Aluminum alloy plate for truck dump bucket and processing method thereof

Abstract

The application provides an aluminum alloy sheet for truck tipping and a processing method thereof. The aluminum alloy sheet has the following mass percentage of components: Si 0.05-0.10%, Fe 0.15-0.20%, Cu≤0.05%, Mn 0.4-0.5%, Mg 4.3-4.5%, Cr 0.05-0.08%, Zn≤0.05%, Ti 0.02-0.04%, and the balance of Al and inevitable impurities. The main processing method of the aluminum alloy sheet comprises the following steps: batching, smelting, refining, casting, sawing, milling, heating, hot rolling, cold rolling, product annealing, cross cutting and packaging. The application is improved from the aspects of component design and processing method, and the internal structure, mechanical properties and bending properties of the sheet are ensured to be good.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy processing and manufacturing, and particularly relates to an aluminum alloy plate for a truck dump box and a processing method thereof. Background Art

[0002] Aluminum alloy can be used as the material for truck dump boxes. It has the advantage of being lightweight due to its good corrosion resistance and high specific strength. From the perspective of sheet metal processing, there is a need for a cheap and high-quality 5083H32 aluminum alloy plate with good bending performance. It is best to be able to bend at 90° without cracking, and the bending R angle is 0.5t (t is the plate thickness). In this way, the sheet metal workpiece has small springback and a sharp and angular shape that is more beautiful. The current 5083 aluminum alloy plate on the market is difficult to meet this requirement for the following reasons: (1) The 6.35mm 5083H32 aluminum alloy plate has the following material characteristics: hard, thick, and brittle. When bent at 90° and 0.5t, the outer side is very prone to cracking due to the very small bending R angle. (2) The supply is cheap, so the process cost should be low. According to the traditional cold rolling long process scheme (burden → melting → refining → casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → intermediate annealing → cold rolling → cleaning → finished product annealing → cross-cutting → packaging), the process path is long and the cost is high. In addition, there are slight orange peel-like micro-cracks on the outside of the 90°0.5t bend, and the product barely passes the test. If the latest popular hot rolling temperature control shipment short process scheme (burden → melting → refining → casting → sawing → milling → heating → hot rolling low temperature off-line → cross-cutting → packaging) is followed, although the process path is short and the cost is low, the transverse bending performance is poor, and the 90°0.5t bend cracks are serious, which does not meet the requirements of sheet metal.

[0003] Patent CN104439982A discloses a production process for 5083H32 aluminum alloy plates. This process is the latest popular low-cost solution for direct shipment from hot rolling. Although it can meet the national standard bending requirements, the national standard bending R angle requirement of 2.5t is relatively loose, far exceeding the required 0.5t. Moreover, the products of this hot-rolled direct temperature-controlled production line have large differences in transverse and longitudinal bending performance due to the uneven internal grain structure and a certain fibrous structure (when the bending axis is perpendicular to the rolling direction, the bending is better. When the bending axis is parallel to the rolling direction, the bending is poor and prone to cracking). Obviously, the low-cost process mentioned in the patent cannot meet the requirements.

[0004] In view of this, it is necessary to develop a 5083H32 aluminum alloy sheet and a processing method thereof to meet the requirements of low cost and high bendability. Summary of the Invention

[0005] The technical task of the present invention is to address the deficiencies of the above existing technologies and to provide an aluminum alloy plate for a truck dump box and a processing method thereof in order to solve the problems of poor bending performance and high process costs of existing aluminum alloy plates.

[0006] The technical solution adopted by the present invention to solve the technical problem is: an aluminum alloy plate for a truck dump box, the mass percentage of the components of which are as follows: Si 0.05% to 0.10%, Fe 0.15% to 0.20%, Cu≤0.05%, Mn 0.4% to 0.5%, Mg4.3% to 4.5%, Cr 0.05% to 0.08%, Zn≤0.05%, Ti 0.02% to 0.04%, and the balance being Al and unavoidable impurities.

