Method for improving thickness accuracy of 7-series aluminum alloy hot-rolled strip

Abstract

The application provides a method for improving thickness precision of 7-series aluminum alloy hot-rolled strip, which comprises the following steps: fixing the sampling time and sampling depth of the casting flow groove mushroom sample and fixing the surface turning depth of the flow groove mushroom; then, by analyzing the correlation between the thickness deviation value of the hot-rolled strip and the Cu and Zn element content in the casting flow groove mushroom sample, a thickness compensation formula of the 7-series aluminum alloy hot-rolled strip is established, and thickness compensation intervention is carried out before hot-rolling production. Thus, the thickness precision of the 7-series aluminum alloy hot-rolled strip is improved, and the product competitiveness is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum plate and strip processing, and relates to a method for improving thickness precision of 7-series aluminum alloy hot-rolled strip. BACKGROUND

[0002] 7-series aluminum alloy plates are widely used in the fields of die manufacturing and mechanical equipment due to high strength, high thermal conductivity and good processing performance. Since high-end die and equipment have high processing precision requirements and there is a demand for reducing the machining milling amount to reduce manufacturing cost, higher requirements are put forward for the initial thickness precision of 7-series aluminum alloy plates.

[0003] According to the European standard "BS EN 485-3-2003 Aluminum and aluminum alloys - Plates, strips and sheets - Part 3: Shape and dimensional tolerances for hot-rolled products", the thickness tolerance of 7-series aluminum alloy hot-rolled strip is ±0.5mm, the width of the strip is 1500-1800mm, and the thickness of the strip is 8-12mm. If the thickness tolerance is required to be ±0.1mm, it is difficult to meet the technical requirements on the market at present, and the main reasons are as follows: the size precision requirement is very strict, far exceeding the corresponding specification tolerance requirement of the European standard, and the control difficulty is high; and the thickness of the hot-rolled strip is measured online by an X-ray thickness gauge, and the error is large.

[0004] The X-ray thickness gauge indirectly obtains the thickness value of the measured material by measuring the transmittance of X-rays to the material. During measurement, the hot-rolled computer system sends the chemical composition of the rolled piece to the thickness gauge in advance, and the thickness gauge automatically calculates the measured thickness of the rolled piece according to the chemical composition and the X-ray penetration attenuation electrical signal. For non-7-series aluminum alloy ingots and rolled pieces, since there is no significant chemical composition macrosegregation, the spectral chemical composition at any depth of the flow channel mushroom can represent the chemical composition of the rolled piece, and the thickness measured by the thickness gauge can be very accurate. However, for 7-series aluminum alloy, on the one hand, the flow channel mushroom and the ingot have obvious chemical composition macrosegregation, and the spectral composition at a certain depth of the surface layer of the mushroom cannot represent the chemical composition of the rolled piece. The hot-rolled computer system sends the spectral composition at a certain depth of the mushroom to the X-ray thickness gauge as the composition of the rolled piece, and the thickness measured by the thickness gauge according to the composition that cannot represent the rolled piece is inaccurate. On the other hand, the content of the solute elements Zn and Cu in 7-series aluminum alloy is relatively high, and compared with other elements in 7-series aluminum alloy, the content measurement deviation of the Zn and Cu elements with relatively large atomic numbers has a more significant influence on the thickness fluctuation measured by the X-ray thickness gauge. The greater the content deviation of the Zn and Cu elements, the greater the thickness measurement error of the 7-series aluminum alloy strip. The above is the fundamental reason why the X-ray thickness measurement of the 7-series aluminum alloy strip is difficult to accurately measure and has a large thickness error. SUMMARY

[0005] The technical task of the present application is to solve the problem of inaccurate thickness measurement and large thickness tolerance of 7-series aluminum alloy hot-rolled strip, according to the preparation process of 7-series aluminum alloy hot-rolled strip: batching, smelting, refining, casting (mushroom-shaped composition of flow tank), heating, hot rolling (X-ray thickness gauge online measurement), finished product, packaging, the present application provides a method for improving the thickness precision of 7-series aluminum alloy hot-rolled strip, which intervenes in thickness compensation before hot rolling production, thereby improving the thickness precision of 7-series aluminum alloy hot-rolled strip and improving the product competitiveness.

