CN112391569B

CN112391569B - Preparation method of 600MPa ultrahigh-strength anti-seismic steel bar

Info

Publication number: CN112391569B
Application number: CN202011096384.3A
Authority: CN
Inventors: 王光文; 唐名标; 熊科林; 涂文兴
Original assignee: Fujian Sanbao Steel Co Ltd
Current assignee: Fujian Sanbao Steel Co Ltd
Priority date: 2020-10-14
Filing date: 2020-10-14
Publication date: 2021-07-20
Anticipated expiration: 2040-10-14
Also published as: CN112391569A

Abstract

The preparation method of the ultrahigh-strength anti-seismic steel bar comprises the steps of adding alloy elements, continuously casting, hot rolling and cooling. The manufactured high-strength high-toughness steel bar has the following characteristics: 1) by controlling the process steps and parameters, the finished product of the almost all-pearlite structural form steel bar is obtained. The pearlite structure has uniform size, even distribution below 35 mu m and even distribution; 2) regulating and controlling the types and contents of alloy elements, matching with process parameters, and controlling the generation of non-chromium carbide which is uniformly distributed on ferrite between pearlite layers; 3) the finished product of the steel bar has excellent mechanical properties, the yield strength and the tensile strength of the steel bar exceed 600MPa, and meanwhile, the steel bar has high strength and toughness and ultrahigh seismic resistance.

Description

Preparation method of 600MPa ultrahigh-strength anti-seismic steel bar

Technical Field

The invention relates to a manufacturing process of a steel bar, in particular to a preparation method of a 600MPa ultrahigh-strength anti-seismic steel bar.

Background

The reinforcing steel bar is a basic material of modern buildings, is widely used for engineering construction of houses, bridges, roads and the like, and the service life and safety of concrete members are directly influenced by the performance of the reinforcing steel bar. At present, China is in the stage of high-speed urbanization development, real estate and capital facilities are developed vigorously, and the yield and consumption of reinforcing steel bars are the first in the world.

The technology for achieving the effects of energy conservation and emission reduction by increasing the strength and the corrosion resistance of the steel bar so as to reduce the steel consumption and prolong the service life is more and more concerned by metallurgy technologists and government industries. Before the 90 s in the 20 th century, high-strength steel bars have been used more in western europe, north america and japan, and the adoption of the high-strength and corrosion-resistant steel bars can obviously reduce the steel consumption and labor cost and obviously improve the engineering quality, thereby having good social and economic benefits. Along with the development of building towards high-rise and large-span structure direction and the demand of taking precautions against geological disasters, the building trade has proposed higher requirement to the intensity of reinforcing bar, and current high-strength reinforcement compares in traditional ordinary reinforcing bar, and it has better mechanical properties, can effectively guarantee engineering quality, simultaneously, also can reduce the use amount of reinforcing bar, is favorable to practicing thrift steel, reduces the cost of engineering goods and materials. The alloy elements and the content of the steel for the steel bar directly influence the mechanical property of the steel bar, but the existing steel bar has lower toughness and is easy to brittle failure.

CN109554613A discloses a production method of HRB500E high-strength aseismic steel bars, which comprises the following steps: manufacturing a steel billet, which comprises the following components: c: 0.20-0.25%, Si: 0.40-0.70%, Mn: 1.30-1.60%, P is less than or equal to 0.045%, S is less than or equal to 0.045%, V: 0.020-0.050%, N: 0.0050-0.0120 wt%, and Fe and inevitable impurities as the rest; the components have the same formula as components for producing HRB400 and HRB400E, and realize the multi-stage of one steel: namely the same chemical component formula, and can produce HRB500E and HRB400E by adjusting the rolling process. Therefore, a uniform production process can be adopted when raw materials are prepared and blanks are prepared, the production efficiency is favorably improved, the frequency of adjusting preparation parameters such as temperature and component proportion is reduced, the stability of products is improved, and the production efficiency is favorably improved.

