High-strength steel large thick plate homogenization stress and local stress peak elimination method

Abstract

The invention provides a peak elimination method for homogenizing stress and local stress of a large and thick high-strength steel plate. Comprising the following steps: 1, stress analysis of an original plate: analyzing a basic material, size parameters and an original shape structure of the plate; 2, a stress homogenization scheme is formulated, specifically, a large relative anti-bending deformation curvature is set at an inlet of a leveler, the original curvature is converted into a single curvature in the same direction, and then small rolling reduction is set at the rear end to continuously reduce the curvature until the curvature is straight; 3, local peak elimination: arranging a base plate in a local defect area according to the original shape structure of the plate so as to eliminate a local stress peak value; 4, feeding and transporting the plates: conveying the plates to be treated through a feeding roller frame and a feeding roller way; 5, performing continuous anti-bending deformation: performing continuous anti-bending deformation on the plate by adjusting the rolling reduction of each working roller; and 6, residual stress detection: carrying out residual stress detection on the homogenized plate, and finally realizing the effects of stress homogenization and local stress peak elimination.

Description

Technical Field

[0001] The invention relates to pretreatment in the field of plate materials, and in particular to a method for averaging stress and eliminating local stress peaks of high-strength steel thick plates. Background Art

[0002] During the processing of steel plates, due to uneven stress and original defects, there will be certain problems such as excessive stress and uneven stress distribution in the plate, which will lead to processing deformation in the subsequent parts manufacturing process, reduce the part qualification rate and precision, increase material waste and production costs, and seriously weaken the performance and reliability of subsequent products.

[0003] In order to eliminate the above-mentioned influences, the uneven stress inside the plate needs to be homogenized. At present, the residual stress homogenization mainly adopts the following methods: stress relief annealing method, pre-stretching method and vibration aging method. Among them, the stress relief annealing method is to heat the steel plate to a certain temperature in a heating furnace on the rolling production line, keep it warm and then slowly cool it, so that the atoms inside the metal are rearranged and the stress is released; the pre-stretching method is to stretch the original plate before further processing of the plate, so that the plate produces a certain plastic deformation, offsetting the influence of residual stress in subsequent processing. The vibration aging method is to use a vibration device to vibrate the plate at a resonant frequency for a period of time, and homogenize the residual stress through the microscopic slip process inside the material.

[0004] However, the inventors of this application found that the above technology has at least the following technical problems in the process of implementing the technical solution of the invention in the embodiment of this application: During the leveling, stress equalization and local stress peak reduction processes of the pretreatment of high-strength plates and plates with a large thickness ratio for ships, the high-strength steel thick plates are not suitable for the above-mentioned stress elimination methods due to their large yield strength and large geometric dimensions. In addition, the existing technical means often regulate and equalize the stress by improving the internal crystal arrangement of the material, which cannot further eliminate the stress peak of the material. Therefore, the currently commonly used stress elimination methods cannot achieve the subsequent processing requirements of high-strength steel thick plates and are difficult to meet the needs of high-precision manufacturing. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present application provides a method for stress equalization and local stress peak reduction of high-strength steel thick plates in the pretreatment process of high-strength steel thick plates. The method implements continuous reverse bending deformation on the plate during the flattening step of plate pretreatment to eliminate and equalize the residual stress of the plate. The method includes the setting of multiple process parameters, including the amount of each working roll, the applied pressure, the working roll speed, and the number of bending deformations. The stress equalization and elimination of high-strength steel thick plates of different sizes and different initial states are achieved through parameter adjustment, the quality and flatness of the plate are improved, the quality and accuracy of subsequent processing are guaranteed, and the technical problems of high-strength steel thick plate pretreatment are solved.

[0006] The solution adopted by the embodiment of the present application to solve the technical problem is: A method for averaging stress and eliminating local stress peaks of a high-strength steel thick plate, in which continuous reverse bending deformation is performed on the plate during the leveling step of plate pretreatment to eliminate and average the residual stress of the plate, comprising the following steps: Step 1: Stress analysis of original sheet metal: Analyze the basic material and dimensional parameters of the plate as well as the original shape structure; Step 2: Develop a stress equalization plan: The opening between the upper and lower working rolls of the leveling machine is adjusted according to the thickness and deformation degree of the plate. By setting a larger relative reverse bending deformation curvature at the entrance, the original curvature is converted into a single curvature in the same direction, and then a smaller reduction is set at the rear end to continuously reduce the curvature until it is straight. Based on this plan, the relevant process parameters are further determined to complete the formulation of the process flow; Step 3: Local peak elimination: According to the original shape and structure of the plate, place the pad in the area where the local defect occurs to eliminate the local stress peak; Step 4: Plate loading and transportation: The plates to be processed are transported via the feed roller stand and feed roller table; Step 5: Continuous reverse bending deformation: The plate is continuously bent by adjusting the pressing amount of each working roll; Step 6: Residual stress detection: The residual stress of the homogenized plate is tested to finally achieve the effect of stress homogenization and elimination of local stress peaks.

