CN103757531A - Thin strip continuous casting economic high-strength binding strip with tensile strength of at least 1000 MPa and manufacturing method thereof - Google Patents
Thin strip continuous casting economic high-strength binding strip with tensile strength of at least 1000 MPa and manufacturing method thereof Download PDFInfo
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Abstract
The invention relates to a thin strip continuous casting economic high-strength binding strip with a tensile strength of at least 1000 MPa and a manufacturing method thereof. The manufacturing method comprises the following steps: 1) casting a casting strip with a thickness of 1.0-4.5 mm through a double-roll continuous casting process, wherein the casting strip comprises the following chemical components in percentage by weight: 0.25-0.40% of C, 0.15-0.40% of Si, 1.3-2.0% of Mn, no more than 0.015% of P, no more than 0.01% of S, no more than 0.012% of N and the balance of Fe and inevitable impurities; 2) cooling the casting strip; 3) performing on-line hot rolling on the casting strip; 4) cooling the hot-rolled strip; 5) coiling; 6) performing cold rolling; and 7) performing blue annealing. According to the high-strength binding strip produced through the economic process of thin strip continuous casting and cold rolling before recovery annealing, the tensile strength is at least 1000 MPa, and the elongation percentage is at least 12%.
Description
Technical field
The present invention relates to high-strength steel tie and manufacture method thereof, relate in particular to thin strap continuous casting economy high-strength steel tie and the manufacture method thereof of a kind of tensile strength >=1000MPa.
Background technology
Steel tie is a kind of thin ribbon shaped deep processed product of steel, is mainly used to tie up steel, non-ferrous metal, light textile goods, building materials, paper roll (plate) and wool and other items.In order to guarantee safe handling of cargo and transportation, require tie to there is higher tensile strength and certain unit elongation.In addition,, because tie is used for a long time in outdoor environment, also require to have certain corrosion resistance.
Steel tie is divided according to intensity, can be divided into low strong, in strong, high-strength and strong four classes of superelevation.High-strength tie wherein, is mainly used in iron and steel enterprise, tying up the products such as coils of hot-rolled steel, round steel, shaped steel, steel pipe, wire rod and pipe line steel, and it is in great demand.
Along with the develop rapidly of metallurgy industry, the steel products turnout of high quality, high strength grade is increasing, and the coil diameter of coil of strip is also increasing, and monovolume reaches 30 tons, and even 40 tons, for the requirement of tie intensity, improve constantly, consumption is also in continuous increase.Therefore the high-strength steel tie that, adopts low cost process to produce has boundless market outlook.
But because high-strength steel tie requires to have higher intensity and unit elongation simultaneously, so production difficulty is larger.At present, the production technique of high-strength steel tie mainly contains three kinds:
The technique of carrying out recovery annealing processing after one, cold rolling
This technique generally includes following steps: 1) utilize reheat+hot continuous rolling process of traditional continuous casting+slab to produce hot-rolled strip; 2) by cold rolling, hot-rolled strip is thinned to the needed thickness of high-strength tie; 3) cold rolling strap is carried out to blue annealing processing.
Hot rolled strip intensity after cold rolling is largely increased, but unit elongation falls too low.After processing by recovery annealing, steel band intensity decreases, but unit elongation is improved, thereby makes steel band reach certain strong plasticity coupling, forms blue layer oxide film in steel strip surface simultaneously, plays oxidation resistant effect.The final microstructure of steel band is generally cold working recovery annealing ferrite matrix and spreads all over the diffusion carbide of matrix.This technological operation is simple, with low cost, energy consumption is few, environmental pollution is little.
Because first tensile strength and the unit elongation of tie be the impact that is subject to hot rolling material performance, then regulate by cold rolling power rate and annealing treating process.For high-strength tie, do not produce custom-designed hot rolling raw material in the market, high-strength tie is produced and conventionally selected main component is the structural alloy steel of C, Si, Mn.Organization type and the fluctuation of various composition phase content of this class hot-rolled product of the market supply of material are larger, determine that its tensile property changes greatly, and it will fluctuate larger to the influence degree of high-strength tie performance like this; The thickness specification of this class hot-rolled product of the market supply of material is relatively limited in addition, if the high-strength tie of different thickness adopts the hot-rolled sheet of similar thickness to produce, the variation range of so cold rolling draft is just larger, for example adopt the Hot Rolling Plate Production thickness of 2.8mm to be respectively the high-strength tie of 1.0mm and 0.5mm, cold rolling draft is respectively 64% and 82%, and its performance impact degree to high-strength tie will fluctuate larger.Above two fluctuations determine for different hot rolling raw materials, just need to adopt different annealing processs to carry out the last adjustment of tie performance, otherwise tie performance have a great difference.In annealing process adjustment process, tie performance is very responsive to parameter and annealing, and when tie tensile strength is higher, unit elongation is conventionally lower; And when the unit elongation of tie is higher, tensile strength is conventionally lower, make tie have higher intensity and unit elongation simultaneously, more difficult.Above-mentioned reason causes, and utilizes the steel tie that carries out the production of recovery annealing treatment process after cold rolling, and its tensile strength and unit elongation are difficult to break through 980MPa and 12%.This technique seems simply, must with production tensile strength and the unit elongation high-strength tie that has better coupling, difficulty is larger.
