CN101182618B - Tenacity excellent high intensity steel for welding heat influenced part - Google Patents
Tenacity excellent high intensity steel for welding heat influenced part Download PDFInfo
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Abstract
The invention relates to a thick steel plate which has an excellent HAZ tenacity even being welded with high heat energy. The invention comprises 0.03 to 0.12 percents of C, less than 0.2 percents (including 0 percent) of Si, 1.0 to 2.0 percents of Mn, less than 0.03 percents (excluding 0 percent) of P, less than 0.015 percents (excluding 0 percent) of S, less than 0.10 percents (excluding 0 percent) of Al, 0.015 to 0.08 percents of Ti, 0.0060 to 0.0120 percents of N, 0.0010 to 0.0050 percents of B, and 0.005 to 0.020 percents of Nb and/or 0.0001 to 0.050 percents of Zr, satisfying the relation in the formula (I); and the invention is less than 0.05um and includes more than 5.0*106 of Ti nitride per 1mm2 in the equivalent circle diameter. The value of [Ti] *16[Si] * (12-40[C]) is less than 0.38(%) to (1), wherein, [Ti], [Si] and [C] respectively present the contents (quality percent) of Ti, Si and C.
Description
Technical field
The present invention relates to the steel plate that welded structure was suitable for of bridge, high-rise and boats and ships etc., especially relate to the steel plate of the tenacity excellent of the heat affected zone (following only the record is " HAZ ") after high heat energy welds.
Background technology
In recent years, along with the maximization of above-mentioned various welded structures, thickness of slab is that the welding of the above Plate Steel of 50mm is inevitable.Therefore, in all areas,, the situation that heat energy is the above high heat energy welding of 50kJ/mm of pointing to is just arranged from this viewpoint of improving of welding procedure efficient.
Yet if carry out the welding of high heat energy, HAZ is added to Xu Leng after the pyritous austenite region, thus near HAZ (particularly the fusion portion of HAZ) organize thickization, have the such problem of the easy deterioration of toughness of this part.The toughness (hereinafter referred to as " HAZ toughness ") of guaranteeing this HAZ well becomes problem all the year round.
The technology of the HAZ toughness deterioration when being used to prevent high heat energy welding has also proposed a lot up to now.Typical example as this technology, shown in for example special public clear 55-26164 number, propose to have a kind of steel, it disperses to separate out fine TiN by making in steel, thickization of the austenite grain that produces at HAZ when carrying out the welding of high heat energy to be suppressed at, thus HAZ flexible deterioration suppressed.Yet in this technology, if welding metal reaches the high temperature more than 1400 ℃, then among HAZ, particularly near the position (fusion portion) of welding metal, the heat that is subjected to during owing to welding causes above-mentioned TiN solid solution to disappear, and can not fully suppress the such problem of HAZ flexible deterioration and exist.
Thus, for example the spy opens in flat 10-298708 number and also proposes, and makes the fine dispersion of TiN by applying flexibly MgO, and its surrogate as the TiN of solid solution when high heat energy welds is applied flexibly, thereby improves HAZ toughness.Yet when utilizing oxide compound, it is very difficult to reach the fine dispersion of the sort of homogeneous that is equal to mutually with TiN, the problem that exists characteristic to depart from easily.
In addition, open the spy and also to propose a kind of technology in 2001-98340 number, it is in order to suppress the generation that particle diameter surpasses the so thick TiN of 0.1 μ m, is suitableization of distribution of the fine TiN of 0.01～0.1 μ m by realizing particle diameter, thereby realizes that the HAZ flexible improves.Yet, just realize suitableization of the distribution of fine TiN, still can not guarantee sufficient HAZ toughness.
So, a kind of steel that HAZ toughness can deterioration yet when welding the time is subjected to the pyritous heat affecting have been proposed in 2005-200716 number even present inventors take the lead in holding the spy.In this technology, by heavy addition N in steel, and suitably control the interpolation balance of Ti and B, the amount of the TiN that exists even still can make not solid solution after welding increases, thereby improves HAZ toughness.
Present inventors also propose a technology (spy opens 2004-218010 number) in addition, and it contains Nb by making the TiN that exists in the welding steel among inclusion energetically, and suppresses the Ti/Nb ratio, and making particle diameter is the every 1mm of number of the inclusion of 0.01～0.25 μ m
2Be 1.0 * 10
4More than individual, thereby guarantee that wide in range heat is there to be the HAZ toughness under the scope.
Yet in the field of welding, practical situation are that requirement HAZ flexible is further improved.In addition, the low-temperature flexibility of also censuring out steel plate (mother metal) the thickness of slab central part of draught reduction reduces such problem.In order to improve the toughness of mother metal, the known valid method is that finishing temperature is reduced, but along with the thickness of slab of steel plate enlarges, and during such Plate Steel, existence can not be guaranteed the problem that sufficient toughness is such more than thickness of slab becomes 80mm.
In addition, the low-temperature flexibility of also censuring out steel plate (mother metal) the thickness of slab central part of draught reduction reduces this problem.In order to improve the toughness of mother metal, the known valid method is that finishing temperature is reduced, but along with the thickness of slab of steel plate enlarges, and during such Plate Steel, existence can not be guaranteed the problem that sufficient toughness is such more than thickness of slab becomes 80mm.
Summary of the invention
The present invention does in view of such situation, and its main purpose is, though provide a kind of when carrying out high heat energy welding the still excellent Plate Steel of HAZ toughness.
In addition, another object of the present invention is to, even provide a kind of when carrying out the welding of high heat energy the still excellent Plate Steel of HAZ toughness, be exactly near the lowest ductility in fusion area that promotes HAZ specifically, and improve flexible mean value, can make near the good Plate Steel of tough sexual balance in fusion area.
The present invention's another purpose in addition is, though provide a kind of when carrying out high heat energy welding HAZ toughness still excellent, and the also excellent Plate Steel of the toughness of mother metal self.
