CN103667878B - A kind of Steel strip for thin-wall oil bucket and manufacture method thereof - Google Patents
A kind of Steel strip for thin-wall oil bucket and manufacture method thereof Download PDFInfo
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Abstract
A kind of Steel strip for thin-wall oil bucket and manufacture method thereof, adopt thin band continuous casting technique, Cast Strip adopts high pressure to spray dry ice mode after going out crystallization roll evenly strengthens cooling to Cast Strip, fast Cast Strip is cooled to less than 1280 DEG C, rate of cooling 200-300 DEG C/s, adopt the band steel of boron process under such type of cooling, the precipitation of thick BN can be promoted, prevent the precipitation of the appearance of low melting point phase B2O3 and tiny AlN, reach homogenizing austenite crystal, reduce the object of yield tensile ratio; Then through the online recrystallize rolling of austenite; Then through atomization cooling, the band steel after hot rolling is cooled; Finally batch.The present invention can obtain the Steel strip for thin-wall oil bucket that yield tensile ratio is lower, punching performance is excellent.The thin-walled oil drum hot rolling thin strip that the method is produced, directly " with hot Dai Leng " can use, cancel cold rolling process, greatly reduce production cost.
Description
Technical field
The present invention relates to continuous casting process, particularly a kind of Steel strip for thin-wall oil bucket and manufacture method thereof.
Background technology
In traditional process Iron and Steel Production, tin (Sn) is typical residual element or harmful element in steel, Sn to be removed fully very difficult and be very expensive in steelmaking process, once containing Sn in steel, substantially cannot thoroughly eliminate, can only be reduced the content of Sn by dilution molten steel, these all cause the rising of steel products cost.
In recent years, because the continuous circulation of steel scrap utilizes, the content of the residual element such as the Sn in steel is caused to raise gradually, Sn in steel is easy segregation element, easily being enriched in crystal boundary causes the defects such as crackle to occur, therefore in traditional technique, the content of Sn element is tightly controlled, and in ordinary construction steel, all has clear and definite requirement to the content of Sn: Sn (wt%)≤0.005%.
Therefore, if " turning harm into good " can be accomplished to residual element such as Sn in steel (particularly steel scrap), active influence will be produced to whole metallurgical boundary; The effective utilization to existing steel scrap or low-quality ore resources inferior (high tin ore) can be realized, promote the recycle of steel, reduce production cost, realize iron and steel industry Sustainable development.
Traditional Thin Strip Steel is mostly produced through multi-pass continuous rolling by the thick strand reaching 70 ~ 200mm, tradition hot rolling technology flow process is: continuous casting+strand reheats insulation+roughing+finish rolling+cool+batch, namely first obtain by continuous casting the strand that thickness is about 200mm, strand to be reheated and after being incubated, carry out roughing and finish rolling again, obtain the steel band that thickness is generally greater than 2mm, finally section cooling carried out to steel band and batch, completing whole hot rolling production process.If produce the steel band that thickness is less than 1.5mm (containing), then difficulty is relatively large, usually will to hot rolled strip carry out follow-up cold rolling and annealing come.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+cool+batch.The key distinction of this technique and traditional technology is: the slab thickness of sheet bar process is greatly thinning, be 50 ~ 90mm, because strand is thin, as long as strand is through 1 ~ 2 passage roughing (slab thickness is 70 ~ 90mm) or do not need through roughing (slab thickness is 50mm), and the continuously cast bloom of traditional technology will through multi-pass rolling repeatedly, required specification before being just thinned to finish rolling; And the strand of sheet bar process is without cooling, directly enter soaking pit and carry out soaking insulation, or mend temperature on a small quantity, therefore sheet bar process substantially reduces technical process, reduces energy consumption, decreases investment, thus reduces production cost.But CSP can cause steel strength to improve due to cooling rate faster, yield tensile ratio improves, thus increase rolling loads, make the thickness specification can producing hot-rolled product economically also can not be too thin, be generally >=1.5mm, see Chinese patent CN200610123458.1, CN200610035800.2 and CN200710031548.2, and these patents all do not relate to element B and Sn.Solving CSP organizes thinner and uneven, 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 metallurgical