CN101418363A - Method for producing low carbon and high ductility X60/X65pipeline steel - Google Patents
Method for producing low carbon and high ductility X60/X65pipeline steel Download PDFInfo
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Abstract
The invention discloses a method for producing low-carbon and high-toughness X60/X65 pipeline steel, wherein molten iron of a blast furnace is poured into a revolving furnace and added with scrap steel for general smelting, and the slag amount at the initial stage of smelting is controlled; argon bottom blowing is performed during the whole process; when the final temperature of molten steel and the compositions are qualified, the molten steel is tapped off, and the tapping time and the total slag amount are controlled; lime, predissolved slag and a slag regulator are added into a ladle; the molten steel enters into an argon blowing station for argon blowing treatment, comes out of the argon blowing station after the temperature and acid-soluble aluminum reach the standard, and is sent to a refining station for desulfurization and mcroalloying treatment, and the compositions and the alkalinity of refined slag are well controlled; the molten steel is poured into an intermediate ladle after the temperature and the compositions of the molten steel meet the requirements, and the superheat degree of the molten steel in the intermediate ladle is controlled; the molten steel is sent into a continuous casting machine and converted into a casting blank; the casting blank is sent into a soaking pit the temperature of which is more than or equal to 1,000 DEG C, and heated at a temperature of between 1,150 and 1,160 DEG C, and the tapping temperature is between 1,120 and 1,150 DEG C; and the molten steel after descaling is rolled into a plate blank by a finishing mill at a finishing temperature of between 860 and 880 DEG C, subjected to laminar cooling, and coiled into a coiled sheet for the pipeline steel at a temperature of between 600 and 620 DEG C.
Description
Technical field
The present invention relates to a kind of production method of line steel hot rolling coiled sheet, relate in particular to the method for a kind of application oxygen top bottom blowing converter (BOF) → CSP (CSP) explained hereafter high ductility X 60/X/X65 pipe line steel with hot-rolled sheet coil.
Background technology
In recent years, along with the new discovery of China's oil and Sweet natural gas and exploitation and city progressively adopt piped gas (or Sweet natural gas) to substitute the situation of bottled Sweet natural gas, the pipe line steel demand that is used for transport gas sharply increases, be significant work-ing life so research and develop corrosion-resistant pipeline steel and improve pipe line steel, especially utilize oxygen coverter → CSP processing line to produce the pipe line steel that satisfies market demand and have more meaning.
Anshan Iron and Steel Company has " exploitation of high-ductility pipe line steel X60-X65 hot-rolled sheet coil ", and the few perlite microalloyed steel of C-Mn-Nb-V system is adopted in its composition design, and carbon content is less than 0.10% (wt), (Nb+V+Ti)≤0.15% (wt); Technological design adopts Clean Steel to smelt continuous casting technology and thermo-mechanical rolling technology (TMCP).Material has good low-temperature flexibility, and-20 ℃ Charpy-V impact power can reach more than the 200J.
" oil and gas is carried the production technology with X42-X65 high tenacity hot rolling coiled sheet and welded tube " of Baoshan Iron and Steel Company, the pipe line steel of being reported are steel series of tool representative in the microalloy control steel.The X60 of Baosteel production and X65 have made pipeline welded tubes such as one capital, Shan with the import coiled sheet, its quality and performance can be quite in kind with import.
" CSP flow process low alloy steel, the exploitation of micro-alloyed steel production technology and application " of Baotou Iron and Steel Company, project is carried out deep in a large number experimental study and technology development work to the physical metallurgy characteristics of continuous casting and rolling technique of sheet bar (being CSP technology), the theory and the technical problem of producing mixed crystal, banded reason, successfully solved the mixed crystal problem of CSP flow process production Nb microalloyed steel, grasp the core technology of thin slab tandem rolling flow process microalloying and TMCP technology, developed complete, supporting CSP flow process Nb micro-alloyed steel controlled rolling production technology.
" development of steel of high tenacity line of pipes " of Wuhan Iron and Steel Company, use microalloying, external refining, controlled rolling and controlled cooling technology etc. such as V, Nb, Ti and successfully develop X52H, X60 and X65H pipe line steel, determined rational chemical, smelting and CONTROL PROCESS.
Publication number is " methods of a kind of low cost production * 65 pipe line steels " of CN101082106 (pearl steel company), and it is 6.0～10.0mm that this method adopts production thickness such as the controlled rolling in EAF+LF steel-smelting technology, thin slab high efficiency continuous casting, hot continuous rolling unit recrystallization zone+non-recrystallization district and controlled cooling technology, meet the X65 line steel hot rolling coiled sheet of API Spec 5L standard.
Publication number is 1351189 (metal institutes of the Chinese Academy of Sciences) " a kind of Ultra-low carbon high tenacity anti-H 2 S steel for gas delivering pipeline ", its main chemical compositions (wt%): C=0.02～0.04, Si=0.15～0.35, Mn=1.4～1.6, P＜0.003, S=0.0007, all the other are Fe.Corresponding TMCP is ℃ (finish to gauge) → 500～400, ℃ (rolling) → 900～830, ℃ (open rolling) → 1000～950,1200 ℃ of (heating) → 1150 ℃ (cold eventually), 15～30 ℃/S (water-cooled).Microstructure adds the M/A constituent element for acicular ferrite AF adds a spot of quasi-polygonal ferrite.
Publication number is 1811002 (Baoshan Iron and Steel Companies) " X 65 pipeline steel for use in acid condition and manufacture method thereof ", and its composition is (wt%) C=0.02～0.05, Si=0.10～0.50, Mn=1.20～1.50, P=0.004～0.012, S≤0.002, Nb=0.05～0.07, Ti=0.005～0.025, Mo=0.05～0.195, Cu≤0.35, Ni≤0.35, N≤0.008, Ca=0.0015～0.0045, Ca/s 〉=2.0.Its manufacture method is: (a) converter or electrosmelting, (b) external refining (comprising that LF desulfurization, RH vacuum outgas, Ca handle), (c) continuous casting, (d) (hot rolling, roughing final temperature are 840～1020 ℃ in controlled rolling, the finish rolling final temperature is 780～840 ℃), (e) batch (coiling temperature of coiled sheet is 500～580 ℃).The impelling strength that when having anti-HIC performance, also has better anti-dynamic tear resistance and Geng Gao.
Document " continuous casting process of EAF-CSP flow process Nb-microalloying pipe line steel " (Zhuan Hanzhou/wide steel company); adopt niobium (Nb) micro-alloying technology successfully to develop pipe line steel X52 and X56; in conjunction with CSP sheet blank continuous casting process characteristic, explored one and overlapped teeming temperature system, crystallizer protecting residue, continuous casting pulling rate and the process control parameters such as crystallizer heat flow density coupling and secondary cooling curve that are fit to contain niobium steel sheet base continuous casting.
Document " development research of EAF-CSP flow process Nb microalloy steel for pipeline " (Zhuan Hanzhou/pearl steel company) utilizes Nb-Ti combined microalloying technology, has successfully developed the X60 pipe line steel of 9.50mm thickness in the EAF-CSP flow process with 60mm thickness strand.Exploitation contain that niobium X60 pipe line steel homogeneous microstructure is tiny, 11.5～12.0 grades of grain fineness numbers, have good toughness and tenacity and good welding property.
Document " development and the application of Anshan iron and steel plant X60/X65 line steel hot rolling coiled sheet " (Anshan iron and steel plant company), the high-intensity high-tenacity pipe line steel X60 hot-rolled sheet coil of developing adopts the few perlitic steel design of C-Mn-Nb-V system, carbon content is less than 0.10%, its technological design adopts Clean Steel to smelt continuous casting process and thermo-mechanical rolling technology (TMCP), has high strength, high tenacity and good welding property.
Document " Anshan iron and steel plant contains the exploitation of niobium pipeline steel and low-carbon bainite steel ", also smelt continuous casting process and thermo-mechanical rolling technology (TMCP) with Clean Steel and develop and contain senior pipe line steel of Nb-microalloying and ultra-low-carbon bainite steel, its product has high strength and high tenacity and good welding property etc.
