High-strength boron steel and heat treatment method and application thereof

Abstract

The invention relates to the field of boron steel materials, and particularly discloses a heat treatment method of high-strength boron steel. According to the high-strength boron steel, the process of annealing, quenching and subzero treatment is adopted, the metallographic structure in the boron steel is optimized, the strength, plasticity and impact resistance of the boron steel are remarkably improved, and meanwhile the service life of the boron steel is further prolonged. The boron steel material with high strength, high plasticity and excellent impact resistance is effectively prepared by utilizing the heat treatment method of the boron steel, and the hydraulic shear blade prepared by utilizing the boron steel material effectively solves the problems of poor hardness, plasticity and impact resistance of a blade of a hydraulic shear in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of boron steel materials, and specifically discloses a high-strength boron steel, its heat treatment method and application. Background Art

[0002] In the fields of automobile manufacturing and repair, hydraulic shears play a crucial role. In the automobile manufacturing process, hydraulic shears are used to precisely cut the metal plates of various automobile parts. For example, in the raw material processing of components such as body frames and car doors, with their powerful shearing force, they can efficiently and high-qualityly complete the plate cutting, ensuring accurate part dimensions and laying a foundation for subsequent assembly. In automobile repair and disassembly work, hydraulic shears are equally indispensable. When a vehicle undergoes severe accident deformation, maintenance personnel can use hydraulic shears to quickly cut open the deformed body structure, facilitating the repair work; and when scrapping and disassembling automobiles, hydraulic shears can quickly cut off the metal frames and parts of the automobiles, achieving efficient recycling.

[0003] However, there are many problems with the current hydraulic shears applied in the automotive field. After frequent high-intensity operations, the shear body structure of automotive hydraulic shears will undergo obvious deformation, which not only affects the shearing accuracy, resulting in large dimensional deviations of the processed products and being unable to meet the requirements of high-precision production; moreover, due to the diverse materials of automotive metal parts and some of them having high strength, the existing blade materials are difficult to withstand such high loads for a long time, leading to a high frequency of blade replacement and affecting work efficiency; the above problems all limit the effectiveness of automotive hydraulic shears in actual work. Therefore, it is of great significance to provide a hydraulic shear with both high strength, high plasticity and strong impact resistance. Summary of the Invention

[0004] Aiming at the problems in the prior art that the blade strength and impact resistance of hydraulic shears are limited and the plasticity is poor, thus resulting in a limited service life of hydraulic shears, the present invention provides a high-strength boron steel, its heat treatment method and application. By using the heat treatment process provided by the present invention to treat boron steel, the purpose of improving the strength, plasticity and impact resistance of boron steel is achieved.

[0005] To achieve the above invention purpose, the present invention provides the following technical solutions.

[0006] The first aspect of the present invention provides a heat treatment method for high-strength boron steel, including the following steps:

[0007] S1. The hot-rolled boron steel is subjected to the first heat preservation at 780°C to 820°C, then heated to 830°C to 850°C for the second heat preservation, and cooled to 580°C to 610°C to obtain the annealed boron steel;

[0008] S2, heating the annealed boron steel to 800° C. to 820° C. for a third heat preservation, then heating the annealed boron steel to 830° C. to 850° C. for a fourth heat preservation, and quenching the boron steel after the heat preservation using a water-based quenching liquid to obtain a quenched boron steel;

[0009] S3, the quenched boron steel is kept at 5°C to 15°C for the fifth time, the boron steel after the heat preservation is kept at -52°C to -48°C for the sixth time, and then the temperature is lowered to -72°C to -68°C for the seventh time, and cooled to obtain high-strength boron steel.

[0010] Currently, vacuum quenching is the primary heat treatment process for boron steel used in hydraulic shears. However, vacuum quenching equipment is expensive and requires subsequent maintenance, including maintenance of the equipment and the vacuum environment, which significantly increases the cost of manufacturing the hydraulic shears. Therefore, in order to reduce manufacturing costs while further improving the strength, plasticity, and impact resistance of boron steel, it is of great significance to propose a heat treatment method for boron steel.

[0011] Compared with the prior art, in the heat treatment method for high-strength boron steel provided by the present invention, in S1, the first holding process can initially homogenize the structure inside the boron steel and reduce the stress generated during the hot rolling process; the second holding process is conducive to further homogenizing the structure in the boron steel, and at the same time can also refine the grains to obtain a fine and uniform pearlite structure, thereby improving the strength of the boron steel and improving the machinability of the boron steel to a certain extent; the present invention further cools the boron steel to a specific temperature after the second holding period, and can also eliminate residual stress in the boron steel, making the boron steel structure more stable, and can further improve the plasticity and impact resistance of the boron steel, thereby increasing the service life of the boron steel.

