CN101381854B - Method for producing low carbon and high niobium content bainite high-strength steel plate - Google Patents
Method for producing low carbon and high niobium content bainite high-strength steel plate Download PDFInfo
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- CN101381854B CN101381854B CN2008102251831A CN200810225183A CN101381854B CN 101381854 B CN101381854 B CN 101381854B CN 2008102251831 A CN2008102251831 A CN 2008102251831A CN 200810225183 A CN200810225183 A CN 200810225183A CN 101381854 B CN101381854 B CN 101381854B
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Abstract
The invention discloses a method for producing bainitic high-strength steel medium plates with low carbon and high niobium, which relates to a method for manufacturing an ultra-low-carbon bainitic steel plate. The method produces the ultra-low-carbon bainitic steel plate which has high niobium content and is compositely added with molybdenum, copper and nickel; and billets are subject to two-stage controlled rolling, namely rolling in a recrystallized zone and rolling in an unrecrystallized zone. During the rolling in the recrystallized zone, the deformation rate is more than 10s<-1>, the accumulated deformation is more than 60 percent, and austenite crystals with the average size less than 25mu m are obtained; and during the rolling in the unrecrystallized zone, the width of flat austenite crystals, which is less than 5mu m, can be obtained by keeping the compression ratio more than 5 times. The laminar cooling adopts the cooling rate of between 20 and 25 DEG C/s, and the final cooling temperature is maintained within the temperature range of between 300 and 400 DEG C. Finally, lath bainite and martensite structures are obtained, and the toughness of a material is synchronously improved. The yield strength sigma s of a final product is more than or equal to 840MPa, the tensile strength is more than or equal to 930MPa, the elongation rate psi is more than or equal to 15 percent, and the Charpy impact energy (20 DEG C below zero) is more than 230J.
Description
Technical field
The present invention relates to a kind of making method of ultra-low-carbon bainite steel plate system, particularly relate to the manufacture method of the ultra-low-carbon bainite steel plate of a kind of high content of niobium and compound interpolation molybdenum, copper, nickel.
Background technology
At present, the ferrous materials that uses in the energy, traffic, material industry and various engineering all requires high strength (general tensile strength greater than 600MPa), high toughness or low-temperature flexibility (particularly at cold district), good welding property and forming property.From reducing the cost of making various equipments and improving product performance, also wish the carbon content and the alloying element content that keep lower.Under the prerequisite of considering more than comprehensively, crystal grain thinning is the unique effective technology thinking that reaches the premium properties requirement.By the refinement original austenite grains, optimize cooling conditions, control generates different types of organizations.The composition design of low-carbon (LC) has thoroughly been eliminated carbon to bainite structure flexible disadvantageous effect.The intensity of steel no longer relies on the carbon content in the steel, and mainly by refined crystalline strengthening, dislocations strengthening and substructure are strengthened, niobium, vanadium, titanium micro-alloyed element precipitation strength.Therefore must guarantee that enough content of niobium can effectively suppress austenite recrystallization, improve recrystallization temperature, enlarge not crystallizing field temperature range, give security for the controlled rolling heavy reduction comes the final tissue of refinement.If Nb content is lower than 0.05%, the non-recrystallization temperature can only be brought up to about 950 ℃, if Nb content is brought up to the 0.05-1.0% scope, then recrystallization temperature can be brought up to more than 1000 ℃, promptly can enlarge the rolling space in non-recrystallization zone greatly, thereby under the constant condition of finishing temperature, guarantee non-recrystallization compression ratio greater than 5 times.
Though the TMCP theory provides thinking for cooling controlling and rolling controlling process, but the contradiction of appointed condition and technological design is inevitable, must consider the supporting capacity of milling train such as the distribution of draught per pass, the design of speed of cooling will be considered the ability of water-cooling system.Therefore the ultra-low-carbon bainite steel plate at high content of niobium and compound interpolation molybdenum, copper, nickel need propose corresponding processing parameter.
Summary of the invention
The objective of the invention is composition design at high niobium low-carbon (LC), in conjunction with actual production conditions, in controlled rolling, the distribution of two stage rolling draught has proposed concrete technic index, according to the influence rule of the rolling draught in recrystallization zone to refine austenite, determine that intermediate blank treats the rolling compression ratio of warm temperature range and non-recrystallization district, optimize the velocity range roll postcooling, the ultra-low-carbon bainite steel plate of realizing high content of niobium and compound interpolation molybdenum, copper, nickel has higher yield strength, higher unit elongation and good low-temperature toughness.
