CN113234988B - Method for producing weathering steel with yield strength of 700MPa grade by online quenching and product thereof - Google Patents

Method for producing weathering steel with yield strength of 700MPa grade by online quenching and product thereof Download PDF

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CN113234988B
CN113234988B CN202110408062.6A CN202110408062A CN113234988B CN 113234988 B CN113234988 B CN 113234988B CN 202110408062 A CN202110408062 A CN 202110408062A CN 113234988 B CN113234988 B CN 113234988B
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李烈军
李炯轶
彭政务
温志林
陈松军
高吉祥
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South China University of Technology SCUT
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Abstract

The invention discloses a method for producing weathering steel with yield strength of 700MPa grade by on-line quenching and a product thereof, comprising the following steps: the method comprises the following steps of molten iron pretreatment, converter smelting, RH furnace refining, LF furnace refining, slab continuous casting, casting blank surface scalping after cooling to room temperature, heating furnace austenitizing, high-pressure water dephosphorization, recrystallization zone controlled rolling, ultra-fast cooling quenching, coiling and air cooling, wherein the cooling rate of the ultra-fast cooling quenching is 30-80 ℃/s, and the quenching termination temperature is 250-400 ℃. The weathering steel produced by alloying design has fine bainite structure, the yield strength is more than or equal to 700MPa, the total elongation at break is more than or equal to 20 percent, the impact energy at minus 20 ℃ is more than or equal to 180J, and the electrochemical corrosion current density is less than or equal to 2.0 multiplied by 10‑5A/cm2Corrosion rate less than or equal to 3.6X 10‑3mm/y, and has good toughness ratio and weather resistance.

Description

Method for producing weathering steel with yield strength of 700MPa grade by online quenching and product thereof
Technical Field
The invention belongs to the technical field of manufacturing of weathering steel plates, and particularly relates to a method for producing weathering steel with yield strength of 700MPa by on-line quenching and a product thereof.
Background
The weathering steel is also called as atmospheric corrosion resistant steel, a compact weathering rust layer is generated by adding elements such as copper, chromium, nickel and the like into the steel, atmospheric corrosion can be resisted for a long time without coating, and the cost is greatly reduced compared with that of stainless steel.
Generally, the yield strength of the high-strength weathering steel is more than or equal to 450MPa, and the weathering steel with higher strength grade is developed and produced to mainly meet the updating and upgrading requirements of steel for the industries such as new-generation containers, railway freight cars, high-speed train cars, communication and power transmission towers, bridges, heavy-duty automobiles and the like, and realize the safety and environmental protection requirements of improving the strength, reducing the self weight, saving energy and reducing consumption.
The development and production of the weathering steel in China are relatively late, and the main manufacturers for producing the weathering steel at present have: baoku group (Bao Steel, Wu Steel), saddle Steel, first Steel, etc. The main weathering steel varieties are: Cu-P-Cr-Ni, Mn-Cu, Cu-P-RE, Cu-P, etc., which are low in strength grade and are not satisfactory. In the production field of high-strength weathering steel, domestic main manufacturers generally adopt Nb, Mo, B, Ti, V and other alloy elements for reinforcement, and are matched with ultra-fast quenching, offline tempering and other treatments, so that the cost is higher, the working procedure is long, the energy consumption is high, and the control difficulty in the production process is higher; and the production of high-strength weathering steel on the traditional hot continuous rolling equipment through the optimized design of the alloy elements of the existing system is a challenging and innovative research work, and the reports are few at present.
Chinese patent application No. 200910301054.0 discloses "high-strength atmospheric corrosion resistant steel and a production method thereof", wherein the weight percentages of chemical components of the steel are as follows: c: less than or equal to 0.12 percent, Si: less than or equal to 0.75 percent, Mn: less than or equal to 1.50 percent, P: less than or equal to 0.025 percent, S: less than or equal to 0.008 percent, Cr: 0.30 to 1.25%, Ni: 0.12-0.65%, Cu: 0.20-0.55%, Ti: 0.006-0.02%, V: 0.09-0.15%, N: 0.01 to 0.02%, Nb: 0.015 to 0.03%, and the balance of Fe and inevitable impurities. The yield strength is more than or equal to 575MPa, and the tensile strength is more than or equal to 690 MPa. The steel is added with Nb, V, Ti and other elements, and the cost is relatively high.