CN103498104A A630 MPa-grade high-strength hot-rolled steel bar comprises the following chemical components in percentage by weight: c: 0.38-0.43%, Cr: 0.8 to 1.1%, Mn: 0.75-1.0%, Mo: 0.15-0.25%, Si: 0.15-0.3%, S: < 0.035%, P: < 0.035%, N: < 0.035%, the balance being Fe. The method comprises the following steps: (1) sending the smelted steel bars into a heating furnace to be heated to 1200 ℃ of-; a first cooling step: water cooling the reinforcing steel bar to 610-630 ℃ at the cooling rate of 15-17 ℃/s; a second cooling step: the method is characterized in that water cooling and air cooling are combined, the reinforcing steel bars are cooled to 350 ℃ at the cooling rate of 1-2 ℃/s by water cooling, then air cooling is carried out to 280 ℃ at 250 ℃ at the cooling rate of 3-5 ℃/s, then the reinforcing steel bars are cooled to 230 ℃ at 210 ℃ at the cooling rate of 3-5 ℃/s by water cooling, and finally air cooling is carried out to the room temperature; (2) the steel bar is hot-rolled to the required size, the hot rolling temperature is 1000-1200 ℃, and the steel bar is rapidly cooled to 600-630 ℃ through compressed air or atomized quenching liquid after hot rolling; (3) directly quenching the steel bars subjected to induction heating by using high-pressure spray water or quenching liquid without heat preservation, wherein the quenching cooling speed is 20-23 ℃/s, and the temperature of the steel bars is cooled to be 10-30 ℃ below the Ms point; (4) heating the quenched steel bar to 520-540 ℃ through a tempering heating furnace, and preserving heat for 15-18 seconds; (5) and cooling the tempered steel bar to room temperature. : the components of the invention are added with Cr: 0.8 to 1.1%, Mn: 0.75-1.0%, Mo: 0.15-0.25%, the method can improve the atomic activity of C and N elements, so that the air mass formed by each atom can form strong interaction with the dislocation, the dislocation is pinned, and a yield platform is generated, so that the dislocation can be started only by providing larger stress from the outside.

Although the prior art has many researches on high-strength steel bars, the prior art also has the defects of uncontrollable micro-structure inside the steel bars, complex preparation method, insufficient mechanical strength, incompatible high-strength and high-toughness and the like.

Disclosure of Invention

The technical problems to be solved by the invention include insufficient strength of the reinforcing steel bar, prevention of brittle fracture, avoidance of overlarge and uneven pearlite structure in the reinforcing steel bar and the like.

The strength of the steel bar is mainly determined by the internal structure and structure of the steel bar. It has been demonstrated that the uniformity of the pearlite structure and the grain size of the morphology play a critical role in the tensile strength of the steel reinforcement. The pearlite structure is a mixed type structure in steel, and is composed of proeutectoid ferrite and proeutectoid cementite (arranged in a lamellar manner). Theoretically, if the average block size of pearlite is controlled to be 35 μm or less, it is proved to provide a significant effect on the tensile strength of the steel bar.

In addition to size, the distribution of tissue morphology is also an important factor affecting the strength of the rebar. The more uniform the distribution of the pearlite structure in the steel bar, the greater the strength of the steel bar, because the more uniform the structure, the higher the chemical and physical stability of the system, and there will not be diffusion (causing unstable properties) caused by too large concentration difference and the phenomenon of 'cathode and anode' (corrosion) generated inside; meanwhile, the uniform structure can eliminate dislocation, holes and segregation phenomena (excessive borrowing, holes and segregation influence the toughness of the steel bar, and the possibility of brittle fracture is increased). In addition, in addition to the main form being pearlite, maintaining a certain proportion of non-pearlite structures, such as bainite, is also positive for strength.

