CN103215501A - Production method of easily formable high-strength medium-thick steel plate - Google Patents
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Abstract
The invention relates to a production method of an easily formable high-strength medium-thick steel plate. The method comprises the following process steps: converter steelmaking, ladle furnace refining, vacuum treatment vacuum treatment, continuous casting, heating, rolling, pre-straightening, on-line quenching and tempering heat treatment. The mass percent composition of the steel is as follows: C = 0.07-0.09, Si = 0.15-0.30, Mn = 1.55-1.60, P <= 0.015, S <= 0.005, Nb + V + Ti <= 0.10, Cr + Mo <= 0.5, Alt => 0.020, and Pcm <= 0.21. The Q620E steel plate with a thickness of 200mm produced by the method is good in cold bending, and the cold bending property of the steel plate real object meets the easily forming requirement of users; the yield ratio of the steel plate is smaller than 0.92, and the uniform elongation rate is larger than 8%, which meets the use requirements of relevant designs; the product of strength and elongation is increased by more than 35%, the capacity of resisting dynamic loading of the high strength steel plate is increased, and the equipment safety is improved; through hot charging and on-line quenching of the continuous casting, the production cost is reduced; and with the component design in which Pcm is smaller than 0.21%, the welding properties welding property of the high strength steel plate is improved.
Description
Technical field
The invention belongs to steel-smelting technology, is the production method of the high-strength steel plate of a kind of easy-formation.
Background technology
Development along with metallurgical industry, huge change has taken place in the production of the above High Strength Steel Plate of surrender 550MPa, from traditional reheat quenching+tempering (being RQ+T) technological development to TMCP, TMCP+T, DQ+T, Q+P, Q+P+T, particularly rolled the online direct quenching in back ((Direct Quenching in recent years, abbreviation DQ)) technology has obtained significant progress, is widely used in the production of High Strength Steel Plate.
The High Strength Structural Steel of DQ explained hereafter is than the High Strength Structural Steel of other explained hereafter now, under the suitable situation of mechanical property, can reduce alloying element content significantly and reduce carbon equivalent, improve processing performances such as welding, receive efficient, material-saving, the energy-conservation and multiple effect that lowers consumption; Under the situation of roughly the same composition, compare with other technologies that armor plate strength is higher, plasticity and toughness is better, routine inspection all can satisfy the requirement of the technical qualification of delivering goods.But in actual use, the yield tensile ratio height of steel plate, particularly the steel plate cold bending cracking causes processability poor, and the user proposes quality objection in a large number, the high strength structure plate that refusal uses DQ to produce.
Anatomize discovery, the high tensile steel plate dislocation desity height of DQ explained hereafter, yield strength height cause the yield tensile ratio height.The delivery requirements cold-bending property verifies as narrow clod wash sample, is wide clod wash and the requirement of the actual use of user is a cold roll forming; Find during the steel plate tensile testing that uniformly extension is low, stretching fracture be ductile rupture really but have layering, the branch aspect is typical brittle rupture simultaneously.
Thick High Strength Steel Plate delivery technical qualification among the low yield strength ratio Q690E: chemical ingredients requires as table 1, factory can add wherein one or more alloying elements as required, maximum value should meet in the table to be stipulated, its content should be reported in quality certificate, at least should add a kind of crystal grain thinning element among Nb, Ti, V, the Al in the steel, wherein the minimum of at least a element is that 0.015%(is Als for Al), also available Alt substitute for Al s, this moment, minimum was 0.018%, CEV=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15; Mechanical property requirements such as table 2, tension test are applicable to horizontal sample, and shock test is applicable to longitudinal test piece, when yield phenomenon is not obvious, adopt Rp
0.2
Table 1 thickness≤50mm Q690E steel chemical composition requires (%)
Table 2 thickness≤50mm Q690E steel mechanical property requirement
DQ explained hereafter High Strength Steel Plate patent such as Chinese patent application 200910046581.1 " a kind of ultrafine crystal bainite high-strength steel and manufacture method thereof ", " 201010101815.0 non-modifier treatment high tensile steel plate of a kind of low-cost Yield strength 700 MPa and manufacture method thereof ", " 201210011762.2 easy welding high-strength steel plate of low yield strength ratio and preparation technology thereof ", 201110181602.8 " adopting the method for direct quenching explained hereafter petroleum storage tank steel plate ".Wherein first three items is a TMCP explained hereafter High Strength Steel Plate, a back employing be DQ+T explained hereafter High Strength Steel Plate, cause that steel plate yield tensile ratio height, steel plate uniform elongation are low, the cold roll forming cracking but contain B in the steel plate composition.
