JP2010261061A - Method for producing Al alloy forged product - Google Patents

Abstract

A high quality forged Al alloy product is obtained while improving productivity and reducing costs.
The production method of the present invention includes Fe: 0.2-0.35%, Cu: 0.05-0.20%, Mn: 0.3-0.6%, Mg: 1.3-2. 0.0%, Zn: 4.6-5.1%, Si: less than 0.30%, Zr: 0.1% or more, and less than 0.2% in total with Ti, “[Ti mass% ] / [Zr mass%] ≧ 0.2 ”, a step of obtaining an Al alloy forging material having an alloy composition with the balance consisting of Al and inevitable impurities, and an Al alloy forging material of 350 to 500 ° C. After performing hot forging at a temperature, a solution treatment is performed at a temperature of 400 to 500 ° C., thereby obtaining an Al alloy forged product, and without subjecting the Al alloy forged product to natural aging treatment. Performing an aging treatment.
[Selection] Figure 1

Description

  The present invention relates to a method for producing an Al alloy forged product for producing an Al alloy product by forging and related techniques.

  2. Description of the Related Art In recent years, a technique for manufacturing a motorcycle part requiring high strength by a forged product of an aluminum (Al) alloy is well known. Such a forged product is manufactured by forging a forging material of an Al—Zn—Mg alloy as shown in Patent Document 1 below, for example.

  In the forging of a general Al—Zn—Mg alloy material, as shown in the following Patent Document 1, in order to improve stress corrosion cracking resistance and tensile strength, in the T6 heat treatment step after mold forming, about 100 hours. Artificial aging treatment is performed after natural aging treatment is performed at room temperature.

JP-A-10-168553

  However, in the conventional forging method described above, since natural aging treatment is performed for a long time after mold forming, the cycle time required for production becomes long, resulting in a decrease in production efficiency and an increase in cost. . In some cases, the storage period of the workpiece by natural aging treatment becomes longer, which causes corrosion due to condensation or the like, resulting in a problem that the quality of the product is deteriorated.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a manufacturing method of an Al alloy forged product and related technology capable of obtaining a high quality Al alloy forged product while improving production efficiency and reducing costs. The purpose is to provide.

  In order to achieve the above object, the present invention comprises the following arrangement.

[1] Fe: 0.2 to 0.35 mass%, Cu: 0.05 to 0.20 mass%, Mn: 0.3 to 0.6 mass%, Mg: 1.3 to 2.0 mass% Zn: 4.6-5.1% by mass, Si: less than 0.30% by mass, Zr: 0.1% by mass or more and less than 0.2% by mass in total with Ti, “[Ti mass %] / [Zr mass%] ≧ 0.2 ”, and obtaining an Al alloy forging material having an alloy composition with the balance consisting of Al and inevitable impurities,
A process of obtaining an Al alloy forged product by performing a solution treatment at a temperature of 400 to 500 ° C. after hot forging at a temperature of 350 to 500 ° C. with respect to the Al alloy forged material,
A step of performing artificial aging treatment on the Al alloy forged product without performing natural aging treatment on the Al alloy forged product.

[2] The method further includes a step of obtaining an Al alloy cast member by subjecting the Al alloy molten metal having the alloy composition to a homogenization treatment to an Al alloy ingot obtained by continuous casting,
The method for producing an Al alloy forged product according to item 1, wherein the Al alloy cast member is used as the Al alloy forged material.

  [3] The Al alloy according to the above item 1 or 2, wherein the artificial aging treatment is maintained at a temperature of 90 to 120 ° C. for 2 to 12 hours, and immediately maintained at a temperature of 130 to 170 ° C. for 2 to 12 hours. Manufacturing method for forged products.

  [4] The method for producing an Al alloy forged product according to any one of items 1 to 3, wherein the artificial aging treatment is performed within 1 hour for the Al alloy forged product after the solution treatment.

