CN101041880B - Steel plate having welding joint with excellent tenacity and manufacturing method thereof - Google Patents
Steel plate having welding joint with excellent tenacity and manufacturing method thereof Download PDFInfo
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- CN101041880B CN101041880B CN200610067687A CN200610067687A CN101041880B CN 101041880 B CN101041880 B CN 101041880B CN 200610067687 A CN200610067687 A CN 200610067687A CN 200610067687 A CN200610067687 A CN 200610067687A CN 101041880 B CN101041880 B CN 101041880B
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Abstract
The invention discloses a steel board, which comprises the following parts: 0.02-0.12% C, 0.002-0.010% N, 0.005-0.025% Ti, 0.003-0.025% Nb, wherein the Ti nitrate and Nb carbonitride is evolved and dispersed over 100 per square millimeter; the adaptor of steel board possesses excellent flexibility.
Description
Technical field
The present invention relates to a kind of welded-joint, self also has the steel plate of excellent toughness the especially tenacity excellent of welding heat affected zone, and mother metal.Relate to for example general shipbuilding with headed by the steel plate, be applied to expose to the open air for example shipbuilding under the cold condition with low temperature steel plate and liquefied petroleum gas (LPG) storage container situation with steel plate etc. under, also demonstrate the excellent toughness and the steel plate of welding joint tenacity excellent.
Background technology
Now, at each field steel plate of demand low-temperature flexibility excellence all.For example, the low temperature of storage solution liquefied oil gas (LPG) and liquefied ammonia is with container etc., because will use at the low temperature below about-60 ℃ for gas is remained liquefaction, so require also can guarantee excellent toughness under such cold condition.In addition in the low temperature steel plate that shipbuilding is used, because will be when carrying, so require to bear cryogenic toughness about-20 ℃ in the ocean navigation that is lower than the sub-zero temperature zone.Be used in the particularly welded-joint of the steel plate of purposes like this, because make the toughness deterioration easily, so the steel plate of the low-temperature flexibility excellence of tight demand welded-joint by the variation of the microtexture due to the welding heat.
Therefore, open in the clear 54-19412 communique, proposed to improve the low-temperature flexibility of welded-joint by the chemical ingredients of adjusting steel plate for example spy.In this look-ahead technique, be conceived to island martensite body in the welded-joint generation, this island martensite body becomes the destructive starting point easily because C (carbon) is spissated hard phase, so reduce the C amount of steel (mother metal) in order to reduce this island martensite body.But recently, the low-temperature flexibility that surmounts the adjustment that utilizes chemical ingredients improves, and requires the improvement of further low-temperature flexibility.For example, the time be heated in the pyritous zone about 1400 ℃ [heat affected zone (below, comprise that sometimes welded-joint all is called HAZ) etc.] in welding, because coarsening and low-temperature flexibility deterioration, so require the improvement of further low-temperature flexibility.
Therefore, open in the flat 9-165656 communique, proposed to disperse, thereby be suppressed at the method for thickization of the crystal grain of HAZ portion by the trickle precipitate that makes TiN etc. the spy.But, when carrying out the welding of high heat energy, have than described HAZ portion also the zone of high temperature (more than 1400 ℃) (for example, near the welding line during high heat energy welding etc.), because the precipitate solid solution of TiN etc. in such zone is so can not expect the thickization inhibition effect of crystal grain.In addition, heating part at the two-phase temperature field, because ferrite and austenite become equilibrium state, C moves to austenite from this ferrite, C is concentrated in austenite, so final island martensite body generates (such phenomenon is called as two phase region embrittlement), but above-mentioned trickle precipitate lacks the effect that prevents of two phase region embrittlement.
The applicant is good as anti-ammonia stress corrosion cracking in addition, and the also excellent Steel Plates For Low Temperature Service of the toughness of HAZ portion, has proposed the special technology of opening flat 11-131178 communique record.This invention, be to improve anti-ammonium stress corrosion cracking below 0.06% by C content is suppressed at, and contain the toughness of improving HAZ portion by the TiN that makes specified quantitative, special metal structure is based on ferrite, form perlite at the ferrite crystal boundary and be stratiform dispersive pearlitic structure, improve 2 such demand characteristicss of anti-nitrogen stress corrosion cracking and HAZ toughness therefrom.
