CN100422370C - High tensile steel excellent in toughness of welded zone and offshore structure - Google Patents
High tensile steel excellent in toughness of welded zone and offshore structure Download PDFInfo
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- CN100422370C CN100422370C CNB2004800349962A CN200480034996A CN100422370C CN 100422370 C CN100422370 C CN 100422370C CN B2004800349962 A CNB2004800349962 A CN B2004800349962A CN 200480034996 A CN200480034996 A CN 200480034996A CN 100422370 C CN100422370 C CN 100422370C
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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Abstract
A high tensile steel, characterized in that it has a chemical composition, in mass %, that C: 0.01 to 0.10 %, Si: 0.5 % or less, Mn: 0.8 to 1.8 %, P: 0.020 % or less, S: 0.01 % or less, Cu: 0.8 to 1.5 %, Ni: 0.2 to 1.5 %, Al: 0.001 to 0.05 %, N: 0.0030 to 0.0080 %, O: 0.0005 to 0.0035 %, optionally one or two of Ti: 0.005 to 0.03 %, Nb: 0.003 to 0.03 % and Mo: 0.1 to 0.8 %, and the balance: Fe or impurities, with the proviso that N/Al is 0.3 to 3.0.
Description
Technical field
The present invention relates to high-strength steel and offshore structure, particularly the welding of excellent in toughness of welded zone is with high-strength steel and offshore structure.
More particularly, the present invention relates in buildings, civil structure spare, construction implement, boats and ships, pipeline, jar, offshore structure etc., be used as the welding high-strength steel that welding structural element uses, be particularly related to that employed welding for example relates to yield strength at 420N/mm with high-strength steel and offshore structure in the offshore structure
2More than, thickness of slab more than 50mm thick high-strength steel plate and used its offshore structure.
Background technology
In recent years, energy requirement has the tendency that increases gradually, and is very active for the exploration of submarine oil resource.Wherein employed offshore structure, for example platform, self-elevating drilling platform progressively maximize, and accompany with it, and used steel such as steel plate are wall thickening progressively, thereby further guarantees to become important problem for security.
Though in common offshore structure, using yielding stress is the middle intensity steel of 300～360MPa level, yet in foregoing large-sized structural parts, wanting working strength sometimes is the high strength of 460～700MPa level, the utmost point thickness high intensity steel material that thickness of slab surpasses 100mm.
In addition, move to cold zone or deepwater regions the exploration region of submarine oil resource in recent years, and the offshore structure of working in these regions or marine site is exposed in the very harsh meteorology and ocean condition.
For this reason, for employed steel in these offshore structures, require to have the toughness in the very harsh low-temperature region below for example-40 ℃, and also require to have weldability certainly.
In addition, consider that user's inspection benchmark is also very strict,, except the regulation of in the past pendulum impact value, also all will estimate toughness by the CTOD value that is defined under the minimum use temperature for mother metal, weld part from the aspect of security.Promptly, even in to pendulum impact experiment, obtaining under the situation of stable properties with the evaluation experimental of the small experiment slice of the size of 10mm * 10mm cutting sampling, also often occur in the situation that can't satisfy desired characteristic in the CTOD characteristic of estimating with the experiment slice of the actual (real) thickness of structural part, in addition, be required more strict CTOD characteristic now.
Be not limited in by the steel that use in the offshore structure in being located at the frozen water marine site like this, for the steel that the cable tubing that is used for cold zone that uses under than its more gentle environment or large welded structures spares such as boats and ships, LNG jar use, also require to improve the low-temperature flexibility of welding heat affected zone (below be called HAZ) consumingly.
On the other hand, in order in the low-temperature region below-40 ℃, to obtain high tenacity, have under the welding conditions of the low heat input of welding efficiency difference, weld.Welding procedure cost shared in the laid down cost of offshore structure is bigger.The most directly method that reduces the welding procedure cost is that employing can realize the high-level efficiency welding process of large-line energy welding, reduces the welding number of plies.
So, now significantly, to consider the toughness of HAZ and carry out the alap welding of welding procedure cost the strict structural part of low-temperature flexibility towards cold zone.
Toughness for the HAZ that makes steel improved greatly in the past, known low Cization is an effective means, in order to remedy the intensity reduction that causes by low Cization, the high strength that various alloys bring, the high strength that has utilized timeliness precipitation-hardening effect have been realized adding.For example, in ASTM A710, announce the steel that the timeliness precipitation-hardening effect that has utilized Cu is arranged, implemented some reports based on this kind method.
For example, open flat 5-186820 communique the fair 7-81164 communique of spy, spy, the spy opens in the flat 5-179344 communique, the Cu that has proposed the good-toughness of weld part separates out shaped steel.
But the pendulum impact characteristics of the welding joint that in the fair 7-81164 communique of spy, only estimated thickness of slab 30mm, obtains with weld heat input 40kJ/cm is difficult to think and material that the large-line energy welding is corresponding.
Open in the flat 5-186820 communique the spy, proposed to add the high-strength steel of tensile strength more than 686MPa of 0.5～4.0% Cu, yet for low-temperature flexibility, owing to only represent to be-30 ℃, therefore be difficult to think the low temperature CTOD characteristic that to guarantee utmost point Plate Steel with the transition temperature of pendulum impact experiment.
Open in the flat 5-179344 communique the spy, separate out shaped steel though proposed the good Cu of pendulum impelling strength of weld part, yet only estimated the pendulum impact characteristics of the welding joint that obtains with weld heat input 5kJ/mm, be difficult to think the security of the structural part that can satisfy large-line energy when welding fully.
