CN115976429B - 600 MPa-level corrosion-resistant steel bar and preparation method thereof - Google Patents

Abstract

The invention provides a 600MPa grade corrosion-resistant steel bar and a preparation method thereof. The steel bar comprises the chemical components in percentage by mass, and comprises the working procedures of molten iron pretreatment, converter smelting, molten steel refining, billet continuous casting, hot continuous rolling and temperature control and cooling control in the ：Cr:1.00～1.10％、Mo:0.15～0.30％、Ni:0.45～0.50％、Cu:0.50～0.55％、V:0.01～0.02％、P:0.01～0.03％、C:0.10～0.13％、Si:0.30～0.40％、Mn:0.80～1.60％、S:0.001～0.025％. method. The yield strength of the steel bar can reach more than 600MPa, and compared with the HRB600E steel bar, the steel bar has the chlorine ion corrosion resistance, the relative corrosion rate is lower than 70 percent, and the steel bar is particularly suitable for being applied to coastal construction and ocean engineering.

Description

A 600MPa grade corrosion-resistant steel bar and a preparation method thereof

Technical Field

The present invention relates to the technical field of metallurgy, and more particularly to a 600MPa-grade corrosion-resistant steel bar and a preparation method thereof.

Background technique

According to the requirements of actively expanding the space for marine economic development in our country's plan, promoting the acceleration of marine economic development and comprehensive development of coastal areas, and then driving the accelerated development of marine engineering and coastal infrastructure, the demand for chloride ion corrosion-resistant steel bars will increase.

Steel bar corrosion caused by chloride ions has always been an unavoidable problem in coastal building structures. It not only causes the loss and waste of natural resources, but the cracks or damage caused by corrosion will also affect the normal use of the overall structure, reduce the service life of coastal buildings, and endanger human life and property safety.

In order to meet the urgent development needs of the coastal economic zone and improve the reliability of marine engineering construction, domestic and foreign manufacturers have developed a variety of corrosion-resistant steel bars and anti-corrosion measures. Among them, although stainless steel bars with good corrosion resistance are suitable for various corrosive environments in marine economic construction, they are expensive and complex in process. The selling price can be 5 to 6 times that of ordinary hot-rolled ribbed steel bars. At present, they cannot be put into use on a large scale along my country's long coastline. For other anti-corrosion measures, such as pre-coating of protective coatings on the surface of steel bars and hot-dip coating of other inert metals, it is necessary to reasonably control the thickness and uniformity of the protective layer. Different thickness and uniformity will lead to uneven corrosion resistance of steel bars. In addition, during the service life of the building structure, the coating and the coated metal are easy to detach from the surface of the substrate, resulting in local corrosion and promoting the positive corrosion process.

Summary of the invention

In view of the deficiencies in the prior art, one of the purposes of the present invention is to solve one or more problems in the prior art. For example, one of the purposes of the present invention is to provide a corrosion-resistant steel bar with high yield strength and good corrosion resistance.

One aspect of the present invention provides a 600MPa grade corrosion-resistant steel bar, whose chemical composition, measured by mass percentage, may include: Cr: 1.00-1.10%, Mo: 0.15-0.30%, Ni: 0.45-0.50%, Cu: 0.50-0.55%, V: 0.01-0.02%, P: 0.01-0.03%, C: 0.10-0.13%, Si: 0.30-0.40%, Mn: 0.80-1.60%, S: 0.001-0.025%, the remainder being iron and unavoidable impurities, and the carbon equivalent Ceq is not greater than 0.58.

In an exemplary embodiment of the 600 MPa grade corrosion-resistant steel bar of the present invention, the chemical composition thereof, by mass percentage, may be 1.98-2.00% Cr+Mo+Ni+Cu.

In an exemplary embodiment of the 600 MPa grade corrosion-resistant steel bar of the present invention, the tensile strength of the steel bar may be ≥750 MPa, the strength-to-yield ratio may be ≥1.5, the elongation after fracture may be ≥15%, and the total elongation under maximum force may be ≥8%.

