CN101363101B - Large thickness quenched high strength steel and production method thereof - Google Patents
Large thickness quenched high strength steel and production method thereof Download PDFInfo
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Abstract
The invention belongs to the field of metal materials and discloses a large-thickness and high-strength quenched and tempered steel plate and a production method thereof. The steel plate mainly consists of the following chemical components by weight percentages: not more than 0.18% of C, 0.1-0.4% of Si, not more than 1.2% of Mn, 0.7-1.7% of Ni, 1.0-1.5% of Cr, 0.4-0.6% of Mo, 0.03-0.08% of V, 0.02-0.04% of Al, 0.0005-0.0020% of B, Fe and unavoidable impurities. The molten steel designed according to the components of the invention can be rolled into the large-thickness steel plate by smeltingprocess, casting process, heating process, rolling process, water cooling process and quenching and tempering process. The steel plate has the advantages of reasonable component design, good comprehensive properties and low production cost, can be applied to off-shore oil production platform engineering, power stations, engineering scaffolds and other industries and has good application prospect.
Description
Technical field
The invention belongs to metal material field, relate in particular to a kind of large thickness quenched high strength steel and production method thereof.
Background technology
The DILLMAX690 steel plate that domestic construction machinery industry is produced from import such as Japanese WELTEN80C, SUMITEN80, Sweden SUMTIN780, U.S. A514Gr.B and German DILLINGER Iron And Steel Company mostly with 80kg level high-strength steel, the DILLMAX690 steel plate that Germany DILLINGER Iron And Steel Company produces, higher, the Cr (1.50%) of C (0.18%) content in these inlet plates, Ni (1.80%) alloy content are higher, and the steel plate cost value rises.Above-mentioned several import steel price is generally very high.
Increase gradually along with high-strength steel presents consumption in the manufacturing at home, especially China's offshore oil production platform exists serious problem in short supply with high tensile steel plate, is in the unfavorable situation of dependence on import for a long time.The steel plate of domestic some this intensity rank of iron and steel manufacturer production, specification limit is generally narrower, all below 60mm, can't satisfy the growing slab market requirement.
Summary of the invention
At the problems referred to above, the object of the present invention is to provide that a kind of composition is reasonable in design, good combination property, large thickness quenched high strength steel that production cost is low.
Simultaneously, the present invention also aims to provide a kind of production method of large thickness quenched high strength steel.
To achieve these goals, technical program of the present invention lies in having adopted a kind of large thickness quenched high strength steel, mainly be made up of the chemical ingredients of following weight percent: C≤0.18%, Si0.10～0.40%, Mn≤1.20%, Ni0.70～1.70%, Cr1.00～1.50%, Mo0.40～0.60%, V0.03～0.08%, Al0.020～0.040%, B0.0005～0.002%, surplus are Fe and unavoidable impurities.
As optimization, the P in the described unavoidable impurities≤0.025%, S≤0.020%.
Further, described large thickness quenched high strength steel mainly is made up of the chemical ingredients of following weight percent: C0.15～0.17%, Si0.15～0.40%, Mn1.00～1.10%, Ni1.15～1.25%, Cr1.10～1.20%, Mo0.40～0.60%, V0.050～0.060%, Al0.020～0.040%, B0.0012～0.0020%, surplus are Fe and unavoidable impurities.
As optimization, the P in the described unavoidable impurities≤0.015%, S≤0.006%.
For obtaining better system steel effect, can also include Nb0.02～0.04% in the described large thickness quenched high strength steel.
Described large thickness quenched high strength steel thickness is 100～114mm.