More importantly, the inventor finds that specific carbide is formed in the steel by adding/supplementing specific alloy elements. By controlling the process, carbide is precipitated between pearlite sheet layers and preferentially attached to ferrite. The carbide structure of the pearlite layer can prevent dislocation and concentration diffusion movement. In the case of pearlite, the control of the thickness of the carbide attached to the ferrite layer also makes it possible to adjust the interlamellar spacing of ferrite and cementite in the pearlite and to enhance toughness. This organization results in increased resistance to the generation and propagation of microcracks, thereby improving strength, ductility, and toughness. In steel having a pearlite-based structure, the addition of alloy elements effective for controlling the composition range and the kind of elements can achieve both strength and toughness.

In order to achieve the purpose, the invention provides the following technical scheme:

a preparation method of a 600MPa ultrahigh-strength anti-seismic steel bar comprises the following steps:

s1: adding carbide with the mass fraction of 0.01-0.09% into molten steel which is smelted to form an alloy element, blowing argon gas at the bottom of the molten steel to roll the surface of the molten steel, controlling the flow of the argon gas according to the condition that the diameter of the exposed surface of the molten steel at a gas outlet point is less than or equal to 90mm, stirring for 5-10 min, and controlling the temperature in the whole process to be 1000-1100 ℃;

s2: pouring and continuously casting to obtain a casting blank; the continuous casting comprises the steps of heating uniformly in a range of 1100-1150 ℃ on a bar manufacturing line, and removing iron oxide scales on the surface of a billet by high-pressure water spraying before rolling;

s3: rolling the casting blank to obtain a steel bar, and cooling to obtain a finished product; the rolling process comprises the following steps: heating the casting blank to 950-1130 ℃ to heat the casting blank to roll the casting blank into a steel bar, cooling the steel bar at a cooling speed of not less than 15 ℃/s for 600-625 ℃ after obtaining the hot rolled steel bar, then staying at the temperature or in the middle for 40-60 seconds, then cooling the steel bar again to below 200 ℃ at a cooling speed of 8-15 ℃/s, and cooling the steel bar at room temperature to obtain a finished product;

the steel bar has the following structural form: in a cross section perpendicular to the longitudinal direction of the steel bar, a pearlite structure is uniformly distributed with an area ratio of 90% or more, and the remaining area of a non-pearlite structure is not more than 10%, the non-pearlite structure includes a carbide structure, and carbides formed by the alloy elements are dispersedly distributed on lamellar ferrite in pearlite.

The invention mainly controls the heating temperature in the process not to exceed 1100 ℃, and basically controls the bead size growth and the morphology distribution below the temperature, thereby preventing excessive growth of other tissues. Meanwhile, in the hot rolling stage of the casting blank, too low heating temperature can cause too large deformation resistance of rolling, and adverse effect is caused on the forming of the steel bar. In addition, the control of the cooling rate also restricts the size of pearlite to a greater extent. More importantly, the control of the temperature affects the formation and distribution of carbides. The temperature range and the heat preservation time are selected in the process stage of the invention to control the carbide to be precipitated and uniformly grown between pearlite sheet layers, and simultaneously, the carbide form can be furthest reserved in the cooling process.

In the above method for preparing the 600MPa ultrahigh-strength anti-seismic steel bar, preferably, the carbide forming elements are one or more of Nb, V and Mo.

Preferably, the smelting process of the molten steel comprises the following steps: the low-carbon low-chromium clean steel which is smelted in a converter or an electric furnace and subjected to vacuum treatment is used as a raw material, FeOx cored wires are fed into a molten steel tank in the vacuum treatment to increase oxygen, the oxygen increase amount in the molten steel is controlled to be 8-20 ppm, and the molten steel is stirred for 2-5 min by weak argon blowing.

