CN116555687A - Complete annealing method of heat-treatable reinforced aluminum alloy sheet - Google Patents
Complete annealing method of heat-treatable reinforced aluminum alloy sheet Download PDFInfo
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- 238000000137 annealing Methods 0.000 title claims abstract description 142
- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 83
- 238000000034 method Methods 0.000 title claims abstract description 50
- 238000010438 heat treatment Methods 0.000 claims abstract description 78
- 239000000463 material Substances 0.000 claims abstract description 76
- 238000001816 cooling Methods 0.000 claims description 62
- 238000004321 preservation Methods 0.000 claims description 24
- 229910052751 metal Inorganic materials 0.000 claims description 22
- 239000002184 metal Substances 0.000 claims description 22
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- 238000010583 slow cooling Methods 0.000 abstract description 9
- 239000007789 gas Substances 0.000 description 20
- 229910000979 O alloy Inorganic materials 0.000 description 13
- 238000007599 discharging Methods 0.000 description 10
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- 238000004140 cleaning Methods 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 9
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- 238000001953 recrystallisation Methods 0.000 description 4
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- 238000001125 extrusion Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
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- 230000000737 periodic effect Effects 0.000 description 1
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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
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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Abstract
According to the complete annealing method of the heat-treatable reinforced aluminum alloy sheet, firstly, an air cushion type continuous heat treatment furnace is adopted to carry out first-order annealing treatment on alloy, then a box type annealing furnace is adopted to carry out second-order annealing treatment on alloy, the first-order annealing treatment is carried out after uncoiling, the first-order annealing treatment process is matched, oil stains on the surface of an aluminum alloy coiled material are completely volatilized, annealing oil spots are not formed, the second-order annealing treatment of the box type annealing furnace is matched, the complete annealed aluminum alloy coiled material can be obtained, and the following slow cooling of the box type annealing furnace is realized; the fully annealed heat-treatable reinforced aluminum alloy sheet produced by the method has the advantages of softer mechanical property, excellent surface quality and uniform and fine grain structure, and can meet the use requirements of high-end fields such as aerospace and the like.
Description
Technical Field
The invention relates to the technical field of aluminum alloy plate processing, in particular to a complete annealing method of a heat-treatable reinforced aluminum alloy sheet.
Background
The complete annealing is one of the heat treatment methods for aluminum alloy products, and mainly aims to reduce the work hardening and residual stress introduced in the rolling, extrusion or forging production process of aluminum alloy workpieces. In order to ensure the minimum strength after annealing, the traditional process for fully annealing the heat-treatable reinforced aluminum alloy is to heat the product to a temperature above the recrystallization temperature (generally 320-410 ℃) and keep the temperature for a period of time, cool the product to 260 ℃ or even 200 ℃ at a slow cooling rate (generally along with slow cooling, the cooling rate is less than or equal to 30 ℃/h) and then discharge the product from the furnace for air cooling after the product is fully recrystallized. The essence of the heat treatment process is that: the product is organized from a deformation state with higher energy storage above the recrystallization temperature, and new crystal grains without distortion are formed again through recrystallization; a very slow cooling rate is provided during the annealing cooling process, avoiding the quenching effect from re-hardening the alloy.