The so-called Plate Steel of the present invention that can solve above-mentioned problem, it has following main points: contain the C:0.03～0.12% (meaning of " quality % ", down together), Si:0.2% following (containing 0%), Mn:1.0～2.0%, P:0.03% following (not containing 0%), S:0.015% following (not containing 0%), Al:0.10% following (not containing 0%), Ti:0.015～0.08%, N:0.0065～0.0120% and B:0.0010～0.0050%, contain Nb:0.005～0.009% in addition, and satisfy the relation of following (1) formula, and be calculated as with equivalent circle diameter and contain the every 1mm of Ti nitride below the 0.05 μ m
2Have 5.0 * 10
6More than individual.
[Ti]×16[Si]×(12-40[C])＜0.38(％)…(1)
Wherein, [Ti], [Si] and [C] represent the content (quality %) of Ti, Si and C respectively.
And, be calculated as containing among the Ti nitride below the 0.05 μ m with described equivalent circle diameter, be calculated as containing Ti nitride number and accounting for more than 75% of 0.01～0.03 μ m with equivalent circle diameter with respect to all containing the Ti nitride.
Also have, above-mentioned what is called " equivalent circle diameter ", be the size that is conceived to contain the Ti nitride, try to achieve the circular diameter that equates with its area of supposition, the diameter of the nitride that on transmission electron microscope (TEM) sightingpiston, confirms (too) about the size of oxide compound described later.The present invention as object to contain the aim that the Ti nitride has be to comprise TiN certainly, but also comprise the nitride of having been replaced the part (is about 50% with atomic ratio measuring) of Ti by other nitride forming element (for example Nb, Zr, V etc.).Below, the invention that will have the Plate Steel of above-mentioned this formation is called basic invention.
In above-mentioned Plate Steel of the present invention (basic invention), also Zr:0.0001～0.050% can be arranged, by adopting this formation, the heterogeneity that becomes of the tissue after can preventing to weld makes HAZ flexible balance good.
In above-mentioned Plate Steel of the present invention, except mentioned component, can also make it to contain the element of selecting the group who constitutes from Ca, Mg and REM more than a kind as required, add up to 0.0005～0.0050%, by containing such element, correspondence contains the kind of element, and the characteristic of Plate Steel will further improve.
In above-mentioned Plate Steel of the present invention (basic invention), also can have below the Al:0.01%, at least contain Zr among Nb and/or the Zr, contain REM:0.001～0.05% and/or Ca:0.0003～0.02% in addition, and, be calculated as the every 1mm of oxide compound of 0.2～5 μ m with equivalent circle diameter as the oxide compound that contains REM and/or Ca, Ti and Zr
2Exist more than 500,, can make the toughness of mother metal also good by adopting this formation.
Also have, the meaning of " equivalent circle diameter " in the oxide compound is identical with the situation of above-mentioned nitride.In addition, the oxide compound as object among the present invention comprises oxide monomer certainly, compoundly in the oxide compound separates out the oxide compound that sulfide and nitride (nitride that does not contain Ti) wait other compounds but be also contained in.
In above-mentioned Plate Steel of the present invention, adopt above-mentioned any formation, can make it again as required to contain as inferior element: (a) element of from the group that Cu, Ni and Cr constituted, selecting more than a kind: add up to 0.1～1.5%; (b) Mo:0.5% following (not containing 0%) and/or V:0.1% following (not containing 0%), by containing such element, corresponding its kind, the characteristic of Plate Steel will further be improved.
Embodiment
Even the molten Ti nitride (following by the TiN representative) that contains that stays is increased, though present inventors have obtained success (above-mentioned spy opens 2005-200716 number) in this direction, but, further improve HAZ toughness and research repeatedly for based on this technology.
When welding, fine TiN fusion, and thick TiN will demonstrate the such movement (Ostwald (Ostwald) growth) of grain growth.Present inventors are conceived to this movement and find, disperse in a large number by making fine TiN as much as possible, in order still to make the TiN fine homogeneous that distributes after growing up at grain, as long as will be controlled to be every 1mm with the TiN that equivalent circle diameter is calculated as below the 0.05 μ m
2Have 5.0 * 10
6Individual above getting final product.
In addition, if the distribution of sizes (dispersion) of TiN is big, above-mentioned such Ostwald grows up and is then promoted, tissue after the welding heterogeneity that becomes easily, be conceived to this point, in order to suppress this phenomenon as far as possible, the idea that obtains is, make the ratio of fine TiN shared in the TiN integral body reach a certain amount of more than, and disperse equably in this way to get final product.What distinguish specifically is, if the fine TiN number that is calculated as 0.01～0.03 μ m with equivalent circle diameter occupies more than 75% with respect to whole TiN, and the heterogeneity that becomes of the tissue after then can preventing to weld.
In steel plate of the present invention, according to control described later, based on fine TiN and make it to disperse.Therefore, even contain some thick TiN (for example equivalent circle diameter is than the big TiN of 0.05 μ m), how big this thick TiN can not cause influence to the characteristic of steel plate yet, and therefore " all TiN " its aim also comprises this thick TiN.Also have, the fine TiN number of 0.01～0.03 μ m ratio (hereinafter referred to as " occupation rate ") shared with respect to whole TiN is preferably more than 77%, more preferably more than 80%.
, disperse in a large number, then need to make the content of Ti and N to increase (Ti is more than 0.015%, and N is more than 0.0060%) in order to make TiN.Yet TiN 1500 ℃ when steel are cast easily generates up and down, further is in the situation of easy thickization owing to the increment of Ti, N at the TiN of this temperature field generation.Consequently be difficult to reach the distribution of above-mentioned suitable like this TiN.
TiN amount that high temperature territory when therefore, present inventors cast in order to be reduced in generates and further research.Why TiN generates in the high temperature territory easily, and can be estimated as is because the active height of Ti.So reducing the idea that obtains when studying under this imagination in the activity that makes Ti is if suitably control the Si of the activity rising that makes Ti and the relation of Ti, then can be reduced in the TiN amount that the high temperature territory generates.
