CN114107763A - Novel 7XXX aluminum alloy thin strip for thin strip continuous casting and preparation method thereof - Google Patents
Novel 7XXX aluminum alloy thin strip for thin strip continuous casting and preparation method thereof Download PDFInfo
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- CN114107763A CN114107763A CN202010868120.9A CN202010868120A CN114107763A CN 114107763 A CN114107763 A CN 114107763A CN 202010868120 A CN202010868120 A CN 202010868120A CN 114107763 A CN114107763 A CN 114107763A
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C21/00—Alloys based on aluminium
- C22C21/10—Alloys based on aluminium with zinc as the next major constituent
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- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
- B22D11/003—Aluminium alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
- B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- 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
- C22F1/053—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 of alloys with zinc as the next major constituent
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Abstract
A novel 7XXX aluminum alloy thin strip for thin strip continuous casting and a preparation method thereof are disclosed, the aluminum alloy comprises the following components by mass percent: 4.8 to 6.3 percent of Zn, 1.6 to 2.5 percent of Mg, 1.6 to 2.5 percent of Cu, 0.1 to 0.15 percent of Zr, 0.01 to 0.08 percent of Ti, 0.001 to 0.008 percent of B, the balance of Al and other inevitable impurities, wherein the content of single impurity is less than or equal to 0.1 percent, and the content of total impurities is less than or equal to 0.2 percent. The invention adopts a twin-roll thin strip continuous casting process to prepare the aluminum alloy thin strip, the microstructure of the aluminum alloy thin strip is a fine isometric crystal matrix structure, compared with the existing 7XXX aluminum alloy, the strength is higher by more than 10%, and the elongation is higher by more than 20%; compared with a steel plate, the steel plate realizes the weight reduction of more than 30 percent. The composite material can be widely applied to the field of aerospace, such as various airplane fuselages, wing spars, cabin wall plates, high-stress aircraft structural members, airplane skins, high-strength structural parts in airplane rockets and the like, and can provide wide space for high strengthening and light weight of aerospace, energy consumption reduction and fuel economy improvement.
Description
Technical Field
The invention relates to the field of aluminum alloy preparation, in particular to a novel 7XXX aluminum alloy thin strip for thin strip continuous casting and a preparation method thereof.
Background
The thin strip continuous casting technology is a leading technology in the metallurgy field at present, and the idea was originally proposed by Henry Bessemer in 1865 (US Patent: 49053). The continuous casting of the thin strip integrates the procedures of continuous casting, rolling, even heat treatment and the like, so that the produced thin strip blank can be formed into an industrial finished product at one time through subsequent rolling, the production procedure of the aluminum alloy thin strip is greatly simplified, the production period is shortened, and the production flow of the aluminum alloy thin strip is more compact, more continuous, more efficient and more environment-friendly; meanwhile, the production cost is obviously reduced, and the quality and the performance of the produced thin strip product are not inferior to or even superior to those of the traditional process.
Typical short-flow new processes include a Hatzerland (Hazelett) continuous casting and rolling process, a twin-roll thin-strip continuous casting and rolling process and the like. However, the conventional horizontal twin-roll thin strip continuous casting and rolling process can only produce rolled aluminum foil strips and relatively simple thin strip products of 1XXX and 3XXX series of alloy systems, and cannot produce high-end aluminum alloy products of 6XXX, 7XXX and the like. And the traditional horizontal twin-roll casting machine has a slow speed which is usually only 1-3m/min, and the production efficiency is low.
In recent years, many famous manufacturers of twin roll casting machines for thin aluminum alloy strips have made many developments in increasing casting speed and width of thin aluminum alloy strips, aiming at improving production efficiency and wider application. The more well-known companies include FataHunter, Italy and Puji, France, Speedcaster developed by FataHunterTMThe ultrathin high-speed casting and rolling machine is characterized in that: the double rollers are driven by double drives, the inclination is 15 degrees, the diameter of the casting roller is 1118mm, the plate width reaches 2184mm, the rolling force is 3000t, the maximum casting speed can reach 38m/min, and the thickness can reach 0.635mm at the thinnest. The Junbo3CM casting and rolling machine developed by Puji corporation is characterized in that: the rolling force is 2900t, the plate width reaches 2020mm, the cast-rolling thickness is 1mm at the thinnest, and the maximum cast-rolling speed can reach 15 m/min. These devices still do not produce high-end aerospace 7XXX series aluminum alloy products.
Currently, 7XXX aluminum alloys, such as 7075 aluminum alloy and 7050 aluminum alloy, have attracted considerable attention, mainly because of their irreplaceable roles in structural parts in the aerospace and automotive industries, and 7XXX aluminum alloys have the advantages of low density, high strength, excellent processability and anodic reaction, and excellent stress resistance, spalling corrosion resistance, etc., and are widely used in the aerospace field, such as various aircraft fuselages, wing spars, cabin panels, aircraft high-stress structural members, aircraft skins, aircraft rocket high-strength structural parts, etc.
