Heat treatment process for improving structure performance of maritime work steel

Abstract

The invention discloses a heat treatment process for improving the structure property of maritime work steel, which comprises the following steps: quenching: putting a sample into a heating furnace, heating to 820-850 DEG C, preserving heat for 120 minutes, then taking out the sample, and cooling in water; tempering: putting the quenched sample into a heating furnace, heating the sample to 530-550 DEG C, carrying out high-temperature tempering treatment, carrying out heat preservation for 60 minutes, then taking out the sample, and cooling the sample in air; the marine work steel comprises the following chemical components in percentage by weight: 0.08 to 0.10 percent of C, 0.13 to 0.17 percent of S i, 1.15 to 1.3 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.010 percent of S, 0.4 to 0.5 percent of Cr, 0.08 to 0.12 percent of Mo, 0.01 to 0.02 percent of T i, 0.04 to 0.05 percent of V, 0.7 to 0.9 percent of N i and the balance of Fe and impurities. The purpose of the invention is to endow the material with good comprehensive mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat treatment processes for metal materials, and particularly relates to a heat treatment process for improving the microstructure and properties of offshore steel. Background Art

[0002] In order to better develop and utilize marine resources, China has developed many marine platform steels with high strength, high toughness, good weldability and corrosion resistance. E690 is a low-carbon, low-alloy high-strength marine platform steel studied in recent years, and most of the domestic-produced E690 is delivered in the quenched and tempered state.

[0003] The quenching and tempering process usually includes quenching + tempering. As the last step of the process, tempering has a great influence on the microstructure and properties of the material. Multiple studies have found that as the tempering temperature increases, the strength of E690 steel decreases, the microstructure becomes coarser, and the spheroidization behavior of carbides is obvious. Studies at different tempering temperatures have found that as the tempering temperature increases, the microstructure changes from lath bainite to granular bainite, and the precipitation of precipitates also increases. It has also been found that as the tempering temperature increases, the microstructure in the steel changes from martensite formed by quenching to tempered martensite and sorbite, and the hardness decreases accordingly. Some people have studied Q690D quenched at 930°C with different tempering treatments and found that as the tempering temperature increases, the quenched microstructure gradually transforms into tempered martensite, troostite and sorbite, the overall strength decreases, and the yield ratio increases. Heat treatment can adjust the internal microstructure of steel, making it have higher corrosion resistance during use. Through the heat treatment process, a uniform microstructure can be formed, microdefects can be reduced, and the risk of stress corrosion cracking can be lowered. The strength and toughness of steel can be enhanced to ensure that it is not prone to fracture or deformation during long-term use in the soil. This is crucial for maintaining the overall stability and safety of the structure. Summary of the Invention

[0004] The purpose of the present invention is to provide a heat treatment process for improving the microstructure and properties of offshore steel, so that it has good comprehensive mechanical properties, thereby significantly improving the overall life and safety of offshore steel.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A heat treatment process for improving the microstructure and properties of offshore steel according to the present invention includes:

[0007] Quenching: Put the sample into a heating furnace, heat it to 820 - 850°C, hold for 120 min, then take out the sample and cool it in water;

[0008] Tempering: Put the quenched sample into a heating furnace, heat it to 530 - 550°C for high-temperature tempering treatment, hold for 60 min, then take out the sample and cool it in air;

[0009] The chemical composition of the offshore steel is C 0.08-0.10%, Si 0.13-0.17%, Mn 1.15-1.3%, P≤0.025%, S≤0.010%, Cr 0.4-0.5%, Mo 0.08-0.12%, Ti 0.01-0.02%, V 0.04-0.05%, Ni 0.7-0.9%, and the balance is Fe and unavoidable impurities.

[0010] Further, the chemical composition of the offshore steel is C 0.08%, Si 0.15%, Mn 1.27%, P 0.012%, S 0.006%, Cr 0.45%, Mo 0.1%, Ti 0.01%, V 0.043%, Ni 0.8%, and the balance is Fe and unavoidable impurities.

[0011] Further, the chemical composition of the offshore steel is C 0.10%, Si 0.17%, Mn 1.19%, P 0.013%, S 0.004%, Cr 0.46%, Mo 0.13%, Ti 0.02%, V 0.044%, Ni 0.75%, and the balance is Fe and unavoidable impurities.

[0012] Further, the chemical composition of the offshore steel is C 0.09%, Si 0.13%, Mn 1.22%, P 0.014%, S 0.007%, Cr 0.43%, Mo 0.09%, Ti 0.015%, V 0.044%, Ni 0.76%, and the balance is Fe and unavoidable impurities.

[0013] Further, it is carried out according to the following steps:

[0014] (1) Quenching: Put the rough-machined offshore steel blank sample into a heating furnace, heat it up to 850°C, hold for 120 min, and then carry out quenching, water quenching;

[0015] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 550°C, hold for 60 min, and then take out the sample and cool it in the air.

[0016] Further, it is carried out according to the following steps:

[0017] (1) Quenching: Put the rough-machined offshore steel blank sample into a heating furnace, heat it up to 840°C, hold for 120 min, and then carry out quenching, water quenching;

[0018] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 540°C, hold for 60 min, and then take out the sample and cool it in the air.

