CN101967604B - Boron-nitrogen composite microalloyecd steel allowing for high heat input welding and manufacturing method - Google Patents
Boron-nitrogen composite microalloyecd steel allowing for high heat input welding and manufacturing method Download PDFInfo
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Abstract
The invention discloses boron-nitrogen composite microalloyecd steel allowing for high heat input welding and a manufacturing method, which belong to the technical field of microalloyecd steel. The steel comprises the following chemical components: 0.04 to 0.09 percent of C, 1.00 to 1.80 percent of Mn, 0.10 to 0.50 percent of Si, less than or equal to 0.010 percent of S, less than or equal to 0.015 percent of P, 0.10 to 0.30 percent of Mo, 0.03 to 0.10 percent of V, 0.005 to 0.030 percent of Ti, 0.010 to 0.025 percent of N, 0.0005 to 0.0025 percent of B, less than or equal to 0.015 percent of Al, and the balance of Fe and inevitable impurities. The ratio of the boron content and nitrogen content of the steel meets the condition that 2N-15B is more than or equal to 0.010 and less than or equal to 0.018 and the condition that Ti+V+10B is more than or equal to 4.525N-0.002. The production is organized by adopting a process including electric furnace or converter smelting, external refining, continuous casting, rolling and tempering in turn. The steel has the advantages that: the steel yield strength is more than or equal to 550MPa; the tensile strength is more than or equal to 670MPa; the elongation is more than or equal to 18 percent; the charpy impact power (-40 DEG C) is more than or equal to 200J; when the welding heat input is 45 to 80Kj/cm, the charpy impact power (-40 DEG C) of areas close to seams is more than or equal to 47J; and the process is simple and convenient.
Description
Technical field
The invention belongs to the micro-alloyed steel technical field, a kind of boron nitrogen composite micro-alloyed steel and method of manufacture that can adopt high heat input welding particularly is provided.
Background technology
Nitrogen-increasing steel generally is meant the low-carbon (LC) vanadium nitrogen micro-alloyed steel of nitrogen content more than 0.01wt%.Nitrogen pick-up in this type steel in conjunction with third generation TMCP technology, can be optimized V-N particle separating out in austenite and ferritic, and significantly the refinement ferrite crystal grain improves the precipitation strength increment, thereby improves the intensity and the toughness of steel simultaneously.In addition, keeping under the prerequisite of certain strength level, in nitrogen pick-up, can also suitably reduce the carbon content in the steel, making steel not preheating or can avoid welding nearly seam district through lower preheating temperature and produce cold crack before weldering.At present, but vanadium nitrogen microalloy technology has obtained widespread use in products such as welded high-strength reinforcing bar, section bar, sheet material, hot rolled strip.
But experimental study shows, as heat input (the corresponding t of above-mentioned nitrogen-increasing steel with>=45kj/cm
8/5>=when 30s) welding, because near the nearly seam district of steel (corresponding peak temperature is 1350 ℃), the V-N particle promotes a large amount of thick grain boundary ferrites to change, and the M-A island hardness that subsequent transition forms is higher, size is big, dispersity is lower.The polyphase structure that is made up of them is when withstanding shocks load; Tend to make tiny crack directly with little cleavage mode at soft or hard phase interface place forming core; And tiny crack is easy in thick ferrite crystal grain, expand; Finally forming with accurate cleavage or cleavage is the fracture apperance of principal character, belongs to brittle rupture in essence, and-40 ℃ of ballistic works generally all are lower than 27J.
