JP2015085381A - Constant temperature forged component and manufacturing method for constant temperature forged component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-quality constant temperature forged component which can realize a high intensity and a high toughness equal to or more than those of a conventional steel component in spite of being an aluminum alloy component by having a complex texture dotted with flat crystal grains and micro recrystallization grains formed at least in a part.SOLUTION: A constant temperature forged component, manufactured by forging an Al-Mg-Si-based aluminum alloy at a constant temperature, has flat crystal grains elongated by being crushed under forging molding formed at least in a part of crystal grains and has a complex texture dotted with micro recrystallization grains with an average grain diameter of 10 nm - 1000 nm in a deformed tissue of the flat crystal grains or a recovery tissue region, or a grain boundary region of the crystal grains with a tensile strength of 360 MPa or more and an elongation of 14% or more.

Description

  The present invention relates to a high-strength, high-toughness, high-quality constant-temperature forged part obtained by performing constant-temperature forging of an aluminum alloy at high speed, and a method for producing the same.

Forging has been conventionally known as a means for improving the strength and quality of metals.
In the hot forging method that does not heat the mold, the material temperature drops rapidly during processing and the moldability deteriorates, so defects are likely to occur, shape flexibility is lacking, and post-processing such as a cutting process is required. Thus, there is a problem that the mass production is lacking and the use is limited.
In addition, the conventional isothermal forging method can improve strength and quality, but it is a method that uses a large press to slow down the processing speed extremely, so it can be used for mass production and small parts manufacturing. Is unsuitable, and has been used only for the production of large-scale small parts such as aircraft bodies and legs, and has a problem that it cannot be applied to mass-produced products.
In particular, parts manufacturing for automobiles, railway vehicles, aircraft, etc. are required to reduce the weight of the vehicle body and fuselage in response to environmental issues such as improved fuel economy and exhaust gas regulations in recent years. Some parts are made of aluminum alloy. However, from the aspect of ensuring strength and quality, the transition to lightweight alloys has not progressed, and high-temperature constant temperature forged parts with high strength, high toughness and high quality can be realized, and high-speed machining is possible, which is excellent in mass productivity. The establishment of a manufacturing method for constant temperature forged parts has been strongly desired.

On the other hand, a method for producing a metal material has been proposed in which a metal such as an aluminum alloy is heated and pressed at a recrystallization temperature or lower to refine crystal grains and improve strength.
For example, (Patent Document 1) states that “a bulk aluminum material made of aluminum or an aluminum alloy is heated to a recrystallization temperature or lower, and the bulk aluminum material heated to a temperature lower than the recrystallization temperature is converted to the x-axis direction, y-axis direction, and z "A method for producing aluminum and aluminum alloy materials having ultrafine crystal grains, characterized in that crystal grains in the massive aluminum material are made ultrafine crystal grains by repeatedly forging in the axial direction." .
However, in (Patent Document 1), forging is repeatedly performed from the respective directions of the x-axis, y-axis, and z-axis, but it is necessary to rotate the sample by 90 ° for each forging and to reheat to 523K each time. However, there are problems that the process is complicated, time is required for processing, and mass productivity is lacking.
Moreover, in order to obtain a desired shape, it is necessary to perform various post-processing such as cutting and polishing, and there is a problem that resource saving is lacking.
In addition, by performing reheating for each forging, the temperature of the sample repeatedly rises and falls, the heating temperature is likely to vary, and the crystal grain is not uniform, resulting in variations in rigidity and toughness, resulting in a decrease in yield. There was a problem that it was easy and lacked in stability of quality and mass productivity.

  Therefore, as a result of earnest research, the applicant of the present application disclosed (patent document 2) that “a mold heating process for heating the upper mold and the lower mold, and the temperature of the upper mold and / or the lower mold is measured and monitored. Mold temperature monitoring process and heating that adjusts the heating temperature in the mold heating process so that the surface temperature inside the mold converges and maintains the processing temperature of the metal material based on the temperature measured in the mold temperature monitoring process A temperature adjustment step, a material heating step of heating the solution-treated metal material to 100 ° C. or more and below the recrystallization temperature of the metal material, and the metal material heated in the material heating step to the processing temperature in the heating temperature adjustment step A constant temperature forging molding method including a forging molding process in which a temperature-adjusted mold is placed and forged by molding is disclosed.