The invention that this Te Kaiping 11-131178 communique is put down in writing, under lower-temperature atmosphere, also demonstrate excellent anticorrosion stress-resistant crackle, and when carrying out the welding of high heat energy, also can guarantee the toughness of welding heat affected zone well, just can be called the Cryogenic Steel of excellence from this point.But do not need person's requirement can not stay in this, particularly require the low-temperature flexibility of welding heat affected zone that further improvement is arranged.
Summary of the invention
The present invention is conceived to above-mentioned such situation, its purpose is to propose a kind of steel plate, it is being used as general shipbuilding etc., or as low temperature shipbuilding more with and low temperature with container with etc. and when using, has excellent toughness as mother metal itself, and in HAZ toughness, can bring into play the characteristic that outmatches on the described previous application invention.
Can solve the steel plate of the present invention of above-mentioned problem, contain:
C:0.02～0.12% (meaning of quality %, below identical),
N：0.002～0.010％、
Ti:0.005～0.025% and
Nb：0.013～0.025％，
In the cross section of described steel plate, there is 100/mm in the compound precipitate of Ti nitride and Nb carbonitride
2More than.
Above-mentioned steel of the present invention preferably contain Mn:0.5～1.8%, satisfy below the Si:0.7%, below the Al:0.1%.In addition in these steel, the further improvement of expection low-temperature flexibility can contain at least one side of B:0.0005～0.005% and Ni:0.01～0.5%.In addition, for the characteristic with steel plate improves one-level, characteristic as required, contain following also effective: promptly from the group that Zr:0.0003～0.05%, Ca:0.0005～0.005%, Mg:0.0005～0.005%, REM:0.0005～0.01% are formed, choose at least a kind wantonly, perhaps, from the group that Cu:0.01～0.5%, Cr:0.05～0.5%, Mo:0.01～0.5%, V:0.005～0.1% are formed, choose at least a kind wantonly.
In addition, manufacture method of the present invention, method as the steel plate that can more positively obtain having above-mentioned characteristic, be to possess the invention of certain position, it has following feature, when the steel of prerequisite of above-mentioned chemical ingredients are satisfied in hot rolling, the draft of the temperature field more than 800 ℃ is controlled at more than 40%, and, make the compound precipitate that disperses to separate out Ti nitride and Nb carbonitride in the steel plate being controlled at more than 30% at the draft that is lower than 800 ℃ temperature field.
When implementing this manufacture method,, quicken cooling with the speed of 1～50 ℃/sec if after above-mentioned hot rolling finishes, perhaps further after this quickens cooling, carry out tempering with the temperature more than 500 ℃, below the Acl transformation temperature, because the performance of steel plate can be improved one-level, institute thinks preferred.
Steel plate of the present invention, by carbon content is suppressed for low-level, make N and Ti also have Nb to contain in right amount in addition, in steel, the compound precipitate of Ti nitride and Nb carbonitride is generated with the fine dispersion state, thereby improve the toughness of mother metal self, and can more positively prevent thickization of the crystal grain in HAZ portion especially, and the steel plate of HAZ portion flexible brilliance is provided.
Description of drawings
Fig. 1 is the microphotograph of form of the compound precipitate of expression TiN and Nb (CN).
Embodiment
Present inventors expect the solution of above-mentioned such problem and research with keen determination repeatedly, consequently draw following understanding, and can solve the described problem of the intent of the present invention satisfactorily, thereby finish described the present invention, the carbon content that is about to steel is suppressed at low-level, as prerequisite, an amount of Ti and N is contained, an amount of Nb is contained, in steel, make trickle the separating out of forming by Ti nitride and Nb carbonitride of compound precipitate thus.