It is the microalloy element complex intensifying that large thickness quenched high strength steel of the present invention adopts Cr-Ni-Mo-B, through rational heat treatment technology, obtains good obdurability coupling, does not reduce the welding property of slab simultaneously again.C content≤0.18% among the present invention, the development of high-strength steel is the process that progressively reduces C content, the reduction of C content, help improving the toughness of steel on the one hand, can improve the welding property of steel on the other hand significantly, the large-scale steel structure members of the stressed complexity of suitable more high tenacity of the present invention and welding property; Si content is between 0.10～0.40%, and Si mainly improves the intensity of steel with the solution strengthening form, but can not too high levels, in order to avoid reduce the toughness of steel; Mn content≤1.20%, Mn mainly play solution strengthening and reduce transformation temperature and improve armor plate strength, and Mn can significantly improve the hardening capacity of steel, and with the increase of Mn content, the plasticity and the low-temperature impact toughness of steel plate slightly descend, and intensity significantly improves; Cr content is 1.0～1.5%, and Ni content is 0.70～1.70%, and Cr, Ni can increase austenite and cross cold energy power, reduces the transition temperature of martensite and bainite, promotes martensitic formation, improves low-temperature impact toughness and reduces Cold Brittleness Transition Temperature; Mo content is 0.4～0.6%, B content is 0.0005～0.002%, an amount of Mo and B can significantly increase the hardening capacity of steel, postpone supercooled austenite to perlitic transformation, compound interpolation by Mo and B, cool off fast through ACC again after steel plate rolls, can eliminate ferrite and pearlitic generation in the steel substantially; V content is 0.03～0.08%, and after the controlled rolling of V process II type, the C of V, Nization thing are separated out, and significantly improve the intensity of steel plate; Al content is 0.020～0.040%, and Al is a deoxidant element, can be used as the AlN forming element, effectively crystal grain thinning; Nb content is 0.02～0.04%, for effectively realizing the steel plate refined crystalline strengthening by controlled rolling process, need to add the Nb element, to reach the raising steel plate recrystallization temperature, heating solid solution Nb stops austenite crystal to be grown up, high temperature is separated out C, the Nization thing of Nb during cooling, improves the intensity and the toughness of steel, improves the hardening capacity of steel; The upper limit of impurity element P, S is controlled at P≤0.025%, S≤0.020%, and impurity element P, S equal size lower limit do not limit, and reduces as far as possible under the processing unit ability, and is pure to reach steel, the uniform purpose of mechanical property.
Simultaneously, technical program of the present invention also lies in providing a kind of production method of large thickness quenched high strength steel, may further comprise the steps:
(1) smelting technology: molten steel is after smelting, send into the refining furnace refining, feed Al line 600～800m, fine setting Mn, Mo, Ni, Cr, V content, bull ladle vacuum-treat during 1600～1650 ℃ of big bag temperature, transfer Ti, B before the bull ladle, and carry out Ca and handle vacuum tightness 0.5～1.0 torr, when keeping 15～25min, vacuum destroys vacuum, solved molten steel and depended merely on the deoxidation of Al line, the phenomenon that nonmetallic inclusionsin steel content is higher has guaranteed the purity of steel;
(2) casting process: the empty back temperature of destroying of fidelity is cast subsequently at 1550～1560 ℃;
(3) heating process: occur bursting for fear of the Hi-Stren steel ingot surface, steel ingot realizes that temperature is sent, Wen Qing, temperature dress, stove 30～50min dries in the air before the dress steel, stewing steel 0.5～1h, simultaneously tiny in order to guarantee the abundant solid solution of alloying element, γ crystal grain, adopt low speed to burn steel, heat-up rate below 1000 ℃ is 80～120 ℃/h, and the Heating temperature scope is 1230～1250 ℃;
(4) rolling technology: adopt II type controlled rolling process, the fs is the austenite recrystallization stage, between 950～1150 ℃, makes austenite generation perfect recrystallization, with refine austenite crystal grain; Subordinate phase is the non-recrystallize stage of austenite, start rolling temperature is 900～920 ℃, finishing temperature is 850～900 ℃, in this stage, austenite crystal is elongated, and forms high-density mechanical twin and deformed belt in the austenite of non-recrystallization in elongation, and microalloy carbon, nitride are separated out because of deformation induced simultaneously, thereby increased ferritic nucleation site, refinement ferrite crystal grain;
(5) water-cooling process: the steel plate behind the online cold rolling, returning red temperature is 700～750 ℃, stacking slow cooling 20～24h after steel plate rolls off the production line prevents that the steel plate internal stress from having little time to discharge and form internal fissure;
(6) hardening and tempering process: steel plate carries out modified i.e. quenching+temper, the quenching technology temperature is 920～940 ℃, soaking time is 2.3～2.5min/mm, carry out tempering behind the steel plate quenching again, tempering temperature is 630～640 ℃, be 3～4min/mm total heat-up time, and inspection by sampling obtains qualified finished product steel plate.
