High corrosion resistance 600mpa grade cr-ni system reinforcing bar and its production method

Abstract

The present application relates to a kind of high corrosion resistance 600MPa Cr-Ni system reinforcing bar and its production method, belong to hot-rolled ribbed bar technical field.The present application uses " high-temperature opening rolling + pre-water cooling + low-temperature finish rolling + slow cooling after rolling " process, on the basis of traditional reinforcing bar, reasonably control the content of Cr, Ni and V and other elements, corrosion-resistant steel material is added with the alloy that can prevent corrosion, such as Ni, Cr etc., improve corrosion resistance.Compared with traditional alloy corrosion-resistant reinforcing bar, reduce alloy content, wherein Cr:3.0~5.5%, Ni:0.50~0.55%, substantially reduce production cost.The corrosion-resistant reinforcing bar prepared by the present application has the performance of Rp 0.2 ≥650MPa, Rm≥850MPa, Agt≥9%, relative corrosion rate is 40~60%, with excellent corrosion resistance.The present application solves the problem that the corrosion-resistant reinforcing bar cannot have corrosion resistance, mechanical properties and cost.

Description

Technical Field

[0001] This invention belongs to the technical field of hot-rolled ribbed steel bars, specifically relating to a high corrosion-resistant 600MPa grade Cr-Ni steel bar and its production method. Background Technology

[0002] Rapid construction and development across my country have led to an increased demand for building steel. Simultaneously, people are placing higher demands on the safety and lifespan of buildings, requiring steel reinforcement to possess not only excellent seismic resistance but also superior corrosion resistance. Corrosion-resistant steel reinforcement, while maintaining its mechanical properties, significantly improves corrosion resistance by altering the types of trace alloying elements it contains. This changes the structure and chemical properties of the rust layer formed during corrosion, thereby inhibiting the corrosion process.

[0003] In recent years, China has accelerated its research on corrosion-resistant steel bars. For example, the Jiangsu (Shagang) Iron and Steel Research Institute has developed a high-strength and high-corrosion-resistant steel bar, "Crl0M01" (containing approximately 10 wt.% Cr and 1 wt.% Mo), through optimized design of alloy composition and production process. The Beijing Iron and Steel Research Institute has also developed a fine-grained Cu-P series corrosion-resistant steel bar. However, due to the high content of alloying elements, low strength-to-yield ratio, poor plasticity, high price, and low corrosion resistance, the application scope of these corrosion-resistant steel bars is limited, making it difficult to promote their use on a large scale.

[0004] Traditional corrosion-resistant steel bars have limited applications and are difficult to promote on a large scale due to their high alloy content, low strength-to-yield ratio, poor plasticity, high price, and low corrosion resistance. Therefore, it is essential to develop a low-cost, high-corrosion-resistant, and high-strength steel bar. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the present invention aims to provide a 600MPa grade chloride ion corrosion resistant steel bar, which has excellent corrosion resistance, comprehensive mechanical properties and weldability, and can be manufactured with low material and process costs, making it suitable for widespread use in marine engineering.

[0006] A method for producing high corrosion-resistant 600MPa grade Cr-Ni steel bars includes the following steps:

[0007] (1) Converter roughing: High-quality scrap steel is used. The amount of nickel-iron added is determined according to the amount of trace alloying elements collected in special scrap steel, and it is added into the furnace with the scrap steel at the lower limit. The final slag basicity is controlled at R=2.8~3.2, and the final lance pressing time is >40s. Bottom blowing argon gas is used for stirring throughout the converter blowing process. The converter tapping temperature is 1640℃~1660℃. Bottom blowing argon gas is turned on 1~2 minutes before tapping, and large volume stirring is carried out during the tapping process. Clean turnover steel ladle is used to ensure red ladle tapping. Double slag blocking is used with slag plug + slag blocking cone to prevent large amount of slag from falling. The slag layer thickness in the ladle is <50mm. Low-aluminum ferrosilicon, ferromanganese silicomanganese, low-carbon ferrochrome, etc. are used for deoxidation and alloying in the steel ladle. Slag washing: Lime and quartz sand are added with the steel stream during the tapping process. The timing of addition is when 1 / 3 of the steel is tapped, and it is added together with the alloy. Bottom blowing argon gas is used for stirring throughout the tapping process. The steel ladle is blown in the argon station for 3 minutes and then sampled.

