JP5083816B2 - Al-Zn-Mg-Cu alloy extruded material excellent in warm workability, production method thereof, and warm worked material using the extruded material - Google Patents

Description

  The present invention relates to an Al—Zn—Mg—Cu alloy extruded material excellent in warm workability, a method for producing the same, and an aluminum alloy warm worked material obtained from the extruded material.

  Since Al—Zn—Mg—Cu alloys have high strength, they are widely used in the field of transportation equipment that is strongly required to be lightweight. Particularly in motorcycles, since there is a high need for weight reduction, Al-Zn-Mg-Cu alloy materials are often used for structural members such as frames.

  Conventionally, when an Al-Zn-Mg-Cu alloy material is used after being plastically processed, it is plastically processed with O tempering and used as T6 or T7 tempering through the steps of solution treatment, quenching, and aging treatment. ing. However, if solution treatment is performed after plastic working, deformation occurs at high temperatures or distortion occurs during quenching, so strain correction is often required after quenching, which causes an increase in manufacturing costs. It was.

  For this reason, for the purpose of reducing the manufacturing process and reducing the cost, a process of performing plastic working with T4 tempering after solution treatment without softening treatment has been proposed. In particular, the material strength is improved by performing restoration processing before plastic working. It has been studied to reduce and secure stable workability.

  For example, in order to obtain a motorcycle front fork outer tube material having excellent stress corrosion cracking resistance, an Al-Zn-Mg-Cu alloy extruded tube is subjected to solution treatment and quenching, and natural aging is performed for 100 hours or more at room temperature. After that, a heat treatment is performed at a temperature of 150 to 250 ° C. for 30 seconds to 10 minutes, and in this heat treatment, the temperature rise time from at least 100 ° C. to the heat treatment temperature is set to 1 ° C./second or more, and finally an artificial aging treatment is performed. It has been proposed (see Patent Document 1).

Further, as a method for forming a high-strength aluminum alloy, a process of performing a restoration process at 150 to 350 ° C. immediately before forming has been proposed (see Patent Document 2). Furthermore, in order to obtain a high-strength aluminum alloy tube excellent in tube expansion workability, it has been proposed to further heat-treat the T4 tempered material at a temperature of 105 to 250 ° C. for 30 seconds to 180 minutes (see Patent Document 3). .
Japanese Patent No. 3638188 Japanese Patent Laid-Open No. 7-305151 JP 2007-119853 A

  However, all of the proposed methods are based on the premise that the processing after restoration processing is performed at room temperature. Therefore, there is a problem that workability becomes insufficient when performing strong processing. It is desired to improve the performance.

  In order to improve the plastic workability after natural aging in the process of solution aging, quenching, natural aging, and then plastic working and artificial aging treatment of the extruded material of Al-Zn-Mg-Cu alloy. In the process of studying the above method, heat treatment is performed in a specific temperature range after quenching, and further, warm plastic processing is performed in a specific temperature range, so that the strength obtained by artificial aging treatment after plastic processing is not impaired. The present inventors have found that plastic workability can be improved.

  The present invention was made as a result of repeated experiments and examinations based on the above knowledge, and the purpose of the present invention is to perform heat treatment in a specific temperature range after quenching, thereby achieving high plastic workability by warm working. Al-Zn-Mg-Cu alloy extrudate excellent in warm workability without damaging the strength obtained by artificial aging treatment after plastic working, its production method, and the extrudate The object is to provide a warm-working material using the above.

  The Al—Zn—Mg—Cu alloy extrudate excellent in warm workability according to claim 1 for solving the above object is Zn: 5.0-7.5%, Mg: 1.6-3. 3%, Cu: 1.1 to 2.5%, Cr: 0.30% or less, Mn: 0.60% or less, Zr: 0.30% or less, and Ti : Containing at least one of 0.06% or less, B: 0.005% or less, further limiting Fe and Si as impurities to 0.25% or less respectively, and comprising the balance Al and unavoidable impurities An aluminum alloy extruded material of W tempering or T4 tempering, the inside of the depth of 200 μm or more from the surface is composed of a fibrous structure consisting of sub-crystal grains, and the main direction of the texture is the Brass direction, ODF (Crystallite Orientation istribution Function; integration to Brass orientation represented by the crystal orientation distribution function) is equal to or is at least 10 times the random orientation.

  The Al—Zn—Mg—Cu alloy extrudate excellent in warm workability according to claim 2 is a heat analysis by DSC (Differential Scanning Calorimetry) in the extrudate according to claim 1, An endothermic peak and an exothermic peak appear in the range of 100 to 200 ° C.

  The extruded material of Al-Zn-Mg-Cu alloy having excellent warm workability according to claim 3 is the extruded material according to claim 1 or 2, further after solution treatment and quenching, within 30 days at 40 ° C or less. The Vickers hardness in the W tempering or T4 tempering obtained by natural aging is 190 or less, and then the Vickers hardness when further subjected to heat treatment at 180 ° C. for 1 minute is 100 or more and 180 or less. Features.

  The Al—Zn—Mg—Cu alloy extruded material excellent in warm workability according to claim 4 is a nominal obtained by a uniaxial tensile test at room temperature in the extruded material according to claim 1. The n value (work hardening index) in the range of 5% to 10% strain is 0.15 or more.

