A rare earth carbonitride precipitation strengthened high-strength hot-rolled anti-seismic HRB640E steel bar and a preparation method thereof

Abstract

The application discloses a rare earth carbonitride precipitation strengthening high-strength hot-rolled anti-seismic HRB640E steel bar and a preparation method thereof. The steel bar comprises the following chemical components and alloy components: C 0.24-0.28%, Si 0.20-0.75%, Mn 1.1-1.45%, V 0.09-0.15%, Nb 0.01-0.025%, N 0.02-0.03% and RE 0.0010-0.005%, and the balance is Fe and inevitable impurities. The steel bar is based on the synergistic effect among the components, directly alloys manganese, vanadium and niobium oxide minerals, replaces lime with limestone and dolomite without calcination process, and strictly controls the adding process of rare earth and nitrogen elements to promote the precipitation of rare earth carbonitride and hinder dislocation movement, so that the comprehensive performance of the steel is improved and the iron alloy preparation process is saved. The yield strength ReL of the steel bar prepared by the provided scheme is greater than or equal to 640 MPa, the tensile strength Rm is greater than or equal to 820 MPa, the maximum total elongation rate Agt is greater than or equal to 10%, the reduction of area A is greater than or equal to 18%, the strength yield ratio Rm / ReL is greater than or equal to 1.27, the yield index ratio is less than or equal to 1.30, the microstructure of the steel bar is ferrite + pearlite, and the steel bar can meet large-scale industrial production and multi-field application.

Description

TECHNICAL FIELD

[0001] The application relates to a high-strength steel bar, in particular to a rare-earth carbon-nitride precipitation strengthening high-strength hot-rolled anti-seismic HRB640E steel bar and a preparation method thereof, and belongs to the technical field of steel bar production. BACKGROUND

[0002] The steel bar is an indispensable basic industrial raw material for social development and progress of human civilization. With the rise of global green environmental protection and carbon control, high-strength, anti-seismic and economical steel bars have gradually become the inevitable market demand. In 2018, the new national standard GB / T1499.2-2018 “Steel for Reinforced Concrete Part 2: Hot Rolled Ribbed Steel Bar” was issued in China, which added 600MPa grade steel bars, and cancelled the 335MPa grade steel bars. The high-strength building steel bars with a grade of 600MPa and above have the effects of saving the amount of steel used, reducing the weight of the structure, shortening the construction period, saving energy and reducing emissions, and being green and environmentally friendly, and greatly improving the safety and stability of the building structure. The high-strength building steel bars can be widely used in national defense key projects, structure buildings in earthquake zones and high-rise buildings, and will become the new favorite in the market.

[0003] The high-strength anti-seismic HRB600E steel bar is in the ascendant stage of research and development, production and market application. The main technical problems of the 600MPa grade steel bar developed at present are that the yield strength of the steel bar is low and the surplus is small, the Rm / Rel ratio of the hot-rolled steel bar cannot reach 1.25 or more by 100%, it is difficult to meet the anti-seismic requirements of the steel bar, and the proportion of the steel bar with a maximum total elongation of more than 9% to meet the standard requirements is less than 100%. In order to improve the performance of the steel bar and reduce the alloy cost, the controlled rolling and controlled cooling process is adopted, especially the water cooling after rolling, which will bring harmful martensite or other organizations in addition to the standard ferrite + pearlite organization. In addition, the development of the HRB600E steel bar is mostly concentrated in the composition design, and the conventional smelting, refining, continuous casting and rolling processes of the HRB500 or HRB400 are used for production, the total alloy content is high, resulting in high production cost, low quality and unstable performance index value, etc.

[0004] CN111172459 A A kind of "600MPa grade anti-seismic threaded steel bar and its manufacturing method" applied by Shagang Iron and Steel Research Institute This application discloses a HRB600E vanadium-titanium microalloying high-strength anti-seismic hot-rolled steel bar, characterized in that: its chemical composition includes: C: 0.22~0.28%, Si+Mn: 1.50~3.00%, V+Ti: 0.10~0.25%, V≤0.12%, P≤0.035%, S≤0.035%, N: 0.02~0.04%, the rest is Fe and inevitable impurities; Mn=(1~4)×Si, V=(1~3)×Ti, carbon equivalent Ceq=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15≤0.56 by mass percentage; its production method includes: smelting process; continuous casting process; rolling process; cold bed cooling process. The present application adds V, Ti microalloying elements, feeds silicon nitride iron cored wire in the smelting process to increase nitrogen; high temperature heating and low temperature opening rolling process are used in the rolling process to ensure the solid solution of V and play the role of TiN fine crystal; then in the cooling process, dispersed fine Ti(C / N)+V(C / N) composite particles are precipitated, and precipitation strengthening and fine-grain strengthening synergistic effect is formed. The threaded steel produced by the above composition and process has a microstructure of ferrite+beihite, and the lower yield strength is ≥620MPa. The method has the following problems: (1) vanadium+ titanium are used as microalloying elements, and the Mn / Si ratio and V / Ti are limited, which limits the smelting composition control process window, making smelting more difficult; (2) the smelting, rolling and other processes are not significantly different from HRB500E, titanium is used as one of the main microalloying elements, which makes it difficult to control the steel bar smelting, continuous casting and rolling process parameters, and easily causes unstable and large fluctuation of steel bar performance. (3) nitrogenized silicon cored wire is used in the ladle for nitrogen-increasing treatment, because the melting point of nitrogenized silicon is 1800℃, the wire feeding treatment is carried out in the ladle, the temperature of molten steel in the ladle is below 1700℃, which causes poor nitrogen-increasing effect of molten steel and unstable nitrogen content in molten steel, thereby affecting the stability of steel bar performance;

[0005] Shagang Steel Research Institute also applied for "CN 201310149509 A small size 600 MPa grade anti-seismic threaded steel bar and its manufacturing method", the invention discloses a small size 600 MPa grade anti-seismic threaded steel bar, which contains the following components in percentage by weight: C 0.23-0.28%, Si 0.60-0.80%, Mn 1.00-1.60%, V 0.12-0.14%, N 0.010-0.030%, Cr 0.55-0.60%, and the balance of Fe and inevitable impurities. It also contains any one or a combination of more than two of Nb 0.001-0.040%, Ti 0.001-0.020%, Al 0.001-0.010%, Cu 0.001-0.050%. Its manufacturing method is: adopting converter or electric furnace smelting, small billet continuous casting and rolling, and short process of cooling bed cooling. The small size threaded steel bar produced by the above components and method has high tensile strength, high yield strength, high elongation after fracture, and the ratio of strength to yield is >1.25, meeting the requirements of anti-seismic steel bar. The invention focuses on the component design of the steel bar, and the main difference from the above CN111172459 A disclosed components is that it contains 0.55-0.60% Gr and Nb, Al and other micro-alloying elements. There is almost no essential difference in smelting, continuous casting, rolling and other processes. The main problems are (1) using 0.55-0.6 Gr, the welding carbon equivalent is high, which causes poor weldability of the steel bar, and at the same time limits the use of cheap C strengthening elements, affecting the production cost and performance improvement of the steel bar; (2) using titanium, aluminum and other micro-alloying elements, because titanium and aluminum are extremely active elements, it is difficult to control the smelting process, and it is also easy to cause the surface and internal quality (inclusions) of the casting blank to be poor, thereby affecting the stability of the performance of the steel bar.

[0006] CN 106636917 A A kind of HRB600E vanadium-containing high-strength hot-rolled anti-seismic steel bar and production method applied by Hebei Iron and Steel Chengde Iron and Steel Company; the present application discloses a kind of HRB600E vanadium-containing high-strength hot-rolled anti-seismic steel bar and production method thereof, and the chemical composition and its weight percentage are as follows: C: 0.23~0.30%, Si: 0.5~0.8%, Mn: 1.20~1.60%, V: 0.15~0.20%, P≤0.035%, S≤0.030%, N: 0.015~0.025%, the rest is Fe and inevitable impurities; its production method includes converter or electric furnace smelting, secondary refining, continuous casting, billet heating, rolling and cold bed air cooling. The main features of the present application are: (1) by controlling the V, N content in steel, the formation of V(C, N) fine particles is promoted and precipitated, and the steelmaking and rolling process parameters are strictly controlled, which significantly improves the strength of the steel bar and has certain resistance to hydrogen corrosion, and the steel bar meets the requirements of anti-seismic steel bar, has the practical significance of energy saving, emission reduction, safety and environmental protection; (2) the production method or process includes converter or electric furnace smelting, secondary refining, continuous casting, billet heating, rolling and cold bed air cooling, which has no essential difference from the current HRB500E or HRB400E production process; (3) the present application adopts high vanadium content design, the vanadium content is more than 0.15%, the precipitation strengthening efficiency of vanadium is deviated, the steel bar is strengthened by solid solution vanadium, the strengthening contribution is not high, which causes waste of expensive and scarce vanadium resources; the V content is 0.15~0.20%, the high vanadium content is easy to cause vanadium segregation in steel, and the performance of the steel bar is unstable.

[0007] Hebei Iron and Steel Chengde Iron and Steel Company also applied CN107365946A A kind of hot-rolled 600MPa grade anti-seismic screw thread steel bar and production method: C: 0.26~0.28%, Si: 0.6~0.8%, Mn: 1.40~1.60%, V: 0.12~0.15%, Nb: 0.015~0.030%, Mo: 0.05~0.10%, P≤0.045%, S≤0.045%, Ceq≤0.58%, the rest is Fe and inevitable impurities; gold chemical element, which brings certain difficulty to subsequent rolling process parameter setting, and silicon manganese and other common features of the present application are (1) the chemical composition of the steel bar is designed, V, Nb, Mo, multiple micro-alloying elements are used in the composition system and controlled according to the upper limit of the standard, which is easy to cause component segregation of silicon or manganese; (2) only the temperature of the billet out of the heating furnace is limited to 1100~1150℃, and high-temperature opening is used, which has high energy consumption and large steel billet oxidation loss, and multiple micro-alloying elements are used, especially expensive and scarce molybdenum resources.

[0008] The invention abstract of "CN 108913995 A HRB600E high-strength anti-seismic steel bar and its production method" applied by Hanzhong Iron and Steel of Shaanxi Steel Group is: The present application discloses a HRB600E high-strength anti-seismic steel bar, which is composed of the following components in percentage by weight: C: 0.23-0.28%, Si: 0.50-0.70%, Mn: 1.30-1.60%, Cr: 0.20-0.50%, V: 0.060-0.080%, and the rest is Fe, with the impurity content controlled as follows: S≤0.045%, P≤0.045%, and the sum of the weight percentages of the components is 100%. The present application also discloses a production method of the HRB600E high-strength anti-seismic steel bar. First, the components are melted and cast into a billet, heated, and then subjected to rough rolling, medium rolling and finish rolling in sequence, and the rolled piece is water-cooled and recovered, and finally naturally cooled to room temperature to obtain the HRB600E high-strength anti-seismic steel bar. The HRB600E high-strength anti-seismic steel bar has good microstructure and performance, simple manufacturing process and low cost. The characteristics of the present application are: (1) The composition system is designed, and the conventional alloy elements such as silicon and manganese in the composition system are controlled according to the upper limit of the standard, which is easy to cause composition segregation of silicon or manganese; although the vanadium content in the composition system is not high, 0.2-0.5% Gr is used, which causes poor weldability of the steel bar (high welding carbon equivalent), and at the same time limits the use of cheap C strengthening elements, affecting the improvement of steel bar production cost and steel bar performance; (2) The water cooling process is used for post-rolling heat treatment of the steel bar, which is easy to cause the microstructure of the steel bar not to meet the national standard requirements, and affects the performance stability of the steel bar.

