High-strength corrosion-resistant steel bar and production method thereof

Abstract

The invention provides a high-strength corrosion-resistant steel bar and a production method thereof, the steel bar comprises, by weight, 0.015%-0.03% of C, 0.5%-0.8% of Si, 1.2%-1.6% of Mn, 0.1%-0.3% of Cu, 0.08%-0.11% of Ni, 9.5%-11.5% of Cr, 1.0%-1.5% of Mo, 0.02%-0.05% of Nb, 0.05%-0.08% of V, 0.022%-0.040% of N, 0.05%-0.15% of Sb, 0.01%-0.03% of P, less than or equal to 0.004% of S, less than or equal to 0.003% of O, less than or equal to 0.01% of As and the balance iron and inevitable impurities, and all the elements further meet the conditions that the corrosion resistance coefficient K is 3%-3.7%, and the strength and plasticity coefficient The steel bar disclosed by the invention has relatively high strength-plasticity and extremely high corrosion resistance.

Description

Technical Field

[0001] This application relates to the technical field of steel smelting, and particularly relates to a corrosion-resistant steel bar and a production method thereof. Background Art

[0002] There are many cases of premature failure in reinforced concrete structures in actual projects, which not only increases the maintenance cost, but also causes great waste of energy and resources. Due to the influence of harsh environments such as high chloride and sulfate content, high temperature, and high humidity, ordinary deformed steel bars usually far from reach the designed theoretical service life, resulting in serious economic losses, waste of energy and resources, and a large amount of waste emissions. At present, means such as corrosion inhibitors, surface protective layers, cathodic protection, and coated steel bars have a certain effect on extending the service life of reinforced concrete structures. However, as the core of reinforced concrete structures, improving the corrosion resistance of the steel bar itself is the key to solving the corrosion problem of reinforced concrete structures. And it is difficult to coordinately control the three aspects of corrosion resistance, energy conservation, and cost reduction. Summary of the Invention

[0003] The purpose of this application is to provide a corrosion-resistant steel bar, which solves the problem that it is difficult to coordinately control the three aspects of corrosion resistance, energy conservation, and cost reduction in the prior art.

[0004] In order to achieve one of the above-mentioned invention purposes, an embodiment of this application provides a corrosion-resistant steel bar, which includes, by weight percentage: C: 0.015 - 0.03%, Si: 0.5 - 0.8%, Mn: 1.2 - 1.6%, Cu: 0.1 - 0.3%, Ni: 0.08 - 0.11%, Cr: 9.5 - 11.5%, Mo: 1.0 - 1.5%, Nb: 0.02 - 0.05%, V: 0.05 - 0.08%, N: 0.022 - 0.040%, Sb: 0.05 - 0.15%, P: 0.01 - 0.03%, S ≤ 0.004%, O ≤ 0.003%, As: ≤ 0.01%, and the rest is iron and inevitable impurities. The elements also satisfy: corrosion resistance coefficient K = [Ni] + 0.25[Cr] + 0.5[Mo] + 5[Nb] - 2.5[C] is 3 - 3.7%, and the strength and plasticity coefficient T = 8{C} + {Si} + 0.4{Mn} + 0.25({Cr} + {Mo}) + 0.17({Nb} + {V}) / {N} is 4.4 - 5.3. [Ni], [Cr], [Mo], [Nb], and [C] are the weight percentages of the corresponding elements, and {C}, {Si}, {Mn}, {Cr}, {Mo}, {Nb}, {V}, and {N} are 100 times the weight percentages of the corresponding elements.

[0005] In one embodiment of the present application, the corrosion-resistant steel bar has a two-phase structure of ferrite and bainite, with the volume fraction of ferrite being 17 - 22% and the volume fraction of bainite being 78 - 83%, and the size of ferrite being 5.9 - 7.7 μm.

[0006] In one embodiment of the present application, the yield strength of the corrosion-resistant steel bar is ≥700 MPa, the tensile strength is ≥950 MPa, and the total elongation at maximum force is ≥7.5%.

[0007] In one embodiment of the present application, in the salt spray corrosion test, the average weight loss corrosion rate of the corrosion-resistant steel bar is 0.01 - 0.04 g / (m 2 ·h); in the simulated concrete pore solution with a chloride ion concentration ≥3 mol / L, the self-corrosion current density of the steel bar is ≤0.12 μA / cm 2 .

[0008] One embodiment of the present application also provides a production method of a corrosion-resistant steel bar, including smelting, refining, continuous casting, billet heating, rolling, cooling, and heat treatment processes carried out in sequence. Among them, In the billet heating process, the billet is heated to 1200 - 1250 °C and held for 80 - 110 min; In the rolling process, it is controlled that the billet starts to be rolled at 1120 - 1150 °C, and the billet is rolled into a steel bar; In the cooling process, after rolling is completed, when the steel bar is at 820 - 850 °C, it is sent to the cooling bed. After being sent to the cooling bed, when the temperature of the steel bar is 850 - 800 °C, it is air-cooled. The forward speed of the cooling bed is controlled at 1.3 - 1.5 m / min, and the cooling rate of the steel bar is controlled at 1.2 - 1.6 °C / min; when the temperature of the steel bar is 800 - 750 °C, the forward speed of the cooling bed is controlled at 1.3 - 1.5 m / min, the fan is turned on, and the cooling rate of the steel bar is controlled at 1.5 - 1.7 °C / min; when the temperature of the steel bar is 750 - 700 °C, the forward speed of the cooling bed is controlled at 0.8 - 1.0 m / min, the fan is turned on, and the cooling rate of the steel bar is controlled at 1.7 - 1.9 °C / min, and then it is air-cooled.

[0009] In one embodiment of the present application, in the heat treatment process, when 4.4 ≤ T ≤ 4.6, the heat treatment temperature is controlled at 480 - 510 °C, and the holding time is controlled at 0.9 - 1.3 h; when the strength-plasticity coefficient 4.6 < T ≤ 4.9, the heat treatment temperature is controlled at 520 - 550 °C, and the holding time is controlled at 1.1 - 1.5 h; when the strength-plasticity coefficient 4.9 < T ≤ 5.3, the heat treatment temperature is controlled at 560 - 590 °C, and the holding time is controlled at 1.4 - 1.8 h.

[0010] In one embodiment of the present application, in the converter smelting process, dephosphorization is first carried out. After the P content ≤ 0.035%, the phosphorus-rich slag is poured out; then decarburization is carried out to make the C content 0.35 - 0.55% and the P content ≤ 0.025%, and the slag is poured out for the second time; at the end of smelting, the C content is controlled to be 0.04 - 0.07% and the P content ≤ 0.020%, and the slag is poured out again at the end; the tapping temperature is controlled to be 1670 - 1720 °C; after 1 / 4 of the tapping, ferrochrome alloy with low carbon, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferrocolumbium alloy are added in sequence for preliminary alloying. Among them, the C content in the ferrochrome alloy with low carbon ≤ 0.03%.

