Fire-resistant and corrosion-resistant steel bar and method for manufacturing the same

Abstract

The application relates to the technical field of steel bars, and discloses a fire-resistant and corrosion-resistant steel bar and a preparation method thereof. The fire-resistant and corrosion-resistant steel bar comprises a steel bar body and a coating, and the steel bar body is composed of the following components in percentage by mass: C 0.15%-0.22%, Si 0.3%-0.5%, Mn 0.8%-1.2%, Cr 0.11%-0.25%, Mo 0.25%-0.35%, P <=0.02%, S <=0.02%, Cu 0.1%-0.15%, Ni 0.06%-0.1%, Nb <=0.08%, Ti <=0.06%, and the balance is Fe and inevitable impurities; the mass content of Cr, Mo and Cu satisfies the relationship formula: 2Cr+3Mo+2Cu=1.45%-1.55%. Through the technical scheme, the problem of insufficient fire resistance and corrosion resistance of the steel bar in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of reinforcing steel technology, specifically to a fire-resistant and corrosion-resistant reinforcing steel and its preparation method. Background Technology

[0002] As modern architecture continues to develop towards high-rise buildings, saline-alkali land, and industrial corrosion zones, the fire risks and corrosion threats faced by building structures are becoming increasingly severe. Therefore, higher requirements are placed on the reinforcing steel, the core load-bearing component of building structures: it must not only maintain high-strength mechanical support under high fire temperatures, but also resist the erosion of various corrosive factors such as chloride ions to ensure the safe operation of building structures under combined corrosion and fire conditions.

[0003] However, existing steel reinforcement materials have significant technical shortcomings in balancing fire resistance and corrosion resistance. Firstly, corrosion-resistant steel reinforcement focuses on improving corrosion resistance but suffers from insufficient fire resistance. This is because improving corrosion resistance mainly involves increasing alloying elements such as Cu and Ni, but high alloy content can lead to grain coarsening or the precipitation of harmful phases at high temperatures, causing a sharp decrease in strength and failing to meet the fire resistance requirements of building structures. Secondly, while fire-resistant steel reinforcement improves high-temperature mechanical stability by adding refractory alloying elements, it reduces corrosion resistance. This is because the addition of these refractory elements and the resulting carbonitride precipitates disrupt the uniformity of the passivation film on the steel surface, significantly reducing the corrosion resistance of the steel reinforcement in corrosive environments. Therefore, developing a fire-resistant and corrosion-resistant steel reinforcement is of great significance. Summary of the Invention

[0004] This invention proposes a fire-resistant and corrosion-resistant steel bar and its preparation method, which solves the problem of insufficient fire resistance and corrosion resistance of steel bars in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a fire-resistant and corrosion-resistant reinforcing steel bar, comprising a steel bar body and a coating. The steel bar body is composed of the following components by mass percentage: C 0.15%~0.22%, Si 0.3%~0.5%, Mn 0.8%~1.2%, Cr 0.11%~0.25%, Mo 0.25%~0.35%, P≤0.02%, S≤0.02%, Cu 0.1%~0.15%, Ni 0.06%~0.1%, Nb≤0.08%, Ti≤0.06%, with the balance being Fe and unavoidable impurities. The mass content of Cr, Mo, and Cu satisfies the relationship: 2Cr + 3Mo + 2Cu = 1.45%~1.55%.

[0006] As a further technical solution, the mass content of Cr, Mo, and Cu satisfies the relationship: 2Cr + 3Mo + 2Cu = 1.5%.

[0007] As a further technical solution, the mass content of Mo and Cu satisfies the relationship: 2≤Mo / Cu≤3.

[0008] As a further technical solution, the mass content of Mo and Cu satisfies the relationship: Mo / Cu=2.5.

[0009] This invention also proposes a method for preparing fire-resistant and corrosion-resistant reinforcing bars, comprising the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast to obtain the billet; S2. The cast billet undergoes heat treatment, rough rolling, fine rolling, quenching, tempering, and cooling to obtain the steel bar body; S3. After the coating is applied to the steel bar body, it is cured to form a coating, thus obtaining a fire-resistant and corrosion-resistant steel bar.

