CN111270126B - Niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar and production method thereof - Google Patents
Niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar and production method thereof Download PDFInfo
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Abstract
The invention provides a niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar and a production method thereof, belonging to the technical field of steel smelting, wherein the niobium-titanium-nitrogen microalloyed HRB400E steel bar comprises the following chemical components in percentage by mass: c: 0.21 to 0.25%, Si: 0.50 to 0.65%, Mn: 1.40-1.55%, P is less than or equal to 0.045%, S is less than or equal to 0.045%, Ti: 0.015 to 0.025%, Nb: 0.010-0.020%, N: 0.0070-0.0110%, and the balance Fe and other impurities; adding ferrosilicon, silicomanganese and carburant when tapping 1/4, and finishing adding all alloys when tapping 3/4; adding the titanium-nitrogen alloy in an argon blowing station, wherein the argon blowing time is more than or equal to 6 minutes; the continuous casting adopts high-drawing-speed casting powder, billet heating, rolling and cooling bed feeding, and finally the finished product is obtained. According to the invention, titanium-nitrogen-containing alloy is added at the exposed molten steel position of the argon blowing station, so that the titanium yield is improved; the influence of the contents of niobium and titanium on the quality of the high-pulling-speed continuous casting billet is reduced, so that titanium inclusion in the steel is reduced, the castability of molten steel meets the requirement, and the casting blank quality is improved by adopting the high-pulling-speed continuous casting covering slag.
Description
Technical Field
The invention relates to the technical field of steel smelting, in particular to a microalloyed HRB400E steel bar and a production method thereof.
Background
Niobium, vanadium and titanium are important microalloying elements, in the production process of HRB400E deformed steel bars, most steel mills use vanadium and niobium, and few steel mills use titanium, mainly because the titanium is active in nature and is very easy to react with elements such as oxygen, sulfur, nitrogen and the like in molten steel.
However, vanadium alloys are much more expensive than titanium alloys. Since 2018 and 7 months, the price of the vanadium-nitrogen alloy is continuously increased, and in the market price of the alloy in 10 months, the vanadium nitrogen is 79.8 ten thousand yuan/ton, the titanium nitrogen is 5 ten thousand yuan/ton, and the niobium-titanium-nitrogen alloy is 15 ten thousand yuan/ton. If the yield of titanium can be improved and the problem of titanium microalloying is solved, the vanadium alloy is replaced by titanium element, which saves a large amount of production cost.
Titanium is one of the chemically very active metal elements, it has very strong affinity with nitrogen, oxygen and carbon, and stronger affinity with sulfur than iron. Therefore, the titanium is easy to react with elements such as oxygen, sulfur, nitrogen and the like in the molten steel, and the yield of the titanium element is reduced. If the niobium-titanium-nitrogen composite alloy is added in the converter tapping process, the molten steel has strong oxidizability because of incomplete deoxidation, a large amount of titanium can be oxidized, and the yield is extremely low. During the addition, the titanium component can be stabilized only after the molten steel is deeply deoxidized.
Under the conditions that the quality of steel products is guaranteed to meet the national standard requirements, the yield strength is stable, and the production aging is not greatly influenced, if two alloys of titanium-nitrogen alloy and niobium-titanium-nitrogen alloy with low price can be adopted for simultaneous use, the vanadium-nitrogen alloy is completely replaced to produce the high-strength hot-rolled ribbed anti-seismic steel bar, and the method has extremely important significance for relieving the national shortage of vanadium resources and controlling the production cost of enterprises.
Disclosure of Invention
Aiming at the defects and shortcomings in the background technology, the invention provides a production method of niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bars, which can effectively improve the yield of titanium element under the condition of ensuring the quality of steel to reach the standard, does not influence the production efficiency, and achieves the effect of reducing the production cost of enterprises.
The second purpose of the invention is to provide the niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar, the components of the steel are scientifically and reasonably designed, the yield of titanium element can be improved under the condition of ensuring the quality standard of the steel, and the problems of high viscosity of continuous casting molten steel and continuous casting billet cracks can be solved.
