CN112111687A - Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bar and preparation method thereof - Google Patents
Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bar and preparation method thereof Download PDFInfo
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- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention discloses a Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bar and a preparation method thereof, belonging to the technical field of hot-rolled ribbed steel bars for reinforced concrete structures. The steel in the steel bar comprises, by weight, 0.22-0.28% of C, 0.60-0.80% of Si, 1.40-1.60% of Mn, less than or equal to 0.035% of P, less than or equal to 0.035% of S, 0.020-0.040% of Ti, and the balance of Fe and inevitable impurity elements. The invention combines Ti microalloying components with steel making and rolling processes, and the preparation process comprises converter smelting, LF ladle refining and continuous casting to 150mm2The steel billet and the heating furnace are heated and then rolled into the steel bar by the rolling mill, the mechanical property of the steel is improved by utilizing the principle that titanium is precipitated and strengthened in the steel and refined grains are strengthened, the 635 MPa-grade high-strength steel bar with high strength and high plasticity is produced on the premise of not reducing the ductility index, the yield strength of the prepared steel bar is more than or equal to 635MPa, the tensile strength is more than or equal to 795MPa, the elongation after fracture is more than or equal to 15 percent, and the requirements of markets and high-rise and large-span building structures on the 635 MPa-grade steel bar.
Description
Technical Field
The invention belongs to the technical field of hot-rolled ribbed steel bars for reinforced concrete structures, and particularly relates to 635 MPa-grade high-strength steel for hot-rolled ribbed steel bars and a preparation method thereof.
Background
The hot-rolled ribbed steel bar is widely applied to various reinforced concrete structures, and plays an important role in ensuring the service life and the use safety of reinforced concrete buildings. At present, 400MPa grade, HRB400 and HRB400E (E represents aseismic reinforcing steel bars) are commonly used in China, reinforcing steel bars for reinforced concrete structures in developed countries such as Europe and America mainly have 500MPa grade, and 600MPa grade also has certain application. In recent years, with the coming of a series of high-strength steel bar popularization and application policies in China, the percentage of the use amount of the high-strength steel bars with the strength level of 500MPa or above is increased year by year.
Compared with the reinforcing steel bars of 400MPa level, the 635MPa level high-strength reinforcing steel bars have higher strength and better comprehensive performance, can solve the problems of overweight beam columns, excessive beam column node reinforcing steel bars, difficult construction and the like of high-rise and large-span buildings, is an important novel energy-saving environment-friendly building material, and has important significance for the construction of resource-saving and environment-friendly society and the promotion of structural adjustment and transformation upgrading of the steel industry and the building industry. It can be predicted that 635MPa high-strength steel bars will be the development of market demand.
The patent document of Chinese patent application No. 201310444163.4 discloses 'a 630 MPa-grade high-strength hot-rolled steel bar and a production process thereof'. The steel bar comprises the following components: 0.38 to 0.43 percent of C, 0.8 to 1.1 percent of Cr, 0.75 to 1.0 percent of Mn, 0.15 to 0.25 percent of Mo, 0.15 to 0.3 percent of Si, less than or equal to 0.035 percent of S, P, less than or equal to 0.035 percent of N, and the balance of Fe. The manufacturing method of the steel bar adopts a heating furnace to heat to 1000-. It has the following disadvantages: (1) c, Cr, the content is too high, although the strength index can be greatly improved, the ductility index is not good, and the steel bar is easy to have no yield phenomenon and brittle fracture; (2) mo is a precious metal, is expensive, has high production cost and is not beneficial to popularization and use; (3) most of domestic steel bar production lines do not have an online tempering device, and the production process is difficult to realize.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, combines Ti microalloyed components with steel making and rolling processes, and provides a preparation method of a Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bar.
The invention aims to solve another technical problem and overcome the defects in the prior art, and provides a Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bar, which has the yield strength of more than or equal to 635MPa, the tensile strength of more than or equal to 795MPa and the elongation after fracture of more than or equal to 15 percent and meets the market demand on 635 MPa-grade steel bars.