[0009] CN102796962.A Nb-Ti-B micro alloy HRB600 high strength anti-seismic steel bar and its preparation, its invention abstract is: the present application provides a kind of Nb-Ti-B micro alloy HRB600 high strength anti-seismic steel bar and its preparation, after molten steel smelting, molten steel pouring, billet controlled rolling and controlled cooling, obtain the chemical composition of Nb-Ti-B micro alloy HRB600 high strength anti-seismic steel bar with following mass ratio:C:0.14~0.18wt%, Si:0.30~0.50wt%, Mn:0.50~0.75wt%, Cr:0.50~0.70wt%, Nb:0.030~0.050wt%, B:0.0015~0.0030wt%, Ti:0.020~0.040wt%, S≤0.045wt%, P≤0.045wt%, the rest is Fe and inevitable impurities.The characteristics of the present application are:(1) low-carbon, low-silicon, low-manganese component design is adopted, but 0.5~0.7%Gr is used, and Gr makes the welding carbon equivalent high, causes the poor weldability of steel bar, limits the use of cheap C strengthening element at the same time, affects the production cost and the improvement of steel bar performance;(2) Nb, B and Ti are used as micro alloying elements, the content of Nb is 0.03~0.05%, the content is higher, the rolling process parameter window range is narrow, and high temperature heating and high temperature rolling are needed to play the strengthening effect of niobium;The use of B and Ti elements makes the smelting process control difficult, and the internal quality and surface quality of casting blank are easily deteriorated, and the performance of steel bar is easily unstable;(2) the invention adopts water cooling after rolling, which easily causes the inconsistency of surface and core organization of steel bar, or the hardness difference between surface and core exceeds the standard;Surface fine-grained structure, poor weldability, or surface corrosion and other defects;

[0010] CN 111020393 A A preparation method of a nitrogen-rich vanadium micro-alloyed large-size anti-seismic reinforcing bar, the abstract of the invention is: The present application discloses a preparation method of a nitrogen-rich vanadium micro-alloyed large-size anti-seismic reinforcing bar. In the process of steel tapping in the converter and the process of LF furnace refining, a certain amount of vanadium-containing pig iron is added to replace the expensive vanadium-containing or vanadium-nitrogen alloy, which increases the V content of the molten steel. In the process of steelmaking deoxidation and alloying, high-nitrogen vanadium alloy and appropriate silicon-nitrogen alloy are added. The molten steel is treated by nitrogen blowing in the LF furnace refining process, which increases the nitrogen content in the molten steel and significantly reduces the V / N ratio in the steel, which significantly improves the precipitation strengthening effect of the steel. The present application integrates innovation in chemical composition design, converter smelting, deoxidation and alloying, LF furnace refining, continuous casting, rolling heating system, rolling temperature and controlled cooling process. The produced reinforcing bar has excellent and stable mechanical properties, fine and uniform microstructure, good plasticity and toughness, low strain aging property, excellent anti-seismic performance and other advantages, which reduces the production cost, improves the anti-seismic performance and improves the market competitiveness of the product. The characteristics of the present application are: (1) Vanadium micro-alloying of reinforcing bar is carried out by using vanadium-containing pig iron to partially replace vanadium-nitrogen alloy. Although it can partially replace the use of valuable vanadium-nitrogen alloy, the vanadium content of vanadium-containing pig iron is relatively low, less than 3%, compared with vanadium-nitrogen alloy containing more than 75% vanadium. Under the premise of the same vanadium content in the steel, the amount of vanadium-containing pig iron is more than 25 times the amount of vanadium-nitrogen alloy, which requires a significant increase in tapping temperature, which will bring a series of disadvantages such as serious erosion of furnace lining, shortening of service life, increase of steel and iron consumption due to over-oxidation of molten steel, low and unstable alloy yield, large fluctuation of reinforcing bar smelting composition, etc.; (2) Compared with conventional HRB500E or HRB400E, there is no essential difference in the subsequent process. The present application only uses vanadium-containing pig iron to replace part of the vanadium-nitrogen alloy for smelting;

[0011] The invention discloses a kind of Φ28 ~ 36mm HRB600 high-strength anti-seismic reinforcing steel for hydropower station engineering, and its features are that the chemical composition of steel is as follows: C 0.23 ~ 0.26wt%, Si 0.50 ~ 0.65wt%, Mn 1.45 ~ 1.55wt%, S 0.025 ~ 0.035wt%, P 0.030 ~ 0.040wt%, Cr 0.12 ~ 0.18wt%, Mo 0.020 ~ 0.035wt%, V 0.125 ~ 0.140wt%, and the rest is Fe and unavoidable impurities.The invention also discloses a preparation method of the large-size HRB600 high-strength anti-seismic reinforcing steel, which adopts vanadium, chromium and molybdenum composite micro-alloying process, adds vanadium-nitrogen alloy, chromium iron and molybdenum iron and other micro-alloy strengthening elements into the steel, and adopts pre-penetration water control cooling device (4.9m long) to control lower final rolling temperature in the rolling process, so that the formation and precipitation of fine dispersed micro-alloy carbon (nitrogen) compound second phase are promoted, the strength of the steel is improved, and the plasticity and toughness are significantly improved.The reinforcing steel product prepared by the invention can be used in the construction engineering of dam and flood control tunnel of Jinshajiang Hydropower Station and road and bridge engineering, and has the advantages of low production cost, strong process applicability, reliable operation and stable product.The invention has the following characteristics: (1) silicon is limited, and manganese is designed to be above the standard upper limit, especially the upper limit of manganese, which is difficult to control and is prone to manganese segregation; (2) vanadium, chromium and molybdenum are used for composite micro-alloying, the chromium content is 0.12% ~ 0.18%, the welding carbon equivalent is high due to the presence of chromium, the weldability of the reinforcing steel is poor, the use of cheap C strengthening element is limited, and the production cost and performance of the reinforcing steel are affected; the molybdenum content is 0.020% ~ 0.035wt%, molybdenum is a rare and expensive metal, which causes resource waste and cost increase; (3) the rolling process adopts controlled cooling process, and the performance meets the requirements through the process of strong water penetration after finish rolling, but on the one hand, the production process is complex and the water penetration capacity of the equipment is high, and on the other hand, it is difficult to guarantee that the water penetration organization is ferrite + pearlite.The use of chromium, molybdenum and high content of manganese elements with high hardenability causes the surface quenching layer of the reinforcing steel to be deep, the surface and core organizations are different, the surface and core hardness difference is out of limit, and the performance stability of the reinforcing steel is poor; at the same time, on the one hand, the welding performance of the reinforcing steel is seriously affected, and on the other hand, the water penetration process parameters are sensitive, and harmful organization is easily formed.

[0012] The invention abstract of "CN102851580A HRB600E anti-seismic steel bar and its production method" applied by Shandong Laiwu Iron and Steel Group Co., Ltd. is as follows: The present application provides a kind of HRB600E anti-seismic steel bar and its production method, which is composed of the following elements by weight percentage: C: 0.17%~0.25%; Si: 0.40%~0.80%; Mn: 1.10%~1.50%; V: 0.07%~0.11%; P≤0.035%; S≤0.035%; N: 0.017~0.023%; the rest is Fe and inevitable impurities. Its production method includes steelmaking process, continuous casting process and rolling process. In the initial smelting process of the steelmaking process, the molten steel in the ladle is deoxidized and alloyed to obtain HRB600E high-strength anti-seismic steel bar containing 0.07%~0.11% V and 0.017~0.023% N by weight. The steel bar has high yield strength, high tensile strength, high strength and high elongation, which meets the requirements of anti-seismic steel bar; the characteristics of the patent are: the composition design is focused on, vanadium and nitrogen are used as micro-alloying elements, and the composition content is similar to that of HRB500E. The performance of the steel bar meets the performance requirements of HRB600E by adopting post-rolling controlled cooling means. Due to the relatively low composition content, the process parameter window for controlling the performance of HRB600E steel bar is narrow, which is difficult to control, and it is easy to cause the performance indicators such as Rel, Rm or Rm / Rel value to be unqualified, the difference between the surface and core organizations is large, or the surface and core hardness difference is unqualified, which leads to poor performance stability of the steel bar;

[0013] The invention abstract of "CN102851605A HRB600E steel bar and its production method" applied by Shandong Laiwu Iron and Steel Co., Ltd. is: The present application discloses a kind of HRB600E steel bar and production method, the steel bar is by following elements according to weight percentage: C:0.20~0.28%, Mn:1.30~1.60%, Si:0.30~0.80%, V:0.08~0.12%, S≤0.020%, P≤0.030%, Cr:0.05~0.40%, the rest is Fe and inevitable impurities. Its production method includes smelting process, continuous casting process and rolling process, in the smelting process, the molten steel in ladle is alloyed, so that the molten steel contains 0.08~0.12% V and 0.05~0.40% Cr according to weight percentage. The vanadium content of the steel bar of the present application is reduced by about 30~40% compared to the vanadium content of the same grade steel bar with yield strength, and it has the advantages of high yield strength, high tensile strength, high strength ratio and high elongation. The characteristics of this patent are almost similar to CN102851580A: the composition system is similar to

[012] , and the composition design is emphasized. In addition to using vanadium and nitrogen as micro-alloying elements, 0.05~0.40% Cr is also used, and the composition content is similar to HRB500E. The performance of the steel bar meets the performance requirements of HRB600E by adopting post-rolling controlled cooling means. Due to the relatively low composition content, the process parameter window for controlling the performance of HRB600E steel bar is narrow, which is difficult to control, and it is easy to cause the performance indicators such as Rel, Rm or Rm / Rel value to be out of standard, the difference between the surface and core organizations is large, or the surface and core hardness difference exceeds the standard, which leads to poor performance stability of the steel bar.

[0014] The invention abstract of "CN114836686A HRB600E general speed hot-rolled ribbed steel bar with a strength-ductility ratio greater than 1.26" applied by Liuzhou Iron and Steel in Guangxi is: The present application provides a kind of HRB600E general speed hot-rolled ribbed steel bar with a strength-ductility ratio greater than 1.26, the production method of the HRB600E general speed hot-rolled ribbed steel bar with a strength-ductility ratio greater than 1.26 includes: the following process stages are carried out in turn: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, LF refining, bloom continuous casting, hot continuous rolling, fixed-length shearing and inspection; The temperature control in hot continuous rolling is: control the heating temperature of casting blank to 1150-1200℃, billet heating time is 60-90 minutes, and the opening temperature is 1020-1080℃. The general speed hot-rolled ribbed steel bar adopts the above production method. The main features of the present application are: (1) the chemical composition of the steel bar is: C: 0.23-0.28%, Si: 0.65-0.80%, Mn: 1.45-1.60%, P≤0.040%, S≤0.035%, V: 0.12-0.17%, Nb: 0.010-0.025%, N: 0.020-0.035%, B: 0.0015-0.0040%; The design of carbon, silicon and manganese content with partial standard upper limit is easy to cause C and Mn composition segregation, which brings difficulty to the control of smelting, continuous casting and rolling process parameters; (2) 0.0015-0.0040% B is used as a micro-alloying element, which increases the smelting difficulty; B element is easy to cause crack and other defects, and the yield of B in smelting and refining process is unstable, which brings large smelting composition fluctuation; B can form precipitates to achieve two-phase particle strengthening effect, but also form inclusions to cause discontinuous matrix structure, affect the performance of steel, and also coarsen grains and reduce the performance of steel bar, thus causing unstable performance of steel bar and even quality defects; (3) The control parameters of smelting, refining, continuous casting and rolling have no big difference with HRB500E, and there is no innovative description;

[0015] The invention abstract of "CN113388781A high-speed bar production HRB600E threaded steel bar method and high-speed bar production HRB600E threaded steel bar" applied by Guangxi Liuzhou Iron and Steel Co., Ltd. is: The present application provides a kind of high-speed bar production HRB600E threaded steel bar method and high-speed bar production HRB600E threaded steel bar, the high-speed bar production HRB600E threaded steel bar method includes: the following steps are sequentially carried out: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, argon blowing, LF refining, bloom continuous casting, heating furnace heating, rough rolling, medium rolling, pre-rolling, pre-rolling controlled cooling and recovery, finishing rolling, post-rolling controlled cooling and recovery;The composition of the high-speed bar production HRB600E threaded steel bar is: C: 0.23-0.28wt%, Si: 0.65-0.80wt%, Mn: 1.25-1.45wt%, P: ≤0.04wt%, S: ≤0.035wt%, V: 0.065-0.10wt%, Nb: 0.008-0.02wt%, N: 0.015-0.028wt%, B: 0.0015-0.0035wt%, Cr: 0.1-0.2wt%. The production cost is reduced, the production efficiency is high, and the surface quality is good. The main features of the present application are: (1) the following steps are sequentially carried out: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, argon blowing, LF refining, bloom continuous casting, heating furnace heating, rough rolling, medium rolling, pre-rolling, pre-rolling controlled cooling and recovery, finishing rolling, post-rolling controlled cooling and recovery;And for the high-speed bar production HRB600E threaded steel bar with a size of 10mm, the final rolling speed is 42m / S, and its adaptability is limited;(2) the composition system design is mainly carried out, and V, B, Nb, Gr, N multiple elements are used for micro-alloying, which brings difficulty to the control of smelting, refining, continuous casting and rolling process parameters, especially B element is easy to cause crack and other defects, B has unstable yield in smelting and refining process, which brings large fluctuation of smelting composition, B can form precipitates to play the effect of two-phase particle strengthening, also can form inclusions to cause discontinuous matrix structure, affect the performance of steel, also can coarsen grains, reduce the performance of steel bar, thus causing unstable performance of steel bar, even causing quality defects;