[0008] (2) LF refining operation: lime + ferrosilicon powder is used for slag making, and fluorite is added to ensure the refining submerged arc operation; the top slag R is controlled between 1.5 and 2.5; after the composition and temperature are qualified, soft blowing argon is carried out, and the soft blowing time shall not be less than 10 minutes;

[0009] (3) Rolling: After rolling, the steel bars are obtained by cooling.

[0010] Further, in step (3), the heating temperature for rolling is 1150℃~1200℃, and after holding for 100~120 minutes, hot continuous rolling is carried out. The initial rolling temperature is 1100~1150℃, and the finishing rolling temperature is controlled to be 900℃~1050℃ through a pre-water cooling process. The final rolling temperature is 890℃~1040℃.

[0011] Furthermore, in the rolling process described in step (3), the temperature of the upper cooling bed is 900℃~1050℃, the cooling method after rolling is slow cooling, and the cooling rate is controlled at 0.5~1℃ / s.

[0012] A high corrosion-resistant 600MPa grade Cr-Ni steel bar is prepared by the above method. Its chemical composition, by mass percentage, includes: C: 0.08~0.10%, Si: 0.45~0.55%, Mn: 1.1~1.3%, Cr: 3.0~5.5%, Ni: 0.50~0.55%, P: 0.02~0.03%, S: 0.008~0.01%, V: 0.05~0.08%, Ti≤0.1%, Al≤0.1%, with the balance being Fe and unavoidable impurities.

[0013] Furthermore, the high corrosion-resistant 600MPa grade Cr-Ni steel bar has a yield strength ≥650MPa, a tensile strength ≥847MPa, and a total elongation ≥9.2% under maximum force.

[0014] Furthermore, the microstructure of the high corrosion resistance 600MPa grade Cr-Ni steel bar is ferrite and bainite.

[0015] Furthermore, the grain size of the high corrosion resistance 600MPa grade Cr-Ni steel bar is 10-10.5.

[0016] Furthermore, the high corrosion resistance 600MPa grade Cr-Ni steel reinforcement exhibited an average corrosion rate of 2.748-3.512 g / (m²) in a 72-hour accelerated immersion corrosion test. 2 •h), with a relative corrosion rate of no more than 60%.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] This invention, based on traditional reinforcing steel, rationally controls the content of elements such as Cr, Ni, and V. Corrosion-resistant steel is made by adding alloys that inhibit corrosion, such as Ni and Cr. These alloys accumulate in the inner rust layer, blocking cracks and fissures within the rust layer and generating a Cr-rich α-FeOOH amorphous oxide product layer, thus improving corrosion resistance. Compared to traditional alloy corrosion-resistant reinforcing steel, the reduced alloy content (Cr: 3.0~5.5%, Ni: 0.50~0.55%) significantly lowers production costs. The corrosion-resistant reinforcing steel exhibits the following properties: Rp 0.2 With a strength ≥650MPa, Rm≥850MPa, Att≥9%, and a relative corrosion rate of 40~60%, this invention exhibits excellent corrosion resistance. It solves the problem of simultaneously achieving corrosion resistance, mechanical properties, and cost-effectiveness in chloride ion corrosion-resistant steel bars.

[0019] This invention optimizes the alloy composition system, purifies steelmaking, and rationally controls the heating temperature, initial rolling temperature, finishing rolling temperature, cooling bed temperature, and cooling method. It adopts a process of "high-temperature initial rolling + pre-water cooling + low-temperature finishing rolling + slow cooling after rolling" to make the steel reinforcement structure ferrite, pearlite, and bainite, thereby achieving good strength, toughness, and high corrosion resistance. Attached Figure Description

[0020] Figure 1 This is a flow chart of the production method of the high corrosion resistance 600MPa grade Cr-Ni steel bar of the present invention;

[0021] Figure 2 The corrosion morphology of the 600MPa grade Cr-Ni chloride ion resistant steel bars and ordinary steel bars in Example 2 after immersion in a 2% NaCl solution for 72 hours is shown.