and a cutting edge technology in investigation of materials field, its Iron And Steel Industry that appears as brings a revolution, it changes the production process that tradition controls steel band in metal working industry, continuous casting, rolling, even thermal treatment etc. are integrated, make the strip base of production through the online hot rolling of a time just thin steel band of disposable formation, enormously simplify production process, shorten the production cycle, its processing line length only about 50m; 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 a kind of thin band continuous casting technique uniquely 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 and to relatively rotate by two and in the molten bath that surrounds of the crystallization roll that can cool fast and lateral seal, molten steel solidifies in the peripheral surface that crystallization roll rotates and forms solidified shell and grow gradually, and then form the thick Cast Strip of 1 ~ 5mm at the two minimum places of crystallization roll roll gap gap (nip point), steel band sends into via guide plate guiding pinch roll the strip being rolled into 0.7 ~ 2.5mm in milling train, cool through apparatus for supercooling subsequently, after shear arrangement crop, finally send into reeling machine and batch rolling.
Adopt thin strap continuous casting to produce thin-walled oil drum steel, due to thinner thickness, thickness is less than to the Thin Specs hot-rolled product of 1.5mm (containing), thin band continuous casting technique has stronger manufacture and cost advantage.The consumption of Steel strip for thin-wall oil bucket in worldwide is very large, the product specification characteristic thickness that hot-rolled sheet state is directly supplied 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 current domestic manufacturer that can stablize the hot-rolled sheet supply of material mainly contains Baosteel, Wuhan Iron and Steel Plant and Taiyuan Iron and Steel Co. etc., a lot of producer is 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, which increases the production cost of thin-walled oil drum steel.
When hot rolled strip uses as Thin Specs hot-rolled sheet or " with hot Dai Leng " product, require very high to strip surface quality.The thickness of general requirement belt steel surface oxide skin gets over Bao Yuehao, this just needs the generation of each the stage control iron scale follow-up in Cast Strip, namely in casting roll until inlet of rolling mill all adopts confined chamber device to prevent Cast Strip to be oxidized, add hydrogen as US Patent No. 6920912 and control oxygen content in US Patent No. 20060182989 in confined chamber device and be less than 5%, all can control the scale thickness of strip surface.But relate to the little RELATED APPLICATIONS of thickness batching this section of course of conveying how controlled oxidization skin at milling train, especially in the process adopting section cooling or spraying cooling to cool band steel, the band steel of high temperature contacts with water coolant, and the scale thickness of strip surface increases very fast.Meanwhile, the band steel of high temperature contacts with water coolant and also can bring a lot of problem:
One, water spots (rust staining) can be formed at belt steel surface, affect surface quality;
Two, the water coolant of section cooling or spraying cooling easily causes belt steel surface Local cooling uneven, causes the uneven of band steel interior microscopic tissue, thus causes the uneven of strip property, affect quality product;
Three, belt steel surface Local cooling is uneven, can cause the deterioration of plate shape, affect strip shape quality.
But, thin strap continuous casting due to the fast solidification technology characteristic of itself, the steel grade ubiquity structure refinement of production but problem uneven, that unit elongation is on the low side, yield tensile ratio is higher, formability is bad; Cast Strip austenite crystal has obvious ununiformity simultaneously, and the finished product obtained after causing austenite phase transformation are organized also uneven, thus cause 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 Specs hot rolled strip uses as thin-walled oil drum product made from steel, require that steel grade has strong plasticity coupling preferably in mechanical property, there is higher unit elongation (unit elongation reaches more than 24%), and there is good punching performance (press depth reaches 9 ~ 12mm) in processing performance.In the face of performance requriements high like this, this steel grade is produced to employing thin strap continuous casting there is certain challenge, therefore, when adopting thin strap continuous casting production Steel strip for thin-wall oil bucket, indiscriminately imitating traditional Composition And Process is to produce qualified thin-walled oil drum steel, needs there is breakthrough on composition and technique.