In order to realize the purpose, the invention adopts the following technical scheme to realize the purpose:
a production method of niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bars comprises the working procedures of converter smelting, argon blowing, continuous casting, heating, rolling and cooling bed cooling, and the specific control conditions comprise:
(1) deoxidizing the molten steel by adopting a silicon-aluminum-barium and silicon-calcium-barium compound deoxidizer, and adding the deoxidizer into a steel ladle during tapping;
(2) adding ferrosilicon, silicomanganese and a carburant when tapping 1/4, and completely adding ferrosilicon, silicomanganese and a carburant alloy when tapping 3/4;
(3) after tapping, improving argon blowing pressure to expose molten steel on the liquid surface, putting the niobium-titanium-nitrogen alloy and the titanium-nitrogen alloy into the exposed molten steel blown by argon in an argon blowing station, and ensuring that the argon blowing time is more than or equal to 6 minutes and the molten steel components are uniform;
(4) feeding calcium silicate wires into an argon blowing station for calcification treatment, and then carrying out soft argon blowing for more than or equal to 3 minutes to homogenize the components of molten steel;
(5) the continuous casting tundish covering slag is alkaline covering slag, the continuous casting ladle and the tundish adopt a long nozzle for casting protection, the continuous casting adopts high-pulling-speed covering slag, and a crystallizer is started for electromagnetic stirring;
(6) and (3) conveying the billet into a heating furnace for heating, rolling and loading on a cooling bed to obtain a finished product.
Further measures taken are: and during converter operation, high-pulling carbon is adopted to improve the end point carbon, and the mass percentage content of the end point of tapping carbon is controlled to be 0.04-0.15%.
Further measures taken are: after deoxidation alloying in a converter, the oxygen content of molten steel entering an argon blowing station is reduced to below 50ppm, and then niobium-titanium-nitrogen alloy and titanium-nitrogen alloy are added.
Further measures taken are: when the converter is used for deoxidation, the addition amount of the silicon, aluminum and barium is 0.16-0.50 kg/t, and the addition amount of the silicon, calcium and barium is 0-0.50 kg/t.
Further measures taken are: the addition amount of the niobium-titanium-nitrogen alloy is 0.8kg/t, and the addition amount of the titanium-nitrogen alloy is 1.0 kg/t.
Further measures taken are: when tapping and slagging are carried out, the slagging amount is controlled to be below 50 mm.
Further measures taken are: the length of the calcium silicate wire fed by the argon blowing station is 100 m.
Further measures taken are: in the electromagnetic stirring of the crystallizer, the current is 320-350A, and the frequency is 5 Hz; the water distribution of the crystallizer is set to 165m3The water quantity of the secondary cooling section is set to be 40m3/h。
Further measures taken are: the temperature of the tundish molten steel is 1515-1535 ℃; the casting blank pulling speed is 3.8-4.1 m/min; the temperature of a soaking section during heating of the steel billet is 1050-1120 ℃; the initial rolling temperature is 1020-1050 ℃; the temperature of the cooling bed is 920-1000 ℃.
The invention also provides a niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar, which is characterized in that: in the steel bar with the diameter of 12 mm-22 mm, the chemical components of the steel bar comprise the following components in percentage by mass:
c: 0.21 to 0.24%, Si: 0.50 to 0.65%, Mn: 1.40-1.55%, P is less than or equal to 0.045%, S is less than or equal to 0.045%, Ti: 0.015 to 0.025%, Nb: 0.010-0.020%, N: 0.0070-0.0110%, and the balance Fe and other impurities.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, the converter end point is controlled to be 0.04-0.15% by improving the end point carbon, and silicon-calcium-barium and silicon-aluminum-barium are adopted for deoxidation, so that the oxygen content of HRB400E molten steel entering an argon blowing station is reduced to 50PPm, and the titanium alloy yield is favorably improved; and the slag discharging during the steel tapping of the converter is controlled to be less than 50mm, so that the reaction of oxidizing slag and titanium is reduced, the yield of the titanium alloy is further improved, the yield of the titanium reaches 50-74%, and the requirement of titanium micro-combination can be met.
(2) The invention adopts the design of low titanium and low niobium components, and the Ti: 0.015 to 0.025%, Nb: 0.010-0.020%, and microalloying the niobium-titanium-nitrogen and titanium-nitrogen composite alloy, thereby further reducing the influence of the content of niobium and titanium on the quality of the high-pulling-speed continuous casting billet, meeting the requirement of the continuous casting process, simultaneously reducing the content of niobium and titanium, reducing the titanium inclusion in the steel, and ensuring that the castability and the inclusion of molten steel meet the requirements.
