CN102796943B - Thin strip steel for thin-wall oil drum and manufacturing method of thin strip steel - Google Patents
Thin strip steel for thin-wall oil drum and manufacturing method of thin strip steel Download PDFInfo
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Abstract
The invention discloses a thin strip steel for a thin-wall oil drum and a manufacturing method of the thin strip steel. Double-roll thin strip continuous production is adopted; a dry ice spray mode is adopted after a cast strip is discharged from a crystallization roll; uniform enhanced cooling is performed on the cast strip; the cast strip is quickly cooled to be below 1,280 DEG C; the cooling rate is 200-300 DEG C/s; in such a cooling mode, separation of coarse BN (Boron Nitride) can be promoted and low-melting-point phase B2O3 and fine AlN (Aluminum Nitride) separation are prevented to fulfill the aims of uniformizing austenite crystal grains and reducing the yield ratio; and then austenite is recrystallized and rolled on line, and the strip steel which is subjected to hot rolling is cooled through anti-oxidation quick cooling, wherein the cooling rate is 80-200 DEG C/s and the coiling temperature is 500-600 DEG C. Through the invention, the thin strip steel for the thin-wall oil drum with low yield ratio and superior impact performance can be obtained. According to the thin strip steel for the thin-wall oil drum produced by the method, the hot thin strip steel can be directly used in place of a cold one, a cold rolling step is removed, and the production cost is greatly reduced.
Description
Technical field
The present invention relates to continuous casting process, particularly Thin Strip Steel and manufacture method thereof for a kind of thin-walled oil drum.
Background technology
In traditional process Iron and Steel Production, tin (Sn) is typical residual element or harmful element in steel, in steelmaking process, to remove fully Sn very difficult and be very expensive, once contain Sn in steel, substantially cannot thoroughly eliminate, the content that can only reduce by dilution molten steel Sn, these all cause the rising of steel products cost.
In recent years, due to the continuous circulation utilization of steel scrap, cause the content of the residual element such as the Sn in steel to raise gradually, Sn in steel is easy segregation element, easily being enriched in crystal boundary causes defects i.e.cracks to occur, therefore in traditional technique, the content of Sn element is strictly controlled, and with in steel, the content of Sn is all had to clear and definite requirement: Sn(wt% at ordinary construction)≤0.005%.
Therefore,, if can accomplish " turning harm into good " to residual element such as Sn in steel (particularly steel scrap), will produce active influence to whole metallurgical boundary; Can realize the effective utilization to existing steel scrap or low-quality ore resources inferior (high tin ore), promote the recycle of steel, reduce production costs, realize iron and steel industry Sustainable development.
Traditional strip is mostly to be produced through multi-pass continuous rolling by the strand of the thick 70-200mm of reaching, tradition hot rolling technology flow process is: continuous casting+strand reheats insulation+roughing+finish rolling+cooling+batch, first obtain by continuous casting the strand that thickness is 200mm left and right, after strand is reheated and is incubated, carry out again roughing and finish rolling, obtain the steel band that thickness is generally greater than 2mm, finally steel band is carried out to laminar flow cooling and batch, complete whole hot rolling production process.If produce thickness be less than 1.5mm(containing) steel band, difficulty is relatively large, conventionally will carry out hot rolled strip follow-up cold rolling and annealed.And technical process is long, energy consumption is high, unit equipment is many, capital construction cost is high, causes production cost higher.
Continuous casting and rolling technique of sheet bar flow process is: continuous casting+strand insulation soaking+hot continuous rolling+cooling+batch.The key distinction of this technique and traditional technology is: the slab thickness of sheet bar process attenuate greatly, for 50-90mm, because strand is thin, strand needs only through 1 ~ 2 passage roughing (when slab thickness is 70-90mm) or does not need through roughing (when slab thickness is 50mm), and the continuously cast bloom of traditional technology will be through multi-pass rolling repeatedly, just can be thinned to required specification before finish rolling; And the strand of sheet bar process is without cooling, directly enters soaking pit and carries out soaking insulation, or a small amount of temperature of mending, therefore sheet bar process has shortened technical process greatly, has reduced energy consumption, has reduced investment, thereby has reduced production cost.But CSP improves because cooling rate faster can cause steel strength, yield tensile ratio improves, thereby increase rolling load, the thickness specification that makes to produce economically hot-rolled product also can not be too thin, Yi Ban Wei≤1.5mm, see patent CN200610123458.1, CN200610035800.2 and CN200710031548.2, and these patents all do not relate to element B and Sn.Solution CSP is organized thinner and inhomogeneous, and the higher problem of yield tensile ratio is suggested as a very important problem.
