CN102925799B - A kind of production method of ultra-high strength steel plate - Google Patents

A kind of production method of ultra-high strength steel plate Download PDF

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CN102925799B
CN102925799B CN201210429941.8A CN201210429941A CN102925799B CN 102925799 B CN102925799 B CN 102925799B CN 201210429941 A CN201210429941 A CN 201210429941A CN 102925799 B CN102925799 B CN 102925799B
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CN102925799A (en
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杨云清
曹志强
刘建兵
杨俊�
曹波
吴清明
雷辉
袁仁平
罗登
钱亚军
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Hunan Hualing Xiangtan Iron and Steel Co Ltd
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Abstract

A production method for ultra-high strength steel plate, the operational path of employing is converter steelmaking → external refining → continuous casting → heating → rolling → accelerating cooling → thermal treatment, and the chemical composition percent mass of steel consists of C=0.21 ~ 0.24, Si=0.45 ~ 0.55, Mn=1.40 ~ 1.46, P≤0.015, S≤0.010, Al=0.03 ~ 0.06, Nb=0.02 ~ 0.03, V=0.05 ~ 0.06, Ti=0.035 ~ 0.050, Mo=0.25 ~ 0.35, B=0.0017 ~ 0.0022.Steel plate Composition Design is succinct, does not add a large amount of alloying elements, reduces the production cost of ultra-high strength steel plate; Add Ti in steel plate composition, improve the welding property of steel plate; The complicated carbide that steel plate is organized as ultra-fine lath martensite+nano level lath residual austenite and is settled out after Q+P process, the over-all properties of armor plate strength and plasticity is better than dual phase steel, TRIP steel and general martensite steel sections.Steel plate is after roller quenching machine quenching, and template is good; Operation is simple, technique easily realizes, and solves tradition quenching, tempering can not the difficult problem of production ultra-high strength steel plate, realizes the batch production of 1300MPa level ultra-high strength steel plate.

Description

A kind of production method of ultra-high strength steel plate
Technical field
The invention belongs to steel-smelting technology, is a kind of production method of ultra-high strength steel plate.
Technical background
Ultrahigh-strength steel refers to that its tensile strength is at more than 1000MPa, close to or more than 2000MPa, percentage of total elongation > 10 %, and the structure iron that price is more honest and cleaner.Traditional quenching-tempering process can not meet high-strength steel and have certain toughness and cheap requirement concurrently.At present, general high-strength steel is all make steel grade performance up to standard by adding alloying element substantially, and the high-strength steel cost obtained like this is higher, is unfavorable for saving energy and reduce the cost.In order to reduce production cost, increase economic benefit, must constantly to novel process, new technology research experiment.
Perlite (non-deformation state) and the more difficult tensile strength of steel that makes of bainite structure are up to 2000MPa, and martensitic stucture is when being competent at.For having certain toughness concurrently, the tissue of steel should be made to be dislocation strip martensitic stucture.Have recognized that in the past that the residual austenite physical efficiency in hardened steel improved plasticity and the toughness of steel half century, as strip martensite surround by the residual austenite of a few nanometer thickness, add toughness; Utilize austenitic thermostabilization phenomenon, propose tool steel without distortion quenching and rapid steel workpiece without be out of shape tempering heat treatment process.Experiment proves, hydrogen embrittlement crackle is hampered by fcc austenite, the 300M steel (residual austenite about 3 %) containing 1.3 % Si through 300 DEG C of tempering contrasts 4340 steel (paralympic < 2 %), separates out ε-carbide equally, but the slow order of magnitude of stress corrosion speed.Xu Zuyao once tentatively set forth the vital role of residual austenite in soft steel.Utilize the electron microscope experiment results such as Thomas, Xu Zuyao calculates proof: during soft steel quenching, carbon diffuses to residual austenite by martensite.Speer etc. propose the Q+P thermal treatment process of steel, namely quench after between (Q) to Ms ~ Mf, through certain temperature insulation, make carbon distribute (partition) to austenite from martensite, a certain amount of austenite is stablized to room temperature to ensure toughness.For hindering the precipitation of Fe3C, containing 1% ~ 2 %Si in the Q+P steel designed by them.Xu Zuyao, on the Q+P Process ba-sis such as Speer, introduces precipitation hardening mechanism, preliminary proposition Q+P+T technique, namely in steel, carbon compound forming element is added, after quenching outside carbon distributes, and make diffusion-precipitation complicated carbide in martensite, obtain higher-strength and toughness cooperation.