However, the microstructure of the currently produced 7XXX aluminum alloys still has many problems that prevent the wide application of the aluminum alloys, such as grain and precipitation coarsening, hot cracking, and the distribution of intermetallic compounds and eutectic phases along grain boundaries, and the microstructure of the aluminum alloys largely determines the mechanical properties of the aluminum alloys.
Disclosure of Invention
The invention aims to provide a novel 7XXX aluminum alloy thin strip for thin strip continuous casting and a preparation method thereof, the produced 7XXX aluminum alloy thin strip has a fine isometric crystal structure, the combination improvement of strength and elongation can be realized, and compared with the existing 7XXX aluminum alloy, the strength is higher by more than 10%, and the elongation is higher by more than 20%; compared with a steel plate, the steel plate realizes the light weight of more than 30 percent; the composite material can be used in the field of aerospace, such as various airplane fuselages, wing spars, cabin wall plates, high-stress aircraft structural members, airplane skins, high-strength structural parts in airplane rockets and the like, and can provide wide space for high strengthening and light weight of aerospace, energy consumption reduction and fuel economy improvement.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a novel 7XXX aluminum alloy thin strip for thin strip continuous casting comprises the following components in percentage by mass: zn: 4.8-6.3%, Mg: 1.6-2.5%, Cu: 1.6-2.5%, Zr: 0.1 to 0.15%, Ti: 0.01-0.08%, B: 0.001-0.008% and the balance of Al and other inevitable impurities, wherein the content of single impurity is less than or equal to 0.1%, and the content of total impurities is less than or equal to 0.2%.
The microstructure of the aluminum alloy thin strip is a fine isometric crystal matrix structure.
The aluminum alloy thin strip can realize the yield strength of 470-550MPa, the tensile strength of 540-630MPa and the elongation of 12-15% under the artificial aging condition, namely T6 state.
In the composition design of the novel 7XXX aluminum alloy thin strip provided by the invention:
zn: is the main alloying element of a 7XXX aluminum alloyFirstly, the fluidity, the castability and the machinability can be improved in the aluminum alloy, and stable MgZn can be formed by adding Mg at the same time2The strength of the aluminum alloy is improved by the strengthening phase, but the addition of a large amount of Zn increases the hot shortness and lowers the corrosion resistance. Therefore, the Zn content is controlled in the range of 4.8 to 6.3% in the present invention.
Mg: is one of the main alloy elements of the 7XXX aluminum alloy, is added with Zn at the same time, and can form stable MgZn2The strengthening phase can improve the strength, hardness, heat resistance, corrosion resistance and machinability of the aluminum alloy, but the addition of a large amount of Mg tends to cause hot brittleness and cracks in the alloy. Therefore, the Mg content is controlled in the range of 1.6 to 2.5% in the present invention.
Cu: is an important alloy element in 7XXX aluminum alloy, has certain solid solution strengthening effect and CuAl precipitated by aging2The copper alloy has obvious aging strengthening effect, and Cu can improve the hardness, heat resistance and cutting performance and improve the casting fluidity; however, too high a Cu content affects the corrosion resistance and plasticity of the aluminum alloy and increases the tendency to hot cracking. Therefore, the Cu content is controlled in the range of 1.6 to 2.5% in the present invention.
Zr: is a common additive element in aluminum alloy, and ZrAl is formed by Zr and Al3The compound can effectively block the recrystallization process and refine recrystallized grains; zr also refines the cast structure, and in 7XXX aluminum alloys Zr is used to refine the recrystallized structure instead of Cr and Mn because Zr has less effect on quench sensitivity than Cr and Mn. Therefore, in the present invention, the Zr content is controlled to be in the range of 0.1 to 0.15%.
Ti: the grain structure can be obviously refined by adding a trace amount of Ti into the aluminum alloy, the mechanical property of the alloy is effectively improved, and the hot cracking tendency of the alloy is reduced; however, the addition of too much Ti not only increases the alloy cost, but also affects the conductivity. Therefore, the Ti content is controlled in the range of 0.01 to 0.08% in the present invention.
B: b is added into the aluminum alloy through the aluminum boron intermediate alloy, a large amount of high-melting-point particles can be generated after a small amount of aluminum boron intermediate alloy is added into the alloy solution, the aluminum boron intermediate alloy can be used as an external crystal nucleus to refine the grain structure when the alloy is solidified, and the effect of improving the strength and the plasticity of the aluminum alloy can be achieved. In addition, the conductivity and corrosion resistance of the aluminum alloy can be increased. Therefore, the content of B is controlled in the range of 0.001 to 0.008% in the present invention.
