Initial residual stress distribution prediction method based on strip steel longitudinal cutting lateral bending

Abstract

The invention discloses an initial residual stress distribution prediction method based on strip steel longitudinal cutting lateral bending. The method comprises the steps that 1, geometric dimension parameters and mechanical property parameters of strip steel and slitting dimension parameters and slitting deformation parameters after longitudinal cutting are determined; 2, setting a basic form of an initial residual stress distribution function of the strip steel; 3, establishing a strip steel initial residual stress function equation set according to a force balance and moment balance relation; 4, the parameters in the step 1 are substituted into the strip steel initial residual stress function equation set, unknown coefficients in the strip steel initial residual stress distribution function are solved, and the strip steel initial residual stress distribution function is determined. The maximum lateral bending amount is determined based on the lateral bending deformation condition of the strip steel after longitudinal cutting, so that the initial residual stress of the strip steel is predicted according to the balance relation, and guidance is provided for improving the residual stress in the production process.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-rolled plate shape control and relates to a method for predicting initial residual stress distribution based on strip longitudinal cutting and side bending. Background Art

[0002] During the hot rolling process, the strip will inevitably produce residual stress due to the complex thermal-mechanical coupling and the subsequent cooling process. The distribution of these residual stresses directly affects the geometric stability, mechanical properties and subsequent processing performance of the strip. In order to meet the needs of different downstream manufacturers and product processes, hot-rolled strips often need to be cut into narrow strips of different widths according to the required size specifications after uncoiling. In the longitudinal cutting process of strip steel, side bending is one of the common defects, which is manifested as the bending deformation of the strip steel along the width direction after longitudinal cutting. This deformation is usually caused by the uneven distribution of residual stress, which brings many problems to product quality and subsequent processing. Therefore, seeking technical means to obtain the initial residual stress of hot-rolled strip steel is of great significance to reduce defects, improve product quality and save production costs.

[0003] Traditional residual stress distribution prediction methods usually rely on experimental tests or finite element simulations. Although these methods can provide a certain degree of prediction accuracy, they also have some problems. Experimental testing is costly and requires professional testing equipment, such as X-ray diffractometers or stress release test devices, which are complex and time-consuming to operate. Finite element simulations are computationally intensive and require the construction of accurate mathematical models. They have high computational costs and require professional finite element software and a large amount of computing resources. The accuracy of the simulation results is affected by many factors, such as model parameter settings and boundary conditions, and their promotion and application in actual industrial production is limited. Therefore, there is an urgent need for a method that can accurately, efficiently and simply predict the initial residual stress distribution of strip steel in order to improve the quality and efficiency of strip steel longitudinal cutting and improve the residual stress distribution. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a method for predicting the initial residual stress distribution based on the lateral bending of the strip steel after longitudinal cutting. Based on the lateral bending deformation of the strip steel after longitudinal cutting, the maximum lateral bending amount is determined, so as to predict the initial residual stress of the strip steel according to the equilibrium relationship, and provide guidance for improving the residual stress in the production process.

[0005] The present invention provides a method for predicting the initial residual stress distribution based on strip longitudinal cutting and side bending, comprising: Step 1: Determine the geometrical dimension parameters, mechanical property parameters, and strip dimension parameters and strip deformation parameters after longitudinal cutting of the strip; Step 2: Set the basic form of the strip initial residual stress distribution function; Step 3: Establish the initial residual stress function equation group of the strip according to the force balance and moment balance relationship; Step 4: Substitute the parameters in step 1 into the strip initial residual stress function equation group, solve the unknown coefficients in the strip initial residual stress distribution function, and determine the strip initial residual stress distribution function.

[0006] The present invention proposes a method for predicting the initial residual stress distribution based on the lateral bending of the strip steel after longitudinal slitting, constructs an initial residual stress function equation group based on the maximum lateral bending amount of the strip steel after longitudinal slitting, and finally obtains the initial residual stress distribution function expression of the strip steel by solving the curvature of the neutral plane of the strip steel after lateral bending, combining the force balance and moment balance relationship. It can quickly and easily predict the initial residual stress distribution of the strip steel in actual industrial applications, and provide a reference for the optimization of process parameters in the strip steel production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a flow chart of a method for predicting initial residual stress distribution based on strip longitudinal cutting and side bending of the present invention; Figure 2 This is a graph of the distribution function of the initial residual stress of the steel strip calculated in this embodiment; Figure 3 This is a comparison chart between the calculated results and the measured results of the initial residual stress distribution of the steel strip in this embodiment. DETAILED DESCRIPTION

[0008] The invention is further described below in conjunction with the accompanying drawings and specific implementation methods. In the actual production process, uneven residual stress is introduced due to the uneven plastic deformation, temperature distribution and phase change of the strip, but the residual stress detection methods currently on the market cannot be widely used in industrial sites, which increases the difficulty of improving the residual stress distribution by optimizing the production process. The present invention can calculate the side bending rate of the cut strip based on the deformation of the side bending after the strip is longitudinally cut, and further obtain the initial residual stress distribution of the strip, thereby providing a reference for process optimization.

[0009] The specific implementation method of the present invention is described by taking the cutting process of 750L automobile beam steel by a certain automobile beam steel processing enterprise as an example. Figure 1 As shown, a method for predicting the initial residual stress distribution based on strip longitudinal cutting and side bending of the present invention comprises the following steps: Step 1: Determine the geometric size parameters, mechanical property parameters, and strip size parameters and strip deformation parameters after longitudinal cutting of the strip.