Summary of the invention
Here, the objective of the invention is to, provide and in general improved the weld part low-temperature flexibility, particularly improved the welding high-strength steel of HAZ low-temperature flexibility.
The inventor etc. have carried out various experiments in order to develop the thick high-strength steel plate of excellent in toughness of welded zone to composition of steel and manufacture method thereof, and the result has obtained following opinion.
(i) add steel as base steel with Cu, except adjusting the content of N, Al, control N/Al ratio.
In high Cu composition material, in order to improve large-line energy HAZ toughness, the fine dispersion of carbonitrides such as TiN, Ti (C, N), AlN is effective.So, after using high Cu-Ti interpolation material to carry out research, found adjustment, the validity of the way of control N/Al ratio except N, Al content.This be because, when N/Al when too small, then separate out thick AlN, except himself causes the detrimentally affect toughness, also can hinder fine/a large amount of dispersion of TiN.On the other hand, when N/Al when excessive, except solid solution N increased, the branch bulk density of AlN, TiN became sparse.
(ii), need disperse fine Cu particle as much as possible in order to improve yield strength.
(iii), particularly guarantee low temperature CTOD characteristic, need make Cu particle thickization to a certain extent, and suppress dispersion amount in order to ensure toughness.
(iv), suppress the generation of the Cu particle of ageing treatment in the last stage as far as possible, and utilize the condition of ageing treatment to control Cu dispersion of particles state in order to make Cu dispersion of particles state homogenizing.
(v), put in order, just can control the strength and toughness balance by mean value and the plane transformed area rate of using the diameter of equivalent circle of trying to achieve according to the TEM photo for the distribution of Cu particle.
(vi) the lattice defect (mainly be dislocation) of Cu particle in steel gone up easily and generated, and when dislocation desity was high, then just separating out of Cu particle promoted.In addition, the Cu particle on the dislocation can hinder moving of dislocation, and yield strength is improved.
(vii) the dislocation desity in the steel can utilize calendering and water-cooled condition to control.In addition, the increase of the reduction of rolling temperature, total reduction, water-cooled begin the rising of temperature, the increase of speed of cooling, the reduction that water-cooled stops temperature and all can increase dislocation desity.
(viii) with high Cu composition as base steel, the hardenability control that utilizes the adjustment by C, Mn, Mo amount to realize can realize large-line energy welded H AZ flexible stabilization.
That is, in high Cu composition material, reduce crack sensitivity indices P cm value, then can improve HAZ toughness more, find thus, low C, low Mnization are effective.But, in order to ensure high strength, need utilize filling up of other elements, by the addition of control Mo, just can realize intensity/flexible stabilization.
The present invention is based on this kind opinion and constitutes, and its purport is as follows.
(1) a kind of high-strength steel, it is characterized in that, % represents with quality, contain that C:0.01～0.10%, Si:0.5% are following, Mn:0.8～1.8%, P:0.020% is following, S:0.01% is following, Cu:0.8～1.5%, Ni:0.2～1.5%, Al:0.001～0.05%, N:0.0030～0.0080%, O:0.0005～0.0035%, remainder is Fe and impurity, and N/Al is 0.3～3.0.
(2) high-strength steel of being put down in writing according to described (1) is characterized in that % represents with quality, contains Ti:0.005～0.03%.
(3) high-strength steel of being put down in writing according to described (1) or (2) is characterized in that % represents with quality, contains Nb:0.003～0.03%.
(4) according to any high-strength steel of being put down in writing in described (1)～(3), it is characterized in that % represents with quality, contain Mo:0.1～0.8%.
(5) according to any high-strength steel of being put down in writing in described (1)～(4), it is characterized in that % represents with quality, contain more than one of Cr:0.03～0.80%, V:0.001～0.05%, B:0.0002～0.0020.
(6) according to any high-strength steel of being put down in writing in described (1)～(5), it is characterized in that % represents with quality, contain more than one of Ca:0.0005～0.005%, Mg:0.0001～0.005%, REM:0.0001～0.01%.
(7) according to any high-strength steel of being put down in writing in described (1)～(6), it is characterized in that, the Pcm that represents for following (I) formula is below 0.25, the Cu particle of dispersive major diameter more than 1nm in steel, the mean value of diameter of equivalent circle is 4～25nm, and plane rate conversion abundance is 3～20%.
Pcm＝C+(Si/30)+(Mn/20)+(Cu/20)+(Ni/60)+(Cr/20)+(Mo/15)+(V/10)+5B…(I)
(8) a kind of offshore structure that has used any high-strength steel of being put down in writing in described (1)～(7).
According to the present invention, though not to be specially limited in this, welding processs such as CO 2 gas-shielded electric welding utilized; the manufacturing of the high-strength steel that can be achieved as follows promptly, can realize the welding of weld heat input more than 300KJ/cm; excellent weldability, yielding stress is at 420N/mm
2More than.Consequently, site welding operating efficiency and security improve significantly.In addition, even the high-strength steel that also can use under the very harsh environment of offshore structure and so on can be provided.
Embodiment
The present invention is described in detail.At first, narration is defined as the reason that aforesaid steel is formed with the present invention.And in this specification sheets, " % " that the expression steel is formed represents with " quality % ".
C produces in order to ensure the intensity of steel and when adding Nb, V etc. and organizes the effect of miniaturization to add.If less than 0.01%, then these effects are just insufficient.But, when C is too much, then in weld part, will generate the sclerotic tissue that is known as island martensite body (M-A:martensite-austeniteconstituent), and HAZ toughness is worsened, and the toughness and the weldability of mother metal caused detrimentally affect.So C is made as below 0.10%.Preferred 0.02～0.08%, more preferably 0.02～0.05%.