[0012] In S2, the present invention controls the temperature of the third and fourth insulation times, which not only promotes the transformation of pearlite structure into austenite structure, but also promotes the homogenization of austenite structure, and further utilizes water-based quenching liquid to quench the boron steel, so that the austenite structure is transformed into martensite structure, which greatly improves the strength of the boron steel. At the same time, by quenching with water-based quenching liquid, the martensite structure is also refined to a certain extent, thereby significantly improving the plasticity and impact resistance of the boron steel. In addition, the present invention can also avoid the problem of cracking of boron steel during quenching by selecting water-based quenching liquid to quench boron steel, thereby improving the service life of boron steel.

[0013] In S3, the quenched boron steel is subjected to cryogenic treatment. The fifth low-temperature heat preservation is beneficial to further adjust the internal structure of the boron steel. Then, the sixth and seventh heat preservations are carried out under specific ultra-low temperature conditions, which can transform the retained austenite structure inside the boron steel into martensite structure, greatly improving the strength of the boron steel. Through the above cryogenic treatment method, the grains inside the boron steel can also be refined, reducing the micro-defects inside the boron steel, making the metallographic structure of the boron steel more compact, thereby improving the impact resistance of the boron steel. The dense structure and stable internal structure inside the boron steel are also beneficial for the boron steel to better resist stress during use and extend the service life of the boron steel.

[0014] In the heat treatment method of the high-strength boron steel provided by the present invention, the process of annealing + quenching + cryogenic treatment is adopted, which optimizes the metallographic structure inside the boron steel, significantly improves the strength, plasticity and impact resistance of the boron steel, and at the same time, further extends the service life of the boron steel.

[0015] Preferably, in S1, the hot-rolled boron steel includes the following chemical components by mass percentage: C: 0.33% - 0.37%, Si: 0.15% - 0.35%, Mn: 1.00% - 1.30%, P ≤ 0.035%, S: 0.01% - 0.04%, Cr: 0.45% - 0.65%, B: 0.0005% - 0.003%, Ti ≤ 0.035%, Al: 0.015% - 0.065%, Cu ≤ 0.025%, Ni ≤ 0.3%, Mo: 0.05% - 0.10%, Pb ≤ 0.02%, Sn ≤ 0.03% and As ≤ 0.03%.

[0016] Preferably, in S1, the time of the first heat preservation is 35 min - 45 min.

[0017] Preferably, in S1, the time of the second heat preservation is 230 min - 250 min.

[0018] The present invention limits the time of the first and second heat preservations, which is beneficial to further optimize the metallographic structure of the boron steel, obtain fine and uniform pearlite structure, and further improve the comprehensive performance of the boron steel.

[0019] Preferably, in S1, the hot-rolled boron steel is heated to 780°C - 820°C at a rate of 50°C / h - 70°C / h.

[0020] Preferably, in S1, the heating rate is 50°C / h - 70°C / h.

[0021] The preferred heating rate can avoid the problems of cracking and deformation of the boron steel.

[0022] Preferably, in S1, the condition for cooling is: cooling is carried out by furnace cooling.

[0023] Preferably, in S2, the time for the third heat preservation is 35 min to 45 min.

[0024] Preferably, in S2, the time for the fourth heat preservation is 170 min to 190 min.

[0025] By limiting the time for the third heat preservation and the fourth heat preservation, it can ensure that the pearlite structure inside the boron steel is transformed into a uniform austenite structure to the greatest extent. The sufficient heat preservation time can also ensure that the austenite structure grows sufficiently to obtain an austenite structure of appropriate size, thereby improving the comprehensive performance of the boron steel.

[0026] Preferably, in S2, the heating rate is 50 °C / h to 70 °C / h.

[0027] An appropriate heating rate can avoid the problems of cracking and deformation of the boron steel.

[0028] Preferably, in S2, the model of the water-based quenching liquid is SJ1304.

[0029] Preferably, in S2, the quenching time is 30 min to 35 min.

[0030] By selecting a specific water-based quenching liquid and quenching time, it is beneficial to transform the austenite structure in the boron steel into a martensite structure of a specific size, and can also avoid the problem of cracking of the boron steel during quenching, improving the service life of the boron steel.

