CN102471843A - High-strength steel plate and high-strength steel pipe with superior low-temperature toughness for use in line pipes - Google Patents
High-strength steel plate and high-strength steel pipe with superior low-temperature toughness for use in line pipes Download PDFInfo
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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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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
- C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- 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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P10/20—Recycling
Abstract
Disclosed are a steel plate and a steel pipe for use in line pipes that have superior low-temperature toughness and are ideal for steel pipes that are used, for example, in line pipes for the transportation of petroleum, natural gas, and the like. The steel plate and steel pipe comprise, in mass%, 0.03 to 0.08% carbon, 0.01 to 0.5% silicon, 1.5 to 2.3% manganese, 0.001 to 0.05% niobium, 0.0010 to 0.0050% nitrogen, and 0.0001 to 0.0050% calcium; have a limit of no more than 0.015% phosphorus, no more than 0.0020% sulfur, no more than 0.030% titanium, no more than 0.030% aluminum, and no more than 0.0035% oxygen; have a residue comprising iron and obligatory impure elements; fulfill S/Ca < 0.5; and furthermore have a limit of a maximum hardness of no higher than 400 Hv for a center segregation section and a length of no longer than 0.1 mm for a non-pressure bonded section.
Description
Technical field
The present invention relates to be suitable for most line-pipes steel plate purposes such as line pipe, excellent in low temperature toughness and the line-pipes steel pipe of transfer oil, Sweet natural gas etc.
Background technology
In recent years, as the long-distance delivery method of crude oil and Sweet natural gas, the importance ever more important of pipeline.Now, as the line pipe that long distances is used, be the basic of design with the specification X65 of API (API), actual usage quantity is also many for overwhelmingly., for improving the transport efficiency utilize high-pressure trend and (2), (1) improves the site operation efficient that the attenuating by the external diameter of line pipe and weight brings, the more high-intensity line pipe of expectation always.The present practicability of the line pipe till the X80 (tensile strength is more than the 620MPa), but to the demand enhancing of more high-intensity line pipe.Now, about the research of high-strength line-pipe pipe manufacturer method, the manufacturing technology (non-patent literature 1 and 2) of X80 line pipe, the manufacturing technology of X100 (more than the tensile strength 760MPa) line pipe and the manufacturing technology (patent documentation 1 and 2) of X120 line pipe have been reported.; So the double-strength pipe spool also requires brittle rupture crack propagation stop performance and high speed ductile fracture crack propagation stop performance; If do not solve relevant therewith problem, even can make steel plate and steel pipe, also can not be and practicability as line pipe.
About brittle rupture crack propagation stop performance, even, brittle rupture is stopped particularly from the circumference weld part generation brittle rupture of pipe connecting spool.The velocity of propagation of brittle rupture is more than the 350m/s, and brittle rupture has the possibility of the long distance fracture from 100m to several km, because the seriousness of imaginary infringement is therefrom coming into one's own always.As the small-scale test of estimating this brittle rupture crack propagation stop performance, at DWTT (Drop Weight Tear Test: DWTT), require under the specification temperature, to have the ductile fracture rate more than 85%.
On the other hand, high speed ductile fracture crack propagation stop performance is the phenomenon that ductile fracture is grown propagation with the high speed more than the 100m/s on the tube axial direction of steel pipe.About this high speed ductile fracture, the possibility of the long distance fracture from 100m to several km is also arranged, come into one's own owing to the seriousness of imaginary infringement therefrom always.It is relevant to think that this high speed ductile fracture and the Charpy bar of steel pipe absorb ability, can prevent through guaranteeing that Charpy bar absorbs.
But, these prevent benchmark to 70ksi (steel pipe of=strength level below 490MPa) is established, exploitation in recent years have 80ksi (=560MPa) in the steel plate of above tensile strength, the employing above-mentioned parameter maybe be not enough.Predict the also not establishment of method of the high speed ductile fracture crack propagation stop performance that this has the above steel plate of 80ksi.Corresponding; For the double-strength pipe spool, the Propagation of Energy of the fracture that has proposed to form, crackle opening angle (CTOA) or the Propagation of Energy and the corresponding thinking of high speed ductile fracture crack propagation stop performance that form by the DWTT that was once taking place with the presplitting line after the ductile fracture by DWTT.
