inventors, it was found that it is preferable to draw out an extruded material or a cast material in order to obtain a magnesium-based alloy pipe that is longer and excellent in both strength and ductility (elongation). It was. At this time, plastic workability is improved by heating the base material tube during drawing, and drawing can be performed easily. However, in order to improve productivity, the number of times of heating during drawing is reduced. It is desirable to process at room temperature without or at all. In order to realize such a requirement, it was found that it is preferable to apply at least one of the following methods. The present invention is defined based on these findings.

  Method 1. After heat treatment, heat treatment is performed and then drawing is performed.

  In a base tube made of a magnesium-based alloy, a part plastically deformed by mouth-opening processing, specifically, a part gripped by a chuck of a drawing machine during drawing, and a drawn material such as a plug (mandrel) The contacted portion is the portion where cracking or the like is most likely to occur during the drawing process. Therefore, when a specific heat treatment is performed on the plastically deformed portion after the lip processing, distortion (work hardening) associated with the plastic processing is removed, and the metal structure can be controlled to be uniform and fine crystal grains. And by such control of the metal structure, it is possible to realize cold drawing (room temperature).

  Method 2. After pulling out the extruded material made of magnesium-based alloy under specific conditions, heat treatment is performed and then the second pass is pulled out.

  An extruded material made of a magnesium-based alloy has an unstable metal structure and may include particles whose crystal particle size exceeds 100 μm, or there may be large variations in crystal particle size. When such an extruded material is pulled out at room temperature, if the degree of processing (cross-sectional reduction rate) is too large, it may not be pulled out due to cracks and the like. Therefore, when the extruded material made of a magnesium-based alloy is drawn at room temperature, it is preferably performed at a specific degree of processing. Further, by performing an intermediate heat treatment after the drawing, the strain introduced by the drawing process can be removed and a structure having uniform crystal grains can be obtained. Therefore, after drawing the first pass, intermediate heat treatment is performed to adjust the metal structure, and then the second pass is drawn. At this time, since the metal structure can be stabilized by the intermediate heat treatment, the drawing at room temperature can be realized.

  Method 3. The base pipe made of magnesium alloy is subjected to surface treatment and then drawn.

  When producing a pipe by drawing, there is a problem that seizure occurs due to metal contact. In particular, when drawing is performed at room temperature, the pulling force is large because of low plastic workability, and seizure is likely to occur. Therefore, it is conceivable to use a lubricant to prevent seizure. At this time, if the surface of the base material pipe is roughened to some extent to facilitate the drawing of the lubricant, the drawing can be performed more stably even at room temperature.

  As another method for improving productivity, it is conceivable to increase the degree of processing in one drawing process. Therefore, as Method 4, when performing multi-pass drawing in multiple stages, it is proposed to perform hot drawing and perform intermediate heat treatment every two passes.

  As described above, since the magnesium-based alloy has low plastic workability, cracks and the like are likely to occur when the degree of work is increased. However, since the plastic workability can be improved by heating, the degree of work can be increased when the drawing process is performed warm. Moreover, the distortion | strain introduce | transduced is reduced by drawing | extracting warm compared with the case of the drawing process by cold. Therefore, the number of intermediate heat treatments can be reduced as compared with the case where a plurality of passes of drawing are performed cold.

  According to the manufacturing method of the magnesium-based alloy pipe of the present invention defined on the basis of the above knowledge, a pipe can be produced without causing cracks even if the base metal pipe is drawn at room temperature. Can do. Therefore, it is possible to reduce the cost by reducing the heating means at the time of drawing, and to improve the productivity. In addition, when drawing is performed warmly, the degree of processing can be increased, so that the number of drawing passes can be reduced as compared with cold processing, and the number of intermediate heat treatments can be reduced. Therefore, productivity can be improved.

  In particular, in the present invention, a magnesium-based alloy pipe having high strength and excellent ductility can be obtained by employing a drawing process. Therefore, it is possible to apply the obtained pipe to a structural material.

  The present invention will be described in detail below.