[0031] It should be further noted that the temperature of the fourth heat preservation is the quenching temperature.

[0032] Preferably, in S3, the time for the fifth heat preservation is 55 min to 65 min.

[0033] Preferably, in S3, the time for the sixth heat preservation is 55 min to 65 min.

[0034] Preferably, in S3, the time for the seventh heat preservation is 230 min to 250 min.

[0035] By limiting the time for the preferably fifth heat preservation, sixth heat preservation and seventh heat preservation, it is beneficial to obtain a uniform and fine martensite structure in the boron steel, greatly improving the strength, plasticity and impact resistance of the boron steel.

[0036] The second aspect of the present invention provides a high-strength boron steel, which is obtained by heat treatment using the above heat treatment method for high-strength boron steel.

[0037] The third aspect of the present invention provides the application of the above high-strength boron steel in the preparation of hydraulic shears.

[0038] In summary, the present invention provides a heat treatment method for high-strength boron steel. By adopting the process of annealing + quenching + cryogenic treatment, a boron steel material with high strength, high plasticity and excellent impact resistance is effectively obtained. The hydraulic shear blades made of this boron steel material effectively solve the problems of poor hardness, plasticity and impact resistance of the blades of hydraulic shears in the prior art. Brief Description of the Drawings

[0039] Figure 1 It is the metallographic structure diagram of the boron steel heat-treated in Example 1. Detailed Embodiments

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] Example 1

[0042] This example provides a heat treatment process for high-strength boron steel, which specifically includes the following steps:

[0043] S1. Heat the hot-rolled boron steel at a rate of 50 °C / h to 780 °C and hold for 35 min, then heat it at a rate of 50 °C / h to 850 °C and hold for 250 min, and cool it in the furnace to 580 °C to obtain the annealed boron steel.

[0044] S2. Heat the annealed boron steel at a rate of 50 °C / h to 820 °C and hold for 35 min, then heat it at a rate of 50 °C / h to 850 °C and hold for 190 min, and quench the boron steel after the holding ends with the water-based quenching liquid SJ1304 for 30 min to obtain the quenched boron steel.

[0045] S3. Keep the quenched boron steel at 5 °C for 65 min, keep the boron steel after the holding ends at -48 °C for 55 min, then cool it to -72 °C and hold for 230 min, and then cool it to obtain the high-strength boron steel.

[0046] The boron steel after hot rolling includes chemical components with the following mass percentages: C: 0.37%, Si: 0.15%, Mn: 1.00%, P: 0.035%, S: 0.04%, Cr: 0.45%, B: 0.0005%, Ti: 0.035%, Al: 0.065%, Cu: 0.025%, Ni: 0.3%, Mo: 0.10%, Pb: 0.02%, Sn: 0.03% and As: 0.03%.

[0047] Example 2

[0048] This example provides a heat treatment process for high-strength boron steel, which specifically includes the following steps:

[0049] S1. Heat the boron steel after hot rolling at a rate of 50 °C / h to 820 °C and hold for 35 min, then heat it at a rate of 50 °C / h to 830 °C and hold for 250 min, and then cool it in the furnace to 610 °C to obtain annealed boron steel;

[0050] S2. Heat the annealed boron steel at a rate of 50 °C / h to 800 °C and hold for 35 min, then heat it at a rate of 50 °C / h to 830 °C and hold for 190 min, and quench the boron steel after holding with the water-based quenching liquid SJ1304 for 30 min to obtain quenched boron steel;

[0051] S3. Hold the quenched boron steel at 15 °C for 65 min, then hold the boron steel after holding at -52 °C for 55 min, and then cool it to -68 °C and hold for 230 min, and then cool it to obtain high-strength boron steel;

[0052] The boron steel after hot rolling includes chemical components with the following mass percentages: C: 0.33%, Si: 0.35%, Mn: 1.30%, P: 0.025%, S: 0.01%, Cr: 0.65%, B: 0.003%, Ti: 0.015%, Al: 0.015%, Cu: 0.020%, Ni: 0.1%, Mo: 0.05%, Pb: 0.01%, Sn: 0.02% and As: 0.015%.