[0007] Furthermore, the leveling machine adapted to the method is a large seven-roller leveling machine; Furthermore, the working rolls of the leveling machine are of the type that the upper and lower sides can be adjusted separately and are arranged with different roll spacings.

[0008] Positive effects: The technical solution provided in the embodiments of the present application has at least the following technical effects or advantages: Since the embodiment of the present application adopts the technical means of repeated bending and rebounding in the form of large deformation plus small residual in pretreatment, the plate is elastically deformed to eliminate the uneven stress inside the plate, which effectively solves the technical problem of pretreatment of high-strength steel thick plates in the prior art, thereby achieving the technical effect of stress equalization.

[0009] 2. Since the embodiment of the present application adopts a technical means to achieve internal stress equalization while improving flatness by means of the plate leveling process in the plate pretreatment stage, it effectively solves the technical problems of pretreatment of large and thick high-strength steel plates in the prior art, and there is no need to provide additional pretreatment links, thereby achieving full utilization of resources and thus achieving the technical effect of production efficiency.

[0010] The invention is suitable for application as a method for stress homogenization and local stress peak elimination of high-strength steel thick plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0012] Figure 1 This is a schematic diagram of the process flow of this embodiment; Figure 2 This is a schematic diagram of continuous reverse bending deformation in this embodiment; Figure 3 Schematic diagram of the pad arrangement in this embodiment. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Although the embodiments of the present invention have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the attached claims and their equivalents. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention.

[0014] As shown in the figure, a method for averaging stress and eliminating local stress peaks of thick high-strength steel plates is to perform continuous reverse bending deformation on the plates during the leveling step of plate pretreatment to eliminate and average the residual stress of the plates, including the following steps: Step 1: Stress analysis of original sheet metal: Analyze the basic material and dimensional parameters of the plate as well as the original shape structure; Specifically, firstly, analyze the stress distribution of the plate before processing through table inspection and instrument measurement, formulate the corresponding stress equalization plan according to the basic material parameters and stress unevenness of the plate, complete the formulation of relevant process flow, and further determine the process parameters of the leveling machine's working roll pressure, applied pressure, working roll speed and bending deformation times; Step 2: Develop a stress equalization plan: The opening between the upper and lower working rolls of the leveling machine is adjusted according to the thickness and deformation degree of the plate. By setting a larger relative reverse bending deformation curvature at the entrance, the original curvature is converted into a single curvature in the same direction, and then a smaller reduction is set at the rear end to continuously reduce the curvature until it is straight. Based on this plan, the relevant process parameters are further determined to complete the formulation of the process flow; For details, see the attached manual. Figure 2 , by setting a continuous reverse bending deformation scheme with large deformation and small residual, the upper working roll includes roll 2, roll 4 and roll 6, and the lower working roll includes roll 1, roll 3, roll 5 and roll 7. The upper working roll and the lower working roll are arranged alternately, and a large deformation scheme is adopted at rolls 1 to 3, and a larger pressure bending rate is set. The larger the total pressure bending rate of the working rolls is set, the smaller the residual curvature range of the plate after flattening. Therefore, by obtaining a large elastic-plastic deformation at the beginning of processing, the original irregular curvature can be converted into a single curvature value in the same direction, and then the residual is continuously reduced according to the pressure bending law at rolls 4 to 7, and finally the plate is flattened, and stress equalization is achieved at the same time; Step 3: Local peak elimination: According to the original shape and structure of the plate, place the pad in the area where the local defect occurs to eliminate the local stress peak; For details, see the attached manual. Figure 3 During the loading and unloading, transportation and storage of the plate, local deformation may occur, resulting in local stress peaks, which are usually manifested as transverse defects such as side waves and middle waves. In view of the excessive internal residual stress caused by the local original defects of the plate, a pad of appropriate size and thickness is arranged under the defect, and the loading platform is used for synchronous transportation and processing, so as to finally achieve local stress peak elimination. Step 4: Plate loading and transportation: The plates to be processed are transported via the feed roller stand and feed roller table; Specifically, the high-strength steel thick plates are loaded through the loading platform, and after centering, the plates are transported by the feed roller frame and the feed roller table, and the feed roller speed is synchronously matched with the speed between the two rows of working rollers to carry out continuous reverse bending deformation; Step 5: Continuous reverse bending deformation: The plate is continuously bent by adjusting the pressing amount of each working roll; Specifically, the plate enters the working rollers arranged in an alternating manner, and the pressing amount of the working rollers is adjusted according to the set process parameters. After multiple deformations, the purpose of stress homogenization of the plate is achieved. Step 6: Residual stress detection: The residual stress of the homogenized plate is tested to finally achieve the effect of stress homogenization and elimination of local stress peaks.