[0010] As a further technical solution, in step S1, argon gas is introduced during the continuous casting process, and the pressure of the argon gas is 0.1~0.3MPa.

[0011] As a further technical solution, in step S2, the temperature of the heat treatment is 1100~1150℃.

[0012] As a further technical solution, in step S2, the initial rolling temperature during the rough rolling process is 1050~1120℃, and the final rolling temperature during the rough rolling process is 1000~1100℃. The initial rolling temperature during the finishing rolling process is 950~1050℃, and the final rolling temperature during the finishing rolling process is 850~900℃.

[0013] As a further technical solution, in step S2, the quenching treatment is water quenching; During water quenching, the temperature is first cooled to 400°C at a rate of 50-60°C / s, and then cooled to 150°C at a rate of 30-40°C / s.

[0014] In this invention, during water quenching, the steel reinforcement is first cooled to 400℃ at a rate of 50~60℃ / s, and then cooled to 150℃ at a rate of 30~40℃ / s. This improves the corrosion resistance of the refractory and corrosion-resistant steel reinforcement. Cooling at a rate of 50~60℃ / s can inhibit the transformation of austenite to pearlite or ferrite, promoting the transformation of austenite into a fine, high-density martensite structure, thus avoiding localized grain coarsening caused by uneven cooling. Then, cooling at a rate of 30~40℃ / s can reduce the huge structural stress caused by excessive temperature difference in the cross section, effectively preventing the generation of quenching cracks and ensuring the integrity of the material. The dense structure and low stress state reduce the penetration rate of corrosive media such as chloride ions in the matrix, thereby improving the corrosion resistance of the steel reinforcement.

[0015] As a further technical solution, in step S2, the tempering temperature is 450~500℃ and the tempering time is 100~150s.

[0016] As a further technical solution, in step S3, the raw materials of the coating include the following components by weight: 40-60 parts aluminum dihydrogen phosphate, 40-60 parts magnesium dihydrogen phosphate, 8-12 parts styrene-acrylic emulsion, 1-3 parts zinc nitrate, 1-3 parts zinc oxide, 2-5 parts silica sol, and 200 parts water.

[0017] As a further technical solution, the preparation method of the coating is as follows: the raw materials of the coating are mixed evenly to obtain the coating.

[0018] The working principle and beneficial effects of this invention are as follows: This invention improves the corrosion resistance and fire resistance of reinforcing steel by limiting the mass content of Cr, Mo, and Cu to satisfy the relationship: 2Cr + 3Mo + 2Cu = 1.45%~1.55%. Specifically, Cr strengthens grain boundaries and enhances the structural stability at high temperatures, effectively increasing the creep resistance and high-temperature strength of the reinforcing steel, thus improving its fire resistance. Mo enhances the high-temperature creep resistance of the steel, and the alloy phase it forms with the steel matrix strengthens grain boundary bonding, ensuring that the reinforcing steel maintains high structural strength and stability under high-temperature conditions such as fires. Cu forms a copper sulfate passivation film on the surface of the reinforcing steel, effectively blocking corrosive media such as chloride ions. These three elements work synergistically, achieving a combined improvement in fire resistance and corrosion resistance through the high-temperature protection system constructed by Cr and Mo, and the corrosion media barrier system constructed by Cr and Cu. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In the following examples and comparative examples: Styrene-acrylic emulsion, model: Acronal 5041; silica sol, solid content: 40wt%.