[0022] Figure 3The corrosion morphology images are of 600MPa grade Cr-Ni chloride ion resistant steel bars and ordinary steel bars from Examples 1, 3, 4, and 5, after being immersed in a 2% NaCl solution for 72 hours. Detailed Implementation

[0023] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] To facilitate understanding of the present invention, a more comprehensive description of the invention will be given below with reference to the accompanying drawings, and several embodiments of the invention will be provided. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0025] Example 1

[0026] A production method for high corrosion-resistant 600MPa grade Cr-Ni steel bars, the process is as follows: Figure 1 As shown, it includes the following steps:

[0027] (1) Converter roughing: High-quality scrap steel is used to reduce the mixing of impurities; the amount of nickel-iron added is determined according to the amount of trace alloying elements recovered in special scrap steel, and the lower limit is added into the furnace with the scrap steel; the basicity of the final slag is controlled at R=2.8~3.2, and the final lance pressing time is >40s; bottom blowing argon gas is used for stirring throughout the converter blowing process; the converter tapping temperature is controlled between 1640℃~1660℃; a steel ladle with good permeability is used with permeable bricks, and bottom blowing argon gas is turned on 1~2 minutes in advance before tapping. The steelmaking process involves high-volume stirring to ensure full melting of alloys; clean turnover ladles are used to ensure clean steel tapping; a double slag-blocking system using slag plugs and cones prevents excessive slag discharge, with a slag layer thickness of less than 50mm inside the ladle; low-aluminum ferrosilicon, ferromanganese silicomanganese, and low-carbon ferrochrome are used for deoxidation and alloying within the ladle; slag washing during tapping: lime and quartz sand are added with the steel stream during tapping, at the point when 1 / 3 of the steel has been tapped, along with the alloys; bottom-blowing argon stirring is performed throughout the tapping process, and the ladle is blown into the argon station for 3 minutes before sampling.

[0028] (2) LF refining operation: lime + ferrosilicon powder is used for slag formation, and fluorite is added to ensure the submerged arc refining operation. The top slag R is controlled between 1.5 and 2.5; after the composition and temperature are qualified, soft blowing argon is carried out, and the soft blowing time shall not be less than 10 minutes; the ladle temperature at the end of LF refining is combined with the continuous casting steel temperature.

[0029] (3) Rolling: The heating temperature is controlled at 1150℃~1200℃, and after holding at the temperature for 100~120 minutes, hot continuous rolling is carried out. The initial rolling temperature is 1100~1150℃, the finishing rolling temperature is 1000~1020℃, and the final rolling temperature is 1020℃~1040℃. No water quenching is performed during the rolling process. The upper cooling bed temperature is 1020℃~1050℃, and the post-rolling cooling method is slow cooling, with the cooling rate controlled at 0.5~1℃ / s.

[0030] The φ28mm steel bars obtained in this embodiment have a yield strength of 650 MPa, a tensile strength of 840 MPa, and a total elongation ≥9.8% under maximum force. The microstructure of the steel bars consists of ferrite and bainite. In a 72-hour accelerated corrosion immersion test, the average corrosion rate was 3.512 g / (m²). 2 ·h), with a relative corrosion rate of 59%.

[0031] A high-corrosion-resistant 600MPa grade Cr-Ni steel bar, prepared using the above method, has the following chemical composition by mass percentage: C: 0.08%, Si: 0.55%, Mn: 1.2%, Cr: 3.5%, Ni: 0.55%, P: 0.02%, S: 0.008%, V: 0.06%, Ti≤0.1%, Al≤0.1%, with the balance being Fe and unavoidable impurities. The corrosion-resistant steel incorporates corrosion-inhibiting alloys such as Ni and Cr. These alloys accumulate in the inner rust layer, blocking cracks and fissures within the rust layer and generating a Cu- and Cr-rich α-FeOOH amorphous oxide product layer, thus improving corrosion resistance.

