CN106903166B - A Method for Warpage Prediction and Optimization in Asynchronous Rolling of Aluminum Alloy Plates - Google Patents

Abstract

The invention belongs to the field of metal material processing, and relates to a warpage prediction and optimization method in the process of asynchronous rolling of aluminum alloy plates, which can significantly reduce or completely eliminate the warpage of asynchronous rolling plates, and does not require special modification of existing rolling mills , just adjust the rolling parameters (such as plate thickness, rolling pass reduction, different speed ratio, etc.) to control the degree of plate warpage in the asynchronous rolling process and give the warpage. The advantages of the present invention are: based on the simulation of the asynchronous rolling process, combined with the actual rolling experiment to analyze the asynchronous rolling non-warping process of the aluminum alloy plate, the warping direction of the asynchronous rolling plate under the actual working condition can be known, and the Judging the running status of asynchronous rolling plate, providing a visual solution for actual process adjustment; pre-obtaining the rolling process parameters (such as pass reduction) to make asynchronous rolling plate zero warpage based on simulation simulation, which can significantly improve the quality of the plate shape and avoid Transform rolling equipment or install forced straightening device.

Description

A Method for Warpage Prediction and Optimization in Asynchronous Rolling of Aluminum Alloy Plates

technical field

The invention discloses a warpage prediction and optimization method in the process of asynchronous rolling of aluminum alloy plates, which can significantly reduce or completely eliminate the warpage of asynchronous rolling plates, and belongs to the field of metal material processing.

Background technique

High-performance aluminum alloy (such as Al-Zn-Mg-Cu series) medium-thick plate is widely used in the manufacture of fuselage frames and bulkheads due to its excellent specific strength, corrosion resistance, toughness and fatigue resistance, and has become an important important aeronautical structural materials. The traditional hot rolling process is currently the main processing method for preparing such high-strength and tough aluminum alloy plate, but there is a common problem of uneven deformation along the thickness direction of the plate in the process of producing plate by this process, which eventually leads to microstructure in the thickness direction of the plate. Inhomogeneous mechanical properties seriously affect and limit the life and wide application of such alloy sheets.

As an advanced strong plastic deformation process, asynchronous rolling can be realized by modifying the synchronous rolling mill. Rolling at the same speed and asynchronously (the upper and lower rolls have different diameters and the same speed). During the asynchronous rolling process, due to the asymmetry of the deformation of the upper and lower rolls on the rolled piece, severe additional shear deformation occurs inside the rolled piece, thereby improving the uniformity of the deformation of the rolled material along the thickness direction, and contributing to the improvement of the comprehensive performance of the plate. improve. Based on the advantages of asynchronous rolling technology in improving the uniformity and performance of metal and alloy materials, this technology is widely used in the rolling research and production of aluminum/magnesium and other metals and alloys, and has achieved good results. Invention patents (CN101524707A, CN105603341A) announced a metal rolling process that uses asynchronous rolling to obtain fine grains, significantly improved formability and strength; invention patents (such as CN201210590806.1, CN200410021496.7, CN200510046810.1) use asynchronous rolling The technology improves the performance of grain-oriented silicon steel; the invention patent (CN201010524366.0) uses asynchronous rolling technology to realize the nanometerization of the material surface. However, due to the asymmetry of the deformation of the metal or alloy in contact with the upper and lower rolls during the rolling process, the asynchronously rolled sheet will appear upturned or bent down, making it difficult for the sheet to bite continuously, reducing the rolling efficiency, and causing serious warpage It may even cause plate sticking to rolls, damage to rolling mill equipment, and increased production costs. At present, the application research of asynchronous rolling technology is still focused on thin plate and strip, because the coiling tension applied by the coiler significantly suppresses the warpage of thin plate and strip, so the related warpage problem has not received much attention. However, when the medium-thick plate is processed in asynchronous rolling, there is no coiler to provide tension on both sides of the roll. Therefore, how to improve or optimize the shape of the asynchronously rolled medium-thick plate and reduce/eliminate the warping problem caused by asynchronous rolling appear particularly prominent and important. To solve this problem, it is generally achieved by transforming the rolling mill equipment, such as installing a horizontal hydraulic roll bending system on the rolling mill or installing forced straightening equipment on the rolling production line. The investment is huge and it is difficult to replace it in a short period of time. Aiming at the problem of warping of medium and heavy plates in asynchronous rolling, the invention patent CN104624664A proposes to control the warpage phenomenon of the rough rolling head of the 400mm cast slab by adjusting the height of the rolling line and the biting speed of the upper/lower work rolls. The invention patent (CN03114584 .1. CN200520079602.7) discloses a method of adjusting the height of the guide plate of the rolling mill and utilizing a designed lead-in angle variable device to solve the warpage problem in the asynchronous rolling process. However, the rolling table system of the rolling mill in the actual production line is long and fixed, and the method provided by the above-mentioned invention patent has difficulties in realizing continuous rolling of asynchronous rolling of plates.