In a word, the high tensile steel plate that traditional direct quenching+tempering process (DQ+T) is produced has following shortcoming: all contain the B element in the steel plate composition, steel plate hardening capacity is good, produce the armor plate strength height, impact high, unit elongation is higher, but uniformly extension＜7%, steel plate yield tensile ratio＞0.96; Steel plate yield tensile ratio height is difficult to satisfy the actual service requirements of relevant design; The steel plate uniformly extension is low, and demixing phenomenon appears in fracture during the steel plate tension test, and the user thinks that there is demixing phenomenon in steel plate; Steel plate is qualified according to standard code inspection by sampling clod wash, but the most of cracking of wide clod wash and actual steel plate bending, i.e. cold roll forming poor performance; Steel plate rolls speed of cooling＞35 ℃/s in the traditional DQ technology in back, causes yield tensile ratio uncontrolled.
Summary of the invention
This patent purport has the production method that the high-strength steel plate of a kind of easy-formation is provided, and producing thickness is thick High Strength Steel Plate among 8～30mm easy-formation, easy welding, the low yield strength ratio Q690E, satisfies the demand of manufacturings such as engineering machinery, mine equipment.
Technical scheme of the present invention:
The production method of the high-strength steel plate of a kind of easy-formation, its processing step are converter steelmaking → ladle furnace refining → vacuum-treat → continuous casting → heating → rolling → pre-straightening → press quenching → tempering heat treatment.It is characterized in that:
The quality percentage composition of steel is: C=0.07 ~ 0.09, Si=0.15 ~ 0.30, Mn=1.55 ~ 1.60, P≤0.015, S≤0.005, Nb+V+ Ti≤0.10, Cr+ Mo≤0.5, Alt 〉=0.020, Pcm≤0.21.
The main technique step is:
A. converter steelmaking: molten steel sulfur content is controlled at S≤0.020%, temperature 〉=1250 ℃, and molten iron is taken off slag totally before going into converter; The converter terminal controlled target is that C-T coordinates tapping P≤0.015%, S≤0.020%; Pushing off the slag go out slag thick≤50mm, tapping time 4 ~ 7min; Tapping 1/5 adds alloy, and tapping 2/5 adds alloy; Squeeze into the Al line after the tapping and be no less than 250～300m deoxidation.
B. ladle furnace refining: LF stove control molten steel conduction time 〉=20min, total argon blowing time 〉=40 minutes, white slag hold-time 〉=15min; Feed the Al line and transfer Alt, the molten steel oxygen≤5ppm that goes out to stand firm; Feed SiCa line or FeCa line 400 ~ 700m during departures, before the departures molten steel is carried out the operation of soft blow argon, the soft blow argon time should be greater than 5min; VD stove control molten steel advances the omnidistance Argon of VD stove, total argon blowing time 〉=35 minutes; Vacuumize below target 0.5 tor, the hold-time is not less than 15min; Molten steel went out the soft blow of VD stokehold greater than 12 minutes, and continuous casting platform temperature is 1553 ~ 1562 ℃ in the departures.
C. continuous casting: 15 ℃ of target molten steel overheats, 1516 ℃ of liquidus temperatures, 1526 ~ 1531 ℃ of middle bag representative temperatures; It is 1.3 m/min, 1.2 m/min, 1.0 m/min, 0.80 m/min. that the maximum pulling rate of slab thickness 180 mm, 220mm, 260mm, 300mm is respectively.
D. rolling: 1210～1240 ℃ of process furnace heating zone temperature, 1200～1220 ℃ of soaking zone temperature, slab adopts the heating of hot charging stove, rate of heating 9 ~ 11min/cm; Roughing
Stage start rolling temperature 〉=1050 ℃, finishing temperature 〉=980 ℃, intermediate blank thickness is more than or equal to 3 times of finished product thicknesses,
Stage rolling adopts big reduction system, and guaranteeing has continuous 2 percentage pass reductions 〉=15% behind the broadening; Finish rolling
880 ~ 1000 ℃ of stage start rolling temperatures, 830 ~ 920 ℃ of finishing temperatures, several percentage pass reductions before the finish rolling 〉=13%.