  [5] A method for manufacturing a motorcycle frame part, wherein the Al alloy forged product manufactured by the manufacturing method according to any one of items 1 to 4 is finished into a motorcycle frame part.

  According to the method for producing an Al alloy forged product of the invention [1], a high quality Al—Zn—Mg based alloy forged product can be obtained while improving the production efficiency and reducing the cost.

  According to the method for producing an Al alloy forged product of the inventions [2] and [3], in addition to the above effects, an Al alloy forged product suitable for a high-strength welded structure can be obtained more reliably.

  In the present invention, “high-strength weld structure” means a structure suitable for a welded structure material that requires high strength.

  According to the method for producing an Al alloy forged product of the invention [4], the production efficiency can be further improved.

  According to the method for manufacturing a motorcycle frame part of the invention [5], a high-quality motorcycle frame part can be obtained while improving the production efficiency and reducing the cost.

FIG. 1 is a graph showing the relationship between the Zr content and the Ti content in the alloy compositions of the samples of the examples (comparative) and comparative examples. FIG. 2 is a perspective view showing a disk sample for alloy composition analysis. FIG. 3 is a perspective view showing an example of a motorcycle frame as an Al alloy forged product.

  In this embodiment, forging is performed using an Al alloy cast member as a forging material.

  The Al alloy cast member as the forging material in the present embodiment is regulated by a specific alloy composition, and is controlled to have a specific crystal grain size and distribution state in the metal structure.

  This Al alloy cast member is obtained by continuously casting an Al alloy molten metal having a predetermined composition under predetermined conditions to obtain an Al alloy ingot, and subjecting the Al alloy ingot to a predetermined homogenization treatment. Is obtained.

  First, the configuration of the Al alloy cast member will be described in detail according to the manufacturing procedure.

  The molten Al alloy as a casting material in the present invention is 0.2 to 0.35 mass% Fe, 0.05 to 0.20 mass% Cu, 0.3 to 0.6 mass% Mn, and Mg. 1.3 to 2.0 mass%, Zn is 4.6 to 5.1 mass%, Si is less than 0.30 mass%, Zr is 0.1 mass% or more, and 0.2 mass in total with Ti %, Satisfying the relationship of “[Ti mass%] / [Zr mass%] ≧ 0.2”, and the balance has an alloy composition consisting of Al and inevitable impurities.

  Among the above alloy compositions, Fe is an element that suppresses ingot cracking during casting and weld cracking during welding and suppresses coarse recrystallization. In the present invention, the Fe content (concentration) is 0. It is necessary to adjust to 2 to 0.35 mass%.

  When the Fe content is less than 0.2% by mass, the above effects are small, and when it exceeds 0.35% by mass, coarse Al-Fe-Mn based crystals are increased, and the plastic workability during forging is impaired. Further, when the forged product after forging is finally assembled to a vehicle body or the like, the ductility (ductility), toughness, fatigue strength, and impact characteristics of the forged product (assembled part) are deteriorated.

  Cu is an element that imparts strength by being dissolved in an aluminum matrix and increasing the degree of supersaturation of the solute in the solid solution. In the present invention, the Cu content (concentration) is 0.05 to 0. It is necessary to adjust to 20% by mass.

  When the Cu content is less than 0.05% by mass, a sufficient strength improvement effect cannot be obtained. When the Cu content exceeds 0.20% by mass, the strength is improved, but the stress corrosion cracking resistance is remarkably lowered, so This is not desirable because there is a risk of generation.

  Mn is an element that suppresses coarse recrystallization. In the present invention, it is necessary to adjust the content (concentration) of Mn to 0.3 to 0.6% by mass.

  When the content of Mn is less than 0.3% by mass, the above effect is small, and when it exceeds 0.6% by mass, the Al-Fe-Mn series coarse crystallized matter increases, and the plastic workability during forging is impaired. Further, when the forged product after forging is finally assembled to a vehicle body or the like, the ductility, toughness, and fatigue strength of the forged product (assembled part) are lowered, which is not desirable.

