CN103305755A - Manufacturing method of thin-strip continuous casting low-carbon micro-alloy high-strength steel strip - Google Patents
Manufacturing method of thin-strip continuous casting low-carbon micro-alloy high-strength steel strip Download PDFInfo
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Abstract
The invention discloses a manufacturing method of a thin-strip continuous casting low-carbon micro-alloy high-strength steel strip. The manufacturing method comprises the following steps of: (1) smelting and performing thin-strip continuous casting, wherein the steel strip comprises the following chemical components in percentage by weight: 0.01-0.25 percent of C, less than or equal to 0.4 percent of Si, 0.6-2.0 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.01 percent of S, less than or equal to 0.006 percent of N, less than or equal to 0.008 percent of O, 0.0005-0.004 percent of B, 0.005-0.1 percent of Nb, 0.005-0.1 percent of V, 0.005-0.1 percent of Ti, 0.05-0.5 percent of Mo and the balance of Fe and inevitable impurities, and casting a cast strip with the thickness of 1-5mm in a double-roll continuous casting machine; (2) cooling the cast strip, wherein the cooling rate is greater than 20 DEG C/s; (3) performing hot rolling, wherein the hot rolling temperature is 1,050-1,250 DEG C, the reduction rate is 20-50 percent, and the deformation rate is greater than 20s<-1>; and (4) cooling and rolling. According to the manufacturing method, austenite is re-crystallized on line after the hot rolling of the cast strip is realized, the austenite grains are thinned and the dimensional uniformity of the austenite grains is improved, meanwhile, the hardenability of the re-crystallized austenite is improved, and a more uniform structure of bainite and acicular ferrite is obtained, so that the product simultaneously has high strength and extensibility.
Description
Technical field
The present invention relates to thin band continuous casting technique, be particularly related to the high-strength steel band manufacture method of a kind of thin strap continuous casting low-carbon microalloy, yield strength 〉=the 340MPa of the high-strength steel band that obtains, tensile strength 〉=450MPa, unit elongation 〉=15%, have good strong plasticity coupling, the microstructure that obtains steel band mainly is made of uniform bainite and acicular ferrite.
Background technology
At present, producing the thin gauge steel carries product of low carbon high-strength that contains the microalloy elements such as Nb, V, Ti, Mo, mainly is to realize by traditional hot rolling and cold-rolling process.But utilize traditional hot rolling or cold-rolling process to produce, have some problems:
At first, conventional process flow is long, energy consumption is high, unit equipment is many, the capital construction cost is high, causes production cost high.
Secondly, when utilizing traditional hot rolling technology production to contain the high-strength thin slab product of microalloy of the microalloy elements such as Nb, V, Ti, Mo, because microalloy element can not remain sosoloid in course of hot rolling, generating unit analyzes, and causes steel strength to improve, and therefore can significantly increase rolling load, increase energy consumption and roller consumption, damage to equipment is larger, can be economically and produce practically the thickness range of hot-rolled product thereby just limited, normally 〉=2mm.Traditional hot-rolled product is proceeded cold rolling, can further be reduced thickness of strips, yet the high strength of hot rolled strip causes cold rollingly also having difficulties.The one, high cold rolling load is had relatively high expectations to equipment, damages larger; The 2nd, the second-phase of being separated out by alloying element in the hot-rolled product significantly increases the recrystallization annealing temperature of cold rolling rear steel band.
Again, when utilizing traditional hot rolling technology production to contain the high-strength product of microalloy of the microalloy elements such as Nb, V, Ti, Mo, normally utilize deformation refine austenite crystal grain principle, therefore the start rolling temperature of finish rolling is usually less than 950 ℃, finishing temperature is rolled about 850 ℃ at a lower temperature, adds the increase of carrying out deformation quantity with the operation of rolling, can cause steel band intensity significantly to increase, this also can significantly increase hot rolling difficulty and consumption.
In a word, although utilize traditional hot rolling and cold-rolling process can realize the production of the high-strength thin gauge steel carries product of low-carbon microalloy, cost is all relatively high, and is commercially also uneconomical.
Strip continuous casting technology is a cutting edge technology in metallurgy and the 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 the metal working industry, to cast continuously, rolling even thermal treatment etc. integrates, make the online hot rolling of strip base process a time of production with regard to the thin steel band of disposable formation, greatly simplified production process, shortened the production cycle, its processing line length is only about 50m.Facility investment is corresponding minimizing also, and product cost significantly reduces.
Twin-roll thin strip continuous casting technique is a kind of principal mode of thin band continuous casting technique, also is a kind of thin band continuous casting technique of in the world unique realization industrialization.In Twin-roll Strip Continuous Casting, molten steel is from ladle process long nozzle, tundish and submerged nozzle, be introduced within the molten bath that the crystallization roll of a pair of relative rotation and internal water cooling and side seal board form, form solidified shell at mobile roll surface, the roll gap place of solidified shell between crystallization roll flocks together, and forms from the Cast Strip that roll gap is pulled out downwards.By swing guide, pinch roll the Cast Strip is delivered to roller-way afterwards, passes through again in-line hot rolling mill, spraying cooling, flying shear is until reeling machine is finished the production of thin strap continuous casting product.