According to the invention, Ti is selectively added into the 7XXX aluminum alloy, so that the grain structure can be obviously refined, the mechanical property of the alloy is effectively improved, and the hot cracking tendency of the alloy can be reduced.
According to the invention, Cu element is selectively added into the 7XXX aluminum alloy, so that Cu is dissolved into the aluminum alloy in a solid solution manner, the strength, hardness, heat resistance and cutting performance of the aluminum alloy are improved, and the casting fluidity can be improved; in addition, the CuAl precipitated by aging2Has obvious aging strengthening effect.
In the invention, Zr element is selectively added into 7XXX aluminum alloy, and Zr and Al form ZrAl3The compound can effectively obstruct the recrystallization process, refine recrystallized grains, and Zr can also refine casting structures.
According to the invention, the B element of the aluminum-boron intermediate alloy is introduced into the 7XXX aluminum alloy, a small amount of the aluminum-boron intermediate alloy is added into the aluminum alloy liquid, so that a large amount of high-melting-point particles can be generated, the aluminum alloy liquid can be used as an external crystal nucleus to refine the grain structure when being solidified, and the effects of improving the strength, plasticity, conductivity and corrosion resistance of the aluminum alloy can be achieved.
The invention relates to a preparation method of a novel 7XXX aluminum alloy thin strip for thin strip continuous casting, which comprises the following steps:
1) smelting
Smelting according to the component requirements;
2) standing, degassing, and filtering
Introducing the smelted aluminum alloy liquid into a standing furnace for standing, conveying the aluminum alloy liquid to a front box through a runner, and then degassing and filtering; the temperature of the aluminum alloy introduced into the standing furnace is 660-760 ℃;
3) continuous casting
The continuous casting adopts double-roller thin strip continuous casting to obtain an aluminum alloy cast strip with the thickness of 1.5-10mm and the width of 1000-2200 mm; the temperature of the aluminum alloy liquid is 640-680 ℃ when the aluminum alloy liquid enters the double-roller casting machine; the temperature of the aluminum alloy cast strip is 440-480 ℃, the diameter of the crystallization roller is 400-1200mm, water is introduced into the crystallization roller for cooling, and the casting speed of the casting machine is 30-120 m/min;
4) cooling down
The aluminum alloy cast strip is cooled to 380-420 ℃ after coming out of the casting machine through water quenching;
5) first hot rolling
Sending the cooled aluminum alloy cast strip to a rolling mill after pinch roll and crop treatment, and carrying out first hot rolling, wherein the temperature of the first hot rolling is 340-390 ℃, and the reduction rate of the first hot rolling is less than or equal to 50%;
6) cooling and second hot rolling
Air cooling or water cooling the aluminum alloy thin strip after the first hot rolling, then performing the second hot rolling,
the second hot rolling temperature is 250-330 ℃, and the second hot rolling reduction rate is less than or equal to 60%; the thickness of the aluminum alloy thin strip after the second hot rolling is 0.3-4mm, preferably 0.5-3 mm;
7) coiling
Sending the aluminum alloy thin strip subjected to the second hot rolling to a coiler for coiling through a pinch roll, wherein the coiling temperature is 170-280 ℃;
8) post-treatment
And (3) after the aluminum alloy thin strip is coiled, sequentially carrying out solution heat treatment and quenching.
Further, carrying out artificial aging after quenching in the step 8).
Preferably, the artificial aging temperature is 100-150 ℃, and the time is 18-28 h.
Preferably, in the step 8), the temperature of the solution heat treatment is 440-480 ℃, and the time is 50-100 min.
Preferably, in the step 8), the temperature of the aluminum alloy thin strip after quenching is between room temperature and 120 ℃.
Preferably, before the post-treatment process of the step 8), one or more of off-line cold rolling, tension straightening, edge cutting, flattening, surface inspection, plate shape inspection and forming processes can be carried out on the aluminum alloy thin strip.
Preferably, in the step 3), a vertical casting machine, a horizontal casting machine or an inclined casting machine is used for the continuous casting.
Preferably, in step 3), the crystallization roller is a copper roller, and the surface of the crystallization roller is provided with texture, grooves or embossing.
Preferably, the surface of the crystallization roller is subjected to chromium electroplating treatment, and the thickness of the chromium plating layer is 0.05-0.10 mm.
The aluminum alloy liquid smelted by the method is subjected to standing, degassing and filtering, and then is subjected to twin-roll thin strip continuous casting.