[0006] The technical solution adopted by the present application to solve its technical problems is: a method for improving the thickness precision of 7-series aluminum alloy hot-rolled strip, comprising: fixing the sampling time and sampling depth of the casting flow tank mushroom sample, and fixing the surface turning depth of the flow tank mushroom sample; then, by analyzing the correlation between the thickness deviation value of the hot-rolled strip and the Cu and Zn element content in the casting flow tank mushroom sample, a thickness compensation formula for 7-series aluminum alloy hot-rolled strip is established, and thickness compensation intervention is performed before hot rolling production.

[0007] Further, the sampling time of the casting flow tank mushroom sample is fixed, that is, the flow tank mushroom sample is taken when the ingot is cast to a length of 1-1.2 m each time.

[0008] Further, the sampling depth is fixed, that is, the depth is 100-120 mm from the flow tank aluminum water liquid surface.

[0009] Further, the surface turning depth of the flow tank mushroom sample is fixed, that is, the turning depth is 8-10 mm from the surface.

[0010] Further, the thickness deviation value of the hot-rolled strip = measured thickness-target thickness, wherein the measured thickness is the actual measurement of the strip thickness after the hot-rolled strip is cooled offline using a micrometer, and the target thickness is the predetermined thickness of the hot-rolled strip.

[0011] Further, the thickness compensation formula for 7-series aluminum alloy hot-rolled strip is Y=A*Cu%+B*Zn%+C, wherein Y is the compensation value, that is, the thickness deviation value of the hot-rolled strip, Cu% and Zn% are the mass percentage content of Cu and Zn elements in the flow tank mushroom sample, and A, B and C are fitting coefficients.

[0012] Further, the target thickness of the 7-series aluminum alloy hot-rolled strip is 8-12.5 mm.

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] 1.The present application fixes the sampling time and depth of the casting runner mushroom sample, and fixes the sample surface turning depth, so that the runner mushroom sample spectrum composition has a certain corresponding correlation with the chemical composition of the rolled piece, that is: runner mushroom sample composition-rolled piece composition-X-ray penetration ability-thickness variation, the four form a correlation, have linear corresponding relationship, lay the foundation for linear fitting of subsequent data.

[0015] 2.The present application establishes a thickness compensation formula for 7-series aluminum alloy hot-rolled strip by analyzing the correlation between the thickness deviation (actual thickness and target thickness deviation) of the hot-rolled strip and the Cu and Zn element content in the casting runner mushroom sample, and intervenes in thickness compensation before hot rolling production, thereby improving the thickness precision of the 7-series aluminum alloy hot-rolled strip. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the present application will be 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 present application and do not limit the present application.

[0017] A method for improving the thickness precision of 7-series aluminum alloy hot-rolled strip, comprising: fixing the sampling time and depth of the casting runner mushroom sample, and fixing the surface turning depth of the runner mushroom sample; then, by analyzing the correlation between the thickness deviation value of the hot-rolled strip and the Cu and Zn element content in the casting runner mushroom sample, a thickness compensation formula for 7-series aluminum alloy hot-rolled strip is established, and thickness compensation intervention is performed before hot rolling production.

[0018] Wherein, the sampling time of the casting runner mushroom sample is fixed, that is, the runner mushroom sample is taken when the ingot is cast to 1-1.2m in length.

[0019] Wherein, the sampling depth is fixed, that is, the depth is 100-120mm from the surface of the runner.

[0020] Wherein, the surface turning depth of the runner mushroom sample is fixed, that is, the turning depth is 8-10mm from the surface.

[0021] Wherein, the thickness deviation value of the hot-rolled strip = measured thickness-target thickness, wherein the measured thickness is the actual measured thickness of the hot-rolled strip after cooling, and the target thickness is the predetermined thickness of the hot-rolled strip.

[0022] The thickness compensation formula of the 7-series aluminum alloy hot-rolled strip is Y=A*Cu%+B*Zn%+C, wherein Y is a compensation value, i.e., a thickness deviation value of the hot-rolled strip, Cu% and Zn% are mass percentage contents of Cu and Zn elements in the mushroom-like flow tank, and A, B and C are fitting coefficients. The specific operation is as follows: a large amount of data of thickness deviation values and Cu and Zn element contents of past 7-series aluminum alloy hot-rolled strips are sorted; secondly, the thickness deviation values and Cu and Zn element contents of the 7-series aluminum alloy hot-rolled strip are linearly fitted by using Minitab software, a fitting formula is obtained, and the fitting coefficient values of A, B and C are obtained.