Mg is an element that precipitates MgZn ₂ intermetallic compound (η phase) and improves mechanical strength by coexisting with Zn. In the present invention, it is necessary to adjust the Mg content (concentration) to 1.3 to 2.0 mass%.

  When the Mg content is less than 1.3% by mass, the above effect is small, and when it exceeds 2.0% by mass, the stress corrosion cracking property and quenching sensitivity are lowered, which is not desirable.

As described above, Zn is an element that improves mechanical strength by precipitating MgZn ₂ intermetallic compound (η phase) by coexisting with Mg. In the present invention, it is necessary to adjust the Zn content (concentration) to 4.6 to 5.1 mass%.

  When the Zn concentration is less than 4.6% by mass, the above effect is small, and when it exceeds 5.1% by mass, the stress corrosion cracking property and quenching sensitivity are lowered, which is not desirable.

  It is necessary to adjust the Si content to an amount not exceeding 0.30 mass%. That is, if the Si content is too large, the ductility, toughness, fatigue strength and w impact property of the product are lowered, which is not desirable. Furthermore, if the Si content increases, it reacts with Mg, the aging precipitation behavior changes, and natural aging during heat treatment is required, which is not preferable.

  Zr is an element that suppresses coarse recrystallization and promotes refinement of the crystal grain of the weld. In the present invention, the content (concentration) of Zr is adjusted to 0.1% by mass or more, and “Ti It is necessary to adjust so that the total amount (content) of Zr and Zr does not exceed 0.2% by mass.

The effect is small when the concentration of Zr is less than 0.1% by mass. When a large amount of Zr is added, it reacts with B of TiB ₂ added for crystal grain refinement during casting to produce ZrB ₂ and inhibit crystal grain refinement. For this reason, it becomes necessary to add a TiB ₂ in large quantities. However, since TiB ₂ and ZrB ₂ are hard particles, when cutting a forged product after forging, in order to shorten the tool life at the time of cutting, it is not desirable to add too much. Therefore, it is necessary to adjust the addition amount (concentration) of Zr to 0.1% by mass or more as described above, and to adjust the total addition amount of Ti and Zr to less than 0.2% by mass.

  In the present invention, it is more preferable to set the addition amount of Ti to 0.03 to 0.05 mass% and the addition amount of Zr to 0.10 to 0.15 mass%.

  Furthermore, in the Al alloy composition of the present invention, it is necessary to satisfy the relationship “[Ti mass%] / [Zr mass%] ≧ 0.2” between Ti and Zr.

That is, as described above, Zr reacts with B of TiB ₂ added for crystal grain refinement at the time of casting to produce ZrB ₂ and inhibits crystal grain refinement. Therefore, if the TiB ₂ addition amount relative to the Zr addition amount is small, the crystal grains at the time of casting become coarse, resulting in a decrease in mechanical strength and elongation (elongation). and the mass ratio of Zr (Ti wt% / Zr mass%) is such that 0.2 or more, it is necessary to control the amount of TiB ₂ and Zr.

  In the Al alloy composition of the present invention, it is preferable to satisfy the relationship of “[Si mass%] ≦ 0.2 × [Mg mass%] − 0.1” between Si and Mg.

  That is, Si is an element contained as an impurity, and when the Si content is too large, the ductility, toughness, and fatigue strength of the forged product after forging may be reduced. In addition, when the Si content is too high, it reacts with Mg, changes the aging precipitation behavior, and requires natural aging during heat treatment, which is not desirable. Since these behaviors are related not only to the single function of Si but also to the amount of Mg, as described above, [Si mass%] ≦ 0.2 × [Mg mass%] − 0.1. It is preferable to control the content.

  In this embodiment, an Al alloy ingot is obtained by continuously casting a molten Al alloy having the above alloy composition.

  Furthermore, in this embodiment, homogenization process is performed with respect to said Al alloy ingot, and an Al alloy cast member is obtained.