In addition, also find method, make the temperature range of the state graph of steel represented " δ territory " dwindle also effective as thickization of high temperature that suppresses TiN.Present inventors are improved as target with the HAZ toughness of steel plate very early and study, ring as this research, discovery is dwindled by the temperature range in δ territory represented in the state graph that makes steel, even same Ti, N addition, still can make the fine dispersion of TiN, the meaning of this technology has been identified and has carried out applying for (special former 2006-31457 number) earlier.In the present invention, also use this discovery.
Above-mentioned what is called " δ territory " meaning is the zone of containing δ iron in the state graph of iron.Should " zone of containing δ iron " except the zone of only containing δ iron, also comprise contain δ mutually with other zones of state mutually.So so-called " temperature range in δ territory " is meant the temperature range that contains δ iron (ceiling temperature in δ territory and lower limit temperature poor).Here in the steel of specific composition, for example when the temperature range of the temperature range of having only δ iron and δ+γ iron, the temperature range that adds up to the δ territory of these temperature ranges.The temperature range in this δ territory is input to the comprehensive calculation of thermodynamics software (Themo-calc can buy from the CRC synthetic study) by the chemical constitution with steel and calculates.
In above-mentioned such δ iron because the velocity of diffusion of Ti is fast, so if the temperature range in δ territory is wide, then time of existing of δ long, think that the thick Ti nitride that contains is formed easily.In above-mentioned technology, calculating with Themo-calc, by special component is only changed 1 chemical ingredients amount as benchmark, when investigating each chemical ingredients to the influencing of the temperature range in δ territory, find that C, Si, Mn, Nb etc. can intervene, and to have tried to achieve with these compositions be the relational expression of the regulation of key element.Among the mentioned component, C is a useful especially composition on the temperature range of dwindling the δ territory in addition.
Except " δ territory temperature range is dwindled effect " that such C brings, " the TiN amount reduces effect " under the high temperature territory that the relation of above-mentioned Si of suitable control and Ti also considered is brought, (C, Si and Ti) to the influence that HAZ causes, further studies by experiment about these compositions.It found that, when mentioned component satisfies concerning of following formula (1), is brought into play effectively from " δ territory temperature range is dwindled effect " and the amount reduction of the TiN under the high temperature territory effect of C, and it is extremely good that HAZ toughness can become.
[Ti]×16[Si]×(12-40[C])＜0.38(％)…(1)
Wherein, [Ti], [Si] and [C] represent the content (quality %) of Ti, Si and C respectively.
If each chemical ingredients amount is in proper range, then the value on the left side of following formula (1) ([Ti] 16[Si] * (12-40[C]): hereinafter referred to as " Z value " become more little, above-mentioned " δ territory temperature range is dwindled effect " and/or " the TiN amount reduces effect " brought into play more effectively, and HAZ toughness is good more.Be limited on this Z value and be lower than 0.38 (%), but be limited to 0.35 (%) on preferred, be limited to below 0.30 (%) on preferred.Also have, the lower limit of Z value is determined according to the appropriate amount of each chemical ingredients, is about 0.0 (%).
Exploitation according to above-mentioned this technology, though the HAZ toughness in the time of can further improving the welding of high heat energy, but during particularly as Plate Steel such more than the thickness of slab 80mm, distinguish that the thickness of slab central part (1/2 one of thickness of slab) at steel plate (mother metal) can not be guaranteed good low-temperature flexibility.
According to the present invention, in having only TiN dispersive Plate Steel, can not guarantee the reason of good low-temperature flexibility at the thickness of slab central part, examined for being because different in the dispersion of the thickness direction TiN of slab.That is,,, consider that skin section and central part TiN in size with on distributing deviation can take place when casting so be subjected to the influence of solidifying segregation because TiN generates.
Therefore present inventors are conceived to effectively utilize simultaneously at thickness direction and can compare homogeneous dispersive oxide compound, and further research.Consequently distinguish,, and make the every 1mm of oxide compound that is calculated as 0.2～5 μ m with equivalent circle diameter if contain REM and/or Ca, Ti and Zr
2Exist more than 500, then the low-temperature flexibility of mother metal is further improved.Distinguish also that in addition being dispersed on the further raising HAZ toughness of such oxide compound is also effective.Promptly distinguish, in order in Plate Steel of the present invention, to improve HAZ toughness, with fine TiN is that main body makes it to disperse, but it is thickization owing to above-mentioned Ostwald grows up, and lost the tough property improvement effect of HAZ, as the surrogate of the TiN that has lost the tough property improvement effect of HAZ, oxide compound can play a role effectively.
In order to have given play to the above-mentioned effect that the oxide compound dispersion brings, need be controlled to be the every 1mm of oxide compound that is calculated as 0.2～5 μ m with equivalent circle diameter
2Exist more than 500.When the size of oxide compound is calculated as this fine oxide that is lower than 0.2 μ m with equivalent circle diameter, make it to disperse also not play a role, be calculated as with equivalent circle diameter and surpass 5 μ m like this during thick oxide compound, it becomes the brittle rupture starting point and can cause flexible on the contrary and reduce.
Also have, in order to realize the dispersion state of above-mentioned such oxide compound, on the basis that the soluble oxygen content in the molten steel is controlled to be about 0.0020～0.010%, add Ti, then carry out the interpolation of REM and/or Ca and Zr, the speed of cooling in 1500～1300 ℃ the temperature range during with casting is controlled at more than 10 ℃/minute and gets final product.Above-mentioned soluble oxygen content is lower than at 0.0020% o'clock, though above-mentioned each element of compound interpolation, because the oxygen quantity not sufficient, so still can not guarantee to help the oxide compound dispersion amount of mother metal and the raising of HAZ toughness.In addition, if soluble oxygen content surpasses 0.010%,,, not only be not preferred on the melting operation, and generate thick composite oxides easily so the reaction of the oxygen in the molten steel and above-mentioned each element is violent then because the oxygen amount in the molten steel is too much.
