A 500mpa grade high-strength anti-seismic reinforcing steel bar for railway with a nominal diameter of 18-25mm and a preparation method thereof

Abstract

The application discloses a kind of 500MPa grade high-strength anti-seismic reinforcing steel for railway with nominal diameter 18-25mm and a preparation method thereof.The anti-seismic reinforcing steel has the following chemical components by weight percentage: C 0.22-0.24wt%, Si 0.45-0.60wt%, Mn 0.70-0.85wt%, Cr 0.70-0.80wt%, Cu 0.17-0.21wt%, V 0.060-0.070wt%, Nb 0.010-0.013wt%, S≤0.040wt%, P≤0.040wt%, O≤0.0030wt%, N 0.0160-0.0185wt%, and the rest is Fe and unavoidable impurities.The anti-seismic reinforcing steel has yield strength of 530-560MPa, tensile strength of 695-750MPa, ratio of strength to yield ≥1.31, elongation after fracture ≥23%, and maximum force total elongation ≥10.5%.The application has low production cost, strong process applicability and controllability, and the produced reinforcing steel has excellent and stable process mechanical properties, fine and uniform microstructure, good plasticity and toughness, excellent corrosion resistance and anti-seismic performance, etc., and has significant economic and social benefits.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel smelting, and particularly relates to a 500MPa-grade high-strength anti-seismic steel bar for railways with a nominal diameter of 18-25mm and a preparation method thereof. BACKGROUND

[0002] Anti-seismic steel bars are the main reinforcing materials for highway, railway and other transportation infrastructure structures, and bear stress and strain such as tensile and compressive stress and strain in the structure. With the continuous development of high anti-seismicity, high strength and corrosion resistance of China's high-speed railway infrastructure construction, the development of high-strength and high-toughness anti-seismic steel bars for railways with a strength grade of 500MPa and above has become an important task for the steel industry to improve its technical level.

[0003] At present, there are reports on the production technology of 400MPa-grade high-strength anti-seismic steel bars for railways in China, but there are few reports on the preparation process of 500MPa and above strength grade anti-seismic steel bars for railways with a nominal diameter of 18-25mm. The preparation of 400MPa-grade high-strength anti-seismic steel bars for railways mainly uses vanadium-nitrogen micro-alloying process, and the V content in the steel is mostly controlled at 0.020-0.040wt%, and the 400MPa-grade straight anti-seismic steel bars required by GB / T 37439-2019 for high-speed railways are obtained by controlling the rolling temperature and rolling passes. When producing 400MPa-grade high-strength anti-seismic steel bars for railways using vanadium micro-alloying, the addition of a certain amount of valuable vanadium alloy in the steel results in high alloy cost, which is not conducive to the improvement of product competitiveness.

[0004] The present application aims to provide a 500MPa-grade high-strength anti-seismic steel bar for railways with a nominal diameter of 18-25mm. SUMMARY

[0005] The first object of the present application is to provide a 500MPa-grade high-strength anti-seismic steel bar for railways with a nominal diameter of 18-25mm, and the second object of the present application is to provide a preparation method of the anti-seismic steel bar.

[0006] The first object of the present application is achieved by a 500MPa-grade high-strength anti-seismic steel bar for railways with a nominal diameter of 18-25mm, which has the following chemical composition by weight percentage: C 0.22-0.24wt%, Si 0.45-0.60wt%, Mn 0.70-0.85wt%, Cr 0.70-0.80wt%, Cu 0.17-0.21wt%, V 0.060-0.070wt%, Nb 0.010-0.013wt%, S≤0.040wt%, P≤0.040wt%, O≤0.0030wt%, N 0.0160-0.0185wt%, and the rest is Fe and unavoidable impurities.

[0007] The second object of the present application is achieved by the method for preparing 18-25 mm 500 MPa grade high-strength anti-seismic reinforcing steel for railway, which is achieved according to the following steps:

[0008] A, molten steel smelting: according to 260-270 kg / t 钢 , 1.3-1.7 kg / t 钢 of cold material charging ratio, adding scrap steel and copper plate in the LD converter respectively; then according to 785-795 kg / t 钢 of molten iron charging ratio, adding molten iron with a temperature of ≥1310℃ in the LD converter, carrying out conventional top and bottom combined blowing, and the chemical composition of the molten iron is: C 4.1-4.3wt%, Si 0.15-0.30wt%, Mn 0.20-0.45wt%, P 0.070-0.080wt%, S≤0.030wt%, and the rest is Fe and inevitable impurities; then adding lime and light-burned dolomite slag according to the amount of 15-20 kg / t 钢 , 15-18 kg / t 钢 , controlling the end point carbon content ≥0.07wt%, and the tapping temperature ≤1600℃; before tapping, adding active lime to the bottom of the ladle according to the amount of 1.5 kg / t 钢 for slag washing;

[0009] B, deoxidation and alloying: after the smelting of the molten steel is completed, when the amount of molten steel in the ladle is greater than 1 / 4, according to the deoxidation and alloying sequence of silicon-calcium-barium→silicon-iron→silicon-manganese alloy→high-carbon chromium iron→nitrogen-rich alloy→niobium-phosphorus iron alloy, silicon-calcium-barium, silicon-iron, silicon-manganese alloy, high-carbon chromium iron, silicon-nitrogen alloy and high-vanadium-nitrogen alloy are added to the ladle according to the amount of 2 kg / t 钢 , 3.2-5.4 kg / t 钢 , 9.7-12.1 kg / t 钢 , 12.6-14.6 kg / t 钢 , 0.9-1.0 kg / t 钢 , 0.25-0.30 kg / t 钢 , respectively, and the above alloys are added when the amount of molten steel in the ladle reaches 4 / 5;

[0010] C, molten steel argon station treatment: the molten steel of step B is lifted to the argon station treatment station, and the alloy is added through the alloy slot according to 10.0-11.0 kg / t 钢vanadium-containing pig iron with a surface temperature ≥ 350℃ after roasting, and nitrogen gas with a flow rate of 25-30 NL / min is used to treat the molten steel by blowing nitrogen for 3 minutes after the vanadium-containing pig iron is added; the vanadium-containing pig iron has the following mass ratio components: C 3.5wt%, Si 0.45wt%, Mn 1.85wt%, V 5.0wt%, P 1.02wt%, S 0.065wt%, and the rest is Fe and unavoidable impurities;

[0011] D. LF furnace refining of molten steel: the molten steel of step C is hoisted to the LF furnace for refining, and after the refining is completed, the molten steel is treated by soft blowing nitrogen at a small flow rate of 20-25 NL / min for 2 min, and then a covering agent is added to the molten steel in an amount of 1.0 kg / t 钢 , and then the molten steel is hoisted to the casting station;