Improve brittle-cracking propagation stopping characteristics and the ductility crackle propagation halt characteristic of this DWTT, need make ductility-brittle transition temperature below the specification temperature.Reduce ductility-brittle transition temperature, promptly improve low-temperature flexibility, be necessary to make the size of microcrystal miniaturization.As the microstructure of double-strength pipe spool, be the tissue of bainite+martensite main body.As the method for the crystal grain miniaturization in the tissue that makes bainite+martensite main body, known have a method that makes the refinement of a blob of slag (pancake) thickness.But the refinement of blob of slag thickness has boundary.And under the situation of tissue that is bainite+martensite main body, known { the 100} aggregation with rolling direction is being axle and on rolling surface tilts 40 ° face (below be called 40 ° of faces).{ 100} is the cleavage surface of iron, if there are embrittlement portions such as center segregation, then begins to take place brittle rupture from this embrittlement portion, and brittle rupture propagates into aggregation at a heat to be had, and { 40 ° of faces of 100} are difficult to shift to ductile fracture.It more than is the big problem that DWTT ductility and brittle rupture temperature in the tissue of bainite+martensite main body do not move to low temperature side.Therefore; Formation generates ferritic polyphase structure from the tissue of bainite+martensite main body; Create and not make that { the 100} aggregation is at the tissue of 40 ° of faces, even existing under the situation of center segregation etc., also can suppress the organizational controls (patent documentation 3) of brittle rupture at once.Creating under the so ferritic situation, reach the out-of-limit system ferrite content of HS more.If the restriction ferrite content then can not be suppressed at { the aggregation of 100}, thereby brittle crack is propagated at this face easily of 40 ° of faces.In addition, ferritic being evenly dispersed in the steel pipe integral also is problem.
The prior art document
Patent documentation
Patent documentation 1: Japan internationality discloses specification sheets No. 96/023083
Patent documentation 2: Japan internationality discloses specification sheets No. 96/023909
Patent documentation 3: TOHKEMY 2008-013800 communique
Non-patent literature
Non-patent literature 1:NKK skill is reported No.138 (1992), pp24-31
Non-patent literature 2:The 7th Offshore Mechanics and Arctic Engineering (1988), Volume V, pp179-185
Summary of the invention
The problem that invention will solve
In the past, as the method for the crystal grain miniaturization in the tissue that makes bainite+martensite main body, known had the method that makes the refinement of blob of slag thickness, but the thickness of strand has the upper limit, thereby the refinement of blob of slag thickness also has boundary.And under the situation of tissue that is bainite+martensite main body, known { the 100} aggregation with rolling direction is being axle and to tilt 40 ° face (below be called 40 ° of faces) of rolling surface.Following big problem is arranged: { 100} is the cleavage surface of iron, if there are embrittlement portions such as center segregation, just begins to take place brittle rupture from this embrittlement portion, and brittle rupture propagates into aggregation at a heat to be had, and { 40 ° of faces of 100} do not shift to ductile fracture.
The present invention is in view of truth so and accomplish; Its objective is provides a kind of low-temperature flexibility, particularly brittle rupture crack propagation stop performance and good line-pipes steel plate and the line pipe steel pipe of high speed ductile fracture crack propagation stop performance, and the conveying that is used for oil, Sweet natural gas etc. is with line pipe etc.
Be used to solve the means of problem
Present inventors are to studying intensively for obtaining the condition that steel that effective steel plate of high-strength line-pipe that tensile strength is the excellent in low temperature toughness more than the 600MPa and the effective steel pipe of high-strength line-pipe adopt should satisfy, so that invented the line-pipes steel plate and the high-intensity line-pipes steel pipe of new superstrength.And, even in the tissue of bainite+martensite main body, also can relax the such embrittlement phase of center segregation significantly,, then can reduce ductility-brittle transition temperature of DWTT etc. if the low-temperature flexibility here improves.Main idea of the present invention is following.