And (3) feeding the aluminum alloy cast strip subjected to water quenching cooling into a four-roll mill for primary hot rolling through pinch rolls and head cutting, wherein the hot rolling temperature range is 340-390 ℃, and the reduction rate is less than or equal to 50%. In order to ensure that the aluminum alloy cast strip does not deviate and ensure the smooth production, the pinch roll has the functions of deviation rectification and centering.
Although the method of the present invention is described in the above embodiment as having two stands in the rolling step to achieve the target thickness, one skilled in the art can contemplate other embodiments, such as using any suitable number of hot rolling and subsequent cold rolling stands in the rolling step to achieve the appropriate product target thickness.
The post-treatment in the step 8) comprises the working procedures of solution heat treatment, quenching, artificial aging and the like.
After coiling, carrying out solution heat treatment and quenching on the aluminum alloy thin strip, wherein the temperature of the solution heat treatment is 440-480 ℃, and the time is 50-100 min; the temperature range of the quenched aluminum alloy thin strip is between room temperature and 120 ℃.
After the solution heat treatment and quenching, artificial aging treatment can be carried out, wherein the artificial aging temperature is as follows: 100-150 ℃, duration: 18-28 h. The state of the aluminum alloy product after solution heat treatment and artificial aging after quenching is referred to as the T6 state, which means that the final product has been solution heat treated, quenched and artificially aged.
The preparation method can select other process treatments before the post-treatment in the step 8), including off-line cold rolling, tension straightening, trimming, flattening, surface inspection, plate shape inspection, forming and the like, and then can perform solid solution heat treatment and quenching after reaching the final specification or forming to the final shape so as to avoid the problem of difficult forming due to high strength.
The twin roll casting machine for continuous casting according to the present invention may be in the form of a vertical type, a horizontal type or an inclined type. The crystallizing roller for twin-roll strip casting is copper roller, and the surface of the crystallizing roller is processed into grains, grooves or embossing, etc. to raise the heat conducting efficiency of the interface and thus raise the strip casting speed. After the surface appearance of the crystallization roller is processed, the chromium electroplating treatment is needed, the thickness of the chromium coating is controlled to be 0.05-0.10mm, the surface hardness and the wear resistance of the crystallization roller can be greatly improved through the chromium electroplating treatment, and the service life of the crystallization roller is prolonged.
The aluminum alloy thin strip is coiled in a double-coiling mode, and also can be coiled in a carrousel coiling mode, so that the continuous production of the aluminum alloy is ensured. The coiling machine reel has an automatic centering function so as to ensure good coil shape when the aluminum alloy thin strip is coiled and ensure smooth production.
The invention is distinguished and improved from the prior art:
the existing thin strip continuous casting production aluminum alloy products do not adopt the improvement of aluminum alloy components by adding Ti, B, Cu and Zr, and the 7XXX aluminum alloy is directly prepared by a double-roller thin strip continuous casting process, which is not reported directly.
Chinese patent CN104321451A discloses an improved 7XXX aluminum alloy and a preparation method thereof, the aluminum alloy sheet has 2.0-22 wt% of Zn, and the Zn is a main alloy element except Al in the aluminum alloy sheet; also included are particulate matter having a size of greater than or equal to 30 um. The aluminum alloy plate has a sandwich structure of two outer regions and one inner region, the Zn content of the two outer regions is greater than that of the inner region, and the particle concentration contained in the inner region is greater than that of the outer regions, so that the aluminum alloy plate is a non-uniform internal structure. The invention is obviously different from the patent, the product composition of the patent does not relate to Mg, Cu, Zr, Ti, B and other elements, and also does not relate to measures such as semi-solid treatment and the like, and the microstructure of the aluminum alloy thin strip is uniform and fine isometric crystal structure.
Chinese patent CN105121690A discloses a heat-treatable aluminum alloy containing Mg and Zn and a preparation method thereof, wherein the aluminum alloy contains 3.0-6.0 wt% of Mg and 2.5-5.0 wt% of Zn, and can be produced by preparing an aluminum alloy body for cold working after solid solution, cold working by at least 25% and then heat treatment, so that the improvement of strength property can be realized, and the components of the product are not related to Cu, Ti, B and other elements.
Chinese patent CN200810098094 discloses "a continuous casting process of an aluminum alloy thin strip blank", and proposes that 5052 aluminum alloy can be produced by adopting a vertical twin-roll thin strip continuous casting process, and the invention does not relate to 7XXX aluminum alloy.