Next, be grouped into regard to the one-tenth of steel of the present invention (mother metal) and describe.As above-mentioned, steel plate of the present invention satisfies the relational expression of following formula (1) even its chemical ingredients is formed, if but the content of each chemical ingredients (element) be not in the proper range, still can not reach the excellent toughness of HAZ (or mother metal and HAZ).Therefore, in Plate Steel of the present invention, good except the distribution situation that contains Ti nitride (or containing Ti nitride and oxide compound), and chemical ingredients satisfies following formula (1) in addition, also needs to make the amount of each chemical ingredients to be in the proper range of following record.The scope of these compositions limits and the reasons are as follows.
[C：0.03～0.12％]
C be used to guarantee steel plate intensity the element that can not be short of, in addition as described above, the effective element that C still makes the temperature range in the δ territory in the state graph of steel dwindle.C content is lower than at 0.03% o'clock, not only can not guarantee the intensity of steel plate, and can not bring into play the effect of dwindling in δ territory, contains the Ti nitride with thickization.C is preferably more than 0.04%, more preferably more than 0.05%.Yet,, can generate island martensite body phase (MA phase) in a large number at HAZ when welding, thereby cause the toughness deterioration of HAZ if surpass 0.12%.Therefore C need be suppressed at below 0.12% and (preferably be suppressed at below 0.010%).Particularly when making the heterogeneity of the tissue after fine TiN is to prevent from more than 75% to weld with respect to whole TiN, the upper limit of the content of C can be 0.1%.
[Si:0.2% following (containing 0%)]
Si is guaranteeing useful element aspect the intensity of steel plate by solution strengthening, but if make it to contain superfluously, even then satisfy following formula (1), owing to improved the activity of Ti, still can cause thickization that contains the Ti nitride.From this viewpoint, need make Si content is below 0.2%, preferably to be suppressed at below 0.15%.Also have, when HAZ was had requiring of high tenacity more, Si can be suppressed at below 0.3%.In addition, if from guaranteeing this viewpoint of HAZ toughness, then Si content also can be 0%.
[Mn：1.0～2.0％]
Mn is guaranteeing element useful on the intensity of steel plate, in order to bring into play this effect effectively, need make it to contain more than 1.0%.Be preferably more than 1.2%.But if make it to contain above 2.0% superfluously, then the intensity of HAZ excessively rises, the toughness deterioration, so Mn content is below 2.0%.Be preferably below 1.8%.
[P:0.03% following (not containing 0%)]
P as impurity element causes detrimentally affect because cause intercrystalline failure easily to toughness, so its content is preferably few as much as possible.From guaranteeing this viewpoint of HAZ toughness, P content need be suppressed at below 0.03%, preferably below 0.02%.But, make P in the steel reach 0% very difficult industrial.
[S:0.015% following (not containing 0%)]
S is the impurity that encourages the heat cracking of HAZ, and preferably its content is few as much as possible.From guaranteeing this viewpoint of HAZ toughness, S content need be suppressed at below 0.015%, preferably at (more preferably below 0.0008%) below 0.01%.Particularly when making the heterogeneity of the tissue after fine TiN is to prevent from more than 75% to weld with respect to whole TiN, the upper limit of the content of S can be 0.01%.But, make S in the steel reach 0% very difficult industrial.
[Al:0.10% following (not containing 0%)]
Al is useful as deoxidant element, but superfluous if its content becomes, and then therefore HAZ toughness deterioration need be suppressed at below 0.10%, preferably below 0.05%.In addition, in order effectively to bring into play the deoxidation effect that Al brings, preferably make it to contain more than 0.01%.But, make above-mentioned such oxide compound (contain REM and/or Ca, Ti and Zr, be calculated as the oxide compound of 0.2～5 μ m with equivalent circle diameter) disperse when improving the low-temperature flexibility of mother metal, in order to reduce Al is the influence that oxide compound causes, Al content is preferably below 0.01%, more preferably below 0.008%.
[Ti：0.015～0.08％]
Ti and N form fine nitride and oxide compound, are the elements that helps the toughness raising of mother metal and HAZ.In order to bring into play this effect effectively, need make it to contain more than 0.015%, be preferably more than 0.018%.But, therefore should be suppressed at below 0.08% if superfluous the interpolation then contains the Ti nitride and become thick and make HAZ toughness deterioration.Be preferably below 0.060%.But when making the heterogeneity of the tissue after fine TiN is to prevent from more than 75% to weld with respect to whole TiN, the upper limit of the content of Ti can be 0.040%.
[N：0.0060～0.0120％]
N at high temperature melts the nitride (containing the Ti nitride) that stays by forming, thereby is guaranteeing on the HAZ toughness it is useful element.By making N content is (to be preferably more than 0.0070%) more than 0.0060%, and the molten Ti nitride that contains that stays increases under the high temperature with making.But if N content surplus, then solid solution N amount increases HAZ toughness deterioration.Therefore, N need be suppressed at below 0.0120%, preferably below 0.010%.
[B：0.0010～0.0050％]
Combine with N in the steel in the process that the HAZ that B the time is heated in welding is cooled and separate out BN, make the tough property improvement of HAZ.In order to bring into play this effect effectively, need make it to contain more than 0.001%.Be preferably more than 0.0015%.But, becomes superfluous as if B content, then make thickization of bainite structure of HAZ, thereby therefore the toughness deterioration need make it below 0.0050%.Be preferably below 0.0040%.
[Nb:0.005～0.020% and/or Zr:0.0001～0.05%]
Nb and Zr are effective elements on toughness improves.Wherein Nb helps HAZ toughness to improve, and also helps the toughness of mother metal to improve.Zr and N form fine nitride in addition, are the elements that helps HAZ toughness to improve, but by forming fine oxide compound, also are the elements that helps the HAZ toughness raising of mother metal.When particularly forming toughness that above-mentioned such oxide compound (be the oxide compound that contains REM and/or Ca, Ti and Zr, be calculated as the oxide compound of 0.2～5 μ m with equivalent circle diameter) also makes mother metal and improving, must contain Zr.In order to bring into play such effect, preferred Nb contains more than 0.005%, and Zr contains more than 0.0001%.Yet if the content surplus of Nb makes thickization of bainite structure among the HAZ, thereby therefore the toughness deterioration need (be preferably below 0.015%) below 0.020%.In addition, if the content surplus of Zr, then oxide compound becomes thick and makes HAZ toughness deterioration, therefore need (be preferably below 0.040%) below 0.05%.
