CN107614724A

CN107614724A - Steel plate and welding point

Info

Publication number: CN107614724A
Application number: CN201680028437.3A
Authority: CN
Inventors: 河盛诚; 汤濑文雄; 名古秀德; 冈崎喜臣; 伊庭野朗; 衣笠润郎; 衣笠润一郎
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2015-05-22
Filing date: 2016-05-16
Publication date: 2018-01-19
Also published as: JP2016216819A; KR20170138505A; EP3299486A1; EP3299486A4

Abstract

It is an object of the present invention to, there is provided a kind of excellent steel plate of resistance to SO_2.In the steel plate of the present invention, contain C：0.01~0.12%, Si：0.02~0.50%, Mn：0.6~2.0%, P：Higher than 0% and below 0.030%, S：Higher than 0% and below 0.004%, Al：0.010~0.080%, Cr：0.10~1.50%, Nb：0.002~0.050%, REM：0.0002~0.05%, Zr：0.0003~0.01%, Ca：0.0003~0.006%, N：Higher than 0% and below 0.010%, O：Higher than 0% and below 0.0040%, surplus is iron and inevitable impurity, in steel in the composition of wide more than 1 μm contained of field trash, the Zr amounts in debris that meet be 1~40%, REM amounts be 5~50%, Al amounts are 3~30%, Ca amounts are 5~60%.

Description

Steel plate and welding point

Technical field

The present invention relates to steel plate and welding point, is to be related to line-pipes, marine structure use etc. to make in more detail By the suitable steel plate of the former material steel plate of energy structural material and the welding point using the steel plate.

Background technology

In recent years, with the increase of global energy needs, the various energy including regenerative resource Develop, practical be in progress.On the other hand, the oil, natural gas, coal as fossil fuel are in occupation of energy resources It is most of, it is special on the energy ensures and the problem of important if producing, conveying and storing the fossil energy safe efficiently When not being production, conveying of the fossil energy etc., the energy steel of height energy supply are essential.

The energy steel, once not bearing its function when accident occurs, harm is very big, therefore it is required that very high Security.

One of energy steel have line-pipes steel, and it is used for the conveying of petroleum gas, in same steel, not only Ask the intensity as structural material, characteristic as toughness, but also require for the petroleum gas that passes through in pipe Tolerance.In recent years, in the oil well gas well of petroleum gas, the oil of output, the quality deterioration of gas, H₂S is largely mixed into, and is removed Up to now beyond specification, also it is strongly required hydrogen induced cracking resistance, i.e. resistance to SO_2 representated by hic resistance.

In addition, in line-pipes steel, from the viewpoint of cost cutting when conveying and construction, it is desirable to the thin-walled of pipe Change.For this reason, it may be necessary to improve the intensity of steel, but the raising of steel strength have concurrently make hydrogen induced cracking resistance deteriorate as lack Point.In particular by seam weld when steel plate to be processed into pipe, i.e. wire bonding, and the girth welding this 2 when pipe is engaged with each other The T-shaped cross weld portion of thermal process, because by anxious heat, the complicated thermal process of chilling, in welding heat affected zone：HAZ, Intensity, namely hardness rise, and the crackle for being referred to as sulfide-stress cracking easily occurs.Hereinafter, should for sulfide Power corrosion cracking, it is SSCC also to describe：sulfide stress corrosion cracking.Therefore, in order to realize high intensity Line pipe steel, the anti-SSCC in T-shaped cross weld portion is also one of problem.

For the purpose of reaching the hic resistance of mother metal or the anti-SSCC in T cross welds portion in the prior art, have specially Technology described in sharp document 1 etc..The technology described in patent document 1 is, is considered as the poor stick of hic resistance by reducing The bainite structure of shape, and make uniform top bainite or acicular ferrite structure flourishing, so as to which one side ensures the anti-of mother metal HIC, while realizing the X70 grade high-strength steel plates of API specifications.

On the other hand, the technology described in patent document 2 is that the precipitation brought using fine Nb, V carbonitride is strong Change, tensile strength 56kgf/mm can be reached²High intensity above.But the not no hic resistance on mother metal in the document Describe, be also the HAZ for only accounting for wire bonding in addition, on anti-SSCC.Moreover, the experimental condition described in embodiment, not It is this very harsh condition of sulphur environment, i.e. largely contain H in simulation₂It is 21 to make dip time in the solution of S environment My god.

In addition, being described in patent document 3 has such a composition system, its suppression is believed to make T cross welds portion The hardness of anti-SSCC deteriorations rises.But anti-SSCC is not evaluated in itself in the technology described in the document, in addition, on mother The hic resistance of material is not also recorded.

【Prior art literature】

【Patent document】

【Patent document 1】The clear 61-165207 publications of Japanese Laid-Open

【Patent document 2】The flat 1-96329 publications of Japanese Laid-Open

【Patent document 3】Japanese Laid-Open 2005-186162 publications

The content of the invention

The present invention is desired to be solved the problems, such as above-mentioned existing and does, its object is to, there is provided a kind of resistance to SO_2, particularly resist Steel plate excellent HIC.In addition, another object of the present invention is to, there is provided it is a kind of to realize the anti-of T-shaped cross weld portion The steel plate of welding point excellent SSCC, and the excellent welding points of anti-SSCC in T-shaped cross weld portion.

The steel plate of the present invention, it is characterised in that be to contain C in terms of quality %：0.01~0.12%, Si：0.02~ 0.50%th, Mn：0.6~2.0%, P：Higher than 0% and below 0.030%, S：Higher than 0% and below 0.004%, Al： 0.010~0.080%, Cr：0.10~1.50%, Nb：0.002~0.050%, REM：0.0002~0.05%, Zr：0.0003 ~0.01%, Ca：0.0003~0.006%, N：Higher than 0% and below 0.010%, O：Higher than 0% and 0.0040% with Under, surplus is the steel plate of iron and inevitable impurity, in the composition of wide more than 1 μm of the field trash contained in steel, is expired Zr amounts in sufficient field trash are that 1~40%, REM amounts are that 5~50%, Al amounts are that 3~30%, Ca amounts are 5~60%.

In addition, in the steel plate of the present invention, the S amounts in preferably described field trash are higher than 0% and below 20%.

In addition, in the steel plate of the present invention, preferably [Cr]/[Nb] is more than 10.Wherein, in the formula, [] represents matter Measure %.