Si is an effective elements in the preparation deoxidation of molten steel, yet because not solid solution in cementite, therefore when by heavy addition, can hinder not abnormal austenite particle and be decomposed into ferrite particle and cementite, encourages the generation of island martensite body.Based on these reasons, the interpolation of Si is made as, and content is below 0.5% in the steel.Preferred below 0.2%, more preferably below 0.15%.
Mn is the element of guaranteeing that intensity is essential, and also is effective elements as reductor.For this reason, the content of Mn need be made as more than 0.8%.But the too much interpolation of Mn will increase hardenability too much, and weldability and HAZ toughness are worsened.In addition, because Mn is counted as encouraging the element of center segregation, therefore consider that from the viewpoint that suppresses center segregation its content should be no more than 1.8%.So the content of Mn is made as below 0.8～1.8%.Preferred 0.9～1.5%.
P is the impurity element that contains inevitably, owing to be the grain boundary segregation element, therefore becomes the crystal boundary reasons of cracks of HAZ.In addition, in order to improve the toughness of base metal tenacity, welding metal portion and HAZ, and reduce the steel billet center segregation, the content of P is made as below 0.020%.Preferred below 0.015%, more preferably below 0.01%.
When S exists in large quantities, will generate the monomeric precipitate of the MnS that becomes the weld crack starting point.For this reason, the content of S is made as below 0.01%.Preferred below 0.008%, more preferably below 0.005%.
Cu has intensity and the flexible effect that improves steel, and also less for the detrimentally affect of HAZ flexible.Particularly, owing to separate out ascending effect on the intensity that causes by ε-Cu when being expected to obtain ageing treatment, therefore need be more than 0.8%.But, when Cu content uprises, then to weld the high temperature crack sensitivity and uprise, it is complicated that welding procedures such as preheating become, so the content of Cu is made as below 1.5%.Preferred 0.9～1.1%.
Ni is for intensity that improves steel and toughness, and improves HAZ toughness and effective elements.But, if below 0.2%, then there are not these effects, in addition, when surpassing 1.5%, then owing to can't obtain and cost rising corresponding effects, therefore the content with Ni is made as 0.2～1.5%.Preferred 0.4～1.2%.
Al is the element essential for deoxidation.But when containing quantitative change for a long time, the easy variation of toughness in HAZ particularly then.This is because form the alumina type inclusion particle of thick bunch shape easily.For this reason, the content with Al is made as 0.001～0.05%.Preferred 0.001～0.03%.More preferably 0.001～0.015%.
N helps the grain refined organized because of forming nitride, yet under the situation of adding too much, toughness is worsened.So, the content of N is made as 0.003～0.008%.Preferred 0.0035～0.0065%.
By the N/Al ratio is controlled to be 0.3～3.0, just can realize large-line energy HAZ toughness, the particularly improvement of joint CTOD characteristic.
This be because, when N/Al than less than 0.3 the time, then can separate out thick AlN, except himself causes the detrimentally affect toughness, also can hinder fine/a large amount of dispersion of TiN.On the other hand, when the N/Al ratio surpassed 3.0, then solid solution N increased, and except making the deterioration of HAZ toughness, also made the branch bulk density of AlN, TiN become sparse.The preferred range that is used for further bringing into play effect is 0.4～2.5.
O (oxygen) generates very effective for the oxide compound that becomes the ferrite product nucleus.On the other hand, when existing in large quantities, then the deterioration owing to purity becomes obviously, so mother metal, welding metal portion and HAZ are difficult to guarantee practical toughness.So, the content of O is made as 0.0005～0.0035%.Preferred 0.0008～0.0018%.
Ti has following effect, that is and, generate nitride and suppress thickization of crystal grain, and with phase-change organization's miniaturization.But,, in addition, under the situation of adding in large quantities, then base metal tenacity and toughness of welded zone are caused detrimentally affect if, then can't bring into play described effect less than the interpolation of specified quantitative.So, the content of Ti is made as 0.005～0.03%.Preferred 0.007～0.015%.
Nb separates out intensity and the toughness that improves mother metal by grain refined and carbide.On the other hand, when adding too much, then the performance of mother metal raising effect is saturated, and can damage the toughness of HAZ significantly.So, the content of Nb is made as 0.003～0.03%.Preferred 0.003～0.015%.
Though Mo has the hardenability of guaranteeing, improve HAZ flexible effect, yet when adding too much, can cause the significant sclerosis among the HAZ, toughness is worsened.So, the content of Mo is made as 0.1～0.8%.Preferred 0.1～0.5%.
Though Cr is in the hardenability that increases steel, guarantee that the intensity aspect is effective, yet, can't bring into play the raising effect if trace adds, under the situation of adding too much, then there is the sclerosis that makes welding metal portion and HAZ to prevent and welds the tendency that the low temperature crack sensitivity increases.So, when adding Cr, the content of Cr is made as 0.03～0.80%.Preferred 0.05～0.60%.
B has and improves the effect that hardenability improves intensity.On the other hand, when adding too much, the effect that then improves intensity is saturated, and the tendency that the toughness of mother metal, HAZ worsens all becomes obvious.So, when adding B, the content of B is made as 0.0002～0.002%.Preferred 0.003～0.0015%.
V has following effect, that is and, generate carbonitride and suppress thickization of crystal grain, and with phase-change organization's miniaturization.But,, in addition, under the situation of adding in large quantities, then base metal tenacity and toughness of welded zone are caused detrimentally affect if, then can't bring into play described effect less than the interpolation of specified quantitative.So, when adding V, the content of V is made as 0.001～0.05%.Preferred 0.005～0.04%.