How to suppress the embrittlement tendency in nitrogen-increasing steel nearly seam district under high heat input welding conditions, this is the major issue that present v n micro alloying technology faces.A kind of possible approach is to break through the traditional microalloying thinking of such steel, in nitrogen-increasing steel, adds the boron of trace, through the scope and the proportioning of reasonable control boron content and nitrogen content, in steel, forms the favourable boron and the distribution of nitrogen.Wherein, a part of boron is existed with the form of solid solution, when postwelding cooled off continuously, solid solution boron NONEQUILIBRIUM SEGREGATION is austenite grain boundary in nearly seam district, to suppress the formation of thick grain boundary ferrite; Part of boron combines with part nitrogen, forms boron nitride particles, and another part nitrogen combines with vanadium, forms the VN particle, and two kinds of particles all promote the ferritic formation of intracrystalline, place restrictions on the alligatoring of granular bainite.Promptly through boron nitrogen combined microalloying technology; Continuous cools tissue to control nearly seam district changes; Obtain the intracrystalline ferritic and the granular bainite of refinement; The embrittlement tendency that suppresses the hard phase in M-A island finally makes the composite micro-alloyed nitrogen-increasing steel of this boron nitrogen when welding with higher heat input, also can obtain good impelling strength in nearly seam district.
At present, from domestic and international disclosed document and patent, the also visible instance that in steel, contains a certain amount of boron and nitrogen simultaneously.As R.J.Glodowski people such as " N Strain aging in ferritic steels " (Wire J.Int., 28 (2005) 1:70) one literary composition and Yuan Hui " developing history of low-carbon boron-containing steel and current situation " (Shoudu Iron and Steel Co is scientific and technological, 2005; (6): 21-23) introduce in the literary composition; Nitrogen content in the electric steel is higher, and generally high-content can be near 0.01wt%, if the nitrogen that electric furnace is produced in the wire rod exists with the form of free nitrogen; Then can produce strain aging embrittlement, reduce the drawing processing characteristics.As in steel, adding right amount of boron, boron is combined with nitrogen, with the free nitrogen in the fixing steel, then can improve the processing characteristics of wire rod.But this microalloying method that relates to the application with the purpose that will reach all have different.
And for example French Crusoe company is at Chinese patents " welding structure iron assembly and method of manufacture thereof " (application number 200380103645.8); Proposition is controlled at the boron in the steel and nitrogen respectively in 5～100ppm and the≤250ppm scope, and the qualification of boron content and nitrogen content (ppm) is also met B>=1/3 * N+0.5.But, the purpose of this patented technology be for the hardening capacity that improves steel to obtain martensite-bainite tissue, the therefore high as far as possible boron of requirement and the proportioning of nitrogen.
And for example Exxon Mobil upper reaches research company proposes boron in the steel and nitrogen are controlled at 4～20ppm and≤20～50ppm respectively in Chinese patents " ultra-high strength triple phase steels with excellent low-temperature flexibility " (application number 99814735.4).The steel that this patented technology relates to is as passing through welding, and its weak point is that N content is on the low side, and the quantity of the VN of formation and BN particle is on the low side, can not significantly promote nearly seam to distinguish the ferritic formation of intracrystalline and place restrictions on growing up of bainite ferrite.
And for example Japanese Patent " spy opens clear 62-190016 " proposes to adopt TiN and BN to make the method for nearly seam district ferritic refinement.The weak point of this patented technology is that the proportioning of boron and nitrogen is on the low side; When adopting high heat input to weld; Produce enough solid solution boron at austenite grain boundary place, nearly seam district and gather partially, still can not effectively suppress the formation of thick grain boundary ferrite, still can cause coarse-grain embrittlement phenomenon.
And for example Japanese Patent " spy opens clear 59-159968 " proposes to utilize crystal boundary solid solution boron to prevent netted thick grain boundary ferrite and improve nearly seam district flexible method.The weak point of this method is that the proportioning of boron and nitrogen is higher, when welding with the input of higher heat, still can promote the formation of thick granular bainite and can not suppress the local embrittlement phenomenon that the M-A island causes.
