CN1537966A - Low carbon 520MPa grade composite fortified ultra fine crystal grain band steel - Google Patents
Low carbon 520MPa grade composite fortified ultra fine crystal grain band steel Download PDFInfo
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- CN1537966A CN1537966A CNA2003101048620A CN200310104862A CN1537966A CN 1537966 A CN1537966 A CN 1537966A CN A2003101048620 A CNA2003101048620 A CN A2003101048620A CN 200310104862 A CN200310104862 A CN 200310104862A CN 1537966 A CN1537966 A CN 1537966A
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Abstract
A 520 MPa-class low-carbon band steel with superfine crystal grains contains C (0.12-0.15 wt.%), Si (0.15-0.40), Mn (1.10-1.30), Nb (0.007-0.015), P (0-0.01), S (0-0.001 and Fe (rest), and is prepared through smelting, conticasting, heating, rolling twice, cooling and winding. Its advantages are multi-phase structure including ferrite, bainite and pearlite, high yield strength (520-570 MPa), high tension strength (620-690 MPa) and low cost. It can replace high-strength low-alloy steel.
Description
Affiliated technical field
The present invention relates to a kind of preparation method of low-carbon high strength steel, particularly relate to a kind of low-carbon (LC) 520MPa grade composite strengthening ultrafine grain belt steel.
Background technology
At present, ferrous materials remains the main body of structured material.But along with society and expanding economy, the pressure of the saving resource that Iron And Steel Industry faced, save energy, protection environment is increasing.So, traditional ferrous materials is adopted special complete processing, increase substantially its performance, increase the service life, improve the utilization ratio and the rate of recovery of resource effectively, become the focus of ferrous materials research field.
Japan, Korea S started structured material research project geared to the 21st century in succession in 1997 and 1998, and its target is under the constant substantially prerequisite of composition, and the practical intensity and the structural life-time of existing steel is doubled.The technological line of being taked is that low temperature gross distortion, multiaxis such as depress at limit means, and the limit target of pursuing the TMCP grain refining is less than 1 μ m.This processing and manufacturing difficulty is very big, and the decline of the unit elongation of material obviously, and yield tensile ratio is too high, is very limited in actual applications.
China has started state key fundamental research evolutionary operation(EVOP) project from 1998, one of its target is to existing other ordinary steel of 200MPa level, under the constant substantially condition of composition, by special complete processing, yield strength is doubled, and good plasticity and toughness are arranged.The rolling technique under the applicant Northeastern University and the investigators of tandem rolling automated laboratory, through arduous development in a few years, tentatively make the yield strength of common SS400 steel reach 400MPa, and at " iron and steel " magazine, calendar year 2001, delivered in the 36th volume 39 pages of the 5th phases and be entitled as " the industrial rolling test of super super-SS400 steel " paper.Experiment is disclosed in the article through laboratory simulationt test and twice industrial experiment.Its conclusion be when finishing temperature be 800 ℃, when coiling temperature was lower than 450 ℃, the microstructure of super-SS400 steel was a ferrite and perlite and bainite on a small quantity, yield strength has surpassed 400MPa, tensile strength surpasses 540MPa, and unit elongation surpasses 27%, and wide clod wash is qualified.But from the mechanical property of the industrial experiment super-SS400 steel first time, although most of yield strength reaches more than the 400MPa, tensile strength is relatively low, and yield tensile ratio is bigger like this.From the second time Experimental Mechanics performance see that the yield strength major part of steel is lower than 400MPa, for once when coiling temperature was lower than 450 ℃, yield strength reached 400MPa.Still can illustrate all from the metallographic structure of steel that from the mechanical property of above-mentioned steel the tensile strength of the super-SS400 steel that obtains of experiment is still on the low side, yield tensile ratio is bigger, makes in the application formability relatively poor; Gap from twice test mechanical performance data is bigger in addition, illustrates that it is that processing condition that the carbon manganese steel of 200MPa level is brought up to 400MPa level structure steel still remain further research that this technical scheme makes existing yield strength, solves.
Summary of the invention
The objective of the invention is in order to overcome above-mentioned known technology weak point, redesign by chemical ingredients on the basal component basis of super-SS400 structure iron, cooling controlling and rolling controlling process further perfect, reach that really to make present yield strength be that the yield strength of the carbon manganese structure iron of 200MPa level is enhanced about more than once, reach 520～570MPa, tensile strength is at 620～690MPa, unit elongation is 23～30%, the structural strip steel that has good use properties simultaneously, its metallographic structure grain-size is the ferrite of 2～4 μ m, 10～20% bainite and＜5% pearlitic heterogeneous structure.
Low-carbon (LC) 520MPa grade composite strengthening ultrafine grain belt steel of the present invention, form by C, Si, Mn, Nb, P, S and Fe chemical ingredients, main points are that the chemical component weight proportioning is C:0.12～0.15%, Si:0.15～0.40%, Mn:1.10～1.30%, Nb:0.007～0.015%, P＜0.01%, S＜0.01%, all the other are the Fe of equal amount; The metallographic structure of its band steel is the ferrite matrix of 2～4 μ m, and all the other are the pearlitic heterogeneous structure of 10～20% bainite and＜5%.