[0011] In one embodiment of the present application, the refining process includes LF refining. During the process of heating up by electrifying in LF refining, ferrochrome alloy with low carbon is added according to the method of multiple times and small amounts, and metal Sb is added to complete Sb alloying. The tapping temperature in LF refining is controlled to be 1590 - 1620 °C, the C content ≤ 0.2%, and the Cr content is 9.8 - 10.5%.

[0012] In one embodiment of the present application, the refining process further includes RH refining after LF refining. After the RH refining evacuates the vacuum for 3 - 4 min, oxygen blowing starts. The total amount of oxygen blowing is 350 - 400 Nm 3 , and oxygen blowing ends when the C content ≤ 0.03%. Subsequently, ferrochrome alloy with low carbon is added for alloying, and then net circulation treatment is carried out. The time when the vacuum degree is less than 2 mbar ≥ 5 min. At the end of net circulation, the C content is controlled ≤ 0.008%. The alloy composition is finely adjusted by using ferrochrome alloy with low carbon, ferrovanadium alloy, and ferrosilicon nitride. The tapping temperature is controlled to be 1590 - 1620 °C.

[0013] In one embodiment of the present application, in the continuous casting process, the tundish temperature is controlled to be 1548 - 1568 °C, and the casting speed is controlled to be 2.6 - 3.1 m / min.

[0014] One or more technical solutions provided by the present application have at least the following technical effects or advantages: In the corrosion-resistant steel bars provided by the present application, an ultra-low carbon content is adopted. Combining alloy elements Ni, Cr, Mo, and Nb makes the oxide film of the steel bars dense and the matrix has strong corrosion-resistant repair ability while controlling the cost; cooperating with strengthening alloy elements Si, Mn, Cr, Mo and alloy strengthening elements Nb, V, and N element, the alloy elements play the effects of solid solution strengthening, precipitation strengthening, and structure strengthening. After heat treatment, it is ensured that the strength and plasticity of the steel bars are synergistically regulated. Specific embodiments

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

[0016] An embodiment of the present application provides a corrosion-resistant steel bar, which includes, by weight percentage: C: 0.015 - 0.03%, Si: 0.5 - 0.8%, Mn: 1.2 - 1.6%, Cu: 0.1 - 0.3%, Ni: 0.08 - 0.11%, Cr: 9.5 - 11.5%, Mo: 1.0 - 1.5%, Nb: 0.02 - 0.05%, V: 0.05 - 0.08%, N: 0.022 - 0.040%, Sb: 0.05 - 0.15%, P: 0.01 - 0.03%, S ≤ 0.004%, O ≤ 0.003%, As: ≤ 0.01%, and the balance is iron and unavoidable impurities. The following relationships also hold among the elements: K = [Ni] + 0.25[Cr] + 0.5[Mo] + 5[Nb] - 2.5[C] is 3 - 3.7%, and T = 8{C} + {Si} + 0.4{Mn} + 0.25({Cr} + {Mo}) + 0.17({Nb} + {V}) / {N} is 4.4 - 5.3. Here, [Ni], [Cr], [Mo], [Nb], and [C] are the weight percentages of the corresponding elements, and {C}, {Si}, {Mn}, {Cr}, {Mo}, {Nb}, {V}, and {N} are 100 times the weight percentages of the corresponding elements.

[0017] The present application adopts an ultra-low carbon content, combined with the strengthening alloying elements Si, Mn, Mo and the micro-alloying strengthening elements Nb and V and the N element. The alloying elements exert the effects of solid solution strengthening, precipitation strengthening and microstructure strengthening. A relatively large amount of Cr is used to promote the formation of ferrite, so that the strength and plasticity of the heat-treated steel bar can be synergistically regulated.

[0018] Combined with the alloying elements Ni, Cr, Mo, Nb, while controlling the cost, the oxide film of the steel bar is made dense and the matrix has strong corrosion-resistant repair ability, greatly improving the corrosion resistance of the steel bar.

[0019] The functions and mechanisms of each element are specifically described as follows: Carbon (C): An austenite-forming element. In low-carbon steel, when the C content is reduced below the solubility limit of ferrite, it is beneficial to improve the uniformity of the steel microstructure and composition distribution, reduce the potential difference between different regions inside the steel bar, and thus reduce the corrosion rate.

[0020] Silicon (Si): Si dissolved in ferrite can enhance strength, and can also inhibit the diffusion rate of C element in austenite, delay the transformation of ferrite and pearlite, and improve the yield strength and tensile strength of steel bars. However, when the Si content is too high, it will affect the welding process performance of steel bars.

[0021] Manganese (Mn): An important deoxidizer and desulfurizer. It can play a role in solid solution strengthening, is a strengthening and toughening element, and is also an austenite-forming element. However, when the Mn content in the steel is too high, the plasticity and impact toughness of the steel bars will decrease, and at the same time, the welding performance of the steel bars will also decrease.

[0022] Copper (Cu): A corrosion-resistant element, which helps to improve the corrosion resistance of steel. However, too much Cu in the steel will cause a decrease in the plasticity of the material, resulting in hot rolling cracking.

[0023] Chromium (Cr): An important corrosion-resistant element. It can generate a passivation film on the surface of the steel bar, effectively prevent the oxidation of the steel bar and improve the corrosion resistance of the steel bar matrix. And when compounded with Mo, Ni, etc., better corrosion resistance can be obtained. Although a certain degree of corrosion resistance can be obtained by adding Cr alone to the steel bar, it is easy to cause pitting corrosion. At the same time, it can improve the hardenability of the steel bar.

[0024] Molybdenum (Mo): An important corrosion-resistant element, which can generally improve the corrosion resistance of steel. It can cause passivation on the surface of the steel in reducing acids and strongly oxidizing salt solutions, and can also prevent pitting corrosion of the steel in chloride solutions. Its inhibitory effect on the transformation of pearlite is very obvious. At the same time, it refines the carbides precipitated from ferrite, replaces V in the carbides in MC-type carbides to form composite carbides, and combines with the carbide-forming element Cr to promote the formation of bainite. When the Mo content is relatively high, it will deteriorate the oxidation resistance of the steel. In terms of tissue properties, Mo can promote grain refinement, improve the hardenability and thermal strength of steel.

[0025] Nickel (Ni): It has high corrosion resistance to acids and alkalis, has rust and heat resistance at high temperatures, and is an austenite-forming element, which can make the steel have a uniform austenite structure to improve corrosion resistance. However, it itself is not an effective antioxidant element, so it is rarely used alone as an alloying element for corrosion-resistant steel.

[0026] Nitrogen (N): An austenite-forming element. If it is too high, it is not conducive to controlling the proportion of ferrite and bainite in the plasticity of the steel bar and the structure. If it is too low, it is not conducive to improving the strength of the steel bar.