The box-type annealing furnace is a periodical heat treatment furnace, alloy sheets are placed on a heat-resistant material rack in a coiled material form and distributed by a trolley capable of entering and exiting the furnace, and steel sleeves penetrate through the middle of the coiled materials to enable the coiled materials to be supported at two ends of the material rack. After the materials are prepared, the heat treatment coiled material and the whole material rack and the sleeve are fed into a furnace together for heat treatment. The heat treatment method has good heat preservation effect, can control the cooling speed of furnace cooling, and is a main method for completely annealing the heat-treatable reinforced aluminum alloy sheet in the industry at present. However, when the box-type annealing furnace is used for carrying out complete annealing heat treatment, the aluminum alloy sheet is in a coiled strip form and is not fully unfolded during production, so that oil stains on the surface of the aluminum alloy sheet are not easy to volatilize completely, and part of the oil stains can remain on the surface of the aluminum alloy to form annealed oil stains all the time, and finally the surface quality of the aluminum alloy sheet is lower. The sheet is heated in a box annealing furnace in a tape coiling mode, heat is gradually transferred from outside to inside the roll by conduction, and the heating time is increased along with the increase of the diameter of the tape coiling; meanwhile, due to the influence of stacking of the material rack, the sleeve and the coiled material, the heating and temperature equalizing time is sometimes as long as tens of hours. In such a long heating process, most of the deformation energy storage accumulated in the plate is consumed by the recovery process, so that the recrystallization nucleation rate is reduced, meanwhile, the temperature difference exists between the inner layer and the outer layer of the coil, the outer layer of the coil is at a high temperature for a long time, the grain growth is particularly serious, and as a result, the serious uneven grain growth between the inner layer and the outer layer of the coil is caused, so that the physical property and the mechanical property of the thin plate are inconsistent.
The air cushion type continuous heat treatment furnace is also a periodic heat treatment furnace, coiled materials pass through a furnace body of a heat treatment section in an uncoiler in an uncoiling mode, and furnace wind blows to the surface of the strip from the upper side and the lower side in the vertical direction, so that the thin plate floats and moves under the action of air flow. The production mode can realize the rapid heating of the sheet band and can also obtain high-quality surface quality. However, since the sheet strip is cooled in an expanded form, and the condition for realizing "slow cooling" is not provided, it is considered that the sheet strip is not suitable for the heat treatment for the complete annealing of the heat treatable reinforced aluminum alloy.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a complete annealing method of a heat-treatable reinforced aluminum alloy sheet, which is characterized in that a first-order annealing is carried out in an air cushion type continuous heat treatment furnace, and after the first-order annealing is finished, the sheet is reeled and enters a box type annealing furnace to carry out a second-order annealing, and finally the aluminum alloy sheet with good surface quality and uniform and fine grains in a complete annealing state is obtained.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a method of fully annealing a heat treatable reinforced aluminum alloy sheet, comprising the steps of:
(1) First-order annealing treatment: the furnace gas in the furnace is at 320-410 ℃, the uncoiled aluminum alloy sheet continuously passes through an air cushion type continuous heat treatment furnace at the speed of 5-30 m/min, the aluminum alloy sheet is cooled to room temperature by entering a cooling section after passing through a heating furnace body, and the aluminum alloy sheet is coiled into a coiled tape form again to obtain a coiled tape of first-order annealing;
(2) Second-order annealing treatment:
2.1 Feeding the first-order annealed coiled tape into a box-type annealing furnace, and raising the furnace gas of the annealing furnace to 40-60 ℃ above the required annealing temperature at the highest speed;
2.2 When the measured metal temperature reaches 40-60 ℃ below the required annealing temperature, the furnace gas temperature setting is changed into the required annealing temperature upper limit;
2.3 When the measured metal temperature reaches the lower limit of the required annealing temperature, calculating the heat preservation time, wherein the heat preservation time is 2.8-3.2 h;
2.4 After the operation of the heat preservation section is finished, the aluminum alloy coiled material is discharged from the furnace after being cooled to 200-260 ℃ along with the furnace, and the aluminum alloy coiled material is cooled to room temperature by air, thus obtaining the aluminum alloy sheet in a complete annealing state.
Further, the furnace gas in the step (1) is at a constant temperature of 380-410 ℃, the uncoiled aluminum alloy sheet continuously passes through an air cushion type continuous heat treatment furnace at a speed of 8-30 m/min, the aluminum alloy sheet enters a cooling section to cool to room temperature after passing through a heating furnace body, and the aluminum alloy sheet is curled into a coiled tape form again to obtain a first-order annealed coiled tape.