In addition, in the steel plate of the present invention, preferably in terms of quality %, also contain Mg：Higher than 0% and below 0.005%, Ti：0.003~0.030%, Ni：0.01~1.50%, Cu：0.01~1.50%, Mo：0.01~1.50%, V：0.003~ 0.08% and B：More than one or both of 0.0002~0.0032%, [Cr]+[Mo]+[Ni]+[Cu] are less than 2.1.Its In, in the formula, [] represents quality %.

In addition, in the steel plate of the present invention, preferably in terms of quality %, contain Ni：0.01~1.50%, 0.25 × [Cr]+ [Ni] is 0.10~1.50.Wherein, in the formula, [] represents quality %.

In addition, the welding point of the present invention, it is characterised in that containing any one above-mentioned steel plate of the invention and go in ring Weld metal.

In the welding point of the present invention, the leaching of steel plate preferably tried to achieve by following formula, described and the girth weld metal Stain potential difference Δ E is below 25mV.

Dipping current potential behind 1 hour of dipping current potential (mV)-steel plate behind 1 hour of Δ E=girth weld metals (mV)

Among invention disclosed by the invention, if the representational effect that simple declaration is acquired, as follows.

According to an embodiment of the invention, using the teaching of the invention it is possible to provide the excellent steel plate of resistance to SO_2.In addition, use the present invention's Steel plate, using the teaching of the invention it is possible to provide the welding point excellent anti-SSCC in T-shaped cross weld portion.

Embodiment

The present inventors in order to reach the problem of the invention, except play steel plate characteristic on as substantially Beyond the composition composition of steel, also from the viewpoint of the Control and Inclusion Removal in steel, study, inquire into repeatedly with keen determination.The discovery of its result, Formed by the way that wide more than 1 μm of thick field trash is remained into specific composition, the excellent steel plate of resistance to SO_2 can be obtained, So as to complete the present invention.Here, the field trash in the so-called present invention, means thick in molten steel and caused by solidification Grain is separated out, specifically, means the grain of the formation such as the oxide of alloying component in steel, carbide, sulfide, nitride Son.

First, estimated when the viewpoint of the hic resistance based on mother metal is studied, when hydrogen is invaded in sulphur environment, in steel, MnS etc. thick and bigger than the coefficient of thermal expansion of steel field trash can form thick hole, therefore the hydrogen collection invaded around it In overstock in the hole, under the pressure of its gasification, there is crackle in steel, i.e., hydrogen induced cracking occur, progress.Therefore confirm, lead to Cross more than 1 μm of thick field trash of the hydrogen induced cracking origin cause of formation, the field trash big from the coefficient of thermal expansion than steel, be converted into comparing The small field trash of the coefficient of thermal expansion of steel and built, then can improve, ensure the hic resistance of steel.Further, as coefficient of thermal expansion The field trash smaller than steel, specifically effectively Zr, Al, REM oxide etc..

On the other hand, during the viewpoint research of the anti-SSCC based on T-shaped cross weld portion, it is known that in T-shaped cross weld portion, If hardness occurs drastically to change from the neighborhood of welding metal to mother metal, anti-SSCC is reduced.This is considered as because hardness becomes Changing causes the position that violent stress concentration occurs.From the neighborhood of the welding metal to the violent firmness change of mother metal, recognized For be due to welding metal neighborhood have hard martensite generate, in contrast, leaving one from welding metal to mother metal side Determine the position of degree, then generate soft ferrite.

In order to suppress the violent firmness change, the reduction these two aspects of reduction, hard martensite from soft ferritic Studied.Its results verification, on the reduction of soft ferritic, by adding alloying element in steel plate, make hardenability Improve, just can suppress ferrite generation.

In addition, the reduction on hard martensite, is largely disperseed by the field trash for the starting point for making to be used as phase transformation, promote brilliant Interior bainitic transformation, and make [Cr]/[Nb] be more than 10, reduction makes the Nb that the karyogenesis driving force of crystal boundary rises to crystal boundary Segregation, bainite is promoted to be generated from crystal boundary, its results verification arrives, and can reduce the martensite growing amount of welding metal neighborhood.Its In, in the formula, [] represents quality %.

It may also confirm that in addition, addition Cr and Nb ensures hardenability, can improve strength of parent.

Hereinafter, in addition to composition composition, tissue, the field trash of the steel plate of the present invention form, also to intersecting for T-shaped The welding metal of weld part, it is described in detail including its regulation reason.Hereinafter, as composition expression unit % The entirely quality % meaning.

(the composition composition of steel plate)

[C：0.01~0.12%]

C is for ensuring that indispensable element required for the intensity of steel plate, it is necessary to be allowed to containing more than 0.01%. Preferably more than 0.02%, more preferably more than 0.03%.But if C amounts are superfluous, island martensite is easily generated in mother metal Body, this turns into the starting point of hydrogen induced cracking and deteriorates the hic resistance of mother metal.Therefore, C amounts are needed for less than 0.12%.Preferably Less than 0.10%, more preferably less than 0.08%.

[Si：0.02~0.50%]

Si is effective to deoxidation.This obtains these effects and makes Si amounts be more than 0.02%.Preferably more than 0.04%, more Preferably more than 0.06%.But if Si amounts are superfluous, island-like martensite is easily generated in mother metal, this turns into hydrogen induced cracking Starting point and deteriorate the hic resistance of mother metal.Therefore, Si amounts need to suppress below 0.50%.Preferably less than 0.45%, it is more excellent Elect less than 0.35% as.

[Mn：0.6~2.0%]

Mn is in order to ensure the integral element required for the intensity of steel plate is, it is necessary to be allowed to containing more than 0.6%. Preferably more than 0.8%, more preferably more than 1.0%.But if Mn amounts are superfluous, generation MnS and hic resistance deterioration, so The upper limit of Mn amounts is set to 2.0%.Preferably less than 1.9%, more preferably less than 1.8%.

[P：Higher than 0% and below 0.030%]

P be in steel unavoidably by comprising element, if its content is higher than 0.030%, to hic resistance, anti- SSCC brings adverse effect.Therefore, P amounts are suppressed below 0.030% in the present invention.Preferably less than 0.020%, more Preferably less than 0.010%.