In the present invention promptly, at first as first prerequisite, carbon content must be included in 0.02～0.12% scope. its reason is because in order to ensure the structural strength as steel necessity, C more than 0.02% (carbon) is essential, be lower than this moment intensity with deficiency. can be more preferably more than 0.03%. on the other hand, the present invention's supposition as described above, it for example is the purposes that is applied to expose to the open air at so-called cold condition below-20 ℃ or-60 ℃, guarantee to stand the base metal tenacity that uses down in cold condition so, and to prevent the toughness deterioration of HAZ portion, C amount must be suppressed at below 0.12% so. more preferably the C amount on be limited to 0.10%, more preferably below 0.07%.
Secondly, N (nitrogen) amount need be controlled at 0.002～0.010% scope.In the present invention promptly, the generation source that N and Ti be combined into described later are nitride, and become the generation source of Nb carbonitride, be indispensable element particularly improving on the HAZ toughness, when being lower than 0.002%, the quantitative change of separating out as above-mentioned nitride gets insufficiently, is difficult to obtain the tough property improvement effect of expection level.But, then, therefore should be suppressed at below 0.010% because the increase of non-metallic inclusion content makes the toughness deterioration on the contrary if the N quantitative change gets too much.More preferably the N amount is more than 0.004%, but below 0.008%.
Ti is in the generation by the Ti nitride, goes up important element and compound precipitate with the Nb carbonitride is generated, and must contain promising more than 0.005% but below 0.025%.When being lower than 0.005%, the growing amount deficiency of Ti nitride, and also become insufficient with the growing amount of the compound precipitate of Nb carbonitride, can't obtain the HAZ toughness that makes the people satisfied.But if too much, then because become the reason that makes the toughness deterioration on the contrary, so must be suppressed at below 0.025%.More preferably Ti content is more than 0.008% but below 0.020%.
Nb is the element that characteristics are arranged among the present invention most, is combined into the generation source of Nb carbonitride with carbon and nitrogen, generates compound precipitate with above-mentioned Ti nitride, gives the HAZ flexible and improves with significant effect.In order to make effect performance like this effectively, must make it at least to contain more than 0.003%, can be preferably more than 0.005%, further preferably make it to contain more than 0.010%.But so the additive effect of Nb is about 0.025% saturated, if become many more than this, then hardenability becomes superfluous, because HAZ portion becomes the many top bainites of island martensite body, HAZ toughness variation, so can be at most below 0.025%, preferably be suppressed at below about 0.020%.
In the present invention, as explanation simply before, also just like the detailed description that appends, its maximum is characterised in that, by making the compound precipitate of separating out Ti nitride and Nb carbonitride in the steel in right amount, thereby improve HAZ toughness, necessary element for this reason is 4 kinds of elements of C, N, Ti, Nb, but, preferably satisfy below the Si:0.7% as the basal component of steel; Mn:0.5～1.8%; Below the Al:0.1%.
Above-mentioned Si if content in steel becomes too much, then makes the increase of island martensite body, has strengthened making the tendency of the low-temperature flexibility deterioration of welded-joint, so can to suppress be below 0.7%, is preferably below 0.5%, more preferably below 0.3%.Also have, because Si is used in the deoxidation of molten steel more, so almost invariably will sneak in the steel.In addition, owing to also help the intensity of steel plate to improve, so Si can preferably contain more than about 0.05% for more than about 0.01%.
In addition, Mn has the effect that improves hardenability and improve the intensity of steel plate, can preferably contain more than 0.5%, more preferably more than 0.7%, more preferably more than 1.0%.But excessive if the Mn quantitative change gets, the tendency of the low-temperature flexibility deterioration that makes HAZ portion then because increasing, the island martensite body is arranged, thus can preferably be suppressed at below 1.8%, more preferably below 1.6%.