The patent of the invention controls the shape of the asynchronous rolling plate by directly adjusting the rolling parameters on-line to solve the warping problem of the asynchronous rolling plate, and at the same time, it can ensure the deformation in the thickness direction and the uniformity of the structure, and avoid large-scale operations on the rolling mill. Technical and cost issues brought about by the transformation.

Contents of the invention

The present invention aims to provide a method for quickly predicting the warpage of asynchronously rolled aluminum alloy plates, and at the same time provide a method for obviously improving or solving the warping problems of such plates. The present invention does not require any special modification of the existing rolling mill, and only needs to adjust the rolling parameters (such as plate thickness, rolling pass reduction, different speed ratio, etc.) to control the warping degree of the plate during the asynchronous rolling process and give A solution to the warping problem.

The technical solution of the present invention is: a method for forecasting and optimizing warpage of asynchronous rolling of metal or alloy plates, comprising the following steps:

Step 1: Use the simulation analysis software to establish the two-dimensional plane strain model of the asynchronously rolled alloy plate and the geometric model of the rolling process; define the model material properties (including specific heat capacity, thermal conductivity, elastic modulus, thermal expansion coefficient, Poisson's ratio, density etc. (simulation software will use automatic interpolation to obtain the function value under the corresponding conditions)); grid division (due to the regular shape of the plate, the automatic division function of the software can be used, and the grid is a four-node quadrilateral unit); set the hot rolling process Boundary conditions such as heat exchange (including the efficiency of plastic work into heat, friction work into heat), friction, etc.; set rolling parameters and perform simulation calculations; input different asynchronous rolling conditions (such as rolling temperature , different speed ratio, reduction and initial thickness of the plate), and output the shape of the asynchronously rolled plate.

Step 2: Calculate the warping curvature ρ of the asynchronously rolled plate under different simulated working conditions, and obtain the relationship between the initial thickness of the rolled plate, the reduction in each pass, the different speed ratio of the upper and lower rolls, and the warping curvature of the rolled plate at a certain rolling temperature , the relationship is determined by the two-dimensional curves in the X-Y space established by different working condition parameter values and corresponding curvature values.

Step 3: When the warping curvature of asynchronous rolling plate is close to zero, the critical values of rolling plate thickness, pass reduction, and different speed ratio are calculated, and the relationship of the critical working condition without warping of asynchronous rolling plate is established. The mentioned in this step The critical operating condition value can be determined according to the following steps:

(1) According to the two-dimensional curves of different working condition parameter values and curvature values established in step 2, find the intersection point between the curve and the X axis (that is, the axis where the rolling parameters are located), and the parameter value corresponding to the intersection point can be determined as the critical parameter reference point.

(2) Take the reference point as the object, fluctuate 5% up and down, carry out simulation verification, and finally use the value of the curvature closest to zero within the ±5% range of the reference point as the critical parameter value.

