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

Abstract

The present application provides a high-strength, corrosion-resistant steel bar and a production method thereof. The steel bar comprises, by weight percentage, the following: 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%, with the remainder being iron and unavoidable impurities. The elements further satisfy the following conditions: a corrosion resistance coefficient K of 3-3.7% and a strength-ductility coefficient T of 4.4-5.3. The steel bar of the present application has high strength-ductility and extremely strong corrosion resistance.

Description

Technical Field

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

[0002] In actual engineering, there are numerous cases of premature failure of reinforced concrete structures, which not only increases maintenance costs but also results in a significant waste of energy and resources. Due to the influence of harsh environments such as those rich in chloride ions and sulfates, high temperatures, and high humidity, ordinary rebar often falls far short of its designed theoretical service life, causing serious economic losses, wasting energy and resources, and leading to large-scale waste emissions. Currently, corrosion inhibitors, surface protective layers, cathodic protection, and coated steel bars have achieved certain results in extending the service life of reinforced concrete structures. However, as the core of reinforced concrete structures, improving the corrosion resistance of the steel matrix itself is the key to solving the problem of corrosion damage to reinforced concrete structures. However, the coordinated regulation of corrosion resistance, energy conservation, and cost reduction is quite difficult. Summary of the Invention

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

[0004] In order to achieve one of the above-mentioned objects of the invention, an embodiment of the present application provides a corrosion-resistant steel bar, which comprises, 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 It is iron and inevitable impurities, and the elements also meet the following requirements: corrosion resistance coefficient K=[Ni]+0.25[Cr]+0.5[Mo]+5[Nb]-2.5[C] is 3~3.7%, 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], [C] are the weight percentages of the corresponding elements, {C}, {Si}, {Mn}, {Cr}, {Mo}, {Nb}, {V}, {N} are 100 times the weight percentages of the corresponding elements, respectively.

[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 proportion of ferrite being 17-22%, the volume proportion 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 bars is 0.01~0.04g / (m 2 h); in simulated concrete pore fluid with a chloride ion concentration of ≥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 further provides a method for producing corrosion-resistant steel bars, comprising the steps of smelting, refining, continuous casting, heating of the ingot, rolling, cooling and heat treatment performed in sequence, wherein:

[0009] In the billet heating process, the billet is heated to 1200~1250℃ and kept at this temperature for 80~110min;

[0010] During the rolling process, the casting is controlled to start rolling at 1120~1150℃ and the casting is rolled into steel bars;

[0011] In the cooling process, after rolling is completed, the steel bars are placed on the cooling bed when the temperature is 820~850℃. After being placed on the cooling bed, air cooling is carried out when the temperature of the steel bars is 850~800℃, and the forward speed of the cooling bed is controlled to be 1.3~1.5m / min, and the cooling rate of the steel bars is controlled to be 1.2~1.6℃ / min; when the temperature of the steel bars is 800~750℃, the forward speed of the cooling bed is controlled to be 1.3~1.5m / min, the fan is turned on, and the cooling rate of the steel bars is controlled to be 1.5~1.7℃ / min; when the temperature of the steel bars is 750~700℃, the forward speed of the cooling bed is controlled to be 0.8~1.0m / min, the fan is turned on, and the cooling rate of the steel bars is controlled to be 1.7~1.9℃ / min, followed by air cooling.

[0012] In one embodiment of the present application, in the heat treatment process, when 4.4≤T≤4.6, the heat treatment temperature is controlled to 480~510℃, and the holding time is controlled to 0.9~1.3h; when the strength-plastic coefficient is 4.6<T≤4.9, the heat treatment temperature is controlled to 520~550℃, and the holding time is controlled to 1.1~1.5h; when the strength-plastic coefficient is 4.9<T≤5.3, the heat treatment temperature is controlled to 560~590℃, and the holding time is controlled to 1.4~1.8h.

[0013] In one embodiment of the present application, in the converter smelting process, dephosphorization is first carried out, and after the P content is ≤0.035%, the phosphorus-rich slag is poured out; then decarburization is carried out to make the C content 0.35~0.55%, the P content ≤0.025%, and the slag is poured out twice; the C content is controlled to be 0.04~0.07% and the P content ≤0.020% at the end of smelting, and the slag is poured out again at the end; the tapping temperature is controlled to be 1670~1720℃; after 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying, wherein the C content in the low-carbon ferrochromium alloy is ≤0.03%.

[0014] In one embodiment of the present application, the refining process includes LF refining, during which low-carbon ferrochromium alloy is added in small amounts multiple times during the LF refining power-on temperature rise process, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1590~1620°C, the C content is ≤0.2%, and the Cr content is 9.8~10.5%.

[0015] In one embodiment of the present application, the refining process further includes RH refining after LF refining. After RH refining, vacuum is drawn for 3 to 4 minutes before oxygen blowing begins. The total amount of oxygen blown is 350 to 400 Nm 3 When the C content is ≤0.03%, oxygen blowing is stopped, and then low-carbon ferrochromium alloying is added, followed by net circulation treatment. The vacuum degree is less than 2mbar for ≥5min. At the end of the net circulation, the C content is controlled to be ≤0.008%. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1590~1620℃.

[0016] In one embodiment of the present application, during 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.