[S：Higher than 0% and below 0.004%]

It is a large amount of to generate MnS if S is excessive, hic resistance is significantly deteriorated, therefore make the upper limits of S amounts be in the present invention 0.004%.Preferably less than 0.003%, more preferably less than 0.0025%, more preferably less than 0.0020%.

[Al：0.010~0.080%]

Al is by reducing the coefficient of thermal expansion of field trash, so as to reduce the hole with steel parent phase, has for improving hic resistance Effect.In addition, the field trash of the Al containing appropriate amount, promotes the generation of transgranular bainite, therefore good anti-SSCC can be obtained Property.In order that these effects show, at least need to be allowed to containing more than 0.010%.Al amounts are preferably more than 0.020%, more excellent Elect more than 0.025% as.But if Al amounts are superfluous, Al oxides cluster-shaped generates, and turns into the starting point of hydrogen induced cracking.Therefore, Al amounts are needed for less than 0.080%.Al amounts are preferably less than 0.060%, more preferably less than 0.050%.

[Cr：0.10~1.50%]

Cr is to ensure that the integral element required for intensity, in addition, suppressing the soft iron element in T-shaped cross weld portion Body, so as to also contribute to anti-SSCC improvement.In order that these effects show, at least need to be allowed to containing more than 0.10%. Cr amounts are preferably more than 0.15%, more preferably more than 0.17%, more preferably more than 0.20%.But if Cr amounts It is surplus, then the increase of the hard martensite in T-shaped cross weld portion is brought, anti-SSCC is reduced, therefore is less than 1.50%.Cr amounts are excellent Elect less than 1.00%, more preferably less than 0.80% as.

[Nb：0.002~0.050%]

Nb is to ensure that the integral element required for intensity, in addition, suppressing the soft iron element in T-shaped cross weld portion Body, it helps anti-SSCC improvement.In order that these effects play, at least need to be allowed to containing more than 0.002%.Nb amounts Preferably more than 0.005%, more preferably more than 0.010%.But if Nb amounts are superfluous, bring the hard of T-shaped cross weld portion The increase of matter martensite, anti-SSCC are reduced, therefore are less than 0.050%.Nb amounts are preferably less than 0.033%, more preferably Less than 0.030%.

[REM：0.0002~0.05%]

REM (rare earth element) reduces the coefficient of thermal expansion of field trash, so as to reduce the hole with steel parent phase, for ensuring to resist HIC is effective.In addition, the field trash of the REM containing appropriate amount, promotes the generation of transgranular bainite, therefore can obtain good Anti- SSCC.In order that these effects are played, it is necessary to make REM contain more than 0.0002%.REM amounts be preferably 0.0005% with On, more preferably more than 0.0010%.On the other hand, if containing REM superfluously, REM is in cyrystal boundary segregation for solid solution, makes crystal boundary strong Degree reduces, and deteriorates anti-SSCC.Therefore, the upper limit for making REM amounts is 0.05%.From the blocking of dipping spray nozzle when suppressing to cast And from the viewpoint of improving productivity ratio, preferably less than 0.03%, more preferably less than 0.01%, more preferably Less than 0.005%.Further, in the present invention, so-called REM, 15 from La to the Lu element in periodic table, i.e. group of the lanthanides are meant Element, and Sc and Y.

[Zr：0.0003~0.01%]

Zr reduces the coefficient of thermal expansion of field trash, so as to reduce the hole with steel parent phase, improves hic resistance.In addition, contain The Zr of appropriate amount field trash, promote the generation of transgranular bainite, therefore good anti-SSCC can be obtained.In order that these Effect is played, it is necessary to make Zr contain more than 0.0003%.Zr amounts be preferably more than 0.0005%, more preferably 0.0010% with On.On the other hand, if make Zr contain superfluously, the solid solution Zr increases in molten steel, in casting, to surround the side of oxysulfide Formula crystallizes out, and deteriorates hic resistance.Therefore, the upper limit for making Zr amounts is 0.01%.Zr amounts are preferably less than 0.007%, more excellent Elect less than 0.005% as.

[Ca：0.0003~0.006%]

Ca forms CaS and fixes S, has the function that to reduce MnS growing amounts, so that anti-SSCC improves.In addition, contain The Ca of appropriate amount field trash, promote the generation of transgranular bainite, therefore good anti-SSCC can be obtained.In order that these Effect is played, it is necessary to make Ca contain more than 0.0003%.Ca amounts be preferably more than 0.0005%, more preferably 0.0010% with On.On the other hand, if make Ca contain superfluously, CaS is largely generated, its aggegation and deteriorate hic resistance.Therefore, Ca amounts are made The upper limit be 0.006%.Ca amounts are preferably less than 0.005%, more preferably less than 0.004%.

[N：Higher than 0% and below 0.010%]

N is inevitable impurity, but reduces grain-boundary strength in cyrystal boundary segregation, deteriorates anti-SSCC.Therefore, make The upper limit of N amounts is 0.010%.N amounts are preferably less than 0.008%, more preferably less than 0.006%.

[O：Higher than 0% and below 0.0040%]

O (oxygen) is the element to form field trash, surplus addition cause thick oxide largely to generate, hydrogen induced cracking using its as Starting point occurs.Therefore, the upper limit for making O amounts is 0.0040%.O amounts be preferably less than 0.0030%, more preferably 0.0020% with Under.

[[Cr]/[Nb] is more than 10]

In addition, the steel plate of the present invention, meets the composition composition, and preferably [Cr]/[Nb] is more than 10.Wherein, [] represents quality % in formula.Steel plate meets this condition, in T-shaped cross weld portion, makes what the karyogenesis driving force of crystal boundary rose Segregations of the Nb to crystal boundary is reduced, and bainite is promoted from the generation of crystal boundary.Thus, generated in the martensite of welding metal neighborhood Amount is reduced, and improves anti-SSCC.It is therefore preferable that [Cr]/[Nb] is more than 10.More preferably more than 12, more preferably More than 15.

Though in addition, not being the necessary element of steel plate of the present invention, when containing Ni as composition composition, make 0.25 × [Cr] + [Ni] is adjusted for 0.10~1.50, by meeting this condition, can also improve anti-SSCC.Wherein, in formula [] Represent quality %.Further, meet 0.25 × [Cr]+[Ni] when be 0.10~1.50 this condition, be not necessarily intended to satisfaction [Cr]/ [Nb] is more than 10 such conditions.Details are aftermentioned.