Step 4: According to the warpage-free critical condition of asynchronous rolling established in step 3, use the experimental rolling mill to conduct tests, correct the simulation results, and finally establish the warpage-free critical rolling parameters matched with the rolling mill.

In the present invention, the two-dimensional model of the asynchronous rolling system set up by the simulation analysis software described in step 1 is specifically:

(1) The two-dimensional plane strain model is mainly based on the elastic-plastic constitutive relationship of metal or alloy materials, that is, there is a functional relationship between deformation resistance (true stress) and strain (true strain), deformation rate and deformation temperature:

Among them, the elastic stage still follows Hooke's law, the plastic deformation stage needs to meet the Von-Mises yield criterion, and the plastic relationship of aluminum alloy can be used Zener-Hollomon relationship to represent, where σ is the true stress (MPa), ε is the true strain, is the deformation rate (s ^-1 ), T is the deformation temperature (K), ΔH is the deformation activation energy, and R is the gas constant. The correlation constants of the above relationship can be obtained through the true stress-strain curves at different temperatures, and the relationship is fixed when the conditions such as temperature and deformation rate are determined. It can be obtained through thermomechanical simulation experiments, and in the actual rolling simulation calculation process In , call the relevant data of metal or alloy materials under different deformation conditions, such as stress and strain values.

(2) Set up the geometric model of asynchronous rolling roll and rolling plate, wherein the realization mode of asynchronous rolling among the present invention is that the upper and lower rolls have the same roll diameter and different roll speeds; the rolls are simplified to ideal rigid-plastic model, and the rolling plate material is an elastic-plastic model ; The determination of the convective heat transfer coefficients between the rolling plate and the roll, between the rolling plate and the air helps to accurately describe the influence of temperature during the rolling process.

(3) During the rolling process, the friction difference between the rolling plate and the upper and lower rolls was ignored, and Coulomb's friction law was used to deduce the actual rolling friction coefficient as 0.35 according to the experiment. This value corresponds to the friction coefficient between the aluminum alloy and the roll, and the friction coefficient between other metal or alloy plates and the roll can be obtained from the literature or determined by a combination of simulation and experiment.

(4) The working conditions during the rolling simulation simulation process are as follows: the diameter of the _upper and _lower rolls is the same as Φ=400mm; s, 1.2m/s, 1.3m/s, the corresponding speed ratio DSR is 1.1, 1.2, 1.3 respectively; the initial thickness of the plate H<50mm. During the rolling simulation process, the temperature of the rolling plate is set as the actual rolling temperature, such as 400°C for the 7050 aluminum alloy in the patent of the present invention.

The calculation method of warping curvature (ρ) in step 2 of the present invention calculates according to the parameter marked in Fig. 1 and following formula:

In Figure 1, r is the bending radius of the plate after warping, L is the distance between two points selected on the bending arc, and c is the top height of the selected bending arc.

Step 4 Select a 40mm thick 7050 aluminum alloy plate, and perform an air furnace heat preservation treatment on the rolled plate at 400°C-3 hours before rolling to make the temperature uniform in the thickness of the rolled plate; during the rolling process, the rolls are not lubricated, and simulated Calculate and predict the pass reduction of the non-warped plate shape for experimental rolling.

Compared with the traditional straightening scheme, the process provided by the present invention has the following advantages:

1. This method is based on the simulation of the asynchronous rolling process, and combined with the actual rolling experiment to analyze the warpage-free process of asynchronous rolling of aluminum alloy plates. The running status of asynchronous rolling plate provides a visual solution for actual process adjustment;

2. This method can directly adjust the asynchronous rolling process parameters. For example, according to the actual rolling plate thickness and the speed ratio adopted, the rolling process parameters (such as pass reduction quantity), which can significantly improve the quality of the plate shape, and avoid the transformation of rolling equipment or the installation of forced straightening devices.

Description of drawings

Fig. 1 is the calculation model and parameters of warping curvature of asynchronous rolling plate of the present invention.

