CN110408843B - 500MP a-grade coiled steel bar and preparation method thereof - Google Patents
500MP a-grade coiled steel bar and preparation method thereof Download PDFInfo
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- CN110408843B CN110408843B CN201910746757.8A CN201910746757A CN110408843B CN 110408843 B CN110408843 B CN 110408843B CN 201910746757 A CN201910746757 A CN 201910746757A CN 110408843 B CN110408843 B CN 110408843B
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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
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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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
- 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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- 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
- C22C38/002—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
- C22C38/12—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
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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Abstract
The invention discloses a 500Mpa coiled steel bar and a preparation method thereof, and the coiled steel bar comprises the following components by mass percent: c: 0.22 to 0.25%, Mn: 1.30-1.60%, Si: 0.15-0.60%, P: less than or equal to 0.045%, S: less than or equal to 0.045%, V: 0.010-0.035%, N: 0.0070-0.0180% and the balance of Fe and inevitable impurities. By adopting composite vanadium-nitrogen alloying, low heating temperature range and controlled rolling and cooling, the tensile strength can still reach the level of 500Mpa under the condition that V in the steel bar is reduced from 0.085-0.105% to 0.010-0.035%, the vanadium-nitrogen alloy consumption of about 8.4KG per ton of steel is saved, the cost of composite vanadium-nitrogen newly added for nitrogen reinforcement is deducted to be about 17 yuan per ton, and the cost of composite vanadium-nitrogen for nitrogen reinforcement is reduced to be about 150 yuan per ton of steel, so that the production cost of the steel bar is effectively reduced.
Description
Technical Field
The invention relates to a steel bar, in particular to a low-cost 500MP a-grade coiled steel bar and a preparation method thereof.
Background
GB/T1499.2-2018 Steel for reinforced concrete part 2: compared with the old national standard, the new national standard of hot rolling ribbed steel bars has the biggest change that the structure of the finished steel bars is specified, the steel bars are mainly required to be composed of ferrite and pearlite, tempered martensite cannot appear on a base circle, the process of cooling and strengthening mechanical properties through water which is generally adopted originally cannot be used continuously, and the steel bars can only be produced by micro-alloying strengthening methods such as V and the like. However, as the ferrovanadium price is increased from about 12 ten thousand yuan/ton to about 65 ten thousand yuan/ton, the production cost of the steel bar is greatly increased, and even negative profit is generated; in order to reduce the production cost of the 500MPa coiled steel bar and realize the profit of the coiled steel bar product, the smelting and rolling process of the 500MPa coiled steel bar must be optimized.
Disclosure of Invention
The purpose of the invention is as follows: in order to reduce the production cost, the invention provides a 500MP a-grade coiled steel bar.
The invention also aims to provide a preparation method of the 500MP a-grade coiled steel bar
The technical scheme is as follows: the 500MP a-grade coiled steel bar comprises the following components in percentage by mass: c: 0.22 to 0.25%, Mn: 1.30-1.60%, Si: 0.15-0.60%, P: less than or equal to 0.045%, S: less than or equal to 0.045%, V: 0.010-0.035%, N: 0.0070-0.0180% and the balance of Fe and inevitable impurities.
The preparation method of the 500MP a-grade coiled steel bar adopts the following technical scheme: the process route comprises converter smelting → casting blank heating → rolling → cooling after rolling; wherein, in the smelting process of the converter, the end point sulfur of the converter is controlled to be less than or equal to 0.030 percent, the end point phosphorus is controlled to be less than or equal to 0.030 percent, the tapping temperature is controlled to be more than or equal to 1620 ℃, a red ladle and slag stopping tapping are adopted, and the tapping time is controlled to be more than or equal to 150 s; when tapping to 1/3, adding deoxidizer and alloy according to the end point condition to deoxidize and alloy, adding alloy according to the target value of the components, and adding 0.26 Kg/t-0.90 Kg/t of composite vanadium-nitrogen alloy according to the detected nitrogen content and the calculation of adding 0.1Kg of composite vanadium-nitrogen to each ton of molten steel to increase the nitrogen content by 0.0010%, wherein the composite vanadium-nitrogen alloy contains 28% of nitrogen.