Because being used as reductor more, uses Al, so be the element of in the manufacturing processed of molten steel, unavoidably sneaking into, but if too much, then because the increase of oxide based inclusion content, thereby make the toughness deterioration of steel, so can be suppressed at below 0.1%, preferably below 0.08%, more preferably below 0.06%.On the other hand, be precipitate because Al generates AlN, have the effect that the HAZ toughness when high heat energy is welded improves, so, when wanting to utilize Al to make HAZ toughness improve the effect performance effectively, Al is for example contained more than 0.01%, be preferably more than 0.02% also effective.
Steel plate of the present invention except that described element, also can comprise other element according to necessity, and for example, toughness improves element [B:0.005% is following, Ni:0.5% with inferior]; Precipitate forming element [Zr:0.05% is following, Ca:0.005% following, Mg:0.005% is following and REM:0.01% with inferior]; Intensity improves element [Cu:0.5% is following, Cr:0.5% is following, Mo:0.5% is following, V:0.1% with inferior].
Toughness improves element: B, Ni etc.
B has fixing effect to the deleterious solid solution N of HAZ toughness by the generation of BN.The lower limit of B content does not have special stipulation, but is bringing into play energetically this time spent of doing, and can make it to contain more than 0.0003%, is preferably more than 0.0005%.But, because if B content becomes excessive, the HAZ toughness deterioration when high heat energy is welded, institute can be suppressed at below 0.005%, preferably below 0.004%.
Ni helps making toughness to improve.The lower limit of Ni content is not particularly limited, but the time spent can make it to contain more than 0.01% this work of positive performance, is preferably more than 0.05%.But because if Ni content is too much, then the oxide skin scab becomes and takes place easily, so can be suppressed at below 0.5%, is preferably below 0.4%.Above-mentioned toughness improves element, can add separately, also can compound interpolation 2 kinds.
Precipitate forming element: Zr, Ca, Mg, REM etc.
Zr and described Ti form nitride equally, and the HAZ flexible when helping high heat energy to weld improves.The lower limit of Zr content is not particularly limited, but expecting that actively this work can make it to contain more than 0.0003% the time spent, is preferably more than 0.0005%.But,, then cause and, be preferably the toughness deterioration below 0.005% so can be suppressed at below 0.05% owing to the reduction of purity becomes because if Zr content is too much.
Ca, Mg and REM (rare earth element) form oxide compound, sulfide, oxysulfide etc., have the effect of thickization of the crystal grain that suppresses HAZ portion, the anisotropic effect that in addition alleviates mother metal in addition.The lower limit of Ca, Mg and REM content is not specially limited, but in order to apply flexibly this effect energetically, can make it to contain Ca is (to be preferably more than 0.0010%) more than 0.0005%, Mg (is preferably more than 0.0010%) more than 0.0005%, and REM (is preferably more than 0.0010%) more than 0.0005%.But, because if these Ca, Mg, REM are too much, then the purity of steel reduces and becomes the reason of rerum natura deterioration, so can suppress Ca is (to be preferably below 0.003%) below 0.005%, Mg (is preferably below 0.003%) below 0.005%, REM (is preferably below 0.005%, is preferably especially below 0.003%) below 0.01%.Above-mentioned precipitate forming element can add separately, also can be to make up compound interpolation arbitrarily more than 2 kinds.
Intensity improves element: Cu, Cr, Mo, V etc.
Cu improves effective elements to separating out the intensity that makes steel by solution strengthening and reinforcement, and the lower limit of addition is not specially limited, but is applying flexibly energetically this time spent of doing, and can make it to contain more than 0.01%, is preferably more than 0.05%.But, because if Cu content is too much, the hot workability deterioration of steel then, crackle will enter surface of steel plate easily, so can be suppressed at below 0.5%, be preferably below 0.3%.
Any all works Cr and Mo effectively to the intensity raising of mother metal.The lower limit of the addition of Cr and Mo is not specially limited, but when expecting this action effect energetically, can contain Cr is (to be preferably more than 0.10%) more than 0.05%, and Mo (is preferably more than 0.05%) more than 0.01%.But, because if Cr and Mo become excessive, the tendency of the HAZ toughness deterioration when high heat energy is welded is arranged then, (be preferably below 0.3%) below 0.5% so should be suppressed at Cr, Mo (is preferably below 0.3%) below 0.5%.