Summary of the invention
The object of the present invention is to provide a kind of production method with low carbon and high ductility pipe line steel of anti-fatigue performance, corrosion resistance nature and good welds performance and processing characteristics.
For achieving the above object, the technical solution used in the present invention is: the production method of a kind of low carbon and high ductility pipe line steel of the present invention, and technical process is:
Oxygen top bottom blowing converter (BOF) smelting → Argon station blowing → LF stove refining desulfuration → sheet billet continuous casting → roller bottom type soaking pit heating → finishing tandem rolling unit is rolling → and laminar flow cools off → batches, surface quality inspection → packing warehouse-in.
Blast-melted (or in the hot metal mixer molten iron) poured in 100 tons of oxygen top bottom blowings converter (BOF) stove, and (generally be controlled at 3～5%wt), the molten iron of pouring converter into requires P≤0.10% (wt), S≤0.04% (wt) to be blended into a certain proportion of steel scrap.Add lime, fluorite or rhombspar and carry out the routine smelting in the converter stove, omnidistance BOTTOM ARGON BLOWING (Ar) guarantees that the bottom blowing stirring is good simultaneously.
Carry out dephosphorization when the converter steelmaking initial stage is carried out the oxidation sweetening process, reach at phosphor partition ratio (P)/[P]=100 o'clock, the quantity of slag is controlled at 70～100kg/t
SteelIn converter, add rhombspar to produce a large amount of CO at the steel-making initial stage
2Gas forms a malleation layer and stops molten steel to inhale nitrogen from atmosphere, guarantees low nitrogen content in the molten steel.
Tapping before measurement dimension water temp, chemical ingredients in the sampling analysis steel.When Molten Steel End Point T=1670～1690 ℃ and molten steel terminal point composition (wt%): [C]≤0.04, [P]≤0.010, [S]≤0.030, and guarantee residual element composition (wt%) in the steel: [Cu]≤0.08, [As]≤0.03, [Sn]≤0.02, (Cu+5As+8Sn)≤0.3 o'clock tapping, tap is controlled at 100 ± 5 tons/stove.
At preceding about 30 seconds blowing argon gas in ladle of converter tapping.
Guarantee in the tapping process that the tap hole situation is intact, the tapping time is 3～5min, and the control tap hole entrainments slag down, and the quantity of slag is controlled at 3.0～5.0kg/t under the converter tapping
Steel
In ladle molten steel, add lime 5.0～6.0kg/t at tapping process
Steel, pre-melted slag 2.0～3.0kg/t
Steel, slag supplying agent 1.5～2.5kg/t
SteelTapping process adds the wash heat desulfurization of tapping of raw materials such as lime powder, fluorite and aluminium powder in ladle molten steel, the tapping process desulfurization degree can reach about 34%.
Sending the Argon station that molten steel is carried out Argon the ladle of filling molten steel handles.The omnidistance Argon (Ar) of ladle, Argon pressure is 0.3～0.4MPa.Ladle advances thermometric behind the Argon 3min of Argon station, the sampling analysis molten steel composition, and feed aluminum steel according to molten steel composition and transfer aluminium and adjust other composition.After liquid steel temperature 〉=1570 ℃ and composition were up to standard, ladle went out the Argon station and send LF stove refining station.
Molten steel after Argon is handled send LF stove refining station that molten steel is carried out refining treatment (as desulfurization etc.), and [Als] that will advance the converter molten steel of LF stove refining station earlier is transferred to 0.020～0.004% (wt).
After converter molten steel advances LF stove refining station, big argon gas (Ar) flow with 500～600NL/min stirs 1～2min earlier, so that the change slag, the blowing argon gas flow remains on 200～300NL/min during feeding temperature-raising, and the blowing argon gas flow is increased to 400～500NL/min during desulfurization (S).The exposed diameter of the top of the slag is less than 100mm during the soft blow argon, and the soft blow argon time is greater than 6min.Normal Argon (Ar) pressure in LF stove refining station is 0.3～0.4MPa, but maximum Argon pressure is no more than 0.8MPa.
When the refining of LF stove, in molten steel, add lime, pre-melted slag and slag supplying agent and carry out residue adjustment, with the quaternary basicity (CaO+MgO/SiO of bits according to the sulphur content in slag condition and the molten steel
2+ Al
2O
3) be controlled at 2.0, i.e. R=2.0, and in the control slag iron protoxide and manganese oxide weight percent content sum less than 1.0%, i.e. (FeO+MnO)＜1.0% (wt).
Because of the liquidus temperature of pipe line steel steel grade of the present invention is 1523 ℃, so molten steel is controlled at temperature about 1600 ℃ when the desulfurization of LF stove refining station and is advisable, out-station temperature to the first stove molten steel that goes on foot operation (go up continuous caster) down is controlled at 1575～1585 ℃ simultaneously, and the molten steel out-station temperature of each heat can be controlled in 1565～1575 ℃ of scopes in casting process.
Through LF stove molten steel after refining composition (wt%) be: [C]≤0.06, [Si]=0.20～0.35, [Mn]=1.2～1.4, [Nb]=0.02～0.04, [Ti]=0.015～0.030, [V]=0.02～0.04, [P]≤0.020, [S]≤0.008, [Als]=0.025～0.050 molten steel are gone into the continuous casting tundish, are controlled at 0.025～0.045% (wt) but connect [Als] that water the first stove molten steel.The weight percent of fusion aluminium in selected [Als] expression molten steel.
Pour into the continuous casting tundish through LF stove molten steel after refining, measure liquid steel temperature when middle Baogang water waters 10 tons and 14 ton hours, the superheating temperature of control molten steel is 25～35 ℃ scope.Molten steel surface covers low-carbon steel protecting slag in casting process.
Employing is stretched into the formula mouth of a river crystallizer that continuous casting tundish molten steel injects continuous caster is carried out continuous casting of molten steel, can regulate cooling curve according to pulling rate and liquid steel temperature in the continuous casting of molten steel process, selects vibration curve according to negative slip time, negative slip rate and depth of chatter mark.
Strand behind the continuous casting is sent into soaking in the soaking pit, strand charging temperature 〉=1000 ℃, and the Heating temperature of strand in soaking pit is not less than 1150 ℃, and as when producing the Nb micro-alloyed steel, Soaking Pit Temperature remains on 1100～1150 ℃.The strand head and tail temperature difference is ± 10 ℃, and the strand tapping temperature is controlled at 1120～1150 ℃.
Strand from soaking pit after the heating is removed the iron scale on surface with the high-pressure water descaling machine, and the intake pressure of the high pressure descaling water of scale breaker is that 160～200Pa, top hole pressure are 200～300Pa, also can adjust according to field condition.
Strand after surperficial de-scaling enters the finishing tandem rolling unit of being made up of seven frames and is rolled, control the rolling load (KN) or the draft (%) of each frame well, draft 〉=45% as the first frame F1, the draft of the second frame F2 〉=45%, it is rolling that frame is got rid of in the 4th frame F4 or the 5th frame F5 implementation, and the draft of other frame is by system's automatic setting.The steel billet temperature that is rolled out by the 7th frame F7 is controlled at 860～880 ℃.Steel plate (cooling mode is selected the A pattern) after the laminar flow cooling is batched by reeling machine and becomes coiled sheet, and coiling temperature is controlled at 600～620 ℃.
A kind of method that adopts converter → sheet blank continuous casting roll process production flow line steel that adopts that as above technical scheme provides compared with prior art, technique effect is:
1. be that 2,400,000 tons CSP production line enterprise research and development are produced X60, X65 pipeline steel hot rolled steel plate volume and be can be enterprise every year and increase about 1,500 ten thousand yuan of profits to a yearly capacity, the user's that offers line steel hot rolling coiled sheet composition homogeneous microstructure, stable performance, surface quality be good, all conform to quality requirements.
2. on BOF-LF～CSP flow process, successfully develop X60～X65 series pipe line steel, the BOF-LF-CSP flow process further is optimized, lay a solid foundation, provide experience, accelerated tempo of development for the exploitation other products.