[0053] Example 3

[0054] This example provides a heat treatment process for high-strength boron steel, which specifically includes the following steps:

[0055] S1. Heat the boron steel after hot rolling at a rate of 60 °C / h to 800 °C and hold for 40 min, then heat it at a rate of 60 °C / h to 840 °C and hold for 240 min, and then cool it in the furnace to 600 °C to obtain annealed boron steel;

[0056] S2. Heat the annealed boron steel at a rate of 50 °C / h to 810 °C and hold for 40 min, then heat at a rate of 60 °C / h to 840 °C and hold for 180 min. Quench the boron steel after the holding is completed using the water-based quenching liquid SJ1304. The quenching time is 32 min to obtain the quenched boron steel;

[0057] S3. Hold the quenched boron steel at 10 °C for 60 min, hold the boron steel after the holding is completed at -50 °C for 60 min, then cool to -70 °C and hold for 240 min, and then cool to obtain the high-strength boron steel;

[0058] The boron steel after hot rolling includes the following chemical components by mass percentage: C: 0.35%, Si: 0.25%, Mn: 1.20%, P: 0.015%, S: 0.02%, Cr: 0.55%, B: 0.001%, Ti: 0.005%, Al: 0.035%, Cu: 0.010%, Ni: 0.05%, Mo: 0.07%, Pb: 0.005%, Sn: 0.01%, and As: 0.01%.

[0059] Comparative Example 1

[0060] This comparative example provides a heat treatment method for boron steel. The difference from Example 1 is that in S1, the temperature during the second holding is increased to 880 °C, and other steps and components remain unchanged. The specific steps are as follows:

[0061] S1. Heat the hot-rolled boron steel at a rate of 50 °C / h to 780 °C and hold for 35 min, then heat at a rate of 50 °C / h to 880 °C and hold for 250 min, and then cool with the furnace to 580 °C to obtain the annealed boron steel;

[0062] S2. Heat the annealed boron steel at a rate of 50 °C / h to 820 °C and hold for 35 min, then heat at a rate of 50 °C / h to 850 °C and hold for 190 min. Quench the boron steel after the holding is completed using the water-based quenching liquid SJ1304. The quenching time is 30 min to obtain the quenched boron steel;

[0063] S3. Hold the quenched boron steel at 5 °C for 65 min, hold the boron steel after the holding is completed at -48 °C for 55 min, then cool to -72 °C and hold for 230 min, and then cool to obtain the high-strength boron steel;

[0064] The boron steel after hot rolling comprises the following chemical components by mass percentage: C: 0.37%, Si: 0.15%, Mn: 1.00%, P: 0.035%, S: 0.04%, Cr: 0.45%, B: 0.0005%, Ti: 0.035%, Al: 0.065%, Cu: 0.025%, Ni: 0.3%, Mo: 0.10%, Pb: 0.02%, Sn: 0.03% and As: 0.03%.

[0065] Comparative Example 2

[0066] This comparative example provides a heat treatment method for boron steel, which is different from that of Example 1 in that: in S2, only one heat preservation is carried out, and other steps and components remain unchanged. The specific steps are as follows:

[0067] S1. Heat the boron steel after hot rolling to 780 °C at a rate of 50 °C / h and keep it warm for 35 min, then heat it to 850 °C at a rate of 50 °C / h and keep it warm for 250 min, and then cool it with the furnace, and cool it down to 580 °C to obtain annealed boron steel;

[0068] S2. Heat the annealed boron steel to 820 °C at a rate of 50 °C / h and keep it warm for 35 min, and quench the boron steel after heat preservation with the water-based quenching liquid SJ1304, and the quenching time is 30 min to obtain quenched boron steel;

[0069] S3. Keep the quenched boron steel at 5 °C for 65 min, keep the boron steel after heat preservation at -48 °C for 55 min, and then cool it down to -72 °C and keep it warm for 230 min, and then cool it to obtain high-strength boron steel;

[0070] The boron steel after hot rolling comprises the following chemical components by mass percentage: C: 0.37%, Si: 0.15%, Mn: 1.00%, P: 0.035%, S: 0.04%, Cr: 0.45%, B: 0.0005%, Ti: 0.035%, Al: 0.065%, Cu: 0.025%, Ni: 0.3%, Mo: 0.10%, Pb: 0.02%, Sn: 0.03% and As: 0.03%.

