CN113770180B - Hot rolling method for refining 7000 series aluminum alloy thick plate grains - Google Patents
Hot rolling method for refining 7000 series aluminum alloy thick plate grains Download PDFInfo
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- CN113770180B CN113770180B CN202110954380.2A CN202110954380A CN113770180B CN 113770180 B CN113770180 B CN 113770180B CN 202110954380 A CN202110954380 A CN 202110954380A CN 113770180 B CN113770180 B CN 113770180B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/38—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling sheets of limited length, e.g. folded sheets, superimposed sheets, pack rolling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/48—Tension control; Compression control
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
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Abstract
The invention discloses a hot rolling method for refining 7000 series aluminum alloy thick plate grains, which relates to the technical field of aluminum alloy rolling and heat treatment, and comprises the following steps: performing two-stage homogenizing annealing treatment at 400-450 ℃ and 460-500 ℃ on 7000 series aluminum alloy casting blanks, reducing large-size crystalline phase in the solidification process, and changing the occurrence state of alloy elements; and after heating, carrying out rough rolling and finish rolling treatment, wherein the rough rolling process reaches the reduction rate of more than 70%, the pass reduction rate adopts a decreasing mode of 5-9 passes, and the reduction rate of at least the first 3 passes is more than 50%. The invention refines the crystal grains of the aluminum alloy thick plate after the traditional rolling treatment, and the hot rolling treatment method of the invention can refine the hot rolling crystal grains of the 7000 series aluminum alloy thick plate from more than 80 mu m to less than 60 mu m.
Description
Technical Field
The invention belongs to the technical field of aluminum alloy hot rolling, and particularly relates to a hot rolling method for refining 7000 series aluminum alloy thick plate grains.
Background
Currently, high-strength steel, composite materials, aluminum alloys, and the like are main materials for realizing lightweight automobiles. Among them, aluminum alloy is considered to be the most promising material for lightweight automobiles because of its advantages of low density, good corrosion, easy machining, excellent surface quality, and easy recycling.
At present, aluminum alloys for automobiles are mainly 5000 series aluminum alloys and 6000 series aluminum alloys, and although the formability of the aluminum alloys and the formability of the aluminum alloys are good, the strength of the aluminum alloys is low, the weight reduction of a bearing structural part is difficult to realize, and the advantage of the weight reduction of the aluminum alloys cannot be fully exerted. With the further development of automobile light weight, 7000 series aluminum alloys, which are light in weight and high in strength, have gradually become a hot spot of research and development. 7000 series aluminum alloys, belonging to the Al-Zn-Mg- (Cu) series, commonly used include 7075, 7050, 7055, and the like. At present, studies on 7000-series aluminum alloys have been mainly focused on medium plate materials for aviation, and the fields of the studies have been mainly focused on the optimization of alloy composition, the development of heat treatment system, and the thermo-mechanical processing, but the use of the 7000-series aluminum alloys in automobile structural members (safety parts) has been limited by poor formability, poor natural aging stability, poor corrosion resistance, and the like, because of the lack of the studies.
Grain refinement and texture formation in the hot rolling process of the aluminum alloy thick plate are key factors influencing the formability, the corrosion resistance and the natural aging stability of the aluminum alloy thick plate, and the grain refinement of the 7000 series aluminum alloy thick plate after hot rolling can be realized by effectively controlling the rolling schedule in the hot rolling process, including the rolling temperature, pass reduction rate distribution and the rolling rhythm.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a hot rolling method for refining 7000 series aluminum alloy thick plate grains, which realizes effective grain refinement of an aluminum alloy thick plate after hot rolling by combining double-stage uniform post-treatment, control of pass reduction rate in a hot rolling process, formulation of rolling temperature and regulation and control of rolling rhythm, regulates orientation and texture constitution of matrix grains, and improves the performances of stability, corrosion resistance and the like in a natural aging process.
The technical scheme adopted by the invention is as follows:
a hot rolling method for refining 7000 series aluminum alloy thick plate grains comprises the following steps:
the method comprises the following steps: performing two-stage homogenization treatment on 7000 series aluminum alloy casting blanks;
step two: heating the heating furnace to perform rough rolling and finish rolling treatment, adopting 5-9 times of rough rolling, and decreasing the reduction rate of each time.
Further: the two-stage homogenization treatment in the first step is to heat the mixture to 400-450 ℃ at the heating rate of 5-15 ℃/min, keep the temperature for 4-8 h, heat the mixture to 460-500 ℃ at the heating rate of 10-20 ℃/min, and keep the temperature for 4-8 h.