The technical process shorter than CSP is sheet-band continuous casting and rolling technique, strip continuous casting technology is a cutting edge technology in metallurgy and investigation of materials field, its Iron And Steel Industry that appears as is brought a revolution, it has changed traditional production process of controlling steel band in metal working industry, by continuous casting, rolling, even thermal treatment etc. integrates, make the online hot rolling of strip base process a time of producing with regard to the thin steel band of disposable formation, greatly simplify production process, shortened the production cycle, its processing line length is 50m left and right only; Facility investment is corresponding minimizing also, and product cost significantly reduces, and is a kind of hot rolled thin strip production technique of low-carbon environment-friendly.Twin-roll thin strip continuous casting technique is a kind of principal mode of thin band continuous casting technique, is also unique a kind of thin band continuous casting technique of realizing industrialization in the world.
The typical technical process of twin-roll thin strip continuous casting is: the molten steel in large bag is by large bag long nozzle, tundish and flow distribution device cast directly over one relatively rotate by two and molten bath that crystallization roll that can be cooling fast and lateral seal surround in, molten steel solidifies and forms solidified shell growth gradually in the peripheral surface of crystallization roll rotation, and then form the thick steel band of 1-5mm at the minimum places of two crystallization roll roll gap gaps (nip point), steel band sends into via guide plate guiding pinch roll the strip that is rolled into 0.7-2.5mm in milling train, cooling through apparatus for supercooling subsequently, after shear arrangement crop, finally send into reeling machine and batch rolling.
Adopt thin strap continuous casting produce thin-walled oil drum steel, due to thinner thickness, for thickness be less than 1.5mm(contain) thin size hot-rolled product, thin band continuous casting technique has stronger manufacture and cost advantage.The consumption in worldwide is very large with Thin Strip Steel for thin-walled oil drum, the hot-rolled sheet state directly product specification characteristic thickness of the supply of material is 1.25mm and 1.5mm, the product specification characteristic thickness of cold-reduced sheet and the supply of material of cold rolling hot dip galvanizing state is 1.0mm, 1.2mm and 1.5mm, because product thickness is thinner, therefore adopt traditional hot continuous rolling process production cost higher, the domestic manufacturer that can stablize the hot-rolled sheet supply of material at present mainly contains Baosteel, Wuhan Iron and Steel Plant and Taiyuan Iron and Steel Co. etc., a lot of producers are due to the capabilities limits of traditional hot-rolling line, the producer of original available hot-rolled sheet supply of material transfers employing Cold Rolled Sheet Steel to or cold rolling hot dip galvanizing steel sheet replaces the supply of material, this has also increased the production cost of thin-walled oil drum steel.
When hot rolled strip uses as thin size hot-rolled plate or " with hot Dai Leng " product, require very high to strip surface quality.The thickness of general requirement belt steel surface oxide skin is got over Bao Yuehao, this just need to be follow-up in Cast Strip the generation of each stage control iron scale, in typical process, at crystallization roll until inlet of rolling mill all adopts confined chamber device to prevent Cast Strip oxidation, in confined chamber device, be less than 5% as patent US6920912 adds hydrogen and control oxygen content in patent US20060182989, all can control the scale thickness on surface, Cast Strip.But milling train to batch thickness that how this section of course of conveying to control oxide skin seldom relevant patent relate to, especially adopting the cooling or spraying cooling of laminar flow to carrying out in cooling process with steel, the band steel of high temperature contacts with water coolant, and the scale thickness on surface, Cast Strip increases very fast.Meanwhile, the band steel of high temperature contacts with water coolant also can bring a lot of problems: one, can form water spots (rust staining) at belt steel surface, and affect surface quality; Its two, the water coolant that laminar flow is cooling or spraying cooling is used easily causes belt steel surface Local cooling inhomogeneous, causes inhomogeneous with steel interior microscopic tissue, thereby causes the inhomogeneous of strip property, affects quality product; Its three, belt steel surface Local cooling is inhomogeneous, can cause the deterioration of plate shape, affects strip shape quality.
But thin strap continuous casting is due to the fast solidification technology characteristic of itself, the steel grade ubiquity structure refinement of production, the problem that unit elongation is on the low side, yield tensile ratio is higher, formability is bad; Simultaneously Cast Strip austenite crystal has obvious ununiformity, and the finished product that can cause obtaining after austenite phase transformation are organized also inhomogeneous, thereby causes the unstable properties of product.Therefore adopt thin strap continuous casting production line to produce the product with good formability of some automobile industries, petrochemical industry, oil drum manufacturing needs, tool acquires a certain degree of difficulty.When thin size hot-rolled band steel uses with product made from steel as thin-walled oil drum, require steel grade in mechanical property, to there is preferably strong plasticity coupling, there is higher unit elongation (unit elongation reaches more than 24%), and in processing performance, there is good punching performance (press depth reaches 9-12mm).In the face of high like this performance requriements, there is certain challenge to adopting thin strap continuous casting to produce this steel grade, therefore, while adopting thin strap continuous casting production thin-walled oil drum to use Thin Strip Steel, indiscriminately imitating traditional Composition And Process is to produce qualified thin-walled oil drum steel, need in composition and technique, have breakthrough.