Chinese patent application No. 200610035800.2 discloses a method for producing 700MPa V-N microalloyed high-strength weather-resistant steel plate based on a thin slab continuous casting and rolling process, which comprises the following chemical components in percentage by weight: c: less than or equal to 0.08 percent, Si: 0.25 to 0.75%, Mn: 0.8-2.0%, P: 0.070-0.150%, S: less than or equal to 0.040%, Cu: 0.25-0.60%, Cr: 0.30 to 1.25%, Ni: less than or equal to 0.65%, V: 0.05-0.20%, N: 0.015-0.03%. The yield strength of the steel plate is more than or equal to 700 MPa. The patent adopts a thin slab continuous casting and rolling process technology, and the process flow is long.
Chinese patent application No. 200910301054.0 discloses "a high-strength atmospheric corrosion resistant steel and a production method thereof", the chemical components of the atmospheric corrosion resistant steel plate manufactured by the method are C less than or equal to 0.12 wt%, Si less than or equal to 0.75 wt%, Mn less than or equal to l.5 wt%, P less than or equal to 0.025 wt%, S less than or equal to 0.008 wt%, Cr: 0.30-1.25 wt%, Ni: o.12-0.65 wt%, Cu: o.2-0.55 wt%, Nb: 0.015 to 0.03 wt%, V: 0.09-0.15 wt%, Ti: 0.006-0.02 wt%, N: 0.0l to 0.02 wt%, the balance being Fe and unavoidable impurities. The method adds noble alloys such as Nb, V and the like into the steel, and has high production cost.
Chinese patent application No. 201210262485.2 discloses a method for preparing vanadium-nitrogen microalloyed high-strength weathering steel, which comprises the following chemical components in percentage by weight: carbon: 0.08 to 0.13 percent; silicon: 0.15 to 0.20 percent; manganese: 1.55 to 2.00 percent; sulfur: less than or equal to 0.008 percent; phosphorus: less than or equal to 0.020%; copper: 0.25 to 0.50 percent; chromium: 0.50 to 0.70 percent; nickel: 0.20 to 0.30 percent; vanadium: 0.12 to 0.20 percent; nitrogen: 0.031% -0.045%; rare earth: 0.01 to 0.03 percent; the balance being iron. The yield strength of the steel plate is more than or equal to 650MPa, and the elongation is more than or equal to 15%.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for producing weathering steel with yield strength of 700MPa grade by on-line quenching and a product thereof, which adopts the traditional hot continuous rolling production line combined with an ultra-fast cooling process to obtain a more excellent and finer microstructure, has high strength and corrosion resistance, can produce thin weathering steel with good plate shape in batches, reduces the production cost and shortens the delivery period.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for producing weathering steel with yield strength of 700MPa grade by on-line quenching comprises the following steps:
(1) KR is carried out on the molten iron raw material for S removal, then thick slag and slag skimming treatment are carried out, the molten iron is skimmed until the bright area of the molten iron is more than or equal to 90 percent, and the end point [ S ] of the molten iron is less than or equal to 0.0020 percent by weight;
(2) converter smelting is carried out, an argon blowing process is adopted in the whole process, the final slag alkalinity is 3.0-4.0, and pellet and iron scale are used as cooling agents; fluorite is added 2min before the blowing begins to reach the blowing end point, double-slag-blocking tapping is carried out by adopting a slag-blocking cone and a slag-blocking plug, the slag thickness is less than or equal to 45mm, and ferrosilicon or silicon-manganese alloy is used for deoxidation and alloying in converter tapping; and Al-containing materials are not adopted for deoxidation and alloying;
(3) refining in an RH furnace, controlling the clearance of a ladle to be 400-600 mm after RH is reached, controlling the thickness of molten steel top slag to be less than 100mm, controlling the temperature of molten steel to be 1590-1620 ℃, and firstly carrying out RH light treatment: the vacuum degree is less than or equal to 500Pa, the treatment time is 15-20 minutes, and metal is added for alloying; then starting a five-stage vacuum pump for vacuum circulation treatment;
(4) after treatment, refining in an LF furnace, feeding an aluminum wire and a titanium wire or a Ti alloy in sequence before LF refining is out of the station, and adjusting the components of AlS and Ti;
(5) performing slab continuous casting, wherein the continuous casting adopts long water gap protection casting and Ar sealing, a carbon-free alkaline tundish slag is covered in the tundish, the superheat degree is controlled at 10-30 ℃, the electromagnetic stirring is performed in a crystallizer in the continuous casting process, a dynamic continuous casting soft reduction process is adopted in a sector section, the continuous casting drawing speed is controlled at 1.0-1.4 m/min, and the thickness of a continuous casting blank is 220-450 mm;
(6) cooling the plate blank to room temperature, and removing a layer of surface skin on the surface of the continuous casting blank;
(7) feeding the plate blank into a heating furnace for heating, wherein the heating temperature is 1200-1250 ℃, and the temperature of the plate blank taken out of the heating furnace is more than or equal to 1150 ℃;
(8) removing phosphorus by high-pressure water after the slag is taken out of the heating furnace;
(9) after dephosphorization, performing controlled rolling in a recrystallization zone for 8-15 times, wherein the final rolling temperature is more than or equal to 950 ℃, and the final reduction rate is less than or equal to 15%; so as to ensure accurate thickness and good plate shape;
(10) quenching the rolled plate by using an ultra-fast cooling device after the rolled plate is taken out of the rolling mill, wherein the cooling rate is 30-80 ℃/s, and the quenching termination temperature is 250-400 ℃;
(11) and (4) coiling by a coiling machine, and stacking and cooling. The steel plate is coiled after quenching and then stacked and cooled, and isothermal operation in a heat preservation pit for a long time is not needed in the traditional process.