Ca, Mg, REM become the ferritic oxide compound of nuclear, the element of sulfide of separating out of intragranular.In addition, also control the form of sulfide, low-temperature flexibility is improved.In order to obtain the effect of this kind Ca, Mg, REM, for the situation of Ca, need contain more than 0.0005%, for the situation of Mg, REM, need contain more than 0.0001%.On the other hand, for the situation of Ca, when surpassing 0.005%, for the situation of Mg, REM, when surpassing 0.01%, then can generate Ca, Mg class large-scale inclusion or bunch and the purity of steel is worsened.So, when adding Ca, the content of Ca is made as 0.0005～0.005%, when adding Mg, REM, the content of Mg, REM is made as 0.0001～0.01%.
In addition, the Pcm that steel of the present invention is preferably represented with following (I) formula is below 0.25, and for for the Cu particle of dispersive major diameter in the steel more than 1nm, the mean value of its diameter of equivalent circle is 4～25nm, and plane rate conversion abundance is 3～20%.
Pcm＝C+(Si/30)+(Mn/20)+(Cu/20)+(Ni/60)+(Cr/20)+(Mo/15)+(V/10)+5B…(I)
Pcm is the index of expression crack sensitivity, if its value then can not produce weld crack below 0.25 under common welding procedure condition.So Pcm is made as below 0.25.When reducing Pcm, the preheating in the time of just can omitting welding.Preferred below 0.22, more preferably below 0.20.
Below, the diameter of equivalent circle mean value and the plane rate conversion abundance of Cu precipitate are narrated.With the Cu particle of major diameter more than 1nm be as the reason of object, less less than the particle of 1nm to the help that improves intensity.For the upper limit of the major diameter of Cu particle, though be not particularly limited, be in the scope of 4～25nm at mean value, and the particle of 100nm can not appear surpassing.And, though the Cu particle to separate out form approximate spherical, yet because instrumentation three-dimensional shape and being not easy, so shape of instrumentation institute projection.
Here, so-called diameter of equivalent circle is to have and the shadow area of particle circular diameter of the same area, specifically, utilizes d=√ (4a/pai) a: shadow area (nm
2), d: diameter of equivalent circle (nm), pai:3.14 tries to achieve.
For plane rate conversion abundance, by steel are processed as film like, implement tem observation for part, by being that 100000 times TEM photo is measured the area occupation ratio when the Cu particle plane projection of film like experiment slice neutral body ground distribution is calculated to multiplying power with the thickness that is about 0.2 micron.
Here, the reason for stipulating diameter of equivalent circle, plane rate conversion abundance as described above is described in further detail.
Feature as employed steel in the offshore structure, owing to will tolerate the external force that causes by huge wave, therefore often adopt the utmost point thickness high intensity steel of maximum thickness of slab, in addition near 100mm, owing to will under harsh situation, use from now on, therefore require to satisfy more strict CTOD value.
When separating out intensity because of Cu and become too high, then the CTOD value reduces, and when Cu separated out deficiency, even then CTOD value is high, intensity also can deficiency.
Cu in the past adds in the steel, owing to be not used in the suitable example of offshore structure basically, does not have strict CTOD value requirement, does not therefore need to control closely the mean diameter or the abundance of this kind Cu precipitation particles.
So, in optimal way of the present invention, separate out by Cu in order to obtain that the intensity that causes rises and the balance of the reduction of CTOD value, the mean diameter or the abundance of Cu precipitation particles are stipulated as described above.
It is balance for strength and toughness that diameter of equivalent circle is made as 4～25nm, and it also is balance for strength and toughness that plane rate conversion abundance is made as 3～20%.
As the factor of control Cu particle dia, abundance, can consider following content.
(1) the Cu addition is many more, and then abundance is just many more.For the influence that causes to particle dia, if appropriate interpolation scope, then main temperature and time by the tissue before the ageing treatment, ageing treatment decides median size.If be less than appropriate addition, then the Cu particle separate out insufficiently, particle dia is little, if more, then particle dia has the tendency of increase.
(2) influence of tissue is bigger before the timeliness, as organizing the fine tissue that preferably is made as ferrite and bainite main body before the timeliness.
Because dislocation or crystal crystal boundary etc. become the drop out point of Cu particle, therefore form when containing the organizing of this kind drop out point morely, the Cu particle dia is diminished, abundance is increased.Just need control the composition of steel for this reason rightly, and set rolling condition rightly, water-cooled condition thereafter also need be selected according to the mode of the micro organization that becomes the ferrite-bainite main body.
(3) aging temperature, time are important factors.By utilizing the ageing treatment condition to adjust the velocity of diffusion of Cu, the speed of growth of particle closely, just may be controlled to required particle dispersion state.
As long as suitably adjust described 3 factors, make steel of the present invention and get final product, according to above published content, to those skilled in the art, enforcement of the present invention is not difficult.
Below, the manufacture method of high-strength steel of the present invention is described.
Even aforesaid composition of steel is formed, in order to bring into play the precipitation-hardening of Cu fully, in addition, for the intensity and the high equably malleableize of toughness of each position of thickness of slab direction of making the thick-wall materials of thickness more than 50mm, and in order to improve yield strength, manufacture method must be suitable.
Until system steel operation,, be not particularly limited in the present invention as long as utilize customary way.After system steel operation, will obtain steel billet, yet consider, and preferably utilize Continuous casting process to make steel billet from the viewpoint that cost reduces.