In an exemplary embodiment of the 600 MPa grade corrosion-resistant steel bar of the present invention, the average corrosion rate may be 4.27 g/m ² ·h in 72 hours of immersion corrosion.

In an exemplary embodiment of the 600 MPa grade corrosion-resistant steel bar of the present invention, the relative corrosion rate may be no greater than 69% after 72 hours of immersion corrosion.

In an exemplary embodiment of the 600 MPa grade corrosion-resistant steel bar of the present invention, in an aqueous solution with a mass fraction of NaCl of 3.5%, the self-corrosion potential of the steel bar may be -0.575 V, and the self-corrosion current density may be 24.9 μA·cm ^-2 .

Another aspect of the present invention provides a method for preparing 600MPa grade corrosion-resistant steel bars, which may include molten iron pretreatment, converter smelting, molten steel refining, billet continuous casting, hot rolling and temperature control and cooling processes, wherein the temperature control and cooling process includes: after the billet continuous casting is completed, the heating temperature is controlled at 1150°C±50°C, and hot rolling is performed after keeping warm for 30 to 50 minutes, the starting rolling temperature is 1140±50°C, the intermediate rolling temperature is 950°C~970°C, and the final rolling temperature is 1080°C~1100°C.

In an exemplary embodiment of the method for preparing 600 MPa grade corrosion-resistant steel bars of the present invention, no water penetration treatment is performed during the rolling process, the upper cooling bed temperature is 840° C. to 870° C., and the cooling is performed after rolling, and the cooling rate is controlled at 1° C./second.

In an exemplary embodiment of the method for preparing 600 MPa grade corrosion-resistant steel bars of the present invention, at the end point of converter smelting, C≧0.05% and P≦0.02% in the molten steel by mass percentage.

Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

(1) The steel bar of the present invention has a yield strength of more than 600 MPa, a significant yield platform of the stress-strain curve, good seismic performance, and a relative corrosion rate of less than 70% of the chloride ion corrosion resistance of HRB600E steel bar. The steel bar has strong corrosion resistance and is particularly suitable for use in coastal buildings and marine engineering.

(2) The welding performance and mechanical properties of the steel bars of the present invention meet the requirements of "GB/T 1499.2-2018 Steel for Reinforced Concrete Part 2: Hot-rolled Ribbed Steel Bars" for 600MPa grade earthquake-resistant steel bars, and can effectively extend the service life of coastal buildings and projects.

(3) The steel bar and preparation method of the present invention achieve the performance described in this article by rationally designing the respective contents and synergistic relationship of the corrosion-resistant alloying elements Cr, Mo, Ni and Cu with a small amount of Cr, Mo, Ni and Cu added, thereby saving smelting costs; and the preparation process is simple, which is suitable for popularization in coastal buildings and marine engineering.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become more apparent from the following description in conjunction with the accompanying drawings, in which:

FIG. 1 is a microstructure diagram of the core of the corrosion-resistant steel bar in Example 1 of the present invention.

FIG. 2 is a microstructure diagram of the edge of the corrosion-resistant steel bar in Example 1 of the present invention.

FIG3 is a microstructure diagram of the corrosion-resistant steel bar at 1/4 of the circumference in Example 1 of the present invention.

FIG. 4 is a microstructure morphology diagram of the corrosion-resistant steel bar at different magnifications in Example 1 of the present invention.

FIG5 is a comparison chart of the weight loss from corrosion of each sample of Example 1 of the present invention and Comparative Example 1 after a 72-hour immersion test.

FIG6 is a comparison chart of the corrosion rates of samples of Example 1 of the present invention and Comparative Example 1 in a 72-hour immersion test.

