CN110951953B - HRB500E steel bar and vanadium-nitrogen microalloying process thereof - Google Patents
HRB500E steel bar and vanadium-nitrogen microalloying process thereof Download PDFInfo
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- CN110951953B CN110951953B CN201911328570.2A CN201911328570A CN110951953B CN 110951953 B CN110951953 B CN 110951953B CN 201911328570 A CN201911328570 A CN 201911328570A CN 110951953 B CN110951953 B CN 110951953B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/78—Combined heat-treatments not provided for above
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C21—METALLURGY OF IRON
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/001—Heat treatment of ferrous alloys containing Ni
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- C21—METALLURGY OF IRON
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- 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
- C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- 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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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
Abstract
The invention discloses an HRB500E steel bar and a vanadium-nitrogen microalloying process thereof, belonging to the technical field of steel bar rolling, and the preparation process comprises the following steps: preparing a billet; heating a steel billet; rolling; and (5) post-treatment. The steel billet comprises, by mass, 0.11-0.25% of C, 0.34-0.80% of Si, less than or equal to 1.10% of Mn, less than or equal to 0.045% of P, less than or equal to 0.045% of S, less than or equal to 0.08% of Ti, less than or equal to 0.12% of Ni, 0.03-0.07% of V and 0.004-0.015% of N; the balance of Fe and impurities; and Ceq ≦ 0.44%; the post-treatment method comprises the following specific steps: heating the rolled and formed steel bar to the temperature of 300-500 ℃, preserving the heat for 1000-3600s, and then cooling to the room temperature. The HRB500E steel bar obtained finally has high strength, high elongation at break and high toughness.
Description
Technical Field
The invention belongs to the technical field of steel bar rolling, and particularly relates to an HRB500E steel bar and a vanadium-nitrogen microalloying process thereof.
Background
HRB500 is a concept proposed in national standard GB1499.2-2018 Hot rolled ribbed steel bars for reinforced concrete, and means that in various properties, the yield strength is not lower than 500MPa, while HRB500E steel bars refer to hot rolled ribbed steel bars, in particular to steel bars with certain shock resistance, compared with common steel bars, HRB500E has higher yield ratio, yield ratio and maximum force total elongation, so that the strength and the ductility and toughness are stronger, and when the steel bars encounter natural disasters such as earthquakes, the time from deformation to fracture can be prolonged, and longer escape time is strived for people. It can be seen that the ductility and toughness of the HRB500E steel bar is an important performance parameter, and a great deal of research has been conducted by researchers.
The Chinese patent application CN102876968A (a production process of a high-strength anti-seismic HRB500E hot-rolled ribbed steel bar and the steel bar) discloses a production process of an HRB500E steel bar, optimizes the chemical components of the steel bar, adjusts the heating process before rolling, and prepares a finished product of the steel bar with the nominal diameter of 40 mm. Carrying out microalloying treatment on the steel bar through the optimized design of chemical components; the heating process before rolling is adjusted, the effects of precipitation strengthening and grain refining of the V-N alloy in steel can be fully exerted, the yield strength, toughness, tensile strength and the like of the steel bar are finally improved, and the steel bar has high anti-seismic performance. In chinese patent application CN103225043A (a HRB500, HRB500E spiral shell production process), the production process of the steel bar includes: firstly, heating a steel billet by adopting a three-section type heating mode, wherein the steel billet is subjected to V or VN microalloying, the first-section heating temperature is 800-; then temperature control rolling is carried out, the rolling starting temperature is 950-; then the temperature is controlled for cooling, the spinning temperature is 820-. And then, the formed reinforcing steel bars are rolled, inspected and packaged. The Chinese patent application CN106399855A (HRB500E ribbed bar and production process thereof) optimizes the chemical element composition of the bar, adopts the working procedures of converter smelting, LF furnace refining and billet continuous casting to smelt a billet with composite requirements, and the billet is heated, subjected to rough and medium rolling, pre-finish rolling and finish rolling to obtain a finished product. By adopting the vanadium-chromium-copper composite addition technology, the initial rolling temperature is low, and the stability of the yield ratio is obviously improved. The Chinese patent application CN108913999A (a production method of phi 36-40mm HRB500E twisted steel) firstly adds molten iron, scrap steel and slag charge into a converter for smelting, deoxidizes and alloys the molten steel, then refines in an LF refining furnace and continuously casts, and the finished product is obtained after billet pressing. The finished product steel bar with good mechanical property and stability is finally obtained by adjusting and controlling the content of chemical elements in the steel bar, particularly VN, and adjusting parameters such as production composition temperature. The chinese patent application CN109554613A (a method for producing HRB500E high-strength aseismic steel bar) first prepares a billet, preferably the chemical composition of the billet, and adjusts the rolling process to obtain the high-strength aseismic steel bar.