[0021] Example 1 A fire-resistant and corrosion-resistant steel bar includes a steel bar body and a coating. The steel bar body is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 0.8%, Cr 0.25%, Mo 0.25%, P 0.01%, S 0.01%, Cu 0.1%, Ni 0.06%, Nb 0.06%, Ti 0.04%, with the balance being Fe and unavoidable impurities. The mass content of Cr, Mo, and Cu satisfies the following relationship: 2Cr + 3Mo + 2Cu has a value of 1.45%, and the Mo / Cu ratio is 2.5. A method for preparing fire-resistant and corrosion-resistant steel bars includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast under argon protection to obtain the billet; S2. The billet is subjected to heat treatment (heated to 1100℃ and held for 60 min), rough rolling (the initial rolling temperature of rough rolling is 1050℃, the final rolling temperature is 1000℃, and the total reduction rate is 30%), and finish rolling (the initial rolling temperature of finish rolling is 950℃, the final rolling temperature is 850℃, and the total reduction rate is 45%). Then, it is water quenched (during water quenching, it is first cooled to 400℃ at a rate of 50℃ / s, and then cooled to 150℃ at a rate of 30℃ / s). After that, it is tempered at 450℃ for 150s. After tempering, it is air-cooled to room temperature to obtain the steel bar body. S3. After mixing the raw materials of the coating, the coating is applied to the steel bar body and cured to form a coating, thus obtaining fire-resistant and corrosion-resistant steel bars. The raw materials for the coating include the following components by weight: 40 parts aluminum dihydrogen phosphate, 40 parts magnesium dihydrogen phosphate, 8 parts styrene-acrylic emulsion, 1 part zinc nitrate, 1 part zinc oxide, 2 parts silica sol, and 200 parts water.

[0022] Example 2 A fire-resistant and corrosion-resistant steel bar includes a steel bar body and a coating. The steel bar body is composed of the following components by mass percentage: C 0.18%, Si 0.4%, Mn 1%, Cr 0.25%, Mo 0.25%, P 0.015%, S 0.015%, Cu 0.1%, Ni 0.08%, Nb 0.07%, Ti 0.05%, with the balance being Fe and unavoidable impurities. The mass content of Cr, Mo, and Cu satisfies the following relationship: 2Cr + 3Mo + 2Cu = 1.45%, and the Mo / Cu ratio is 2.5. A method for preparing fire-resistant and corrosion-resistant steel bars includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast under argon protection at 0.2MPa to obtain the billet. S2. The billet is subjected to heat treatment (heated to 1120℃ and held for 70 min), rough rolling (the initial rolling temperature of rough rolling is 1080℃, the final rolling temperature is 1050℃, and the total reduction rate is 30%), and finish rolling (the initial rolling temperature of finish rolling is 1000℃, the final rolling temperature is 880℃, and the total reduction rate is 45%). Then, it is water quenched (during water quenching, it is first cooled to 400℃ at a rate of 50℃ / s, and then cooled to 150℃ at a rate of 30℃ / s). After that, it is tempered at 470℃ for 120s. After tempering, it is air-cooled to room temperature to obtain the steel bar body. S3. After mixing the raw materials of the coating, the coating is applied to the steel bar body and cured to form a coating, thus obtaining fire-resistant and corrosion-resistant steel bars. The raw materials for the coating include the following components by weight: 50 parts aluminum dihydrogen phosphate, 50 parts magnesium dihydrogen phosphate, 10 parts styrene-acrylic emulsion, 2 parts zinc nitrate, 2 parts zinc oxide, 4 parts silica sol, and 200 parts water.