The Al—Zn—Mg—Cu alloy extruded material excellent in warm workability according to claim 5 is the extruded material according to any one of claims 1 to 4, wherein the extruded material is a tubular shaped extruded material, and remains naturally aged. in case the limit pipe expansion ratio when the limit pipe expansion ratio in the case of performing the tube expanding process was pipe expanding at room temperature after heat treatment of R _0, 180 ° C. for 1 minute was defined as R _1, R _{1 /} R ₀ Is 1.1 or more.

  The method for producing an extruded material of Al-Zn-Mg-Cu alloy excellent in warm workability according to claim 6 is a method for producing the extruded material according to any one of claims 1 to 5, wherein Zn: 5 0.0 to 7.5%, Mg: 1.6 to 3.3%, Cu: 1.1 to 2.5%, Cr: 0.30% or less, Mn: 0.60% or less, One or more of Zr: 0.30% or less, and Ti: 0.06% or less, B: 0.005% or less, and Fe and Si as impurities are each 0 .. Limiting to 25% or less, melting and casting an aluminum alloy having a composition comprising the balance Al and inevitable impurities, homogenizing the obtained ingot, performing hot extrusion, further solution treatment and quenching Within 5 minutes after quenching, at a temperature of 50 ° C. to 100 ° C. for 1 minute to 3 Min and performing the following heat treatment.

  The method for producing an extruded material of Al—Zn—Mg—Cu alloy excellent in warm workability according to claim 7 is the method according to claim 6, wherein the homogenization treatment is performed at a temperature of 400 ° C. or more and 500 ° C. or less, and then 300 An additional heat treatment is performed at a temperature of not lower than 400 ° C. and not higher than 400 ° C., followed by hot extrusion.

  The aluminum alloy warm work material according to claim 8 is an Al-Zn-Mg-Cu alloy extrudate excellent in warm workability according to any one of claims 1 to 5, and is 100 ° C or higher and 200 ° C or lower. It is characterized by being obtained by performing plastic working at temperature and further performing artificial aging treatment.

  According to the present invention, there is provided a warm-worked material produced by a warm-working method for obtaining high plastic workability, an Al-Zn-Mg-Cu alloy extruded material suitable for the warm-working, and a method for producing the same. Provided. The warm-worked material can obtain a sufficiently high strength in the artificial aging treatment after plastic working.

  Explaining the significance and reason for limitation of the alloy element of the Al-Zn-Mg-Cu alloy extrudate excellent in warm workability according to the present invention, Zn is an element that functions to improve the strength, and its preferred content range is 5.0-7.5%. If it is less than the lower limit, the strength becomes insufficient, and if it exceeds the upper limit, the stress corrosion cracking resistance (hereinafter referred to as SCC resistance) is lowered. The more preferable content range of Zn is 5.5 to 7.0%, and the most preferable content range is 5.9 to 6.5%.

  Mg is an element that functions to improve the strength, and its preferable content range is 1.6 to 3.3%. If it is less than the lower limit, the strength becomes insufficient, and if it exceeds the upper limit, the SCC resistance is lowered. The more preferable content range of Mg is 1.9 to 3.0%, and the most preferable content range is 2.2 to 2.7%.

Cu is an element that functions to improve strength and maintain moderate strength during warm working, and its preferred content range is 1.1 to 2.5%. If it is less than the lower limit, no exothermic peak appears in the range of 100 to 200 ° C. in DSC thermal analysis, and the material strength during warm working is too low. In addition, the n value is less than the lower limit, and non-uniform deformation is likely to occur. Depending on the warm working method, wrinkling may occur, and sufficient warm workability may not be obtained. Furthermore, the strength finally obtained is also reduced. If the content exceeds the upper limit, the ratio R ₁ / R ₀ of the critical tube expansion ratio before and after the heat treatment becomes too low, the strength becomes too high during warm working, causing deterioration of workability, and stress corrosion resistance. The crackability is reduced. The more preferable content range of Cu is 1.3 to 2.2%, and the most preferable content range is 1.6 to 2.0%.

  Cr, Mn, and Zr are elements that are selectively contained. By containing one or more of these elements, the crystal structure of the extruded material is made fibrous and functions to improve the SCC resistance. Further, the main direction of the texture can be controlled to the Brass direction. Preferable content ranges are Cr: 0.30% or less, Mn: 0.60% or less, Zr: 0.30% or less, and when any content exceeds the upper limit, a coarse intermetallic compound is formed, and ductility is achieved. As well as a decrease in warm workability. Further preferable content ranges are Cr: 0.05 to 0.25%, Mn: 0.05 to 0.50%, Zr: 0.05 to 0.25%, and the most preferable content range is Cr: 0. .10 to 0.23%, Mn: 0.10 to 0.40%, Zr: 0.10 to 0.20%.

  Ti and B are both elements that contribute to the refinement of the cast structure, and preferable content ranges are Ti: 0.06% or less and B: 0.005% or less. If the content exceeds the upper limit, a coarse intermetallic compound is formed, ductility is lowered, and warm workability is lowered.

  Fe and Si are elements contained as impurities, and allowable ranges are Fe: 0.25% or less and Si: 0.25% or less. When it contains exceeding an upper limit, while ductility will fall, warm workability will fall. Further preferable allowable content ranges are Fe: 0.20% or less, Si: 0.20% or less, and most preferable allowable content ranges are Fe: 0.15% or less, Si: 0.15% or less. is there.

