Rapid strengthening method for hot-rolled ultrahigh-strength steel based on pulsed electric field treatment

Abstract

The invention discloses a method for rapidly strengthening hot-rolled ultrahigh-strength steel based on pulsed electric field treatment, and belongs to the technical field of metal material processing and performance improvement. The method comprises the following steps: preparing an ultrahigh-strength steel hot-rolled plate; the ultrahigh-strength steel hot-rolled plate is cut into a stretching standard part; the stretching standard part is preprocessed; arranging the stretching standard part on a pulse electric field generating device; performing pulsed electric field treatment on the tensile standard part according to preset pulsed electric field parameters; removing an oxide layer on the surface of the tensile standard component and measuring the thickness of the tensile standard component. The pulsed electric field treatment is applied to the subsequent treatment of the hot-rolled ultrahigh-strength steel for the first time, and compared with a traditional heat treatment process, the process time is remarkably shortened, the tensile strength of the material is effectively improved, and the strength and plasticity levels of a heat treatment process sample are achieved; the method is more environment-friendly and energy-saving, and a green and efficient novel solution is provided for preparing the ultrahigh-strength steel with excellent comprehensive performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material processing and performance improvement, and specifically relates to a method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment. Background Art

[0002] Ultra-high-strength steels are widely used in the automotive, construction, aerospace and other fields due to their excellent mechanical properties. However, traditional heat treatment methods face many challenges in improving the strength and toughness of these steels. For example, quenching and tempering (QT) and quenching and partitioning (QP) processes can improve the mechanical properties of materials to a certain extent, but they are often accompanied by longer process cycles, higher energy consumption and environmental impacts. In addition, inappropriate process parameters such as long heat treatment may lead to grain growth, thereby affecting the toughness and ductility of the material.

[0003] Pulsed current treatment is a novel treatment method that can improve a material's microstructure and macroscopic mechanical properties. Specifically, it improves grain size, resulting in grain refinement; optimizes the material's internal structure, reducing microdefects; and repairs microcracks, increasing its service life. Compared with traditional heat treatment processes, pulsed current treatment can achieve the same heat-treated material properties in a fraction of the time. However, the application of pulsed electric field treatment to improve the performance of ultra-high-strength steel is still in its early stages of exploration and requires sufficient experimental data to study and optimize process parameters and microstructure control. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and provide a method for rapid strengthening of hot-rolled ultra-high-strength steel based on pulsed electric field treatment, so as to solve the problems of limited performance improvement effect, long process time, high energy consumption and poor environmental protection of existing ultra-high-strength steel in traditional processes, as well as insufficient optimization of pulsed electric field treatment parameters and challenges of compatibility with existing processes.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for rapid strengthening of hot-rolled ultra-high strength steel based on pulsed electric field treatment, comprising the following steps:

[0007] S1. Preparation of ultra-high strength steel hot-rolled plates;

[0008] S2, cutting the ultra-high strength steel hot-rolled plate into tensile standard parts;

[0009] S3. Pre-processing the tensile standard parts;

[0010] S4, placing the tensile standard component on a pulse electric field generating device;

[0011] S5. performing pulse electric field treatment on the stretching standard component according to preset pulse electric field parameters;

[0012] S6. Remove the oxide layer on the surface of the tensile standard part and measure the thickness of the tensile standard part.

[0013] Furthermore, in S1, preparing an ultra-high strength steel hot-rolled plate comprises:

[0014] Hot rolling the ultra-high strength steel after continuous casting to produce ultra-high strength steel hot-rolled plates;

[0015] Among them, hot rolling operations include: heating, width setting, rough rolling, finishing rolling, cooling, coiling and shearing.

[0016] Furthermore, in S2, the ultra-high strength steel hot-rolled plate is cut using a wire electric discharge machine to obtain a tensile standard part;

[0017] The thickness of the tensile standard part is 2 mm, and the gauge length b0 is 8 mm.

[0018] Furthermore, in S3, preprocessing specifically includes:

[0019] The upper and lower surfaces of the tensile standard parts are ground and polished, and then placed in an alcohol solution for ultrasonic cleaning. Finally, the tensile standard parts that have completed ultrasonic cleaning are placed in a vacuum drying oven for drying.

[0020] Furthermore, in S4, the stretching standard component is placed on the pulse electric field generating device, specifically including:

[0021] Two identical clamps are selected, the two clamps are electrically connected to the pulse electric field generating device respectively, and the two clamps are clamped at both ends of the stretching standard part respectively, and the center of the stretching standard part along the length direction is located at the center position of the two clamps.