Molten steel is through electric arc furnace smelting in the described step (1), the refining of LF refining furnace, the vacuum-treat of VD stove; Adopt 27.6T slab ingot mould to cast in the step (2), guarantee that big thickness, big substance steel plate have the enough draught and the raw material of becoming a useful person; Steel plate in the step (5) after rolling carries out online cooling in the ACC quickly cooling device; Consider that from the economy of quenching the heat-eliminating medium that quenches in the step (6) is a water.
The Ca processing is to add SiCa piece 100～150kg before vacuum in the described step (1).
The fs percentage pass reduction is 8～25% in the described step (4), accumulative total draft 〉=70%; The subordinate phase draft should be 10%～20%, accumulative total draft 〉=50%.
After testing, the mechanical property of steel plate of the present invention reaches following requirement: Rp0.2 〉=670MPa, Rm 〉=730MPa, A 〉=16%, ℃ impact of collision merit AKV 〉=34J of thickness of slab 1/4 place-40, ℃ impact of collision merit AKV 〉=34J of thickness of slab 1/2 place-27.Carbon equivalent Ceq≤0.79% has good welding property.Lower yield tensile ratio, generally reach≤0.90, reality is all less than 0.85.
Steel plate of the present invention has excellent comprehensive performances, mechanical property satisfies the standard-required of offshore oil production platform industry to the thick A514GrQ steel of 114mm fully, intensity and impelling strength have sizable rich amount, not only being suitable for the manufacturing of offshore oil production platform industrial structure part uses, but also wide popularization and application in the power station, engineering rack and other industry, have good application prospects.
The present invention has the following advantages:
(1) steel of the present invention is owing to adopt electrosmelting, P≤0.015%, and S≤0.006%, so steel is purer;
(2) carbon equivalent of the present invention is low, has guaranteed the welding property that steel plate is good;
(3) steel of the present invention had both satisfied steel plate obdurability demand because of the noble metal content that adds is few, played the saving alloy again, and the effect that reduces cost has the powerful market competitiveness;
(4) steel plate thickness is big, and maximum ga(u)ge can reach 114mm, can be used for the import substitution product, fills up the domestic market blank, satisfies the demand that the home and abroad production vessel constantly increases slab market consumption;
(5) intensity rank height reaches the 800Mpa rank, guarantees the supporting capacity of steel construction;
(6) anti-lamellar tearing is functional, full thickness direction Z 〉=35%;
(7) lower yield tensile ratio, reality is all less than 0.85;
(8) thickness of slab 1/4 place-40 ℃ and thickness of slab 1/2 place-27 ℃ low-temperature flexibility are good;
(9) the steel plate template is good, and roughness reaches≤5mm/m, can reduce 50 yuan/ton of the making mangling expenses of making side.
Embodiment
Embodiment 1
A kind of large thickness quenched high strength steel, chemical ingredients by following weight percent is formed: C0.16%, Si0.22%, Mn1.03%, Ni1.18%, Cr1.13%, Mo0.52%, V0.053%, Al0.028%, B0.0013%, Nb0.033%, P0.011%, S0.003%, surplus is Fe and inevitably is mingled with.Ceq is 0.75%, is rolled into the 114mm steel plate.