In the process of heating the casting blank, the furnace temperature of the preheating section is controlled to be 500-900 ℃, the furnace temperature of the first heating section is controlled to be 750-1000 ℃, the furnace temperature of the second heating section is controlled to be 850-1120 ℃, and the furnace temperature of the soaking section is controlled to be 950-1100 ℃.
In the rolling process, controlling the initial rolling temperature: 890 ℃ to 950 ℃, inlet temperature of the finishing mill: 860 ℃ to 940 ℃, reduced diameter inlet temperature: 740 to 840 ℃.
Controlling the spinning temperature in the cooling process after rolling: 740-820 ℃, and the starting air volume of the fan is as follows: 1.7 x 10 of first fan behind laying head5～1.8×105m3H, the second fan is 1.5 multiplied by 105～1.7×105m3H, 1.2 x 10 of third and fourth fans5～1.4×105m3H, 0.8 multiplied by 10 of the fifth and sixth fans5～1.0× 105m3/h。
In the production process of the 500MP a-grade coiled steel bar, the finishing mill group controls rolling in an austenite non-recrystallization region, and aims to elongate austenite grains, form a large number of deformation zones in grains, increase the crystal nucleus generation energy when the austenite is converted into the ferrite, obtain extremely fine ferrite grains and improve the toughness of the steelAnd carbides and nitrides of vanadium are formed in the steel to suppress recrystallization. The reducing and sizing mill is controlled rolling in the two-phase region of austenite and ferrite, and the strength of the steel is improved by work hardening and hardening of pearlite precipitation during rolling. Finally, through the rapid cooling of the air cooling line, the growth of the structure is inhibited, a very fine F + P structure is formed, the grain size can reach 12-14 levels, and the precipitation strengthening effect of vanadium is assisted, so that the 500MP a-level coiled steel bar has higher strength and extensibility. Compared with the prior art, the rolling temperature of the finishing mill group and the reducing and sizing mill group is above 950 ℃, 4 groups of air cooling lines are opened, and the opening air volume of the fan is as follows: the first fan and the second fan (1.0-1.2) multiplied by 10 behind the laying head5m3H, third and fourth fans (0.8-1.0) x 105m3The air cooling line only plays a role in reducing the coiling temperature of the coiled steel bar, the grain size of the coiled steel bar in the process is generally only 8-10 grades, and a large amount of vanadium alloy needs to be added to ensure that the final strength of the coiled steel bar meets the requirement.
Has the advantages that: the 500MP a-grade coiled steel bar adopts composite vanadium-nitrogen alloying to improve the strength of the coiled steel bar. The addition of nitrogen changes the distribution of vanadium in phases and promotes the transfer of vanadium from a solid solution state to a V (C, N) precipitation phase, so that the vanadium has a stronger precipitation strengthening effect. V (C, N) particles can be dispersed and precipitated in a eutectoid ferrite or in a ferrite area in a pearlite body in the cooling process, and the precipitation strengthening function can strengthen the ferrite and the pearlite simultaneously; in addition, the ferrite can be precipitated on a grain boundary to pin the grain boundary and prevent the grain from growing, so that ferrite grains are refined; the strengthening effect of the vanadium is exerted to a greater extent. The heating process is controlled in a lower heating temperature range, and a controlled rolling and cooling process is adopted, so that the tensile strength can still reach the 500MP a level under the condition that the V in the steel bar is reduced from 0.085-0.105% to 0.010-0.035%, the vanadium-nitrogen alloy consumption of about 8.4KG per ton of steel is saved, the cost of the newly added composite vanadium-nitrogen for nitrogen reinforcement is deducted to be about 17 yuan per ton, and the cost of the steel per ton is reduced to be about 150 yuan, thereby effectively reducing the production cost of the 500MPa level coiled steel bar.