Research shows, residual austenite physical efficiency effectively improves plasticity and the toughness of material, for obtaining a certain amount of stable retained austenite in hardened steel, quenching (Quenching)-carbon is adopted to distribute (Partitioning)-tempering (Tempering) technique when proposing thermal treatment, be called for short Q-P-T technique, i.e. held for some time after steel plate quenching to certain temperature, carbon is dispensed to retained austenite from martensite, then after certain temperature tempering suitable time, it is made to separate out complicated carbide, to increase strengthening effect.Carried out the thermal modeling test of similar Q-P-T technique to 0.2%C-Mn-Ti-B, and carried out structure observation to the sample after thermal analogy, organizing of obtaining is lath martensite tissue and a certain amount of residual austenite substantially.
Adopt Q-P-T technique to carry out experimental study to 0.2%C-Mn-Ti-B, on each motherboard, then cut two tension specimens, two groups of impact specimens, a metallographic specimen and hardness specimens, the performance obtained is as table 1.As can be seen from the table, not only strength ratio increased originally, and impact, unit elongation, hardness geometric ratio test before all increase.
The performance test results that table 1 adopts Q-P-T technique to test 0.2%C-Mn-Ti-B
Known by above-mentioned experimental study, adopt Q-P-T technique really can improve the performance of high-strength steel, but also alloying element addition can be reduced.Therefore, by Q-P-T technique about 0.15% the trial-production of carbon content high-strength steel, optimize the super-high strength steel chemical composition reaching more than 1100MPa level on the basis of few addition element, to reduce the production cost of high-strength steel, improve plasticity and the toughness of high-strength steel simultaneously.
Chinese patent application 200610018011.8 " easy-weld hardening high-strength steel plate and production method thereof ", Chinese patent application 200710193023.9 " a kind of high tensile steel plate and preparation method thereof ", Chinese patent application 200710193027.7 " high tensile steel plate and preparation method thereof ", be respectively 80kg, 100kg, 110kg level High Strength Steel Plate production technology, adopt out-line quenching+tempering process (Q+T), steel plate is finally organized as tempered martensite.Above patent light plate composition with the addition of the precious alloys such as Mo, Ni, V, Ti, Nb of high-content, and to ensure the adaptability of plate property and technique, production cost is high.
So in prior art, High Strength Steel Plate production Problems existing is: with the addition of the precious alloys such as Mo, Ni, V, Ti, Nb of high-content in High Strength Steel Plate composition, to ensure the adaptability of plate property and technique, Plate Production cost is high; When High Strength Steel Plate intensity reaches 1000MPa, steel plate plasticity and poor toughness, its unit elongation is less than 10%; (Q+T) and TMCP production technique can not produce the demand that more than 1100MPa high tensile steel plate meets manufacturing at present; The maturation process that more than 1200Mpa superstrength Wide and Thick Slab is not produced in batches at present and production method.
Summary of the invention
The present invention aims to provide a kind of production method of ultra-high strength steel plate, and employing Q+P explained hereafter thickness is the 1300MPa grade super strength structural steel and iron of 8 ~ 60mm low cost, meets the demand of manufacturing, realizes theory that is energy-saving and cost-reducing, green iron and steel.Its feature is succinct Composition Design; Yield strength is not less than 1300Mpa, and tensile strength is not less than 1400 Mpa, and unit elongation is greater than 10%, and-20 DEG C of impacts of collision are not less than 47J; Steel plate is organized as stable tiny lath martensite and residual austenite, and is distributed with the carbide of coherence and half coherence, to improve the reasonable coordination of armor plate strength and obdurability.
