CN103667878A - Steel strip for thin-wall oil bucket and manufacturing method thereof - Google Patents
Steel strip for thin-wall oil bucket and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a steel strip for a thin-wall oil bucket and a manufacturing method thereof. The manufacturing method comprises the following steps: casting a crystal roller from a cast strip by using a thin strip casting process, subsequently uniformly reinforcing and cooling the cast strip in a mode that dry ice is sprayed at a high pressure, and rapidly cooling the cast strip to be less than 1,280 DEG C, wherein the cooling velocity is 200-300 DEG C/s; when the steel strip is subjected to boron treatment in such a mode, large boron nitride separation is prompted, occurrence of low-melting-point phase B2O3 and separation of fine AlN are prevented, and the purposes of uniformly austenite grains and reducing the yield ratio are achieved; subsequently performing on-line recrystallization and rolling on the austenite; subsequently atomizing and cooling so as to cool down the hot-rolled steel strip; finally coiling the steel strip. By adopting the manufacturing method, the thin-wall with low yield ratio and excellent stamping property for the thin-wall oil bucket is manufactured. The hot-rolled steel strip for the thin-wall oil bucket can be used in hotness instead of coldness, and a cold-rolling procedure is omitted, so that the production cost is greatly lowered.
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, can only by dilution molten steel, reduce the content of Sn, these all cause the rising of steel products cost.
In recent years, continuous circulation utilization due to steel scrap, cause the content of the residual element such as 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 at ordinary construction, with in steel, the content of Sn is all had to clear and definite requirement: Sn (wt%)≤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 Thin Strip Steel is mostly to be produced through multi-pass continuous rolling by the thick strand that reaches 70～200mm, tradition hot rolling technology flow process is: continuous casting+strand reheats insulation+roughing+finish rolling+cooling+batch, first by continuous casting, obtain 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 the 1.5mm steel band of (containing), 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 is attenuate greatly, be 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 mend temperature, so sheet bar process shortened technical process greatly, reduced energy consumption, reduced investment, thereby 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, 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.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 simplified 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 by two, relatively rotate 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 Cast Strip 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 to produce thin-walled oil drum steel, due to thinner thickness, be less than the thin size hot-rolled product of 1.5mm (containing) for thickness, 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 with steel.
When hot rolled strip is used as thin size hot-rolled plate or " with hot Dai Leng " product, to strip surface quality, require very high.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 casting roll until inlet of rolling mill all adopts confined chamber device to prevent Cast Strip oxidation, in confined chamber device, as US Patent No. 6920912, add hydrogen and control oxygen content in US Patent No. 20060182989 being less than 5%, all can control the scale thickness on surface, Cast Strip.But relate to batching the seldom relevant patent of thickness how this section of course of conveying to control oxide skin at milling train, 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 also contacts and can bring a lot of problems with water coolant:
One, can form water spots (rust staining) at belt steel surface, affect surface quality;
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;
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 but problem inhomogeneous, 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 is used 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, to adopting thin strap continuous casting to produce this steel grade, there is certain challenge, 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 Thin Strip Steel and manufacture method thereof for a kind of thin-walled oil drum, the method is by adding micronutrient boron (B) containing in the soft steel composition of Sn, at thin strip continuous casting strip steel, go out after crystallization roll, to band steel both sides, adopt mode that high pressure sprays dry ice (solid-state CO2) to carry out Quick uniform to band steel cooling, the effect that improves cooling uniformity and cooling intensity and reach 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 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, 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 requirementss 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.
At thin-walled oil drum of the present invention, use in the chemical composition design of Thin Strip Steel,
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, so 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 due to the gap solid solution of C with separate out the plasticity of steel and toughness are had to larger harm, and too high C content is unfavorable to welding property, so C content can not be too high, 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, by solution strengthening, improve the intensity of steel, simultaneously substantially harmless to the plasticity of steel and toughness, be the topmost strengthening element 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 with 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 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≤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 steel with the precipitated phase of B effect generation BN, and needing has 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, so 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, when Sn add-on is less than 0.04%, little on the impact of heat flow density, on the not impact of thin strip solidification process.Fig. 4 is the relation of Sn content and surfaceness.Because the crackle on surface, Cast Strip is all the fold place generation at Cast Strip surface irregularity conventionally, a situation arises by surfaceness, to carry out characterization of surfaces crackle.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 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, so 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,, the inferior position that formability bad higher with steel yield tensile ratio that solve that thin strap continuous casting produces.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 thin-walled oil drum of the present invention, it comprises the steps:
A) smelt
According to following compositions, require to smelt, molten steel 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;
B) casting
Adopt twin-roll thin strip continuous casting, molten steel is formed to the thick Cast Strip of 1.5～3mm;
Casting roll diameter 500～1500mm, casting rate 60～150m/min;
C) secondary is cooling
After Cast Strip goes out crystallization roll, Cast Strip temperature is at 1420～1480 ℃, both sides in Cast Strip arrange two device for cooling 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, 200～300 ℃/s of Cast Strip rate of cooling; Being used for to both sides, Cast Strip, adopting immediately after band the mode of spraying dry ice to carry out Quick uniform to Cast Strip is cooled to below 1280 ℃;
D) online hot rolling
The cooled Cast Strip of secondary goes out confined chamber and by pinch roll, delivers to the band steel that is rolled into 0.7～2.5mm thickness in milling train, wherein, 1050～1200 ℃ of rolling temperatures, draft is 20～50%.
