Aluminum alloy sheet for hydrogen energy automobile hydrogen storage cylinder and processing method thereof

Abstract

The application provides an aluminum alloy plate for hydrogen energy automobile hydrogen storage bottles and a processing method thereof, the aluminum alloy plate is composed of the following chemical elements in percentage by mass: Si: 0.6% to 0.7%, Fe: 0.3% to 0.5%, Cu: 0.2% to 0.4%, Mn: less than or equal to 0.15%, Mg: 0.9% to 1.1%, Cr: 0.15% to 0.25%, Zn: less than or equal to 0.10%, Ti: 0.015% to 0.025%, single impurity: less than or equal to 0.03%, total impurities: less than or equal to 0.10%, and the balance is Al; the processing method comprises the following steps: batching, smelting, refining, casting, sawing, milling, homogenization heating, hot rolling, annealing, straightening, sawing, flaw detection and finished product.The application optimizes the proportion of alloy elements, so that the plate has high mechanical properties after heat treatment, and the safety of the hydrogen storage bottle is improved; the application adopts a push type heating furnace for homogenization treatment, eliminates intracrystalline segregation of chemical components, prevents uneven recrystallization grains caused by component segregation, and controls the rolling temperature of the hot rolled plate to make the plate produce certain deformation energy storage and provide driving force for recrystallization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum alloy processing and manufacturing, and relates to an aluminum alloy plate for a hydrogen energy automobile hydrogen storage bottle and a processing method thereof. BACKGROUND

[0002] With the increasing seriousness of environmental pollution in the world and the increasing aggravation of global energy crisis, automobiles also develop more towards energy saving and environmental protection. Hydrogen energy becomes an important direction of development of new energy vehicles due to its advantages of wide resources and no air pollution.

[0003] Aluminum alloy becomes a main material for replacing steel and being applied to the inner liner of the hydrogen storage bottle due to its advantages of small density (about one third of the density of steel), high specific strength, easy processing and forming, good corrosion resistance and weldability.

[0004] 6061 aluminum alloy belongs to an Al-Mg-Si alloy, and main alloying elements are magnesium and silicon. The main strengthening phase Mg2Si thereof belongs to heat treatable strengthening aluminum alloy. The 6061-O aluminum alloy plate produced by a common process has the following defects due to small deformation energy storage of the material during rolling and easy occurrence of insufficient annealing or grain coarsening during annealing: (1) deep drawing is prone to cracking; (2) grain is coarse, and orange peel appears on the surface during deep drawing, reducing the fatigue life of the hydrogen storage bottle; (3) the strength of the material is low after heat treatment, affecting the safety of the hydrogen storage bottle; and (4) the ear forming rate is high, and the material utilization rate is low. SUMMARY

[0005] The technical task of the application is to solve the problems of stamping cracking, grain coarsening, low heat treatment strength and high deep drawing ear forming rate of the existing 6061-O aluminum alloy plate, and the application provides an aluminum alloy plate for a hydrogen energy automobile hydrogen storage bottle and a processing method thereof.

[0006] The technical scheme adopted by the application to solve the technical problem is that the aluminum alloy plate for the hydrogen energy automobile hydrogen storage bottle is composed of the following chemical elements in percentage by mass: Si: 0.6% to 0.7%, Fe: 0.3% to 0.5%, Cu: 0.2% to 0.4%, Mn≤0.15%, Mg: 0.9% to 1.1%, Cr: 0.15% to 0.25%, Zn≤0.10%, Ti: 0.015% to 0.025%, single impurity≤0.03%, total impurities≤0.10%, and the balance is Al.

[0007] Further, the aluminum alloy plate is in a 6061-O state, and the thickness is 14.0 to 25.0 mm. The plate after rolling is annealed to reduce the tensile property to a full soft state.

[0008] Further, the mechanical strength of the aluminum alloy plate in the O state is: tensile strength ≤ 150 MPa, yield strength ≤ 80 MPa, elongation ≥ 22%; and the mechanical strength after quenching and artificial aging to the T62 state is: tensile strength ≥ 320 MPa, yield strength ≥ 280 MPa, elongation ≥ 10%. The O state plate is strengthened to a high strength state through heat treatment when the finished product is mechanically detected, which meets the use requirements of the hydrogen storage bottle.