[0032] The process of rolling in the recrystallization zone of austenite, followed by rolling in the non-recrystallization zone of austenite, and then rapid cooling, primarily refines the original austenite grains through recrystallization during rolling in the fully recrystallized zone. In the non-recrystallized zone, the grains are fully flattened, resulting in uniform and fine grains during the subsequent phase transformation, thus effectively improving the overall performance of the steel plate. The deformation during the rough rolling stage causes austenite recrystallization, resulting in a refinement effect. Simultaneously, in the finish rolling stage, austenite does not recrystallize; instead, the deformation flattens and elongates the austenite grains, forming strain-accumulated austenite in the form of dislocations, deformation bands, and cellular structures. This promotes the nucleation and growth of ferrite on defects within the deformed austenite grains, thereby achieving the goal of refining the phase transformation structure.

[0033] As the rolling temperature decreases, the number of dislocations and internal stresses within the microstructure increases, leading to a greater refinement of the original austenite grains and providing more nucleation sites for phase transformation. This results in an increased nucleation rate for ferrite and pearlite phase transformations. Secondly, as the rolling temperature decreases, the growth rate of ferrite and pearlite after nucleation slows down, thus lowering the rolling temperature yields finer ferrite and pearlite grains. Furthermore, statistical analysis of different phase volume fractions reveals that as the rolling temperature decreases, the volume fraction of ferrite decreases while the volume fraction of pearlite increases. This is because as the rolling temperature decreases, the undercooling increases, resulting in a greater driving force for pearlite phase transformation, thereby increasing the pearlite volume fraction.

[0034] Because the experimental steel contained a significant amount of alloying elements, a high heating temperature and sufficient holding time were employed to ensure complete alloy solution and reduce segregation. On the other hand, to improve the plasticity and bending performance of the steel reinforcement, the microstructure control aimed to avoid the formation of large-sized bainite. Due to the addition of alloying elements, bainite formation was highly likely during rapid cooling; therefore, the cooling rate was strictly controlled. Slow cooling was employed to increase the ferrite volume fraction and reduce the formation of large-sized bainite. Furthermore, the rolling process was adjusted to refine the grains, and pre-water cooling was used to lower the finishing rolling temperature, thereby refining the ferrite grains.

[0035] Example 2

[0036] A method for producing high corrosion-resistant 600MPa grade Cr-Ni steel bars includes the following steps:

[0037] (1) Converter roughing: High-quality scrap steel is used to reduce the mixing of impurities; the amount of nickel-iron added is determined according to the amount of trace alloying elements recovered in special scrap steel, and the lower limit is added into the furnace with the scrap steel; the basicity of the final slag is controlled at R=2.8~3.2, and the final lance pressing time is >40s; bottom blowing argon gas is used for stirring throughout the converter blowing process; the converter tapping temperature is controlled between 1640℃~1660℃; a steel ladle with good permeability is used with permeable bricks, and bottom blowing argon gas is turned on 1~2 minutes in advance before tapping. The steelmaking process involves high-volume stirring to ensure full melting of alloys; clean turnover ladles are used to ensure clean steel tapping; a double slag-blocking system using slag plugs and cones prevents excessive slag discharge, with a slag layer thickness of less than 50mm inside the ladle; low-aluminum ferrosilicon, ferromanganese silicomanganese, and low-carbon ferrochrome are used for deoxidation and alloying within the ladle; slag washing during tapping: lime and quartz sand are added with the steel stream during tapping, at the point when 1 / 3 of the steel has been tapped, along with the alloys; bottom-blowing argon stirring is performed throughout the tapping process, and the ladle is blown into the argon station for 3 minutes before sampling.