Summary of the invention
The object of the present invention is to provide a kind of thin-walled oil drum Thin Strip Steel and manufacture method thereof, by adding micronutrient boron containing in the soft steel composition of Sn, go out after crystallization roll at thin strip continuous casting strip steel, adopt and spray dry ice (solid-state CO to band steel both sides
2) mode that band steel is carried out to Quick uniform is cooling, improve cooling uniformity and cooling intensity and reach the effect of anti-oxidation, even austenite crystal tissue, reduction rolling temperature; Adopt the online recrystallize rolling of austenite simultaneously, realize the online recrystallize of austenite after the hot rolling of Cast Strip; Then adopt anti-oxidation method for rapid cooling can reduce belt steel surface scale thickness, improve belt steel temperature homogeneity, improve strip surface quality.Thin strap continuous casting is in the time producing this type of steel grade, can solve the problem that in thin band continuous casting technique process, tissue odds is even, unit elongation is on the low side, yield tensile ratio is higher, formability is bad, meet the service requirements such as bending and molding, impact briquetting, thereby meet the service requirements of cold rolling base and " with hot Dai Leng " product.
For achieving the above object, technical scheme of the present invention is:
A kind of thin-walled oil drum Thin Strip Steel, its chemical component weight per-cent is: C:0.04-0.12%, Si:0.2-0.4%, Mn:0.4-1.0%, P :≤0.055%, S :≤0.008%, N:0.004-0.010%, Al:0.01-0.06%, Sn:0.005-0.04%, B:0.001-0.006%, all the other are Fe and inevitable impurity.
In chemical composition design of the present invention:
C:C is strengthening element most economical, the most basic in steel, improves the intensity of steel by solution strengthening and precipitation strength.C separates out the requisite element of cementite in austenitic transformation process, therefore the height of C content determines the intensity rank of steel to a great extent, i.e. the higher higher intensity rank of C content correspondence.But because the gap solid solution of C and plasticity and the toughness of separating out steel have larger harm, and too high C content is unfavorable to welding property, therefore C content can not be too high, and the intensity of steel makes up by suitable interpolation alloying element.Therefore the C content range that the present invention adopts is 0.04-0.12%.
Si:Si plays solution strengthening effect in steel, and in steel, adds Si and can improve purity of steel and deoxidation, but Si too high levels can cause weldability and welding heat influence area toughness to worsen.Therefore the Si content range that the present invention adopts is 0.2-0.4%.
Mn:Mn is one of alloying element that price is the most cheap, it can improve the hardening capacity of steel, in steel, there is sizable solid solubility, improve the intensity of steel by solution strengthening, plasticity to steel and toughness are substantially harmless simultaneously, are the topmost strengthening elements of intensity that improves steel in C content situation reducing.But Mn too high levels can cause weldability and welding heat influence area toughness to worsen.Therefore the Mn content range that the present invention adopts is 0.4-1.0%.
P:P can significantly improve the corrosion resistance nature of steel, and can improve intensity.But the P of high-content, easily at grain boundary segregation, increases the cold shortness of steel, and welding property is degenerated, and reduces plasticity, and cold-bending property is degenerated.In thin band continuous casting technique, solidifying with rate of cooling of Cast Strip is exceedingly fast, and can effectively suppress the segregation of P, thereby can effectively avoid the inferior position of P, gives full play to the advantage of P, and oil drum is objectively also requiring steel grade to have certain erosion resistance with steel.Therefore in the present invention, adopt P content higher while producing thin-walled oil drum steel compared with traditional technology, suitably relax the content of P element, in steel making working procedure, cancel dephosphorization operation, in actually operating, do not need deliberately to carry out dephosphorization operation, do not need additionally to add phosphorus, scope≤0.055% of P content yet.
S: S is harmful element in steel under normal conditions, makes steel produce red brittleness, reduces ductility and the toughness of steel, causes crackle in the time of rolling.S also can reduce welding property and erosion resistance.Therefore in the present invention, S also controls as impurity element, its content range is≤and 0.008%.
Al:Al is the element adding for deoxidation in steel, and the Al that adds 0.01-0.06% content is conducive to improve the toughness and tenacity of steel.
N: similar with C element, N element can improve by gap solid solution the intensity of steel, the present invention will utilize N in the steel precipitated phase with B effect generation BN, and needing has certain N content in steel.But plasticity and the toughness of the gap solid solution of N to steel has larger harm, the existence of free N can improve the yield tensile ratio of steel, and therefore N content can not be too high.The N content range that the present invention adopts is 0.004-0.010%.
Sn:Sn element is acknowledged as the harmful element in steel, because Sn is easy segregation element, a small amount of Sn will be in crystal boundary enrichment, and causing is that defects i.e.cracks occurs, and therefore in traditional technique, the content of Sn element is strictly controlled.Thin strap continuous casting is due to rapid solidification, and element reduces greatly in interdendritic segregation, can greatly improve the solid solution capacity of element, and therefore, under thin band continuous casting technique condition, the scope of Sn element can expand, and therefore can greatly reduce steel-making cost.Fig. 3 is the relation of Sn element and mean heat flux.As seen from Figure 3, in the time that Sn add-on is less than 0.04%, little on the impact of heat flow density, thin strip solidification process is not affected.Fig. 3 is the relation of Sn content and surfaceness.Because the crackle on surface, Cast Strip is all to produce at the fold place of Cast Strip surface irregularity conventionally, a situation arises to carry out characterization of surfaces crackle by surfaceness.If roughness is large, the probability that crackle occurs is high.As shown in Figure 4, the increase of Sn content does not exert an adverse impact to the surface quality of Cast Strip under rapid solidification condition.From the result of Fig. 3 and Fig. 4, Sn does not produce detrimentally affect to solidifying with surface quality of Cast Strip.The content range of Sn is at 0.005-0.04%.