And for example Chinese patent " a kind of method for producing strong annealed steel hot-rolled sheet coil " (application number 200710035787.5) proposes boron in the steel and nitrogen are controlled at 0.0015～0.0060% and 0.010～0.018% respectively.But this steel is as passing through welding; Its weak point is the proportioning of boron content and nitrogen content not to be proposed to limit requirement; Still might make the proportioning between the two higher or on the low side; Thereby make the nearly seam of high heat input welding district form the tissue of thick grain boundary ferrite or thick granular bainite or thick grain boundary ferrite and the coexistence of thick granular bainite, cause significantly deficiency of impelling strength.
In sum; Existing related patent U.S. Patent No. and the related technology of document; Nitrogen content in the steel is on the low side, do not belong to nitrogen-increasing steel, or the proportioning of boron and nitrogen is improper, or the proportioning of boron and nitrogen is not limited; The scope of passing through reasonable control boron content and nitrogen content that proposes with the application and proportioning, compare, difference is all arranged to improve the method that the nearly seam of the high heat input of nitrogen-increasing steel welding distinguishes impelling strength.
Summary of the invention
The object of the present invention is to provide a kind of boron nitrogen composite micro-alloyed steel and method of manufacture that can adopt high heat input welding; Solved otherwise steel in nitrogen content on the low side, do not belong to nitrogen-increasing steel; The proportioning of boron and nitrogen is improper, or the proportioning of boron and nitrogen such as is not limited at problem.
The chemical ingredients of the boron nitrogen composite micro-alloyed steel of high heat input welding of the present invention is (wt%): C:0.04～0.09, Mn:1.00～1.80, Si:0.10～0.50; S :≤0.010, P :≤0.015, Mo:0.10～0.30; V:0.03～0.10, Ti:0.005～0.030, N:0.010～0.025; B:0.0005～0.0025, Al :≤0.015, surplus is Fe and unavoidable impurities.
The relation of boron content (wt%) and nitrogen content (wt%) is wherein limited, make proportioning between them meet the requirement of 0.010≤2N-15B≤0.018 and Ti+V+10B>=4.525N-0.002 simultaneously.
Method of manufacture of the present invention is accomplished manufacturing processed according to electric furnace or converter smelting, external refining, continuous casting, operational path rolling and temper.The following technical parameter of control in technology:
The smelting of steel and continuous cast method: in the converter tapping process, in ladle, add composite deoxidant and argon bottom-blowing carries out preliminary dexidation; At the CAS station, carry out deep deoxidation by in ladle, adding aluminium in the impregnating cover earlier, and acid-soluble aluminum content is≤0.015% in the control molten steel; Add VN alloy again; Make content of vanadium and nitrogen content in the water near target value, and Argon is handled simultaneously, to improve deoxidation effect and homogeneity of ingredients; At the LF station, make white slag earlier, carry out the adjustment of dark desulfurization and target component, after feed calcium line, titanium wire and boron line successively, and simultaneously Argon is handled, and makes composition even, confirms through sampling analysis that each elemental composition reaches target value in the molten steel and requires the back to tap, and send the continuous casting platform again; Casting process is taked the whole process protection cast.
Steel rolling: the Heating temperature of steel billet in soaking pit is 1150～1200 ℃, and be 4～8 hours heat-up time; Start rolling temperature is 1100～1150 ℃, and finishing temperature is 850～900 ℃, and total draft is 70%～90%; Steel plate after finish to gauge is that 770～820 ℃, speed of cooling are 10～30 ℃/s, to return hot temperature be 480～550 ℃ in the cold temperature of opening of ACC section; Steel plate goes out to stop behind the ACC and carries out heat behind the 30S and rectify, and is strong if plate shape better can directly be carried out heat.
In addition, carry out temper one to rolling the attitude steel plate, technology point comprises: tempering temperature is 550～600 ℃, and tempering time is 1min/mm * thickness of slab (mm)+30min.