[0022] Furthermore, a thermocouple is connected to the geometric center of the surface of the tensile standard part.

[0023] Furthermore, in S5, the preset pulse electric field parameters include:

[0024] Adopt bidirectional pulse mode, 5 bidirectional pulses form a group;

[0025] The interval between pulse groups is 500ms to 100ms;

[0026] The pulse frequency is 50Hz;

[0027] The pulse voltage is 2V~2.4V.

[0028] Furthermore, in S6, the oxide layers on the upper and lower surfaces of the tensile standard part are removed by grinding.

[0029] The method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment provided by the present invention has the following characteristics:

[0030] Beneficial effects:

[0031] 1. The present invention applies pulsed electric field treatment to the subsequent treatment of hot-rolled ultra-high-strength steel for the first time. Compared with the traditional heat treatment process (quenching-tempering), it significantly shortens the process time, effectively improves the tensile strength of the material, and reaches the strength and plasticity level of heat-treated process samples. In addition, the method of the present invention is more environmentally friendly and energy-saving, providing a green and efficient new solution for the preparation of ultra-high-strength steel with excellent comprehensive performance.

[0032] 2. The present invention proposes a new environmentally friendly pulsed electric field treatment technology to precisely control the microstructure of the material, avoid the grain growth problem in traditional heat treatment, enhance the mechanical properties of the material in a very short time, and provide a new efficient, energy-saving and environmentally friendly approach for the research and development and application of high-performance steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a comparison chart of the tensile properties of ultra-high strength steel hot-rolled plates and samples after heat treatment and pulse electric field treatment; Figure 1 UT is the original comparison sample, which represents the hot-rolled ultra-high strength steel tensile standard sample; QT900 represents quenching at 900°C; QT870-24 represents the sample obtained by holding at 870°C for 24 minutes; EPT1 represents the sample in Example 2; EPT2 represents the sample in Example 3; EPT3 represents the sample in Example 4;

[0034] Figure 2 The present invention implements the pulse electric field treatment schematic diagram in 1;

[0035] Figure 3 This is a microstructure picture of the ultra-high strength steel (EPT3) in Example 4 of the present invention;

[0036] Figure 4 This is a microstructure picture of the hot-rolled ultra-high strength steel (UT) in Comparative Example 1 of the present invention.

[0037] Figure 5 This is a flow chart of a method for rapid strengthening of hot-rolled ultra-high strength steel based on pulsed electric field treatment according to Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0039] Example 1

[0040] This embodiment provides a method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment. By optimizing the setting of the pulse electric field treatment process, the material structure can be improved and the performance of the material can be significantly improved. Finally, ultra-high strength steel with excellent performance can be obtained by different parameters. Figure 5 , which specifically includes the following:

[0041] S1. Preparation of ultra-high strength steel hot-rolled plates;

[0042] The ultra-high strength steel in this embodiment is preferably 34MnB5, and the ultra-high strength steel is continuously cast and then hot rolled to produce an ultra-high strength steel hot-rolled plate.

[0043] Among them, hot rolling operations include: heating, width setting, rough rolling, finishing rolling, cooling, coiling and shearing.

[0044] S2, cutting the ultra-high strength steel hot-rolled plate into tensile standard parts;

[0045] In this embodiment, an electric spark wire cutting machine is used to cut the ultra-high strength steel hot-rolled plate to obtain a tensile standard part;

[0046] Among them, the thickness of the tensile standard part is 2mm and the gauge length b0 is 8mm.

[0047] S3. Pre-processing the tensile standard parts;

[0048] The preprocessing in this embodiment specifically includes:

[0049] The upper and lower surfaces of the tensile standard parts are ground and polished, and the ground and polished tensile standard parts are placed in an alcohol solution for ultrasonic cleaning. Finally, the ultrasonically cleaned tensile standard parts are placed in a vacuum drying oven for drying.

[0050] S4, placing the tensile standard component on a pulse electric field generating device;

[0051] For the placement of the tensile standard parts in this embodiment, refer to Figure 2 , specifically including:

[0052] Select two identical clamps, electrically connect the two clamps to the pulse electric field generator respectively, and clamp the two clamps at the two ends of the tensile standard part respectively, and the center of the tensile standard part along the length direction is located at the center position of the two clamps, so that the parallel section of the tensile standard part sample is fully circulated by current.

[0053] In order to further collect the temperature information of the tensile standard part, a thermocouple is connected at the geometric center of the surface of the tensile standard part.