However, in the preparation process of the steel bar in the above patent, the steel bar is directly cooled after being rolled, the temperature in the rolling process is often higher, and the direct cooling often generates stress concentration in the steel bar, so that the fracture strength and the toughness of the steel bar are reduced, and the actual requirements of buildings are difficult to meet.
Disclosure of Invention
The invention aims to solve the technical problem that in the prior art, the production process of the HRB500E steel bar is easy to cause stress concentration in the steel bar, so that the fracture strength and the toughness of the steel bar are reduced.
In order to solve the technical problem, the invention discloses an HRB500E steel bar vanadium-nitrogen alloying production process, which specifically comprises the following steps:
(1) preparing a billet; (2) heating a steel billet; (3) rolling; (4) post-treatment;
the steel billet comprises, by mass, 0.11-0.25% of C, 0.34-0.80% of Si, less than or equal to 1.10% of Mn, less than or equal to 0.045% of P, less than or equal to 0.045% of S, less than or equal to 0.08% of Ti, less than or equal to 0.12% of Ni, 0.03-0.07% of V and 0.004-0.015% of N; the balance of Fe and impurities; and Ceq ≦ 0.44%;
in the chemical element composition of the steel bar, the element C is the most main element and mainly plays a role in improving the strength of the steel bar material, the yield strength and the tensile strength are increased along with the increase of the content of C, but the elongation, the bending strength and the corrosion resistance are gradually reduced, and for the steel bar material, the steel bar material needs to have better bending performance and higher elongation, so the content of C cannot be too high, and the content of C in the steel bar material is limited to be between 0.11 and 0.25 percent.
Si is added into the steel bar to be used as a deoxidizer, so that the internal structure of the steel bar is more uniform, the crystal grains are finer, the strength of the steel bar is further improved, but the brittleness of the steel bar is increased due to the higher content of Si, and the content of Si in the steel bar is 0.34-0.80%. Mn has similar action with Si, can be used as a weak deoxidizer, strengthens the uniformity of a steel bar structure, improves the strength of the steel bar, and can cause the steel bar to become brittle due to excessive Mn, so that the Mn content is limited to less than or equal to 1.10 percent.
P and S are generally considered harmful elements in steel, and the same is true of the HRB500E steel bar, the presence of P and S can increase the cold brittleness of the steel, deteriorate the welding performance and the cold bending performance of the steel and reduce the strength of the steel, so the content of P and S is less than or equal to 0.045%.
In the steel bar material, the Ti element is firstly combined with the C element to form titanium carbide in the heat treatment process, so that intergranular corrosion can be prevented, the internal structure of the steel bar is more compact and uniform, and the welding performance can be improved. However, the surface quality of the steel bar is reduced due to excessive Ti, so that the content of Ti is less than or equal to 0.08 percent in the invention.
Ni cannot form a compound with C, so that the compound has a positive promoting effect on stable austenite formed in the heat treatment process of the steel bar, the toughness of the steel bar can be improved due to the existence of Ni, and the high strength and the plasticity of the steel bar can be ensured, but Ni is relatively rare and has high cost, so that the content of Ni limited by the invention is less than or equal to 0.12%.
V and N are important elements of vanadium-nitrogen microalloying in the preparation process of the HRB500E steel bar, V is a deoxidizer with excellent performance, and the existence of V can obviously improve the strength and toughness of the steel bar; n can improve the strength, low-temperature toughness and welding performance of the steel bar. The V and N elements are added into the HRB500E steel bar at the same time, the V and N can be microalloyed to play a role in refining grains so as to improve the yield and tensile strength of the steel bar, and the V and N elements can also form compounds with C respectively so as to improve the corrosion resistance of the steel bar. The dosage needs to be controlled in the V and N microalloying process, and the microalloying effect can be weakened by too much or too little of any element, so that the performance of the steel bar is deteriorated, therefore, the content of V is limited to be 0.03-0.07%, and the content of N is limited to be 0.004-0.015%.