Technical scheme of the present invention:
A production method for ultra-high strength steel plate, the operational path of employing is converter steelmaking → external refining → continuous casting → heating → rolling → accelerating cooling → thermal treatment.
The chemical composition percent mass of steel consists of C=0.21 ~ 0.24, Si=0.45 ~ 0.55, Mn=1.40 ~ 1.46, P≤0.015, S≤0.010, Al=0.03 ~ 0.06, Nb=0.02 ~ 0.03, V=0.05 ~ 0.06, Ti=0.035 ~ 0.050, Mo=0.25 ~ 0.35, B=0.0017 ~ 0.0022.
A. make steel: molten steel sulfur content S≤0.010% after hot metal pretreatment, temperature >=1250 DEG C, slag is taken off totally before entering converter by molten iron; Converter terminal control C-T coordinates tapping, P≤0.012%, S≤0.015%; Slag-stopping tapping, slag is thick≤50mm, tapping time 4 ~ 7min, tapping 1/5 adds alloy, and tapping 2/5 adds alloy; Squeeze into the deoxidation of Al line after tapping and be no less than 250m.
B. refining: the refining of LF stove makes white slag and deoxidation operation to molten steel; The refining later stage adds V-Fe, Nb-Fe, Ti-Fe alloy carries out trimming; The Si-Ca line that before departures, feeding is appropriate, adds B-Fe after blowing Ar5min, and the add-on of B-Fe controls according to 0.018 ~ 0.020; In front 5min after VD extracting vacuum starts, ladle bottom Ar stirring gas flow is reduced to zero; After extracting vacuum starts 3min, Quick condition of high vacuum degree, to below 0.5tor, protects more than vacuum circulation degassing 15min.
C. continuous casting: liquidus line 1508 DEG C, middle bag superheating temperature controls 5 ~ 15 DEG C; During pulling speed of continuous casting adopts, plate strand production allusion quotation pulling rate performs; Produce thickness of strand 300mm, continuous casting whole process carries out protective casting.
D. heat: Heating temperature 1190 ~ 1210 DEG C, slab heart portion temperature of coming out of the stove is greater than 1150 DEG C; Rate of heating 9 ~ 11min/cm, total time inside furnace is greater than 5h.
E. rolling: roughing adopts high temperature, large pressure, at a slow speed rolling technique; Select maximum reduction in pass by the ability of milling train, draft reaches more than 15%; Start rolling temperature 1040 ~ 1060 DEG C, finishing temperature 960 ~ 980 DEG C; Finish rolling adds up draft and is greater than 60%, and last three percentage pass reductions are greater than 12%, start rolling temperature 830 ~ 820 DEG C, finishing temperature 780 ~ 810 DEG C.
F. roller repairing: roll rear ACC cold by force, opens cold temperature 770 ~ 790 DEG C, is cooled to 580 ~ 630 DEG C of air coolings, speed of cooling 5 ~ 14 DEG C/s.
G. thermal treatment: quenching temperature 890 ~ 910 DEG C, time inside furnace calculates by 1.3 ~ 1.5min/mm × thickness of slab min, quenching press speed 20 ~ 40m/min; After steel plate quenching, the quick tempering stove of sending into of temperature 250 ~ 310 DEG C carries out carbon distribution; Carbon dispense temperature 180 ~ 200 DEG C, time inside furnace is pressed 0.9min/mm × thickness of slab min and is calculated; Air cooling after coming out of the stove.
The plate property actual achievement of producing by this technical scheme as shown in Table 1.
table 1 1300MPa level ultra-high strength steel plate service check actual achievement
The technology of the present invention principle:
The present invention possesses tissue characteristic and the requirement of super-high strength steel: the fine strip shape martensite of (1) tool high dislocation density, and lath thickness is tens nanometer; (2) martensite is separated out tiny coherence complicated carbide to gain in strength further; (3) cementite Fe3C is avoided to separate out; (4) residual austenite of proper amt (thickness), necessarily carbon content is contained between martensite bar to improve toughness and the plasticity of steel; (5) original austenite Ying Ju fine grained texture.