Chinese patent 02109635.X open " a kind of high-intensity packing steel belt and thermal treatment process ", it adopts composition is C0.22-0.29%, Si0.015%, Mn1.30-1.50%, P≤0.015%, S≤0.010%, Als0.015%, Nb0.012%, surplus is the hot-rolled sheet raw material of Fe, after cold rolling, carry out electrically heated blue annealing processing, annealing furnace temperature is 550-650 ℃, and steel belt operating speed is that its speed of 2.5-3.5m/min(is directly proportional to furnace temperature and body of heater length).The steel tie tensile strength of utilizing this patent to produce reaches 920MPa, and unit elongation reaches 11%.
Chinese patent 200410031162.8 open " high-intensity packing steel belt and manufacturing process thereof ", employing composition is C0.25-0.28%, Si0.02-0.06%, Mn1.30-1.50%, P0.01-0.02%, S0.001-0.012%, Als0.03-0.06%, surplus is the hot-rolled sheet raw material of Fe, hot-rolled sheet thickness is 1.8-3.75mm, and after 68-83% is cold rolling, obtaining thickness is 0.3-1.2mm steel band, utilize continuous furnace to carry out anneal, steel band Heating temperature is 450-550 ℃.The steel tie tensile strength >=930MPa that utilizes this patent to produce, unit elongation >=8%.
Chinese patent 201210232927.9 open " production method of high strength blue steel strip ", adopt C0.19-0.21%, Mn1.62-1.71%, Si0.02-0.028%, P0.014-0.018%, S0.0042-0.006%, Als0.033-0.05%, surplus is the Composition Design of Fe, through processing steps such as smelting, continuous casting, hot rolling, cold rolling, blue annealings, carries out the production of steel tie.Cold rolling draft is 70%, and blue annealing temperature is 580-700 ℃, and the time of turning blue is 100-160s.The steel tie tensile strength of utilizing this patent to produce is 950-960MPa, and unit elongation is 11.5-12%.
Two, cold rolling laggard quadrat is bathed the technique of means of isothermal quenching
This technique generally includes following steps: 1) utilize reheat+hot continuous rolling process of traditional continuous casting+slab to produce hot-rolled strip; 2) by cold rolling, hot-rolled strip is thinned to the needed thickness of high-strength tie; 3) steel band after cold rolling is heated to austenitizing; 4) lead patenting.
By lead patenting, obtain bainite structure, thereby obtain intensity and plasticity that steel band will be wanted.The greatest problem of utilizing this explained hereafter is production unit complex structure, expensive, and equipment cost is high; Lead bath cooling power is limited, needs time enough to complete austenite to bainite transformation, and production efficiency is low; Can cause serious environmental pollution; Production cost is high.Some countries have started restriction and have used.And although utilize the steel tie intensity of this explained hereafter higher, unit elongation is lower, and brittle failure in use easily occurs.
US Patent No. 6814817 disclosed " Steel Strap Composition ", by composition, be C0.30-0.36%, Mn0.90-1.25%, the cold-rolled steel strip of Si0.75-1.10%, first be preheating to 370-510 ℃, then be heated to 815-900 ℃ and carry out Ovshinsky, then carry out 370-510 ℃ of lead patenting and process.Utilize the steel tie tensile strength >=1170MPa of this explained hereafter, unit elongation >=6.5%.
Chinese patent 200810200449.7 open " a kind of heat treating method of steel belt for packages ", employing composition is C0.29-0.35%, Si0.15-0.35%, Mn1.20-1.55%, P0.030%, S0.030%, the hot-rolled sheet that surplus is Fe, after cold rolling, first in lead bath, be preheating to 355-365 ℃, warm up time, 6.75-9s, was then heated to 860 ± 20 ℃, and insulation 30-40s carries out austenitizing, carry out 355-365 ℃ of lead patenting again and process, isothermal quenching time is 21-28s.Utilize the steel tie tensile strength >=1350MPa of this explained hereafter, unit elongation >=6%.
