A method for predicting the overall strength and plasticity of a high-strength steel thick plate

Abstract

The application provides a method for predicting the overall strength and plasticity of a high-strength steel thick plate. The method comprises the following steps: performing original plate thickness tensile tests and small-size tensile tests on a plurality of high-strength thick plates, performing correlation analysis on the test results of the two tests, and establishing a prediction model. The method can predict the mechanical properties of the original plate thickness of the thick plate through a standard-size sample in the subsequent design process. The prediction structure is accurate and reliable. After the prediction model is established, a large-tonnage tensile testing machine is not required in the subsequent prediction process. Therefore, the corresponding test and prediction can be performed in a conventional laboratory, the test difficulty and cost are significantly reduced, and great convenience is provided for the use and design of high-strength thick plates in application scenarios such as ships, offshore platforms and polar equipment.

Description

Technical Field

[0001] This invention relates to the field of mechanical property testing technology for metallic materials, and more specifically, to a method for predicting the overall strength and plasticity of high-strength steel thick plates. Background Technology

[0002] As container ships, bulk carriers, and offshore engineering platforms become increasingly larger, the stress levels in the hull structure have significantly increased. To ensure the strength and rigidity of the hull structure, high-strength thick steel plates are increasingly used in the design and construction process. Currently, the design and construction of 10,000 TEU container ships generally use high-strength ultra-thick plates with a yield strength of not less than 40 kg, accounting for nearly 20% of the total steel plate usage, with thicknesses mostly exceeding 60 mm. Furthermore, high-strength ultra-thick steel plates with thicknesses exceeding 80 mm have also been used on ultra-large container ships. To ensure the safe operation of ultra-large container ships, bulk carriers, and offshore engineering platforms under high loads and high sea state environments, thick hull structural steel should possess good strength and ductility. The strength and ductility of hull structural steel are crucial parameters in ship design, directly determining several core design principles, including steel grade, application location, and stress levels within the hull structure.

[0003] Chinese patent CN113793654A discloses a method and system for predicting the mechanical properties of steel materials based on unsupervised identification. The method includes: sampling the material and acquiring microscopic images using an optical microscope or scanning electron microscope; using a machine learning algorithm to divide the image into several superpixels based on color and edge information; calculating the texture features of each superpixel; clustering the superpixels based on the texture features to identify various microstructures of the steel material in the image; establishing a representative volume element model based on the material microstructure identification results and the mechanical properties of each single-phase microstructure; calculating the virtual tensile process of the material to obtain the stress and strain values ​​at each node; statistically obtaining the overall stress and strain of the material; and analyzing and calculating various mechanical property parameters. This patent predicts the mechanical properties of materials by observing their microstructure, and has the advantages of small sampling area and simple method. However, due to limitations of existing production conditions and processes, the mechanical properties of thick ship hull structural steel are not uniform from the surface to the core. The small sampling area of ​​this patent means that it can only predict the mechanical properties of a small area and cannot analyze the overall strength and toughness of thick ship hull structural steel.

[0004] The uneven mechanical properties of thick ship hull structural steel from the surface to the core can adversely affect the overall safety performance of the thick hull structure. This is manifested in two aspects: Firstly, current ship hull steel technical standards do not require tensile testing of the original plate thickness, but only stipulate that small tensile specimens be taken at a specific thickness for strength-plasticity testing. This makes it impossible to assess the strength-plasticity distribution in the thickness direction. For example...Figure 1 This diagram illustrates the yield strength distribution along the thickness of a typical high-strength steel plate. The red data points represent measurements of small-sized samples at different thicknesses, while the black dashed line represents measurements of large-sized samples of the original plate thickness. Figure 1 It is known that the surface strength is significantly higher than that of the core. Test data using 1 / 4 plate thickness or the core will deviate from the original plate thickness results and cannot represent the overall mechanical properties of the thick plate. This can lead to insufficient safety margins in ships, creating safety hazards, or excessive safety redundancy, resulting in economic inefficiency. On the other hand, current ship design treats structural steel as a material with uniform performance, requiring the overall strength and ductility of thick plates to meet specified requirements. Since small-scale tensile tests at specific locations cannot obtain full-thickness data, it is necessary to use large-scale original-thickness specimens for testing. These tests are relatively large (see...). Figure 2 As shown), for example, for a 50mm thick plate of 600MPa high-strength steel, the original plate thickness tensile test specimen size needs to be at least 200×600×50mm, which is much larger than the ordinary round bar tensile test specimen size of 100×Φ10mm (see...). Figure 3 As shown, the tensile force of the original plate thickness tensile testing equipment needs to exceed 300 tons or even 500 tons to break the sample, while most tensile testing machines at present are in the 10-ton range, which limits the adaptability of the original plate thickness tensile test and seriously restricts the application of thick structural steel in the design of new ships. Summary of the Invention