[0017] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0018] The corrosion-resistant steel bars provided in the present application use ultra-low carbon content and are combined with alloying elements Ni, Cr, Mo, and Nb to control costs while making the oxide film of the steel bars dense and the matrix corrosion-resistant and repairing ability stronger; combined with strengthening alloying elements Si, Mn, Cr, Mo and alloy strengthening elements Nb and V as well as N elements, the alloying elements exert solid solution strengthening, precipitation strengthening and tissue strengthening effects, ensuring that the strength and plasticity of the steel bars are coordinated and regulated after heat treatment. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0020] The embodiment of the present application provides a corrosion-resistant steel bar, which comprises, 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 unavoidable impurities, and the elements also satisfy the following: K=[Ni]+0.25[Cr]+0.5[Mo]+5[Nb]-2.5[C] is 3~3.7%, 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, respectively.

[0021] This application adopts ultra-low carbon content, combined with strengthening alloy elements Si, Mn, Mo and micro-alloy strengthening elements Nb and V as well as N elements. The alloy elements exert solid solution strengthening, precipitation strengthening and organizational strengthening effects, and a large amount of Cr is used to promote the production of ferrite, so that the strength and plasticity of the steel bars after heat treatment are synergistically regulated.

[0022] The combination of alloy elements Ni, Cr, Mo, and Nb can make the steel bar's oxide film dense and the matrix's corrosion resistance and repair ability stronger while controlling costs, greatly improving the steel bar's corrosion resistance.

[0023] The following is a detailed description of the role and mechanism of each element:

[0024] Carbon (C): Austenite-forming element. In low-carbon steel, the C content is reduced to below the solubility limit of ferrite, which is beneficial to improving the uniformity of the steel structure and component distribution, reducing the potential difference between various areas inside the steel bar, and thus reducing the corrosion rate.

[0025] Silicon (Si): Silicon dissolves in ferrite to increase strength and inhibit the diffusion of carbon in austenite, delaying the ferrite-pearlite transformation and increasing the yield strength and tensile strength of the steel. However, excessive Si content can affect the weldability of the steel.

[0026] Manganese (Mn): An important deoxidizer and desulfurizer. It provides solid solution strengthening and toughening, and is also an austenite-forming element. However, when the Mn content in steel is too high, the plasticity and impact toughness of the steel bar decrease, as does the weldability of the steel bar.

[0027] Copper (Cu): A corrosion-resistant element that helps improve the corrosion resistance of steel. However, excessive Cu in steel can reduce the plasticity of the material and lead to hot rolling cracking.

[0028] Chromium (Cr): An important corrosion-resistant element. It forms a passivation film on the surface of steel bars, effectively preventing oxidation and improving the corrosion resistance of the steel matrix. Furthermore, adding it in combination with Mo, Ni, and other elements can provide even better corrosion resistance. While adding it alone can provide some corrosion resistance, it is more susceptible to pitting corrosion. It also improves the hardenability of steel bars.

[0029] Molybdenum (Mo): A crucial corrosion-resistant element, it generally improves the corrosion resistance of steel. It passivates the steel surface in both reducing acids and strongly oxidizing salt solutions, and prevents pitting corrosion in chloride solutions. It significantly inhibits pearlite transformation, refines carbides precipitating from ferrite, replaces vanadium in MC-type carbides to form composite carbides, and, in combination with the carbide-forming element Cr, promotes the formation of bainite. High Mo content can deteriorate the oxidation resistance of steel. Regarding microstructure and properties, Mo promotes grain refinement, improving the steel's hardenability and hot strength.

[0030] Nickel (Ni): It has high corrosion resistance to acids and alkalis, is rust-resistant and heat-resistant at high temperatures, and is an austenite-forming element, which can give steel a uniform austenitic structure and improve corrosion resistance. However, it is not an effective antioxidant on its own and is rarely used alone as an alloying element in corrosion-resistant steel.

[0031] Nitrogen (N): an austenite-forming element. If it is too high, it will be detrimental to the plasticity of steel bars and the control of the ratio of ferrite and bainite in the structure. If it is too low, it will be detrimental to improving the strength of steel bars.

[0032] Vanadium (V): A microalloying strengthening element that can precipitate V(C,N) compounds during the rolling process, which has a certain precipitation strengthening effect. It also prevents the growth of austenite and ferrite grains and has a fine grain strengthening effect. However, too high a V content will reduce the plasticity of the material and increase the cost.

[0033] Niobium (Nb): A microalloying element, combined with controlled rolling and controlled cooling, can contribute to precipitation strengthening and grain refinement during the rolling process. Nb densifies the oxide layer and increases the Cr concentration in the passive film, improving its stability and thus the pitting potential, ultimately enhancing corrosion resistance. However, excessive Nb content can reduce material plasticity and increase cost.

[0034] Antimony (Sb): The Sb element can increase the self-corrosion potential of the matrix and improve the properties of the rust layer. The combined addition of Sb and Nb can better optimize the rust layer structure, promote the formation of more protective rust layer products, and help improve the corrosion resistance of the material.

[0035] Phosphorus (P): It can improve the strength and corrosion resistance of steel bars, but it is easy to segregate in steel, and too high a P content will lead to poor mechanical properties at low temperatures.

[0036] Sulfur (S): Sulfur can form inclusions, destroying the corrosion resistance of steel, especially localized corrosion.

[0037] Oxygen (O): Controlling the oxygen content during smelting and continuous casting can effectively improve the cleanliness of steel and enhance its corrosion resistance.

[0038] Arsenic (As): In acidic environments, such as HCl, arsenic compounds may dissolve and destroy the passive film of steel.

