Aluminum alloy stretching plate flatness control method

Abstract

The invention belongs to an aluminum alloy stretching plate flatness control technology, and particularly discloses an aluminum alloy stretching plate flatness control method. The problem that the flatness of a stretching plate is not qualified is solved. The technological process comprises the steps of hot rolling, edge cutting, pre-stretching, solid solution quenching, stretching, aging and packaging inspection, the finish rolling temperature of hot rolling ranges from 260 DEG C to 360 DEG C, and the cooling mode is fan blowing cooling; the edge cutting amount is 15 to 50 mm; the stretch rate of pre-stretching is 0.5%-1.0%; in the solid solution quenching treatment, the flow ratio of quenching water to water is 0.65-0.85, the transfer speed is 100-500mm / s, the temperature of quenching water is 20-37 DEG C, and the hot rolled plate is secondarily cooled after being discharged from the furnace; the stretching rate of the stretching treatment is 1.5%-3.0%, and the stretching retention time is within 30 min. The method is beneficial for controlling the final product plate shape and improving the economic benefits and social benefits of enterprises.

Description

Technical Field

[0001] The invention belongs to the flatness control technology of an aluminum alloy stretched plate, and in particular relates to a method for controlling the transverse and longitudinal flatness of an aluminum alloy stretched plate. Background Art

[0002] Aluminum alloy stretched plates have strict requirements on the flatness of the final product. If the flatness is not up to standard, it will be scrapped. Therefore, plate shape optimization is an indispensable point for stretched plates. Using a roller hearth quenching furnace to produce quenched plates is a good choice. The roller hearth quenching furnace can control the plate shape by controlling the temperature gradient during the quenching of the plate, thereby producing a better plate shape than the salt bath furnace. However, the roller hearth quenching furnace has stricter requirements on factors such as the plate shape of the blank before quenching, the original internal stress, and the quenching water flow rate.

[0003] There are three traditional ways to adjust the plate shape: pressure straightening, roller straightening and stretch straightening. These three methods are ways to correct the plate shape after quenching, and do not take into account the influence of the blank plate shape and original internal stress before quenching, nor the influence of the cooling rate on the plate shape during quenching.

[0004] If the plate shape and original internal stress before quenching are too large, the flatness of the plate out of the oven will definitely be too poor. Pressure straightening, roller straightening and stretch straightening can only adjust the flatness to a certain extent. The flatness of the plate with poor original flatness will not be very good after straightening. The same is true for the cooling rate. The faster the cooling rate, the greater the internal stress, and the more difficult it is to control the plate shape. At the same time, the quality of the plate shape after heat treatment directly affects the size of the residual stress of the final product, and the size of the residual stress directly affects the customer's use.

[0005] At present, the shape of hot-rolled plates cannot be controlled within extremely high requirements due to the influence of plate temperature, cooling rate, width, thickness, etc., and there is no clear regulation on the cooling rate during quenching. Therefore, a complete set of production processes must be adopted to ensure the plate shape before solid solution, the degree of internal stress and the plate shape after heat treatment to ensure that all material indicators meet the downstream customers' requirements for the product. Summary of the invention

[0006] The purpose of the present invention is to provide a method for controlling the flatness of an aluminum alloy stretched plate, so as to effectively solve the problem of unqualified flatness of the aluminum alloy stretched plate.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A method for controlling the flatness of an aluminum alloy stretched plate comprises the following steps: S1, hot rolling: an ingot is obtained by semi-continuous casting or continuous casting, the ingot is hot-rolled to obtain a hot-rolled plate, the final rolling temperature of the hot rolling treatment is 260-360°C, and the plate is cooled by a fan blowing cooling method at room temperature.

[0009] S2. Edge trimming: The hot rolled plate is edge trimmed with an amount of 15-50 mm.

[0010] S3. Pre-stretching: The hot-rolled plate after trimming is pre-stretched, and the stretching rate is 0.5%-1.0%.

[0011] S4. Solution quenching: The pre-stretched hot-rolled plate is subjected to solution quenching treatment, the upper and lower water flow ratio of quenching is 0.65-0.85, the transfer speed is 100-500mm / s, and the quenching water temperature is 20-37℃.

[0012] When the hot rolled plate is taken out of the furnace, the temperature is ensured to drop below 100°C. After taking out of the furnace, the hot rolled plate is immediately returned to the quenching zone for secondary cooling to below 35°C.

[0013] S5. Stretching: The hot-rolled plate after solution quenching is stretched, with a stretching rate of 1.5%-3.0% and a stretching residence time of less than 30 minutes.