Detailed Description
Example the preparation method of the present invention is used for controlling the production process of 500MP a-grade coiled steel bars, and particularly, for controlling the production process of HRB500 and HRB500E coiled steel bars with reduced cost.
The components of the designed steel bar comprise, by weight: 0.22 to 0.25%, Mn: 1.30-1.60%, Si: 0.15-0.60%, P: less than or equal to 0.045%, S: less than or equal to 0.045%, V: 0.010-0.035%, N: 0.0070-0.0180% and the balance of Fe and inevitable impurities.
The processing procedures of the HRB500 and HRB500E coiled steel bars are as follows: 100t converter → argon blowing stirring → full protection continuous casting production (150X 150mm small square billet continuous casting machine) → casting blank cooling → casting blank inspection → heating → descaling → controlled rolling → controlled cooling → finished product inspection → packaging → sign → warehouse entry.
According to the designed chemical components, adopting a BOF + argon blowing stirring method for smelting. And (3) actual control of the end point: t is 1620-1678 ℃, P is less than or equal to 0.029%, and S is less than or equal to 0.026%. And (4) adopting a red ladle and slag-stopping tapping, wherein the tapping time is more than or equal to 212 s. And (4) tapping to 1/3, adding a deoxidizer and an alloy according to the end point condition for deoxidation alloying, and adding the alloy according to the target value of the components. 50-100 kg of composite vanadium-nitrogen alloy is added into each furnace. And (3) after blowing argon for 3 minutes, measuring the temperature and sampling, and carrying out fine adjustment according to the components of the molten steel. The total argon blowing time after the furnace is ensured to be more than 5 minutes.
The continuous casting tundish uses low-carbon covering agent or carbonized rice husk, and the superheat degree is 20-45 ℃. The crystallizer uses special covering slag for deformed steel bar, and the drawing speed is less than or equal to 3.0 m/min.
The specific chemical cost control ranges are shown in table 1:
TABLE 1 chemical composition ranges (wt%) of 500MPa grade coil bar stock produced in the examples
| Numbering | C | Si | Mn | P | S | V | N |
| Require that | 0.22～0.25 | 0.15～0.60 | 1.30～1.60 | ≤0.045 | ≤0.045 | 0.010～0.035 | 0,0070～0,0180 |
| Practice of | 0.23～0.25 | 0.44～0.55 | 1.43～1.56 | 0.018～0.035 | 0.011～0.028 | 0.026～0.035 | 0.0091～0.0135 |
The low heating temperature and controlled rolling and controlled cooling process is adopted to produce the coiled steel bars with the specifications of phi 8 mm-phi 10mm HRB500 and HRB 500E. Actual control parameterComprises the following steps: preheating section furnace temperature: 600-870 ℃, heating for one-stage furnace temperature: 750-990 ℃, and the heating second-stage furnace temperature: 950-1100 ℃, furnace temperature of soaking section: 1000-1070 ℃; the initial rolling temperature: 890 ℃ to 930 ℃, finishing mill inlet temperature: 860 ℃ to 920 ℃, reduced diameter inlet temperature: 740 to 800 ℃; spinning temperature: 740-810 ℃, the cover is fully opened, the roller speed is as follows: 80rpm, 101%, 90%, 80%, 101%, and blower opening air volume are respectively: 1.7 x 10 of first fan behind laying head5～1.8×105m3H, the second fan is 1.5 multiplied by 105～1.7×105m3H, 1.2 x 10 of third and fourth fans5～1.4×105m3H, 0.8 multiplied by 10 of the fifth and sixth fans5～1.0×105m3/h。
The specific physical and chemical properties are shown in table 2:
TABLE 2 physical and chemical properties of 500MPa coiled steel bar produced by the present invention
The 500MP a-grade ribbed steel bar is used for reinforced concrete structures of civil buildings, roads, bridges, tunnels and the like, has good performance in downstream customer detection and test, and completely meets the use requirements of customers.