  As the base material pipe made of the magnesium-based alloy, for example, a pipe obtained by extrusion or casting can be used. In addition, the drawn tube that has been drawn after the heat treatment by the method 1 and subjected to heat treatment may be subjected to an intermediate heat treatment as described in the method 2, and further subjected to a drawing process. The drawn tube that has been drawn and then drawn may be subjected to a surface treatment as in the above method 3 and further drawn. Further, the surface treatment as in the above method 3 may be subjected to drawing and intermediate heat treatment as in the above methods 2 and 4. Alternatively, an intermediate heat treatment may be performed on the drawn tube that has been heat-treated after mouth-attaching by the method 1 and then withdrawn warmly as in the method 4 described above.

  The staking process is performed in order to reduce the diameter of the tip of the base material pipe so that the tip of the base material pipe can be inserted into a drawing die during the drawing process in a subsequent process. Such a splicing process may be performed by a splicing machine such as a swaging machine.

  In the portion plastically deformed by the squeezing process, distortion associated with the plastic process occurs. This plastically deformed part is the part that is gripped by the chuck of the drawing machine at the time of drawing or is in contact with the die and plug (mandrel) used for drawing and undergoes initial machining, so it is the most cracked or broken Is likely to occur. Therefore, in the present invention, a specific heat treatment is performed on the tip portion of the base metal pipe that has been subjected to the crimping process to remove the strain, and the metal structure that has become unstable due to plastic working is adjusted. More specifically, the present invention realizes cold drawing, that is, drawing at room temperature, by forming a structure having uniform fine crystal grains.

  The heat treatment performed after the lip processing includes a heating step and a cooling step. In the heating step, the higher the heating temperature, the easier it is to remove the strain associated with plastic working or it can be removed reliably, but the crystal grain size tends to increase. On the other hand, the lower the heating temperature, the smaller the crystal grain size and the easier to obtain fine crystal grains, but there is a risk that the removal of the strain will be insufficient. Considering these circumstances, in the present invention, the heating temperature is set to 200 ° C. or higher and lower than 450 ° C. More preferably, it is 250 ° C. or higher and 400 ° C. or lower.

  The heating in the heating step may be performed on the entire base material pipe. However, in consideration of productivity, at least a portion of the base material pipe that has been subjected to the mouth-opening process, specifically, the tip of the base material pipe is heated. That's fine. The heating time may be appropriately selected according to the pipe diameter and thickness of the base material pipe to be heated, and the heating temperature, and may be about 15 to 60 minutes.

  Examples of the cooling means include natural cooling such as air cooling, and forced cooling such as blast. The adjustment of the cooling rate can be performed by the air volume or the wind speed. In this cooling step, the temperature of the base material tube is lowered from the heating temperature to about room temperature.

  In the present invention, the base material pipe cooled to room temperature by the cooling step is drawn out. As described above, by controlling the metal structure by heat treatment after the lip processing, the metal structure can be extracted at room temperature without additional heating during the drawing process. Specifically, it is possible to perform a drawing process with a high degree of processing such that the cross-sectional reduction rate in one drawing process is 6% or more. In the present invention, the cross-section reduction rate in one drawing process can be increased as described above, but the upper limit of the cross-section reduction rate is preferably 20% in consideration of the occurrence of cracks and the like. In consideration of the mechanical properties of the pipe after the drawing, the cross-sectional reduction rate in one drawing is preferably 8% or more and 15% or less.

  Furthermore, at the time of scouring, at least the tip of the base material pipe to be scoured is heated to perform the scouring with improved plastic workability, thereby suppressing the occurrence of cracks and the like. Can be easily performed. The higher the heating temperature is, the easier it is to perform the squeezing process by increasing the workability. However, if the heating temperature is too high, problems such as oxidation of the surface occur. Therefore, the upper limit of the heating temperature is preferably 450 ° C. On the other hand, considering the effect of heating, the lower limit is preferably 200 ° C. A particularly preferable heating temperature is 250 to 350 ° C.

  The heating may be continuously performed during the mouth-opening process until a desired reduced diameter state is obtained, and may be performed so that the heating temperature is maintained throughout the process. Until it is cooled, the mouth-opening process may be performed without heating, and when it reaches room temperature, it may be heated again and the mouth-opening process may be performed again.

  In addition, the heating in the above-mentioned splicing process may be performed on the entire base material pipe, but in consideration of productivity, the heating may be performed only on the tip portion of the base material pipe. The heating means is not particularly limited. A general heater or the like may be used. The temperature may be adjusted by previously heating the tip of the base material tube with a heater or the like, and changing the time taken to introduce it into a mouth-forming machine such as a swaging machine. In order to efficiently perform the splicing process, it is desirable that the temperature decrease from when the base material pipe is heated to when the base material pipe is introduced into the splicing machine is small.