Here, heating, hot rolling, cooling and the tempered condition for steel billet describes.At first, the steel billet that described one-tenth is grouped into is heated to 900～1120 ℃, carries out hot rolling.Among the present invention, in order to obtain high tenacity, at the thickness of slab central part of thick-wall materials, even generate the top bainite structure, also need be with sufficient degree with austenite particle grain refined, in the heating phase, the grain refined of the austenite particle in the steel billet heavy wall is very important.If less than 900 ℃ lower temperature, then this solutionizing effect is insufficient, can't expect sufficient precipitation-hardening in temper.But, if surpass 1120 ℃ Heating temperature, then can't and remain whole grain with the austenite particle grain refined before the calendering, in calendering thereafter, the austenite particle also can't be by grain refined equably.So, the Heating temperature of steel billet is made as 900～1120 ℃.Preferred 900～1050 ℃, more preferably 900～1000 ℃.
In calendering, preferably the total reduction below 900 ℃ is made as more than 50%.After hot rolling, carry out following quench treatment, that is, and from Ar
1The above temperature of point begins water-cooled, stops in the temperature below 600 ℃.This is in order to realize organizing miniaturization, and limit as far as possible ageing treatment in the last stage Cu particle separate out.If from less than Ar
1The water-cooled that the temperature of point begins perhaps is cooled to air cooling, then can cause the disappearance of machining deformation, becomes the reason that intensity and toughness reduce.
The rolling processing temperature is preferred more than 700 ℃, and cooling begins preferred 680 ℃～750 ℃ of temperature, stops preferred 1～50 ℃/s of speed of cooling of temperature until cooling.When water-cooled stopped temperature above 600 ℃, then the precipitation strength effect of temper just became insufficient.
And, Ar
1Point can utilize the method for the volume change of measuring small experiment slice to try to achieve.
Then, after hot rolling, by water-cooled steel heating as required thereafter, at Ac more than 540 ℃
1Carry out ageing treatment under the temperature below the point, then cooling.
Here, when when aging temp all heats, to until the average rate of heating of aging temp-100 ℃ and control until 500 ℃ average cooling rate.Because this ageing treatment is that the control of heating/speed of cooling is implemented in order to make Cu dispersion of particles homogenizing for the precipitate precipitation-hardening fully that makes Cu.So the average rate of heating that rate of heating preferably is made as until target temperature-100 ℃ is 5～50 ℃/minute, the hold-time is preferred more than 1 hour, and speed of cooling is 5～60 ℃/minute until 500 ℃ average cooling rate preferably.
Here, this specification sheets Heating temperature is made as the furnace atmosphere temperature, the heating back hold-time is made as maintenance temperature under the furnace atmosphere temperature, calendering end temp and water-cooled are begun/stop the skin temperature that temperature is made as steel, the heating/cooling V-bar when heating once more utilize steel thickness 1/2 position temperature computation and calculate.
When constituting the large ocean structural part,, use yet in general be used as steel plate though be to utilize welding to assemble steel such as sheet material, tubing and section bar by high-strength steel of the present invention.
Mention " weldability " in this specification sheets when good, as a rule be meant and carry out the arc welding of weld heat input more than 300kJ/cm, yet, in addition, also can be submerged arc welding, coating arc welding etc. as welding process.
Here, as offshore structure, be not only platform, self-elevating drilling platform at submarine laying, also comprise semi-submersible rig (the semi-diving type oil excavates drilling unit) etc., so long as be required the offshore structure of weldability and low-temperature flexibility, just be not particularly limited.And, when mentioning " large-scale ", be meant the wherein meaning of thickness more than 50mm of employed steel.
Embodiment
In this example, utilize Continuous casting process to make the thick steel billet of 300mm of chemical ingredients with table 1 and table 2.Here, viewpoint according to the inclusion of controlling the thickness of slab central position, in the continuous casting process, exceedingly do not improve the temperature of molten steel, for the temperature of solidification of forming decision by molten steel, according to its difference is controlled in interior mode at 50 ℃, preceding induction stirring, depressing when solidifying have been carried out being about to solidify in addition.
Expression has the processing conditions of the steel billet of the chemical ingredients shown in table 1 and the table 2 in table 3 and the table 4.Here, the processing conditions shown in table 3, the table 4 is the processing conditions that has the steel billet of the chemical ingredients shown in table 1, the table 2 respectively.
For the thick steel billet of 300mm, after each Heating temperature, each heating heat-up time, carried out after the hot rolling, begin temperature to water-cooled from water-cooled and stop temperature, cool off with the average speed of cooling of 5 ℃/s, made the steel plate of thickness of slab 77mm.(, in table 3 and table 4, being expressed as initial stage heating rolling condition) for these conditions
, once more be heated to each aging temp, kept each hold-time thereafter.Here, rate of heating is to control according to the mode that makes average rate of heating until aging temp-100 ℃ reach 10 ℃/minute, and speed of cooling is to reach 10 ℃/minute mode until 500 ℃ average cooling rate and control according to making.(, in table 3 and table 4, being expressed as the ageing treatment condition) for these conditions
The stretching experiment of the steel that so obtains is according to the ASTM specification, from taking the stretching experiment sheet of parallel portion 12.5mm diameter and implement with the meet at right angles thickness of slab central authorities of direction of rolling direction.
Similarly, the CTOD of the steel of gained experiment is according to the BS7448 specification, from taking complete 3 thick crooked experiment sheets with the rectangular direction of rolling direction, implements under-40 ℃.