Utilize strip continuous casting technology to produce the high-strength thin specification steel band of low-carbon microalloy, main advantage is as follows:
(1) thin strap continuous casting has saved the repeatedly complex process such as hot rolling of heating of plate blank, multi-pass, and to directly carrying out the online hot rolling of a time in thin Cast Strip, production cost significantly reduces.
(2) the Cast Strip thickness of thin strap continuous casting is usually at 1-5mm, and by being hot-rolled down to online expected product thickness, usually at 1-3mm, the production of thin slab product does not need through cold rolling.
(3) thin band continuous casting technique is produced low-carbon micro steel-alloy, the alloying elements such as the Nb that adds, V, Ti, Mo mainly exist with the solid solution attitude in course of hot rolling, so steel band intensity are relatively low, thereby make the single chassis hot rolling draft can be up to 30-50%, steel band attenuate efficient be high.
(4) thin band continuous casting technique is produced low-carbon micro steel-alloy, the direct hot rolling in high temperature Cast Strip, and the alloying elements such as the Nb that adds, V, Ti, Mo mainly exist with the solid solution attitude, can improve the alloy utilization ratio.Alloying element occurs separate out thereby overcome in the traditional technology slab process of cooling, alloying element returned molten insufficient and reduce the problem of alloying element utilization ratio when slab reheated.
Chinese patent 200880023157.9,200880023167.2,200880023586.6 discloses a kind of sheet-band continuous casting and rolling explained hereafter thickness that utilizes in the method for the micro-alloyed steel strip of 0.3-3mm.The method adopts C＜0.25%, Mn 0.20-2.0%, Si 0.05-0.50%, Al＜0.01%, Nb0.01-0.20%, V 0.01-0.20%, Mo 0.05-0.50% (Nb, V, Mo comprise a kind of at least) composition system, be 20-40% at the hot rolling draft, under ℃ processing condition of coiling temperature≤700, the microstructure of hot-rolled strip is bainite+acicular ferrite.This patent suppresses after the austenite hot rolling recrystallize to occur by adding alloying element, keeps the thick feature of thin strap continuous casting austenite crystal with raising hardening capacity, thereby has obtained the room temperature texture of bainite+acicular ferrite.This patent does not provide the temperature range that hot rolling is adopted.
The thin strap continuous casting low-carbon microalloy product made from steel that utilizes this method to produce, intensity is higher, and in above composition system scope, yield strength can reach 650MPa, and tensile strength can reach 750MPa, but that topmost problem is the unit elongation of product is not high.Cause the not high major cause of unit elongation to be: by the Cast Strip that thin band continuous casting technique obtains, austenite grain size is not only thick, and very inhomogeneous, and is little of tens microns, greatly to seven or eight hundred microns even millimeter magnitude.And thin band continuous casting technique hot rolling draft is no more than 50% usually, effect by the deformation crystal grain thinning is very little, if not by the recrystallization softening austenite crystal, thick inhomogeneous austenite can effectively not improved after hot rolling, also very inhomogeneous by the bainite+acicular ferrite structure that produces behind the thick inhomogeneous austenite phase transformation of size, so unit elongation is not high.Cause thus product to be used than the field of high-elongation at ask for something and be restricted, Punching Steel for example, automobile steel etc.
Chinese patent 02825466.X is also open, because the thin strap continuous casting product has the factors such as alloying elements such as having added Si, Cr, Ni, V, Nb in thick austenite crystal grain character, the Cast Strip or microalloy element, rolling speed are low, low rate under less than 1050 ℃ is rolling, and austenite recrystallization is only local after the hot rolling.The finished product be organized as the heterogene structure with coarse grain, unfavorable to the performance of product.This patent has proposed another and has utilized sheet-band continuous casting and rolling explained hereafter thickness in the method for the micro-alloyed steel strip of 1-6mm in order to improve the strong plasticity coupling of thin strap continuous casting micro-alloyed steel.The micro-alloyed steel composition system that the method adopts is C 0.02-0.20%, Mn 0.1-1.6%, Si0.02-2.0%, Al＜0.05%, S＜0.03%, P＜0.1%, Cr 0.01-1.5%, Ni 0.01-0.5%, Mo＜0.5%, N 0.003-0.012%, Ti＜0.03%, V＜0.10%, Nb＜0.035%, B＜0.005%, surplus are Fe and inevitable impurity.The hot-rolled temperature of Cast Strip in 1150-(Ar1-100) ℃ scope, corresponding austenitic area, the austenite ferrite two-phase region, perhaps ferrite area carries out hot rolling, the hot rolling draft is 15-80%.The method is behind the sheet-band continuous casting and rolling unit, designed the on-line heating system, the Heating temperature scope is 670-1150 ℃, purpose be so that the Cast Strip after different phase region hot rollings, after insulation for some time perfect recrystallization occuring, thereby makes steel band obtain preferably strong plasticity coupling.