[0016] Yangchun Xinsteel's "CN 114058770 A. A production method of HRB600E high-strength anti-seismic steel bar" invention abstract: The present application provides a production method of HRB600E high-strength anti-seismic steel bar, relating to the technical field of steel bar production, including the following steps: blast furnace smelting, converter charging, LF furnace refining, continuous casting cooling and rolling finished product; the present application adopts the process route of blast furnace molten iron, converter, LF, high-speed continuous casting and rolling mill, through optimizing the converter smelting process, micro-alloying process, LF furnace refining and inclusion removal process, continuous casting electromagnetic stirring, automatic water distribution process and optimizing the hot rolling opening rolling temperature, post-rolling controlled cooling and other hot rolling processes, without adopting water cooling process, high-quality high-strength anti-seismic steel bar can be obtained, and through converter smelting, the present application adopts niobium and vanadium nitrogen micro-alloying process to produce high-strength anti-seismic steel bar, which is similar to the ordinary threaded steel smelting process, easy to operate, strong applicability, easy to promote, and adding niobium iron and vanadium nitrogen alloy during tapping process, high alloy yield, can accurately control the composition of molten steel, and stably control the performance of the product. The main features of the invention patent are: from claim 9, it can be known that: the invention mainly aims at the invention of wire rod (9. Claim 1 describes a production method of HRB600E high-strength anti-seismic steel bar, characterized in that: in step five, the temperature of the heating furnace is controlled at 1000±15℃; the air cooling line fan is opened by 50%); adopts vanadium and niobium micro-alloying process, realizes through five process steps of smelting, tapping, refining, continuous casting and rolling, and the process control parameters have no essential difference with HRB500E; and the invention mainly aims at the wire rod rolling line, and its application range is limited;

[0017] The invention abstract of "CN106967928A A kind of 650MPa grade high-strength anti-seismic steel bar steel and its preparation method" applied by Beijing Jiaotong University is: a kind of 650MPa grade high-strength anti-seismic steel bar steel, including the following mass percentage components: C:0.10~0.4wt%; Mn:1.5~3.0wt%; Si:0.00~2.0wt%; Cr:0.20~1.0wt%; Al:0.20~1.6wt%; P:0.001~0.15wt%; S:0.001~0.015wt%; the rest is Fe and inevitable impurity elements.The present application also discloses a kind of 650MPa grade high-strength anti-seismic steel bar steel preparation method.Compared with the existing anti-seismic steel bar, the anti-seismic steel bar produced by the preparation method of the present application can increase the strength of steel structure, reduce the reinforcement density, improve the seismic performance of building, increase the safety margin of anti-seismic, and the microstructure is ferrite+be bainite+martensite complex phase structure, or bainite+martensite complex phase structure, and contains a certain amount of residual austenite.The yield strength Rp0.2 of the anti-seismic steel bar of the present application is greater than or equal to 650MPa, the ratio of strength to yield is greater than or equal to 1.45, the elongation rate under maximum force is greater than or equal to 14.5%, and the strength-plasticity product is greater than or equal to 25000MPa.%.The characteristics of the patent are:(1) the upper limit of C, Si and Mn is much higher than the upper limit of the national standard design, so there will be a risk of violating the national steel reinforcement mandatory standard in the actual popularization and use process, which will bring the risk of unenforceable popularization and use;(2) the use of chromium 0.20~1.0wt% makes the welding carbon equivalent high, which causes the poor weldability of steel bar, and at the same time limits the use of cheap C strengthening elements, affecting the production cost and performance improvement of steel bar;(3) Al is used as a micro-alloying element, and the content of Al is 0.20~1.6wt%, which is very high, which brings great difficulty to smelting and casting, and also easily causes secondary oxidation of molten steel, continuous casting nozzle clogging, and many other difficulties such as continuous casting and continuous casting furnace number limitation;(4) according to the process defined in the present application, the steel bar is a steel bar after steel bar heat treatment, the process links are increased, the energy consumption is increased, which is not conducive to energy saving and environmental protection, and the process cost is increased;(5) the final structure of the steel bar is ferrite+be bainite+martensite complex phase structure, or bainite+martensite complex phase structure, and contains a certain amount of residual austenite, which is contrary to the national standard, and the steel bar cannot be directly welded for use, which increases the difficulty and cost of steel bar use.

[0018] In summary, the current relevant HRB600E steel mainly focuses on the component system design thereof, and alloying of the molten steel by using ferroalloy or scrap steel containing alloying elements as the source of alloying elements. The process control parameters of smelting, refining, continuous casting and rolling are similar, and the post-rolling controlled cooling process or post-rolling steel heat treatment process is adopted. As described above, the disclosed invention has different defects, and therefore, the market urgently needs a hot-rolled high-strength anti-seismic steel bar capable of reducing the use amount of solid solution alloying elements while obtaining stable performance. SUMMARY

[0019] In view of the problems in the prior art, a first object of the present application is to provide a rare earth carbonitride precipitation strengthened high-strength hot-rolled anti-seismic HRB640E steel bar, which greatly improves the mechanical properties of the steel bar by adding alloying elements and rare earth nitrides.

[0020] Tests show that the yield strength ReL of the HRB640E steel bar provided by the present application is ≥640 MPa, the tensile strength Rm is ≥820 MPa, the maximum force total elongation Agt is ≥10%, the reduction of area A is ≥18%, the strength yield ratio Rm / ReL is ≥1.27, the yield index ratio is ≤1.30, the microstructure of the steel bar is ferrite + pearlite, and the cold bending is defect-free.

[0021] A second object of the present application is to provide a preparation method of a rare earth carbonitride precipitation strengthened high-strength hot-rolled anti-seismic HRB640E steel bar capable of reducing the use amount of solid solution alloying elements while obtaining stable performance.

[0022] In order to achieve the above technical objects, the present application provides a rare earth carbonitride precipitation strengthened high-strength hot-rolled anti-seismic HRB640E steel bar, which comprises the following chemical components and alloying elements: C 0.24-0.28%, Si 0.20-0.75%, Mn 1.1-1.45%, V 0.09-0.15%, Nb 0.01-0.025%, N 0.02-0.03%, and RE 0.0010-0.005%, and the balance is Fe and unavoidable impurity elements.

[0023] As a preferred scheme, the yield strength of the steel bar is ≥640 MPa, the tensile strength is ≥820 MPa, the maximum force total elongation Agt is ≥10%, the reduction of area A is ≥18%, the strength yield ratio Rm / ReL is ≥1.27, the yield index ratio is ≤1.30, the cold bending is defect-free, and the microstructure of the steel bar is ferrite + pearlite.

[0024] As a further preferred scheme, the yield strength ReL of the reinforcing bar is 660-690 MPa, the tensile strength Rm is 850-880 MPa, the maximum force total elongation Agt is 11%-12%, the reduction of area A is 19%-23%, the strength ratio Rm / ReL is 1.28-1.29, the yield ratio is 1.03-1.07, the cold bending is defect-free, and the microstructure of the reinforcing bar is ferrite + pearlite.

[0025] The application also provides a preparation method of a rare earth carbon nitride precipitation reinforced high-strength hot-rolled anti-seismic HRB640E reinforcing bar, comprising the following steps: adding raw materials including molten iron into a converter, adding raw ore or physically processed raw ore of limestone and dolomite as basic slag material into the converter during the converter smelting process, performing slagging in the converter to remove phosphorus, silicon, sulfur and impurities, and blowing oxygen to decarburize and oxidize phosphorus and silicon in the molten iron; after the above treatment, adding oxides containing alloy elements accounting for 40%-60% of the target mass content of Mn, V and / or Nb alloy elements of the reinforcing bar, respectively, and converting the bottom blowing gas in the converter into reducing gas, with a bottom blowing intensity of 0.10-0.15 Nm3 / t.min; controlling the binary basicity of the converter final slag at 2.5-2.8, and controlling the molten steel temperature at the converter endpoint at 1590-1650 ℃; before and during tapping, supplementing the oxides containing alloy elements and adjusting the alloy content of the reinforcing bar according to the lower limit of the target mass content of the alloy elements, and adding a deoxidizer during tapping to perform molten steel deoxidation and alloying; transporting the molten steel after tapping to LF refining, adding slagging agents or reducing agents, and stirring by bottom blowing reducing gas in the ladle, with a blowing intensity of 0.2-0.5 Nm 3 / t.min, controlling the binary basicity of the top slag of the ladle to be 1.8-2.5 and adding the remaining target alloy elements for fine adjustment, so that the composition of the molten steel meets the target composition requirements of the reinforcing bar, and after the refining is completed, the reinforcing bar is obtained by sequentially performing continuous casting and casting and heating rolling of the casting blank.

[0026] The molten iron of the present application can be directly added into the converter without pretreatment. In the prior art process, almost all alloying elements are added by using ferroalloy products, and the preparation process of ferroalloy is indispensable, which increases energy consumption and environmental pollution. In the present application, oxide ore or pre-reduced ore of alloying elements is used, and reducing gas such as hydrogen and natural gas is blown from the bottom for direct alloying, so that the preparation process of ferroalloy can be saved, and the content of alloying elements in the steel can be accurately controlled, thereby stabilizing the production of high-quality high-strength steel bar products. Therefore, in the method of the present application, the blast furnace molten iron can be directly introduced into the converter, and limestone and dolomite ore can be used as the basic slagging agent instead of lime and light-burned dolomite for smelting; manganese ore, vanadium-containing or niobium-containing oxide ore can be added during the converter smelting process or the steel tapping and deoxidizing alloying process, and reducing gas hydrogen and / or natural gas can be blown from the bottom of the converter or ladle for direct reduction and alloying, and the reduced white slag is formed in the LF furnace, and the alloying components and temperature of the molten steel are accurately controlled; the soft blowing is performed in the later stage of the LF refining to remove inclusions, and the molten steel is cast by continuous casting, heated and rolled, and controlled cooling, and the high-performance HRB640E steel bar is obtained.

[0027] As a preferred scheme, the raw material further comprises scrap steel, and the addition amount of the scrap steel accounts for 0-50% of the total Fe loading amount.

[0028] As a preferred scheme, within 1-3 minutes from the beginning of the converter blowing, limestone 24-40 kg / ton of steel, dolomite 6-12 kg / ton of steel, and slagging agent 6-10 kg / ton of steel are added into the converter.

[0029] As a preferred scheme, at 6-8 minutes of the converter blowing, limestone 10-12 kg / ton of steel and dolomite 8-10 kg / ton of steel are added.

[0030] As a preferred scheme, the reducing gas is hydrogen and / or natural gas.

[0031] As a preferred scheme, the converter blowing process adopts low-high-low-high oxygen lance position control. The final slag parameters after the end of the converter blowing are as follows: binary basicity R2.5-2.8, mass content of MgO 7-9%, and mass content of TFe 8-12%.

[0032] As a preferred scheme, the end-point composition of the converter molten steel is as follows: C 0.12-0.18%, P≤0.035%, and S≤0.035%, in terms of mass content.

[0033] As a preferred scheme, the mass content of metallic manganese in the oxide containing alloying element Mn is not less than 40% (preferably 40%-55%). The manganese-containing pre-reduced manganese ore can be selected from one or a combination of the following: carbon-containing manganese pellets, solid-state reduced manganese pellets, and high-grade manganese ore.

[0034] As a preferred solution, the vanadium-containing oxide has a vanadium metal content of not less than 50% (preferably 50%-60%). It can be selected from one or a combination of vanadium-containing pre-reduced vanadium oxides, including carbon-coated vanadium oxide pellets, solid-state reduced vanadium oxide pellets.

[0035] As a preferred solution, the niobium-containing oxide has a niobium metal content of not less than 45% (preferably 45%-55%). It can be selected from one or a combination of niobium-containing pre-reduced niobium oxides, including carbon-coated niobium oxide pellets, or solid-state reduced niobium oxide pellets;

[0036] As a preferred solution, a slag-forming solvent is added during the slag formation in the converter for dephosphorization, desiliconization, desulfurization, and removal of impurities, which is selected from at least one of dust, sludge, iron oxide scale, iron ore, and fluorite.

[0037] As a preferred solution, a low-high-low-high oxygen lance position control method is used for blowing.

[0038] As a preferred solution, the type and amount of deoxidizer added in the early stage of tapping are determined according to the end-point carbon or oxygen content in the end-point molten steel composition of the steelmaking furnace.

[0039] As a preferred solution, 1 / 3-1 / 2 of the total amount of deoxidizer is added in the initial stage of tapping, and the remaining deoxidizer is added when the tapping weight reaches 1 / 4 of the total molten steel weight.