[0015] Specifically, the leveling machine adapted to this method is a large seven-roller leveling machine; Specifically, the working rolls of the leveling machine are individually adjustable on the upper and lower sides and arranged with different roll spacings.

[0016] It is worth noting that the contents not described in detail in the specification belong to the prior art known to those skilled in the art, and the model parameters of the leveling machine are not specifically limited and can be determined using conventional equipment. In this technical solution, the electrical control components not mentioned are not shown in the figure because they belong to the prior art and will not be described here.

[0017] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for averaging stress and eliminating local stress peaks in thick high-strength steel plates, characterized by: During the leveling step of the plate pretreatment, the plate is subjected to continuous reverse bending deformation to eliminate and equalize the residual stress of the plate, including the following steps: Step 1: Stress analysis of original sheet metal: Analyze the basic material and dimensional parameters of the plate as well as the original shape structure; Step 2: Develop a stress equalization plan: The opening between the upper and lower working rolls of the leveling machine is adjusted according to the thickness and deformation degree of the plate. By setting a larger relative reverse bending deformation curvature at the entrance, the original curvature is converted into a single curvature in the same direction, and then a smaller reduction is set at the rear end to continuously reduce the curvature until it is straight. Based on this plan, the relevant process parameters are further determined to complete the formulation of the process flow; Step 3: Local peak elimination: According to the original shape and structure of the plate, place the pad in the area where the local defect occurs to eliminate the local stress peak; Step 4: Plate loading and transportation: The plates to be processed are transported via the feed roller stand and feed roller table; Step 5: Continuous reverse bending deformation: The plate is continuously bent by adjusting the pressing amount of each working roll; Step 6: Residual stress detection: The residual stress of the homogenized plate is tested to finally achieve the effect of stress homogenization and elimination of local stress peaks.

2. The method for averaging stress and eliminating local stress peaks of a thick high-strength steel plate according to claim 1 is characterized by: The leveling machine is a large seven-roller leveling machine.

3. The method for averaging stress and eliminating local stress peaks of a thick high-strength steel plate according to claim 1, characterized in that: The working rolls of the leveling machine are of the type that the upper and lower sides can be adjusted separately and are arranged with different roll spacings.

4. The method for averaging stress and eliminating local stress peaks of a thick high-strength steel plate according to claim 1, characterized in that: In the step one, firstly, the stress distribution of the plate before processing is analyzed through table inspection and instrument measurement, and the corresponding stress equalization plan is formulated according to the basic material parameters and stress unevenness of the plate, and the relevant process flow is formulated to further determine the process parameters of the leveling machine, such as the working roll pressure, applied pressure, working roll speed and number of bending deformations.

5. The method for averaging stress and eliminating local stress peaks of a thick high-strength steel plate according to claim 1, characterized in that: In the second step, a continuous reverse bending deformation scheme with large deformation and small residual is set, the upper working roll includes a roll (2), a roll (4) and a roll (6), the lower working roll includes a roll (1), a roll (3), a roll (5) and a roll (7), the upper working roll and the lower working roll are arranged alternately, a large deformation scheme is adopted at the rolls (1) to (3), a large bending rate is set, and then the residual is continuously reduced according to the bending law at the rolls (4) to (7), and finally the plate is flattened and stress equalization is achieved at the same time.

6. The method for averaging stress and eliminating local stress peaks of a thick high-strength steel plate according to claim 1, characterized in that: In the step three, the plate is locally deformed during factory loading and unloading, transportation and storage, resulting in local stress peaks, which usually appear as lateral defects such as side waves and middle waves. By arranging pads of appropriate size and thickness under the defects, the loading platform is used to synchronously transport and process them, thereby ultimately achieving local stress peak elimination.

7. The method for averaging stress and eliminating local stress peaks of a thick high-strength steel plate according to claim 1, characterized in that: In the step 4, the high-strength steel thick plate is loaded through the loading platform, and after centering, the plate is transported by the feed roller frame and the feed roller table, and the feed roller speed is synchronously matched with the speed between the two rows of working rollers to carry out continuous reverse bending deformation.

8. The method for averaging stress and eliminating local stress peaks of a thick high-strength steel plate according to claim 1, characterized in that: In the step five, the plate enters the working rollers arranged in an upper and lower staggered manner, and the pressing amount of the working rollers is adjusted according to the set process parameters. After multiple deformations, the purpose of stress homogenization of the plate is achieved.

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