Preferably, the cast slab obtained after slab continuous casting in step (5) comprises the following chemical components in percentage by weight: 0.03 to 0.07 percent of C, 0.30 to 0.45 percent of Si, 1.00 to 1.50 percent of Mn1, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.60 to 1.10 percent of Cu, 0.45 to 0.55 percent of Cr, 1.20 to 1.80 percent of Ni, 0.08 to 0.12 percent of Ti, and the balance of Fe and impurities.
Preferably, the temperature zone of the rolling in the step (9) is 950-1150 ℃, and the thickness of the outlet of the rolling mill is 6-12 mm. Under the condition of equipment allowance, the rolling pass is reduced, the rolling pass reduction rate is improved, and the retention time after rolling is properly prolonged, so that the austenite grains of the rolled plate can be fully recrystallized and refined.
Preferably, the temperature of the molten iron raw material in the step (1) is more than 1230 ℃ and less than or equal to 0.020wt percent of [ S ].
Preferably, the fluorite in the step (2) is added in batches; the addition amount of fluorite per ton of steel is less than or equal to 4.5kg in single slag, and the addition amount of fluorite per ton of steel is less than or equal to 6kg in double slag.
Preferably, the vacuum degree of the five-stage vacuum pump in the step (3) is less than 67Pa within 3 minutes of starting.
Preferably, the time for the five-stage vacuum pump to perform vacuum cycle treatment in step (3) is 15-25 minutes.
Preferably, the metal in step (3) includes ferrosilicon, ferromanganese, ferrochrome, ferronickel, ferrotitanium and copper metal plate.
Preferably, the heating time in the step (7) is more than or equal to 200 min.
Preferably, the pressure of the high-pressure water in the step (8) is more than or equal to 10 MPa.
Preferably, the cooled convolution steel obtained in step (11) is subjected to flattening, finishing and inspection in a flattening unit.
The yield strength of the weathering steel produced by the method is 700 MPa.
The invention carries out continuous casting, hot rolling, on-line quenching, coiling and air cooling on molten iron and scrap steel after converter steelmaking and RH + LF furnace refining. The method specifically comprises the following steps: blast furnace molten iron → molten iron pretreatment → converter smelting → RH furnace refining → LF furnace refining → conventional slab continuous casting → cooling to room temperature → slab inspection → surface skimming of casting blank → heating furnace → high pressure water dephosphorization → rough rolling → high pressure water dephosphorization → recrystallization zone controlled rolling → ultra-rapid cooling quenching → coiling → air cooling → open leveling → finishing → inspection.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) the invention greatly reduces the phase transition temperature by properly improving Cu and Ni through reasonable alloying design, and simultaneously avoids adding noble alloys such as Nb, Mo, V, B and the like.
(2) Compared with the traditional process, the process does not need to adopt the controlled rolling process of a non-recrystallization zone, the heat preservation process of a heat preservation pit and the like, reduces the energy consumption, shortens the process flow, reduces the addition of precious alloy, saves social resources and reduces the production cost.
(3) The steel finally obtains a fine bainite structure, the yield strength is more than or equal to 700MPa, the total elongation at break is more than or equal to 20 percent, the impact energy at minus 20 ℃ is more than or equal to 180J, the electrochemical parameters after polarization in 3.5wt percent NaCl solution are shown in a table 1, and the structure is shown in a figure 1. The data show that the steel grade has good obdurability matching and weather resistance.
TABLE 1 electrochemical parameters
Figure BDA0003023063280000061
Drawings
FIG. 1 is a metallographic structure diagram of a weathering steel prepared in example 1.
Detailed Description
The invention is further described with reference to specific embodiments, which do not limit the scope of the invention.