Summary of the invention
The object of the present invention is to provide a kind of Steel strip for thin-wall oil bucket and manufacture method thereof, the method by adding micronutrient boron (B) in containing the soft steel composition of Sn, after thin strip continuous casting strip steel goes out crystallization roll, the mode adopting high pressure to spray dry ice (solid-state CO2) to band steel both sides carries out Quick uniform cooling to band steel, improves cooling uniformity and cooling intensity and reaches anti-oxidation, uniform austenitic grain structure, reduces the effect of 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 Spray Way can reduce belt steel surface scale thickness, improve belt steel temperature homogeneity, improve strip surface quality.Thin strap continuous casting is when producing this type of steel grade, uneven microstructure in thin band continuous casting technique process can be solved, unit elongation is on the low side, yield tensile ratio is higher, problem that formability is bad, meet the service requirements such as bending and molding, impact briquetting, thus 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 Steel strip for thin-wall oil bucket, 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 the chemical composition design of Steel strip for thin-wall oil bucket of the present invention,
C:C is strengthening element most economical, the most basic in steel, is improved 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, the intensity rank that namely higher C content is corresponding higher.But because the gap solid solution of C has larger harm with precipitation to the plasticity of steel and toughness, and too high C content is unfavorable to welding property, and therefore C content can not be too high, and the intensity of steel is by suitably adding alloying element to make up.Therefore the C content scope that the present invention adopts is 0.04 ~ 0.12%.
Si:Si plays solution strengthening effect in steel, and adds Si in steel 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, there is sizable solid solubility in steel, the intensity of steel is improved by solution strengthening, simultaneously to the plasticity of steel and toughness substantially harmless, be reducing the topmost strengthening element of intensity improving steel in C content situation.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 is easily at grain boundary segregation, increases the cold shortness of steel, welding property is degenerated, reduce plasticity, cold-bending property is degenerated.In thin band continuous casting technique, solidifying of Cast Strip is exceedingly fast with rate of cooling, effectively can suppress the segregation of P, thus effectively can avoid the inferior position of P, gives full play to the advantage of P, and oil drum steel is objectively also requiring that steel grade has certain erosion resistance.Therefore in the present invention, adopt compared with P content higher during traditional technology production thin-walled oil drum steel, suitably relax the content of P element, cancel dephosphorization operation in steel making working procedure, 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 when 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≤0.008%.
Al:Al is the element added in order to deoxidation in steel, and the Al adding 0.01 ~ 0.06% content is conducive to the toughness and tenacity improving steel.