[0054] S5. performing pulse electric field treatment on the stretching standard component according to preset pulse electric field parameters;

[0055] Preset pulsed electric field parameters include:

[0056] A bidirectional pulse mode is used, with 5 bidirectional pulses as a group; the purpose of setting this parameter is to form a uniform and refined basic microstructure.

[0057] The interval between pulse groups is 100ms to 500ms. The purpose of setting this parameter is to allow the material enough time to adjust and recover its internal structure to avoid stress deformation or cracking.

[0058] The pulse frequency is 50 Hz; the purpose of setting this parameter is to ensure that the energy input between each pulse group is consistent.

[0059] The pulse voltage is 2V to 2.4V. The purpose of setting this parameter is to ensure that the material obtains enough energy to achieve the phase transformation from pearlite and ferrite to austenite, and then transform into high-strength martensite during the subsequent cooling process.

[0060] S6. Remove the oxide layer on the surface of the tensile standard part and measure the thickness of the tensile standard part;

[0061] In this embodiment, the upper and lower surfaces of the tensile standard sample after the pulse electric field treatment are polished to remove the oxide layer, and the thickness of the tensile standard sample is remeasured to ensure that an accurate tensile strength value is obtained through the tensile test.

[0062] Example 2

[0063] This embodiment is a preferred embodiment of the solution in Example 1. This embodiment improves the material structure through a pulsed electric field treatment process, significantly improves the material performance, and obtains ultra-high-strength steel with excellent performance through different parameters. The embodiment specifically includes the following steps:

[0064] T1. Preparation of ultra-high strength steel hot-rolled plates;

[0065] Among them, the ultra-high strength steel is 34MnB5, which is hot rolled after continuous casting; specifically, the hot rolling process is heating, width setting, rough rolling, finish rolling, cooling, coiling and shearing.

[0066] T2. According to the standard GB / T 228.1-2021, use an electric spark wire cutting machine to cut the ultra-high strength steel hot-rolled plate into tensile standard parts. The thickness of the tensile standard parts is 2 mm and the gauge length b0 is 8 mm.

[0067] T3. Pre-process several standard tensile parts;

[0068] Specifically, the upper and lower surfaces of the tensile standard parts are ground and polished, and the ground and polished tensile standard parts are placed in an alcohol solution for ultrasonic cleaning. Finally, the ultrasonically cleaned tensile standard parts are placed in a vacuum drying oven for drying.

[0069] T4, placing the pre-treated tensile standard into a pulsed electric field;

[0070] Specifically, two identical fixtures are selected, each electrically connected to a pulsed electric field generator. The fixtures are then clamped at either end of a tensile standard, with the center of the standard length located at the center of the two fixtures. This ensures that the current flows fully through the parallel sections of the tensile standard sample. A thermocouple is connected at the geometric center of the surface of the tensile standard to collect its temperature information.

[0071] T5 performs pulse electric field treatment on the tensile standard parts according to the preset pulse electric field parameters;

[0072] Specifically, in order to form a uniform and refined basic microstructure, a bidirectional pulse mode is adopted, with 5 bidirectional pulses in a group, and the pulse frequency is set to 50Hz to ensure that the energy input between each pulse group is consistent; the pulse voltage is set to 2.2V to ensure that the material obtains sufficient energy to realize the phase transformation of pearlite and ferrite to austenite, and then transforms into high-strength martensite during the subsequent cooling process; the interval between groups is set to 50ms, so that the material has enough time to adjust and recover the internal structure to avoid stress deformation or cracking.

[0073] T6. Polish the upper and lower surfaces of the tensile standard sample after pulse electric field treatment to remove the oxide layer, and remeasure the sample thickness to ensure that the tensile strength value is accurately obtained through the tensile test.

[0074] Example 3

[0075] This embodiment is a preferred embodiment of the solution in Example 1. This embodiment improves the material structure through a pulsed electric field treatment process, significantly improves the material performance, and obtains ultra-high-strength steel with excellent performance through different parameters. The embodiment specifically includes the following steps:

[0076] A1. Preparation of ultra-high strength steel hot-rolled plates;

[0077] Among them, the ultra-high strength steel is 34MnB5, which is hot rolled after continuous casting; specifically, the hot rolling process is heating, width setting, rough rolling, finish rolling, cooling, coiling and shearing.

[0078] A2. According to the standard GB / T 228.1-2021, ultra-high-strength steel hot-rolled plates are cut into tensile standard parts using a wire-cut electric discharge machine. The thickness of the tensile standard parts is 2 mm and the gauge length b0 is 8 mm.