Example 1
A method for producing weathering steel with yield strength of 700MPa by ultra-fast cooling online quenching comprises the following steps:
(1) KR desS is firstly carried out on qualified molten iron with the temperature of 1250 ℃ and the temperature of 0.018 percent (mass percent of S in the molten iron), slag removing treatment is carried out after S removing is finished, the bright area of the molten iron is 94 percent, the end point of the molten iron [ S ] is 0.0010 percent (mass percent of S in the molten iron), argon blowing technology is adopted in the whole process, and the final slag alkalinity is 3.5;
(2) performing converter smelting, and adding pellets and iron oxide scales as cooling agents; adding 3.0kg of fluorite into each ton of steel in batches, strictly prohibiting adding the fluorite 2min before the blowing end point, carrying out double-slag-stopping tapping by adopting a slag-stopping cone and a slag-stopping plug, wherein the slag thickness is 42mm, and carrying out deoxidation and alloying on ferrosilicon for converter tapping;
(3) refining in an RH furnace, measuring and recording the content of [ O ] (mass percent of O in steel) in steel by using a rapid oxygen determination probe after reaching RH, emptying a ladle at 420mm, the thickness of molten steel top slag at 95mm, and the temperature of molten steel: 1596 deg.C, RH lightening treatment: vacuum degree of 496Pa, processing time of 15 minutes, adding different alloys in sequence for alloying, such as ferrosilicon, ferromanganese, ferrochrome, ferronickel, ferrotitanium, copper plate and the like; starting a five-stage vacuum pump, and performing vacuum circulation treatment for 20 minutes;
(4) after treatment, refining in an LF furnace, feeding an aluminum wire and a titanium wire or a Ti alloy in sequence before LF refining is out of the station, and adjusting the components of AlS and Ti;
(5) carrying out conventional slab continuous casting, wherein the continuous casting adopts long nozzle protective casting and Ar sealing, a tundish is covered with carbon-free alkaline tundish slag, a special weather-resistant steel crystallizer is used for covering slag, the superheat degree is controlled at 16 ℃, the crystallizer is put into the continuous casting process for electromagnetic stirring, a dynamic continuous casting soft reduction process is adopted in a sector section, the continuous casting drawing speed is controlled at 1.0m/min, and the thickness of a continuous casting blank is 220 mm;
(6) cooling the slab to room temperature, checking the quality and the surface of the slab, and removing a layer of surface skin on the surface of the continuous casting slab;
(7) feeding the steel plate into a furnace for heating, wherein the heating time in the heating furnace is 300min, the heating temperature is 1220 ℃, the temperature of the plate blank taken out of the heating furnace is 1180 ℃, recrystallization zone rolling is adopted, rolling passes are reduced under the condition of equipment allowance, the rolling pass reduction rate is improved, and the residence time after rolling is properly prolonged, so that the recrystallization quantity of deformed austenite is increased, and the tissue is homogenized;
(8) after the phosphorus is removed from the heating furnace, high-pressure water phosphorus removal is carried out, wherein the phosphorus removal pressure is 14 MPa;
(9) after removing phosphorus, performing controlled rolling in a recrystallization zone for 8 times, wherein the final reduction rate is 7.5 percent, the outlet thickness of a rolling mill is 12mm, and the outlet temperature is 960 ℃;
(10) quenching the rolled plate by using an ultra-fast cooling device after the rolled plate is taken out of the rolling mill, wherein the cooling rate is 30 ℃/s, and the quenching termination temperature is 310 ℃;
(11) coiling by a coiling machine, and carrying out stacking cooling;
(12) and opening, finishing and inspecting in a flattening unit.
In this embodiment, the chemical components and mass contents of the casting blank obtained after the conventional slab continuous casting in step (5) are as follows: 0.05% of C, 0.32% of Si, 1.12% of Mn1, 0.010% of P, 0.002% of S, 0.89% of Cu, 0.53% of Cr, 1.45% of Ni, 0.10% of Ti, and the balance of Fe and inevitable impurities.
Through the detection of a standard tensile test and an electrochemical corrosion test, the yield strength of the product is 710MPa, the tensile strength is 920MPa, the total elongation at break is 23%, and the impact energy at the temperature of minus 20 ℃ is 182J; electrochemical corrosion potential-0.932V and corrosion current density of 1.90X 10-5A/cm 2, corrosion rate of 3.42 x 10-3mm/y, has good obdurability matching and weather resistance, and meets and surpasses the technical conditions of the national standard GB/T4171-2008.
The metallographic structure of the weathering steel prepared in this example is shown in fig. 1, and the structure type is fine bainite.