(1) the effective steel plate of a kind of high-strength line-pipe of excellent in low temperature toughness is characterized in that,
In quality %, contain:
C：0.03～0.08％、
Si：0.01～0.5％、
Mn：1.6～2.3％、
Nb：0.001～0.05％、
N：0.0010～0.0050％、
Ca：0.0001～0.0050％，
Following element is limited in:
Below the P:0.015%,
Below the S:0.0020%,
Ti：0.001～0.030％、
Below the Al:0.030%,
Below the O:0.0035%,
Surplus comprises Fe and unavoidable impurities element,
Satisfy S/Ca＜0.5, and then,
The maximum hardness of center segregation portion is limited in below the 400Hv;
In addition, with the limitation of length of the not pressure contact portion of center segregation portion below 0.1mm;
In addition, will be with rolling direction axle, to rolling surface tilt 40 ° the position { the aggregation degree of 100} is limited in below 4.0;
Tensile strength is more than the 600MPa.
(2) according to the effective steel plate of high-strength line-pipe of (1) described excellent in low temperature toughness, it is characterized in that, in quality %, further contain in the following element more than a kind or 2 kinds:
Ni：0.01～2.0％、
Cu：0.01～1.0％、
Cr：0.01～1.0％、
Mo：0.01～0.60％、
W：0.01～1.0％、
V：0.01～0.10％、
Zr：0.0001～0.050％、
Ta：0.0001～0.050％、
B：0.0001～0.0020％。
(3) according to the effective steel plate of high-strength line-pipe of (1) or (2) described excellent in low temperature toughness, it is characterized in that, in quality %, further contain in the following element more than a kind or 2 kinds:
REM：0.0001～0.01％、
Mg：0.0001～0.01％、
Y：0.0001～0.005％、
Hf：0.0001～0.005％、
Re：0.0001～0.005％。
(4) according to the effective steel plate of high-strength line-pipe of each the described excellent in low temperature toughness in (1)～(3), wherein, has bainite+martensitic stucture.
(5) according to the effective steel plate of high-strength line-pipe of (4) described excellent in low temperature toughness, wherein, the median size of the original austenite parent phase of said bainite+martensitic stucture is below the 10 μ m.
(6) according to the effective steel plate of high-strength line-pipe of (4) or (5) described excellent in low temperature toughness, wherein, the ferritic branch rate in said bainite+martensitic stucture is lower than 10%.
According to the effective steel plate of high-strength line-pipe of each the described excellent in low temperature toughness in (1)～(6), it is characterized in that (7) the maximum Mn degree of segregation of center segregation portion is below 2.0, the Nb degree of segregation is below 4.0, the Ti degree of segregation is below 4.0.
(8) the effective steel pipe of a kind of high-strength line-pipe of excellent in low temperature toughness is characterized in that,
Mother metal contains in quality %:
C：0.03～0.08％、
Si：0.01～0.5％、
Mn：1.6～2.3％、
Nb：0.001～0.05％、
N：0.0010～0.0050％、
Ca：0.0001～0.0050％，
Following element is limited in:
Below the P:0.015%,
Below the S:0.002%,
Ti：0.001～0.030％、
Below the Al:0.030%,
Below the O:0.0035%,
Surplus comprises Fe and unavoidable impurities element,
Satisfy S/Ca＜0.5, and then,
The maximum hardness of center segregation portion is limited in below the 400Hv;
In addition, with the limitation of length of the not pressure contact portion of center segregation portion below 0.1mm;
In addition, will be with rolling direction axle, to rolling surface tilt 40 ° the position { the aggregation degree of 100} is limited in below 4.0;
Tensile strength is more than the 600MPa.
(9) according to the effective steel pipe of high-strength line-pipe of (8) described excellent in low temperature toughness, it is characterized in that, in quality %, further contain in the following element more than a kind or 2 kinds:
Ni：0.01～2.0％、
Cu：0.01～1.0％、
Cr：0.01～1.0％、
Mo：0.01～0.60％、
W：0.01～1.0％、
V：0.01～0.10％、
Zr：0.0001～0.050％、
Ta：0.0001～0.050％、
B：0.0001～0.0020％。
(10) according to the effective steel pipe of high-strength line-pipe of (8) or (9) described excellent in low temperature toughness, it is characterized in that, in quality %, further contain in the following element more than a kind or 2 kinds:
REM：0.0001～0.01％、
Mg：0.0001～0.01％、
Y：0.0001～0.005％、
Hf：0.0001～0.005％、
Re：0.0001～0.005％。
(11) according to the effective steel pipe of high-strength line-pipe of each the described excellent in low temperature toughness in (8)～(10), wherein, has bainite+martensitic stucture.