  The Al alloy cast member thus obtained is used as a forging material. That is, an Al alloy forged product is manufactured by hot forging the forging material as the Al alloy cast member at a temperature of 350 to 500 ° C.

  Here, when the temperature during hot forging is lower than 350 ° C., the plastic workability during forging deteriorates, and not only a forged product having a desired shape is obtained, but also die breakage, cracking of the forged product. Cause. When the temperature during hot forging is higher than 500 ° C., hole defects may occur near the surface of the forged product or aggregation of metals having a low melting point may occur due to eutectic melting. Therefore, in this invention, it is desirable to adjust the temperature conditions at the time of hot forging to 350-500 degreeC.

  In the present invention, the mechanical strength of the forged product can be further improved by performing a solution treatment at 400 to 500 ° C. on the Al alloy forged product obtained as described above.

  In this solution treatment, when the treatment temperature is lower than 400 ° C., the solid solution amount of the precipitation strengthening element is reduced, so that the precipitation amount in the subsequent artificial aging treatment is reduced and sufficient mechanical strength cannot be obtained. There is a fear. Further, when the processing temperature is higher than 500 ° C., hole defects and aggregation of a metal having a low melting point may occur near the surface of the forged product due to eutectic melting.

  In the present invention, the Al alloy forged product subjected to solution treatment is subjected to artificial aging treatment without performing natural aging treatment.

  Here, the aging treatment in the present invention is roughly divided into a natural aging treatment and an artificial aging treatment.

  The natural aging treatment is a treatment in which, after solution treatment, the product is left at room temperature and aging proceeds at a low temperature. Specifically, it is kept at room temperature (about 0 to 50 ° C.) for 24 to 72 hours. It is a process like this.

  On the other hand, the artificial aging treatment is a treatment in which, after solution treatment, the product is put into a heat treatment furnace and aging is advanced at a high temperature. Specifically, the temperature of the forged product is increased from room temperature to 100 ° C. over 1 hour and held for 6 hours. Thereafter, the temperature is raised from 100 ° C. to 150 ° C. over 1 hour, held for 8 hours, and then treated so that the temperature is lowered to room temperature by air cooling.

  In the present invention, for the Al alloy forged product, the following treatment (artificial aging treatment) is performed immediately after the solution treatment without leaving it for a long time in order to improve productivity, reduce costs and improve quality. It is preferred to do so. Specifically, the artificial aging treatment is preferably performed on the Al alloy forged product within 1 hour after the solution treatment, preferably immediately after the solution treatment.

  In the present invention, by performing this artificial aging treatment, the ductility, toughness, fatigue strength, and impact characteristics can be sufficiently improved, and a high-quality forged product having a desired mechanical strength can be reliably obtained. be able to.

  As described above, according to the method for producing an Al alloy forged product of the present invention, after the solution treatment is performed after the forging die forming, the artificial aging treatment is performed immediately without performing the natural aging treatment. Therefore, it is possible to improve production efficiency and reduce costs.

  Moreover, the Al alloy forged product obtained by the production method of the present invention can prevent the occurrence of defects such as cracks, hole defects, and coarse recrystallization, as is clear from the examples described later, and is sufficient. It has tensile strength and elongation at break and has excellent properties. Furthermore, since the forged product is not left for a long time due to natural aging, it is possible to reliably prevent the occurrence of corrosion due to dew condensation or the like due to the long time leaving, and to maintain high product quality.

  In addition, since the Al alloy forged product obtained by the production method of the present invention has excellent mechanical properties as described above, it should be suitably used as a component for a high-strength welded structure such as a vehicle frame component. Can do. For example, as shown in FIG. 3, the forged product according to the present invention can be used as a motorcycle frame (1) in which a shaft (2) is inserted and fixed at an end portion.

  Next, examples and comparative examples of the present invention will be described in detail with reference to Table 1 and FIG.

