CN102925803A - Production method of ultrahigh-strength steel plate - Google Patents

Abstract

The invention provides a production method of an ultrahigh-strength steel plate. A process route adopted by the method is converter steelmaking-secondary refining-continuous casting-heating-rolling-cooling after rolling and heat treatment. The production method is characterized in that the steel comprises the following chemical components by weight percent: 0.26-0.28% of C, 1.15-1.25% of Si, 1.50-1.60% of Mn, no more than 0.015% of P, no more than 0.010% of S, no more than 0.020% of Al, 0.02-0.03% of Nb, 0.055-0.065% of V, 0.045-0.060% of Ti, 0.25-0.035% of Ni, 0.55-0.65% of Mo and 0.0017-0.0022% of B. The production method has the following advantages: the components of the steel plate are designed concisely and plenty of alloying elements are not added, thus the production cost of the ultrahigh-strength steel plate is lowered; the Ti oxide metallurgy technology is adopted, thus the welding property of the steel plate is improved; after the steel plate is subjected to Q+P treatment, the tissues of the steel plate are ultrafine lath martensite+nanoscale lath retained austenite and precipitated complex carbides, and the combination properties of strength and plasticity of the steel plate are superior to the combination properties of dual-phase steel, TRIP steel and common martensitic steel; after the steel plate is quenched by a roller quenching machine, the plate shape is good; and the production method has simple procedure and easily achieved process, is conductive to solving the problem that the ultrahigh-strength steel plate cannot be produced by traditional quenching and tempering, and achieves volume production of the 1700MPa grade ultrahigh-strength steel plate.

Description

A kind of production method of super-high strength steel plate

Technical field

The invention belongs to steel-smelting technology, is a kind of production method of super-high strength steel plate.

Technical background

Ultrahigh-strength steel refers to its tensile strength more than 1000MPa, approaches or surpasses 2000MPa, percentage of total elongation〉10 %, and the more honest and cleaner structure iron of price.Traditional quenching-tempering process can not satisfy high-strength steel and have certain toughness and cheap requirement concurrently.At present, general high-strength steel all is to make the steel grade performance up to standard by adding alloying element basically, and the high-strength steel cost that obtains like this is higher, is unfavorable for saving energy and reduce the cost.In order to reduce production costs, increase economic benefit, must be constantly to novel process, new technology research experiment.

The difficult tensile strength that makes steel of perlite (non-deformation attitude) and bainite structure is up to 2000MPa, and martensitic stucture is when being competent at.For having certain toughness concurrently, should make the tissue of steel be dislocation strip martensitic stucture.Have recognized that in the past that the residual austenite physical efficiency in the hardened steel improved plasticity and the toughness of steel half century, surrounded by the residual austenite of several nanometer thickness such as strip martensite, increased toughness; Utilize austenitic thermostabilization phenomenon, propose tool steel without being out of shape quenching and rapid steel workpiece without the distortion tempering heat treatment process.Experiment showed, that the hydrogen embrittlement crackle is hampered by the fcc austenite, the 300M steel (about 3 % of residual austenite) that contains 1.3 % Si through 300 ℃ of tempering contrasts 4340 steel (paralympic＜2 %), separates out equally ε-carbide, but the slow order of magnitude of stress corrosion speed.Xu Zuyao once tentatively set forth the vital role of residual austenite in the soft steel.Utilize the electron microscope experiment results such as Thomas, Xu Zuyao calculates proof: carbon diffused to residual austenite by martensite when soft steel quenched.Speer etc. propose the Q+P thermal treatment process of steel, namely quench (Q) after between Ms～Mf, through the certain temperature insulation, make carbon distribute (partition) to austenite from martensite, make a certain amount of austenite stable to room temperature to guarantee toughness.For hindering separating out of Fe3C, contain 1%～2 %Si in their the designed Q+P steel.Xu Zuyao introduces precipitation hardening mechanism on the Q+P technique bases such as Speer, tentatively propose Q+P+T technique, namely in steel, add the carbon compound forming element, outside quenching distributes by carbon, and make diffusion-precipitation complicated carbide in the martensite, obtain higher-strength and toughness and cooperate.