[0039] The corrosion resistance coefficient K = Ni + 0.25Cr + 0.5Mo + 5Nb - 2.5C is of great significance in measuring the corrosion resistance of steel bars, ensuring the density of the steel oxide film and the corrosion resistance of the steel matrix. The strength-ductility coefficient T = 8C + Si + 0.4Mn + 0.25 (Cr + Mo) + 0.17 (Nb + V) / N is of great significance in measuring and ensuring the strength and ductility of steel bars. The alloying elements exert the effects of solid solution strengthening, precipitation strengthening, and structural strengthening, resulting in high-strength and high-ductility steel bars after heat treatment.

[0040] In one embodiment of the present application, the corrosion-resistant steel bar has a two-phase structure of ferrite and bainite, with the volume proportion of ferrite being 17-22%, the volume proportion of bainite being 78-83%, and the size of ferrite being 5.9-7.7 μm.

[0041] The high bainite content makes the steel bar have higher strength, and the ferrite improves the plasticity of the steel bar, resulting in a synergistic improvement in the strength and plasticity of the steel bar.

[0042] 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%.

[0043] In one embodiment of the present application, in the salt spray corrosion test, the average weight loss corrosion rate of the corrosion-resistant steel bars is 0.01~0.04g / (m 2 h); in simulated concrete pore fluid with a chloride ion concentration of ≥3 mol / L, the self-corrosion current density of the steel bar is ≤0.12 μA / cm 2 .

[0044] With the synergistic effect of the aforementioned components, the corrosion resistance of the steel bars is greatly improved. The average weight loss corrosion rate of the steel bars is 1 / 45 of that of HRB400; the self-corrosion current density of the steel bars is 1 / 56 of that of HRB400, which can resist corrosion in harsh environments.

[0045] The present application also provides a method for producing corrosion-resistant steel bars, comprising the steps of smelting, refining, continuous casting, heating the ingot, rolling, cooling, and heat treatment, wherein:

[0046] In the billet heating process, the billet is heated to 1200~1250℃ and kept at this temperature for 80~110min;

[0047] During the rolling process, the casting is controlled to start rolling at 1120~1150℃ and the casting is rolled into steel bars;

[0048] In the cooling process, after rolling is completed, the steel bars are placed on the cooling bed when the temperature is 820~850℃. After being placed on the cooling bed, air cooling is carried out when the temperature of the steel bars is 850~800℃, and the forward speed of the cooling bed is controlled to be 1.3~1.5m / min, and the cooling rate of the steel bars is controlled to be 1.2~1.6℃ / min; when the temperature of the steel bars is 800~750℃, the forward speed of the cooling bed is controlled to be 1.3~1.5m / min, the fan is turned on, and the cooling rate of the steel bars is controlled to be 1.5~1.7℃ / min; when the temperature of the steel bars is 750~700℃, the forward speed of the cooling bed is controlled to be 0.8~1.0m / min, the fan is turned on, and the cooling rate of the steel bars is controlled to be 1.7~1.9℃ / min, followed by air cooling.

[0049] A higher heating temperature is used in combination with a high rolling start temperature to ensure that the rolling process is carried out in the high-temperature non-recrystallization zone, which is conducive to controlling the grain size to be larger and remelting the large-sized precipitates formed by continuous casting, thereby improving the strength.

[0050] When the rebar temperature is between 850°C and 800°C, the upper cooling bed is air-cooled, allowing the rebar to cool through the ferrite transformation zone at a slower rate. This ensures a larger pro-eutectoid phase transformation grain size and a certain proportion of pro-eutectoid structure, while also promoting the precipitation of V(C,N) in this zone. During the last two stages, the fan below the cooling bed is activated, gradually increasing the cooling intensity to ensure uniformity across the core and surface, while also increasing the thickness of the rebar's surface oxide scale and strengthening the bond between the surface oxide scale and the substrate.

[0051] After the steel bar temperature drops to 700°C, it is air-cooled, allowing the steel bar to slowly pass through the bainite transformation zone, obtaining a higher content of bainite structure.

[0052] In one embodiment of the present application, in the heat treatment process, when 4.4≤T≤4.6, the heat treatment temperature is controlled to be 480~510℃, and the holding time is controlled to be 0.9~1.3h; when the strength-plastic coefficient is 4.6<T≤4.9, the heat treatment temperature is controlled to be 520~550℃, and the holding time is controlled to be 1.1~1.5h; when the strength-plastic coefficient is 4.9<T≤5.3, the heat treatment temperature is controlled to be 560~590℃, and the holding time is controlled to be 1.4~1.8h.

[0053] The higher the strength-ductility coefficient T, the lower the ferrite content in the steel bar structure, the higher the bainite content, and the lower the total elongation at maximum force. Therefore, as the strength-ductility coefficient T increases, the heat treatment temperature and holding time are increased to improve the plasticity of the steel bar.

[0054] In one embodiment of the present application, in the converter smelting process, dephosphorization is first carried out, and after the P content is ≤0.035%, the phosphorus-rich slag is poured out; then decarburization is carried out to make the C content 0.35~0.55%, the P content ≤0.025%, and the slag is poured out twice; the C content is controlled to be 0.04~0.07% and the P content ≤0.020% at the end of smelting, and the slag is poured out again at the end; the steel tapping temperature is controlled to be 1670~1720℃; after 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying, wherein the C content in the low-carbon ferrochromium alloy is ≤0.03%.

[0055] Among them, the chromium content in low-carbon ferrochromium alloy is 50~60%, the carbon content is ≤0.03%, and the balance is iron and inevitable impurities; the molybdenum content in ferromolybdenum alloy is 50~60%, and the balance is iron and inevitable impurities; the silicon content in silicomanganese alloy is 17~20%, the manganese content is 65~70%, and the balance is iron and inevitable impurities; the silicon content in ferrosilicon alloy is 70~75%, and the balance is iron and inevitable impurities; the niobium content in ferroniobium alloy is 60~70%, and the balance is iron and inevitable impurities.