[0012] E. Casting of molten steel: under the conditions that the temperature of the tundish is 1525-1535℃, the withdrawal speed is 3.1-3.3 m / min, the cooling water flow rate of the crystallizer is 135-145 m 3 / h, and the specific water quantity of the secondary cooling is 1.6-1.8 L / kg, the molten steel is cast into a billet with a cross section of 165 mm x 165 mm; the straightening temperature of the cast billet is controlled to be 1010-1030℃;

[0013] F. Heating of billet: the billet of step E is sent to a heating furnace with a furnace temperature of 1110-1150℃ for heating for 70 minutes, and then the billet is pushed to a full continuous bar mill for rolling;

[0014] G. Controlled rolling and controlled cooling of billet: the billet of step F is rolled by a rough rolling mill at a rolling speed of 0.4-0.8 m / s for 6 passes, and then rolled by a medium rolling mill at a rolling speed of 1.2-2.0 m / s for 4 passes; and then rolled by a pre-precision rolling mill at a rolling speed of 6.0-8.0 m / s for 3-6 passes; before entering the precision rolling, the rolling piece is controlled to cool by a water cooling device with a length of 10 m, and the cooling water quantity is 60-80 m 3 / h; the temperature of the rolling piece entering the first group of precision rolling is controlled to be 880-900℃; the rolling piece is rolled by the first group of precision rolling mill at a rolling speed of 9.0-10.0 m / s for 1-2 passes; before entering the second group of precision rolling mill, the rolling piece is controlled to cool by a water cooling device with a length of 8 m, and the cooling water quantity is 80-100 m 3 / h; the temperature of the rolling piece entering the second group of precision rolling is controlled to be 830-850℃; and then the rolling piece is rolled by the second group of precision rolling mill at a rolling speed of 11.0-13.0 m / s for 2 passes; after the precision rolling, the rolling piece is controlled to cool by a water cooling device with a length of 5 m, and the cooling water quantity is 40-50 m 3 / h; the temperature of the reinforcing steel on the cooling bed is controlled at 890-920 DEG C after controlled cooling, and then the reinforcing steel is naturally air-cooled to room temperature on the cooling bed to obtain the 18-25 mm nominal diameter 500 MPa grade high-strength anti-seismic reinforcing steel for railway.

[0015] The present application adds a certain amount of vanadium-containing pig iron to the molten steel at the argon station after the molten steel is tapped, to replace the expensive vanadium alloy in full amount, to increase the V content of the molten steel, and to greatly reduce the micro-alloy cost; the silicon-nitrogen alloy is added in the process of steelmaking deoxidization and alloying, and the molten steel is treated by nitrogen blowing through the LF furnace refining, to significantly increase the nitrogen content in the molten steel, to promote the transfer of V and Nb from the solid solution state to the carbon nitride precipitate phase in the rolling process, to form and precipitate a large amount of fine dispersed V(C,N) and Nb(C,N) precipitate phase, to significantly improve the precipitation strengthening effect of the steel; a certain amount of chromium and copper is added to the steel, to improve the passivation corrosion resistance of the steel, to make the corrosion rate only 1 / 3 of the 400 MPa grade reinforcing steel for railway, and to significantly improve the hardenability and secondary hardening effect of the steel, to increase the pearlite content, to promote the improvement of the tensile strength of the steel, and to further promote the improvement of the anti-seismic performance of the steel; a small amount of niobium is added to the steel to generate a small amount of granular bainite, to optimize the microstructure ratio of the steel, to promote the optimal matching of the tensile strength and yield strength of the steel, and to improve the anti-seismic performance of the steel; the rolling steel is controlled at a higher opening rolling temperature, to promote the full solid solution of the V and Nb micro-alloy elements; the rolling piece is controlled at a lower entry finish rolling temperature by using a longer water cooling device after pre-finish rolling; the rolling piece is rolled by using two groups of finish rolling mills, and the finish rolling temperature is controlled at a lower level by using a water cooling device between the first group and the second group of finish rolling mills; the water cooling device is used for controlled cooling after finish rolling; by using the multiple graded limited controlled cooling process of pre-finish rolling controlled cooling, finish rolling mill group controlled cooling low temperature rolling, and post-finish rolling controlled cooling, the original austenite grains are significantly refined, the formation and precipitation of a large amount of fine dispersed V(C,N) and VN precipitate phase are promoted, the nucleation position and nucleation rate of ferrite grains are increased, the ferrite grains are refined, the grain size is up to 11.0 level or above, the fine grain strengthening effect is significant, the strength of the steel is greatly improved, and the plasticity and toughness of the steel are improved.

[0016] The process of the present application fully plays the multiple reinforcement effects of precipitation strengthening and fine grain strengthening by the integrated innovation of chemical composition design, converter smelting, deoxidization and alloying, argon station treatment, continuous casting, rolling heating system, rolling temperature and controlled cooling process, the process has low production cost, strong process applicability and control property, the produced 18-25 mm nominal diameter 500 MPa grade anti-seismic reinforcing steel for railway has excellent and stable process mechanical properties, fine and uniform microstructure, good plasticity and toughness, excellent corrosion resistance and anti-seismic performance, and the like, and has significant economic and social benefits. DETAILED DESCRIPTION

[0017] The application will be further described in detail in connection with the following examples, but the application is not limited in any way by the examples, and any transformation or improvement based on the teaching of the application falls within the protection scope of the application.

[0018] The application provides a 500MPa-grade high-strength anti-seismic steel bar for a railway with a nominal diameter of 18-25mm, the anti-seismic steel bar has the following chemical components in percentage by weight: C 0.22-0.24wt%, Si 0.45-0.60wt%, Mn 0.70-0.85wt%, Cr 0.70-0.80wt%, Cu 0.17-0.21wt%, V 0.060-0.070wt%, Nb 0.010-0.013wt%, S≤0.040wt%, P≤0.040wt%, O≤0.0030wt%, N 0.0160-0.0185wt%, and the rest is Fe and inevitable impurities; the process mechanical properties, microstructure, Vickers hardness difference and corrosion resistance of the anti-seismic steel bar are shown in Table 1 and Table 2.