Welded-joint is according to the BS7448 specification, and the FCAW welding (Flux Cored Arc Welding) of the steel plate docking section of having carried out the processing of K groove being implemented 10.0kJ/cm obtains.For the joint that so obtains, the mode of welding line that becomes the line part side of double V-groove according to the fatigue notch that makes the CTOD experiment slice (notch) is processed, and to the experiment slice that so obtains, has implemented the CTOD experiment under-40 ℃.
In addition, in order to confirm adaptability to large-line energy welding, for identical steel, carried out 20 ° of V grooves processing after, dock, utilize heat input to make welding joint for the CO 2 gas-shielded electric welding (EGW) of 350kJ/cm.For the welding joint of made this moment, implemented CTOD experiment according to ASTM E1290.The CTOD experiment slice is processed according to the mode that makes fatigue notch become welding line, has measured critical CTOD value under experimental temperature-10 ℃.
In addition, the mean value of the diameter of equivalent circle of Cu particle is to being that viewed major diameter each precipitate more than 1nm is measured diameter of equivalent circle in 100000 times infiltration type electron microscope (TEM) photo in multiplying power, and the mean value in each visual field is calculated in the photo by this diameter is tried to achieve.And in order to reduce the deviation of mensuration, mensuration is 1/4 position to the original thickness of steel, observes 10 visuals field (1 visual field is the rectangle of 900 * 700nm) of TEM photo, has used its mean value.
Table 1 is the table of confession experiment material of having represented to satisfy the chemical ingredients of defined among the present invention.These are become the material that Cu dispersion of particles state as shown in table 5 all satisfies specialized range for experimental steel at the material of making after handling under the processing conditions shown in the table 3.Thus, all strength of parent for experimental steel, mother metal CTOD characteristic, joint CTOD characteristics (40 ℃ and-10 ℃) have all reached very high value.
No.40 in the middle of the table 2 is the numbering of confession experiment material of having represented to satisfy the chemical ingredients of defined among the present invention, and No.41～No.60 is any numbering of the extraneous confession experiment material of defined in the present invention of having represented the chemical ingredients scope.These have been formed Cu dispersion of particles state as shown in table 6 for experimental steel at the material of making after handling under the processing conditions shown in the table 4.
For No.40, though satisfy the chemical constitution of defined among the present invention, yet because Cu dispersion of particles state does not satisfy specialized range, so strength of parent becomes lower value.So,, preferably satisfy the Cu dispersion of particles state of defined among the present invention in order to realize large-line energy welding characteristic and strength of parent simultaneously.
In addition, for No.41～No.60, because therefore the chemical constitution of defined in the discontented unabridged version invention can't satisfy strength of parent, mother metal CTOD characteristic, joint CTOD characteristic (40 ℃ and-10 ℃) simultaneously.
[table 3]
[table 4]
[table 5]
| Composition | Cu particle diameter (nm) | Plane rate conversion abundance (%) | Ys (N/mm2) | Ts (N/mm2) | Mother metal CTOD-40 ℃ (mm) | Little heat input welding joint CTOD-40 ℃ (mm) | Large-line energy welding joint CTOD-10 ℃ (mm) |
| 1 | 16 | 5 | 510 | 571 | ＞1.3 | 0.61 | 0.31 |
| 2 | 14 | 16 | 580 | 627 | ＞1.3 | 0.98 | 0.41 |
| 3 | 15 | 17 | 589 | 640 | 1.10 | 0.79 | 0.32 |
| 4 | 15 | 14 | 563 | 637 | 1.09 | 0.61 | 0.40 |
| 5 | 15 | 15 | 571 | 641 | ＞1.3 | 1.10 | 0.42 |
| 6 | 16 | 10 | 512 | 572 | 0.89 | 0.62 | 0.29 |
| 7 | 14 | 16 | 592 | 646 | ＞1.3 | 0.83 | 0.31 |
| 8 | 17 | 17 | 509 | 578 | ＞1.3 | 1.12 | 0.28 |
| 9 | 16 | 15 | 506 | 564 | 1.20 | 0.62 | 0.29 |
| 10 | 15 | 16 | 499 | 552 | 1.00 | 0.70 | 0.31 |
| 11 | 16 | 15 | 520 | 579 | ＞1.3 | 0.56 | 0.30 |
| 12 | 14 | 14 | 497 | 552 | ＞1.3 | 0.80 | 0.42 |