The invention has the beneficial effects that:
1. according to the invention, Ti is selectively added into the 7XXX aluminum alloy, so that the grain structure can be obviously refined, the mechanical property of the alloy is effectively improved, and the hot cracking tendency of the alloy can be reduced. According to the invention, Cu element is selectively added into the 7XXX aluminum alloy, so that Cu is dissolved into the aluminum alloy in a solid solution manner, the strength, hardness, heat resistance and cutting performance of the aluminum alloy are improved, and the casting fluidity can be improved; in addition, the CuAl precipitated by aging2Has obvious aging strengthening effect. In the invention, Zr element is selectively added into 7XXX aluminum alloy, and Zr and Al form ZrAl3The compound can effectively obstruct the recrystallization process, refine recrystallized grains, and Zr can also refine casting structures.
2. The invention introduces B element into the aluminum alloy through the aluminum boron intermediate alloy, and a small amount of aluminum boron intermediate alloy is added into the aluminum alloy liquid to generate a large amount of high-melting-point particles, and the aluminum boron intermediate alloy can be used as an external crystal nucleus to refine the grain structure when the aluminum alloy liquid is solidified, so that the strength, the plasticity, the conductivity and the corrosion resistance of the aluminum alloy can be improved. Meanwhile, the content of the B element can be further improved to 0.008 percent due to the combination of a double-roller thin strip continuous casting sub-rapid solidification process.
3. Compared with the traditional aluminum alloy production process, the invention has the following advantages:
a) short flow, investment saving, low cost and low energy consumption: the double-roll thin strip casting and rolling equipment can replace the traditional DC casting machine, heating furnace and hot rolling mill, and the equipment cost is greatly reduced; the occupied area is only 1/4 of the traditional flow (casting and hot rolling workshop), and the energy consumption is only 50 percent of that of the traditional flow;
b) the production efficiency is high, the processing time of the semi-finished product is greatly shortened, and 5 working procedures (1, sawing the head and the tail of the ingot; 2. homogenizing annealing (which is a long-time process and takes up to 50 hours); 3. milling a surface; 4. heating before hot rolling; 5. hot rolling), from aluminum alloy liquid to hot rolled coil, from 20 days required by the traditional flow, to 20 minutes;
c) the yield is greatly improved: greatly reducing the consumption of head cutting, tail removing and face milling, and improving the yield by more than 20 percent;
d) the production line has a high degree of flexibility: the continuous casting machine of the production line can replace the alloy at any time without stopping the machine, thereby realizing seamless transition among aerospace, automobile, industry, household appliances and packaging market products.
4. Compared with the product produced by the traditional aluminum alloy production process, the invention has the advantages of obvious structure performance:
a) the density is high, and macrosegregation is almost not generated: the produced aluminum alloy thin strip has fine isometric crystal microstructure characteristic of quick solidification characteristic, has high density, and avoids the cracking problem in the subsequent rolling process; almost no macrosegregation and almost no anisotropy exist, and the mechanical property is greatly improved after heat treatment;
b) the surface quality is good: compared with the traditional double-roller casting (the casting speed is only 1-3m/min), the casting speed can be greatly improved to 30-120m/min, the problem of uneven cooling of the upper surface and the lower surface of the traditional horizontal double-roller casting can be avoided, the surface quality is greatly improved, and the harsh requirements of the automobile industry can be met;
c) excellent performance, obvious light weight advantage: compared with the existing 7XXX aluminum alloy, the 7XXX aluminum alloy thin strip produced by the invention has the advantages that the strength is higher by more than 10%, and the elongation is higher by more than 20%; compared with a steel plate, the steel plate realizes the weight reduction of more than 30 percent.
5. The traditional double-roller cast-rolling aluminum alloy production usually adopts steel rollers, and the cooling and heat transfer efficiency is low, so that the drawing speed is only 1-3m/min, and the production efficiency is low.
The crystallization roller used for twin-roller thin strip continuous casting adopts a copper roller, the surface of the crystallization roller is processed into shapes such as textures, grooves or embossing, and the like, so that the interface heat conduction efficiency can be greatly improved, and the thin strip continuous casting speed can be improved; after the surface appearance of the crystallization roller is processed, chromium electroplating treatment is carried out, so that the surface hardness and the wear resistance of the crystallization roller can be greatly improved, and the service life of the crystallization roller is prolonged.
Drawings
Fig. 1 is a schematic view of a process of vertical twin roll strip casting according to a first embodiment of the present invention.
Fig. 2 is a schematic view of the process of the second embodiment of the present invention (horizontal twin roll strip casting).
Detailed Description
The present invention is further illustrated by the following examples and the accompanying drawings, which are not intended to limit the present invention, and those skilled in the art can make modifications or improvements based on the basic idea of the invention, but within the scope of the present invention, without departing from the basic idea of the invention.
Referring to fig. 1, in a first embodiment of the present invention, a vertical casting machine is used to prepare a novel 7XXX aluminum alloy thin strip.