Carbon height manganese Composition Design during 1300MPa level ultra-high strength steel plate of the present invention uses, ensures the intensity of steel plate; High Si composition suppresses the formation of Fe3C, stablizes ε-carbide, and makes steel can carry out carbon distribution (Partitioning) process; Containing stable austenite elements such as Mn, Ms is declined; Containing complicated carbide forming element as Nb, V, Ti, Mo element makes Ms decline, in precipitation hardening and fining austenite grains; Ti adds the welding property improving ultra-high strength steel plate.
The production method of Clean Steel is adopted to produce high-quality continuously cast bloom; TMCP rolling technology refinement steel plate hot tissue before treatment; Lesser temps austenitizing, can obtain thin brilliant austenite structure; Be quenched to 250 ~ 310 DEG C (Ms ~ Mf) to obtain appropriate martensite, improve armor plate strength; Carry out carbon distribution at 180 ~ 200 DEG C, the rich carbon of more residual austenites is also stablized to room temperature; Dispense temperature complicated carbide coherence and half coherent precipitate can improve intensity and plasticity, the toughness of steel; The complicated carbide that steel plate is organized as lath martensite+lath residual austenite and is settled out after Q+P process, the over-all properties of armor plate strength and plasticity is better than dual phase steel, TRIP steel, general martensite steel sections.
Therefore, compared with prior art, the present invention has the following advantages: steel plate Composition Design is succinct, does not add a large amount of alloying elements, reduces the production cost of ultra-high strength steel plate; Add Ti in steel plate composition, improve the welding property of steel plate; The complicated carbide that steel plate is organized as ultra-fine lath martensite+nano level lath residual austenite and is settled out after Q+P process, the over-all properties of armor plate strength and plasticity is better than dual phase steel, TRIP steel and general martensite steel sections.Steel plate is after roller quenching machine quenching, and template is good; Operation is simple, technique easily realizes, and solves tradition quenching, tempering can not the difficult problem of production ultra-high strength steel plate, realizes the batch production of 1300MPa level ultra-high strength steel plate.
Accompanying drawing explanation
Accompanying drawing is the organization chart that the present invention produces steel plate.
Embodiment
Embodiment 1:1300MPa level super-high strength steel board production technology, the composition quality percentage composition of steel is: C=0.22, Si=0.52, Mn=1.45, P=0.015, S=0.009, Al=0.048, Nb=0.024, V=0.056, Ti=0.041, Mo=0.26, B=0.0018, all the other are Fe.
Its main technological steps and parameter as follows:
Enter stove molten iron and first must carry out hot metal pretreatment, molten steel sulfur content S≤0.010% after process, temperature >=1250 DEG C, must take off slag totally before molten iron enters converter.Converter steelmaking process adds molten iron and steel scrap, and molten iron and steel scrap proportioning are molten iron about 85%, steel scrap about 15%.Converter terminal control C-T coordinates tapping, P≤0.012%, S≤0.015%; Strict slag-stopping tapping, slag is thick≤50mm, tapping time 4 ~ 7min, tapping 1/5 adds alloy, and tapping 2/5 adds alloy; Squeeze into the deoxidation of Al line after tapping and be no less than 250m, and suitably adjust depending on the change of Intake Quantity, terminal C, molten steel oxidation.Then molten steel is transported to LF refining furnace and carries out refining operation.