| 13 | 14 | 16 | 521 | 578 | ＞1.3 | 0.72 | 0.42 |
| 14 | 15 | 16 | 493 | 572 | 1.10 | 0.37 | 0.41 |
| 15 | 13 | 14 | 523 | 589 | ＞1.3 | 0.46 | 0.31 |
| 16 | 14 | 15 | 512 | 584 | ＞1.3 | 0.53 | 0.37 |
| 17 | 12 | 13 | 530 | 600 | ＞1.3 | 0.26 | 0.27 |
| 18 | 14 | 14 | 524 | 591 | ＞1.3 | 0.53 | 0.32 |
| 19 | 15 | 17 | 519 | 587 | 1.20 | 0.41 | 0.33 |
| 20 | 13 | 16 | 541 | 612 | 1.30 | 0.63 | 0.41 |
| 21 | 17 | 9 | 497 | 558 | 1.10 | 0.35 | 0.29 |
| 22 | 18 | 8 | 489 | 553 | ＞1.3 | 0.31 | 0.41 |
| 23 | 13 | 14 | 531 | 603 | 1.10 | 0.56 | 0.36 |
| 24 | 14 | 13 | 528 | 600 | 1.20 | 0.71 | 0.31 |
| 25 | 16 | 15 | 512 | 574 | ＞1.3 | 0.38 | 0.29 |
| 26 | 14 | 16 | 510 | 581 | ＞1.3 | 0.42 | 0.31 |
| 27 | 15 | 14 | 507 | 572 | ＞1.3 | 0.61 | 0.36 |
| 28 | 13 | 13 | 482 | 551 | ＞1.3 | 0.31 | 0.29 |
| 29 | 12 | 14 | 500 | 571 | ＞1.3 | 0.42 | 0.31 |
| 30 | 13 | 16 | 510 | 581 | ＞1.3 | 0.35 | 0.31 |
| 31 | 12 | 15 | 502 | 573 | ＞1.3 | 0.32 | 0.36 |
| 32 | 14 | 14 | 501 | 569 | ＞1.3 | 0.31 | 0.34 |
| 33 | 14 | 16 | 580 | 627 | 1.10 | 0.94 | 0.40 |
| 34 | 15 | 17 | 584 | 642 | 0.94 | 0.79 | 0.35 |
| 35 | 15 | 14 | 560 | 637 | 1.09 | 0.54 | 0.41 |
| 36 | 15 | 15 | 569 | 640 | 1.10 | 0.63 | 0.42 |
[table 6]
| Composition | Cu particle diameter (nm) | Plane rate conversion abundance (%) | Ys (N/mm2) | Ts (N/mm2) | Mother metal CTOD-40 ℃ (mm) | Little heat input welding joint CTOD-40 ℃ (mm) | Large-line energy welding joint CTOD-10 ℃ (mm) |
| 40 | 28 | 2 | 417 | 472 | ＞1.3 | 0.67 | 0.30 |
| 41 | 17 | 16 | 626 | 711 | 0.12 | 0.09 | 0.006 |
| 42 | 14 | 14 | 642 | 720 | 0.19 | 0.12 | 0.006 |
| 43 | 14 | 13 | 632 | 691 | 0.41 | 0.06 | 0.007 |
| 44 | 17 | 17 | 578 | 632 | 0.08 | 0.09 | 0.007 |
| 45 | 10 | 15 | 384 | 420 | 0.84 | 0.71 | 0.006 |
| 46 | 17 | 15 | 574 | 623 | 0.12 | 0.04 | 0.006 |
| 47 | 16 | 15 | 621 | 716 | 0.10 | 0.03 | 0.007 |
| 48 | 18 | 23 | 619 | 701 | 0.08 | 0.02 | 0.007 |
| 49 | 14 | 16 | 512 | 589 | 0.08 | 0.03 | 0.006 |
| 50 | 15 | 15 | 623 | 712 | 0.08 | 0.04 | 0.007 |
| 51 | 14 | 16 | 621 | 700 | 0.09 | 0.01 | 0.008 |
| 52 | 13 | 14 | 552 | 636 | 0.08 | 0.02 | 0.008 |
| 53 | 13 | 15 | 541 | 617 | 0.09 | 0.01 | 0.006 |
| 54 | 17 | 13 | 543 | 675 | 0.09 | 0.03 | 0.008 |
| 55 | 14 | 17 | 567 | 648 | 0.08 | 0.04 | 0.009 |
| 56 | 14 | 13 | 511 | 652 | 0.04 | 0.03 | 0.008 |
| 57 | 14 | 14 | 498 | 612 | 0.06 | 0.02 | 0.008 |
| 58 | 16 | 15 | 470 | 530 | 0.06 | 0.03 | 0.009 |
| 59 | 16 | 16 | 502 | 580 | 0.21 | 0.16 | 0.018 |
| 60 | 15 | 15 | 491 | 565 | 0.22 | 0.17 | 0.019 |
Claims (8)
1. high-strength steel, it is characterized in that, % represents with quality, contain that C:0.01～0.10%, Si:0.5% are following, Mn:0.8～1.8%, P:0.020% is following, S:0.01% is following, Cu:0.8～1.5%, Ni:0.2～1.5%, Al:0.001～0.05%, N:0.003～0.008%, O:0.0005～0.0035%, remainder is Fe and impurity, and N/Al is 0.3～3.0;
The Pcm that following (I) formula is represented is below 0.25, and for for the Cu particle of dispersive major diameter in the steel more than 1nm, the mean value of its diameter of equivalent circle is 4～25nm, and plane rate conversion abundance is 3～20%,
Pcm＝C+(Si/30)+(Mn/20)+(Cu/20)+(Ni/60)+(Cr/20)+(Mo/15)+(V/10)+5B…(I)。
2. the high-strength steel of putting down in writing according to claim 1 is characterized in that, % represents with quality, contains Ti:0.005～0.03%.
3. according to claim 1 or 2 high-strength steels of being put down in writing, it is characterized in that % represents with quality, contain Nb:0.003～0.03%.
4. according to claim 1 or 2 high-strength steels of being put down in writing, it is characterized in that % represents with quality, contain Mo:0.1～0.8%.
5. according to the high-strength steel of claim 1 or 2 records, it is characterized in that % represents with quality, contain more than one of Cr:0.03～0.80%, B:0.0002～0.002%.
6. according to claim 1 or 2 high-strength steels of being put down in writing, it is characterized in that % represents with quality, contain V:0.001～0.05%.
7. according to claim 1 or 2 high-strength steels of being put down in writing, it is characterized in that % represents with quality, contain more than one of Ca:0.0005～0.005%, Mg:0.0001～0.005%, REM:0.0001～0.01%.
8. offshore structure that has used claim 1 or 2 high-strength steels of being put down in writing.