Fig. 2 is a simulation model diagram of asynchronous rolling process rolls and rolled plates in the present invention.

Fig. 3 simulates the variation trend of plate warpage with the increase of pass reduction during the process of asynchronous rolling of H=30mm plate (different speed ratio DSR=1.2).

Fig. 4 In the present invention, through simulation calculation, the critical pass reduction for plates with different thicknesses under different speed ratio conditions to obtain a non-warping plate shape.

Fig. 5 is a schematic diagram of the comparison between the critical reduction of the warpage-free asynchronous rolling process obtained by simulation and the rolling experimental value.

Figure 6 shows the relationship between the maximum initial rolling plate thickness and the critical thickness reduction when the different speed ratio is 1.2 and the roll radius is 600 mm (the solid line in the figure is the linear fitting and the dotted line is the nonlinear fitting) (R ² Correlation coefficients for linear or nonlinear fits).

Detailed ways

The present invention will be further described below with examples in conjunction with the accompanying drawings.

As shown in Figures 1-2, the present invention provides a warpage prediction and optimization method for asynchronous rolling of aluminum alloy plates. The method specifically includes the following steps:

Step 1. Utilize simulation calculation software to establish a two-dimensional plane strain model of asynchronously rolled metal or alloy plate, which is defined as rigid-plastic upper roll and lower roll with the same diameter, leading roll and defined as elasto-plastic rolling piece. The rotational angular velocity of the upper roll and the lower roll can be independently adjusted to realize the asynchronous rolling function, define the material properties of the model, divide the grid, and set the heat exchange and friction boundary conditions during the asynchronous rolling process;

Step 2. Input the different working conditions of asynchronous rolling, including the speed ratio of the upper and lower rolls, the initial thickness of different rolled plates, and the different reductions of each pass, into the two-dimensional plane strain model built in step 1 and perform simulation calculations, and output the asynchronous rolled plate According to the plate shape, the warpage curvature ρ of the simulated asynchronous rolling plate under different working conditions is calculated, and the relationship between the initial plate thickness, pass reduction, different speed ratio of the upper and lower rolls and the warpage curvature is established, and the obtained Relationship lines;

Step 3. According to the relationship curve between the curvature and rolling parameters established in step 2, find the plate thickness, pass reduction and speed ratio corresponding to the intersection point of the curve and the X-axis, and this value is the The critical working conditions of the asynchronous rolling plate without warpage corresponding to the parameters;

Step 4 calculates the obtained asynchronous rolling critical condition condition according to step 3, carries out the asynchronous rolling experiment of metal or alloy plate on the rolling mill, according to the experimental result, the simulation results of step 1-step 3 are processed according to the following conditions:

Condition 1: When the profile of the asynchronously rolled plate obtained by rolling is straight or the vertical height of the upward warping of the plate head is not greater than the opening of the next rolling mill, the degree of warping of the asynchronously rolled plate can meet the requirements of continuous asynchronous rolling Requirements, the simulation results may not be corrected at this time;

Condition 2: When the vertical height of the upward warping of the head of the asynchronous rolling plate obtained by rolling is greater than the opening of the next rolling mill or the downward bending causes the rolling plate to collide with the conveying roll of the rolling mill, the simulation results should be compared according to the specific results. The critical rolling condition without warpage shall be corrected accordingly;

Step 5. Using the corrected asynchronous rolling critical working condition close to the actual situation obtained in step 4 can realize warp-free asynchronous rolling of metal or alloy plates, thereby solving the problems in the asynchronous rolling process of such alloy plates. warping problem.

The defined model material properties in the step 1 include specific heat capacity, thermal conductivity, elastic modulus, thermal expansion coefficient, Poisson's ratio and density.

The calculation formula of the warping curvature ρ in the step 2 is, and the formula is as follows:

In the formula, L is the distance between two selected points on the curved arc, and c is the top height of the selected curved arc.