Example 2
A method for producing weathering steel with yield strength of 700MPa by ultra-fast cooling online quenching comprises the following steps:
(1) KR desS is firstly carried out on qualified molten iron with the temperature of 1256 ℃ and the temperature of [ S ] of 0.013% (mass percentage of S in the molten iron), slag removing treatment is carried out after S removing is finished, the bright area of the molten iron is 95%, the molten iron end point [ S ] is 0.0010% (mass percentage of S in the molten iron), an argon blowing process is adopted in the whole process, and the final slag alkalinity is 3.0;
(2) performing converter smelting, and adding pellet and iron scale as cooling agents; adding 3.1kg of fluorite into each ton of steel in batches, strictly prohibiting adding the fluorite 2min before the blowing end point, carrying out double-slag-stopping tapping by adopting a slag-stopping cone and a slag-stopping plug, wherein the slag thickness is 40mm, and carrying out deoxidation and alloying on ferrosilicon for converter tapping;
(3) refining in an RH furnace, measuring and recording the content of [ O ] (mass percent of O in steel) in steel by using a rapid oxygen determination probe after reaching RH, emptying a ladle at 470mm, the thickness of molten steel top slag at 85mm, and the temperature of molten steel: 1603 ℃, RH light treatment is firstly carried out: the vacuum degree is 490Pa, the treatment time is 17 minutes, add different alloys to carry on the alloying sequentially, such as ferrosilicon, ferromanganese, ferrochrome, ferronickel, ferrotitanium and metal copper plate, etc., open the five-stage vacuum pump, carry on the vacuum cycle treatment for 20 minutes;
(4) after treatment, refining in an LF furnace, feeding an aluminum wire and a titanium wire or a Ti alloy in sequence before LF refining is out of the station, and adjusting the components of AlS and Ti;
(5) carrying out conventional slab continuous casting, wherein the continuous casting adopts long nozzle protective casting and Ar sealing, a tundish is covered with carbon-free alkaline tundish slag, a special weather-resistant steel crystallizer is used for covering slag, the superheat degree is controlled at 26 ℃, the crystallizer is put into the continuous casting process for electromagnetic stirring, a dynamic continuous casting soft reduction process is adopted in a sector section, the continuous casting drawing speed is controlled at 1.2m/min, and the thickness of a continuous casting blank is 220 mm;
(6) cooling the slab to room temperature, checking the quality and the surface of the slab, and removing a layer of surface skin on the surface of the continuous casting slab;
(7) feeding the steel plate into a furnace for heating, heating the steel plate in the furnace for 320min at 1250 ℃, taking the steel plate blank out of the furnace for 1230 ℃, rolling the steel plate by adopting a recrystallization zone, reducing rolling passes under the condition of equipment allowance, improving the rolling pass reduction rate, and properly prolonging the retention time after rolling to increase the recrystallization quantity of deformed austenite and homogenize the structure;
(8) after the phosphorus is removed from the heating furnace, high-pressure water phosphorus removal is carried out, wherein the phosphorus removal pressure is 14 MPa;
(9) after removing phosphorus, performing controlled rolling in a recrystallization zone for 10 times, wherein the final reduction rate is 7.8%, the outlet thickness of a rolling mill is 10mm, and the outlet temperature is 985 ℃;
(10) quenching the rolled plate by using an ultra-fast cooling device after the rolled plate is taken out of the rolling mill, wherein the cooling rate is 40 ℃/s, and the quenching termination temperature is 300 ℃;
(11) coiling by a coiler and air cooling;
(12) and opening, finishing and inspecting in a flattening unit.
In this embodiment, the chemical components and mass contents of the casting blank obtained after the conventional slab continuous casting in step (5) are as follows: 0.05% of C, 0.35% of Si, 1.20% of Mn1, 0.010% of P, 0.002% of S, 1.02% of Cu, 0.56% of Cr, 1.72% of Ni, 0.11% of Ti, and the balance of Fe and inevitable impurities.
Through the detection of a standard tensile test and an electrochemical corrosion test, the yield strength of the product is 720MPa, the tensile strength is 935MPa, the total elongation at break is 22%, and the impact energy at the temperature of minus 20 ℃ is 190J; electrochemical corrosion potential-0.935V, corrosion current density 1.91X 10-5A/cm 2, corrosion rate of 3.45 x 10-3mm/y, has good obdurability matching and weather resistance, and the performance of the alloy meets and exceeds the technical conditions of the national standard GB/T4171-2008.