JP 2004-176134 A JP 2010-137284 A

The constant temperature forging molding method of (Patent Document 2) can easily and reliably maintain the material temperature in the mold at a predetermined temperature, appropriately maintain the processing speed at the time of forging, and the material is predetermined. It can be reliably prevented from being heated above the temperature, the crystal grains can be refined, high-strength, high-toughness and high-quality parts can be processed at high speed, and no post-processing heat treatment is required. It was excellent in mass productivity that could minimize processing.
However, in order to stably supply high-quality aluminum alloy parts that are equal to or better than conventional steel parts and apply them to actual automobile parts, etc., further homogenization, improved strength and toughness, and faster processing There was a strong demand.

  The present invention meets the above-mentioned demands, and has a composite structure in which flat crystal grains and fine recrystallized grains formed at least in part are scattered, so that it is a conventional steel part while being an aluminum alloy part. Providing high-quality constant temperature forged parts that can achieve high strength and toughness equivalent to or better than the above, and mass production that enables high-speed processing of high-quality parts that have both high strength and toughness by refining crystal grains An object of the present invention is to provide a method for producing a constant temperature forged part that is excellent in temperature.

Means for solving the problems, and actions and effects obtained thereby

In order to solve the above problems, the constant temperature forged part and the method for manufacturing a constant temperature forged part of the present invention have the following configurations.
The constant temperature forged part according to claim 1 of the present invention is a constant temperature forged part manufactured by isothermal forging of an Al-Mg-Si based aluminum alloy, and at least part of the crystal grains is crushed by forging. Are formed to be elongated, and fine recrystallized grains having an average grain size of 10 nm to 1000 nm are scattered in the deformed or recovered structure area of the flat crystal grains or the grain boundary area of the crystal grains. The tensile strength is 360 MPa or more, and the elongation is 14% or more.
This configuration has the following operations and effects.
(1) At least a part of crystal grains is formed into flat crystal grains which are crushed and elongated by forging, and an average grain is formed in a deformed or recovered structure region of flat crystal grains or a grain boundary region of crystal grains. By having a composite structure in which fine recrystallized grains having a diameter of 10 nm to 1000 nm are scattered, the region of the deformed or recovered structure of the flat crystal grains mainly contributes to the increase in strength, and the fine recrystallized grains It is thought that it contributes to the improvement of toughness. Thereby, it is possible to realize a high-quality constant temperature forged part capable of realizing unprecedented high strength and high toughness.
(2) A region in which deformation or stress is likely to be concentrated due to the presence of fine recrystallized grains having an average particle size of 10 nm to 1000 nm in the region of the deformed or recovered structure of the flat crystal grain or the grain boundary region of the crystal grain. Thus, it is possible to form a structure having both strength and toughness of the region where fracture starts, and in particular, fine recrystallized grains formed along crystal grain boundaries and grain boundary triple points undergo plastic deformation. As a result, the stress concentration at the grain boundary, which is the starting point of fracture, can be alleviated and the toughness of the product can be greatly improved, and a constant temperature forged part with high toughness, durability and long life can be realized.
(3) Since the tensile strength is 360 MPa or more and the elongation is 14% or more, high toughness can be realized while having high strength, and durability and long life are excellent.
(4) Tensile strength is 360 MPa or more, elongation is 14% or more, JIS H4040
Since it greatly exceeds the standard value of A6061BE-T6 (tensile strength of 265 MPa or more, elongation of 10% or more), it can be suitably used for automobile parts and the like, and the weight of the parts and the improvement of fuel consumption can be achieved. .