V is the element that the intensity of steel is risen by precipitation strength, and the lower limit of addition still, is being applied flexibly this time spent of doing energetically not by special stipulation, can contain more than 0.005% (to be preferably more than 0.010%).But, because if V is too much, the HAZ toughness deterioration when then high heat energy welds (is preferably below 0.05%) so can be suppressed at below 0.1%.
Above-mentioned intensity improves element, can add separately, also can be to make up arbitrarily and to use more than 2 kinds.
The remainder composition of steel of the present invention comes down to Fe and unavoidable impurities, as unavoidable impurities, can list for example P and S etc.These P and S, reduction is also effective energetically, and for example, P can be reduced to below 0.015%.This is because if P becomes weldability deterioration at most, so can preferably be suppressed at below 0.010%.Also have P,, then can produce practical harm hardly if be below about 0.001%.
In addition, S can be suppressed at below 0.005%.This is because if the sulfide-based at most inclusion of S quantitative change increases, the base metal tenacity of the steel plate easy deterioration that becomes.Be preferably below 0.003%.Also have,, then can produce practical harm hardly if S is below 0.001% degree.
The one-tenth of the steel that adopt in the present invention is grouped into as above to be stated, but in the present invention except these one-tenth are grouped into, be present in Ti in the steel plate cross section and Nb carbonitride have a form, also of crucial importance on raising HAZ toughness, the compound precipitate of Ti nitride and Nb carbonitride is separated into 100/mm in the cross section of steel plate
2More than, have the feature that existing material does not possess.Promptly, so-called this compound precipitate, for example if according to TEM (transmission electron microscope) photo, then show an one example as Fig. 1 (drawing substitutes microphotograph), be lateral margin and corner portion, adhere to such state and the compound precipitate of separating out with the Nb carbonitride at thicker Ti nitride.
Then, select the steel grade of HAZ tenacity excellent among a large amount of as described later embodiment, the comparative example, when carrying out TEM/EDS (the type X ray ultimate analysis of loosing) analysis, at Fig. 1 precipitate indicated by the arrow is the Ti nitride, what separate out with the state of the periphery that is attached to the precipitate of being made up of this nitride and corner portion is the Nb carbonitride, Ti nitride and Nb carbonitride are dispersed with 100/mm as compound precipitate in the steel plate cross section like this
2More than, 200/mm more preferably
2Above steel all are identified and demonstrate excellent HAZ toughness.
Therefore, in the time spent of doing of further pursuing this compound precipitate, the steel plate of separating out separately with the Ti nitride compares, and defines the following effect of performance.Promptly, when welding, be heated in the pyritous HAZ zone about 1400 ℃, even for example the Ti nitride exists, thereby lose crystal grain granular effect in the fusion of this high-temperature area Ti nitride, with respect to this, because the compound precipitate of Ti nitride and Nb carbonitride is difficult to fusion at high-temperature area, in becoming pyritous HAZ zone, also be difficult to complete fusion, so given play to high crystal grain granular effect, in addition, the part of this compound precipitate also can fusion in the high temperature territory, but, because these exist with partial multiviscosisty state, so during the cooling after being subjected to welding heat, separate out again as trickle crystal grain easily,, bring into play crystal grain granular effect thereby be identified because it works as ferrite transformation nuclear.
Also have in the present invention, above-mentioned compound precipitate quantitatively, be that the cross section for the examination steel plate is carried out mirror ultrafinish, carry out tem observation after the electrolytic corrosion, for its size and number, choose at random 20 zones from cross-section photograph, measure the size and the number of compound precipitate, try to achieve as its mean value with 15000 times of shootings of multiplying power.Above-mentioned compound precipitate, shown in the microphotograph of Fig. 1, it has the size about 100nm substantially as described, following fine existence hardly about 10nm.Thereby according to the TEM photo of above-mentioned multiplying power, the whole compound precipitate quantity that investigation can be observed is scaled area 1mm with it
2In number and try to achieve.