(12) according to the effective steel pipe of high-strength line-pipe of each the described excellent in low temperature toughness in (8)～(11), wherein, the median size of the original austenite parent phase of said bainite+martensitic stucture is below the 10 μ m.
(13) according to the effective steel pipe of high-strength line-pipe of each the described excellent in low temperature toughness in (8)～(12), wherein, the ferritic branch rate in said bainite+martensitic stucture is lower than 10%.
According to the effective steel pipe of high-strength line-pipe of each the described excellent in low temperature toughness in (8)～(13), it is characterized in that (14) the maximum Mn degree of segregation of restriction center segregation portion is below 2.0, the Nb degree of segregation is below 4.0, the Ti degree of segregation is below 4.0.
The invention effect
According to the present invention, can make the rising of the maximum hardness that has suppressed center segregation portion and suppress line-pipes steel plate and the line-pipes steel pipe etc. of excellent in low temperature toughness of length of the not pressure contact portion of center segregation, be very significant to the contribution on the industry.
Description of drawings
Fig. 1 illustrates length and the degree of segregation of not pressure contact portion of the center segregation portion in the 0.04C-1.9Mn-Ni-Cu-Mo system to the influence of DWTT ductile fracture rate.
Embodiment
Below, content of the present invention is elaborated.The present invention relates to have the invention of superstrength line pipe of the excellent in low temperature toughness of the above tensile strength (TS) of 600MPa.The superstrength line pipe of this intensity level is compared with the X65 of main flow in the past can anti-high pressure, therefore can carry more gas with identical size.Under the situation of X65, for pressurize needs to increase wall thickness, thereby materials cost, pipage, site welding construction cost improve, and the pipe laying expense is risen significantly.This is the reason of superstrength line pipe that need have the high speed ductile fracture characteristic good of the above tensile strength (TS) of 600MPa.On the other hand, if reach HS then the unusual difficulty of the manufacturing of steel pipe.In such cases; Obtain comprising the target property of seam welding portion; Particularly need improve the high speed fracture characteristics, improve mother metal low-temperature flexibility, improve the low-temperature flexibility of welding base metal and welded heat affecting zone, in addition, also need make body disrumpent feelings through bursting test.
High speed ductile fracture characteristic in the face of mother metal describes down.Inventors have carried out research with keen determination in order to satisfy the high speed ductile fracture characteristic of mother metal to the fracture toughness property of mother metal steel plate, and the result finds following situation.
Present inventors think, improve anti-brittle rupture crack propagation characteristic and high speed ductile fracture crack propagation characteristic, and mother metal need have high fracture propagation stop performance.In order to reach this purpose, known critical be for example to improve ductile fracture rate in the DWTT (DWTT), and improve the fracture propagation energy.Under high-intensity situation with the tensile strength more than the 600MPa, form the tissue of bainite or martensite main body basically, in such cases, begin to cool down from the temperature more than the Ar3 point, form steel plate.In this case, the 100} aggregation with rolling direction be the axle and with respect to rolling surface be 40 the degree the position.After, in this manual, with aggregation with rolling direction be the axle and with respect to rolling surface be 40 the degree locational face be called " 40 ° of faces ".Particularly, the aggregation when random is compared the aggregation that has more than 2 times.After, in this manual, compare in the time of will be random with this { degree of the aggregation of 100} is called the aggregation degree.