[0007] Furthermore, the mechanical properties of the aluminum alloy plate are as follows: tensile strength 340-355 MPa, yield strength 245-263 MPa, elongation 15.5-17.6%; in a 90° 0.5t bending test, the outer corners are smooth and crack-free.

[0008] Furthermore, the aluminum alloy plate has an alloy state of 5083-H32 and a thickness of 5.0 to 6.5 mm.

[0009] The main processing methods of the above-mentioned aluminum alloy plates include: batching → smelting → refining → casting → sawing → milling → heating → hot rolling → cold rolling → finished product annealing → cross-cutting → packaging.

[0010] Furthermore, the processing method comprises the following main steps:

[0011] A. Place the ingredients of each chemical element of the aluminum alloy into a melting furnace according to mass percentage for melting, furnace refining, online degassing, online filtration, and cast the aluminum liquid into aluminum alloy ingots;

[0012] B. After the aluminum alloy ingot is cooled, the head and tail are cut off, and then the shell layer on the surface of the ingot is milled off with a milling machine;

[0013] C. Place the milled ingot in a pusher heating furnace, and heat the metal to a temperature of 470°C to 500°C for 3 to 5 hours;

[0014] D. After heating, the hot rolled strip is taken out of the furnace and rolled using a 1+4 hot rolling mill. The thickness of the hot rolled strip is controlled (reserving a cold working rate of 25-28%). The coiling temperature of the hot rolled strip is 310-340°C. The hot rolled coil is then cooled naturally and self-annealed using the high temperature residual heat of the coil.

[0015] E. After the hot rolled coil is naturally cooled to room temperature, it is cold rolled to the finished thickness in a single-stand cold rolling mill, and then directly transferred to a box annealing furnace, eliminating the cleaning step and directly annealing the finished product;

[0016] F. After the coil enters the annealing furnace, when the metal temperature rises to 230-240℃, keep it warm for 4-6 hours to complete the tempering, then force cool it to below 100℃ and take it out of the furnace to cool naturally.

[0017] Furthermore, step A follows the following process: the ingredients are sequentially put into the smelting furnace for smelting, and stirring is started after the materials in the furnace are melted. After obtaining qualified chemical composition, they are refined with Ar-Cl2 mixed gas to adsorb hydrogen and fine slag impurities in the aluminum liquid, and then float and gather to the surface of the aluminum liquid for separation, thereby purifying the melt.

[0018] Furthermore, during the casting process, a two-stage ceramic plate filter is used to reduce slag inclusions in the melt and ensure melt purity. Al-5Ti-B wire is used for online grain refinement to ensure a fine ingot grain size.

[0019] Furthermore, in step E, the cold working rate is 25-28%.

[0020] Furthermore, in step F, after entering the annealing furnace, negative pressure and purge functions are turned on to assist in oil removal.

[0021] Furthermore, in steps C and F, the heating rate is controlled to be ≤30°C / h.

[0022] Furthermore, in step F, when the furnace gas reaches 170-180°C, the temperature is suspended and kept warm, and nitrogen protection is started in the furnace to control the oxygen volume content to ≤0.5%. After the nitrogen filling is completed, the furnace gas continues to heat up to 235-245°C and keep warm. When the metal reaches 230-240°C, it is kept warm for 4-6 hours to complete the tempering.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention strictly controls chemical elements that are detrimental to bending forming: Si is 0.05% to 0.10%, and Fe is 0.15% to 0.20%. The Fe content is ensured to be greater than Si. This ensures that during ingot solidification, the favorable α-AlFeSi phase (skeletal and non-fractured) is primarily formed, while the harmful β-AlFeSi phase (needle-shaped and easily fractured) is avoided. Mn is 0.4% to 0.5%, and Cr is 0.05% to 0.08%. This prevents the formation of large amounts of coarse intermetallic compounds such as MnAl6 and CrAl7, which would disrupt the continuity of the aluminum alloy matrix and impair bending performance. The primary strengthening element, Mg, is controlled at 4.3% to 4.5%, ensuring a balance between strength and plasticity. The Ti element is controlled at 0.02% to 0.04%, which can ensure fine grains and fine primary second phases in the cast state, which is beneficial to improving the plasticity of the alloy; Cu and Zn are general impurity elements and have an impact on the corrosion resistance of the alloy. They are controlled in the range of Cu≤0.05% and Zn≤0.05%.