3. enlarged the product scope of CSP flow process.
Embodiment
The specific embodiment of the present invention is described in further detail below in conjunction with implementing.
The production method of a kind of low carbon and high ductility pipe line steel of the present invention is divided into following several sections:
1. the composition of low-carbon microalloyed pipe line steel design;
2. rolling, the laminar flow cooling of converter smelting, molten steel Argon (Ar) processing, the refining of LF stove, continuous caster continuous casting, soaking pit heating, scale breaker de-scaling, hot continuous rolling unit, reeling machine batches becomes coiled sheet.
Composition design (wt%) for the X60 pipe line steel is: C≤0.06, Si=0.20～0.35, Mn=1.20～1.40, P≤0.020, S≤0.008, Nb=0.03～0.05, V=0.03～0.05, Ti=0.015～0.03, Als=0.015～0.035 and N＜50ppm; And for the composition design (wt%) of X65 pipe line steel be: C≤0.06, Si=0.20～0.35, Mn=1.20～1.40, P≤0.015, S≤0.008, Nb=0.04～0.06, V=0.03～0.05, Ti=0.02～0.04, Als=0.015～0.035 and N＜50ppm.
1. the carbon in the pipe line steel (C) content being controlled at below 0.06% (wt) is C＜0.06%, and low carbon content can improve toughness, plasticity and the welding property of pipe line steel, and low carbon content also produces favourable influence to segregation.C when pipe line steel〉0.06% (wt), Mn〉during 1.10% (wt), increase carbon content and will be directed at the anti-hydrogen induced cracking of pipe line steel (HIC) ability drop, the responsive rate of its crack length rate and crackle all increases with the raising of manganese content.Segregation line is directly relevant in the deterioration of HIC performance and the steel, and the carbon content in the pipe line steel is reduced to the improvement that certain degree helps carbon segregation.As C〉during 0.06% (wt), the segregation of manganese and phosphorus aggravation is in order to reduce the segregation of phosphorus (P), carbon content in the need assurance pipe line steel is less than 0.06%, be C≤0.06% (wt), the carbon content in the molten steel is controlled at below 0.04% when converter tapping for this reason, i.e. [C]≤0.04%.Improve the hit rate of converter tapping simultaneously and reduce after-blow.
2. sulphur (S) can reduce the low-temperature impact toughness of pipe line steel, is the principal element that influences anti-HIC ability of pipe line steel steel and resisting sulfide stress corrosion crack (SSC) ability.When sulphur content in the steel greater than 0.005% when (be S〉0.005%wt), along with the susceptibility of the hydrogen induced cracking (HIC) of the increase steel of sulphur content in the steel significantly increases; (when being S＜0.002%wt), the hydrogen induced cracking of steel (HIC) obviously reduces, even can ignore HIC less than 0.002% and when sulphur content in the steel.So the sulphur content in the assurance pipe line steel is 50 * 10
-6Below (being S＜0.005%) can reduce the formation of sulphur band, improve the ability of the anti-HIC of pipe line steel.
3. phosphorus (P) is a kind of easy segregation element in pipe line steel, phosphorus has a negative impact to the welding property of pipe line steel, phosphorus can also significantly reduce the low-temperature impact toughness of steel and improve the ductile-brittle transition temperature of steel, it is cold short that steel pipe is taken place, especially for the high grade pipe line steel that uses under the low temperature environment, when phosphorus content in the steel can aggravate the segregation of phosphorus greater than 0.015% when (P〉0.015%), thus converter molten steel in molten steel after the refining of LF stove [P]≤0.016% for well.
4. nitrogen (N) increases the weight of the timeliness of steel, the cold-forming property of reduction steel, causes the welded heat affecting zone embrittlement, aggravates the cold short of steel.Nitride can decompose in argon union-melt weld heat affected zone (HAZ), causes free hydrogen richness to increase, especially near weld seam.Nitrogen content increases, can form a small amount of fragility martensite and austenite in the heat affected zone, the low temperature brittleness transition temperature of low-carbon micro steel-alloy is raise, the toughness variation, be raised to 60ppm as nitrogen content from 20ppm, transition temperature is elevated to 0 ℃ from-50 ℃, thus the nitrogen content in the pipe line steel less than 50ppm, i.e. N＜50ppm.
5. the microalloy element in the pipe line steel (as Nb, V and Ti), they are principal elements of microalloyed steel.
Niobium (Nb) has intensive grain refining effect in pipe line steel, the grain refining effect of niobium mainly is because the austenite recrystallization in delay or the prevention hot rolling back frame, Nb reduces grain growth speed by reducing austenite to ferrite transformation temperature (Ar3) when improving the ferrite nucleation rate.Nb promotes the formation and the precipitation strength effect of bainite structure in addition.
Vanadium (V) has higher solubleness in steel, be microalloyed steel the most frequently used also be one of the most effective strengthening element.Vanadium add-on in the steel generally is controlled between 0.03～0.12% (wt).The effect of V is to influence the tissue and the performance of steel by forming V (C, N), and the intensity and the flexible effect that play the refinement ferrite crystal grain, improve steel can improve 150～300MPa as adding vanadium (V) back intensity in the steel.In addition, the nitrogen in vanadium and the steel (N) has stronger avidity, so fixing " freedom " nitrogen in the steel of vanadium.V combines with C and " freedom " N and forms V (C, N) compound, greatly reduces " freedom " nitrogen (N) content in the steel, has avoided the strain aging of steel.
Titanium (Ti) is the strong carbide forming element, and it and N, O, C have extremely strong avidity.In addition, the avidity of Ti and S is greater than the avidity of Fe and S, and therefore the preferential titanium sulfide that generates in containing the Ti steel has reduced the probability that generates iron sulphide, can reduce the red brittleness of steel.In addition, extremely strong, the stabilizer pole of carbide bonding force that Ti and C form is difficult for decomposing, and has only just to begin to dissolve in lentamente in the sosoloid when Heating temperature reaches more than 1000 ℃, and before not dissolving in, the TiC particulate has the grow up effect of alligatoring of crystalline grain of steel that stops.In addition, Ti is as lively as a cricket metallic element, and Ti can also generate the carbide particle of indissoluble with Fe and C, is enriched in the crystal boundary place of steel, stops the grain coarsening of steel; Ti also can dissolve in r mutually and α mutually in, form sosoloid, make steel produce reinforcement.The add-on of Ti should be greater than 0.025% (wt) in the general steel.
The production method of a kind of low carbon and high ductility pipe line steel of the present invention, technical process is:
Pour in the 100t oxygen top bottom blowing converter (BOF) blast-melted, the molten iron of pouring converter into requires P≤0.10% (wt), S≤0.04% (wt), by weight in converter, be blended into 3～5% steel scrap and add slag former (as lime), flux (fluorite or rhombspar) carries out routine smelting, is controlled at 70～100kg/t in the converter smelting initial stage quantity of slag
SteelOmnidistance BOTTOM ARGON BLOWING (Ar), its Argon intensity will guarantee that the bottom blowing stirring is good, and its BOTTOM ARGON BLOWING (Ar) intensity control is at 0.04～0.06Nm
3/ (mint
Steel).Thermometric before the tapping, sampling analysis molten steel chemical ingredients (wt%).
When Molten Steel End Point is that 1670～1690 ℃ and converter reach with molten steel composition (wt%) for refining: [C]≤0.04, [P]≤0.010, [S]≤0.030, and guarantee residual element composition (wt%) in the molten steel: [Cu]≤0.08, [As]≤0.03, [Sn]≤0.02 and (Cu+5As+8Sn)≤0.3 o'clock tap.Tap is controlled at 100 ± 5 tons (promptly 95～105 tons).The molten steel Control for Oxygen Content is at 700～900ppm during converter tapping, i.e. [O]=0.07～0.09%, during tapping the molten steel oxygen level low give follow-up deoxidation of molten steel, desulfurization, alloying, continuously, Control and Inclusion Removal provides a series of assurance.The slag blanket that covers on the bottom blowing gas brick is controlled in the 100mm, molten steel terminal point [%C] [%O] is controlled between 0.22～0.30%.