(3) According to the invention, the niobium-titanium-nitrogen alloy and the titanium-nitrogen alloy are added in the argon blowing station by adjusting the adding mode of the steelmaking alloy, so that the yield of the titanium alloy is improved, and meanwhile, the exposed part of the molten steel is added, so that the yield of the titanium is more favorably improved; feeding 100m calcium silicate wire in an argon blowing station for calcification treatment, and keeping the soft argon blowing time for more than 3 minutes so as to ensure that the components of the molten steel are uniformly mixed; and the continuous casting ladle and the tundish adopt long nozzles to protect casting and prevent titanium from oxidation, thereby achieving the effect of simultaneously ensuring the titanium yield and the molten steel quality.
(4) According to the invention, the casting powder is continuously cast at a high drawing speed, the casting is protected by the long nozzle, the quality of the casting blank is improved, the control of continuous casting cooling is optimized, the water quantity is reduced by adopting weak cooling, the electromagnetic stirring of the continuous casting crystallizer is started to improve the quality of the steel blank, the influence of niobium and titanium on the thermoplasticity of the steel blank is avoided, and the problems of continuous casting leakage, casting blank square-off and the like easily caused by adding niobium-titanium alloy under the condition of high drawing speed are solved.
Detailed Description
In order to clearly understand the technical solutions adopted by the present invention, the following description is made on the preferred embodiments of the present invention, and it should be understood that the embodiments described herein are only used for illustrating and explaining the present invention, and are not used to limit the present invention.
Examples 1 to 36: the niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar comprises the following chemical components and percentages thereof in percentage by mass in steel bars with the diameter of 12 mm-22 mm, and the balance of Fe and other impurities.
Table 1: chemical component ratio table of steel material in each example
The niobium-titanium-nitrogen microalloyed HRB400E steel bar in the embodiment 1 to the embodiment 9 in the table 1 is prepared by the following production method, and comprises the working procedures of converter smelting, argon blowing, continuous casting, heating, rolling and cooling bed, and the specific control conditions comprise:
(1) during converter operation, high-pulling carbon is adopted to improve the end point carbon, and the end point of tapping carbon is controlled to be 0.04-0.05%; deoxidizing the molten steel by adopting a silicon-aluminum-barium and silicon-calcium-barium compound deoxidizer, wherein the adding amount of the silicon-aluminum-barium is 0.30-0.50 kg/t, and the adding amount of the silicon-calcium-barium is 0.30-0.50 kg/t, and adding the deoxidizer into a steel ladle during tapping;
(2) adding ferrosilicon, silicomanganese and a carburant when tapping 1/4, finishing adding all ferrosilicon, silicomanganese and carburant alloy when tapping 3/4, and controlling the slag discharge amount when tapping slag discharge to be below 50 mm;
(3) after tapping of the converter is finished, after the oxygen content of molten steel entering an argon blowing station is reduced to be below 50ppm, the argon blowing pressure is increased, the molten steel on the liquid surface is exposed, the niobium-titanium-nitrogen alloy is added into the exposed molten steel blown by argon according to the adding amount of 0.8kg/t and the titanium-nitrogen alloy is added into the exposed molten steel blown by the argon according to the adding amount of 1.0kg/t, and the argon blowing time is 6 minutes;
(4) feeding 100m calcium silicate wire into an argon blowing station for calcification treatment, and then carrying out soft argon blowing for 3 minutes to homogenize the components of molten steel;
(5) the continuous casting tundish covering slag is alkaline covering slag, the continuous casting ladle and the tundish are cast in a long-nozzle protective mode, and the temperature of tundish molten steel is 1515-1525 ℃; high-pulling-speed casting powder is adopted for continuous casting, the pulling speed of a casting blank is 4.0m/min, a crystallizer is started to carry out electromagnetic stirring, the current is 320-350A, the frequency is 5Hz, and the water distribution of the crystallizer is set to be 165m3The water quantity of the secondary cooling section is set to be 40m3/h；
(6) The billet steel is sent to a heating furnace for heating, and the temperature of a soaking section is 1050-1060 ℃; rolling at the initial rolling temperature of 1020 ℃; and (4) feeding the mixture to a cooling bed, wherein the temperature of the cooling bed is 920-960 ℃, and finally obtaining a finished product.