[0038] (2) LF refining operation: lime + ferrosilicon powder is used for slag formation, and fluorite is added to ensure the submerged arc refining operation. The top slag R is controlled between 1.5 and 2.5; after the composition and temperature are qualified, soft blowing argon is carried out, and the soft blowing time shall not be less than 10 minutes; the ladle temperature at the end of LF refining is combined with the continuous casting steel temperature.

[0039] (3) Rolling: The heating temperature is controlled at 1150℃~1200℃. After holding at this temperature for 100~120 minutes, hot continuous rolling is carried out. The initial rolling temperature is 1120~1140℃, the finishing rolling temperature is 900~920℃, and the final rolling temperature is 890℃~910℃. Water treatment is performed before finishing rolling to reduce the finishing rolling temperature. The upper cooling bed temperature is 900℃~930℃. The cooling method after rolling is slow cooling, and the cooling rate is controlled at 0.5~1℃ / s.

[0040] The φ28mm steel bars obtained in this embodiment have a yield strength of 662 MPa, a tensile strength of 847 MPa, and a total elongation ≥11% under maximum force. The microstructure of the steel bars consists of ferrite and bainite. In a 72-hour accelerated corrosion immersion test, the average corrosion rate was 3.483 g / (m²). 2 The relative corrosion rate is 58.5% (·h).

[0041] A high corrosion-resistant 600MPa grade Cr-Ni steel bar is prepared by the above method. Its chemical composition, by mass percentage, includes: C: 0.08%, Si: 0.55%, Mn: 1.2%, Cr: 3.5%, Ni: 0.55%, P: 0.02%, S: 0.008%, V: 0.06%, Ti≤0.1%, Al≤0.1%, with the balance being Fe and unavoidable impurities.

[0042] The corrosion morphology of the 600MPa grade Cr-Ni chloride-resistant steel bars and ordinary steel bars prepared in this embodiment after immersion in a 2% NaCl solution for 72 hours is shown in the following figures. Figure 2 As shown.

[0043] Example 3

[0044] A method for producing high corrosion-resistant 600MPa grade Cr-Ni steel bars includes the following steps:

[0045] (1) Converter roughing: High-quality scrap steel is used to reduce the mixing of impurities; the amount of nickel-iron added is determined according to the amount of trace alloying elements recovered in special scrap steel, and the lower limit is added into the furnace with the scrap steel; the basicity of the final slag is controlled at R=2.8~3.2, and the final lance pressing time is >40s; bottom blowing argon gas is used for stirring throughout the converter blowing process; the converter tapping temperature is controlled between 1640℃~1660℃; a steel ladle with good permeability is used with permeable bricks, and bottom blowing argon gas is turned on 1~2 minutes in advance before tapping. The steelmaking process involves high-volume stirring to ensure full melting of alloys; clean turnover ladles are used to ensure clean steel tapping; a double slag-blocking system using slag plugs and cones prevents excessive slag discharge, with a slag layer thickness of less than 50mm inside the ladle; low-aluminum ferrosilicon, ferromanganese silicomanganese, and low-carbon ferrochrome are used for deoxidation and alloying within the ladle; slag washing during tapping: lime and quartz sand are added with the steel stream during tapping, at the point when 1 / 3 of the steel has been tapped, along with the alloys; bottom-blowing argon stirring is performed throughout the tapping process, and the ladle is blown into the argon station for 3 minutes before sampling.

[0046] (2) LF refining operation: lime + ferrosilicon powder is used for slag formation, and fluorite is added to ensure the submerged arc refining operation. The top slag R is controlled between 1.5 and 2.5; after the composition and temperature are qualified, soft blowing argon is carried out, and the soft blowing time shall not be less than 10 minutes; the ladle temperature at the end of LF refining is combined with the continuous casting steel temperature.