As described above, surplus is iron and inevitable impurity to the composition composition of the steel of steel plate of the present invention.In addition, except Beyond above-mentioned element, by containing selected in the group formed from Mg, Ti, Ni, Cu, Mo, V and B of following amounts at least one again Kind is two or more, can realize hic resistance and anti-SSCC raising etc..Hereinafter, these elements are illustrated.

[Mg：Higher than 0% and below 0.005%]

Mg forms MgS, makes sulfide fine dispersion, so as to have the function that to improve the anti-SSCC of mother metal.But even if It is higher than 0.005% containing Mg, effect is also saturation, therefore the upper limit of Mg amounts is preferably 0.005%.More preferably 0.004% with Under, more preferably less than 0.003%.

[Ti：0.003~0.030%]

Ti is to contribute to the element that the intensity of steel plate improves by precipitation strength.In order to play this effect, preferably It is allowed to containing more than 0.003%.More preferably more than 0.004%, more preferably more than 0.005%.On the other hand, if Ti Content is excessive, then brings the increase of the hard martensite in T-shaped cross weld portion, reduces anti-SSCC, therefore is preferably Less than 0.030%.More preferably less than 0.025%, more preferably less than 0.020%.

[Ni：0.01~1.50%]

Ni contributes to the element that the intensity of steel plate improves.In order to play this effect, preferably it is allowed to containing 0.01% More than.More preferably more than 0.05%, more preferably more than 0.10%.On the other hand, if Ni contents are excessive, T is brought The increase of the hard martensite in shape cross weld portion, reduce anti-SSCC, therefore preferably less than 1.50%.More preferably Less than 1.00%, more preferably less than 0.50%.

[Cu：0.01~1.50%]

Cu contributes to the element that the intensity of steel plate improves.In order to play this effect, preferably it is allowed to containing 0.01% More than.More preferably more than 0.05%, more preferably more than 0.10%.On the other hand, if Cu contents are excessive, T is brought The increase of the hard martensite in shape cross weld portion, reduce anti-SSCC, therefore preferably less than 1.50%.More preferably Less than 1.00%, more preferably less than 0.50%.

[Mo：0.01~1.50%]

Mo contributes to the element that the intensity of steel plate improves.In order to play this effect, preferably it is allowed to containing 0.01% More than.More preferably more than 0.05%, more preferably more than 0.10%.On the other hand, if Mo contents are excessive, T is brought The increase of the hard martensite in shape cross weld portion, reduce anti-SSCC, therefore preferably less than 1.50%.More preferably Less than 1.00%, more preferably less than 0.50%.

[V：0.003~0.08%]

V contributes to the element that the intensity of steel plate improves.In order to play this effect, preferably it is allowed to containing 0.003% More than.More preferably more than 0.005%, more preferably more than 0.010%.On the other hand, if V content is excessive, T is brought The increase of the hard martensite in shape cross weld portion, reduce anti-SSCC, therefore preferably less than 0.08%.More preferably Less than 0.07%, more preferably less than 0.05%.

[B：0.0002~0.0032%]

B contributes to the element that the intensity of steel plate improves.In order to play this effect, preferably it is allowed to containing 0.0002% More than.More preferably more than 0.0005%, more preferably more than 0.0010%.On the other hand, if B content is excessive, band Carry out the increase of the hard martensite in T-shaped cross weld portion, reduce anti-SSCC, therefore preferably less than 0.0032%.It is more excellent Elect less than 0.0030%, more preferably less than 0.0025% as.

[[Cr]+[Mo]+[Ni]+[Cu] is less than 2.1]

In addition, the steel plate of the present invention, after the composition composition is met, preferably [Cr]+[Mo]+[Ni]+[Cu] is It is 2.1 following.Wherein, [] represents quality % in formula.If the addition of these elements is higher than 2.1, T-shaped cross weld portion is brought The increase of hard martensite, reduce anti-SSCC.It is therefore preferable that [Cr]+[Mo]+[Ni]+[Cu] is less than 2.1.More preferably For less than 1.9, more preferably less than 1.7.

[dipping potential difference Δ E (the dipping current potential of dipping current potential-steel plate of girth weld metal) is below 25mV]

In T-shaped cross weld portion, when the potential difference of mother metal and girth weld metal is big, because dissimilar metal contacts effect, Cause the hydrogen in the selective corrosion and girth weld metal of mother metal to invade to be promoted, therefore anti-SSCC is reduced.Particularly from Impregnate and do not formed stable and uniform sulfide envelope within 1 hour, drawn by the potential difference of girth weld metal and steel plate The hydrogen intrusion risen becomes notable.It is therefore preferable that tried to achieve by following formula, when steel plate and girth weld metal impregnate in the solution 1 Dipping potential difference Δ E after hour is below 25mV.More preferably below 20mV, more preferably below 15mV.

Further, in the solution impregnating metal when the electrode potential that shows be defined as the situation of corrosion potential, mixed potential, But " dipping current potential " is referred to as in the present invention.

[0.25 × [Cr]+[Ni] is 0.10~1.50]

In T-shaped cross weld portion, when the potential difference of mother metal and girth weld metal is big, because dissimilar metal contacts effect, Intrusion of the hydrogen into mother metal or girth weld metal is caused to be promoted, so anti-SSCC is reduced.Therefore, thick steel of the invention Plate, formed in the composition, after condition as particularly Ni content satisfaction 0.10~1.50%, further preferably 0.25 × [Cr]+[Ni] is 0.10~1.50.If in, [] represents quality % in formula.The addition of these elements, make the steel plate as mother metal Current potential improve, suppress because dissimilar metal contact effect caused by intrusion of the hydrogen to T-shaped cross weld portion, contribute to T-shaped to intersect The anti-SSCC of weld part improvement.

Therefore, it is preferably more than 0.10 by 0.25 × [Cr]+[Ni] values tried to achieve, more preferably more than 0.15, further Preferably more than 0.20.On the other hand, if the value tried to achieve by 0.25 × [Cr]+[Ni] is superfluous, the current potential of steel plate is than welding gold The current potential of category is greatly improved, and the selective corrosion of welding metal caused by couple corrosion is carried out, and anti-SSCC is reduced.Therefore, by The upper limit for the value that 0.25 × [Cr]+[Ni] is tried to achieve is 1.50.The upper limit be more preferably less than 1.00, more preferably 0.70 with Under.