[0014] During stretching, a lifting trolley is used to lift the material, and the height parameters are: when the thickness of the hot-rolled plate is 6-15mm, the lifting height of the lifting trolley is 18-20mm; when the thickness of the hot-rolled plate is 15-30mm, the lifting height of the lifting trolley is 15-18mm; when the thickness of the hot-rolled plate is 30-50mm, the lifting height of the lifting trolley is 10-15mm; when the thickness of the hot-rolled plate is 50-80mm, the lifting height of the lifting trolley is 5-12mm; when the thickness of the hot-rolled plate is ≥80mm, the lifting height of the lifting trolley is ≤5mm.

[0015] S6. Aging: The hot-rolled plate after stretching is subjected to aging treatment, using natural aging treatment or artificial aging treatment.

[0016] S7. Carry out packaging inspection on the hot-rolled plates after aging treatment.

[0017] Furthermore, in step S4, the angle of the inlet water jet is adjusted so that the spraying points of the upper water jet and the lower water jet correspond to each other, and the quenching water sprayed by the upper water jet and the lower water jet overlap on a line of the hot-rolled plate to ensure uniform deformation of the upper and lower surfaces of the hot-rolled plate.

[0018] Furthermore, in step S4, the solution quenching treatment is performed using a roller hearth quenching furnace.

[0019] Further, in step S6, artificial aging treatment is performed using an aging furnace.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are:

[0021] The present invention ensures the shape and internal stress of the blank before quenching by controlling the hot rolling final rolling temperature, trimming, pre-stretching and other processes, and controls the shape of the final product by controlling the water flow, transfer speed, water temperature and secondary cooling of the solid solution quenching process, effectively solving the problem of unqualified flatness of the stretched plate, which is beneficial to controlling the shape of the final product and improving the economic and social benefits of the enterprise. DETAILED DESCRIPTION

[0022] A method for controlling the flatness of an aluminum alloy stretched plate comprises the following steps: (1) hot rolling: an ingot is prepared by semi-continuous casting or continuous casting, and the ingot is hot-rolled to obtain a hot-rolled plate. The final rolling temperature of the hot rolling treatment is 260-360°C, and the temperature should not be too high to prevent the hot-rolled plate from collapsing under high temperature when it is cooled, which may affect the plate shape.

[0023] The cooling is accelerated by using a fan to cool at room temperature to prevent the hot-rolled plate from collapsing due to staying at high temperature for too long and to control the flatness after hot rolling. However, accelerated cooling will increase internal stress, and subsequent trimming and pre-stretching treatment are required to eliminate the transverse and longitudinal internal stress of the hot-rolled plate. The hot-rolled plate can be cooled in the last few rolling processes to reduce the temperature before final rolling and prevent the temperature from being too high after final rolling.

[0024] (2) Trimming: Trimming the hot-rolled plate with a trimming amount of 15-50 mm. The hot-rolled plate is sawn longitudinally to release the internal stress after hot rolling, especially the transverse internal stress.

[0025] (3) Pre-stretching: The hot-rolled plate after trimming is pre-stretched with a stretching rate of 0.5%-1.0%. Through pre-stretching and straightening, the internal stress is further released, especially the longitudinal internal stress, to ensure the plate shape and internal stress before quenching, prevent deformation caused by stress release during the solution process, and thus ensure the plate shape before leaving the furnace.

[0026] (4) Solution quenching: The pre-stretched hot-rolled plate is solution quenched in a roller-bottom quenching furnace.

[0027] I. The upper and lower water flow ratio of quenching is 0.65-0.85 to ensure the cooling uniformity of the upper and lower surfaces of the hot-rolled plate. After the cooling water below is sprayed out, it will fall quickly from the surface of the hot-rolled plate due to the action of gravity.

[0028] Here we need to pay attention to: ① The height and angle of the inlet water jet. For roller-bottom quenching furnaces, the inlet water jet is the first part to contact the surface of the plate during quenching, but the water flow is relatively small, and both the upper and lower water jets have only one row of nozzles, and their main function is to prevent the water in the quenching zone from splashing outside the quenching zone. The quenching water sprayed by the upper and lower water jets needs to overlap on a line of the plate to ensure uniform deformation of the upper and lower surfaces of the plate.