  The drawing process may be performed in multiple stages until a pipe having a desired size is obtained. When the drawing process is performed at room temperature, it is preferable to perform an intermediate heat treatment for each pass. By performing the drawing process once, strain and twin deformation occur in the drawn pipe. Especially when drawing at room temperature, more strain and twin deformation are introduced. Therefore, when performing a plurality of passes of drawing in a cold state, it is preferable to perform an intermediate heat treatment for each pass in order to remove distortion introduced along with the drawing and promote recrystallization of the metal structure. . By such an intermediate heat treatment, a metal structure consisting of uniform fine crystal grains is formed, so that drawing at room temperature becomes possible again.

  As an optimal intermediate heat treatment for effectively removing the strain as described above and recrystallizing the metal structure, a process of heating the drawn pipe to a heating temperature of 200 ° C. or higher and lower than 450 ° C., heating A treatment comprising a step of cooling later is preferred. The cooling after heating is preferably performed to about room temperature. The heating condition and the cooling condition may be the same as those in the heat treatment performed after the mouth-opening process.

  When the cross-sectional reduction rate in one drawing process is increased, the drawing process is preferably performed warm in order to improve plastic workability. Specifically, it is preferable to heat the base material tube to 100 ° C. to 300 ° C., particularly preferably 120 ° C. to 200 ° C., and pull it out. The heating method to the drawing temperature is preferably performed by immersing the base material tube in preheated lubricating oil, heating in an atmospheric furnace, heating in a high-frequency heating furnace, or heating a drawing die. The drawing temperature can be adjusted by changing the cooling time until the base material tube is introduced into the drawing die after heating. The rate of temperature increase to the drawing temperature is preferably 1 ° C./sec to 100 ° C./sec. Further, the drawing speed of the drawing process is preferably 1 m / min or more. The cooling rate after drawing is preferably 0.1 ° C./sec or more. The cooling means after the drawing includes air cooling, blast, etc., and the speed can be adjusted by the wind speed, the air volume, and the like.

  When the drawing process is performed in the warm condition as described above, the cross-sectional reduction rate in one drawing process can be set to 26% or less. Particularly, it is preferably 10 to 20%.

  And, when performing the warm drawing in multiple stages in multiple passes, if an intermediate heat treatment is performed on the drawn tube every two passes, it is possible to effectively remove strain and recrystallize the metal structure. This is preferable. The intermediate heat treatment may be performed under the same conditions as in the case where a plurality of cold drawing processes are performed.

  By repeatedly drawing a plurality of passes as described above, a thinner pipe can be obtained. At this time, the total cross-sectional reduction rate in the drawing process is preferably 25% or more. A more preferable total cross-section reduction rate is 40% or more. By drawing such a total cross-section reduction rate of 25% or more, it becomes possible to obtain a pipe having both strength and toughness.

  When using a base metal tube made of a magnesium-based alloy obtained by extrusion, the first pass drawing process is performed at room temperature with a cross-section reduction rate of 15% or less, and this drawing process is followed by an intermediate heat treatment, Following the heat treatment, the second pass drawing may be performed at room temperature. By applying an intermediate heat treatment after the first pass drawing process, the distortion introduced by the first pass drawing process is removed, recrystallization is promoted, and the second pass drawing process is also performed at room temperature. Can do. In particular, by the intermediate heat treatment, the second pass drawing can be performed with a high degree of processing of 20% or less. The intermediate heat treatment may be the same as described above.

  In the drawing process, it is preferable to use a lubricant in order to prevent seizure due to frictional heat. And it is preferable to perform the process which roughens the surface of a preform | base_material pipe | tube before drawing | extracting so that the preform | base_material pipe | tube consisting of a magnesium base alloy may pull in this lubricant easily. By performing such a surface treatment, seizure hardly occurs even when the drawing process is performed at room temperature, and a stable drawing process can be performed.

  The surface treatment may be performed using sandpaper or the like. In addition, when the surface treatment is performed so that the surface roughness of the base material tube after the treatment is 10 μm or more, the lubricant is easily drawn. However, if it is too coarse, the product accuracy is lowered, so the upper limit is preferably 15 μm or less. As the lubricant, powder or lubricating oil is used. It is preferable that the lubricant is forcibly supplied by applying a pressure between the drawing die and the base material pipe during the drawing process.