[0047] (3) Rolling: The heating temperature is controlled at 1150℃~1200℃, and after holding at the temperature for 100~120 minutes, hot continuous rolling is carried out. The initial rolling temperature is 1130~1150℃, the finishing rolling temperature is 1020~1040℃, and the final rolling temperature is 1000℃~1020℃. No water quenching is performed during the rolling process. The upper cooling bed temperature is 1020℃~1050℃. The cooling method after rolling is slow cooling, and the cooling rate is controlled at 0.5~1℃ / s.

[0048] The φ14mm steel bars obtained in this embodiment have a yield strength of 665 MPa, a tensile strength of 854 MPa, and a total elongation ≥10% under maximum force. The microstructure of the steel bars consists of ferrite and bainite. In a 72-hour accelerated corrosion immersion test, the average corrosion rate was 3.500 g / (m²). 2 The relative corrosion rate is 58.8% (·h).

[0049] A high corrosion-resistant 600MPa grade Cr-Ni steel bar is prepared by the above method. Its chemical composition, by mass percentage, includes: C: 0.08%, Si: 0.55%, Mn: 1.2%, Cr: 3.5%, Ni: 0.55%, P: 0.02%, S: 0.008%, V: 0.05%, Ti≤0.1%, Al≤0.1%, with the balance being Fe and unavoidable impurities.

[0050] Example 4

[0051] A method for producing high corrosion-resistant 600MPa grade Cr-Ni steel bars includes the following steps:

[0052] (1) Converter roughing: High-quality scrap steel is used to reduce the mixing of impurities; the amount of nickel-iron added is determined according to the amount of trace alloying elements recovered in special scrap steel, and the lower limit is added into the furnace with the scrap steel; the basicity of the final slag is controlled at R=2.8~3.2, and the final lance pressing time is >40s; bottom blowing argon gas is used for stirring throughout the converter blowing process; the converter tapping temperature is controlled between 1640℃~1660℃; a steel ladle with good permeability is used with permeable bricks, and bottom blowing argon gas is turned on 1~2 minutes in advance before tapping. The steelmaking process involves high-volume stirring to ensure full melting of alloys; clean turnover ladles are used to ensure clean steel tapping; a double slag-blocking system using slag plugs and cones prevents excessive slag discharge, with a slag layer thickness of less than 50mm inside the ladle; low-aluminum ferrosilicon, ferromanganese silicomanganese, and low-carbon ferrochrome are used for deoxidation and alloying within the ladle; slag washing during tapping: lime and quartz sand are added with the steel stream during tapping, at the point when 1 / 3 of the steel has been tapped, along with the alloys; bottom-blowing argon stirring is performed throughout the tapping process, and the ladle is blown into the argon station for 3 minutes before sampling.

[0053] (2) LF refining operation: lime + ferrosilicon powder is used for slag formation, and fluorite is added to ensure the submerged arc refining operation. The top slag R is controlled between 1.5 and 2.5; after the composition and temperature are qualified, soft blowing argon is carried out, and the soft blowing time shall not be less than 10 minutes; the ladle temperature at the end of LF refining is combined with the continuous casting steel temperature.

[0054] (3) Rolling: The heating temperature is controlled at 1150℃~1200℃, and after holding at the temperature for 100~120 minutes, hot continuous rolling is carried out. The initial rolling temperature is 1100~1120℃, the finishing rolling temperature is 990℃~1030℃, and the final rolling temperature is 1000℃~1040℃. Pre-water treatment is carried out during the rolling process. The upper cooling bed temperature is 1000℃~1050℃. The post-rolling cooling method is slow cooling, and the cooling rate is controlled at 0.5~1℃ / s.

[0055] The φ28mm steel bars obtained in this embodiment have a yield strength of 670MPa, a tensile strength of 980MPa, and a total elongation ≥9.2% under maximum force. The microstructure of the steel bars consists of ferrite and bainite. In a 72-hour accelerated corrosion immersion test, the average corrosion rate was 2.864 g / (m²). 2 The relative corrosion rate was 48.1% (·h).