[0023] Example 3 A fire-resistant and corrosion-resistant steel bar includes a steel bar body and a coating. The steel bar body is composed of the following components by mass percentage: C 0.22%, Si 0.5%, Mn 1.2%, Cr 0.25%, Mo 0.25%, P 0.02%, S 0.02%, Cu 0.1%, Ni 0.1%, Nb 0.08%, Ti 0.06%, with the balance being Fe and unavoidable impurities. The mass content of Cr, Mo, and Cu satisfies the following relationship: 2Cr + 3Mo + 2Cu has a value of 1.45%, and the Mo / Cu ratio is 2.5. A method for preparing fire-resistant and corrosion-resistant steel bars includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast under argon protection at 0.3MPa to obtain the billet. S2. The billet is subjected to heat treatment (heated to 1150℃ and held for 80 min), rough rolling (the initial rolling temperature of rough rolling is 1120℃, the final rolling temperature is 1100℃, and the total reduction rate is 30%), and finish rolling (the initial rolling temperature of finish rolling is 1050℃, the final rolling temperature is 900℃, and the total reduction rate is 45%). Then, it is water quenched (during water quenching, it is first cooled to 400℃ at a rate of 50℃ / s, and then cooled to 150℃ at a rate of 30℃ / s). After that, it is tempered at 500℃ for 100s. After tempering, it is air cooled to room temperature to obtain the steel bar body. S3. After mixing the raw materials of the coating, the coating is applied to the steel bar body and cured to form a coating, thus obtaining fire-resistant and corrosion-resistant steel bars. The raw materials for the coating include the following components by weight: 60 parts aluminum dihydrogen phosphate, 60 parts magnesium dihydrogen phosphate, 12 parts styrene-acrylic emulsion, 3 parts zinc nitrate, 3 parts zinc oxide, 5 parts silica sol, and 200 parts water.

[0024] Example 4 The difference between this embodiment and Embodiment 2 is only that the steel reinforcement body in this embodiment is composed of the following components by mass percentage: C 0.18%, Si 0.4%, Mn 1%, Cr 0.18%, Mo 0.3%, P 0.015%, S 0.015%, Cu 0.12%, Ni 0.08%, Nb 0.07%, Ti 0.05%, with the balance being Fe and unavoidable impurities; the value of 2Cr+3Mo+2Cu is 1.5%, and the value of Mo / Cu is 2.5.

[0025] Example 5 The difference between this embodiment and Embodiment 2 is only that the steel reinforcement body is composed of the following components by mass percentage: C 0.18%, Si 0.4%, Mn 1%, Cr 0.11%, Mo 0.35%, P 0.015%, S 0.015%, Cu 0.14%, Ni 0.08%, Nb 0.07%, Ti 0.05%, with the balance being Fe and unavoidable impurities; the value of 2Cr+3Mo+2Cu is 1.55%, and the value of Mo / Cu is 2.5.

[0026] Example 6 The difference between this embodiment and Embodiment 2 is only that the steel reinforcement body is composed of the following components by mass percentage: C 0.18%, Si 0.4%, Mn 1%, Cr 0.2%, Mo 0.3%, P 0.015%, S 0.015%, Cu 0.1%, Ni 0.08%, Nb 0.07%, Ti 0.05%, with the balance being Fe and unavoidable impurities; the value of 2Cr+3Mo+2Cu is 1.5%, and the value of Mo / Cu is 3.

[0027] Example 7 The difference between this embodiment and Embodiment 2 is only that the steel reinforcement body is composed of the following components by mass percentage: C 0.18%, Si 0.4%, Mn 1%, Cr 0.15%, Mo 0.3%, P 0.015%, S 0.015%, Cu 0.15%, Ni 0.08%, Nb 0.07%, Ti 0.05%, with the balance being Fe and unavoidable impurities; the value of 2Cr+3Mo+2Cu is 1.5%, and the value of Mo / Cu is 2.

[0028] Example 8 The only difference between this embodiment and Embodiment 2 is that during water quenching, the temperature is first cooled to 400°C at a rate of 55°C / s, and then cooled to 150°C at a rate of 35°C / s.

[0029] Example 9 The only difference between this embodiment and Embodiment 2 is that during water quenching, the temperature is first cooled to 400°C at a rate of 60°C / s, and then cooled to 150°C at a rate of 40°C / s.

[0030] Example 10 The only difference between this embodiment and Embodiment 2 is that during water quenching, the temperature is first cooled to 400°C at a rate of 35°C / s, and then cooled to 150°C at a rate of 55°C / s.

[0031] Example 11 The only difference between this embodiment and Embodiment 2 is that the water quenching is performed at a rate of 55°C / s to 150°C.