The remarkable effect of B:B in steel is that the boron of denier just can make the hardening capacity of steel be multiplied, thereby B can preferentially separate out thick BN particle in high temperature austenite suppresses separating out of tiny AlN, weaken the pinning effect of tiny AlN to crystal boundary, improve the energy for growth of crystal grain, thus alligatoring austenite crystal; The B of some solid solution simultaneously segregation has suppressed ferrite forming core at austenite grain boundary, has reduced ferritic nucleation rate, thereby reaches the effect that reduces yield tensile ratio, improves processability; B can effectively prevent crystal boundary low melting point phase B with the combination of N in addition
2o
3appearance.
B is active easily segregation element, and easily at Grain Boundary Segregation, when traditional technology is produced containing B steel, B content general control very strict, generally in 0.001-0.003% left and right; And in thin band continuous casting technique, solidify with rate of cooling comparatively fast, and can effectively suppress the segregation of B, the more B content of solid solution, therefore the content of B can suitably relax; Can also generate thick BN particle by rational technology controlling and process, suppress tiny AlN and separate out, play the effect of fixed nitrogen, solve, inferior position that formability bad higher with steel yield tensile ratio that thin strap continuous casting is produced.Therefore in the present invention, adopt the B content higher compared with traditional technology, scope is 0.001-0.006%.
The manufacture method of Thin Strip Steel for a kind of thin-walled oil drum of the present invention, it comprises the steps:
A) smelt
Smelt according to following chemical composition, molten steel chemical composition is: C:0.04-0.12%, Si:0.2-0.4%, Mn:0.4-1.0%, P :≤0.055%, S :≤0.008%, N:0.004-0.010%, Al:0.01-0.06%, Sn:0.005-0.04%, B:0.001-0.006%, all the other are Fe and inevitable impurity;
B) casting
Adopt twin-roll thin strip continuous casting, continuous casting of molten steel is formed to the Cast Strip that 1.5-3mm is thick, crystallization roll diameter 500-1500mm, casting rate 60-150m/min;
C) secondary is cooling
Take out of after crystallization roll at thin-belt continuous casting, Cast Strip temperature, at 1420-1480 DEG C, arranges two device for cooling in the both sides of Cast Strip along Cast Strip width, and beginning to cool down of two device for cooling is a little arranged on from nip point 250-750mm, whole two cold but segment length 200-500mm; Cast Strip goes out to adopt to both sides, Cast Strip immediately after crystallization roll the mode of spraying dry ice to carry out Quick uniform to Cast Strip to be cooled to below 1280 DEG C, rate of cooling 200-300 DEG C/s;
D) online hot rolling
The band steel that is rolled into 0.7-2.5mm thickness in milling train will be delivered to through pinch roll after going out confined chamber in the cooled Cast Strip of secondary with steel, rolling temperature 1050-1200 DEG C, and draft is 20-50%;
E) band steel rolls rear cooling
To rolling the anti-oxidation fast cooling mode of rear cooling employing with steel after online hot rolling, dry ice is injected directly on to belt steel surface, cooling with accelerated band steel, rate of cooling 80-200 DEG C/s;
F) strip coiling
Cooled hot rolled strip, after crop shears excise second-rate head, directly batches rolling, coiling temperature 500-600 DEG C.
Further, above-mentioned secondary is cooling to carry out in confined chamber under Cast Strip, dry ice is injected directly on surface, Cast Strip by the strengthening method of cooling adopting, and wherein dry ice and rare gas element or nitrogen mixed volume ratio are 5:1 ~ 10:1, with the pressure of 0.5-5MPa directly by dry ice blasting on surface, Cast Strip.
Again, hot rolling draft 30-50%.After hot rolling, the thickness of steel band is 1.2-2.0mm.Hot rolling temperature 1050-1150 DEG C.
Have, the anti-oxidation fast cooling mode of the present invention, injects directly on belt steel surface by dry ice again, and wherein dry ice and rare gas element or compressed nitrogen mixed volume ratio are 5:1 ~ 10:1, with the pressure of 0.2-3MPa directly by dry ice blasting at belt steel surface.
In addition, batch two reeling machine forms that adopt.