[0040] As a preferred solution, the deoxidizer is at least one of aluminum, steel-cored aluminum, silicon-aluminum-barium alloy, aluminum-manganese alloy, or at least one of silicon carbide, ferrosilicon, silicon-manganese, metallic silicon, and calcium-silicon, or one of carbon, calcium, calcium carbide, and ferrocalcium.

[0041] As a preferred solution, the content of manganese, vanadium, or niobium in the finished steel is controlled according to the target lower limit value based on the end-point molten steel composition, and the molten steel is deoxidized and alloyed. The addition of oxides containing alloying elements and alloying elements for adjusting the composition of the reinforcing steel is completed in the early stage of tapping until the tapping weight reaches 4 / 5 of the total molten steel weight. The alloying elements for adjusting the composition of the reinforcing steel are ferrosilicon, silicon-manganese alloy, vanadium-nitrogen alloy, niobium-iron alloy, rare earth-nitrogen alloy, or rare earth-micro-nitrogen alloy.

[0042] As a preferred solution, the rare earth-nitrogen alloy and / or micro-nitrogen alloy is added in an amount of 0.65-0.75 kg / ton of steel. As a preferred solution, the rare earth-nitrogen alloy and / or micro-nitrogen alloy contains at least one of lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, holmium, thulium, scandium, and yttrium, with a total rare earth content of 3-12% and a nitrogen content of 20-38%.

[0043] As a preferred scheme, the converter tapping process is added with lime, reducing slagging material and slagging solvent, and the steel slag is mixed and washed, and the ladle top slag is prepared by LF refining. The inert or reducing gas is blown at the bottom of the ladle during the tapping process of the converter to stir the molten steel. The inert gas is selected from one of argon and nitrogen. The reducing gas is selected from one of hydrogen and natural gas. The reducing slagging material is a reducing single-element slagging material. The reducing single element can be carbon, aluminum and / or calcium, etc.

[0044] As a preferred scheme, the molten steel is transferred to the LF refining, the slagging material or reducing agent is added, the power is sent, the reducing gas is blown at the bottom for stirring, the binary basicity of the ladle top slag is controlled between 1.8-2.5; the foamed white slag lasts for 5-10 minutes, sampling, temperature measurement, according to the composition of the molten steel and the target composition value of the finished steel, the alloy containing C, Si, Mn, V, Nb, N and RE elements is added, and the narrow-range regulation of the alloy element content of the molten steel is carried out; in the later stage of refining, the power is turned off, the top slag is fully covered, and the soft argon blowing is carried out on the molten steel in the ladle for 5-8 minutes, and the molten steel is tapped when the temperature meets the requirements of continuous casting.

[0045] As a preferred scheme, in the LF refining process, the slagging material is lime, the addition amount is 3.0-6.0 Kg / ton of steel, calcium aluminate pre-melted slag is also added, the addition amount is 1-2 Kg / ton of steel, and the addition amount of the slag modifier is 0.5-1.5 Kg / ton of steel. The molten steel in the ladle is soft-blowing argon for 5-8 minutes under the condition of maintaining the foaming of the top slag. After the refining is completed, the temperature of the molten steel at the station is 1560-1580℃. The slag modifier is a slag containing CaO, MgO and other alkali metal oxides, which is used to adjust the basicity, melting point and viscosity of the slag.

[0046] As a preferred scheme, in the LF refining process, according to the foaming condition of the ladle top slag, 1-3 Kg / ton of steel of foaming slag and 1-4 Kg / ton of steel of reducing slag are added to the molten steel, the medium-power power is sent for 12-18 minutes, the white foaming slag is formed, the thickness of the foaming white slag layer is controlled between 100-400 mm, the foaming slag lasts for 8-16 minutes, and the hydrogen and / or natural gas is blown at the bottom of the ladle for stirring, the blowing intensity is 0.2-0.5 m 3 / t.min. By this operation, the binary basicity of the ladle top slag can be well controlled between 1.8-2.5.

[0047] The power is turned off, sampling, temperature measurement, according to the composition of the molten steel and the target composition value of the finished steel, the alloy containing C, Si, Mn, V, Nb, N and RE elements is added, and the narrow-range regulation of the alloy element content of the molten steel is carried out; in the later stage of refining, the low-power power is sent for 2-12 minutes, the molten steel in the ladle is soft-blowing argon under the condition of maintaining the foaming of the top slag, and after the refining is completed, the temperature of the molten steel at the station is 1560-1580℃.

[0048] The composition of the LF furnace molten steel is C=0.24-0.28%, Si 0.20-0.75%, Mn 1.10-1.45%, V 0.09-0.15%, Nb 0.01-0.025%, N 0.022-0.030%, and RE 0.0010-0.0050%.

[0049] As a preferred scheme, the process of the continuous casting is as follows: the superheat of the molten steel is controlled at 10-15°C, the casting speed is 3.0-4.0 m / min, the crystallizer cooling is relatively weak, the secondary cooling is strong, the crystallizer does not use electromagnetic stirring, the electromagnetic stirring is performed at the solidification end, the casting blank is straightened at 950-1000°C, the cross-sectional size of the casting blank is (150-170) X (150-170) mm, and the hot blank is directly hot sent to the rolling heating furnace.

[0050] As a preferred scheme, the process of the heating rolling is as follows: the hot blank is sent to the rolling heating furnace, the temperature of the casting blank entering the heating furnace is 650-950°C, the steel blank is heated to 1150-1200°C within 50-60 min, the heating is kept for 50-60 min, the rolling temperature is 1070-1100°C, the 12-40 mm steel bar is obtained after 14-18 racks of continuous rolling, the last two racks of the total reduction amount are 20-30%, the water quenching and weak cooling gas mist control cooling are performed after the rolling is finished, and the temperature of the steel bar on the cooling bed is 910-950°C.

[0051] The preparation method provided by the present application directly alloys manganese, vanadium and niobium oxides, that is, directly alloying in a converter and a ladle (LF furnace) after tapping. Chemical heat is utilized in the converter by oxidizing carbon, silicon, phosphorus and other elements in the molten iron, and hydrogen gas and / or natural gas are blown in the bottom of the converter or the ladle in the LF furnace as reducing agents. At the same time, hydrogen gas and / or natural gas improve the kinetic conditions of the molten pool in the stirring process. Moreover, compared with the conventional use of lime and light-burned dolomite, the present application can save the calcination process of limestone or dolomite because limestone or dolomite is used to replace lime or light-burned dolomite for slagging operation. In the traditional preparation process, limestone and dolomite have poor activity, high impurity content, high smelting energy consumption and other disadvantages compared with lime and light-burned dolomite. In the present application, the chemical heating of the converter smelting decomposes into CaO and MgO and CO2 in the steelmaking process, and the CaO and MgO generated in the steelmaking process have lower energy consumption, higher activity and better metallurgical effect than CaO and MgO produced by external calcination. At the same time, the generated CO2 is stirred from the inside of the molten pool, which improves the smelting kinetics and improves the metallurgical effect, and overcomes the technical defects. Through the addition amount of manganese, vanadium and niobium oxides, limestone and dolomite, the composition of the molten iron, the final slag basicity of the converter, the final composition of the molten steel in the converter, and the final temperature of the converter, they constitute a model that restricts each other, and together with the process parameters of the converter or the ladle bottom blowing H2 or natural gas, the manganese, vanadium and niobium oxide minerals are directly alloyed, and the rare earth carbonitride precipitation reinforced high-strength hot-rolled anti-seismic HRB640E steel bars are efficiently and low-energy-consumption produced.

[0052] The present application also uses rare earth nitride alloy to perform nitrogen and rare earth micro-alloying treatment during the tapping process, and simultaneously performs synergistic treatment with vanadium, niobium and other micro-alloying elements. In the solidification, heating, rolling and post-rolling controlled cooling process of the molten steel, different types of rare earth carbonitride are formed, which are dispersedly distributed and small in size, hinder dislocation movement and grain growth, so that a rare earth carbonitride precipitation reinforced high-strength hot-rolled anti-seismic HRB640E steel bar is obtained with low emission and low energy consumption.

[0053] Compared with the prior art, the present application has the following beneficial technical effects:

[0054] 1) The HRB640E steel bar provided by the present application is based on the synergistic effect between the components. The steel bar is based on the synergistic effect between the components, and the mechanical properties of the steel bar are greatly improved by adding alloy elements and rare earth nitrides. The yield strength ReL of the HRB640E steel bar provided by the present application is greater than or equal to 640 MPa, the tensile strength Rm is greater than or equal to 820 MPa, the maximum total elongation rate Agt is greater than or equal to 10%, the reduction of area A is greater than or equal to 18%, the strength yield ratio Rm0 / R0e L is greater than or equal to 1.27, the yield ratio is less than or equal to 1.30, and the cold bending is defect-free. The structure is ferrite + pearlite.

[0055] 2) The HRB640E steel reinforcing bar preparation method provided by the application can effectively solve the problem of low yield-toughness ratio of the 640MPa high-strength reinforcing bar, improve the mechanical properties and anti-seismic performance of the material, and realize stable high-quality production of high-strength hot-rolled anti-seismic reinforcing bar HRB640E by directly alloying manganese, vanadium and niobium oxide minerals, directly reducing oxides by stirring and blowing hydrogen or natural gas on molten steel, and using limestone or dolomite instead of lime or lightly calcined dolomite for slagging operation, adding rare earth nitrogen alloy or micro-nitrogen alloy containing multiple rare earth elements to perform rare earth micro-alloying treatment on the molten steel, using multiple rare earth carbonitrides to hinder dislocation movement and improve the comprehensive performance of the steel, and omitting the preparation process of ferroalloy to save energy and reduce emissions.

[0056] 3) In the technical solution provided by the application, the manganese, vanadium and niobium oxides are directly reduced and alloyed by stirring the molten steel while blowing hydrogen or natural gas, which greatly saves the energy consumption of the above-mentioned ferroalloy production, and further, the vanadium, niobium and rare earth nitrogen micro-alloying process is used to strengthen the reinforcing bar matrix by controlling the precipitation of rare earth carbonitrides through casting blank heating, rolling deformation and post-rolling cooling, which can greatly reduce the use amount of solid solution alloy elements. DETAILED DESCRIPTION

[0057] The following examples can make those skilled in the art more fully understand the present application, but are not limited to the present application; the test methods described in the following examples are all conventional methods unless otherwise specified; and the reagents and materials described in the following examples can be obtained from commercial channels unless otherwise specified.

[0058] Example 1

[0059] In a 100-ton converter, 115 tons of molten iron from a blast furnace was directly charged into the 100-ton converter, accounting for 100% of the total charge. The molten iron composition was: C 4.2%, Si 0.45%, Mn 0.50%, P 0.12%, S 0.045%, and the temperature was 1320°C. Within 2 minutes and 30 seconds of starting the converter blowing, 31 Kg / ton of steel limestone lump ore, 12 Kg / ton of steel dolomite fine ore, and 8 Kg / ton of steel sludge pellets were added. The low gun position was operated, the temperature was quickly raised, and the limestone and dolomite were quickly decomposed and melted into slag. Then the gun position was raised, the ferrous oxide content in the slag was increased, and the slag fluidity and dephosphorization capacity were enhanced. At 6 minutes of converter blowing, 12 Kg / ton of steel limestone and 8 Kg / ton of steel dolomite were added again, and the gun position was lowered to promote carbon oxidation. At 8 minutes of blowing, 50% of the Mn target content in the high-strength anti-vibration steel bar HRB640E was added, which contained 42.1% of pre-treated manganese oxide pellets (manganese in manganese ore was reduced into steel water at a recovery rate of 85%), and 8% of carbon content. The V and Nb target content was 40%, and the V and Nb pre-reduced ore (V or Nb reduced into steel water at a recovery rate of 95%) was added. Among them, the vanadium pre-reduced ore was vanadium oxide pellets with a vanadium content of 51.8% and an internal carbon content of 6.6%, and the niobium pre-reduced ore was niobium oxide pellets with a niobium content of 52.1% and an internal carbon content of 6.2%. The converter bottom blowing gas was switched to hydrogen, and the bottom blowing intensity was 0.10 Nm 3 / t.min; low-high-low-high oxygen lance position control method was adopted for blowing, and the converter blowing was controlled at low gun position for 2-3 minutes, and then the gun position was raised for 2-3 minutes. The converter blowing was controlled at low gun position for 3-4 minutes, and then the gun position was raised for 2-3 minutes. The final slag parameters were controlled: the final slag binary basicity R=2.56, MgO=7.3%, TFe=8.9%, the converter steel final composition was: C=0.125%, P=0.031%, S=0.032%, and the steel temperature was: 1647°C, the tapping amount was 110 tons.