In order to solve the technical problem, the technical scheme is that the preparation method of the Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bar comprises the following steps:
s1, smelting the steelmaking raw materials into crude molten steel, decarburizing and heating by adopting top-blown oxygen, reducing the position of an oxygen lance when the smelting end point is approached, wherein the time lasts for more than 20 seconds, the weight content of C in the crude molten steel at the smelting end point is more than or equal to 0.06%, the weight content of P and S is less than or equal to 0.025%, then tapping, and deoxidizing and alloying in a steel ladle in the tapping process;
s2, enabling the ladle to enter a refining furnace, determining oxygen content to be less than 20ppm, starting bottom blowing inert gas for the ladle of the refining furnace to blow the liquid level of the steel slag without violent turnover, then reducing the flow of the inert gas, starting an electrode to heat and raise temperature, adding a slagging material to make white slag, adding a blocky titanium-containing alloy or adding a titanium-containing cored wire in a wire feeding mode after the set heating time and temperature are reached, sampling, inspecting and finely adjusting components to enable the wire to meet the component requirements of the steel bar, then reducing the inert flow to blow for 10-15min, enabling the ladle to exit from a refining station, and leaving the station at a temperature of 1540-;
s3, hoisting the steel ladle to a continuous casting platform, and casting the steel ladle into a steel billet, wherein in the casting process, the steel ladle, the tundish and the crystallizer are all subjected to whole-process protective casting, the temperature of molten steel in the tundish is 1510-; the continuously cast steel billet enters a heating furnace, is heated to 1100-1200 ℃ in the heating furnace, and is kept warm for 60-90min to obtain the steel billet for rolling the steel bar;
s4, cooling the steel billet for the rolled steel bar to 1000-plus-1050 ℃, then rolling, carrying out rough rolling, intermediate rolling and final rolling, then rolling to the required specification, and cooling by controlling after the final rolling, wherein the temperature of an upper cooling bed is 830-plus-880 ℃, thus obtaining the Ti microalloyed 635 MPa-level hot rolled ribbed steel bar.
The preparation method of the Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bar is further improved as follows:
preferably, the chemical components of the steel billet in the step S3 are as follows by weight: 0.22 to 0.28 percent of C, 0.60 to 0.80 percent of Si, 1.40 to 1.60 percent of Mn, less than or equal to 0.035 percent of P, less than or equal to 0.035 percent of S, 0.020 to 0.040 percent of Ti, and the balance of Fe and inevitable impurity elements.
Preferably, in step S1, the apparatus for smelting steel-making raw materials into crude molten steel is a converter, the steel-making raw materials are molten iron and scrap steel, and the weight ratio of the molten iron to the scrap steel is 85: 15.
Preferably, when the equipment for smelting the steelmaking raw materials into the crude molten steel is a converter, the tapping temperature of the crude molten steel in the step S1 is 1650-1700 ℃, and the specific steps of deoxidizing and alloying in a steel ladle in the tapping process are as follows: and (3) beginning to add the compound deoxidizer, the silicon-manganese alloy and the silicon-iron alloy in sequence at the steel tapping amount of 1/5, finishing adding at the steel tapping amount of 4/5, and enabling the adding amount to meet the requirements of chemical components of the steel billet.
Preferably, in step S1, the apparatus for smelting steel-making raw materials into molten raw steel is an electric furnace, the steel-making raw materials are all steel scraps or a mixture of steel scraps and molten iron, and when the steel scraps and the molten iron are mixed, the weight ratio of the steel scraps to the molten iron is 85: 15.
Preferably, when the device for smelting the steelmaking raw materials into the crude molten steel is an electric furnace, the tapping temperature of the crude molten steel in the step S1 is 1610-1670 ℃, and the specific steps of deoxidizing and alloying in a steel ladle in the tapping process are as follows: and (3) beginning to add the compound deoxidizer, the silicon-manganese alloy and the silicon-iron alloy in sequence when the steel tapping amount is 1/3, and finishing adding when the steel tapping amount is 9/10.
Preferably, the smelting end point in the step S1 is: 0.06 percent of C, 0.018 percent of P and 0.011 percent of S, and the tapping temperature is 1650 ℃; the billet in step S3 contains, by weight, 0.28% of C, 0.60% of Si, 1.60% of Mn, 0.025% of P, 0.020% of S, 0.020% of Ti, and the balance Fe and inevitable impurity elements.
Preferably, the refining furnace in step S2 is an LF furnace, or a combination of an LF furnace and any one of an RH furnace, a VOD furnace, and a VD furnace.
Preferably, the oxygen determination in step S2 specifically comprises: and (3) measuring the oxygen content of the molten steel, and if the oxygen content is more than or equal to 20ppm, adding a composite deoxidizer for deoxidation until the oxygen content is less than 20 ppm.
