Heat treatment process of corrosion-resistant reinforcing steel bar for frozen soil environment

Abstract

The invention discloses a heat treatment process of a corrosion-resistant reinforcing steel bar for a frozen soil environment, a heat treatment sample is the corrosion-resistant reinforcing steel bar for the HRB400E-LC frozen soil environment, and the heat treatment is performed according to the following steps: (1) quenching: putting a roughly machined round steel blank sample for a sucker rod into a heating furnace, heating to 500 + / -20 DEG C, preserving heat for 120 minutes, then taking out the sample, and cooling in air; the heat-treated sample is subjected to mechanical property inspection, the yield strength at the normal temperature is larger than or equal to 460 MPa, the tensile strength is larger than or equal to 580 MPa, and the ductility is larger than or equal to 25%; the total impact absorption KV2 at-50 DEG C is greater than or equal to 100J.

Description

Technical Field

[0001] The invention belongs to the technical field of manufacturing corrosion-resistant steel bars for frozen soil environments, and in particular relates to a heat treatment process for corrosion-resistant steel bars for frozen soil environments. Background Art

[0002] A reasonable heat treatment system is essential for corrosion-resistant steel bars for soil environments. A reasonable heat treatment system can significantly improve the durability and reliability of corrosion-resistant steel bars for soil environments, extend their service life, and reduce maintenance and replacement costs. Heat treatment can adjust the internal organizational structure of steel bars, making them more corrosion-resistant in soil environments. Through the heat treatment process, a uniform microstructure can be formed, micro defects can be reduced, and the risk of stress corrosion cracking can be reduced. The strength and toughness of the steel bars can be enhanced to ensure that they are not prone to breakage or deformation during long-term use in the soil. This is essential to maintaining the overall stability and safety of the structure. The traditional heat treatment process for low-temperature steel bars requires quenching + tempering. This patent studies different heat treatment processes for HRB400E-LC corrosion-resistant steel bars for frozen soil environments and finds that the performance effect of quenching + tempering can be achieved only by tempering. Through multiple tests, it was found that the tempering temperature should be controlled at 480-530°C. Tempering has a great influence on the performance of the material. With the increase of the tempering temperature, the strength of the material decreases, the plasticity and toughness increase, and it has good comprehensive mechanical properties at around 480-530°C.

[0003] Announcement No. CN 110423948 B introduces a low-temperature resistant hot-rolled steel bar and its production method, including chemical composition, production steps, etc. The steel bar can meet the mechanical property requirements of different grades and has greatly improved low-temperature resistance. This patent discloses a heat treatment process for corrosion-resistant steel bars for HRB400E-LC frozen soil environments, which achieves the performance effect of quenching + tempering only through tempering, and introduces the process steps and advantages. This patent proposes an innovative heat treatment process for steel bars in a specific environment (frozen soil environment), and simplifies the process and achieves good performance through a unique tempering process, which is more targeted and innovative.

[0004] Announcement No. CN 111088463 B introduces a steel bar resistant to corrosion in a low-temperature atmospheric environment and its production method, and introduces the chemical composition range of the steel bar, including the continuous casting billet soaking temperature, rolling temperature, cooling stage control, etc. in the production method, and improves the corrosion resistance and mechanical properties of the steel bar in a low-temperature atmospheric environment through composition design and process adjustment. This patent introduces a heat treatment process for corrosion-resistant steel bars for frozen soil environments, and introduces the tempering heat treatment steps and process advantages of HRB400E-LC corrosion-resistant steel bars for frozen soil environments. The tempering temperature is controlled at 480-530°C, which can save the quenching step, save energy and improve the consistency of material properties. This patent focuses on the innovation of the heat treatment process for steel bars used in frozen soil environments, and saves the quenching step and improves performance through a specific tempering process.