Example 3
A method for producing weathering steel with yield strength of 700MPa by ultra-fast cooling online quenching comprises the following steps:
(1) KR desS is carried out on qualified molten iron with the temperatures of 1266 ℃ and [ S ] of 0.011 percent (mass percentage of S in the molten iron), slag removing treatment is carried out after S removing is finished, the bright area of the molten iron is 94 percent, the end point [ S ] of the molten iron is 0.0010 percent (mass percentage of S in the molten iron), argon blowing technology is adopted in the whole process, and the final slag alkalinity is 4.0;
(2) performing converter smelting, and adding pellets and iron oxide scales as cooling agents; adding 3.7kg of fluorite into each ton of steel in batches, strictly prohibiting adding the fluorite 2min before the blowing end point, carrying out double-slag-stopping tapping by adopting a slag-stopping cone and a slag-stopping plug, wherein the slag thickness is 40mm, and carrying out deoxidation and alloying on ferrosilicon for converter tapping;
(3) RH furnace refining, after reaching RH, measuring and recording the content of [ O ] (the mass percent of O in steel) in steel by using a rapid oxygen determination probe, emptying a steel ladle at 450mm, the thickness of molten steel top slag at 75mm, and the temperature of molten steel: 1590 ℃, and RH light treatment is firstly carried out: the vacuum degree is 480Pa, the treatment time is 15 minutes, different alloys are sequentially added for alloying, such as ferrosilicon, ferromanganese, ferrochrome, ferronickel, ferrotitanium, a metal copper plate and the like, a five-stage vacuum pump is started, and the vacuum circulation treatment is carried out for 20 minutes;
(4) after treatment, refining in an LF furnace, feeding an aluminum wire and a titanium wire or a Ti alloy in sequence before LF refining is out of the station, and adjusting the components of AlS and Ti;
(5) carrying out conventional slab continuous casting, wherein the continuous casting adopts long nozzle protective casting and Ar sealing, a tundish is covered with carbon-free alkaline tundish slag, a special weather-resistant steel crystallizer is used for covering slag, the superheat degree is controlled at 21 ℃, the crystallizer is put into the continuous casting process for electromagnetic stirring, a dynamic continuous casting soft reduction process is adopted in a sector section, the continuous casting drawing speed is controlled at 1.2m/min, and the thickness of a continuous casting blank is 220 mm;
(6) cooling the slab to room temperature, checking the quality and the surface of the slab, and removing a layer of surface skin on the surface of the continuous casting slab;
(7) feeding the blank into a furnace for heating, wherein the heating time in the heating furnace is 300min, the heating temperature is 1245 ℃, the temperature of the blank out of the heating furnace is 1220 ℃, the recrystallization zone is adopted for rolling, the rolling pass is reduced under the condition of equipment allowance, the rolling pass reduction rate is improved, and the retention time after rolling is properly prolonged, so that the recrystallization quantity of the deformed austenite is increased, and the tissue is homogenized;
(8) after the phosphorus is removed from the heating furnace, high-pressure water phosphorus removal is carried out, wherein the phosphorus removal pressure is 14 MPa;
(9) after dephosphorization, adopting a recrystallization zone to control rolling for 8 times, wherein the final reduction rate is 7.8 percent, the outlet thickness of a rolling mill is 10mm, and the outlet temperature is 995 ℃;
(10) quenching the rolled plate by using an ultra-fast cooling device after the rolled plate is taken out of the rolling mill, wherein the cooling rate is 35 ℃/s, and the quenching termination temperature is 320 ℃;
(11) coiling by a coiling machine, and stacking and cooling;
(12) and opening, finishing and inspecting in a flattening unit.
In this embodiment, the chemical components and mass contents of the casting blank obtained after the conventional slab continuous casting in step (5) are as follows: 0.05% of C, 0.43% of Si, 1.35% of Mn1, 0.010% of P, 0.002% of S, 1.15% of Cu, 0.48% of Cr, 1.78% of Ni, 0.12% of Ti, and the balance of Fe and inevitable impurities.
Through the detection of a standard tensile test and an electrochemical corrosion test, the yield strength of the product obtained by the method is 735MPa, the tensile strength is 944MPa, the total elongation at break is 24 percent, the impact energy is 185J at the temperature of minus 20 ℃, and the corrosion current density is 1.89 multiplied by 10 at the electrochemical corrosion potential of minus 0.939V-5A/cm 2, corrosion rate of 3.49 x 10-3mm/y, has good obdurability matching and weather resistance, and the performance of the alloy meets and exceeds the technical conditions of the national standard GB/T4171-2008.