Studies show that, plasticity and the toughness of residual austenite physical efficiency Effective Raise material, for in hardened steel, obtaining a certain amount of stable retained austenite, adopt (the Quenching)-carbon that quenches to distribute (Partitioning)-tempering (Tempering) technique when proposing thermal treatment, be called for short Q-P-T technique, be that steel plate quenching is incubated certain hour after certain temperature, carbon is dispensed to retained austenite from martensite, then after suitable time of certain temperature tempering, make it separate out complicated carbide, to increase strengthening effect.0.2%C-Mn-Ti-B has been carried out the thermal modeling test of similar Q-P-T technique, and the sample after the thermal analogy has been carried out structure observation, organizing of obtaining is lath martensite tissue and a certain amount of residual austenite basically.

Adopt Q-P-T technique that 0.2%C-Mn-Ti-B has been carried out experimental study, then cut two tension specimens, two groups of impact specimens, a metallographic specimen and a hardness sample, the performance such as the table 1 that obtain at each motherboard.From table, can find out that not only strength ratio increased originally, and all increase before impact, unit elongation, the test of hardness geometric ratio.

The performance test results that table 1 adopts Q-P-T technique that 0.2%C-Mn-Ti-B is tested

By above-mentioned experimental study as can be known, adopt Q-P-T technique really can improve the performance of high-strength steel, but also can reduce the alloying element addition.Therefore, can be by the trial-production of the carbon content high-strength steel of Q-P-T technique about 0.15%, optimization reaches the super-high strength steel chemical ingredients more than the 1100MPa level on the basis of few addition element, to reduce the production cost of high-strength steel, improve simultaneously plasticity and the toughness of high-strength steel.

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 off-line quenching+tempering technique (Q+T), steel plate finally is organized as tempered martensite.Above patent light plate composition has added the precious alloys such as Mo, Ni, V, Ti, the Nb of high-content, and to guarantee the adaptability of plate property and technique, production cost is high.

So the problem that High Strength Steel Plate production exists in the prior art is: added the precious alloys such as Mo, Ni, V, Ti, Nb of high-content in the High Strength Steel Plate composition, to guarantee the adaptability of plate property and technique, the 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 have been produced the demand that the above high tensile steel plate of 1100MPa satisfies manufacturing at present; The above superstrength Wide and Thick Slab of 1200Mpa does not have maturation process and the production method of batch production at present.

Summary of the invention

The present invention aims to provide a kind of production method of super-high strength steel plate, and adopting Q+P explained hereafter thickness is cheaply 1700MPa grade super strength structural steel and iron of 8～60mm, satisfies the demand of manufacturing, realizes theory energy-saving and cost-reducing, green iron and steel.Its characteristics are succinct Composition Design; Yield strength is not less than that 1700MPa, tensile strength are not less than 1800 MPa, unit elongation is not less than 47J greater than 10% ,-20 ℃ of impact of collision; 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.

The technical scheme of invention: a kind of production method of super-high strength steel plate, adopting process route are the rear cooling → thermal treatment of converter steelmaking → external refining → continuous casting → heating → rolling → roll.The chemical constitution mass percent of steel is: C=0.26～0.28, Si=1.15～1.25, Mn=1.50～1.60, P≤0.015, S≤0.010, Al≤0.020, Nb=0.02～0.03, V=0.055～0.065, Ti=0.045～0.060, Ni=0.25～0.35, Mo=0.55～0.65, B=0.0017～0.0022.Processing step is:

(1) converter steelmaking: sulphur content S≤0.010% after the hot metal pretreatment, temperature 〉=1250 ℃, molten iron is taken off slag totally before entering converter; Converter terminal control C-T coordinates tapping, P≤0.012%, S≤0.015%, tapping time 4～7min, tapping 1/5 adds ferrosilicon and ferromanganese carries out deoxidation to molten steel, and the alloy except Al adds by normal requirement, and tapping 2/5 adds alloy, tapping finishes backsight terminal point oxygen level and adds an amount of modification agent and lime, blows Ar and is undertaken by normal requirement.