In the step 2, the establishment of the relationship between the initial plate thickness, the pass reduction, the speed ratio of the upper and lower rolls, and the warpage curvature is obtained by simulating the rolling conditions according to the simulation calculation model established in the step 1. Specific curvature value, and establish a curve with the curvature value as the Y axis and the rolling parameters as the X axis.

In step 3, the pass reduction range of the obtained critical working condition is 5-55%, and the speed ratio is 1.0-1.7.

The correction method in the step 4 is:

(1) When the rolling test is carried out under the critical working conditions without warpage obtained by simulation, if the rolling plate at the exit of the rolling mill is bent to the side of the upper roll, that is, the rolling plate is warped, it means that under the rolling conditions , the actual critical pass reduction required to reach the warpage-free state is greater than the simulated value, which can be solved in the following two ways:

1.1 Continue to increase the pass reduction and the rolling mill can still meet the natural bite conditions of the plate, without changing the initial plate thickness and speed ratio, repeat steps 1-3 by increasing the pass reduction until To obtain a flat rolled plate, the increase in the reduction of each repeated pass is no more than 5%.

1.2 Continue to increase the pass reduction and the rolling mill cannot meet the natural bite conditions of the plate, the method of increasing the pass reduction will hinder the continuity of rolling. At this time, the initial plate thickness and pass reduction can be kept unchanged Under the conditions, by reducing the different speed ratio and repeating step 1-step 3, until obtaining a straight rolling plate, the reduction of the different speed ratio is 5-10% every repetition.

(2) When rolling under the non-warp critical working condition obtained by simulation, if the rolling plate at the exit of the rolling mill is bent to the side of the lower roll, that is, the rolling plate is buckled, it means that under the rolling condition , the actual critical pass reduction required to reach the warpage-free state is less than the simulated value. At this time, step 1-step 3 can be repeated by reducing the pass reduction until the flat rolled plate is obtained. The reduction rate of reduction in one pass shall not exceed 5%.

In step 5, the actual rolling process needs to be based on the rolling natural bite condition, that is, α<arctanμ, where α is the rolling bite angle, μ is the friction coefficient, and the relationship between the initial plate thickness and the critical reduction To determine the rollable initial plate thickness that matches the actual rolling capacity, only when the initial plate thickness is less than or equal to the rollable initial plate thickness can a rolled plate without warpage be obtained.

Example 1:

In order to improve or solve the warping problem of asynchronously rolled aluminum alloy medium-thick plates, firstly, a two-dimensional plane strain model of asynchronous rolling is established by using finite element simulation analysis software (as shown in Figure 2), which specifically includes the following steps:

Step 1. Establishment of geometric and material models: the upper and lower rolls in the model are simplified to an ideal rigid-plastic model, the diameter of the upper and lower rolls is 400mm, the speed of the upper roll is 1m/s, and the speed of the lower roll is 1.2m/s, corresponding to different speeds Ratio is 1.2; Define the material performance parameter of rolling plate in the simulation process, as the specific heat of material under different temperature conditions, thermal conductivity, Poisson's ratio etc. , etc. Finite element simulation of aluminum alloy thick plate quenching residual stress and its influence on processing deformation. Acta Aeronautica Sinica, 2004, 4:429-432.]); the stress-strain curve of the plate was obtained by thermal compression experiments. The grid size of the rolled plate is 2mm×2mm, the total number of grids varies according to the initial thickness of the simulated plate (for example, when the initial thickness is 30mm, the thickness direction of the plate is divided into 15 layers), and the length of the simulated plate is 200mm.

Step 2. Establishment of the contact heat transfer model between the roll and the rolling plate: According to the empirical formula, the radiation heat transfer coefficient between the rolling plate and the air is 6.8w/m ² °C, and the contact heat transfer coefficient between the rolling plate and the rolling plate is 55Kw/m ² ·K: During the rolling process, the conversion rate of deformation work and friction between the roll and the rolling plate into heat is set at 95%.