[0005] Publication No. CN 112828033 A introduces a low-temperature resistant steel bar rolling process, and introduces the rolling control, temperature control, deformation process control and cooling control processes of low-temperature resistant steel bars made of nickel-chromium-molybdenum steel, including the temperature range of each stage and the steel bar rolling process flow. This patent is a heat treatment process for corrosion-resistant steel bars for frozen soil environments, and introduces the heat treatment process and effect of only tempering of HRB400E-LC corrosion-resistant steel bars for frozen soil environments. The heat treatment process for corrosion-resistant steel bars for frozen soil environments involved in this patent simplifies the process steps and has energy-saving advantages through the innovative method of only tempering, while meeting the steel bar performance requirements in special environments. Summary of the invention

[0006] The purpose of the present invention is to provide a heat treatment process for corrosion-resistant steel bars for use in frozen soil environments, so that they have good comprehensive mechanical properties, thereby significantly improving the overall life and safety of corrosion-resistant steel bars for use in frozen soil environments.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention discloses a heat treatment process for corrosion-resistant steel bars for use in frozen soil environments, which is HRB400E-LC steel, and is carried out according to the following steps:

[0009] Tempering: Place the sample in a heating furnace, heat to 480-530°C, keep warm for 120 minutes, then take out the sample and cool it in the air.

[0010] Further, proceed as follows:

[0011] The sample was placed in a heating furnace, heated to 480°C, kept warm for 120 min, and then taken out and cooled in air.

[0012] Further, proceed as follows:

[0013] The sample was placed in a heating furnace, heated to 500°C, kept warm for 120 min, and then the sample was taken out and cooled in air.

[0014] Further, proceed as follows:

[0015] The sample was placed in a heating furnace, heated to 530°C, kept warm for 120 min, and then the sample was taken out and cooled in air.

[0016] Furthermore, the impact toughness level of the quenching + tempering treatment can be reached or approached by tempering treatment alone, and the strength of the tempering process alone is higher than that of quenching + tempering.

[0017] Furthermore, the chemical composition of the HRB400E-LC steel in mass percentage is C 0.10-0.15%, Si 0.18-0.28%, MN 1.20-1.40%, P≤0.020%, S≤0.015%, V 0.40-0.50%, Cu 0.28-0.35%, Cr 0.22-0.30%, Ni 0.22-0.30%, and the rest is Fe and unavoidable impurities.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are:

[0019] (1) Direct use of tempering can eliminate the quenching step, significantly reducing energy consumption and production costs; (2) Quenching requires strict control of the cooling rate to prevent stress concentration or material cracking. Using only tempering simplifies the heat treatment process, reduces the requirements for equipment and operations, and reduces the risk of errors. (3) Using only tempering can treat the material more evenly, avoiding uneven hardness or uneven phase change caused by quenching, thereby improving the overall performance consistency of the material; (4) By optimizing the tempering process to achieve the same effect as traditional quenching + tempering, more economical, efficient and sustainable production can be achieved without sacrificing material performance. DETAILED DESCRIPTION

[0020] The heat treatment process of corrosion-resistant steel bars for frozen soil environments of the present invention determines a set of heat treatment systems that can ensure the stable performance of steel by studying the heat treatment heating system, including the influence of quenching temperature, tempering temperature and holding time on the organization and performance; on the premise of ensuring the organization and performance after heat treatment, the heating temperature range is narrowed, the holding time is reduced, the energy consumption of heat treatment is reduced, and the efficiency of heat treatment is improved. It can be found from the test results of the embodiments and comparative examples that the impact toughness level of quenching + tempering treatment can be reached or approached only by tempering treatment, and the strength of the tempering process alone is higher than that of quenching + tempering, and it has certain advantages of energy saving and simplified process.

[0021] Embodiment 1:

[0022] The heat treatment process of the present invention is performed in the following steps:

[0023] The sample was placed in a heating furnace, heated to 480°C, kept warm for 120 min, and then taken out and cooled in air.

[0024] Embodiment 2:

[0025] The heat treatment process of the present invention is performed in the following steps:

[0026] The sample was placed in a heating furnace, heated to 500°C, kept warm for 120 min, and then the sample was taken out and cooled in air.

[0027] Embodiment 3:

[0028] The heat treatment process of the present invention is performed in the following steps:

[0029] The sample was placed in a heating furnace, heated to 530°C, kept warm for 120 min, and then the sample was taken out and cooled in air.