Because the chemical ingredients of steel is the nearly key factor of stitching district's microstructure and impelling strength of influence welding; The present invention welds the coarse-grain embrittlement in nearly seam district and the local embrittlement that the M-A island causes in order to suppress the high heat input of nitrogen-increasing steel; Chemical ingredients to said steel; Particularly to the chemical ingredients of micro alloying element wherein, carried out special qualification, major cause is:
1, carbon is the principal element that influences the welding property of steel, when carbon content is higher than 0.09%, is prone to form high-carbon M-A island in the nearly seam of welding district, and hardness is higher and quantity is more, causes local embrittlement, reduces impelling strength.But, when carbon content is lower than 0.04%, be difficult to make steel to reach needed intensity.Therefore, carbon content should be controlled in 0.04～0.09% the scope.
2, manganese is postponed austenite to ferritic transformation in the nearly seam of welding district, to thinning microstructure, to improve impelling strength favourable.When the content of manganese was lower than 1.00%, above-mentioned effect was not remarkable, and made the intensity of said steel on the low side.When the content of manganese was higher than 1.80%, inner being prone to of steel plate formed tangible banded segregation, even do not disappear through heat during welding yet, thereby in nearly seam district the local hardened structure that produces, reduce impelling strength.Therefore, manganese content should be controlled in 1.00～1.80% the scope.
3, silicon promotes the formation on M-A island in the nearly seam district, and the embrittlement tendency is increased, and therefore, the content of silicon should not be higher than 0.50%; But because silicon is the most effective one of deoxidant element of when steel-making, when silicone content was lower than 0.10%, molten steel was prone to oxidized.Therefore, silicone content should be controlled in 0.10～0.50% the scope.
4, the toughness in the nearly seam of sulphur and phosphorus heavy damage steel and welding district.Therefore, sulphur, phosphorus content should be controlled at respectively≤0.010% and≤below 0.015%.
5, molybdenum suppresses the formation of thick grain boundary ferrite in the nearly seam of high heat input welding district, and is favourable to improving low-temperature flexibility.When molybdenum content was lower than 0.10%, above-mentioned effect was not remarkable; But when molybdenum content was higher than 0.30%, granular bainite prosperity and quantity were on the high side in the nearly seam district, and low-temperature flexibility is reduced.Therefore, molybdenum content should be controlled at 0.10～0.30%.
6, vanadium combines to form the VN particle with nitrogen in said steel, and VN particle separating out in austenite can be improved the ferritic nucleation rate, thinning microstructure; VN particle separating out in ferritic has significant precipitation strength effect.When the content of vanadium was lower than 0.03%, the above-mentioned effect of vanadium was not remarkable.But along with the increase of content of vanadium, the quantity of M-A island fragility phase increases in the nearly seam of the welding district, reduces impelling strength, and its content should not surpass 0.10%.Therefore, content of vanadium should be controlled at 0.03～0.10%.
7, trace amount of titanium combines to form TiN with nitrogen, and the alligatoring that can effectively suppress to weld nearly seam district original austenite grain improves low-temperature flexibility, and its content should not be lower than 0.005%.But too much titanium on the one hand, is prone in the molten steel solidification process, form thick inclusion; Reduce the impelling strength of steel and welded heat affecting zone, on the other hand, in steel, " seize " too much nitrogen; The precipitation strength effect of reduction vanadium, its content should not surpass 0.030%.Therefore, suitable titanium content should be controlled at 0.005～0.030%.
8, aluminium is a kind of important deoxidant element in the steelmaking process, even in molten steel, add the aluminium of trace, also can effectively reduce the inclusion content in the steel, and crystal grain thinning.But too much aluminium equally can " seize " too much nitrogen in steel, both be unfavorable for bringing into play the effect of TiN, the also precipitation strength effect of weakening ratio vanadium, and therefore, aluminium content should be controlled at below 0.015%.