At preceding 30 seconds blowing argon gas in ladle of converter tapping.
Guarantee that in the converter tapping process tap hole situation is intact, the tapping time is 3.0～5.0min, and the control converter taphole entrainments slag down, and the tapping quantity of slag down reduces as far as possible, and promptly the quantity of slag is controlled at 3.0～5.0kg/t under the converter tapping
Steel, secondly converter oxidation sludge upgrading is become the reduction and desulfurization slag, just the ladle top slag upgrading.
In the converter tapping process, in ladle molten steel, add lime 5.0～6.0kg/t
Steel, pre-molten slag 2.0～3.0kg/t
Steel, slag supplying agent 1.5～2.5kg/t
SteelDescribed lime is slag former, and pre-molten slag is the calcium aluminate slag charge through roasting, and slag supplying agent is the calcium aluminate slag charge of containing metal aluminium, is market and can buys product, and the wash heat desulfurization that is to tap of its purpose also is called ladle wash heat.
Sending the Argon station that molten steel is carried out Argon the ladle that fills with molten steel handles: the omnidistance Argon (Ar) of ladle, Argon pressure is 0.3～0.4MPa.Molten steel advances thermometric and sampling analysis behind the Argon 3min of Argon station.When the liquid steel temperature after Argon is handled during more than or equal to 1570 ℃ (be T 〉=1570 ℃) and molten steel after feeding aluminum steel accent aluminium and making acid-soluble aluminum content in the molten steel [Als]=0.020%～0.040% (wt) and other composition up to standard, molten steel goes out the Argon station.
Send LF stove refining station the molten steel of handling through Argon, first argon (Ar) airshed with 500～600NL/min stirred 1～2min after converter molten steel advanced LF stove refining station, so that change slag; The blowing argon gas flow is 200～300NL/min during feeding temperature-raising, and the blowing argon gas flow is increased to 400～500NL/min during molten steel desulfurizing; The exposed diameter of the top of the slag is less than 100mm during blowing argon gas, and the blowing argon gas time, blowing argon gas pressure was 0.3～0.4MPa greater than 6min, and maximum Argon pressure is not more than 0.8MPa.
In molten steel, add lime, pre-molten slag and slag supplying agent in LF stove refining station and carry out residue adjustment.In order to obtain excellent desulfurizing effect and deoxidation effect, the refining slag composition (wt%) in the refining of LF stove is: CaO=50～55, Al
2O
3=30～35, (SiO
2+ MgO)＜10.0, (FeO+MnO)＜1.0.Quaternary basicity (CaO+MgO)/(Al with refining slag
2O
3+ SiO
2) R is controlled at about 2.0, and the quaternary basicity R of desulfurization refining slag when finishing is greater than 4.0, and the weight percent content sum that makes iron protoxide and manganese oxide in the slag is less than 1.0%, i.e. (FeO+MnO)＜1.0%.When LF stove refining station molten steel desulfurizing, liquid steel temperature is controlled at (1590～1610 ℃) about 1600 ℃, helps desulfurization.Molten steel after the desulfurization send continuous caster, and the out-station temperature of the first stove molten steel of last continuous caster need be controlled at 1575～1585 ℃, and the liquid steel temperature of each heat of casting process can be controlled in 1565～1575 ℃.
Molten steel adds ferrocolumbium (Fe-Nb), ferro-titanium (Fe-Ti) and ferro-vanadium (Fe-Ti) in molten steel when the refining of LF stove refining station, molten steel is carried out microalloying handle.Make and after the refining of LF stove, supply each component content of molten steel (wt%) of continuous caster continuous casting to be: [C]≤0.06, [Si]=0.20～0.35, [Mn]=1.20～1.40, [Nb]=0.02～0.04, [Ti]=0.015～0.030, [V]=0.02～0.04, [P]≤0.020, [S]≤0.008, [Als]=0.025～0.050, and [Als] in the continuous casting first stove molten steel need be controlled between 0.025～0.045%.
To pour into the continuous casting tundish earlier through LF stove molten steel after refining, and on the molten steel surface of continuous casting tundish, cover soft steel and protect slag.Unwrap greatly and water the back and measure liquid steel temperature (thermometric) at 10 tons of continuous casting tundish, 14 ton hours, the superheating temperature of control molten steel is 25～35 ℃ of scopes, if superheating temperature is lower than 15 ℃ or be higher than 50 ℃ and forbid to open and water.
With stretching into the formula mouth of a river continuous casting tundish molten steel injection continuous caster (crystallizer) is cast continuously cast bloom, the mold oscillation frequency is 200～220 times/min, and amplitude is 7.0mm.The continuous casting pulling rate is controlled at 3.5～5.0m/min, cools off continuous casting is bad with 7# or 8# cooling curve.
Strand behind the continuous casting is sent in the soaking pit and is heated, and described soaking pit can be selected roller bottom type soaking pit or tunnel like soaking pit for use.Continuously cast bloom is gone into charging temperature 〉=1000 ℃ of soaking pit, and the Heating temperature of continuously cast bloom in soaking pit is not less than 1150 ℃ (generally getting 1150～1160 ℃), and the head and tail temperature difference of continuously cast bloom in soaking pit equal ± and 10 ℃ or less than ± 10 ℃.Continuously cast bloom tapping temperature after soaking is controlled at 1120～1150 ℃.
Strand high-pressure water descaling machine de-scaling after from soaking pit, coming out, as iron scale and other inclusion on surface, the intake pressure of high pressure descaling water is 160～200Pa, top hole pressure is 200～300Pa, can adjust according to field condition.Strand temperature after the de-scaling decreases.As cast condition slab after de-scaling directly enters the finishing tandem rolling unit of being made up of seven frames and is rolled, and does not have the roughing passage before.For obtaining the intensity and the toughness levels of pipeline steel plate optimum, must be when the finishing train hot rolling with dendritic as-cast structure compacting, and realize (acquisition) fine grained texture therefore stopping to be rolled more than the temperature at the beginning at recrystallize, in non-recrystallization temperature scope, carry out finish rolling.Temperature on the first frame F1 of finishing train and distortion must be high as much as possible, to guarantee eliminating original as-cast structure by perfect recrystallization, therefore the start rolling temperature of the first frame F1 need remain on 1060～1080 ℃, the draft of the first frame F1 should be more than or equal to 45% (promptly 〉=45%), be generally about 50%, and the draft of the second frame F2 〉=45%.When the as cast condition slab enters the first frame F1 when rolling, grain-size, chemical ingredients and temperature are fixed, so have only by distortion and could satisfy the recrystallize dynamic conditions, be to skip the 3rd frame F3 and the 4th frame F4 so solve the gordian technique of mixed crystal problem, strengthen the draft of the first frame F1 and the second frame F2, increase the passage pitch time that F2 exports to the F5 inlet, can make like this to contain the Nb pipe line steel austenite perfect recrystallization takes place between F2 and F5 frame.Add aximal deformation value and can obtain good austenite recrystallization condition to eliminate mixed grain structure, especially to thick specification product.In the finishing tandem rolling unit operation of rolling, control water coolant between frame well: the water coolant aperture is 25～35% between the F1-F2 frame, the water coolant aperture is 45～55% between the F2-F3 frame, the water coolant aperture is 45～55% between the F3-F4 frame, the water coolant aperture is 25～35% between the F4-F5 frame, the water coolant aperture is 25～35% between the F5-F6 frame, the water coolant aperture is 15～25% between F6～F7 frame, with the 7th
#Or 8
#Cooling curve cools off continuously cast bloom.
By the rolling steel billet temperature (being finishing temperature) that comes out of the 7th frame F7 of finishing tandem rolling unit is 860～880 ℃, and steel plate is batched by reeling machine through laminar flow cooling back becomes the pipe line steel coiled sheet, laminar flow cooling mode employing A pattern.Described A pattern is that leading portion is concentrated cooling mode.Coiling temperature is controlled at 600～620 ℃.