E. press quenching: open cold temperature 〉=800 ℃, final cooling temperature≤160 ℃, 25～35 ℃/s of cooling rate.
F. tempering heat treatment: 630 ~ 650 ℃ of tempering temperatures, tempering time (thickness of slab+70) min, air cooling.
Patent of the present invention possesses the High Strength Steel Plate characteristics of easy-formation, is organized as tempering ferrite bainite+tempering acicular ferrite+a small amount of tempering granular bainite.Its know-why is the speed of cooling of control press quenching, the dislocation desity of steel plate behind the reduction press quenching, thereby the yield tensile ratio of reduction yield strength, reduction steel plate; Do not add the content that the B element improves acicular ferrite behind the steel plate quenching in the steel, thus the uniformly extension when increasing substantially steel plate deformation; The raising of uniformly extension and dislocation desity reduce and have reduced steel plate horizontal rimose possibility when cold roll forming; The following composition of Pcm0.21% designs, and has improved the welding property of steel plate, and this steel plate can normally weld under the condition of not preheating and low preheating; The hot-cast base is directly adorned and press quenching has reduced the fuel consumption that heats; Reduction, the removal of off-line quenching technology route, the measures such as direct shove charge of hot-cast base significantly of alloy have greatly reduced the production cost of steel plate.
Therefore, compare with the high-strength steel technology of existing DQ explained hereafter, the present invention has the following advantages: the wide clod wash of steel plate 200mm is intact, and steel plate cold-bending property in kind satisfies the requirement of user's easy-formation; The steel plate yield tensile ratio is less than 0.92, and uniform elongation satisfies the service requirements of relevant design greater than 8%; Strength and ductility product improves more than 35%, has improved High Strength Steel Plate opposing dynamic load ability to function, has promoted the security of equipment; The hot charging and the press quenching of continuously cast bloom have reduced production cost; The following composition of Pcm0.21% designs, and has improved the welding property of High Strength Steel Plate.
Description of drawings
Fig. 1, Fig. 2 are respectively Q690E steel metallographic structure figure, the stress strain curve figure that the inventive method is produced.
Embodiment
Embodiment 1:20mm Q690E steel plate production method
The chemical constitution such as the table 3 of steel.
Table 320mm Q690E
Steel plate composition actual achievement(%)
| Chemical Composition | C | Si | Mn | P | S | Nb+V+ Ti | Cr+ Mo | Alt | Pcm | CEV |
| Actual achievement | 0.08 | 0.20 | 1.57 | 0.013 | 0.001 | 0.068 | 0.42 | 0.035 | 0.20 | 0.49 |
A. molten steel sulfur content [S]≤0.020%, temperature 〉=1250 ℃, molten iron must be taken off slag totally before going into converter.Converter terminal controlled target: C-T coordinates tapping, [P] 0.014%, [S] 0.018%; Strict pushing off the slag tapping, slag is thick≤50mm, tapping time 7min, tapping 1/5 adds alloy, and tapping 2/5 adds alloy; Squeeze into Al line 280m deoxidation after the tapping.
B. molten steel is at LF stove 23min conduction time, total argon blowing time 43min, white slag hold-time 17min.Feed the Al line and transfer Alt, the argon station is handled molten steel and is finished Als0.038%, the molten steel oxygen 4ppm that goes out to stand firm.Feed Fe-Ca line, feed quantity 560m during departures.Before the departures molten steel is carried out the operation of soft blow argon, soft blow argon time 7min.Molten steel advanced the VD stove and promptly opens omnidistance Argon, the total argon blowing time of VD stove 37 minutes.Vacuumize 0.4 tor, hold-time 17min.Compositions such as [C], [Si], [Mn] in the molten steel are finely tuned.Molten steel goes out VD stokehold soft blow 19min.1559 ℃ of continuous casting platform temperature are gone up in the molten steel departures.
C. the bag temperature is 1528 ℃ in, pulling rate 1.0m/min.Continuous casting becomes 260X2280 section slab.
D. process furnace heating zone temperature is controlled at 1230～1240 ℃, and the soaking zone temperature is controlled at 1210～1220 ℃.Hot slab rate of heating 9min/cm.