[0005] In view of this, the present invention aims to provide a method for predicting the overall strength and plasticity of thick plates by taking small-scale tensile tests along the thickness direction. This method can avoid many drawbacks of large-scale tests on large original plates, meet the safety design requirements of structures such as deep-sea submersibles, large container ships, and offshore platforms, and improve the safety level of material design.

[0006] This invention discloses a method for predicting the overall strength and ductility of high-strength steel thick plates, comprising the following steps:

[0007] Step S1: For high-strength thick plates, tensile tests of the original plate thickness and tensile tests of small dimensions are carried out respectively to obtain mechanical property parameters under the two test conditions. The mechanical property parameters include one or more of yield strength, tensile strength and elongation.

[0008] Step S2: Analyze the correlation between the same parameters obtained from the original thickness tensile test and the small-size tensile test, and establish a predictive model for mechanical properties based on the correlation:

[0009] σ s大 =a1·σ s小 +b1 (1)

[0010] σ m大 =a2·σ m小 +b2 (2)

[0011] A 大 =a3·A 小 +b3 (3)

[0012] Where, σ s大 σ is the yield strength detected in the tensile test of the original plate thickness. s小 σ represents the yield strength detected in small-scale tests. m大 σ is the tensile strength detected in the tensile test of the original plate thickness. m小 A represents the tensile strength detected in small-scale tests. 大 A represents the elongation detected in the tensile test of the original plate thickness. 小 The elongation detected in small-size tests, a1, b1, a2, b2, a3, and b3 are all undetermined coefficients; where the unit of strength is MPa and the unit of elongation is percentage;

[0013] Step S3: Substitute the yield strength detected in step S1 into equation (1), the tensile strength into equation (2), and the elongation into equation (3) to obtain the values ​​of a1, b1, a2, b2, a3, and b3.

[0014] Furthermore, after step S3, the following steps are also included:

[0015] Step S4: For the high-strength thick plate to be tested, take two or more samples of different thicknesses along the thickness direction of the plate and perform small-size tensile tests. Take the average value of the yield strength, tensile strength and elongation of the samples.

[0016] Step S5: Take the average yield strength from step S4 as σ in equation (1). s小 σ is calculated s大 That is, the predicted value of the full-thickness yield strength of the high-strength thick plate; and / or, the average tensile strength in step S4 is taken as σ in equation (2). m小 σ is calculated m大 This is the predicted value of the tensile strength of the high-strength thick plate over its full thickness; the average elongation in step S4 is taken as A in equation (3). 小 Calculate and obtain A 大 This is the predicted value of the full thickness elongation of a high-strength thick plate.

[0017] Furthermore, in step S1, the original plate thickness tensile test is performed by sampling the full thickness of the high-strength thick plate. The gauge length of the full-thickness specimen is more than 3 times the plate thickness, and the width is more than 2 times the plate thickness.

[0018] Furthermore, in steps S1 and S4, the specimens used in the small-size test are standard round bar tensile specimens.

[0019] Furthermore, the thickness t of the high-strength thick plate ranges from 30mm to 100mm.

[0020] Furthermore, in steps S1 and S4, the small-size tensile test involves taking samples at two or more different thicknesses along the thickness direction of the plate for testing.

[0021] Furthermore, for high-strength thick plates with a thickness of 30mm≤t<60mm, the sampling locations for small-size tensile tests are the surface and the center.

[0022] Furthermore, for high-strength thick plates with a thickness of 60mm≤t≤100mm, the sampling locations for small-size tensile tests are the surface, 1 / 4 of the thickness, and the center.

[0023] Furthermore, the prediction method is applicable to the prediction of the strength and plasticity of high-strength thick plates at temperatures ranging from -60°C to room temperature.