[0071] Comparative Example 3

[0072] This comparative example provides a heat treatment method for boron steel, which is different from that of Example 1 in that: in S1, it is cooled down to 650 °C, and other steps and components remain unchanged. The specific steps are as follows:

[0073] S1. Heat the boron steel after hot rolling to 780 °C at a rate of 50 °C / h and keep it warm for 35 min, then heat it to 850 °C at a rate of 50 °C / h and keep it warm for 250 min, and then cool it with the furnace, and cool it down to 650 °C to obtain annealed boron steel;

[0074] S2. Heat the annealed boron steel at a rate of 50 °C / h to 820 °C and hold for 35 min, then heat at a rate of 50 °C / h to 850 °C and hold for 190 min. Quench the boron steel after the holding using the water-based quenching liquid SJ1304 for 30 min to obtain the quenched boron steel;

[0075] S3. Hold the quenched boron steel at 5 °C for 65 min, then hold the boron steel after the holding at -48 °C for 55 min, and then cool to -72 °C and hold for 230 min, and then cool to obtain the high-strength boron steel;

[0076] The boron steel after hot rolling includes the following chemical components by mass percentage: C: 0.37%, Si: 0.15%, Mn: 1.00%, P: 0.035%, S: 0.04%, Cr: 0.45%, B: 0.0005%, Ti: 0.035%, Al: 0.065%, Cu: 0.025%, Ni: 0.3%, Mo: 0.10%, Pb: 0.02%, Sn: 0.03% and As: 0.03%.

[0077] Comparative Example 4

[0078] This comparative example provides a heat treatment method for boron steel, which is different from Example 1 in that: in S3, the seventh holding is not carried out, and other steps and components remain unchanged. The specific steps are as follows:

[0079] S1. Heat the hot-rolled boron steel at a rate of 50 °C / h to 780 °C and hold for 35 min, then heat at a rate of 50 °C / h to 850 °C and hold for 250 min, and then cool with the furnace to 580 °C to obtain the annealed boron steel;

[0080] S2. Heat the annealed boron steel at a rate of 50 °C / h to 820 °C and hold for 35 min, then heat at a rate of 50 °C / h to 850 °C and hold for 190 min. Quench the boron steel after the holding using the water-based quenching liquid SJ1304 for 30 min to obtain the quenched boron steel;

[0081] S3. Hold the quenched boron steel at 5 °C for 65 min, then hold the boron steel after the holding at -48 °C for 55 min, and then cool to obtain the high-strength boron steel;

[0082] The boron steel after hot rolling includes chemical components with the following mass percentages: C: 0.37%, Si: 0.15%, Mn: 1.00%, P: 0.035%, S: 0.04%, Cr: 0.45%, B: 0.0005%, Ti: 0.035%, Al: 0.065%, Cu: 0.025%, Ni: 0.3%, Mo: 0.10%, Pb: 0.02%, Sn: 0.03% and As: 0.03%.

[0083] Comparative Example 5

[0084] This comparative example provides a heat treatment method for boron steel, which is different from Example 1 in that: in S3, the temperature of the sixth heat preservation is -62°C, and other steps and components remain unchanged. The specific steps are as follows:

[0085] S1. Heat the boron steel after hot rolling at a rate of 50°C / h to 780°C and keep it warm for 35 minutes, then heat it at a rate of 50°C / h to 850°C and keep it warm for 250 minutes, and then cool it in the furnace to 580°C to obtain annealed boron steel;

[0086] S2. Heat the annealed boron steel at a rate of 50°C / h to 820°C and keep it warm for 35 minutes, then heat it at a rate of 50°C / h to 850°C and keep it warm for 190 minutes. Quench the boron steel at the end of heat preservation with the water-based quenching liquid SJ1304, and the quenching time is 30 minutes to obtain quenched boron steel;

[0087] S3. Keep the quenched boron steel at 5°C for 65 minutes, keep the boron steel after heat preservation at -62°C for 55 minutes, then cool it to -72°C and keep it warm for 230 minutes, and then cool it to obtain high-strength boron steel;

[0088] The boron steel after hot rolling includes chemical components with the following mass percentages: C: 0.37%, Si: 0.15%, Mn: 1.00%, P: 0.035%, S: 0.04%, Cr: 0.45%, B: 0.0005%, Ti: 0.035%, Al: 0.065%, Cu: 0.025%, Ni: 0.3%, Mo: 0.10%, Pb: 0.02%, Sn: 0.03% and As: 0.03%.