Under the situation of plow-steel, if the level error of center segregation for example then begins to take place brittle rupture from center segregation, this brittle rupture is propagated along 40 ° of faces, and DWTT ductile fracture rate and Propagation of Energy significantly reduce.Inventors investigate the length of the not pressure contact portion that is present in center segregation portion and the relation of DWTT ductile fracture rate and DWTT Propagation of Energy, find that the length of pressure contact portion does not have bigger influence to DWTT ductile fracture rate or DWTT Propagation of Energy.Fig. 1 illustrates length and the degree of segregation of not pressure contact portion of the center segregation portion in the 0.04C-1.9Mn-Ni-Cu-Mo system to the influence of DWTT ductile fracture rate.If find the maximum hardness of center segregation is suppressed at below the 350Hv; And not the length of pressure contact portion more than 0.1mm; Then DWTT ductile fracture rate is lower than 85%; If but the maximum hardness of center segregation is suppressed at below the 350Hv, and pressure contact portion is not below 0.1mm, and then DWTT ductile fracture rate reaches more than 85%.Inventors think through the inhibition like this length of pressure contact portion not, make the reasons are as follows that DWTT ductile fracture rate significantly improves.
In this manual, what is called is pressure contact portion not, refers to after through converter and 2 refining meltings; Alloying element and impurity concentrate when solidification shrinkage; Simultaneously form the space, but when being negative pressure, do not have the part of crimping when getting into produce in the space rolling because of gaseous constituent in this space at central part.In addition, in this manual, spissated place is called center segregation portion at the center with alloying element and impurity.If depress when rolling then the space reduces, but pressure improves with being inversely proportional to.So if the size in space is big, air pressure is high, even then through rolling, the length of pressure contact portion is not long yet.This not pressure contact portion be defective, if the low-temperature flexibility deterioration of this defective periphery then generates brittle rupture easily, the occurrence features of fracture significantly descends.So, beginning to rupture from center segregation easily, brittle rupture expands to 40 ° of faces.Relative therewith, if pressure contact portion is not little, then difficult generation brittle rupture, the drag value of brittle rupture improves.
To the length of pressure contact portion not be suppressed at below the 0.1mm, need the hydrogen amount in the steel be controlled at below the 2.5ppm.Hydrogen in the steel forms the space at central part after through converter and 2 refining meltings when solidification shrinkage, but is under the situation of negative pressure in this space, H
2Gaseous constituent enter into the space.At H
2Situation under, contain about 2.5ppm the equilibrated H when heating as slab
2Amount.If depress when rolling then the space reduces, but pressure improves with being inversely proportional to.Detailed investigation result shows, if the hydrogen amount is suppressed at below the 2.5ppm, after then rolling is below the 0.1mm by solidifying the not pressure contact portion that the space forms.
Distinguish in addition: maximum hardness is suppressed at below the 350Hv, it is effective reducing maximum Mn degree of segregation, Ti degree of segregation, Nb degree of segregation.Particularly, if maximum Mn degree of segregation below 2.0, the Ti degree of segregation below 4.0, the Nb degree of segregation is below 4.0, then can maximum hardness be suppressed at below the 350Hv.
Here, in the present invention, so-called maximum Mn degree of segregation is the Mn amount with respect to the maximum of the center segregation portion of the amount of the average Mn except that center segregation portion of steel plate and steel pipe.Equally, as shown in Figure 2, Nb degree of segregation and Ti degree of segregation are the Nb amounts (Ti amount) of the maximum that obtains with respect to the making center segregation portion equalization of the amount of the average N b except that center segregation portion (Ti amount) of steel plate and steel pipe.
In addition; When measuring maximum Mn degree of segregation, can be through EPMA (electron probe microanalyzer: Electron Probe Micro Analyzer) maybe can carry out CMA (the area of computer aided differential analyzer: the Mn concentration distribution of mensuration steel plate and steel pipe Computer Aided Micro Analyzer) of picture processing to the mensuration result of EPMA.About Nb degree of segregation and Ti degree of segregation too, measure Nb concentration distribution and Ti concentration distribution respectively through EPMA or CMA.