Detailed ways

Hereinafter, a 600 MPa grade corrosion-resistant steel bar and a production method thereof according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

One aspect of the present invention provides a 600MPa grade corrosion-resistant steel bar. In an exemplary embodiment of the 600MPa grade corrosion-resistant steel bar, the steel bar chemical composition, by mass percentage, includes: Cr: 1.00-1.10%, Mo: 0.15-0.30%, Ni: 0.45-0.50%, Cu: 0.50-0.55%, V: 0.01-0.02%, P: 0.01-0.03%, C: 0.10-0.13%, Si: 0.30-0.40%, Mn: 0.80-1.60%, S: 0.001-0.025%, the balance is iron and unavoidable impurities, and the carbon equivalent Ceq is not more than 0.58. For example, in some embodiments, the chemical composition is calculated by mass percentage, Cr: 1.02-1.08%, Mo: 0.18-0.27%, Ni: 0.48-0.49%, Cu: 0.51-0.54%, V: 0.011-0.018%, P: 0.012-0.027%, C: 0.11-0.12%, Si: 0.32-0.39%, Mn: 0.81-1.58%, S: 0.001-0.022%, the balance is iron and unavoidable impurities, and the carbon equivalent Ceq is not greater than 0.55 or not greater than 0.53 or not greater than 0.48 or not greater than 0.45 or not greater than 0.42. It is known in the art that carbon equivalent Ceq = C + Mn / 6 + (Cr + V + Mo) / 5 + (Cu + Ni) / 15.

Among them, in the above chemical composition, for the Cr element, adding a mass fraction of 1.00 to 1.10% of the Cr element can effectively reduce the self-corrosion potential during the corrosion of the steel bar and promote the formation of an α-phase passivation film on the surface of the steel bar; the Cr element exists in the rust layer in the form of oxides, which can increase the density and stability of the rust layer and prevent chloride ions from corroding the steel bar matrix; if more than 1.10% of Cr is added by mass, the plasticity and toughness of the steel bar will be reduced, affecting the mechanical properties of the steel bar. Preferably, the Cr content can be 1.02% to 1.10%, which can effectively avoid the loss of mechanical properties of the steel bar in coordination with the content of other chemical components of the steel bar. For example, the Cr content can be 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08% or 1.09%.

For the Ni element, the mass percentage of 0.45-0.50% Ni and 1.00-1.10% Cr cooperate with each other, which can significantly improve the corrosion resistance of the steel bars recorded in this article in a chloride ion environment, and the synergistic effect of Ni and Cr can further improve the composition of the corrosion oxide film to improve the density of the oxide film. The Ni content is also related to the properties of the passive film on the surface of the steel bar. Within the Ni content range of the present invention, the properties of the passive film on the surface of the substrate can be improved with the increase of the Ni content, making the passive film thinner and more protective. In some embodiments, the Ni content can be 0.45% to 0.48%. For example, the Ni content can be 0.46% or 0.47%.

For the Mo element, the addition of 0.15-0.30% Mo element can effectively inhibit the pitting process dominated by chloride ion corrosion and promote the formation of a passive film on the surface of the steel bar; and under the addition of the Mo element content of the present invention, the grains can be further effectively refined to improve the toughness and wear resistance of the steel bar. In some embodiments, the Mo content can be controlled at 0.15% to 0.27%, for example, the Mo content can be 0.17%, 0.18%, 0.19%, 0.22%, 0.24% or 0.25%.

As for the Cu element, the Cu element has excellent corrosion resistance. The Cu element content of 0.50-0.55% can slow down the growth rate of the rust layer on the surface of the steel bar, and the oxide formed by it can also inhibit the invasion of oxygen and chloride ions; and the enrichment of Cu on the surface of the steel bar can reduce the conductivity of the surface of the steel bar and delay the corrosion process; the content of Cu and P in the present invention can synergistically promote the formation of the α-phase passivation film. In some embodiments, the Cu content can be controlled at 0.51% to 0.54%, for example, the Cu content is 0.52% or 0.53%.