Example 4
A method for producing weathering steel with yield strength of 700MPa grade by on-line quenching comprises the following steps:
(1) KR desS is carried out on qualified molten iron with the temperatures of 1268 ℃ and [ S ] of 0.011 percent (mass percentage of S in the molten iron), slag removing treatment is carried out after S removing is finished, the bright area of the molten iron is 94 percent, the end point [ S ] of the molten iron is 0.0010 percent (mass percentage of S in the molten iron), argon blowing technology is adopted in the whole process, and the final slag alkalinity is 4.0;
(2) performing converter smelting, and adding pellets and iron oxide scales as cooling agents; adding 3.6kg of fluorite into each ton of steel in batches, strictly prohibiting adding the fluorite 2min before the blowing end point, carrying out double-slag-stopping tapping by adopting a slag-stopping cone and a slag-stopping plug, wherein the slag thickness is 40mm, and carrying out deoxidation and alloying on ferrosilicon for converter tapping;
(3) RH furnace refining, after reaching RH, measuring and recording the content of [ O ] (the mass percent of O in steel) in steel by using a rapid oxygen determination probe, emptying a steel ladle at 450mm, the thickness of molten steel top slag at 75mm, and the temperature of molten steel: 1595 ℃, RH light treatment is firstly carried out: the vacuum degree is 480Pa, the treatment time is 15 minutes, different alloys are sequentially added for alloying, such as ferrosilicon, ferromanganese, ferrochrome, ferronickel, ferrotitanium, a metal copper plate and the like, a five-stage vacuum pump is started, and the vacuum circulation treatment is carried out for 20 minutes;
(4) after treatment, refining in an LF furnace, feeding an aluminum wire and a titanium wire or a Ti alloy in sequence before LF refining is out of the station, and adjusting the components of AlS and Ti;
(5) carrying out conventional slab continuous casting, wherein the continuous casting adopts long nozzle protective casting and Ar sealing, a tundish is covered with carbon-free alkaline tundish slag, a special weather-resistant steel crystallizer is used for covering slag, the superheat degree is controlled at 23 ℃, the crystallizer is put into the continuous casting process for electromagnetic stirring, a dynamic continuous casting soft reduction process is adopted in a sector section, the continuous casting drawing speed is controlled at 1.2m/min, and the thickness of a continuous casting blank is 220 mm;
(6) cooling the plate blank to room temperature, checking the quality and the surface of the plate blank, and removing a layer of surface skin on the surface of the continuous casting blank;
(7) feeding the blank into a furnace for heating, wherein the heating time in the heating furnace is 300min, the heating temperature is 1245 ℃, the temperature of the blank out of the heating furnace is 1220 ℃, the recrystallization zone is adopted for rolling, the rolling pass is reduced under the condition of equipment allowance, the rolling pass reduction rate is improved, and the retention time after rolling is properly prolonged, so that the recrystallization quantity of the deformed austenite is increased, and the tissue is homogenized;
(8) after the phosphorus is removed from the heating furnace, high-pressure water phosphorus removal is carried out, wherein the phosphorus removal pressure is 14 MPa;
(9) after removing phosphorus, performing controlled rolling in a recrystallization zone for 8 times, wherein the final reduction rate is 7.8 percent, the outlet thickness of a rolling mill is 10mm, and the outlet temperature is 990 ℃;
(10) quenching the rolled plate by using an ultra-fast cooling device after the rolled plate is taken out of the rolling mill, wherein the cooling rate is 35 ℃/s, and the quenching termination temperature is 320 ℃;
(11) coiling by a coiling machine, and stacking and cooling;
(12) and opening, finishing and inspecting in a flattening unit.
In this embodiment, the chemical components and mass contents of the casting blank obtained after the conventional slab continuous casting in step (5) are as follows: 0.05% of C, 0.45% of Si, 1.30% of Mn1, 0.010% of P, 0.002% of S, 1.08% of Cu, 0.46% of Cr, 1.80% of Ni, 0.11% of Ti, and the balance of Fe and inevitable impurities.
Subjected to standard tensile testThe test and the electrochemical corrosion test detect that the product obtained by the method has the yield strength of 735MPa, the tensile strength of 944MPa, the total elongation at break of 24 percent, the impact energy of 185J at the temperature of minus 20 ℃, the electrochemical corrosion potential of minus 0.940V and the corrosion current density of 1.92 multiplied by 10-5A/cm 2, corrosion rate of 3.52 x 10-3mm/y, has good obdurability matching and weather resistance, and the performance of the alloy meets and exceeds the technical conditions of the national standard GB/T4171-2008.