[0019] Table 1 Process mechanical properties and corrosion resistance of the 500MPa-grade high-strength anti-seismic steel bar for a railway with a nominal diameter of 18-25mm produced by the application

[0020]

[0021] Table 2 Metallographic structure and Vickers hardness of the 500MPa-grade high-strength anti-seismic steel bar for a railway with a nominal diameter of 18-25mm produced by the application

[0022]

[0023] The application further provides a preparation method of the 500MPa-grade high-strength anti-seismic steel bar for a railway with a nominal diameter of 18-25mm, and the method is realized according to the following steps:

[0024] A, smelting of molten steel: according to the proportion of 260-270kg / t 钢 , 1.3-1.7kg / t 钢 of cold charge, waste steel and copper plate are added into the LD converter; then according to the proportion of 785-795kg / t 钢 of hot metal charge, hot metal with a temperature of ≥1310℃ is added into the LD converter to perform conventional top and bottom combined blowing, and the chemical components of the hot metal are as follows: C 4.1-4.3wt%, Si 0.15-0.30wt%, Mn 0.20-0.45wt%, P 0.070-0.080wt%, S≤0.030wt%, and the rest is Fe and inevitable impurities; then according to the proportion of 15-20kg / t 钢 , 15-18kg / t 钢lime, light-burned dolomite, and the end-point carbon content is controlled to be ≥0.07wt%, and the tapping temperature is ≤1600℃; before tapping, 1.5kg / t 钢 of active lime is added to the bottom of the ladle for slag washing;

[0025] B, deoxidation and alloying: after the smelting is completed, the molten steel is tapped, and when the amount of molten steel in the ladle is greater than 1 / 4, silicon-calcium-barium, silicon-iron, silicon-manganese alloy, high-carbon chromium-iron, nitrogen-rich alloy, and niobium-phosphorus-iron alloy are added to the ladle in the order of deoxidation and alloying, in amounts of 2kg / t 钢 , 3.2-5.4kg / t 钢 , 9.7-12.1kg / t 钢 , 12.6-14.6kg / t 钢 , 0.9-1.0kg / t 钢 , 0.25-0.30kg / t 钢 , respectively, and the above alloys are added to the ladle when the amount of molten steel in the ladle reaches 4 / 5;

[0026] C, argon station treatment of molten steel: the molten steel of step B is lifted to the argon station treatment station, and roasted vanadium-containing pig iron with a surface temperature ≥350℃ is added through the alloy feeding slot in an amount of 10.0-11.0kg / t 钢 , and after the vanadium-containing pig iron is added, nitrogen gas with a flow rate of 25-30NL / min is used to treat the molten steel by blowing nitrogen for 3 minutes; the vanadium-containing pig iron has the following mass ratio composition: C 3.5wt%, Si 0.45wt%, Mn 1.85wt%, V 5.0wt%, P 1.02wt%, S 0.065wt%, and the rest is Fe and unavoidable impurities;

[0027] D, LF furnace refining of molten steel: the molten steel of step C is lifted to the LF furnace for refining, and after the refining is completed, the molten steel is treated by soft blowing nitrogen at a small flow rate of 20-25NL / min for 2min, and then 1.0kg / t 钢 of covering agent is added to the molten steel, and then the molten steel is lifted to the casting station;

[0028] E, casting of molten steel: under the conditions of a tundish temperature of 1525-1535℃, a withdrawal speed of 3.1-3.3m / min, a crystallizer cooling water flow rate of 135-145m 3 / h, and a secondary cooling water amount of 1.6-1.8L / kg, the molten steel is cast into a billet with a cross-section of 165mm x 165mm; the casting billet is straightened at a straightening temperature of 1010-1030℃;

[0029] F, billet heating: the billet of step E is sent into a heating furnace with a furnace temperature of 1110-1150 DEG C for 70 minutes, and the billet temperature is 1040-1060 DEG C, and then pushed to a full continuous bar mill for rolling;

[0030] G, billet controlled rolling and controlled cooling: the billet of step F is rolled by a rough rolling mill group under the rolling condition of a speed of 0.4-0.8 m / s for 6 passes, and then rolled by a medium rolling mill group under the rolling condition of a speed of 1.2-2.0 m / s for 4 passes; and then rolled by a pre-precision rolling mill group under the rolling condition of a speed of 6.0-8.0 m / s for 3-6 passes; the rolled piece is cooled by a water cooling device with a length of 10 m before entering the precision rolling mill group for controlled cooling, the cooling water flow is 60-80 m 3 / h, the temperature of the rolled piece entering the precision rolling mill group is controlled to be 880-900 DEG C; the rolled piece is rolled by the precision rolling mill group under the rolling condition of a speed of 9.0-10.0 m / s for 1-2 passes; the rolled piece is cooled by a water cooling device with a length of 8 m before entering the second precision rolling mill group for controlled cooling, the cooling water flow is 80-100 m 3 / h, the temperature of the rolled piece entering the second precision rolling mill group is controlled to be 830-850 DEG C; and then the rolled piece is rolled by the second precision rolling mill group under the rolling condition of a speed of 11.0-13.0 m / s for 2 passes; the rolled piece is cooled by a water cooling device with a length of 5 m after the precision rolling for controlled cooling, the cooling water flow is 40-50 m 3 / h; the temperature of the rebar on the cooling bed after controlled cooling is controlled to be 890-920 DEG C, and then the rebar is naturally air-cooled to room temperature on the cooling bed to obtain the 18-25 mm nominal diameter 500 MPa grade high-strength anti-seismic rebar for railway.

[0031] In step A, the chemical composition of the scrap steel is: C 0.19-0.25wt%, Si 0.32-0.55wt%, Mn 1.30-1.52wt%, P 0.024-0.045wt%, S 0.023-0.045wt%, and the rest is Fe and inevitable impurities; the chemical composition of the copper plate is: Cu 99.3wt%, P 0.035wt%, S 0.041wt%, and the rest is inevitable impurities.

[0032] In step A, the molten steel tapping process adopts a full-range bottom blowing nitrogen process, and the nitrogen flow is controlled to be 20-25 NL / min.

[0033] In Step B, the chemical composition of the calcium barium silicide is: Si 52.5wt%, Ca 9.85wt%, Ba 12.15wt%, Al 2.45wt%, and the rest is Fe and inevitable impurities; the chemical composition of the ferrosilicon is: Si 73.5wt%, and the rest is Fe and inevitable impurities; the chemical composition of the ferrosilicon-manganese alloy is: Mn 65.2wt%, Si 17.9wt%, C 1.1wt%, and the rest is Fe and inevitable impurities; the chemical composition of the high-carbon ferrochrome is: Cr 54.2wt%, C 7.4wt%, P 0.072wt%, S 0.062wt%, and the rest is Fe and inevitable impurities; the chemical composition of the nitrogen-rich alloy is: Si 57.4wt%, N 40.3wt%, C 1.75wt%, P 0.075wt%, S 0.038wt%, and the rest is Fe and inevitable impurities; the chemical composition of the niobium-phosphorus ferroalloy is: Nb 44.2wt%, Si 3.5wt%, C 1.75wt%, P 1.65wt%, S 0.045wt%, and the rest is Fe and inevitable impurities.

[0034] In Step D, during the refining process, nitrogen gas with a flow rate of 15-20 NL / min is used to treat the molten steel, and then the electrode is lowered with gear 6-8 for slagging; after 3 minutes of power-on slagging, the electrode is lifted to observe the slag in the furnace; if the slag sample is too thin and the color is too black, add 4.0-5.0 kg / t of lime 钢 Adjust the slag, otherwise add 1.0-2.0 kg / t of premelted refining slag 钢 Adjust; then measure the temperature and take samples, and according to the steel sample and temperature test results, add alloys to adjust the composition and temperature of the molten steel, and lower the electrode to heat up to ensure that the composition and temperature are qualified.