Further, the aluminum alloy sheet in the step (1) includes 7075-O aluminum alloy sheet, 2219-O aluminum alloy sheet, 2024-O aluminum alloy sheet.
Further, the aluminum alloy sheet in the step (1) is firstly uncoiled, cleaned and washed on an air cushion type continuous heat treatment machine, and the cleaned and uncoiled aluminum alloy sheet is then sent into an air cushion type continuous heat treatment furnace to be subjected to first-stage annealing treatment.
Further, the coiled tape subjected to the first-order annealing in the step 2.1) is fed into a box-type annealing furnace, and the furnace gas of the annealing furnace is increased to 50-60 ℃ above the required annealing temperature at the highest speed.
Further, before the first-order annealed coiled tape in the step 2.1) is conveyed to the box-type annealing furnace, material distribution is finished by means of a material rest and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the first-order annealed coiled tape.
Further, in the step 2.2), when the measured metal temperature reaches 50 ℃ to 60 ℃ below the required annealing temperature, the furnace gas temperature setting is changed to the required annealing temperature allowable upper limit.
Further, the step 2.3) starts to calculate the heat preservation time when the measured metal temperature reaches the lower limit of the required annealing temperature, and the heat preservation time is 3.0-3.2 h.
And further, after the operation of the heat preservation section in the step 2.4) is finished, the aluminum alloy coiled material is discharged from the furnace after being cooled to 230-260 ℃ along with the furnace, and the aluminum alloy coiled material is cooled to room temperature by air, so that the aluminum alloy sheet in a complete annealing state can be obtained.
Further, the furnace cooling rate in the step 2.4) is less than or equal to 30 ℃/h.
The invention relates to a complete annealing method of a heat-treatable reinforced aluminum alloy sheet, which mainly aims at the following problems: 1) When the box-type annealing furnace is adopted for complete annealing heat treatment, annealing oil spots can be formed, and the internal and external physical properties and the mechanical properties of the coil are inconsistent; 2) The air cushion type continuous heat treatment furnace does not have the condition of 'slow cooling along with furnace'. The key points of the method of the invention are as follows: the complete annealing process is carried out in two stages, specifically: firstly, carrying out first-order annealing treatment on the alloy by adopting an air cushion type continuous heat treatment furnace, then carrying out second-order annealing treatment on the alloy by adopting a box type annealing furnace, uncoiling the first-order annealing treatment, matching with a first-order annealing treatment process, completely volatilizing oil stains on the surface of an aluminum alloy coiled material, avoiding forming annealing oil spots, matching with the second-order annealing treatment of the box type annealing furnace, obtaining a completely annealed aluminum alloy coiled material, and realizing 'slow cooling along with the furnace' of the box type annealing furnace; the fully annealed heat-treatable reinforced aluminum alloy sheet produced by the method has the advantages of softer mechanical property, excellent surface quality and uniform and fine grain structure, and can meet the use requirements of high-end fields such as aerospace and the like.
According to the complete annealing method of the heat-treatable reinforced aluminum alloy sheet, disclosed by the invention, the aluminum alloy sheet is firstly cleaned after being uncoiled and then is sent into the air cushion type continuous heat treatment furnace for first-order annealing treatment, so that annealing oil spots are less likely to be formed, and the produced complete annealing state heat-treatable reinforced aluminum alloy sheet has better surface quality and higher stability of surface quality; the inner and outer rings of the first-order annealed coiled belt are respectively provided with a temperature thermocouple, so that the real-time temperature inside and outside the coiled belt can be conveniently monitored, the process control of second-order annealing treatment is facilitated, and the annealing operation is simpler and more convenient; and (3) strictly controlling the furnace cooling rate in the second-order annealing treatment step 2.4), and producing the aluminum alloy sheet with higher structural uniformity, finer grains and more stable performance.
Drawings
Fig. 1 is a process flow diagram of example 1 of the present invention.