The present invention regulation contain element such as above-mentioned, surplus is iron and unavoidable impurities, as this unavoidable impurities, can allow sneaking into of element (for example Sn, As, the Pb etc.) that brought into by the situation of raw material, goods and materials, producing apparatus etc.In addition, it is also effective that following element is contained, the kind of the corresponding composition that is contained, and the characteristic of steel plate is further improved.Particularly preferably improving beyond the HAZ toughness, the characteristic that correspondence will be improved suitably selects to add element.
[element of from the group that Ca, Mg and REM constituted, selecting more than a kind: add up to 0.0005～0.0050%]
Ca, Mg and REM (rare earth element) they are by making shape miniaturization, the balling of the inclusion (oxide compound and sulfide etc.) of sneaking into inevitably in the steel, thus the element that helps HAZ toughness to improve.The heterogeneity of the tissue after preventing to weld and be useful element when making tough sexual balance good particularly.In order to bring into play this effect effectively, make it preferably to contain that (total) is more than 0.0005% more than a kind or 2 kinds.More preferably more than 0.0008%.But superfluous if the content of these elements becomes, thickization of inclusion and therefore HAZ toughness deterioration preferably is suppressed at below 0.0050% then.More preferably below 0.0030%.
[REM:0.0001～0.05% and/or Ca:0.0003～0.02%]
REM (rare earth element) is the same with above-mentioned Zr with Ca, is the element that constitutes the oxide compound of the toughness raising that helps mother metal and HAZ, will realize the miniaturization of oxide compound by containing them.(be the oxide compound that contains REM and/or Ca, Ti and Zr particularly forming above-mentioned such oxide compound, be calculated as the oxide compound of 0.2～5 μ m with equivalent circle diameter) when also making the toughness raising of mother metal, the preferred content (below 0.01%) that reduces Al, and must contain Zr, and contain these elements in above-mentioned scope.In order to bring into play this effect effectively, preferably containing REM is more than 0.0001%, and containing Ca is more than 0.0003%.More preferably REM is more than 0.001%, and Ca is more than 0.0005%.But if the content surplus of these elements, thickization of inclusion (oxide compound) then, mother metal and HAZ toughness deterioration, therefore preferred REM is below 0.05%, Ca is below 0.02%.More preferably REM is below 0.03%, and Ca is below 0.015%.
Also have, in the present invention, so-called REM (rare earth element) is the meaning that contains lanthanon (from 15 elements of La to Ln) and Sc (scandium) and Y (yttrium).
In Plate Steel of the present invention, corresponding except HAZ toughness improves and the characteristic of improving, the above-mentioned so any composition of suitable selection also makes it to contain, but improve element as common characteristic in addition, can enumerate following element, although variant with chemical ingredients, improve on the basic characteristic of Plate Steel useful.
[element of from the group that Cu, Ni and Cr constituted, selecting more than a kind: add up to 0.1～1.5%]
Cu, Ni and Cr are all to the not influence of HAZ toughness, thus but the element that the raising hardenability effectively plays a role on the intensity that improves steel plate.In order to bring into play this effect, preferably contain it more than a kind or 2 kinds (total) more than 0.1%.More preferably more than 0.15%.If but the content surplus of these elements, then the MA of HAZ increases mutually, thereby causes HAZ toughness deterioration, therefore preferably is suppressed at below 1.5%.More preferably below 1.0%.
[Mo:0.5% following (not containing 0%) and/or V:0.1% following (not containing 0%)]
Mo and V be improve mother metal and HAZ two aspect intensity on the element that effectively plays a role.This effect increases and increases along with its content, but in order more effectively to bring into play their effect, preferably containing Mo0 is more than the .1%, and containing V is more than 0.01%.Yet if the content surplus of these elements makes thickization of bainite structure among the HAZ, thereby therefore the toughness deterioration preferably is suppressed at Mo (more preferably below 0.4%) below 0.5%, and V is suppressed at (more preferably below 0.08%) below 0.1%.
In the present invention, for control in the above described manner contains the Ti nitride, effective means is to adopt to satisfy the steel that above-mentioned various chemical ingredients is formed, and controls the speed of cooling when casting.That is, be recommended in that 10 ℃/min is above to be cooled off and form slab 1500～1300 ℃ temperature range.In addition, for such controlled chilling speed, can enumerate that slab thickness is reduced, the method that cooling water inflow is increased.
What the present invention relates to is Plate Steel, and so-called Plate Steel is defined as JIS in this field, and referring generally to thickness of slab is the above steel plate of 3.0mm.But the thickness of slab of Plate Steel of the present invention is preferably more than the 80mm.That is, Plate Steel of the present invention is that thickness of slab is the above steel plate of 80mm, is high heat energy welding more than the 50kJ/mm even it is carried out heat energy, still demonstrates good HAZ toughness.But the thickness of steel plate of the present invention is not defined as more than the 80mm, and it is above or be lower than application on this steel plate to be not precluded within 50mm.
The Plate Steel of the present invention that so obtains can be as for example material of the works of bridge, high-rise and boats and ships etc., and little～middle heat energy welding is from needless to say, even also can prevent the toughness deterioration of mother metal and welded heat affecting zone in high heat energy welding.
Embodiment
Below, illustrate in greater detail the present invention by embodiment, but following embodiment does not limit character of the present invention, also can in the scope that can meet the forward and backward aim of stating, suitably be changed enforcement, these all are included in the technical scope of the present invention.
(embodiment 1)
According to common smelting process, the steel of the composition shown in the following table 1 of melting, the speed of cooling of (1500～1300 ℃ temperature ranges) is cooled off this molten steel simultaneously during the control casting, become slab (behind cross-sectional shape: the 200mm * 250mm), be heated to 1100 ℃ and carry out hot rolling, become thickness of slab: the hot-rolled sheet of 50mm, rolling laggard line space is cold and become test board.Also have, in the 1st table, REM is about 50% and to contain Ce be that the form of about 25% mishmetal is added to contain La.In addition, element is not added in "-" expression in the table 1.