Preferably, before the FeOx cored wire is fed for oxygenation treatment, the molten steel adopts the raw materials of which the components are, by weight, less than or equal to 0.03 percent of C, less than or equal to 10PPm of [ O ], less than or equal to 0.008 percent of P, less than or equal to 0.02 percent of Nb, less than or equal to 0.30 percent of Cu, less than or equal to 0.20 percent of Ni, less than or equal to 0.01 percent of Mo, less than or equal to 0.03 percent of V, less than or equal to 0.003 percent of S, less than or equal to 0.0008 percent of B, less than or equal to 0.20 percent of Cr, less than or equal to 0.007 percent of Al, less than or equal to 1.0 percent of Mn, less than or equal to 0.30 percent of Si, less than or equal to 0.02 percent of Ti, less than or equal to 5PPm of Mg, less than or equal to 5PPm of Ca, less than or equal to 60PPm of N, and the balance of Fe and inevitable impurity elements in the steel.

The preparation method of the 600MPa ultrahigh-strength anti-seismic reinforcing steel bar preferably controls [ H ] in the steel to be less than or equal to 2 PPm.

Preferably, the form of the added alloy is one of spherical, plate-shaped and linear.

Preferably, the non-pearlite structure further comprises 1-5% of bainite.

Preferably, in the pearlite structure, the average distance between ferrite and cementite is 50-100 nm.

The steel bar obtained by the technical scheme of the invention has the following technical effects:

1) by controlling the process steps and parameters, the finished product of the almost all-pearlite structural form steel bar is obtained. The pearlite structure has a uniform size, an average distribution of 35 μm or less, and a uniform distribution.

2) Regulating and controlling the types and contents of alloy elements, matching with process parameters, controlling the generation of non-chromium carbide, and uniformly distributing the non-chromium carbide on ferrite between pearlite layers.

3) The finished product of the steel bar has excellent mechanical properties, the yield strength and the tensile strength of the steel bar exceed 600MPa, and simultaneously, the steel bar has high strength and high toughness.

Drawings

Fig. 1 is an SEM photograph of a cross section of the sample reinforcing bar of example 1.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar modules or modules having the same or similar functionality throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The method adopts a production mode of a large-tonnage (100T) converter, LF furnace refining, RH furnace vacuum treatment and 250mm section casting machine to carry out billet smelting. The method comprises the following steps of smelting molten iron in a converter, wherein P is less than or equal to 0.110%, S is less than or equal to 0.010%, the temperature of the molten iron is more than or equal to 1300 ℃, deoxidizing is carried out by forming elements by weak oxides in the tapping process after smelting, and the tapping feeding sequence is as follows: active lime-manganese alloy-silicon alloy. The adding amount of the active lime is 350-450kg, and 30kg of calcium carbide is added during tapping. And (4) tapping is started until the tapping 3/4 is kept at argon full opening, then the flow is switched to a small flow, and the small flow is opened for 200L/min multiplied by 3-5 minutes after tapping. The temperature after the furnace is more than or equal to 1540 ℃. In the LF furnace treatment process, the white slag holding time is required to be more than or equal to 15min, and the components are adjusted to target components. During heating, the submerged arc operation is maintained, the micro-positive pressure state and the reducing atmosphere in the furnace are ensured, aluminum particles can be added for deoxidation, but the aluminum particles are gradually added for many times, the total Al content in the steel is controlled not to exceed 0.007%, and the FeO and MnO in the furnace slag after refining is controlled not to exceed 1.5%. And (5) performing Ti alloying treatment after LF (ladle furnace) is out of the station, and adjusting the titanium to a target range. RH processing vacuum pressure maintaining (less than or equal to 60Pa) time is more than or equal to 20min, fine adjustment is carried out on alloy components after the air is broken, and the components meet the requirements before FeOx cored wire feeding and oxygenation are ensured. After RH of the original molten steel is taken out of the station, 280 plus 340 meters of FeOx cored wires are fed, the oxygen increasing amount is 8-19PPm respectively, and after the wires are fed for oxygen increasing, weak argon blowing and stirring are carried out for 2-5 min, so that the increased oxygen is uniformly distributed in the steel.

The compositions of the molten steel raw materials obtained in the examples of the present invention before adding the carbide-forming alloy elements of the present invention after oxygen enrichment are shown in table 1:

TABLE 1

The balance of Fe and inevitable impurity elements in the steel.

