JPH0588302B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field This invention is applicable to JIS 2000 series, 6000 series or
The present invention relates to a method of manufacturing an aluminum alloy material having fine grains made of a heat-treatable aluminum alloy for drawing, typified by the No. 7000 series, and in particular to a method of manufacturing an aluminum alloy material optimal for superplastic working materials. BACKGROUND OF THE INVENTION In recent years, techniques for performing superplastic working using the superplastic phenomenon of metal materials having fine crystal grains have been attracting attention. The superplastic phenomenon caused by fine crystal grains is also observed in heat-treated aluminum alloys for drawing, and when the crystal grains are reduced to 25 μm
It is known that if it is made as fine as possible, it will exhibit superplasticity when processed in a predetermined superplastic temperature range. Conventionally, methods for manufacturing heat-treated rolled aluminum alloy sheets with grains fine enough to enable such superplastic working include (a) precipitating coarse particles of intermetallic compounds through overaging treatment; A method of applying strain through warm working (e.g., JP-A-53-132420); (b) A method of rapidly cooling after solution treatment and applying strain through cold rolling (e.g., JP-A-60-86251); (c) A method of slow cooling from the solution treatment temperature and cold rolling (for example, JP-A-60-12-5354) is known. Problems to be Solved by the Invention Among the methods for manufacturing aluminum alloy rolled sheets having fine grains as described above, method (a) requires overaging treatment and warm working, which reduces productivity. The problem is that it has no choice but to become low. Further, in the method (b), the crystal grains can be made finer, but there is a problem that rolling after solution treatment and rapid cooling becomes difficult. Furthermore, although the method (c) has good rolling properties, there is a problem in that intense cold working of 90% or more is required to obtain fine grains. This invention was made against the background of the above circumstances, and it is possible to practically obtain a material having fine crystal grains suitable for superplastic working without causing problems such as a decrease in productivity and a decrease in cold rollability. The purpose is to provide a method that can be used. Means for Solving the Problems The method of the present invention basically consists of coarsely precipitating precipitated particles by slow cooling from a temperature near the solution treatment temperature, and using these as recrystallization nuclei. Subsequent quenching from 40 to 70% of the solution treatment temperature improves cold rollability compared to when quenching from the solution treatment temperature (complete quenching) and removes residual alloying elements. It aims at solid solution or fine precipitation to increase the dislocation density and deformation bands in the matrix, thereby increasing the frequency of nucleation during recrystallization and making the crystal grains finer. Specifically, the method of the first invention is a heat-treated aluminum alloy for drawing, and Mn0.05~
1.5%, Cr0.05~0.4%, Zr0.05~0.3%
An aluminum alloy containing one or more species is used as a material, and the alloy ingot is homogenized by heating at a temperature of 90% or more of the solution treatment temperature of the alloy for 0.5 to 24 hours, and then 0.001 to 0.05℃/sec
70-90% of solution treatment temperature with cooling rate within the range of
After cooling to a temperature of to 180°C or less, preferably to room temperature, at a cooling rate of 0.1°C/sec or more,
After that, after performing cold working at a processing rate of 60% or more,
The alloy is characterized by being recrystallized by raising the temperature to a temperature higher than the recrystallization temperature of the alloy at a heating rate of 1° C./sec or higher. Further, the method of the second invention is a heat-treated aluminum alloy for drawing, and furthermore, 0.05 to 1.5% of Mn and
An aluminum alloy containing one or more of Cr0.05~0.4% and Zr0.05~0.3% is used as a material, and the alloy ingot is subjected to homogenization treatment at a solution treatment temperature of the alloy. 0.5 at temperatures above 90% of
Heating for ~24 hours, then cooling to room temperature at a cooling rate in the range of 0.001-0.05 °C/sec, then reheating to a temperature of 70-90% of the solution treatment temperature, either immediately or at that temperature for 24 hours. Hot rolling is started after the temperature is maintained within 180°C, preferably at room temperature, and the hot rolling is completed at a temperature of 40 to 70% of the solution treatment temperature. After cooling to a temperature of 60% or more, the alloy is heated to a temperature higher than the recrystallization temperature of the alloy by 1℃/
This method is characterized by recrystallization by increasing the temperature at a rate of sec or more. Function First, the aluminum alloy targeted by this invention will be explained. The method of this invention uses an A-Cu alloy (JIS
It can be applied to all heat-treated alloys for expansion, such as A-Mg-Si alloys (JIS 6000 series), A-Mg-Mg alloys (JIS 7000 series). be. However, Cu, Mg and
In addition to Si, Zn, Mg, etc., essential components include Mn0.05-1.5%, Cr0.05-0.4%, Zr0.05
It is necessary that one or more selected from ~0.3% be contained. That is,
Mn, Cr, and Zr are all effective elements for grain refinement through the formation of intermetallic compound precipitated particles.