The 1st table
*Surplus: Fe and unavoidable impurities.
Each test board for above-mentioned such manufacturing, measure its individual number density that contains the Ti nitride (be calculated as the number that contains the Ti nitride below the 0.05 μ m and be calculated as the occupation rate that contains the Ti nitride of 0.01～0.03 μ m with equivalent circle diameter), the tensile strength of Plate Steel, HAZ toughness by following main points with equivalent circle diameter.These results are with Z value [=[Ti] * 16[Si] * (12-40[C])], the speed of cooling during casting is presented in the 2nd table.
(mensuration that contains the number of Ti nitride)
With transmission electron microscope (TEM),, t (thickness of slab)/4 position of each steel plate is observed with the field of view of 60,000 times observation multiplying powers, 2 * 2 (μ m), the condition of observing 5 in place.Measure the area that respectively contains the Ti nitride in this visual field by image analysis then, calculate the equivalent circle diameter of each nitride by this area.Also have, the differentiation that contains the Ti nitride utilizes EDX (energy dispersion type X ray detector).
Conversion is also tried to achieve every 1mm
2In equivalent circle diameter be the following number that contains the Ti nitride of 0.05 μ m, and calculate equivalent circle diameter be 0.01～0.03 μ m fine contain the Ti nitride with respect to all contain the Ti nitride (also comprise with equivalent circle diameter calculate surpass 0.05 μ m contain the Ti nitride) number ratio (occupation rate: %).
(tension test)
From t (thickness of slab)/4 position of each steel plate, No. 4 test films extract JIS Z 2201 with respect to the rectangular direction of rolling direction carry out tension test by the main points of JIS Z 2241, measure 0.2% yielding stress (YS).Then, YS be 400MPa above be evaluated as qualified.
(evaluation of HAZ flexible)
From t (thickness of slab)/4 position of each steel plate, at No. 4 test films that extract JIS Z 2201 with respect to the rectangular direction of rolling direction, simulated the thermal cycling test of high heat energy welding, estimate HAZ toughness.At this moment thermal cycling test be with above-mentioned test film be heated to 1400 ℃ and keep 60 seconds after, spend 800～500 ℃ temperature range of cooling in about 500 seconds, apply the thermal cycling that welding heat energy is equivalent to 65kJ thus.According to JIS Z 2242, carry out pendulum impact test at-40 ℃, measuring absorption can (vE
-40).At this moment absorbing for 5 test films can (vE
-40) measure, try to achieve its mean value and Schwellenwert.Then, vE
-40Mean value be 200kJ above be evaluated as HAZ tenacity excellent, vE
-40Minimum value be that the above stabilization that is evaluated as of 120kJ improves.
The 2nd table
Can carry out following investigation (also have, following No. represents table 1,2 steel No.) by table 1,2.The example of regulation important document of the present invention is satisfied in No.1～15th, and chemical ingredients is formed, Z value and to contain the fine dispersion of Ti nitride all suitable, can access the good steel plate of toughness of welded heat affecting zone as can be known.
With respect to this, No.16～30 break away from the example of a certain important document of the present invention's regulation, the toughness deterioration of welded heat affecting zone.In detail as following.
C content in its steel plate of No.16 surpasses the preferred upper limit, even it is good to contain the form of Ti nitride, and HAZ toughness or deterioration.
Si content in its steel plate of No.17 exceeds the scope of the present invention regulation, and the form that contains the Ti nitride bad (do not obtain fine contain Ti nitride) can't obtain good HAZ toughness.Mn content in its steel plate of No.18 exceeds the scope of the present invention's regulation, even it is good to contain the form of Ti nitride, and HAZ toughness or deterioration.
P in No.19,20 its steel plates and the content of S exceed the scope of the present invention's regulation, even it is good to contain the form of Ti nitride, and HAZ toughness or deterioration.Nb content in its steel plate of No.21 exceeds the scope of the present invention's regulation, even it is good to contain the form of Ti nitride, and HAZ toughness or deterioration.
Ti content in its steel plate of No.22 is lower than the scope of the present invention's regulation, and the number density fully and the occupation rate that contain the Ti nitride do not reach HAZ toughness deterioration.Ti content in its steel plate of No.23 exceeds the scope of the present invention's regulation, contains thickization of Ti nitride, and the number density fully and the occupation rate that contain the Ti nitride do not reach HAZ toughness deterioration.
N content in its steel plate of No.24 is lower than the scope of the present invention's regulation, and the number density fully and the occupation rate that contain the Ti nitride do not reach HAZ toughness deterioration.N content in its steel plate of No.25 exceeds the scope of the present invention's regulation, and solid solution N increases, HAZ toughness deterioration.
B content in its steel plate of No.26 is lower than the scope of the present invention's regulation, even it is good to contain the form of Ti nitride, and HAZ toughness or deterioration.The Z value breaks away from the scope of the present invention's regulation in its chemical ingredients of No.27, and the number density fully and the occupation rate that contain the Ti nitride do not reach HAZ toughness deterioration.B content in its steel plate of No.28 exceeds the scope of the present invention's regulation, even it is good to contain the form of Ti nitride, and HAZ toughness or deterioration.
The speed of cooling of No.29 when casting is low, contains thickization of Ti nitride, and the number density fully and the occupation rate that contain the Ti nitride do not reach HAZ toughness deterioration.Speed of cooling when the Z value of its chemical ingredients of No.30 and casting all is in beyond the proper range, contains remarkable thickization of Ti nitride, and the number density fully and the occupation rate that contain the Ti nitride do not reach HAZ toughness deterioration.