Then according to the manufacturing method of the invention, alloy elements are added, and the high-strength and high-toughness steel bar is manufactured by continuous casting, hot rolling and cooling, and the process flow is as follows:

1) adding carbide alloy elements: feeding the alloy (in a ball, plate or wire shape), and controlling the total amount of the added alloy elements to be 100-500 PPm. And then, the argon is blown down and stirred immediately through the bottom of the tank, the flow of the argon is controlled according to the condition that the diameter (average diameter length) of the exposed surface of the molten steel at the gas outlet point is less than or equal to 80mm, the stirring time is 5-8 min, and the temperature is controlled at 1000-1100 ℃.

2) And after the carbide alloy elements are added, the mixture is poured on a continuous casting machine within 8-15 min, the superheat degree of a tundish is controlled to be 15-25 ℃, and the size of the cast blank is controlled. Soaking the obtained casting blank in a temperature range of 1150-1250 ℃, and then removing the iron oxide scale on the surface of the blank by high-pressure water spraying.

3) Rolling the casting blank at 950-1130 ℃ for more than 300 minutes in a furnace, removing the iron oxide scales on the surface of the billet by high-pressure water spraying before rolling, and controlling the rolling to the size of a finished product by a rough and fine stage. The accumulated reduction rate of the first stage of rolling is more than or equal to 50%, the rough rolling is carried out for 5-10 times, and the reduction rate of the second time is more than or equal to 15%. The cumulative reduction in the second stage of rolling was 50%. And after rolling, watering and cooling, cooling at a cooling speed of not less than 15 ℃/s for 600-625 ℃, then staying at the temperature for 40-60 s, then cooling again at a cooling speed of 8-15 ℃/s to below 200 ℃, and cooling at room temperature to obtain a finished product.

Example 1

1) Adding carbide alloy elements: feeding a V alloy wire with the feeding amount of 490 meters, and controlling the total amount of the added alloy elements to be 450 PPm. Then, argon is blown weakly at the bottom of the tank to stir, the flow of the argon is controlled according to the diameter (average diameter length) of 78mm of the exposed surface of the molten steel at the gas outlet point, the stirring time is 8min, and the temperature is controlled at 1100 ℃.

2) And after the carbide alloy elements are added, pouring on a continuous casting machine within 9min, controlling the superheat degree of a tundish to be 15-25 ℃, and controlling the size of a cast blank. The obtained casting blank is soaked in a temperature range of 1150 ℃, and the iron oxide scale on the surface of the blank is removed through high-pressure water spraying.

3) Rolling a casting blank: the rolling temperature interval is 1000 ℃, the furnace time is more than 300 minutes, the oxide scales on the surface of the billet are removed by high-pressure water spraying before rolling, and the rolling is controlled to the size of the finished product by the rough and fine stage. The accumulated reduction rate of the first stage of rolling is 60%, the reduction rate of the second stage of rough rolling is 30% after 7 times of rough rolling. The cumulative reduction in the second stage of rolling was 50%. After rolling, the steel is cooled by watering, cooled to 615 ℃ at a cooling rate of 20 ℃/second, then kept at the temperature for 40 seconds, cooled again to below 200 ℃ at a cooling rate of 15 ℃/second, and cooled at room temperature to obtain a finished product.

Fig. 1 is an SEM photograph of a cross section of the sample reinforcing bar of example 1, showing the structural morphology of the inside of the steel. In the cross section vertical to the longitudinal direction of the steel bar, pearlite structures are uniformly distributed and have an area ratio of more than 90%, the pearlite is composed of lamellar ferrite and cementite, carbide structures of alloy elements are precipitated on the lamellar ferrite, and the structures are favorable for enhancing the mechanical property of the steel bar.

Example 2

1) Adding carbide alloy elements: feeding Nb alloy wire with the feeding amount of 350 m, and controlling the total amount of the added alloy elements to be 340 PPm. Then, the mixture is immediately stirred by weakly blowing argon from the bottom of the tank, the flow of the argon is controlled according to the standard that the diameter (average diameter length) of the exposed surface of the molten steel at the gas outlet point is 69mm, the stirring time is 8min, and the temperature is controlled at 1050 ℃.