With producing thickness as upper type is that 5.2～12.5mm, width are the X60 pipe line steel of 1010～1550mm, and its yield strength is that 450～555MPa, tensile strength are that 540～635MPa, unit elongation are 27～39%, V-type impelling strength (0 ℃) is 110～189J; Production thickness is that 5.6～12.5mm, width are the X65 pipe line steel of 1010～1550mm, and yield strength is that 495～560MPa, tensile strength are that 570～625MPa, unit elongation are 28～36%, V-type impelling strength (0 ℃) is 112～195J.
Embodiment 1:
Pour in the converter of oxygen top bottom blowing blast-melted, and by weight the steel scrap that is blended into 4% in converter, add lime and fluorite and carry out the routine smelting, the quantity of slag at control converter smelting initial stage is 85kg/t
Steel, with Argon intensity 0.04Nm
3/ (mint
Steel) carry out omnidistance BOTTOM ARGON BLOWING.
Tapping before measurement dimension water terminal temperature and sampling analysis molten steel chemical ingredients (wt%): tapping when Molten Steel End Point T=1670 ℃, [C]=0.040, [P]=0.010, [S]=0.020 and [Cu]=0.08, [As]=0.03, [Sn]=0.02.At preceding 30 seconds blowing argon gas in ladle of converter tapping, converter molten steel to be poured in the ladle, the control converter taphole entrainments slag down, and the quantity of slag is 5.0kg/t under the converter tapping
Steel, the tapping time is 4.0min; In the converter tapping process, in ladle molten steel, add 5.0kg/t
SteelLime, 2.5kg/t
SteelPre-molten slag and 2.0kg/t
SteelSlag supplying agent.
Sending the Argon station that molten steel is carried out Argon the ladle that fills with molten steel handles: the omnidistance blowing argon gas of ladle, blowing argon gas pressure is 0.4MPa, molten steel advances thermometric and sampling analysis behind the Argon 3min of Argon station, and molten steel goes out the Argon station when liquid steel temperature equals [Als]=0.02% in 1575 ℃ and the molten steel.
Send the molten steel after handling through Argon LF stove refining station to carry out molten steel desulfurizing and microalloying processing, converter molten steel uses the argon flow amount of 550NL/min to stir 1.5min earlier after advancing LF stove refining station, the blowing argon gas flow is 300NL/min during feeding temperature-raising, and the blowing argon gas flow is increased to 450NL/min during molten steel desulfurizing; The exposed diameter of the top of the slag is 95mm during the soft blow argon, and the soft blow argon time is 6.5min, and blowing argon gas pressure is 0.4MPa; In molten steel, add lime, pre-melted slag and slag supplying agent in LF stove refining station, make the composition of the refining slag in the refining of LF stove be: CaO=55%, Al
2O
3=33%, (SiO
2+ MgO)=9.5%, (FeO+MnO)=0.95%, and the quaternary basicity R=2.0 of refining slag, the quaternary basicity R=4.3 of refining slag when desulfurization finishes, the liquid steel temperature when LF stove refining station molten steel desulfurizing is 1600 ℃; Molten steel after the desulfurization send continuous caster, and the out-station temperature of the first stove molten steel of last continuous caster is 1575 ℃, and the liquid steel temperature of each heat is controlled at 1565～1575 ℃ in casting process; Composition (wt%) for the continuous caster continuous casting steel after the refining of LF stove is: [C]=0.06, [Si]==0.35, [Mn]=1.30, [Nb]=0.02, [Ti]=0.025, [V]=0.02, [P]=0.020, [S]=0.008, [Als]=0.025, [Als] is controlled at 0.025% in the continuous casting first stove molten steel.
LF stove molten steel after refining is poured into the continuous casting tundish, cover low-carbon steel protecting slag at molten steel surface; Unwrap greatly and water the back at 10 tons of continuous casting tundish and 14 ton hour thermometrics, molten steel overheat is 35 ℃.
With stretching into the formula mouth of a river continuous casting tundish molten steel is injected continuous caster, the mold oscillation frequency is 220 times/min, and amplitude is 7mm, and the continuous casting pulling rate is 3.5m/min.
The charging temperature that continuously cast bloom is gone into soaking pit is 1000 ℃, and the Heating temperature of strand in soaking pit is 1150 ℃, the head and tail temperature difference of strand equals ± and 10 ℃, the tapping temperature of strand is 1120 ℃ after the soaking.
The strand that from the roller bottom type soaking pit, comes out high-pressure water descaling machine de-scaling, the intake pressure of high pressure descaling water is 160Pa, top hole pressure is 200Pa.
Strand after de-scaling directly enters the finishing tandem rolling unit of being made up of seven frames and is rolled, the start rolling temperature of the first frame F1 of finishing train is 1070 ℃, the draft that the draft of the first frame F1 equals 50%, the second frame F2 equals between 45%. frames that water coolant aperture: F1～F2 is 25%, F2-F3 is 40%, F3-F4 is 45%, F4～F5 is 35%, F5-F6 is 25%, F6-F7 is 20%.The steel billet temperature that shuts out from the 7th frame F7 is 880 ℃, and steel plate batches after the laminar flow cooling becomes the pipe line steel coiled sheet, and coiling temperature is controlled at 610 ℃.
Production thickness is that 5.2mm, width are the X60 pipe line steel of 1250mm, and yield strength is that 460MPa, tensile strength are that 550MPa, unit elongation are 39%, V-type impelling strength (0 ℃) is 156J; Production thickness is that 9.0mm, width are the X65 pipe line steel of 1010mm, and yield strength is that 520MPa, tensile strength are that 600MPa, unit elongation are 28%, V-type impelling strength (0 ℃) is 195J.
Embodiment 2
Pour in the converter of oxygen top bottom blowing blast-melted, and by weight the steel scrap that is blended into 3% in converter, add lime and rhombspar and carry out the routine smelting, the quantity of slag at control converter smelting initial stage is 70kg/t
Steel, with Argon intensity 0.05Nm
3/ (mint
Steel) carry out omnidistance BOTTOM ARGON BLOWING.
Tapping before measurement dimension water terminal temperature and sampling analysis molten steel chemical ingredients (wt%): tapping when Molten Steel End Point T=1680 ℃, [C]=0.035, [P]=0.010, [S]=0.025 and [Cu]=0.07, [As]=0.03, [Sn]=0.02.At preceding 30 seconds blowing argon gas in ladle of converter tapping, converter molten steel to be poured in the ladle, the control converter taphole entrainments slag down, and the quantity of slag is 3.0kg/t under the converter tapping
Steel, the tapping time is 3.0min; In the converter tapping process, in ladle molten steel, add 5.5kg/t
SteelLime, 2.0kg/t
SteelPre-molten slag and 2.5kg/t
SteelSlag supplying agent.
Sending the Argon station that molten steel is carried out Argon the ladle that fills with molten steel handles: the omnidistance blowing argon gas of ladle, blowing argon gas pressure is 0.3MPa, molten steel advances thermometric and sampling analysis behind the Argon 3min of Argon station, and molten steel goes out the Argon station when liquid steel temperature equals [Als]=0.03% in 1570 ℃ and the molten steel.
Send the molten steel after handling through Argon LF stove refining station to carry out molten steel desulfurizing and microalloying processing, converter molten steel uses the argon flow amount of 500NL/min to stir 2.0min earlier after advancing LF stove refining station, the blowing argon gas flow is 250NL/min during feeding temperature-raising, and the blowing argon gas flow is increased to 400NL/min during molten steel desulfurizing; The exposed diameter of the top of the slag is 90mm during the soft blow argon, and the soft blow argon time is 6.5min, and blowing argon gas pressure is 0.35MPa; In molten steel, add lime, pre-melted slag and slag supplying agent in LF stove refining station, make the composition of the refining slag in the refining of LF stove be: CaO=53%, Al
2O
3=35%, (SiO
2+ MgO)=9.5%, (FeO+MnO)=0.9%, and the quaternary basicity R=2.0 of refining slag, the quaternary basicity R=4.2 of refining slag when desulfurization finishes, the liquid steel temperature when LF stove refining station molten steel desulfurizing is 1600 ℃; Molten steel after the desulfurization send continuous caster, and the out-station temperature of the first stove molten steel of last continuous caster is 1580 ℃, and the liquid steel temperature of each heat is controlled at 1565～1575 ℃ in casting process; Content (wt%) for each composition of continuous caster continuous casting steel after the refining of LF stove is: [C]=0.05, [Si]=0.20, [Mn]=1.40, [Nb]=0.03, [Ti]=0.015, [V]=0.04, [P]=0.015, [S]=0.007, [Als]=0.035, [Als] is controlled at 0.035% in the continuous casting first stove molten steel.