FIG. 2 is a diagram showing a metallographic structure 100 times that of a 2.0mm thick fully annealed 2024-O alloy sheet prepared in example 1 according to the present invention.
FIG. 3 is a photograph of the surface quality of a 2.0mm thick fully annealed 2024-O alloy sheet prepared in example 1 of the present invention.
FIG. 4 is a diagram showing a metallographic structure 100 times that of a 3.5mm thick fully annealed 2219-O alloy sheet prepared in example 3 of the present invention.
FIG. 5 is a photograph showing the surface quality of a 3.5mm thick fully annealed 2219-O alloy sheet prepared in example 3 of the present invention.
FIG. 6 is a diagram showing a metallographic structure 100 times that of a 2.0mm thick sheet of 2024-O alloy in a fully annealed state, which was prepared in comparative example 1 according to the present invention.
FIG. 7 is a photograph showing the surface quality of a 2.0mm thick sheet of 2024-O alloy in a fully annealed state, which was prepared in comparative example 1 of the present invention.
Detailed Description
The following examples will assist those skilled in the art in a more complete understanding of the invention, but are not intended to limit the invention in any way.
Example 1:
the process is adopted to produce the 2024-O alloy sheet with the thickness of 2.0mm in the complete annealing state, and the production steps are as follows:
(1) Uncoiling: uncoiling the 2024 alloy coil on an air cushion type continuous heat treatment machine array;
(2) Cleaning: cleaning the uncoiled 2024 alloy sheet on an air cushion type continuous heat treatment machine array;
(3) Heating: the preset heating temperature of the heating section of the air cushion furnace is 380 ℃, and the 2024 alloy thin plate strip continuously passes at the speed of 8 m/min;
(4) And (3) cooling: the 2024 alloy sheet strip continuously passes through the cooling section of the air cushion furnace at the speed of 8m/min, and the temperature of the strip at the outlet of the cooling section is reduced to the ambient temperature by adjusting the air quantity of the cooling section;
(5) And (3) coiling: the strip is reeled up again and is taken off line from the air cushion type continuous heat treatment machine;
(6) Feeding: before 2024 alloy rolls are conveyed to a box-type annealing furnace, material distribution is completed by means of a material rest and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the coiled material;
(7) Heating and heat preservation: the furnace gas of the box-type annealing furnace is heated to 430 ℃ with the fastest heating power, and when the measured metal temperature high point reaches 330 ℃, the furnace gas temperature is changed to 390 ℃; when the measured metal temperature low point reaches 375 ℃, entering a heat preservation stage and calculating time;
(8) Cooling along with the furnace: after the operation of the heat preservation section is finished for 3 hours, discharging the coiled material after the coiled material is cooled to 260 ℃ along with the furnace, and starting a purging fan and the like for auxiliary cooling in the process, wherein the cooling rate is required to be less than or equal to 30 ℃/h;
(9) Discharging and air cooling: air cooling the coiled material to room temperature to obtain a cooled coiled material;
(10) Uncoiling and shearing: and taking the cooled coiled material, and uncoiling and shearing according to a fixed length to obtain the 2024-O aluminum alloy sheet in a complete annealing state.
The room temperature tensile properties of the sheet were as follows:
comparative example 1
The 2.0mm thick fully annealed 2024-O alloy sheet was produced by conventional techniques as follows:
(1) Before 2024 alloy rolls are conveyed to a box-type annealing furnace, material distribution is completed by means of a material rest and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the coiled material;
(2) The furnace gas of the box-type annealing furnace is heated to 430 ℃ with the fastest heating power, when the measured metal temperature high point reaches 330 ℃, the furnace gas temperature is changed to 390 ℃, and the temperature is raised while nitrogen is purged in the process. When the measured metal temperature low point reached 375 ℃, a soak phase was entered and the time was calculated. After the operation of the heat preservation section is finished for 3 hours, discharging the coiled material after the coiled material is cooled to 260 ℃ along with the furnace, and starting a purging fan and the like for auxiliary cooling in the process, wherein the cooling rate is required to be less than or equal to 30 ℃/h;
(3) And (3) cooling the coiled material to room temperature by air, and shearing according to a fixed length to obtain the 2024-O aluminum alloy sheet in a complete annealing state.