  In the present invention, the drawing process is performed by passing the base material tube through a drawing die or the like. At that time, a method having a proven track record in pipe drawing of copper alloy or aluminum alloy may be used. For example, (1) plug pulling in which a plug is arranged inside the workpiece, (2) mandrel pulling using a mandrel penetrating a die, and the like can be mentioned. Examples of plug pulling include fixed plug pulling, floating plug pulling, and semi-floating plug pulling. The mandrel pulling may be performed by placing a mandrel penetrating the die over the entire length of the workpiece.

  The present invention is effective for a magnesium-based alloy having an hcp structure with poor workability at about room temperature regardless of the alloy composition. For example, a magnesium base alloy for casting or a magnesium base alloy for drawing can be used. Specifically, Al containing 0.1% by mass to 12% by mass, Zn: 0.1% by mass to 10% by mass and Zr: 0.1% by mass to 2.0% by mass, etc. The thing containing 5.0 mass% or less of the outstanding rare earth elements is mentioned. When Al is contained, it further contains one or more selected from Mn: 0.1 mass% to 2.0 mass%, Zn: 0.1 mass% to 5.0 mass%, Si: 0.1 mass% to 5.0 mass% Things. As the above alloy composition, AST, AS, AM, ZK, EZ and the like in typical ASTM symbols can be used. The content of Al may be distinguished from 0.1 to less than 2.0% by mass and 2.0 to 12.0%. In general, it is used as an alloy containing Mg and impurities in addition to the above chemical components. Impurities include Fe, Si, Cu, Ni, Ca and the like.

  Examples of the AZ-based Al content of 2.0 to 12.0% by mass include AZ31, AZ61, and AZ91. AZ31 is magnesium containing, for example, Al: 2.5 to 3.5%, Zn: 0.5 to 1.5%, Mn: 0.15 to 0.5%, Cu: 0.05% or less, Si: 0.1% or less, and Ca: 0.04% or less in mass%. It is a base alloy. AZ61 is, for example, a magnesium-based alloy containing Al: 5.5 to 7.2%, Zn: 0.4 to 1.5%, Mn: 0.15 to 0.35%, Ni: 0.05% or less, and Si: 0.1% or less in mass%. AZ91 is, for example, a magnesium-based alloy containing Al: 8.1-9.7%, Zn: 0.35-1.0%, Mn: 0.13% or more, Cu: 0.1% or less, Ni: 0.03% or less, Si: 0.5% or less in mass% It is. Examples of the AZ-based Al content of 0.1 to less than 2.0% by mass include AZ10 and AZ21. AZ10 is, for example, a magnesium group containing Al: 1.0 to 1.5%, Zn: 0.2 to 0.6%, Mn: 0.2% or more, Cu: 0.1% or less, Si: 0.1% or less, Ca: 0.4% or less in mass% It is an alloy. AZ21 is, for example, a magnesium-based alloy containing Al: 1.4 to 2.6%, Zn: 0.5 to 1.5%, Mn: 0.15 to 0.35%, Ni: 0.03% or less, and Si: 0.1% or less in mass%.

  As an example in which the content of Al in the AS system is 2.0 to 12.0% by mass, AS41 and the like can be mentioned. AS41 is magnesium containing, for example, Al: 3.7 to 4.8%, Zn: 0.1% or less, Cu: 0.15% or less, Mn: 0.35 to 0.60%, Ni: 0.001% or less, Si: 0.6 to 1.4% by mass It is a base alloy. AS21 etc. are mentioned as the content of Al in the AS system being less than 0.1 to 2.0% by mass. AS21 is a magnesium group containing, for example, Al: 1.4 to 2.6% by mass, Zn: 0.1% or less, Cu: 0.15% or less, Mn: 0.35 to 0.60%, Ni: 0.001%, Si: 0.6 to 1.4% It is an alloy.