By containing these, it becomes possible to obtain a microcrystalline structure capable of superplastic processing, which is the objective of the present invention. Here, if the content of Mn, Cr, or Zr is less than 0.05%, it will be difficult to obtain fine crystal grains, whereas if the content of Mn, Cr, or Zr is less than 0.05%, it will be difficult to obtain fine crystal grains.
If the Zr content exceeds 0.3%, or if the Zr content exceeds 0.3%, these elements will not be sufficiently solid-dissolved during casting, resulting in the formation of giant intermetallic compounds, making it impossible to obtain sufficient elongation. Therefore, Mn is 0.05-1.5% and Cr is 0.05-0.4.
%, Zr was within the range of 0.05 to 0.3%. Note that the term heat-treatable alloy for drawing is used here in the broadest sense, and as mentioned above, A-Cu
2000 series alloys, such as JIS standards and
AA standard 2014 alloy, 2017 alloy, 2024 alloy, 2219
6000, which is an alloy or A-Mg-Si alloy
series alloys, such as 6061 alloy, and even A-Zn
- There are 7000 series alloys, which are Mg-based alloys, such as 7075 alloy, 7475 alloy, 7N01 alloy, and 7003 alloy.
In the case of this invention, as mentioned above, Mn, Cr,
The composition of components other than Zr is not particularly limited as long as it can be heat treated, and may be determined depending on the application and required characteristics. For example, A-
In the case of Cu-based alloys, it contains about 1.5 to 6.3% Cu, and if necessary, about 0.2 to 1.8% Mg and 0.2% Si.
It is sufficient that the content is about 1.3%, and A
-In the case of Mg-Si alloy, Si is about 0.20 to 1.2%,
It is sufficient to contain about 0.35 to 1.5% Mg, and if necessary, about 0.10 to 0.40% Cu, and in the case of an A-Zn-Mg alloy, Zn is about 0.8 to 1.5%.
6.1%, Mg about 0.5 to 2.9%, and Cu about 1.2 to 2.0% if necessary. Next, the process in the method of this invention will be explained. First, an ingot of a heat-treated aluminum alloy containing one or more of Mn, Cr, and Zr as described above is produced by continuous casting or semi-continuous casting according to a conventional method. Next, the ingot is subjected to homogenization treatment. This homogenization treatment is performed at a temperature close to the solution treatment temperature of the target alloy, that is, at a temperature of 90% or more of the solution treatment temperature (however, 90% or more of Celsius temperature; the same applies to the percentage of temperatures below). This is done by heating for ~24 hours. If the temperature of the homogenization treatment is less than 90% of the solution treatment temperature, homogenization will be insufficient and the alloying elements will not be sufficiently solutionized.
If the homogenization treatment time is less than 0.5 hours, homogenization and solutionization will be insufficient, while if it exceeds 24 hours, the effect will be saturated and it will only be economically disadvantageous. Note that the solution treatment temperature here is the temperature between the solidus temperature and the solubility curve in the α phase region of the target alloy, and the specific optimum temperature varies depending on the alloy composition, but typically is AA standard or
Typical solution treatment temperatures are shown in the JIS standard, and according to this, for 2014 alloy, it is 495-505℃,
495-510℃ for 2017 alloy, 2024 alloy (plate material)
490~500℃, 515~550℃ for 6061 alloy, 460~500℃ for 7075 alloy (plate material), 460~499 for 7475 alloy
℃, approximately 450℃ for 7N01 alloy is said to be optimal.