1060 ℃ of stage start rolling temperatures, 990 ℃ of finishing temperatures.Intermediate blank thickness 75mm, continuous 2 percentage pass reductions 〉=18%, finished product thickness 20mm.
910 ℃ of stage start rolling temperatures, 870 ℃ of finishing temperatures.
E. press quenching: open 860 ℃ of cold temperature, 33 ℃/s of speed of cooling, 68 ℃ of final cooling temperatures.
F. 640 ℃ of tempering temperatures, tempering time 90 min, air cooling.
Actual measurement 20mm Q690E plate property: intact ,-40 ℃ of ballistic work Kv of yield strength 767MPa, tensile strength 854 MPa, yield tensile ratio 0.90, unit elongation 19.5%, uniform elongation 9.3%, the wide clod wash of 200mm (D=3a, 180 °)
2Mean value 228J.
Embodiment 2:30mm Q690E steel plate production method
The chemical constitution such as the table 4 of steel.
Table 4 30mm Q690E steel plate composition actual achievement (%)
| Chemical Composition | C | Si | Mn | P | S | Nb+V+ Ti | Cr+ Mo | Alt | Pcm | CEV |
| Actual achievement | 0.08 | 0.23 | 1.58 | 0.013 | 0.002 | 0.075 | 0.43 | 0.030 | 0.21 | 0.49 |
The main technique step:
A. molten steel sulfur content [S]≤0.020%, temperature 〉=1250 ℃, molten iron must be taken off slag totally before going into converter.Converter terminal controlled target: C-T coordinates tapping, [P] 0.012%, [S] 0.017%; Strict pushing off the slag tapping, slag is thick≤50mm, tapping time 6min, tapping 1/5 adds alloy, and tapping 2/5 adds alloy; Squeeze into Al line 280m deoxidation after the tapping.
B. molten steel is at LF stove 26min conduction time, total argon blowing time 43min, white slag hold-time 17min.Feed the Al line and transfer Alt, the argon station is handled molten steel and is finished Als0.040%, the molten steel oxygen 4ppm that goes out to stand firm.Feed Fe-Ca line, feed quantity 590m during departures.Before the departures molten steel is carried out the operation of soft blow argon, soft blow argon time 7min.Molten steel advanced the VD stove and promptly opens omnidistance Argon, the total argon blowing time of VD stove 37 minutes.Vacuumize 0.4 tor, hold-time 18min.Compositions such as [C], [Si], [Mn] in the molten steel are finely tuned.Molten steel goes out VD stokehold soft blow 19min.1560 ℃ of continuous casting platform temperature are gone up in the molten steel departures.
C. the bag temperature is 1530 ℃ in, pulling rate 1.0m/min.Continuous casting becomes 260X2280 section slab.
D. process furnace heating zone temperature is controlled at 1220～1230 ℃, and the soaking zone temperature is controlled at 1200～1220 ℃.Hot slab rate of heating 8.5min/cm.
1050 ℃ of stage start rolling temperatures, 980 ℃ of finishing temperatures.Intermediate blank thickness 90mm, continuous 2 percentage pass reductions 〉=19%, finished product thickness 30mm.
880 ℃ of stage start rolling temperatures, 860 ℃ of finishing temperatures.
E. press quenching: open 840 ℃ of cold temperature, 27 ℃/s of speed of cooling, 49 ℃ of final cooling temperatures.
F. 630 ℃ of tempering temperatures, tempering time 100min, air cooling.
Actual measurement 30mm Q690E plate property: intact ,-40 ℃ of ballistic work Kv of yield strength 783MPa, tensile strength 862 MPa, yield tensile ratio 0.91, unit elongation 20%, uniform elongation 9.0%, the wide clod wash of 200mm (D=3a, 180 °)
2Mean value 227J.