For achieving the above object, the method for the production low-carbon high-niobium content high-strength steel plate of moderate thickness of the present invention's proposition comprises the steps:
1) smelt the ingot casting that to meet the set component span of control in vacuum induction melting furnace, ingot casting makes it to become the hot rolling slab that the thickness specification is 230～250mm through forging; Also can adopt sophisticated continuous casting production process, directly continuous casting of molten steel be become steel billet;
2) blank is carried out equal thermal treatment, the control blank is in 1150～1250 ℃ of temperature ranges, and insulation 120～240min makes the abundant Hui Rong of niobium, vanadium, titanium elements in the steel;
3) slab after coming out of the stove is carried out dephosphorize by high pressure water and handle, remove the iron scale that slab is produced in heat-processed;
4) blank after the dephosphorization is carried out the controlled rolling of two stages immediately, promptly the recrystallization zone is rolling rolling with the non-recrystallization district.The recrystallization zone is rolling, and rate of deformation is greater than 10s
-1, cumulative deformation is greater than 60%, and finishing temperature is controlled in 1020～1080 ℃ of scopes, obtain intermediate blank, intermediate blank air cooling to 980 ± 30 ℃, it is rolling to carry out the non-recrystallization district again, the rolling compression ratio in non-recrystallization district is remained on more than 5 times, and finishing temperature is controlled in 750～800 ℃ of scopes;
5) to carrying out the laminar flow cooling at the plate of moderate thickness of 6-20mm after the finish to gauge, the speed of cooling scope is controlled between 20～25 ℃/s, and final cooling temperature is controlled in 300～400 ℃ of scopes, with the cooled steel plate air cooling of laminar flow to room temperature.
Above-mentioned set component span of control is by weight percentage: 0.02～0.05%C, 0.1～0.4%Si, 1.5～2.0%Mn, 0.004～0.012%P, 0.01～0.02%Ti, 0.001～0.005%S, 0.3～0.6%Cu, 0.3～0.6%Ni, 0.2～0.5%Mo, 0.05～0.1%Nb, surplus is Fe and inevitably is mingled with.
The invention has the advantages that:
1) the ultra-low-carbon bainite steel plate by high content of niobium (0.05-0.10%) and compound interpolation molybdenum, copper, nickel;
2) blank is carried out the controlled rolling of two stages, promptly the recrystallization zone is rolling rolling with the non-recrystallization district.In recrystallization zone distortion, with the increase of deflection, the austenite recrystallization grain refining effect is obvious, and with the progressively increasing of deflection, the recrystal grain thinning effect slows down gradually; When deflection reached 60% left and right sides, grain-size reached a near limit state substantially, increases deflection once more, and the austenite recrystallization grain refining effect is not obvious.Studies show that the recrystallization zone is rolling, rate of deformation is greater than 10s
-1, finishing temperature is when 1050 ℃ of left and right sides, and deflection can obtain the austenite crystal of mean sizes less than 25 μ m greater than 60% o'clock.
3) at 1020 ℃～1080 ℃ intermediate blank air coolings, niobium carbonitride second is separated out obviously mutually, and austenite grain boundary has obtained effective pinning, and crystal grain has good stability, and tangible coarsening phenomenon can not take place.
4) 980 ± 30 ℃ to begin to carry out the non-recrystallization district rolling, compression ratio remains on more than 5 times, can obtain the flat austenite crystal width less than 5 μ m.When flat austenite crystal width during less than 5 μ m, the lath tissue after the phase transformation obtains effective refinement, and the steel plate toughness and tenacity improves synchronously.
5) roll the postcooling stage, in the speed of cooling scope of 0.5 ℃/s～50 ℃/s, all can obtain bainite structure.Along with the raising of speed of cooling, bainite begins the corresponding reduction of transformation temperature, and speed of cooling increases to 50 ℃/s from 0.5 ℃/s, and bainite begins transformation temperature and descended 110 ℃, changes end temp and has reduced by 152 ℃.And along with the increase of speed of cooling, microstructure gradually by granular bainite to ferrite bainite and martensitic transformation, and phase-change organization is all the more tiny.The upper bainite tissue of avoiding degenerating greater than the cooling rate of 20 ℃/s forms cooling rate, and the cooling rate of 25 ℃/s has obtained the lower bainite tissue of maximum, and therefore cooling rate is best speed of cooling scope between 20～25 ℃/s, and final cooling temperature is set at 300 ~ 400 ℃.
6) final lath tissue is along become 50～60 degree wide-angle growths with flat austenite grain boundary, austenite grain boundary has played the effect of restriction lath Shu Shengchang, with the reduction of austenite grain boundary width, lath Shu Youxiao grain-size obtains refinement, and the material toughness and tenacity is improved synchronously.The intensity of the finished product and toughness index can satisfy following requirement: yield strength σ s 〉=840MPa, tensile strength sigma b 〉=930MPa, unit elongation Ψ 〉=15%, (-20 ℃) Charpy-V impact power 〉=230J.