Here, as the Al—Mg—Si based aluminum alloy, a 6000 based aluminum alloy specified in JIS standard is preferable, and A6061 and A6063 are particularly preferably used.
Of the aluminum crystal grains, the flat crystal grains are those in which atoms aligned in a direction that is easily deformed are crushed by forging to be elongated and deformed into a flat shape. Further, fine recrystallized grains are instantaneously formed in a flat crystal grain region or a grain boundary where deformation is concentrated by isothermal forging according to the degree and speed of deformation. The ultrafine precipitate suppresses the recovery and recrystallization of crystal grains, but is considered to play a role of suppressing the growth of crystal grains recrystallized in the strong deformation region.
For example, a conventional A6061 aluminum alloy that has been cold forged and treated with T8 has a structure including crystal grains having an average grain diameter of 10 to 100 μm and fine precipitates of Mg ₂ Si having an average length of 150 to 200 nm. It is known that In this forged product, a flat deformed grain structure is first formed by cold forging, and this is treated with T8 to make a part or all of it a recovered crystal grain, and the strength is increased by precipitation.
On the other hand, the constant temperature forged component of the present invention aims to improve both strength and toughness by forming flat crystal grains having a deformed structure or a recovery structure and fine recrystallized grains instantaneously and simultaneously. . In the formation of these structures, the ultrafine precipitate formed by dynamic precipitation makes it difficult to recover or recrystallize flat crystal grains (deformed crystal grains or recovered crystal grains). It is thought that it is formed. In addition, the fine recrystallized grains are thought to contribute to an increase in strength.

The invention described in claim 2 is the constant-temperature forged part according to claim 1, wherein the crystal grains are maintained in an outer shape during solution treatment before forging after the forging and have a thickness of 10 μm in the matrix. It has the structure containing the granular crystal grain which has the deformation | transformation zone | band formed below.
With this configuration, in addition to the operations and effects of claim 1, the following operations and effects are provided.
(1) When the crystal grains include granular crystal grains having a deformation band formed to have a thickness of 10 μm or less in the parent phase while maintaining the outer shape at the time of the solution treatment before forging, the crushing is performed by forging. It has the effect of relatively increasing the forging ratio of the flat crystal grains that have been elongated for a long time, can form a composite structure with strength and toughness, and has an unprecedented durability and long life. Forged parts can be realized.

Here, the granular crystal grain is a crystal grain in which atoms are arranged in a direction in which deformation is difficult, and while maintaining the outer shape at the time of solution treatment before forging, a deformation band having a thickness of 10 μm or less is still in the matrix. Is formed. By leaving the granular crystal grains maintaining the outer shape before forging, the flat crystal grains are subjected to more severe deformation, and the forging ratio of the flat crystal grains becomes relatively high, so that the strength is enhanced.
It is assumed that twin deformation may have occurred in the region of this deformation zone.

The invention according to claim 3 is the constant-temperature forged part according to claim 2, wherein the fine recrystallized grains are scattered in the region of the deformation band of the granular crystal grains. Yes.
With this configuration, the following functions and effects are obtained in addition to the functions and effects of the second aspect.
(1) Since the fine recrystallized grains are scattered in the region of the deformation zone of the granular crystal grains, the strength and toughness of the entire structure can be improved, and high quality and quality uniformity are excellent.

  Here, as described above, fine recrystallized grains are formed in the deformed region of the flat crystal grain or the region of the recovery structure or the grain boundary where the deformation is concentrated by isothermal forging. Since strain also concentrates in the region during forging, recrystallization occurs instantaneously and fine recrystallized grains are formed.

The invention according to claim 4 is the constant temperature forged part according to any one of claims 1 to 3, wherein the Vickers hardness is 120 or more.
With this configuration, in addition to the operation and effect of any one of claims 1 to 3, the following operation and effect are provided.
(1) When the Vickers hardness is 120 or more, high strength exceeding the Vickers hardness Hv = 110 to 120, which is the limit value of the conventional cold forging of A6061 aluminum alloy + T6 product, can be realized. As a substitute for low- and medium-carbon steel forgings, it is possible to reduce the weight, and it has excellent versatility.
(2) The strength specification of carbon steel S35C forged steel products is at the level of Vickers hardness Hv = 155, but depending on the product part, the same hardness as this forged steel product can be obtained. There is almost no need to increase the weight, the weight can be reduced, and design flexibility and workability are excellent.