[0056] During the smelting process, the C and P contents are controlled at low levels at the end of the smelting process to prevent the C and P in the alloy from increasing the C and P content in the molten steel to high values ​​during tapping and alloying, which would be difficult to remove later. A higher tapping temperature is used to prevent the large amount of alloy added during tapping and alloying from causing the molten steel temperature to drop, which would be detrimental to the subsequent refining stage. Copper and nickel are also added during the tapping and alloying process to achieve target values.

[0057] Before converter smelting, the molten steel must be desulfurized. The molten steel temperature must be ≥1330°C, the Si content must be 0.35-0.55%, the S content must be ≤0.04%, and the post-desulfurization S content must be ≤0.002%. The slag removal rate must be ≥95%. Keeping the S content low prevents alloying from causing sulfur to rise above the target S content, making desulfurization difficult during refining.

[0058] In one embodiment of the present application, the refining process includes LF refining. During the LF refining power-on temperature rise process, low-carbon ferrochrome is added in small amounts multiple times, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1590~1620℃, the C content is ≤0.2%, and the Cr content is 9.8~10.5%.

[0059] During the LF refining process, argon is blown from the bottom at a flow rate of 80-160 L / min to maintain soft stirring of the molten steel. Low-carbon ferrochromium alloy is added in small amounts and multiple times to avoid excessive addition of chromium, which may result in a high Cr content.

[0060] In one embodiment of the present application, the refining process further includes RH refining after LF refining. After RH refining, vacuuming is performed for 3 to 4 minutes before oxygen blowing begins. The total amount of oxygen blown is 350 to 400 Nm 3 When the C content is ≤0.03%, oxygen blowing is stopped, and then low-carbon ferrochromium alloying is added, followed by net circulation treatment. The vacuum degree is less than 2mbar for ≥5min. At the end of the net circulation, the C content is controlled to be ≤0.008%. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1590~1620℃.

[0061] RH refining involves oxygen decarburization, reducing the carbon content to below the maximum carbon content previously mentioned. Even after oxygen blowing ends, the oxygen continues to react with carbon in the molten steel, reducing the carbon content to an extremely low value. Finally, vanadium-ferroalloy and ferrosilicon nitride, with correspondingly low V and N contents, are added, along with a low-carbon ferrochromium alloy to bring the final chromium content to the target value.

[0062] In one embodiment of the present application, during 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.

[0063] Before continuous casting, the tundish is purged with argon for ≥5 minutes to remove the solidified molten steel and protective slag remaining in the tundish. The higher the temperature of the tundish, the higher the fluidity of the molten steel and the better the uniformity of the alloy elements in the molten steel.

[0064] The continuous casting process uses argon sealing of large ladle long nozzle + alkaline tundish covering agent + submerged nozzle + low-carbon protective slag to complete full protective pouring. The argon sealing pressure is 0.25~0.35MPa, the immersion depth of the submerged nozzle is 70~100mm, and the thickness of the crystallizer liquid slag layer is 7~9mm.

[0065] The continuous casting billet size is small square billet of 140~170mm, the water flow rate of the crystallizer is 1850~1870L / min, the inlet and outlet water temperature difference is ≤10℃, the crystallizer electromagnetic stirring current is 280~300A, the frequency is 5~8Hz, and the end electromagnetic stirring current is 400~450A, the frequency is 10~12Hz, to ensure the quality of the continuous casting surface and core.

[0066] The technical solution of the present application is further described below with reference to some specific embodiments.

[0067] Table 1 Chemical composition of steel bars in Examples 1 to 6 (%)

[0068]

[0069] It should be noted here that the value of the strength-plasticity coefficient T does not include "%".

[0070] Example 1

[0071] The following steps were carried out in sequence to produce corrosion-resistant steel bars with the chemical composition described in Table 1.

[0072] Hot metal desulfurization: Hot metal temperature is 1339℃, Si content is 0.36%, S content is 0.01%, after desulfurization, S content is 0.001%, and slag skimming rate is 96%.

[0073] Converter smelting process: first dephosphorization, sampling and testing, after the P content is 0.028%, the phosphorus-rich slag is poured out; then decarburization is carried out, sampling and testing again, the C content is 0.37%, the P content is 0.021%, and the slag is poured out a second time; the C content is controlled at 0.04% and the P content is 0.015% at the end of smelting, and the slag is poured out again at the end; the tapping temperature is controlled at 1693℃; after 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying, among which the C content of the low-carbon ferrochromium alloy is 0.02%.

[0074] LF refining process: argon is blown from the bottom throughout the entire process, with an argon flow rate of 88L / min. During the power-on temperature rise process, low-carbon ferrochrome is added in small amounts multiple times, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1599°C, the C content is 0.18%, and the Cr content is 9.9%.

[0075] RH refining process: start blowing oxygen after 3 minutes of vacuuming, with a total oxygen volume of 377Nm 3, sampling and testing, when the C content is 0.024%, the oxygen blowing is stopped, and then low-carbon ferrochromium alloy is added, followed by net circulation treatment, the vacuum degree is less than 2mbar for 5 minutes, and the C content is controlled at 0.007% at the end of the net circulation. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1605℃.

[0076] Continuous casting process: control the tundish temperature to 1550℃ and the casting speed to 2.7m / min.

[0077] Ingot heating process: heat the ingot to 1235℃ and keep it warm for 89 minutes.