[0027] Vanadium (V): A micro-alloying strengthening element, which can precipitate V(C,N) compounds during the rolling process, has a certain precipitation strengthening effect, and at the same time prevents the growth of austenite and ferrite grains, having a fine grain strengthening effect; but too high V content will reduce the plasticity of the material and increase the cost.

[0028] Niobium (Nb): A microalloying strengthening element, combined with controlled rolling and controlled cooling, can play a role in precipitation strengthening and grain refinement strengthening during the rolling process. On the one hand, Nb can make the oxide layer more dense, on the other hand, it can increase the Cr concentration in the passive film, improve the stability of the passive film, thereby increasing the pitting potential and comprehensively enhancing the corrosion resistance. However, too high Nb content will reduce the plasticity of the material and increase the cost.

[0029] Antimony (Sb): The Sb element can increase the self-corrosion potential of the substrate and improve the properties of the rust layer at the same time. The combined addition of Sb and Nb can better optimize the rust layer structure and promote the formation of more protective rust layer products, which is beneficial to improving the corrosion resistance of the material.

[0030] Phosphorus (P): It can improve the strength and corrosion resistance of steel bars, but it is prone to segregation in steel, and too high P content will lead to poor mechanical properties at low temperatures.

[0031] Sulfur (S): Sulfur elements can form inclusions and damage the corrosion resistance of steel, especially unfavorable for local corrosion.

[0032] Oxygen (O): Controlling the oxygen content during smelting and continuous casting can effectively improve the cleanliness of steel and enhance the corrosion resistance of steel.

[0033] Arsenic (As): In an acidic environment, such as HCl, arsenic compounds may dissolve and damage the passive film of steel.

[0034] The corrosion resistance coefficient K = Ni + 0.25Cr + 0.5Mo + 5Nb - 2.5C is of obvious significance for measuring the corrosion resistance of steel bars and can ensure the denseness of the oxide film of steel bars and the corrosion resistance of the steel bar matrix. The strength-plasticity coefficient T = 8C + Si + 0.4Mn + 0.25(Cr + Mo) + 0.17(Nb + V) / N is of obvious significance for measuring and ensuring the strength and plasticity of steel bars. The alloying elements play the effects of solid solution strengthening, precipitation strengthening and microstructure strengthening, and high-strength and high-plasticity steel bars can be obtained after heat treatment.

[0035] In an embodiment of the present application, the corrosion-resistant steel bar is a two-phase structure of ferrite and bainite. The volume ratio of ferrite is 17 - 22%, the volume ratio of bainite is 78 - 83%, and the size of ferrite is 5.9 - 7.7 μm.

[0036] The relatively high bainite content makes the steel bar have relatively high strength, and the ferrite improves the plasticity of the steel bar, so that the strength and plasticity of the steel bar are synergistically improved.

[0037] In an embodiment of the present application, the yield strength of the corrosion-resistant steel bar ≥ 700 MPa, the tensile strength ≥ 950 MPa, and the total elongation at maximum force ≥ 7.5%.

[0038] In an embodiment of the present application, in the salt spray corrosion test, the average weight loss corrosion rate of the corrosion-resistant steel bar is 0.01 - 0.04 g / (m 2 ·h); in the simulated concrete pore solution with a chloride ion concentration ≥ 3 mol / L, the self-corrosion current density of the steel bar ≤ 0.12 μA / cm 2 .

[0039] Under the combined synergistic effect of the foregoing components, the corrosion resistance of the steel bar is greatly improved. The average weight loss corrosion rate of the steel bar is 1 / 45 of that of HRB400; the self-corrosion current density of the steel bar is 1 / 56 of that of HRB400, and it can resist corrosion in harsh environments.

[0040] The embodiment of the present application also provides a production method of the corrosion-resistant steel bar, including the smelting, refining, continuous casting, billet heating, rolling, cooling, and heat treatment processes carried out in sequence. Among them, In the billet heating process, the billet is heated to 1200 - 1250 °C and kept warm for 80 - 110 min; In the rolling process, it is controlled that the billet starts to be rolled at 1120 - 1150 °C, and the billet is rolled into a steel bar; In the cooling process, after rolling is completed, when the steel bar is at 820 - 850 °C, it is sent to the cooling bed. After being sent to the cooling bed, when the temperature of the steel bar is 850 - 800 °C, it is air-cooled. The forward speed of the cooling bed is controlled at 1.3 - 1.5 m / min, and the cooling rate of the steel bar is controlled at 1.2 - 1.6 °C / min; when the temperature of the steel bar is 800 - 750 °C, the forward speed of the cooling bed is controlled at 1.3 - 1.5 m / min, the fan is turned on, and the cooling rate of the steel bar is controlled at 1.5 - 1.7 °C / min; when the temperature of the steel bar is 750 - 700 °C, the forward speed of the cooling bed is controlled at 0.8 - 1.0 m / min, the fan is turned on, and the cooling rate of the steel bar is controlled at 1.7 - 1.9 °C / min, and then it is air-cooled.

[0041] Adopting a higher heating temperature and combining with a high rolling start temperature to ensure that the rolling process is carried out in the non-recrystallization zone at high temperature, which is beneficial to controlling the grain size to be larger and remelting the large-size precipitates formed by continuous casting, thereby improving the strength.

[0042] When the temperature of the steel bar is 850 - 800 °C, it is sent to the cooling bed for air-cooling, so that the steel bar passes through the ferrite transformation zone at a slower cooling rate, ensuring a larger proeutectoid phase transformation grain size and a certain proportion of proeutectoid structure. At the same time, the precipitation of V(C,N) is promoted in this interval. In the latter two sections, the fan below the cooling bed is turned on to gradually increase the cooling intensity, ensuring the uniformity of the core and the surface, and at the same time increasing the thickness of the oxide scale on the surface of the steel bar and enhancing the bonding force between the oxide scale on the surface of the steel bar and the matrix.

[0043] After the temperature of the steel bar drops to 700 °C, air cooling is carried out, so that the steel bar slowly passes through the bainite transformation zone, and a bainite structure with a higher content is obtained.

[0044] In an embodiment of the present application, in the heat treatment process, when 4.4 ≤ T ≤ 4.6, the heat treatment temperature is controlled at 480 - 510 °C, and the holding time is controlled at 0.9 - 1.3 h; when the strength-plasticity coefficient 4.6 < T ≤ 4.9, the heat treatment temperature is controlled at 520 - 550 °C, and the holding time is controlled at 1.1 - 1.5 h; when the strength-plasticity coefficient 4.9 < T ≤ 5.3, the heat treatment temperature is controlled at 560 - 590 °C, and the holding time is controlled at 1.4 - 1.8 h.