The niobium-titanium-nitrogen microalloyed HRB400E steel bars of examples 10 to 18 in the table 1 are prepared by the following production method, including converter smelting, argon blowing, continuous casting, heating, rolling and cooling bed cooling procedures, and the specific control conditions comprise:
(1) during converter operation, high carbon drawing is adopted to improve the end point carbon, and the tapping carbon end point is controlled to be 0.06-0.07%; deoxidizing the molten steel by adopting a silicon-aluminum-barium and silicon-calcium-barium compound deoxidizer, wherein the adding amount of the silicon-aluminum-barium is 0.35-0.40 kg/t, and the adding amount of the silicon-calcium-barium is 0.30-0.40 kg/t, and adding the deoxidizer into a steel ladle during tapping;
(2) adding ferrosilicon, silicomanganese and a carburant when tapping 1/4, finishing adding all alloys when tapping 3/4, and controlling the slag discharge amount when tapping slag to be below 50 mm;
(3) after tapping of the converter is finished, after the oxygen content of molten steel entering an argon blowing station is reduced to be below 50ppm, the argon blowing pressure is increased, the molten steel on the liquid surface is exposed, the niobium-titanium-nitrogen alloy is added into the exposed molten steel blown by argon according to the adding amount of 0.8kg/t and the titanium-nitrogen alloy is added into the exposed molten steel blown by the argon according to the adding amount of 1.0kg/t, and the argon blowing time is 7 minutes;
(4) feeding 100m calcium silicate wire into an argon blowing station for calcification treatment, and then carrying out soft argon blowing for 3 minutes to homogenize the components of molten steel;
(5) the continuous casting tundish covering slag is alkaline covering slag, the continuous casting ladle and the tundish are cast in a long-nozzle protective mode, and the temperature of tundish molten steel is 1526-1535 ℃; high-pulling-speed casting powder is adopted for continuous casting, the pulling speed of a casting blank is 3.8m/min, a crystallizer is started to carry out electromagnetic stirring, the current is 320-350A, the frequency is 5Hz, and the water distribution of the crystallizer is set to be 165m3The water quantity of the secondary cooling section is set to be 40m3/h；
(6) Conveying the steel billets to a heating furnace for heating, wherein the temperature of a soaking section is 1080-1090 ℃; rolling at the initial rolling temperature of 1030 ℃; and (4) putting the mixture on a cooling bed, wherein the temperature of the cooling bed is 960-1000 ℃, and finally obtaining a finished product.
The niobium-titanium-nitrogen microalloyed HRB400E steel bars of the embodiments 19 to 27 in the table 1 are prepared by the following production methods, including converter smelting, argon blowing, continuous casting, heating, rolling and cooling bed cooling procedures, and the specific control conditions comprise:
(1) during converter operation, high-pulling carbon is adopted to improve the end point carbon, and the end point of tapping carbon is controlled to be 0.08-0.12%; deoxidizing the molten steel by adopting a silicon-aluminum-barium and silicon-calcium-barium compound deoxidizer, wherein the adding amount of the silicon-aluminum-barium is 0.16-0.30 kg/t, and the adding amount of the silicon-calcium-barium is 0.10-0.30 kg/t, and adding the deoxidizer into a steel ladle during tapping;
(2) adding ferrosilicon, silicomanganese and a carburant when tapping 1/4, finishing adding all alloys when tapping 3/4, and controlling the slag discharge amount when tapping slag to be below 50 mm;
(3) after tapping of the converter is finished, after the oxygen content of molten steel entering an argon blowing station is reduced to be below 50ppm, the argon blowing pressure is increased, the molten steel on the liquid surface is exposed, the niobium-titanium-nitrogen alloy is added into the exposed molten steel blown by argon according to the adding amount of 0.8kg/t and the titanium-nitrogen alloy is added into the exposed molten steel blown by the argon according to the adding amount of 1.0kg/t, and the argon blowing time is 9 minutes;
(4) feeding 100m calcium silicate wire into an argon blowing station for calcification treatment, and then carrying out soft argon blowing for 3 minutes to homogenize the components of molten steel;
(5) the continuous casting tundish covering slag is alkaline covering slag, the continuous casting ladle and the tundish are cast in a long-nozzle protective mode, and the temperature of tundish molten steel is 1515-1525 ℃; high-pulling-speed casting powder is adopted for continuous casting, the pulling speed of a casting blank is 4.1m/min, a crystallizer is started to carry out electromagnetic stirring, the current is 320-350A, the frequency is 5Hz, and the water distribution of the crystallizer is set to be 165m3The water quantity of the secondary cooling section is set to be 40m3/h；
(6) The steel billet is sent to a heating furnace for heating, and the temperature of a soaking section is 1110-1120; rolling at the initial rolling temperature of 1050 ℃; and (4) feeding the mixture to a cooling bed, wherein the temperature of the cooling bed is 920-960 ℃, and finally obtaining a finished product.