In the step (4), the method comprises the following steps: heating the rolled and formed steel bar to 300-500 ℃, preserving the heat for 30-3600s, and then cooling to room temperature. The step is the post-treatment of the steel bar, and the stress concentration exists in the steel bar structure and the toughness of the steel bar is reduced due to the cooling of the processed and formed steel bar after rolling. The steel bar is subjected to medium-temperature tempering post-treatment, the heating temperature and the heat preservation time are limited, the problem of stress concentration can be obviously eliminated, and the toughness of the steel bar is improved.
Further, in the step (4), the rolled and formed steel bar is heated to 350-.
Further, the heating speed is 20-60 ℃/s.
Further, the cooling speed is 20-100 ℃/s.
Further, in the step (2), the heating of the billet is performed in a converter or an electric arc furnace.
Further, in the step (2), the heating of the steel billet is divided into three steps, and the first heating temperature is 850-; the second step heating temperature is 1000-1100 ℃; the third step heating temperature is 1150-1250 ℃.
Further, the first heat preservation time is 10-30 min; the second step of heat preservation is carried out for 30-80 min; and the third step is carried out for 10-30 min.
Further, the rolling process in the step (3) comprises rough rolling and finish rolling.
The invention also claims an HRB500E steel bar obtained by the HRB500E steel bar vanadium-nitrogen microalloying process.
Further, the nominal diameter of the HRB500E steel bar is 6-10 mm.
The steel bar disclosed by the invention optimizes the chemical element composition of the steel bar, designs the contents of elements vanadium and nitrogen, adopts three steps of heating treatment in the heating step of the steel bar, carries out vanadium-nitrogen microalloying treatment, and fully exerts the high strength and high toughness brought by the vanadium-nitrogen microalloying treatment to the steel bar; meanwhile, after the steel bar is rolled, low-temperature tempering treatment is carried out, the problem of stress concentration inside the steel bar is solved, and the toughness of the steel bar is further improved.
Compared with the prior art, the HRB500E steel bar and the vanadium-nitrogen microalloying production process thereof have the following advantages:
(1) the production process is simple.
(2) The preparation process is basically the same as that of the traditional HRB500E steel bar, no additional production equipment is needed, and the production cost is low.
(3) The HRB500E steel bar product obtained finally not only has higher strength, elongation at break and the like, but also has higher toughness.
Detailed Description
The technical solution of the present invention is explained by the description of the specific embodiment below.
In the steel billet, the contents of the chemical elements are shown in the following table 1 by mass percent, and the balance is Fe and impurities. Examples and comparative examples were set up separately.
TABLE 1 chemical composition (wt%) of steel billet in examples and comparative examples
| Numbering | C | Si | Mn | P | S | Ti | Ni | V | N | Ceq(％) |
| Example 1 | 0.21 | 0.58 | 0.7 | 0.009 | 0.024 | 0.03 | 0.1 | 0.04 | 0.008 | 0.34 |
| Example 2 | 0.15 | 0.78 | 0.5 | 0.004 | 0.031 | 0.01 | 0.11 | 0.07 | 0.015 | 0.25 |
| Comparative example 1 | 0.24 | 0.63 | 1.3 | 0.028 | 0.034 | 0.07 | 0.18 | 0.13 | 0.006 | 0.49 |
Pieces of steel billets having the chemical compositions of examples 1 and 2 and comparative example 1 above were prepared, heated, rolled and post-treated to give 1-8# HRB500E steel bars, in which: under the chemical components of example 1 in table 1, 6 products, which are respectively marked as 1-6# HRB500E steel bars, were prepared by different preparation processes; under the chemical composition of example 2, 1 piece of product was prepared, which was marked as 7# HRB500E steel bar; under the chemical composition of comparative example 1, 1 piece of product was prepared, which was marked as 8# HRB500E steel bar. The specific preparation process is as follows.
The preparation process of the 1# HRB500E steel bar comprises the following steps:
(1) preparing a steel billet: the chemical composition of the steel slab is the chemical composition given in example 1 in table 1.