N: similar with C element, N element improves the intensity of steel by gap solid solution, and the present invention will utilize the N in steel to generate the precipitated phase of BN with B effect, needs there is certain N content in steel.But the gap solid solution of N has larger harm to the plasticity of steel and toughness, 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 scope 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 in crystal boundary enrichment, and cause being that the defects such as crackle occur, therefore in traditional technique, the content of Sn element is tightly controlled.Thin strap continuous casting is due to rapid solidification, and element reduces greatly in interdendritic segregation, greatly can 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 greatly can reduce steel-making cost.Fig. 3 is the relation of Sn element and mean heat flux.As seen from Figure 3, when Sn add-on is less than 0.04%, little on the impact of heat flow density, namely thin strip solidification process is not affected.Fig. 4 is the relation of Sn content and surfaceness.Because the crackle of strip surface is all produce at the rough fold place of strip surface usually, a situation arises to carry out characterization of surfaces crackle by surfaceness.If roughness is large, then the probability of crackle generation 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 solidifying and surface quality generation detrimentally affect not to Cast Strip.The content range of Sn is 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, B can preferentially separate out thick BN particle thus suppress the precipitation of tiny AlN in high temperature austenite, 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 inhibits ferrite forming core at austenite grain boundary, reduces ferritic nucleation rate, thus reaches the effect reducing yield tensile ratio, improve processability; The combination of B and N effectively can prevent crystal boundary low melting point phase B 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 about 0.001 ~ 0.003%; And in thin band continuous casting technique, solidify with rate of cooling very fast, effectively can suppress the segregation of B, the more B content of solid solution, therefore the content of B can suitably relax; Thick BN particle can also be generated by rational technology controlling and process, suppress tiny AlN to separate out, play the effect of fixed nitrogen, solve the inferior position that band steel yield tensile ratio is higher, formability is bad 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 Steel strip for thin-wall oil bucket of the present invention, it comprises the steps:
A) smelt
Require to smelt according to following compositions, ladle chemistry weight percent 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) cast
Adopt twin-roll thin strip continuous casting, by Cast Strip thick for molten steel formation 1.5 ~ 3mm;
Casting roll diameter 500 ~ 1500mm, casting rate 60 ~ 150m/min;
C) cooling twice
After Cast Strip goes out crystallization roll, Cast Strip temperature is at 1420 ~ 1480 DEG C, in the both sides of Cast Strip, two device for cooling are set along Cast Strip width, 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 rate of cooling 200 ~ 300 DEG C/s; Spray the mode of dry ice for adopting to both sides, Cast Strip immediately after going out band Quick uniform is carried out to Cast Strip be cooled to less than 1280 DEG C;
D) online hot rolling
Deliver in milling train the band steel being rolled into 0.7 ~ 2.5mm thickness after Cast Strip after cooling twice goes out confined chamber through pinch roll, wherein, rolling temperature 1050 ~ 1200 DEG C, draft is 20 ~ 50%.
E) roller repairing
Carry out roller repairing to the band steel after online hot rolling, cooling adopts the mode of atomization cooling, and the cooling water smoke of atomization is sprayed directly on steel strip surface, and rate of cooling scope is 10-70 DEG C/s;
F) strip coiling
Cooled hot rolled strip excises after second-rate head through crop shears, directly carries out batching rolling.The coiling temperature controlling hot-rolled strip is 650 ~ 750 DEG C; The performance of final Steel strip for thin-wall oil bucket reaches more than yield strength 215MPa, and tensile strength reaches more than 275MPa, and unit elongation reaches more than 25%, yield tensile ratio lower than 0.8, more than press depth 10mm.
Further, cooling twice adopts and dry ice is injected directly on strip surface, and wherein dry ice and rare gas element or nitrogen pre-mixing volume ratio are 5: 1 ~ 10: 1, with the pressure of 0.5 ~ 5MPa directly by dry ice blasting at strip surface.
Preferably, hot rolling draft 30 ~ 50%, rolling rear belt steel thickness is 1.2 ~ 2.0mm.Rolling temperature 1050 ~ 1150 DEG C.
In addition, being atomized rate of cooling is 30 ~ 70 DEG C/s.
In manufacture method of the present invention,
Cooling twice adopts after Cast Strip goes out crystallization roll, arranges two device for cooling in the both sides of Cast Strip along Cast Strip width, adopts spray dry ice (solid-state CO to both sides, Cast Strip
2) mode Quick uniform carried out to Cast Strip be cooled to less than 1280 DEG C, cooling uniformity and the cooling intensity of band steel can be significantly improved, promote the precipitation of BN in steel.
Above-mentioned cooling twice carries out in confined chamber under Cast Strip, and the strengthening method of cooling of employing is by dry ice (solid-state CO
2) inject directly on steel strip surface, to accelerate the cooling of steel band, by dry ice blasting in steel strip surface, serve the effect reducing temperature of steel strips on the one hand, the solid-state dry ice of another aspect is sprayed onto hot belt steel surface and can gasifies, highdensity atomizing gas is formed, carbonic acid gas (CO at belt steel surface
2) belong to a kind of inert atmosphere, can belt steel surface be coated on, play the effect that band steel is anti-oxidation, thus effectively control the growth of belt steel surface oxide skin.