  Examples of AM systems include AM60 and AM100. AM60 is a magnesium-based alloy containing, for example, Al: 5.5-6.5% by mass, Zn: 0.22% or less, Cu: 0.35% or less, Mn: 0.13% or more, Ni: 0.03% or less, Si: 0.5% or less It is. AM100 is, for example, magnesium group containing Al: 9.3 to 10.7%, Zn: 0.3% or less, Cu: 0.1% or less, Mn: 0.1 to 0.35%, Ni: 0.01% or less, Si: 0.3% or less in mass% It is an alloy.

  In the ZK system, for example, ZK40, ZK60 and the like can be mentioned. ZK40 is, for example, a magnesium-based alloy containing Zn: 3.5 to 4.5% by mass% and Zr: 0.45% or more. ZK60 is, for example, a magnesium-based alloy containing Zn: 4.8 to 6.2% and Zr: 0.45% or more by mass.

  Although it is difficult to obtain sufficient strength with magnesium alone, preferable strength can be obtained by including the above chemical components.

  The magnesium-based alloy pipe obtained by the above production method is a high-strength pipe having a tensile strength of 280 MPa or more and an elongation of 5% or more. Further, by subjecting the obtained pipe to a heat treatment at a heating temperature of 200 to 300 ° C., a pipe excellent in ductility with a tensile strength of 250 MPa or more and an elongation of 10% or more can be obtained, and can be sufficiently used as a structural material.

  Embodiments of the present invention will be described below.

(Test Example 1-1)
Prepare an extruded material (base material pipe: outer diameter φ26.0mm, thickness 1.5mm, length 2000mm) equivalent to AM60 alloy, AZ31 alloy, AZ61 alloy and ZK60 alloy with ASTM symbol, and perform scouring with a swaging machine After that, the base material pipe was subjected to a heat treatment and then drawn under the following conditions.

(Alloy composition)
AM60 alloy: Mag-based alloy containing Al: 6.1% and Mn: 0.44% by mass, with the balance being Mg and impurities
AZ31 alloy: Mass%, Al: 3.0%, Zn: 1.0%, Mn: 0.15% Magnesium-based alloy with Mg and impurities remaining
AZ61 alloy: Magnesium-based alloy containing Al: 6.4% by mass, Zn: 1.0%, Mn: 0.28%, with the balance being Mg and impurities
ZK60 alloy: Magnesium-based alloy containing, by mass, Zn: 5.5% and Zr: 0.45%, with the balance being Mg and impurities.

(Kiping)
In this example, the splicing process was performed by heating the tip of the base tube to 350 ° C.

(Heat treatment)
In this example, the heat treatment was performed by a procedure in which the tip end portion of the spliced base metal tube was heated at a temperature of 350 ° C. for 1 hour and then cooled to room temperature (20 ° C.).

(Drawing)
The drawing process was a plug drawing using a plug, and four types of processes (conditions 1-A to 1-D) having different cross-sectional reduction rates were performed by changing the plug diameter. In this test, a die diameter: φ24.5mm, plug diameter: φ21.6mm (cross-sectional reduction rate: 9.1%), φ21.7mm (same: 12.0%), φ21.9mm (same: 17.9%), φ22 Four types of plugs of 0.0 mm (20.9%) were used. In addition, the drawing process was performed without heating, and the temperature of the base material tube was about room temperature (20 ° C.). Further, the drawing process was performed while supplying a lubricant between the drawing die and the base material pipe. In the following tests, the drawing process was performed while supplying the lubricant in the same manner.

  In this test, 10 base metal tubes of each component were prepared for each condition, and plugging was performed. Table 1 shows the number of wires that could be drawn without cracking under each condition.

  As shown in Table 1, it can be seen that any sample can be drawn at room temperature regardless of the alloy type. In particular, it can be seen that even when the degree of cross-section reduction is as high as 9.1%, it can be drawn at room temperature. However, when the workability (cross-sectional reduction rate) was 17.9%, 2 to 4 of 10 cracks occurred, and when the workability exceeded 20%, all 10 cracks occurred. From this, it was confirmed that the cross-sectional reduction rate is preferably 20% or less, particularly preferably 15% or less.

  Further, when the lower limit of the cross-section reduction rate was examined, it was found that 6% or more, particularly 8% or more is preferable in consideration of the mechanical characteristics and productivity of the pipe.