[0025] The present invention uses a double-stage ceramic plate filter during the casting process, thereby reducing slag inclusion in the melt, ensuring the purity of the melt, thereby preventing the slag inclusion from destroying the continuity of the aluminum alloy matrix, and facilitating the improvement of the bending performance.

[0026] The application adopts a pushing heating furnace, controls the temperature rising speed to be less than or equal to 30 ℃ / h, ensures that the low melting point phase Mg2Al3 can be dissolved completely at below 440 ℃ in advance (the eutectic point of Mg2Al3 phase is 450 ℃), avoids overburning phenomenon, and thus damages the bending performance. The metal is then kept at 470 ℃-500 ℃ for 3-5 hours, can promote the CrAl7 phase in the ingot to uniformly disperse and precipitate, ensures that the recrystallized grains of the subsequent hot-rolled coiled material are small and uniform, and thus improves the bending performance.

[0027] The application adopts a method of controlling the coiling temperature of the hot-rolled strip, and using the high-temperature waste heat of the hot-rolled coil for self-annealing, which omits the subsequent cold-rolling intermediate annealing process, shortens the process flow, reduces the energy consumption and production processing cost, and has good economic benefits.

[0028] The application adopts a proper reserved cold working rate and a clever annealing oil removal process, realizes the cleanliness of the surface of the coiled material without oil spots and oil mark defects under the premise of ensuring good internal structure, mechanical properties and bending performance of the plate. The method omits the cleaning process of the finished coiled material, shortens the process flow, reduces the production processing cost, and has good economic benefits. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0030] The application provides an aluminum alloy plate for truck tipping, which has the following mass percentage of components: Si 0.05%-0.10%, Fe 0.15%-0.20%, Cu≤0.05%, Mn 0.4%-0.5%, Mg 4.3%-4.5%, Cr 0.05%-0.08%, Zn≤0.05%, Ti 0.02%-0.04%, and the balance of Al and inevitable impurities.

[0031] The main processing method of the aluminum alloy plate includes: batching, melting, refining, casting, sawing, milling, heating, hot rolling, cold rolling, finished product annealing, cross cutting and packaging. The processing method includes the following main steps:

[0032] A. The aluminum alloy's chemical elements are placed into a smelting furnace according to mass percentages for smelting. Once the materials are melted, stirring begins. Once the desired chemical composition is achieved, the material is refined with an Ar-Cl2 gas mixture to absorb hydrogen and fine slag impurities from the molten aluminum. These impurities then float to the surface for separation, purifying the melt. The molten aluminum is then degassed and filtered online before being cast into aluminum alloy ingots. During the casting process, a two-stage ceramic plate filter is used to reduce slag inclusions and ensure melt purity. Al-5Ti-B wire is used for online grain refinement to ensure a fine grain size in the ingot.

[0033] B. After the aluminum alloy ingot is cooled, the head and tail are cut off, and then the shell layer on the surface of the ingot is milled off with a milling machine;

[0034] C. Place the milled ingot in a pusher heating furnace, control the heating rate to ≤30℃ / h, and keep the metal temperature at 470℃~500℃ for 3~5 hours;

[0035] D. After heating, the hot rolled strip is taken out of the furnace and rolled using a 1+4 hot rolling mill. The thickness of the hot rolled strip is controlled (reserving a cold working rate of 25-28%). The coiling temperature of the hot rolled strip is 310-340°C. The hot rolled coil is then cooled naturally and self-annealed using the high temperature residual heat of the coil.