The room temperature tensile properties of the sheet were as follows:
example 2:
the process is adopted to produce the 2024-O alloy sheet with the thickness of 1.0mm in a complete annealing state, and the production steps are as follows:
(1) Uncoiling: uncoiling the 2024 alloy coil on an air cushion type continuous heat treatment machine array;
(2) Cleaning: cleaning the uncoiled 2024 alloy sheet on an air cushion type continuous heat treatment machine array;
(3) Heating: the preset heating temperature of the heating section of the air cushion furnace is 320 ℃, and the 2024 alloy thin plate strip continuously passes at the speed of 5 m/min;
(4) And (3) cooling: the 2024 alloy sheet strip continuously passes through the cooling section of the air cushion furnace at the speed of 5m/min, and the temperature of the strip at the outlet of the cooling section is reduced to the ambient temperature by adjusting the air quantity of the cooling section;
(5) And (3) coiling: the strip is reeled up again and is taken off line from the air cushion type continuous heat treatment machine;
(6) Feeding: before 2024 alloy rolls are conveyed to a box-type annealing furnace, material distribution is completed by means of a material rest and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the coiled material;
(7) Heating and heat preservation: the furnace gas of the box-type annealing furnace is heated to 440 ℃ with the fastest heating power, and when the measured metal temperature high point reaches 340 ℃, the furnace gas temperature is changed to 390 ℃; when the measured metal temperature low point reaches 375 ℃, entering a heat preservation stage and calculating time;
(8) Cooling along with the furnace: after the operation of the heat preservation section is finished for 2.8 hours, discharging the coiled material from the furnace after the coiled material is cooled to 200 ℃ along with the furnace, and starting a purging fan and the like for auxiliary cooling in the process, wherein the cooling rate is required to be less than or equal to 30 ℃/h;
(9) Discharging and air cooling: air cooling the coiled material to room temperature to obtain a cooled coiled material;
(10) Uncoiling and shearing: and taking the cooled coiled material, and uncoiling and shearing according to a fixed length to obtain the 2024-O aluminum alloy sheet in a complete annealing state.
The room temperature tensile properties of the sheet were as follows:
example 3:
the process is adopted to produce the 2219-O alloy sheet with the thickness of 3.5mm in a complete annealing state, and the production steps are as follows:
(1) Uncoiling: uncoiling the 2219 alloy coil on an air cushion type continuous heat treatment machine column;
(2) Cleaning: cleaning the uncoiled 2219 alloy sheet on an air cushion type continuous heat treatment machine array;
(3) Heating: the preset heating temperature of the heating section of the air cushion furnace is 410 ℃, and the 2219 alloy thin plate strip continuously passes at the speed of 30 m/min;
(4) And (3) cooling: the 2219 alloy sheet plate strip continuously passes through the cooling section of the air cushion furnace at the speed of 30m/min, and the temperature of the plate strip at the outlet of the cooling section is reduced to the ambient temperature by adjusting the air quantity of the cooling section;
(5) And (3) coiling: the strip is reeled up again and is taken off line from the air cushion type continuous heat treatment machine;
(6) Feeding: before 2219 alloy coil is conveyed to a box-type annealing furnace, material distribution is completed by means of a material rest and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the coiled material;
(7) Heating and heat preservation: the furnace gas of the box-type annealing furnace is heated to 455 ℃ at the fastest heating power, and when the measured metal temperature high point reaches 435 ℃, the furnace gas temperature is changed to 415 ℃; when the measured metal temperature low point reaches 405 ℃, entering a heat preservation stage and calculating time;
(8) Cooling along with the furnace: after the operation of the heat preservation section is finished for 3.2 hours, discharging the coiled material from the furnace after the coiled material is cooled to 260 ℃ along with the furnace, and starting a purging fan and the like for auxiliary cooling in the process, wherein the cooling rate is required to be less than or equal to 30 ℃/h;
(9) Discharging and air cooling: air cooling the coiled material to room temperature to obtain a cooled coiled material;
(10) Uncoiling and shearing: and taking the cooled coiled material, and uncoiling and shearing according to a fixed length to obtain the 2219-O aluminum alloy sheet in a complete annealing state.