Step 3. Friction model: Coulomb's friction law (τ=μ p) is adopted in the rolling process, that is, the shear friction stress (τ) is proportional to the normal pressure (p) on the rolling plate, and the friction coefficient (μ) is according to the literature 0.35 .

The material performance parameters and thermal parameters of each part of the two-dimensional finite element model are assigned respectively.

By adjusting the size of the roll gap to change the pass reduction, the simulation calculation is carried out,

Output the plate shape effect diagram of the asynchronously rolled plate, and calculate the warpage curvature value ρ of the plate at this time according to the method shown in Figure 1. Figure 3 shows the change of plate shape with the increase of rolling pass reduction after the 7050 aluminum alloy plate with an initial thickness of 30mm is asynchronously rolled with a speed ratio of 1.2. When the reduction is 30%, the asynchronous rolling plate is bent to the side of the slow roll, and when the reduction is increased to 40%, the shape of the asynchronous rolling plate is basically straight, and the warpage curvature calculated at this time is almost 0. Therefore, the pass reduction at this time is the critical pass reduction under the asynchronous rolling condition to make the plate without warping; continue to increase the reduction to 45%, and the warping direction of the rolled plate will change, that is, the bending direction will be fast. roll side.

Adjust the speed of the lower roll to 1.1m/s, and the corresponding speed ratio is 1.1, repeat steps (1)-(6), and calculate the warping curvature of the asynchronous rolling plate.

Adjust the speed of the lower roll to 1.3m/s, and the corresponding speed ratio is 1.3, repeat steps (1)-(6), and calculate the warping curvature of the asynchronous rolling plate.

Under the condition that the speed ratio is 1.1-1.3, the initial thickness of the rolled plate is selected to be 10-40 mm, and steps (1)-(6) are repeated to calculate the warping curvature of the asynchronous rolled plate.

Calculate the warpage curvature of the plate under each asynchronous rolling process condition according to the asynchronous rolling plate shape obtained by the simulation in the above steps, and find the critical pass reduction of the non-warp asynchronous rolling process corresponding to each working condition Based on these data, the change relationship diagram between different initial plate thicknesses, different speed ratios and the critical pass reduction of asynchronous rolling (corresponding to no warpage) was established, as shown in Figure 4. It can be seen from the figure that as the speed ratio increases, the critical reduction corresponding to a certain initial thickness of 7050 aluminum alloy plate increases significantly; at the same time, the larger the initial thickness, the greater the corresponding critical reduction.

Example 2:

A 7050 aluminum alloy plate with an initial thickness of 40 mm was used to carry out experimental rolling using the non-warping asynchronous rolling process simulated in the present invention, and the experimental rolling parameters were the same as those set in the simulation. After obtaining the experimental rolled plate, the warpage curvature of the rolled plate was measured, and the measured values are shown in Figure 5. Compared with the simulation results, the measured critical reduction is basically consistent with the simulation results, indicating that the above method can accurately and reliably predict the warpage of 7050 aluminum alloy plate under different asynchronous rolling conditions.

Table 1 further shows the simulated calculation results and experimental results of the plate thickness and critical pass reduction of the 40mm thick 7050 aluminum alloy plate under the condition of different speed ratio of 1.2 after different passes of asynchronous rolling. very good. It can be seen from the table that in the multi-pass asynchronous rolling process, after adopting the critical pass reduction for each pass, there are corresponding critical pass reductions for plates of different thicknesses to ensure that the asynchronous rolled plate is flat and straight .

Example 3:

The above examples prove that asynchronous rolling without warpage can be achieved by using the critical pass reduction method. However, due to the limitation of the rolling capacity of the rolling mill in actual production, not all initial thicknesses can pass the above critical pass reduction. method to achieve warpage optimization. Therefore, it is necessary to obtain the maximum rollable initial plate thickness that can achieve warpage optimization by using the critical pass reduction method based on the common rolling mill equipment conditions in the existing industrial production. According to the rolling bite condition, the relationship between the bite angle (α) and the friction coefficient (μ) needs to be satisfied: α<arctanμ; and there is a relationship between the bite angle and the roll radius R and the pass reduction (Δh). Relation: cos α=1-(Δh/2R). According to these two relationships, it can be known that there is a relationship between the maximum reduction Δh _max and the maximum bite angle α _max of a certain rolling equipment: Δh _max =2R(1-cosα _max ). Using the friction coefficient of 0.35 given above and the working roll radius of 600 mm, it can be known that the maximum reduction Δh _max = 67.4 mm can be realized by the rolling mill.