  Further, when the tensile strength and elongation of each alloy type pipe obtained by the drawing process under Condition 1-B were examined, the tensile strength was 280 MPa or more and the elongation was 5% or more. When these pipes were separately heat-treated at 200 to 300 ° C. for 30 minutes, pipes having a high strength with a tensile strength of 250 MPa or more and an elongation of 10% or more and excellent ductility were obtained.

(Test Example 1-2)
In Test Example 1-1, plugging was performed in the same manner as in Test Example 1-1 by changing the heating temperature of the heat treatment to be performed after the mouth-opening process in the range of 150 to 450 ° C. In this test, two types of processing with a cross-section reduction rate of 12.0% and 17.9% were performed (Conditions 2-B and 2-C). The heating time was 30 minutes at any heating temperature. Table 2 shows the results when using an extruded material made of AZ31 alloy.

  As shown in Table 2, it can be seen that the drawing process can be performed even at room temperature by performing the heat treatment after the staking process. In particular, when the heating temperature of the heat treatment is 200 ° C. or higher, even when the cross-section reduction rate is 17.9% and the degree of processing is high, cracking or the like does not occur in 60% or more of 10 pieces, and drawing processing is possible. . Further, when the heating temperature was 250 ° C. or higher and 400 ° C. or lower, cracking or the like did not occur in 80% or more of 10 pieces, and the drawing process could be performed. On the other hand, when the heating temperature was 450 ° C., cracks occurred in 60% of the 10 pieces. From this, it was confirmed that the heating temperature of the heat treatment applied after the lip processing is preferably 200 ° C. or higher and lower than 450 ° C., particularly preferably 250 ° C. or higher and 400 ° C. or lower. Similar results were obtained for AM60 alloy, AZ61 alloy, and ZK60 alloy other than AZ31 alloy.

(Test Example 1-3)
In the above test example 1-1, the heating process at the time of performing the staking process was changed in the range of 100 to 500 ° C., and the staking process was performed. As a result, in any of the alloy types, when the heating temperature was 200 ° C. or higher, it was possible to perform the sticking process without causing cracks. Further, in any alloy type, the higher the temperature, the easier it was to carry out the sticking process, but when the temperature exceeded 450 ° C., oxidation was observed on the surface. From this, it was confirmed that the heating temperature at the time of scouring is preferably 200 ° C. or higher and 450 ° C. or lower.

(Test Example 1-4)
The pipes of each alloy type that were subjected to the drawing process shown in Table 1 Condition 1-A using a die diameter of φ24.5mm and a plug diameter of φ21.6mm were each heat treated and then drawn under the following conditions. It was.

(Heat treatment)
In this example, the heat treatment was performed by a procedure in which the entire drawn pipe was heated at a temperature of 350 ° C. for 1 hour and then cooled to room temperature (20 ° C.).

(Drawing)
The drawing process was a plug drawing using a plug, and four types of processes (conditions 3-E to 3-H) with different cross-section reduction rates were performed by changing the plug diameter. In this test, the die diameter: φ23.0mm, plug diameter: φ20.2mm (cross-section reduction rate: 9.5%), φ20.4mm (same: 15.6%), φ20.5mm (same: 18.7%), φ20 Four types of plugs of .6 mm (21.7%) were used. The drawing process was performed without heating, and the temperature of the base material tube was room temperature (20 ° C.). In this test, similarly to Test Example 1-1, 10 base metal tubes of the same components as in Test Example 1-1 were prepared for each condition, and plugging was performed. Table 3 shows the number of pipes that could be drawn without cracking under each condition.

  As shown in Table 3, even if the pipe has been once drawn, it can be understood that any sample can be drawn at room temperature regardless of the alloy type by performing heat treatment after drawing. . In particular, it can be seen that even when the degree of cross-section reduction is as high as 9.5%, it can be pulled out at room temperature. However, when the degree of processing (cross-sectional reduction rate) exceeded 20%, all 10 pieces were cracked. From this, it was confirmed that the cross-sectional reduction rate is preferably 20% or less.

  Further, when the tensile strength and elongation of the pipes of each alloy type obtained by the drawing process under Condition 3-F were examined, the tensile strength was 280 MPa or more and the elongation was 5% or more. When these pipes were separately heat-treated at 200 to 300 ° C. for 30 minutes, pipes having a high strength with a tensile strength of 250 MPa or more and an elongation of 10% or more and excellent ductility were obtained.