[0035] In Step E, R9m straight arc continuous straightening 5 machine 5 flow billet caster is used for casting.

[0036] Example 1

[0037] A, molten steel smelting: according to 260 kg / t 钢 , 1.3 kg / t 钢 of cold charge into the ratio of cold charge into the ratio, add the following mass ratio of scrap steel (chemical composition: C 0.19wt%, Si 0.32wt%, Mn 1.30wt%, P 0.024wt%, S 0.023wt%, and the rest is Fe and inevitable impurities) and copper plate (chemical composition: Cu 99.3wt%, P 0.035wt%, S 0.041wt%, and the rest is inevitable impurities) in the LD converter; then according to 785 kg / t 钢The molten iron is charged into the LD converter with the following temperature and mass ratio: molten iron temperature 1310°C, molten iron composition C 4.1wt%, Si 0.15wt%, Mn 0.20wt%, P 0.070wt%, S 0.018wt%, and the rest Fe and inevitable impurities; after the scrap steel, copper plate and molten iron are charged into the LD converter, the conventional top and bottom combined blowing is carried out, the conventional lime and light-burned dolomite are added, the lime addition amount is 15kg / t 钢 , the light-burned dolomite addition amount is 15kg / t 钢 , the end-point carbon content is controlled to be 0.07wt%, and the tapping temperature is 1580°C; before tapping, the active lime is added to the bottom of the ladle at an amount of 1.5kg / t 钢 , and the slag washing is carried out, the nitrogen blowing process is adopted during the whole tapping process, and the nitrogen flow rate is controlled to be 20NL / min.

[0038] B, deoxidation and alloying: the molten steel of the A step is tapped, when the molten steel amount in the ladle is greater than 1 / 4, the following deoxidation and alloying sequence is adopted: silicon calcium barium→silicon iron→silicon manganese alloy→high-carbon chromium iron→nitrogen-rich alloy→niobium phosphorus iron alloy, the following substances are sequentially added into the ladle: the silicon calcium barium with the following mass ratio is added at an amount of 2.0kg / t 钢 : Si 52.5wt%, Ca 9.85wt%, Ba 12.15wt%, Al 2.45wt%, and the rest Fe and inevitable impurities; the silicon iron with the following mass ratio is added at an amount of 3.2kg / t 钢 : Si 73.5wt%, and the rest Fe and inevitable impurities; the silicon manganese alloy with the following mass ratio is added at an amount of 9.7kg / t 钢 : Mn 65.2wt%, Si 17.9wt%, C 1.1wt%, and the rest Fe and inevitable impurities; the high-carbon chromium iron with the following mass ratio is added at an amount of 12.6

[0039] kg / t 钢 : Cr 54.2wt%, C 7.4wt%, P 0.072wt%, S 0.062wt%, and the rest Fe and inevitable impurities; the silicon-nitrogen alloy with the following mass ratio is added at an amount of 0.9kg / t 钢 : Si 57.4wt%, N 40.3wt%, C 1.75wt%, P 0.075wt%, S 0.038wt%, and the rest Fe and inevitable impurities; the niobium phosphorus iron alloy is added at an amount of 0.25

[0040] kg / t 钢, the following mass ratio of niobium phosphorus iron alloy: Nb 44.2wt%, Si 3.5wt%, C1.75wt%, P1.65wt%, S 0.045wt%, the rest is Fe and inevitable impurities; the steel ladle steel water reaches 3 / 4 when adding the above alloy; after the completion of tapping, the molten steel is hoisted to the argon station for adding vanadium-containing pig iron and nitrogen blowing refining treatment.

[0041] C, molten steel argon station treatment: the molten steel of B step is hoisted to the argon station treatment station, and 10.0kg / t 钢 of the alloy is added through the alloy slot, and the alloy is roasted with the following mass ratio: C 3.5wt%, Si 0.45wt%, Mn 1.85wt%, V 5.0wt%, P 1.02wt%, S 0.065wt%, the rest is Fe and inevitable impurities, the roasting time of vanadium-containing pig iron is 8 minutes, and the surface temperature of the pig iron after roasting is 350℃; after the vanadium-containing pig iron is added, the nitrogen gas is started, and the nitrogen gas with a flow rate of 25NL / min is used to blow nitrogen to the molten steel, and the nitrogen blowing time is 3 minutes.

[0042] D, LF furnace refining of molten steel: the molten steel of C step is hoisted to the LF furnace refining station and connected to the nitrogen gas belt, the nitrogen gas with a flow rate of 15NL / min is started to blow nitrogen to the molten steel, then the electrode is lowered to adjust the slag with gear 6-8; after 3 minutes of power-on slagging, the electrode is lifted to observe the slagging in the furnace; if the slag sample is too thin and the color is too black, add 4.0kg / t 钢 of lime to adjust the slag, otherwise add 1.0kg / t 钢 of premelted refining slag; then measure the temperature and take samples, and according to the steel sample and temperature detection results, add alloy to adjust the composition of the molten steel and lower the electrode to increase the temperature, so as to ensure that the composition and temperature are qualified; after the refining is completed, the molten steel is subjected to soft blowing of nitrogen with small flow rate, the nitrogen blowing time is 2 minutes, and the nitrogen flow rate is controlled to be 20NL / min; after the nitrogen blowing is completed, the molten steel is added with a covering agent, the adding amount is 1.0 kg / t 钢 , and then the molten steel is hoisted to the casting station.

[0043] E, molten steel casting: under the conditions that the temperature of the tundish is 1535℃, the withdrawal speed is 3.1m / min, the crystallizer cooling water flow rate is 135m 3 / h, and the secondary cooling water flow rate is 1.8L / kg, the molten steel of C step is cast into a steel billet with a cross section of 165mmx165mm by using R9m straight arc continuous straightening 5-machine 5-flow small square billet caster; the casting billet is straightened at a temperature of 1010℃ out of the straightening machine.

[0044] F, billet heating: the steel billet of E step is sent into the heating furnace with a furnace temperature of 1110℃, and heated for 75 minutes, the steel billet temperature is 1040℃, and then pushed to the full continuous bar mill for rolling.