[0079] A3. Pre-process several standard tensile parts;

[0080] Specifically, the upper and lower surfaces of the tensile standard parts are ground and polished, and the ground and polished tensile standard parts are placed in an alcohol solution for ultrasonic cleaning. Finally, the ultrasonically cleaned tensile standard parts are placed in a vacuum drying oven for drying.

[0081] A4. Place the pre-treated tensile standard into a pulsed electric field;

[0082] Specifically, two identical fixtures are selected, each electrically connected to a pulsed electric field generator. The fixtures are then clamped at either end of a tensile standard, with the center of the standard length located at the center of the two fixtures. This ensures that the current flows fully through the parallel sections of the tensile standard sample. A thermocouple is connected at the geometric center of the surface of the tensile standard to collect its temperature information.

[0083] A5 performs pulse electric field treatment on the tensile standard component according to preset pulse electric field parameters;

[0084] Specifically, in order to form a uniform and refined basic microstructure, a bidirectional pulse mode is adopted, with 5 bidirectional pulses in a group, and the pulse frequency is set to 50Hz to ensure that the energy input between each pulse group is consistent; the pulse voltage is set to 2.3V to ensure that the material obtains sufficient energy to realize the phase transformation of pearlite and ferrite to austenite, and then transforms into high-strength martensite during the subsequent cooling process; the interval between groups is set to 50ms, so that the material has enough time to adjust and recover the internal structure to avoid stress deformation or cracking.

[0085] A6. Polish the upper and lower surfaces of the tensile standard sample after pulse electric field treatment to remove the oxide layer, and remeasure the sample thickness to ensure that the tensile strength value is accurately obtained through the tensile test.

[0086] Example 4

[0087] This embodiment is a preferred embodiment of the solution in embodiment 1. This embodiment improves the material structure through the pulse electric field treatment process, significantly improves the performance of the material, and obtains ultra-high strength steel with excellent performance through different parameters. The microstructure is as follows Figure 3As shown, it is composed of high-strength martensite grains, which specifically includes the following steps:

[0088] B1. Preparation of ultra-high strength steel hot-rolled plates;

[0089] Among them, the ultra-high strength steel is 34MnB5, which is hot rolled after continuous casting; specifically, the hot rolling process is heating, width setting, rough rolling, finish rolling, cooling, coiling and shearing.

[0090] B2. According to the standard GB / T 228.1-2021, ultra-high-strength steel hot-rolled plates are cut into tensile standard parts using a wire-cut electric discharge machine. The thickness of the tensile standard parts is 2 mm and the gauge length b0 is 8 mm.

[0091] B3. Pre-process several standard tensile parts;

[0092] Specifically, the upper and lower surfaces of the tensile standard parts are ground and polished, and the ground and polished tensile standard parts are placed in an alcohol solution for ultrasonic cleaning. Finally, the ultrasonically cleaned tensile standard parts are placed in a vacuum drying oven for drying.

[0093] B4. Place the pre-treated tensile standard into the pulsed electric field;

[0094] Specifically, two identical fixtures are selected, each electrically connected to a pulsed electric field generator. The fixtures are then clamped at either end of a tensile standard, with the center of the standard length located at the center of the two fixtures. This ensures that the current flows fully through the parallel sections of the tensile standard sample. A thermocouple is connected at the geometric center of the surface of the tensile standard to collect its temperature information.

[0095] B5 performs pulse electric field treatment on the tensile standard component according to preset pulse electric field parameters;

[0096] Specifically, in order to form a uniform and refined basic microstructure, a bidirectional pulse mode is adopted, with 5 bidirectional pulses in a group, and the pulse frequency is set to 50 Hz to ensure that the energy input between each pulse group is consistent; the pulse voltage is set to 2.4 V to ensure that the material obtains sufficient energy to realize the phase transformation of pearlite and ferrite to austenite, and then transforms into high-strength martensite during the subsequent cooling process; the interval between groups is set to 50 ms, so that the material has enough time to adjust and recover the internal structure to avoid stress deformation or cracking.

[0097] B6. Polish the upper and lower surfaces of the tensile standard sample after pulse electric field treatment to remove the oxide layer, and remeasure the sample thickness to ensure that the tensile strength value is accurately obtained through the tensile test.

[0098] Comparative Example 1

[0099] C1. Preparation of ultra-high strength steel hot-rolled plates;

[0100] The ultra-high strength steel is 34MnB5, which is hot rolled after continuous casting;

[0101] Specifically, the hot rolling process includes heating, width setting, rough rolling, finish rolling, cooling, coiling and shearing.