[0045] The higher the strength-plasticity coefficient T, the lower the ferrite content and the higher the bainite content in the structure of the steel bar, and the lower the total elongation at maximum force. Therefore, with the increase of the strength-plasticity coefficient T, both the heat treatment temperature and the holding time are increased to improve the plasticity of the steel bar.

[0046] In an embodiment of the present application, in the converter smelting process, first dephosphorization is carried out. After the P content ≤ 0.035%, the phosphorus-rich slag is poured out; then decarburization is carried out to make the C content 0.35 - 0.55% and the P content ≤ 0.025%, and the slag is poured out for the second time; at the end of smelting, the C content is controlled at 0.04 - 0.07% and the P content ≤ 0.020%, and the slag is poured out again at the end; the tapping temperature is controlled at 1670 - 1720 °C; after 1 / 4 of the tapping, low-carbon ferrochrome alloy, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferrocolumbium alloy are added in sequence for preliminary alloying. Among them, the C content in the low-carbon ferrochrome alloy ≤ 0.03%.

[0047] Among them, the chromium content in the low-carbon ferrochrome alloy is 50 - 60%, the carbon content ≤ 0.03%, and the balance is iron and inevitable impurities; the molybdenum content in the ferromolybdenum alloy is 50 - 60%, and the balance is iron and inevitable impurities; the silicon content in the silicomanganese alloy is 17 - 20%, the manganese content is 65 - 70%, and the balance is iron and inevitable impurities; the silicon content in the ferrosilicon alloy is 70 - 75%, and the balance is iron and inevitable impurities; the niobium content in the ferrocolumbium alloy is 60 - 70%, and the balance is iron and inevitable impurities.

[0048] In the smelting process, the C and P contents are controlled at a low level at the end of smelting to avoid the C and P in the alloy causing the C and P contents in the molten steel to rise to a high value during tapping alloying, which is difficult to remove subsequently. A higher tapping temperature is adopted to avoid the low temperature of the molten steel caused by the large amount of alloy added during tapping alloying, which is not conducive to the subsequent refining stage. Metal copper and metal nickel are also added during tapping alloying to make them reach the target values.

[0049] Before converter smelting, the molten steel needs to be desulfurized. The temperature of the hot metal is ≥1330 °C, the Si content is 0.35 - 0.55%, the S content is ≤0.04%, the S content after desulfurization is ≤0.002%, and the slag removal rate is ≥95%. Control the S content at a low level to avoid sulfur increase higher than the target S content due to alloying, which makes desulfurization difficult during the refining process.

[0050] In an embodiment of the present application, the refining process includes LF refining. During the process of heating up by electrifying in LF refining, low-carbon ferrochromium alloy is added according to the method of multiple times with small amounts, and metal Sb is added to complete Sb alloying. The tapping temperature in LF refining is controlled at 1590 - 1620 °C, the C content is ≤0.2%, and the Cr content is 9.8 - 10.5%.

[0051] During the LF refining process, argon is blown from the bottom throughout the process, and the argon flow rate is 80 - 160 L / min to maintain soft stirring of the molten steel. Add low-carbon ferrochromium alloy according to the method of small amounts and multiple times to avoid excessive addition and high Cr content.

[0052] In an embodiment of the present application, the refining process further includes RH refining after LF refining. After RH refining evacuates the vacuum for 3 - 4 min, oxygen blowing starts. The total amount of oxygen blown is 350 - 400 Nm 3 , and oxygen blowing ends when the C content is ≤0.03%. Subsequently, low-carbon ferrochromium is added for alloying, and then net circulation treatment is carried out. The time when the vacuum degree is less than 2 mbar is ≥5 min. After the net circulation ends, control the C content ≤0.008%. Use low-carbon ferrochromium alloy, ferroniobium alloy, and ferrosilicon nitride to fine-tune the alloy composition, and control the tapping temperature at 1590 - 1620 °C.

[0053] During RH refining, oxygen blowing is used to decarburize, reducing the carbon content below the maximum value of the aforementioned C content. After oxygen blowing ends, oxygen still continues to react with carbon in the molten steel, reducing the C content to an extremely low value. Finally, ferroniobium alloy and ferrosilicon nitride corresponding to lower contents of V and N are added, and low-carbon ferrochromium alloy is added to make the final Cr content reach the target value.

[0054] In an embodiment of the present application, during the continuous casting process, control the tundish temperature at 1548 - 1568 °C and control the casting speed at 2.6 - 3.1 m / min.

[0055] Before continuous casting, purge the tundish with argon for a time ≥5 min to remove the residual solidified molten steel and protective slag in the tundish. The tundish has a relatively high temperature, resulting in relatively high fluidity of the molten steel and good uniformity of alloying elements in the molten steel.

[0056] The continuous casting process is completed by using the method of argon sealing of the large ladle long nozzle + basic tundish covering agent + submerged nozzle + low-carbon protective slag. The argon sealing pressure is 0.25 - 0.35 MPa, the immersion depth of the submerged nozzle is 70 - 100 mm, and the thickness of the liquid slag layer in the mold is 7 - 9 mm.

[0057] The continuous casting billet is a small square billet with a size of 140 - 170 mm. The water flow rate of the mold is 1850 - 1870 L / min, the temperature difference between the inlet and outlet water is ≤ 10 °C, the current of the mold electromagnetic stirring is 280 - 300 A, the frequency is 5 - 8 Hz, the current of the final electromagnetic stirring is 400 - 450 A, and the frequency is 10 - 12 Hz, ensuring the quality of the continuous casting surface and core.

[0058] The technical solution of the present application will be further described below in conjunction with some specific embodiments.

[0059] Table 1 Chemical composition of the steel bars in Examples 1 - 6 (%)

[0060] It should be supplemented and explained here that the value of the strong plasticity coefficient T does not carry "%".

[0061] Example 1 According to the following procedures in sequence, a corrosion - resistant steel bar with the chemical composition as described in Table 1 is prepared.

[0062] Hot metal desulfurization: The hot metal temperature is 1339 °C, the Si content is 0.36%, the S content is 0.01%, after desulfurization, the S content is 0.001%, and the slag - skimming rate is 96%.

[0063] Converter smelting process: First, dephosphorization is carried out. After sampling and detecting that the P content is 0.028%, the phosphorus - rich slag is poured out; then decarburization is carried out. After sampling and detecting again, the C content is 0.37% and the P content is 0.021%, and the slag is poured out for the second time; at the end of smelting, the C content is controlled at 0.04% and P is 0.015%, and the slag is poured out again at the end; the tapping temperature is controlled at 1693 °C; after 1 / 4 of the tapping, low - carbon ferrochrome alloy, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying. Among them, the C content in the low - carbon ferrochrome alloy is 0.02%.

[0064] LF refining process: Bottom - blowing argon is carried out throughout the process, the argon flow rate is 88 L / min. During the process of heating by energization, low - carbon ferrochrome alloy is added according to the method of multiple times and small amounts, and metal Sb is added to complete Sb alloying. The tapping temperature of LF refining is controlled at 1599 °C, the C content is 0.18%, and the Cr content is 9.9%.