9, nitrogen is a kind of micro alloying element of key in said steel, effectively to utilize simultaneously the effect of VN and TiN, needs to have in the steel abundant N to cooperate with V and Ti, and its content should not be lower than 0.010%.But too high nitrogen pick-up level is except that continuous casting operation and slab quality are had the negative impact; Also in steel, form nomadic nitrogen; Increase the timeliness fragility of steel and welded heat affecting zone, should its content be controlled at below 0.025%, and adopt little combination elements such as Ti, V, B to fix.In addition, improve with the nitrogen pick-up level, with the high heat input welding of >=45kj/cm the time, thick grain boundary ferrite quantity is tending towards increasing in the nearly seam district, also need limit too high nitrogen content.Therefore, except needs are controlled at nitrogen content 0.010～0.025%, also need the content (wt%) of Ti in the steel, V, B and N to meet Ti+V+10B >=4.525N-0.002.
10, boron also is a kind of micro alloying element of key in said steel, and trace B form with solid solution boron in steel is gathered at the austenite grain boundary place partially, can postpone austenite to ferritic transformation, suppresses the formation of thick grain boundary ferrite, promotes bainite transformation.Boron also has similar effect in the nearly seam of the high heat input of said steel welding district.Be unfavorable for bringing into play above-mentioned effect but cross low boron, therefore, its content should not be lower than 0.0005%.But too high boron content can promote the formation of thick granular bainite in the nearly seam of the high heat input welding district of >=45kj/cm, and the local embrittlement tendency that the M-A island is caused increases, and its content should not surpass 0.0025%.Therefore, suitable boron content should be controlled at 0.0005～0.0025%.On the other hand, the add-on of boron also must adapt with the nitrogen pick-up level, promptly must control the proportioning of rational boron content and nitrogen content, just can maximize favourable factors and minimize unfavourable ones, and makes boron bring into play above-mentioned advantageous effect.Reason is: in the nearly seam of high heat input welding district, when the proportioning of boron and nitrogen was on the low side, boron was on the weak side to the restraining effect that thick grain boundary ferrite forms, and nitrogen is strong partially to the promoter action that thick grain boundary ferrite forms, and still can cause coarse-grain embrittlement phenomenon; When the proportioning of boron and nitrogen is higher; Boron is strong partially to the promoter action that thick granular bainite forms; And that nitrogen induces the intracrystalline ferritic to limit the effect that bainite ferrite grows up through the VN particle is on the weak side; Still a fairly large number of thick granular bainite can be produced, and the local embrittlement phenomenon that the M-A island causes can not be suppressed.Therefore, except should being controlled at the above-mentioned scope by high hot boron content and the nitrogen content of importing in the nitrogen-increasing steel that welds said, also wherein the proportioning of boron content and nitrogen content is controlled in the scope of 0.010≤2N-15B≤0.018.
The present invention has following advantage:
1, boron nitrogen composite micro-alloyed steel that can high heat input welding of the present invention is input as 45～80Kj/cm, corresponding t in heat
8/5Be under the condition of 30～100s through after the welding, the microstructure in nearly seam district mainly is made up of intracrystalline ferritic, granular bainite and grain boundary ferrite M-A island, wherein the ferritic percentage composition of intracrystalline>=30%;-40 ℃ of charpy impact merit>=47J in nearly seam district.
2, boron nitrogen composite micro-alloyed steel that can high heat input welding of the present invention, microstructure contains quasi-polygonal ferrite and bainite, wherein the volume(tric)fraction of bainite >=40%; Ys >=550MPa, tensile strength >=670MPa, unit elongation >=18% ,-40 ℃ of charpy impact merit >=100J.
3, the method for manufacture of boron nitrogen composite micro-alloyed steel that can high heat input welding of the present invention, production technique is easy, is specially adapted to require adopt the production of the steel plate of high heat input welding.
Description of drawings
Fig. 1 be the mixed structure that is made up of quasi-polygonal ferrite and bainite for the metallographic structure of boron nitrogen composite micro-alloyed steel that can high heat input welding of the present invention.
Fig. 2 can be input as 30Kj/cm (corresponding t at welding heat by the high hot boron nitrogen composite micro-alloyed steel of importing welding for of the present invention
8/5Be 15s) time, nearly seam district forms the mixed structure that is made up of intracrystalline ferritic (needle-like or bulk), grain boundary ferrite and granular bainite.