[0009] The processing method of the above-mentioned aluminum alloy plate for hydrogen energy automobile hydrogen storage bottle comprises: batching, smelting, refining, casting, sawing, milling, homogenization heating, hot rolling, annealing, straightening, sawing, flaw detection, and finished product. The main steps include:

[0010] A. According to the predetermined mass percentage, the batching of each chemical element of the aluminum alloy is put into a smelting furnace for smelting, in-furnace refining, online degassing, and online filtering, and the aluminum liquid is cast into an aluminum alloy ingot;

[0011] B. After the aluminum alloy ingot is cast, the head and tail are cut after cooling, and the condensate layer on the surface of the ingot is milled off;

[0012] C. The sawed and milled ingot is placed in a push-type heating furnace for homogenization treatment, the metal temperature is 520-570℃, the temperature is kept for 2-10 hours to eliminate grain segregation, and after the homogenization is finished, the temperature is lowered to 420-500℃ and kept for 2-20 hours;

[0013] D. After the heating is finished, the plate is directly rolled out of the furnace, the final pass processing rate of hot rolling is controlled to be greater than 10%, and the final rolling temperature of hot rolling is 240-320℃;

[0014] E. After rolling, annealing is carried out, the annealing metal temperature is 360-420℃, the holding time is 1-5 hours, after the holding is finished, it is naturally cooled to room temperature, and then it is transferred to a straightening machine for straightening and precision sawing to cut the plate to size.

[0015] Further, the final rolling temperature of hot rolling in step D is 250-300℃, so as to avoid excessive temperature release of deformation energy and affect the grain refinement effect.

[0016] Further, the penultimate and third passes of hot rolling in step D need to be controlled by pass processing rate distribution and emulsion spraying to control the final rolling temperature of the pass, so as to avoid that the final rolling temperature cannot be controlled in the required range.

[0017] Further, step E uses a plate annealing furnace for complete recrystallization annealing.

[0018] Further, the heating speed in step E is greater than 100℃ / h during annealing, which increases the recrystallization nucleation rate and refines the grains.

[0019] Further, the method further comprises the following steps: F, ultrasonic nondestructive detection is performed on the finished plate, and the internal structure of the plate is detected according to the A-grade detection standard; and the water immersion detector is used in step F to perform nondestructive detection.

[0020] The present application has the following beneficial effects:

[0021] The present application provides an aluminum alloy plate for hydrogen energy automobile hydrogen storage bottle, which needs to have high strength and hardness to ensure good use performance, and needs to have sufficient strengthening phase Mg2Si in the microstructure, in addition, in order to control the surface quality after anodic oxidation, the iron content is controlled in the lower limit (0.3% or less), the silicon content is controlled to be 0.6% or less, and the copper content is controlled in the lower limit. In the present application, the finished product is in the O state, and subsequent processing is deep drawing, which needs to have sufficient plastic deformation capacity and fine grain size, and does not need to be treated by surface anodic oxidation. In the chemical composition design, the iron content is controlled to be 0.3% to 0.5%, which is beneficial to grain refinement, in the case of meeting the chemical composition ratio of Mg2Si, some excess silicon is added, the silicon is controlled in the upper limit, on the one hand, the acicular FeAl3 phase is eliminated, which is easy to cause cracking in the subsequent deep drawing process, on the other hand, the heat treatment performance of the material is higher, therefore, the silicon content is controlled to be 0.6% to 0.7%, the magnesium content is 0.9% to 1.1%, and the copper is beneficial to the increase of the strength after heat treatment, therefore, the copper element is controlled to be 0.2% to 0.4%; the chromium content has the effect of refining grains, but also reduces the plasticity, which is not conducive to subsequent stamping, therefore, the chromium content is controlled to be 0.15% to 0.25%.

[0022] The present application adopts ingot casting homogenization process to eliminate grain segregation and prevent recrystallized grains from being uneven due to composition segregation; the final pass processing rate and the rolling end temperature are controlled to improve the deformation energy storage of the plate; the recrystallization nucleation rate is improved by rapid heating during annealing, the recrystallized grains are refined, and orange peel defects are prevented during deep drawing;

[0023] The present application adopts high-temperature short-time annealing to complete recrystallization while avoiding grain growth and preventing deep drawing cracking.