(Test Example 1-5)
Prepare an extruded material similar to the extruded material used in Test Example 1-1, and after performing the same mouth heat treatment as in Test Example 1-1, perform the same heat treatment, and then perform the drawing process under the following conditions: went.

  The drawing process was a plug drawing using a plug, and a multi-pass plug drawing was performed in multiple stages using a die having a die diameter shown in Table 4 and a plug having a plug diameter. In addition, the drawing process includes a cold working with the temperature of the base material pipe set to room temperature (20 ° C) and a temperature at which the processing temperature (the temperature of the base material pipe immediately before being inserted into the drawing die) is 140 ° C. And inter-working. The base material tube in the warm working was heated by being immersed in a lubricating oil heated to 180 ° C.

  In cold working, two types of drawing were performed for each pass, a process in which an intermediate heat treatment was performed at 300 ° C. for 30 minutes and a process in which no intermediate heat treatment was performed. In warm processing, there are three types of drawing: a process where an intermediate heat treatment is performed at 300 ° C for 30 minutes every pass, a process where an intermediate heat treatment is performed at 300 ° C for 30 minutes every two passes, and a process where no intermediate heat treatment is performed Went. Table 4 shows the results when using an extruded material made of AZ31 alloy. In Table 4, “◯” indicates that the drawing process was performed without causing cracks, “×” indicates that the drawing process was not possible due to cracks, and “−” indicates that the drawing process was not performed.

  As shown in Table 4 Sample 1, it can be seen that by performing an intermediate heat treatment for each pass, it is possible to perform a multi-pass drawing process in multiple stages even at room temperature. In particular, it can be seen that a drawing process with a high degree of processing of 10% or more is possible. On the other hand, as shown in Sample 4 in Table 4, it can be seen that when drawing is performed warm, a plurality of passes can be performed in multiple stages by performing heat treatment every two passes. In particular, it can be seen that the drawing can be performed even at a high degree of processing of 10% or more. On the other hand, when no intermediate heat treatment was performed between the passes, the first pass was pulled out even at room temperature as shown in Table 4 Sample 2, but cracking occurred in the middle of the second pass. From this, it was confirmed that by performing heat treatment for each pass, a plurality of passes can be drawn in multiple stages even at room temperature. Similar results were obtained for AM60 alloy, AZ61 alloy, and ZK60 alloy other than AZ31 alloy.

  Further, when the tensile strength and elongation of the pipes of the respective alloy types obtained by the drawing process under the conditions shown in Sample 1 were examined, the tensile strength was 280 MPa or more and the elongation was 5% or more. Further, when these pipes were separately heat-treated at 250 ° C. for 30 minutes, pipes having a tensile strength of 250 MPa or more and an elongation of 10% or more and excellent ductility were obtained.

(Test Example 1-6)
Prepare an extruded material similar to the extruded material used in Test Example 1-1, and after performing the mouth-opening process in the same manner as in Test Example 1-1, without subjecting to heat treatment, a drawing process was performed under the following conditions: .

  The drawing process was a plug drawing using a plug, and a one-pass plug drawing was performed using a plug having a die diameter of φ24 mm and a plug diameter of φ21.1 mm. In addition, the drawing process includes a cold working with the temperature of the base material pipe set to room temperature (20 ° C) and a temperature at which the processing temperature (the temperature of the base material pipe immediately before being inserted into the drawing die) is 140 ° C. And inter-working. The base material tube was heated in the warm working by immersing in a lubricating oil heated to 200 ° C.

  As a result, in cold working, all the tubes were disconnected in the middle of drawing and could not be drawn. On the other hand, in the warm working, it could be pulled out without disconnection. Further, when plug drawing of a plurality of passes was performed in multiple stages in the same manner as in Test Example 1-5, it was possible to perform drawing in multiple stages by performing heat treatment every two passes in the same manner as described above.

(Test Example 2)
Test Example 1-4 When ten AZ61 alloy pipes obtained by drawing under Condition 3-G were examined for the surface, seizure was observed in two of the ten pipes. In addition, when the surface roughness of 10 pipes of AZ61 alloy obtained by the drawing process of Test Example 1-4 Condition 3-G, that is, the drawing process of Test Example 1-1 Condition 1-A was examined, 10 points were obtained. The average roughness was 1.2 to 1.5 μm.