[0078] Rolling process: The casting temperature is controlled to start rolling at 1146℃, and the casting is rolled into steel bars.

[0079] Cooling process: After rolling is completed, the steel bars are placed on the cooling bed at 850℃. After being placed on the cooling bed, air cooling is carried out when the steel bar temperature is 850~800℃, the cooling bed forward speed is controlled at 1.3m / min, and the steel bar cooling rate is 1.2℃ / min; when the steel bar temperature is 800~750℃, the cooling bed forward speed is controlled at 1.4m / min, the fan under the cooling bed is turned on, and the air volume is 58% of the fan's maximum air volume, and the steel bar cooling rate is 1.5℃ / min; when the steel bar temperature is 750~700℃, the cooling bed forward speed is controlled at 0.9m / min, the fan under the cooling bed is turned on, and the air volume is 85% of the fan's maximum air volume, the steel bar cooling rate is 1.8℃ / min, and then air cooling is carried out.

[0080] Heat treatment process: The heat treatment temperature is controlled at 570°C and the holding time is controlled at 1.5h.

[0081] Example 2

[0082] The following steps were carried out in sequence to produce corrosion-resistant steel bars with the chemical composition described in Table 1.

[0083] Hot metal desulfurization: The hot metal temperature is 1341℃, 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%.

[0084] Converter smelting process: first dephosphorization, sampling and testing, after the P content reaches 0.025%, the phosphorus-rich slag is poured out; then decarburization is carried out, sampling and testing are carried out again, the C content is 0.050%, the P content is 0.015%, and the slag is poured out a second time; the C content is controlled at 0.07% and the P content is 0.020% at the end of smelting, and the slag is poured out again at the end; the tapping temperature is controlled at 1670℃; after 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying, among which the C content in the low-carbon ferrochromium alloy is 0.03%.

[0085] LF refining process: argon is blown from the bottom throughout the entire process, with an argon flow rate of 118L / min. During the power-on temperature rise process, low-carbon ferrochrome is added in small amounts multiple times, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1601°C, the C content is 0.14%, and the Cr content is 9.9%.

[0086] RH refining process: start blowing oxygen after 3 minutes of vacuuming, with a total oxygen volume of 388Nm 3 , sampling and testing, when the C content is 0.03%, the oxygen blowing is stopped, and then low-carbon ferrochromium alloy is added, followed by net circulation treatment, the vacuum degree is less than 2mbar for 7 minutes, and the C content is controlled at 0.005% at the end of the net circulation. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1590℃.

[0087] Continuous casting process: control the tundish temperature to 1553℃ and the casting speed to 2.9m / min.

[0088] Ingot heating process: Heat the ingot to 1221℃ and keep it warm for 80 minutes.

[0089] Rolling process: The casting temperature is controlled to start rolling at 1137℃, and the casting is rolled into steel bars.

[0090] Cooling process: After rolling is completed, the steel bar is placed on the cooling bed at 827℃. After being placed on the cooling bed, air cooling is carried out when the steel bar temperature is 850~800℃, the cooling bed forward speed is controlled at 1.5m / min, and the steel bar cooling rate is 1.4℃ / min; when the steel bar temperature is 800~750℃, the cooling bed forward speed is controlled at 1.5m / min, the fan under the cooling bed is turned on, and the air volume is 65% of the fan's maximum air volume, and the steel bar cooling rate is 1.6℃ / min; when the steel bar temperature is 750~700℃, the cooling bed forward speed is controlled at 0.9m / min, the fan under the cooling bed is turned on, and the air volume is 85% of the fan's maximum air volume, the steel bar cooling rate is 1.8℃ / min, and then air cooling is carried out.

[0091] Heat treatment process: The heat treatment temperature is controlled at 560°C and the holding time is controlled at 1.6h.

[0092] Example 3

[0093] The following steps were carried out in sequence to produce corrosion-resistant steel bars with the chemical composition described in Table 1.

[0094] Hot metal desulfurization: Hot metal temperature is 1342℃, Si content is 0.43%, S content is 0.03%, S content after desulfurization is 0.002%, and slag skimming rate is 97%.

[0095] Converter smelting process: first dephosphorization, sampling and testing, after the P content is 0.034%, the phosphorus-rich slag is poured out; then decarburization is carried out, sampling and testing again, the C content is 0.44%, the P content is 0.019%, and the slag is poured out a second time; the C content is controlled at 0.05% and the P content is 0.017% at the end of smelting, and the slag is poured out again at the end; the tapping temperature is controlled at 1714℃; after 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying, among which the C content in the low-carbon ferrochromium alloy is 0.03%.

[0096] LF refining process: argon is blown from the bottom throughout the entire process, with an argon flow rate of 154L / min. During the power-on temperature rise process, low-carbon ferrochrome is added in small amounts multiple times, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1619°C, the C content is 0.20%, and the Cr content is 10.3%.

[0097] RH refining process: oxygen blowing starts 3 minutes after vacuuming, with a total oxygen blowing volume of 394 Nm 3 , sampling and testing, when the C content is 0.02%, the oxygen blowing is stopped, and then low-carbon ferrochromium alloy is added, followed by net circulation treatment, the vacuum degree is less than 2mbar for 6 minutes, and the C content is controlled at 0.004% at the end of the net circulation. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1620℃.

[0098] Continuous casting process: control the tundish temperature to 1565℃ and the casting speed to 3.1m / min.

[0099] Ingot heating process: heat the ingot to 1220℃ and keep it warm for 103 minutes.

[0100] Rolling process: The casting temperature is controlled to start rolling at 1144℃, and the casting is rolled into steel bars.