The room temperature tensile properties of the sheet were as follows:
example 4
The process is adopted to produce the 7075-O alloy sheet with the thickness of 3.0mm in a complete annealing state, and the production steps are as follows:
(1) Uncoiling and cleaning the 7075 alloy coil on an air cushion type continuous heat treatment machine column;
(2) The preset heating temperature of the heating section of the air cushion furnace is 410 ℃, and the plate belt continuously passes at the speed of 6 m/min;
(3) The plate belt continuously passes through the cooling section of the air cushion furnace at the speed of 6m/min, and the temperature of the outlet of the plate belt at the cooling section is reduced to the ambient temperature by adjusting the air quantity of the cooling section;
(4) The strip is reeled up again and is taken off line from the air cushion type continuous heat treatment machine;
(5) Before 7075 alloy coils are conveyed to a box-type annealing furnace, material distribution is completed by means of a material rest and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the coiled materials;
(6) The furnace gas of the box-type annealing furnace is heated to 430 ℃ with the fastest heating power, and when the measured metal temperature high point reaches 330 ℃, the furnace gas temperature is changed to 390 ℃. When the measured metal temperature low point reached 375 ℃, a soak phase was entered and the time was calculated. After the operation of the heat preservation section is finished for 3 hours, discharging the coiled material from the furnace after the coiled material is cooled to 200 ℃ along with the furnace, and starting a purging fan and the like for auxiliary cooling in the process, wherein the cooling rate is required to be less than or equal to 30 ℃/h;
(7) And (3) cooling the coiled material to room temperature by air, and shearing according to a fixed length to obtain the 7075-O aluminum alloy sheet in a complete annealing state.
The room temperature tensile properties of the sheet were as follows:
example 5
The 7075-O alloy sheet with the thickness of 1.5mm and in the complete annealing state is produced by adopting the process, and the production steps are as follows:
(1) Uncoiling and cleaning the 7075 alloy coil on an air cushion type continuous heat treatment machine column;
(2) The preset heating temperature of the heating section of the air cushion furnace is 320 ℃, and the plate belt continuously passes at the speed of 5 m/min;
(3) The plate belt continuously passes through the cooling section of the air cushion furnace at the speed of 5m/min, and the temperature of the outlet of the plate belt at the cooling section is reduced to the ambient temperature by adjusting the air quantity of the cooling section;
(4) The strip is reeled up again and is taken off line from the air cushion type continuous heat treatment machine;
(5) Before 7075 alloy coils are conveyed to a box-type annealing furnace, material distribution is completed by means of a material rest and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the coiled materials;
(6) The furnace gas of the box-type annealing furnace is heated to 440 ℃ with the fastest heating power, and when the measured metal temperature high point reaches 340 ℃, the furnace gas temperature is changed to 390 ℃. When the measured metal temperature low point reached 375 ℃, a soak phase was entered and the time was calculated. After the operation of the heat preservation section is finished for 2.8 hours, discharging the coiled material from the furnace after the coiled material is cooled to 200 ℃ along with the furnace, and starting a purging fan and the like for auxiliary cooling in the process, wherein the cooling rate is required to be less than or equal to 30 ℃/h;
(7) And (3) cooling the coiled material to room temperature by air, and shearing according to a fixed length to obtain the 7075-O aluminum alloy sheet in a complete annealing state.