LF stove molten steel after refining is poured into the continuous casting tundish, cover low-carbon steel protecting slag at molten steel surface; Unwrap greatly and water the back at 10 tons of continuous casting tundish and 14 ton hour thermometrics, molten steel overheat is 30 ℃.
With stretching into the formula mouth of a river continuous casting tundish molten steel is injected continuous caster, the mold oscillation frequency is 210 times/min, and amplitude 7mm, continuous casting pulling rate are 4.0m/min.
Continuously cast bloom is gone into charging temperature=1000 ℃ of soaking pit, and the Heating temperature of strand in soaking pit is 1155 ℃, and the head and tail temperature difference of strand equals ± and 10 ℃, the tapping temperature of strand is 1150 ℃ after the soaking.
The strand that from the roller bottom type soaking pit, comes out high-pressure water descaling machine de-scaling, the intake pressure of high pressure descaling water is 200Pa, top hole pressure is 250Pa.
Strand after de-scaling directly enters the finishing tandem rolling unit of being made up of seven frames and is rolled, the start rolling temperature of the first frame F1 of finishing tandem rolling unit is 1060 ℃, the draft of the first frame F1 equals 45%, the draft of the second frame F2 equals 50%, and water coolant aperture: F1-F2 is 30% between frame, F2-F3 is 45%, F3-F4 is 55%, F4-F5 is 30%, F5-F6 is 35%, F6-F7 is 15%.The steel billet temperature that shuts out from the 7th frame F7 is 870 ℃, and steel plate batches after the laminar flow cooling becomes the pipe line steel coiled sheet, and coiling temperature is controlled at 600 ℃;
Production thickness is that 8.5mm, width are the X60 pipe line steel of 1010mm, and yield strength is that 470MPa, tensile strength are that 560MPa, unit elongation are 35%, V-type impelling strength is 110J; Production thickness is that 5.6mm, width are the X65 pipe line steel of 1350mm, and its yield strength is that 520MPa, tensile strength are that 610MPa, unit elongation are 32%, V-type impelling strength (0 ℃) is 112J.
Embodiment 3
Pour in the converter of oxygen top bottom blowing blast-melted, and by weight the steel scrap that is blended into 5% in converter, add lime and fluorite and carry out the routine smelting, the quantity of slag at control converter smelting initial stage is 100kg/t
Steel, with Argon intensity 0.06Nm
3/ (mint
Steel) carry out omnidistance BOTTOM ARGON BLOWING.
Tapping before measurement dimension water terminal temperature and sampling analysis molten steel chemical ingredients (wt%): tapping when Molten Steel End Point T=1690 ℃, [C]=0.040, [P]=0.009, [S]=0.030 and [Cu]=0.08, [As]=0.02, [Sn]=0.01.At preceding 30 seconds blowing argon gas in ladle of converter tapping, converter molten steel to be poured in the ladle, the control converter taphole entrainments slag down, and the quantity of slag is 4.0kg/t under the converter tapping
Steel, the tapping time is 5.0min; In the converter tapping process, in ladle molten steel, add 6.0kg/t
SteelLime, 3.0kg/t
SteelPre-molten slag and 1.5kg/t
SteelSlag supplying agent.
Sending the Argon station that molten steel is carried out Argon the ladle that fills with molten steel handles: the omnidistance blowing argon gas of ladle, blowing argon gas pressure is 0.35MPa, molten steel advances thermometric and sampling analysis behind the Argon 3min of Argon station, and molten steel goes out the Argon station when liquid steel temperature equals [Als]=0.04% in 1570 ℃ and the molten steel.
Send the molten steel after handling through Argon LF stove refining station to carry out molten steel desulfurizing and microalloying processing, converter molten steel uses the argon flow amount of 600NL/min to stir 1.0min earlier after advancing LF stove refining station, the blowing argon gas flow is 200NL/min during feeding temperature-raising, and the blowing argon gas flow is increased to 500NL/min during molten steel desulfurizing; The exposed diameter of the top of the slag is 95mm during the soft blow argon, and the soft blow argon time is 6.5min, and blowing argon gas pressure is 0.3MPa.In molten steel, add lime, pre-melted slag and slag supplying agent in LF stove refining station, make the composition of the refining slag in the refining of LF stove be: CaO=50%, Al
2O
3=30%, (SiO
2+ MgO)=9.0%, (FeO+MnO)=0.9%, and the quaternary basicity R=2.0 of refining slag, the quaternary basicity R=4.2 of refining slag when desulfurization finishes, the liquid steel temperature when LF stove refining station molten steel desulfurizing is 1590 ℃; Molten steel after the desulfurization send continuous caster, and the out-station temperature of the first stove molten steel of last continuous caster is 1585 ℃, and the liquid steel temperature of each heat is controlled at 1565～1575 ℃ in casting process; Content (wt%) for each composition of continuous caster continuous casting steel after the refining of LF stove is: [C]=0.06, [Si]==0.25, [Mn]=1.20, [Nb]=0.04, [Ti]=0.030, [V]=0.03, [P]=0.020, [S]=0.008, [Als]=0.050, [Als] is controlled at 0.045% in the continuous casting first stove molten steel.
LF stove molten steel after refining is poured into the continuous casting tundish, cover low-carbon steel protecting slag at molten steel surface; Unwrap greatly and water the back at 10 tons of continuous casting tundish and 14 ton hour thermometrics, 25 ℃ of molten steel overheats.
With stretching into the formula mouth of a river continuous casting tundish molten steel is injected continuous caster, the mold oscillation frequency is 200 times/min, and amplitude 7mm, continuous casting pulling rate are 5.0m/min.
The charging temperature that continuously cast bloom is gone into soaking pit is 1050 ℃, and the Heating temperature of strand in soaking pit is 1160 ℃, the head and tail temperature difference of strand equals ± and 10 ℃, the tapping temperature of strand is 1140 ℃ after the soaking.
The strand that from the roller bottom type soaking pit, comes out high-pressure water descaling machine de-scaling, the intake pressure of high pressure descaling water is 180Pa, top hole pressure is 300Pa.
Strand after de-scaling directly enters the finishing tandem rolling unit of being made up of seven frames and is rolled, the start rolling temperature of the first frame F1 of finishing tandem rolling unit is 1080 ℃, the draft of the first frame F1 equals 45%, the draft of the second frame F2 equals 45%, and water coolant aperture: F1～F2 is 35% between frame, F2-F3 is 55%, F3-F4 is 40%, F4～F5 is 25%, F5-F6 is 30%, F6-F7 is 25%.The steel billet temperature that shuts out from the 7th frame F7 is 860 ℃, and steel plate batches after the laminar flow cooling becomes the pipe line steel coiled sheet, and coiling temperature is controlled at 620 ℃.
Production thickness is that 12.5mm, width are the X60 pipe line steel of 1550mm, and yield strength is that 450MPa, tensile strength are that 540MPa, unit elongation are 27%, V-type impelling strength is (0 ℃) 189J; Production thickness is that 12.5mm, width are the X65 pipe line steel of 1550mm, and yield strength is that 510MPa, tensile strength are that 590MPa, unit elongation are 36%, V-type impelling strength (0 ℃) is 154J.