Protection of inert gas band steel need not be led in addition in the confined chamber at above-mentioned cooling twice place, directly utilize the CO spraying dry ice and evaporate
2gas realizes the protection against oxidation to band steel.Gas collector is set on confined chamber, to be used for collecting too much high-density CO 2 gas.
The theoretical basis of the BN precipitated phase that the Cast Strip cooling twice that the present invention designs relates to:
In steel boron and nitrogen, aluminium and the nitrogen thermodynamical equilibrium equation in γ-Fe 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 at about 1280 DEG C, and when 980 DEG C, the precipitation of BN tends to balance, and the now precipitation of AlN just just starts (Precipitation Temperature of AlN is at about 980 DEG C), from thermodynamics, the precipitation of BN will have precedence over AlN.Therefore the present invention is by rational technology controlling and process means, promotes the combination of B and N, generates thick BN particle, thus uniform austenitic grain structure, suppress tiny AlN to separate out.
Usually, any cooling provision is not adopted in confined chamber under thin strap continuous casting, 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, the danger such as the cracking at underframe welding junction place also easily occur.Therefore a lot of work has been done in the cooling of confined chamber by a lot of producer, the light factory thin strap continuous casting of such as Nippon Steel adopts the form of water wall to reach the object of cooling 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 (see patent US5960856A) of U.S. Nucor adopts the form of " water-cooled pillow " to reach the object of cooling, concrete scheme be from band steel slightly close to place arrange water-cooled pillow, the logical recirculated water in the inside, form as in large room (confined chamber) a little heat insulation room (water-cooled pillow surround) is set, pass water-cooled with steel and rest the head on the little heat insulation room surrounded, temperature is absorbed, while the cooling of band steel, play 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, while realizing cooling rapidly to band steel, the temperature of confined chamber is also played to the effect of effective temperature-reducing; Effective reduction of confined chamber temperature, plays cooling effect to the underframe (being generally steel construction) of whole confined chamber and confined chamber wall, effectively can prevent the distortion of confined chamber underframe.
Online hot rolling, the band steel after cooling twice, delivers to band steel the thin strip being rolled into 0.7-2.5mm thickness in milling train 13 through pinch roll 12 after going out confined chamber 10.Wherein, rolling temperature control is 1050-1200 DEG C, and object is austenite generation perfect recrystallization after guarantee hot rolling.Controlling hot rolling draft is 20-50%, and the increase of hot rolling draught can promote austenite recrystallization, and preferably, hot rolling draft scope is 30-50%.After hot rolling, the thickness range of steel band is 0.7-2.5mm, and preferably, thickness is 1.2-2.0mm.
Relatively low rolling temperature 1050-1200 DEG C is realized 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, larger rolling load cannot be applied, be difficult to effective rolling.
Roller repairing, adopt the mode of atomization cooling, the cooling water smoke of atomization is sprayed directly on steel strip surface by atomization refrigerating unit, the problem that atomization cooling can avoid traditional laminar flow cooling zone, belt steel surface homogeneous temperature is declined, improve belt steel temperature homogeneity, thus reach the effect of homogenizing interior microscopic tissue; Spray cooling is even simultaneously, can improve the strip shape quality of band steel; Reduce the scale thickness of belt steel surface, be convenient to follow-up pickling when making cold rolling base.
Strip coiling, cooled hot rolled strip excises after second-rate head through crop shears, directly carries out batching rolling.To make hot-rolled strip, there is ferrite and add pearlitic tissue signature.Reeling machine employing is two batches form, ensures the continuous seepage of band steel.
Through above-mentioned manufacturing processed, the performance of final Steel strip for thin-wall oil bucket reaches more than yield strength 215MPa, and tensile strength reaches more than 275MPa, and unit elongation reaches more than 25%, yield tensile ratio lower than 0.8, more than press depth 10mm.