[0089] Comparative Example 6

[0090] This comparative example provides a heat treatment method for boron steel, which is different from Example 1 in that: in S3, the temperature of the fifth heat preservation is 20°C, and other steps and components remain unchanged. The specific steps are as follows:

[0091] S1. Heat the hot-rolled boron steel at a rate of 50 °C / h to 780 °C and hold for 35 min, then heat it at a rate of 50 °C / h to 850 °C and hold for 250 min, and cool it in the furnace to 580 °C to obtain annealed boron steel;

[0092] S2. Heat the annealed boron steel at a rate of 50 °C / h to 820 °C and hold for 35 min, then heat it at a rate of 50 °C / h to 850 °C and hold for 190 min. Quench the boron steel after the holding with water-based quenching liquid SJ1304 for 30 min to obtain quenched boron steel;

[0093] S3. Hold the quenched boron steel at 20 °C for 65 min, hold the boron steel after the holding at -48 °C for 55 min, then cool it to -72 °C and hold for 230 min, and then cool it to obtain high-strength boron steel;

[0094] The hot-rolled boron steel includes the following chemical components by mass percentage: C: 0.37%, Si: 0.15%, Mn: 1.00%, P: 0.035%, S: 0.04%, Cr: 0.45%, B: 0.0005%, Ti: 0.035%, Al: 0.065%, Cu: 0.025%, Ni: 0.3%, Mo: 0.10%, Pb: 0.02%, Sn: 0.03% and As: 0.03%.

[0095] Comparative Example 7

[0096] This comparative example provides a commercially available boron steel material with the model number 40MnB.

[0097] To further demonstrate the technical effects of the present invention, the present invention conducted the following performance tests on the boron steel materials obtained in Examples 1-3 and the boron steel materials obtained in Comparative Examples 1-7. The hardness and tensile strength of each boron steel material were measured according to the GB / T3077-2015 standard; the impact energy of each boron steel was measured according to the GB / T229-2020 standard; the elongation after fracture of each boron steel was measured according to the GB / T228.1-2021 standard; the results are shown in Table 1.

[0098] Table 1 Performance test results of each boron steel material

[0099]

[0100] It can be seen from Table 1 that the impact resistance, plasticity and strength of the high-strength boron steel material provided in the examples of the present invention are more excellent than those of the boron steel materials provided in the comparative examples.

[0101] To further demonstrate the performance of the boron steel material provided by the present invention, the present invention also conducted a metallographic structure test on the boron steel material obtained in Example 1,Figure 1 It can be seen that the structure of the boron steel prepared according to the embodiments of the present invention is a martensite structure that is dense and evenly distributed.

[0102] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A heat treatment method for high-strength boron steel, characterized in that: It includes the following steps: S1. The hot-rolled boron steel is subjected to the first heat preservation at 780°C to 820°C, then heated to 830°C to 850°C for the second heat preservation, and cooled to 580°C to 610°C to obtain annealed boron steel; S2. The annealed boron steel is heated to 800°C to 820°C for the third heat preservation, then heated to 830°C to 850°C for the fourth heat preservation, and the boron steel after the heat preservation is quenched with an aqueous quenching liquid to obtain quenched boron steel; S3. The quenched boron steel is subjected to the fifth heat preservation at 5°C to 15°C, the boron steel after the heat preservation is subjected to the sixth heat preservation at -52°C to -48°C, then cooled to -72°C to -68°C for the seventh heat preservation, and cooled to obtain high-strength boron steel.

2. The heat treatment method of the high-strength boron steel according to claim 1, characterized in that: In S1, the time of the first heat preservation is 35 min to 45 min; and / or In S1, the time of the second heat preservation is 230 min to 250 min.

3. The heat treatment method of the high-strength boron steel according to claim 1, characterized in that: In S2, the time of the third heat preservation is 35 min to 45 min.

4. The heat treatment method of the high-strength boron steel according to claim 1, characterized in that: In S2, the time of the fourth heat preservation is 170 min to 190 min.

5. The heat treatment method of the high-strength boron steel according to claim 1, characterized in that: In S2, the model of the aqueous quenching liquid is SJ1304.

6. The heat treatment method of the high-strength boron steel according to claim 1 or 5, characterized in that: In S2, the time of quenching is 30 min to 35 min.

7. The heat treatment method of the high-strength boron steel according to claim 1, characterized in that: In S3, the time of the fifth heat preservation is 55 min to 65 min.

8. The heat treatment method of the high-strength boron steel according to claim 1, characterized in that: In S3, the time of the sixth heat preservation is 55 min to 65 min; and / or In S3, the time of the seventh heat preservation is 230 min to 250 min.

9. A high-strength boron steel, characterized in that: It is prepared by heat treatment using the heat treatment method of the high-strength boron steel according to any one of claims 1-8.

10. An application of the high-strength boron steel according to claim 9 in the preparation of a hydraulic shear.

Images