Also have, the manufacture method with steel plate of above-mentioned such characteristic is not limited especially, but as preferred method, will satisfy the steel of the prerequisite that described such one-tenth is grouped into, and rolling after melting, the casting, at this moment controlled rolling is effective as following.Promptly, in the hot-rolled process after casting, to be adjusted at the draft of the temperature province more than 800 ℃ more than 40%, more preferably more than 50%, and, the draft that is lower than 800 ℃ temperature province can be controlled at more than 30%, more preferably more than 50%, if adopt such hot-rolled condition, become to be grouped into controlled steel as described above like that by using, the compound precipitate of the quantity of above-mentioned the best is generated.
In addition, when the draft 800 ℃ temperature province is lower than 40%, because draft deficiency in the recrystallization temperature zone, so austenitic grain refining becomes insufficient, in addition when being lower than 30% at the draft that is lower than 800 ℃ temperature province, because the draft deficiency in the non-recrystallization zone, so become insufficient to the separating out of Nb (CN) of TiN nuclear, any situation all is difficult to guarantee the compound precipitate of the quantity of target of the present invention.
Also have, the thickness of slab of steel plate of the present invention is not limited especially, can be applicable to the steel plate (comprising dull and stereotyped and corrugated plate etc.) of various thickness, but effect of the present invention is more effectively brought into play, be that thickness is the steel plate of 7mm degree above (being preferably more than the 10mm).The upper limit of thickness of slab is not limited especially, but is generally about 50mm following (especially 30mm is following).
[embodiment]
Below, enumerate experimental example and be described more specifically the present invention, but the present invention is surely not owing to following experimental example is restricted, and can suitably be changed in meeting the scope of forward and backward described aim certainly and implements, and these all are contained in technical scope of the present invention.Also have, the evaluation of the steel plate that is obtained by following experimental example is carried out as follows.
[affirmation of the compound precipitate of Ti nitride and Nb carbonitride]
In the degree of depth t/4 position of the steel plate that obtains by controlled rolling (t is the thickness of steel plate), cutting out the cross section parallel with rolling direction grinds, to this cross section, by (the visual field number: 20), investigate the number of Ti nitride, Nb carbonitride and their compound precipitate of the tem analysis after the electrolytic corrosion.
[HAZ toughness (1)]
The HAZ toughness evaluation assessment of the thermal cycling when carrying out the welding of high heat energy (8kJ/mm) single face backing plate as simulation, be with Heating temperature: 1400 ℃, 800～500 ℃ cooling time (Tc): 100 seconds thermal cycling and to each after steel plate heat-treats for examination, the pendulum that is determined at temperature-60 ℃ absorbs energy (V notch).Also have,, use the bar-shaped of size 10mm * 10mm * 55mm, form the test film of the V notch of the degree of depth: 2mm at the central part single face as test film.
[HAZ toughness (2)]
The HAZ toughness evaluation assessment of the thermal cycling when carrying out high heat energy (50kJ/mm) SEGARC welding as simulation, be with Heating temperature: 1400 ℃, 800～500 ℃ cooling time (Tc): 500 seconds thermal cycling and to each after steel plate heat-treats for examination, the pendulum that is determined at temperature-20 ℃ absorbs energy (V notch).Also have, test film is same as described above, uses the bar-shaped of size 10mm * 10mm * 55mm, forms the test film of the V notch of the degree of depth: 2mm at the central part single face.
Experimental example 1
At the steel that contain C:0.05%, Si:0.15%, Mn:1.50%, P:0.009%, S:0.002%, Al:0.030%, Ti:0.014%, N:0.0045% (steel grade label Z; Remainder is Fe and unavoidable impurities) in, add the Nb of following the amount of Table 1, and then the steel of melting and casting, by with various condition as shown in table 1 to its controlled rolling, thereby obtain the steel plate of thickness of slab 15mm.