Three, after cold rolling, carry out the technique of two-phase region quench treatment
This technique generally includes following steps: 1) utilize reheat+hot continuous rolling process of traditional continuous casting+slab to produce hot-rolled strip; 2) by cold rolling, hot-rolled strip is thinned to the needed thickness of high-strength tie; 3) steel band after cold rolling is heated to ferrite and austenite two-phase region; 4) rapid quenching.
By two-phase region, quench, the microstructure of acquisition is martensite+cold working recovery annealing ferrite matrix and the diffusion carbide that spreads all over matrix, thereby obtains intensity and the plasticity that steel band will be wanted.The steel tie that utilizes this explained hereafter, intensity and unit elongation are all higher.But the electromagnetic induction rapid-heating device of this technique Structure of need complexity and powerful water cooling equipment, equipment cost is high; Production process is more complicated, and production cost is higher; And thin plate plate shape after quenching in two-phase region is often not ideal enough.
US Patent No. 6635127 disclosed " Steel strapping and method of making ", employing composition is C≤0.2%, Mn≤2.0%, Si0.2-0.4%, Ti0.025-0.045%, V0.05-0.07%, Cr≤0.25%, Ni≤0.30%, Mo≤0.10%, Cu≤0.20%, Al≤0.08%, Nb≤0.005%, N≤0.005%, P≤0.035%, S≤0.02%, the steel billet that surplus is Fe through hot rolling, cold rolling after, induction heating to 750 ℃, is incubated 2s fast, is then rapidly quenched to room temperature.Utilizing the steel tie tensile strength of this explained hereafter is 970-1070MPa, and unit elongation is 10-14%.
Chinese patent 200910046229.8 disclosed " tensile strength is higher than high-strength binding band steel and the manufacture method thereof of 1100MPa ", adopt C0.25-0.35%, Mn1.24-2.0%, Si≤0.45%, S≤0.04%, the Composition Design of P≤0.04%, carries out the production of steel tie through processing steps such as smelting, continuous casting, hot rolling, cold rolling, ferrite+austenite two-phase region quenching, tempering.Quenching temperature is 730-790 ℃, quenching velocity >=100 ℃/s, and tempering temperature is 430-530 ℃.Utilize the steel tie tensile strength >=1100MPa of this explained hereafter, unit elongation >=10%.
In above-mentioned patent, produce the hot-rolled strip raw material that high-strength tie adopts, be all to utilize traditional continuous casting+hot rolling technology flow process to produce.Due to the restriction of the specification of hot-rolled strip raw material own, tissue, aspect of performance, and the restriction of the operation such as follow-up cold rolling, thermal treatment itself, make to utilize the high-strength tie production cost of above-mentioned explained hereafter or performance to be difficult to obtain and break through.
At present, some emerging technologies, CSP for example, thin strap continuous castings etc., also can be used for producing hot-rolled strip.Wherein, 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 hot rolled strip 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.Facility investment is corresponding minimizing also, and product cost significantly reduces.
The patent of relevant thin strap continuous casting product and manufacturing process thereof, mainly concentrate on soft steel and low-carbon microalloy product made from steel and manufacturing process thereof, the aspects such as product surface quality improvement, as Chinese patent 201080008606.X " hot rolled thin cast steel strip product and manufacture method thereof "; " high strength thin cast strip product and preparation method thereof " of Chinese patent 201080017436.1, " thin strip slab that tiny crack is reduced " of Chinese patent 200880109715.3 etc.
The steel band of manufacturing by above-mentioned thin strap continuous casting patent, is not all to produce and design for high-strength tie, has not yet to see the precedent that the steel band of thin band continuous casting technique production is produced for high-strength tie.In fact, the final performance of high-strength tie is heated and is rolled the specification of carrying raw material, and hot-rolled strip tissue and performance impact larger, while especially adopting the first technique that comparatively economic high-strength tie produces.Therefore, want to adopt the steel band of thin band continuous casting technique production as raw material, produce to economy the high-strength tie of excellent performance, thin strap continuous casting steel band is carried out to specialized designs and manufacture, most important.
Summary of the invention
The object of the present invention is to provide the high-strength tie of thin strap continuous casting economy and the manufacture method thereof of a kind of tensile strength >=1000MPa, by reasonable component design and processes, design, solve the problem that environmental pollution is serious, production efficiency is lower, production cost is high that prior art exists, and the strong plasticity of high-strength tie of utilizing existing economy technology to produce is mated undesirable problem.