(2) Heating a steel billet: heating the steel billet in a converter, wherein the heating of the steel billet is divided into three steps:
the first step is as follows: heating at 900 deg.C for 30 min; the second step is that: heating at 1080 deg.C for 60 min; the third step: the heating temperature is 1200 ℃, and the heat preservation time is 28 min.
(3) Rolling: and rolling the heated billet, wherein rough rolling is performed firstly, and then finish rolling is performed.
(4) And (3) post-treatment: heating the rolled and formed steel bar to 360 ℃, and preserving the heat for 2900S, wherein the heating speed is controlled to 45 ℃/S; then oil cooling is carried out to the room temperature, and the cooling speed in the oil cooling process is 80 ℃/s.
Finally obtaining a 1# HRB500E steel bar product, wherein the nominal diameter of the steel bar is 6-8 mm.
II, a preparation process of 2# HRB500E steel bars:
(1) preparing a steel billet: the chemical composition of the steel slab is the chemical composition given in example 1 in table 1.
(2) Heating a steel billet: heating the steel billet in a converter, wherein the heating of the steel billet is divided into three steps:
the first step is as follows: heating at 900 deg.C for 10 min; the second step is that: heating at 1080 deg.C for 30 min; the third step: the heating temperature is 1200 ℃, and the heat preservation time is 28 min.
(3) Rolling: and rolling the heated billet, wherein rough rolling is performed firstly, and then finish rolling is performed.
(4) And (3) post-treatment: heating the rolled and formed steel bar to 360 ℃, and preserving the heat for 2900S, wherein the heating speed is controlled to 45 ℃/S; then oil cooling is carried out to the room temperature, and the cooling speed in the oil cooling process is 150 ℃/s.
Finally obtaining a 2# HRB500E steel bar product, wherein the nominal diameter of the steel bar is 6-8 mm.
The preparation process of the No. 3 HRB500E steel bar comprises the following steps:
(1) preparing a steel billet: the chemical composition of the steel slab is the chemical composition given in example 1 in table 1.
(2) Heating a steel billet: heating the steel billet in a converter, wherein the heating of the steel billet is divided into three steps:
the first step is as follows: heating at 900 deg.C for 30 min; the second step is that: heating at 1080 deg.C for 80 min; the third step: the heating temperature is 1200 ℃, and the heat preservation time is 30 min.
(3) Rolling: and rolling the heated billet, wherein rough rolling is performed firstly, and then finish rolling is performed.
(4) And (3) post-treatment: heating the rolled and formed steel bar to 360 ℃, and preserving the heat for 2900S, wherein the heating speed is controlled to be 100 ℃/S; then oil cooling is carried out to the room temperature, and the cooling speed in the oil cooling process is 80 ℃/s.
Finally obtaining a 3# HRB500E steel bar product, wherein the nominal diameter of the steel bar is 6-8 mm.
The preparation process of the No. 4 HRB500E steel bar comprises the following steps:
(1) preparing a steel billet: the chemical composition of the steel slab is the chemical composition given in example 1 in table 1.
(2) Heating a steel billet: heating the steel billet in a converter, wherein the heating of the steel billet is divided into three steps:
the first step is as follows: heating at 900 deg.C for 30 min; the second step is that: heating at 1080 deg.C for 60 min; the third step: the heating temperature is 1200 ℃, and the heat preservation time is 10 min.
(3) Rolling: and rolling the heated billet, wherein rough rolling is performed firstly, and then finish rolling is performed.
(4) And (3) post-treatment: heating the rolled and formed steel bar to 500 ℃, and preserving heat for 3600S, wherein the heating speed is controlled to be 20 ℃/S; then oil cooling is carried out to the room temperature, and the cooling speed in the oil cooling process is 20 ℃/s.
Finally obtaining a 4# HRB500E steel bar product, wherein the nominal diameter of the steel bar is 6-8 mm.
The preparation process of the 5# HRB500E steel bar comprises the following steps:
(1) preparing a steel billet: the chemical composition of the steel slab is the chemical composition given in example 1 in table 1.
(2) Heating a steel billet: heating the steel billet in a converter, wherein the heating of the steel billet is divided into three steps:
the first step is as follows: heating at 500 deg.C for 30 min; the second step is that: heating at 800 deg.C for 30 min; the third step: the heating temperature is 1200 ℃, and the heat preservation time is 28 min.