[0024] Furthermore, a1=1.01, b1=-6.1, a2=0.97, b2=14, a3=0.98, b3=0.56.

[0025] Compared with existing technologies, the method for predicting the overall strength and plasticity of high-strength steel thick plates described in this invention has the following advantages:

[0026] (1) By conducting tensile tests on the original thickness and small-size tensile tests on various high-strength thick plates, the correlation analysis of the test results of the two is carried out and a prediction model is established, so that the mechanical properties of the original thickness of the thick plate can be predicted by standard-size specimens in the subsequent design process. The prediction structure is accurate and reliable.

[0027] (2) The prediction method provided by this invention has a clear principle and a simple method. It can be used with the commonly used 10-ton multi-functional testing machine without the need for separate design and manufacturing of tooling. However, the original plate thickness sample requires equipment capacity of more than 300 tons, or even more than 500 tons. Only a few units in China have the testing conditions, and the test is time-consuming and labor-intensive.

[0028] (3) It is highly adaptable and can measure structural steel with different yield strengths. The prediction accuracy remains high when the test temperature changes. The temperature can be as low as -60℃, which is convenient for evaluating structural steel of ships that are in service in low temperature environments. This avoids the harsh requirement of needing both a large tonnage testing machine and a low temperature environment. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram showing the distribution of yield strength along the thickness direction of an 80mm thick plate with a strength of 890MPa under measured conditions.

[0031] Figure 2 This is a schematic diagram of a tensile specimen with the original plate thickness.

[0032] Figure 3 A schematic diagram showing the dimensions of a standard round bar tensile specimen.

[0033] Figure 4 This is a schematic diagram of the sampling location during detection by the prediction method described in this embodiment of the invention;

[0034] Figure 5 This is the prediction model for yield strength described in the embodiments of the present invention;

[0035] Figure 6 This is the prediction model for tensile strength described in the embodiments of the present invention;

[0036] Figure 7 This is the prediction model for yield strength described in the embodiments of the present invention. Detailed Implementation

[0037] To make the technical means and objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below with reference to specific illustrations.

[0038] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are only used to explain the relative positional relationships and connections between components in a specific state (as shown in the accompanying drawings). They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0039] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] A method for predicting the overall strength and ductility of high-strength steel thick plates includes the following steps:

[0042] Step S1: For high-strength thick plates, tensile tests of the original plate thickness and tensile tests of small dimensions are carried out respectively to obtain mechanical property parameters under the two test conditions. The mechanical property parameters include one or more of yield strength, tensile strength and elongation.

[0043] Step S2: Analyze the correlation between the same parameters obtained from the original thickness tensile test and the small-size tensile test, and establish a predictive model for mechanical properties based on the correlation:

[0044] σ s大 =a1·σ s小 +b1 (1)

[0045] σ m大 =a2·σ m小 +b2 (2)

[0046] A 大 =a3·A 小 +b3 (3)

[0047] Where, σ s大 σ is the yield strength detected in the tensile test of the original plate thickness. s小 σ represents the yield strength detected in small-scale tests. m大 σ is the tensile strength detected in the tensile test of the original plate thickness. m小 A represents the tensile strength detected in small-scale tests. 大 A represents the elongation detected in the tensile test of the original plate thickness.小 The elongation detected in small-size tests, a1, b1, a2, b2, a3, and b3 are all undetermined coefficients; where the unit of strength is MPa and the unit of elongation is percentage;

[0048] Step S3: Substitute the yield strength detected in step S1 into equation (1), the tensile strength into equation (2), and the elongation into equation (3) to obtain the values ​​of a1, b1, a2, b2, a3, and b3.