The production method of this steel plate is as follows:
(1) smelting technology: the molten steel of this composition design is smelted through ultra-high power electric arc furnace, melting period is adopted big quantity of slag stream slag operation, send into the refining of LF refining furnace, and feed Al line 700m, when wrapping 1635 ℃ of temperature greatly, the vacuum-treat of bull ladle VD stove, add SiCa piece 140kg before the vacuum, vacuum tightness 0.7 torr destroys vacuum when vacuum keeps 20min, solve molten steel and depended merely on the deoxidation of Al line, the higher phenomenon of nonmetallic inclusionsin steel content, guaranteed the purity of steel.
(2) casting process: the empty back temperature of destroying of fidelity adopts 27.6T slab ingot mould to cast at 1555 ℃ then, guarantees that big thickness, big substance steel plate have the enough draught and the raw material of becoming a useful person.
(3) heating process: occur bursting for fear of the Hi-Stren steel ingot surface, steel ingot realizes that temperature is sent, Wen Qing, temperature dress, stove 45min dries in the air before the dress steel, stewing steel 0.9h, tiny for guaranteeing the abundant solid solution of alloying element, γ crystal grain, adopt low speed to burn steel, heat-up rate below 1000 ℃ is 90 ℃/h, and maximum heating temperature is 1245 ℃.
(4) rolling technology: adopt II type controlled rolling process, the fs is the austenite recrystallization stage, and between 1110～1130 ℃, this stage percentage pass reduction is 20～23%, and accumulative total draft 85% makes austenite generation perfect recrystallization, with refine austenite crystal grain; Subordinate phase is the non-recrystallize stage of austenite, start rolling temperature is 915 ℃, finishing temperature is 860 ℃, and in this stage, austenite crystal is elongated, form high-density mechanical twin and deformed belt in the austenite of non-recrystallization in elongation, simultaneously microalloy carbon, nitride are separated out because of deformation induced, thereby have increased ferritic nucleation site, refinement ferrite crystal grain, this stage draft should be 18～20%, and the accumulative total draft is 80%;
(5) water-cooling process: the steel plate after rolling carries out online cooling at the ACC quickly cooling device, and returning red temperature is 740 ℃; Stacking slow cooling was 23 hours after steel plate rolled off the production line, and prevented that the steel plate internal stress from having little time to discharge and form internal fissure;
(6) thermal treatment process: steel plate carries out modified (quenching+tempering) and handles quenching technology: select water as heat-eliminating medium, quenching temperature is 928 ℃, soaking time is 2.45min/mm, carry out tempering behind the steel plate quenching again, tempering temperature is 638 ℃, and be 4min/mm total heat-up time.
Its mechanical property: yield strength: 750MPa, tensile strength: 830MPa, A are 21%, thickness of slab 1/4 place-40 ℃ ballistic work AKV (vertically) 149,121,182J, thickness of slab 1/2 place-27 ℃ ballistic work AKV (vertically) 130,167,135J, cold bending test D=3a, 180 ° are intact.
Embodiment 2
A kind of large thickness quenched high strength steel, chemical ingredients by following weight percent is formed: C0.15%, Si0.40%, Mn1.1%, Ni0.7%, Cr1.2%, Mo0.60%, V0.05%, Al0.040%, B0.002%, Nb0.02%, P0.025%, S0.02%, surplus is Fe and inevitably is mingled with.Ceq is 0.75%, is rolled into the 112mm steel plate.
The production method of this steel plate is as follows:
(1) smelting technology: the molten steel of this composition design is smelted through ultra-high power electric arc furnace, melting period is adopted big quantity of slag stream slag operation, send into the refining of LF refining furnace, and feed Al line 800m, when wrapping 1650 ℃ of temperature greatly, the vacuum-treat of bull ladle VD stove, add SiCa piece 150kg before the vacuum, vacuum tightness 1.0 torrs destroy vacuum when vacuum keeps 15min, solve molten steel and depended merely on the deoxidation of Al line, the higher phenomenon of nonmetallic inclusionsin steel content, guaranteed the purity of steel.