Utilize this method to produce thin strap continuous casting low-carbon microalloy product made from steel, really can make steel band obtain good strong plasticity coupling, for example composition is C 0.048%, Mn 0.73%, and Si 0.28%, Cr0.07%, Ni 0.07%, and Cu 0.18%, and Ti 0.01%, Mo 0.02%, and S 0.002%, and P 0.008%, Al 0.005%, the steel band yield strength of N 0.0065% is 260MPa, and tensile strength 365MPa, unit elongation are 28%.But utilize this method to produce, need to when producing the line design, increase online heating system, and because the length of heat-up time depends on belt speed and process furnace length, process furnace must have sufficient length, the guarantee heating uniformity.This has not only increased cost of investment, also can significantly increase the floor space that sheet-band continuous casting and rolling produces line, has reduced the advantage of this product line.
Summary of the invention
The object of the present invention is to provide the high-strength steel band manufacture method of a kind of thin strap continuous casting low-carbon microalloy, by reasonable component and technological design, do not increasing in the production equipment situation, the online recrystallize of austenite after the realization Cast Strip hot rolling, refine austenite crystal grain also improves the austenite grain size homogeneity, improve simultaneously austenitic hardening capacity behind the recrystallize, obtain to distribute more uniformly that bainite adds acicular ferrite structure, thereby make product have simultaneously higher intensity and unit elongation.
For achieving the above object, technical scheme of the present invention is:
The high-strength steel band manufacture method of a kind of thin strap continuous casting low-carbon microalloy, it comprises the steps:
1) smelting, thin strap continuous casting
High-strength steel band chemical component weight per-cent is: C 0.01-0.25%, Si≤0.4%, Mn0.6-2.0%, P≤0.015%, S≤0.01%, N≤0.006%, O≤0.008%, B0.0005-0.004%; Also comprise among Nb, V, Ti, the Mo more than one, Nb 0.005-0.1%, V 0.005-0.1%, Ti 0.005-0.1%, Mo:0.05-0.5%, all the other are Fe and inevitable impurity;
Cast thickness is the Cast Strip of 1-5mm in double-roller continuous casting machine;
2) Cast Strip is cooled off, rate of cooling is greater than 20 ℃/s;
3) hot rolling
Hot rolling is carried out in the Cast Strip, and hot-rolled temperature is 1050-1250 ℃, and the hot rolling draft is 20-50%, hot rolling deformation rate＞20s
-1, the thickness of steel band is 0.5-3.0mm after the hot rolling; The online recrystallize of austenite occurs after the Band by Hot-rolling;
4) cool off, batch
Hot rolled strip is cooled off, batches, and rate of cooling is 10-80 ℃/s, and coiling temperature is 500-650 ℃.
The final microstructure that obtains steel band mainly is made of uniform bainite and acicular ferrite.
Further, described step 1) in, the content range of C is 0.01-0.1%, by weight percentage.
Described step 1) in, the content range of B is 0.0005-0.003%, by weight percentage.
Described step 1) in, the content range of Nb, V, Ti is 0.005-0.05%, or the content of Nb, V, Ti is 0.005-0.01%, by weight percentage.
Described step 1) in, the content range of Mo is 0.05-0.25%, by weight percentage.
Again, described step 3) in, hot-rolled temperature is 1100-1250 ℃, or hot-rolled temperature is 1150-1250 ℃; The hot rolling draft is 30-50%; Hot rolling deformation rate＞30s
-1
In addition, described step 4) in, the hot-rolled strip rate of cooling is 30-80 ℃/s; Coiling temperature is 500-600 ℃.
The fundamental difference of the present invention and aforementioned existing technique is, adopt different processing technology routines, control realizes the online recrystallize of austenite after the hot rolling, produces to have the steel band that uniform bainite adds acicular ferrite structure, thereby has good intensity and unit elongation coupling.
Technical conceive of the present invention is as follows:
(1) an amount of microalloy element that adds in soft steel, mainly bring into play the three aspects: effect:
The first is brought into play its solution strengthening effect, improves steel band intensity;
It two is by solute atoms towing austenite grain boundary, suppress to a certain extent Austenite Grain Growth, thereby refine austenite crystal grain promotes austenite recrystallization.Austenite grain size is more tiny, and the dislocation desity that produces during deformation is higher, and deformation stores can will be larger, thereby increases the recrystallize motivating force and promote the carrying out of recrystallization process; And Recrystallization is mainly at former big angle grain boundaries or near forming core it, so grain-size thinner (grain boundary area is larger), and Recrystallization nucleation is easier, thereby promotes the carrying out of recrystallization process;
It three is to improve austenitic hardening capacity behind the recrystallize, adds acicular ferrite structure to obtain bainite.