E) roll rear cooling
Band steel after online hot rolling is rolled rear cooling, the cooling mode of cooling employing atomization, is sprayed directly on steel strip surface by the cooling water smoke of atomization, and rate of cooling scope is 10-70 ℃/s;
F) 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 650～750 ℃; More than final thin-walled oil drum reaches yield strength 215MPa by the performance of Thin Strip Steel, more than tensile strength reaches 275MPa, unit elongation reaches more than 25%, and yield tensile ratio is lower than 0.8, more than press depth 10mm.
Further, the cooling employing of secondary injects directly on surface, Cast Strip by dry ice, and wherein dry ice and rare gas element or nitrogen pre-mixing volume ratio are 5: 1～10: 1, directly that dry ice blasting is surperficial in Cast Strip with the pressure of 0.5～5MPa.
Preferably, hot rolling draft 30～50%, rolling rear belt steel thickness is 1.2～2.0mm.1050～1150 ℃ of rolling temperatures.
In addition, atomization rate of cooling is 30～70 ℃/s.
In manufacture method of the present invention,
The cooling employing of secondary goes out after crystallization roll in Cast Strip, in the both sides of Cast Strip, along Cast Strip width, two device for cooling is set, and adopts spray dry ice (solid-state CO to both sides, Cast Strip
2) mode Quick uniform carried out in Cast Strip be cooled to below 1280 ℃, 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, 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, played on the one hand the effect that reduces temperature of steel strips, solid-state dry ice is sprayed onto hot belt steel surface and can gasifies on the other hand, at belt steel surface, forms highdensity vaporific gas, carbonic acid gas (CO
2) belong to a kind of inert atmosphere, can be coated on belt steel surface, play with the anti-oxidation effect of steel, thereby effectively controlled the growth of belt steel surface oxide skin.
In the confined chamber at the cooling place of above-mentioned secondary, need not lead in addition protection of inert gas band steel, directly utilize and spray the CO that dry ice evaporates
2gas is realized the protection against oxidation with 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 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 ℃ of left and right, and in the time of 980 ℃, separating out of BN tended to balance, and now separating out just of AlN just starts (Precipitation Temperature of AlN is 980 ℃ 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 ℃, 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, the danger such as cracking at underframe welding junction place also easily occur.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 of U.S. Nucor (seeing patent US5960856A) 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), with steel, pass the hot room of septulum that water-cooled pillow surrounds, temperature is absorbed, and when 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, to when 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, plays cooling effect to the underframe of whole confined chamber (being generally steel construction) and confined chamber wall, can effectively prevent the distortion of confined chamber underframe.
Online hot rolling, the cooled band steel of secondary, goes out confined chamber 10 and will with steel, deliver to the thin strip that is rolled into 0.7-2.5mm thickness in milling train 13 by pinch roll 12.Wherein, controlled rolling temperature is 1050-1200 ℃, and object is austenite generation perfect recrystallization after assurance hot rolling.Controlling hot rolling draft is 20-50%, and hot rolling draught increases 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.
By secondary cooling apparatus, realize relatively low rolling temperature 1050-1200 ℃, relatively low rolling temperature, for rolling, be favourable, 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 ℃, and even more than 1250 ℃, band steel is now very soft, cannot apply larger rolling load, be difficult to effective rolling.
Roll rear cooling, adopt the cooling mode of atomization, atomization refrigerating unit is sprayed directly on steel strip surface by the cooling water smoke of atomization, the cooling problem that can avoid traditional laminar flow cooling zone of atomization, belt steel surface temperature is evenly declined, improve belt steel temperature homogeneity, thereby reach the effect of homogenizing interior microscopic tissue; Spray cooling is even simultaneously, 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.
Strip coiling, cooled hot rolled strip, after crop shears excise second-rate head, directly batches rolling.So that having ferrite, hot-rolled strip adds pearlitic tissue signature.Reeling machine adopts two forms of batching, and guarantees the continuous production with steel.
Through above-mentioned manufacturing processed, more than final thin-walled oil drum reaches yield strength 215MPa by the performance of Thin Strip Steel, more than tensile strength reaches 275MPa, unit elongation reaches more than 25%, and yield tensile ratio is lower than 0.8, more than press depth 10mm.
The present invention is adding B element containing in the soft steel of Sn, by rational two cold patterns, at thin strip continuous casting strip steel, go out after crystallization roll, to band steel both sides, adopt mode that high pressure sprays dry ice (solid-state CO2) to carry out Quick uniform to band steel cooling, the effect that improves cooling uniformity and cooling intensity and reach anti-oxidation, even austenite crystal tissue, reduction 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 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 requirementss 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 cooling iron scale thickness that effectively reduces Surfaces of Hot Rolled Strip of rear atomization is 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, at band steel, solidify after two rollers, 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 ℃/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.