[0029] The water jet heights of plates with different thicknesses are different when they are taken out of the furnace, because it is necessary to prevent the plates from being stuck in the water jet position after deformation and unable to be taken out of the furnace. Therefore, the thicker the plates, the higher the corresponding water jet heights. These heights are set by the equipment manufacturer during installation. The height of the water jet generally does not need to be adjusted manually, so the adjustment of the angle of the inlet water jet is particularly important. It is necessary to ensure that the quenching water sprayed by the upper and lower water jets is sprayed on one point of the plate, and to ensure that the upper and lower surfaces of the plate are cooled more evenly when they initially contact the quenching water, without deformation (this is especially important for plates with a thickness of less than 40mm), and to ensure the plate shape before quenching.

[0030] ②Try to adjust the water flow to make the plate flat or slightly concave out of the oven, because it is more convenient, faster and more accurate to measure the flatness of a slightly concave plate; it is more troublesome to measure a convex plate, and it is more difficult to measure the truly accurate flatness data. Then, when stretching, use the material trolley to push up to adjust the flatness after stretching.

[0031] II. The transfer speed is 100-500mm / s. A fast transfer speed can reduce the temperature gradient before and after the plate. If the speed is too slow, it will cause longitudinal waves in the plate. The transfer speed should be increased while ensuring the hardenability and related performance requirements of the plate.

[0032] III. The quenching water temperature is 20-37℃. A high quenching water temperature can reduce the temperature gradient between the surface and the core of the plate, which is conducive to obtaining a plate with good plate shape and low residual stress. Therefore, the quenching water temperature should be increased as much as possible while ensuring performance. The quenching water temperature should be kept within a certain temperature range to ensure the stability of quenching. In addition, the capacity of the water tank should be large enough to avoid the quenching water temperature rising too quickly.

[0033] IV. Secondary cooling. Try to increase the transfer speed and ensure that the temperature of the hot-rolled plate drops below 100°C when it comes out of the furnace; after coming out of the furnace, if the temperature of the hot-rolled plate is too high, return the hot-rolled plate to the quenching zone for secondary cooling immediately, and continue to cool it down to below 35°C, which not only ensures the performance but also the temperature of the hot-rolled plate, and prevents the aging hardening effect of the hot-rolled plate due to excessive temperature.

[0034] (5) Stretching: The hot-rolled plate after solution quenching is stretched with a stretching rate of 1.5%-3.0% to eliminate internal stress and ensure the final finished plate shape. The stretching residence time is within 30 minutes. The plate is stretched in a short time during the natural aging process. At this time, the plate performance is lower, which can better control the plate shape and eliminate residual stress.

[0035] Reasonable setting of the lifting height of the lifting trolley during stretching can flatten the slightly concave or slightly concave plate before stretching, and appropriate reduction of the lifting height can also flatten the convex plate after stretching. Because the stretching process is a stress release process, there is some cold deformation in this process. During stretching, only the head and tail are clamped to hold the plate, and the middle position is suspended. Therefore, reasonable use of the lifting trolley to lift the plate can change the flatness of the plate after stretching to a certain extent.

[0036] During stretching, a lifting trolley is used to lift the material, and the height parameters are: when the thickness of the hot-rolled plate is 6-15mm, the lifting height of the lifting trolley is 18-20mm; when the thickness of the hot-rolled plate is 15-30mm, the lifting height of the lifting trolley is 15-18mm; when the thickness of the hot-rolled plate is 30-50mm, the lifting height of the lifting trolley is 10-15mm; when the thickness of the hot-rolled plate is 50-80mm, the lifting height of the lifting trolley is 5-12mm; when the thickness of the hot-rolled plate is ≥80mm, the lifting height of the lifting trolley is ≤5mm.

[0037] (6) Aging: The stretched hot-rolled sheet is subjected to aging treatment, and natural aging treatment or artificial aging treatment is performed according to actual conditions to improve the performance of the hot-rolled sheet and further eliminate residual stress. In some embodiments, the artificial aging treatment uses an aging furnace.

[0038] (7) Carry out packaging inspection on hot-rolled plates after aging treatment.

[0039] The present invention is further described in detail below with reference to specific embodiments and comparative examples.

[0040] Example 1: The plate is a 7050 alloy with a size of 35mm (thickness) * 1200mm (width) * 13000mm (length), and the flatness control method of the aluminum alloy stretched plate of the present invention is used for flatness control, wherein the final rolling temperature is 300°C, fan cooling is adopted, the trimming amount is 30mm, the elongation rate of the pre-stretching treatment is 0.7%, and secondary cooling is carried out at a transfer speed of 500mm / s during the solution quenching treatment. The flatness after stretching treatment is -0.3mm / full width.