For the P element, adding 0.01 to 0.03% of the P element can promote the formation of an α-phase passivation film, block the corrosion of chloride ions on the steel bar matrix, and reduce the corrosion rate; during the corrosion process, the P element is oxidized to form PO ₄ ^3- , and the P element is enriched in the rust layer in the form of phosphate, which can protect the steel bar matrix. If the content of the P element is greater than 0.03%, the brittleness of the steel bar will increase and its ductility will be reduced. In some embodiments, the P content may be 0.015%, 0.018%, 0.02%, 0.025% or 0.028%.

As for the V element, adding 0.01-0.02% by mass of the V element can further refine the grain structure of the steel bar and improve the strength and toughness of the steel bar. In some embodiments, the V element content can be 0.012%, 0.015%, 0.017% or 0.019%.

As mentioned above, the steel bars described in this article ensure the chloride ion corrosion resistance of the corrosion-resistant steel bars by adding a reasonable and small amount of Cr, Ni, Mo, Cu, P, and V elements and the synergistic effect of the elements.

As for carbon equivalent, by controlling the carbon equivalent Ceq to no more than 0.58, the content of Mn, Cr, V, Mo, Cu and Ni elements can be limited to ensure good corrosion resistance while making the steel bar have good welding performance, avoiding brittle fracture of corrosion-resistant steel bars during welding.

Furthermore, the chemical composition of the steel bar can be 1.98-2.00% by mass percentage of Cr+Mo+Ni+Cu. Cr+Mo+Ni+Cu is the main corrosion-resistant alloying element. By controlling Cr+Mo+Ni+Cu to 1.98-2.00%, the steel bar yield strength can be greater than 600MPa, the tensile strength ≥750MPa, the strength-yield ratio ≥1.5, the elongation after fracture ≥15%, the total elongation under maximum force ≥8% and has good corrosion resistance at a relatively low addition amount of Cr, Mo, Ni and Cu elements, which can further save the production cost of the steel bar. In some embodiments, Cr+Mo+Ni+Cu can be 1.99%, Mn+P+Si can be 1.52%, or Mn+P+Si can be 1.55%, or Mn+P+Si can be 1.58%, or Mn+P+Si can be 1.60%, or Mn+P+Si can be 1.63%.

Further, the tensile strength of the steel bar is ≥750MPa, the strength-yield ratio is ≥1.5, the elongation after fracture is ≥15%, and the total elongation under maximum force is ≥8%. In some embodiments, the tensile strength is ≥780MPa or the tensile strength is ≥790MPa or the tensile strength is ≥800MPa, the strength-yield ratio is ≥1.5 or the strength-yield ratio is ≥1.7 or the strength-yield ratio is ≥1.9 or the strength-yield ratio is ≥2.0, the elongation after fracture is ≥15% or the elongation after fracture is ≥17% or the elongation after fracture is ≥18% or the elongation after fracture is ≥20% or the elongation after fracture is ≥21%, the total elongation under maximum force is ≥8% or the total elongation under maximum force is ≥8.5% or the total elongation under maximum force is ≥8.9% or the total elongation under maximum force is ≥9.5%.

Furthermore, the 600MPa grade corrosion-resistant steel bar described in this article has excellent corrosion resistance. The average corrosion rate of the steel bar can be 4.23-4.31g/m ² ·h. For example, the average corrosion rate can be 3.2g/m ² ·h, 3.8g/m ² ·h, 4.27g/m ² ·h or 4.3g/m ² ·h. The above average corrosion rate is obtained by a 72-hour immersion corrosion test according to the method described in "YB/T 4367 Test Method for Corrosion of Steel Bars in Chloride Ion Environment". The parameters of the immersion corrosion test are: the treated sample is placed in a immersion test box, and the test solution is a NaCl solution with a mass fraction of 2%; the test temperature is: 45℃±2℃; the test environment humidity is: 70%±5RH; the total test time is: 72 hours; the test single cycle setting is: 60min/cycle, the immersion time is 12min/cycle, the drying time is 48min/cycle, and the test is continuous and the average corrosion rate for 72 hours is obtained.