The room temperature tensile properties of the sheet were as follows:
example 6
The process is adopted to produce the 7075-O alloy sheet with the thickness of 2.0mm in a complete annealing state, and the production steps are as follows:
(1) Uncoiling and cleaning the 7075 alloy coil on an air cushion type continuous heat treatment machine column;
(2) The preset heating temperature of the heating section of the air cushion furnace is 410 ℃, and the plate belt continuously passes at the speed of 30 m/min;
(3) The plate belt continuously passes through the cooling section of the air cushion furnace at the speed of 30m/min, and the temperature of the outlet of the plate belt at the cooling section is reduced to the ambient temperature by adjusting the air quantity of the cooling section;
(4) The strip is reeled up again and is taken off line from the air cushion type continuous heat treatment machine;
(5) Before 7075 alloy coils are conveyed to a box-type annealing furnace, material distribution is completed by means of a material rest and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the coiled materials;
(6) The furnace gas of the box-type annealing furnace is heated to 420 ℃ with the fastest heating power, and when the measured metal temperature high point reaches 320 ℃, the furnace gas temperature is changed to 390 ℃. When the measured metal temperature low point reached 375 ℃, a soak phase was entered and the time was calculated. After the operation of the heat preservation section is finished for 3.2 hours, discharging the coiled material from the furnace after the coiled material is cooled to 260 ℃ along with the furnace, and starting a purging fan and the like for auxiliary cooling in the process, wherein the cooling rate is required to be less than or equal to 30 ℃/h;
(7) And (3) cooling the coiled material to room temperature by air, and shearing according to a fixed length to obtain the 7075-O aluminum alloy sheet in a complete annealing state.
The room temperature tensile properties of the sheet were as follows:
from the above detection results, the method for completely annealing the heat-treatable reinforced aluminum alloy sheet mainly aims at the following problems: 1) When the box-type annealing furnace is adopted for complete annealing heat treatment, annealing oil spots can be formed, and the internal and external physical properties and the mechanical properties of the coil are inconsistent; 2) The air cushion type continuous heat treatment furnace does not have the condition of 'slow cooling along with furnace'. The key points of the method of the invention are as follows: the complete annealing process is carried out in two stages, specifically: firstly, carrying out first-order annealing treatment on the alloy by adopting an air cushion type continuous heat treatment furnace, then carrying out second-order annealing treatment on the alloy by adopting a box type annealing furnace, uncoiling the first-order annealing treatment, matching with a first-order annealing treatment process, completely volatilizing oil stains on the surface of an aluminum alloy coiled material, avoiding forming annealing oil spots, matching with the second-order annealing treatment of the box type annealing furnace, obtaining a completely annealed aluminum alloy coiled material, and realizing 'slow cooling along with the furnace' of the box type annealing furnace; the fully annealed heat-treatable reinforced aluminum alloy sheet produced by the method has the advantages of softer mechanical property, excellent surface quality and uniform and fine grain structure, and can meet the use requirements of high-end fields such as aerospace and the like; the aluminum alloy sheet is firstly cleaned after being uncoiled and then is sent into an air cushion type continuous heat treatment furnace for first-order annealing treatment, so that annealing oil spots are not easy to form, the surface quality of the produced aluminum alloy sheet can be strengthened by heat treatment in a complete annealing state, and the stability of the surface quality is higher; the inner and outer rings of the first-order annealed coiled belt are respectively provided with a temperature thermocouple, so that the real-time temperature inside and outside the coiled belt can be conveniently monitored, the process control of second-order annealing treatment is facilitated, and the annealing operation is simpler and more convenient; and (3) strictly controlling the furnace cooling rate in the second-order annealing treatment step 2.4), and producing the aluminum alloy sheet with higher structural uniformity, finer grains and more stable performance.
While the invention has been described in detail in the foregoing general description and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the invention and are intended to be within the scope of the invention as claimed.