[0056] A high corrosion-resistant 600MPa grade Cr-Ni steel bar is prepared by the above method. Its chemical composition, by mass percentage, includes: C: 0.08%, Si: 0.45%, Mn: 1.2%, Cr: 5.5%, Ni: 0.55%, P: 0.02%, S: 0.008%, V: 0.05%, Ti≤0.1%, Al≤0.1%, with the balance being Fe and unavoidable impurities.

[0057] Example 5

[0058] A method for producing high corrosion-resistant 600MPa grade Cr-Ni steel bars includes the following steps:

[0059] (1) Converter roughing: High-quality scrap steel is used to reduce the mixing of impurities; the amount of nickel-iron added is determined according to the amount of trace alloying elements recovered in special scrap steel, and the lower limit is added into the furnace with the scrap steel; the basicity of the final slag is controlled at R=2.8~3.2, and the final lance pressing time is >40s; bottom blowing argon gas is used for stirring throughout the converter blowing process; the converter tapping temperature is controlled between 1640℃~1660℃; a steel ladle with good permeability is used with permeable bricks, and bottom blowing argon gas is turned on 1~2 minutes in advance before tapping. The steelmaking process involves high-volume stirring to ensure full melting of alloys; clean turnover ladles are used to ensure clean steel tapping; a double slag-blocking system using slag plugs and cones prevents excessive slag discharge, with a slag layer thickness of less than 50mm inside the ladle; low-aluminum ferrosilicon, ferromanganese silicomanganese, and low-carbon ferrochrome are used for deoxidation and alloying within the ladle; slag washing during tapping: lime and quartz sand are added with the steel stream during tapping, at the point when 1 / 3 of the steel has been tapped, along with the alloys; bottom-blowing argon stirring is performed throughout the tapping process, and the ladle is blown into the argon station for 3 minutes before sampling.

[0060] (2) LF refining operation: lime + ferrosilicon powder is used for slag formation, and fluorite is added to ensure the submerged arc refining operation. The top slag R is controlled between 1.5 and 2.5; after the composition and temperature are qualified, soft blowing argon is carried out, and the soft blowing time shall not be less than 10 minutes; the ladle temperature at the end of LF refining is combined with the continuous casting steel temperature.

[0061] (3) Rolling: The heating temperature is controlled at 1150℃~1200℃, and after holding at the temperature for 100~120 minutes, hot continuous rolling is carried out. The initial rolling temperature is 1100~1120℃, the finishing rolling temperature is 990℃~1050℃, and the final rolling temperature is 1000℃~1040℃. Pre-water treatment is carried out during the rolling process. The upper cooling bed temperature is 1000℃~1050℃. The post-rolling cooling method is slow cooling, and the cooling rate is controlled at 0.5~1℃ / s.

[0062] The φ14mm steel bars obtained in this embodiment have a yield strength of 678MPa, a tensile strength of 990MPa, and a total elongation ≥9.3% under maximum force. The microstructure of the steel bars consists of ferrite and bainite. In a 72-hour accelerated corrosion immersion test, the average corrosion rate was 2.748 g / (m²). 2 The relative corrosion rate was 46.2% (·h).

[0063] A high-corrosion-resistant 600MPa grade Cr-Ni steel bar, prepared by the above method, has the following chemical composition by mass percentage: C: 0.08%, Si: 0.45%, Mn: 1.2%, Cr: 5.5%, Ni: 0.55%, P: 0.02%, S: 0.008%, V: 0.05%, Ti≤0.1%, Al≤0.1%, with the balance being Fe and unavoidable impurities. This invention achieves this by controlling the content of alloying elements such as C, Si, Mn, Cu, Cr, Ni, P, and S.

[0064] Figure 3 The corrosion morphology images are of 600MPa grade Cr-Ni chloride ion resistant steel bars and ordinary steel bars from Examples 1, 3, 4, and 5, after being immersed in a 2% NaCl solution for 72 hours.

[0065] Table 1 is a comparison table of the 72h corrosion rates of 600MPa grade Cr-Ni series chloride ion corrosion resistant steel bars and ordinary steel bars;

[0066]

[0067] Table 2 shows the mechanical properties of 600MPa grade Cr-Ni series chloride ion corrosion resistant steel bars.