[0049] The overall strength-plasticity refers to the strength-plasticity of a high-strength thick plate at its original thickness. This value is usually obtained through tensile testing at the original thickness. However, tensile testing of high-strength thick plates at their original thickness requires a large-tonnage tensile testing machine, which is typically not available in conventional laboratories. Outsourcing testing is time-consuming, labor-intensive, and costly, thus limiting the acquisition of the strength-plasticity of high-strength thick plates. In this example, step S1 targets high-strength thick plates with various strength and thickness levels. By setting up the above steps, a quantitative relationship is systematically established between the original thickness tensile test data and standardized small-size tensile test data, linking the overall performance, which is difficult to obtain directly, with the easily obtainable local performance, thereby constructing a reliable predictive model that has been experimentally calibrated. Step S1 involves comparative tests on high-strength steel plates with varying strengths and thicknesses to ensure the broad representativeness of the collected data, laying the foundation for the model's universal applicability across multiple steel types. Subsequently, step S2 involves correlation analysis and the establishment of a prediction model, linking the overall performance of the high-strength thick plate with the results of small-scale tests. Step S3 utilizes experimental data fitting to determine the correlation coefficient, ensuring that the prediction model formed in step S2 is based on a large amount of experimental data and forms an empirical formula, thereby guaranteeing the high objectivity and reliability of the prediction results. This setup eliminates the need for full-thickness tensile testing when the strength and ductility of high-strength thick plates are required; small-scale tensile tests suffice. This fundamentally avoids the absolute dependence on ultra-large tonnage tensile testing equipment, providing a new and feasible technical path for evaluating the overall performance of thick plates under conventional laboratory conditions. Optionally, in step S3, during the small-scale tensile test, two or more specimens are taken from different thickness positions along the thickness direction of the high-strength thick plate. The average value of the test values ​​for the same material is then used for fitting, where the average yield strength corresponds to σ. s小 The average tensile strength corresponds to σ. m小 The average elongation corresponds to A. 小 .

[0050] Preferably, after step S3, the method further includes:

[0051] Step S4: For the high-strength thick plate to be tested, take two or more samples of different thicknesses along the thickness direction of the plate and perform small-size tensile tests. Take the average value of the yield strength, tensile strength and elongation of the samples.

[0052] Step S5: Take the average yield strength from step S4 as σ in equation (1). s小 σ is calculated s大 That is, the predicted value of the full-thickness yield strength of the high-strength thick plate; and / or, the average tensile strength in step S4 is taken as σ in equation (2). m小 σ is calculated m大 This is the predicted value of the tensile strength of the high-strength thick plate over its full thickness; the average elongation in step S4 is taken as A in equation (3). 小 Calculate and obtain A 大 This is the predicted value of the full thickness elongation of a high-strength thick plate.

[0053] It should be understood that, since there are significant differences in the strength and plasticity of high-strength thick plates along the thickness direction, taking the average value of samples from two or more different thicknesses along the thickness direction can minimize the offset of the input data and greatly reduce the deviation of the prediction results caused by sampling issues. The original thickness strength and plasticity prediction value obtained through the above settings has a very small deviation and can accurately reflect the overall strength and plasticity performance of the high-strength thick plate.

[0054] Specifically, such as Figure 2 As shown, in step S1, the original plate thickness tensile test is performed by sampling the full thickness of the high-strength thick plate. The gauge length of the full-thickness specimen is more than 3 times the plate thickness, and the width is more than 2 times the plate thickness.

[0055] The above settings ensure that the full-thickness specimen has a sufficiently large gauge length and width, which guarantees that the stress state within the gauge section can be fully developed and homogenized during tensile testing. This avoids the interference of end constraint effects and stress concentration caused by excessively small dimensions on the test results, allowing the measured yield strength, tensile strength, and elongation to more accurately reflect the mechanical properties of the material and ensure accurate test results.

[0056] In steps S1 and S4, the specimens used in the small-size tests are standard round bar tensile specimens. Figure 3For example, the diameter of the parallel section of the specimen is 10mm, the gauge length is 50mm, and the length of the parallel section is more than 60mm. The diameter and length of the remaining clamping ends can be set according to specific needs, and will not be elaborated here. It should be understood that the above specimen size is the most commonly used round bar tensile specimen size in the prior art, so that the prediction method provided in this example can be seamlessly connected with the experimental equipment of conventional laboratories, greatly reducing the demand for experimental equipment. After establishing the relevant prediction model through a large number of experiments in the early stage, when it is necessary to understand the overall strength and plasticity of high-strength thick plates in the future, it is only necessary to use standard round bar tensile specimens to conduct small-size tensile tests, and substitute the test results into formulas (1), (2), and (3) respectively to predict the overall strength and plasticity of high-strength thick plates. This significantly reduces the dependence on large-tonnage tensile testing equipment, so that the laboratories of most enterprises, universities and research institutes have the corresponding implementation conditions. Moreover, when conducting small-size specimen tests, the specimen processing cycle is short and the material consumption is low, which significantly reduces the test cost.