(2) external refining: the refining of LF stove adopts Oxides Metallurgy Technology that molten steel is carried out slag making and deoxidation operation, the refining later stage according to LF stove molten steel sample composition add V-Fe, Nb-Fe, the Ti-Fe alloy carries out trimming, the an amount of Si-Ca line of feeding before the departures adds B-Fe=0.018～0.020 after blowing Ar5min; In the front 5min after the VD extracting vacuum begins ladle bottom Ar is stirred gas flow and be reduced to zero, after extracting vacuum begins 3min, require the Quick condition of high vacuum degree to more than the degassed 15min of the following fidelity idle loop of 0.5tor.

(3) continuous casting: 1497 ℃ of liquidus lines, 5～15 ℃ of middle bag superheating temperature controls, plate strand production allusion quotation pulling rate during pulling speed of continuous casting adopts, thickness of strand 300mm is produced in the casting of strict implement stable state, the omnidistance protective casting of carrying out of continuous casting.

(4) heating: 1240～1260 ℃ of Heating temperatures, the slab heart section temperature of coming out of the stove be greater than 1150 ℃, rate of heating 9～11min/cm, and total time inside furnace is greater than 5h.

(5) rolling: roughing adopts high temperature, depresses greatly, rolling technique at a slow speed, and the reduction schedule establishment is selected maximum reduction in pass by the ability of milling train, and maximum percentage pass reduction reaches more than 15%, 1030～1060 ℃ of start rolling temperatures, 940～980 ℃ of finishing temperatures; Finish rolling accumulative total draft is greater than 60%, and last three percentage pass reductions are greater than 12%, 860～880 ℃ of start rolling temperatures, 850～870 ℃ of finishing temperatures.

(6) roll rear cooling: roll the strong cold technique of rear selection, open 820～840 ℃ of cold temperature, be cooled to 510～550 ℃ of air coolings, 5～14 ℃/s of speed of cooling.

(7) thermal treatment: 920～940 ℃ of quenching temperatures, time inside furnace calculates by 1.5～1.7min/mm * thickness of slab min, quenching press speed 20～40m/min, temperature is 210～260 ℃ behind the steel plate quenching, sends into fast tempering stove behind the steel plate quenching and carries out the carbon distribution; 180～200 ℃ of carbon dispense temperature, time inside furnace are pressed 1.1min/mm * thickness of slab min and are calculated, the rear air cooling of coming out of the stove.

Plate property actual achievement such as table 2 by technique scheme production.

Table 2 1700MPa level super-high strength steel plate service check actual achievement

Know-why of the present invention:

The present invention designs by tissue characteristic and the requirement of super-high strength steel: the fine strip shape martensite of (1) tool high dislocation density, lath thickness are tens nanometer; (2) separate out tiny coherence complicated carbide on the martensite further to gain in strength; (3) avoid cementite Fe3C to separate out; (4) contain the residual austenite of proper amt (thickness), certain carbon content between the martensite bar to improve toughness and the plasticity of steel; (5) original austenite is answered tool fine grained texture.

The high manganese Composition Design of carbon during 1700MPa level super-high strength steel plate of the present invention uses, the intensity of assurance steel plate; High Si composition suppresses the formation of Fe3C, stablizes ε-carbide, and makes steel can carry out carbon distribution (Partitioning) processing; Contain the stable austenite elements such as Mn, Ms is descended; Contain complicated carbide forming element such as Nb, V, Ti, the Mo element descends Ms, is precipitation hardening and refine austenite crystal grain; The adding of Ti has improved the welding property of super-high strength steel plate.

Adopt the production method of Clean Steel to produce high-quality continuously cast bloom; Tissue before TMCP rolling technology refinement steel plate hot is processed; The lesser temps austenitizing can obtain thin brilliant austenite structure; Be quenched to 210～260 ℃ of (Ms～Mf) to obtain an amount of martensite, improve armor plate strength; Carry out carbon at 180～200 ℃ and distribute, the rich carbon of more residual austenites is also stable to room temperature; Dispense temperature complicated carbide coherence and half coherent precipitate can improve the intensity of steel and plasticity, toughness; The complicated carbide that steel plate is organized as lath martensite+lath residual austenite and is settled out after Q+P processes, the over-all properties of armor plate strength and plasticity are better than dual phase steel, TRIP steel, general martensite steel sections.