The present invention adds B element in containing the soft steel of Sn, by rational two cold patterns, after thin strip continuous casting strip steel goes out crystallization roll, the mode adopting high pressure to spray dry ice (solid-state CO2) to band steel both sides carries out Quick uniform cooling to band steel, improves cooling uniformity and cooling intensity and reaches anti-oxidation, uniform austenitic grain structure, reduces the effect of rolling temperature; Band steel after rolling adopts the atomization type of cooling can reduce belt steel surface scale thickness, improves belt steel temperature homogeneity, improves strip surface quality.Thin strap continuous casting, when producing this type of steel grade, can solve uneven microstructure in thin band continuous casting technique process, unit elongation is on the low side, yield tensile ratio is higher, problem that formability is bad, thus meets 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 report up to now, conclude advantage as follows:
(1) eliminate heating of plate blank, the multi-pass complex process such as hot rolling repeatedly, directly carry out the online hot rolling of a time to thin Cast Strip, production cost significantly reduces.
(2) Cast Strip thickness itself is thinner, and by being hot-rolled down to expected product thickness online, 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, greatly can reduce the passage of follow-up rolled thickness reduction, greatly save production cost.
(3) steel scrap containing Sn is utilized, Sn in steel is accomplished " turning harm into good ", realizes the effective utilization to existing steel scrap or low-quality ore resources inferior (high tin ore), promote the recycle of steel, reduce production cost, realize iron and steel industry Sustainable development.Add B element, the problem that uneven microstructure in thin band continuous casting technique process, yield tensile ratio are higher can be solved, thus meet the service requirements of cold rolling base; Be easy to bending, impact briquetting simultaneously.
(4) there is alloying element in traditional technology slab process of cooling to separate out, when slab reheats, often reduce alloying element utilization ratio because alloying element back dissolving is insufficient.In thin band continuous casting technique, the direct hot rolling in high temperature Cast Strip, the alloying element added mainly exists with solid solution state, can improve alloy utilization rate.
Major advantage of the present invention:
1. adopt thin band continuous casting technique production Steel strip for thin-wall oil bucket, after carrying out hot rolling, directly supply market uses, and reaches the object of the Thin Specs hot-rolled sheet supply of material and meets cold rolling base and require and " cold with the torrid zone " object, can significantly improve the cost performance of Strip.
2. the present invention adopts the boron adding trace, and reach and effectively reduce band steel yield tensile ratio, improve the effect of band steel processability, production cost is more traditional and thin slab production technique is obviously cheap.Improve the volume of comprehensive utilization to harmful residual element P in steel simultaneously further, cancel the dephosphorization operation in steel-making, make that production cost is more traditional and thin slab production technique is obviously cheap.
3. utilize the steel scrap containing Sn, the Sn in steel is accomplished " turning harm into good ", realizes the effective utilization to existing steel scrap or low-quality ore resources inferior (high tin ore), promote the recycle of steel, reduce production cost, 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 the effect effectively reducing confined chamber temperature and prevent confined chamber steel structure frame to be out of shape.Adopt and roll the iron scale thickness that rear atomization cooling effectively reduces Surfaces of Hot Rolled Strip, greatly can improve plate surface quality.
5. rationally process parameter control has widened the state space of production line flexibly, can meet the need of production of variant production specification.
The difference of the present invention and prior art and improvements:
A kind of method and device of casting black metal strip is mentioned in patent EP0830223A1/CN1180325A/US5960856A/DE69700737D, after band steel solidifies two roller, a pair contactless heat absorber for cooling with steel being set, being used for the latent heat of solidification discharged 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 contact with the strip and force cooling, the cooling intensity of 200 DEG C/more than s can be realized, far away higher than the cooling performance of contactless heat absorber, effectively reduce rolling temperature, be conducive to the raising of rolling strip shape quality.