Embodiment 4
Pour in the converter of oxygen top bottom blowing blast-melted, and by weight the steel scrap that is blended into 3.5% in converter, add lime and rhombspar and carry out the routine smelting, the quantity of slag at control converter smelting initial stage is 75kg/t
Steel, with Argon intensity 0.05Nm
3/ (mint
Steel) carry out omnidistance BOTTOM ARGON BLOWING.
Tapping before measurement dimension water terminal temperature and sampling analysis molten steel chemical ingredients (wt%): tapping when Molten Steel End Point T=1685 ℃, [C]=0.035, [P]=0.010, [S]=0.025 and [Cu]=0.07, [As]=0.03, [Sn]=0.02.At preceding 30 seconds blowing argon gas in ladle of converter tapping, converter molten steel to be poured in the ladle, the control converter taphole entrainments slag down, and the quantity of slag is 3.5kg/t under the converter tapping
Steel, the tapping time is 4.5min; In the converter tapping process, in ladle molten steel, add 5.0kg/t
SteelLime, 3.0kg/t
SteelPre-molten slag and 2.0kg/t
SteelSlag supplying agent.
Sending the Argon station that molten steel is carried out Argon the ladle that fills with molten steel handles: the omnidistance blowing argon gas of ladle, blowing argon gas pressure is 0.3MPa, molten steel advances thermometric and sampling analysis behind the Argon 3min of Argon station, and molten steel goes out the Argon station when liquid steel temperature equals [Als]=0.02% in 1575 ℃ and the molten steel.
Send the molten steel after handling through Argon LF stove refining station to carry out molten steel desulfurizing and microalloying processing, converter molten steel uses the argon flow amount of 540NL/min to stir 2.0min earlier after advancing LF stove refining station, the blowing argon gas flow is 280NL/min during feeding temperature-raising, and the blowing argon gas flow is increased to 450NL/min during molten steel desulfurizing; The exposed diameter of the top of the slag is 90mm during the soft blow argon, and the soft blow argon time is 6.5min, and blowing argon gas pressure is 0.35MPa; In molten steel, add lime, pre-melted slag and slag supplying agent in LF stove refining station, make the composition of the refining slag in the refining of LF stove be: CaO=53%, Al
2O
3=35%, (SiO
2+ MgO)=9.5%, (FeO+MnO)=0.9%, and the quaternary basicity R=2.0 of refining slag, the quaternary basicity R=4.5 of refining slag when desulfurization finishes, the liquid steel temperature when LF stove refining station molten steel desulfurizing is 1595 ℃; Molten steel after the desulfurization send continuous caster, and the out-station temperature of the first stove molten steel of last continuous caster is 1580 ℃, and the liquid steel temperature of each heat is controlled at 1565～1575 ℃ in casting process; Content (wt%) for each composition of continuous caster continuous casting steel after the refining of LF stove is: [C]=0.05, [Si]=0.25, [Mn]=1.35, [Nb]=0.03, [Ti]=0.020, [V]=0.03, [P]=0.015, [S]=0.007, [Als]=0.045, [Als] is controlled at 0.035% in the continuous casting first stove molten steel.
LF stove molten steel after refining is poured into the continuous casting tundish, cover low-carbon steel protecting slag at molten steel surface; Unwrap greatly and water the back at 10 tons of continuous casting tundish and 14 ton hour thermometrics, molten steel overheat is 28 ℃.
With stretching into the formula mouth of a river continuous casting tundish molten steel is injected continuous caster, the mold oscillation frequency is 210 times/min, and amplitude 7mm, continuous casting pulling rate are 3.8m/min.
Continuously cast bloom is gone into charging temperature=1050 ℃ of soaking pit, and the Heating temperature of strand in soaking pit is 1160 ℃, and the head and tail temperature difference of strand equals ± and 10 ℃, the tapping temperature of strand is 1150 ℃ after the soaking.
The strand that from the roller bottom type soaking pit, comes out high-pressure water descaling machine de-scaling, the intake pressure of high pressure descaling water is 180Pa, top hole pressure is 200Pa.
Strand after de-scaling directly enters the finishing tandem rolling unit of being made up of seven frames and is rolled, the start rolling temperature of the first frame F1 of finishing tandem rolling unit is 1070 ℃, the draft of the first frame F1 equals 47%, the draft of the second frame F2 equals 50%, and water coolant aperture: F1-F2 is 30% between frame, F2-F3 is 46%, F3-F4 is 50%, F4-F5 is 28%, F5-F6 is 30%, F6-F7 is 18%.The steel billet temperature that shuts out from the 7th frame F7 is 865 ℃, and steel plate batches after the laminar flow cooling becomes the pipe line steel coiled sheet, and coiling temperature is controlled at 600 ℃;
Production thickness is that 6.5mm, width are the X60 pipe line steel of 1300mm, and yield strength is that 520MPa, tensile strength are that 620MPa, unit elongation are 30%, V-type impelling strength is 160J; Production thickness is that 6.5mm, width are the X65 pipe line steel of 1200mm, and its yield strength is that 495MPa, tensile strength are that 570MPa, unit elongation are 30%, V-type impelling strength (0 ℃) is 135J.
Embodiment 5
Pour in the converter of oxygen top bottom blowing blast-melted, and by weight the steel scrap that is blended into 4.5% in converter, add lime and rhombspar and carry out the routine smelting, the quantity of slag at control converter smelting initial stage is 90kg/t
Steel, with Argon intensity 0.055Nm
3/ (mint
Steel) carry out omnidistance BOTTOM ARGON BLOWING.
Tapping before measurement dimension water terminal temperature and sampling analysis molten steel chemical ingredients (wt%): tapping when Molten Steel End Point T=1675 ℃, [C]=0.040, [P]=0.009, [S]=0.030 and [Cu]=0.08, [As]=0.02, [Sn]=0.02.At preceding 30 seconds blowing argon gas in ladle of converter tapping, converter molten steel to be poured in the ladle, the control converter taphole entrainments slag down, and the quantity of slag is 4.5kg/t under the converter tapping
Steel, the tapping time is 3.5min; In the converter tapping process, in ladle molten steel, add 6.0kg/t
SteelLime, 2.0kg/t
SteelPre-molten slag and 2.5kg/t
SteelSlag supplying agent.
Sending the Argon station that molten steel is carried out Argon the ladle that fills with molten steel handles: the omnidistance blowing argon gas of ladle, blowing argon gas pressure is 0.4MPa, molten steel advances thermometric and sampling analysis behind the Argon 3min of Argon station, and molten steel goes out the Argon station when liquid steel temperature equals [Als]=0.04% in 1570 ℃ and the molten steel.
Send the molten steel after handling through Argon LF stove refining station to carry out molten steel desulfurizing and microalloying processing, converter molten steel uses the argon flow amount of 580NL/min to stir 1.0min earlier after advancing LF stove refining station, the blowing argon gas flow is 300NL/min during feeding temperature-raising, and the blowing argon gas flow is increased to 460NL/min during molten steel desulfurizing; The exposed diameter of the top of the slag is 90mm during the soft blow argon, and the soft blow argon time is 6.5min, and blowing argon gas pressure is 0.40MPa; In molten steel, add lime, pre-melted slag and slag supplying agent in LF stove refining station, make the composition of the refining slag in the refining of LF stove be: CaO=54%, Al
2O
3=32%, (SiO
2+ MgO)=9.0%, (FeO+MnO)=0.95%, and the quaternary basicity R=2.0 of refining slag, the quaternary basicity R=4.1 of refining slag when desulfurization finishes, the liquid steel temperature when LF stove refining station molten steel desulfurizing is 1605 ℃; Molten steel after the desulfurization send continuous caster, and the out-station temperature of the first stove molten steel of last continuous caster is 1585 ℃, and the liquid steel temperature of each heat is controlled at 1565～1575 ℃ in casting process; Content (wt%) for each composition of continuous caster continuous casting steel after the refining of LF stove is: [C]=0.06, [Si]=0.30, [Mn]=1.25, [Nb]=0.04, [Ti]=0.025, [V]=0.035, [P]=0.020, [S]=0.008, [Als]=0.040, [Als] is controlled at 0.045% in the continuous casting first stove molten steel.