[0045] G, controlled rolling and controlled cooling of the billet: the billet of step F is rolled by 6 passes through a rough rolling mill set at a rolling speed of 0.8 m / s; then the rolled piece is rolled by 4 passes through a medium rolling mill set at a rolling speed of 2.0 m / s; then the rolled piece is rolled by 6 passes through a pre-precision rolling mill set at a rolling speed of 8.0 m / s; then the rolled piece enters a pre-precision cooling control by a water cooling device with a length of 10 m before entering the precision rolling, with a cooling water flow of 60 m 3 / h, and the temperature of the rolled piece entering the precision rolling is controlled at 900℃; then the rolled piece is rolled by 2 passes through a precision rolling mill set at a rolling speed of 10.0 m / s; the rolled piece enters a cooling control by a water cooling device with a length of 8 m before entering the second precision rolling mill set, with a cooling water flow of 80 m 3 / h, and the temperature of the rolled piece entering the precision rolling is controlled at 900℃; then the rolled piece is rolled by 2 passes through a precision rolling mill set at a rolling speed of 10.0 m / s; the rolled piece enters a cooling control by a water cooling device with a length of 8 m before entering the second precision rolling mill set, with a cooling water flow of 80 m 3 / h; after the cooling control, the temperature of the reinforcing bar on the cooling bed is controlled at 920℃, and then the reinforcing bar is naturally air-cooled to room temperature on the cooling bed, thereby obtaining a 500MPa grade high-strength anti-seismic reinforcing bar with a nominal diameter of 18 mm for railway, having the following chemical composition by weight percentage: C 0.22wt%, Si 0.45wt%, Mn 0.70wt%, Cr 0.70wt%, Cu 0.17wt%, V 0.060wt%, Nb 0.010wt%, S 0.020wt%, P 0.020wt%, O 0.0016wt%, N 0.0160wt%, and the balance being Fe and inevitable impurities. The process mechanical properties, microstructure, Vickers hardness difference, and corrosion resistance of the anti-seismic reinforcing bar are shown in Table 3 and Table 4.

[0046] Table 3 Process mechanical properties and corrosion resistance of the 500MPa grade high-strength anti-seismic reinforcing bar with a nominal diameter of 18 mm for railway produced in Example 1

[0047]

[0048] Table 4 Metallographic microstructure and Vickers hardness of the 500MPa grade high-strength anti-seismic reinforcing bar with a nominal diameter of 18 mm for railway produced in Example 1

[0049]

[0050] Example 2

[0051] A, smelting of the molten steel: 265 kg / t 钢 , 1.5 kg / t 钢The cold charge ratio is as follows: In the LD converter, scrap steel (chemical composition: C 0.22wt%, Si 0.42wt%, Mn 1.40wt%, P 0.037wt%, S 0.033wt%, balance being Fe and unavoidable impurities) and copper plate (chemical composition: Cu 99.3wt%, P 0.035wt%, S 0.041wt%, balance being unavoidable impurities) are added in the following mass ratio; then, at 790 kg / t... 钢 The molten iron was added to the LD converter at the following temperature and mass ratio: molten iron temperature 1320℃, molten iron composition C 4.2wt%, Si 0.22wt%, Mn 0.32wt%, P 0.076wt%, S 0.021wt%, with the remainder being Fe and unavoidable impurities; after the scrap steel, copper plates, and molten iron were added to the LD converter, conventional top and bottom combined blowing was carried out, with conventional lime and lightly calcined dolomite added for slag formation, the lime addition amount being 19kg / t. 钢 The amount of lightly calcined dolomite added is 17 kg / t. 钢 The final carbon content was controlled at 0.08 wt%, and the tapping temperature was 1595℃; before tapping, 1.5 kg / t of water was added to the bottom of the ladle. 钢 The amount of quicklime added is used for slag washing, and the tapping process adopts a full bottom blowing nitrogen process with nitrogen flow rate controlled at 20NL / min.

[0052] B. Deoxidation and Alloying: After tapping the molten steel from step A, when the ladle contains more than 1 / 4 tonnes of molten steel, add the following substances to the ladle in the following deoxidation and alloying sequence: silicon-calcium-barium → ferrosilicon → silicon-manganese alloy → high-carbon ferrochrome → nitrogen-rich alloy → niobium-phosphorus ferrochrome, at a rate of 2.0 kg / t. 钢 Add the following mass ratio of silicon, calcium, and barium: Si 52.5wt%, Ca 9.85wt%, Ba 12.15wt%, Al 2.45wt%, with the remainder being Fe and unavoidable impurities; at a rate of 4.2 kg / t. 钢 Add the following mass ratio of ferrosilicon: Si 73.5wt%, the remainder being Fe and unavoidable impurities; at a rate of 10.6 kg / t. 钢 The following silicon-manganese alloy was added in the specified mass ratio: Mn 65.2 wt%, Si 17.9 wt%, C 1.1 wt%, with the remainder being Fe and unavoidable impurities; according to 13.7...

[0053] kg / t 钢 Add the following high-carbon ferrochrome in the specified mass ratio: Cr 54.2wt%, C 7.4wt%, P 0.072wt%, S 0.062wt%, with the remainder being Fe and unavoidable impurities; at a rate of 1.0 kg / t. 钢wt%, C 1.75wt%, P 0.075wt%, S 0.038wt%, the rest is Fe and inevitable impurities; the above alloy is added when the ladle steel reaches 3 / 4 of the capacity; after the steel is tapped, the molten steel is lifted to the argon station for adding vanadium-containing pig iron and nitrogen blowing refining treatment.

[0054] kg / t 钢 wt%, C 1.75wt%, P 1.65wt%, S 0.045wt%, the rest is Fe and inevitable impurities; the above alloy is added when the ladle steel reaches 3 / 4 of the capacity; after the steel is tapped, the molten steel is lifted to the argon station for adding vanadium-containing pig iron and nitrogen blowing refining treatment.

[0055] C, molten steel argon station treatment: the steel in step B is lifted to the argon station treatment station, and the alloy is added through the alloy slot at an amount of 10.7kg / t 钢 wt%, C 1.75wt%, P 1.65wt%, S 0.045wt%, the rest is Fe and inevitable impurities; the above alloy is added when the ladle steel reaches 3 / 4 of the capacity; after the steel is tapped, the molten steel is lifted to the argon station for adding vanadium-containing pig iron and nitrogen blowing refining treatment.

[0056] D, molten steel LF furnace refining: the steel in step C is lifted to the LF furnace refining station and connected to the nitrogen gas belt, the nitrogen gas is turned on and the nitrogen gas flow is 20NL / min, then the electrode is lowered and the slag is melted at gear 6-8; after 3 minutes of melting, the electrode is lifted to observe the slag in the furnace; if the slag sample is too thin and the color is too black, add 5.0kg / t 钢 lime to adjust the slag, otherwise add 2.0kg / t 钢 pre-melted refining slag for adjustment; then measure the temperature and take a sample, according to the steel sample and temperature test results, add alloy to adjust the composition of the molten steel and lower the electrode to increase the temperature, to ensure that the composition and temperature are qualified; after the refining is completed, the molten steel is softly blown with nitrogen at a small flow rate for 2 minutes, and the nitrogen flow rate is controlled at 25NL / min; after the nitrogen blowing is completed, the molten steel is added with a covering agent at an amount of 1.0kg / t 钢 , and then the molten steel is lifted to the casting station.