Chinese patent CN1472019A discloses a kind of method for continuous casting sheet band and device, in crystallization roll exit, to high temperature Cast Strip in the width direction blowing gas to Cast Strip realize cooling.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 a definite limitation, this patent adopts high pressure to spray the method for dry ice, directly contact with the strip and force cooling, the cooling intensity of 200 DEG C/more than s can be realized, effectively reduce rolling temperature, be conducive to the raising of rolling strip shape quality.
Japanese Patent JP-A-5-277654 adds the driven roll of a pair external diameter Φ 200mm at crystallization roll exit lower end 300-400mm, by the transmission of heat by contact of driven roll and Cast Strip, reaches the cooling effect to band steel.The present invention is completely different from the means that the method adopts, and the present invention is by directly carrying out to band steel the method that high pressure sprays dry ice, band tape transport heat of steel.The main drawback of patent JP-A-5-277654 is that cooling intensity is limited, and be secondly the speeds match problem of crystallization roll and pony roll, if mate bad, easily give a discount in Cast Strip, and production operation is inconvenient, controls dumb.
Accompanying drawing explanation
Fig. 1 is that production technique of the present invention arranges schematic diagram.
Fig. 2 is the thermomechanical curve that BN, AlN separate out.
Fig. 3 is the relation schematic diagram of Sn content and mean heat flux.
Fig. 4 is the relation schematic diagram of Sn content and strip surface roughness.
Embodiment
See 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 and relatively rotate and the crystallization roll 5a that can cool fast by two, 5b and side seal board device 6a, in the molten bath 7 that 6b surrounds, molten steel is at crystallization roll 5a, the peripheral surface that 5b rotates is solidified, and then form solidified shell and grow gradually and form the thick Cast Strip of 1.5-3mm 11 at the two minimum places of crystallization roll roll gap gap (nip point) subsequently, Cast Strip is through two device for cooling 8 in confined chamber 10, dry ice (solid-state CO is sprayed to both sides, Cast Strip 11 immediately after going out band
2), control its rate of cooling, make Cast Strip 11 Quick uniform be cooled to less than 1280 DEG C.Then by swing guide 9, pinch roll 12, hot rolls 13 is delivered in Cast Strip, the hot-rolled strip of 0.7-2.5mm is formed after hot rolling, again through roller repairing device 14, the cooling water smoke of atomization is sprayed directly on belt steel surface, controlled cooling model speed, after rollgang 15 is delivered to shear arrangement 16 crop, 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; By coil of strip from after reeling machine takes off, naturally cool to room temperature.
Protection of inert gas Cast Strip need not be led in addition in the confined chamber 10 at above-mentioned cooling twice place, directly utilize the CO that high pressure sprinkling dry ice evaporates
2gas realizes 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 does not add B element in thin band continuous casting technique composition; Comparative example 2 is the Steel strip for thin-wall oil bucket that traditional hot rolling technology is produced, and does not add B element in composition.
In sum, utilize the Steel strip for thin-wall oil bucket that thin band continuous casting technique technology manufactures by steel grades scope of design provided by the invention, yield strength reaches more than 215MPa, tensile strength reaches more than 275MPa, unit elongation reaches more than 25%, yield tensile ratio is lower than 0.8, and press depth is at more than 10.0mm, and cold working buckling performance is qualified.Obtain Steel strip for thin-wall oil bucket by the present invention, effectively can solve the ubiquitous uneven microstructure of steel grade that thin strap continuous casting is produced, the problem that yield tensile ratio is higher, formability is bad, meet the stamping forming service requirements of thin-walled oil drum steel.