  FIG. 1 is a graph showing the relationship between the Zr content and the Ti content in the alloy compositions of the samples of Examples and Comparative Examples. In the graph, “actual” indicates an example, “ratio” indicates a comparative example, a circle number indicates each number of the example and comparative example, the example indicates “◯”, and the comparative example indicates “×”. Yes. Further, in the graph, the line segment (A1) is “Zr mass% = 0.1 mass%”, and the line segment (A2) is “[Ti mass%] + [Zr mass%] = 0.2 mass%”. The minute (A3) indicates a line segment specified by “[Ti mass%] / [Zr mass%] = 0.2”. Therefore, the region surrounded by these line segments (A1) to (A3) is a portion corresponding to the gist of the present invention based on the relationship between Zr and Ti. Further, a region surrounded by a broken line in FIG. 1 is a preferable range of the present invention.

<Examples 1-6>
As shown in Table 1 and FIG. 1, in order to produce each sample of Examples 1 to 6, an Al alloy having a composition corresponding to each sample was melted, and a molten Al alloy corresponding to each sample was prepared.

  Each of the Al alloy melts thus obtained was cast into a mold, and a disk sample (3) having a shape as shown in FIG. 4 was collected and analyzed by emission spectroscopic analysis described in JIS H 1305.

  Various sizes (s1) to (s6) of the disk sample (3) are as follows. That is, s1 is 18 mm, s2 is 30 mm, s3 is 50 mm, s4 is 35 mm, s5 is 5 mm, and s6 is 5 mm.

  As a result of analysis, after confirming that each sample of the target component values shown in Table 1 was obtained, continuous casting was performed on the Al alloy molten metal corresponding to each sample using a gas pressurization type hot top casting machine. A round bar-shaped Al alloy cast member (ingot) having a diameter of 55 mm corresponding to each sample was produced. Thereafter, the continuously cast member was cut into a standard length and subjected to a homogenization treatment at 460 ° C. for 7 hours.

  Further, the continuously cast round bar after the homogenization treatment was subjected to outer peripheral cutting to a diameter of 50 mm and cut to a length of 60 mm to obtain a forging material. The forged material was preheated at 450 ° C., and then placed at a thickness of 10 mm from the side of the round bar. Thereafter, the upsetting product (Al alloy forged product) was subjected to a solution treatment at 460 ° C. After solution treatment, artificial aging treatment was performed immediately on each upset product without natural aging. As an artificial aging treatment, after holding at 110 ° C. for 6 hours, the temperature was continuously raised and held at 150 ° C. for 8 hours.

<Comparison of Examples 1-7 (with natural aging)>
After performing solution treatment on Al alloy forged product (fixed product) and before performing artificial aging treatment, it was the same as the above example except that natural aging was carried out at room temperature (25 ° C) for 100 hours. Thus, forged product samples of proportionality 1 to 6 were obtained.

<Comparative Examples 1-16>
In the same manner as in the above examples, as shown in Table 1, forging materials were produced as Al alloy cast members having an alloy composition corresponding to each comparative example.

  Further, the forging material was preheated under the conditions shown in Table 1, and then placed to a thickness of 10 mm from the side surface of the round bar. Subsequently, the upsetting product (forged product) was subjected to a solution treatment under the conditions shown in Table 1.

  Thereafter, the artificial aging treatment similar to that described above was performed on the installed product after performing natural aging similar to the above or immediately without performing natural aging.

  <Evaluation>

  As shown in Table 2, the obtained sample (sample) was checked for the presence of cracks and hole defects on the sample surface by a solvent-removable penetrant flaw detection test (color check), and then the sample was cut and the cross section was polished. . Thereafter, the polished sample was etched and observed with a metal microscope having a polarizing glass inserted in the optical path to confirm the presence or absence of coarse recrystallization on the surface and inside.

  The crystal grain size is measured by a section method on an optical microscope photograph. When there are crystal grains of 500 μm or more, it is determined that there is a coarse recrystallized grain “exist”, and otherwise, the coarse recrystallized grain “ It was judged as “None”.

  In addition, it was also confirmed whether there was any Ti-based intermetallic compound that deteriorated the machinability during microscopic observation.