  The extruded Al—Zn—Mg—Cu alloy material having excellent warm workability according to the present invention is composed of a fibrous structure in which the inside of a depth of 200 μm or more from the surface is composed of sub-crystal grains in W tempering or T4 tempering. Furthermore, it is preferable that the main orientation of the texture is the Brass orientation {110} <112>, and the degree of accumulation in the Brass orientation expressed in ODF is 10 times or more of the random orientation.

  Recrystallized grains may exist within a depth of less than 200 μm from the surface, but if there are recrystallized grains inside the surface at a depth of 200 μm or more from the surface, processing cracks will occur when plastic working is warm. May cause a decrease in warm workability. In addition, when the main orientation of the texture is other than the Brass orientation, or when the degree of accumulation in the Brass orientation is less than 10 times the random orientation, processing cracks may occur when performing plastic working warmly, It causes a decrease in warm workability. Furthermore, the preferable integration degree in the Brass orientation is 20 times or more of the random orientation.

  The measurement of ODF is performed at the center of the thickness by the X-ray diffraction method. In the case of a flat plate shape, a surface perpendicular to the plate thickness direction is cut and polished with water-resistant abrasive paper, and then residual stress and deposits are removed by etching to produce a test piece for ODF measurement. In the case of a pipe shape, after cutting the outer inner diameter, a test piece having a thickness of 100 μm is collected from the center of the wall thickness by dissolving the outer inner diameter with caustic soda, and flattened by elastic deformation to obtain a test piece for ODF measurement. Is produced. In the case of a round bar, it is regarded as a pipe having an inner diameter of 0 mm and a wall thickness equal to that of the radius, and an ODF measurement test piece is produced by the same method as that for the pipe material described above.

  Moreover, it is preferable that the Al-Zn-Mg-Cu alloy extruded material excellent in warm workability according to the present invention has an endothermic peak and an exothermic peak in a range of 100 to 200 ° C by thermal analysis by DSC. Since 7000 series aluminum alloy forms GP zone by natural aging after quenching, in the case of W tempering or T4 tempering other than just after quenching, an endothermic peak appears in the range of 100 to 200 ° C. Decomposition occurs. An endothermic peak does not appear immediately after quenching. When such decomposition of the GP zone occurs, the strength is lowered and the workability is improved. On the other hand, when an exothermic peak appears in the range of 100 to 200 ° C., precipitation of η ′ phase occurs during warm working and the strength increases. Therefore, when an endothermic peak and an exothermic peak appear in the range of 100 to 200 ° C., decomposition of the GP zone and precipitation of the η ′ phase occur simultaneously during warm working. Decomposition of the GP zone improves warm workability, and the η 'phase precipitates moderately increases the strength of the work material, so that the material strength during warm work does not decrease too much and is less likely to cause non-uniform deformation. Thus, sufficient warm workability can be obtained. When no endothermic peak or exothermic peak appears, warm workability is reduced. In addition, the thermal analysis by DSC is performed at a temperature increase rate of 10 to 20 ° C./min.

  Furthermore, the Al—Zn—Mg—Cu alloy extruded material excellent in warm workability according to the present invention has a Vickers hardness when subjected to natural aging within 40 days at 40 ° C. or lower after solution treatment and quenching. It is 190 or less (excluding 0), and it is preferable that the Vickers hardness when the heat treatment is further performed at 180 ° C. for 1 minute is 100 or more and 180 or less. If the Vickers hardness after natural aging within 30 days at 40 ° C. or lower exceeds the upper limit, processing cracks are likely to occur during warm working.

  In addition, when the Vickers hardness when the heat treatment is performed at 180 ° C. for 1 minute is less than the lower limit, the material strength during the warm working is too low, and non-uniform deformation is easily caused, and the warm workability is improved. If the upper limit is exceeded, processing cracks are likely to occur during warm working. A more preferable range of the Vickers hardness before the heat treatment is 100 or more and 180 or less, and a further preferable range of the Vickers hardness after the heat treatment is 100 or more and 170 or less.

  The Al-Zn-Mg-Cu alloy extruded material excellent in warm workability according to the present invention has an n value of 0.15 or more in a range of nominal strain of 5 to 10% obtained by a uniaxial tensile test at room temperature. It is preferable. The warm n value is proportional to the normal temperature n value. For this reason, the higher the n value at room temperature, the easier the work hardening during warm working occurs, the local deformation is suppressed, and the warm workability is improved. When the n value is less than the lower limit, local deformation is likely to occur during warm working, which causes a decrease in warm workability.

In the case of an Al-Zn-Mg-Cu alloy extruded material having excellent warm workability according to the present invention, when the tube shape is used, the limit tube expansion ratio when the tube expansion processing is performed with natural aging is R ₀ , 180 ° C. When the limiting tube expansion rate is R ₁ when the tube expansion is performed at room temperature after performing heat treatment for 1 minute, it is preferable that R ₁ / R ₀ is 1.1 or more. The limit tube expansion ratio R is calculated by R = L ₁ / L ₀ where L _{0 is} the outer circumferential length of the tube before the tube expansion processing and L ₁ is the outer circumferential length of the tube at the limit where cracking occurs. When R ₁ / R ₀ is less than the lower limit, the decomposition of the GP zone in the warm working becomes insufficient, resulting in a decrease in warm workability.

  Next, the manufacturing method of the Al-Zn-Mg-Cu alloy extrudate excellent in warm workability according to the present invention will be described. First, an Al—Zn—Mg—Cu alloy having a predetermined composition is melted and ingot-formed by a semi-continuous casting method. The obtained ingot is homogenized to form a billet for extrusion.