Here, for example, a conventional A6061 aluminum alloy that has been cold forged and T8 treated has a negative correlation between Vickers hardness and elongation. Therefore, when the hardness is increased, it tends to become brittle, impact resistance, and durability. Lack.
On the other hand, the constant temperature forged part of the present invention can increase the elongation in spite of the increase in hardness compared to the conventional product, so that it does not become brittle even if the hardness of the part is increased, Excellent durability and long life.

The method for producing a constant temperature forged part according to claim 5 of the present invention is the method for producing a constant temperature forged part according to any one of claims 1 to 4, wherein the temperature of the solution-treated aluminum alloy is set to a temperature. It has the structure provided with the forge molding process which throws in the adjusted metal mold | die and forge-molds at 150 degreeC-static recrystallization temperature.
This configuration has the following operations and effects.
(1) By introducing a solution-cast aluminum alloy into a temperature-controlled mold and forging at a temperature of 150 ° C. to static recrystallization, the inside of the mold and the metal in the mold The manufacturing conditions can be kept substantially constant by keeping the temperature of the material at a predetermined temperature, and high-quality constant temperature forged parts with little variation can be manufactured, and the quality reliability and high quality are excellent.
(2) Increasing strength in conventional cold forging by having a forging process in which solutionized aluminum alloy is put into a temperature-controlled mold and forged at 150 ° C. to static recrystallization temperature. In contrast, work hardening and precipitation hardening were performed separately focusing on only the above, but the present invention not only increases strength by work hardening, precipitation hardening and grain refinement hardening, but also toughness by isothermal forging. At the same time, it is possible to produce high-temperature, high-toughness, high-quality constant-temperature forged parts without additional heat treatment after the forging process, and the shape is close to the final shape of the product. Since it can be molded, post-processing such as cutting is unnecessary, the number of processing steps can be greatly reduced, the material yield can be improved, and productivity and resource saving are excellent.

Here, during the forging process, the temperature can be measured and monitored at an arbitrary position of the mold, but the temperature at the set measurement position and the surface temperature inside the mold (internal mold surface temperature) By obtaining the relationship in advance, the internal (inner surface) temperature of the mold can be set to a predetermined temperature. Therefore, the measurement position and number of temperatures can be selected appropriately according to the shape and temperature of the mold, and it is not always necessary to directly measure the internal (inner surface) temperature of the mold. The temperature of the mold can be easily and reliably measured using a thermocouple or the like inside the outside (outer surface) or inside the insertion hole formed from the outer surface of the mold.
The pressing force in the forging process can be selected as appropriate according to the shape, dimensions, etc. of the parts to be manufactured, but the pressing force can be kept lower than usual by heating the mold. The processing speed can be increased. As a result, the burden on the mold can be reduced, and the life of the mold can be extended.

  Although the temperature of the metal raw material in a forge molding process can be selected suitably, Preferably it is 120 degreeC-static recrystallization temperature, More preferably, it is 150 degreeC-static recrystallization temperature, More preferably, it is 150 degreeC-260 degreeC. As the temperature of the metal material in the forging process becomes lower than 150 ° C., the moldability tends to decrease, and as it becomes higher than 260 ° C., the grain size of the crystal grains increases and the strength decreases. It tends to be easier. In addition, depending on the size and shape of the product, when the temperature of the metal material in the forging process is lower than 120 ° C., the physical properties deteriorate significantly, making it difficult to mold a complicated shape. When the temperature is higher than the static recrystallization temperature, the structure is rearranged to be in an annealed state. The static recrystallization temperature of an aluminum alloy varies depending on the type and degree of processing of the aluminum alloy, but is about 300 ° C., and the static recrystallization temperature tends to decrease if the degree of processing is high even in the same alloy. .