According to the above simulation calculation process of critical reduction and warpage curvature, it can be calculated that there is a relationship between the initial plate thickness and critical reduction when the speed ratio is 1.2 and the roll radius is 600mm, as shown in Figure 6. When the initial plate with a thickness of H obtains a warpage-free critical pass reduction less than Δh _max /H, the warpage-free asynchronous rolling can be achieved by increasing the pass reduction (critical pass reduction) , otherwise it cannot. It can be seen from the figure that the maximum initial plate thickness corresponding to the above-mentioned rolling conditions to achieve no warpage is between 130-150mm. Further simulations for 130mm, 140mm and 150mm thick plates show that the 130mm thick plate can adopt the critical path Asynchronous rolling without warping can be achieved by sub-reduction, while 140mm and 150mm thick plates will appear upturned, which cannot guarantee a flat shape. Of course, by reducing the differential speed ratio, the critical pass reduction can also be used to achieve warpage-free asynchronous rolling. The initial thickness of the asynchronous rolling can also be increased.

It can be seen that using the finite element simulation method provided by the present invention can well predict the degree of warping and the corresponding shape of aluminum alloy medium and thick plates under different asynchronous rolling conditions. At the same time, the present invention provides a method for effectively solving the warping problem of asynchronous rolling aluminum alloy medium and thick plates, that is, adjusting the reduction amount of asynchronous rolling passes to a critical value, so that a flat plate shape can be obtained, which greatly contributes to the Continuation of asynchronous rolling process for alloy medium and thick plates.

The warpage prediction and optimization solution method of asynchronous rolling alloy plate provided by the present invention provides reliable and effective technical reference and production guidance for the practical application of asynchronous rolling technology

Apparently, the above examples are only examples to illustrate the practicability of the method, rather than limiting the implementation and rolled materials. For those of ordinary skill in the art, other changes or changes in different forms can also be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation methods here, and the obvious changes or changes derived therefrom are still in the

Within the protection scope of the present invention.

Table 1 Comparison of finite element simulation results and rolling measurement results

Claims (5)