The evaluation result of resulting steel plate is represented at following table 1.
Can carry out following parsing by table 1.
Because numbering 1-1,1-2, Nb contains quantity not sufficient, so the number of the compound precipitate of TiN and Nb (CN) does not reach specified quantity of the present invention, the HAZ toughness that test is estimated according to the thermal cycling pendulum is insufficient. number 1-4 in addition, 1-10,1-11,1-12,1-13,1-16,1-17, though Nb content satisfies the prerequisite of regulation, but because rolling condition is improper, so the number of the compound precipitate of TiN and Nb (CN) does not reach specified quantity of the present invention, really, the HAZ poor toughness that test is estimated according to the thermal cycling pendulum. numbering 1-18, because Nb content surpasses prescribed value, so TiN and Nb (CN) though the number of compound precipitate reached specified quantity of the present invention, it is superfluous that but hardenability becomes, the tissue of HAZ portion becomes the many top bainites of island martensite body, HAZ toughness deterioration. except that above-mentioned, because Nb content is suitable and rolling condition is also suitable, so the compound precipitate of TiN and Nb (CN) has abundant amount to generate, and do not have the hardenability surplus yet, can access impact characteristics after the excellent thermal cycling.
Experimental example 2
The steel that one-tenth shown in melting, the following table 2 of casting is grouped into carry out controlled rolling with the various condition shown in the following table 3,4, make thickness of slab to 15mm.
The evaluation result of resulting steel plate is in table 3,4 expressions.
Can carry out following parsing by table 2～4.
Numbering 2-1～2-20 and 2-27～2-34, because chemical ingredients, rolling condition is all brought preferable range into, so the number of the compound precipitate of TiN and Nb (CN) has abundant amount to generate, can access excellent HAZ toughness. with respect to this, numbering 2-22,2-23,2-25,2-26, because Nb amount or Ti quantity not sufficient, so the number of the compound precipitate of TiN and Nb (CN) does not reach specified quantity of the present invention, the HAZ toughness that test is estimated according to the thermal cycling pendulum is insufficient. number 2-21 in addition, 2-24, chemical ingredients satisfies specialized range of the present invention, but because rolling condition is inappropriate, so the number of the compound precipitate of TiN and Nb (CN) does not reach specified quantity of the present invention, the HAZ poor toughness.
Experimental example 3
At the steel that contain C:0.08%, Si:0.15%, Mn:1.50%, P:0.007%, S:0.002%, Al:0.025%, Ti:0.013%, N:0.0050% (steel grade label Y; Remainder is Fe and unavoidable impurities) in, add the Nb of following the amount of Table 5, and then the steel of melting and casting, to its controlled rolling, obtain the steel plate of thickness of slab 60mm with various condition as shown in table 1 therefrom.
The evaluation result of resulting steel plate is represented at following table 5.
Can carry out following parsing by table 5.
Numbering 3-1,3-2, because Nb contains quantity not sufficient, so the number of the compound precipitate of TiN and Nb (CN) does not reach specified quantity of the present invention, the HAZ toughness that test is estimated according to the thermal cycling pendulum is insufficient. number 3-4 in addition, 3-10,3-11,3-12,3-13,3-16,3-17, though Nb content satisfies the regulation prerequisite, but because rolling condition is inappropriate, so the number of the compound precipitate of TiN and Nb (CN) does not reach specified quantity of the present invention, the HAZ poor toughness that test is estimated according to the thermal cycling pendulum. numbering 3-18, because Nb content surpasses prescribed value, so TiN and Nb (CN) though the number of compound precipitate reach specified quantity of the present invention, but hardenability surplus, the tissue of HAZ portion becomes the many top bainites of island martensite body, HAZ toughness deterioration.
Except that above-mentioned because Nb content suitably and rolling condition also suitable, so the compound precipitate of TiN and Nb (CN) has abundant amount to generate, and does not have the hardenability surplus yet, can access impact characteristics after the excellent thermal cycling.