For achieving the above object, technical scheme of the present invention is:
The present invention adopts the processing technology routine that carries out recovery annealing processing after cold rolling to produce high-strength tie.Take this operational path to produce high-strength tie, its functional design is mainly considered three aspects: the one, and the proper property by thin band continuous casting technique institute's production Cast Strip, is mainly determined by composition and tissue morphology; The 2nd, cold rolling working hardening, is mainly determined by cold rolling draft; The 3rd, recovery annealing is softening, mainly by the annealing process after cold rolling, is determined.Contact between these three aspects is very tight, each side all needs stable control, and the stable control of a step must obtain being just achieved on the stable basis of controlling at back afterwards, thereby realize comparatively perfect match of the strong plasticity of high-strength tie, realize effect of the present invention.
The present invention designs by chemical composition and thin band continuous casting technique, the microstructure type of hot-rolled strip and composition phase content quantitatively controlled, and then the stable mechanical property of controlling hot-rolled strip, and the impact on high-strength tie mechanical property.By thin band continuous casting technique, design, the thickness specification of hot-rolled strip is accurately controlled, and then stablize and control the cold rolling draft that the high-strength tie production of different thickness adopts, and the impact on high-strength tie mechanical property.And design is suitable for the blue annealing processing parameter of thin strap continuous casting hot-rolled strip microstructure type and cold rolling draft.By carrying out the economic production technique of recovery annealing after thin strap continuous casting+cold rolling, realize the more excellent coupling of high-strength tie tensile strength and unit elongation.
Concrete, the high-strength tie of thin strap continuous casting economy of tensile strength >=1000MPa of the present invention, its chemical component weight per-cent is: C0.25-0.40%, Si0.15-0.40%, Mn1.3-2.0%, P≤0.015%, S≤0.01%, N≤0.012%, 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 can be dissolved in and in ferrite, form interstitial solid solution, but at room temperature its solubleness in ferrite is very limited, so its solution strengthening effect is restricted.Under processing condition of the present invention, C mainly separates out with cementite form, as pearlitic integral part.Pearlitic content and C content are closely related, and when C content increases, content of pearlite in alloy increases, and intensity, the hardness of steel improve thereupon, and plasticity, the corresponding reduction of toughness.Therefore C content can not be too high, and the C content range that the present invention adopts is 0.25-0.40%.
Preferably, C content range is 0.28-0.38%, and steel band can obtain more suitably content of pearlite in alloy, can have more excellent tensile strength and unit elongation coupling.
Si:Si plays solution strengthening effect in steel.When Si content is suitable, not only make the intensity of steel be improved, and little on plasticity impact.The Si content range that the present invention adopts is 0.15-0.4%.
Preferably, Si content range is 0.25-0.35%, and steel band can have more excellent tensile strength and unit elongation coupling.
Mn:Mn is one of alloying element that price is the most cheap, it has sizable solid solubility in steel, improves the intensity of steel by solution strengthening, and its content is when suitable, substantially harmless to the plasticity of steel, be the topmost strengthening element of intensity that improves steel in C content situation reducing.The Mn content range that the present invention adopts is 1.3-2.0%.
Preferably, Mn content range is 1.5-1.8%, and steel band can have more excellent tensile strength and unit elongation coupling.
P:P solubleness in α-Fe is very large.Compare with other elements, P caused solid solution strengthening effect in α-Fe is larger.But when P content is higher, along with the intensity raising of steel, its plasticity obviously reduces.Particularly in steel, P occurs in segregation situation, will cause larger cold shortness.In the present invention, P controls as impurity element, its content≤0.015%.
The solubleness of S:S in Fe is minimum, and the S in steel mostly chemical combination is FeS, and its harm is can cause the red brittleness of steel when carrying out hot-work, reduces ductility and the toughness of steel, causes crackle when rolling.In the present invention, S controls as impurity element, its content≤0.01%.
N: similar with C element, N element can improve the intensity of steel by gap solid solution, and still, the gap solid solution of N has larger harm to the plasticity of steel and toughness, so N content can not be too high.N content≤0.012% that the present invention adopts.
The high-strength tie manufacture method of thin strap continuous casting economy of tensile strength >=1000MPa of the present invention, comprises the steps:
1) adopt the Cast Strip that twin-roll thin strip continuous casting cast thickness is 1.0-4.5mm, its chemical component weight per-cent is: C0.25-0.40%, Si0.15-0.40%, Mn1.3-2.0%, P≤0.015%, S≤0.01%, N≤0.012%, all the other are Fe and inevitable impurity;
2) Cast Strip is carried out cooling, rate of cooling is 20-80 ℃/s;
3) online hot rolling is carried out in Cast Strip, finishing temperature >=900 ℃, hot rolling draft≤10%, after hot rolling, the thickness of steel band is 0.9-4.0mm;
4) hot-rolled strip is carried out cooling, rate of cooling is 10-50 ℃/s;
5) hot-rolled strip is batched, coiling temperature is 530-630 ℃; Hot-rolled strip microstructure is by 65-80% perlite, 20-35% acicular ferrite, and a small amount of polygonal ferrite forms, and in perlite, cemetite lamellae layer thickness is nanometer scale, cemetite lamellae interlamellar spacing is nanometer or sub-micrometer scale.