Fig. 3 is for being increased to 45Kj/cm (corresponding t in the welding heat input by 30Kj/cm by the high hot boron nitrogen composite micro-alloyed steel of importing welding when described
8/5Be 30s) time, nearly seam district tissue morphology is almost constant, and the intracrystalline ferritic still occupies the majority, and the quantity of grain boundary ferrite and granular bainite slightly increases.
Fig. 4 can further be increased to 60Kj/cm (corresponding t in the welding heat input by 45Kj/cm by the high hot boron nitrogen composite micro-alloyed steel of importing welding for of the present invention
8/5Be 60s) time, organizational composition is constant in the nearly seam district, and the quantity of grain boundary ferrite and granular bainite increases, size increases, but the intracrystalline ferritic still occupies sizable ratio.
Fig. 5 be comparative steel 1 (separately nitrogen pick-up, do not add boron) when welding heat is input as 60Kj/cm, nearly seam district forms the mixed structure that is made up of a large amount of thick grain boundary ferrites, little granular bainite and intracrystalline ferritic.
Fig. 6 be comparative steel 2 (adding boron, not nitrogen pick-up separately) when welding heat is input as 60Kj/cm, nearly seam district forms the mixed structure that is made up of a large amount of thick granular bainites and a small amount of intracrystalline ferritic.
Fig. 7 be according to the invention can high heat input welding nitrogen-increasing steel (Fig. 7 a), comparative steel 1 (Fig. 7 b; Separately nitrogen pick-up, do not add boron) and comparative steel 2 (Fig. 7 c; Add boron, not nitrogen pick-up separately) when welding heat was input as 60Kj/cm, the M-A island pattern that nearly seam district adopts color etching to show was explained the present invention compound interpolation boron and nitrogen in steel; Compare with adding boron separately, the quantity that can make high heat input weld M-A island, nearly seam district reduces, the density reduction; Compare with independent nitrogen pick-up, closely the quantity on M-A island, seam district reduces, size reduces, more even distribution can to make high heat input welding.
Fig. 8 can high hot boron nitrogen composite micro-alloyed steel and the comparative steel of importing welding closely stitch the variation tendency of district-40 ℃ charpy impact merit with the heat input for according to the invention; The welding that steel of the present invention is described is closely stitched the district and is had more excellent low-temperature flexibility relatively; Even when the welding heat input is increased to 80Kj/cm;-40 ℃ of ballistic works in nearly seam district still are higher than 47J, and comparative steel is closely stitched-40 ℃ of ballistic works in district and is lower than 47J when welding heat input >=45Kj/cm.
Embodiment
Below in conjunction with specific embodiment a kind of boron nitrogen composite micro-alloyed steel and the method for manufacture that can high heat input welding that the present invention relates to be done further to describe in detail.
By a kind of boron nitrogen composite micro-alloyed steel and method of manufacture that can high heat input welding according to the invention, have manufactured experimently the test steel of 3 kinds of different boron content and nitrogen content, as embodiment.The test steel adopts 150 tons of converter smeltings.Follow following technology point when smelting and continuous casting trial-production:
1, in the converter tapping process, in ladle, adds composite deoxidant and argon bottom-blowing carries out preliminary dexidation;
2,, carry out deep deoxidation by in ladle, adding aluminium in the impregnating cover earlier, and acid-soluble aluminum content is≤0.015% in the control molten steel at the CAS station; Add VN alloy again; Make content of vanadium and nitrogen content in the water near target value, and Argon is handled simultaneously, to improve deoxidation effect and homogeneity of ingredients;
3, at the LF station, make white slag earlier, carry out the adjustment of dark desulfurization and target component; After feed calcium line, titanium wire and boron line successively, and simultaneously Argon is handled, and makes composition even; Confirm that through sampling analysis each elemental composition is tapped after reaching the target value requirement in the molten steel, send the continuous casting platform again;
4, casting process is taked the whole process protection cast.