(2) casting process: the empty back temperature of destroying of fidelity adopts 27.6T slab ingot mould to cast at 1560 ℃ then, guarantees that big thickness, big substance steel plate have the enough draught and the raw material of becoming a useful person.
(3) heating process: occur bursting for fear of the Hi-Stren steel ingot surface, steel ingot realizes that temperature is sent, Wen Qing, temperature dress, stove 50min dries in the air before the dress steel, stewing steel 1h, tiny for guaranteeing the abundant solid solution of alloying element, γ crystal grain, adopt low speed to burn steel, heat-up rate below 1000 ℃ is 120 ℃/h, and maximum heating temperature is 1250 ℃.
(4) rolling technology: adopt II type controlled rolling process, the fs is the austenite recrystallization stage, between 1100～1150 ℃, this stage percentage pass reduction is 22～25%, the accumulative total draft is 90%, makes austenite generation perfect recrystallization, with refine austenite crystal grain; Subordinate phase is the non-recrystallize stage of austenite, start rolling temperature is 920 ℃, finishing temperature is 900 ℃, and in this stage, austenite crystal is elongated, form high-density mechanical twin and deformed belt in the austenite of non-recrystallization in elongation, simultaneously microalloy carbon, nitride are separated out because of deformation induced, thereby have increased ferritic nucleation site, refinement ferrite crystal grain, this stage draft should be 18～20%, and the accumulative total draft is 70%;
(5) water-cooling process: the steel plate after rolling carries out online cooling at the ACC quickly cooling device, and returning red temperature is 750 ℃; Stacking slow cooling was 24 hours after steel plate rolled off the production line, and prevented that the steel plate internal stress from having little time to discharge and form internal fissure;
(6) thermal treatment process: steel plate carries out modified (quenching+tempering) and handles quenching technology: select water as heat-eliminating medium, quenching temperature is 930 ℃, soaking time is 2.5min/mm, carry out tempering behind the steel plate quenching again, tempering temperature is 640 ℃, and be 3.5min/mm total heat-up time.
Its mechanical property: yield strength: 760MPa, tensile strength: 820MPa, A are 16%, thickness of slab 1/4 place-40 ℃ ballistic work AKV (vertically) 130,105,122J, thickness of slab 1/2 place-27 ℃ ballistic work AKV (vertically) 120,180,130J, cold bending test D=3a, 180 ° are intact.
Embodiment 3
A kind of large thickness quenched high strength steel, chemical ingredients by following weight percent is formed: C0.18%, Si0.10%, Mn1.2%, Ni1.15%, Cr1.00%, Mo0.40%, V0.03%, Al0.020%, B0.0005%, Nb0.04%, P0.015%, S0.006%, surplus is Fe and inevitably is mingled with.Ceq is 0.74%, is rolled into the 108mm steel plate.
The production method of this steel plate is as follows:
(1) smelting technology: the molten steel of this composition design is smelted through ultra-high power electric arc furnace, melting period is adopted big quantity of slag stream slag operation, send into the refining of LF refining furnace, and feed Al line 600m, when wrapping 1600 ℃ of temperature greatly, the vacuum-treat of bull ladle VD stove, add SiCa piece 100kg before the vacuum, vacuum tightness 0.6 torr destroys vacuum when vacuum keeps 18min, solve molten steel and depended merely on the deoxidation of Al line, the higher phenomenon of nonmetallic inclusionsin steel content, guaranteed the purity of steel.
(2) casting process: the empty back temperature of destroying of fidelity adopts 27.6T slab ingot mould to cast at 1550 ℃ then, guarantees that big thickness, big substance steel plate have the enough draught and the raw material of becoming a useful person.
(3) heating process: occur bursting for fear of the Hi-Stren steel ingot surface, steel ingot realizes that temperature is sent, Wen Qing, temperature dress, stove 30min dries in the air before the dress steel, stewing steel 0.5h, tiny for guaranteeing the abundant solid solution of alloying element, γ crystal grain, adopt low speed to burn steel, heat-up rate below 1000 ℃ is 80 ℃/h, and maximum heating temperature is 1230 ℃.