The smelted aluminum alloy liquid which is designed according to the chemical composition of the invention is led into a standing furnace 3 from a smelting furnace 1 through a launder 2 for standing. The aluminum alloy liquid is transferred from the standing furnace 3 to the front box 4 through the launder 2, degassed 5, filtered 6, and then poured into the tundish 7.
Molten aluminum alloy is directly fed from the bottom of a tundish 7 through a submerged nozzle 8 and a flow distribution device 9 into a molten pool 11 surrounded by two relatively rotating and rapidly-cooled crystallization rollers 10a and 10b and side closing plate devices 12a and 12 b. The aluminum alloy liquid is solidified on the circumferential surfaces of the crystallization rolls 10a, 10b rotating, and then an aluminum alloy cast strip 15 having a thickness of 1.5-10mm and a width of 1000-2200mm is formed at the minimum gap (nip point) between the two crystallization rolls 10a, 10 b. The diameter of the crystallization rollers 10a and 10b is 400-1200mm, and water is introduced for cooling. The casting speed of the casting machine ranges from 30 to 120m/min depending on the thickness of the aluminum alloy cast strip 15.
The aluminum alloy casting strip 15 comes out of the twin-roll strip caster and directly enters the closed chamber 14, the closed chamber 14 is communicated with inert gas to protect the aluminum alloy casting strip 15, and the aluminum alloy casting strip is cast15, the atmosphere for protecting against oxidation may be N2Ar, or other non-oxidizing gas, such as CO obtained by sublimation of dry ice2Gas, etc., the oxygen concentration in the closed chamber 14 is controlled to be<5 percent, and the closed chamber 14 protects the aluminum alloy cast strip 15 from oxidation to the inlet of the No. 1 pinch roll 17. An aluminum alloy cast strip 15 passes through a conveying roller way 20 on a swing guide plate 13, is cooled by a water quenching cooling device 16, enters a No. 1 pinch roller 17, is subjected to head cutting by a flying shear 18, enters a four-roller No. 1 hot rolling mill 19 for hot rolling, the flying shear 18 guides the cut strip head into a waste hopper 26 through a guide plate 25, and the flying shear 18 also has the function of on-line cutting between coils, so that the continuous production can be ensured. In order to ensure that the aluminum alloy cast strip 15 does not deviate and ensure the smooth production, the 1# pinch roll 17 has the functions of deviation rectification and centering.
After the aluminum alloy cast strip 15 is hot-rolled by a No. 1 hot rolling mill 19, an aluminum alloy thin strip running on a conveying roller way 20 enters an air cooling/water cooling device 21 for cooling, then the aluminum alloy thin strip enters a four-roll No. 2 hot rolling mill 22 for hot rolling again to form a hot-rolled aluminum alloy thin strip of 0.3-4mm, and the rolled aluminum alloy thin strip enters a No. 2 pinch roll 23 and then directly enters a coiling machine 24 for coiling.
The coiling machine 24 adopts a double-coiling mode and can also adopt a carrousel coiling mode to ensure the continuous production of the aluminum alloy. The coiling machine 24 has an automatic centering function, so that good coil shape is ensured when the aluminum alloy is coiled, and smooth production is ensured.
Referring to fig. 2, in the second embodiment of the present invention, a horizontal casting machine is used to prepare a novel 7XXX aluminum alloy thin strip.
The smelted aluminum alloy liquid which is designed according to the chemical composition of the invention is led into a standing furnace 3 from a smelting furnace 1 through a launder 2 for standing. The aluminum alloy liquid is transferred from the standing furnace 3 to the front box 4 through the launder 2, degassed 5, filtered 6, and then poured into the tundish 7.
Molten aluminum alloy is directly fed from the bottom of a tundish 7 through a submerged nozzle 8 and a flow distribution device 9 into a molten pool 11 surrounded by two relatively rotating and rapidly-cooled crystallization rollers 10a and 10b and side closing plate devices 12a and 12 b. The aluminum alloy liquid is solidified on the circumferential surfaces of the crystallization rolls 10a, 10b rotating, and then an aluminum alloy cast strip 15 having a thickness of 1.5-10mm and a width of 1000-2200mm is formed at the minimum gap (nip point) between the two crystallization rolls 10a, 10 b. The diameter of the crystallization rollers 10a and 10b is 400-1200mm, and water is introduced for cooling. The casting speed of the casting machine ranges from 30 to 120m/min depending on the thickness of the aluminum alloy cast strip 15.