[0036] E. After the hot rolled coil is naturally cooled to room temperature, it is cold rolled in a single-stand cold rolling mill to a finished thickness of 5.0-6.5 mm, with a cold working rate of 25-28%. It is then directly transferred to a box annealing furnace, eliminating the cleaning step and directly annealing the finished product;

[0037] F. After the coil enters the annealing furnace, the negative pressure and purge functions are activated to assist in oil removal. When the negative pressure fan is running, the negative pressure in the furnace can reach 630mm H2O. The furnace gas heating rate is controlled to ≤30℃ / h. When the furnace gas reaches 170-180℃, the heating is suspended and the temperature is maintained. At this time, the rolling oil adsorbed on the coil surface has largely evaporated and no oil marks have formed. The furnace begins to be filled with nitrogen for protection, and the oxygen volume content is controlled to ≤0.5% to prevent the small amount of residual oil on the coil surface from oxidative polymerization at high temperatures later, forming oil spots. After the nitrogen filling is completed, the furnace gas temperature is continued to rise to 235-245℃ and maintained. This temperature is just slightly above the initial distillation point of 230℃ for the rolling oil and far below the final distillation point of 280℃. This accelerates the volatilization of oil and gas and prevents the formation of oil spots. When the metal reaches 230-240℃, it is maintained at this temperature for 4-6 hours to complete the tempering. At this time, the rolling oil is completely evaporated and the aluminum coil surface is free of oil spots and oil marks. Then the furnace's side cooling fan is started, and the coil is forced to cool below 100°C in the furnace and then taken out of the furnace to cool naturally. The coil is then transferred to the cross-cutting process and cut into fixed length plates.

[0038] The preferred embodiment of the present invention will be described in detail below using a 5083-H32 aluminum alloy plate with a thickness of 6.35 mm for a truck dump box. Specific processing parameters are detailed in each embodiment.

[0039] Example 1

[0040] An aluminum alloy plate for a truck dump box and a processing method thereof, comprising the following steps:

[0041] A. Place the ingredients of each chemical element of 5083 aluminum alloy into a melting furnace according to the predetermined mass percentage, perform melting, furnace refining, online degassing, and online filtration, and cast the aluminum liquid with qualified composition (see Table 1) into aluminum alloy ingots;

[0042] B. After the aluminum alloy ingot is cooled, the head and tail are cut off, and then the shell layer on the surface of the ingot is milled off with a milling machine;

[0043] C. Place the sawn and milled ingot in a pusher heating furnace, use automatic heating and intelligent temperature control (heating rate ≤ 30℃ / h) to prevent overheating of Mg2Al3. After the metal temperature reaches 475℃, keep it warm for 3 hours.

[0044] D. After heating, the hot rolled strip is taken out of the furnace and rolled to a thickness of 8.82 mm (reserving a 28% cold working rate). The coiling temperature of the hot rolled strip is controlled at 315 ± 5 ° C. After completion, the hot rolled coil is placed in an intelligent high-bay warehouse and self-annealed using the high temperature waste heat of the coil;

[0045] E. The hot rolled coils are naturally cooled to room temperature before being shipped out of the warehouse. They are then cold rolled in one pass to a finished thickness of 6.35mm, with a cold working rate of 28%, and then directly transferred to a box annealing furnace.

[0046] F. After the coil enters the furnace, negative pressure and purge are applied, and the heating rate is controlled at ≤30°C / h. When the furnace gas reaches 170°C, the heating is paused and maintained. The furnace is filled with nitrogen for protection (oxygen content ≤0.5% by volume), and then the furnace gas temperature is continued to rise to 235°C. When the metal reaches 230°C, it is held at this temperature for 4 hours, completing the quenching and tempering. Subsequently, the side cooling fan is activated to force-cool the coil to below 100°C before it is removed from the furnace. After the coil cools naturally to room temperature, it is cut to length on a cross-cutting machine, sampled and tested, and directly packaged and stored if qualified.