[0101] Cooling process: After rolling is completed, the steel bar is placed on the cooling bed at 841℃. After being placed on the cooling bed, air cooling is carried out when the steel bar temperature is 850~800℃, the cooling bed forward speed is controlled at 1.3m / min, and the steel bar cooling rate is 1.5℃ / min; when the steel bar temperature is 800~750℃, the cooling bed forward speed is controlled at 1.3m / min, the fan under the cooling bed is turned on, and the air volume is 55% of the maximum air volume of the fan, and the steel bar cooling rate is 1.5℃ / min; when the steel bar temperature is 750~700℃, the cooling bed forward speed is controlled at 0.9m / min, the fan under the cooling bed is turned on, and the air volume is 85% of the maximum air volume of the fan, the steel bar cooling rate is 1.7℃ / min, and then air cooling is carried out.

[0102] Heat treatment process: The heat treatment temperature is controlled at 550℃ and the holding time is controlled at 1.5h.

[0103] Example 4

[0104] The following steps were carried out in sequence to produce corrosion-resistant steel bars with the chemical composition described in Table 1.

[0105] Hot metal desulfurization: Hot metal temperature is 1347℃, Si content is 0.54%, S content is 0.04%, S content after desulfurization is 0.002%, and slag skimming rate is 95%.

[0106] Converter smelting process: first dephosphorization, sampling and testing, after the P content is 0.025%, the phosphorus-rich slag is poured out; then decarburization is carried out, sampling and testing are again carried out, the C content is 0.55%, the P content is 0.024%, and the slag is poured out a second time; the C content is controlled at 0.06% and the P content is 0.020% at the end of smelting, and the slag is poured out again at the end; the tapping temperature is controlled at 1720℃; after 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying, among which the C content in the low-carbon ferrochromium alloy is 0.02%.

[0107] LF refining process: argon is blown from the bottom throughout the entire process, with an argon flow rate of 135L / min. During the power-on temperature rise process, low-carbon ferrochrome is added in small amounts multiple times, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1605℃, the C content is 0.18%, and the Cr content is 10.0%.

[0108] RH refining process: oxygen blowing starts 3 minutes after vacuuming, with a total oxygen blowing volume of 378 Nm 3 , sampling and testing, when the C content is 0.02%, the oxygen blowing is stopped, and then low-carbon ferrochromium alloy is added, followed by net circulation treatment, the vacuum degree is less than 2mbar for 10 minutes, and the C content is controlled at 0.006% at the end of the net circulation. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1615℃.

[0109] Continuous casting process: control the tundish temperature to 1558°C and the casting speed to 3.0m / min.

[0110] Ingot heating process: heat the ingot to 1229℃ and keep it warm for 95 minutes.

[0111] Rolling process: The casting is controlled to start rolling at 1135℃ and the casting is rolled into steel bars.

[0112] Cooling process: After rolling is completed, the steel bars are placed on the cooling bed at 820℃. After being placed on the cooling bed, air cooling is carried out when the steel bar temperature is 850~800℃, the cooling bed forward speed is controlled at 1.5m / min, and the steel bar cooling rate is 1.6℃ / min; when the steel bar temperature is 800~750℃, the cooling bed forward speed is controlled at 1.5m / min, the fan under the cooling bed is turned on, and the air volume is 65% of the fan's maximum air volume, and the steel bar cooling rate is 1.6℃ / min; when the steel bar temperature is 750~700℃, the cooling bed forward speed is controlled at 0.9m / min, the fan under the cooling bed is turned on, and the air volume is 85% of the fan's maximum air volume, the steel bar cooling rate is 1.8℃ / min, and then air cooling is carried out.

[0113] Heat treatment process: The heat treatment temperature is controlled at 570°C and the holding time is controlled at 1.4h.

[0114] Example 5

[0115] The following steps were carried out in sequence to produce corrosion-resistant steel bars with the chemical composition described in Table 1.

[0116] Hot metal desulfurization: The hot metal temperature is 1348℃, the Si content is 0.53%, the S content is 0.03%, the S content after desulfurization is 0.001%, and the slag skimming rate is 96%.

[0117] Converter smelting process: first dephosphorization, sampling and testing, after the P content reaches 0.030%, the phosphorus-rich slag is poured out; then decarburization is carried out, sampling and testing are carried out again, the C content is 0.41%, the P content is 0.025%, and the slag is poured out a second time; the C content is controlled at 0.06% and the P content is 0.02% at the end of smelting, and the slag is poured out again at the end; the tapping temperature is controlled at 1707℃; after 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying, among which the C content of the low-carbon ferrochromium alloy is 0.02%.

[0118] LF refining process: argon is blown from the bottom throughout the entire process, with an argon flow rate of 125L / min. During the power-on temperature rise process, low-carbon ferrochrome is added in small amounts multiple times, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1602°C, the C content is 0.14%, and the Cr content is 10.3%.

[0119] RH refining process: oxygen blowing starts 3 minutes after vacuuming, with a total oxygen blowing volume of 378 Nm 3 , sampling and testing, when the C content is 0.02%, the oxygen blowing is stopped, and then low-carbon ferrochromium alloy is added, followed by net circulation treatment, the vacuum degree is less than 2mbar for 8 minutes, and the C content is controlled at 0.005% at the end of the net circulation. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1608℃.

[0120] Continuous casting process: control the tundish temperature to 1550℃ and the casting speed to 2.8m / min.

[0121] Ingot heating process: Heat the ingot to 1230℃ and keep it warm for 110 minutes.

[0122] Rolling process: The casting temperature is controlled to start rolling at 1141℃, and the casting is rolled into steel bars.