Chinese patent CN1472019A discloses a kind of method for continuous casting sheet band and device, in crystallization roll exit, to high temperature Cast Strip broad ways blowing gas, Cast Strip is realized 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 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 ℃/more than s cooling intensity, effectively reduce rolling temperature, be conducive to the raising of rolling strip shape quality.
The driven roll that Japanese 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 by spray the method for 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 is inconvenient, controls dumb.
Accompanying drawing explanation
Fig. 1 is that production technique of the present invention is arranged schematic diagram.
Fig. 2 is BN, the thermomechanical curve that AlN separates 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 a crystallization roll 5a who relatively rotates by two and can be cooling fast, 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 of 5b rotation is solidified, and then form solidified shell and grow and at the minimum places of two crystallization roll roll gap gaps (nip point), form the thick Cast Strip 11 of 1.5-3mm subsequently gradually, Cast Strip is through two device for cooling 8 in confined chamber 10, after going out to be with, to Cast Strip, dry ice (solid-state CO are sprayed in 11 both sides immediately
2), control its rate of cooling, Cast Strip 11 Quick uniforms are cooled to below 1280 ℃.Then by swing guide 9, pinch roll 12, hot rolls 13 is delivered to in Cast Strip, after hot rolling, form the hot-rolled strip of 0.7-2.5mm, refrigerating unit 14 after rolling again, the cooling water smoke of atomization is sprayed directly on to belt steel surface, control rate of cooling, after rollgang 15 is delivered 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 high pressure to 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 215MPa, more than tensile strength reaches 275MPa, unit elongation reaches more than 25%, yield tensile ratio is lower than 0.8, and press depth is more than 10.0mm, and cold working buckling performance is qualified.By the present invention, obtain thin-walled oil drum Thin Strip Steel, 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 steel for thin-walled oil drum.
The chemical composition (wt.%) of table 1 embodiment steel
Processing parameter and the product performance of table 2 embodiment steel
Claims (6)
1. 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.
2. the manufacture method of Thin Strip Steel for thin-walled oil drum, it comprises the steps:
A) smelt
According to following compositions, require to smelt, molten steel 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;
B) casting
Adopt twin-roll thin strip continuous casting, molten steel is formed to the thick Cast Strip of 1.5～3mm; Casting roll diameter 500～1500mm, casting rate 60～150m/min;
C) secondary is cooling
After Cast Strip goes out crystallization roll, Cast Strip temperature is at 1420～1480 ℃, both sides in Cast Strip arrange two device for cooling 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, 200～300 ℃/s of Cast Strip rate of cooling; Cast Strip goes out crystallization roll adopt to spray dry ice immediately mode to both sides, Cast Strip and Quick uniform is carried out in Cast Strip is cooled to below 1280 ℃;
D) online hot rolling
The cooled Cast Strip of secondary goes out confined chamber and by pinch roll, delivers to the band steel that is rolled into 0.7～2.5mm thickness in milling train, wherein, 1050～1200 ℃ of rolling temperatures, draft is 20～50%.
E) roll rear cooling
Band steel after online hot rolling is rolled rear cooling, the cooling mode of cooling employing atomization, is sprayed directly on belt steel surface by the cooling water smoke of atomization, and rate of cooling is 10-70 ℃/s;
F) 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 650～750 ℃; More than final thin-walled oil drum reaches yield strength 215MPa by the performance of Thin Strip Steel, more than tensile strength reaches 275MPa, unit elongation reaches more than 25%, and yield tensile ratio is lower than 0.8, more than press depth 10mm.
3. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 2, it is characterized in that, the cooling employing of secondary injects directly on steel strip surface by dry ice, wherein dry ice is 5: 1～10: 1 with rare gas element or nitrogen mixed volume ratio, with the pressure of 0.5～5MPa directly by dry ice blasting at belt steel surface.
4. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 2, is characterized in that, hot rolling draft 30～50%, and rolling rear belt steel thickness is 1.2～2.0mm.
5. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 2, is characterized in that 1050～1150 ℃ of rolling temperatures.
6. the manufacture method of Thin Strip Steel for thin-walled oil drum as claimed in claim 2, is characterized in that, atomization rate of cooling is 30～70 ℃/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 |
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| 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 |
| 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 |
| 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 |
| WO2021052429A1 (en) * | 2019-09-19 | 2021-03-25 | 宝山钢铁股份有限公司 | Thin-gauge checkered steel plate/strip and manufacturing method therefor |
| WO2021052312A1 (en) * | 2019-09-19 | 2021-03-25 | 宝山钢铁股份有限公司 | Martensitic steel strip and manufacturing method therefor |
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| CN115283629A (en) * | 2022-08-02 | 2022-11-04 | 太原科技大学 | Method for preparing nickel-based high-temperature alloy by using double-roller casting and rolling process |
| 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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