[0065] RH refining process: After evacuating for 3 min, oxygen blowing starts. When the total oxygen - blowing volume is 377 Nm 3 ³, after sampling and detecting that the C content is 0.024%, the oxygen - blowing ends. Subsequently, low - carbon ferrochrome alloying is added, and then the net - cycle treatment is carried out. The time when the vacuum degree is less than 2 mbar is 5 min. At the end of the net - cycle, the C content is controlled at 0.007%. Low - carbon ferrochrome alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine - tune the alloy composition, and the tapping temperature is controlled at 1605 °C.

[0066] Continuous casting process: Control the tundish temperature at 1550 °C and the casting speed at 2.7 m / min.

[0067] Billet heating process: Heat the billet to 1235 °C and hold for 89 min.

[0068] Rolling process: Control the billet to start rolling at 1146 °C and roll the billet into steel bars.

[0069] Cooling process: After rolling is completed, when the steel bars reach 850 °C, they are transferred to the cooling bed. After being transferred to the cooling bed, when the temperature of the steel bars is between 850 and 800 °C, air cooling is carried out. The forward speed of the cooling bed is controlled at 1.3 m / min, and the cooling rate of the steel bars is 1.2 °C / min; when the temperature of the steel bars is between 800 and 750 °C, the forward speed of the cooling bed is controlled at 1.4 m / min, the blower below the cooling bed is turned on, and the air volume is 58% of the maximum air volume of the blower, and the cooling rate of the steel bars is 1.5 °C / min; when the temperature of the steel bars is between 750 and 700 °C, the forward speed of the cooling bed is controlled at 0.9 m / min, the blower below the cooling bed is turned on, and the air volume is 85% of the maximum air volume of the blower, and the cooling rate of the steel bars is 1.8 °C / min, and then air cooling is carried out.

[0070] Heat treatment process: Control the heat treatment temperature at 570 °C and the holding time at 1.5 h.

[0071] Example 2 Carry out in sequence according to the following processes to obtain corrosion-resistant steel bars with the chemical composition as described in Table 1.

[0072] Hot metal desulfurization: The hot metal temperature is 1341 °C, the Si content is 0.41%, the S content is 0.02%, the S content after desulfurization is 0.002%, and the slag skimming rate is 97%.

[0073] Converter smelting process: First, carry out dephosphorization, take samples for testing, after the P content is 0.025%, pour out the phosphorus-rich slag; then carry out decarburization, take samples for testing again, the C content is 0.050%, the P content is 0.015%, and carry out secondary slag pouring; control the C content at 0.07% and P at 0.020% at the end of smelting, and carry out final slag pouring again; control the tapping temperature at 1670 °C; after 1 / 4 of the tapping, add low-carbon ferrochromium alloy, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferrocolumbium alloy in sequence for preliminary alloying. Among them, the C content in the low-carbon ferrochromium alloy is 0.03%.

[0074] LF refining process: Bottom-blow argon gas throughout the process, the argon gas flow rate is 118 L / min. During the process of heating by electricity, add low-carbon ferrochromium alloy in the method of adding multiple times in small amounts, and add metal Sb to complete Sb alloying. The tapping temperature of LF refining is controlled at 1601 °C, the C content is 0.14%, and the Cr content is 9.9%.

[0075] RH refining process: After evacuating for 3 minutes, oxygen blowing starts, and the total amount of oxygen blown is 388 Nm 3 , sampling and testing are carried out. When the C content is 0.03%, oxygen blowing ends. Subsequently, low-carbon ferrochrome is added for alloying, and then net circulation treatment is carried out. The time with a vacuum degree less than 2 mbar is 7 minutes. At the end of the net circulation, the C content is controlled at 0.005%. Low-carbon ferrochrome alloy, ferrovanadium alloy, and ferrosilicon nitride are used to finely adjust the alloy composition, and the tapping temperature is controlled at 1590 °C.

[0076] Continuous casting process: Control the tundish temperature at 1553 °C and the casting speed at 2.9 m / min.

[0077] Slab heating process: Heat the slab to 1221 °C and hold for 80 minutes.

[0078] Rolling process: Control the slab to start rolling at 1137 °C and roll the slab into steel bars.

[0079] Cooling process: After rolling is completed, when the steel bars reach 827 °C, they are sent to the cooling bed. After being sent to the cooling bed, when the temperature of the steel bars is 850 - 800 °C, air cooling is carried out. The advancing speed of the cooling bed is controlled at 1.5 m / min, and the cooling rate of the steel bars is 1.4 °C / min; when the temperature of the steel bars is 800 - 750 °C, the advancing speed of the cooling bed is controlled at 1.5 m / min, the fan below the cooling bed is turned on, and the air volume is 65% of the maximum air volume of the fan. The cooling rate of the steel bars is 1.6 °C / min; when the temperature of the steel bars is 750 - 700 °C, the advancing speed of the cooling bed is controlled at 0.9 m / min, the fan below the cooling bed is turned on, and the air volume is 85% of the maximum air volume of the fan. The cooling rate of the steel bars is 1.8 °C / min, and then air cooling is carried out.

[0080] Heat treatment process: Control the heat treatment temperature at 560 °C and the holding time at 1.6 h.

[0081] Example 3 According to the following processes in sequence, corrosion-resistant steel bars with the chemical compositions described in Table 1 are obtained.

[0082] Hot metal desulfurization: The hot metal temperature is 1342 °C, the Si content is 0.43%, the S content is 0.03%, the S content after desulfurization is 0.002%, and the slag skimming rate is 97%.

[0083] Converter smelting process: First, dephosphorization is carried out. After sampling and testing, when the P content is 0.034%, the phosphorus-rich slag is poured out; then decarburization is carried out. After sampling and testing again, the C content is 0.44%, the P content is 0.019%, and the slag is poured out for the second time; at the end of smelting, the C content is controlled at 0.05%, P at 0.017%, and the slag is poured out again at the end; the tapping temperature is controlled at 1714 °C; after 1 / 4 of the tapping, low-carbon ferrochrome alloy, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferrocolumbium alloy are added in sequence for preliminary alloying. Among them, the C content in the low-carbon ferrochrome alloy is 0.03%.

[0084] LF refining process: Argon is blown from the bottom throughout the process, with an argon flow rate of 154 L / min. During the process of heating by energization, low-carbon ferrochromium alloy is added in multiple small amounts, and metallic Sb is added to complete Sb alloying. The tapping temperature in LF refining is controlled at 1619 °C, with a C content of 0.20% and a Cr content of 10.3%.