[0032] Example 12 The only difference between this embodiment and Embodiment 2 is that the water quenching is performed at a rate of 35°C / s to 150°C.

[0033] Comparative Example 1 The only difference between this comparative example and Example 2 is that the steel bar body in this comparative example is composed of the following components by mass percentage: C 0.18%, Si 0.4%, Mn 1%, Mo 0.25%, P 0.015%, S 0.015%, Cu 0.1%, Ni 0.08%, Nb 0.07%, Ti 0.05%.

[0034] Comparative Example 2 The only difference between this comparative example and Example 2 is that the steel reinforcement body in this comparative example is composed of the following components by mass percentage: C 0.18%, Si 0.4%, Mn 1%, Cr 0.25%, P 0.015%, S 0.015%, Cu 0.1%, Ni 0.08%, Nb 0.07%, Ti 0.05%.

[0035] Comparative Example 3 The only difference between this comparative example and Example 2 is that the steel reinforcement body in this comparative example is composed of the following components by mass percentage: C 0.18%, Si 0.4%, Mn 1%, Cr 0.25%, Mo 0.25%, P 0.015%, S 0.015%, Ni 0.08%, Nb 0.07%, Ti 0.05%.

[0036] Experimental Example 1 The fire-resistant and corrosion-resistant steel bars obtained in Examples 1-7 and Comparative Examples 1-3 were tested according to the following methods: 1. Yield Strength: The yield strength of the sample shall be tested according to the test method specified in GB / T 228.1-2021 "Metallic Materials - Tensile Testing - Part 1: Test at Room Temperature". According to Method A, the test rate for yield strength is 0.002 s. -1 The test results are shown in Table 1 below. 2. Corrosion resistance: The steel reinforcement was subjected to a neutral salt spray test (5% NaCl solution, temperature 35℃, relative humidity 95%) according to the test method specified in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test" for 500 hours. The test spray pressure was 126 kPa, the saturated tower hot water temperature was 50℃, and the sample size was 3mm × 15mm × 40mm. The corrosion area (%) = corrosion area / sample area. The test results are shown in Table 1 below.

[0037] Table 1. Performance test results of the steel reinforcement in Examples 1-7 and Comparative Examples 1-3

[0038] As shown in Table 1, the room temperature yield strength and the yield strength at 600℃ of Examples 1-7 are higher than those of Comparative Examples 1-3, and the corrosion area of ​​Examples 1-7 is lower than that of Comparative Examples 1-3. This indicates that the present invention improves the fire resistance and corrosion resistance of steel bars by limiting the mass content relationship of Cr, Mo and Cu to 2Cr+3Mo+2Cu=1.45%~1.55%.

[0039] Experimental Example 2 The fire-resistant and corrosion-resistant steel reinforcement bodies obtained in Examples 2 and 8-12 were tested according to the following methods: Corrosion resistance: The steel reinforcement was subjected to a neutral salt spray test (5% NaCl solution, temperature 35℃, relative humidity 95%) according to the test method specified in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test" for 500 hours. The test spray pressure was 126 kPa, the saturated tower hot water temperature was 50℃, and the sample size was 3mm × 15mm × 40mm. The corrosion area (%) = corrosion area / sample area. The test results are shown in Table 2 below.

[0040] Table 2 Performance test results of the steel reinforcement in Examples 2 and 8-12

[0041] The corrosion area of ​​Examples 2 and 8-9 is lower than that of Examples 10-12, indicating that the present invention further improves the corrosion resistance of the steel bar body by limiting the cooling rate during water quenching.

[0042] Experimental Example 3 The fire-resistant and corrosion-resistant steel bars obtained in Examples 1-3 and Example 8 were tested according to the following method: Corrosion resistance: The steel reinforcement body was subjected to a neutral salt spray test (5% NaCl solution, temperature 35℃, relative humidity 95%) according to the test method specified in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test" for 500 hours. After that, the corrosion resistance level was determined according to the test method specified in QB / T 3832-1999 "Evaluation of Corrosion Test Results of Metal Coatings of Light Industrial Products". The test results are expressed as corrosion resistance level 1 to 10. The test results are shown in Table 3 below.