6) hot-rolled strip is carried out cold rolling, cold rolling draft is 60-70%, and cold rolling rear thickness of strips is 0.3-1.2mm;
7) cold rolling strap is carried out to blue annealing, annealing temperature is 475-525 ℃, and annealing time is 120-180s; Microstructure after cold rolling strap annealing, is the cementite distributing on the ferrite matrix of recovery annealing and ferrite matrix, part cementite generation nodularization, and part cementite still keeps the strip after distortion, and its diameter is nanometer scale; Tensile strength >=the 1000MPa of high-strength tie, unit elongation >=12%.
Further, in described step 1), the content range of C is 0.28-0.38%, by weight percentage.
In described step 1), the content range of Mn is 1.5-1.8%, by weight percentage.
In described step 1), the content range of Si is 0.25-0.35%, by weight percentage.
Again, described step 2) in, Cast Strip rate of cooling is 30-60 ℃/s.
In described step 3), hot rolling draft is 5-10%.
In described step 4), hot-rolled strip rate of cooling is 10-40 ℃/s.
In described step 5), the tensile strength of hot-rolled strip is 700-750MPa, unit elongation >=15%.
In addition, in manufacture method of the present invention, can also increase as required that step 8) is painted to steel band or the subsequent disposal such as zinc-plated.
In manufacturing process of the present invention:
1) thin strap continuous casting
Within molten steel is introduced in the crystallization roll of a pair of relative rotation and internal water cooling and the molten bath of side seal board formation, after rapid solidification, direct pouring goes out the Cast Strip that thickness is 1.0-4.5mm.This thickness specification is by high-strength tie finished product thickness, and the online hot rolling draft of subsequent design and the required draft inverse of cold rolling strengthening obtain.
2) Cast Strip is cooling
Cast Strip from crystallization roll continuous casting out, through confined chamber, in confined chamber, carry out cooling.In order to control inside, Cast Strip and surface quality, prevent that austenite crystal from high temperature growing up too fastly simultaneously, the rate of cooling of controlling Cast Strip is 20-80 ℃/s.Preferably, the rate of cooling of Cast Strip is 30-60 ℃/s.The cooling employing air cooling in Cast Strip mode, the pressure of cooling gas, the gentle nozzle location of flow can regulation and control.Cooling gas can be the rare gas elementes such as argon gas, nitrogen, helium, or the mixed gas of several gases.By controlling type, pressure, the flow of cooling gas, and nozzle is to the distance between Cast Strip etc., realizes the control to Cast Strip rate of cooling.
3) the online hot rolling in Cast Strip, cooling and batch
The tensile property of hot-rolled strip has a significant impact the performance of high-strength tie.The high-strength tie of producing same intensity rank, the performance of hot-rolled strip used should not change too large, otherwise just can not realize the stable control to high-strength tie performance.The performance of hot-rolled strip is determined by composition and organization type.Control hot-rolled strip stable performance, its organization type and composition phase content should be stablized as far as possible.Because organization type is resisted the ability of recrystallize after to cold rolling band steel, also have considerable influence, therefore tissue is stable is also conducive to cold rolled annealed technological design.
Organization type and organize the control of phase content mainly to realize by hot rolling reeling process.
The present invention controls temperature >=900 ℃ processed eventually, and hot rolling is carried out in austenitic area.
The present invention controls hot rolling draft≤10%, and preferred, hot rolling draft is 5-10%.After hot rolling, the thickness range of steel band is 0.9-4.0mm.In actual production, the thickness of hot-rolled strip is by the high-strength tie thickness specification that will produce, and cold rolling machining needs draft to carry out inverse.For example, the high-strength tie that production thickness is 0.5mm, required cold rolling draft is 65%, the thickness of hot-rolled strip should be 1.43mm so.By adjustment thin band continuous casting technique parameter, can realize product thickness specification and change flexibly, this is a large advantage of strip continuous casting technology.