In manufacture method of the present invention,
Secondary is cooling, takes out of after crystallization roll at thin-belt continuous casting, and Cast Strip temperature, at 1420-1480 DEG C, arranges two device for cooling in the both sides of Cast Strip along Cast Strip width, after going out band, adopts and sprays dry ice (solid-state CO immediately to both sides, Cast Strip
2) mode Quick uniform carried out in Cast Strip be cooled to below 1280 DEG C, can significantly improve cooling uniformity and cooling intensity with steel, promote separating out of BN in steel.
Above-mentioned secondary is cooling to carry out in confined chamber under Cast Strip, adopts strengthening method of cooling by dry ice (solid-state CO
2) inject directly on surface, Cast Strip, to accelerate the cooling of Cast Strip, play on the one hand the effect that reduces Cast Strip temperature, solid-state dry ice is sprayed onto hot surface, Cast Strip meeting gasification on the other hand, forms highdensity vaporific gas, carbonic acid gas (CO on surface, Cast Strip
2) belong to a kind of inert atmosphere, can be coated on surface, Cast Strip, play the anti-oxidation effect in Cast Strip, thereby effectively controlled the growth of Cast Strip surface scale.
The theoretical basis of the cooling BN precipitated phase relating to of Cast Strip secondary of the present invention's design:
In steel, boron and nitrogen, aluminium and the nitrogen thermodynamical equilibrium equation in γ-Fe is as follows:
BN=B+N；Log[B][N]＝-13970/T+5.24 (1)
AlN=Al+N；Log[Al][N]=-6770/T+1.03 (2)
As shown in Figure 2, in steel, the beginning Precipitation Temperature of BN is 1280 DEG C of left and right, and 980 DEG C time, separating out of BN tended to balance, and now separating out just of AlN just starts (Precipitation Temperature of AlN is 980 DEG C of left and right), and from thermodynamics, separating out of BN will have precedence over AlN.Therefore the present invention, by rational technology controlling and process means, promotes the combination of B and N, generates thick BN particle, thereby even austenite crystal tissue suppresses tiny AlN and separates out.
Conventionally, under thin strap continuous casting, in confined chamber, do not adopt any cooling provision, in long-term casting situation, the envrionment temperature of confined chamber is up to more than 800 DEG C, the load-bearing under long-term high temperature of the confined chamber underframe of steel construction and confined chamber wall is on active service, can deform, affect intensity and the precision of whole mechanical framework structure, go back the danger such as the easy cracking that underframe welding junction place occurs.Therefore a lot of work has been done aspect confined chamber cooling by a lot of producers, such as the light factory thin strap continuous casting of Nippon Steel adopts the form of water wall to reach cooling object with regard to having reported time confined chamber wall, concrete scheme is that lower confined chamber wall adopts two block plate welding, middle logical recirculated water; The Castrip (seeing patent US5960856A) of U.S. Nucor adopts the form of " water-cooled pillow " to reach cooling object, concrete scheme is from steel, the place close to slightly arranges water-cooled pillow, the logical recirculated water in the inside, form (confined chamber) just as in large room arranges a hot room of septulum (water-cooled pillow surrounds), pass water-cooled with steel and rest the head on the hot room of septulum surrounding, temperature is absorbed, and in being with steel cooling, plays the temperature drop effect to big room (confined chamber).The present invention sprays dry ice at confined chamber inner high voltage, adopts " distillation " physical property of dry ice self, can absorb a large amount of heats, in being with steel realization cooling rapidly, the temperature of confined chamber is also played to the effect of effective temperature-reducing; Effective reduction of confined chamber temperature, underframe (being generally steel construction) and confined chamber wall to whole confined chamber play cooling effect, can effectively prevent the distortion of confined chamber underframe.
Online hot rolling, the band steel that is rolled into 0.7-2.5mm thickness in milling train will be delivered to through pinch roll after going out confined chamber in the cooled Cast Strip of secondary with steel, controlled rolling temperature 1050-1200 DEG C, object is austenite generation perfect recrystallization after guarantee hot rolling.Controlling hot rolling draft is 20-50%, and hot rolling draught increases can promote austenite recrystallization.
Realize relatively low rolling temperature 1050-1200 DEG C by secondary cooling apparatus, relatively low rolling temperature, be favourable for rolling, rolling temperature is lower, is more conducive to the control of rolling strip shape quality, in conventional strip technological process, temperature before milling train is often up to more than 1200 DEG C, and even more than 1250 DEG C, band steel is now very soft, cannot apply larger rolling load, be difficult to effective rolling.Ensureing under the prerequisite of the online recrystallize of austenite, preferably, rolling temperature 1050-1150 DEG C.
Band steel rolls rear cooling, the band steel after online hot rolling is rolled rear cooling, and the anti-oxidation fast cooling mode of cooling employing is by dry ice (solid-state CO
2) inject directly on belt steel surface, to accelerate the cooling of steel band, play on the one hand the effect that reduces belt steel temperature, CO on the other hand
2belong to a kind of inert atmosphere, its proportion is larger than oxygen, can be coated on belt steel surface, plays the effect anti-oxidation with steel, thereby has effectively controlled the growth of Surfaces of Hot Rolled Strip oxide skin.This kind of problem that the type of cooling can avoid traditional laminar flow cooling zone, evenly declines belt steel surface temperature, improves belt steel temperature homogeneity, thereby reaches the effect of homogenizing interior microscopic tissue; Simultaneously cooling even, can improve the strip shape quality with steel; Reduce the scale thickness of belt steel surface, the follow-up pickling while being convenient to make cold rolling base.