The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (8)

1. The method for producing the weathering steel with the yield strength of 700MPa by on-line quenching is characterized by comprising the following steps of:
(1) KR is carried out on the molten iron raw material for S removal, then thick slag and slag skimming treatment are carried out, the molten iron is skimmed until the bright area of the molten iron is more than or equal to 90 percent, and the end point [ S ] of the molten iron is less than or equal to 0.0020 percent by weight;
(2) converter smelting is carried out, an argon blowing process is adopted in the whole process, the final slag alkalinity is 3.0-4.0, and pellet ore and iron scale are used as cooling agents; fluorite is added 2min before the blowing begins to reach the blowing end point, double-slag-blocking tapping is carried out by adopting a slag-blocking cone and a slag-blocking plug, the slag thickness is less than or equal to 45mm, and ferrosilicon or silicon-manganese alloy is used for deoxidation and alloying in converter tapping;
(3) and (3) RH furnace refining, controlling the clearance of a steel ladle to be 400-600 mm after RH is reached, controlling the thickness of molten steel top slag to be less than 100mm, controlling the temperature of molten steel to be 1590-1620 ℃, and firstly carrying out RH light treatment: the vacuum degree is less than or equal to 500Pa, the treatment time is 15-20 minutes, and metal is added for alloying; then starting a five-stage vacuum pump to carry out vacuum circulation treatment;
(4) after treatment, refining in an LF furnace, feeding an aluminum wire and a titanium wire or a Ti alloy in sequence before LF refining is out of the station, and adjusting the components of AlS and Ti;
(5) performing continuous slab casting, wherein the continuous casting adopts long water gap protection casting and Ar sealing, a carbon-free alkaline tundish slag is covered in the tundish, the superheat degree is controlled at 10-30 ℃, the electromagnetic stirring is performed in a crystallizer in the continuous casting process, a dynamic continuous casting soft reduction process is adopted in a sector section, the continuous casting drawing speed is controlled at 1.0-1.4 m/min, and the thickness of a continuous casting blank is 220-450 mm; the casting blank obtained after slab continuous casting comprises the following chemical components in percentage by weight: 0.03 to 0.07 percent of C, 0.30 to 0.45 percent of Si, 1.00 to 1.50 percent of Mn1, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.60 to 1.10 percent of Cu, 0.45 to 0.55 percent of Cr, 1.20 to 1.80 percent of Ni, 0.08 to 0.12 percent of Ti, and the balance of Fe and impurities;
(6) cooling the plate blank to room temperature, and removing a layer of surface skin on the surface of the continuous casting blank;
(7) feeding the plate blank into a heating furnace for heating, wherein the heating temperature is 1200-1250 ℃, and the temperature of the plate blank taken out of the heating furnace is more than or equal to 1150 ℃;
(8) removing phosphorus by high-pressure water after the slag is taken out of the heating furnace;
(9) after dephosphorization, performing controlled rolling in a recrystallization zone for 8-15 times, wherein the final rolling temperature is more than or equal to 950 ℃, and the final reduction rate is less than or equal to 15%; the rolling temperature zone is 950-1150 ℃, and the thickness of the outlet of the rolling mill is 6-12 mm;
(10) quenching the rolled plate by using an ultra-fast cooling device after the rolled plate is taken out of the rolling mill, wherein the cooling rate is 30-80 ℃/s, and the quenching termination temperature is 250-400 ℃;
(11) coiling by a coiling machine, and carrying out stacking cooling;
the yield strength of the prepared steel is more than or equal to 700MPa, the total elongation at break is more than or equal to 20 percent, and the impact energy at minus 20 ℃ is more than or equal to 180J.
2. The process defined in claim 1 wherein the temperature of the hot metal feed stock in step (1) is >1230 ℃, [ S ] is ≦ 0.020 wt.%.
3. The method according to claim 1, wherein the fluorite is added in portions in step (2); the addition amount of fluorite per ton of steel is less than or equal to 4.5kg in single slag, and the addition amount of fluorite per ton of steel is less than or equal to 6kg in double slag.
4. The method according to claim 1, wherein in the step (3), the five-stage vacuum pump is started within 3 minutes, and the vacuum degree is less than 67 Pa; the time for the five-stage vacuum pump to carry out vacuum circulation treatment is 15-25 minutes.
5. The method of claim 1, wherein the heating time in step (7) is 200min or more.
6. The method according to claim 1, wherein the pressure of the high-pressure water in the step (8) is not less than 10MP a.
7. The method of claim 1, wherein the cooled convoluted steel of step (11) is opened, finished and inspected in a temper mill.
8. Weathering steel with a yield strength of 700MPa produced by the process according to any of claims 1 to 7.
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