[0085] RH refining process: Oxygen blowing starts after evacuating for 3 min. The total amount of oxygen blown is 394 Nm 3 , sampling and testing are carried out. When the C content reaches 0.02%, oxygen blowing ends. Subsequently, low-carbon ferrochromium alloying is added, followed by net circulation treatment. The time with a vacuum degree less than 2 mbar is 6 min. At the end of net circulation, the C content is controlled at 0.004%. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the tapping temperature is controlled at 1620 °C.

[0086] Continuous casting process: Control the tundish temperature at 1565 °C and the casting speed at 3.1 m / min.

[0087] Slab heating process: Heat the slab to 1220 °C and keep it warm for 103 min.

[0088] Rolling process: Control the slab to start rolling at 1144 °C and roll the slab into steel bars.

[0089] Cooling process: After rolling is completed, when the steel bars reach 841 °C, they are sent to the cooling bed. After being sent to the cooling bed, when the temperature of the steel bars is between 850 and 800 °C, air cooling is carried out. The forward speed of the cooling bed is controlled at 1.3 m / min, and the cooling rate of the steel bars is 1.5 °C / min; when the temperature of the steel bars is between 800 and 750 °C, the forward speed of the cooling bed is controlled at 1.3 m / min, the fan below the cooling bed is turned on, and the air volume is 55% of the maximum air volume of the fan, and the cooling rate of the steel bars is 1.5 °C / min; when the temperature of the steel bars is between 750 and 700 °C, the forward speed of the cooling bed is controlled at 0.9 m / min, the fan below the cooling bed is turned on, and the air volume is 85% of the maximum air volume of the fan, and the cooling rate of the steel bars is 1.7 °C / min, and then air cooling is carried out.

[0090] Heat treatment process: Control the heat treatment temperature at 550 °C and the holding time at 1.5 h.

[0091] Example 4 According to the following processes in sequence, corrosion-resistant steel bars with the chemical compositions described in Table 1 are prepared.

[0092] Hot metal desulfurization: The hot metal temperature is 1347 °C, the Si content is 0.54%, the S content is 0.04%, the S content after desulfurization is 0.002%, and the slag skimming rate is 95%.

[0093] Converter smelting process: First, dephosphorization is carried out, and samples are taken for detection. After the P content reaches 0.025%, the phosphorus-rich slag is poured out; then decarburization is carried out, and samples are taken for detection again. The C content is 0.55% and the P content is 0.024%, and the slag is poured out for the second time; at the end of smelting, the C content is controlled at 0.06% and P at 0.020%, and the slag is poured out again at the end; the tapping temperature is controlled at 1720°C; after 1 / 4 of the tapping, low-carbon ferrochrome alloy, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying. Among them, the C content in the low-carbon ferrochrome alloy is 0.02%.

[0094] LF refining process: Argon is blown from the bottom throughout the process, and the argon flow rate is 135 L / min. During the process of heating by power supply, low-carbon ferrochrome alloy is added in the method of multiple times and small amounts, and metal Sb is added to complete Sb alloying. The tapping temperature of LF refining is controlled at 1605°C, the C content is 0.18%, and the Cr content is 10.0%.

[0095] RH refining process: Oxygen blowing starts after evacuating for 3 min, and the total oxygen blowing volume is 378 Nm 3 , samples are taken for detection. When the C content reaches 0.02%, oxygen blowing ends, and then low-carbon ferrochrome alloying is added. Subsequently, net circulation treatment is carried out. The time when the vacuum degree is less than 2 mbar is 10 min. At the end of net circulation, the C content is controlled at 0.006%. Low-carbon ferrochrome alloy, ferrovanadium alloy, and nitrided ferrosilicon are used to fine-tune the alloy composition, and the tapping temperature is controlled at 1615°C.

[0096] Continuous casting process: Control the tundish temperature at 1558°C and the casting speed at 3.0 m / min.

[0097] Slab heating process: Heat the slab to 1229°C and keep it warm for 95 min.

[0098] Rolling process: Control the slab to start rolling at 1135°C and roll the slab into steel bars.

[0099] Cooling process: After rolling is completed, when the steel bar reaches 820°C, it is sent to the cooling bed. After being sent to the cooling bed, when the temperature of the steel bar is 850 - 800°C, air cooling is carried out. The forward speed of the cooling bed is controlled at 1.5 m / min, and the cooling rate of the steel bar is 1.6°C / min; when the temperature of the steel bar is 800 - 750°C, the forward speed of the cooling bed is controlled at 1.5 m / min, the fan below the cooling bed is turned on, and the air volume is 65% of the maximum air volume of the fan. The cooling rate of the steel bar is 1.6°C / min; when the temperature of the steel bar is 750 - 700°C, the forward speed of the cooling bed is controlled at 0.9 m / min, the fan below the cooling bed is turned on, and the air volume is 85% of the maximum air volume of the fan. The cooling rate of the steel bar is 1.8°C / min, and then air cooling is carried out.

[0100] Heat treatment process: Control the heat treatment temperature at 570°C and the holding time at 1.4 h.

[0101] Example 5 The following processes are carried out in sequence to obtain the corrosion-resistant steel bars with the chemical composition as described in Table 1.

[0102] Hot metal desulfurization: The hot metal temperature is 1348 °C, the Si content is 0.53%, the S content is 0.03%, the S content after desulfurization is 0.001%, and the slag removal rate is 96%.

[0103] Converter smelting process: First, dephosphorization is carried out, and after sampling and detecting that the P content is 0.030%, the phosphorus-rich slag is poured out; then decarburization is carried out, and after sampling and detecting again, the C content is 0.41% and the P content is 0.025%, and the slag is poured out for the second time; the C content at the end of smelting is controlled to be 0.06% and P is 0.02%, and the slag is poured out again at the end; the tapping temperature is controlled to be 1707 °C; after 1 / 4 of the tapping, low-carbon ferrochrome alloy, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferrocolumbium alloy are added in sequence for preliminary alloying, among which the C content in the low-carbon ferrochrome alloy is 0.02%.

[0104] LF refining process: Bottom blowing argon gas is carried out throughout the process, the argon gas flow rate is 125 L / min, low-carbon ferrochrome alloy is added in the method of multiple times and small amounts during the process of heating by power supply, and metal Sb is added to complete Sb alloying. The tapping temperature of LF refining is controlled to be 1602 °C, the C content is 0.14%, and the Cr content is 10.3%.

[0105] RH refining process: After evacuating for 3 min, oxygen blowing starts, the total amount of oxygen blowing is 378 Nm 3 , after sampling and detecting that the C content is 0.02%, the oxygen blowing ends, then low-carbon ferrochrome alloying is added, and then the net circulation treatment is carried out. The time when the vacuum degree is less than 2 mbar is 8 min. The C content is controlled to be 0.005% at the end of the net circulation. Low-carbon ferrochrome alloy, ferrovanadium alloy, and nitrided ferrosilicon are used to finely adjust the alloy composition, and the tapping temperature is controlled to be 1608 °C.