At this moment, the numerical value of maximum Mn degree of segregation changes according to the probe diameter of EPMA (or CMA).Present inventors find, through probe diameter being defined as 2 μ m, can suitably estimate the segregation of Mn.About Nb degree of segregation and Ti degree of segregation too, learn, can suitably estimate segregation through probe diameter being defined as 2 μ m.But under the situation of Nb, Ti, segregation Nb, the Ti amount that is difficult to maximum is measured, therefore will the thickness of slab direction make the location equalization respectively and the value that draws as degree of segregation.Have, if having MnS, TiN, Nb inclusiones such as (C, N), then maximum Mn degree of segregation, Ti degree of segregation, Nb degree of segregation increase on apparent again, therefore are defined in when running into inclusion to estimate after its value removed.
Below, the qualification reason of the chemical ingredients of the mother metal among the present invention is discussed.
C:C is the element that improves the intensity of steel, as its effective lower limit, needs to add more than 0.03%.On the other hand,, then promote the generation of carbide, damage the low-temperature flexibility of center segregation portion, thereby the upper limit is defined as below 0.08% if the C amount surpasses 0.08%.In addition, for low-temperature flexibility, weldableness and the flexible that suppresses normal portion descends, preferably the upper limit with the C amount is defined as below 0.07%.
Si:Si is a deoxidant element, needs to add more than 0.01%.On the other hand, if the Si amount surpasses 0.5%, the toughness of welded heat affecting zone (HAZ) is reduced, thereby the upper limit is defined as below 0.5%.
Mn:Mn improves intensity and flexible element, needs to add more than 1.6%.On the other hand, if the Mn amount surpasses 2.3%, the low-temperature flexibility of center segregation portion and HAZ toughness are reduced, thereby the upper limit is defined as below 2.3%.For suppressing the low-temperature flexibility deterioration of center segregation portion, preferably the upper limit with the Mn amount is defined as below 2.0%.
Nb:Nb forms carbide, nitride, the element that helps intensity to improve.In order to obtain effect, need to add the Nb more than 0.001%., if add Nb superfluously, then the Nb degree of segregation increases, and causes the aggregation of the carbonitride of Nb, and HIC-resistance descends.So in the present invention, the upper limit that Nb is measured is defined as below 0.05%.
N:N is the element that forms nitride such as TiN, NbN, and the austenite particle diameter miniaturization when heating in order to utilize nitride to make need be defined as the lower value of N amount more than 0.0010%., if the content of N surpasses 0.0050%, then the easy aggregation of the carbonitride of Ti and Nb damages HIC-resistance.So, the upper limit of N amount is defined as below 0.0050%.Have, requiring under the situation of toughness etc., in order to suppress thickization of TiN, preferably the upper limit with the N amount is defined as below 0.0035% again.
P:P is an impurity, if content surpasses 0.015%, then damages HIC-resistance, and the toughness of HAZ reduces.So, with the ceiling restriction of P content below 0.01%.
S:S generates the MnS that extends to rolling direction, the element that low-temperature flexibility is reduced when hot rolling.So, in the present invention, need to reduce the S amount, the upper limit is controlled at below 0.0020%.In addition, in order to improve toughness, preferably the S gauge is decided to be below 0.0010%.The S amount is few more good more, but difficulty is lower than 0.0001%, and the viewpoint from manufacturing cost preferably is decided to be undergage more than 0.0001%.
Ti:Ti usually is used for the element of grain refining as reductor and nitride forming element, but in the present invention, is through forming the element that carbonitride reduces HIC-resistance and toughness.So, the upper limit of Ti content is limited to below 0.030%.In addition, be lower than at 0.001% o'clock, can not get the effect of crystal grain miniaturization, thereby undergage is decided to be 0.001% in interpolation.
Al:Al is a deoxidant element, but in the present invention, if addition surpasses 0.030%, then finds the aggregation nanocluster of Al oxide compound, thereby the Al amount is limited in below 0.030%.Requiring under the flexible situation, preferably the upper limit with the Al amount is defined as below 0.017%.The lower value of Al amount does not have special qualification, but for the oxygen amount in the molten steel is reduced, preferably adds the Al more than 0.0005%.
O:O is an impurity, for the aggregation through the inhibited oxidation thing improves low-temperature flexibility, with ceiling restriction below 0.0035%.For the generation through the inhibited oxidation thing improves mother metal and HAZ toughness, preferably the higher limit with the O amount is defined as below 0.0030%.Be limited to below 0.0020% on the best of O amount.