In addition, in the 72-hour weekly immersion corrosion test, according to the "GB/T33953-2017 Corrosion-resistant Steel Bars for Reinforced Concrete" and "YB/T 4367 Test Method for Corrosion of Steel Bars in Chloride Ion Environment", the steel bars described in this article have a relative corrosion rate lower than 70% compared to the steel bars of grade HRB600E, for example, a relative corrosion rate lower than 69% or lower than 68% or lower than 67%.

In a 3.5% aqueous solution of NaCl mass fraction simulating seawater environment, the self-corrosion potential E _corr of the steel bar is -0.564～-0.576V, and the self-corrosion current density I _corr is 23.7～24.9μA·cm ^-2 . Compared with the corrosion-resistant steel bar with the grade of HRB600E, its self-corrosion potential positive shift exceeds 0.4V, and the self-corrosion current density I corr is more than 5μA·cm ^-2 smaller, which has stronger corrosion resistance than ordinary steel bars. For example, the self-corrosion potential of the steel bar can be -0.575V, and the self-corrosion current density can be 24.9μA·cm ^-2 . Among them, the specific method of the electrochemical corrosion test is as follows: the electrochemical test is carried out in accordance with GB/T24196-2009 "Guidelines for Constant Potential and Dynamic Potentiodynamic Polarization Measurements of Electrochemical Test Methods for Corrosion of Metals and Alloys", using a three-electrode system, the reference electrode is a saturated calomel electrode, the auxiliary electrode is a Pt sheet, and the test solution is a 3.5% mass fraction NaCl solution to simulate the seawater environment; the polarization curve test scanning range is -300 to 600 mV relative to the sample self-corrosion potential, and the scanning frequency is 1 mV/s; the electrochemical impedance test scanning frequency range is 10 ⁵ to 10 ^-2 Hz, and the AC excitation signal amplitude is ±5 mV.

Furthermore, the microstructure of the corrosion-resistant steel bar is bainite and ferrite.

Another aspect of the present invention provides a method for preparing 600MPa grade corrosion-resistant steel bars. In an exemplary embodiment of the method for preparing 600MPa grade corrosion-resistant steel bars of the present invention, the preparation method may include a molten iron pretreatment process (e.g., molten iron pre-desulfurization) process, a converter smelting process, a molten steel refining process (e.g., an LF furnace refining process), a square-pit continuous casting process, a hot rolling process, and a temperature control and cooling process.

Furthermore, the molten iron pretreatment process is known to those skilled in the art, and the molten iron is pretreated by conventional methods in the art.

Furthermore, in the converter smelting process, the elements contained in the molten steel at the end of the converter smelting can be C≥0.05% and P≤0.02% by mass percentage. For example, the end of the converter smelting can be C greater than 0.07% and P less than 0.015%.

Furthermore, in the converter smelting process, the following alloys with different compositions and contents may be added for deoxidation and alloying of the molten steel, including 2.5kg/t～2.85kg/t of ferrosilicon, 15.12kg/t～19.34kg/t of ferrochrome, 11.21kg/t～15.35kg/t of silicon manganese, 5.10kg/t～5.97kg/t of copper plate, 6.21kg/t～8.12kg/t of nickel plate, 3.11kg/t～5.17kg/t of ferrovanadium, and 3.85kg/t～4.78kg/t of ferromolybdenum. For example, in some embodiments, ferrosilicon 2.59kg/t to 2.75kg/t, ferrochrome 15.86kg/t to 18.34kg/t, silicomanganese 12.21kg/t to 15.12kg/t, copper plate 5.31kg/t to 5.67kg/t, nickel plate 6.38kg/t to 7.83kg/t, ferrovanadium 3.17kg/t to 4.85kg/t, and ferromolybdenum 3.97kg/t to 4.68kg/t may be included. For example, ferrosilicon 2.67kg/t, ferrochrome 17.27kg/t, silicomanganese 13.57kg/t, copper plate 5.56kg/t, nickel plate 7.10kg/t, ferrovanadium 4.21kg/t, and ferromolybdenum 4.25kg/t.