(2) suitably raising promotes austenite recrystallization at the hot-rolled temperature (Deformation recrystallization temperature) of austenitic area.Recrystallization nucleation rate and growth rate all are the growth (Yong Qilong work, micro-alloyed steel-physics and mechanics are metallurgical) of exponential type relation with the rising of deformation temperature, temperature is higher, and recrystallize more easily occurs.
(3) control hot rolling draft (deformation quantity) promotes austenite recrystallization in suitable scope.Deformation is the basis that recrystallize occurs, and is the motivating force of recrystallize---recrystallize owing to just recrystallize can occur after must surpassing certain motivating force, just can occur afterwards therefore only have above certain deformation quantity in the source of deformation storage energy.Deformation quantity is larger, and deformation stores can be larger, and deformation store can be larger, Recrystallization nucleation and growth rate are all larger, begin and finish recrystallize even at a lower temperature also can rapid enough ground.And, deformation quantity increases, also can reduce the grain-size behind the austenite recrystallization, this is because the Recrystallization nucleation rate is growth (the Yong Qilong work that exponential type concerns with the rising that deformation stores energy, micro-alloyed steel-physics and mechanics are metallurgical), therefore being conducive to obtain the product of more tiny γ → α phase transformation, all is favourable to the strong plasticity that improves steel band.
(4) the control deformation rate promotes austenite recrystallization in suitable scope.Increase deformation rate, will increase deformation and store energy, thereby increase the recrystallize motivating force, promote the carrying out of recrystallization process.
In chemical composition design of the present invention:
C:C is strengthening element most economical, the most basic in the steel, improves the intensity of steel by solution strengthening and precipitation strength.C separates out the requisite element of cementite in the 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 because the gap solid solution of C and plasticity and the toughness of separating out steel have larger harm, so C content can not be too high, and the intensity of steel remedies by suitable interpolation alloying element.The C content range that the present invention adopts is 0.01-0.25%.
Si:Si plays solution strengthening effect in steel, and adds Si in the steel and can improve purity of steel and deoxidation, but the Si too high levels can be damaged the welding property of steel.The Si content that the present invention adopts≤0.4%.
Mn:Mn is one of the most cheap alloying element of price, it has sizable solid solubility in steel, improve the intensity of steel by solution strengthening, substantially harmless to plasticity and the toughness of steel simultaneously, be the topmost strengthening element of intensity that improves steel in the C content situation reducing.But the Mn too high levels can be damaged welding property and the corrosion resistance of steel.The Mn content range that the present invention adopts is 0.6-2.0%.
P: P is harmful element in the steel under normal conditions, increases the cold shortness of steel, and welding property is degenerated, and reduces plasticity, and cold-bending property is degenerated.In the present invention, P controls as impurity element, its content≤0.015%.
S: S also is harmful element in the 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.In the present invention, S controls as impurity element, its content≤0.01%.
Nb: in four kinds of microalloy elements of Nb, V, Ti, Mo commonly used, Nb is the alloying element of austenite recrystallization after the strongest inhibition hot rolling.In the steel that traditional controlled rolling is used, generally all add Nb, the one, play the effect of reinforcement, the 2nd, austenite generation recrystallize after the inhibition hot rolling, the purpose of realization deformation refine austenite crystal grain.Nb can pass through the solute atoms drag mechanism, and the niobium carbonitrides Second Phase Particles pinning mechanism of separating out and effectively stop the migration of big angle crystal boundary and subgrain boundary, thereby stop significantly recrystallization process, it is more remarkable that wherein Second Phase Particles stops the effect of recrystallize.
In thin band continuous casting technique, because its unique steel band rapid solidification and quick cooling characteristic can make the alloy element Nb of interpolation mainly be present in the steel band with the solid solution attitude, even the steel band cool to room temperature does not almost observe separating out of Nb yet.Therefore, although the Nb element can suppress austenite recrystallization effectively, but only depend on solute atoms and do not bring into play Second Phase Particles be used for stoping recrystallize, very difficult under many circumstances, for example in the situation that deformation temperature is higher, deformation quantity is larger, even add the Nb element, recrystallize also can occur in austenite.
On the other hand, the Nb element of solid solution in steel can pull austenite grain boundary by solute atoms, suppresses to a certain extent Austenite Grain Growth, thus refine austenite crystal grain, and on this point, Nb is for promoting that recrystallize is favourable after the austenite hot rolling.
The present invention should bring into play the intensity of the solution strengthening effect raising steel of Nb, and reduce Nb is to the restraining effect of recrystallize again, and designing its content range is 0.005-0.1%.
Preferably, the content range of Nb is 0.005-0.05%, or 0.005-0.01%, and steel band can have more excellent intensity and plasticity proportioning.