The chemical composition (wt.%) of table 1 embodiment steel
The processing parameter of table 2 embodiment steel and product performance
Claims (5)
1. a manufacture method for Steel strip for thin-wall oil bucket, it comprises the steps:
A) smelt
Require to smelt according to following compositions, ladle chemistry weight percent 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) cast
Adopt twin-roll thin strip continuous casting, molten steel is formed the thick Cast Strip of 1.5 ~ 3mm; Casting roll diameter 500 ~ 1500mm, casting rate 60 ~ 150m/min;
C) cooling twice
After Cast Strip goes out crystallization roll, Cast Strip temperature is at 1420 ~ 1480 DEG C, in the both sides of Cast Strip, two device for cooling are set along Cast Strip width, 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 rate of cooling 200 ~ 300 DEG C/s; Cast Strip goes out crystallization roll and adopts to both sides, Cast Strip immediately and spray the mode of dry ice and carry out Quick uniform to Cast Strip and be cooled to less than 1280 DEG C;
D) online hot rolling
Deliver in milling train the band steel being rolled into 0.7 ~ 2.5mm thickness through pinch roll after Cast Strip after cooling twice goes out confined chamber, wherein, rolling temperature 1050 ~ 1200 DEG C, draft is 20 ~ 50%;
E) roller repairing
Carry out roller repairing to the band steel after online hot rolling, cooling adopts the mode of atomization cooling, and the cooling water smoke of atomization is sprayed directly on belt steel surface, and rate of cooling is 10-70 DEG C/s;
F) strip coiling
Cooled hot rolled strip excises after second-rate head through crop shears, directly carries out batching rolling; The coiling temperature controlling hot rolled strip is 650 ~ 750 DEG C; The performance of final Steel strip for thin-wall oil bucket reaches more than yield strength 215MPa, and tensile strength reaches more than 275MPa, and unit elongation reaches more than 25%, yield tensile ratio lower than 0.8, more than press depth 10mm.
2. the manufacture method of Steel strip for thin-wall oil bucket as claimed in claim 1, it is characterized in that, cooling twice adopts and dry ice is injected directly on steel strip surface, wherein dry ice and rare gas element or nitrogen mixed volume are than being 5:1 ~ 10:1, with the pressure of 0.5 ~ 5MPa directly by dry ice blasting at belt steel surface.
3. the manufacture method of Steel strip for thin-wall oil bucket as claimed in claim 1, it is characterized in that, hot rolling draft 30 ~ 50%, rolling rear belt steel thickness is 1.2 ~ 2.0mm.
4. the manufacture method of Steel strip for thin-wall oil bucket as claimed in claim 1, is characterized in that, rolling temperature 1050 ~ 1150 DEG C.
5. the manufacture method of Steel strip for thin-wall oil bucket as claimed in claim 1, is characterized in that, atomization rate of cooling is 30 ~ 70 DEG C/s.
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| CN106392484A (en) * | 2016-11-11 | 2017-02-15 | 成都三壹八科技有限公司 | Manufacturing method of automobile sheet metal parts |
| MY193493A (en) * | 2017-06-30 | 2022-10-17 | Jfe Steel Corp | Structural steel material and structure |
| CN107309271B (en) * | 2017-07-31 | 2018-11-23 | 中冶赛迪技术研究中心有限公司 | A method of inhibiting hot rolled H-shaped surface red rust |
| CN110899644A (en) * | 2018-09-14 | 2020-03-24 | 宝山钢铁股份有限公司 | Production method of ultrathin hot rolled strip steel |
| WO2021052314A1 (en) * | 2019-09-19 | 2021-03-25 | 宝山钢铁股份有限公司 | Fire-resistant weathering steel plate/strip and manufacturing method therefor |
| EP4033000A4 (en) * | 2019-09-19 | 2023-03-15 | Baoshan Iron & Steel Co., Ltd. | Martensitic steel strip and manufacturing method therefor |
| 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 |
| WO2021052315A1 (en) * | 2019-09-19 | 2021-03-25 | 宝山钢铁股份有限公司 | 30crmo hot rolled steel sheet/strip and production method therefor |
| CN115283629B (en) * | 2022-08-02 | 2024-04-12 | 太原科技大学 | Method for preparing nickel-based superalloy by using double-roller casting and rolling process |
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