The present invention adopts high-speed gas to wrap dry ice (CO
2) to spray belt steel surface cooling for broken phosphorus and strengthening, can become CO because dry ice touches after hot band steel can absorb heat fast
2gas, affects surface quality of strips and composition so can not embed belt steel surface; In addition, due to the quick heat-absorbing action of dry ice, can play quick cooling effect to band; The more important thing is, after dry ice volatilization, become atmospheric carbon dioxide (CO
2), completely cut off and oxygen (O
2) contact, restriction strip surface oxide skin further generate.
Strip coiling, cooled hot rolled strip, after crop shears excise second-rate head, directly batches rolling.The coiling temperature of controlling hot-rolled strip is 500-600 DEG C, so that hot-rolled strip has the tissue signature of bainite.Reeling machine adopts two forms of batching, and ensures the continuous production with steel.
The present invention, adding B element containing in the soft steel of Sn, by rational two cold patterns, goes out after crystallization roll at thin strip continuous casting strip steel, adopts high pressure to spray dry ice (solid-state CO to band steel both sides
2) mode that band steel is carried out to Quick uniform is cooling, improve cooling uniformity and cooling intensity and reach the effect of anti-oxidation, even austenite crystal tissue, reduction rolling temperature; Band steel after rolling adopts anti-oxidation Cooling Mode can reduce belt steel surface scale thickness, improves belt steel temperature homogeneity, improves strip surface quality.Thin strap continuous casting, in the time producing this type of steel grade, can solve the problem that in thin band continuous casting technique process, tissue odds is even, unit elongation is on the low side, yield tensile ratio is higher, formability is bad, thereby meet the service requirements such as bending and molding, impact briquetting.
Utilize strip continuous casting technology to produce boracic (B) thin-walled oil drum steel, there is not yet up to now report, conclude advantage as follows:
(1) saved heating of plate blank, the multi-pass complex process such as hot rolling repeatedly, to directly carrying out the online hot rolling of a time in thin Cast Strip, production cost significantly reduces.
(2) Cast Strip thickness itself is thinner, and by being hot-rolled down to online expected product thickness, the production of thin slab product does not need through cold rolling, directly " with hot Dai Leng "; On the other hand, due to thinner thickness, during for cold rolling base, can greatly reduce the passage of follow-up cold rolling attenuate, greatly save production cost.
(3) utilize the steel scrap containing Sn, the Sn in steel is accomplished to " turning harm into good ", realize the effective utilization to existing steel scrap or low-quality ore resources inferior (high tin ore), promote the recycle of steel, reduce production costs, realize iron and steel industry Sustainable development.Add B element, can solve the problem that in thin band continuous casting technique process, tissue odds is even, yield tensile ratio is higher, thereby meet the service requirements of cold rolling base; Be easy to bending, impact briquetting simultaneously.
(4) in traditional technology slab process of cooling, there is alloying element and separate out, when slab reheats, tend to reduce because alloying element back dissolving is insufficient alloying element utilization ratio.In thin band continuous casting technique, the direct hot rolling in high temperature Cast Strip, the alloying element adding mainly exists with solid solution state, can improve alloy utilization ratio.
Major advantage of the present invention:
1. adopt thin band continuous casting technique to produce thin-walled oil drum Thin Strip Steel, carry out after hot rolling directly supply market and use, reach the object of the thin size hot-rolled plate supply of material and meet that cold rolling base requires and " cold with the torrid zone " object, can significantly improve the cost performance of Strip.
2. the present invention adopts and adds micro-boron, reaches effective reduction band steel yield tensile ratio, improves the effect with steel processability, and production cost is more traditional and thin slab production technique is obviously cheap.The further volume of comprehensive utilization improving harmful residual element P in steel, cancels the dephosphorization operation in steel-making simultaneously, makes production cost more traditional obviously cheap with thin slab production technique.
3. utilize the steel scrap containing Sn, the Sn in steel is accomplished to " turning harm into good ", realize the effective utilization to existing steel scrap or low-quality ore resources inferior (high tin ore), promote the recycle of steel, reduce production costs, realize iron and steel industry Sustainable development.
4. adopt secondary cooling apparatus to realize relatively low rolling temperature, be conducive to online hot rolling, be conducive to the control of rolling strip shape quality; In addition utilize the physics heat-absorbing action of dry ice " distillation ", play effective reduction confined chamber temperature and prevent the effect that confined chamber steel structure frame is out of shape.The rear anti-oxidation cooling iron scale thickness that effectively reduces Surfaces of Hot Rolled Strip is fast rolled in employing, can greatly improve plate surface quality.
5. reasonable process parameter control has flexibly been widened the state space of production line, can meet the need of production of variant production specification.