The aluminum alloy cast strip 15 comes out of the twin-roll strip caster, the cast strip temperature is 440-480 ℃, the cast strip directly enters the closed chamber 14, the closed chamber 14 is filled with inert gas to protect the aluminum alloy cast strip 15, the anti-oxidation protection of the aluminum alloy cast strip 15 is realized, and the atmosphere of the anti-oxidation protection can be N2Ar, or other non-oxidizing gas, such as CO obtained by sublimation of dry ice2Gas, etc., the oxygen concentration in the closed chamber 14 is controlled to be<5 percent, and the closed chamber 14 protects the aluminum alloy cast strip 15 from oxidation to the inlet of the No. 1 pinch roll 17. The aluminum alloy cast strip 15 directly comes out of the upper roller channel 20 of the crystallizing rollers 10a and 10b, is cooled by the water quenching cooling device 16, enters the 1# pinch roller 17, is cut by the flying shear 18, and then enters the four-roller 1# hot rolling mill 19 for hot rolling, the flying shear 18 guides the cut strip head into the waste hopper 26 through the guide plate 25, and the flying shear 18 also has the function of on-line cutting between coils, so that the continuous production can be ensured. In order to ensure that the aluminum alloy cast strip 15 does not deviate and ensure the smooth production, the 1# pinch roll 17 has the functions of deviation rectification and centering.
After the aluminum alloy cast strip 15 is hot-rolled by a No. 1 hot rolling mill 19, an aluminum alloy thin strip running on a conveying roller way 20 enters an air cooling/water cooling device 21 for cooling, then the aluminum alloy thin strip enters a four-roll No. 2 hot rolling mill 22 for hot rolling again to form a hot-rolled aluminum alloy thin strip of 0.3-4mm, and the rolled aluminum alloy thin strip enters a No. 2 pinch roll 23 and then directly enters a coiling machine 24 for coiling.
The coiling machine 24 adopts a double-coiling mode and can also adopt a carrousel coiling mode to ensure the continuous production of the aluminum alloy. The coiling machine 24 has an automatic centering function, so that good coil shape is ensured when the aluminum alloy is coiled, and smooth production is ensured.
After coiling, the aluminum alloy strip may be subjected to a series of post-treatment processes, such as solution heat treatment, quenching, artificial aging, and the like. Other processes including off-line cold rolling, tension straightening, trimming, leveling, surface inspection, plate shape inspection, forming and the like can also be performed before the post-treatment, and then a series of post-treatment processes can be performed after the final specification is reached.
The chemical components of the aluminum alloy thin strip of the embodiment of the invention are shown in table 1, and the balance of the components is Al and other unavoidable impurities. The technological parameters of the preparation method of the embodiment of the invention are shown in Table 2, the parameters of the post-treatment process are shown in Table 3, and the properties of the finally obtained aluminum alloy thin strip are shown in Table 4.
In conclusion, the aluminum alloy thin strip manufactured according to the design range and the manufacturing method of the aluminum alloy composition provided by the invention can realize the yield strength of 470-550MPa, the tensile strength of 540-630MPa and the elongation of 12-15% under the artificial aging condition (T6 state). Compared with the existing 7XXX aluminum alloy, the strength is higher than 10%, and the elongation is higher than 20%; compared with a steel plate, the light weight of more than 30% is easily realized.
The aluminum alloy thin strip produced by the invention can be widely applied to the field of aerospace, such as various airplane fuselages, wing spars, cabin wall plates, high-stress aircraft structural parts, airplane skins, high-strength structural parts in airplane rockets and the like, and can provide wide space for high strengthening and light weight of aerospace, energy consumption reduction and fuel economy improvement.
Table 1 units: mass percent
| Serial number | Zn | Mg | Cu | Zr | Ti | B |
| Example 1 | 4.8 | 1.9 | 1.8 | 0.14 | 0.03 | 0.002 |
| Example 2 | 5.8 | 2.3 | 1.9 | 0.12 | 0.01 | 0.001 |
| Example 3 | 5.5 | 2.2 | 2.5 | 0.13 | 0.02 | 0.004 |
| Example 4 | 5.7 | 2.3 | 2.2 | 0.12 | 0.05 | 0.008 |
| Example 5 | 5.2 | 2.5 | 2.4 | 0.14 | 0.08 | 0.007 |
| Example 6 | 5.4 | 1.8 | 2.3 | 0.11 | 0.07 | 0.008 |
| Example 7 | 6.2 | 2.1 | 1.6 | 0.15 | 0.07 | 0.005 |
| Example 8 | 5.5 | 2.4 | 1.8 | 0.13 | 0.06 | 0.006 |
| Example 9 | 5.3 | 1.6 | 2.0 | 0.10 | 0.05 | 0.003 |
| Example 10 | 6.3 | 2.0 | 2.1 | 0.12 | 0.04 | 0.004 |
Claims (12)
1. A novel 7XXX aluminum alloy thin strip for thin strip continuous casting comprises the following components in percentage by mass: zn: 4.8-6.3%, Mg: 1.6-2.5%, Cu: 1.6-2.5%, Zr: 0.1 to 0.15%, Ti: 0.01-0.08%, B: 0.001-0.008% and the balance of Al and other inevitable impurities, wherein the content of single impurity is less than or equal to 0.1%, and the content of total impurities is less than or equal to 0.2%.
