A method for predicting the initial residual stress distribution based on longitudinal bending of strip steel

Abstract

This invention discloses a method for predicting the initial residual stress distribution based on the lateral bending of longitudinally cut strip steel. The method includes: Step 1: Determining the geometric dimensions, mechanical properties, and the dimensions and deformation parameters of the longitudinally cut strip steel; Step 2: Establishing the basic form of the initial residual stress distribution function of the strip steel; Step 3: Establishing a system of equations for the initial residual stress function of the strip steel based on force balance and moment balance relationships; Step 4: Substituting the parameters from Step 1 into the system of equations for the initial residual stress function of the strip steel, solving for the unknown coefficients in the initial residual stress distribution function, and determining the initial residual stress distribution function of the strip steel. Based on the lateral bending deformation of the strip steel after longitudinal cutting, the maximum lateral bending amount is determined, thereby predicting the initial residual stress of the strip steel according to the equilibrium relationship, providing guidance for improving residual stress during production.

Description

Technical Field

[0001] This invention belongs to the field of hot-rolled strip shape control technology, and relates to a method for predicting the initial residual stress distribution based on the longitudinal bending of strip steel. Background Technology

[0002] During the hot rolling process, residual stress is inevitably generated in steel strip due to complex thermo-mechanical coupling and subsequent cooling. The distribution of these residual stresses directly affects the geometric stability, mechanical properties, and subsequent processing performance of the strip. To meet the needs of different downstream manufacturers and product processes, hot-rolled strip often needs to be cut into narrow strips of different widths after uncoiling. In the longitudinal cutting process of strip, side bending is one of the common defects, manifested as bending deformation along the width direction of the strip after longitudinal cutting. This deformation is usually caused by 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 is of great significance for reducing defect generation, improving product quality, and saving production costs.

[0003] Traditional methods for predicting residual stress distribution typically rely on experimental testing or finite element simulation. While these methods offer a certain level of prediction accuracy, they also have several drawbacks. Experimental testing is costly, requiring specialized equipment such as X-ray diffractometers or stress release testing devices, and is complex and time-consuming to operate. Finite element simulation involves substantial computation, requiring the construction of accurate mathematical models, resulting in high computational costs, specialized finite element software, and significant computational resources. Furthermore, the accuracy of simulation results is affected by various factors such as model parameter settings and boundary conditions, limiting its widespread application in actual industrial production. Therefore, there is an urgent need for a method that can accurately, efficiently, and easily predict the initial residual stress distribution of strip steel to improve the quality and efficiency of strip steel slitting and to improve residual stress distribution. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a method for predicting the initial residual stress distribution based on the longitudinal bending of strip steel. Based on the lateral bending deformation of the strip steel after longitudinal cutting, the maximum lateral bending amount is determined, thereby predicting the initial residual stress of the strip steel according to the equilibrium relationship, providing guidance for improving residual stress during the production process.

[0005] This invention provides a method for predicting the initial residual stress distribution based on longitudinal bending of strip steel, comprising:

[0006] Step 1: Determine the geometric dimensions, mechanical properties, and slit dimensions and deformation parameters of the strip after longitudinal cutting;

[0007] Step 2: Set the basic form of the initial residual stress distribution function of the strip;

[0008] Step 3: Establish the initial residual stress function equations for the strip steel based on the force balance and moment balance relationships;

[0009] Step 4: Substitute the parameters from Step 1 into the equation set of initial residual stress function of the strip, solve for the unknown coefficients in the initial residual stress distribution function of the strip, and determine the initial residual stress distribution function of the strip.

[0010] This invention proposes a method for predicting the initial residual stress distribution based on the lateral bending of longitudinally cut strips. It constructs a set of initial residual stress function equations based on the maximum lateral bending of the strip after longitudinal cutting. By solving for the curvature of the strip's neutral plane after lateral bending, and combining force and moment balance relationships, the initial residual stress distribution function expression of the strip is finally obtained. This method enables rapid and convenient prediction of the initial residual stress distribution of strips in practical industrial applications, providing a reference for optimizing process parameters in strip production. Attached Figure Description

[0011] Figure 1 This is a flowchart of a method for predicting the initial residual stress distribution based on longitudinal bending of strip steel according to the present invention;

[0012] Figure 2 This is a graph showing the initial residual stress distribution function of the strip calculated in this embodiment;

[0013] Figure 3 This is a comparison chart of the calculated and measured results of the initial residual stress distribution of the strip in this embodiment. Detailed Implementation

[0014] The invention will be further described below with reference to the accompanying drawings and specific embodiments. In actual production, uneven residual stress is introduced due to the plastic deformation, temperature distribution, and uneven phase transformation of the strip steel. However, current residual stress detection methods cannot be widely applied in industrial settings, which increases the difficulty of improving the residual stress distribution through production process optimization. This invention can calculate the lateral bending rate of the cut strip based on the lateral bending deformation after longitudinal cutting, and further determine the initial residual stress distribution of the strip steel, thus providing a reference for process optimization.

[0015] The specific implementation of this invention will be described using the cutting and processing process of 750L automotive beam steel by a certain automotive beam steel processing company as an example. Figure 1 As shown, the present invention provides a method for predicting the initial residual stress distribution based on longitudinal bending of strip steel, comprising the following steps:

[0016] Step 1: Determine the geometric dimensions, mechanical properties, and slit dimensions and deformation parameters of the strip after longitudinal cutting.