The design of chemical composition of the invention described above, especially C content is controlled at 0.12～0.15%, in the time of for proof strength, avoids the infringement of C content raising to plasticity, toughness and weldability.Mn content is controlled at 1.10～1.30%, in order suitably to enlarge austenite not in the crystalline scope, reduces the phase occurrence temperature A of strain inducing
D3, reduce to obtain the speed of cooling of part bainite, to make full use of the controlled rolling of austenite non-recrystallization and to roll the back controlled chilling.The Nb of interpolation 0.007～0.015% is for crystal grain thinning and increases the precipitation strength effect.
Realizing low-carbon (LC) 520MPa grade composite strengthening ultrafine grain belt steel of the present invention, is to be prepared from by a kind of new cooling controlling and rolling controlling process method, and its concrete processing method is:
1) rolling technology: blank heating temperature is 1190～1210 ℃; In the austenite recrystallization district, non-recrystallization district and the controlled rolling of deformation induced phase change zone, the roughing start rolling temperature is 1140～1160 ℃, the roughing finishing temperature is 1040～1050 ℃, intermediate blank thickness is 32～45mm, the finish rolling start rolling temperature is 1000～980 ℃, the finish rolling finishing temperature is 790～820 ℃, carries out water-cooled between finishing stand.
2) roll postcooling technology: speed of cooling is 20～30 ℃/s, and coiling temperature is 430～470 ℃.
Low-carbon (LC) 520MPa grade composite strengthening ultrafine grain belt steel of the present invention is a kind of new structural state, it is different from the ferrite pearly-lustre tissue of general low carbon-structural steel and Ultrafine Grained Steel, but be matrix with the ferrite of ultra-fine 2～4 μ m, other is 10～20% bainite and＜5% pearlitic heterogeneous structure.
Ultrafine grain belt steel of the present invention has following advantage and effect compared to the prior art:
Since the chemical composition design suitable proportioning of the ultra-fine band steel of the present invention, and the foundation of the cooling controlling and rolling controlling process that adopts is: by the austenite recrystallization controlled rolling of high-temperature zone, abundant refine austenite crystal grain; By water-cooled between the passage in finish rolling stage, reduce the rolled piece temperature, increase the distortion in austenite non-recrystallization district, the finish rolling finishing temperature is controlled at 790～820 ℃, makes and produces a small amount of deformation induced ferrite in the operation of rolling; By rolling fast batching of cooling and lesser temps of back, an amount of bainite that obtains distributing on the ferrite matrix of super-refinement phase constitution.The ferrite matrix material of super-refinement has higher yield strength, good plasticity, and the low-temperature flexibility of the toughness, particularly material of material is greatly improved simultaneously.Introduce an amount of bainite in the tissue, can effectively improve tensile strength, improve work hardening capacity, reduce yield tensile ratio, make material when improving intensity, also have good formability.
Perfect based on apolegamy rationally of the chemical ingredients of the invention described above structural strip steel and processing condition all reached the over-all properties of ultrafine grain belt steel of the present invention and gives the standard of asking: σ
s520～570MPa, σ
b620～690MPa, δ
523～30%, T
c-90 ℃, wide clod wash B=35mm, d=a is intact.
Because the present invention really makes existing other carbon steel yield strength of 200MPa level be enhanced about more than once, can replace Hi-Stren steel with intensity rank, open up the saving alloying element, reduced steel product cost, increased substantially performance, promoted the new way that rolling shapes update.
Description of drawings
Fig. 1 is the metallographic structure picture of low-carbon (LC) 520MPa grade composite strengthening ultrafine grain belt steel of the present invention.
Embodiment
The chemical ingredients scope that ultra-fine crystal zone steel is set according to the present invention is chosen two groups, be numbered A, B, C and smelt in 200 tons of converters respectively, and continuous casting becomes the continuously cast bloom of 250mm * 1300mm * 10020mm, and is rolling on 2050 hot continuous mills.Selected chemical ingredients is listed table 1 in, and the TMCP processing condition are listed table 2 in, and corresponding mechanical property is listed table 3 in, and the metallographic structure detected result is listed table 4 in, and metallographic structure as shown in Figure 1.