Preferably, the cross-section of the billet in the step S3 is 150 × 150mm2。
In order to solve another technical problem, the technical scheme is that the Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bar prepared by any one of the preparation methods is adopted.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides a method for producing a 635 MPa-grade high-strength steel bar with high strength and high plasticity by combining Ti microalloyed components with steel making and rolling processes, wherein the yield strength of the prepared steel bar is more than or equal to 635MPa, the tensile strength is more than or equal to 795MPa, and the elongation after fracture is more than or equal to 15%, so that the requirements of the market on the 635 MPa-grade steel bar are met.
2. By adopting Ti microalloying component design, the precipitation strengthening and fine grain strengthening effects of Ti (C, N) are fully utilized, and the yield of the steel bar can be greatly improved on the premise of ensuring the extensibilityAnd tensile strength. But the following key technical problems need to be solved: the oxidizability of Ti is high, and if the oxygen content in molten steel is high, the recovery rate of Ti is influenced; if Ti is oxidized off, the strengthening effect cannot be exerted; or the large fluctuation of the Ti content can cause the instability of the mechanical property of the steel bar; ② in the continuous casting process, Ti is easy to be secondarily oxidized to generate TiO with high melting point2Blocking a water gap to influence the sequential production of casting blanks; thirdly, the steel bar is heated and rolled, the finishing temperature is slightly higher than the initial rolling temperature, the precipitation of TiC particles (low-temperature precipitation) after rolling is influenced, and the strengthening effect of the TiC particles is weakened.
Aiming at the problems, the chemical components of the raw materials of the invention are specially designed: setting the end point C to be more than or equal to 0.06 percent according to the end point carbon-oxygen balance of the converter, wherein the oxygen content of molten steel in the converter is generally less than or equal to 500 ppm; the traditional steelmaking process adopts aluminum deoxidation, but high melting point A is formed2O3The inclusion not only influences the plasticity of the steel bar, but also easily blocks a water gap during continuous casting to influence production; the invention utilizes the component design of high Si and high Mn, adopts Si and Mn for deoxidation and is refined by an LF furnace, a compound deoxidizer, a silicon-manganese alloy and a silicon-iron alloy are added in the tapping process to play a good deoxidation role, the oxygen content is less than or equal to 20ppm after the deoxidation, and the oxygen is determined firstly after the steel enters a ladle station of a refining furnace, so that the oxygen content of molten steel can be strictly controlled, the recovery rate of Ti is improved and stabilized, the performance stability of the steel bar is ensured, and the smooth production can be ensured;
aiming at the problem II, the steel-making and rolling process is specially designed: in the preparation method, the continuous casting adopts the whole-process protective casting, reduces the secondary oxidation of Ti and solves the problem of TiO2The accumulation of impurities at the nozzle reduces the nozzle blockage; meanwhile, the Ti content in the steel is stabilized, and the stability of the performance of the steel bar is ensured; aiming at the problem III, the temperature of an upper cooling bed is controlled after finish rolling, so that TiC particles precipitated in ferrite after phase change generate strong precipitation strengthening effect; during rolling, TiN particles are mainly precipitated to prevent austenite grains from growing large by controlling the initial rolling temperature, and the fine grain strengthening effect is achieved. Wherein the heating temperature is controlled at 1100-1200 ℃ to promote the dissolution of Ti in the steel in preparation for the precipitation of Ti carbonitrides during the rolling process, and austenite does not exist in the temperature rangeCoarsening to influence the performance of the steel bar; the initial rolling temperature is controlled at 1050 ℃ and 1000-; and the temperature of the upper cooling bed is controlled at 830-880 ℃ by controlling cooling after finish rolling, thus being beneficial to the precipitation of TiC particles, playing the role of precipitation strengthening, and reducing the required temperature of the upper cooling bed along with the increase of the specification of the steel bar. The key technical scheme of the invention is that Ti microalloying component design and metallurgical quality control are organically combined, and high strength performance is obtained while excellent elongation performance is obtained.