If the processing speed in the forging process is adjusted based on the temperature of the mold, it is possible to prevent the processing speed from becoming too high and the metal material temperature to be higher than a predetermined temperature. Excellent uniformity.
The processing speed in the forging process varies depending on the temperature of the metal material and the shape and dimensions of the parts to be manufactured. For example, when the part to be molded is 300 g or less and the temperature of the metal material is 120 ° C. to static recrystallization temperature The processing speed is preferably 30 mm / s to 150 mm / s.
As the processing speed in the forging process becomes slower than 30 mm / s, the mass productivity tends to decrease, and as the speed becomes faster than 150 mm / s, the temperature of the metal material is likely to rise and maintain a predetermined temperature. This tends to be difficult and tends to cause variations in quality, both of which are not preferred.

The figure which shows the relationship between the temperature and tensile strength of the metal raw material in an Example and a comparative example. The figure which shows the relationship between the temperature and elongation of a metal raw material in an Example and a comparative example. The figure which shows the relationship between the temperature of a metal raw material in an Example and a comparative example, and Vickers hardness The figure which shows the correlation of Vickers hardness and elongation in an Example and a comparative example The image of EBSP which observed the structure | tissue of the constant temperature forge part of Example 3 Image of EBSP in which granular crystal grains in structure of constant temperature forged part of Example 3 were observed Image of EBSP observed by enlarging crystal grains in the structure of the constant temperature forged part of Example 3 EBSP image observed by enlarging the grain boundary region of the crystal grain in the structure of the constant temperature forged part of Example 3

(Embodiment 1)
A method for manufacturing a constant temperature forged part according to Embodiment 1 of the present invention will be described.
First, the lower mold and the upper mold are heated by a mold heating process.
When heating of the lower mold and the upper mold is started, the temperature near the surface inside the lower mold and the upper mold is measured and monitored, and the internal surface temperature of the mold is determined based on the measured temperature. The heating temperature in the mold heating process is adjusted so as to converge and maintain at a predetermined temperature.
The temperature of the mold was adjusted to 80 ° C. to 210 ° C. according to the shape and dimensions of the parts to be manufactured.
When the inner surface temperature of the lower mold and the upper mold converges to a predetermined temperature, in the forging process, a metal material (Al-Mg-Si based aluminum alloy) is put into the mold, and the lower mold The metal material sandwiched between the upper mold and the upper die was pressed and forged at 150 ° C. to static recrystallization temperature. It was found that when the temperature of the metal material in the forging process is lower than 150 ° C., the moldability is likely to deteriorate, and when the temperature is higher than the static recrystallization temperature, the structure is rearranged and annealed. is there.
In addition, before throwing a metal raw material in a metal mold | die in a forge molding process, the metal raw material previously solution-formed in the raw material heating process was heated to 120 degreeC-static recrystallization temperature.
The metal material once solutionized is heated to 120 ° C to static recrystallization temperature, put into a temperature-controlled mold and subjected to isothermal forging at 150 ° C to static recrystallization temperature. Not only increased strength due to hardening and grain refinement hardening, but also toughness could be improved at the same time, and high-temperature constant temperature forged parts with high strength and high toughness could be manufactured.
The processing speed in the forging process can be appropriately selected according to the temperature of the metal material, the shape and dimensions of the parts to be manufactured, and the like. In particular, by adjusting the processing speed in the forging process based on the temperature of the metal material, it is possible to prevent the processing speed in the forging process from becoming too fast and the metal material temperature from becoming higher than a predetermined temperature. Excellent in manufacturing condition uniformity.