Hot rolling draft is controlled to such scope, and reason has three: the first, by a small amount of hot rolling, can further improve inside, Cast Strip and surface quality; The second, in order to make austenite that recrystallize not occur after hot rolling, hot rolling draught can not be too large.Deformation is the basis of generation recrystallize, is the motivating force of recrystallize---deformation stores the source of energy, after must surpassing certain motivating force, just recrystallize can occur, therefore only have over just recrystallize occurring after certain deformation quantity.Deformation quantity is larger, and deformation stores can be larger, and deformation storage can be larger, and Recrystallization nucleation and growth rate are all larger, even if also can start rapid enough and complete recrystallize at a lower temperature.Once there is recrystallize in austenite after hot rolling, austenite structure stability is just difficult to control, and then cause by controlling follow-up cooling perlite and the acicular ferrite content generation larger fluctuation obtaining with coiling technique parameter, thereby affect the stable control of steel band tensile property.The 3rd, make unlikely subtract too thin of hot-rolled strip thickness.Because produce high-strength tie, also need in follow-up cold rolling step, guarantee certain draft, the control thinking of draft refers to below.
Adopt that aerosol is cooling, laminar flow is cooling or the mode such as spraying cooling is carried out cooling to hot-rolled strip.The flow of water coolant, flow velocity, and water outlet position etc. can regulate, thus realize the control to hot-rolled strip rate of cooling.The rate of cooling that the present invention controls hot-rolled strip is 10-50 ℃/s, and preferred, the rate of cooling of hot-rolled strip is 10-40 ℃/s.The speed of rate of cooling determines last coiling temperature.In technological process, need take different rate of cooling according to the difference of thin strap continuous casting steel band pulling rate and tape thickness, coiling temperature be controlled in the scope of hope.
The coiling temperature that the present invention controls hot-rolled strip is 530-630 ℃, within the scope of this coiling temperature, can control the microstructure of hot-rolled strip by 65-80% perlite, 20-35% acicular ferrite, and a small amount of polygonal ferrite forms.And cemetite lamellae layer thickness is nanometer scale in perlite, cemetite lamellae interlamellar spacing is nanometer or sub-micrometer scale.The hot-rolled strip with this microstructure, its tensile strength is 700-750MPa, unit elongation >=15%.
4) to hot-rolled strip, carry out cold rolling
The cold rolling draft of hot-rolled strip is very large to the performance impact of high-strength tie, is the important parameter that improves tie performance, and the performance of tie can increase along with the increase of cold rolling draft.The high-strength tie of producing same intensity rank, cold rolling draft should not change too large, otherwise just can not realize the stable control to high-strength tie performance.And cold rolling draft changes and also has considerable influence to resisting the ability of recrystallize after cold rolling band steel too greatly, have influence on thus the selection of parameter and annealing, this also can affect the stable control to high-strength tie performance.In addition, cold rolling draft total amount design, should meet the requirement of high-strength tie functional design, guarantees that again material does not ftracture in cold-rolled process, can not form tiny crack at material internal.The hot-rolled strip that the present invention obtains, in microstructure, 65-80% is perlite, cemetite lamellae layer thickness is nanometer scale, the distortion of form such as in cold-rolled process, can elongate, crooked, is difficult for occurring broken, so just can not cause defect at material internal.Based on above-mentioned consideration, it is 60-70% that the present invention controls cold rolling draft, in 10% scope, changes.
5) cold rolling strap blue annealing
The selection of parameter and annealing is most important.In annealing process, matrix is replied, and causes steel band strength decreased, and unit elongation improves.Temperature can not be too high or the time can not be long, otherwise can cause steel band strength degradation too many, temperature can not be too low or the time is too short, otherwise can cause unit elongation to go up not.Also will consider, the height of annealing temperature is very large with hot-rolled strip microstructure type and cold rolling draft relation simultaneously.The hot-rolled strip that the present invention obtains, in microstructure, 65-80% is perlite, cemetite lamellae layer thickness is nanometer scale, cemetite lamellae interlamellar spacing is nanometer or sub-micrometer scale, make material relatively strong to Recovery and recrystallization resistivity in annealing process, therefore can suitably improve annealing temperature and or annealing time.
In view of above-mentioned, it is 475-525 ℃ that the present invention controls annealing temperature, and annealing time is 120-180s.Under this annealing process condition, on the ferrite matrix that the microstructure of steel band is recovery annealing, the disperse diameter that distributing is the cementite particle of nanometer scale or cementite bar, rod.Final comparatively desirable tensile strength and the coupling of unit elongation of obtaining of tie.
6) japanning or the subsequent disposal such as zinc-plated
Can be according to the application target of high-strength tie and environment for use etc., the steel band after blue annealing is painted or the subsequent disposal such as zinc-plated.