[0047] Example 2

[0048] An aluminum alloy plate for a truck dump box and a processing method thereof, comprising the following steps:

[0049] A. Place the ingredients of each chemical element of 5083 aluminum alloy into a melting furnace according to the predetermined mass percentage, perform melting, furnace refining, online degassing, and online filtration, and cast the aluminum liquid with qualified composition (see Table 1) into aluminum alloy ingots;

[0050] B, after the cooling of the aluminum alloy ingot, the head and tail are cut off, and the condensed shell layer on the surface of the ingot is milled off by a milling machine;

[0051] C, the sawed and milled ingot is placed in a push-type heating furnace, automatic heating is adopted, intelligent temperature control (heating speed ≤ 30 ℃ / h) is adopted to prevent overburning of Mg2Al3, and after the metal temperature reaches 495 ℃, the temperature is kept for 5 hours;

[0052] D, after the heating is completed, the furnace is opened for rolling, and hot rolling is performed to a thickness of 8.47 mm (25% of the cold working rate is reserved), the coiling temperature of the hot rolled strip is controlled at 335±5 ℃, and after completion, the hot rolling coil is placed in an intelligent high-bay warehouse, and self-annealing is performed by utilizing the high-temperature residual heat of the coil;

[0053] E, after the hot rolling coil is naturally cooled to room temperature, it is taken out of the warehouse, cold rolling is performed in one pass to a finished product thickness of 6.35 mm, the cold working rate is 25%, and then it is directly transferred to a box-type annealing furnace;

[0054] F, after the coil enters the furnace, negative pressure and blowing are started, the temperature rising speed is controlled at ≤30 ℃ / h, when the furnace gas reaches 180 ℃, the temperature rising is paused and the temperature is kept, the furnace is filled with nitrogen protection (the oxygen volume content is ≤0.5%), then the furnace gas continues to rise to 245 ℃, when the metal reaches 240 ℃, the temperature is kept for 6 hours, and the quenching and tempering are completed. Subsequently, the side cooling fan is started, and the coil is rapidly cooled to below 100 ℃ and then taken out of the furnace. After the coil is naturally cooled to room temperature, it is cut to size on a cross-cutting machine, sampling and detection are performed, and after passing the detection, it is directly packaged and stored in the warehouse.

[0055] Example 3

[0056] An aluminum alloy plate for a truck tipping bucket and a processing method thereof, comprising the following steps:

[0057] A, according to the predetermined mass percentage, the ingredients of each chemical element of 5083 aluminum alloy are put into a smelting furnace for smelting, furnace refining, online degassing, and online filtering, and the aluminum liquid with qualified composition (see Table 1) is cast into an aluminum alloy ingot;

[0058] B, after the cooling of the aluminum alloy ingot, the head and tail are cut off, and the condensed shell layer on the surface of the ingot is milled off by a milling machine;

[0059] C, the sawed and milled ingot is placed in a push-type heating furnace, automatic heating is adopted, intelligent temperature control (heating speed ≤ 30 ℃ / h) is adopted to prevent overburning of Mg2Al3, and after the metal temperature reaches 480 ℃, the temperature is kept for 4 hours;

[0060] D, after the heating is completed, the furnace is opened for rolling, and hot rolling is performed to a thickness of 8.74 mm (27% of the cold working rate is reserved), the coiling temperature of the hot rolled strip is controlled at 325±5 ℃, and after completion, the hot rolling coil is placed in an intelligent high-bay warehouse, and self-annealing is performed by utilizing the high-temperature residual heat of the coil;

[0061] E. The hot rolled coils are naturally cooled to room temperature before being shipped out, and then cold rolled in one pass to a finished thickness of 6.35mm, with a cold working rate of 27%, and then directly transferred to a box annealing furnace;

[0062] F. After the coil enters the furnace, negative pressure and purge are applied, and the heating rate is controlled at ≤30°C / h. When the furnace gas reaches 175°C, the heating is suspended and maintained. The furnace is filled with nitrogen for protection (oxygen content ≤0.5% by volume). The furnace gas temperature is then continued to rise to 240°C. When the metal reaches 235°C, it is held at this temperature for 5 hours, completing the quenching and tempering. The side cooling fan is then activated to force-cool the coil to below 100°C before it is removed from the furnace. After the coil cools naturally to room temperature, it is cut to length on a cross-cutting machine, sampled and tested, and directly packaged and stored if qualified.