According to the manufacturing method of the constant temperature forged part in Embodiment 1 comprised as mentioned above, it has the following effects.
(1) By introducing a solution-cast aluminum alloy into a temperature-controlled mold and forging at a temperature of 150 ° C. to static recrystallization, the inside of the mold and the metal in the mold The manufacturing conditions can be kept substantially constant by keeping the temperature of the material at a predetermined temperature, and high-quality constant temperature forged parts with little variation can be manufactured, and the quality reliability and high quality are excellent.
(2) Since there is a forging process in which the metal material heated in advance in the material heating process is put into a temperature-adjusted mold and forged, the metal material will not cool down and the processing pressure will be reduced and high speed will be achieved. It can be processed and has excellent mass productivity.
(3) Increasing strength in conventional cold forging by having a forging process in which a solution-treated aluminum alloy is put into a temperature-controlled mold and forged at 150 ° C. to static recrystallization temperature In contrast, work hardening and precipitation hardening were performed separately focusing on only the above, but the present invention not only increases strength by work hardening, precipitation hardening and grain refinement hardening, but also toughness by isothermal forging. At the same time, it is possible to produce high-temperature, high-toughness, high-quality constant-temperature forged parts without additional heat treatment after the forging process, and the shape is close to the final shape of the product. Since it can be molded, post-processing such as cutting is unnecessary, the number of processing steps can be greatly reduced, the material yield can be improved, and productivity and resource saving are excellent.

According to the constant-temperature forged part manufactured by the method for manufacturing a constant-temperature forged part in Embodiment 1 configured as described above, the following effects are obtained.
(1) At least a part of crystal grains is formed into flat crystal grains which are crushed and elongated by forging, and an average grain is formed in a deformed or recovered structure region of flat crystal grains or a grain boundary region of crystal grains. By having a composite structure in which fine recrystallized grains having a diameter of 10 nm to 1000 nm are scattered, the region of the deformed or recovered structure of the flat crystal grains mainly contributes to the increase in strength, and the fine recrystallized grains It is thought that it contributes to the improvement of toughness. Thereby, it is possible to realize a high-quality constant temperature forged part capable of realizing unprecedented high strength and high toughness.
(2) A region in which deformation or stress is likely to be concentrated due to the presence of fine recrystallized grains having an average particle size of 10 nm to 1000 nm in the region of the deformed or recovered structure of the flat crystal grain or the grain boundary region of the crystal grain. Thus, it is possible to form a structure having both strength and toughness of the region where fracture starts, and in particular, fine recrystallized grains formed along crystal grain boundaries and grain boundary triple points undergo plastic deformation. As a result, the stress concentration at the grain boundary, which is the starting point of fracture, can be alleviated and the toughness of the product can be greatly improved, and a constant temperature forged part with high toughness, durability and long life can be realized.
(3) Since the tensile strength is 360 MPa or more and the elongation is 14% or more, high toughness can be realized while having high strength, and durability and long life are excellent.
(4) Tensile strength is 360 MPa or more, elongation is 14% or more, JIS H4040
Since it greatly exceeds the standard value of A6061BE-T6 (tensile strength of 265 MPa or more, elongation of 10% or more), it can be suitably used for automobile parts and the like, and the weight of the parts and the improvement of fuel consumption can be achieved. .
(5) When the crystal grains include granular crystal grains having a deformation band formed to have a thickness of 10 μm or less in the parent phase while maintaining the outer shape at the time of the solution treatment before forging, the crystals are crushed by forging. It has the effect of relatively increasing the forging ratio of the flat crystal grains that have been elongated for a long time, can form a composite structure with strength and toughness, and has an unprecedented durability and long life. Forged parts can be realized.
(6) Since the fine recrystallized grains are scattered in the region of the deformation zone of the granular crystal grains, the strength and toughness of the whole structure can be improved, and high quality and quality uniformity are excellent.
(7) When the Vickers hardness is 120 or more, it is possible to realize a high strength exceeding the Vickers hardness Hv = 110 to 120, which is the limit value of the conventional cold forging of A6061 aluminum alloy + T6 processed product. As a substitute for low- and medium-carbon steel forgings, it is possible to reduce the weight, and it has excellent versatility.
(8) The strength specification of carbon steel S35C forged steel products is at the level of Vickers hardness Hv = 155, but depending on the product part, the same hardness as this forged steel product can be obtained. There is almost no need to increase the weight, the weight can be reduced, and design flexibility and workability are excellent.