[0102] C2. Using a wire-cut electric discharge machine (EDM) according to GB / T 228.1-2021, cut ultra-high-strength steel hot-rolled plates into standard tensile parts. The thickness of the standard tensile parts is 2 mm, and the gauge length b0 is 8 mm.

[0103] C3. Grind and polish the upper and lower surfaces of the tensile standard parts, and then place the ground and polished tensile standard parts in an alcohol solution for ultrasonic cleaning. Finally, place the ultrasonically cleaned tensile standard parts in a vacuum drying oven to dry.

[0104] In order to verify the effect of the method of the present invention, an appropriate amount of hot-rolled ultra-high strength steel tensile standard sample was taken as the original comparison sample UT without pulse electric field treatment. Figure 4 As shown in the figure, it is composed of pearlite and ferrite bands, with excellent plasticity but low strength.

[0105] For the above embodiments of the present invention, refer to Figure 1 In the figure, QT900 indicates that the steel was quenched at 900℃, while QT870-24 was obtained by keeping the steel at 870℃ for 24 minutes. Figure 1 It can be seen that compared with the original hot-rolled plate (original comparison sample UT), the elongation of the ultra-high strength steel after the pulse electric field treatment process decreases, but the elongation is higher than that of the heat-treated sample. After different treatment processes, the tensile strength of the samples is significantly improved, among which the tensile strength of EPT3 is about 1932MPa, which is 205.7% higher than UT. And the pulse electric field treatment process only takes about 100s to achieve an excellent effect similar to the heat treatment process, and under specific parameters, the tensile strength of EPT3 is higher than that of the heat-treated sample. It can be seen from this that the hot-rolled ultra-high strength steel performance improvement technology based on electric field treatment of the present invention significantly improves the comprehensive performance of the material, and the pulse electric field treatment technology is more environmentally friendly and significantly shortens the process time.

[0106] Although the specific embodiments of the invention are described in detail in conjunction with the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for rapid strengthening of hot-rolled ultra-high strength steel based on pulsed electric field treatment, characterized in that: The following steps are involved: S1. Preparation of ultra-high strength steel hot-rolled plates; S2, cutting the ultra-high strength steel hot-rolled plate into tensile standard parts; S3. Pre-processing the tensile standard parts; S4, placing the tensile standard component on a pulse electric field generating device; S5. performing pulse electric field treatment on the stretching standard component according to preset pulse electric field parameters; S6. Remove the oxide layer on the surface of the tensile standard part and measure the thickness of the tensile standard part.

2. The method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment according to claim 1, characterized in that: In S1, preparing the ultra-high strength steel hot-rolled plate comprises: Hot rolling the ultra-high strength steel after continuous casting to produce ultra-high strength steel hot-rolled plates; Among them, hot rolling operations include: heating, width setting, rough rolling, finishing rolling, cooling, coiling and shearing.

3. The method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment according to claim 1, characterized in that: In S2, the ultra-high strength steel hot-rolled plate is cut by a wire-cut electric discharge machine to obtain a tensile standard part; The thickness of the tensile standard part is 2 mm, and the gauge length b0 is 8 mm.

4. The method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment according to claim 1, characterized in that: In S3, the preprocessing specifically includes: The upper and lower surfaces of the tensile standard parts are ground and polished, and then placed in an alcohol solution for ultrasonic cleaning. Finally, the tensile standard parts that have completed ultrasonic cleaning are placed in a vacuum drying oven for drying.

5. The method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment according to claim 1, characterized in that: In the above S4, the stretching standard component is placed on the pulse electric field generating device, which specifically includes: Two identical clamps are selected, the two clamps are electrically connected to the pulse electric field generating device respectively, and the two clamps are clamped at both ends of the stretching standard part respectively, and the center of the stretching standard part along the length direction is located at the center position of the two clamps.

6. The method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment according to claim 5, characterized in that: A thermocouple is connected to the geometric center position of the surface of the stretching standard part.

7. The method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment according to claim 1, characterized in that: In said S5, the preset pulse electric field parameters include: Adopt bidirectional pulse mode, 5 bidirectional pulses form a group; The interval between pulse groups is 500ms to 100ms; The pulse frequency is 50Hz; The pulse voltage is 2V~2.4V.

8. The method for rapid strengthening of hot-rolled ultra-high strength steel based on pulse electric field treatment according to claim 1, characterized in that: In the step S6, the oxide layers on the upper and lower surfaces of the tensile standard component are removed by grinding.

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