(welding metal)

For the metal of girth welding, in order to ensure the intensity and toughness of welding metal, and in order to improve corrosion resistance, Preferably following composition composition.That is, preferably C is contained in terms of quality %：0.02~0.10%, Si：0.10~0.60%, Mn： 0.90~2.50%, Ni：0.20~1.00%.In addition, as composition other than the above, can allow for containing P：0.015% with Under, S：Less than 0.010%, Cu：Less than 1.0%, Mo：Less than 1.0%, Nb：Less than 0.5%, V：Less than 0.3%, Ti：0.05% Below, Al：Less than 0.1%.Composition in addition, it is desirable to be iron and inevitable impurity.Hereinafter, for welding metal The restriction reason of composition composition is illustrated.

[C：0.02~0.10%]

C ensures it is necessary element in intensity in welding metal., cannot be defined strong if C content is fewer than 0.02% Degree.But if C content is superfluous, cause the coarsening of grain boundary carbide, turn into the reason for toughness reduces, therefore be 0.10% Below.

[Si：0.10~0.60%]

Si ensures it is necessary element in intensity in welding metal., cannot be defined if Si contents are fewer than 0.10% Intensity.But the reason for reduction as toughness, therefore it is less than 0.60% if Si contents become superfluous.

[Mn：0.90~2.50%]

Mn is ensuring the intensity of welding metal, in the balance of toughness is being necessary element.In order to obtain such effect, Mn Content need for more than 0.90%.But if Mn contents are excessive, segregation is encouraged, turn into the reason for toughness reduces, therefore need To be less than 2.50%.

[Ni：0.20~1.00%]

Ni improves the current potential of welding metal, and effect is played on corrosion resistance is improved.In addition, its improve hardenability and Ensure intensity, and it is also effective element to improve in low-temperature flexibility.In order to obtain such effect, Ni content needs are More than 0.20%.On the other hand, if Ni contents are superfluous, there is the possibility for causing fire check, improve welding gold in addition superfluously The current potential of category, the reason for turning into the selective corrosion for causing mother metal, less than 1.00% is thus limited to thereon.

(the field trash composition in steel plate)

[composition of wide more than 1 μm of the field trash contained in steel]

[Zr amounts are 1~40%]

In the present invention, the Zr in wide more than 1 μm of field trash, exist mainly as oxide.The Zr oxides compare steel Coefficient of thermal expansion it is small, if therefore can ensure that the Zr amounts in field trash, the hole with the steel parent phase of surrounding can be reduced, make to resist HIC improves.In addition, the oxide containing appropriate Zr, can promote the generation of transgranular bainite, therefore can obtain good Anti- SSCC.In order to play such effect, it is 1~40% to make the Zr amounts in field trash.If Zr amounts are less than 1% or are higher than 40%, then the anti-SSCC in the hic resistance of mother metal or T-shaped cross weld portion is insufficient.

[REM amounts are 5~50%]

In the present invention, the REM in wide more than 1 μm of field trash, exist as oxide and oxysulfide etc..Wherein, REM oxides are smaller than the coefficient of thermal expansion of steel, if therefore can ensure that the REM amounts in field trash, can reduce and the steel of surrounding is female The hole of phase, improve hic resistance.In addition, in the presence of as oxysulfide, it fixes S, can suppress MnS etc. to hic resistance band Come the generation of sulfide adversely affected.In addition, these REM systems field trashes promote the generation of transgranular bainite, therefore can obtain To good anti-SSCC.In order to play such effect, it is 5~50% to make the REM amounts in field trash.If REM amounts are less than 5% Or higher than 50%, then the anti-SSCC in the hic resistance of mother metal or T-shaped cross weld portion is insufficient.

[Al amounts are 3~30%]

In the present invention, the Al in wide more than 1 μm of field trash, exist mainly as Al oxides.The Al oxides ratio The coefficient of thermal expansion of steel is small, therefore, if can ensure that the Zr amounts in field trash, can reduce the hole with the steel parent phase of surrounding, right In improving, hic resistance is effective.In addition, the oxide containing appropriate Al, promotes the generation of transgranular bainite, therefore can obtain Good anti-SSCC.In order to play such effect, it is 3~30% to make the Al amounts in field trash.If Al amounts are less than 3% or high In 30%, then the anti-SSCC in the hic resistance of mother metal or T-shaped cross weld portion is insufficient.

[Ca amounts are 5~60%]

In the present invention, the Ca in wide more than 1 μm of field trash, in T-shaped cross weld portion during welding, structure of steel is contributed to Miniaturization, promote the generation using field trash as the transgranular bainite structure of starting point.Thus the T-shaped cross weld portion after welding Structure of steel becomes fine, can obtain good anti-SSCC.In order to play such effect, it is 5 to make the Ca amounts in field trash ~60%.When Ca amounts are less than 5% or higher than 60%, it is impossible to improve the anti-SSCC in T-shaped cross weld portion.

[S amounts are higher than 0% and below 20%]

S amounts in wide more than 1 μm of field trash, can be reduced in the following way, i.e. by the content of the S in steel plate, and The content of sulfide-based field trash miniaturization scattered Zr, REM etc. alloying component is set to be defined to the composition composition, then in the past The mode of stating controls field trash to form.If the composition composition and field trash composition are not controlled appropriately, described to be mingled with S amounts in thing are higher than 20%, and thick sulfide is superfluous, as a result, the hic resistance of mother metal or T-shaped cross weld portion is anti- SSCC is insufficient.On the other hand, the S amounts in the field trash are controlled in the steel plate below 20%, can be obtained good Hic resistance and anti-SSCC.S amounts in the field trash more it is few more preferably, but for 0% when, S completely can not be by field trash It is fixed, it is believed that the hic resistance of mother metal or the anti-SSCC in T-shaped cross weld portion become insufficient.

The total number of the field trash, as long as not damaging the effect of the present invention significantly, but it is not particularly limited, but in steel plate In preferably disperse 500~5000/cm²Left and right.If it is less than 500/cm², then the starting point deficiency of transgranular bainite, cannot fill The tissue miniaturization effect divided, it is believed that anti-SSCC is reduced.If in addition, it is higher than 5000/cm², then lighted as rising for destruction Effect, there is the possibility for causing hic resistance, anti-SSCC to deteriorate together.