  Furthermore, a JIS 14A proportional test piece was taken from a direction parallel to the original material longitudinal direction, and tensile strength, 0.2% proof stress, and elongation at break were measured.

In addition, a test piece of 2 mm × 4.3 mm × 42.4 mm is cut out from the installed product, and it corresponds to 70% of the proof stress using a three-point bending jig in the center of the 4.3 mm × 42.4 mm surface. Stress was applied. During the load, the test piece and the jig were electrically insulated. As a corrosive liquid, 36 g of chromium (IV) oxide, 30 g of potassium dichromate, 3 sodium chloride per liter of pure water
The solution which melt | dissolved g and was hold | maintained at 95-100 degreeC was prepared. After the test piece loaded with stress was immersed in the corrosive liquid for 16 hours, the appearance of the test piece was observed to confirm whether cracks were generated.

  In Table 2, the samples of Examples 1 to 7 and the samples of Comparative Examples 1 to 7 (same as those of Examples 1 to 7 except that natural aging was performed so that the data can be easily compared) ) In the same bank. That is, in each column of “Example / Comparison”, the column of “Natural aging [B]” describes the physical property values (tensile strength, 0.2% proof stress, elongation at break) of the Example sample. In the column “Aging [A]”, the physical property values (tensile strength, 0.2% proof stress, elongation at break) of the comparative sample are described. Furthermore, for each evaluation of “presence / absence of cracks and hole defects”, “presence / absence of coarse recrystallization”, and “presence / absence of stress corrosion cracking”, the evaluation results are the same for both the example and the comparative example. It is listed in the same column.

  In each of Comparative Examples 1 to 16, the physical property values (tensile strength, 0.2% proof stress, elongation at break) were those subjected to natural aging (“natural aging present [A]”) and natural aging was not performed. The evaluation results for each of the two types of samples are described. In addition, the evaluation results for “existence of cracks and hole defects”, “existence of coarse recrystallization”, and “existence of stress corrosion cracking” are the same regardless of whether there is natural aging. It is described in.

<Result>
About Examples 1-6 which satisfy | fill all the requirements of this invention, a crack and a hole defect did not generate | occur | produce in the sample, but the coarse recrystallization was not recognized by the surface and the inside. Further, Examples 1 to 7 were excellent in tensile strength, 0.2% proof stress, and elongation at break, and had excellent physical properties (characteristics). In judging the quality of these physical properties, those having a tensile strength of 400 MPa or more, a 0.2% proof stress of 350 MPa or more, and an elongation of 10% or more were evaluated as “excellent”.

  In the case where natural aging is not performed (example [B]), the reduction rate ([A] / [B]) of each characteristic value when natural aging is performed (comparative [A]) is also described in the example. Those of Nos. 1 to 7 were not inferior to the proportionality, and excellent evaluation was obtained.

  In this example, when determining whether the rate of decrease in the physical property value due to the presence or absence of natural aging was good or bad, those having a rate of decrease of 1.05 or less were evaluated as “excellent”.

  In Comparative Example 1, since the Mg content was small, the tensile strength and 0.2% proof stress were insufficient regardless of the presence or absence of natural aging. In addition, when natural aging was omitted, properties such as tensile strength and 0.2% proof stress were lowered.

  In Comparative Example 2, since the contents of Mg and Zn were small, the specifications such as tensile strength and 0.2% proof stress were lowered in cases where natural aging was omitted.

  In Comparative Example 3, the content of Fe, Mn, and Zr was small, and therefore, regardless of the presence or absence of natural aging, coarse recrystallization occurred on the surface and inside when the processing strain was released by solution treatment. Further, this coarse recrystallization significantly reduced the tensile properties, particularly the elongation.

  In Comparative Example 4, the Ti-B addition amount was small, and as a result, the Ti content was small, so that the crystal grains could not be refined during casting, and ingot cracking occurred.