1. A method for warpage prediction and optimization of aluminum alloy plate asynchronous rolling, characterized in that, the method specifically comprises the following steps: Step 1. Use simulation calculation software to establish a two-dimensional plane strain model of asynchronously rolled metal or alloy plates, which is defined as rigid-plastic upper and lower rolls with the same diameter, leading rolls and elastic-plastic rolling pieces. The rotational angular velocity of the upper roll and the lower roll can be independently adjusted to realize the asynchronous rolling function, define the material properties of the model, divide the grid, and set the heat exchange and friction boundary conditions during the asynchronous rolling process; Step 2. Input the different working conditions of asynchronous rolling, including the speed ratio of the upper and lower rolls, the initial thickness of different rolled plates, and the different reductions of each pass, into the two-dimensional plane strain model built in step 1 and perform simulation calculations, and output the asynchronous rolled plate type, and calculate the warpage curvature r of the simulated asynchronous rolling plate under different working conditions according to the plate shape, and establish the relationship between the initial plate thickness, pass reduction, different speed ratio of the upper and lower rolls and the warpage curvature, and obtain Relationship lines; The calculation formula of warping curvature is as follows: In the formula, L is the distance between two points selected on the curved arc, and c is the top height of the selected curved arc; Step 3. According to the relationship curve between curvature and rolling parameters established in step 2, find the plate thickness, pass reduction and speed ratio corresponding to the intersection point of the curve and the X-axis, and this value is the The critical working conditions of the asynchronous rolling plate without warpage corresponding to the parameters; Step 4. Calculate the obtained asynchronous rolling critical working conditions according to step 3, carry out the asynchronous rolling experiment of metal or alloy plate on the rolling mill, according to the experimental results, the simulation results of step 1-step 3 are processed according to the following conditions: Condition 1: When the profile of the asynchronously rolled plate obtained by rolling is straight or the vertical height of the upward warping of the plate head is not greater than the opening of the next rolling mill, the degree of warping of the asynchronously rolled plate can meet the requirements of continuous asynchronous rolling Requirements, the simulation results may not be corrected at this time; Condition 2: When the vertical height of the upward warping of the head of the asynchronous rolling plate obtained by rolling is greater than the opening of the next rolling mill or the downward bending causes the rolling plate to collide with the conveying roll of the rolling mill, the simulation results should be compared according to the specific results. The critical rolling condition without warpage shall be corrected accordingly; The correction method in the step 4 is: (1) When the rolling test is carried out using the critical working condition without warpage obtained by simulation, if the rolling plate at the exit of the rolling mill is bent to the side of the upper roll, that is, the rolling plate is warped, it means that under the rolling condition , the actual critical pass reduction required to reach the warpage-free state is greater than the simulated value, which can be solved in the following two ways: 1.1 Continue to increase the pass reduction and the rolling mill can still meet the natural bite conditions of the plate, without changing the initial plate thickness and speed ratio, repeat steps 1.1-1.3 by increasing the pass reduction until the obtained For flat rolled plates, the increase in reduction for each repeated pass shall not exceed 5%; 1.2 Continue to increase the pass reduction and the rolling mill cannot meet the natural bite conditions of the plate, the method of increasing the pass reduction will hinder the continuity of rolling. At this time, the initial plate thickness and pass reduction can be kept unchanged Under the condition, by reducing the different speed ratio and repeating steps 1.1-1.3, until obtaining straight rolling plate, the decline rate of the different speed ratio of each repetition is 5-10%; (2) When rolling under the non-warping critical working conditions obtained by simulation, if the rolling plate at the exit of the rolling mill is bent to the side of the lower roll, that is, the rolling plate is buckled, it means that under the rolling conditions , the actual critical pass reduction required to reach the warpage-free state is less than the simulated value. At this time, steps 1.1-1.3 can be repeated by reducing the pass reduction until a straight rolled plate is obtained. The reduction rate of the pass reduction is not more than 5%; Step 5. The asynchronous rolling without warping of metal or alloy plates can be realized by adopting the corrected asynchronous rolling critical condition close to the actual situation obtained in step 4, so as to solve the problems in the asynchronous rolling process of such alloy plates. warping problem. 2. The method according to claim 1, wherein the defined model material properties in the step 1 include specific heat capacity, thermal conductivity, modulus of elasticity, coefficient of thermal expansion, Poisson's ratio and density. 3. The method according to claim 1, characterized in that, in said step 2, the establishment of the relationship between the initial plate thickness, the pass reduction, the speed ratio of the upper and lower rolls and the warpage curvature is based on the establishment of step 1 The simulation calculation model of the rolling working condition is simulated and calculated to obtain a specific curvature value, and a curve is established with the curvature value on the Y axis and the rolling parameters on the X axis. 4. The method according to claim 1, characterized in that, in step 3, the range of the pass reduction of the obtained critical working condition is 5-55%, and the speed ratio is 1.0-1.7. 5. The method according to claim 1, characterized in that, in step 5, the actual rolling process needs to be based on the rolling natural bite condition, i.e. α < arctan μ, where α is the rolling bite angle, μ The relationship between the friction coefficient, the initial thickness and the critical reduction is used to determine the initial rolling thickness that matches the actual rolling capacity. Only when the initial thickness is less than or equal to the rolling initial thickness can no warpage be obtained. rolled plates.