[0030] Comparative Example 1: The heat treatment process of the present invention is performed in the following steps:

[0031] (1) Quenching: The rough-processed corrosion-resistant steel bar blank for frozen soil environment is placed in a heating furnace, heated to 870°C, kept at this temperature for 50 min, and then quenched and water quenched;

[0032] (2) Tempering: Place the quenched sample in a heating furnace, heat to 480°C, keep warm for 120 minutes, then take out the sample and cool it in air.

[0033] Comparative Example 2: The heat treatment process of the present invention is performed in the following steps:

[0034] (1) Quenching: The rough-processed corrosion-resistant steel bar blank for frozen soil environment is placed in a heating furnace, heated to 900°C, kept at this temperature for 50 min, and then quenched and water quenched;

[0035] (2) Tempering: Place the quenched sample in a heating furnace, heat to 500°C, keep warm for 120 minutes, then take out the sample and cool it in air.

[0036] Comparative Example 3: The heat treatment process of the present invention is performed in the following steps:

[0037] (1) Quenching: The rough-processed corrosion-resistant steel bar blank for frozen soil environment is placed in a heating furnace, heated to 930°C, kept at this temperature for 50 min, and then quenched and water quenched;

[0038] (2) Tempering: Place the quenched sample in a heating furnace, heat to 530°C, keep warm for 120 minutes, then take out the sample and cool it in air.

[0039] After the heat treatment of each embodiment is completed, the rough-machined blank sample is fine-machined and various performance tests are performed. The chemical composition is shown in Table 1, and the test results are shown in Table 2 and Table 3. It can be seen from Table 1, Table 2 and Table 3 that various performance indicators are higher than the index requirements, and the performance of the sample after heat treatment is qualified.

[0040] Table 1 Chemical composition of test steel (mass fraction %)

[0041] Examples C Si Mn P S V Cu Cr Ni Example 1 0.12 0.25 1.27 0.012 0.006 0.043 0.31 0.25 0.25 Example 2 0.14 0.21 1.29 0.013 0.004 0.044 0.32 0.26 0.25 Example 3 0.13 0.23 1.32 0.014 0.007 0.045 0.30 0.27 0.26 Comparative Example 1 0.12 0.24 1.33 0.015 0.005 0.046 0.33 0.28 0.27 Comparative Example 2 0.11 0.25 1.35 0.014 0.006 0.043 0.32 0.27 0.27 Comparative Example 3 0.12 0.25 1.31 0.010 0.006 0.042 0.31 0.28 0.26

[0042] Table 2 Mechanical properties at room temperature after heat treatment

[0043]

[0044] Table 3 Impact toughness after heat treatment

[0045]

[0046] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A heat treatment process for corrosion-resistant steel bars for frozen soil environments, characterized in that: It is HRB400E-LC steel and is carried out as follows: Tempering: Place the sample in a heating furnace, heat to 480-530°C, keep warm for 120 minutes, then take out the sample and cool it in the air.

2. The heat treatment process for corrosion-resistant steel bars for frozen soil environments according to claim 1, characterized in that: Proceed as follows: The sample was placed in a heating furnace, heated to 480°C, kept warm for 120 min, and then taken out and cooled in air.

3. The heat treatment process for corrosion-resistant steel bars for frozen soil environments according to claim 1, characterized in that: Proceed as follows: The sample was placed in a heating furnace, heated to 500°C, kept warm for 120 min, and then the sample was taken out and cooled in air.

4. The heat treatment process for corrosion-resistant steel bars for frozen soil environments according to claim 1, characterized in that: Proceed as follows: The sample was placed in a heating furnace, heated to 530°C, kept warm for 120 min, and then the sample was taken out and cooled in air.

5. The heat treatment process for corrosion-resistant steel bars for frozen soil environments according to claim 1, characterized in that: Only through tempering treatment can the impact toughness level of quenching + tempering treatment be achieved or approached, and the strength of tempering process alone is higher than that of quenching + tempering.

6. The heat treatment process for corrosion-resistant steel bars for frozen soil environments according to claim 1, characterized in that: The chemical composition of the HRB400E-LC steel by mass percentage is C 0.10-0.15%, Si 0.18-0.28%, MN 1.20-1.40%, P≤0.020%, S≤0.015%, V 0.40-0.50%, Cu 0.28-0.35%, Cr0.22-0.30%, Ni0.22-0.30%, and the rest is Fe and unavoidable impurities.

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