[0057] E, molten steel casting: the temperature of the tundish is 1530℃, the withdrawal speed is 3.2m / min, and the crystallizer cooling water flow rate is 140m 3 / h, and the R9m straight-arc continuous straightening 5-machine 5-flow small billet caster was used to cast the molten steel of the C step into a steel billet with a section of 165 mm x 165 mm under the condition that the secondary cooling water quantity was 1.7 L / kg; the temperature of the cast billet out of the straightening machine was controlled to be 1020°C.

[0058] F, billet heating: the steel billet of the E step was sent into a heating furnace with a furnace temperature of 1130°C, and was heated for 75 minutes, and the billet out of the furnace had a temperature of 1050°C, and then was pushed to the full continuous bar mill for rolling.

[0059] G, controlled rolling and controlled cooling of the billet: the steel billet of the F step was rolled by 6 passes through the rough rolling mill group under the rolling condition that the speed was 0.6 m / s; then the rolled piece was rolled by 4 passes through the intermediate rolling mill group under the rolling condition that the speed was 1.6 m / s; then the rolled piece was rolled by 5 passes through the pre-precision rolling mill group under the rolling condition that the speed was 7.0 m / s; then the rolled piece entered the front of the precision rolling and passed through a group of water cooling devices with a length of 10 m for front controlled cooling, and the cooling water quantity was 70 m 3 / h, the temperature of the rolled piece into the second group of the precision rolling was controlled to be 845°C; then the rolled piece was rolled by 2 passes through the second group of the precision rolling mill group under the rolling condition that the speed was 12.0 m / s; after the precision rolling, the rolled material passed through a group of water cooling devices with a length of 5 m for post-rolling controlled cooling, and the cooling water quantity was 50 m 3 / h, the temperature of the rolled piece into the second group of the precision rolling was controlled to be 845°C; then the rolled piece was rolled by 2 passes through the second group of the precision rolling mill group under the rolling condition that the speed was 12.0 m / s; after the precision rolling, the rolled material passed through a group of water cooling devices with a length of 5 m for post-rolling controlled cooling, and the cooling water quantity was 50 m 3 / h; after the controlled cooling, the temperature of the steel bar on the cooling bed was controlled to be 900°C, and then the steel bar was naturally air-cooled to room temperature on the cooling bed, and thus a 500 MPa grade high-strength anti-seismic steel bar for railway with a nominal diameter of 22 mm was obtained, which had the following weight percentage chemical components: C 0.23 wt%, Si 0.52 wt%, Mn 0.78 wt%, Cr 0.75 wt%, Cu 0.19 wt%, V 0.065 wt%, Nb 0.012 wt%, S 0.032 wt%, P 0.031 wt%, O 0.0024 wt%, N 0.0172 wt%, and the rest was Fe and inevitable impurities. The process mechanical properties, microstructure, Vickers hardness difference, and corrosion resistance of the anti-seismic steel bar were shown in Tables 5 and 6.

[0060] Table 5 Process mechanical properties and corrosion resistance of the 500 MPa grade high-strength anti-seismic steel bar for railway with a nominal diameter of 22 mm produced in Example 2

[0061]

[0062] Table 6 Metallographic microstructure and Vickers hardness of the high-strength anti-seismic steel bar with nominal diameter of 22 mm produced in Example 2

[0063]

[0064] Example 3

[0065] A, molten steel smelting: according to 270 kg / t 钢 , 1.7 kg / t 钢 of cold charge loading ratio, the following mass ratio of scrap steel (chemical composition: C 0.25wt%, Si 0.55wt%, Mn 1.52wt%, P 0.045wt%, S 0.045wt%, the rest is Fe and inevitable impurities) and copper plate (chemical composition: Cu 99.3wt%, P 0.035wt%, S 0.041wt%, the rest is inevitable impurities) is added in the LD converter; then according to 795 kg / t 钢 of hot metal loading ratio, the following temperature and mass ratio of hot metal is added in the LD converter: hot metal temperature 1330℃, hot metal composition C 4.3wt%, Si 0.30wt%, Mn 0.45wt%, P 0.080wt%, S 0.030wt%, the rest is Fe and inevitable impurities; after the scrap steel, copper plate and hot metal are charged into the LD converter, the conventional top and bottom combined blowing is carried out, the conventional lime and light-burned dolomite are added for slagging, the lime addition amount is 20 kg / t 钢 , the light-burned dolomite addition amount is 18 kg / t 钢 , the end point carbon content is controlled to be 0.10wt%, and the tapping temperature is 1600℃; before tapping, active lime is added to the bottom of the ladle at an amount of 1.5 kg / t 钢 for slag washing, and the full-process bottom blowing nitrogen process is adopted during the tapping process, and the nitrogen flow rate is controlled to be 25 NL / min.

[0066] B, deoxidization and alloying: after the molten steel in step A is smelted, when the amount of molten steel in the ladle is greater than 1 / 4, the following deoxidization and alloying sequence is carried out: silicon calcium barium→silicon iron→silicon manganese alloy→high-carbon chromium iron→nitrogen-rich alloy→niobium phosphorus iron alloy, and the following substances are sequentially added into the ladle: according to 2.0 kg / t 钢 , the following mass ratio of silicon calcium barium is added: Si 52.5wt%, Ca 9.85wt%, Ba 12.15wt%, Al 2.45wt%, the rest is Fe and inevitable impurities; according to 5.4 kg / t 钢 , the following mass ratio of silicon iron is added: Si 73.5wt%, the rest is Fe and inevitable impurities; according to 12.1 kg / t 钢The following silicon-manganese alloy was added in the specified mass ratio: Mn 65.2 wt%, Si 17.9 wt%, C 1.1 wt%, with the remainder being Fe and unavoidable impurities; at a ratio of 14.6...

[0067] kg / t 钢 Add the following high-carbon ferrochrome in the specified mass ratio: Cr 54.2wt%, C 7.4wt%, P 0.072wt%, S 0.062wt%, with the remainder being Fe and unavoidable impurities; at a rate of 1.0 kg / t. 钢 The following silicon-nitrogen alloy was added in the specified mass ratio: Si 57.4 wt%, N 40.3 wt%, C 1.75 wt%, P 0.075 wt%, S 0.038 wt%, with the remainder being Fe and unavoidable impurities; at 0.30...

[0068] kg / t 钢 The following niobium-phosphorus-iron alloy was added in the specified mass ratio: Nb 44.2wt%, Si 3.5wt%, C 1.75wt%, P 1.65wt%, S 0.045wt%, with the remainder being Fe and unavoidable impurities. The alloy was added when the ladle was 3 / 4 full. After tapping, the molten steel was hoisted to the argon station for vanadium-containing pig iron addition and nitrogen blowing refining.