Hereinafter, the present invention will be specifically described by way of examples. The present invention is not limited to these examples.
The constant temperature forged part was manufactured by the method for manufacturing the constant temperature forged part described in the first embodiment.
Example 1
As a metal material, an aluminum alloy (A6061-T6 material) solution-treated (heated at 540 ° C. for 2 hours and then water-cooled) is put into a temperature-controlled mold, and the temperature of the metal material is set to 170 ° C. The forging process was performed at an equivalent strain of 0.5 and a processing speed of 30 mm / s.
(Example 2)
Molding was performed in the same manner as in Example 1 except that the temperature of the metal material in the forging process was 220 ° C. (Comparative Example 1)
Molded in the same manner as in Example 1 except that the temperature of the metal material in the forging process was 20 ° C. (Comparative Example 2)
Molding was performed in the same manner as in Example 1 except that the temperature of the metal material in the forging process was 120 ° C. (Example 3)
Molding was performed in the same manner as in Example 1 except that the equivalent strain was 1.0 (Example 4).
Molded in the same manner as in Example 2 except that the equivalent strain was 1.0 (Comparative Example 3).
Molded in the same manner as in Example 1 except that the temperature of the metal material in the forging process was 20 ° C. and the equivalent strain was 1.0 (Comparative Example 4).
Molded in the same manner as in Example 1 except that the temperature of the metal material in the forging process was 70 ° C. and the equivalent strain was 1.0 (Comparative Example 5).
Molding was performed in the same manner as in Example 1 except that the temperature of the metal material in the forging process was 120 ° C. and the equivalent strain was 1.0.

Test pieces were collected from the constant temperature forged parts of Examples 1 to 4 and Comparative Examples 1 to 5 obtained as described above. The specimen for the tensile test was based on a JIS Z2201 No. 14A specimen, the initial parallel portion was φ10 mm × length 60 mm, and the gauge distance was 50 mm. Tensile strength and elongation were measured in accordance with JIS Z 2241 “Metal Material Tensile Test Method”. A universal testing machine UH-F500kNX manufactured by Shimadzu Corporation was used for the measurement. Further, the Vickers hardness was measured with a test force of 100 gf using a Mitutoyo micro hardness tester HM-221.
The results are shown in Table 1 and FIGS.
As shown in Table 1 and FIGS. 1 and 2, the tensile strength and elongation of Examples 1 to 4 and Comparative Examples 1 to 5 are both standard values of JIS H4040 A6061BE-T6 in conventional forged products ( The tensile strength was 265 MPa or more and the elongation was 10% or more.
In particular, the tensile strengths of Examples 1 to 4 exceeded 360 MPa and the elongation exceeded 14%, and the characteristics of Comparative Examples 1 to 5 could be greatly improved.
Further, as shown in Table 1 and FIG. 3, the Vickers hardness of Comparative Examples 1 to 5 is the limit value of the conventional A6061 aluminum alloy cold forging + T6 treated product. However, the Vickers hardness of Examples 1 to 4 exceeded this value.
In addition, as shown in FIG. 4, when the relationship between Vickers hardness and elongation of Comparative Examples 1 to 5 and Examples 1 to 4 is seen, Examples 1 to 4 are harder than Comparative Examples 1 to 5. However, even if the hardness of the component is increased, it does not become brittle and it can be said that it has excellent durability and long life.
From these results, by setting the temperature of the metal material in the forging process to 150 ° C. to static recrystallization temperature, not only the increase in strength due to work hardening, precipitation hardening, and grain refinement hardening, but also toughness at the same time. It was found that high-quality constant temperature forged parts can be manufactured with high strength and toughness.