The thickness specification of continuously cast bloom is 220mm, on 3.5 meters milling trains, further each test billet rolling is become the sheet material of 20mm and two kinds of thickness specifications of 30mm.Follow following technology point when rolling:
1, billet heating temperature is 1180 ± 20 ℃, and be 5 hours heat-up time;
2, start rolling temperature is 1100～1150 ℃, and finishing temperature is 850～900 ℃, and three kinds of total drafts of different thickness specification test steel plate are respectively 90%, 86% and 82%;
3, the steel plate after finish to gauge is that 770～820 ℃, speed of cooling are 15 ℃/s, to return hot temperature be 480～550 ℃ in the cold temperature of opening of ACC section;
4, it is strong that steel plate goes out to stop behind the ACC to carry out behind the 30S heat.
Roll the back steel plate is carried out temper one, tempering temperature is 560 ± 10 ℃, and three kinds of different thickness specification steel plate tempering times are respectively 50,60 and 70min.
The chemical ingredients of 3 kinds of test steel is seen table 1.As comparing, its chemical ingredients is also listed in table 1 to alternative with two kinds of commercial hot-rolled sheets.
Table 1: the chemical ingredients of steel (wt%)
Can find out that from table 1 according to three kinds of test steel of the present invention's preparation, chemical ingredients all meets requirement according to the invention.Wherein the level of boron content is respectively high, medium and low, and the proportioning of boron content and nitrogen content also promptly meets qualification requirement according to the invention.Comparative steel 1 is for not adding boron but the suitable low-carbon (LC) vanadium nitrogen micro-alloy high-strength steel of other chemical ingredients and embodiment 3.Comparative steel 2 is the common low carbon bainitic steel of not nitrogen pick-up.
Each embodiment is tested steel plate and comparative steel sampling; According to GB/T 13239-2006 standard; Adopt MTS NEW810 type tensile testing machine, stretch, the test tensile performance in wale-wise with 3mm/min constant chuck rate travel; Sampling point is 1/2 place of thickness of slab, and test-results is got the MV of 2 samples.According to GB/T 229-2007 standard, adopt NCS series 500J instrumentation Charpy impact machine tester, test-40 ℃ of charpy impact merits, sampling point is 1/2 place of thickness of slab, test-results is got the MV of 3 samples.Steel plate Mechanics Performance Testing result sees table 2.
Table 2: the mechanical property of steel
Can find out that according to the test steel of the present invention's preparation, ys reaches Q550～Q620 level, ,-40 ℃ of charpy impact merits are all more than 200J.Suitable with the mechanical property of comparative steel.
To test steel and comparative steel and further be processed into the test specimen that is of a size of 10 * 10 * 80 (mm); Adopt the nearly seam of Gleeble3500 trier simulation welding district tissue earlier; Corresponding thermal circulation parameters comprises: not preheating before the weldering; 1350 ℃ of maximum heating temperatures, welding heat input (Kj/cm) is respectively 20,25,30,45,60,80, corresponding t
8/5Be respectively 6s, 10s, 15s, 30s, 60s, 100s, end 100 ℃ of cooling temperatures.According to GB/T 229-2007 standard, adopt NCS series 500J instrumentation Charpy impact machine tester then, test simulation closely stitches district's ℃ charpy impact merit, and the result sees table 3.
Table 3: the low temperature notched toughness in the nearly seam of welding district
Can find out that from table 3-40 ℃ of ballistic works in five kinds of steel welding nearly seam districts all present downtrending generally with the raising of heat input.But; According to three kinds of test steel of the present invention's preparation, the nearly seam of welding district is under the condition of identical heat input, and-40 ℃ of ballistic works all are higher than the respective value of comparative steel; And as heat input >=45Kj/cm, invention steel and the nearly seam of comparative steel welding low temp area flexible difference are more remarkable.Wherein, embodiment 3 compares with comparative steel 1, because the former contains micro-B, (under >=45Kj/cm) the welding conditions, the formation of thick grain boundary ferrite is suppressed in the nearly seam district, so low-temperature impact work is 2～3 times of the latter in the higher thermal input.Embodiment 2 compares with comparative steel 2, because the latter do not have nitrogen pick-up, the proportioning of boron content and nitrogen content is higher, the higher thermal input (under >=45Kj/cm) the welding conditions, the serious alligatoring of granular bainite during nearly seam is distinguished, so low-temperature flexibility is far below the former.