[0057] Optionally, in steps S1 and S4, the small-size tensile test involves taking samples from two or more locations with different thicknesses along the plate thickness direction for testing. For example... Figure 1 As shown, the mechanical properties of high-strength thick plates vary greatly along the thickness direction. Using test results from a single location can only represent the performance of that local area, and using it to evaluate the overall performance can easily introduce large deviations. Specifically, the small-size tensile test takes samples from two or more locations with different thicknesses along the thickness direction and then tests them. The average value is then used for fitting in step S3 or prediction in step S5, thereby providing more accurate and representative input data for the prediction model and improving the accuracy of the prediction results.

[0058] In this example, the thickness t of the high-strength plate ranges from 30mm to 100mm. Different sampling locations are selected for high-strength plates of different thicknesses to improve the accuracy of the prediction results.

[0059] Specifically, for high-strength thick plates with a thickness of 30mm ≤ t < 60mm, the sampling locations for small-scale tensile tests are the surface and the center. The surface location refers to the position where the axis of the standard round bar tensile specimen is close to the surface, just large enough to allow sampling. The center location refers to the position where the axis of the standard round bar tensile specimen coincides with the centerline of the high-strength thick plate along its thickness direction. For high-strength thick plates with a thickness less than 60mm, the performance gradient from the surface to the center is relatively gentle, and about 1 / 4 of the way to the surface is considered close. Selecting the two most representative points—the surface (where strength and plasticity are usually the highest) and the center (where strength and plasticity are usually the lowest)—and averaging their values ​​can effectively capture the performance distribution trend and overall level of the high-strength thick plate, thus reducing the workload of sampling and testing while ensuring prediction accuracy.

[0060] Furthermore, such as Figure 4 As shown, for high-strength thick plates with a thickness of 60mm ≤ t ≤ 100mm, the sampling locations for small-scale tensile tests are the surface, 1 / 4 thickness, and center. The 1 / 4 thickness location refers to the point where the axis of the standard round bar tensile specimen coincides with the 1 / 4 thickness line in the thickness direction of the high-strength thick plate. For very thick high-strength thick plates with a thickness greater than 60mm, the performance gradient is more significant. Therefore, adding a 1 / 4 thickness sampling point increases the detection point on the performance distribution curve by adding a key performance testing point. The predicted strength and plasticity value obtained by averaging the values ​​from the above three sampling points has higher accuracy.

[0061] As an example of the present invention, the prediction method is applicable to the prediction of the strength and plasticity of high-strength thick plates at temperatures ranging from -60°C to room temperature. It should be noted that the high-strength thick plates in this example are mainly used in structures such as ships, offshore platforms, and polar equipment, which often need to operate in low-temperature environments. The low-temperature strength and plasticity of materials is crucial for safety assessment. The prediction method provided in this example can be simultaneously applied to low-temperature environments, thereby facilitating timely understanding of the overall strength and plasticity of high-strength thick plates in low-temperature environments, providing a relevant reference for engineering design and application.

[0062] The high-strength thick plate refers to high-strength steel with a strength of 400MPa to 1000MPa. The high-strength steel is stainless steel or low-alloy steel. The prediction method provided in this example can serve multiple industrial sectors requiring thick high-strength steel plates, such as shipbuilding, marine engineering, construction, and pressure vessels, and has broad application prospects.

[0063] Example 1

[0064] In this embodiment, based on the requirements for establishing the overall strength and plasticity prediction model, five typical hull steels with different thicknesses and strengths were selected. First, tensile tests of the original plate thickness were carried out at room temperature and -60°C. Then, small-sized samples were taken along the plate thickness direction to carry out small-sized tensile tests, and the strength and plasticity data of the original plate thickness samples and the small-sized samples were obtained.