[0023] The thickness compensation intervention before hot-rolling production means that the corresponding thickness deviation value of the 7-series aluminum alloy hot-rolled strip is added to the target thickness, so that the measured thickness is closer to the target thickness, and the specific operation is to directly correct the target thickness on the hot continuous rolling mill.

[0024] The preferred embodiments of the present application will be described in detail below by taking 7075 aluminum alloy hot-rolled strips with a width of 1500-1800 mm and a thickness of 8-12.5 mm as examples.

[0025] The preparation process of the 7-series aluminum alloy strip in each embodiment is as follows: batching, smelting, refining, casting (mushroom-like spectral composition of the flow tank), heating, hot-rolling (X-ray thickness gauge online measurement), finished product, and packaging.

[0026] Example 1

[0027] Five rolls of 7075 aluminum alloy hot-rolled strips with a thickness of about 12 mm and a width of 1500 mm are selected; a method for improving the thickness precision of the 7-series aluminum alloy hot-rolled strip includes the following methods:

[0028] A: when the length of the 7075 aluminum alloy ingot is cast to 1.2 m, the mushroom-like flow tank is taken at a position 100 mm away from the depth of the aluminum water liquid surface of the flow tank, and is naturally cooled. Then, the surface of the mushroom-like flow tank is turned to a depth of 10 mm, and spectral composition analysis is performed to obtain the chemical composition of the mushroom-like flow tank, which is sent to the thickness gauge by the hot-rolling computer system.

[0029] B: Before the hot rolling production of 7075 aluminum alloy, firstly, sort the data of thickness deviation value of a large number of produced 12mm thick 7075 aluminum alloy hot rolling strip and Cu, Zn element content in the casting flow groove mushroom; then analyze the correlation between the thickness deviation value (measured thickness-target thickness) of 12mm thick 7075 aluminum alloy hot rolling strip and the mass percentage content of Cu, Zn element in the casting flow groove mushroom, linear fitting is carried out through Minitab software, the thickness compensation formula of 12mm thick 7075 aluminum alloy strip is established: Y=1.542*Cu%+1.015*Zn%-8.01, the compensation value Y, i.e. the thickness deviation value of hot rolling strip is calculated according to the formula, and thickness compensation intervention is carried out before hot rolling production. After production, actual thickness measurement is carried out, which meets the requirements, and the finished product is packaged and stored.

[0030] Example 2

[0031] Select 5 rolls of 7075 aluminum alloy hot rolling strip with a thickness of about 10mm and a width of 1600mm; a method for improving the thickness precision of 7 series aluminum alloy hot rolling strip, comprising the following methods:

[0032] A: When the ingot length of 7075 aluminum alloy ingot casting is 1.2m, take the flow groove mushroom at a position 100mm away from the depth of the flow groove aluminum water surface, and naturally cool it. Then, turn the surface of the flow groove mushroom to a depth of 10mm, and perform spectral composition analysis to obtain the chemical composition of the flow groove mushroom, which will be sent to the thickness gauge by the hot rolling computer system.

[0033] B: Before the hot rolling production of 7075 aluminum alloy, firstly, sort the data of thickness deviation value of a large number of produced 10mm thick 7075 aluminum alloy hot rolling strip and Cu, Zn element content in the casting flow groove mushroom; then analyze the correlation between the thickness deviation value (measured thickness-target thickness) of 10mm thick 7075 aluminum alloy hot rolling strip and the mass percentage content of Cu, Zn element in the casting flow groove mushroom, linear fitting is carried out through Minitab software, the thickness compensation formula of 10mm thick 7075 aluminum alloy strip is established: Y=2.548*Cu%-0.903*Zn%+1.88, the compensation value Y, i.e. the thickness deviation value of hot rolling strip is calculated according to the formula, and thickness compensation intervention is carried out before hot rolling production. After production, actual thickness measurement is carried out, which meets the requirements, and the finished product is packaged and stored.

[0034] Example 3

[0035] Select 5 rolls of 7075 aluminum alloy hot rolling strip with a thickness of about 8mm and a width of 1600mm; a method for improving the thickness precision of 7 series aluminum alloy hot rolling strip, comprising the following methods:

[0036] A:7075 aluminum alloy ingot casting, when the ingot length casting to 1.2m, at a distance of 100mm from the runner aluminum water level position, take the runner mushroom, and then naturally cool. Then, turning the surface depth of 10mm of the runner mushroom, and then the spectral composition analysis, and the runner mushroom chemical composition will be sent to the thickness gauge through the hot rolling computer system.