[0010] The geometrical dimension parameters of the strip include: the length, width and thickness of the strip. The mechanical property parameter of the strip is the elastic modulus. The dimension parameters of the cut strip include: the length and width of the cut strip. The deformation parameters of the cut strip include: the bending direction and the maximum bending amount of the cut strip.

[0011] In this embodiment, the steel grade is 750L, and the basic parameter information of the strip steel is shown in Table 1.

[0012] Table 1 Basic parameter information of 750L strip steel The strip is cut longitudinally at 180mm from the edge along the width direction. The length of the strip is 12000mm and the width is 180mm. After longitudinal cutting, the strip is bent outward with a maximum side bending of 70mm.

[0013] Step 2: Set the basic form of the strip initial residual stress distribution function to a sixth-order function, specifically:

[0014] In the formula, A and B is the unknown coefficient to be solved; x is the strip width direction coordinate, x =0 corresponds to the center position of the strip width.

[0015] Step 3: According to the force balance and moment balance relationship, the function equation group of initial residual stress of the strip is established, which is as follows: Step 3.1: Calculate the lateral curvature of the neutral plane of the cut strip based on the maximum lateral curvature of the cut strip n n :

[0016] In the formula, d is the maximum lateral bending of the cut strip; L is the length of the cut strip; W S is the width of the cut strip; when the cut strip bends outward, n n Take a positive value, when the cut strip bends inward, n n Takes negative value.

[0017] In this embodiment, d =70mm, L =12000mm, W S =180 mm, and finally the lateral curvature of the neutral plane of the cut strip is obtained n n =1 / 1800090.

[0018] Step 3.2: Establish the initial residual stress function equations of the strip according to the force balance and moment balance relationship:

[0019] In the formula, E is the elastic modulus; h is the strip thickness; x n is the horizontal coordinate of the neutral plane of the cut strip, B is the strip width;

[0020]

[0021] In the formula, x 1, x 2 They are the horizontal coordinates of the two end points in the width direction of the cut strip.

[0022] In this embodiment, E= 206GPa, h =5mm, x 1=570mm, x 2=750mm, x n =660mm, B =1500mm.

[0023] Step 4: Substitute the parameters in step 1 into the strip initial residual stress function equation group, solve the unknown coefficients in the strip initial residual stress distribution function, and determine the strip initial residual stress distribution function.

[0024] In this embodiment, the final result is , The results of the initial residual stress distribution function of the strip are as follows: Figure 2 shown.

[0025] Afterwards, the same coil of steel strip was sampled and the residual stress at different positions in the width direction of the steel strip was measured using the AIS3000 residual stress detector. A total of 23 points were taken in the width direction of the steel strip. The calculated initial residual stress distribution results of the steel strip were compared with the measured results. Figure 3 As shown in the figure, the comparison of results proves that the method can accurately predict the initial residual stress distribution of the strip, and illustrates the feasibility of predicting the initial residual stress distribution based on the longitudinal cutting side bending of the strip.

[0026] The above description is only a preferred embodiment of the present invention and is not intended to limit the concept of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for predicting the initial residual stress distribution based on strip longitudinal bending, characterized in that: include: Step 1: Determine the geometrical dimension parameters, mechanical property parameters, and strip dimension parameters and strip deformation parameters after longitudinal cutting of the strip; Step 2: Set the basic form of the strip initial residual stress distribution function; Step 3: Establish the initial residual stress function equation group of the strip according to the force balance and moment balance relationship; Step 4: Substitute the parameters in step 1 into the strip initial residual stress function equation group, solve the unknown coefficients in the strip initial residual stress distribution function, and determine the strip initial residual stress distribution function.

2. The method for predicting the initial residual stress distribution based on strip slitting and side bending according to claim 1, characterized in that: The geometrical dimension parameters of the strip include: the length, width and thickness of the strip; The mechanical property parameter of the strip is the elastic modulus; The strip size parameters include: the length and width of the strip; The deformation parameters of the cut strips include: the bending direction and the maximum bending amount of the cut strips.

3. The method for predicting the initial residual stress distribution based on strip slitting and side bending according to claim 1, characterized in that: The basic form of the initial residual stress distribution function of the strip in step 2 is a sextic function, specifically: In the formula, A and B is the unknown coefficient to be solved; x is the strip width direction coordinate, x =0 corresponds to the center position of the strip width.

4. The method for predicting the initial residual stress distribution based on strip slitting and side bending according to claim 1, characterized in that: The step 3 is specifically as follows: Step 3.1: Calculate the lateral curvature of the neutral plane of the cut strip based on the maximum lateral curvature of the cut strip n n : In the formula, d is the maximum lateral bending of the cut strip; L is the length of the cut strip; W S is the width of the cut strip; when the cut strip bends outward, n n Take a positive value, when the cut strip bends inward, n n Take negative values; Step 3.2: Establish the initial residual stress function equations of the strip according to the force balance and moment balance relationship: In the formula, E is the elastic modulus; h is the strip thickness; x n is the horizontal coordinate of the neutral plane of the cut strip, B is the strip width; In the formula, x 1, x 2 They are the horizontal coordinates of the two end points in the width direction of the cut strip.

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