Drawings
FIG. 1 is a SEM photograph of a steel bar sample prepared in example 1 of the present invention;
FIG. 2 is a metallographic structure diagram of a steel bar sample prepared in example 1 of the present invention, wherein a ruler is 100 μm, and in the metallographic structure diagram: the black structure is pearlite, the white structure is ferrite, and the grain size of the ferrite is 11.5 grade;
FIG. 3 is a metallographic structure diagram of a steel bar sample prepared in example 2 of the present invention, wherein a ruler is 100 μm, and in the metallographic structure diagram: the black structure is pearlite, the white structure is ferrite, and the ferrite grain size is grade 10.0.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments, and all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.
Example 1
The embodiment provides a preparation method of a Ti microalloyed 635MPa hot-rolled ribbed steel bar, which comprises the following steps:
the steel comprises the following chemical components in parts by weight: 0.28% of C, 0.60% of Si, 1.60% of Mn, 0.025% of P, 0.020% of S, 0.020% of Ti, and the balance of Fe and inevitable impurity elements;
a converter process: the final points are 0.06% of C, 0.018% of P and 0.011% of S, and the tapping temperature is 1650 ℃;
an LF furnace process: oxygen content is 20ppm, argon is blown in station for 6min, white slag is refined and removed with P, S and O, ferrotitanium is added, argon is blown in weak condition for 15min before the white slag is taken out of station, and the temperature of the white slag is 1540 ℃;
and (3) continuous casting process: the whole process is protected and poured, the temperature of the tundish is 1510 ℃, and the working pulling speed is 2.8 m/min;
a steel rolling procedure: heating temperature is 1100 ℃, starting rolling temperature is 1000 ℃, steel bar with phi 12mm is rolled by rough rolling, intermediate rolling and final rolling, and steel bar sample 1 is prepared by controlling cooling after rolling and the temperature of the steel bar on a cooling bed is 880 ℃.
The steel bar sample 1 prepared in the example 1 is scanned by a projection electron microscope, and a scanning photo is shown in fig. 1, so that a large amount of Ti (C, N) second phase particles which are approximately round and have the size of about 20nm are dispersed and separated out in a fine mode, and the toughness of the steel bar can be obviously improved;
FIG. 2 is prepared as in example 1
The metallographic structure of the steel bar sample 1 of the specification is shown in fig. 2, and the steel bar has a small grain size of 11.5 grade, and the structure of ferrite and pearlite.
Example 2
The embodiment provides a preparation method of a Ti microalloyed 635MPa hot-rolled ribbed steel bar, which comprises the following steps:
the steel comprises the following chemical components in parts by weight: 0.22% of C, 0.80% of Si, 1.40% of Mn, 0.020% of P, 0.015% of S, 0.040% of Ti, and the balance of Fe and inevitable impurity elements;
a converter process: the finishing points are 0.08 percent of C, 0.019 percent of P and 0.013 percent of S, and the tapping temperature is 1700 ℃;
an LF furnace process: oxygen content is 18ppm, argon blowing is carried out for 5min when the furnace is in operation, white slag is refined and removed with P, S and O, ferrotitanium is added, argon is blown for 10min before the furnace is out of operation, and the temperature of the furnace is 1610 ℃;
and (3) continuous casting process: the whole process is protected and poured, the temperature of the tundish is 1550 ℃, and the working pulling speed is 2.0 m/min;
a steel rolling procedure: heating to 1200 ℃, starting to roll at 1050 ℃, rolling the steel bar into a steel bar with the diameter of 25mm by rough rolling, intermediate rolling and final rolling, and controlling and cooling the steel bar after rolling to reach the temperature of 830 ℃ on a cooling bed to obtain a steel bar sample 2.
FIG. 3 is prepared as in example 2
As can be seen from fig. 3, the metallographic structure of the steel bar sample 2 of the specification is larger in grain size of the steel bar, the grain size is 10.0 grade, and the structure of the steel bar is ferrite and pearlite. This is because the smaller the gauge, the faster the cooling rate, and the finer the crystal grains, and thus the crystal grain size of the steel bar sample 3 is larger than that of the sample 2.