[0123] Cooling process: After rolling is completed, the steel bar is placed on the cooling bed at 839℃. After being placed on the cooling bed, air cooling is carried out when the steel bar temperature is 850~800℃, the cooling bed forward speed is controlled at 1.5m / min, and the steel bar cooling rate is 1.2℃ / min; when the steel bar temperature is 800~750℃, the cooling bed forward speed is controlled at 1.3m / min, the fan under the cooling bed is turned on, and the air volume is 65% of the fan's maximum air volume, and the steel bar cooling rate is 1.5℃ / min; when the steel bar temperature is 750~700℃, the cooling bed forward speed is controlled at 0.9m / min, the fan under the cooling bed is turned on, and the air volume is 85% of the fan's maximum air volume, the steel bar cooling rate is 1.7℃ / min, and then air cooling is carried out.

[0124] Heat treatment process: The heat treatment temperature is controlled at 480°C and the holding time is controlled at 1.2h.

[0125] Example 6

[0126] The following steps were carried out in sequence to produce corrosion-resistant steel bars with the chemical composition described in Table 1.

[0127] Hot metal desulfurization: Hot metal temperature is 1351℃, Si content is 0.52%, S content is 0.02%, after desulfurization, S content is 0.002%, slag skimming rate is 95%.

[0128] Converter smelting process: first dephosphorization, sampling and testing, after the P content is 0.031%, the phosphorus-rich slag is poured out; then decarburization is carried out, sampling and testing again, the C content is 0.043%, the P content is 0.020%, and the slag is poured out a second time; the C content is controlled at 0.06% and the P content is 0.018% at the end of smelting, and the slag is poured out again at the end; the steel tapping temperature is controlled at 1718℃; after 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying, among which the C content of the low-carbon ferrochromium alloy is 0.03%.

[0129] LF refining process: argon is blown from the bottom throughout the entire process, with an argon flow rate of 109L / min. Low-carbon ferrochrome is added in small amounts multiple times during the power-on heating process, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1600℃, with a C content of 0.13% and a Cr content of 9.9%.

[0130] RH refining process: After 3 minutes of vacuuming, oxygen blowing begins, with a total oxygen blowing volume of 361 Nm 3 , sampling and testing, when the C content is 0.02%, the oxygen blowing is stopped, and then low-carbon ferrochromium alloy is added, followed by net circulation treatment, the vacuum degree is less than 2mbar for 5 minutes, and the C content is controlled at 0.004% at the end of the net circulation. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1620℃.

[0131] Continuous casting process: control the tundish temperature to 1555℃ and the casting speed to 2.8m / min.

[0132] Ingot heating process: heat the ingot to 1248℃ and keep it warm for 108min.

[0133] Rolling process: The casting temperature is controlled to start rolling at 1120℃, and the casting is rolled into steel bars.

[0134] Cooling process: After rolling is completed, the steel bar is placed on the cooling bed at 846℃. After being placed on the cooling bed, air cooling is carried out when the steel bar temperature is 850~800℃, the cooling bed forward speed is controlled at 1.4m / min, and the steel bar cooling rate is 1.3℃ / min; when the steel bar temperature is 800~750℃, the cooling bed forward speed is controlled at 1.5m / min, the fan under the cooling bed is turned on, and the air volume is 70% of the fan's maximum air volume, and the steel bar cooling rate is 1.6℃ / min; when the steel bar temperature is 750~700℃, the cooling bed forward speed is controlled at 1.0m / min, the fan under the cooling bed is turned on, and the air volume is 90% of the fan's maximum air volume, the steel bar cooling rate is 1.8℃ / min, and then air cooling is carried out.

[0135] Heat treatment process: The heat treatment temperature is controlled at 520°C and the holding time is controlled at 1.3h.

[0136] The corrosion-resistant steel bars obtained in Examples 1 to 6 were polished and etched with 4% nitric acid to obtain metallographic specimens. The specimens were photographed using a ZEISS optical microscope and analyzed using Miaps-M software to obtain the microstructure and dimensions of the corrosion-resistant steel bars as shown in Table 2. The steel bars were subjected to tensile testing in accordance with the room temperature test method specified in GB T 228.1-2021, Metallic Materials - Tensile Tests, Part 1, to obtain the mechanical properties of the corrosion-resistant steel bars as shown in Table 2.

[0137] The corrosion performance evaluation is carried out in accordance with GB / T 10125-2021 artificial atmosphere corrosion test-salt spray corrosion test. The solution is 50g / L±5g / L NaCl, the pH is 6.5~7.2, the solution temperature is 35℃±2℃, and the test is continuous to obtain the average weight loss corrosion rate after 168h.

[0138] The test was carried out in accordance with GB / T 24196-2009 "Guide for Constant Potentiodynamic and Potentiodynamic Polarization Measurements of Metals and Alloys by Electrochemical Test Methods". A three-electrode system was used, with a saturated calomel electrode as the reference electrode, a Pt sheet as the auxiliary electrode, and a 3.5% NaCl solution as the test solution. The polarization curve test scan range was -300~600mV relative to the sample's self-corrosion potential, with a scan frequency of 1mV / s. The electrochemical impedance spectroscopy test scan frequency range was 10 5 ~10 -2 Hz, the AC excitation signal amplitude is ±5mV, and the self-corrosion current density is obtained.