  The homogenization treatment temperature is desirably 400 ° C. or more and 500 ° C. or less, and the homogenization treatment time is desirably 1 hour or more and 20 hours or less. These processing conditions are general processing conditions applied to the Al—Zn—Mg—Cu alloy. Further, after the homogenization treatment, it is preferable to perform additional heat treatment at a temperature of 300 ° C. or more and 400 ° C. or less. By combining this additional heat treatment and subsequent hot extrusion, the main orientation of the texture is changed to the Brass orientation. The degree of integration of the Brass azimuth expressed in ODF can be increased, and can be made 10 times or more of the random azimuth. The additional heat treatment may be performed by cooling the extrusion billet from the homogenization temperature to the additional heat treatment temperature after the homogenization treatment. After the homogenization treatment of the extrusion billet, the temperature once lower than the additional heat treatment, for example, You may carry out by cooling to room temperature and reheating.

  Next, the billet is heated prior to extrusion, and the heating temperature is preferably within ± 50 ° C. with respect to the temperature of the additional heat treatment after the homogenization treatment. Extrusion is usually performed by once cooling the billet from the homogenization temperature or additional heat treatment temperature, generally cooling to room temperature, and reheating to the extrusion temperature. You may carry out by cooling from temperature to extrusion temperature. Although the billet heating method is not particularly limited, an atmospheric furnace or an induction furnace is preferably used. The billet heated to a predetermined temperature is hot extruded into a predetermined shape. As the extrusion method, a direct extrusion method may be used, but an indirect extrusion method is more preferable. By heating the billet to the above temperature range and performing hot extrusion by the indirect extrusion method, the main orientation of the texture can be controlled to the Brass orientation, and the integration degree of the Brass orientation expressed by ODF is higher. can do. After hot extrusion, it is cooled to room temperature and then cut into a predetermined length. After extrusion, softening and cold working are performed as necessary.

  The extruded material or the cold worked material is subjected to a solution treatment. The solution treatment temperature is desirably 400 ° C. or higher and 500 ° C. or lower. The holding time varies depending on the shape, but it is sufficient that the target temperature is reached up to the center of the thickness. Quenching is performed after the solution treatment. As a cooling solvent, an aqueous solution of water, oil or poval, polyethylene glycol, polyalkylene glycol or the like is used.

  In the present invention, after solution treatment and quenching, it is preferable to perform a heat treatment for 1 minute to 30 minutes at a temperature of 50 ° C. to 100 ° C. within 5 minutes after quenching. By performing this heat treatment, the Vickers hardness in W tempering or T4 tempering obtained by natural aging within 30 days at 40 ° C. or lower can be reduced to 190 or lower, and further excellent warm workability can be obtained. . If the heat treatment conditions are outside the above conditions, the strength obtained by the artificial aging treatment after warm working may be reduced.

  The plastic working of the W material or T4 tempered material obtained in the present invention is preferably warm working at 100 ° C. or higher and 200 ° C. or lower. The workpiece may be subjected to plastic working after being heated to a predetermined temperature by heat treatment, or the workpiece at normal temperature may be heated to 100 ° C. or more and 200 ° C. or less by heat generated by cold working. The type of plastic working is not particularly limited, and examples thereof include rolling, swaging, and spinning.

  When the processing temperature is less than 100 ° C. or when the processing temperature exceeds 200 ° C., any cracks are likely to occur. A more preferred temperature range for warm working is 120 ° C. to 200 ° C., and a most preferred temperature range for warm working is 140 ° C. to 200 ° C. In addition, after warm processing, plastic processing at normal temperature can also be performed within a range where cracks do not occur.

  Artificial aging treatment is applied to the workpiece after warm processing. Artificial aging treatment conditions vary depending on the targeted tempering or strength, and thus cannot be defined unconditionally. In general, however, it is preferable to perform treatment at a temperature of 100 ° C. or more and 200 ° C. or less for about 1 to 50 hours.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects of the present invention. In addition, these Examples show one Embodiment of this invention, and this invention is not limited to these.

Example 1
A 150 mm diameter aluminum alloy ingot having a composition of alloys A to J shown in Table 1 was prepared according to a conventional method, and the obtained ingot was subjected to homogenization treatment at 450 ° C. for 10 hours, and further in a furnace at 380 ° C. After cooling to 380 ° C. for 10 hours, it was cooled to room temperature to form billets for extrusion. These billets for extrusion were heated to 380 ° C. in an induction heating furnace and thickened by hot extrusion. A plate-like extruded material having a thickness of 6 mm and a width of 100 mm was produced.

  The obtained aluminum alloy extruded material was placed in an air furnace heated and held at a temperature of 460 ° C., and subjected to a solution treatment by holding for 60 minutes. Next, after quenching with normal temperature tap water, further heat treatment at 70 ° C. for 10 minutes, cooling to normal temperature, and natural aging at 40 ° C. for 30 days to obtain a T4 tempered material, 10 was obtained.

  For each of the test materials 1 to 10, a microstructure observation, an ODF measurement, a thermal analysis test, a Vickers hardness test, and an n-value measurement were performed according to the methods described later. Further, each test material was placed in an oil bath heated and held at 180 ° C., held for 1 minute, cooled to room temperature, and immediately subjected to a Vickers hardness test described later.