The niobium-titanium-nitrogen microalloyed HRB400E steel bars in the embodiments 28 to 36 in the table 1 are prepared by the following production methods, including converter smelting, argon blowing, continuous casting, heating, rolling and cooling bed cooling, and the specific control conditions comprise:
(1) during converter operation, high-carbon-pulling is adopted to improve the end point carbon, and the end point of tapping carbon is controlled to be 0.13-0.15%; deoxidizing the molten steel by adopting a silicon-aluminum-barium and silicon-calcium-barium compound deoxidizer, wherein the adding amount of the silicon-aluminum-barium is 0.16-0.20 kg/t, and the adding amount of the silicon-calcium-barium is 0-0.16 kg/t, and adding the deoxidizer into a steel ladle during tapping;
(2) adding ferrosilicon, silicomanganese and a carburant when tapping 1/4, finishing adding all alloys when tapping 3/4, and controlling the slag discharge amount when tapping slag to be below 50 mm;
(3) after tapping of the converter is finished, after the oxygen content of molten steel entering an argon blowing station is reduced to be below 50ppm, the argon blowing pressure is increased, the molten steel on the liquid surface is exposed, the niobium-titanium-nitrogen alloy is added into the exposed molten steel blown by argon according to the adding amount of 0.8kg/t and the titanium-nitrogen alloy is added into the exposed molten steel blown by the argon according to the adding amount of 1.0kg/t, and the argon blowing time is 8 minutes;
(4) feeding 100m calcium silicate wire into an argon blowing station for calcification treatment, and then carrying out soft argon blowing for 3 minutes to homogenize the components of molten steel;
(5) the continuous casting tundish covering slag is alkaline covering slag, the continuous casting ladle and the tundish are cast in a long-nozzle protective mode, and the temperature of tundish molten steel is 1526-1535 ℃; high-pulling-speed casting powder is adopted for continuous casting, the pulling speed of a casting blank is 3.9m/min, a crystallizer is started to carry out electromagnetic stirring, the current is 320-350A, the frequency is 5Hz, and the water distribution of the crystallizer is set to be 165m3The water quantity of the secondary cooling section is set to be 40m3/h；
(6) Conveying the steel billet to a heating furnace for heating, wherein the temperature of a soaking section is 1090-1100 ℃; rolling at the initial rolling temperature of 1020-1050 ℃; and (4) putting the mixture on a cooling bed, wherein the temperature of the cooling bed is 960-1000 ℃, and finally obtaining a finished product.
The steel tapping amount and the Ti yield of each example were measured, and the results are shown in table 2 below; from the reinforcing steel bars with the finished product specification of 12 mm-22 mm obtained in the example, 2 samples are randomly selected from the reinforcing steel bars with each specification, named as sample 1 and sample 2 respectively, and mechanical property tests are performed respectively, and the experimental results are shown in the following table 3.
Table 2: actual measurement results of the steel output and yield in each example
Table 3: the actual measurement result of the mechanical test of the steel bar with the specification of 12 mm-22 mm
The invention adopts niobium-titanium-nitrogen alloy and titanium-nitrogen alloy for micro-alloying, and fully utilizes the fine grain strengthening and precipitation strengthening of niobium and titanium so as to improve the strength. In the aspect of component design, the components with low niobium and titanium are controlled, the quality of a casting blank is ensured under the condition of continuous casting and high drawing speed, and meanwhile, the niobium-titanium-nitrogen composite alloy contains a small amount of rare earth, so that the microalloying capacity is further improved.