V: in four kinds of microalloy elements of Nb, V, Ti, Mo commonly used, V is the most weak to the restraining effect of austenite recrystallization.In recrystallize controlled rolling steel, normally add V, both can play strengthening effect, smaller again comparatively speaking to the restraining effect of recrystallize simultaneously, the purpose of realization recrystallization softening austenite crystal.
In thin band continuous casting technique, V also mainly is present in the steel band with the solid solution attitude, even the steel band cool to room temperature does not almost observe separating out of V yet.Therefore, V element is very limited to the restraining effect of austenite recrystallization.Improve the intensity of steel at the solution strengthening effect that should bring into play alloying element, reduce again alloying element in the inhibiting situation of recrystallize, V is more satisfactory alloying element, design the most according to the invention.
On the other hand, the V element of solid solution in steel can pull austenite grain boundary by solute atoms, suppresses to a certain extent Austenite Grain Growth, thus refine austenite crystal grain, and on this point, V is for promoting that recrystallize is favourable after the austenite hot rolling.
It is 0.005-0.1% that the present invention adopts the content range of V.
Preferably, the content range of V is 0.005-0.05%, or 0.005-0.01%, and steel band can have more excellent intensity and plasticity proportioning.
Ti: in four kinds of microalloy elements of Nb, V, Ti, Mo commonly used, Ti inferior to Nb, but is higher than Mo, V to the restraining effect of austenite recrystallization.On this point, Ti is to promoting that austenite recrystallization is disadvantageous.But Ti has an outstanding advantage, and its solid solubility is very low, and the size that it can at high temperature form quite stable is about the Second Phase Particles TiN about 10nm, AUSTENITE GRAIN COARSENING in the time of can stoping soaking, therefore, in recrystallize controlled rolling steel, usually add trace Ti, refine austenite crystal grain.
In thin band continuous casting technique, Ti mainly is present in the hot steel band with the solid solution attitude, if the steel band cool to room temperature may be observed separating out of a little Ti.Therefore, the Ti element is limited to the restraining effect of austenite recrystallization.And, in the present invention, also to add the hardening capacity that B improves steel, by the fix N that separates out of Ti, be very important for the hardening capacity effect of bringing into play B.
On the other hand, the Ti element of solid solution in steel can pull austenite grain boundary by solute atoms, suppresses to a certain extent Austenite Grain Growth, thereby refine austenite crystal grain on this point, is favourable for recrystallize after the hot rolling of promotion austenite.
The present invention should bring into play the intensity of the strengthening effect raising steel of Ti, brings into play to a certain extent its solid N effect simultaneously, and reduce Ti is to the restraining effect of recrystallize again, and designing its content range is 0.005-0.1%.
Preferably, the content range of Ti is 0.005-0.05%, or 0.005-0.01%, and steel band can have more excellent intensity and plasticity proportioning.
Mo: in four kinds of microalloy elements of Nb, V, Ti, Mo commonly used, Mo also is weak to the restraining effect of austenite recrystallization comparatively speaking, only is higher than V.
In thin band continuous casting technique, Mo also mainly is present in the steel band with the solid solution attitude, even the steel band cool to room temperature does not almost observe separating out of Mo yet.Therefore, the Mo element is very limited to the restraining effect of austenite recrystallization.
On the other hand, the Mo element of solid solution in steel can pull austenite grain boundary by solute atoms, suppresses to a certain extent Austenite Grain Growth, thus refine austenite crystal grain, on this point, for promoting that austenite recrystallization is favourable.
It is 0.05-0.5% that the present invention adopts the content range of Mo.
Preferably, the content range of Mo is 0.05-0.25%, and steel band can have more excellent intensity and plasticity proportioning.
B:B improves the very competent of steel hardenability, and the B of minute quantity just can significantly improve the hardening capacity of steel, and effect of its raising hardening capacity is the hundred times of manganese, molybdenum, chromium, nickel and even thousands of times.Why B can improve the hardening capacity of steel, its reason be B atom segregation in austenite grain boundary, suppressed the formation of proeutectoid ferrite.The hardening capacity effect of B can descend along with the increase of carbon content in the steel and alloying element content, Gu the very suitable hardening capacity that is used for improving low-carbon micro steel-alloy of B.Only have the B competence exertion hardening capacity effect of solid solution attitude, and the avidity of the C in B and the steel, O, N, particularly N is very strong.Generate corresponding compound if B and C, O, N react, especially reacting with N generates BN, just inoperative to improving hardening capacity, and this is because the compound that reaction generates may preferentially become the nucleation site of ferritic transformation.For this reason, must control B content at optimum range, add simultaneously with the stronger Ti of N avidity and come solid N, control in addition N, O content also is very important.
Thin band continuous casting technique has unique steel band rapid solidification and quick cooling characteristic, is unfavorable for separating out of B, keeps solid solution condition and be conducive to B, thereby effectively brings into play the effect that it improves hardening capacity.