[0041] Comparative Example 1: The plate is a 7050 alloy of 35mm (thickness) * 1200mm (width) * 13000mm (length). The difference from Example 1 is that the final rolling temperature is 370°C, natural cooling, no trimming, no pre-stretching, the transfer speed during solution quenching treatment is 200mm / s and no secondary cooling is performed, and the flatness after stretching treatment is -2.4mm / full width.

[0042] Example 2: The plate is a 7050 alloy with a size of 80mm (thickness) * 1800mm (width) * 90000mm (length), and the flatness control method of the aluminum alloy stretched plate of the present invention is used for flatness control, wherein the final rolling temperature is 290°C, fan cooling is adopted, the trimming amount is 30mm, the elongation rate of the pre-stretching treatment is 0.7%, and secondary cooling is carried out at a transfer speed of 200mm / s during the solution quenching treatment. The flatness after stretching treatment is -0.2mm / full width.

[0043] Comparative Example 2: The plate is 7050 alloy with a size of 80 mm (thickness) * 1800 mm (width) * 90000 mm (length). The difference from Example 2 is that the final rolling temperature is 370°C, natural cooling, no trimming, no pre-stretching, the transfer speed during solution quenching treatment is 130 mm / s and no secondary cooling is performed, and the flatness after stretching treatment is +1.6 mm / full width.

[0044] In summary, the plate flatness result of Example 1 is better than the plate flatness result of Comparative Example 1, and the plate flatness result of Example 2 is better than the plate flatness result of Comparative Example 2, indicating that the flatness value of the aluminum alloy stretched plate manufactured by the aluminum alloy stretched plate flatness control method of the present invention is significantly better than the flatness value of the aluminum alloy stretched plate manufactured by the traditional method. The present invention effectively solves the problem of unqualified flatness of the stretched plate, is beneficial to controlling the plate shape of the final product, and improving the economic and social benefits of the enterprise.

[0045] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for controlling the flatness of an aluminum alloy stretched plate, characterized in that: The following steps are involved: S1. Hot rolling: an ingot is obtained by semi-continuous casting or continuous casting, and the ingot is hot-rolled to obtain a hot-rolled plate. The final rolling temperature of the hot rolling is 260-360°C, and the plate is cooled by a fan at room temperature; S2. Edge trimming: Edge trimming of hot rolled plate, the amount of edge trimming is 15-50mm; S3, pre-stretching: pre-stretching the hot-rolled plate after trimming, with a stretching rate of 0.5%-1.0%; S4, solution quenching: the pre-stretched hot-rolled plate is subjected to solution quenching treatment, the upper and lower water flow ratio of quenching is 0.65-0.85, the transfer speed is 100-500mm / s, and the quenching water temperature is 20-37°C; When the hot rolled plate is taken out of the furnace, the temperature is ensured to be lower than 100°C. After it is taken out of the furnace, the hot rolled plate is immediately returned to the quenching zone for secondary cooling to below 35°C. S5. Stretching: The hot-rolled plate after solution quenching is stretched, the stretching rate is 1.5%-3.0%, and the stretching residence time is within 30 minutes; During stretching, a material lifting trolley is used to lift the material, and the height parameters are: when the thickness of the hot-rolled plate is 6-15mm, the lifting height of the material lifting trolley is 18-20mm; when the thickness of the hot-rolled plate is 15-30mm, the lifting height of the material lifting trolley is 15-18mm; when the thickness of the hot-rolled plate is 30-50mm, the lifting height of the material lifting trolley is 10-15mm; when the thickness of the hot-rolled plate is 50-80mm, the lifting height of the material lifting trolley is 5-12mm; when the thickness of the hot-rolled plate is ≥80mm, the lifting height of the material lifting trolley is ≤5mm; S6. Aging: Aging treatment is performed on the hot-rolled plate after stretching, using natural aging treatment or artificial aging treatment; S7. Carry out packaging inspection on the hot-rolled plates after aging treatment.

2. The method for controlling the flatness of an aluminum alloy stretched plate according to claim 1, characterized in that: In step S4, the angle of the inlet water jet is adjusted so that the spraying points of the upper water jet and the lower water jet correspond to each other, and the quenching water sprayed by the upper water jet and the lower water jet overlap on a line of the hot-rolled plate to ensure uniform deformation of the upper and lower surfaces of the hot-rolled plate.

3. The method for controlling the flatness of an aluminum alloy stretched plate according to claim 2, characterized in that: In step S4, the solution quenching treatment is performed using a roller hearth quenching furnace.

4. The method for controlling the flatness of an aluminum alloy stretched plate according to claim 3, characterized in that: In step S6, artificial aging treatment is performed using an aging furnace.