LF stove molten steel after refining is poured into the continuous casting tundish, cover low-carbon steel protecting slag at molten steel surface; Unwrap greatly and water the back at 10 tons of continuous casting tundish and 14 ton hour thermometrics, molten steel overheat is 35 ℃.
With stretching into the formula mouth of a river continuous casting tundish molten steel is injected continuous caster, the mold oscillation frequency is 210 times/min, and amplitude 7mm, continuous casting pulling rate are 4.5m/min.
Continuously cast bloom is gone into charging temperature=1000 ℃ of soaking pit, and the Heating temperature of strand in soaking pit is 1155 ℃, and the head and tail temperature difference of strand equals ± and 10 ℃, the tapping temperature of strand is 1140 ℃ after the soaking.
The strand that from the roller bottom type soaking pit, comes out high-pressure water descaling machine de-scaling, the intake pressure of high pressure descaling water is 200Pa, top hole pressure is 250Pa.
Strand after de-scaling directly enters the finishing tandem rolling unit of being made up of seven frames and is rolled, the start rolling temperature of the first frame F1 of finishing tandem rolling unit is 1080 ℃, the draft of the first frame F1 equals 45%, the draft of the second frame F2 equals 50%, and water coolant aperture: F1-F2 is 35% between frame, F2-F3 is 53%, F3-F4 is 55%, F4-F5 is 32%, F5-F6 is 34%, F6-F7 is 23%.The steel billet temperature that shuts out from the 7th frame F7 is 875 ℃, and steel plate batches after the laminar flow cooling becomes the pipe line steel coiled sheet, and coiling temperature is controlled at 610 ℃;
Production thickness is that 10.0mm, width are the X60 pipe line steel of 1450mm, and yield strength is that 555MPa, tensile strength are that 635MPa, unit elongation are 37%, V-type impelling strength is 175J; Production thickness is that 10.0mm, width are the X65 pipe line steel of 1400mm, and its yield strength is that 560MPa, tensile strength are that 625MPa, unit elongation are 34%, V-type impelling strength (0 ℃) is 185J.
Claims (1)
1, the production method of a kind of low carbon and high ductility X 60/X/X65 pipe line steel, it is characterized in that: pour in the converter of oxygen top bottom blowing blast-melted, and by weight the steel scrap that in converter, is blended into 3～5%, add slag former and flux and carry out the routine smelting, the quantity of slag at converter smelting initial stage is controlled at 70～100kg/t
SteelWithin the scope, omnidistance BOTTOM ARGON BLOWING, its Argon intensity control is at 0.04～0.06Nm
3/ (mint
Steel);
Tapping before measurement dimension water terminal temperature and sampling analysis molten steel chemical ingredients (wt%): tapping in the time of when Molten Steel End Point T=1670～1690 ℃, [C]≤0.040, [P]≤0.010, [S]≤0.030, [Cu]≤0.08, [As]≤0.03, [Sn]≤0.02 and (Cu+5As+8Sn)≤0.3;
At preceding 30 seconds blowing argon gas in ladle of converter tapping, converter molten steel to be poured in the ladle, the control converter taphole entrainments slag down, and the quantity of slag is controlled at 3.0～5.0kg/t under the converter tapping
Steel, the tapping time is 3.0～5.0min; In the converter tapping process, in ladle molten steel, add 5.0～6.0kg/t
SteelLime, 2.0～3.0kg/t
SteelPre-molten slag and 1.5～2.5kg/t
SteelSlag supplying agent;
Sending the Argon station that molten steel is carried out Argon the ladle that fills with molten steel handles: the omnidistance blowing argon gas of ladle, blowing argon gas pressure is 0.3～0.4MPa, molten steel advances thermometric and sampling analysis behind the Argon 3min of Argon station, when liquid steel temperature during more than or equal to [Als]=0.02～0.04% in 1570 ℃ and the molten steel molten steel go out the Argon station;
Send the molten steel after handling through Argon LF stove refining station to carry out molten steel desulfurizing and microalloying processing, first argon flow amount with 500～600NL/min stirred 1.0～2.0min after converter molten steel advanced LF stove refining station, the blowing argon gas flow is 200～300NL/min during feeding temperature-raising, and the blowing argon gas flow is increased to 400～500NL/min during molten steel desulfurizing; The exposed diameter of the top of the slag is less than 100mm during the soft blow argon, and the soft blow argon time, blowing argon gas pressure was 0.3～0.4MPa greater than 6min; In molten steel, add lime, pre-melted slag and slag supplying agent in LF stove refining station, make the composition of the refining slag in the refining of LF stove be: CaO=50～55%, Al
2O
3=30～35%, (SiO
2+ MgO)＜10.0%, (FeO+MnO)＜1.0%, and the quaternary basicity R=2.0 of refining slag, the quaternary basicity R of refining slag when desulfurization finishes〉4.0, the liquid steel temperature when LF stove refining station molten steel desulfurizing is controlled at 1590～1610 ℃ of scopes; Molten steel after the desulfurization send continuous caster, and the out-station temperature of the first stove molten steel of last continuous caster is 1575～1585 ℃, and the liquid steel temperature of each heat is controlled at 1565～1575 ℃ in casting process; Molten steel adds ferrocolumbium, ferro-titanium, ferro-vanadium in molten steel when the LF stove is concise, molten steel is carried out microalloying to be handled, content (wt%) for each composition of continuous caster continuous casting steel after the refining of LF stove is: [C]≤0.06, [Si]=0.20～0.35, [Mn]=1.20～1.40, [Nb]=0.02～0.04, [Ti]=0.015～0.030, [V]=0.02～0.04, [P]≤0.020, [S]≤0.008, [Als]=0.025～0.050, and [Als] is controlled at 0.025～0.045% in the continuous casting first stove molten steel;
LF stove molten steel after refining is poured into the continuous casting tundish, cover low-carbon steel protecting slag at molten steel surface; Unwrap greatly and water the back at 10 tons of continuous casting tundish and 14 ton hour thermometrics, the control molten steel overheat is between 25～35 ℃;
With stretching into the formula mouth of a river continuous casting tundish molten steel injection continuous caster is cast continuously cast bloom, the continuous casting pulling rate is 3.5～5.0m/min, and the vibrational frequency of crystallizer is 200-220 time/min, and amplitude is 7.0mm;
Continuously cast bloom is gone into charging temperature 〉=1000 ℃ of soaking pit, and the Heating temperature of continuously cast bloom in soaking pit is 1150～1160 ℃, and the head and tail temperature difference of continuously cast bloom is equal to or less than ± and 10 ℃, the tapping temperature of continuously cast bloom is controlled at 1120～1150 ℃ after the soaking;
The strand that from the roller bottom type soaking pit, comes out high-pressure water descaling machine de-scaling, the intake pressure of high pressure descaling water is 160～200Pa, top hole pressure is 200～300Pa;
Strand after de-scaling directly enters the finishing tandem rolling unit of being made up of seven frames and is rolled, and the start rolling temperature of the first frame F1 of finishing tandem rolling unit remains on 1060～1080 ℃, and the draft of F1 is more than or equal to 45%; The water coolant aperture is 25%～35% between frame F1-F2, the water coolant aperture is 45%～55% between frame F2-F3, the water coolant aperture is 45%～55% between frame F3-F4, the water coolant aperture is 25%～35% between frame F4-F5, the water coolant aperture is 25～35% between frame F5～F6, the water coolant aperture is 15%～25% between frame F6-F7; The finishing temperature of the steel plate that shuts out from the 7th frame F7 is 860～880 ℃, and steel plate batches after the laminar flow cooling becomes the pipe line steel coiled sheet, and coiling temperature is controlled at 600～620 ℃; Wherein
Slag former: be selected from lime;
Flux: be selected from fluorite or rhombspar;
Pre-molten slag: be selected from calcium aluminate slag charge through roasting;
Slag supplying agent: the calcium aluminate slag charge that is selected from containing metal aluminium.
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