As previously mentioned, the present invention is intended to by the online recrystallize of austenite after the hot rolling of Cast Strip, and refine austenite crystal grain also improves the austenite grain size homogeneity, and this helps the uniform microstructure of the final acquisition of steel band, improves the plasticity of steel band.But compare with the thick austenite crystal that does not pass through recrystallize, the refine austenite crystal grain hardening capacity of recrystallize can reduce, and is easier to change into polygonal ferrite and perlite in follow-up process of cooling, and the intensity of corresponding steel band can decrease.Add microalloy element B, can significantly improve the hardening capacity of steel, even austenite is through recrystallization softening, it is in subsequent cooling process, still than being easier to change into bainite and acicular ferrite structure, the thick austenitic transformation by the non-recrystallization bainite and the acicular ferrite structure that come are more even, thereby have good intensity and unit elongation coupling.
For achieving the above object, to adopt the content range of B be 0.0005-0.004% in the present invention.
Preferably, the content range of B is 0.0005-0.003%.
N: similar with the C element, the N element can improve by the gap solid solution intensity of steel, and still, the gap solid solution of N has larger harm to plasticity and the toughness of steel, so N content can not be too high.And, reduce N content, be conducive to B and keep solid solution condition.The N content that the present invention adopts≤0.006%.
O: O content directly determines inclusion content in the steel, in order to control the amount of steel inclusion, and the reaction that reduces O and B, the O content that the present invention adopts≤0.008%.
In manufacturing process of the present invention:
Thin strap continuous casting, namely molten steel is introduced within the molten bath that the crystallization roll of a pair of relative rotation and internal water cooling and side seal board form, and goes out the Cast Strip that thickness is 1-5mm through direct pouring behind the rapid solidification.
Cast Strip cooling, the Cast Strip from the crystallization roll continuous casting out after, through confined chamber, in confined chamber, cool off.For fast reducing Cast Strip temperature, with prevent austenite crystal at high temperature grow up too fast, control the Cast Strip rate of cooling greater than 20 ℃/s.The air cooling mode is adopted in Cast Strip cooling, and 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 type, pressure, the flow of control cooling gas, and nozzle is realized the control to the Cast Strip rate of cooling to the distance between the Cast Strip etc.
The online hot rolling in Cast Strip, controlled rolling temperature are 1050-1250 ℃, and purpose is austenite generation perfect recrystallization after the realization hot rolling, refine austenite crystal grain.In chemical composition design of the present invention, Nb, V, Ti, Mo, B alloying element have been added, as previously mentioned, the interpolation of alloying element has certain restraining effect to austenite recrystallization, although this restraining effect can reduce under thin band continuous casting technique, but carry out hot rolling under 1050 ℃ being lower than, be difficult to occur austenite perfect recrystallization.And carry out hot rolling under 1250 ℃ being higher than, because the band hardness of steel is low, so that course of hot rolling is difficult to control.Therefore the present invention selects 1050-1250 ℃ of rolling temperature scope.Preferably, the hot-rolled temperature scope is 1100-1250 ℃, or 1150-1250 ℃.Control hot rolling draft is 20-50%, and the hot rolling draught increases can promote austenite recrystallization, refine austenite crystal grain, and preferred, hot rolling draft scope is 30-50%.Control hot rolling deformation rate＞20s
-1, deformation rate increases can promote austenite recrystallization, preferred deformation rate scope is＞30s
-1The thickness range of steel band is 0.5-3.0mm after the hot rolling.
The hot-rolled strip cooling adopts the modes such as aerosol cooling, laminar flow cooling or spraying cooling that hot-rolled strip is cooled off.The flow of water coolant, flow velocity, and water outlet position etc. can regulate, thus realize the control to the hot-rolled strip rate of cooling.The rate of cooling of control hot-rolled strip is 10-80 ℃/s, cooling hot-rolledly takes needed coiling temperature to.Rate of cooling is one of important factor that affects the actual beginning of austenite phase transformation temperature, rate of cooling is larger, the actual beginning of austenite phase transformation temperature is lower, what obtain after the phase transformation like this organizes grain-size also just more tiny, obdurability to the raising steel band all is favourable, and preferred rate of cooling scope is 30-80 ℃/s.
Hot-rolled strip batches, and the coiling temperature of control hot-rolled strip is 500-650 ℃, so that hot-rolled strip has bainite and acicular ferrite structure's feature.Preferably, the coiling temperature scope is 500-600 ℃.
Compare with existing patent 200880023157.9,200880023167.2,200880023586.6, difference of the present invention is: Chinese patent 200880023157.9,200880023167.2,200880023586.6 is by adding the recrystallize after microalloy element suppresses the austenite hot rolling, the high-hardenability that keeps thick austenite crystal, make steel band obtain bainite and acicular ferrite structure, intensity is higher, and unit elongation is lower.The present invention is by control microalloy element Nb, V, Ti, Mo addition, hot-rolled temperature, hot rolling draft, hot rolling deformation rate, the online recrystallize of austenite after the realization hot rolling, refine austenite crystal grain; By adding alloying element B, improve the hardening capacity of the refine austenite crystal grain of recrystallize, make steel band obtain distribution more uniformly bainite and acicular ferrite structure, have good strong plasticity coupling.