  Each test material was placed in an oil bath heated and maintained at 180 ° C., held for 1 minute, and then the oil bath oil was adhered to the surface of the material, and the temperature of 180 ° C. was 15 per pass. The rolling was continuously repeated at a workability of ˜20%, and the limit rolling rate at which no cracks occurred was measured. At this time, a roll with a roll diameter of 350 mm was used, and the roll rotation speed was set to 1 rotation / second.

  Further, each test material was placed in an oil bath heated and held at 180 ° C., held for 1 minute, then rolled at a temperature of 180 ° C. with a cross-section reduction rate of 30%, cooled to room temperature, and then 120 An artificial aging treatment for 6 hours was performed at 0 ° C., and a tensile test and a stress corrosion cracking test described later were performed. The test results are shown in Table 2.

  Microstructural observation: A test specimen for microstructural observation having a length of 10 mm and a width of 10 mm is cut and collected from the center of the width of the plate-shaped test material, and the thermosetting resin is resin so that the plane perpendicular to the width direction becomes the observation plane. After filling and rough polishing with water-resistant polishing paper, finish polishing with alumina powder and etching with Keller's solution to obtain a sample for microstructure observation. About each sample, a 100 times as many structure | tissue photograph is image | photographed with an optical microscope, and the presence or absence of a recrystallized grain is investigated inside 200 micrometers or more from the surface.

  ODF measurement: A test piece having a length of 20 mm and a width of 20 mm is cut and collected from the center of the width of the plate-shaped test material, and after chamfering so that the surface perpendicular to the thickness direction becomes the measurement surface, water-resistant abrasive paper Polish to No. 1200 until the thickness becomes 3 mm (1/2 of the original plate thickness), perform corrosion for 10 seconds with a macro corrosive liquid mixed with nitric acid, hydrochloric acid and hydrofluoric acid, and test specimen for X-ray diffraction Is made. For each specimen, create a pole figure by the X-ray reflection method, perform a three-dimensional orientation analysis by a series expansion method using a spherical harmonic function, investigate the main orientation, and the direction of the Brass orientation ({110} <112>) The density is measured with a random ratio. The series expansion order is assumed to be 22nd.

  Thermal analysis test: A disk-shaped test piece having a thickness of 1 mm and a diameter of 5 mm from the center of the width of the plate-shaped test material and a thickness of 5 mm, and the thickness direction of the plate-shaped test material and the thickness direction of the disk-shaped test material are Cutting and sampling are performed in the matching direction, and heating is performed from room temperature to 250 ° C. at a heating rate of 20 ° C./min using a heat flow rate type differential scanning calorimeter (DSC), and the change in the amount of heat is measured. At this time, pure aluminum having a purity of 99.999% is used as a reference. And the presence or absence of the endothermic peak and exothermic peak in the range of 100-200 degreeC is investigated from a thermal analysis result.

  Vickers hardness test: A test piece having a length of 20 mm and a width of 20 mm is cut and sampled from the central portion of the plate-like test material and the thickness center portion, and water-resistant polishing is performed so that the surface perpendicular to the thickness direction becomes the measurement surface. Polish to a depth of 0.5 mm with paper, and finish with No. 1200. Using the polished surface as a measurement surface, Vickers hardness measurement is performed according to JIS Z 2244 with a load of 98N. In addition, in the hardness measurement after heat processing for 1 minute at 180 degreeC, grinding | polishing is performed before heat processing and a Vickers hardness measurement is performed within 5 minutes after heat processing.

  n-value measurement: No. 5 test piece shown in JIS Z 2201 is molded from the center of the width of the plate-shaped test material. According to JIS Z 2241, a tensile test is performed at a crosshead speed of 10 mm / min at normal temperature, the nominal stresses at nominal strains of 5% and 10% are measured, and the n value is calculated according to JIS Z 2253.

  Tensile test: No. 5 test piece shown in JIS Z 2201 is molded from the center of the width of the plate-shaped test material. According to JIS Z 2241, a tensile test is performed at a normal temperature and a crosshead speed of 10 mm / min, and tensile strength, proof stress, and elongation are measured.

  Stress corrosion cracking test: A tensile test piece having a parallel part width of 3 mm and a parallel part length of 15 mm was formed so that the tensile direction coincided with the width direction of the extruded material, and a tensile stress of 70% of the proof stress was applied, and 25 ° C. A cycle of 10 minutes in a 3.5% NaCl aqueous solution at a temperature of 50 minutes and 50 minutes in the air is repeated for a maximum of 500 hours, and the time at which breakage occurs is measured.

  As can be seen in Table 2, none of the test materials 1 to 10 according to the present invention has a recrystallized structure in the depth of 200 μm or more from the surface, the main direction of the texture is the Brass direction, and ODF Vickers when the degree of integration in the Brass orientation is more than 10 times that of the random orientation, and there is an endothermic peak and an exothermic peak between 100 and 200 ° C. in thermal analysis by DSC, and natural aging is performed at 40 ° C. for 30 days. The hardness was 190 or less and the Vickers hardness after heat treatment at 180 ° C. for 1 minute was in the range of 100 to 180. In addition, the n value in the range of nominal strain of 5% to 10% is 0.15 or more, and a high critical rolling ratio of 70% or more is exhibited, and both tensile properties and stress corrosion cracking resistance are excellent.