(3) Rolling: and rolling the heated billet, wherein rough rolling is performed firstly, and then finish rolling is performed.
(4) And (3) post-treatment: heating the rolled and formed steel bar to 360 ℃, and preserving the heat for 2900S, wherein the heating speed is controlled to 45 ℃/S; then oil cooling is carried out to the room temperature, and the cooling speed in the oil cooling process is 80 ℃/s.
Finally obtaining a 5# HRB500E steel bar product, wherein the nominal diameter of the steel bar is 6-8 mm.
The preparation process of the six and 6# HRB500E steel bars comprises the following steps:
(1) preparing a steel billet: the chemical composition of the steel slab is the chemical composition given in example 1 in table 1.
(2) Heating a steel billet: heating the steel billet in a converter, wherein the heating of the steel billet is divided into three steps:
the first step is as follows: heating at 900 deg.C for 5 min; the second step is that: heating at 1080 deg.C for 10 min; the third step: the heating temperature is 1200 ℃, and the heat preservation time is 50 min.
(3) Rolling: and rolling the heated billet, wherein rough rolling is performed firstly, and then finish rolling is performed.
(4) And (3) post-treatment: heating the rolled and formed steel bar to 300 ℃, and preserving heat for 1500 seconds, wherein the heating speed is controlled to be 60 ℃/S; then oil cooling is carried out to the room temperature, and the cooling speed in the oil cooling process is 80 ℃/s.
Finally obtaining a 6# HRB500E steel bar product, wherein the nominal diameter of the steel bar is 6-8 mm.
Seven, 7# HRB500E steel bar preparation process:
(1) preparing a steel billet: the chemical composition of the steel slab is the chemical composition given in example 2 in table 1.
(2) Heating a steel billet: heating the steel billet in a converter, wherein the heating of the steel billet is divided into three steps:
the first step is as follows: heating at 900 deg.C for 30 min; the second step is that: heating at 1000 deg.C for 30 min; the third step: the heating temperature is 1200 ℃, and the heat preservation time is 28 min.
(3) Rolling: and rolling the heated billet, wherein rough rolling is performed firstly, and then finish rolling is performed.
(4) And (3) post-treatment: heating the rolled and formed steel bar to 360 ℃, and keeping the temperature for 3000S, wherein the heating speed is controlled to be 45 ℃/S; then oil cooling is carried out to the room temperature, and the cooling speed in the oil cooling process is 100 ℃/s.
Finally obtaining a 7# HRB500E steel bar product, wherein the nominal diameter of the steel bar is 6-8 mm.
Eight, 8# HRB500E steel bar preparation process:
(1) preparing a steel billet: the chemical composition of the steel slab was as given in comparative example 1 in table 1.
(2) Heating a steel billet: heating the steel billet in a converter, wherein the heating of the steel billet is divided into three steps:
the first step is as follows: heating at 850 deg.C for 30 min; the second step is that: heating at 1000 deg.C for 30 min; the third step: the heating temperature is 1100 deg.C, and the holding time is 10 min.
(3) Rolling: and rolling the heated billet, performing rough rolling and finish rolling, performing no post-treatment, and naturally cooling to room temperature to obtain the product.
Finally obtaining the 8# HRB500E steel bar product, wherein the nominal diameter of the steel bar is 6-8 mm.
Some process parameters of the above preparation processes are shown in table 2 below.
TABLE 2 partial preparation Process parameters for different HRB500E products
Note: - -indicates that no corresponding treatment was performed.
The steel bar product 1-8# HRB500E obtained in Table 2 above was subjected to performance testing:
(1) reference is made to GB/T14992.2018 "steel for reinforced concrete part 2: the method for detecting the hot-rolled ribbed steel bar comprises the steps of detecting the lower yield strength Rel, the tensile strength Rm, the elongation A after fracture, the maximum force total elongation Agt, R degrees m/Rel and R degrees el/Rel of the steel bar.
(2) And (3) impact performance test: a standard pattern of U-notches having dimensions of 55 mm. times.10 mm and a depth of 2mm was made at room temperature on a pendulum impact tester of 450J.
The test results are shown in table 3 below.