  Therefore, ten AZ61 alloy extruded materials similar to those in Test Example 1-1 were subjected to the same heat treatment as in Test Example 1-1, and then subjected to the same heat treatment as shown in Table 1 Condition 1-A. 10 pipes were produced. Then, the obtained 10 pipes were roughened with sandpaper (10-point average roughness: 5.2 to 8.2 μm). Ten pipes subjected to these surface treatments were subjected to a drawing process under Condition 3-G in Table 3, and the surface of the obtained pipe was examined. As a result, no seizure phenomenon was observed. From this, it was confirmed that seizure due to drawing can be effectively prevented by roughening the surface of the base material tube with a 10-point average roughness of 5 μm or more before drawing.

  Similarly, when 2-pass drawing is performed at room temperature (heated to 140 ° C) instead of room temperature as shown in Table 3, Condition 3-G, the surface of the base material tube is also subjected to 10-point average roughening before drawing. Now, it was found that seizure due to drawing can be prevented by roughening to 5 μm or more. From this, it was confirmed that the effect of this surface treatment can be obtained regardless of whether it is cold or warm.

  The present invention is optimal when producing a magnesium-based alloy pipe having high strength and excellent ductility with high productivity.

Claims (12)

A mouth opening process for performing mouth attaching to the tip of a base material pipe made of a magnesium-based alloy;
A heat treatment step of performing a heat treatment on the spliced base metal pipe;
A drawing step of drawing the base material pipe subjected to the heat treatment,
The heat treatment step includes
Heating at least the tip of the base tube to 200 ° C. or higher and lower than 450 ° C .;
A process of cooling after heating,
The method for producing a magnesium-based alloy pipe, wherein the drawing process is performed at room temperature without heating the base material pipe after the heat treatment step.   2. The method for producing a magnesium-based alloy pipe according to claim 1, wherein a cross-sectional reduction rate in one drawing is 6% or more and 20% or less.   2. The method for producing a magnesium-based alloy pipe according to claim 1, wherein the staking process is performed by heating at least a tip portion of the base material pipe to 200 ° C. or higher and 450 ° C. or lower.   The drawing of the magnesium-based alloy pipe according to claim 1, wherein the drawing process includes an intermediate heat treatment process in which a plurality of passes are performed at room temperature in multiple stages, and heat treatment is performed on the drawn tube drawn for each pass. Production method. The base material pipe made of a magnesium-based alloy is obtained by extrusion,
A first drawing step of drawing the base material tube that has been heat-treated after the lip processing, after the heat treatment step, without heating the base material tube at a room temperature reduction rate of 15% or less at room temperature;
Subsequent to the first drawing step, an intermediate heat treatment step for performing a heat treatment on the drawn drawing tube,
2. The method for producing a magnesium-based alloy pipe according to claim 1, further comprising a second drawing step of drawing the drawn tube obtained at room temperature without heating the intermediate heat treatment step. The intermediate heat treatment process
Heating the drawn tube to 200 ° C or higher and lower than 450 ° C;
6. The method for producing a magnesium-based alloy pipe according to claim 4, further comprising a step of cooling after heating. Furthermore, a surface treatment process for roughening the surface of the base material pipe drawn after the heat treatment ,
2. The method for producing a magnesium-based alloy pipe according to claim 1, further comprising a third drawing step in which the base material pipe subjected to the surface treatment is subjected to a drawing process using a lubricant.   8. The method for producing a magnesium-based alloy pipe according to claim 7, wherein the surface roughness of the base material pipe after the surface treatment is 5 μm or more in terms of a 10-point average roughness. 8. The method for producing a magnesium-based alloy pipe according to claim 7, wherein the drawing process in the third drawing step is performed at room temperature.   10. The method for producing a magnesium-based alloy pipe according to claim 1, wherein the magnesium-based alloy contains 0.1 to 12% by mass of Al, and the balance is made of Mg and impurities.   11. The magnesium-based alloy further contains at least one selected from Mn: 0.1 to 2.0%, Zn: 0.1 to 5.0%, and Si: 0.1 to 5.0% by mass%. Method for producing magnesium-based alloy pipes.   The magnesium-based alloy according to any one of claims 1 to 9, wherein the magnesium-based alloy contains Zn: 0.1 to 10% and Zr: 0.1 to 2.0% by mass, with the balance being Mg and impurities. Pipe manufacturing method.