[0017] The geometric dimensions of the strip include its length, width, and thickness. The mechanical property of the strip is its modulus of elasticity. The dimensional parameters of the cut strip include its length and width. The deformation parameters of the cut strip include its bending direction and maximum bending amount.

[0018] In this embodiment, the steel grade is 750L, and the basic parameter information of the strip is shown in Table 1.

[0019] Table 1 Basic Parameter Information of 750L Strip Steel

[0020]

[0021] The strip is longitudinally cut 180mm from the outermost edge along the width direction. The length of the cut strip is 12000mm and the width is 180mm. After longitudinal cutting, the strip bends outward, with a maximum lateral bending amount of 70mm.

[0022] Step 2: Set the basic form of the initial residual stress distribution function of the strip steel as a sixth-order function, specifically as follows:

[0023]

[0024] In the formula, A and B The unknown coefficients to be solved; x These are the coordinates along the width of the strip. x =0 corresponds to the center position of the strip width.

[0025] Step 3: Establish the initial residual stress function equations for the strip steel based on the force balance and moment balance relationships, specifically:

[0026] Step 3.1: Calculate the lateral curvature of the neutral surface of the cut strip based on the maximum lateral curvature of the cut strip. n n :

[0027]

[0028] In the formula, d This represents the maximum lateral bending amount of the cut strip; L The length of the strip; W S This refers to the width of the cut strip; when the cut strip bends outwards, n n Take a positive value; when the cut strip bends inward, n n Take the negative value.

[0029] In this embodiment, d =70mm, L =12000mm, W S=180 mm, and finally the lateral curvature of the neutral surface of the cut strip is obtained. n n =1 / 1800090.

[0030] Step 3.2: Establish the initial residual stress function equations for the strip based on the force balance and moment balance relationships:

[0031]

[0032] In the formula, E It is the elastic modulus; h For strip thickness; x n Let x be the x-coordinate of the neutral plane of the slicing strip. B The width of the strip;

[0033]

[0034]

[0035] In the formula, x 1, x 2 These are the x-coordinates of the two endpoints of the cut strip along its width.

[0036] In this embodiment, E= 206 GPa, h =5mm, x 1 = 570mm x 2=750mm, x n =660mm, B =1500mm.

[0037] Step 4: Substitute the parameters from Step 1 into the equation set of initial residual stress function of the strip, solve for the unknown coefficients in the initial residual stress distribution function of the strip, and determine the initial residual stress distribution function of the strip.

[0038] In this embodiment, the final result is obtained , The results of the initial residual stress distribution function of the strip are as follows: Figure 2 As shown.

[0039] Subsequently, samples were taken from the same coil of strip steel, and the residual stress at different locations along the width direction of the strip steel was measured using an AIS3000 residual stress analyzer. A total of 23 points were taken along the width direction of the strip steel. The calculated initial residual stress distribution of the strip steel was compared with the measured results. Figure 3 As shown, the results comparison proves that the method can accurately predict the initial residual stress distribution of strip steel, demonstrating the feasibility of predicting the initial residual stress distribution based on the longitudinal bending of strip steel.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the ideas of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting the initial residual stress distribution based on longitudinal bending of strip steel, characterized in that, include: Step 1: Determine the geometric dimensions, mechanical properties, and slit dimensions and deformation parameters of the strip after longitudinal cutting; Step 2: Set the basic form of the initial residual stress distribution function of the strip; Step 3: Establish the initial residual stress function equations for the strip steel based on the force balance and moment balance relationships; Step 4: Substitute the parameters from Step 1 into the equation set of initial residual stress function of the strip, solve for the unknown coefficients in the initial residual stress distribution function of the strip, and determine the initial residual stress distribution function of the strip. In step 2, the basic form of the initial residual stress distribution function of the strip is a sixth-order function, specifically: σ 0 (x)=Ax 6 +B In the formula, A and B are the unknown coefficients to be solved; x is the coordinate of the strip width direction, and x = 0 corresponds to the center position of the strip width; Step 3 specifically involves: Step 3.1: Calculate the lateral curvature n of the neutral surface of the cut strip based on the maximum lateral curvature of the cut strip. n : In the formula, d is the maximum lateral bending of the cut strip; L is the length of the cut strip; W S n is the width of the slicing strip; when the slicing strip bends outward, n n Take a positive value; when the cut strip bends inward, n n Take the negative value; Step 3.2: Establish the initial residual stress function equations for the strip based on the force balance and moment balance relationships: In the formula, E is the elastic modulus; h is the strip thickness; x n Let B be the abscissa of the neutral plane of the strip, and B be the width of the strip. x2-x1=W S In the formula, x1 and x2 are the x-coordinates of the two endpoints of the cut strip in the width direction, respectively.

2. The method for predicting the initial residual stress distribution based on longitudinal bending of strip steel as described in claim 1, characterized in that: The geometric dimensions of the strip include: the length, width, and thickness of the strip; The mechanical property parameter of the strip steel is its elastic modulus; The dimensions of the cut strips include: the length and width of the cut strips; The deformation parameters of the cut strip include: the lateral bending direction and the maximum lateral bending amount of the cut strip.

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