(4) rolling technology: adopt II type controlled rolling process, the fs is the austenite recrystallization stage, and between 950～1000 ℃, this stage percentage pass reduction is 8～10%, and the accumulative total draft is 70%, makes austenite generation perfect recrystallization, with refine austenite crystal grain; Subordinate phase is the non-recrystallize stage of austenite, start rolling temperature is 900 ℃, finishing temperature is 850 ℃, and in this stage, austenite crystal is elongated, form high-density mechanical twin and deformed belt in the austenite of non-recrystallization in elongation, simultaneously microalloy carbon, nitride are separated out because of deformation induced, thereby have increased ferritic nucleation site, refinement ferrite crystal grain, this stage draft should be 10～12%, and the accumulative total draft is 50%;
(5) water-cooling process: the steel plate after rolling carries out online cooling at the ACC quickly cooling device, and returning red temperature is 700 ℃; Stacking slow cooling was 20 hours after steel plate rolled off the production line, and prevented that the steel plate internal stress from having little time to discharge and form internal fissure;
(6) thermal treatment process: steel plate carries out modified (quenching+tempering) and handles quenching technology: select water as heat-eliminating medium, quenching temperature is 920 ℃, soaking time is 2.3min/mm, carry out tempering behind the steel plate quenching again, tempering temperature is 630 ℃, and be 3min/mm total heat-up time.
Its mechanical property: yield strength: 755MPa, tensile strength: 823MPa, A are 20%, thickness of slab 1/4 place-40 ℃ ballistic work AKV (vertically) 140,111,176J, thickness of slab 1/2 place-27 ℃ ballistic work AKV (vertically) 133,170,138J, cold bending test D=3a, 180 ° are intact.
Embodiment 4
A kind of large thickness quenched high strength steel, chemical ingredients by following weight percent is formed: C0.17%, Si0.15%, Mn0.5%, Ni1.25%, Cr1.10%, Mo0.50%, V0.08%, Al0.031%, B0.0016%, P0.014%, S0.005%, surplus is Fe and inevitably is mingled with.Ceq is 0.67%, is rolled into the 105mm steel plate.
The production method of this steel plate is as follows:
(1) smelting technology: the molten steel of this composition design is smelted through ultra-high power electric arc furnace, melting period is adopted big quantity of slag stream slag operation, send into the refining of LF refining furnace, and feed Al line 750m, when wrapping 1610 ℃ of temperature greatly, the vacuum-treat of bull ladle VD stove, add SiCa piece 130kg before the vacuum, vacuum tightness 0.8 torr destroys vacuum when vacuum keeps 23min, solve molten steel and depended merely on the deoxidation of Al line, the higher phenomenon of nonmetallic inclusionsin steel content, guaranteed the purity of steel.
(2) casting process: the empty back temperature of destroying of fidelity adopts 27.6T slab ingot mould to cast at 1558 ℃ then, guarantees that big thickness, big substance steel plate have the enough draught and the raw material of becoming a useful person.
(3) heating process: occur bursting for fear of the Hi-Stren steel ingot surface, steel ingot realizes that temperature is sent, Wen Qing, temperature dress, stove 40min dries in the air before the dress steel, stewing steel 0.8h, tiny for guaranteeing the abundant solid solution of alloying element, γ crystal grain, adopt low speed to burn steel, heat-up rate below 1000 ℃ is 100 ℃/h, and maximum heating temperature is 1240 ℃.