[0068]

Claims

1. A method for producing high corrosion-resistant 600MPa grade Cr-Ni steel bars, characterized in that, Includes the following steps: (1) Converter roughing: High-quality scrap steel is used. The amount of nickel-iron added is determined according to the amount of trace alloying elements collected in special scrap steel, and it is added into the furnace with the scrap steel at the lower limit. The basicity of the final slag is controlled at R=2.8~3.2, and the final lance pressing time is >40s. Bottom blowing argon gas is used for stirring throughout the converter blowing process. The converter tapping temperature is 1640℃~1660℃. Bottom blowing argon gas is turned on 1~2 minutes before tapping, and large volume stirring is carried out during the tapping process. Clean turnover steel ladle is used to ensure red ladle tapping. Double slag blocking is used with slag plug + slag blocking cone to prevent large amount of slag from falling. The slag layer thickness in the ladle is <50mm. Low-aluminum ferrosilicon, ferromanganese silicomanganese, and low-carbon ferrochrome are used for deoxidation and alloying in the ladle. Slag washing: Lime and quartz sand are added with the steel stream during the tapping process. The timing of addition is when 1 / 3 of the steel is tapped, and it is added together with the alloy. Bottom blowing argon gas is used for stirring throughout the tapping process. The ladle is blown in the argon station for 3 minutes and then sampled. (2) LF refining operation: lime + ferrosilicon powder is used for slag making, and fluorite is added to ensure the refining submerged arc operation; the top slag R is controlled between 1.5 and 2.5; after the composition and temperature are qualified, soft blowing argon is carried out, and the soft blowing time shall not be less than 10 minutes; (3) Rolling: After rolling and cooling, high corrosion-resistant 600MPa grade Cr-Ni steel bars are obtained; The heating temperature for rolling in step (3) is 1150℃~1200℃. After holding for 100~120 minutes, hot continuous rolling is carried out. The initial rolling temperature is 1100~1150℃. Through the pre-water cooling process, the finishing rolling temperature is controlled to be 900℃~1050℃, and the final rolling temperature is 890℃~1040℃. In the rolling process described in step (3), the temperature of the upper cooling bed is 900℃~1050℃, and the cooling method after rolling is slow cooling with a cooling rate controlled at 0.5~1℃ / s; The chemical composition of the high corrosion-resistant 600MPa grade Cr-Ni steel reinforcement, by mass percentage, includes: C: 0.08~0.10%, Si: 0.45~0.55%, Mn: 1.1~1.3%, Cr: 3.0~5.5%, Ni: 0.50~0.55%, P: 0.02~0.03%, S: 0.008~0.01%, V: 0.05~0.08%, Ti≤0.1%, Al≤0.1%, balance is Fe and unavoidable impurities.

2. The production method of high corrosion-resistant 600MPa grade Cr-Ni steel bars according to claim 1, characterized in that, The high corrosion-resistant 600MPa grade Cr-Ni steel bars have a yield strength ≥650MPa, a tensile strength ≥847MPa, and a total elongation ≥9.2% under maximum force.

3. The production method of high corrosion-resistant 600MPa grade Cr-Ni steel bars according to claim 1, characterized in that, The microstructure of the high corrosion resistance 600MPa grade Cr-Ni steel bar consists of ferrite and bainite.

4. The production method of high corrosion-resistant 600MPa grade Cr-Ni steel bars according to claim 1, characterized in that, The high corrosion-resistant 600MPa grade Cr-Ni steel bar has a grain size of 10-10.

5.

5. The method for producing high corrosion-resistant 600MPa grade Cr-Ni steel bars according to claim 1, characterized in that, The high corrosion-resistant 600MPa grade Cr-Ni steel bars exhibited an average corrosion rate of 2.748-3.512 g / (m²) in a 72-hour accelerated immersion corrosion test. 2 •h), with a relative corrosion rate of no more than 60%.

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