The above alloys can be added in the order of ferrosilicon-silicon manganese-ferrochrome when 1/4 of the steel is tapped, copper plates and nickel plates are loaded into the converter, and the amount of scrap steel loaded is reduced accordingly, and ferromolybdenum and ferrovanadium are added during the molten steel refining process. It should be understood that in certain embodiments, alloys can be added in other ways.

Furthermore, during the steel refining process, the steel after converter smelting is connected to argon gas after the refining process, and the gas volume is adjusted. After the ladle is opened to the refining station, 200-400kg of lime and 0-100kg of fluorite are added, and the temperature is measured and sampled after 8-15 minutes of electrification of slag; deoxidizer is added to make white slag. According to the sampling and analysis results of the LF furnace, alloy is added to fine-tune the composition. After the composition temperature reaches the target, 0-100m of pure calcium wire is fed, and the soft argon blowing time is ≥6min.

Furthermore, during the square-shell continuous casting process, the pouring can be protected throughout the whole process, the long shroud of the large ladle is argon sealed, the long shroud is inserted into the liquid level ≥150mm, and the liquid level of the ladle during normal pouring is ≥500mm.

Furthermore, the temperature and cooling are controlled during the hot rolling process, and the rolling process is carried out in 24 passes. The starting rolling temperature can be 1140±50℃, the intermediate rolling temperature can be 950℃～970℃, and the final rolling temperature can be 1080℃～1100℃. After the rolling is completed, the mechanical properties of the steel bars produced meet the various indicators of "GB/T 1499.2-2018 Steel for Reinforced Concrete Part 2: Hot-rolled Ribbed Steel Bars" for 600MPa grade seismic steel bars. For example, the rolling process is carried out in 24 passes, the starting rolling temperature can be 1170℃, the intermediate rolling temperature can be 960℃, and the final rolling temperature can be 1090℃.

In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

Example 1

The steel bars of Example 1 and Comparative Example 1 shown in Table 1 are all subjected to molten iron pretreatment, converter smelting, LF furnace refining, billet continuous casting, inspection, finishing, cold delivery, and hot continuous rolling. The rolling process adopts 24 passes for rolling, with a starting rolling temperature of 1180°C, an intermediate rolling temperature of 960°C, and a final rolling temperature of 1090°C. They are rolled into Φ12mm threaded steel bars. The mechanical properties of the steel bars of Example 1 are shown in Table 2.

Table 1 Steel bar composition

The microstructure of the corrosion-resistant steel bar of Example 1 is shown in Figures 1 to 4, where (a) in Figure 4 is a microstructure of 2000 times, (b) is a microstructure of 5000 times, (c) is a microstructure of 10000 times, and (d) is a microstructure of 20000 times. It can be seen from the figure that the microstructure of the steel bar is composed of ferrite and bainite.

Table 2 Mechanical properties of steel bars in Example 1 and Comparative Example 1

Referring to GB/T33953-2017 Corrosion-resistant steel bars for reinforced concrete and YB/T 4367 Test method for corrosion of steel bars in chloride ion environment, the type of test solution, solution temperature, ambient humidity, test time, and immersion cycle time are set. The 72-hour cycle immersion experiment is designed as follows:

Test specimen configuration: 5 parallel specimens of Example 1 steel bars, numbered 1 to 5, respectively marked as Example 1-1, Example 1-2, Example 1-3, Example 1-4 and Example 1-5; 5 parallel specimens of comparative example steel bars, numbered 1 to 5, respectively marked as Example 1-1, Example 1-2, Example 1-3, Example 1-4 and Example 1-5, totaling 10 specimens.

Test specimen specifications: The specimens shall be of uniform specifications, with the specification of Φ9mm×50mm.

Test solution type: NaCl solution.

The NaCl concentration in the test solution is: 2% by mass.

The replenishing solution during the experiment was: ultrapure water.

Test temperature: 45℃±2℃; Test environment humidity: 70%±5RH; Total test duration: 72 hours; Test single cycle setting: 60min/cycle, immersion time 12min/cycle, drying time 48min/cycle.