(4) rolling technology: adopt II type controlled rolling process, the fs is the austenite recrystallization stage, between 1100～1120 ℃, this stage percentage pass reduction is 15～20%, the accumulative total draft is 80%, makes austenite generation perfect recrystallization, with refine austenite crystal grain; Subordinate phase is the non-recrystallize stage of austenite, start rolling temperature is 910 ℃, finishing temperature is 880 ℃, and in this stage, austenite crystal is elongated, form high-density mechanical twin and deformed belt in the austenite of non-recrystallization in elongation, simultaneously microalloy carbon, nitride are separated out because of deformation induced, thereby have increased ferritic nucleation site, refinement ferrite crystal grain, this stage draft should be 15～18%, and the accumulative total draft is 60%;
(5) water-cooling process: the steel plate after rolling carries out online cooling at the ACC quickly cooling device, and returning red temperature is 730 ℃; Stacking slow cooling was 22 hours after steel plate rolled off the production line, and prevented that the steel plate internal stress from having little time to discharge and form internal fissure;
(6) thermal treatment process: steel plate carries out modified (quenching+tempering) and handles quenching technology: select water as heat-eliminating medium, quenching temperature is 925 ℃, soaking time is 2.4min/mm, carry out tempering behind the steel plate quenching again, tempering temperature is 635 ℃, and be 3.2min/mm total heat-up time.
Its mechanical property: yield strength: 760MPa, tensile strength: 840MPa, A are 22%, thickness of slab 1/4 place-40 ℃ ballistic work AKV (vertically) 155,131,193J, thickness of slab 1/2 place-27 ℃ ballistic work AKV (vertically) 132,169,140J, cold bending test D=3a, 180 ° are intact.
Embodiment 5
A kind of large thickness quenched high strength steel, chemical ingredients by following weight percent is formed: C0.12%, Si0.13%, Mn1.0%, Ni1.7%, Cr1.5%, Mo0.4%, V0.06%, Al0.037%, B0.0009%, P0.010%, S0.008%, surplus is Fe and inevitably is mingled with.Ceq is 0.79%, is rolled into the 100mm steel plate.
The production method of this steel plate is as follows:
(1) smelting technology: the molten steel of this composition design is smelted through ultra-high power electric arc furnace, melting period is adopted big quantity of slag stream slag operation, send into the refining of LF refining furnace, and feed Al line 650m, when wrapping 1625 ℃ of temperature greatly, the vacuum-treat of bull ladle VD stove, add SiCa piece 120kg before the vacuum, vacuum tightness 0.5 torr destroys vacuum when vacuum keeps 25min, solve molten steel and depended merely on the deoxidation of Al line, the higher phenomenon of nonmetallic inclusionsin steel content, guaranteed the purity of steel.
(2) casting process: the empty back temperature of destroying of fidelity adopts 27.6T slab ingot mould to cast at 1553 ℃ then, guarantees that big thickness, big substance steel plate have the enough draught and the raw material of becoming a useful person.
(3) heating process: occur bursting for fear of the Hi-Stren steel ingot surface, steel ingot realizes that temperature is sent, Wen Qing, temperature dress, stove 35min dries in the air before the dress steel, stewing steel 0.6h, tiny for guaranteeing the abundant solid solution of alloying element, γ crystal grain, adopt low speed to burn steel, heat-up rate below 1000 ℃ is 110 ℃/h, and maximum heating temperature is 1235 ℃.
(4) rolling technology: adopt II type controlled rolling process, the fs is the austenite recrystallization stage, between 970～1115 ℃, this stage percentage pass reduction is 10～13%, the accumulative total draft is 75%, makes austenite generation perfect recrystallization, with refine austenite crystal grain; Subordinate phase is the non-recrystallize stage of austenite, start rolling temperature is 905 ℃, finishing temperature is 890 ℃, and in this stage, austenite crystal is elongated, form high-density mechanical twin and deformed belt in the austenite of non-recrystallization in elongation, simultaneously microalloy carbon, nitride are separated out because of deformation induced, thereby have increased ferritic nucleation site, refinement ferrite crystal grain, this stage draft should be 13～15%, and the accumulative total draft is 57%;
(5) water-cooling process: the steel plate after rolling carries out online cooling at the ACC quickly cooling device, and returning red temperature is 720 ℃; Stacking slow cooling was 21 hours after steel plate rolled off the production line, and prevented that the steel plate internal stress from having little time to discharge and form internal fissure;
(6) thermal treatment process: steel plate carries out modified (quenching+tempering) and handles quenching technology: select water as heat-eliminating medium, quenching temperature is 923 ℃, soaking time is 2.35min/mm, carry out tempering behind the steel plate quenching again, tempering temperature is 632 ℃, and be 3.8min/mm total heat-up time.