[0024] The present application optimizes the proportioning of alloy elements, so that the material has good plasticity after annealing to O state, which is beneficial to the deep drawing forming of the hydrogen storage bottle liner, and can ensure that the hydrogen storage bottle liner has high mechanical properties after solid solution quenching and artificial aging; online hydrogen removal and double-stage filtration are used before casting, so as to reduce the slag content of the melt, ensure the purity of the melt, reduce the organizational defects of the plate, and make the detection grade of the plate reach A grade, thereby avoiding the formation of fatigue crack sources due to organizational defects and reducing the fatigue life. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application and not used to limit the present application.

[0026] The present application provides an aluminum alloy plate for hydrogen energy automobile hydrogen storage cylinder, which is composed of the following chemical elements in percentage by mass: Si: 0.6%~0.7%, Fe: 0.3%~0.5%, Cu: 0.2%~0.4%, Mn≤0.15%, Mg: 0.9%~1.1%, Cr: 0.15%~0.25%, Zn≤0.10%, Ti: 0.015%~0.025%, single impurity≤0.03%, total impurities≤0.10%, and the balance of Al.

[0027] The aluminum alloy plate is in 6061-O state and has a thickness of 14.0~25.0mm. The plate after rolling is annealed to reduce the tensile property to a full soft state.

[0028] The aluminum alloy O-state plate is strengthened to T62 state by quenching and artificial aging when the finished product is mechanically detected, which proves that the O-state plate can be strengthened to a high-strength state by heat treatment, meeting the use requirements of the hydrogen storage cylinder.

[0029] The processing method of the above-mentioned aluminum alloy plate for hydrogen energy automobile hydrogen storage cylinder includes: batching, melting, refining, casting, sawing, milling, homogenization heating, hot rolling, annealing, straightening, sawing, flaw detection, and finished product. The main steps include:

[0030] A. According to the predetermined mass percentage, the batching of each chemical element of the aluminum alloy is put into a melting furnace for melting, in-furnace refining, online degassing, and online filtering, and the aluminum liquid is cast into an aluminum alloy ingot;

[0031] Step A follows the following process: the batching is sequentially put into the melting furnace for melting, and a flux is used for refining coverage. After the materials in the furnace are melted, stirring is started, and then refining, slagging, and obtaining qualified chemical composition are performed. Then, Ar gas is used to bring hydrogen and fine impurities in the aluminum liquid to the surface of the melt, thereby reducing the gas and slag content of the melt. After online degassing and filtering, the melt is cast into an ingot;

[0032] In step A, argon is used to remove hydrogen in the melt through a double-rotor degassing system, and a double-stage filter (including but not limited to: plate-type CFF filter + filter, plate-type CFF filter + deep bed filter, and plate-type CFF filter + pipe-type filter) is used to reduce the slag content of the melt and ensure the purity of the melt. Al-5Ti-B is used for online refining treatment to ensure that the aluminum alloy ingot has fine grains;

[0033] B, after the casting of the aluminum alloy ingot is cooled, the head and tail are cut off, and the condensed shell layer on the surface of the ingot is milled off;

[0034] C, the sawed and milled ingot is placed in a push-type heating furnace for homogenization treatment, the metal temperature is 520-570 DEG C, the temperature is kept for 2-10 hours, the grain segregation is eliminated, after the homogenization is finished, the temperature is lowered to 420-500 DEG C, and the temperature is kept for 2-20 hours;

[0035] D, after the heating is finished, the plate is directly rolled out of the furnace, the final pass processing rate of hot rolling is controlled to be greater than 10%, the final pass rolling end temperature of hot rolling is 240-320 DEG C; preferably, the hot rolling end temperature is 250-300 DEG C, so as to avoid that the temperature is too high to release deformation energy and affect the grain refinement effect; the penultimate and third passes of step D hot rolling need to be controlled by pass processing rate distribution and emulsion spraying to control the rolling end temperature of the pass, so that the final pass end temperature can be controlled in the required range;

[0036] E, after the rolling, the plate is annealed, the heating speed is greater than 100 DEG C / hour, the recrystallization nucleation rate is improved, the grain is refined, the annealing metal temperature is 360-420 DEG C, the temperature is kept for 1-5 hours, after the temperature keeping is finished, the temperature is naturally cooled to room temperature, and the plate is transferred out of the furnace to a straightening machine for straightening and precise sawing to a fixed size;

[0037] F, the finished plate is subjected to ultrasonic nondestructive testing, and the internal structure of the plate is checked according to the A-level testing standard; step F uses a water immersion type flaw detector for nondestructive testing.