Compared with prior art, the present invention has the following advantages: the steel plate Composition Design is succinct, does not add a large amount of alloying elements, has reduced the production cost of super-high strength steel plate; Adopt the Ti Oxides Metallurgy Technology, improved 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 processes, 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 quenches, and template is good; Operation is simple, technique easily realizes, has solved the difficult problem that traditional quenching, tempering can not be produced the super-high strength steel plate, realizes the batch production of 1700MPa level super-high strength steel plate.

Description of drawings

Accompanying drawing is the steel plate organization chart that patent of the present invention is produced.

Embodiment

Embodiment 1:1700MPa level super-high strength steel board production technology.The composition quality percentage composition of steel is: C=0.27, Si=1.21, Mn=1.52, P=0.012, S=0.0023, Al=0.008, Nb=0.026, V=0.059, Ti=0.052, Ni=0.27, Mo=0.56, B=0.0018.

Its main technological steps and parameter are as follows:

Enter the stove molten iron and carry out first hot metal pretreatment, molten steel sulfur content S after processing≤0.010%, temperature 〉=1250 ℃, molten iron must be taken off slag totally before entering 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 pushing off the slag 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 the tapping and be no less than 250m, and the variation of looking Intake Quantity, terminal point C, molten steel oxidation is suitably adjusted.Then molten steel is transported to the LF refining furnace and carries out refining operation.

The LF refining is made white slag and deoxidation operation to molten steel, guarantees that the content of the element such as oxygen, sulphur in the steel is controlled at lower level; The refining later stage is added an amount of 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; An amount of Si-Ca line of feeding before the departures adds B-Fe after blowing Ar5min, and the add-on of B-Fe is according to 0.018 ~ 0.020 control.Then molten steel is transported to the VD stove and carries out vacuum-treat.In the front 5min after the VD extracting vacuum begins, ladle bottom Ar is stirred gas flow be reduced to zero, prevent from before vacuum chamber reaches vacuum, molten steel not being stirred, cause the molten steel oxidation; After extracting vacuum begins 3min, require the Quick condition of high vacuum degree to 0.5tor, and under this vacuum tightness the empty 15min of fidelity; During the RH vacuum-treat, vacuum keep is below 0.5tor, and more than circulating degasification 15min under this vacuum tightness.The soft blow of after vacuum-treat finishes molten steel being carried out more than the 15min is processed, and then molten steel is transported to continuous casting and casts.

1497 ℃ of the liquidus lines of this steel grade, 5～15 ℃ of middle bag superheating temperature controls; Plate strand production allusion quotation pulling rate degree was carried out during pulling speed of continuous casting adopted, the casting of strict implement stable state; Produce thickness of strand 300mm(casting machine and produce maximum ga(u)ge); The strict protective casting of the omnidistance implementation of continuous casting prevents molten steel secondary oxidation and nitrogen pick-up.The strand that rolls off the production line carries out the cooling in heap more than 24 hours.

Strand is 1240～1260 ℃ of the Heating temperatures of process furnace, and the slab heart section temperature of coming out of the stove is greater than 1150 ℃; Rate of heating 9～11min/cm, total time inside furnace is greater than 5h.Come out of the stove and carry out the high pressure dephosphorization, then enter roughing." high temperature, depress greatly, at a slow speed " rolling technique is adopted in roughing, does not use automatic rolling, and is manually rolling; The reduction schedule establishment is selected maximum reduction in pass by the ability of milling train, and maximum percentage pass reduction reaches more than 15%; 1030～1060 ℃ of start rolling temperatures, 940～980 ℃ of finishing temperatures.Finish rolling accumulative total draft is greater than 60%, and last three percentage pass reductions are greater than 12%; 860～880 ℃ of start rolling temperatures, 850～870 ℃ of finishing temperatures.Roll rear ACC cooling and select strong cold technique, open 820～840 ℃ of cold temperature, be cooled to 510～550 ℃ of air coolings, 5～14 ℃/s of speed of cooling.

The heat treatment mode that steel plate adopts quenching+carbon to distribute.The temperature of austenitizing is 920～940 ℃; Time inside furnace calculates by 1.5～1.7min/mm * thickness of slab min; Quenching press speed 20～40m/min; Temperature is 210～260 ℃ behind the steel plate quenching, sends into fast tempering stove behind the steel plate quenching and carries out the carbon distribution.180～200 ℃ of carbon dispense temperature; Time inside furnace is pressed 1.1min/mm * thickness of slab min and is calculated; The rear air cooling of coming out of the stove.