Claims (1)
1. The 500MP a-grade coiled steel bar is characterized by comprising the following components in percentage by mass: c: 0.23 to 0.25%, Mn: 1.43-1.56%, Si: 0.44-0.55%, P: 0.018-0.035%, S: 0.011-0.028%, V: 0.026-0.035%, N: 0.0091-0.0135%, and the balance of Fe and inevitable impurities;
the process route of the preparation method comprises converter smelting → casting blank heating → rolling → cooling after rolling;
wherein, in the smelting process of the converter, the end point sulfur of the converter is controlled to be less than or equal to 0.030 percent, the end point phosphorus is controlled to be less than or equal to 0.030 percent, the tapping temperature is controlled to be more than or equal to 1620 ℃, a red ladle and slag stopping tapping are adopted, and the tapping time is controlled to be more than or equal to 150 s; when tapping to 1/3, adding deoxidizer and alloy according to the end point condition for deoxidation alloying, adding the alloy according to the target value of the components, and simultaneously adding 0.26 Kg/t-0.90 Kg/t of composite vanadium-nitrogen alloy according to the detected nitrogen content and the calculation of adding 0.1Kg of composite vanadium-nitrogen to each ton of molten steel to increase the nitrogen content by 0.0010%, wherein the composite vanadium-nitrogen alloy contains 28% of nitrogen; after smelting in a converter, performing argon blowing and stirring, wherein the argon blowing time is more than 5 min;
the continuous casting tundish is covered by a low-carbon covering agent or carbonized rice hulls, and the superheat degree is 20-45 ℃; the crystallizer uses special covering slag for deformed steel bar, and the drawing speed is less than or equal to 3.0 m/min;
in the process of heating the casting blank, controlling the furnace temperature of a preheating section to be 500-900 ℃, the furnace temperature of a first heating section to be 750-1000 ℃, the furnace temperature of a second heating section to be 850-1120 ℃ and the furnace temperature of a soaking section to be 950-1100 ℃;
in the rolling process, controlling the initial rolling temperature: 890 ℃ to 950 ℃, inlet temperature of the finishing mill: 860 ℃ to 940 ℃, reduced diameter inlet temperature: 740 to 840 ℃; controlling the spinning temperature in the cooling process after rolling: 740-820 ℃, and the starting air volume of the fan is respectively as follows: 1.7 x 10 of first fan behind laying head5～1.8×105m3H, the second fan is 1.5 multiplied by 105～1.7×105m3H, 1.2 x 10 of third and fourth fans5～1.4×105m3H, 0.8 multiplied by 10 of the fifth and sixth fans5～1.0×105m3/h。
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| CN111286674A (en) * | 2020-03-31 | 2020-06-16 | 湖南华菱湘潭钢铁有限公司 | Production method of high-strength anchor rod reinforcing steel bar |
| CN113265593B (en) * | 2020-04-17 | 2022-04-12 | 柳州钢铁股份有限公司 | HRB400E wire rod twisted steel bar with small yield strength fluctuation difference in same circle |
| CN111974798B (en) * | 2020-07-24 | 2022-05-27 | 柳州钢铁股份有限公司 | Method for increasing thickness of iron scale on surface of wire rod |
| CN114182158A (en) * | 2021-10-22 | 2022-03-15 | 南京钢铁股份有限公司 | Preparation method of deformed steel bar with short-distance graded cooling control and cost reduction |
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| CN103045935A (en) * | 2012-12-14 | 2013-04-17 | 天津钢铁集团有限公司 | Control method for surface decarburization and ferrite distribution of steel disc bar of spring |
| CN103898403A (en) * | 2014-04-09 | 2014-07-02 | 武汉钢铁(集团)公司 | HRB500 hot-rolled belt rib antiseismic steel bar and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103045935A (en) * | 2012-12-14 | 2013-04-17 | 天津钢铁集团有限公司 | Control method for surface decarburization and ferrite distribution of steel disc bar of spring |
| CN103898403A (en) * | 2014-04-09 | 2014-07-02 | 武汉钢铁(集团)公司 | HRB500 hot-rolled belt rib antiseismic steel bar and preparation method thereof |
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