[0038] The preferred embodiment of the application will be described in detail below by taking a 6061-O aluminum alloy plate with a thickness of 20 mm for a hydrogen energy automobile hydrogen storage bottle as an example.

[0039] Example 1

[0040] A processing method of an aluminum alloy plate for a hydrogen energy automobile hydrogen storage bottle, comprising the following steps:

[0041] A, according to the mass percentage in Table 1, the ingredients of each chemical element of the aluminum alloy are put into a smelting furnace for smelting, furnace refining, online degassing and online filtering, and the aluminum liquid is cast into an aluminum alloy ingot;

[0042] B, after the casting of the aluminum alloy ingot is cooled, the head and tail are cut off, and the condensed shell layer on the surface of the ingot is milled off;

[0043] C, the sawed and milled ingot is placed in a push-type heating furnace for homogenization treatment, the metal temperature is 550 DEG C, the temperature is kept for 7 hours, the grain segregation is eliminated, after the homogenization is finished, the temperature is lowered to 500 DEG C, and the temperature is kept for 2 hours;

[0044] D, after heating, directly out of the furnace and rolling, the final pass processing rate of hot rolling is 12%, the final pass rolling end temperature of hot rolling is 295℃, and the slab is cut;

[0045] E, the slab is stacked and annealed in a slab annealing furnace, rapid heating is performed during annealing, the heating rate is 120℃ / hour, the annealing metal temperature is 390℃, the holding time is 1 hour, and natural cooling is performed to room temperature after the holding ends, the slab is transferred to a straightening machine for straightening and a precision saw for cutting to size.

[0046] F, the finished slab is subjected to ultrasonic nondestructive testing to check the internal structure of the slab.

[0047] Example 2

[0048] A processing method of an aluminum alloy plate for a hydrogen energy automobile hydrogen storage bottle, comprising the following steps:

[0049] A, according to the mass percentage of table 1, the ingredients of each chemical element of the aluminum alloy are put into a smelting furnace for smelting, in-furnace refining, online degassing and online filtering, and the aluminum liquid is cast into an aluminum alloy ingot;

[0050] B, after the aluminum alloy ingot is cast, the head and tail are cut off, and then the condensate layer on the surface of the ingot is milled off;

[0051] C, the sawed and milled ingot is placed in a push-type heating furnace for homogenization treatment, the metal temperature is 560℃, the holding time is 6 hours, the grain segregation is eliminated, and the temperature is lowered to 480℃ after the homogenization ends, and the holding time is 2 hours;

[0052] D, after heating, directly out of the furnace and rolling, the final pass processing rate of hot rolling is 15%, the final pass rolling end temperature of hot rolling is 271℃, and the slab is cut;

[0053] E, the slab is stacked and annealed in a slab annealing furnace, rapid heating is performed during annealing, the heating rate is 120℃ / hour, the annealing metal temperature is 390℃, the holding time is 1 hour, and natural cooling is performed to room temperature after the holding ends, the slab is transferred to a straightening machine for straightening and a precision saw for cutting to size.

[0054] F, the finished slab is subjected to ultrasonic nondestructive testing to check the internal structure of the slab.

[0055] Example 3

[0056] A processing method of an aluminum alloy plate for a hydrogen energy automobile hydrogen storage bottle, comprising the following steps:

[0057] A, according to the mass percentage of table 1, the ingredients of each chemical element of the aluminum alloy are put into a smelting furnace for smelting, in-furnace refining, online degassing and online filtering, and the aluminum liquid is cast into an aluminum alloy ingot;

[0058] B, after the aluminum alloy ingot casting cooling cut head tail, then use the ingot surface milling shell layer;

[0059] C, the sawing, milling ingot after the surface placed in the push type heating furnace, homogenization treatment, metal temperature 570 ℃, 5 hours, homogenization after cooling to 460 ℃, 2 hours;

[0060] D, heating after direct out of furnace rolling, hot rolling final pass processing 12%, hot rolling final pass rolling end temperature 253 ℃, cut into slab;

[0061] E, the slab stack, in the plate annealing furnace annealing, annealing when rapid heating, heating rate 130 ℃ / h, annealing metal temperature 370 ℃, 3 hours, after the end of the holding time, natural cooling to room temperature, out of the furnace to the straightening machine straightening, precision sawing to size cut plate.

[0062] F, the finished plate ultrasonic nondestructive testing, checking the internal structure of the plate.