Compare with existing patent 02825466.X, difference of the present invention is: austenite generation recrystallize is realized by increasing online heating system after the patent 02825466.X control hot rolling.Austenite generation recrystallize was realized by control microalloy element addition, hot-rolled temperature, hot rolling draft, hot rolling deformation rate after the present invention controlled hot rolling.
Beneficial effect of the present invention:
The present invention is by reasonable component design in the thin strap continuous casting production process, reasonably hot-rolled temperature, hot rolling draft, the design of hot rolling deformation rate, do not increasing in the production equipment situation, the online recrystallize of austenite after the control realization Cast Strip hot rolling, improve simultaneously the hardening capacity of the refine austenite crystal grain of recrystallize, produce and have the bainite that is evenly distributed and the steel band of acicular ferrite structure, thereby have good intensity and unit elongation coupling.
Description of drawings
Fig. 1 is thin band continuous casting technique process schematic diagram of the present invention.
Embodiment
Referring to Fig. 1, thin band continuous casting technique process of the present invention is: wrap greatly the molten steel process long nozzle 2 in 1, tundish 3 and submerged nozzle 4, be poured into by two counterrotating water-cooled crystallization roll 5a, 5b and side seal board 6a, in the molten bath 7 that 6b forms, cooling through the water-cooled crystallization roll forms 1-5mm Cast Strip 11, the Cast Strip is through secondary cooling apparatus 8 its rate of cooling of control in confined chamber 10, by swing guide 9, pinch roll 12 is delivered to hot rolls 13 with the Cast Strip, form the hot-rolled strip of 0.5-3mm after the hot rolling, through three refrigerating units 14, hot-rolled strip enters reeling machine 15 afterwards again.After coil of strip taken off from reeling machine, naturally cool to room temperature.
The molten steel of embodiment of the invention 1-10 all adopts electrosmelting to obtain, and specific chemical composition is as shown in table 1.The Cast Strip thickness that obtains behind the thin strap continuous casting, the Cast Strip rate of cooling, hot-rolled temperature, the hot rolling draft, the hot rolling deformation rate, hot-rolled strip thickness, the hot-rolled strip rate of cooling, the processing parameters such as coiling temperature, and the tensile property behind the hot-rolled strip cool to room temperature sees Table 2.
As can be seen from Table 2, the yield strength 〉=340MPa of steel band of the present invention, tensile strength 〉=450MPa, unit elongation 〉=15% has good strong plasticity coupling.
Claims (14)
1. high-strength steel band manufacture method of thin strap continuous casting low-carbon microalloy, it comprises the steps:
1) smelting, thin strap continuous casting
Smelt, high-strength steel chemical component weight per-cent is: C 0.01-0.25%, Si≤0.4%, Mn0.6-2.0%, P≤0.015%, S≤0.01%, N≤0.006%, O≤0.008%, B0.0005-0.004%; Also comprise among Nb, V, Ti, the Mo more than one, Nb 0.005-0.1%, V 0.005-0.1%, Ti 0.005-0.1%, Mo 0.05-0.5%, all the other are Fe and inevitable impurity;
Cast thickness is the Cast Strip of 1-5mm in double-roller continuous casting machine;
2) Cast Strip is cooled off, rate of cooling is greater than 20 ℃/s;
3) hot rolling
Hot rolling is carried out in the Cast Strip, and hot-rolled temperature is 1050-1250 ℃, and the hot rolling draft is 20-50%, hot rolling deformation rate＞20s
-1, the thickness of steel band is 0.5-3.0mm after the hot rolling; The online recrystallize of austenite occurs after the Band by Hot-rolling;
4) cool off, batch
Hot rolled strip is cooled off, batches, and rate of cooling is 10-80 ℃/s, and coiling temperature is 500-650 ℃;
The final microstructure that obtains steel band mainly is made of uniform bainite and acicular ferrite.
2. the high-strength steel band manufacture method of thin strap continuous casting low-carbon microalloy as claimed in claim 1, it is characterized in that: described step 1), the content range of C is 0.01-0.1%, by weight percentage.
3. the high-strength steel band manufacture method of thin strap continuous casting low-carbon microalloy as claimed in claim 1 or 2, it is characterized in that: described step 1), the content range of B is 0.0005-0.003%, by weight percentage.
4. such as claim 1 or the high-strength steel band manufacture method of 2 or 3 described thin strap continuous casting low-carbon microalloys, it is characterized in that: described step 1), the content range of Nb, V, Ti is 0.005-0.05%, or, the content of Nb, V, Ti is 0.005-0.01%, by weight percentage.
5. as claimed in claim 1 or 2 or 3 or 4 the high-strength steel band manufacture method of thin strap continuous casting low-carbon microalloy, it is characterized in that: described step 1), the content range of Mo is 0.05-0.25%, by weight percentage.