(manufacture method)

Then, described in detail below for the manufacture method of the steel plate of the present invention.

[molten steel treatment process]

When obtaining the steel plate of the present invention of the tissue, in molten steel treatment process, in order including following process：(A) Using meeting Fe：0.1~10% slag makes the desulfurization process that S reaches less than 0.004%；(B) dissolved oxygen concentration of molten steel is made Of, with the ratio of the S concentration with molten steel：Of/S meters are in less than 10 deoxidation step；(C) add according to Al, Zr, REM, Ca order Add Al, Zr, REM and Ca, or according to Al is first added, then add Zr and REM simultaneously, the order for then adding Ca is added Process, Ca needs to be added again every more than 4 minutes from REM addition, also, makes Ca added to solidifying time for finishing Within 200 minutes, during casting the cool time of 1300 DEG C~1200 DEG C of slab t/4 positions need within 460 seconds.This Outside, the cool time that 1500~1450 DEG C of slab t/4 positions are made during casting is within 300 seconds.Further, described t display plates It is thick.Hereinafter, illustrated in order for each operation.

(A) desulfurization process

In order to ensure hic resistance, it is important that thick sulfide is reduced, in order to reach this point, it is important that control S Amount.With converter or electric furnace for make molten steel temperature for more than 1550 DEG C the molten steel of melting, using meeting Fe：0.1~10% Slag, S is set to reach less than 0.004%.By improving the Fe concentration in slag, REM, the Zr added after desulfating and deoxidation will not be It is dissolved in molten steel, and can preferentially forms oxide.In order to obtain this effect, the Fe concentration in above-mentioned slag is set to be More than 0.1%.Fe concentration in slag is preferably more than 0.5%, and more preferably more than 1.0%.On the other hand, if in slag Fe concentration is higher than 10%, then oxide largely generates, and oxide turns into the starting point of hydrogen induced cracking.Therefore, the Fe concentration in slag For less than 10%.Preferably less than 8%, more preferably less than 5%.In addition, during addition Ca, fully carry out with the desulfurization of slag and S is suppressed below 0.004%, CaS can be largely formed when thus adding Ca after REM additions, the group of field trash can be prevented Into scope as defined in disengaging, it can be ensured that hic resistance, anti-SSCC

In order that the S is in less than 0.004%, it is more than 10% to make the CaO concentration in slag.Pass through adding for Ca Add, the molten S that deposits in the CaO and molten steel in slag reacts, and becomes CaS, thus the S in molten steel is reduced, i.e. can fully be taken off Sulphur.Then, if at this moment making the CaO concentration in slag be more than 10%, S can be made to be in less than 0.004%.In slag CaO concentration is preferably more than 15%, and more preferably more than 20%.On the other hand, the more mistakes of CaO in slag, desulfurization also can be difficult, Therefore the upper limit is 80% or so.

(B) deoxidation step

In order to improve anti-SSCC, it is important that control oxide, in order to reach this point, it is important that control O amounts. In this process, influential S amounts have increased slightly for hic resistance, and so-called S returns generation, it is therefore important that simultaneously Control O amounts and S amounts.In this process, before REM described later additions, make the dissolved oxygen concentration Of of molten steel, with the S with molten steel The ratio of concentration：Of/S is counted and is in less than 10.When REM is added in molten steel, oxide is also formed while forming its sulfide. When the Of/S is higher than 10, the most of of REM added forms oxide, scope as defined in the composition disengaging of field trash.Its As a result, hic resistance, anti-SSCC are deteriorated.Therefore in the present invention, it is such as described to make Of/S be less than 10.Of/S be preferably 5 with Under, more preferably less than 3.5, more preferably less than 2.Further, Of/S lower limit substantially 0.1 or so.In order that institute State Of/S and be in less than 10, can be reached by implementing the deoxidation of following at least one party：That is, taken off with RH degassers Oxygen, deoxidation is carried out by the input of Mn, Si, Ti etc. deoxidant element.

(C) Al, Zr, REM addition process

The addition of Al, Zr, REM into molten steel, first adds Al, secondly adds Zr, REM.If this is because, by Al and Zr and REM deoxidizing capacity compares, then Zr and REM deoxidizing capacity ratio Al is strong, if therefore before Al add Zr and REM, be mingled with Al amounts in thing can not reach desired value.Therefore, it is necessary to prior to Zr and REM additions Al.

, can be with if considering the desulphurizing ability and deoxidizing capacity of each addition element as described below in addition, when adding Ca Using any one following method：Initially addition Al, Zr is secondly added, REM is added again, finally adds Ca, or, initially add Add Al, then add Zr and REM simultaneously, finally add Ca.But no matter which kind of situation, from REM be added to Ca addition time All it is more than 4 minutes.

Its reason is illustrated.First, if comparing REM and Ca desulphurizing ability, REM desulfurization power is weaker than Ca, because If this addition Ca before REM is added, substantial amounts of CaS is generated, scope as defined in the composition disengaging of field trash, makes hic resistance, resist SSCC is deteriorated.Therefore, it is necessary to before Ca is added addition REM, therefore, Al, Zr, REM and Ca order of addition must be Al → Zr and REM → Ca.In addition, in order to which the composition control of field trash is needed in defined scope, the time from REM added to Ca additions It is spaced more than 4 minutes.Time from REM added to Ca additions is preferably more than 5 minutes, more preferably more than 8 minutes.Also Have, from the viewpoint of productivity ratio, from REM added to the upper limit generally 60 minutes or so of the time of Ca additions.

Secondly, if comparing Zr, REM, Ca deoxidizing capacity, in general deoxidizing capacity is most strong with Ca, it is believed that is Ca ＞ REM ＞ Zr order, Zr are most weak.Therefore, in order that containing Zr in field trash, i.e. formed as oxide system field trash ZrO₂, it is necessary to add Zr before addition the deoxidizing capacity Ca and REM stronger than Zr.Therefore, Al, Zr, REM and Ca order of addition Need for Al → Zr → REM → Ca.But REM is compared with Ca, because deoxidizing capacity is small, even if added with Zr simultaneously, It can make to contain Zr in field trash, therefore its order of addition can also be Al → Zr and REM → Ca.