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| EP2045348B1 (en) * | 2006-07-13 | 2013-03-13 | Nippon Steel & Sumitomo Metal Corporation | Bend pipe and process for producing the same |
| JP5076658B2 (en) * | 2006-12-06 | 2012-11-21 | Ｊｆｅスチール株式会社 | Steel material for large heat input welding |
| KR101142185B1 (en) * | 2007-12-07 | 2012-05-04 | 신닛뽄세이테쯔 카부시키카이샤 | Steel being excellent in ctod characteristic in welding heat affected zone and a method of producing the same |
| JP5172391B2 (en) * | 2008-03-03 | 2013-03-27 | 株式会社神戸製鋼所 | Steel sheet with excellent toughness and uniform elongation of weld heat affected zone |
| KR101318227B1 (en) | 2008-05-23 | 2013-10-15 | 한국기계연구원 | Cu-added complex bainitic steel and manufacturing method thereof |
| RU2458174C1 (en) | 2009-05-19 | 2012-08-10 | Ниппон Стил Корпорейшн | Steel for welded structures and method for its obtaining |
| KR101360737B1 (en) | 2009-12-28 | 2014-02-07 | 주식회사 포스코 | High strength steel plate having excellent resistance to brittle crack initiation and method for manufacturing the same |
| DE102010019563A1 (en) * | 2010-05-05 | 2011-11-10 | Kme Germany Ag & Co. Kg | Corrosion protection arrangement for offshore steel structures and a method for its application |
| JP5846311B2 (en) | 2012-09-06 | 2016-01-20 | Ｊｆｅスチール株式会社 | Thick high-strength steel excellent in welding heat affected zone CTOD characteristics and method for producing the same |
| CN103014498A (en) * | 2012-12-21 | 2013-04-03 | 首钢总公司 | 355MPa low-welding-crack-sensitivity steel plate and producing method |
| CN103225044B (en) * | 2013-04-24 | 2015-06-17 | 马钢(集团)控股有限公司 | Steel for vanadium micro alloying low temperature steel bar and process for rolling steel |
| KR101542709B1 (en) | 2013-08-13 | 2015-08-12 | 신닛테츠스미킨 카부시키카이샤 | Steel plate |
| CN103451536B (en) * | 2013-09-30 | 2015-06-24 | 济钢集团有限公司 | Low-cost thick subsea pipeline steel plate and manufacturing method of low-cost thick subsea pipeline steel plate |
| KR101846759B1 (en) | 2013-12-12 | 2018-04-06 | 제이에프이 스틸 가부시키가이샤 | Steel plate and method for manufacturing same |
| CN103741079A (en) * | 2014-01-09 | 2014-04-23 | 鞍钢股份有限公司 | Super-strength steel plate for oceanographic engineering and production method thereof |
| CN103882312B (en) * | 2014-03-04 | 2016-04-27 | 南京钢铁股份有限公司 | The manufacture method of low-cost high-toughness-140 DEG C of Steel Plates For Low Temperature Service |
| DE102014205392A1 (en) * | 2014-03-24 | 2015-09-24 | Comtes Fht A. S. | Components made of a steel alloy and method for producing high-strength components |
| KR20160127808A (en) | 2014-03-31 | 2016-11-04 | 제이에프이 스틸 가부시키가이샤 | High-tensile-strength steel plate and process for producing same |
| CN105296845B (en) * | 2015-10-21 | 2017-04-26 | 苏州雷格姆海洋石油设备科技有限公司 | Manufacturing method for ultra-low-temperature corrosion-resistant high-strength forge piece blank |
| JP6766425B2 (en) * | 2016-04-21 | 2020-10-14 | 日本製鉄株式会社 | High-strength steel and marine structures |
| BR112020011210B1 (en) * | 2017-12-07 | 2023-04-25 | Jfe Steel Corporation | STEEL WITH HIGH MANGANESE CONTENT (MN) AND METHOD FOR MANUFACTURING THE SAME |
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| JPH08144008A (en) * | 1994-11-28 | 1996-06-04 | Sumitomo Metal Ind Ltd | High tensile strength steel and its production |
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| JPH06220577A (en) * | 1993-01-26 | 1994-08-09 | Kawasaki Steel Corp | High tensile strength steel excellent in hic resistance and its production |
| JP3399125B2 (en) * | 1994-12-19 | 2003-04-21 | 住友金属工業株式会社 | Steel material with excellent toughness of weld heat affected zone |
| JPH108132A (en) * | 1996-06-14 | 1998-01-13 | Sumitomo Metal Ind Ltd | Production of thick steel plate excellent in toughness |
| JP3267170B2 (en) * | 1996-09-25 | 2002-03-18 | 日本鋼管株式会社 | 780MPa class high tensile steel with excellent hot-dip galvanizing crack resistance |
| JP3699639B2 (en) * | 1999-07-22 | 2005-09-28 | 新日本製鐵株式会社 | Steel material excellent in toughness of heat affected zone and its manufacturing method |
| JP3852295B2 (en) * | 2001-03-23 | 2006-11-29 | 住友金属工業株式会社 | Steel with excellent super heat input welding characteristics |
| US20060021682A1 (en) * | 2003-11-12 | 2006-02-02 | Northwestern University | Ultratough high-strength weldable plate steel |
| US8118949B2 (en) * | 2006-02-24 | 2012-02-21 | GM Global Technology Operations LLC | Copper precipitate carburized steels and related method |
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| JPH08144008A (en) * | 1994-11-28 | 1996-06-04 | Sumitomo Metal Ind Ltd | High tensile strength steel and its production |
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