In addition, the niobium-titanium-nitrogen alloy and the titanium-nitrogen alloy are added to the bare molten steel of the steel ladle blown by argon in the argon blowing station, so that the yield of titanium is improved and reaches 50-74 percent. Niobium-titanium-nitrogen alloy and titanium-nitrogen alloy are used, under the condition that the continuous casting drawing speed is up to 3.8-4.1min, the casting blank cracks and stripping are eliminated, HRB400E steel bars are successfully produced in batches, and a series of mechanical tests are passed. The results of tables 2 and 3 show that the mechanical properties of the steel completely meet the national standard requirements, the purpose of reducing the production cost under the condition of not influencing the quality of the steel is achieved, the problem of the current shortage of vanadium resources in China is solved, the supply and demand balance is realized early, and the method is a new production method worthy of popularization and application.
The above description is only for the purpose of illustrating the technical solutions of the present invention and not for the purpose of limiting the same, and other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the scope of the claims of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (6)
1. A production method of niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bars comprises the working procedures of converter smelting, argon blowing, continuous casting, heating, rolling and cooling bed cooling, and is characterized in that the specific control conditions comprise:
deoxidizing the molten steel by adopting a silicon-aluminum-barium and silicon-calcium-barium compound deoxidizer, and adding the deoxidizer into a steel ladle during tapping;
adding ferrosilicon, silicomanganese and a carburant when tapping 1/4, and completely adding ferrosilicon, silicomanganese and a carburant alloy when tapping 3/4;
after tapping, improving argon blowing pressure to expose molten steel on the liquid surface, putting the niobium-titanium-nitrogen alloy and the titanium-nitrogen alloy into the exposed molten steel blown by argon in an argon blowing station, and ensuring that the argon blowing time is more than or equal to 6 minutes and the molten steel components are uniform;
feeding calcium silicate wires into an argon blowing station for calcification treatment, and removing impurities when the argon is blown softly for more than or equal to 3 minutes;
the continuous casting tundish covering slag is alkaline covering slag, the continuous casting ladle and the tundish adopt a long nozzle for casting protection, the continuous casting adopts high-pulling-speed covering slag, and a crystallizer is started for electromagnetic stirring;
the billet is sent to a heating furnace for heating, rolling and loading on a cooling bed to obtain a finished product;
during converter operation, high-pulling carbon is adopted to improve the end point carbon, and the mass percentage content of the end point of the tapping carbon is controlled to be 0.04-0.15%;
after deoxidation alloying in a converter, after the oxygen content of molten steel entering an argon blowing station is reduced to below 50ppm, adding niobium-titanium-nitrogen alloy and titanium-nitrogen alloy;
the addition amount of the niobium-titanium-nitrogen alloy is 0.8kg/t, and the addition amount of the titanium-nitrogen alloy is 1.0kg/t;
in the steel bar with the diameter of 12 mm-22 mm, the chemical components of the steel bar comprise the following components in percentage by mass:
c: 0.21 to 0.24%, Si: 0.50 to 0.65%, Mn: 1.40-1.55%, P is less than or equal to 0.045%, S is less than or equal to 0.045%, Ti: 0.015 to 0.025%, Nb: 0.010-0.020%, N: 0.0070-0.0110%, and the balance Fe and other impurities.
2. The method for producing the niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar as claimed in claim 1, wherein: when the converter is used for deoxidation, the addition amount of the silicon, aluminum and barium is 0.16-0.5 kg/t, and the addition amount of the silicon, calcium and barium is 0-0.5 kg/t.
3. The method for producing the niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar as claimed in claim 1, wherein: when tapping and slagging are carried out, the slagging amount is controlled to be below 50 mm.
4. The method for producing the niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar as claimed in claim 1, wherein: the length of the calcium silicate wire fed by the argon blowing station is 100 m.
5. The method for producing the niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar as claimed in claim 1, wherein: in the electromagnetic stirring of the crystallizer, the current is 320-350A, and the frequency is 5 Hz; and water distribution of the crystallizer is carried out at 165 m/h, and water yield of the second cooling stage is carried out at 40 m/h.
6. The method for producing the niobium-titanium-nitrogen and titanium-nitrogen composite microalloyed HRB400E steel bar as claimed in claim 1, wherein: the temperature of the tundish molten steel is 1515-1535 ℃; the casting blank pulling speed is 3.8-4.1 m/min; the temperature of a soaking section during heating of the steel billet is 1050-1120 ℃; the initial rolling temperature is 1020-1050 ℃; the temperature of the cooling bed is 920-1000 ℃.
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