[0069] C. Molten Steel Argon Station Processing: The molten steel from step B is hoisted to the argon station processing position and processed through the alloy material tank at a rate of 11.0 kg / t. 钢 The following vanadium-containing pig iron with the following mass ratio was added after baking: C 3.5wt%, Si 0.45wt%, Mn 1.85wt%, V 5.0wt%, P 1.02wt%, S 0.065wt%, with the remainder being Fe and unavoidable impurities. The baking time for the vanadium-containing pig iron was 8 minutes, and the surface temperature of the pig iron after baking was 370℃. After the vanadium-containing pig iron was added, nitrogen was purged onto the molten steel at a flow rate of 30NL / min for 3 minutes.

[0070] D. Steel Refining in the LF Furnace: The molten steel from step C is hoisted to the LF furnace refining station and connected to the nitrogen supply. Nitrogen is then applied at a flow rate of 20 NL / min to purge the molten steel. The lower electrode is then used to slag at setting 6-8. After slag formation for 3 minutes, the electrode is raised to observe the slag formation within the furnace. If the slag sample is too thin or too dark, 5.0 kg / t of lime is added. 钢 Adjust the slag; otherwise, add 2.0 kg / t of pre-melted refining slag. 钢Adjustments were made; subsequently, temperature was measured and samples were taken. Based on the steel sample and temperature test results, alloys were added to adjust the composition of the molten steel and the lower electrode temperature was increased to ensure that the composition and temperature were within acceptable limits. After refining, the molten steel was subjected to soft nitrogen blowing at a low flow rate for 2 minutes, with the nitrogen flow rate controlled at 25 NL / min. After nitrogen blowing, a steel covering agent was added at a rate of 1.0 kg / t. 钢 Then the molten steel is hoisted to the casting station.

[0071] E. Steel casting: The tundish temperature is 1525℃, the casting speed is 3.3m / min, and the coolant flow rate in the crystallizer is 145m³ / min. 3 Under the conditions of 1.6 L / kg for secondary cooling water, the molten steel from step C is cast into steel billets with a cross section of 165 mm × 165 mm using a 5-strand small square billet casting machine with an R9m straight arc continuous straightening machine; the straightening temperature of the billet exiting the straightening machine is controlled at 1030℃.

[0072] F. Billet heating: The billet from step E is sent to a heating furnace with a soaking temperature of 1150℃ and heated for 75 minutes. The billet exit temperature is 1060℃, and then it is pushed to a fully continuous bar mill for rolling.

[0073] G. Controlled Rolling and Cooling of Steel Billets: The steel billets from step F are rolled for 6 passes on a roughing mill at a speed of 0.4 m / s; then, the rolled pieces are rolled for 4 passes on an intermediate mill at a speed of 1.2 m / s; finally, the rolled pieces are rolled for 3 passes on a pre-finishing mill at a speed of 6.0 m / s; before entering the finishing mill, the rolled pieces are controlled-cooled by a 10 m long water-cooling device with a cooling water volume of 80 m³ / s. 3 / h, the temperature of the rolled piece entering the finishing mill group is controlled at 880℃; the rolled piece is rolled once in the finishing mill group at a speed of 9.0m / s; before entering the finishing mill group two, the rolled piece is cooled by a water-cooling device with a length of 8m and a cooling water volume of 100m³. 3 The temperature of the rolled piece entering the finishing mill is controlled at 830℃; then, the rolled piece is rolled twice in the finishing mill at a speed of 11.0 m / s; after finishing, the rolled material is cooled by a 5m long water cooling device with a cooling water volume of 50m³. 3 / h; the temperature of the steel bar on the cooling bed after controlled cooling is controlled to be 890°C, and then the steel bar is naturally air-cooled to room temperature on the cooling bed, so that a 500MPa grade high-strength anti-seismic steel bar for railway with a nominal diameter of 25mm having the following weight percentage chemical components is obtained: C 0.24wt%, Si 0.60wt%, Mn 0.85wt%, Cr 0.80wt%, Cu 0.21wt%, V 0.070wt%, Nb 0.013wt%, S 0.040wt%, P 0.040wt%, O 0.0030wt%, N 0.0185wt%, and the rest is Fe and inevitable impurities. The process mechanical properties, microstructure, Vickers hardness difference and corrosion resistance of the 2 anti-seismic steel bar are shown in Tables 7 and 8.

[0074] Table 7 Process mechanical properties and corrosion resistance of the 500MPa grade high-strength anti-seismic steel bar for railway with a nominal diameter of 25mm produced in Example 3

[0075]

[0076] Table 8 Metallographic microstructure and Vickers hardness of the 500MPa grade high-strength anti-seismic steel bar for railway with a nominal diameter of 25mm produced in Example 3

[0077] .