Example 2
An aluminum alloy ingot having a composition of alloys A to J shown in Table 1 having a diameter of 320 mm was produced according to a conventional method, and the obtained ingot was subjected to homogenization treatment at 450 ° C. for 10 hours, and further in a furnace at 380 ° C. After performing additional heat treatment at 380 ° C. for 10 hours, cooling to room temperature, cutting to an outer diameter of 300 mm and an inner diameter of 50 mm to form extrusion billets, these extrusion billets were 380 in an induction heating furnace. Heated to ° C., an extruded tube (outer diameter 65 mm, inner diameter 50 mm) was produced by the indirect extrusion method.

  The produced aluminum alloy extruded tube was placed in an air furnace heated and held at a temperature of 460 ° C., and subjected to a solution treatment by holding for 60 minutes. Next, after quenching with normal temperature tap water, further heat treatment at 70 ° C. for 10 minutes, cooling to normal temperature, and natural aging at 40 ° C. for 30 days to obtain a T4 tempered material, 20 was obtained.

  For each of the test materials 1 to 10, a microstructure observation, an ODF measurement, a thermal analysis test, a Vickers hardness test, an n-value measurement, and a tube expansion test were performed according to the methods described later. Further, each test material was placed in an oil bath heated and held at 180 ° C., held for 1 minute, cooled to room temperature, and immediately subjected to a Vickers hardness test described later.

  In addition, each test material was placed in an oil bath heated and held at 180 ° C., held for 1 minute, and then drawn into a shape having an outer diameter of 60 mm and an inner diameter of 50 mm at a temperature of 180 ° C., and cracks were generated. The presence or absence was investigated. Furthermore, each test material was placed in an oil bath heated and held at 180 ° C., held for 1 minute, then drawn into a shape with an outer diameter of 62 mm and an inner diameter of 50 mm at a temperature of 180 ° C., and cooled to room temperature. Then, an artificial aging treatment was performed at 120 ° C. for 6 hours, and a tensile test described later was performed. The test results are shown in Table 3.

  Microstructural observation: A specimen for microstructural observation having a length of 10 mm and an outer peripheral length of 10 mm is cut and collected from a tubular test material, and the thermosetting resin is embedded in the resin so that the surface perpendicular to the circumferential direction becomes the observation surface. After rough polishing with water-resistant abrasive paper, finish polishing with alumina powder and etching with Keller's solution yield a sample for microstructure observation. About each sample, a 100 times as many structure | tissue photograph is image | photographed with an optical microscope, and the presence or absence of a recrystallized grain is investigated inside 200 micrometers or more from the surface.

  ODF measurement: The outer surface and the inner surface of the tubular test material are each cut by a lathe by 3.7 mm and processed to an outer diameter of 57.6 mm and an inner diameter of 57.4 mm. Thereafter, a test piece having a length of 20 mm and a width of 20 mm is cut and collected, dissolved with caustic soda to a thickness of 0.1 mm, and further attached to a flat jig measuring 20 mm × 20 mm with double-sided tape for X-ray diffraction. A test piece is prepared. For each specimen, create a pole figure by the X-ray reflection method, perform a three-dimensional orientation analysis by a series expansion method using a spherical harmonic function, investigate the main orientation, and the direction of the Brass orientation ({110} <112>) The density is measured with a random ratio. The series expansion order is assumed to be 22nd.

  Thermal analysis test: A disk-shaped test piece having a thickness of 1 mm and a diameter of 5 mm was cut and collected from a tubular test material, and the temperature was increased from room temperature to 250 ° C. using a thermal flow rate type differential scanning calorimeter (DSC) at 20 ° C./min. Heat at a temperature rate and measure the change in heat. At this time, pure aluminum having a purity of 99.999% is used as a reference. And the presence or absence of the endothermic peak and exothermic peak in the range of 100-200 degreeC is investigated from a thermal analysis result.

  Vickers hardness test: A test piece having a length of 20 mm and a width of 20 mm is cut and collected from a tubular test material, and polished to a depth of 0.5 mm with water-resistant abrasive paper so that the surface perpendicular to the extrusion direction becomes the measurement surface. Finish polishing with No. 1200. Using the polished surface as a measurement surface, Vickers hardness measurement is performed according to JIS Z 2244 with a load of 98N. In addition, in the hardness measurement after heat processing for 1 minute at 180 degreeC, grinding | polishing is performed before heat processing and a Vickers hardness measurement is performed within 5 minutes after heat processing.

  n-value measurement: A JIS 12A-shaped tensile test piece having a length of 300 mm is formed from a tubular test material. According to JIS Z 2241, a tensile test is performed at a crosshead speed of 10 mm / min at normal temperature, the nominal stresses at nominal strains of 5% and 10% are measured, and the n value is calculated according to JIS Z 2253.

Tube expansion test: A test piece having a length of 300 mm is cut out from the tubular test material in the longitudinal direction of extrusion, and the end surface of the test piece is cut by a lathe to be flat. After applying a high-viscosity lubricating oil to the inner surface of the test piece, a conical jig having a half-angle of 3 ° coated with the same lubricating oil is pushed into the test piece, and the outer diameter D ₁ (mm) when the end face is broken. And the expansion rate R (limit expansion rate) is measured from the outer diameter D ₀ (mm) before the test according to the following equation.
R = {(D ₁ −D ₀ ) / D ₀ } × 100 (%). At this time, the test speed (speed for pushing the jig) is set to 1 mm / s.