LF refining makes white slag and deoxidation operation to molten steel, guarantees that the content of the element such as oxygen, sulphur in steel controls in lower level; The refining later stage is added the appropriate alloy such as V-Fe, Nb-Fe, Ti-Fe according to LF stove molten steel sample composition and carries out trimming, guarantees that composition all hits; The Si-Ca line that before departures, feeding is appropriate, adds B-Fe after blowing Ar5min, and the add-on of B-Fe controls according to 0.018 ~ 0.020.Then molten steel is transported to VD stove and carries out vacuum-treat.In front 5min after VD extracting vacuum starts, ladle bottom Ar stirring gas flow is reduced to zero, prevents from stirring molten steel before vacuum chamber does not reach vacuum, cause molten steel to be oxidized; After extracting vacuum starts 3min, require that Quick condition of high vacuum degree is to below 0.5tor, and under this vacuum tightness the empty 15min of fidelity; During RH vacuum-treat, vacuum tightness remains on below 0.5tor, and under this vacuum tightness more than circulating degasification 15min.Vacuum-treat terminates rear soft blow process molten steel being carried out to more than 15min, then molten steel is transported to continuous casting and casts.
The liquidus line of this steel grade 1508 DEG C, middle bag superheating temperature controls 5 ~ 15 DEG C; During pulling speed of continuous casting adopts, plate strand production allusion quotation pulling rate degree performs, and strict implement stable state is cast; Produce thickness of strand 300mm(casting machine and produce maximum ga(u)ge); Continuous casting whole process carries out strict protective casting, prevents molten steel secondary oxidation and nitrogen pick-up.The strand that rolls off the production line carries out the cooling in heap of more than 24 hours.
Strand is in the Heating temperature 1190 ~ 1210 DEG C of process furnace, and slab heart portion temperature of coming out of the stove is greater than 1150 DEG C; Rate of heating 9 ~ 11min/cm, total time inside furnace is greater than 5h.Come out of the stove and carry out high pressure dephosphorization, then enter roughing.Roughing adopts " high temperature, large pressure, at a slow speed " rolling technique, does not use automatic rolling, manual rolling; Reduction schedule establishment selects maximum reduction in pass by the ability of milling train, and maximum percentage pass reduction reaches more than 15%; Start rolling temperature 1040 ~ 1060 DEG C, finishing temperature 960 ~ 980 DEG C.Finish rolling adds up draft and is greater than 60%, and last three percentage pass reductions are greater than 12%; Start rolling temperature 830 ~ 820 DEG C, finishing temperature 780 ~ 810 DEG C.Roll rear ACC and cool the strong cold technique of selection, open cold temperature 770 ~ 790 DEG C, be cooled to 580 ~ 630 DEG C of air coolings, speed of cooling 5 ~ 14 DEG C/s.
The heat treatment mode that steel plate adopts quenching+carbon to distribute.The temperature of austenitizing is 890 ~ 910 DEG C; Time inside furnace calculates by (1.3 ~ 1.5min/mm × thickness of slab) min; Quenching press speed 20 ~ 40m/min; Temperature 250 ~ 310 DEG C after steel plate quenching, sends into tempering stove fast and carries out carbon distribution after steel plate quenching.Carbon dispense temperature 180 ~ 200 DEG C; Time inside furnace calculates by (0.9min/mm × thickness of slab) min; Air cooling after coming out of the stove.
Finished steel plate performance test results is: thickness is the steel plate yield strength of 20mm is 1353MPa, and tensile strength is 1449MPa, and unit elongation is 13.1%, and normal temperature impacts for 113/98/95J, and 0 DEG C is impacted for 72/77/68J, and-20 DEG C are impacted for 70/80/59J.Thickness is the steel plate yield strength of 40mm is 1334MPa, and tensile strength is 1448MPa, and unit elongation is 12.8%, and normal temperature impacts for 128/104/93J, and 0 DEG C is impacted for 65/69/90J, and-20 DEG C are impacted for 65/73/68J.
Embodiment 2:1300MPa level super-high strength steel board production technology, the composition quality percentage composition of steel is: C=0.21, Si=0.49, Mn=1.43, P=0.011, S=0.008, Al=0.49, Nb=0.027, V=0.059, Ti=0.038, Mo=0.29, B=0.0017, all the other are Fe.