3) Rolling a casting blank: the rolling temperature range is 1100 ℃, the furnace time is more than 300 minutes, the oxide scales on the surface of the billet are removed by high-pressure water spraying before rolling, and the rolling is controlled to the size of the finished product by the rough and fine stage. The accumulated reduction rate of the first stage of rolling is 70%, the reduction rate of the second stage of rough rolling is 40% after 7 times of rough rolling. The cumulative reduction in the second stage of rolling was 50%. After rolling, the steel is cooled by watering, cooled to 623 ℃ at a cooling rate of 25 ℃/second, then kept at the temperature for 45 seconds, cooled again to below 200 ℃ at a cooling rate of 13 ℃/second, and cooled at room temperature to obtain a finished product.

In a cross section perpendicular to the longitudinal direction of the steel bar, the obtained sample has uniform distribution of a pearlite structure, the area proportion is more than 90%, the area of the rest non-pearlite structure is not more than 20%, the non-pearlite structure comprises a carbide structure, and carbides formed by the alloy elements are dispersedly distributed on lamellar ferrite in pearlite; carbide structure

Example 3

1) Adding carbide alloy elements: feeding Mo alloy wire with the feeding amount of 260 m, and controlling the total amount of the added alloy elements to be 220 PPm. Then, the mixture is immediately stirred by weakly blowing argon from the bottom of the tank, the flow of the argon is controlled according to the condition that the diameter (average diameter length) of the exposed surface of the molten steel at the gas outlet point is 80mm, the stirring time is 8min, and the temperature is controlled at 1100 ℃.

2) And after the carbide alloy elements are added, pouring on a continuous casting machine within 10min, controlling the superheat degree of a tundish to be 15-25 ℃, and controlling the size of a cast blank. The obtained casting blank is soaked in a temperature range of 1150 ℃, and the iron oxide scale on the surface of the blank is removed through high-pressure water spraying.

3) Rolling a casting blank: the rolling temperature interval is 980 ℃, the furnace time is more than 300 minutes, the oxide scales on the surface of the billet are removed by high-pressure water spraying before rolling, and the size of the finished product is controlled by the rough and fine stage rolling. The accumulated reduction rate of the first stage of rolling is 70%, the reduction rate of the second stage of rough rolling is 20% after 8 times of rough rolling. The cumulative reduction in the second stage of rolling was 50%. After rolling, the steel is cooled by watering, cooled to 605 ℃ at a cooling rate of 30 ℃/second, then kept at the temperature for 60 seconds, cooled again to below 200 ℃ at a cooling rate of 10 ℃/second, and cooled at room temperature to obtain a finished product.

Comparative example 1

The steel bar sample of the comparative example was produced by continuous casting, hot rolling and cooling of the molten steel after oxygen enrichment by melting without (addition of) alloying elements, and the process parameters and steps were the same as those of example 1.

Performance testing

The steel bar samples of examples and comparative examples were hot-rolled to form steel bar wires having a diameter of 5mm, and mechanical properties were measured at a predetermined temperature.

The cooled wire rods were used for microstructure observation and tensile strength test of the cross section of the steel bar. For the toughness test, the reinforcing bars of examples and comparative examples were cut to a standard length of 5m, mounted on an axial tensile strength testing machine, and subjected to single-headed drawing with a reduction of area per 1 pass of 16% to 20%. Then, the average value of the ultimate true strain after fracture is obtained, and the toughness index of the steel bar is reflected.

The mechanical properties of the inventive examples and comparative samples are listed in table 2. Compared with a comparative example of the same steel grade, the steel bar of the present invention provides excellent tensile strength, yield strength and elongation properties (toughness) without secondary heat treatment or working; the steel bar has the strength of over 600MPa and the deformation rate of nearly 20 percent, and achieves the aims of high strength and high toughness.