[0063] Examples 1 to 3: A 5083 aluminum alloy strip for a truck dump box, the chemical composition and mass percentage of which are shown in Table 1.

[0064] Table 1 Measured values ​​of alloy composition (%)

[0065]

[0066] The plates obtained by processing in the above Examples 1 to 3 were sampled and tested for surface quality, mechanical properties, bending, etc. according to the corresponding standards. The results are shown in Table 2.

[0067] Table 2 Strip test results.

[0068]

[0069] As can be seen in Table 2, the surface quality, mechanical properties, and bending performance of the plate samples in Examples 1-3 were excellent, meeting customer requirements. They are suitable for truck dump bodies and exhibit excellent post-forming results. Furthermore, according to common bending knowledge, under the same conditions, thicker sheets tend to crack more easily. Therefore, Examples 1-3 were tested using 6.35 mm thick plates. If thicker plates can pass the test successfully, thinner plates will likely do even better.

[0070] The above are merely examples of specific implementations of the present invention and do not constitute any limitation on the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications and variations of the present invention are possible. Any technical solution formed by equivalent transformations or equivalent substitutions falls within the scope of protection of the present invention.

Claims

1. A method for processing aluminum alloy plates for truck dump buckets, characterized in that: The main steps include: A. Place the ingredients of each chemical element of the aluminum alloy into a melting furnace according to mass percentage for melting, furnace refining, online degassing, online filtration, and cast the aluminum liquid into aluminum alloy ingots; B. After the aluminum alloy ingot is cooled, the head and tail are cut off, and then the shell layer on the surface of the ingot is milled off with a milling machine; C. Place the milled ingot in a pusher heating furnace, and heat the metal to a temperature of 470°C to 500°C for 3 to 5 hours; control the heating rate to ≤30°C / h; D. After heating, the hot rolled strip is taken out of the furnace and rolled. The coiling temperature of the hot rolled strip is 310-340℃, and then the hot rolled coil is naturally cooled and self-annealed by using the high temperature residual heat of the coil; E. After the hot rolled coil is naturally cooled to room temperature, it is cold rolled to the finished thickness in a single-stand cold rolling mill, and then directly transferred to a box annealing furnace, eliminating the cleaning step and directly annealing the finished product; F. After the coil enters the annealing furnace, when the furnace gas reaches 170-180℃, stop heating and keep warm, start nitrogen filling in the furnace for protection, and control the oxygen volume content ≤0.5%. After the nitrogen filling is completed, continue to heat the furnace to 235-245℃ and keep warm. When the metal reaches 230-240℃, keep warm for 4-6 hours to complete the tempering. When the metal temperature rises to 230-240℃, keep warm for 4-6 hours to complete the tempering, and then force cool to below 100℃. Take it out of the furnace and cool naturally to obtain the aluminum alloy sheet for truck tipping body; control the heating rate to ≤30℃ / h; The aluminum alloy plate for the truck dump box has the following composition percentages by mass: Si 0.05% to 0.10%, Fe 0.15% to 0.20%, Cu ≤ 0.05%, Mn 0.4% to 0.5%, Mg 4.3% to 4.5%, Cr 0.05% to 0.08%, Zn ≤ 0.05%, Ti 0.02% to 0.04%, with the remainder being Al and unavoidable impurities; its mechanical properties are as follows: tensile strength 340 to 355 MPa, yield strength 245 to 263 MPa, and elongation 15.5 to 17.6%; in a 90° 0.5t bending test, the outer corners are smooth and crack-free; its alloy state is 5083-H32, and the thickness is 5.0 to 6.5 mm.

2. The method for processing an aluminum alloy plate for a truck dump box according to claim 1, characterized in that: Step E: cold working rate 25-28%.

3. The method for processing an aluminum alloy plate for a truck dump box according to claim 1, characterized in that: Step F: After entering the annealing furnace, turn on the negative pressure and purge functions to assist in oil removal.

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