Claims (10)
1. A method for fully annealing a heat treatable reinforced aluminum alloy sheet, comprising the steps of:
(1) First-order annealing treatment: the furnace gas in the furnace is at 320-410 ℃, the uncoiled aluminum alloy sheet continuously passes through an air cushion type continuous heat treatment furnace at the speed of 5-30 m/min, the aluminum alloy sheet is cooled to room temperature by entering a cooling section after passing through a heating furnace body, and the aluminum alloy sheet is coiled into a coiled tape form again to obtain a coiled tape of first-order annealing;
(2) Second-order annealing treatment:
2.1 Feeding the first-order annealed coiled tape into a box-type annealing furnace, and raising the furnace gas of the annealing furnace to 40-60 ℃ above the required annealing temperature at the highest speed;
2.2 When the measured metal temperature reaches 40-60 ℃ below the required annealing temperature, the furnace gas temperature setting is changed into the required annealing temperature upper limit;
2.3 When the measured metal temperature reaches the lower limit of the required annealing temperature, calculating the heat preservation time, wherein the heat preservation time is 2.8-3.2 h;
2.4 After the operation of the heat preservation section is finished, the aluminum alloy coiled material is discharged from the furnace after being cooled to 200-260 ℃ along with the furnace, and the aluminum alloy coiled material is cooled to room temperature by air, thus obtaining the aluminum alloy sheet in a complete annealing state.
2. The method for completely annealing a heat-treatable reinforced aluminum alloy sheet according to claim 1, wherein in the step (1), the furnace gas in the furnace is at a constant temperature of 380-410 ℃, the uncoiled aluminum alloy sheet continuously passes through an air cushion type continuous heat treatment furnace at a speed of 8-30 m/min, the aluminum alloy sheet is cooled to room temperature by entering a cooling section after passing through the heating furnace body, and the aluminum alloy sheet is curled into a coiled tape form again, so that a coiled tape with first-order annealing is obtained.
3. The method of claim 1, wherein the aluminum alloy sheet in step (1) comprises 7075-O aluminum alloy sheet, 2219-O aluminum alloy sheet, 2024-O aluminum alloy sheet.
4. The method for completely annealing a heat-treatable reinforced aluminum alloy sheet according to claim 1, wherein the aluminum alloy sheet in the step (1) is first unwound and cleaned on an air-cushion type continuous heat treatment machine, and the cleaned and unwound aluminum alloy sheet is then fed into an air-cushion type continuous heat treatment furnace for first-order annealing treatment.
5. The method of claim 1, wherein the step 2.1) is carried out by feeding the first-order annealed web into a box annealing furnace, and the furnace gas of the annealing furnace is raised to 50-60 ℃ above the required annealing temperature at the highest speed.
6. The method for completely annealing a heat-treatable reinforced aluminum alloy sheet according to claim 1, wherein before the first-order annealed coiled tape in step 2.1) is conveyed to the box-type annealing furnace, the material distribution is finished by means of a material rack and a feeding trolley, and temperature thermocouples are loaded on the inner ring and the outer ring of the first-order annealed coiled tape.
7. The method of claim 1, wherein the furnace gas temperature setting is changed to the upper limit of the required annealing temperature when the measured metal temperature reaches 50 ℃ to 60 ℃ below the required annealing temperature in step 2.2).
8. The method of claim 1, wherein the step 2.3) is to start calculating the holding time when the measured metal temperature reaches the lower limit of the required annealing temperature, and the holding time is 3.0h to 3.2h.
9. The method for completely annealing a heat-treatable reinforced aluminum alloy sheet according to claim 1, wherein after the operation of the heat preservation section in step 2.4) is completed, the aluminum alloy coiled material is discharged from the furnace after being cooled to 230-260 ℃ along with the furnace, and the aluminum alloy coiled material is cooled to room temperature by air cooling, so that the aluminum alloy sheet in a completely annealed state can be obtained.
10. The method of claim 1, wherein the furnace cooling rate in step 2.4) is not more than 30 ℃/h.
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