Performance test results for # HRB500E Steel Bar products in tables 31-8
| Product number | Rel(MPa) | Rm(MPa) | A(％) | Agt(％) | R°m/Rel | R°el/Rel | Impact work (J) |
| 1# | 600 | 785 | 19 | 15 | 1.42 | 1.2 | 75 |
| 2# | 596 | 724 | 19 | 14 | 1.27 | 1.1 | 72 |
| 3# | 587 | 752 | 17 | 15 | 1.38 | 1.2 | 71 |
| 4# | 559 | 784 | 18 | 13 | 1.29 | 1.2 | 68 |
| 5# | 598 | 741 | 17 | 14 | 1.39 | 1.1 | 70 |
| 6# | 562 | 773 | 19 | 11 | 1.33 | 1.1 | 65 |
| 7# | 580 | 760 | 18 | 13 | 1.41 | 1.2 | 73 |
| 8# | 413 | 650 | 15 | 9 | 1.26 | 1.3 | 24 |
By combining the preparation process parameters in table 2 and the performance test results of the steel bars in table 3, it can be seen that the 1-7# HRB500E steel bars obtained by using the chemical element composition and the vanadium-nitrogen microalloying process of the invention have good mechanical properties, and completely meet the requirements of GB/T14992.2018 steel No. 2 for reinforced concrete: hot rolled ribbed bar.
Meanwhile, the comparison of the performances of the 1-7# HRB500E steel bar products shows that the performance of the prepared 1# HRB500E steel bar products is optimal under the conditions of the optimal chemical element composition and the optimal preparation process parameters. Outside the chemical element composition, the 8# HRB500E steel bar product obtained without the preparation process method has the worst performance; compared with the 8# HRB500E steel bar product which is not subjected to post-treatment, the steel bar product is subjected to a medium-temperature heating post-treatment process in the preparation process, and the impact toughness of the steel bar product is obviously improved.
Meanwhile, the basic process in the preparation process of the HRB500E steel bar is basically the same as that of the traditional HRB500E steel bar, so that the traditional production line can be used, additional new equipment does not need to be purchased, the production cost is low, and the industrial value is high.
While the invention has been described with reference to a preferred embodiment, various modifications may be made thereto without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as no conflict exists. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (6)
1. A vanadium-nitrogen microalloying process for HRB500E steel bars is characterized in that: the method comprises the following steps:
(1) preparing a billet; (2) heating a steel billet; (3) rolling; (4) post-treatment;
the steel billet comprises, by mass, 0.11-0.25% of C, 0.34-0.80% of Si, less than or equal to 1.10% of Mn, less than or equal to 0.045% of P, less than or equal to 0.045% of S, less than or equal to 0.08% of Ti, less than or equal to 0.12% of Ni, 0.03-0.07% of V and 0.004-0.015% of N; the balance of Fe and impurities; and Ceq is less than or equal to 0.44 percent;
in the step (4), the method comprises the following steps: heating the rolled and formed steel bar to the temperature of 500 ℃ at 300-; in the step (4), the heating speed is 20-60 ℃/s;
the cooling speed in the step (4) is 20-100 ℃/s;
in the step (2), the heating of the steel billet is divided into three steps, wherein the first step heating temperature is 850-; the second step heating temperature is 1000-1100 ℃; the third step is heating temperature 1150-1250 ℃;
the first step of heat preservation time is 10-30 min; the second step of heat preservation is carried out for 30-80 min; and the third step is carried out for 10-30 min.
2. The HRB500E steel bar vanadium-nitrogen microalloying process of claim 1, wherein: in the step (4), the rolled and formed steel bar is heated to 400 ℃ at 350-.
3. The HRB500E steel bar vanadium-nitrogen microalloying process of claim 1, wherein: in the step (2), the billet heating is carried out in a converter or an electric arc furnace.
4. The HRB500E steel bar vanadium-nitrogen microalloying process of claim 1, wherein: and (4) the rolling process in the step (3) comprises rough rolling and finish rolling.
5. A HRB500E steel bar obtained by the vanadium-nitrogen microalloying process of the HRB500E steel bar as claimed in any one of claims 1 to 4.
6. The HRB500E steel bar as set forth in claim 5, wherein: the nominal diameter of the HRB500E steel bar is 6-10 mm.
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