Therefore, in the present invention, X% of the solution treatment temperature is preferably X% of the optimal solution treatment temperature of each alloy as described above. The above-mentioned homogenization treatment is performed by cooling to a temperature of 70 to 90% of the solution treatment temperature at a cooling rate within the range of 0.001 to 0.05 °C/sec (in the case of the first invention), and heating to that temperature for 24 hours as necessary. The temperature is maintained within an hour and hot rolling is started at that temperature. Alternatively, after homogenization treatment,
Cool to room temperature at a cooling rate within the range of 0.001 to 0.05°C/sec (in the case of the second invention), then reheat to a temperature of 70 to 90% of the solution treatment temperature, and if necessary, heat to that temperature. Hold for less than 24 hours and start hot rolling at that temperature. After such homogenization process
By slow cooling at a cooling rate of 0.001-0.05℃/sec,
Coarse particles of the reinforcing element are precipitated. Here, if the cooling rate is 0.05° C./sec or more, precipitation will be insufficient, while if the cooling rate is less than 0.001° C./sec, productivity will be inhibited and this will be economically disadvantageous. In addition, if the hot rolling start temperature is less than 70% of the solution treatment temperature, hot rolling becomes difficult;
%, the precipitation of coarse precipitates will be too small and grain refinement in the final plate will be insufficient. Hot rolling started in the temperature range of 70 to 90% of the solution treatment temperature as described above is
Terminate at a temperature of 40-70%, from that temperature 0.1
Quenching is carried out by cooling to 180°C or less, preferably room temperature, at a cooling rate of 0°C/sec or more. By quenching at a temperature of 40 to 70% of the solution treatment temperature, the cold rollability does not decrease as much as with complete quenching (quenching from the solution treatment temperature), and furthermore, precipitation does not occur. It is possible to obtain a fine grain structure in the final plate by increasing the dislocation density and deformation band in the matrix by solid solution or fine precipitation of the remaining alloying elements. It is. Here, if cooling (quenching) is performed from a temperature lower than 40% of the solution treatment temperature, the introduction of dislocations due to solid solution/aging will be reduced and the effect of grain refinement will not be obtained.
On the other hand, if the material is cooled (quenched) from a high temperature that exceeds 70% of the solution treatment temperature, it becomes too hard and hard, making subsequent cold rolling difficult. Further, if the cooling rate for hardening is less than 0.1° C./sec, hardening will not occur sufficiently, strain will not be introduced sufficiently by subsequent rolling, and grain refinement will not be achieved. In addition, the temperature at the end of quenching should be 180°C or less, and if possible, it is desirable to quench to room temperature. If quenching is completed at a temperature higher than 180°C, coarse precipitates will be formed during subsequent cooling, and no quenching effect will be observed. The lower the temperature at the end of quenching, the greater the amount of solute that dissolves in the matrix or precipitates as fine particles, and the subsequent cold rolling increases the dislocation density and deformation bands in the matrix, ultimately resulting in a fine grain structure. Easy to get. As mentioned above, hot rolling is finished at a temperature of 40 to 70% of the solution treatment temperature, and the temperature is reduced by 0.1% from that temperature.
In order to harden at a cooling rate of ℃/sec or higher,
After hot rolling, the coil may be cooled by adding rolling coolant, or by using spray water cooling or forced air cooling equipment.