Experimental example 4
The steel that one-tenth shown in melting, the following table 6 of casting is grouped into, with the various condition controlled rolling shown in the following table 7,8, making thickness of slab is 60mm.
The evaluation result of resulting steel plate is in table 7,8 expressions.
Can carry out following parsing by table 6～8.
Numbering 4-1～4-20 and 4-27～4-34, because chemical ingredients, rolling condition is all brought preferable range into, so the number of the compound precipitate of TiN and Nb (CN) has abundant amount to generate, can access excellent HAZ toughness. with respect to this, numbering 4-22,4-23,4-25,4-26, because Nb amount or Ti quantity not sufficient, so the number of the compound precipitate of TiN and Nb (CN) does not reach specified quantity of the present invention, the HAZ toughness that test is estimated according to the thermal cycling pendulum is insufficient. number 4-21 in addition, 4-24, chemical ingredients satisfies specialized range of the present invention, but because rolling condition is inappropriate, so the number of the compound precipitate of TiN and Nb (CN) does not reach specified quantity of the present invention, the HAZ poor toughness.
[industrial utilize possibility]
Steel plate of the present invention, near the excellent in low temperature toughness of (particularly the sealing wire during high heat energy welding etc.) because HAZ section, be applicable to the steel plate of common purposes and general shipbuilding steel, fundamentally, can be effective as especially be used to for example shipbuilding low temperature steel plate that requires low-temperature flexibility, the low temperature that perhaps is further used for liquefied petroleum gas (LPG) and storage liquefied ammonia is with the steel plate of container etc.
Claims (8)
1. a steel plate is characterized in that, in quality %, comprises:
C：0.02～0.12％、
N：0.002～0.010％、
Ti:0.005～0.025% and
Nb：0.013～0.025％，
In the cross section of described steel plate, there is 100/mm in the compound precipitate of Ti nitride and Nb carbonitride
2More than.
2. according to the steel plate of claim 1 record, it is characterized in that,
Comprise Mn:0.5～1.8%,
Satisfy below the Si:0.7%, and below the Al:0.1%.
3. according to the steel plate of claim 1 record, it is characterized in that,
Comprise at least a of B:0.0005～0.005% and Ni:0.01～0.5%.
4. according to the steel plate of claim 1 record, it is characterized in that,
Comprise from by the following group who constitutes optional at least a kind:
Zr：0.0003～0.05％、
Ca：0.0005～0.005％、
Mg:0.0005～0.005% and
REM：0.0005～0.01％。
5. according to the steel plate of claim 1 record, it is characterized in that,
Comprise from by the following group who constitutes optional at least a kind:
Cu：0.01～0.5％、
Cr：0.05～0.5％、
Mo:0.01～0.5% and
V：0.005～0.1％。
6. method of making steel plate, it is characterized in that, be used to make the described steel plate of claim 1, when hot rolling, the draft of the temperature province more than 800 ℃ is made as more than 40%, and the draft that will be lower than 800 ℃ temperature province is controlled at more than 30%, makes the compound precipitate of Ti nitride and Nb carbonitride disperse to separate out in steel plate.
7. according to the manufacture method of the steel plate of claim 6 record, it is characterized in that, after described hot rolling finishes, quicken cooling with the speed of 1～50 ℃/sec.
8. according to the manufacture method of the steel plate of claim 7 record, it is characterized in that after the described acceleration cooling, with more than 500 ℃, but the temperature below the Acl transformation temperature is carried out tempering.
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| CN104131235B (en) * | 2014-07-22 | 2016-06-29 | 武汉钢铁(集团)公司 | LPG ship storage steel plate for tanks and production method thereof |
| KR102318035B1 (en) * | 2019-12-17 | 2021-10-27 | 주식회사 포스코 | Non-heat treated wire rod having excellent drawability and impact toughness and method for manufacturing thereof |
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| CN1715435A (en) * | 2004-06-30 | 2006-01-04 | 宝山钢铁股份有限公司 | Method for producing X80 pipeline steel having anti-HIC property and its hot-rolled plate |
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