[0139] Table 2 Organization and properties of Examples 1 to 6

[0140]

[0141] In addition, samples of the steel bars from Examples 1 to 6 were sampled and subjected to welding tests using manual welding rods. The welded specimens were then subjected to tensile tests according to GB / T 228.1-2021, Metallic Materials - Tensile Tests, Part 1, Room-Temperature Test Methods. The fracture points of the welded specimens during the tensile tests occurred in the base material, not at the weld points, demonstrating the excellent weldability of the resulting steel bars. The results are shown in Table 3.

[0142] Table 3 Welding tensile test results

[0143]

[0144] It should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0145] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of this application. They are not intended to limit the scope of protection of this application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of this application should be included in the scope of protection of this application.

Claims

1. A corrosion-resistant steel bar, characterized in that: The weight percentage includes: 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 are iron and unavoidable impurities. The following also meets the requirements: corrosion resistance coefficient K = [Ni] + 0.25 [Cr] + 0.5 [Mo] + 5 [Nb] - 2.5 [C] is 3-3.7%, and 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], [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; The corrosion-resistant steel bar has a two-phase structure of ferrite and bainite, with the volume proportion of ferrite being 17-22%, the volume proportion of bainite being 78-83%, and the size of ferrite being 5.9-7.7 μm.

2. The corrosion-resistant steel bar according to claim 1, characterized in that: The yield strength of corrosion-resistant steel bars shall be ≥700MPa, the tensile strength shall be ≥950MPa, and the total elongation at maximum force shall be ≥7.5%.

3. The corrosion-resistant steel bar according to claim 1, characterized in that: In the salt spray corrosion test, the average weight loss corrosion rate of the corrosion-resistant steel bars is 0.01~0.04g / (m 2 h); in simulated concrete pore fluid with a chloride ion concentration of ≥3 mol / L, the self-corrosion current density of the steel bar is ≤0.12 μA / cm 2 .

4. A method for producing corrosion-resistant steel bars according to claim 1, characterized in that: It includes the following steps: smelting, refining, continuous casting, heating of ingots, rolling, cooling and heat treatment, among which: In the billet heating process, the billet is heated to 1200~1250℃ and kept at this temperature for 80~110min; During the rolling process, the casting is controlled to start rolling at 1120~1150℃ and the casting is rolled into steel bars; In the cooling process, after rolling is completed, the steel bars are placed on the cooling bed when the temperature is 820~850℃. After being placed on the cooling bed, air cooling is carried out when the temperature of the steel bars is 850~800℃, and the forward speed of the cooling bed is controlled to be 1.3~1.5m / min, and the cooling rate of the steel bars is controlled to be 1.2~1.6℃ / min; when the temperature of the steel bars is 800~750℃, the forward speed of the cooling bed is controlled to be 1.3~1.5m / min, the fan is turned on, and the cooling rate of the steel bars is controlled to be 1.5~1.7℃ / min; when the temperature of the steel bars is 750~700℃, the forward speed of the cooling bed is controlled to be 0.8~1.0m / min, the fan is turned on, and the cooling rate of the steel bars is controlled to be 1.7~1.9℃ / min, followed by air cooling.

5. The method for producing corrosion-resistant steel bars according to claim 4, characterized in that: In the heat treatment process, when 4.4≤T≤4.6, the heat treatment temperature is controlled at 480~510℃, and the holding time is controlled at 0.9~1.3h; when the strength-plastic coefficient is 4.6<T≤4.9, the heat treatment temperature is controlled at 520~550℃, and the holding time is controlled at 1.1~1.5h; when the strength-plastic coefficient is 4.9<T≤5.3, the heat treatment temperature is controlled at 560~590℃, and the holding time is controlled at 1.4~1.8h.

6. The method for producing corrosion-resistant steel bars according to claim 4, characterized in that: In the converter smelting process, dephosphorization is first carried out. When the P content is ≤0.035%, the phosphorus-rich slag is poured out. Then decarburization is carried out to adjust the C content to 0.35-0.55% and the P content to ≤0.025%, and the slag is poured out twice. The C content is controlled at 0.04-0.07% and the P content is ≤0.020% at the end of smelting, and the slag is poured out again at the end. The tapping temperature is controlled at 1670-1720℃. After 1 / 4 of the steel is tapped, low-carbon ferrochromium alloy, ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, and ferroniobium alloy are added in sequence for preliminary alloying. The C content in the low-carbon ferrochromium alloy is ≤0.03%.

7. The method for producing corrosion-resistant steel bars according to claim 6, characterized in that: The refining process includes LF refining. During the LF refining power-on temperature rise process, low-carbon ferrochrome is added in small amounts multiple times, and metallic Sb is added to complete Sb alloying. The LF refining tapping temperature is controlled at 1590~1620℃, the C content is ≤0.2%, and the Cr content is 9.8~10.5%.

8. The method for producing corrosion-resistant steel bars according to claim 7, characterized in that: The refining process also includes RH refining after LF refining. After RH refining, vacuum is drawn for 3 to 4 minutes and then oxygen blowing is started. The total amount of oxygen blowing is 350 to 400 Nm 3 When the C content is ≤0.03%, oxygen blowing is stopped, and then low-carbon ferrochromium alloying is added, followed by net circulation treatment. The vacuum degree is less than 2mbar for ≥5min. At the end of the net circulation, the C content is controlled to be ≤0.008%. Low-carbon ferrochromium alloy, ferrovanadium alloy, and ferrosilicon nitride are used to fine-tune the alloy composition, and the steelmaking temperature is controlled at 1590~1620℃.

9. The method for producing corrosion-resistant steel bars according to claim 8, characterized in that: During the continuous casting process, the tundish temperature is controlled at 1548~1568℃ and the casting speed is controlled at 2.6~3.1m / min.

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