Example 3
The embodiment provides a preparation method of a Ti microalloyed 635MPa hot-rolled ribbed steel bar, which comprises the following steps:
the steel comprises the following chemical components in parts by weight: 0.26% of C, 0.75% of Si, 1.45% of Mn, 0.021% of P, 0.014% of S, 0.035Ti, and the balance of Fe and inevitable impurity elements;
a converter process: finishing points of 0.07 percent of C, 0.018 percent of P and 0.015 percent of S, and tapping temperature is 1680 ℃;
an LF furnace process: oxygen content is 19ppm, argon blowing is carried out for 5min in station, white slag refining is carried out for P, S and O removal, ferrotitanium is added, argon blowing is carried out for 12min before station leaving, and the temperature of station leaving is 1570 ℃;
and (3) continuous casting process: the whole process is protected and poured, the tundish temperature is 1520 ℃, and the working pulling speed is 2.6 m/min;
a steel rolling procedure: heating to 1180 ℃, starting rolling to 1030 ℃, rolling to form a steel bar with the diameter of 16mm through rough rolling, intermediate rolling and final rolling, and cooling by controlling after rolling to obtain a steel bar sample 3 at the temperature of 860 ℃ on a cooling bed.
Example 4
The embodiment provides a preparation method of a Ti microalloyed 635MPa hot-rolled ribbed steel bar, which comprises the following steps:
the steel comprises the following chemical components in parts by weight: 0.25% of C, 0.70% of Si, 1.55% of Mn, 0.020% of P, 0.013% of S, 0.030% of Ti, and the balance of Fe and inevitable impurity elements;
a converter process: the end point is 0.06 percent of C, 0.017 percent of P and 0.010 percent of S, and the tapping temperature is 1670 ℃;
an LF furnace process: oxygen content is 17ppm, argon blowing is carried out for 5min in a station, white slag refining is carried out for P, S and O removal, ferrotitanium is added, argon blowing is carried out for 13min before the white slag is taken out of the station, and the temperature of the white slag is 1580 ℃;
and (3) continuous casting process: the whole process is protected and poured, the tundish temperature is 1530 ℃, and the working casting speed is 2.5 m/min;
a steel rolling procedure: heating temperature is 1150 ℃, rolling start temperature is 1020 ℃, steel bar with phi of 20mm is rolled through rough rolling, intermediate rolling and final rolling, and steel bar sample 4 is prepared through controlled cooling after rolling and cooling bed temperature of 850 ℃.
The steel bar products obtained in the embodiments 1 to 4 are subjected to mechanical property test by adopting a corresponding test method in GB/T28900, and three repeated tests are performed on a single performance index of each sample, and the results are shown in the following table 1:
table 1 mechanical properties of reinforcing bars prepared in examples 1-2 of the present invention
Wherein: reLIs the yield strength; rmIs tensile strength; a is elongation after fracture.
From the mechanical properties of the samples prepared in examples 1 to 4 in table 1, the mechanical property technical requirements of 635 MPa-level steel bars can be met by the rolled steel bars of various specifications through Ti microalloying component design and combined with the optimized design of the process parameters of steel making, refining, continuous casting and steel rolling processes.
It should be understood by those skilled in the art that the foregoing is only illustrative of several embodiments of the invention, and not of all embodiments. It should be noted that many variations and modifications are possible to those skilled in the art, and all variations and modifications that do not depart from the gist of the invention are intended to be within the scope of the invention as defined in the appended claims.
Claims (10)
1. A preparation method of Ti microalloyed 635 MPa-grade hot-rolled ribbed steel bars is characterized by comprising the following steps:
s1, smelting the steelmaking raw materials into crude molten steel, decarburizing and heating by adopting top-blown oxygen, reducing the position of an oxygen lance when the smelting end point is approached, wherein the time lasts for more than 20 seconds, the weight content of C in the crude molten steel at the smelting end point is more than or equal to 0.06%, the weight content of P and S is less than or equal to 0.025%, then tapping, and deoxidizing and alloying in a steel ladle in the tapping process;
s2, enabling the ladle to enter a refining furnace, determining oxygen content to be less than 20ppm, starting bottom blowing inert gas for the ladle of the refining furnace to blow the liquid level of the steel slag without violent turnover, then reducing the flow of the inert gas, starting an electrode to heat and raise temperature, adding a slagging material to make white slag, adding a blocky titanium-containing alloy or adding a titanium-containing cored wire in a wire feeding mode after the set heating time and temperature are reached, sampling, inspecting and finely adjusting components to enable the wire to meet the component requirements of the steel bar, then reducing the inert flow to blow for 10-15min, enabling the ladle to exit from a refining station, and leaving the station at a temperature of 1540-;
s3, hoisting the steel ladle to a continuous casting platform, and casting the steel ladle into a steel billet, wherein in the casting process, the steel ladle, the tundish and the crystallizer are all subjected to whole-process protective casting, the temperature of molten steel in the tundish is 1510-; the continuously cast steel billet enters a heating furnace, is heated to 1100-1200 ℃ in the heating furnace, and is kept warm for 60-90min to obtain the steel billet for rolling the steel bar;
s4, cooling the steel billet for the rolled steel bar to 1000-plus-1050 ℃, then rolling, carrying out rough rolling, intermediate rolling and final rolling, then rolling to the required specification, and cooling by controlling after the final rolling, wherein the temperature of an upper cooling bed is 830-plus-880 ℃, thus obtaining the Ti microalloyed 635 MPa-level hot rolled ribbed steel bar.