FIG. 5 is an EBSP image obtained by observing the structure of the constant temperature forged part of Example 3, and FIG. 6 is an EBSP image obtained by observing granular crystal grains in the structure of the constant temperature forged part of Example 3. FIG. 8 is an image of EBSP observed by enlarging the crystal grains in the structure of the constant temperature forged part of Example 3, and FIG. 8 is an enlarged view of the grain boundary region of the crystal grains in the structure of the constant temperature forged part of Example 3. It is the image of the observed EBSP.
From FIG. 5, it was found that in the structure of the constant temperature forged part of Example 3, flat crystal grains that were crushed by the forging and extended long were present.
Moreover, from FIG. 6, in the structure of the constant temperature forged part of Example 3, granular crystals in which the outer shape at the time of solution treatment before forging is maintained after forging, as indicated by a1 and a2 surrounded by broken lines. Grains are also observed, but it was found that there were those in which a deformation band having a thickness of 10 μm or less as indicated by b1 and b2 was formed in the matrix.
Further, from FIG. 7, when the crystal grains are enlarged, the deformation structure or the recovery zone of the deformation structure or the recovery structure of the flat crystal grains such as c1 to c3 in the matrix of the a3 crystal grains surrounded by the broken line It was found that fine recrystallized grains having an average grain size of 10 nm to 1000 nm are scattered in the region of.
Further, from FIG. 8, when the grain boundary region of the crystal grains is enlarged, the average grain size is 10 nm to 1000 nm in the grain boundary regions d1 and d2 surrounded by the broken line like the crystal grain a4. It was found that fine recrystallized grains were scattered.
Thus, the structure of the constant temperature forged part of Example 3 is basically a strongly deformed crystal grain or a recovered crystal grain (flat crystal grains having a deformed structure or a region of recovered structure or granular crystal grains having a deformed zone). And fine crystal grains. Strongly deformed crystal grains and recovery crystal grains mainly contribute to improvement of strength, and fine crystal grains contribute not only to improvement of strength but also to toughness.

As described above, according to this example, it was found that a mechanical strength exceeding that can be obtained without performing the heat treatment after forging as in the prior art. In addition, it has been difficult to combine strength and flexibility with a conventional forged product, but it has been found that a constant temperature forged part having extremely excellent strength and flexibility can be realized according to this example.
These results are considered to be due to the formation of deformed or recovered crystal grains responsible for the strength and fine crystal grains responsible for the strength and toughness, as is apparent from the results of the structure observation.
In Examples 1 to 4, JIS standard A6061 was used. However, A6063 and other 6000 series Al—Mg—Si based aluminum alloys can form the same structure, and the strength and It seems that toughness can be improved.

  The present invention has a composite structure in which flat crystal grains and fine recrystallized grains formed at least in part are scattered, so that the strength is equal to or higher than that of conventional steel parts while being an aluminum alloy part. Providing high-quality constant-temperature forged parts that can achieve high toughness, and by refining crystal grains, high-temperature constant-temperature forged parts that can process high-quality parts that have both high strength and toughness at high speed By providing this manufacturing method, it is possible to stably supply high-temperature forged parts made of aluminum alloy with high quality, and to improve the quality and weight of various metal parts such as automobiles, power equipment, and housing-related equipment. Can contribute.

Claims (5)

A constant-temperature forged part produced by constant-temperature forging of an Al-Mg-Si-based aluminum alloy,
At least part of the crystal grains are formed by flattened flat crystal grains that are crushed by forging, and have an average grain size in the deformed or recovered structure region of the flat crystal grains or in the grain boundary region of the crystal grains. Has a composite structure interspersed with fine recrystallized grains of 10 nm to 1000 nm,
A constant-temperature forged part having a tensile strength of 360 MPa or more and an elongation of 14% or more. 2. The crystal grains include granular crystal grains having a deformation band formed to have a thickness of 10 [mu] m or less in a parent phase, wherein an outer shape at the time of solution treatment before forging is maintained after forging. Constant temperature forged parts as described in The isothermal forged part according to claim 2, wherein the fine recrystallized grains are scattered in the region of the deformation band of the granular crystal grains. The constant temperature forged part according to any one of claims 1 to 3, wherein the Vickers hardness is 120 or more. A method for producing a constant temperature forged part according to any one of claims 1 to 4,
A method for producing a constant temperature forged part, comprising a forging process in which the aluminum alloy solution is put into a temperature-controlled mold and forged at a temperature of 150 ° C. to a static recrystallization temperature.