Description of drawings
Fig. 1 is that the optics metallograph of embodiment 1 is observed the original austenite grains that flattens;
Fig. 2 is that the optics metallograph of embodiment 2 is observed the original austenite grains that flattens;
Fig. 3 is that the optics metallograph of Comparative Examples is observed the original austenite grains that flattens;
Fig. 4 is the embodiment 1 final lath bundle TEM morphology analysis that forms;
Fig. 5 is the embodiment 2 final lath bundle TEM morphology analysis that form;
Fig. 6 is the final lath bundle TEM morphology analysis that forms of Comparative Examples.
Embodiment
Embodiment 1
With chemical ingredients percentage ratio meter by weight, C0.041%, Si0.33%, Mn1.97%, Ni0.44%, Cu0.40%, Mo0.29%, Nb0.090%, Ti0.017%, P0.0054%, S0.0013%, surplus is after the molten steel of Fe is molded into ingot, and forging to thickness is the blank of 230mm.
1220 ℃ of soaking, the controlled rolling of two stages is carried out in the dephosphorization of the laggard horizontal high voltage water of insulation 240min blank.The recrystallization zone start rolling temperature is 1189 ℃, and rate of deformation is 12s
-1, after multi-pass was rolling, the recrystallization zone finishing temperature was 1040 ℃, and cumulative deformation is 67%, and the intermediate blank gauge control is at 75mm.The rolling start rolling temperature in non-recrystallization district is 980 ℃, after multi-pass is rolling, reaches final product thickness 12mm, and compression ratio is 6.25, and finishing temperature is 780 ℃.
Laminar flow cooling after the finish to gauge, speed of cooling is 23 ℃/s, final cooling temperature is 383 ℃.Air cooling is to room temperature after the finish to gauge.
Sample to rolling sequence detects, and is illustrated in figure 1 as the original austenite grains of flattening, and its flat grain boundary width is approximately 5 μ m, and the lath tissue obtains effective refinement.Figure 4 shows that the tem observation of the finished product, its lath tissue is because the cause of original austenite refinement has also obtained refinement, and its lath width is 0.5～1 μ m.To the service check of steel sheet product as can be known: its tensile strength sigma
bBe 967MPa, yield strength σ
sBe 853MPa, unit elongation Ψ is 15.5%, and (20 ℃) Charpy-V impact power Akv is 230J.
From the foregoing description as can be known, the production method of low-carbon high-niobium content high-strength steel of the present invention, by cooling control technology, the method for refinement original austenite, effectively refinement final tissue, realized the synchronous raising of strength and toughness.
Embodiment 2
With chemical ingredients percentage ratio meter by weight, C0.041%, Si0.33%, Mn1.97%, Ni0.44%, Cu0.40%, Mo0.29%, Nb0.090%, Ti0.017%, P0.0054%, S0.0013%, surplus is after the molten steel of Fe is molded into ingot, and forging to thickness is the blank of 230mm.
1220 ℃ of soaking, the controlled rolling of two stages is carried out in the dephosphorization of the laggard horizontal high voltage water of insulation 220min blank.The recrystallization zone start rolling temperature is 1189 ℃, and rate of deformation is 12s
-1, after multi-pass was rolling, the recrystallization zone finishing temperature was 1040 ℃, and cumulative deformation is 67%, and the intermediate blank gauge control is at 75mm.The rolling start rolling temperature in non-recrystallization district is 980 ℃, after multi-pass is rolling, reaches final product thickness 10mm, and compression ratio is 7.5, and finishing temperature is 760 ℃.
Laminar flow cooling after the finish to gauge, speed of cooling is 28 ℃/s, final cooling temperature is 377 ℃.Air cooling is to room temperature after the finish to gauge.
Sample to rolling sequence detects, and is illustrated in figure 2 as the original austenite grains of flattening, and the lath tissue obtains effective refinement.Figure 5 shows that the tem observation of the finished product, its lath width is at 0.3～1 μ m.To the service check of steel sheet product as can be known: its tensile strength sigma
bBe 973MPa, yield strength σ
sBe 848MPa, unit elongation Ψ is 16.8%, and (20 ℃) Charpy-V impact power Akv is 253J.
The comparative example
With chemical ingredients percentage ratio meter by weight, C0.041%, Si0.33%, Mn1.97%, Ni0.44%, Cu0.40%, Mo0.29%, Nb0.090%, Ti0.017%, P0.0054%, S0.0013%, surplus is after the molten steel of Fe is molded into ingot, and forging to thickness is the blank of 230mm.