Either means can be efficiently applied on a mass production scale. After quenching at a temperature of 40 to 70% of the solution treatment temperature, cold working such as cold rolling is performed at a processing rate of 60% or more. This cold working is intended to introduce strain and refine the crystal grains during subsequent recrystallization. If the working rate is less than 60%, the introduction of strain will be insufficient and the grains will not be refined enough. I can't plan on it. After the above-mentioned cold working, the temperature is raised above the recrystallization temperature of the target alloy at a heating rate of 1°C/sec or more,
recrystallize. During this recrystallization, the faster the heating rate is, the more advantageous it is to refine the recrystallized grains, and if the heating rate is less than 1°C/sec, fine grains suitable for superplastic processing cannot be obtained. Speed 1℃/sec
limited to the above. In order to rapidly heat at 1°C/sec or more in this way, it is necessary to use a salt bath,
A continuous air heating furnace may be used. Although the recrystallization temperature differs depending on the type of alloy, the solution treatment temperature of the alloy is always higher than the recrystallization temperature, so in actual operation, heat should be aimed at the solution treatment temperature. It is sufficient. Furthermore, after heating for recrystallization, water quenching may be performed in accordance with a conventional method. As mentioned above, after performing homogenization treatment before hot rolling at a temperature range of 90% or more of the solution treatment temperature,
Gradual intermetallic compound particles are coarsely precipitated by slow cooling at a cooling rate of 0.001 to 0.05°C/sec, and subsequent to the completion of hot rolling or after hot rolling, a temperature of 40 to 70% of the solution treatment temperature is applied. By quenching at a cooling rate of 0.1°C/sec or more from a temperature range, the remaining alloying elements are dissolved or finely precipitated, and then cold worked by 60% or more and then recrystallized. As a result, recrystallized grains can be significantly refined. Here, a very large processing rate is not required for cold working to introduce strain before recrystallization, and as mentioned above, if the processing rate is 60% or more, fine crystal grains can be obtained in the end. , cold working can be carried out without reducing productivity or causing difficulties in cold rolling. Examples [Example 1] Regarding alloys 1 to 5 having the composition shown in Table 1,
A 400mm thick slab was cast using the DC casting method. The obtained slabs were subjected to homogenization treatment and hot rolling under the heating conditions and cooling conditions A to H shown in Table 2 to obtain hot rolled sheets with a thickness of 6 mm. Then cold rolling rate 80
%, and rapidly heated in a salt bath to the solution treatment temperature of each alloy for recrystallization, held for 10 minutes, and then water quenched. In addition, some of Alloy 1 that was homogenized and hot rolled under condition code A was rolled at a cold rolling rate of 80% and then recrystallized by raising the temperature at 0.01°C/sec as a comparative method. Let (symbol). As a result of examining the crystal grain size of the plate surface of the final plate after recrystallization obtained as described above, the results shown in Table 3 were obtained. From Table 3, it is clear that the rolled sheets of invention alloys 1 to 4 containing the required amount of Mn, Cr, or Zr treated under the conditions specified in this invention all have extremely small crystal grain sizes of 11 μm or less. and
It has been found that these rolled plates can be sufficiently subjected to superplastic working. On the other hand, when Comparative Alloy 5, which does not substantially contain Mn, Zr, and Cr, was treated within the condition range of the present invention (condition symbol E), the crystal grain size became as large as 35 μm. Furthermore, condition code F was a condition in which the homogenization treatment was not performed at a temperature of 90% or more of the solution treatment temperature, and in this case as well, the crystal grain size was as large as 33 μm.
Furthermore, condition symbol G is an example in which the hot rolling start temperature was too high, and in this case too, the crystal grain size became large at 48 μm. Condition code H means that quenching from 40 to 70% of the solution treatment temperature after hot rolling (cooling at 0.1°C/sec or more) is not performed, and in this case as well, the grain size is It was large at 33μm. Furthermore, the condition symbol is an example in which heating for recrystallization quenching was performed at a slow temperature increase, and in this case, the crystal grain size became coarse to 350 μm.