The difference of the present invention and prior art and improvements:
In patent EP0830223A1/CN1180325A/US5960856A/DE69700737D, mention a kind of method and device of casting black metal strip, solidify after two rollers at band steel, arrange a pair ofly for the cooling contactless heat absorber of steel, be used for the latent heat of solidification that discharges after absorption band steel solidifies completely.This patent is compared with the present invention, the key distinction is in cooling intensity, the present invention adopts high pressure to spray the method for dry ice, directly contacting with the strip, it is cooling to force, can realize 200 DEG C/more than s cooling intensity, higher than the cooling performance of contactless heat absorber, effectively reduce rolling temperature far away, be conducive to the raising of rolling strip shape quality.
Patent CN1472019A discloses a kind of method for continuous casting sheet band and device, in crystallization roll exit, Cast Strip is realized cooling to high temperature Cast Strip broad ways blowing gas.Although this patent can play cooling effect to Cast Strip, but adopt the mode of air cooling, the span of control of rate of cooling has certain limitation, this patent adopts high pressure to spray the method for dry ice, directly contacting with the strip, it is cooling to force, can realize 200 DEG C/more than s cooling intensity, effectively reduce rolling temperature, be conducive to the raising of rolling strip shape quality.
The driven roll that patent JP-A-5-277654 has increased a pair of external diameter Φ 200mm at crystallization roll outlet lower end 300-400mm, by the transmission of heat by contact of driven roll and Cast Strip, reaches the cooling effect with steel.The present invention is completely different from the means that the method adopts, and the present invention is the method by spray dry ice to directly carry out high pressure with steel, band tape transport heat of steel.The main drawback of patent JP-A-5-277654 is that cooling intensity is limited, is secondly the speeds match problem of crystallization roll and pony roll, if mate badly, easily give a discount in Cast Strip, and production operation inconvenience is controlled dumb.
Brief description of the drawings
Fig. 1 is that production technique of the present invention is arranged schematic diagram.
Fig. 2 is the thermomechanical curve schematic diagram that BN, AlN separate out.
Fig. 3 is the schematic diagram that is related to of Sn content and mean heat flux.
Fig. 4 is the schematic diagram that is related to of Sn content and Cast Strip surfaceness.
Embodiment
Referring to Fig. 1, technological process of the present invention: molten steel is through large bag 1, by large bag long nozzle 2, tundish 3 and flow distribution device 4 cast directly over one relatively rotate by two and molten bath 7 that crystallization roll 5a, 5b that can be cooling fast and side seal board device 6a, 6b surround in, molten steel solidifies in the peripheral surface of crystallization roll 5a, 5b rotation, and then forms solidified shell and grow and form the thick Cast Strip 11 of 1.5-3mm at the minimum places of two crystallization roll roll gap gaps (nip point) subsequently gradually.Dry ice (solid-state CO, through two device for cooling 8 in confined chamber 10, are sprayed to 11 both sides, Cast Strip after going out to be with immediately in Cast Strip
2), control its rate of cooling, Cast Strip 11 Quick uniforms are cooled to below 1280 DEG C.Then by swing guide 9, pinch roll 12, hot rolls 13 is delivered to in Cast Strip, after hot rolling, forms the hot rolled strip of 0.7-2.5mm, then after rolling anti-oxidation quickly cooling device 14, by dry ice (solid-state CO
2) inject directly on belt steel surface, cooling with accelerated band steel, controls rate of cooling, through rollgang 15 to shear arrangement 16 crops, crop is fallen in flying shear hole 18 along flying shear guide plate 17, and the hot rolled strip after crop enters reeling machine 19,19 ' and batches.Coil of strip, after reeling machine takes off, is naturally cooled to room temperature.
In the confined chamber 10 at the cooling place of above-mentioned secondary, need not lead in addition protection of inert gas Cast Strip, directly utilize and spray the CO that dry ice evaporates
2gas is realized the protection against oxidation to Cast Strip.Gas collector 20 is set on confined chamber 10, to be used for collecting too much high-density CO 2 gas.
Embodiment of the present invention chemical composition is as shown in table 1.Performance after processing parameter and hot-rolled strip cool to room temperature is in table 2.Comparative example 1 is not added B element in thin band continuous casting technique composition; Comparative example 2 is the thin-walled oil drum Thin Strip Steel that traditional hot rolling technology is produced, and does not add B element in composition.
In sum, the thin-walled oil drum Thin Strip Steel that utilizes thin band continuous casting technique technology to manufacture by steel grades scope of design provided by the invention, more than yield strength reaches 275MPa, more than tensile strength reaches 345MPa, unit elongation reaches more than 24%, yield tensile ratio is lower than 0.8, and press depth is more than 10.0mm, and cold working buckling performance is qualified.Obtain thin-walled oil drum Thin Strip Steel by the present invention, can effectively solve the problem that the ubiquitous tissue odds of steel grade is even, yield tensile ratio is higher, formability is bad that thin strap continuous casting is produced, meet the stamping forming service requirements of thin-walled oil drum steel.