  In Comparative Example 5, since the addition amount of Cu, Mg and Zn was small, physical properties such as tensile strength and 0.2% proof stress were lowered regardless of the presence or absence of natural aging.

  In Comparative Example 6, since both the Mg content and the Si content are too large, the tensile strength and the 0.2% proof stress are excellent, but the characteristics were deteriorated when natural aging was omitted.

  In Comparative Example 7, the elongation was greatly reduced because the Mg content was too high.

  In Comparative Example 8, since the Zn content was small, the precipitation strengthening of the main strengthening component was not sufficiently performed, and the tensile strength and the 0.2% yield strength were reduced.

  In Comparative Example 9, since the Zn content was too large, a large amount of base intermetallic compounds than aluminum precipitated continuously at the grain boundaries, and stress corrosion cracking occurred along these grain boundaries.

  In Comparative Example 10, since the Mg content was too large, a larger amount of intermetallic compounds than aluminum were continuously precipitated at the grain boundaries, and stress corrosion cracking occurred along these grain boundaries.

  In Comparative Example 11, since [Zr amount] + [Ti amount] is 0.2% by mass or more, it is a cause of wear of blades and generation of burrs during machining by observation with an optical microscope. Many intermetallic compounds of the system were observed.

  Since the forging temperature of the comparative example 12 was too low, a critical crack was generated due to insufficient elongation.

  Since the forging temperature of the comparative example 13 was too high, intergranular cracking due to hot embrittlement occurred.

  In Comparative Example 14, since the solution temperature was too low, the precipitation strengthening element was not sufficiently dissolved, and the amount of precipitation was insufficient, so that the tensile strength and 0.2% proof stress were lowered.

  In Comparative Example 15, since the solution temperature was too high, eutectic melting occurred, resulting in hole defects on the surface of the sample.

  As is clear from the above examples, according to the present invention, an Al—Zn—Mg based forged product excellent in various physical properties such as tensile strength, 0.2% proof stress and elongation at break can be obtained without performing natural aging. It is possible to produce a high-quality Al alloy forged product efficiently and inexpensively.

  The method for producing an Al alloy forged product according to the present invention can be applied to a forging technique for producing a high-quality Al forged product.

1: Motorcycle frame (forged products)

Claims (5)

Fe: 0.2-0.35 mass%, Cu: 0.05-0.20 mass%, Mn: 0.3-0.6 mass%, Mg: 1.3-2.0 mass%, Zn: 4.6 to 5.1% by mass, Si: less than 0.30% by mass, Zr: 0.1% by mass or more and less than 0.2% by mass in total with Ti, “[Ti mass%] / Satisfying the relationship of [Zr mass%] ≧ 0.2 ”, and obtaining an Al alloy forging material having an alloy composition with the balance consisting of Al and inevitable impurities;
A process of obtaining an Al alloy forged product by performing a solution treatment at a temperature of 400 to 500 ° C. after hot forging at a temperature of 350 to 500 ° C. with respect to the Al alloy forged material,
A step of performing artificial aging treatment on the Al alloy forged product without performing natural aging treatment on the Al alloy forged product. The method further includes a step of obtaining an Al alloy cast member by subjecting the Al alloy molten metal having the alloy composition to a homogenization treatment for an Al alloy ingot obtained by continuous casting,
The method for producing an Al alloy forged product according to claim 1, wherein the Al alloy cast member is used as the Al alloy forged material.   The Al alloy forged product according to claim 1 or 2, wherein the artificial aging treatment is held at a temperature of 90 to 120 ° C for 2 to 12 hours, and then immediately held at a temperature of 130 to 170 ° C for 2 to 12 hours. Manufacturing method.   The method for producing an Al alloy forged product according to any one of claims 1 to 3, wherein the artificial aging treatment is performed within 1 hour for the Al alloy forged product after the solution treatment.   A method for producing a motorcycle frame part, wherein the Al alloy forged product produced by the production method according to any one of claims 1 to 4 is finished into a motorcycle frame part.

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