The chemical ingredients of the ultra-fine crystal zone of table 1 embodiment steel (weight, %)
Numbering C Si Mn Nb S S Fe
A 0.13 0.20 1.25 0.007 0.009 0.01 surplus
B 0.12 0.35 1.10 0.009 0.008 0.009 surplus
C 0.15 0.40 1.30 0.013 0.007 0.006 surplus
Table 2 TMCP process system
Sample is compiled the roughing open rolling, roughing finish to gauge, and the finish rolling open rolling, finish rolling finish to gauge, speed of cooling is batched,
Number ℃ ℃ ℃ ℃ ℃/S ℃
A1 1150 1050 1000 820 20 450
A2 1150 1045 985 790 26 470
B1 1150 1050 990 806 24 440
B2 1150 1050 995 810 29 465
C1 1150 1050 1000 795 30 430
C2 1150 1045 985 815 30 440
Table 3 mechanical property detected result
Specimen coding σ
sσ
bδ
5Akv, cold change, B=35,
MPa MPa ％ J/mm
2 d＝0.5a
A1 570 690 23 105 is qualified
A2 550 660 27 130 is qualified
B1 535 640 30 126 is qualified
B2 565 690 29 133 is qualified
C1 550 670 28 120 is qualified
C2 550 650 29 110 is qualified
Table 4 metallographic structure detected result
Ferrite grain size, bainite amount either pearlite occurred
Specimen coding
μm ％ ％
A1 2.4 15 4
A2 3.0 10 5
B1 3.6 20 3
B2 4.0 15 3
C1 2.2 12 4.5
C2 3.1 15 3.5
Claims (3)
1, a kind of low-carbon (LC) 520MPa grade composite strengthening ultrafine grain belt steel, form by C, Si, Mn, Nb, P, S and Fe chemical ingredients, it is characterized in that the chemical component weight proportioning is C:0.12～0.15%, Si:0.15～0.40%, Mn:1.10～1.30%, Nb:0.007～0.015%, P＜0.01%, S＜0.01%, all the other are the Fe of equal amount; The metallographic structure of its band steel is the ferrite matrix of 2～4 μ m, and all the other are the pearlitic heterogeneous structure of 10～20% bainite and＜5%.
2, according to the described a kind of low-carbon (LC) 520MPa grade composite strengthening ultrafine grain belt steel of claim 1, it is characterized in that the yield strength with steel is 520～570MPa, tensile strength is 620～690MPa.
3, according to the described a kind of low-carbon (LC) 520MPa grade composite strengthening ultrafine grain belt steel of claim 1, it is characterized in that with chemical ingredients C, Si, Mn, Nb, P, S and Fe be raw material, through smelting, and continuous casting becomes blank and heating, carries out controlled rolling and controlled cooling then, it is characterized in that the chemical component weight proportioning is C:0.12～0.15%, Si:0.15～0.40%, Mn:1.10～1.30%, Nb:0.007～0.015%, P＜0.01%, S＜0.01%.All the other are the Fe of equal amount; Blank heating temperature is 1190～1210 ℃; In the austenite recrystallization district, non-recrystallization district and the controlled rolling of deformation induced phase change zone, the roughing start rolling temperature is 1140～1160 ℃, the roughing finishing temperature is 1040～1050 ℃, intermediate blank thickness is 32～45mm, the finish rolling start rolling temperature is 1000～980 ℃, and the finish rolling finishing temperature is 790～820 ℃, carries out water-cooled between finishing stand, rolling postcooling speed is 20～30 ℃/S, and coiling temperature is 430～470 ℃.
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| CN 200310104862 CN1219101C (en) | 2003-10-20 | 2003-10-20 | Low carbon 520MPa grade composite fortified ultra fine crystal grain band steel |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100419109C (en) * | 2005-11-04 | 2008-09-17 | 东北大学 | Manufacturing method of low carbon 700 MPa composite fertified ultrafine crystal band steel |
| CN102719735A (en) * | 2011-03-29 | 2012-10-10 | 鞍钢股份有限公司 | Superfine crystal grain hot-rolled dual-phase steel plate for automobile and production method thereof |
| CN103447295A (en) * | 2013-08-14 | 2013-12-18 | 武钢集团昆明钢铁股份有限公司 | Manufacturing method of hot rolled steel plate with low alloy structural steel |
| CN104404366A (en) * | 2014-12-08 | 2015-03-11 | 安徽省安工机械制造有限公司 | Formula and production process for high strength-toughness traction bar bracket steel casting |
| CN108213095A (en) * | 2017-12-28 | 2018-06-29 | 东莞科力线材技术有限公司 | A kind of fan net counter-bending steel wire of super-strength thin footpath and preparation method thereof |
-
2003
- 2003-10-20 CN CN 200310104862 patent/CN1219101C/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100419109C (en) * | 2005-11-04 | 2008-09-17 | 东北大学 | Manufacturing method of low carbon 700 MPa composite fertified ultrafine crystal band steel |
| CN102719735A (en) * | 2011-03-29 | 2012-10-10 | 鞍钢股份有限公司 | Superfine crystal grain hot-rolled dual-phase steel plate for automobile and production method thereof |
| CN103447295A (en) * | 2013-08-14 | 2013-12-18 | 武钢集团昆明钢铁股份有限公司 | Manufacturing method of hot rolled steel plate with low alloy structural steel |
| CN103447295B (en) * | 2013-08-14 | 2015-02-04 | 武钢集团昆明钢铁股份有限公司 | Manufacturing method of hot rolled steel plate with low alloy structural steel |
| CN104404366A (en) * | 2014-12-08 | 2015-03-11 | 安徽省安工机械制造有限公司 | Formula and production process for high strength-toughness traction bar bracket steel casting |
| CN108213095A (en) * | 2017-12-28 | 2018-06-29 | 东莞科力线材技术有限公司 | A kind of fan net counter-bending steel wire of super-strength thin footpath and preparation method thereof |
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| Publication number | Publication date |
|---|---|
| CN1219101C (en) | 2005-09-14 |
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