[0019] Further, it is carried out according to the following steps:

[0020] (1) Quenching: Put the rough-machined offshore steel blank sample into a heating furnace, heat it up to 830 °C, hold it for 120 min, and then carry out quenching, water quenching;

[0021] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 530 °C, hold it for 60 min, and then take out the sample and cool it in the air.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are:

[0023] The heat treatment process of the offshore steel of the present invention determines a heat treatment system that can ensure the stable performance of the steel by studying the heat treatment heating system, including the influence of quenching temperature, tempering temperature, and holding time on the structure and properties, so that it has good comprehensive mechanical properties, thereby significantly improving the overall life and safety of the offshore steel. Specific embodiments

[0024] Example 1: The steel part of the heat treatment process of the present invention is E690 offshore steel, and it is carried out according to the following steps:

[0025] (1) Quenching: Put the rough-machined offshore steel blank sample into a heating furnace, heat it up to 850 °C, hold it for 120 min, and then carry out quenching, water quenching;

[0026] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 550 °C, hold it for 60 min, and then take out the sample and cool it in the air.

[0027] Example 2: The steel part of the heat treatment process of the present invention is E690 offshore steel, and it is carried out according to the following steps:

[0028] (1) Quenching: Put the rough-machined offshore steel blank sample into a heating furnace, heat it up to 840 °C, hold it for 120 min, and then carry out quenching, water quenching;

[0029] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 540 °C, hold it for 60 min, and then take out the sample and cool it in the air.

[0030] Example 3: The steel part of the heat treatment process of the present invention is E690 offshore steel, and it is carried out according to the following steps:

[0031] (1) Quenching: Put the rough-machined offshore steel blank sample into a heating furnace, heat it up to 830 °C, hold it for 120 min, and then carry out quenching, water quenching;

[0032] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 530 °C, hold for 60 min, then take out the sample and cool it in air.

[0033] After the heat treatment of each embodiment is completed, finish machining is carried out on the rough-machined blank sample, and various performance inspections are carried out. The chemical compositions are shown in Table 1, and the inspection results are shown in Tables 2 and 3. It can be seen from Tables 1, 2 and 3 that all performance indicators are higher than the specified requirements, and the performance of the sample after heat treatment is qualified.

[0034] Table 1 Chemical composition of the test steel

[0035]

[0036] Table 2 Mechanical properties at room temperature after heat treatment

[0037]

[0038]

[0039] Table 3 Impact toughness after heat treatment

[0040]

[0041] The heat treatment process of the present invention for improving the tissue properties and corrosion resistance of offshore steel determines a set of heat treatment systems that can ensure the stable properties of the steel by studying the heat treatment heating system, including the effects of quenching temperature, tempering temperature and holding time on the structure and properties; on the premise of ensuring the structure and properties after heat treatment, the heating temperature range is reduced, the holding time is reduced, the energy consumption of heat treatment is reduced, and the efficiency of heat treatment is improved.

[0042] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A heat treatment process for improving the structural properties of marine engineering steel, characterized in that: include: Quenching: Place the sample in a heating furnace, heat it to 820-850°C, keep it warm for 120 minutes, then take out the sample and cool it in water; Tempering: put the quenched sample into a heating furnace, heat it to 530-550℃ for high temperature tempering, keep it warm for 60min, then take out the sample and cool it in the air; The chemical composition of the marine engineering steel is C 0.08-0.10%, Si 0.13-0.17%, Mn 1.15-1.3%, P≤0.025%, S≤0.010%, Cr 0.4-0.5%, Mo 0.08-0.12%, Ti 0.01-0.02%, V0.04-0.05%, Ni0.7-0.9%, and the balance is Fe and unavoidable impurities.

2. The heat treatment process for improving the structural properties of marine engineering steel according to claim 1, characterized in that: The chemical composition of the marine engineering steel is C 0.08%, Si 0.15%, Mn 1.27%, P 0.012%, S 0.006%, Cr 0.45%, Mo 0.1%, Ti 0.01%, V 0.043%, Ni 0.8%, and the balance is Fe and unavoidable impurities.

3. The heat treatment process for improving the structural properties of marine engineering steel according to claim 1, characterized in that: The chemical composition of the marine engineering steel is C 0.10%, Si 0.17%, Mn 1.19%, P 0.013%, S 0.004%, Cr 0.46%, Mo 0.13%, Ti 0.02%, V 0.044%, Ni 0.75%, and the balance is Fe and unavoidable impurities.

4. The heat treatment process for improving the structural properties of marine engineering steel according to claim 1, characterized in that: The chemical composition of the marine engineering steel is C 0.09%, Si 0.13%, Mn 1.22%, P 0.014%, S 0.007%, Cr 0.43%, Mo 0.09%, Ti 0.015%, V 0.044%, Ni 0.76%, and the balance is Fe and unavoidable impurities.

5. The heat treatment process for improving the structural properties of marine engineering steel according to claim 2, characterized in that: Proceed as follows: (1) Quenching: Place the rough-processed marine steel blank sample in a heating furnace, heat it to 850°C, keep it warm for 120 minutes, and then quench it with water; (2) Tempering: Place the quenched sample in a heating furnace, heat to 550°C, keep warm for 60 minutes, then take out the sample and cool it in air.

6. The heat treatment process for improving the structural properties of marine engineering steel according to claim 3, characterized in that: Proceed as follows: (1) Quenching: Place the rough-processed marine steel blank sample in a heating furnace, heat it to 840°C, keep it warm for 120 minutes, and then quench it with water; (2) Tempering: Place the quenched sample in a heating furnace, heat to 540°C, keep warm for 60 minutes, then take out the sample and cool it in air.

7. The heat treatment process for improving the structural properties of marine engineering steel according to claim 4, characterized in that: Proceed as follows: (1) Quenching: Place the rough-processed marine steel blank sample in a heating furnace, heat it to 830°C, keep it warm for 120 minutes, and then quench it with water; (2) Tempering: Place the quenched sample in a heating furnace, heat to 530°C, keep warm for 60 minutes, then take out the sample and cool it in air.

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