[0060] In the converter tapping process, according to the end-point molten steel composition of the steelmaking furnace, especially the end-point carbon or oxygen content, the metal aluminum cake and aluminum manganese are determined as deoxidizers before tapping, 1 / 2 of the total amount of deoxidizers is added when the steel stream is seen, and the remaining deoxidizers are added when the tapping is 1 / 4; according to the composition of the end-point molten steel, the content of manganese, vanadium or niobium in the finished steel is controlled according to the lower limit of the target value, the pretreated manganese oxide pellets containing 42.1% manganese and 8% carbon are added before tapping; the vanadium oxide pellets containing 51.8% vanadium and 6.6% carbon are added; the niobium oxide pellets containing 52.1% niobium and 6.2% carbon are added; and the silicon iron, silicon manganese alloy, metal silicon and metal manganese are used to adjust the silicon and manganese content in the steel; the vanadium-nitrogen alloy, niobium-iron alloy, rare earth-nitrogen alloy and the like are added until 4 / 5 of the tapping is completed, so as to adjust the content of vanadium, niobium, rare earth and nitrogen in the molten steel, wherein the rare earth-nitrogen alloy is quantitatively added at 0.68 Kg / ton of steel, containing lanthanum, praseodymium, neodymium, scandium and yttrium rare earth elements, the total content of rare earth elements is 3.16%, and the nitrogen content is 28.2%; lime is added during the tapping process, the amount of lime added is 1.5 Kg / ton of steel, the amount of SiC as reducing slag material is 1.3 Kg / ton of steel, and the amount of solvent fluorite is 0.8 Kg / ton, the steel slag is mixed and stirred to form the LF refining ladle top slag. The molten steel is stirred by bottom argon blowing in the ladle during the tapping process.

[0061] In the LF refining process, 3.5 Kg / ton of lime, 1.2 Kg / ton of calcium aluminate pre-melted slag and 0.5 Kg / ton of slag modifier are added, high-power power transmission is used for 3 minutes to make the top slag uniform, the top slag binary basicity is controlled between 1.8 and 2.0, and hydrogen gas is blown at the bottom of the ladle for stirring, the blowing intensity is 0.25 m 3 / t.min; according to the foaming condition of the ladle top slag, 1.2-1.5 Kg / ton of foaming slag and 1.2 Kg / ton of reducing slag are added to the molten steel, medium-power power transmission is used for 15-16 minutes to form white foam slag, the thickness of the foam white slag layer is controlled at 100-150 mm, the foam slag lasts for 8-9 minutes, and hydrogen gas is blown at the bottom of the ladle for stirring, the blowing intensity is 0.2-0.25 m 3 / t.min; power is cut off, sampling and temperature measurement are carried out, alloys containing C, Si, Mn, V, Nb, N and RE elements are added according to the composition of the molten steel and the target composition value of the finished steel, and the content of alloying elements in the molten steel is controlled in a narrow range; low-power power transmission is used for 2-4 minutes in the later stage of refining, the molten steel in the ladle is softly blown with argon gas for 5-6 minutes under the condition of full coverage of top slag foaming, the steel temperature is 1568℃, the composition is C 0.245%, Si 0.73%, Mn 1.32%, V 0.091%, Nb 0.021%, N 0.028%, and RE 0.0018%.

[0062] The continuous casting is started with the temperature of the molten steel in the tundish being 1513°C, the superheat of the molten steel being 13°C, the casting speed being 3.8 m / min, the relative weak cooling being adopted in the mold, the strong cooling being adopted in the secondary cooling zone, the mold not being subjected to electromagnetic stirring, the electromagnetic stirring being adopted at the solidification end, the casting blank being straightened at 950-960°C, and the hot blank being directly hot charged into the rolling heating furnace.

[0063] The hot blank is charged into the rolling heating furnace, the temperature of the casting blank entering the heating furnace being 650-670°C; the blank is heated to 1150-1160°C within 50-60 min; the blank is kept at 1180-1190°C for 50-60 min, and the rolling starting temperature is 1070-1080°C; the reduction of each pass is reasonably distributed according to the cross-sectional size of the casting blank, and the 12 mm reinforcing bar is obtained after 18-stand continuous rolling, and the large reduction is adopted in the last two stands, accounting for 22% of the total reduction; after the reinforcing bar comes out of the last stand, the water quenching (strong cooling) + gas mist controlled cooling (weak cooling recovery) is carried out to ensure that the temperature of the reinforcing bar on the cooling bed is 940-950°C, and the diameter of the reinforcing bar is 12 mm. After the reinforcing bar is naturally aged for 30 days, the performance indexes of the reinforcing bar are: yield strength ReL = 682 MPa, tensile strength Rm = 878 MPa, maximum force total elongation Agt = 11.1%, cross-sectional reduction A = 19.2%, Rm / ReL = 1.287, and 1.066, meeting the requirement of ≤1.30, the reinforcing bar is not defective in cold bending, and the microstructure of the reinforcing bar is ferrite + pearlite.

[0064] Comparative Example 1

[0065] Compared with Example 1, except that the bottom blowing gas is not switched to bottom blowing hydrogen or natural gas during the converter or LF refining process, and other steps and process control parameters are similar, the obtained reinforcing bar has the composition of C 0.245%, Si 0.73%, Mn 1.26%, V 0.078%, Nb 0.016%, N 0.028%, and RE 0.0017%. After the reinforcing bar is naturally aged for 30 days, the performance indexes of the reinforcing bar are: yield strength ReL = 596 MPa, tensile strength Rm = 766 MPa, maximum force total elongation Agt = 12.3%, cross-sectional reduction A = 22.6%, Rm / ReL = 1.285, and 0.931, meeting the requirement of ≤1.30, and the reinforcing bar is not defective in cold bending. Obviously, Rel does not meet the standard requirement of Rel≥640Mpa.

[0066] Example 2

[0067] The preparation process of this example is completely the same as that of Example 1, and the difference is that:

[0068] 1) A 120 ton converter is used for smelting, 20 tons of scrap steel and 110 tons of molten iron from blast furnace are respectively charged into the 120 ton converter, the molten iron accounts for 84.62% of the total charge, the composition of the molten iron is: C 4.0%, Si 0.38%, Mn 0.42%, P 0.116%, S 0.042%, temperature 1340°C, within 3 minutes of starting the blowing of the converter, 39 Kg / ton of limestone fine size ore, 8.5 Kg / ton of dolomite small size ore, 8 Kg / ton of dust are added; at the 8th minute of the blowing of the converter, 10 Kg / ton of limestone fine size ore and 10 Kg / ton of dolomite ore are added again, and the lance is lowered to promote the oxidation of carbon; at the 10th minute of the blowing, according to 50% of the target content of Mn in the high-strength anti-vibration steel bar HRB640E, the pre-processed manganese oxide pellets containing 44.5% of Mn and 7.5% of carbon are added, and according to 50% of the target content of V and Nb, the pre-reduced ore containing V and Nb is added, wherein the vanadium pre-reduced ore is the vanadium oxide pellets containing 54.6% of vanadium and 6.0% of carbon, and the niobium pre-reduced ore is the niobium oxide pellets containing 54.3% of niobium and 5.8% of carbon; the bottom blowing gas of the converter is switched to hydrogen, the bottom blowing intensity is 0.12 Nm 3 / t.min; the final slag parameters are controlled as follows: binary basicity R=2.75, MgO=8.2%, TFe=8.1%, the final composition of the converter steel is: C=0.14%, P=0.035%, S=0.035%, the temperature of the molten steel is: 1641°C, and the tapping amount is 125 tons.

[0069] 2) The deoxidizer is silicon aluminum barium and metal calcium, according to the composition of the final molten steel, the content of manganese, vanadium or niobium in the finished steel is according to the lower limit of the target value, the pre-processed manganese oxide pellets containing 44.5% of Mn and 7.5% of carbon are added; the vanadium oxide pellets containing 54.6% of vanadium and 6.0% of carbon are added; the niobium oxide pellets containing 54.3% of niobium and 5.8% of carbon are added; the micro-nitrogen alloy is quantitatively added according to 0.73 Kg / ton of steel, containing multiple rare earth elements of cerium, neodymium, samarium and holmium, the total content of rare earth elements is 7.36%, and the nitrogen content is 37.32%; during the tapping process, lime is added, the amount is 2.0 Kg / ton of steel, the amount of SiC as the reducing slag material is 1.0 Kg / ton of steel, the amount of fluorite as the solvent is 1.0 Kg / ton, the steel and slag are mixed and washed to form the top slag of the LF refining ladle.

[0070] 3) During the LF refining process, lime 3.0 Kg / ton of steel, calcium aluminate pre-melted slag 1.5 Kg / ton of steel, slag modifier 1.5 Kg / ton of steel are added, high-power power transmission is used for 4 minutes to make the top slag melt uniformly, to ensure that the binary basicity of the ladle top slag is controlled between 2.2-2.4, at the same time, the ladle is stirred by blowing hydrogen gas, the blowing intensity is 0.20 m 3t.min; according to the foaming condition of the ladle top slag, 1.5-2.0 Kg / ton of steel of foaming slag and 1.5 Kg / ton of steel of reducing slag are added into the molten steel, 16-18 minutes of medium power power supply is adopted, white foam slag is formed, the thickness of the foam white slag layer is controlled to be 200-300 mm, the foam slag lasts for 8-9 minutes, and the ladle is blown with hydrogen gas for stirring, the blowing intensity is 0.2-0.25 m 3 t.min; power is cut off, sampling and temperature measurement are performed, alloy elements containing C, Si, Mn, V, Nb, N, RE and the like are added according to the composition of the molten steel and the target composition of the finished steel, the content of alloy elements in the molten steel is controlled in a narrow range; in the later stage of refining, 2-4 minutes of low power power supply is adopted, 5-6 minutes of soft argon blowing is performed on the molten steel in the ladle under the condition of full coverage of the foaming of the top slag, the temperature of the molten steel is 1568℃, the composition is C 0.245%, Si 0.73%, Mn 1.32%, V 0.091%, Nb 0.021%, N 0.028%, and RE 0.0018%.

[0071] 4) When continuous casting is started, the temperature of the molten steel in the tundish is 1518℃, the superheat of the molten steel is 18℃, the casting and strand drawing rate is 3.5 m / min, the crystallizer cooling adopts relatively weak cooling, the secondary cooling adopts strong cooling process, the crystallizer does not use electromagnetic stirring, the electromagnetic stirring is performed at the solidification end, the cast blank is drawn and straightened at 970-980℃, and the cross-sectional size of the cast blank is 150X150 mm, and the hot blank is directly hot sent to the rolling heating furnace.

[0072] The hot blank is sent to the rolling heating furnace, the temperature of the cast blank entering the heating furnace is 930-950℃; the steel blank is heated to 1180-1200℃ within 50-60 min; the temperature is kept at 1180-1190℃ for 50-60 min, and the rolling start temperature is 1080-1100℃; according to the cross-sectional size of the cast blank, the reduction amount of each pass is reasonably distributed, 40 mm of steel bar is obtained after 16 rack continuous rolling, and it is ensured that the last 2 racks are rolled with large reduction, accounting for 27% of the total reduction; after the steel bar exits the last rack, it is subjected to water penetration (strong cooling) + gas mist controlled cooling (weak cooling recovery), so as to ensure that the temperature of the steel bar on the cooling bed is 910-930℃, and the diameter of the steel bar is 40 mm. After the steel bar is naturally aged for 30 days, the performance index of the steel bar is: yield strength ReL=676 MPa, tensile strength Rm=869 MPa, maximum total elongation Agt=10.8%, Rm / ReL=1.286, and the yield ratio is 1.056, which meets the requirement of ≤1.30, and there is no defect in cold bending. The microstructure of the steel bar is ferrite + pearlite.

[0073] Comparative Example 2

[0074] Compared with the embodiment 2, except that the rare earth nitrogen alloy is not added, the other steps and process control parameters are similar, the composition of the obtained reinforcing bar is: C 0.243%, Si 0.75%, Mn 1.31%, V 0.092%, Nb 0.020%, N 0.0151%, RE trace, almost zero. After the reinforcing bar is naturally aged for 30 days, the performance index of the reinforcing bar is: yield strength ReL = 603 MPa, tensile strength Rm = 761 MPa, maximum force total elongation Agt = 11.7%, reduction of area A = 23.1%, Rm / ReL = 1.262, 0.942, which meets the requirement of ≤1.30, and there is no defect in cold bending. Obviously, Rel does not meet the standard requirement of Rel≥640MPa. The reason is that under the condition of the same material consumption and similar process parameters, the nitrogen content is low and the rare earth alloy element content is trace, which causes that there is almost no rare earth carbonitride precipitate in the rolling and cooling process after rolling, so that the performance of the reinforcing bar is greatly reduced and cannot meet the performance index requirement of the reinforcing bar.