Its main technological steps and parameter as follows:
Enter stove molten iron and first must carry out hot metal pretreatment, molten steel sulfur content S≤0.010% after process, temperature >=1250 DEG C, must take off slag totally before molten iron enters converter.Converter steelmaking process adds molten iron and steel scrap, and molten iron and steel scrap proportioning are molten iron about 85%, steel scrap about 15%.Converter terminal control C-T coordinates tapping, P≤0.012%, S≤0.015%; Strict slag-stopping tapping, slag is thick≤50mm, tapping time 4 ~ 7min, tapping 1/5 adds alloy, and tapping 2/5 adds alloy; Squeeze into the deoxidation of Al line after tapping and be no less than 250m, and suitably adjust depending on the change of Intake Quantity, terminal C, molten steel oxidation.Then molten steel is transported to LF refining furnace and carries out refining operation.
LF refining makes white slag and deoxidation operation to molten steel, guarantees that the content of the element such as oxygen, sulphur in steel controls in lower level; The refining later stage is added the appropriate alloy such as V-Fe, Nb-Fe, Ti-Fe according to LF stove molten steel sample composition and carries out trimming, guarantees that composition all hits; The Si-Ca line that before departures, feeding is appropriate, adds B-Fe after blowing Ar5min, and the add-on of B-Fe controls according to 0.018 ~ 0.020.Then molten steel is transported to VD stove and carries out vacuum-treat.In front 5min after VD extracting vacuum starts, ladle bottom Ar stirring gas flow is reduced to zero, prevents from stirring molten steel before vacuum chamber does not reach vacuum, cause molten steel to be oxidized; After extracting vacuum starts 3min, require that Quick condition of high vacuum degree is to below 0.5tor, and under this vacuum tightness the empty 15min of fidelity; During RH vacuum-treat, vacuum tightness remains on below 0.5tor, and under this vacuum tightness more than circulating degasification 15min.Vacuum-treat terminates rear soft blow process molten steel being carried out to more than 15min, then molten steel is transported to continuous casting and casts.
The liquidus line of this steel grade 1508 DEG C, middle bag superheating temperature controls 5 ~ 15 DEG C; During pulling speed of continuous casting adopts, plate strand production allusion quotation pulling rate degree performs, and strict implement stable state is cast; Produce thickness of strand 300mm(casting machine and produce maximum ga(u)ge); Continuous casting whole process carries out strict protective casting, prevents molten steel secondary oxidation and nitrogen pick-up.The strand that rolls off the production line carries out the cooling in heap of more than 24 hours.
Strand is in the Heating temperature 1190 ~ 1210 DEG C of process furnace, and slab heart portion temperature of coming out of the stove is greater than 1150 DEG C; Rate of heating 9 ~ 11min/cm, total time inside furnace is greater than 5h.Come out of the stove and carry out high pressure dephosphorization, then enter roughing.Roughing adopts " high temperature, large pressure, at a slow speed " rolling technique, does not use automatic rolling, manual rolling; Reduction schedule establishment selects maximum reduction in pass by the ability of milling train, and maximum percentage pass reduction reaches more than 15%; Start rolling temperature 1040 ~ 1060 DEG C, finishing temperature 960 ~ 980 DEG C.Finish rolling adds up draft and is greater than 60%, and last three percentage pass reductions are greater than 12%; Start rolling temperature 830 ~ 820 DEG C, finishing temperature 780 ~ 810 DEG C.Roll rear ACC and cool the strong cold technique of selection, open cold temperature 770 ~ 790 DEG C, be cooled to 580 ~ 630 DEG C of air coolings, speed of cooling 5 ~ 14 DEG C/s.
The heat treatment mode that steel plate adopts quenching+carbon to distribute.The temperature of austenitizing is 890 ~ 910 DEG C; Time inside furnace calculates by (1.3 ~ 1.5min/mm × thickness of slab) min; Quenching press speed 20 ~ 40m/min; Temperature 250 ~ 310 DEG C after steel plate quenching, sends into tempering stove fast and carries out carbon distribution after steel plate quenching.Carbon dispense temperature 180 ~ 200 DEG C; Time inside furnace calculates by (0.9min/mm × thickness of slab) min; Air cooling after coming out of the stove.