1220 ℃ of soaking, the controlled rolling of two stages is carried out in the dephosphorization of the laggard horizontal high voltage water of insulation 240min blank.The recrystallization zone start rolling temperature is 1190 ℃, and rate of deformation is 12s
-1, after multi-pass was rolling, the recrystallization zone finishing temperature was 1080 ℃, and cumulative deformation is 48%, and the intermediate blank gauge control is at 120mm.The rolling start rolling temperature in non-recrystallization district is 950 ℃, after multi-pass is rolling, reaches final product thickness 30mm, and compression ratio is 4, and finishing temperature is 780 ℃.
Laminar flow cooling after the finish to gauge, speed of cooling is 22 ℃/s, final cooling temperature is 400 ℃.Air cooling is to room temperature after the finish to gauge.
Sample to rolling sequence detects, and is illustrated in figure 3 as the original austenite grains of flattening, can significantly observe its flat grain boundary width and be approximately 15 μ m, and the lath feature is obvious, but it is comparatively thick to compare embodiment 1 and 2.Figure 6 shows that the tem observation of the finished product, its lath width is at 1～1.5 μ m.To the service check of steel sheet product as can be known: its tensile strength sigma
bBe 945MPa, yield strength σ
sBe 821MPa, unit elongation Ψ is 11%, and (20 ℃) Charpy-V impact power Akv is 189J.
Claims (1)
1. the bainite high-strength steel Heavy Plate Production method of a low-carbon high-niobium content is characterized in that concrete steps are:
1) blank that the ingot casting of set component span of control is cast carries out equal thermal treatment, and temperature is controlled at 1220 ℃, and insulation 120～240min makes the abundant Hui Rong of niobium, vanadium, titanium elements in the steel;
2) slab after coming out of the stove is carried out dephosphorize by high pressure water and handle, remove the iron scale that slab is produced in heat-processed;
3) blank after the dephosphorization is carried out the controlled rolling of two stages immediately, promptly the recrystallization zone is rolling rolling with the non-recrystallization district, and the recrystallization zone is rolling, and rate of deformation is greater than 10s
-1, cumulative deformation is greater than 60%, and finishing temperature is controlled in 1020～1080 ℃ of scopes, obtain intermediate blank, intermediate blank air cooling to 980 ± 30 ℃, it is rolling to carry out the non-recrystallization district again, the rolling compression ratio in non-recrystallization district is remained on more than 5 times, and finishing temperature is controlled in 750～800 ℃ of scopes;
4) size after the finish to gauge is carried out the laminar flow cooling at the plate of moderate thickness of 6-20mm, the speed of cooling scope is controlled between 20～25 ℃/s, and final cooling temperature is controlled in 300～400 ℃ of scopes, with the cooled steel plate air cooling of laminar flow to room temperature;
Described set component span of control is by weight percentage: 0.02～0.05%C, 0.1～0.4%Si, 1.5～2.0%Mn, 0.004～0.012%P, 0.01～0.02%Ti, 0.001～0.005%S, 0.3～0.6%Cu, 0.3～0.6%Ni, 0.2～0.5%Mo, 0.05～0.1%Nb, surplus is Fe and inevitably is mingled with.
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| US9822422B2 (en) | 2009-09-24 | 2017-11-21 | Ati Properties Llc | Processes for reducing flatness deviations in alloy articles |
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| CN101954376A (en) * | 2010-08-31 | 2011-01-26 | 南京钢铁股份有限公司 | Method for medium plate of controlled rolling at two stages in non-recrystallization region |
| CN102151696A (en) * | 2010-12-28 | 2011-08-17 | 西部钛业有限责任公司 | Temperature control rolling method for Q345 steel plate |
| CN102091880B (en) * | 2011-01-26 | 2013-01-09 | 上海三一科技有限公司 | Process for welding WQ890D thick plate |
| CN104138911B (en) * | 2014-05-27 | 2016-06-29 | 南京钢铁股份有限公司 | A kind of method of cut deal intermediate blank rapid water cooling temperature control |
| CN108296285B (en) * | 2018-02-01 | 2019-07-30 | 湖南华菱湘潭钢铁有限公司 | A kind of milling method of ultralow-carbon bainite steel plate |
| CN108823495B (en) * | 2018-07-09 | 2020-06-05 | 青岛理工大学 | Thick plate and extra-thick plate with uniform tissue in thickness direction and preparation method thereof |
| CN112078201B (en) * | 2020-09-22 | 2022-10-25 | 武汉科技大学 | Method for inhibiting grain boundary corrosion caused by segregation of alloy elements |
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