[0075] Embodiment 3

[0076] In a converter with a nominal capacity of 150 tons, 35 tons of scrap steel and 140 tons of blast furnace molten iron are respectively charged into the converter with a nominal capacity of 150 tons, and the molten iron accounts for 80% of the total charge. The composition of the molten iron is: C 4.30%, Si 0.37%, Mn 0.45%, P 0.121%, S 0.045%, and the temperature is 1350℃. When the converter starts blowing for 1.5 minutes, 30 Kg / ton of limestone powder shaped ore, 6 Kg / ton of dolomite lump ore, and 8 Kg / ton of iron oxide scale are added. The low gun position operation quickly raises the temperature and promotes the rapid decomposition of limestone and dolomite into slag; then the gun position is raised, the ferrous oxide content in the slag is increased, the slag fluidity and dephosphorization capacity are enhanced, and within 8 minutes of converter blowing, 9 Kg / ton of limestone powder shaped ore and 9 Kg / ton of dolomite lump ore are added again, and the gun position is lowered to promote carbon oxidation; at the blowing time of 9 minutes, according to the 50% of the target content of Mn in the high-strength anti-seismic reinforcing bar HRB640E, 48.2% of manganese-containing solid-state pre-reduced manganese oxide pellets are added, 40% of the target content of V and Nb, 56.12% of vanadium-containing solid-state pre-reduced vanadium oxide pellets, and 57.43% of niobium-containing solid-state pre-reduced niobium oxide pellets are added. The converter bottom blowing gas is switched to natural gas, and the bottom blowing intensity is 0.11 Nm 3t / min; the low-high-low-high oxygen lance position control method was adopted for blowing, and the low lance position was operated for 1.5-2 minutes in the first 0-5 minutes of the converter blowing, and the lance position was increased by 3-4 minutes; the low lance position was controlled for 3.5-5 minutes in the 5-12 minutes of the converter blowing, and then the lance position was increased by 2.5-3.5 minutes; the final slag parameters were controlled as follows: the binary basicity R=2.80, MgO=7.8%, and TFe=8.5%; the end point composition of the converter molten steel was as follows: C=0.16%, P=0.032%, and S=0.033%; and the molten steel temperature was 1645°C, and the tapping amount was 168 tons.

[0077] The steel-cored aluminum and carbon powder were added as deoxidizers in the early stage of tapping, 1 / 2 of the total amount of the deoxidizers was added when the molten steel was seen, and the remaining deoxidizers were added when 1 / 4 of the molten steel was tapped; according to the composition of the end point molten steel, the contents of manganese, vanadium or niobium in the finished steel were added in the early stage of tapping, and the contents of the deoxidizers were as follows: the content of the solid-state pre-reduced manganese oxide pellets was 48.2%, the content of the solid-state pre-reduced vanadium oxide pellets was 56.12%, and the content of the solid-state pre-reduced niobium oxide pellets was 57.43%; and the contents of silicon, manganese in the steel were adjusted by adding ferrosilicon, silicon-manganese alloy, calcium-silicon, metallic silicon and metallic manganese, and the contents of vanadium and nitrogen in the steel were adjusted by adding vanadium-nitrogen alloy, niobium-iron alloy and micro-nitrogen alloy until 4 / 5 of the molten steel was tapped; wherein the rare earth-nitrogen alloy was added in a fixed amount of 0.66 Kg / ton of steel, and contained praseodymium, neodymium, gadolinium, holmium and scandium, and the total content of the rare earth elements was 11.47% and the nitrogen content was 32.18%; lime was added during the tapping process, and the addition amount was 1.8 Kg / ton of steel, and the reduction slagging material SiC was 1.5 Kg / ton of steel, and the solvent fluorite was 1.2 Kg / ton, and the molten steel and slag were mixed and stirred to form the LF refining ladle top slag. The molten steel was stirred by bottom blowing natural gas during the tapping process.

[0078] During the LF refining process, lime was added at 4.0 Kg / ton of steel, calcium aluminate pre-melted slag was added at 1.0 Kg / ton of steel, and slag modifier was added at 1.0 Kg / ton of steel, high-power power supply was adopted for 5 minutes to make the top slag melt uniformly, and the binary basicity of the ladle top slag was controlled between 2.0-2.2, and the ladle was stirred by bottom blowing natural gas, and the blowing intensity was 0.30-0.35 m 3 / t.min; according to the foaming condition of the ladle top slag, foaming slag was added to the molten steel at 1.5 Kg / ton of steel, and reduction slag was added at 2 Kg / ton of steel, medium-power power supply was adopted for 15-17 minutes to form white foam slag, the thickness of the foaming white slag layer was controlled between 240-280 mm, the foaming slag lasted for 10-12 minutes, and the ladle was stirred by bottom blowing hydrogen gas, and the blowing intensity was 0.30-0.35 m 3 / min; power off, sampling, temperature measurement, adding alloy containing C, Si, Mn, V, Nb, N and RE elements according to the composition of the molten steel and the target composition of the finished steel, narrow-range regulation of the content of alloying elements in the molten steel; in the late refining stage, low-power power feeding is adopted for 10-12 minutes, under the condition of maintaining the foaming full coverage of the top slag, soft argon blowing is carried out on the molten steel in the ladle for 7-8 minutes, the temperature of the molten steel is 1579°C when it leaves the station, the first furnace is tundished in the tundish, the composition is C=0.271%, Si 0.63%, Mn 1.15%, V 0.11%, Nb 0.018%, N 0.0298%, and RE 0.0012%.

[0079] When continuous casting is started, the temperature of the molten steel in the tundish is 1525°C, the superheat of the molten steel is 25°C, the casting speed is 3.2 m / min, the crystallizer cooling adopts relatively weak cooling, the secondary cooling adopts strong cooling process, the crystallizer does not use electromagnetic stirring, the electromagnetic stirring is carried out at the solidification end, the casting blank is straightened at 960-970°C, and the cross-sectional size of the casting blank is 150X150 mm.

[0080] The hot blank is sent to the rolling heating furnace, the temperature of the casting blank entering the heating furnace is 810-830°C; the blank is heated to 1160-1180°C within 50-60 min; the temperature is kept at 1180-1190°C for 50-60 min, and the rolling temperature is 1070-1090°C; according to the cross-sectional size of the casting blank, the reduction amount of each pass is reasonably distributed, and after 18 racks of continuous rolling, a 20 mm reinforcing bar is obtained, and it is ensured that the last two racks are rolled with large reduction, accounting for 28% of the total reduction; after the reinforcing bar leaves the last rack, it is subjected to water penetration (strong cooling) + gas mist controlled cooling (weak cooling recovery), so as to ensure that the temperature of the reinforcing bar on the cooling bed is 920-940°C, the diameter of the reinforcing bar is 20 mm, the reinforcing bar is three-cut rolled, and after 30 days of natural aging, the performance index of the reinforcing bar is: yield strength ReL=668 MPa, tensile strength Rm=858 MPa, maximum total elongation Agt=11.6%, Rm / ReL=1.284, A=22.3%, and the ratio of yield strength to tensile strength is 1.044, which meets the requirement of ≤1.30, and the reinforcing bar is free of defects. The microstructure of the reinforcing bar is ferrite+pearlite;

[0081] Comparative Example 3: Compared with Example 3, the converter bottom blowing gas is switched to natural gas, and the bottom blowing intensity is 0.05 Nm 3 / min (the bottom blowing range of the converter in the application is 0.10-0.15 Nm 3The composition of the steel bar is: C 0.270%, Si 0.61%, Mn 1.08%, V 0.091%, Nb 0.015%, N 0.0278%, and RE 0.0011. After the steel bar is naturally aged for 30 days, the performance index of the steel bar is: yield strength ReL = 621 MPa, tensile strength Rm = 778 MPa, maximum total elongation rate Agt = 11.8%, Rm / ReL = 1.252, and the area reduction rate A = 21.3%. The yield ratio is 0.97, which meets the requirement of ≤1.30, and the steel bar has no defect in cold bending. The microstructure of the steel bar is ferrite + pearlite. Obviously, the performance of the steel bar is lowered due to the reduction of Mn, V and Nb oxides caused by the decrease of the bottom blowing intensity, and the inclusions in the steel are increased due to the incomplete reduction of the oxides, which causes the performance of the steel bar to be lower than the standard requirement.

[0082] Example 4

[0083] In a 100-ton converter, 50 tons of scrap steel and 50 tons of blast furnace molten iron are respectively charged into a 100-ton converter, and the molten iron accounts for 50% of the total charge. The composition of the molten iron is: C 4.50%, Si 0.51%, Mn 0.48%, P 0.171%, S 0.042%, and the temperature is 1410°C. Within 1.0 minutes of starting the blowing of the converter, 25 Kg / ton of limestone powder shaped into small balls, 6 Kg / ton of dolomite lumps, and 6 Kg / ton of iron ore are added. The low gun position is operated, the temperature is quickly raised, and the limestone and dolomite are quickly decomposed and melted into slag. Then the gun position is raised, the ferrous oxide content in the slag is increased, the slag fluidity and dephosphorization capacity are enhanced, and within 7 minutes of the blowing of the converter, 10 Kg / ton of limestone powder shaped into small balls and 10 Kg / ton of dolomite lumps are added, and the gun position is lowered to promote the oxidation of carbon. At the 10-minute blowing, 40% of the V and Nb target content, i.e. 57.7% of vanadium content, 58.2% of niobium content, and 47.9% of manganese content in the solid-state pre-reduced manganese oxide pellets are added. The bottom blowing gas of the converter is switched to natural gas, and the bottom blowing intensity is 0.15 Nm 3t / min; the low-high-low-high oxygen lance position control method was adopted for blowing, and the low lance position was operated for 1-2.5 minutes in the first 0-5 minutes of the converter blowing, and the lance position was raised for 3.5-4 minutes; the low lance position was controlled for 4-5 minutes in the 5-12 minutes of the converter blowing, and then the lance position was appropriately raised for 3-3.5 minutes; the final slag parameters were controlled as follows: the final slag binary basicity R=2.68, MgO=7.3%, and TFe=8.8%; the final composition of the converter molten steel was as follows: C=0.175%, P=0.035%, and S=0.036%; the molten steel temperature was 1635°C; and the tapping amount was 95 tons.

[0084] The steel-cored aluminum and carbon powder were added as deoxidizers in the early stage of tapping, 1 / 2 of the total amount of the deoxidizers was added when the molten steel was seen, and the remaining deoxidizers were added when 1 / 4 of the molten steel was tapped; according to the composition of the final molten steel, the contents of manganese, vanadium or niobium in the finished steel were added in the early stage of tapping, and the contents of the deoxidizers were as follows: the content of the solid-state pre-reduced manganese oxide pellets containing 47.9% of manganese, the content of the solid-state pre-reduced vanadium oxide pellets containing 57.7% of vanadium, and the content of the solid-state pre-reduced niobium oxide pellets containing 58.2% of niobium; and the contents of silicon, manganese in the steel were adjusted by adding ferrosilicon, silicon-manganese alloy, calcium-silicon, metallic silicon and metallic manganese, and the contents of vanadium and nitrogen were adjusted by adding vanadium-nitrogen alloy, niobium-iron alloy and rare earth-nitrogen alloy until 4 / 5 of the molten steel was tapped; the rare earth-nitrogen alloy was quantitatively added at 0.71 Kg / ton of steel, and contained praseodymium, neodymium, gadolinium, holmium and scandium, the total content of the rare earth elements was 6.23%, and the nitrogen content was 26.11%; lime was added during the tapping process, the addition amount was 1.5 Kg / ton of steel, the amount of SiC as the reducing slag material was 1.0 Kg / ton of steel, and the amount of fluorite as the solvent was 1.3 Kg / ton of steel, the molten steel and slag were mixed and stirred to form the LF refining ladle top slag. The molten steel was stirred by bottom blowing natural gas during the tapping process.