On the addition of each element, the steel plate of desired each element amount can be obtained, for example, can enumerate with Densimeter in molten steel, makes Zr reach 3~100ppm and be added, and thereafter or simultaneously, with the densimeter in molten steel, makes REM Reach 2~500ppm and be added, afterwards after more than 4 minutes, with the densimeter in molten steel, Ca is reached 3~60ppm And it is added.

(casting process)

After the Ca additions, such as within 80 minutes, start to cast rapidly, with the time finished from Ca added to solidification Mode within 200 minutes is cast.Its reason is as follows.That is, Ca is the high element of desulphurizing ability, deoxidizing capacity, therefore companion Time passage after being added with Ca, easily form the CaS and CaO of the composition stabilization of oxide and sulfide, it is impossible to make field trash Composition reach prescribed limit.Therefore in the present invention, the time finished from Ca added to solidification is within 200 minutes.It is preferred that Within 180 minutes, within more preferably 160 minutes.Further, the lower limit of the time, from the viewpoint of making Ca homogenize For 4 minutes or so.

In addition, if the cool time of 1500~1450 DEG C of slab t/4 positions during casting is higher than 300 seconds, oxidation is encouraged The secondary inclusion thing of thing system scope as defined in the composition disengaging of field trash, makes anti-SSCC bad to the composition generation on field trash Change.

In addition, the cool time of 1300 DEG C~1200 DEG C slab t/4 positions when making casting is critically important for 270~460 seconds. If the cool time is higher than the upper limit, sulfide-based secondary inclusion thing is mainly encouraged to the composition generation on field trash, is mingled with Scope as defined in the composition disengaging of thing, deteriorates anti-SSCC.On the other hand, if the cool time is less than this lower limit, cool down Load is significantly increased, therefore is not preferred in practicality.

[the later process of rolling]

After the solidification, it then follows conventional method carries out hot rolling, can manufacture steel plate., can be with addition, using the steel plate The method manufacture line-pipes steel pipe typically carried out.Process on rolling later is not particularly limited, but preferably for example will casting The heating of plate blank made to more than 1100 DEG C, recrystallization temperature domain with more than 40% reduction ratio implement hot rolling, from 780 DEG C with 10~20 DEG C/s cooling velocity carries out acceleration cooling to it.Further, thereafter need not be quenched.

[welding point]

In the present invention, there is provided used the welding point of steel plate of the present invention.Welding point is by steel plate and weldering of going in ring Stitch metal to form, the end that steel plate is welded by girth weld metal obtains.The welding point of the present invention, being tried to achieve by following formula, The dipping potential difference Δ E of steel plate and girth weld metal is preferably below 25mV.

As described above, in T-shaped cross weld portion, when the potential difference of mother metal and girth weld metal is big, because dissimilar metal connects Effect is touched, causes the hydrogen in the selective corrosion and girth weld metal of mother metal to invade and is promoted, therefore anti-SSCC is reduced.It is logical Cross using steel plate of the present invention, dipping potential difference Δ E is below 25mV, can suppress the anti-SSCC of weld part reduction.Leaching Stain potential difference Δ E is more preferably below 20mV, more preferably below 15mV.

In addition, as the metal for girth welding, it is adapted to use above-mentioned welding metal.

Welding method for forming welding point is not particularly limited, and can be carried out by existing known method.For example, Arc welding, Laser Welding, electron beam weldering etc. can be enumerated.

【Embodiment】

Hereinafter, enumerate embodiment and further illustrate the present invention, but the present invention is not limited by following embodiments certainly, in energy Implementation can also suitably be changed in the range of spirit of the invention by enough meeting, and these are included in the technical scope of the present invention It is interior.

(embodiment 1~33, comparative example 1~19)

For the molten steel by conventional method by 240t converter refinings, using LF stoves, carry out desulfurization, deoxidation, composition adjustment, The processing of Control and Inclusion Removal etc., make to have the various molten steel that the steel composition shown in table 1~4 and steel inclusion form via continuous Casting and turn into slab, to carrying out acceleration cooling after its hot rolling, manufacture thick 40mm, wide 3500mm steel plate.Obtained by use The steel plate and girth weld metal arrived, makes welding point described later.Table 5,6 show molten steel processing, continuously casting and Accelerate process conditions main in cooling.Table 7,8 represents all characteristics of so obtained each steel plate.Hereinafter, for shown in table 3,4 Field trash composition analysis method and table 7,8 each characteristic measuring method and evaluation meanses illustrate.

(analysis of the composition of field trash)

The analysis of the composition of field trash is carried out as follows.That is, it is central with thickness of slab in the thickness of slab direction section of rolled stock Centered on portion, observed with Shimadzu Scisakusho Ltd EPMA-8705.In detail, to observe 400 times of multiplying power, Field of view about 50mm²3 sections of middle observation, using wide more than 1 μm of field trash as object, according to the wavelength color of characteristic X-ray Dissipate the composition composition of light splitting quantitative analysis field trash central portion.Further, field of view is the thickness of slab using thickness of slab central part as center Direction 7mm, plate width direction 7mm scope.It is Al, Mn, Si, Mg, Ca, Ti, Zr, S, REM, Nb to analyze object elements.This institute The so-called REM shown, is La, Ce, Nd, Dy, Y.It is using known substance that the relation of the X-ray intensity of each element and concentration of element is pre- First tried to achieve as calibration curve, then, according to the X-ray intensity obtained by the field trash and the quantitative field trash of the calibration curve Concentration of element.Then, being averaged for the content of each element of wide more than 1 μm of field trash in 3 sections is tried to achieve Value, the composition as field trash.

(the yield strength YS of mother metal measurement, evaluation)

From the t/4 positions of each steel plate, JIS Z2241 No. 4 test films are abreast extracted with C directions, with JIS Z2241 Described method carries out tension test and measures yield strength YS, confirms the intensity of each steel plate.

(experiment, the evaluation of hic resistance)

The method for following NACE standard TM0284-2003 defineds is tested, evaluated.Specifically, will try Test 25 DEG C, 5 mass %NaCl+0.5 mass %CH that piece is immersed in after the hydrogen sulfide saturation for making 1atm₃96 in the COOH aqueous solution Hour.In the evaluation of HIC experiments, cut off with 10mm spacing along the longitudinally of each test film, after being ground to its section, used Light microscope observes gross section with 100 times of multiplying power, confirms whether there is HIC crackle of the crack length in more than 1mm.