The finished steel plate performance test results is: thickness is that the steel plate yield strength of 20mm is 1763MPa, and tensile strength is 1848MPa, and unit elongation is 11.8%, and normal temperature impacts and is 115/103/94J, and 0 ℃ of impact is 82/76/91J, and-20 ℃ of impacts are 66/71/60J.Thickness is that the steel plate yield strength of 40mm is 1719MPa, and tensile strength is 1886MPa, and unit elongation is 11.5%, and normal temperature impacts and is 106/98/113J, and 0 ℃ of impact is 69/88/84J, and-20 ℃ of impacts are 62/56/73J.

Embodiment 2:1700MPa level super-high strength steel board production technology.The composition quality percentage composition of steel is: C=0.26, Si=1.18, Mn=1.55, P=0.009, S=0.0026, Al=0.012, Nb=0.031, V=0.057, Ti=0.049, Mo=0.62, B=0.0019.

Its main technological steps and parameter are as follows:

Enter the stove molten iron and carry out first hot metal pretreatment, molten steel sulfur content S after processing≤0.010%, temperature 〉=1250 ℃, molten iron must be taken off slag totally before entering 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 pushing off the slag 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 the tapping and be no less than 250m, and the variation of looking Intake Quantity, terminal point C, molten steel oxidation is suitably adjusted.Then molten steel is transported to the LF refining furnace and carries out refining operation.

The LF refining is made white slag and deoxidation operation to molten steel, guarantees that the content of the element such as oxygen, sulphur in the steel is controlled at lower level; The refining later stage is added an amount of 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; An amount of Si-Ca line of feeding before the departures adds B-Fe after blowing Ar5min, and the add-on of B-Fe is according to 0.018 ~ 0.020 control.Then molten steel is transported to the VD stove and carries out vacuum-treat.In the front 5min after the VD extracting vacuum begins, ladle bottom Ar is stirred gas flow be reduced to zero, prevent from before vacuum chamber reaches vacuum, molten steel not being stirred, cause the molten steel oxidation; After extracting vacuum begins 3min, require the Quick condition of high vacuum degree to 0.5tor, and under this vacuum tightness the empty 15min of fidelity; During the RH vacuum-treat, vacuum keep is below 0.5tor, and more than circulating degasification 15min under this vacuum tightness.The soft blow of after vacuum-treat finishes molten steel being carried out more than the 15min is processed, and then molten steel is transported to continuous casting and casts.

1497 ℃ of the liquidus lines of this steel grade, 5～15 ℃ of middle bag superheating temperature controls; Plate strand production allusion quotation pulling rate degree was carried out during pulling speed of continuous casting adopted, the casting of strict implement stable state; Produce thickness of strand 300mm(casting machine and produce maximum ga(u)ge); The strict protective casting of the omnidistance implementation of continuous casting prevents molten steel secondary oxidation and nitrogen pick-up.The strand that rolls off the production line carries out the cooling in heap more than 24 hours.

Strand is 1240～1260 ℃ of the Heating temperatures of process furnace, and the slab heart section temperature of coming out of the stove is greater than 1150 ℃; Rate of heating 9～11min/cm, total time inside furnace is greater than 5h.Come out of the stove and carry out the high pressure dephosphorization, then enter roughing." high temperature, depress greatly, at a slow speed " rolling technique is adopted in roughing, does not use automatic rolling, and is manually rolling; The reduction schedule establishment is selected maximum reduction in pass by the ability of milling train, and maximum percentage pass reduction reaches more than 15%; 1030～1060 ℃ of start rolling temperatures, 940～980 ℃ of finishing temperatures.Finish rolling accumulative total draft is greater than 60%, and last three percentage pass reductions are greater than 12%; 860～880 ℃ of start rolling temperatures, 850～870 ℃ of finishing temperatures.Roll rear ACC cooling and select strong cold technique, open 820～840 ℃ of cold temperature, be cooled to 510～550 ℃ of air coolings, 5～14 ℃/s of speed of cooling.