Claims (1)
1. the production method of the high-strength steel plate of easy-formation, processing step is converter steelmaking → ladle furnace refining → vacuum-treat → continuous casting → heating → rolling → pre-straightening → press quenching → tempering heat treatment, it is characterized in that:
The quality percentage composition of steel is: C=0.07 ~ 0.09, Si=0.15 ~ 0.30, Mn=1.55 ~ 1.60, P≤0.015, S≤0.005, Nb+V+ Ti≤0.10, Cr+ Mo≤0.5, Alt 〉=0.020, Pcm≤0.21;
The main technique step is:
A. converter steelmaking: molten steel sulfur content is controlled at S≤0.020%, temperature 〉=1250 ℃, and molten iron is taken off slag totally before going into converter; The converter terminal controlled target is that C-T coordinates tapping P≤0.015%, S≤0.020%; Pushing off the slag go out slag thick≤50mm, tapping time 4 ~ 7min; Tapping 1/5 adds alloy, and tapping 2/5 adds alloy; Squeeze into the Al line after the tapping and be no less than 250～300m deoxidation;
B. ladle furnace refining: LF stove control molten steel conduction time 〉=20min, total argon blowing time 〉=40 minutes, white slag hold-time 〉=15min; Feed the Al line and transfer Alt, the molten steel oxygen≤5ppm that goes out to stand firm; Feed SiCa line or FeCa line 400 ~ 700m during departures, before the departures molten steel is carried out the operation of soft blow argon, the soft blow argon time should be greater than 5min; VD stove control molten steel advances the omnidistance Argon of VD stove, total argon blowing time 〉=35 minutes; Vacuumize below target 0.5 tor, the hold-time is not less than 15min; Molten steel went out the soft blow of VD stokehold greater than 12 minutes, and continuous casting platform temperature is 1553 ~ 1562 ℃ in the departures;
C. continuous casting: 15 ℃ of target molten steel overheats, 1516 ℃ of liquidus temperatures, 1526 ~ 1531 ℃ of middle bag representative temperatures; It is 1.3 m/min, 1.2 m/min, 1.0 m/min, 0.80 m/min that the maximum pulling rate of slab thickness 180 mm, 220mm, 260mm, 300mm is respectively;
D. rolling: 1210～1240 ℃ of process furnace heating zone temperature, 1200～1220 ℃ of soaking zone temperature, slab adopts the heating of hot charging stove, rate of heating 9 ~ 11min/cm; Roughing
Stage start rolling temperature 〉=1050 ℃, finishing temperature 〉=980 ℃, intermediate blank thickness is more than or equal to 3 times of finished product thicknesses,
Stage rolling adopts big reduction system, and guaranteeing has continuous 2 percentage pass reductions 〉=15% behind the broadening; Finish rolling
880 ~ 1000 ℃ of stage start rolling temperatures, 830 ~ 920 ℃ of finishing temperatures, several percentage pass reductions before the finish rolling 〉=13%;
E. press quenching: open cold temperature 〉=800 ℃, final cooling temperature≤160 ℃, 25～35 ℃/s of cooling rate;
F. tempering heat treatment: 630 ~ 650 ℃ of tempering temperatures, tempering time (thickness of slab+70) min, air cooling.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103556082A (en) * | 2013-11-12 | 2014-02-05 | 湖南华菱湘潭钢铁有限公司 | Production method of quenched and tempered high-strength Q620F super-thick steel plate |
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| CN102363859A (en) * | 2011-11-14 | 2012-02-29 | 湖南华菱湘潭钢铁有限公司 | Method for producing wear-resisting steel plate |
| CN102899556A (en) * | 2012-11-02 | 2013-01-30 | 湖南华菱湘潭钢铁有限公司 | Production method for low-alloy medium-thick steel plate |
| CN103014554A (en) * | 2011-09-26 | 2013-04-03 | 宝山钢铁股份有限公司 | Low-yield-ratio high-tenacity steel plate and manufacture method thereof |
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Patent Citations (3)
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| CN103014554A (en) * | 2011-09-26 | 2013-04-03 | 宝山钢铁股份有限公司 | Low-yield-ratio high-tenacity steel plate and manufacture method thereof |
| CN102363859A (en) * | 2011-11-14 | 2012-02-29 | 湖南华菱湘潭钢铁有限公司 | Method for producing wear-resisting steel plate |
| CN102899556A (en) * | 2012-11-02 | 2013-01-30 | 湖南华菱湘潭钢铁有限公司 | Production method for low-alloy medium-thick steel plate |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103556082A (en) * | 2013-11-12 | 2014-02-05 | 湖南华菱湘潭钢铁有限公司 | Production method of quenched and tempered high-strength Q620F super-thick steel plate |
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