Claims (2)
1. the boron nitrogen composite micro-alloyed steel that can adopt high heat input welding is characterized in that chemical component weight percentage ratio is: C:0.04～0.09, Mn:1.00～1.80; Si:0.10～0.50, S :≤0.010, P :≤0.015, Mo:0.10～0.30; V:0.03～0.10, Ti:0.005～0.030, N:0.010～0.015; B:0.0005～0.0011, Al :≤0.015, surplus is Fe and unavoidable impurities; Proportioning between boron content and the nitrogen content meets the requirement of 0.010≤2N-15B≤0.018 and Ti+V+10B>=4.525N-0.002 simultaneously.
2. the method for manufacture of the described boron nitrogen of claim 1 composite micro-alloyed steel is characterized in that, the following technical parameter of control in technology:
The smelting of steel and continuous cast method: in the converter tapping process, in ladle, add composite deoxidant and argon bottom-blowing carries out preliminary dexidation; At the CAS station, carry out deep deoxidation by in ladle, adding aluminium in the impregnating cover earlier, and acid-soluble aluminum content is≤0.015% in the control molten steel; Add VN alloy again; Make content of vanadium and nitrogen content in the water near target value, and Argon is handled simultaneously, to improve deoxidation effect and homogeneity of ingredients; At the LF station, make white slag earlier, carry out the adjustment of dark desulfurization and target component, after feed calcium line, titanium wire and boron line successively, and simultaneously Argon is handled, and makes composition even, confirms through sampling analysis that each elemental composition reaches target value in the molten steel and requires the back to tap, and send the continuous casting platform again; Casting process is taked the whole process protection cast;
Steel rolling: the Heating temperature of steel billet in soaking pit is 1150～1200 ℃, and be 4～8 hours heat-up time; Start rolling temperature is 1100～1150 ℃, and finishing temperature is 850～900 ℃, and total draft is 70%～90%; Steel plate after finish to gauge is that 770～820 ℃, speed of cooling are 10～30 ℃/s, to return hot temperature be 480～550 ℃ in the cold temperature of opening of ACC section; It is strong that steel plate goes out to stop behind the ACC to carry out behind the 30s heat;
Carry out temper one to rolling the attitude steel plate, tempering temperature is 550～600 ℃, and tempering time is 1min/mm * thickness of slab mm+30min;
The chemical component weight percentage ratio of described boron nitrogen composite micro-alloyed steel is: C:0.04～0.09, Mn:1.00～1.80, Si:0.10～0.50; S :≤0.010, P :≤0.015, Mo:0.10～0.30; V:0.03～0.10, Ti:0.005～0.030, N:0.010～0.015; B:0.0005～0.0011, Al :≤0.015, surplus is Fe and unavoidable impurities; Proportioning between boron content and the nitrogen content meets the requirement of 0.010≤2N-15B≤0.018 and Ti+V+10B>=4.525N-0.002 simultaneously.
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| CN105349888B (en) * | 2015-11-30 | 2017-06-23 | 钢铁研究总院 | One kind can high heat input welding vanadium nitrogen titanium high-strength steel sheet and preparation method |
| CN107254564B (en) * | 2017-05-24 | 2019-03-26 | 马鞍山市兴达冶金新材料有限公司 | A kind of production method and its production core-spun yarn of high-performance micro alloyed steel |
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| 薛东妹等.硼对V-N微合金钢热影响区组织和性能的影响.《钢铁》.2010,第45卷(第7期),第85-88页. * |
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