The heat treatment mode that steel plate adopts quenching+carbon to distribute.The temperature of austenitizing is 920～940 ℃; Time inside furnace calculates by 1.5～1.7min/mm * thickness of slab min; Quenching press speed 20～40m/min; Temperature is 210～260 ℃ behind the steel plate quenching, sends into fast tempering stove behind the steel plate quenching and carries out the carbon distribution.180～200 ℃ of carbon dispense temperature; Time inside furnace is pressed 1.1min/mm * thickness of slab min and is calculated; The rear air cooling of coming out of the stove.

The finished steel plate performance test results is: thickness is that the steel plate yield strength of 60mm is 1732MPa, and tensile strength is 1839MPa, and unit elongation is 11.1%, and normal temperature impacts and is 112/107/102J, and 0 ℃ of impact is 71/84/83J, and-20 ℃ of impacts are 62/75/54J.

Claims (1)

1. the production method of a super-high strength steel plate, adopting process route are converter steelmaking → external refining → continuous casting → heating → rolling → roll rear cooling → thermal treatment, it is characterized in that:

The chemical constitution mass percent of steel is: C=0.26～0.28, Si=1.15～1.25, Mn=1.50～1.60, P≤0.015, S≤0.010, Alt≤0.020, Nb=0.02～0.03, V=0.055～0.065, Ti=0.045～0.060, Ni=0.25～0.035, Mo=0.55～0.65, B=0.0017～0.0022;

Processing step is:

(1) converter steelmaking: sulphur content S≤0.010% after the hot metal pretreatment, temperature 〉=1250 ℃, molten iron is taken off slag totally before entering converter; Converter terminal control C-T coordinates tapping, P≤0.012%, S≤0.015%, tapping time 4～7min, tapping 1/5 adds ferrosilicon and ferromanganese carries out deoxidation to molten steel, and the alloy except Al adds by normal requirement, and tapping 2/5 adds alloy, tapping finishes backsight terminal point oxygen level and adds an amount of modification agent and lime, blows Ar and is undertaken by normal requirement;

(2) external refining: the refining of LF stove adopts Oxides Metallurgy Technology that molten steel is carried out slag making and deoxidation operation, the refining later stage according to LF stove molten steel sample composition add V-Fe, Nb-Fe, the Ti-Fe alloy carries out trimming, the an amount of Si-Ca line of feeding before the departures adds B-Fe=0.018～0.020 after blowing Ar5min; In the front 5min after the VD extracting vacuum begins ladle bottom Ar is stirred gas flow and be reduced to zero, after extracting vacuum begins 3min, require the Quick condition of high vacuum degree to more than the degassed 15min of the following fidelity idle loop of 0.5tor;

(3) continuous casting: 1497 ℃ of liquidus lines, 5～15 ℃ of middle bag superheating temperature controls, plate strand production allusion quotation pulling rate during pulling speed of continuous casting adopts, thickness of strand 300mm is produced in the casting of strict implement stable state, the omnidistance protective casting of carrying out of continuous casting;

(4) heating: 1240～1260 ℃ of Heating temperatures, the slab heart section temperature of coming out of the stove be greater than 1150 ℃, rate of heating 9～11min/cm, and total time inside furnace is greater than 5h;

(5) rolling: roughing adopts high temperature, depresses greatly, rolling technique at a slow speed, and the reduction schedule establishment is selected maximum reduction in pass by the ability of milling train, and maximum percentage pass reduction reaches more than 15%, 1030～1060 ℃ of start rolling temperatures, 940～980 ℃ of finishing temperatures; Finish rolling accumulative total draft is greater than 60%, and last three percentage pass reductions are greater than 12%, 860～880 ℃ of start rolling temperatures, 850～870 ℃ of finishing temperatures;

(6) roll rear cooling: roll the strong cold technique of rear selection, open 820～840 ℃ of cold temperature, be cooled to 510～550 ℃ of air coolings, 5～14 ℃/S of speed of cooling;

(7) thermal treatment: 920～940 ℃ of quenching temperatures, time inside furnace calculates by 1.5～1.7min/mm * thickness of slab min, quenching press speed 20～40m/min, temperature is 210～260 ℃ behind the steel plate quenching, sends into fast tempering stove behind the steel plate quenching and carries out the carbon distribution; 180～200 ℃ of carbon dispense temperature, time inside furnace are pressed 1.1min/mm * thickness of slab min and are calculated, the rear air cooling of coming out of the stove.