2. The thin strip cast novel 7XXX aluminum alloy of claim 1, wherein the aluminum alloy thin strip microstructure is a fine equiaxed matrix structure.
3. The thin strip of 7XXX aluminum alloy as claimed in claim 1 or 2, wherein the thin strip can achieve yield strength of 470-550MPa, tensile strength of 540-630MPa and elongation of 12-15% under the condition of artificial aging, i.e. T6.
4. The method for preparing the novel 7XXX aluminum alloy thin strip by thin strip continuous casting according to any one of claims 1 to 3, characterized by comprising the following steps:
1) smelting
Smelting according to the composition requirements of claim 1;
2) standing, degassing, and filtering
Introducing the smelted aluminum alloy liquid into a standing furnace for standing, conveying the aluminum alloy liquid to a front box through a runner, and then degassing and filtering; the temperature of the aluminum alloy introduced into the standing furnace is 660-760 ℃;
3) continuous casting
The continuous casting adopts double-roller thin strip continuous casting to obtain an aluminum alloy cast strip with the thickness of 1.5-10mm and the width of 1000-2200 mm; the temperature of the aluminum alloy liquid is 640-680 ℃ when the aluminum alloy liquid enters the double-roller casting machine; the temperature of the aluminum alloy cast strip is 440-480 ℃, the diameter of the crystallization roller is 400-1200mm, water is introduced into the crystallization roller for cooling, and the casting speed of the casting machine is 30-120 m/min;
4) cooling down
The aluminum alloy cast strip is cooled to 380-420 ℃ after coming out of the casting machine through water quenching;
5) first hot rolling
Sending the cooled aluminum alloy cast strip to a rolling mill after pinch roll and crop treatment, and carrying out first hot rolling, wherein the temperature of the first hot rolling is 340-390 ℃, and the reduction rate of the first hot rolling is less than or equal to 50%;
6) cooling and second hot rolling
Air cooling or water cooling is carried out on the aluminum alloy thin strip subjected to the first hot rolling, then the second hot rolling is carried out, the temperature of the second hot rolling is 250-330 ℃, and the reduction rate of the second hot rolling is less than or equal to 60%; the thickness of the aluminum alloy thin strip after the second hot rolling is 0.3-4mm, preferably 0.5-3 mm;
7) coiling
Sending the aluminum alloy thin strip subjected to the second hot rolling to a coiler for coiling through a pinch roll, wherein the coiling temperature is 170-280 ℃;
8) post-treatment
And (3) after the aluminum alloy thin strip is coiled, sequentially carrying out solution heat treatment and quenching.
5. The method for producing thin strip of continuously cast novel 7XXX aluminum alloy as claimed in claim 4, wherein the quenching of step 8) is followed by artificial aging.
6. The method for preparing the novel 7XXX aluminum alloy thin strip by thin strip continuous casting according to claim 5, wherein the artificial aging temperature is 100-150 ℃ and the time is 18-28 h.
7. The method for preparing the novel 7XXX aluminum alloy thin strip by thin strip continuous casting according to claim 4, wherein the solution heat treatment temperature in step 8) is 440-480 ℃ for 50-100 min.
8. The method for producing the thin strip of the novel 7XXX aluminum alloy by strip continuous casting as claimed in claim 4, wherein in the step 8), the temperature of the aluminum alloy thin strip after quenching is between room temperature and 120 ℃.
9. The method for preparing the novel 7XXX aluminum alloy strip by strip continuous casting as claimed in claim 4, wherein before the post-treatment step of step 8), the aluminum alloy strip can be subjected to one or more of off-line cold rolling, tension straightening, edge cutting, flattening, surface inspection, plate shape inspection and forming.
10. The method for preparing the thin strip of the novel 7XXX aluminum alloy as claimed in claim 4, wherein in the step 3), the continuous casting is performed by using a vertical casting machine, a horizontal casting machine or an inclined casting machine.
11. The method for producing thin strip of 7XXX aluminum alloy as defined in claim 4, wherein in step 3), the crystallizing roller is a copper roller, and the surface of the crystallizing roller is textured, grooved or embossed.
12. The method for preparing the novel 7XXX aluminum alloy thin strip by thin strip continuous casting according to claim 4 or 11, wherein the surface of the crystallization roller is electroplated with chromium, and the thickness of the chromium-plated layer is 0.05-0.10 mm.
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