The difference of the present invention and prior art and beneficial effect:
1) technique of carrying out recovery annealing processing after the high-strength tie of existing production cold rolling, the composition phase content in hot rolling raw material microstructure and hot rolling raw thickness specification are not controlled, cause steel band tensile strength and unit elongation coupling undesirable, be difficult to break through 980MPa and 12%.By thin band continuous casting technique of the present invention, design, control the microstructure type of thin strap continuous casting hot-rolled strip, and quantitatively control the content of chief component phase in microstructure; According to the thickness of the high-strength tie thickness specification inverse thin strap continuous casting hot-rolled strip that will produce and accurately control, and then stable mechanical property and the impact of cold rolling draft on high-strength tie mechanical property of controlling hot-rolled strip.Design is suitable for the blue annealing processing parameter of thin strap continuous casting hot-rolled strip microstructure type and cold rolling draft, has realized the more excellent coupling of high-strength tie tensile strength and unit elongation, tensile strength >=1000MPa, unit elongation >=12%.
2) prior art is produced the technique of high-strength tie and is: quench in reheat+hot continuous rolling of traditional continuous casting+slab+cold rolling+recovery annealing or lead patenting or two-phase region.The technique that the present invention produces high-strength tie is: after thin strap continuous casting+online hot rolling+cold rolling, carry out recovery annealing, shortened technical process, simplified processing step, the high-strength tie performance of producing is better than utilizing the high-strength tie that carries out recovery annealing explained hereafter after existing traditional continuous casting+cold rolling, is better than or close to the high-strength tie that utilizes existing lead patenting technique and two-phase region isothermal quenching technique to produce.
3) the present invention produces the technology of high-strength tie, flow process is short, technological operation is simple, with low cost, energy consumption is few, discharge less, environmental pollution is little.Solved the problem that environmental pollution is serious, production efficiency is lower, production cost is high that prior art exists, and the strong plasticity of high-strength tie of utilizing existing economy technology to produce is mated undesirable problem.
Accompanying drawing explanation
Fig. 1 is the microstructure of thin strap continuous casting hot-rolled strip in the embodiment of the present invention 1.
Fig. 2 is the cementite lamella of thin strap continuous casting hot-rolled strip microstructure Medium pearlite in the embodiment of the present invention 1.
Fig. 3 is the microstructure of thin strap continuous casting hot-rolled strip after cold rolling in the embodiment of the present invention 1.
Fig. 4 is the microstructure after cold rolling strap annealing in the embodiment of the present invention 1.
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention will be further described.
The molten steel of embodiment of the present invention 1-5 all adopts electrosmelting to obtain, and specific chemical composition is as shown in table 1.The Cast Strip thickness obtaining after thin strap continuous casting, Cast Strip rate of cooling, hot rolling finishing temperature, hot rolling draft, hot-rolled strip thickness, hot-rolled strip rate of cooling, coiling temperature, cold rolling draft, annealing temperature, the processing parameters such as annealing time are in Table 2, and the tensile property of hot-rolled strip and high-strength tie is in Table 3.
Figure 1 shows that the microstructure of thin strap continuous casting hot-rolled strip in embodiment 1, the perlite by 77%, 20% acicular ferrite, and a small amount of polygonal ferrite forms, is that the microstructure characteristic that obtains after the austenite phase transformation of recrystallize does not occur after typical hot rolling.
Fig. 2 is the cementite lamella of thin strap continuous casting hot-rolled strip microstructure Medium pearlite in embodiment 1, and cemetite lamellae layer thickness is nanometer scale, and cemetite lamellae interlamellar spacing is sub-micrometer scale.
Fig. 3 is the microstructure of hot-rolled strip after cold rolling in embodiment 1, can in ferrite and pearlite crystal grain, observe deformation bands, and crystal grain, along rolling to obviously being elongated, is fibrous distribution.Also there is moulding distortion in the cementite in perlite, be parallel to roll to cementite be elongated, perpendicular to roll to cementite bend.Cold rolling strap inside has no any tiny crack, and quality is fine.
Fig. 4 is the microstructure after cold rolling strap annealing in embodiment 1, for the cementite distributing on the ferrite matrix of recovery annealing and ferrite matrix, part cementite generation nodularization, part cementite still keeps the strip after distortion, its diameter is nanometer scale, thereby makes high-strength tie have good strong plasticity coupling.As can be seen from Table 3, the tensile strength >=1000MPa of the high-strength tie of the present invention, unit elongation >=12%.