Its mechanical property: yield strength: 743MPa, tensile strength: 810MPa, A are 18%, thickness of slab 1/4 place-40 ℃ ballistic work AKV (vertically) 102,121,153J, thickness of slab 1/2 place-27 ℃ ballistic work AKV (vertically) 112,132,120J, cold bending test D=3a, 180 ° are intact.
It should be noted last that: above embodiment is the unrestricted technical scheme of the present invention in order to explanation only, although the present invention is had been described in detail with reference to the foregoing description, those of ordinary skill in the art is to be understood that: still can make amendment or be equal to replacement the present invention, and not breaking away from any modification or partial replacement of the spirit and scope of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.
Claims (3)
1. the production method of a large thickness quenched high strength steel, described steel plate mainly is made up of the chemical ingredients of following weight percent: C≤0.18%, Si 0.10～0.40%, Mn≤1.20%, Ni 0.70～1.70%, Cr 1.00～1.50%, Mo 0.40～0.60%, V 0.03～0.08%, Al 0.020～0.040%, B0.0005～0.0020%, surplus is Fe and unavoidable impurities, it is characterized in that may further comprise the steps:
(1) smelting technology: molten steel is after smelting, send into the refining furnace refining, feed Al line 600～800m, fine setting Mn, Mo, Ni, Cr, V content, the bull ladle vacuum-treat is transferred Ti, B content, and is carried out Ca and handle during 1600～1650 ℃ of big bag temperature before the bull ladle, vacuum tightness 0.5～1.0 holder destroys vacuum when vacuum keeps 15～25min;
(2) casting process: the empty back temperature of destroying of fidelity is cast subsequently at 1550～1560 ℃;
(3) heating process: the stove 30～50min that dries in the air before the dress steel, stewing steel 0.5～1h, low speed burns steel afterwards, and heat-up rate below 1000 ℃ is 80～120 ℃/h, and Heating temperature is 1230～1250 ℃;
(4) rolling technology: adopt II type controlled rolling process, the fs is the austenite recrystallization stage, between 950～1150 ℃; Subordinate phase is the non-recrystallize stage of austenite, and start rolling temperature is 900～920 ℃, and finishing temperature is 850～900 ℃;
(5) water-cooling process: the steel plate behind the online cold rolling, returning red temperature is 700～750 ℃, stacking slow cooling 20～24h after steel plate rolls off the production line;
(6) hardening and tempering process: steel plate carries out modified i.e. quenching+temper, and the quenching technology temperature is 920～930 ℃, and soaking time is 2.3～2.5min/mm, carries out tempering behind the steel plate quenching again, and tempering temperature is 630～640 ℃, and be 3～4min/mm total heat-up time.
2. the production method of large thickness quenched high strength steel as claimed in claim 1 is characterized in that in the step (1), and electric arc furnace smelting is adopted in described smelting, and the refining of LF refining furnace is adopted in described refining, and the vacuum-treat of VD stove is adopted in described vacuum-treat; Adopt 27.6T slab ingot mould to cast in the step (2); Steel plate in the step (5) after rolling carries out online cooling in the ACC quickly cooling device; The heat-eliminating medium that quenches in the step (6) is a water.
3. the production method of large thickness quenched high strength steel as claimed in claim 1 is characterized in that the fs percentage pass reduction is 8～25% in the step (4), accumulative total draft 〉=70%; The subordinate phase percentage pass reduction is 10%～20%, accumulative total draft 〉=50%.
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