  Tensile test: A 12A-shaped tensile test piece shown in JIS Z 2201 is molded from the center of the width of a tubular test material, and a tensile test is performed at a crosshead speed of 10 mm / min at room temperature in accordance with JIS Z 2241. Measure strength, yield strength and elongation.

As seen in Table 3, none of the test materials 11 to 20 according to the present invention has a recrystallized structure in the depth of 200 μm or more from the surface, the main orientation of the texture is the Brass orientation, and ODF Vickers when the degree of integration in the Brass orientation is more than 10 times that of the random orientation, and there is an endothermic peak and an exothermic peak between 100 and 200 ° C. in thermal analysis by DSC, and natural aging at 40 ° C. for 30 days The hardness is 190 or less, and the Vickers hardness after heat treatment at 180 ° C. for 1 minute is in the range of 100 to 180. Further, n value is 0.15 or more in a range of nominal strain 5% to 10%, the ratio of the critical expansion _ratio, together with R 1 / _{R 0} is 1.1 or more, without causing cracks in the drawing processing, Excellent tensile properties were shown.

Comparative Example 1
An aluminum alloy ingot having a composition of alloys K to V shown in Table 4 having a diameter of 150 mm was produced according to a conventional method, and the obtained ingot was homogenized, hot-extruded, and solutionized under the same conditions as in Example 1. Treatment, quenching, heat treatment, and natural aging were performed to obtain T4 tempered plate-like extruded materials 21 to 32 having a thickness of 6 mm and a width of 100 mm.

  For test materials 21 to 32, under the same conditions as in Example 1, microstructure observation, ODF measurement, thermal analysis test, Vickers hardness test (before and after heat treatment at 180 ° C.), n value measurement, limit rolling at 180 ° C. Tensile test and stress corrosion cracking test after rate measurement, warm rolling at 180 ° C. and artificial aging treatment were performed. The test results are shown in Table 5.

  As shown in Table 5, since the test material 21 had a Zn content below the lower limit, the strength after the artificial aging treatment was low. Since the amount of Mg of the test material 22 was less than the lower limit, the strength after the artificial aging treatment was low. Since the amount of Cu in the test material 23 is less than the lower limit, no exothermic peak is observed in the thermal analysis by DSC, the Vickers hardness and n value after the heat treatment are too low, the warm workability is lowered, and after the artificial aging treatment The strength of was inferior.

  Since the test material 24 contained Zn in excess of the upper limit, the stress corrosion cracking resistance was lowered. Since the test material 25 contained the Mg amount exceeding the upper limit, the stress corrosion cracking resistance was lowered. Since the test material 26 contained the Cu amount exceeding the upper limit, the Vickers hardness after the heat treatment exceeded 180, the warm workability was lowered, and the stress corrosion cracking resistance was lowered.

  Since none of Cr, Mn, and Zr was added to the test material 27, recrystallized grains were formed in the interior of a depth of 200 μm or more from the surface, the main orientation of the texture was not Brass, and the degree of accumulation in the Brass orientation was high. It became less than 10, and while warm workability fell, intensity | strength and stress corrosion cracking resistance fell. Since the test material 28 contained Cr exceeding the upper limit, the warm workability was lowered and the elongation was also lowered.

  Since the test material 29 was added with Mn exceeding the upper limit, the warm workability was lowered and the elongation was also lowered. Since the test material 30 was added with Zr exceeding the upper limit, the warm workability was lowered and the elongation was also lowered. Since the test material 31 contained Ti and B exceeding the upper limit, the warm workability was lowered and the elongation was also lowered. Since the test material 32 contained Fe and Si in excess of the upper limit, the warm workability was lowered and the elongation was also lowered.

Comparative Example 2
For the alloy E shown in Table 1, the aluminum alloy ingot having a diameter of 150 mm produced in Example 1 is subjected to homogenization treatment, hot extrusion, solution treatment, and quenching under the same conditions as in Example 1, and 50 ° C. or higher. , T4 tempered plate-like extruded material having a thickness of 6 mm and a width of 100 mm (test material 33), subjected to natural aging at 40 ° C. for 30 days without performing heat treatment at 100 ° C. or lower for 1 minute or more and 30 minutes or less Got.

  For test material 33, under the same conditions as in Example 1, microstructure observation, ODF measurement, thermal analysis test, Vickers hardness test (before and after heat treatment at 180 ° C.), n value measurement, limit rolling rate measurement at 180 ° C., A tensile test and a stress corrosion cracking test were performed after warm rolling at 180 ° C. and artificial aging treatment. The test results are shown in Table 6.

  As shown in Table 6, since the test material 33 was not subjected to heat treatment after quenching, the Vickers hardness after natural aging exceeded the upper limit, and the warm workability was lowered.

Comparative Example 3
For alloy P shown in Table 4, an aluminum alloy ingot having a diameter of 320 mm was produced according to a conventional method, and the obtained ingot was homogenized, cut, hot extruded, and solution treated under the same conditions as in Example 2. Then, quenching, heat treatment and natural aging were performed to obtain a T4 tempered tubular extruded material (test material 34) having an outer diameter of 65 mm and an inner diameter of 50 mm.

  For the test material 34, under the same conditions as in Example 2, microstructure observation, ODF measurement, thermal analysis test, Vickers hardness test (before and after heat treatment at 180 ° C.), n value measurement, tube expansion test, pull-out test, at 180 ° C. Tensile tests after warm drawing and artificial aging were performed. The test results are shown in Table 7.