(the anti-SSCC in T-shaped cross weld portion experiment, evaluation)

In order to simulate wire bonding, the steel plate formed with the steel shown in table 1,2 is processed into 75 ° of X grooves, with bilayer Submerged arc welding method is welded, and makes pipe.Heat input during welding is first layer：3.7kJ/mm, the second layer：5.4kJ/mm.Separately Outside, girth welding when pipe is engaged with each other in order to simulate, with " practical, the Guia Hill of the UOE steel pipes of anti-SSCC excellents Deng, welding technique, in September, 1988 number, P.58 " and as reference, in a manner of weld seam sealing wire is orthogonal, by gas shielded arc welding Implement the disk diffusion method of individual layer, welding point is made.Heat input during welding is 1.0kJ/mm.Welding metal during wire bonding uses Lincolnweld LA-81 (Lincoln societies system), welding metal during girth welding use MX-A55Ni1 ((strain) Kobe systems Steel is made).

Processing is ground for the weld part surface of the pipe conjugant after welding, carries out the removing in the reinforcement portion of built-up welding. Immediately below the built-up welding portion of the pipe conjugant, make longitudinally and heap bonding wire parallel, so extract 115L × 15W × 5t experiment Piece.Using the test film, based on ASTM G39, NACE TM0177-2005B methods, the anti-SSCC of 4 bend test pieces of implementation Evaluation test.Apply the flexure equivalent to load stress 388MPa, 437MPa, the NACE after 1atm hydrogen sulfide saturation is made is molten Liquid A：5 mass %NaCl-0.5 mass %CH₃After being impregnated 720 hours in COOH, seen using 10 times of light microscope of multiplying power Examine, implementing test film surface has the confirmation of flawless.

(dipping potential difference Δ E (the dipping current potential of dipping current potential-steel plate of girth weld metal) evaluation)

The corruption of a part for the steel plate formed with the steel shown in table 1,2 and foregoing girth weld metal will be extracted Corrosion test piece (20mm × thick 2mm in length and breadth), wet lapping is carried out with SiC#600 pouncing papers, after ultrasonic wave cleaning, examination is welded in point Expect the installation of enterprising row conductor.It is coated to epoxy resin beyond the experiment face of steel plate or girth weld metal.The sample is soaked NACE solution A (5 mass %NaCl-0.5 mass %CHs of the stain after 1atm hydrogen sulfide saturation is made₃COOH in), measurement dipping Current potential after 1 hour afterwards.Reference electrode uses saturated calomel electrode, calculates from the dipping current potential of girth weld metal and subtracts thick steel The value of the dipping current potential of plate is as dipping potential difference Δ E.

From the table 7 that shows these results embodiment and table 8 comparative example each characteristic contrast, meet the present invention The steel plate of the embodiment of the composition composition of defined and the composition of wide more than 1 μm of thick field trash in steel, can be obtained High mechanical properties, and crackle does not occur via HIC experiments, hic resistance is excellent.In addition, in embodiment, it is being applied with quite In the SSCC experiments of load stress 388MPa flexure, it can confirm crackle does not occur.In addition, in embodiment 4~33, applying In the anti-SSCC evaluation tests for having added the flexure equivalent to load stress 438MPa, crackle does not also occur, can confirm to have excellent Anti- SSCC.

On the other hand, be unsatisfactory for present invention provide that composition composition or thick field trash composition comparative example thick steel Plate, in the anti-SSCC experiments of the flexure equivalent to load stress 388MPa are tested or applied to hic resistance, confirm the hair of crackle It is raw.

【Table 1】

【Table 2】

【Table 3】

【Table 4】

【Table 5】

【Table 6】

【Table 7】

"-" is unmeasured

【Table 8】

In SSCC experiments, "-" is not carried out for experiment

It is unmeasured to impregnate "-" in potential difference Δ E

In detail and illustrate the present invention with reference to specific embodiment, but can not depart from the spirit and scope of the present invention and It is subject to various changes and modifications, this is tied will be apparent that for practitioner.The application is special based on Japan filed in 22 days Mays in 2015 Profit applies for (patent application 2015-104617) and based on Japanese patent application (patent application filed in 28 days March in 2016 2016-064064), its content is incorporated into this as reference.

Claims

A kind of 1. steel plate, it is characterised in that：Contain C in terms of quality %：0.01~0.12%, Si：0.02~0.50%, Mn： 0.6~2.0%, P：Higher than 0% and below 0.030%, S：Higher than 0% and below 0.004%, Al：0.010~ 0.080%th, Cr：0.10~1.50%, Nb：0.002~0.050%, REM：0.0002~0.05%, Zr：0.0003~ 0.01%th, Ca：0.0003~0.006%, N：Higher than 0% and below 0.010%, O：Higher than 0% and below 0.0040%, Surplus is iron and inevitable impurity,

In steel in the composition of wide more than 1 μm contained of field trash, meet that the Zr amounts in debris are 1~40%, REM amounts are 5 ~50%, Al amounts are that 3~30%, Ca amounts are 5~60%.
2. steel plate according to claim 1, wherein, the S amounts in the field trash are higher than 0% and below 20%.
3. steel plate according to claim 1, wherein, [Cr]/[Nb] is more than 10,

[] represents quality % in the formula.
4. steel plate according to claim 1, wherein, also contain Mg in terms of quality %：Higher than 0% and 0.005% with Under, Ti：0.003~0.030%, Ni：0.01~1.50%, Cu：0.01~1.50%, Mo：0.01~1.50%, V：0.003 ~0.08% and B：More than one or both of 0.0002~0.0032%,

[Cr]+[Mo]+[Ni]+[Cu] is less than 2.1,

Wherein, [] represents quality % in the formula.
5. steel plate according to claim 4, wherein, contain Ni in terms of quality %：0.01~1.50%,

0.25 × [Cr]+[Ni] is 0.10~1.50,

Wherein, [] represents quality % in the formula.
6. a kind of welding point, it is characterised in that contain steel plate according to any one of claims 1 to 5 and girth weld Metal.
7. welding point according to claim 6, wherein, steel plate tried to achieve by following formula, described and the girth weld The dipping potential difference Δ E of metal is below 25mV,

The dipping current potential after 1 hour that impregnates current potential-steel plate behind 1 hour of Δ E=girth weld metals

The unit of the dipping current potential is mV.