[0085] During the LF refining process, lime was added at 5.8 Kg / ton of steel, calcium aluminate pre-melted slag was added at 1.0 Kg / ton of steel, and slag modifier was added at 0.5 Kg / ton of steel, high-power power supply was adopted for 6 minutes to make the top slag melt uniformly, to ensure that the binary basicity of the ladle top slag was controlled between 2.4-2.5, and the ladle was stirred by bottom blowing natural gas, the blowing intensity was 0.50 m 3 / t.min; according to the foaming condition of the ladle top slag, foaming slag was added to the molten steel at 2.5 Kg / ton of steel, and reducing slag was added at 2.5 Kg / ton of steel, medium-power power supply was adopted for 15-17 minutes, white foam slag was formed in 14-15 minutes, the thickness of the foaming white slag layer was controlled at 260-310 mm, the foaming slag lasted for 12-14 minutes, and the ladle was stirred by bottom blowing hydrogen gas, the blowing intensity was 0.25-0.30 m 3 / min; power off, sampling, temperature measurement, adding alloy containing C, Si, Mn, V, Nb, N and RE elements according to the composition of the molten steel and the target composition of the finished steel, narrow range control of the alloy element content of the molten steel; in the late refining stage, low power is supplied for 10-12 minutes, and the molten steel in the ladle is soft-blow argon for 6-8 minutes under the condition of maintaining the foaming full coverage of the top slag, the temperature of the molten steel is 1573°C when leaving the station, the composition of the first furnace tapping in the tundish is C 0.263%, Si 0.28%, Mn 1.41%, V 0.146%, Nb 0.011%, N 0.026%, and RE 0.0045%.

[0086] When the continuous casting is started, the temperature of the molten steel in the tundish is 1520°C, the superheat of the molten steel is 20°C, the casting speed is 3.3 m / min, the crystallizer cooling adopts relatively weak cooling, the secondary cooling adopts strong cooling process, the crystallizer does not use electromagnetic stirring, the electromagnetic stirring is performed at the solidification end, the casting blank is straightened at 990-1000°C, and the cross-sectional size of the casting blank is 150X150 mm.

[0087] The hot blank is sent to the rolling heating furnace, the temperature of the casting blank entering the heating furnace is 780-800°C; the blank is heated to 1170-1190°C within 50-60 min; the temperature is kept at 1180-1190°C for 50-60 min, and the rolling temperature is 1070-1090°C; according to the cross-sectional size of the casting blank, the reduction amount of each pass is reasonably distributed, and after 18 racks of continuous rolling, a 25 mm steel bar is obtained, and it is ensured that the last two racks are rolled with large reduction, accounting for 29% of the total reduction; after the steel bar leaves the last rack, it is subjected to water penetration (strong cooling) + gas mist controlled cooling (weak cooling recovery), so as to ensure that the temperature of the steel bar on the cooling bed is 930-950°C, the diameter of the steel bar is 25 mm, the steel bar is three-cut rolled, and after 30 days of natural aging, the performance index of the steel bar is: yield strength ReL=673 MPa, tensile strength Rm=865 MPa, maximum total elongation Agt=11.3%, Rm / ReL=1.285, and the yield ratio is 1.052, which meets the requirement of ≤1.30, and the steel bar is free of defects. The microstructure of the steel bar is ferrite + pearlite;

[0088] Example 5

[0089] The steelmaking is carried out in a converter with a nominal capacity of 180 tons, 25 tons of scrap and 165 tons of molten iron from blast furnace are respectively charged into the converter with a nominal capacity of 180 tons, the molten iron accounts for 86.8% of the total charge, the composition of the molten iron is: C 4.16%, Si 0.49%, Mn 0.40%, P 0.121%, S 0.047%, the temperature is 1390℃, within 2.0 minutes of starting blowing in the converter, 35 Kg / ton of limestone powder shaped into small ball ore, 8 Kg / ton of dolomite lump ore, 9 Kg / ton of iron ore are added, the low gun position operation is adopted, the temperature is quickly raised and the limestone and dolomite are quickly decomposed and melted into slag; then the gun position is appropriately raised, the content of ferrous oxide in the slag is increased, the slag fluidity and dephosphorization capacity are enhanced, within 7 minutes of blowing in the converter, 9 Kg / ton of limestone powder shaped into small ball ore and 8.5 Kg / ton of dolomite lump ore are further added, and the gun position is lowered to promote the oxidation of carbon; before 9 minutes of blowing, according to 50% of the target content of Mn in the high-strength anti-vibration steel bar HRB640E, the manganese ore containing 48.1% of manganese is added, according to 40% of the value of the target content of V and Nb, the vanadium oxide pellet with a vanadium content of 55.6% and the niobium oxide pellet with a niobium content of 55.7% in solid state pre-reduction are added; and the converter bottom blowing gas is switched to natural gas, the bottom blowing intensity is 0.13 Nm 3 / t.min; the low-high-low-high oxygen lance position control method is adopted for blowing, within 0-5 minutes of blowing in the converter, the low gun position operation is adopted for 1.5-2.0 minutes, the gun position is raised for 3.0-3.5 minutes; within 5-12 minutes of blowing in the converter, the low gun position control is adopted for 4.5-5.5 minutes, and then the gun position is appropriately raised for 2.5-3.0 minutes; the final slag parameters are controlled: the final slag binary basicity R=2.78, MgO=7.5%, TFe=8.9%, the final composition of the molten steel is: C=0.15%, P=0.034%, S=0.032%, the molten steel temperature is 1590℃, and the tapping amount is 182 tons.

[0090] In the converter tapping process, according to the end-point molten steel composition of the steelmaking furnace, especially the end-point carbon or oxygen content, the silicon aluminum barium and calcium carbide are determined as the deoxidizer added before the early tapping stage, 1 / 2 of the total amount of deoxidizer is added when the steel stream is seen, and the remaining deoxidizer is added when the tapping is 1 / 4; according to the composition of the end-point molten steel, the content of manganese, vanadium or niobium in the finished steel is controlled according to the lower limit of the target value, the manganese-containing is added to the early tapping stage, the manganese-containing is 48.1%, the manganese ore; the vanadium content is 55.6%, the solid-state pre-reduced vanadium oxide pellets; the niobium content is 55.7%, the solid-state pre-reduced niobium oxide pellets; and the silicon iron, silicon manganese, manganese iron, metal silicon and metal manganese are used to adjust the silicon and manganese content in the steel, the vanadium-nitrogen alloy, the niobium-iron alloy, the micro-nitrogen alloy and the like are added until the tapping is 4 / 5, so as to adjust the content of vanadium, niobium, rare earth and nitrogen in the molten steel; wherein the rare earth-nitrogen alloy is quantitatively added according to 0.73 Kg / ton of steel, containing cerium, neodymium, samarium, gadolinium, holmium and other rare earths, the total content is 8.46%, and the nitrogen content is 21.23%; lime is added during the tapping process, the amount is 2.1 Kg / ton of steel, the amount of reduced slag-making material metal aluminum powder is 0.8 Kg / ton of steel, and the amount of solvent fluorite is 1.0 Kg / ton, the steel slag is mixed and stirred to form the LF refining ladle top slag. The molten steel is stirred by blowing hydrogen gas at the bottom of the ladle during the tapping process.

[0091] In the LF refining process, 4.8 Kg / ton of lime, 2.0 Kg / ton of calcium aluminate pre-melted slag and 1.5 Kg / ton of slag modifier are added, high-power power transmission of 5.5 minutes is adopted to make the top slag uniform, the top slag binary basicity of the ladle is controlled between 2.3-2.4, and the hydrogen gas is blown at the bottom of the ladle for stirring, the blowing intensity is 0.40 m 3 / t.min; according to the foaming condition of the top slag of the ladle, 2.0 Kg / ton of foaming slag and 3.0 Kg / ton of reducing slag are added to the molten steel, the middle-power power transmission of 13-14 minutes is adopted to make white foam slag, the thickness of the white foam slag layer is controlled between 340-390 mm, the white foam slag lasts for 10-12 minutes, and the hydrogen gas is blown at the bottom of the ladle for stirring, the blowing intensity is 0.35-0.40 m3 / t.min; the power is stopped, sampling and temperature measurement are carried out, and the alloys containing C, Si, Mn, V, Nb, N and RE elements are added according to the composition of the molten steel and the target composition of the finished steel, so as to control the content of alloy elements in the molten steel in a narrow range; low-power power transmission of 6-8 minutes is adopted in the late refining stage, the molten steel in the ladle is softly blown with argon gas for 6-8 minutes under the condition of full coverage of the top slag foaming, the temperature of the molten steel is 1569℃, the composition C=0.273%, Si 0.45%, Mn 1.24%, V 0.116%, Nb 0.015%, N 0.028%, and RE 0.0036%.

[0092] The temperature of the molten steel in the tundish is 1516°C, the superheat of the molten steel is about 16°C, the casting speed is 3.7 m / min, the relative weak cooling is adopted in the mold, the strong cooling is adopted in the secondary cooling zone, the mold is not subjected to electromagnetic stirring, the electromagnetic stirring is adopted at the solidification end, the casting blank is subjected to straightening at 960-970°C, the cross-sectional size of the casting blank is 150X150 mm, and the hot blank is directly sent to the rolling heating furnace.

[0093] The hot blank is sent to the rolling heating furnace, the temperature of the casting blank entering the heating furnace is 680-700°C, the blank is heated to 1170-1190°C within 50-60 min, the temperature is kept at 1180-1190°C for 50-60 min, the rolling temperature is 1070-1080°C, the reduction of each pass is reasonably distributed according to the cross-sectional size of the casting blank, the 16 mm reinforcing steel bar is obtained after 17-stand continuous rolling, the large reduction is adopted in the last two stands, accounting for 24% of the total reduction, the reinforcing steel bar is subjected to water quenching (strong cooling) + gas mist controlled cooling (weak cooling recovery) after leaving the last stand, the temperature of the reinforcing steel bar on the cooling bed is 910-930°C, the diameter of the reinforcing steel bar is 16 mm, the reinforcing steel bar is subjected to three-cut rolling, the performance indexes of the reinforcing steel bar after 30-day natural aging are as follows: yield strength ReL = 672 MPa, tensile strength Rm = 861 MPa, maximum total elongation Agt = 11.9%, Rm / ReL = 1.281, the yield-tensile ratio is 1.05, which meets the requirement of ≤1.30, and the reinforcing steel bar is not defective in cold bending. The microstructure of the reinforcing steel bar is ferrite + pearlite;

[0094] Example 6

[0095] In a 200 ton converter, 30 tons of scrap and 190 tons of molten iron from blast furnace were charged into the 200 ton converter, the molten iron accounted for 86.36% of the total charge, the composition of the molten iron was: C 4.21%, Si 0.46%, Mn 0.45%, P 0.141%, S 0.041%, temperature 1420℃, within 2.5 minutes of starting the blowing of the converter, 32 Kg / ton of limestone ore, 11 Kg / ton of small particle dolomite ore, 6 Kg / ton of iron ore and 1.0 Kg / ton of fluorite were added, low lance position operation, rapid temperature rise and promote the rapid decomposition of limestone and dolomite, melt into slag; then appropriately increase the lance position, increase the ferrous oxide content in the slag, enhance the slag fluidity and dephosphorization capacity, within 8 minutes of the blowing of the converter, 10 Kg / ton of limestone ore and 9 Kg / ton of small particle dolomite ore were added again, and the lance position was lowered to promote the oxidation of carbon; before 10 minutes of blowing, according to 50% of the target content of Mn in the high-strength anti-vibration steel bar HRB640E, 42.8% manganese ore containing manganese was added, 40% of the target content of V and Nb was added, 56.6% vanadium oxide pellets and 54.3% niobium oxide pellets were added, and the bottom blowing gas of the converter was switched to hydrogen, the bottom blowing intensity was 0.14 Nm 3 / t.min; low-high-low-high oxygen lance position control method was adopted for blowing, the converter was blown for 0-5 minutes with low lance position operation for 2.0-2.5 minutes, the lance position was raised for 2.5-3.0 minutes; the converter was blown for 5-12 minutes with low lance position control for 4.0-5.0 minutes, then the lance position was raised for 2.0-3.0 minutes; the final slag parameters were controlled: binary basicity R=2.8, MgO=8.8%, TFe=11.8%, the final composition of the converter steel was: C=0.13%, P=0.037%, S=0.038%, the steel temperature was 1621℃, and the tapping amount was 212 tons.

[0096] In the converter tapping process, according to the end-point molten steel composition of the steelmaking furnace, especially the end-point carbon or oxygen content, aluminum manganese and metal carbon are determined as deoxidizers to be added before the early tapping stage, 1 / 2 of the total amount of deoxidizers is added when the steel stream is seen, and the remaining deoxidizers are added when the tapping is 1 / 4; according to the composition of the end-point molten steel, the content of manganese, vanadium or niobium in the finished steel is controlled at the lower limit of the target value, manganese-containing manganese ore with a manganese content of 42.8% is added before the early tapping stage; vanadium oxide pellets with a vanadium content of 56.6% and niobium oxide pellets with a niobium content of 54.3% are added; silicon carbide, silicon manganese, manganese iron, metal silicon or metal manganese are added to adjust the silicon and manganese content in the steel, vanadium-nitrogen alloy, niobium-iron alloy, micro-nitrogen alloy, etc. are added until 4 / 5 of the tapping is completed, so as to adjust the content of vanadium, niobium, rare earth and nitrogen in the molten steel; among them, the rare earth-nitrogen alloy is quantitatively added at 0.67 Kg / ton of steel, containing lanthanum, praseodymium, holmium, thulium and other rare earths, with a total content of 5.38% and a nitrogen content of 28.36%; during the tapping process, lime is added at a rate of 1.3 Kg / ton of steel, and the amount of reduced slagging material metal aluminum powder is 1.1 Kg / ton of steel, and the amount of solvent fluorite is 0.8 Kg / ton, which is mixed and stirred to form the LF refining ladle top slag. During the tapping process, the ladle is bottom-blown with hydrogen gas to stir the molten steel.