Preferably: heating to 420-440 ℃ at a heating rate of 8-12 ℃/min, and keeping the temperature for 6-8 h.
Preferably: heating to 480-500 ℃ at the heating rate of 15-20 ℃/min, and keeping the temperature for 4-6 h.
Further: and in the second step, 5-9 hot rolling treatments are carried out at 400-460 ℃, the total deformation is more than 70%, and the reduction rate of at least the first 3 passes is more than 50%.
Preferably: hot rolling treatment is carried out for 5-7 passes at 430-460 ℃, and the total deformation is more than 70%.
Further: and in the second step, finish rolling treatment is carried out at 300-400 ℃.
Preferably: and (3) carrying out finish rolling treatment at the temperature of 360-400 ℃.
Further: heating in a heating furnace in the second step to raise the temperature to 420-480 ℃ at the heating rate of 5-15 ℃/min, and preserving the temperature for 30-120 min.
Preferably: heating to 440-460 ℃ at a heating rate of 5-10 ℃/min, and keeping the temperature for 30-60 min.
The invention has the following advantages:
the hot rolling method for refining 7000 series aluminum alloy thick plate grains adopts a synergistic regulation and control mode combining double-stage homogenization treatment and pass reduction type hot rolling method, regulates and controls the occurrence state of alloy elements and the size and orientation of matrix grains, and effectively realizes the refining of the aluminum alloy thick plate grains and the effective rate of the alloy elements.
The method does not need to modify the production flow and equipment, is simple and easy to realize, obviously improves the comprehensive mechanical property of the produced 7000 series aluminum alloy thick plate, and is suitable for industrial production.
Drawings
FIG. 1 is a schematic view of a hot rolling process for refining hot rolled grains of a 7000 series aluminum alloy slab according to one embodiment of the present invention;
FIG. 2 is the crystal grains 7075 after conventional hot rolling of comparative example 1;
FIG. 3 shows the crystal grains 7050 after conventional hot rolling in comparative example 2;
FIG. 4 is a grain of a 7075 aluminum alloy slab after novel hot rolling in example 1;
FIG. 5 is the grains of a new hot rolled thick 7050 aluminum alloy plate of example 2;
FIG. 6 is a statistical comparison of grain sizes of conventional and examples.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention.
The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The invention provides a hot rolling method for refining 7000 series aluminum alloy thick plate grains, which comprises the following steps:
heating a 7000 series aluminum alloy thick plate to 460-480 ℃, preserving heat for 90min, carrying out rough rolling and finish rolling, controlling the rough rolling temperature to be in a temperature range of 420-460 ℃, controlling the total reduction of 5 passes to be more than 70%, and carrying out finish rolling treatment of the first 3 passes with the reduction rate higher than 50%.
The 7000 series aluminum alloys can be used for automotive structural parts and safety parts due to their combination of high strength and plasticity. Typical, but non-limiting, 7000 series aluminum alloy plates are 7075 and 7050.
Example 1
A hot rolling method for refining 7000 series aluminum alloy thick plate grains comprises the following steps:
the method comprises the following steps: smelting 7075 aluminum alloy, and performing double-stage homogenization treatment by keeping the temperature at 460 ℃ for 8 hours and keeping the temperature at 480 ℃ for 6 hours;
step two: heating the 7075 aluminum alloy casting blank obtained in the first step to 470 ℃ in a heating furnace, preserving heat for 90min, discharging, rolling, controlling the rough rolling temperature to be in a temperature range of 420-460 ℃, controlling the total rolling reduction to be more than 70%, and finally performing hot continuous rolling finish rolling treatment, wherein the 5-pass reduction rates are respectively 58%, 54%, 51%, 42% and 35%.
FIG. 4 is a metallographic structure of a hot rolled steel sheet, and it can be seen from FIG. 4 that the structure of the steel sheet after rolling according to the present invention is substantially recrystallized grains, and the average size of the grains is 52 μm.
The 7075 aluminum alloy produced by the rolling method of the present invention has higher yield strength and tensile strength than the samples produced by the conventional hot rolling method, as shown in table 1.
Example 2
A hot rolling method for refining 7000 series aluminum alloy thick plate grains comprises the following steps:
the method comprises the following steps: smelting 7050 aluminum alloy, and performing two-stage homogenization treatment by keeping the temperature at 440 ℃ for 10 hours and keeping the temperature at 470 ℃ for 8 hours;
step two: heating the 7050 aluminum alloy casting blank obtained in the first step to 460 ℃ in a heating furnace, preserving heat for 120min, discharging and rolling, controlling the rough rolling temperature to be within a temperature range of 400-440 ℃, controlling the total rolling reduction to be more than 70%, and finally carrying out finish rolling treatment by hot continuous rolling with 5-pass reduction rates of 56%, 52%, 50%, 41% and 32%.