[0063] Example 1-3 a kind of hydrogen energy automobile hydrogen storage bottle with 6061-O aluminum alloy, the chemical composition and mass percentage see table 1.

[0064] Table 1 the alloy composition measured value (%).

[0065]

[0066] Example 1-3 finished plate O state mechanical properties and T62 state mechanical properties test results as shown in table 2.

[0067] Table 2 plate test results.

[0068]

[0069] From table 2 can be seen, the O state mechanical properties of example 1-3 plate sample is low, plastic, suitable for deep drawing forming, plate grain size is small, deep drawing surface without orange peel, after T62 heat treatment, the performance is higher, the flaw detection A level results show that the organization defects are few or defects are fine, meet the requirements of the standard, the sample deep drawing detection lug rate is less than 3%, can be applied to hydrogen energy automobile hydrogen storage bottle inner deep drawing.

[0070] The above is only the specific implementation of the application of example, the protection of the application does not constitute any limit. For those skilled in the art, the application can have various changes and variations. Any technical solution formed by using equivalent transformation or equivalent substitution, falls within the scope of the protection of the application.

Claims

1. A method for processing aluminum alloy sheets for hydrogen storage cylinders in hydrogen fuel cell vehicles, characterized in that, Includes the following steps: A. According to the predetermined mass percentage, the ingredients of each chemical element of the aluminum alloy are put into the melting furnace for melting, furnace refining, online degassing, and online filtration, and the aluminum liquid is cast into aluminum alloy ingots. The aluminum alloy is composed of the following chemical elements in percentage by mass. Composition: Si: 0.6%~0.7%, Fe: 0.3%~0.5%, Cu: 0.2%~0.4%, Mn≤0.15%, Mg: 0.9%~1.1%, Cr: 0.15%~0.25%, Zn≤0.10%, Ti: 0.015%~0.025%, individual impurities ≤0.03%, total impurities ≤0.10%, balance Al; The online filtration is a two-stage filtration process, using Al-5Ti-B for online refinement. B. After the cast aluminum alloy ingot cools, the head and tail are cut off, and then the solidified shell layer on the surface of the ingot is removed by milling. C. Place the sawn and milled ingots in a pusher furnace for homogenization treatment. The metal temperature is 560℃~570℃ and the temperature is held for 2~10 hours to eliminate grain segregation. After homogenization, the temperature is lowered to 420~500℃ and held for 2~20 hours. D. After heating, the product is directly taken out of the furnace and rolled into a plate. The final processing rate of the hot rolling is controlled to be greater than 10%, and the final rolling temperature of the hot rolling is 240~320℃. E. After rolling, the metal is annealed at a temperature of 360~420℃ for 1~5 hours. After the holding time, it is naturally cooled to room temperature. After being taken out of the furnace, it is transferred to a straightening machine for straightening and precision sawing to cut the plate to the required length to obtain aluminum alloy sheet. The aluminum alloy sheet is in the 6061-O temper and has a thickness of 14.0~25.0 mm.

2. The processing method of aluminum alloy sheet for hydrogen storage cylinders in hydrogen fuel cell vehicles according to claim 1, characterized in that, The mechanical strength of the aluminum alloy sheet in the O state is: tensile strength ≤150MPa, yield strength ≤80MPa, elongation ≥22%; after being hardened to the T62 state by quenching and artificial aging, the mechanical strength is: tensile strength ≥320MPa, yield strength ≥280MPa, elongation ≥10%.

3. The processing method of aluminum alloy sheet for hydrogen storage cylinders in hydrogen fuel cell vehicles according to claim 1, characterized in that, Step D: The hot rolling finishing temperature is 250~300℃.

4. The processing method of aluminum alloy sheet for hydrogen storage cylinders in hydrogen fuel cell vehicles according to claim 1, characterized in that, In step D, the penultimate and penultimate hot rolling passes need to be controlled by adjusting the pass processing rate and emulsion spraying to prevent the final rolling temperature from being unable to be controlled within the required range in the last pass.

5. A method for processing aluminum alloy sheet for hydrogen storage cylinders in hydrogen fuel cell vehicles according to claim 1, characterized in that, Step E uses a plate annealing furnace for complete recrystallization annealing.

6. The processing method of aluminum alloy sheet for hydrogen storage cylinders in hydrogen fuel cell vehicles according to claim 1, characterized in that, During step E annealing, the heating rate is greater than 100℃ / hour.

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