2. The method of claim 1, wherein the billet of step S3 comprises the following chemical components by weight: 0.22 to 0.28 percent of C, 0.60 to 0.80 percent of Si, 1.40 to 1.60 percent of Mn, less than or equal to 0.035 percent of P, less than or equal to 0.035 percent of S, 0.020 to 0.040 percent of Ti, and the balance of Fe and inevitable impurity elements.
3. The method for preparing a hot-rolled ribbed steel bar with a 635MPa Ti microalloyed grade according to claim 1, wherein the equipment for smelting the steel-making raw materials into crude molten steel in the step S1 is a converter, the steel-making raw materials are molten iron and scrap steel, and the weight ratio of the molten iron to the scrap steel is 85: 15.
4. The method for preparing the Ti microalloyed 635MPa grade hot rolled ribbed steel bar as claimed in claim 2, wherein the tapping temperature 1650-1700 ℃ of the crude molten steel in the step S1, and the specific steps of deoxidizing and alloying in a ladle in the tapping process are as follows: and (3) beginning to add the compound deoxidizer, the silicon-manganese alloy and the silicon-iron alloy in sequence at the steel tapping amount of 1/5, finishing adding at the steel tapping amount of 4/5, and enabling the adding amount to meet the requirements of chemical components of the steel billet.
5. The method of claim 1, wherein the step S1 is performed by using an electric furnace as a device for melting steel-making raw materials into molten raw steel, the steel-making raw materials are all steel scraps or a mixture of steel scraps and molten iron, and when the steel scraps and the molten iron are mixed, the weight ratio of the steel scraps to the molten iron is 85: 15.
6. The method for preparing the Ti microalloyed 635MPa grade hot rolled ribbed steel bar as claimed in claim 5, wherein the tapping temperature of the crude molten steel in the step S1 is 1610-1670 ℃, and the specific steps of deoxidizing and alloying in a ladle in the tapping process are as follows: and (3) beginning to add the compound deoxidizer, the silicon-manganese alloy and the silicon-iron alloy in sequence when the steel tapping amount is 1/3, and finishing adding when the steel tapping amount is 9/10.
7. The method for preparing a hot-rolled ribbed steel bar with a Ti microalloyed 635MPa grade according to claim 1, wherein the smelting end point in the step S1 is as follows: 0.06 percent of C, 0.018 percent of P and 0.011 percent of S, and the tapping temperature is 1650 ℃; the billet in step S3 contains, by weight, 0.28% of C, 0.60% of Si, 1.60% of Mn, 0.025% of P, 0.020% of S, 0.020% of Ti, and the balance Fe and inevitable impurity elements.
8. The method of claim 1, wherein the refining furnace in step S2 is an LF furnace or a combination of an LF furnace and any one of an RH furnace, a VOD furnace, and a VD furnace.
9. The method for preparing a hot-rolled ribbed steel bar with Ti microalloyed 635MPa according to claim 1, wherein the oxygen determination in the step S2 includes the following steps: and (3) measuring the oxygen content of the molten steel, and if the oxygen content is more than or equal to 20ppm, adding a composite deoxidizer for deoxidation until the oxygen content is less than 20 ppm.
10. A Ti microalloyed 635MPa grade hot rolled ribbed bar made by the method of any one of claims 1 to 9.
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| CN114107781A (en) * | 2021-11-11 | 2022-03-01 | 安徽吾兴新材料有限公司 | Method for rolling 635 MPa-grade high-strength steel bars by using billet waste heat in short process |
| CN115094334A (en) * | 2022-07-20 | 2022-09-23 | 安徽吾兴新材料有限公司 | High-strength chloride-corrosion-resistant steel bar for concrete structure and production method thereof |
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