FIG. 5 is a metallographic structure of a hot rolled steel sheet, and it can be seen from FIG. 5 that the structure of the steel sheet after rolling according to the present invention is substantially recrystallized grains, and the average size of the grains is 56 μm.
The 7050 aluminum alloy produced by the rolling method of the present invention has higher yield strength and tensile strength than the samples produced by the conventional hot rolling method, as shown in table 1.
Comparative example 1
Heating the 7075 aluminum alloy casting blank obtained in the first step of example 1 in a heating furnace to 470 ℃, preserving heat for 90min, discharging and rolling, controlling the rough rolling temperature to be in a temperature range of 420-460 ℃, and finally performing hot continuous rolling finish rolling treatment, wherein the 7-pass reduction rates are respectively 36%, 38%, 27%, 21% and 19%.
FIG. 2 is a metallographic structure diagram after hot rolling, and it can be seen from FIG. 2 that the structure after conventional rolling is substantially composed of recrystallized grains in the major part, and some of the grains are flattened in the rolling direction to have an average grain size of 87 μm.
Comparative example 2
Heating the 7050 aluminum alloy casting blank obtained in the first step of example 2 in a heating furnace to 460 ℃, preserving heat for 120min, discharging and rolling, controlling the rough rolling temperature to be within a temperature range of 400-440 ℃, and finally performing hot continuous rolling finish rolling treatment, wherein the 7-pass reduction rates are 39%, 32%, 27%, 25% and 21%.
FIG. 3 is a metallographic structure of a hot rolled steel sheet, and it can be seen from FIG. 3 that the structure after the conventional rolling was substantially recrystallized grains, and still had grains partially flattened in the rolling direction, and the average grain size was 92 μm.
TABLE 1 comparison of the mechanical properties of the different samples
While particular embodiments of the present invention have been illustrated and described, it would be obvious that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
Claims (8)
1. A hot rolling method for refining 7000 series aluminum alloy thick plate grains is characterized in that: the method comprises the following steps:
the method comprises the following steps: performing two-stage homogenization treatment on a 7000 series aluminum alloy casting blank, wherein the two-stage homogenization treatment comprises heating to 400-450 ℃ at a heating rate of 5-15 ℃/min, keeping the temperature for 4-8 h, heating to 460-500 ℃ at a heating rate of 10-20 ℃/min, and keeping the temperature for 4-8 h;
step two: heating the heating furnace to perform rough rolling and finish rolling treatment, adopting 5-9 times of rough rolling, gradually decreasing the reduction rate of each time, heating the heating furnace to 420-480 ℃ at the heating rate of 5-15 ℃/min, and keeping the temperature for 30-120 min.
2. The hot rolling method for refining the grains of a 7000 series aluminum alloy slab according to claim 1, wherein: heating to 420-440 ℃ at a heating rate of 8-12 ℃/min, and keeping the temperature for 6-8 h.
3. The hot rolling method for refining the grains of a 7000 series aluminum alloy slab according to claim 1, wherein: heating to 480-500 ℃ at a heating rate of 15-20 ℃/min, and keeping the temperature for 4-6 h.
4. The hot rolling method for refining the grains of a 7000 series aluminum alloy slab according to claim 1, wherein: and in the second step, 5-9 hot rolling treatments are carried out at 400-460 ℃, the total deformation is more than 70%, and the reduction rate of at least the first 3 passes is more than 50%.
5. The hot rolling method for refining the grains of a 7000 series aluminum alloy thick plate according to claim 4, wherein: hot rolling treatment is carried out for 5-7 passes at 430-460 ℃, and the total deformation is more than 70%.
6. The hot rolling method for refining the grains of a 7000 series aluminum alloy slab according to claim 1, wherein: and in the second step, finish rolling treatment is carried out at the temperature of 300-400 ℃.
7. The hot rolling method for refining the grains of a 7000 series aluminum alloy thick plate according to claim 6, wherein: and (3) carrying out finish rolling treatment at the temperature of 360-400 ℃.
8. The hot rolling method for refining the grains of a 7000 series aluminum alloy slab according to claim 1, wherein: heating to 440-460 ℃ at a heating rate of 5-10 ℃/min, and keeping the temperature for 30-60 min.
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