[0106] Continuous casting process: Control the tundish temperature to be 1550 °C and the drawing speed to be 2.8 m / min.

[0107] Slab heating process: Heat the slab to 1230 °C and keep it warm for 110 min.

[0108] Rolling process: Control the slab to start rolling at 1141 °C and roll the slab into steel bars.

[0109] Cooling process: After rolling is completed, when the steel bar reaches 839 °C, it is transferred to the cooling bed. After being transferred to the cooling bed, when the temperature of the steel bar is between 850 °C and 800 °C, it is air-cooled. The forward speed of the cooling bed is controlled at 1.5 m / min, and the cooling rate of the steel bar is 1.2 °C / min. When the temperature of the steel bar is between 800 °C and 750 °C, the forward speed of the cooling bed is controlled at 1.3 m / min, the blower below the cooling bed is turned on, and the air volume is 65% of the maximum air volume of the blower. The cooling rate of the steel bar is 1.5 °C / min. When the temperature of the steel bar is between 750 °C and 700 °C, the forward speed of the cooling bed is controlled at 0.9 m / min, the blower below the cooling bed is turned on, and the air volume is 85% of the maximum air volume of the blower. The cooling rate of the steel bar is 1.7 °C / min, and then it is air-cooled.

[0110] Heat treatment process: The heat treatment temperature is controlled at 480 °C, and the holding time is controlled at 1.2 h.

[0111] Example 6 According to the following processes in sequence, corrosion-resistant steel bars with the chemical components described in Table 1 are prepared.

[0112] Hot metal desulfurization: The hot metal temperature is 1351 °C, the Si content is 0.52%, the S content is 0.02%. After desulfurization, the S content is 0.002%, and the slag tapping rate is 95%.

[0113] Converter smelting process: First, dephosphorization is carried out. After sampling and testing, when the P content is 0.031%, the phosphorus-rich slag is poured out. Then, decarburization is carried out. After sampling and testing again, the C content is 0.043%, the P content is 0.020%, and the slag is poured out for the second time. The C content at the end of smelting is controlled at 0.06%, P is 0.018%, and the slag is poured out again at the end. The tapping temperature is controlled at 1718 °C. After 1 / 4 of the tapping, low-carbon ferrochrome alloy, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferrocolumbium alloy are added in sequence for preliminary alloying. Among them, the C content in the low-carbon ferrochrome alloy is 0.03%.

[0114] LF refining process: Bottom blowing argon is carried out throughout the process, the argon flow rate is 109 L / min. During the process of heating by electricity, low-carbon ferrochrome alloy is added according to the method of multiple times and small amounts, and metal Sb is added to complete Sb alloying. The tapping temperature of LF refining is controlled at 1600 °C, the C content is 0.13%, and the Cr content is 9.9%.

[0115] RH refining process: After vacuum pumping for 3 min, oxygen blowing starts. When the total oxygen blowing volume reaches 361 Nm 3 , sampling and testing are carried out. When the C content reaches 0.02%, oxygen blowing ends. Subsequently, low-carbon ferrochrome alloying is added, and then net circulation treatment is carried out. The time when the vacuum degree is less than 2 mbar is 5 min. At the end of the net circulation, the C content is controlled at 0.004%. Low-carbon ferrochrome alloy, ferrovanadium alloy, and ferrosilicon nitride are used to finely adjust the alloy composition, and the tapping temperature is controlled at 1620 °C.

[0116] Continuous casting process: Control the tundish temperature at 1555 °C and the casting speed at 2.8 m / min.

[0117] Billet heating process: Heat the billet to 1248 °C and hold for 108 min.

[0118] Rolling process: Control the billet to start rolling at 1120 °C and roll the billet into steel bars.

[0119] Cooling process: After rolling is completed, when the steel bars reach 846 °C, they are transferred to the cooling bed. After being transferred to the cooling bed, when the temperature of the steel bars is between 850 and 800 °C, air cooling is carried out. The forward speed of the cooling bed is controlled at 1.4 m / min, and the cooling rate of the steel bars is 1.3 °C / min. When the temperature of the steel bars is between 800 and 750 °C, the forward speed of the cooling bed is controlled at 1.5 m / min, the fan below the cooling bed is turned on, and the air volume is 70% of the maximum air volume of the fan. The cooling rate of the steel bars is 1.6 °C / min. When the temperature of the steel bars is between 750 and 700 °C, the forward speed of the cooling bed is controlled at 1.0 m / min, the fan below the cooling bed is turned on, and the air volume is 90% of the maximum air volume of the fan. The cooling rate of the steel bars is 1.8 °C / min, and then air cooling is carried out.

[0120] Heat treatment process: Control the heat treatment temperature at 520 °C and the holding time at 1.3 h.

[0121] For the corrosion-resistant steel bars obtained in Examples 1 - 6, metallographic specimens are obtained through grinding, polishing, and etching with 4% nitric acid alcohol, photographed using a ZEISS optical microscope, and statistically analyzed using Miaps-M software to obtain the tissue proportion and size of the corrosion-resistant steel bars as shown in Table 2. Tensile tests are carried out on the steel bars according to the room temperature test method standard of GB / T 228.1 - 2021 Metallic materials - Tensile testing - Part 1 to obtain the mechanical properties of the corrosion-resistant steel bars as shown in Table 2.

[0122] The evaluation of corrosion performance is carried out in accordance with GB / T 10125 - 2021 Artificial atmosphere corrosion tests - Salt spray corrosion tests. The solution is 50 g / L ± 5 g / L NaCl, with a pH of 6.5 - 7.2 and a solution temperature of 35 °C ± 2 °C. Continuous tests are carried out to obtain the average weight loss corrosion rate at 168 h.

[0123] In accordance with GB / T 24196 - 2009 "Corrosion of metals and alloys - Electrochemical test methods - Guidelines for potentiostatic and potentiodynamic polarization measurements", a three - electrode system is adopted. The reference electrode is a saturated calomel electrode, the auxiliary electrode is a Pt sheet, and the test solution is 3.5% NaCl solution. The scanning range of the polarization curve test is - 300 to 600 mV relative to the self - corrosion potential of the specimen, and the scanning frequency is 1 mV / s. The scanning frequency range of the electrochemical impedance test is 10 5 ~10 -2 Hz, and the amplitude of the AC excitation signal is ±5 mV to obtain the self - corrosion current density.

[0124] Table 2 Organization and properties of Examples 1 - 6

[0125] In addition, for the steel bars of Examples 1 - 6, samples were taken respectively and welding tests were carried out using manual electrode welding. The welded specimens were subjected to tensile tests in accordance with the room temperature test method standard of GB / T 228.1 - 2021 Metallic materials - Tensile testing - Part 1. The fracture points of the welded specimens in the tensile tests were formed at the steel bar base material, rather than at the welded joint positions. It can be seen that the welded performance of the obtained steel bars is excellent. The results are shown in Table 3.