(embodiment 2)
According to Si, Mn addition the soluble oxygen content in the molten steel is controlled, the steel of forming shown in showing by the following the 3rd by the smelting process melting simultaneously, the speed of cooling of (1500～1300 ℃ temperature ranges) during the control casting, simultaneously this molten steel is cooled off, becoming slab (behind cross-sectional shape: the 200mm * 250mm), is heated to 1100 ℃ and carry out hot rolling, becomes thickness of slab: the hot-rolled sheet of 80mm, direct quenching is implemented in rolling back, carries out tempering and becomes test board at 500 ℃.Also have, in the 3rd table, REM is about 50% and to contain Ce be that the form of about 25% mishmetal is added to contain La.In addition, element is not added in "-" expression in the table 1.
The 3rd table
*
SurplusAmount: Fe and unavoidable impurities.
Each test board for above-mentioned such manufacturing, similarly to Example 1, measure the tensile strength and HAZ toughness (metewand is identical with embodiment 1) of its individual number density that contains the Ti nitride, Plate Steel, and be grouped into and individual number density by following main points mensuration Plate Steel (toughness of mother metal), the one-tenth of oxide compound.At this moment, also calculating equivalent circle diameter is that 0.01～0.03 μ m fine contains the Ti nitride with respect to all the contain Ti nitride number (occupation rate: %) relatively of (also comprise calculate surpass 0.05 μ m's with equivalent circle diameter).These results are with Z value [=[Ti] * 16[Si] * (12-40[C])], the speed of cooling the when soluble oxygen content in the molten steel, casting is presented in following the 4th table.
(mensuration of the composition of oxide compound and a number density)
Using Jin Dao to make made " EPMA-8705 " (trade(brand)name), observe with 1000 times multiplying power, is that the precipitate (oxide compound) of 0.2～5 μ m is divided into compositional analysis for equivalent circle diameter.The field of view area is 1～5cm
2, analyzing number is 100, the wavelength dispersion analysis by characteristic X-ray is grouped at the one-tenth of precipitate central part.The analytic target element is Al, Mn, Si, Ti, Zr, Ca, La, Ce and O.In addition, by cutting apart, convert and try to achieve every 1mm by the field of view area
2The number of middle oxide compound.
(toughness of mother metal)
From t (thickness of slab)/2 position of the test board that obtains, No. 4 test films extract JIS Z 2201 with respect to the rectangular direction of rolling direction according to JIS Z 2242, carry out pendulum impact test under-40 ℃, measure that absorb can (vE
-40).At this moment absorbing for 3 test films can (vE
-40) measure, calculate its Schwellenwert.What this Schwellenwert surpassed 200J is evaluated as the base metal tenacity excellence.
The 4th table
Can carry out following investigation (also have, following No. represents table 3,4 steel No.) by table 3,4.The example of regulation important document of the present invention is satisfied in No.31～45th, and chemical ingredients is formed, Z value and to contain the fine dispersion of Ti nitride all suitable, can access the good steel plate of toughness of mother metal and welded heat affecting zone as can be known.
With respect to this, No.46～60 break away from the example of a certain important document of the present invention's regulation, the toughness deterioration of welded heat affecting zone.In detail as following.
C content in its steel plate of No.46 surpasses the scope of the present invention's regulation, even it is good to contain the form of Ti nitride and oxide compound, and mother metal and HAZ toughness or deterioration.
Si content in its steel plate of No.47 exceeds the scope (Z value greatly) of the present invention regulation, and the form that contains the Ti nitride bad (do not obtain fine contain Ti nitride) can't obtain the toughness of good mother metal and HAZ.Mn content in its steel plate of No.48 exceeds the scope of the present invention's regulation, even it is good to contain the form of Ti nitride, and the toughness of mother metal and HAZ or deterioration.
The content of P in its steel plate of No.49 exceeds the scope of the present invention's regulation, even it is good to contain the form of Ti nitride, and mother metal and HAZ toughness or deterioration.Al content in its steel plate of No.50 exceeds preferred range, even it is good to contain the form of Ti nitride, an oxide compound number density still reduces, the toughness deterioration of mother metal and HAZ.
Ti content in its steel plate of No.51 is lower than the scope of the present invention's regulation, and a number density fully that contains the Ti nitride does not reach the toughness deterioration of mother metal.Ti content in its steel plate of No.52 exceeds the scope of the present invention's regulation, contains thickization of Ti nitride, does not reach number density, mother metal and a HAZ toughness deterioration fully.
N content in its steel plate of No.53 is lower than the scope of the present invention's regulation, contains the Ti nitride and does not reach a number density fully, base metal tenacity deterioration.N content in its steel plate of No.54 exceeds the scope of the present invention's regulation, and solid solution N increases, the toughness deterioration of mother metal and HAZ.
B content in its steel plate of No.55 exceeds the scope of the present invention's regulation, even it is good to contain the form of Ti nitride, and HAZ toughness or deterioration.The Z value breaks away from the scope of the present invention's regulation in its chemical ingredients of No.56, does not reach a number density fully that contains the Ti nitride, the toughness deterioration of mother metal and HAZ.
Al content in its steel plate of No.57 exceeds the preferred upper limit, and the oxide compound that does not contain REM etc. constitutes element (the dispersion deficiency of the oxide compound that regulation is formed), base metal tenacity deterioration.No.58 does not contain Zr in steel plate, mother metal and HAZ toughness is deterioration extremely.
No.59 is in the soluble oxygen content surplus in when casting, thickization of oxide compound and do not reach a number density fully, the toughness deterioration of mother metal and HAZ.Speed of cooling when the Z value of its chemical ingredients of No.60 and casting all is in beyond the proper range, contains remarkable thickization of Ti nitride and oxide compound, does not reach a number density fully, the toughness deterioration of mother metal and HAZ.
According to the present invention, by both satisfying the relation that has of above-mentioned formula (1), the chemical ingredients composition of steel plate is in the suitable scope, and make and contain the suitably fine dispersion of Ti nitride, can fine nitride and the oxide compound homogeneous that solid solution disappears in the steel be dispersed in the steel, therefore can realize the improved Plate Steel of toughness of welded heat affecting zone (HAZ).In addition, except above-mentioned formation, contain the dispersion state (density) of Ti nitride by suitable control, can realize keeping toughness equilibrated Plate Steel well, and, then can realize all improved Plate Steel of toughness of HAZ toughness and mother metal by making the fine dispersion of oxide compound.