TABLE 2

Sample (I)	Yield strength MPa	Tensile strength MPa	Elongation at break%
				Example 1	648.4	837.3	18.4％
Example 2	657.6	839.1	19.1％
				Example 3	632.3	814.7	17.8％
Comparative example 1	439.9	742.5	16.9％

In the description herein, references to the description of "one embodiment," "another embodiment," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. A preparation method of a 600MPa ultrahigh-strength anti-seismic steel bar comprises the following steps:

s1: adding 0.01-0.09% of carbide to form an alloy element into molten steel which is smelted as a raw material, blowing argon gas at the bottom of the molten steel to roll the surface of the molten steel, controlling the flow of the argon gas according to the condition that the diameter of the exposed surface of the molten steel at a gas outlet point is less than or equal to 90mm, stirring for 5-10 min, and controlling the temperature in the whole process to be 1000-1100 ℃;

s2: pouring and continuously casting to obtain a casting blank; the continuous casting comprises the steps of uniformly heating at 1100-1150 ℃ on a bar manufacturing line, and removing iron oxide scales on the surface of a billet by high-pressure water spraying before rolling;

s3: rolling the casting blank to obtain a steel bar, and cooling to obtain a finished product; the rolling process comprises the following steps: heating the casting blank to 950-1130 ℃ to heat the casting blank to roll the casting blank into a steel bar, cooling the steel bar at a cooling speed of not less than 15 ℃/s for 600-625 ℃ after obtaining a hot rolled steel bar, then staying at the temperature for 40-60 seconds, cooling the steel bar again to below 200 ℃ at a cooling speed of 8-15 ℃/s, and cooling the steel bar at room temperature to obtain a finished product;

2. The method for preparing the 600MPa ultrahigh-strength anti-seismic steel bar according to claim 1, wherein the carbide forming elements are one or more of Nb, V and Mo.

3. The method for preparing the 600MPa ultrahigh-strength anti-seismic steel bar according to claim 1, wherein the molten steel smelting process comprises the following steps: the low-carbon low-chromium clean steel which is smelted in a converter or an electric furnace and subjected to vacuum treatment is used as a raw material, FeOx cored wires are fed into a molten steel tank in the vacuum treatment to increase oxygen, the oxygen increase amount in the molten steel is controlled to be 8-20 ppm, and the molten steel is stirred for 2-5 min by weak argon blowing.

4. The method for preparing 600MPa ultrahigh-strength anti-seismic steel bar according to claim 3, characterized in that the molten steel before being subjected to the FeOx cored wire oxygenation treatment comprises, by weight, not more than 0.03% of C, not more than 10PPm of [ O ], not more than 0.008% of P, not more than 0.02% of Nb, not more than 0.30% of Cu, not more than 0.20% of Ni, not more than 0.01% of Mo, not more than 0.03% of V, not more than 0.003% of S, not more than 0.0008% of B, not more than 0.20% of Cr, not more than 0.007% of Al, not more than 1.0% of Mn, not more than 0.30% of Si, not more than 0.02% of Ti, not more than 5PPm of Mg, not more than 5PPm of Ca, not more than 60PPm of N, and the balance Fe and inevitable impurity elements in steel.

5. The method for preparing the 600MPa ultrahigh-strength anti-seismic steel bar according to claim 1, wherein [ H ] in the steel is controlled to be less than or equal to 2 PPm.

6. The method for preparing the 600MPa ultrahigh-strength anti-seismic steel bar according to claim 1, wherein the form of the added alloy is one of spherical, plate-shaped and linear.

7. The method for preparing the 600MPa ultrahigh-strength anti-seismic steel bar according to claim 1, wherein the non-pearlite structure further comprises 1-5% by area of bainite.

8. The method for preparing the 600MPa ultrahigh-strength anti-seismic steel bar according to claim 1, wherein the average distance between ferrite and cementite in a pearlite structure is 50-100 nm.