[0065] Specifically, it includes:

[0066] Five typical ship hull steels were selected for research: 400MPa grade stainless steel (30mm thick), 400MPa grade low-alloy steel (32mm thick), 600MPa grade low-alloy steel (35mm thick), 800MPa grade low-alloy steel (80mm thick), and 1000MPa grade low-alloy steel (70mm thick). Figure 2 The requirement is to process original plate thickness specimens and conduct original plate thickness tensile tests on a 5000-ton large tensile testing machine to measure yield strength, tensile strength and elongation after fracture.

[0067] On the same steel plate sampled for the original thickness tensile test, according to Figure 3 The requirements are as follows: Take surface samples (at the surface), t / 4 samples (at 1 / 4 of the thickness of a plate thicker than 60mm), and center samples (at the center). Figure 3 The material is required to be processed into standard round bar tensile specimens with a parallel section diameter of 10 mm. Tensile tests of small size at room temperature and -60℃ are carried out according to GB / T228.1-2010 "Metallic materials - Tensile testing - Part 1: Room temperature test method" and GB / T13239-2006 "Metallic materials - Low temperature tensile test method" to obtain the mechanical property parameters such as yield strength, tensile strength and elongation after fracture. The specific results of the original plate thickness tensile test and small size tensile test are shown in Table 1.

[0068] Table 1. List of results of tensile tests on original thickness and small-size plates.

[0069] like Figures 5-7 As shown, the mean values ​​of the strength and plasticity parameters obtained from the small-size tensile tests in Table 1 are used as the horizontal axis, and the values ​​of the strength and plasticity parameters obtained from the original plate thickness tensile tests are used as the vertical axis. Predictive models for yield strength, tensile strength, and elongation are established respectively, as shown in equations (1)-(3). After analysis and fitting, we obtain a1=1.01, b1=-6.1, a2=0.97, b2=14, a3=0.98, b3=0.56. Substituting these values ​​into equations (1)-(3) respectively, we can obtain:

[0070] σ s大 =1.01·σ s小 -6.1 (4)

[0071] σ m大 =0.97·σ m小 +14 (5)

[0072] A 大 =0.98·A 小 +0.56 (6)

[0073] Analysis shows that, for example Figures 5-7 As shown, the strength and plasticity of the original plate thickness sample and the small-sized sample have a strong linear correlation, with a correlation coefficient greater than 0.99.

[0074] To verify the accuracy of the above prediction model, a 60mm thick 700MPa high-strength steel was selected for verification. The original thickness strength and plasticity and the small-size strength and plasticity were measured (and the mean was calculated). The original thickness strength and plasticity were calculated according to the prediction model of this patent and compared with the measured value of the original thickness. The results are shown in Table 2. The maximum error does not exceed 1%. However, the results obtained by using specific positions such as the surface, core or 1 / 4 of the thickness deviate significantly from the measured value of the original thickness, with a larger error. This indicates that the prediction model has better stability and accuracy.

[0075] Table 2 Verification Results of 60mm Thick 700MPa Grade Steel Plate

[0076] As can be seen from Table 2, the predicted values ​​of the original plate thickness strength and plasticity obtained by the prediction method provided in this example have an error of less than 1% compared with the actual measured values ​​of the original plate thickness. However, the results obtained by using specific locations such as the surface, core, or 1 / 4 of the plate thickness deviate significantly from the actual measured values ​​of the original plate thickness, with a larger error.

[0077] As can be seen, the prediction model provided in this example can accurately predict the strength and plasticity properties of high-strength thick plates. After the prediction model is established, subsequent predictions only require small-sized specimens, which enables conventional laboratories to easily predict the strength and plasticity of high-strength thick plates. This avoids the dependence on large-tonnage tensile testing equipment for the strength and plasticity of high-strength thick plates, and reduces test conditions and costs.