[0037] B:7075 aluminum alloy hot rolling production, first arrange a large number of 8mm thick 7075 aluminum alloy hot rolling strip thickness deviation value and the data of Cu, Zn element content in the casting runner mushroom; Then analyze the 8mm thick 7075 aluminum alloy hot rolling strip thickness deviation value (actual thickness-target thickness) and the correlation of Cu, Zn element mass percentage in the casting runner mushroom, through the Minitab software for linear fitting, to establish the 8mm thick 7075 aluminum alloy strip thickness compensation formula: Y=1.203*Zn%-0.045*Cu%-6.92, according to the formula to calculate the compensation value Y, that is, the hot rolling strip thickness deviation value, and thickness compensation intervention before hot rolling production. After production, the actual thickness measurement is carried out, which meets the requirements and the finished product is packaged into the warehouse.

[0038] The runner mushroom taken in the above examples 1-3 is measured for chemical composition according to the corresponding standard, and the results are shown in Table 1.

[0039] Table 1: Chemical composition of 7075 aluminum alloy casting runner mushroom (%)

[0040]

[0041]

[0042] The hot rolling strip produced in the above examples 1-3 is sampled, and the actual thickness is measured according to the corresponding standard, and the results are shown in Table 2:

[0043] Table 2: Deviation value of actual thickness and target thickness of 7075 aluminum alloy hot rolling strip

[0044]

[0045] As can be seen from Table 2, the deviation of the actual thickness and the target thickness of the 7075 aluminum alloy strip produced in examples 1-3 is small, and the thickness precision control is good.

[0046] The above is only a specific implementation example of the present application, and does not constitute any limitation on the protection scope of the present application. For those skilled in the art, the present application can have various changes and variations. Any technical solution formed by equivalent transformation or equivalent substitution falls within the protection scope of the present application.

Claims

1. A method for improving the thickness accuracy of 7-series aluminum alloy hot-rolled strip, characterized in that, include: The sampling timing and depth of the casting flow channel mushroom sample are fixed, and the surface turning depth of the casting flow channel mushroom sample is also fixed. Then, by analyzing the correlation between the thickness deviation value of the hot-rolled strip and the Cu and Zn element content in the casting flow channel mushroom sample, a thickness compensation formula for 7-series aluminum alloy hot-rolled strip is established. The thickness deviation value of the hot-rolled strip in the compensation formula is the compensation value. The compensation value is added to the target thickness to directly correct the target thickness of the hot rolling mill, and thickness compensation intervention is performed before hot rolling production. The hot-rolled strip thickness deviation value = measured thickness - target thickness; wherein, the measured thickness is the actual thickness of the hot-rolled strip after cooling after it comes off the production line, and the target thickness is the predetermined hot-rolled strip thickness.

2. The method for improving the thickness accuracy of 7-series aluminum alloy hot-rolled strip according to claim 1, characterized in that, The sampling time for the mushroom-shaped casting trough is fixed, that is, when each ingot is cast to a length of 1-1.2m, the molten aluminum in the trough is taken to make the mushroom-shaped casting trough.

3. The method for improving the thickness accuracy of 7-series aluminum alloy hot-rolled strip according to claim 1, characterized in that, The sampling depth is fixed at 100-120 mm from the surface of the molten aluminum in the flow channel.

4. The method for improving the thickness accuracy of 7-series aluminum alloy hot-rolled strip according to claim 1, characterized in that, The turning depth of the mushroom-shaped surface of the casting groove is fixed, that is, the turning depth is 8-10mm from the surface.

5. The method for improving the thickness accuracy of 7-series aluminum alloy hot-rolled strip according to claim 1, characterized in that, The thickness compensation formula for the 7-series aluminum alloy hot-rolled strip is: Y=A*Cu%+B*Zn%+C, where Y is the compensation value, i.e. the thickness deviation value of the hot-rolled strip, Cu% and Zn% are the mass percentage contents of Cu and Zn elements in the mushroom-shaped casting flow channel, and A, B, and C are fitting coefficients.

6. The method for improving the thickness accuracy of 7-series aluminum alloy hot-rolled strip according to claim 1, characterized in that, The target thickness is 8-12.5 mm.

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