The molten steel chemical composition (wt.%) of table 1 embodiment 1-5
| Embodiment | C | Si | Mn | P | S | N |
| 1 | 0.37 | 0.36 | 2.00 | 0.014 | 0.008 | 0.0060 |
| 2 | 0.28 | 0.24 | 1.30 | 0.011 | 0.007 | 0.012 |
| 3 | 0.34 | 0.34 | 1.45 | 0.012 | 0.003 | 0.0097 |
| 4 | 0.40 | 0.15 | 1.76 | 0.014 | 0.006 | 0.0058 |
| 5 | 0.25 | 0.39 | 1.68 | 0.015 | 0.002 | 0.0074 |
Table 2
Table 3
Claims (13)
1. the high-strength tie of thin strap continuous casting economy of tensile strength >=1000MPa, its chemical component weight per-cent is: C0.25-0.40%, Si0.15-0.40%, Mn1.3-2.0%, P≤0.015%, S≤0.01%, N≤0.012%, all the other are Fe and inevitable impurity.
2. the high-strength tie of thin strap continuous casting economy of tensile strength >=1000MPa as claimed in claim 1, is characterized in that: the content range of C is 0.28-0.38%, by weight percentage.
3. the high-strength tie of thin strap continuous casting economy of tensile strength >=1000MPa as claimed in claim 1, is characterized in that: the content range of Mn is 1.5-1.8%, by weight percentage.
4. the high-strength tie of thin strap continuous casting economy of tensile strength >=1000MPa as claimed in claim 1, is characterized in that: the content range of Si is 0.25-0.35%, by weight percentage.
5. the high-strength tie manufacture method of the thin strap continuous casting economy of tensile strength >=1000MPa, comprises the steps:
1) adopt the Cast Strip that twin-roll thin strip continuous casting cast thickness is 1.0-4.5mm, its chemical component weight per-cent is: C0.25-0.40%, Si0.15-0.40%, Mn1.3-2.0%, P≤0.015%, S≤0.01%, N≤0.012%, all the other are Fe and inevitable impurity;
2) Cast Strip is carried out cooling, rate of cooling is 20-80 ℃/s;
3) online hot rolling is carried out in Cast Strip, finishing temperature >=900 ℃, hot rolling draft≤10%, after hot rolling, the thickness of steel band is 0.9-4.0mm;
4) hot-rolled strip is carried out cooling, rate of cooling is 10-50 ℃/s;
5) hot-rolled strip is batched, coiling temperature is 530-630 ℃.Hot-rolled strip microstructure is by 65-80% perlite, 20-35% acicular ferrite, and a small amount of polygonal ferrite forms, and in perlite, cemetite lamellae layer thickness is nanometer scale, cemetite lamellae interlamellar spacing is nanometer or sub-micrometer scale;
6) hot-rolled strip is carried out cold rolling, cold rolling draft is 60-70%, and cold rolling rear thickness of strips is 0.3-1.2mm;
7) cold rolling strap is carried out to blue annealing, annealing temperature is 475-525 ℃, and annealing time is 120-180s.Microstructure after cold rolling strap annealing, for the diameter that distributing of disperse on the ferrite matrix of recovery annealing is the cementite particle of nanometer scale or cementite bar, rod; Tensile strength >=the 1000MPa of high-strength tie, unit elongation >=12%.
6. the high-strength tie manufacture method of the thin strap continuous casting economy of tensile strength >=1000MPa as claimed in claim 5, is characterized in that: in described composition, the content range of C is 0.28-0.38%, by weight percentage.
7. the high-strength tie manufacture method of the thin strap continuous casting economy of tensile strength >=1000MPa as claimed in claim 5, is characterized in that: in described composition, the content range of Mn is 1.5-1.8%, by weight percentage.
8. the high-strength tie manufacture method of the thin strap continuous casting economy of tensile strength >=1000MPa as claimed in claim 5, is characterized in that: in described composition, the content range of Si is 0.25-0.35%, by weight percentage.
9. the high-strength tie manufacture method of the thin strap continuous casting economy of tensile strength >=1000MPa as claimed in claim 5, is characterized in that: described step 2), Cast Strip rate of cooling is 30-60 ℃/s.
10. the high-strength tie manufacture method of the thin strap continuous casting economy of tensile strength >=1000MPa as claimed in claim 5, is characterized in that: in described step 3), hot rolling draft is 5-10%.
The high-strength tie manufacture method of thin strap continuous casting economy of 11. tensile strength >=1000MPa as claimed in claim 5, is characterized in that: in described step 4), hot-rolled strip rate of cooling is 10-40 ℃/s.
The high-strength tie manufacture method of thin strap continuous casting economy of 12. tensile strength >=1000MPa as claimed in claim 5, is characterized in that: in described step 5), the tensile strength of hot-rolled strip is 700-750MPa, unit elongation >=15%.
The high-strength tie manufacture method of thin strap continuous casting economy of 13. tensile strength >=1000MPa as claimed in claim 5, is characterized in that: can increase as required that step 8) is painted to steel band or the subsequent disposal such as zinc-plated.
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