[0043] Table 3 Performance test results of steel bars in Examples 1-3 and Example 8

[0044] The corrosion resistance rating of Examples 1-3 and Example 8 is 10, therefore the steel bars prepared by this invention have excellent corrosion resistance.

[0045] The above are merely preferred embodiments of the present invention and are 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 fire-resistant and corrosion-resistant reinforcing steel bar, characterized in that, The fire-resistant and corrosion-resistant steel bar comprises a steel bar body and a coating. The steel bar body is composed of the following components by mass percentage: C 0.15%~0.22%, Si 0.3%~0.5%, Mn 0.8%~1.2%, Cr 0.11%~0.25%, Mo 0.25%~0.35%, P≤0.02%, S≤0.02%, Cu 0.1%~0.15%, Ni 0.06%~0.1%, Nb≤0.08%, Ti≤0.06%, with the balance being Fe and unavoidable impurities. The mass content of Cr, Mo, and Cu satisfies the relationship: 2Cr + 3Mo + 2Cu = 1.45%~1.55%. The mass content of Mo and Cu satisfies the following relationship: 2≤Mo / Cu≤3; The method for preparing the fire-resistant and corrosion-resistant steel reinforcement includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast to obtain the billet; S2. The cast billet undergoes heat treatment, rough rolling, fine rolling, quenching, tempering, and cooling to obtain the steel bar body; S3. After the coating is applied to the steel bar body, it is cured to form a coating, thus obtaining a fire-resistant and corrosion-resistant steel bar; In step S2, the quenching process is water quenching; During water quenching, the temperature is first cooled to 400°C at a rate of 50-60°C / s, and then cooled to 150°C at a rate of 30-40°C / s.

2. A method for preparing fire-resistant and corrosion-resistant reinforcing steel bars, used to prepare the fire-resistant and corrosion-resistant reinforcing steel bars as described in claim 1, characterized in that, Includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast to obtain the billet; S2. The cast billet undergoes heat treatment, rough rolling, fine rolling, quenching, tempering, and cooling to obtain the steel bar body; S3. After the coating is applied to the steel bar body, it is cured to form a coating, thus obtaining a fire-resistant and corrosion-resistant steel bar.

3. The method for preparing fire-resistant and corrosion-resistant reinforcing steel according to claim 2, characterized in that, In step S1, argon gas is introduced during the continuous casting process, and the pressure of the argon gas is 0.1~0.3MPa.

4. The method for preparing fire-resistant and corrosion-resistant reinforcing steel according to claim 2, characterized in that, In step S2, the temperature of the heat treatment is 1100~1150℃.

5. The method for preparing a fire-resistant and corrosion-resistant steel bar according to claim 2, characterized in that, In step S2, the initial rolling temperature during rough rolling is 1050~1120℃, and the final rolling temperature during rough rolling is 1000~1100℃. The initial rolling temperature during the finishing rolling process is 950~1050℃, and the final rolling temperature during the finishing rolling process is 850~900℃.

6. The method for preparing a fire-resistant and corrosion-resistant steel bar according to claim 2, characterized in that, In step S2, the tempering temperature is 450~500℃ and the tempering time is 100~150s.

7. The method for preparing fire-resistant and corrosion-resistant reinforcing steel according to claim 2, characterized in that, In step S3, the raw materials of the coating include the following components by weight: 40-60 parts aluminum dihydrogen phosphate, 40-60 parts magnesium dihydrogen phosphate, 8-12 parts styrene-acrylic emulsion, 1-3 parts zinc nitrate, 1-3 parts zinc oxide, 2-5 parts silica sol, and 200 parts water.

8. The method for preparing a fire-resistant and corrosion-resistant steel bar according to claim 7, characterized in that, The coating is prepared by mixing the raw materials of the coating evenly to obtain the coating.

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