After the 72-hour periodic immersion test, the weight loss of steel bar corrosion is shown in Table 3 and Figure 5 (in Figure 5, curve A represents the corrosion weight loss of Examples 1-1 to 1-5, and curve B represents the corrosion weight loss of Comparative Examples 1-1 to 1-5), the corrosion rate is shown in Table 4 and Figure 6 (in Figure 6, curve A represents the corrosion rate of Examples 1-1 to 1-5, and curve B represents the corrosion rate of Comparative Examples 1-1 to 1-5), and the relative corrosion rate is shown in Table 5.

Table 3 Weight loss of steel bar corrosion

Table 4 Steel bar corrosion rate

Table 5 Relative corrosion rate

It can be seen from Table 3 and Figure 5 that the weight loss of the steel bars in Example 1 due to corrosion is less than that in Comparative Example 1, and its steel bar corrosion rate is also smaller, with a relative corrosion rate of 69%.

Example 2 - Example 6

The steel bar compositions of Examples 2 and 5 are shown in Table 6.

Table 6 Steel bar composition of Examples 2 to 6

Examples 2 to 6 were tested according to the method described in Example 1, and their mechanical properties, corrosion rates, and relative corrosion rates are shown in Table 7.

Table 7 Performance of steel bars in Examples 2 to 6

From Tables 2, 4, 5 and 7, it can be seen that the steel bars of Examples 1 to 6 are much better in corrosion resistance than Comparative Example 1. The corrosion-resistant steel bars of the present invention have an average corrosion rate of 4.23 to 4.31 g/m ² ·h, a relative corrosion rate of no more than 69%, and excellent corrosion resistance.

Although the present invention has been described above by combining with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims.

Claims (4)

1. A 600MPa grade corrosion-resistant steel bar, characterized in that the chemical composition, by mass percentage, is Cr: 1.00-1.10%, Mo: 0.15-0.30%, Ni: 0.45-0.50%, Cu: 0.50-0.55%, V: 0.01-0.02%, P: 0.01-0.03%, C: 0.10-0.13%, Si: 0.30-0.40%, Mn: 0.80-1.60%, S: 0.001-0.025%, the balance is iron and inevitable impurities, and the carbon equivalent Ceq is not more than 0.58, wherein the microstructure of the corrosion-resistant steel bar is bainite and ferrite; the tensile strength of the steel bar is ≥750MPa, the strength-to-yield ratio is ≥1.5, the elongation after fracture is ≥15%, and the total elongation under maximum force is ≥8%; the preparation method thereof comprises: molten iron pretreatment, converter smelting, molten steel refining, billet continuous casting, hot rolling and temperature control and cooling process, wherein the temperature control and cooling process comprises: After the continuous casting of the billet is completed, the heating temperature is controlled at 1150℃±50℃, and hot rolling is carried out after keeping warm for 30 to 50 minutes. The starting rolling temperature is 1140±50℃, the intermediate rolling temperature is 950℃～970℃, and the final rolling temperature is 1080℃～1100℃; No water penetration treatment is performed during the rolling process, the upper cooling bed temperature is 840℃～870℃, and the cooling is performed after rolling, and the cooling rate is controlled at 1℃/second; At the end point of converter smelting, C≥0.05% and P≤0.02% in the molten steel by mass percentage. 2. The 600MPa grade corrosion-resistant steel bar according to claim 1, characterized in that the average corrosion rate of the steel bar is 4.23-4.31 g/( ^m2 ·h) in a 72-hour immersion corrosion test. 3. The 600MPa grade corrosion-resistant steel bar according to claim 1 or 2, characterized in that the relative corrosion rate is no more than 69% after 72 hours of immersion corrosion. 4. The 600MPa grade corrosion-resistant steel bar according to claim 1 or 2, characterized in that, in an aqueous solution containing 3.5% NaCl by mass, the steel bar has a self-corrosion potential of -0.564 to -0.576V and a self-corrosion current density of 23.7 to 24.9μA·cm ^-2 .