[0078] The prediction method involved in this invention has a clear principle and is simple in method. It can be implemented using a commonly used 10-ton multi-functional tensile testing machine, which existing conventional laboratories have the necessary testing conditions for, eliminating the need for separately designed and manufactured tooling. However, for original plate thickness samples, equipment capacity exceeding 300 tons, or even 500 tons, is required. Only a few domestic units possess the necessary testing capabilities, and such testing is time-consuming and labor-intensive. Furthermore, low-temperature performance testing of original plate thickness samples often requires the design of extremely complex tooling. In this example, after the prediction model is established, accurate predictions can be made directly using small-sized samples, significantly reducing the design and usage time and cost of tooling. Therefore, the prediction method provided in this example has a better implementation environment and lower testing costs compared to existing technologies.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit 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 overall strength and plasticity of high-strength steel thick plates, characterized in that, Includes the following steps: Step S1: For high-strength thick plates, tensile tests of the original plate thickness and tensile tests of small dimensions are carried out respectively to obtain mechanical property parameters under the two test conditions. The mechanical property parameters include one or more of yield strength, tensile strength and elongation. Step S2: Analyze the correlation between the same parameters obtained from the original thickness tensile test and the small-size tensile test, and establish a predictive model for mechanical properties based on the correlation: s s大 =a1·s s小 +b1 (1) σ m大 =a2·σ m小 +b2 (2) A 大 =a3·A 小 +b3 (3) Where, σ s大 σ is the yield strength detected in the tensile test of the original plate thickness. s小 σ represents the yield strength detected in small-scale tests. m大 σ is the tensile strength detected in the tensile test of the original plate thickness. m小 A represents the tensile strength detected in small-scale tests. 大 A represents the elongation detected in the tensile test of the original plate thickness. 小 The elongation detected in small-size tests, a1, b1, a2, b2, a3, and b3 are all undetermined coefficients; where the unit of strength is MPa and the unit of elongation is percentage; Step S3: Substitute the yield strength detected in step S1 into equation (1), the tensile strength into equation (2), and the elongation into equation (3) to obtain the values ​​of a1, b1, a2, b2, a3, and b3.

2. The method for predicting the overall strength and plasticity of high-strength steel thick plates as described in claim 1, characterized in that, Following step S3, the following is also included: Step S4: For the high-strength thick plate to be tested, take two or more samples of different thicknesses along the thickness direction of the plate and perform small-size tensile tests. Take the average value of the yield strength, tensile strength and elongation of the samples. Step S5: Take the average yield strength from step S4 as σ in equation (1). s小 σ is calculated s大 That is, the predicted value of the full-thickness yield strength of the high-strength thick plate; and / or, the average tensile strength in step S4 is taken as σ in equation (2). m小 σ is calculated m大 This is the predicted value of the tensile strength of the high-strength thick plate over its full thickness; the average elongation in step S4 is taken as A in equation (3). 小 Calculate and obtain A 大 This is the predicted value of the full thickness elongation of a high-strength thick plate.

3. The method for predicting the overall strength and plasticity of high-strength steel thick plates as described in claim 1, characterized in that, In step S1, the original plate thickness tensile test is performed by sampling the full thickness of the high-strength thick plate. The gauge length of the full-thickness specimen is more than 3 times the plate thickness, and the width is more than 2 times the plate thickness.

4. The method for predicting the overall strength and plasticity of high-strength steel thick plates as described in claim 2, characterized in that, In steps S1 and S4, the specimens used in the small-size test are standard round bar tensile specimens.

5. The method for predicting the overall strength and plasticity of high-strength steel thick plates as described in claim 4, characterized in that, The thickness t of the high-strength thick plate ranges from 30mm to 100mm.

6. The method for predicting the overall strength and plasticity of high-strength steel thick plates as described in claim 5, characterized in that, In steps S1 and S4, the small-size tensile test involves taking samples from two or more locations with different thicknesses along the thickness direction of the plate for testing.

7. The method for predicting the overall strength and plasticity of high-strength steel thick plates as described in claim 6, characterized in that, For high-strength thick plates with a thickness of 30mm≤t<60mm, the sampling locations for small-size tensile tests are the surface and the center.

8. The method for predicting the overall strength and plasticity of high-strength steel thick plates as described in claim 6, characterized in that, For high-strength thick plates with a thickness of 60mm≤t≤100mm, the sampling locations for small-size tensile tests are the surface, 1 / 4 of the thickness, and the center.

9. The method for predicting the overall strength and ductility of high-strength steel thick plates as described in any one of claims 1-8, characterized in that, The prediction method is applicable to the prediction of the strength and plasticity of high-strength thick plates at temperatures ranging from -60°C to room temperature.

10. The method for predicting the overall strength and plasticity of high-strength steel thick plates as described in claim 1, characterized in that, a1=1.01, b1=-6.1, a2=0.97, b2=14, a3=0.98, b3=0.56.

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