Claims (9)
1. the Plate Steel of the tenacity excellent of a welded heat affecting zone, it is characterized in that, contain C:0.03～0.12% in quality %, Si:0.2% is following and contain 0%, Mn:1.0～2.0%, P:0.03% is following but do not contain 0%, S:0.015% is following but do not contain 0%, Al:0.10% is following but do not contain 0%, Ti:0.015～0.08%, N:0.0065～0.0120% and B:0.0010～0.0050%, contain Nb:0.005～0.009% in addition, and satisfy the relation of following (1) formula, and count with equivalent circle diameter and to contain the every 1mm of Ti nitride below the 0.05 μ m
2Interior existence 5.0 * 10
6More than individual,
[Ti]×16[Si]×(12-40[C])＜0.38(％)…(1)
Wherein, [Ti], [Si] and [C] represent the content of the quality % of Ti, Si and C respectively,
And, counting containing among the Ti nitride below the 0.05 μ m with described equivalent circle diameter, the number that contains the Ti nitride of counting 0.01～0.03 μ m with equivalent circle diameter accounts for more than 75% with respect to all containing the Ti nitride.
2. Plate Steel according to claim 1 is characterized in that, also contains Zr:0.0001～0.050% in quality %.
3. Plate Steel according to claim 2 is characterized in that, also contains the element of selecting from Ca, Mg and REM more than a kind, and the element more than a kind of this selection adds up to 0.0005～0.0050% in quality %.
4. according to each described Plate Steel in the claim 1～3, it is characterized in that also contain the element of selecting from Cu, Ni and Cr more than a kind, the element more than a kind of this selection adds up to 0.1～1.5% in quality %.
5. according to each described Plate Steel in the claim 1～3, it is characterized in that, also contain below the Mo:0.5% in quality % but do not contain 0% and/or below the V:0.1% but do not contain 0%.
6. Plate Steel according to claim 4 is characterized in that, also contains below the Mo:0.5% in quality % but does not contain 0% and/or below the V:0.1% but do not contain 0%.
7. the Plate Steel of the tenacity excellent of a welded heat affecting zone, it is characterized in that, contain C:0.03～0.12% in quality %, Si:0.2% is following and contain 0%, Mn:1.0～2.0%, P:0.03% is following but do not contain 0%, S:0.015% is following but do not contain 0%, Al:0.01% is following but do not contain 0%, Ti:0.015～0.08%, N:0.0065～0.0120% and B:0.0010～0.0050%, contain Nb:0.005～0.009% in addition, Zr:0.0001～0.050%, also contain REM:0.001～0.05% and/or Ca:0.0003～0.02%, and containing REM and/or Ca, in the oxide compound of Ti and Zr, count the every 1mm of oxide compound of 0.2～5 μ m with equivalent circle diameter
2The interior existence more than 500,
And satisfy the relation of following (1) formula, and count with equivalent circle diameter and to contain the every 1mm of Ti nitride below the 0.05 μ m
2Interior existence 5.0 * 10
6More than individual,
[Ti]×16[Si]×(12-40[C])＜0.38(％)…(1)
Wherein, [Ti], [Si] and [C] represent the content of the quality % of Ti, Si and C respectively,
And, counting containing among the Ti nitride below the 0.05 μ m with described equivalent circle diameter, the number that contains the Ti nitride of counting 0.01～0.03 μ m with equivalent circle diameter accounts for more than 75% with respect to all containing the Ti nitride.
8. Plate Steel according to claim 7 is characterized in that, also contains the element of selecting from Cu, Ni and Cr more than a kind, and the element more than a kind of this selection adds up to 0.1～1.5% in quality %.
9. according to claim 7 or 8 described Plate Steels, it is characterized in that, also contain below the Mo:0.5% in quality % but do not contain 0% and/or below the V:0.1% but do not contain 0%.
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| JP2006307081A JP4356949B2 (en) | 2006-11-13 | 2006-11-13 | Thick steel plate with excellent toughness in weld heat affected zone |
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| JP2006-307081 | 2006-11-13 | ||
| JP2007060781 | 2007-03-09 | ||
| JP2007060781A JP5103037B2 (en) | 2007-03-09 | 2007-03-09 | Thick steel plate with excellent toughness of base metal and weld heat affected zone |
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| JP2010031309A (en) * | 2008-07-25 | 2010-02-12 | Kobe Steel Ltd | Thick steel plate and method for producing the same |
| KR101119378B1 (en) * | 2008-10-20 | 2012-03-06 | 가부시키가이샤 고베 세이코쇼 | Thick steel plate |
| JP5207914B2 (en) * | 2008-10-20 | 2013-06-12 | 株式会社神戸製鋼所 | Thick steel plate with excellent toughness of base metal and weld heat affected zone |
| KR101320220B1 (en) * | 2010-05-20 | 2013-10-29 | 가부시키가이샤 고베 세이코쇼 | Thick steel plate |
| JP5883369B2 (en) * | 2012-09-19 | 2016-03-15 | 株式会社神戸製鋼所 | Thick steel plate with excellent toughness in weld heat affected zone |
| CN106906414A (en) * | 2015-12-22 | 2017-06-30 | 宝山钢铁股份有限公司 | The steel plate and its manufacture method of a kind of Large Heat Input Welding heat affected area tenacity excellent |
| JP6753204B2 (en) * | 2016-08-09 | 2020-09-09 | 日本製鉄株式会社 | Steel plate and steel plate manufacturing method |
| CN115161548B (en) * | 2022-05-25 | 2023-03-24 | 昆明理工大学 | Ti-Zr composite microalloyed 700 MPa-grade high-strength and high-toughness steel plate and preparation method thereof |
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| CN1398302A (en) * | 2000-12-14 | 2003-02-19 | Posco公司 | Steel plate to be precipitating Tin+Zrn for welded structures, method for mfg. same and welding fabric using same |
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