As shown in Table 7, since the Vickers hardness after the heat treatment exceeded the upper limit and the ratio of the limit tube expansion ratio, R ₁ / R ₀ was less than the lower limit, the test material 34 was deteriorated in warm workability.

Example 3
For the alloy A shown in Table 1, the 150 mm diameter aluminum alloy ingot produced in Example 1 was homogenized at 450 ° C. for 10 hours, cooled to room temperature without additional heat treatment, and made into an billet for extrusion. Hot extrusion, solution treatment, quenching, heat treatment and natural aging were performed under the same conditions as in Example 1 to obtain a T4 tempered plate-like extruded material (test material 35) having a thickness of 6 mm and a width of 100 mm.

  For test material 35, under the same conditions as in Example 1, microstructure observation, ODF measurement, thermal analysis test, Vickers hardness test (before and after heat treatment at 180 ° C.), n value measurement, limit rolling rate measurement at 180 ° C., A tensile test and a stress corrosion cracking test were performed after warm rolling at 180 ° C. and artificial aging. The test results are shown in Table 8.

  As shown in Table 8, the test material 35 according to the present invention has no recrystallized structure in the depth of 200 μm or more from the surface, the main orientation of the texture is the Brass orientation, and accumulation in the Brass orientation by ODF. The degree is more than 10 times the random orientation, DSC thermal analysis has an endothermic peak and an exothermic peak between 100-200 ° C, and the Vickers hardness is 190 or less when natural aging is performed at 40 ° C for 30 days The Vickers hardness after heat treatment at 180 ° C. for 1 minute is in the range of 100 to 180. Further, the n value in the range of nominal strains of 5% to 10% was 0.15 or more, and a high limit rolling rate of 70% or more was exhibited, and both tensile properties and stress corrosion cracking resistance were excellent.

Claims (8)

Zn: 5.0 to 7.5% (mass%, the same shall apply hereinafter), Mg: 1.6 to 3.3%, Cu: 1.1 to 2.5%, and Cr: 0.30% The following (not including 0%, the same applies hereinafter), Mn: 0.60% or less, Zr: one or more of 0.30% or less, and Ti: 0.06% or less, B: 0.005% or less It is a W or T4 tempered aluminum alloy extruded material that contains at least one of the above, further limits Fe and Si as impurities to 0.25% or less, and the balance Al and unavoidable impurities. The interior of the surface having a depth of 200 μm or more from the surface is composed of a fibrous structure composed of sub-crystal grains, and the main orientation of the texture is the Brass orientation, and the Brass orientation expressed by ODF (crystal orientation distribution function) The degree of integration is more than 10 times the random orientation. Warm working excellent in Al-Zn-Mg-Cu alloy extruded to. The endothermic peak and the exothermic peak appear in the range of 100 to 200 ° C in thermal analysis by DSC (differential scanning calorimeter), and Al-Zn-Mg- excellent in warm workability according to claim 1 Cu alloy extruded material. After solution heat treatment and quenching, when Vickers hardness in W tempering or T4 tempering obtained by natural aging within 30 days at 40 ° C. or less is 190 or less, and then heat treatment is further performed at 180 ° C. for 1 minute The Al-Zn-Mg-Cu alloy extrudate excellent in warm workability according to claim 1 or 2, wherein the Vickers hardness is 100 or more and 180 or less. The n value (work hardening index) in the range of nominal strain of 5% to 10% obtained by a uniaxial tensile test at room temperature is 0.15 or more. Al-Zn-Mg-Cu alloy extruded material with excellent warm workability. Extruded material in the form of a tube, when the tube expansion is performed with natural aging, the limiting tube expansion rate is R ₀ , the heat treatment for 1 minute at 180 ° C, and then the tube expansion is performed at room temperature. when the rate was _{R 1, R 1} / _{R 0} is excellent warm workability according to any one of the preceding claims, characterized in that 1.1 or more Al-Zn-Mg-Cu Alloy extruded material. Zn: 5.0 to 7.5%, Mg: 1.6 to 3.3%, Cu: 1.1 to 2.5%, Cr: 0.30% or less, Mn: 0.60 % Or less, Zr: one or more of 0.30% or less, and Ti: 0.06% or less, B: one or more of 0.005% or less, and Fe and Si as impurities Each is limited to 0.25% or less, an aluminum alloy having a composition composed of the remaining Al and inevitable impurities is melted and cast, and the resulting ingot is subjected to homogenization treatment and then subjected to hot extrusion to further form a solution. The warm working according to any one of claims 1 to 5, wherein treatment and quenching are performed, and heat treatment is performed for 1 minute to 30 minutes at a temperature of 50 ° C to 100 ° C within 5 minutes after quenching. Of producing an extruded Al-Zn-Mg-Cu alloy having excellent properties. The temperature according to claim 6, wherein the homogenization treatment is performed at a temperature of 400 ° C or higher and 500 ° C or lower, an additional heat treatment is performed at a temperature of 300 ° C or higher and 400 ° C or lower, and then hot extrusion is performed. A method for producing an Al—Zn—Mg—Cu alloy extruded material excellent in inter-workability. Using the Al-Zn-Mg-Cu alloy extruded material excellent in warm workability according to any one of claims 1 to 5, plastic working is performed at a temperature of 100 ° C or higher and 200 ° C or lower, and further an artificial aging treatment An aluminum alloy warm-working material obtained by performing