6. the high-strength steel band manufacture method of thin strap continuous casting low-carbon microalloy as claimed in claim 1, it is characterized in that: described step 3), hot-rolled temperature is 1100-1250 ℃, or hot-rolled temperature is 1150-1250 ℃.
7. such as claim 1 or the high-strength steel band manufacture method of 6 described thin strap continuous casting low-carbon microalloys, it is characterized in that: described step 3), the hot rolling draft is 30-50%.
8. such as claim 1 or the high-strength steel band manufacture method of 6 or 7 described thin strap continuous casting low-carbon microalloys, it is characterized in that: described step 3), hot rolling deformation rate＞30s
-1
9. the high-strength steel band manufacture method of thin strap continuous casting low-carbon microalloy as claimed in claim 1, it is characterized in that: described step 4), the hot-rolled strip rate of cooling is 30-80 ℃/s.
10. such as claim 1 or the high-strength steel band manufacture method of 9 described thin strap continuous casting low-carbon microalloys, it is characterized in that: described step 4), coiling temperature is 500-600 ℃.
11. the high-strength steel band manufacture method of thin strap continuous casting low-carbon microalloy as claimed in claim 1 is characterized in that: the thickness of described steel band is less than 3mm or less than 2mm or less than 1mm.
12. such as claim 1 or the high-strength steel band manufacture method of 11 described thin strap continuous casting low-carbon microalloys, it is characterized in that: the yield strength of described steel band is at least 340MPa or is at least 410MPa or is at least 480MPa or is at least 550MPa or is at least 620MPa or is at least 680MPa.
13. such as claim 1 or the high-strength steel band manufacture method of 11 described thin strap continuous casting low-carbon microalloys, it is characterized in that: the tensile strength of described steel band is at least 450MPa or is at least 520MPa or is at least 585MPa or is at least 620MPa or is at least 680MPa or is at least 750MPa.
14. such as claim 1 or the high-strength steel band manufacture method of 11 described thin strap continuous casting low-carbon microalloys, it is characterized in that: the unit elongation of described steel band is more than 15% or is at least 18% or be at least 22%.
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| CN111041365A (en) * | 2019-12-25 | 2020-04-21 | 江苏沙钢集团有限公司 | 500-700 MPa-level economical high-strength steel based on thin strip casting and rolling and production method thereof |
| CN112203781A (en) * | 2018-04-06 | 2021-01-08 | 纽科尔公司 | High friction rolling of thin metal strip |
| CN112522582A (en) * | 2019-09-19 | 2021-03-19 | 宝山钢铁股份有限公司 | Boron-containing high-strength high-hole-expansion steel and manufacturing method thereof |
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| CN114990453A (en) * | 2022-05-26 | 2022-09-02 | 天津荣程联合钢铁集团有限公司 | Titanium microalloyed low-alloy high-strength steel and production process thereof |
| CN115029627A (en) * | 2022-05-17 | 2022-09-09 | 宁波祥路中天新材料科技股份有限公司 | Hot forming steel with tensile strength not lower than 1500MPa produced by TSR production line and method |
| CN115094346A (en) * | 2022-07-04 | 2022-09-23 | 宁波祥路中天新材料科技股份有限公司 | Hot rolled strip steel with tensile strength not lower than 1200MPa produced by TSR production line and method |
| CN115478203A (en) * | 2022-09-27 | 2022-12-16 | 张家港中美超薄带科技有限公司 | Method for producing hot-rolled thin strip steel based on thin strip casting and rolling and ultrahigh-strength part |
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| CN112203781B (en) * | 2018-04-06 | 2023-10-31 | 纽科尔公司 | High friction rolling of thin metal strips |
| CN112522582A (en) * | 2019-09-19 | 2021-03-19 | 宝山钢铁股份有限公司 | Boron-containing high-strength high-hole-expansion steel and manufacturing method thereof |
| CN112522596A (en) * | 2019-09-19 | 2021-03-19 | 宝山钢铁股份有限公司 | High-strength high-hole-expansion steel based on scrap steel and production method thereof |
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| CN112522593B (en) * | 2019-09-19 | 2022-06-24 | 宝山钢铁股份有限公司 | Thin 30CrMo hot rolled steel plate/strip and production method thereof |
| CN111041365A (en) * | 2019-12-25 | 2020-04-21 | 江苏沙钢集团有限公司 | 500-700 MPa-level economical high-strength steel based on thin strip casting and rolling and production method thereof |
| CN115029627A (en) * | 2022-05-17 | 2022-09-09 | 宁波祥路中天新材料科技股份有限公司 | Hot forming steel with tensile strength not lower than 1500MPa produced by TSR production line and method |
| CN114990453A (en) * | 2022-05-26 | 2022-09-02 | 天津荣程联合钢铁集团有限公司 | Titanium microalloyed low-alloy high-strength steel and production process thereof |
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