[0126] Table 3 Welding tensile test results

[0127] It should be understood that although this specification is described according to the implementation manners, not each implementation manner only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each implementation manner can also be appropriately combined to form other implementation manners that can be understood by those skilled in the art.

[0128] The series of detailed descriptions listed above are only specific descriptions of the feasible implementation manners of this application, and they are not used to limit the protection scope of this application. Any equivalent implementation manners or changes made without departing from the technical spirit of this application should be included in the protection scope of this application.

Claims

1. A corrosion-resistant steel bar, characterized in that, Comprising by weight percentage: C: 0.015 - 0.03%, Si: 0.5 - 0.8%, Mn: 1.2 - 1.6%, Cu: 0.1 - 0.3%, Ni: 0.08 - 0.11%, Cr: 9.5 - 11.5%, Mo: 1.0 - 1.5%, Nb: 0.02 - 0.05%, V: 0.05 - 0.08%, N: 0.022 - 0.040%, Sb: 0.05 - 0.15%, P: 0.01 - 0.03%, S ≤ 0.004%, O ≤ 0.003%, As ≤ 0.01%, the balance being iron and unavoidable impurities, and the following relationships also hold among the elements: the corrosion resistance coefficient K = [Ni] + 0.25[Cr] + 0.5[Mo] + 5[Nb] - 2.5[C] is 3 - 3.7%, and the strength and plasticity coefficient T = 8{C} + {Si} + 0.4{Mn} + 0.25({Cr} + {Mo}) + 0.17({Nb} + {V}) / {N} is 4.4 - 5.3, where [Ni], [Cr], [Mo], [Nb], [C] are the weight percentages of the corresponding elements, and {C}, {Si}, {Mn}, {Cr}, {Mo}, {Nb}, {V}, {N} are 100 times the weight percentages of the corresponding elements respectively.

2. The corrosion-resistant steel bar according to claim 1, characterized in that, The corrosion-resistant steel bar has a two-phase structure of ferrite and bainite, with the volume fraction of ferrite being 17 - 22% and the volume fraction of bainite being 78 - 83%, and the ferrite size being 5.9 - 7.7 μm.

3. The corrosion-resistant steel bar according to claim 2, wherein, The yield strength of the corrosion-resistant steel bar is ≥700 MPa, the tensile strength is ≥950 MPa, and the total elongation at maximum force is ≥7.5%.

4. The corrosion-resistant steel bar according to claim 2, wherein, In the salt spray corrosion test, the average weight loss corrosion rate of the corrosion-resistant steel bars is 0.01 - 0.04 g / (m 2 ·h); in the simulated concrete pore solution with a chloride ion concentration ≥ 3 mol / L, the self-corrosion current density of the steel bars ≤ 0.12 μA / cm 2 .

5. A production method of corrosion-resistant steel bars, characterized in that, Including the processes of smelting, refining, continuous casting, slab heating, rolling, cooling, and heat treatment carried out in sequence, where In the slab heating process, the slab is heated to 1200 - 1250 °C and held for 80 - 110 min; In the rolling process, it is controlled that rolling starts when the slab temperature is 1120 - 1150 °C, and the slab is rolled into steel bars; In the cooling process, after rolling is completed, when the steel bars reach 820 - 850 °C, they are transferred to the cooling bed. After being transferred to the cooling bed, when the temperature of the steel bars is 850 - 800 °C, air cooling is carried out, and the advancing speed of the cooling bed is controlled at 1.3 - 1.5 m / min, and the cooling rate of the steel bars is controlled at 1.2 - 1.6 °C / min; when the temperature of the steel bars is 800 - 750 °C, the advancing speed of the cooling bed is controlled at 1.3 - 1.5 m / min, the fan is turned on, and the cooling rate of the steel bars is controlled at 1.5 - 1.7 °C / min; when the temperature of the steel bars is 750 - 700 °C, the advancing speed of the cooling bed is controlled at 0.8 - 1.0 m / min, the fan is turned on, and the cooling rate of the steel bars is controlled at 1.7 - 1.9 °C / min, and then air cooling is carried out.

6. The production method of the corrosion-resistant steel bar according to claim 5, characterized in that, In the heat treatment process, when 4.4 ≤ T ≤ 4.6, the heat treatment temperature is controlled at 480 - 510 °C, and the holding time is controlled at 0.9 - 1.3 h; when the strength-plasticity coefficient 4.6 < T ≤ 4.9, the heat treatment temperature is controlled at 520 - 550 °C, and the holding time is controlled at 1.1 - 1.5 h; when the strength-plasticity coefficient 4.9 < T ≤ 5.3, the heat treatment temperature is controlled at 560 - 590 °C, and the holding time is controlled at 1.4 - 1.8 h.

7. The production method of the corrosion-resistant steel bar according to claim 5, characterized in that, In the converter smelting process, dephosphorization is carried out first. After the P content ≤ 0.035%, the phosphorus-rich slag is poured out; then decarburization is carried out to make the C content 0.35 - 0.55% and the P content ≤ 0.025%, and the slag is poured out for the second time; at the end of smelting, the C content is controlled at 0.04 - 0.07% and the P content ≤ 0.020%, and the slag is poured out again at the end; the tapping temperature is controlled at 1670 - 1720 °C; after 1 / 4 of the tapping, low-carbon ferrochrome alloy, ferromolybdenum alloy, silicomanganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying. Among them, the C content in the low-carbon ferrochrome alloy ≤ 0.03%.

8. The production method of the corrosion-resistant steel bars according to claim 7, characterized in that, The refining process includes LF refining. During the process of heating up by power supply in LF refining, the low-carbon ferrochrome alloy is added according to the method of multiple small amounts, and metallic Sb is added to complete Sb alloying. The tapping temperature in LF refining is controlled at 1590 - 1620 °C, the C content ≤ 0.2%, and the Cr content is 9.8 - 10.5%.

9. The production method of the corrosion-resistant steel bars according to claim 8, characterized in that, The refining process also includes RH refining after LF refining. Oxygen blowing starts 3 - 4 minutes after the vacuum is pumped in RH refining, and the total amount of oxygen blowing is 350 - 400 Nm 3 , oxygen blowing ends when the C content ≤ 0.03%. Subsequently, low-carbon ferrochrome is added for alloying, followed by net circulation treatment. The time with a vacuum degree less than 2 mbar ≥ 5 minutes. At the end of the net circulation, the C content is controlled ≤ 0.008%. Low-carbon ferrochrome alloy, ferrotitanium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the tapping temperature is controlled at 1590 - 1620 °C.

10. The production method of the corrosion-resistant steel bar according to claim 9, characterized in that, In the continuous casting process, the tundish temperature is controlled at 1548 - 1568 °C, and the casting speed is controlled at 2.6 - 3.1 m / min.

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