Claims

1. A 500 MPa grade high strength anti-seismic reinforcing bar for railway with a nominal diameter of 18-25 mm, characterized in that, The anti-seismic steel bar has the following weight percentage chemical components: C 0.22-0.24wt%, Si 0.45-0.60wt%, Mn 0.70-0.85wt%, Cr 0.70-0.80wt%, Cu 0.17-0.21wt%, V 0.060-0.070wt%, Nb 0.010-0.013wt%, S≤0.040wt%, P≤0.040wt%, O≤0.0030wt%, N 0.0160-0.0185wt%, and the rest is Fe and inevitable impurities; The high-strength anti-seismic steel bar is realized by the following steps: A, molten steel smelting: according to 260-270 kg / t 钢 , 1.3-1.7 kg / t 钢 of cold material is loaded into the proportioning, scrap steel and copper plate are added into the LD converter respectively; then according to 785-795 kg / t 钢 of molten iron loading ratio, molten iron with a temperature of ≥1310℃ is added into the LD converter, and conventional top and bottom combined blowing is carried out, the chemical composition of the molten iron is: C 4.1-4.3wt%, Si 0.15-0.30wt%, Mn 0.20-0.45wt%, P 0.070-0.080wt%, S≤0.030wt%, the rest is Fe and inevitable impurities; then according to 15-20 kg / t 钢 , 15-18 kg / t 钢 of lime and light-burned dolomite is added for slagging, the end point carbon content is controlled to be ≥0.07wt%, and the tapping temperature is ≤1600℃; before tapping, active lime is added to the bottom of the ladle at an amount of 1.5 kg / t 钢 for slag washing; B, deoxidation alloying: the molten steel is tapped after smelting, when the amount of molten steel in the ladle is greater than 1 / 4, silicon calcium barium→ silicon iron→ silicon manganese alloy→ high carbon chromium iron→ rich nitrogen alloy→ niobium phosphorus iron alloy is added into the ladle in the order of deoxidation alloying, respectively 2kg / t 钢 , 3.2~5.4kg / t 钢 , 9.7~12.1kg / t 钢 , 12.6~14.6kg / t 钢 , 0.9~1.0kg / t 钢 , 0.25~0.30kg / t 钢 The amount of silicon calcium barium, silicon iron, silicon manganese alloy, high carbon chromium iron, silicon nitrogen alloy and high vanadium nitrogen alloy is added into the ladle in turn, and the above alloy is added when the amount of molten steel in the ladle reaches 4 / 5. C. Argon station treatment of the molten steel: the molten steel of step B is hoisted to the argon station treatment station, and through the alloy tank, vanadium-containing pig iron with a surface temperature ≥ 350℃ after baking is added in an amount of 10.0-11.0 kg / t 钢 of nitrogen gas with a flow rate of 25-30 NL / min is used to perform nitrogen blowing treatment on the molten steel, and the nitrogen blowing time is 3 minutes; the vanadium-containing pig iron has the following mass ratio components: C 3.5 wt%, Si 0.45 wt%, Mn 1.85 wt%, V 5.0 wt%, P 1.02 wt%, S 0.065 wt%, and the rest is Fe and unavoidable impurities; D. LF refining of the molten steel: the molten steel of step C is hoisted to the LF furnace for refining. After the refining is completed, the molten steel is softly blown with nitrogen at a small flow rate of 20-25 NL / min for 2 min. After the nitrogen blowing is completed, a covering agent is added to the molten steel in an amount of 1.0 kg / t 钢 , and then the molten steel is hoisted to the casting station. E. Casting of molten steel: under the conditions of tundish temperature of 1525-1535 °C, casting speed of 3.1-3.3 m / min, mold cooling water flow of 135-145 m 3 / h, and secondary cooling specific water flow of 1.6-1.8 L / kg, the molten steel is cast into a billet with a cross section of 165 mm x 165 mm; the temperature of the cast billet at the exit of the straightening machine is controlled to be 1010-1030 °C. F. Billet heating: the billet of step E is sent into a heating furnace with a furnace temperature of 1110-1150℃ for 70 minutes, and the billet temperature is 1040-1060℃, and then pushed to a full-continuous bar mill for rolling; G, billet controlled rolling and controlled cooling: the billet of step F is rolled by 6 passes through a rough rolling mill group at a rolling speed of 0.4-0.8 m / s, then rolled by 4 passes through a medium rolling mill group at a rolling speed of 1.2-2.0 m / s, then rolled by 3-6 passes through a pre-precision rolling mill group at a rolling speed of 6.0-8.0 m / s; before entering the precision rolling, the rolling piece is cooled by a water cooling device with a length of 10 m for pre-precision rolling control cooling, the cooling water amount is 60-80 m 3 / h, the temperature of the rolling piece entering the precision rolling is controlled at 880-900 ℃; the rolling piece is rolled by 1-2 passes through a precision rolling mill group at a rolling speed of 9.0-10.0 m / s; before entering the second precision rolling mill group, the rolling piece is cooled by a water cooling device with a length of 8 m for control cooling, the cooling water amount is 80-100 m 3 / h, the temperature of the rolling piece entering the precision rolling is controlled at 880-900 ℃; the rolling piece is rolled by 1-2 passes through a precision rolling mill group at a rolling speed of 9.0-10.0 m / s; before entering the second precision rolling mill group, the rolling piece is cooled by a water cooling device with a length of 8 m for control cooling, the cooling water amount is 80-100 m 3 / h; after the control cooling, the temperature of the reinforcing bar on the cooling bed is controlled at 890-920 ℃, then the reinforcing bar is naturally air-cooled to room temperature on the cooling bed to obtain a 500 MPa grade high-strength anti-seismic reinforcing bar with a nominal diameter of 18-25 mm for railway.

2. The 500 MPa grade high strength anti-seismic reinforcing steel bar for public designated diameter 18-25 mm railway according to claim 1, characterized in that, The anti-seismic steel bar has a yield strength of 530-560MPa, a tensile strength of 695-750MPa, a ratio of strength to yield≥1.31, an elongation after breaking≥23%, and a maximum force total elongation≥10.5%.

3. The 500 MPa grade high strength anti-seismic reinforcing bar for public designated diameter 18-25 mm railway according to claim 1, characterized in that, In step A, the chemical components of the scrap steel are: C 0.19-0.25wt%, Si 0.32-0.55wt%, Mn 1.30-1.52wt%, P 0.024-0.045wt%, S 0.023-0.045wt%, and the rest is Fe and inevitable impurities; and the chemical components of the copper plate are: Cu 99.3wt%, P 0.035wt%, S 0.041wt%, and the rest is inevitable impurities.

4. The 500 MPa grade high strength anti-seismic reinforcing steel bar for public designated diameter 18-25 mm railway according to claim 1, characterized in that, In step A, the whole process of tapping adopts a full-bottom-blowing nitrogen process, and the nitrogen flow is controlled at 20-25NL / min.

5. The 500 MPa grade high strength anti-seismic reinforcing bar for public designated diameter 18-25 mm railway according to claim 1, characterized in that, In step B, the chemical components of the silicon-calcium-barium are: Si 52.5wt%, Ca 9.85wt%, Ba 12.15wt%, Al 2.45wt%, and the rest is Fe and inevitable impurities; the chemical components of the silicon-iron are: Si 73.5wt%, and the rest is Fe and inevitable impurities; the chemical components of the silicon-manganese alloy are: Mn 65.2wt%, Si 17.9wt%, C1.1wt%, and the rest is Fe and inevitable impurities; the chemical components of the high-carbon chromium iron are: Cr 54.2wt%, C 7.4wt%, P 0.072wt%, S 0.062wt%, and the rest is Fe and inevitable impurities; the chemical components of the nitrogen-rich alloy are: Si 57.4wt%, N 40.3wt%, C 1.75wt%, P 0.075wt%, S 0.038wt%, and the rest is Fe and inevitable impurities; and the chemical components of the niobium-phosphorus iron alloy are: Nb 44.2wt%, Si 3.5wt%, C 1.75wt%, P 1.65wt%, S 0.045wt%, and the rest is Fe and inevitable impurities.

6. The 500 MPa grade high strength anti-seismic reinforcing bar for public designated diameter 18-25 mm railway according to claim 1, characterized in that, In Step D, during the refining process, nitrogen is blown into the molten steel at a flow rate of 15-20 NL / min, and then the electrode is lowered at a gear of 6-8 to slag; after 3 minutes of power-on slagging, the electrode is lifted to observe the slag in the furnace; if the slag sample is too thin and the color is too black, 4.0-5.0 kg / t of lime is added 钢 Slag is adjusted, otherwise 1.0-2.0 kg / t of pre-melted refining slag is added 钢 Adjustment; then temperature measurement and sampling, according to the steel sample and temperature detection results, add alloy to adjust the composition of the molten steel and lower the electrode to heat, ensure that the composition and temperature are qualified.

7. The 500 MPa grade high strength anti-seismic reinforcing bar for public designated diameter 18-25 mm railway according to claim 1, characterized in that, In step E, R9m straight arc continuous straightening 5-machine 5-flow small square billet casting is adopted.

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