[0097] During the LF refining process, 3.9 Kg / ton of lime, 1.3 Kg / ton of calcium aluminate pre-melted slag and 1.2 Kg / ton of slag modifier are added, high-power power transmission is used for 4 minutes to make the top slag uniform, and the top slag binary basicity of the ladle is controlled between 2.2 and 2.3, at the same time, the ladle is bottom-blown with hydrogen gas for stirring, the blowing intensity is 0.38 m 3 3 / t.min; according to the foaming condition of the ladle top slag, 2.5 Kg / ton of foaming slag and 2.5 Kg / ton of reducing slag are added to the molten steel, medium-power power transmission is used for 11-13 minutes to form white foam slag, the thickness of the foam white slag layer is controlled at 180-200 mm, the foam slag lasts for 11-13 minutes, at the same time, the ladle is bottom-blown with hydrogen gas for stirring, the blowing intensity is 0.30-0.35 m3 / t.min; power is stopped, sampling and temperature measurement are carried out, according to the composition of the molten steel and the target composition of the finished steel, alloys containing C, Si, Mn, V, Nb, N, RE and other elements are added to control the content of alloying elements in the molten steel within a narrow range; low-power power transmission is used for 4-6 minutes in the later stage of refining, under the condition of keeping the top slag foaming and full coverage, the molten steel in the ladle is soft-blown with argon gas for 7-8 minutes, the steel temperature is 1566℃, the composition C=0.268%, Si 0.56%, Mn 1.34%, V 0.126%, Nb 0.012%, N 0.024%, RE 0.0028%.

[0098] At the beginning of continuous casting, the temperature of molten steel in tundish is 1515℃, the superheat of molten steel is 15℃, the casting speed is 3.3m / min, the relative weak cooling is adopted in mold, the strong cooling is adopted in secondary cooling zone, the mold is not stirred by electromagnetic stirring, the electromagnetic stirring is adopted at the end of solidification, the casting blank is straightened at 970-980℃, the cross section size of casting blank is 150X150mm, and the hot blank is directly sent to rolling heating furnace.

[0099] The hot blank is sent to rolling heating furnace, the temperature of casting blank entering the heating furnace is 730-750℃, the blank is heated to 1190-1200℃ within 50-60min, the blank is kept at 1180-1190℃ for 50-60min, the rolling temperature is 1080-1090℃, the reduction of each pass is reasonably distributed according to the cross section size of casting blank, the 32mm reinforcing steel bar is obtained after 18-stand continuous rolling, and the large reduction is adopted at the last two stands, which accounts for 22% of the total reduction, the reinforcing steel bar is water cooled (strong cooling) + air mist controlled cooling (weak cooling recovery) after leaving the last stand, the temperature of reinforcing steel bar on cooling bed is 910-930℃, the diameter of reinforcing steel bar is 32mm, the reinforcing steel bar is rolled in single line, the performance indexes of reinforcing steel bar after 30-day natural aging are as follows: yield strength ReL=665MPa, tensile strength Rm=856MPa, maximum total elongation Agt=11.5%, Rm / ReL=1.287, and 1.039, which meets the requirement of ≤1.30, and the reinforcing steel bar is not defective in cold bending. The microstructure of reinforcing steel bar is ferrite+pearlite.

Claims

1. A rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar, characterized in that: The steel bar comprises the following chemical components and alloy components: C 0.24-0.28%, Si 0.20-0.75%, Mn 1.1-1.45%, V 0.09-0.15%, Nb 0.01-0.025%, N 0.02-0.03% and RE 0.0010-0.005%, and the balance is Fe; The preparation process of the rare earth carbonitride precipitation strengthening high-strength hot-rolled anti-seismic HRB640E steel bar is as follows: raw materials including blast furnace molten iron are added into a converter, limestone and dolomite as raw ore or physical processing treated raw ore are added into the converter as basic slag materials during the converter smelting process, the converter is treated for dephosphorization, desiliconization, desulfurization and impurity removal, and decarburization and oxidation of phosphorus and silicon elements in the molten iron are carried out by blowing oxygen; after the above treatment, oxides containing alloy elements accounting for 40-60% of the target mass content of alloy elements Mn, V and / or Nb of the steel bar are added respectively, and the converter bottom blowing gas is converted into reducing gas, and the bottom blowing intensity is 0.10-0.15 Nm 3 / t.min; the binary basicity of the converter final slag is controlled to be 2.5-2.8, and the converter endpoint molten steel temperature is controlled to be 1590-1650 DEG C; before and during tapping, the oxides containing alloy elements and the alloys for adjusting the composition content of the steel bar are added according to the lower limit of the target mass content of alloy elements in the steel bar, and a deoxidizer is added during tapping for molten steel deoxidation and alloying; the molten steel after tapping is transported to the LF refining, a slagging agent or a reducing agent is added, and the ladle bottom blowing reducing gas is used for stirring, and the blowing intensity is 0.2-0.5 Nm 3 / t.min, the binary basicity of the ladle top slag is controlled to be 1.8-2.5, and the remaining target alloy elements are added for fine adjustment, so that the molten steel composition reaches the target composition requirement of the steel bar, and after the refining is finished, various different specifications of steel bars are cast and heated by continuous casting billets and billet rolling, and the steel bars are obtained.

2. The rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar according to claim 1, characterized in that: The steel bar has a yield strength of greater than or equal to 640 MPa, a tensile strength of greater than or equal to 820 MPa, a maximum total elongation of greater than or equal to 10%, a ratio of tensile strength to yield strength of greater than or equal to 1.27, a ratio of yield strength to tensile strength of less than or equal to 1.30, no cold bending defects, and a microstructure of ferrite and pearlite.

3. The rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar according to claim 1, characterized in that: The raw material further comprises scrap steel, and the addition amount of the scrap steel accounts for 0-50% of the total Fe loading amount; the reducing gas is hydrogen and / or natural gas; within 2-3 minutes from the start of oxygen blowing in the converter, 24-40 kg / ton of steel of limestone crude ore, 6-12 kg / ton of steel of dolomite crude ore, and 6-10 kg / ton of steel of a slag-making solvent are added into the converter; at 6-8 minutes of oxygen blowing in the converter, 10-12 kg / ton of steel of limestone and 8-10 kg / ton of steel of dolomite are added; at 8-10 minutes of blowing in the converter, oxides containing alloy elements are further added; the mass content of MgO in the final slag at the end of the converter is 7-9%, and the mass content of TFe is 8-12%; the composition of the converter molten steel at the end point is: C 0.12-0.18%, P≤0.035%, S≤0.035%, in terms of mass content; and the temperature at the end point of the converter is 1590-1650℃.

4. The rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar according to claim 1 or 3, characterized in that: The mass content of metallic manganese in the manganese oxide is not less than 40%; the manganese oxide is selected from one or a combination of manganese-containing pre-reduced manganese ore, including carbon-internal-matched manganese pellets, solid-state reduced manganese pellets, and high-grade manganese ore; the mass content of metallic vanadium in the vanadium oxide is not less than 50%; the vanadium oxide is selected from one or a combination of vanadium-containing pre-reduced vanadium oxide, including carbon-internal-matched vanadium oxide pellets and solid-state reduced vanadium oxide pellets; the mass content of metallic niobium in the niobium oxide is not less than 45%; the niobium oxide is selected from one or a combination of niobium-containing pre-reduced niobium oxide, including carbon-internal-matched niobium oxide pellets and solid-state reduced niobium oxide pellets; a slag-making solvent is further added in the process of slag making, dephosphorization, desiliconization, desulfurization and impurity removal in the converter, and the slag-making solvent is selected from at least one of dust ash, sludge, iron oxide scale, iron ore or sintered ore and fluorite; the top-blown oxygen is controlled by a low-high-low-high oxygen lance position control method for blowing.

5. The rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar according to claim 4, characterized in that: The deoxidizer at the time of converter tapping is determined according to the final composition of the molten steel at the end point of the steelmaking furnace Point carbon or oxygen content, determine the amount of deoxidizer required to add; the total amount of deoxidizer added in the initial stage of tapping is 1 / 3~1 / 2, the remaining deoxidizer is added when the tapping weight reaches 1 / 4; before the converter tapping, until the tapping weight is 4 / 5, the oxide containing alloying elements and the alloy for adjusting the composition of the reinforcing bar are added, the alloy for adjusting the composition of the reinforcing bar is selected from ferrosilicon, silicon manganese alloy, vanadium nitrogen alloy, niobium iron alloy, rare earth nitrogen alloy, rare earth micro-nitrogen alloy; the addition amount of the rare earth nitrogen alloy or rare earth micro-nitrogen alloy is 0.65~0.75kg / ton of steel.

6. The rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar according to claim 5, characterized in that: The deoxidizer is at least one of aluminum, steel-cored aluminum, silicon aluminum barium alloy, aluminum manganese alloy, or at least one of silicon carbide, ferrosilicon, silicon manganese, metallic silicon and silicon calcium, or one of carbon, calcium, calcium carbide and calcium iron; the rare earth nitrogen alloy and / or micro-nitrogen alloy contains at least one of lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, holmium, thulium, scandium and yttrium nitrogen alloy, and the nitrogen content is 20~38%; lime, reducing slag material and slag forming solvent are also added during tapping to mix and flush the steel slag, and LF refining is used to form the ladle top slag; inert or reducing gas is used to stir the molten steel in the ladle during tapping; the inert gas is argon or nitrogen, and the reducing gas is hydrogen or natural gas.

7. The rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar according to claim 1, characterized in that: During the LF refining process, the addition amount of lime is 3.0~6.0Kg / ton of steel, the addition amount of calcium aluminate pre-melted slag is 1~2Kg / ton of steel, and the addition amount of slag modifier is 0.5~1.5Kg / ton of steel; according to the foaming condition of the ladle top slag, 1~3Kg / ton of steel of foaming slag and 1~4Kg / ton of steel of reducing slag are added to the molten steel, a medium power power supply is used for 12~18 minutes to form white foam slag, the thickness of the foam white slag layer is controlled to be 100~400mm, the foam slag lasts for 8~16 minutes, and the molten steel is stirred by blowing reducing gas hydrogen and / or natural gas at the bottom of the ladle; according to the composition of the molten steel and the target composition value of the finished steel, alloys containing C, Si, Mn, V, Nb, N and RE elements are added to control the content of alloying elements in the molten steel within a narrow range; under the condition of full coverage of the top slag foaming, the molten steel in the ladle is soft-blown with argon for 5~8min; after the refining is completed, the temperature of the molten steel is 1560~1580℃, the composition C is 0.24~0.28%, the composition Si is 0.20~0.75%, the composition Mn is 1.10~1.45%, the composition V is 0.09~0.15%, the composition Nb is 0.01~0.025%, the composition N is 0.022~0.030%, and the composition RE is 0.0010~0.0050%.

8. The rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar according to claim 1, characterized in that: The process of continuous casting billet casting is as follows: the superheat of the molten steel is controlled to be 10~15℃, the casting and drawing rate is 3.0~4.0m / min, the crystallizer cooling adopts relatively weak cooling, the secondary cooling adopts strong cooling process, the crystallizer does not use electromagnetic stirring, the electromagnetic stirring is carried out at the solidification end, the casting billet is drawn and straightened at 950~1000℃, the cross-sectional size of the casting billet is (150~170)X(150~170)mm, and the hot billet is directly hot sent to the rolling steel heating furnace.

9. The rare earth carbonitride precipitation strengthened high strength hot rolled anti-seismic HRB640E rebar according to claim 1, characterized in that: The process of the heating rolling is as follows: the hot billet is sent to a rolling heating furnace, the temperature of the billet entering the heating furnace is 650-950 DEG C, the billet is heated to 1150-1200 DEG C within 50-60 min, the temperature is kept for 50-60 min, the open rolling temperature is 1070-1100 DEG C, the 12-40 mm steel bar is obtained after 14-18 racks of continuous rolling, the last two racks of the total reduction is 20-30%, and the water quenching and weak cooling gas mist control cooling are carried out after the rolling; the temperature of the steel bar on the cooling bed is 910-950 DEG C.