【table】

【table】

【table】

[Table] [Example 2] Alloy 1 of Example 1 was subjected to homogenization treatment and hot rolling according to condition symbol A in Table 2, with cooling at 3 × 10 ^-3 °C/sec after homogenization treatment. After cooling to room temperature at a high speed, reheating was performed to the hot rolling start temperature. Also, for Alloy 3 of Example 1, when homogenizing and hot rolling according to condition symbol C in Table 2, 3 × 10 ^-3
After cooling to room temperature at a cooling rate of °C/sec, it was reheated to the hot rolling start temperature. The other conditions were the same as in Example 1. The crystal grain size of the obtained rolled plate after recrystallization was 9 μm for Alloy 1 and 10 μm for Alloy 3.
It was found that the particles were sufficiently refined as in the case of . [Example 3] Alloy 1 and Alloy 3 of Example 1 were homogenized and hot rolled according to condition symbols A and C in Table 2, respectively, and then cold rolled at a rolling reduction of 80%, Next, Alloy 1 was heated to 480℃ and Alloy 3 to 490℃ using a continuous annealing furnace at a heating rate of 20℃/sec. A typical recrystallization treatment was performed. When the crystal grain size of the obtained recrystallized plate was examined, it was found that
The diameter was 10 μm for Alloy 1 and 11 μm for Alloy 3, and it was found that both had a fine grain structure. [Example 4] Regarding alloy 3 in Table 1 of Example 1, Example 1
Homogenization treatment and hot rolling were performed under the same conditions as Condition C in Table 2. After that, the cold rolling rate was increased to 55%,
Cold rolling was carried out in three different proportions, 75% and 90%, and then recrystallized by heating in a salt bath in the same manner as in Example 1. Table 4 shows the grain size of the final plate in Example 3 in correspondence with the cold rolling rate.

[Table] Effects of the Invention According to the method of the present invention, an aluminum alloy rolled sheet having fine grains suitable for superplastic working can be obtained.
It is possible to obtain fine grains without reducing cold rolling properties, without increasing the cold working rate, and without performing overaging or warm working, which reduces productivity. It has now become possible to produce rolled aluminum alloy sheets that are practically suitable for superplastic working on a mass production scale without causing any problems such as deformation or difficulty in cold working.

Claims (1)

[Claims] 1. A heat-treated aluminum alloy for drawing, comprising:
Moreover, Mn0.05-1.5% (weight%, same below),
An aluminum alloy containing one or more of Cr0.05~0.4% and Zr0.05~0.3% is used as a material, and the alloy ingot is subjected to homogenization treatment at a solution treatment temperature of the alloy. 0.5 at temperatures above 90% of
Heating for ~24 hours, then cooling at a cooling rate within the range of 0.001~0.05°C/sec to a temperature of 70~90% of the solution treatment temperature, either immediately or after being held at that temperature for no more than 24 hours. Start hot rolling and finish hot rolling at a temperature of 40 to 70% of the solution treatment temperature, and then cool to 180 ° C or less, preferably room temperature, at a cooling rate of 0.1 ° C / sec or more, After that, cold working is performed at a processing rate of 60% or more, and then the temperature is raised to a temperature higher than the recrystallization temperature of the alloy at a heating rate of 1°C/sec or higher to recrystallize. A method for producing an aluminum alloy material having grains. 2. A heat-treated aluminum alloy for drawing,
Moreover, Mn0.05~1.5%, Cr0.05~0.4%, Zr0.05~
The material is an aluminum alloy containing one or more of 0.3%, and the alloy ingot is homogenized at a temperature of 90% or more of the solution treatment temperature of the alloy for 0.5 to 24 hours. heat and then
Cool to room temperature at a cooling rate within the range of 0.001 to 0.05°C/sec, then reheat to a temperature of 70 to 90% of the solution treatment temperature, either immediately or after holding at that temperature for no more than 24 hours before hot processing. Start rolling and finish hot rolling at a temperature of 40 to 70% of the solution treatment temperature,
180℃ or less at a cooling rate of 0.1℃/sec or more,
Preferably, the alloy is cooled to room temperature, then cold worked at a processing rate of 60% or more, and then recrystallized by raising the temperature to a temperature higher than the recrystallization temperature of the alloy at a heating rate of 1°C/sec or higher. A method for producing an aluminum alloy material having fine crystal grains.