The chemical composition (wt.%) of table 1 embodiment steel
Processing parameter and the product performance of table 2 embodiment steel
Claims (7)
1. a manufacture method for Thin Strip Steel for thin-walled oil drum, it comprises the steps:
A) smelt
Smelt according to following chemical composition, molten steel chemical composition is: C:0.04-0.12%, Si:0.2-0.4%, Mn:0.4-1.0%, P :≤0.055%, S :≤0.008%, N:0.004-0.010%, Al:0.01-0.06%, Sn:0.005-0.04%, B:0.001-0.006%, all the other are Fe and inevitable impurity;
B) casting
Adopt twin-roll thin strip continuous casting, continuous casting of molten steel is formed to the Cast Strip that 1.5-3mm is thick, crystallization roll diameter 500-1500mm, casting rate 60-150m/min;
C) secondary is cooling
Take out of after crystallization roll at thin-belt continuous casting, Cast Strip temperature, at 1420-1480 DEG C, arranges two device for cooling in the both sides of Cast Strip along Cast Strip width, and beginning to cool down of two device for cooling is a little arranged on from nip point 250-750mm, whole two cold but segment length 200-500mm; Cast Strip goes out to adopt to both sides, Cast Strip immediately after crystallization roll the mode of spraying dry ice to carry out Quick uniform to Cast Strip to be cooled to below 1280 DEG C, rate of cooling 200-300 DEG C/s;
D) online hot rolling
The band steel that is rolled into 0.7-2.5mm thickness in milling train will be delivered to through pinch roll after going out confined chamber in the cooled Cast Strip of secondary with steel, rolling temperature 1050-1200 DEG C, and draft is 20-50%;
E) band steel rolls rear cooling
To rolling the anti-oxidation fast cooling mode of rear cooling employing with steel after online hot rolling, dry ice is injected directly on to belt steel surface, cooling with accelerated band steel, rate of cooling 80-200 DEG C/s;
F) strip coiling
Cooled hot rolled strip, after crop shears excise second-rate head, directly batches rolling, coiling temperature 500-600 DEG C.
2. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 1, it is characterized in that, described secondary is cooling to carry out in confined chamber under Cast Strip, dry ice is injected directly on surface, Cast Strip by the strengthening method of cooling adopting, wherein dry ice and rare gas element or nitrogen mixed volume be than being 5:1～10:1, with the pressure of 0.5-5MPa directly by dry ice blasting on surface, Cast Strip.
3. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 1, is characterized in that hot rolling draft 30-50%.
4. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 1, is characterized in that, the thickness with steel after hot rolling is 1.2-2.0mm.
5. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 1, is characterized in that hot rolling temperature 1050-1150 DEG C.
6. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 1, it is characterized in that, anti-oxidation cooling mode fast, dry ice is injected directly on to belt steel surface, wherein dry ice and rare gas element or compressed nitrogen mixed volume ratio are 5:1～10:1, with the pressure of 0.2-3MPa directly by dry ice blasting at belt steel surface.
7. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 1, is characterized in that, batches two reeling machine forms that adopt.
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| CN104607473B (en) * | 2014-12-30 | 2016-08-24 | 山东钢铁股份有限公司 | Rolled piece chiller and method |
| CN105014025A (en) * | 2015-07-23 | 2015-11-04 | 烟台万隆真空冶金股份有限公司 | Production method for copper-nickel-tin alloy strip |
| WO2018066019A1 (en) * | 2016-10-06 | 2018-04-12 | Ｊｆｅスチール株式会社 | Steel for crude oil tanker and crude oil tanker |
| CN107245645A (en) * | 2017-05-26 | 2017-10-13 | 宝钢集团新疆八钢铁有限公司 | A kind of system of selection of thin-walled sauce bucket cold-rolled steel sheet and cold-rolled steel sheet |
| CN112522566B (en) * | 2019-09-19 | 2022-10-21 | 宝山钢铁股份有限公司 | Thin-specification patterned steel plate/strip and manufacturing method thereof |
| US20220340993A1 (en) * | 2019-09-19 | 2022-10-27 | Baoshan Iron & Steel Co., Ltd. | Hot-rolled steel plate/strip for sulfuric acid dew point corrosion resistance and manufacturing method therefor |
| CN112522571B (en) * | 2019-09-19 | 2022-03-18 | 宝山钢铁股份有限公司 | Method for producing martensite steel strip by twin-roll thin-strip continuous casting |
| CN112404127B (en) * | 2020-11-20 | 2022-06-24 | 广东宝盛兴实业有限公司 | Cold rolling mill and cold rolling process for steel strip |
| CN114669613B (en) * | 2022-04-19 | 2023-06-20 | 安徽工业大学 | Flexible roller contact type Bao Daizu cooling method |
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| JP3727151B2 (en) * | 1997-09-04 | 2005-12-14 | Ｊｆｅスチール株式会社 | Cold-rolled steel sheet for drums, method for producing the same, and steel high-strength drum |
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