Finished steel plate performance test results is: thickness is the steel plate yield strength of 60mm is 1306MPa, and tensile strength is 1378MPa, and unit elongation is 11.1%, and normal temperature impacts for 146/97/114J, and 0 DEG C is impacted for 71/64/60J, and-20 DEG C are impacted for 61/52/63J.

Claims (1)

1. a production method for ultra-high strength steel plate, the operational path of employing is converter steelmaking → external refining → continuous casting → heating → rolling → accelerating cooling → thermal treatment, it is characterized in that:
The chemical composition percent mass of steel consists of C=0.21 ~ 0.24, Si=0.45 ~ 0.55, Mn=1.40 ~ 1.46, P≤0.015, S≤0.010, Al=0.03 ~ 0.06, Nb=0.02 ~ 0.03, V=0.05 ~ 0.06, Ti=0.035 ~ 0.050, Mo=0.25 ~ 0.35, B=0.0017 ~ 0.0022, all the other are Fe and uncontrollable impurity element; Steel plate be organized as tiny lath martensite and residual austenite;
Processing step is:
A .steel-making: molten steel sulfur content S≤0.010% after hot metal pretreatment, temperature>=1250 DEG C, slag is taken off totally before entering converter by molten iron; Converter terminal control C-T coordinates tapping, P≤0.012%, S≤0.015%; Slag-stopping tapping, slag is thick≤50mm, tapping time 4 ~ 7min, tapping 1/5 adds alloy, and tapping 2/5 adds alloy; Squeeze into the deoxidation of Al line after tapping and be no less than 250m;
B .refining: the refining of LF stove makes white slag and deoxidation operation to molten steel; The refining later stage adds V-Fe, Nb-Fe, Ti-Fe alloy carries out trimming; The Si-Ca line that before departures, feeding is appropriate, adds B-Fe after blowing Ar5min, and the add-on of B-Fe controls according to 0.018 ~ 0.020; In front 5min after VD extracting vacuum starts, ladle bottom Ar stirring gas flow is reduced to zero; After extracting vacuum starts 3min, Quick condition of high vacuum degree, to below 0.5tor, protects more than vacuum circulation degassing 15min;
C .continuous casting: liquidus line 1508 DEG C, middle bag superheating temperature controls 5 ~ 15 DEG C; During pulling speed of continuous casting adopts, plate strand production allusion quotation pulling rate performs; Produce thickness of strand 300mm, continuous casting whole process carries out protective casting;
D .heating: Heating temperature 1190 ~ 1210 DEG C, slab heart portion temperature of coming out of the stove is greater than 1150 DEG C; Rate of heating 9 ~ 11min/cm, total time inside furnace is greater than 5h;
E .rolling: roughing adopts high temperature, large pressure, at a slow speed rolling technique; Select maximum reduction in pass by the ability of milling train, draft reaches more than 15%; Start rolling temperature 1040 ~ 1060 DEG C, finishing temperature 960 ~ 980 DEG C; Finish rolling adds up draft and is greater than 60%, and last three percentage pass reductions are greater than 12%, start rolling temperature 830 ~ 820 DEG C, finishing temperature 780 ~ 810 DEG C;
F .roller repairing: roll rear ACC cold by force, opens cold temperature 770 ~ 790 DEG C, is cooled to 580 ~ 630 DEG C of air coolings, speed of cooling 5 ~ 14 DEG C/s;
G .thermal treatment: quenching temperature 890 ~ 910 DEG C, time inside furnace calculates by 1.3 ~ 1.5min/mm × thickness of slab min, quenching press speed 20 ~ 40m/min; After steel plate quenching, the quick tempering stove of sending into of temperature 250 ~ 310 DEG C carries out carbon distribution; Carbon dispense temperature 180 ~ 200 DEG C, time inside furnace is pressed 0.9min/mm × thickness of slab min and is calculated; Air cooling after coming out of the stove.
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