Ca:Ca generates sulfide CaS, and the generation of the MnS of subtend rolling direction elongation suppresses, and helps significantly to improve the element of low-temperature flexibility.Addition at Ca is lower than at 0.0001% o'clock, can not get effect, thereby lower value is defined as more than 0.0001%.On the other hand, if the addition of Ca surpasses 0.0050%, then the oxide compound aggregation damages low-temperature flexibility, thereby the upper limit is defined as below 0.0050%.
In the present invention, through adding Ca, form CaS and fix S, so the ratio of S/Ca is an important index.If the ratio of S/Ca is more than 0.5, then generate MnS, be formed on the MnS of extensionization when rolling.Consequently, low-temperature flexibility deterioration.So, the ratio of S/Ca be defined as be lower than 0.5.
Have again, in the present invention,, can add the element more than a kind or 2 kinds among Ni, Cu, Cr, Mo, W, V, Zr, Ta, the B as improving intensity and flexible element.
Ni:Ni is to improving toughness and intensity effective elements, in order to obtain its effect, needs to add more than 0.01%, but descends adding 2.0% weldableness when above, so preferably its upper limit is defined as 2.0%.
Cu:Cu be under the situation that toughness is reduced to improving the intensity effective elements, do not have effect being lower than at 0.01% o'clock, if surpass 1.0% then be easy to generate crackle when steel billet heat or when welding.So, preferably its content is defined as below 0.01～1.0%.
Cr: in order to improve the intensity of steel through precipitation strength, the interpolation Cr more than 0.01% is effectively, if but the interpolation of volume ground then makes hardenability rise, generate bainite structure, and low-temperature flexibility is reduced.So, preferably its upper limit is defined as 1.0%.
Mo:Mo is when improving hardenability, forms the element that carbonitride improves intensity, in order to obtain its effect, preferably adds more than 0.01%.On the other hand, add Mo if surpass 0.60% ground volume, then cost rises, thereby preferably the upper limit is defined as below 0.60%.In addition, if the intensity of steel rises, then low-temperature flexibility descends sometimes, therefore the preferred upper limit is defined as below 0.20%.
W:W is to improving the intensity effective elements, preferably add more than 0.01%, more preferably adding more than 0.05%.On the other hand, surpass 1.0% W, then cause flexible sometimes and descend, therefore preferably the upper limit is defined as below 1.0% if add.
V:V forms carbide, nitride, helps to improve the element of intensity, for obtaining effect, preferably adds more than 0.01%.On the other hand, surpass 0.10% V, then cause the decline of low-temperature flexibility sometimes, thereby preferably the upper limit is defined as below 0.10% if add.
Zr, Ta:Zr and Ta and V are same, are to form carbide, nitride, help to improve the element of intensity, for obtaining effect, preferably add more than 0.0001%.On the other hand, add Zr and Ta superfluously, then cause the decline of low-temperature flexibility sometimes, thereby preferably the upper limit is defined as below 0.050% if surpass 0.050% ground.
B:B is the grain boundary segregation to steel, significantly helps to improve the element of hardenability.In order to obtain this effect, preferably add the B more than 0.0001%.In addition, B generates BN, and solid solution N is reduced, and also helps to improve the flexible element of welded heat affecting zone, thereby more preferably adds more than 0.0005%.On the other hand, then superfluous if add B superfluously to the segregation of crystal boundary, cause the decline of low-temperature flexibility sometimes, thereby preferably the upper limit is defined as 0.0020%.
In addition, for inclusiones such as controlled oxidation thing and sulfide, also can contain among REM, Mg, Zr, Ta, Y, Hf, the Re more than a kind or 2 kinds.
REM:REM can be used as reductor and sweetening agent and the element that adds, preferably adds more than 0.0001%.On the other hand,, then generate thick oxide compound, the toughness of HIC property or mother metal and HAZ is reduced, be limited to below 0.010% on preferred if add to surpass 0.010%.
Mg:Mg can be used as reductor and sweetening agent and the element that adds, particularly also helps to improve HAZ toughness through generating fine oxide compound.For obtaining this effect, preferably add the Mg more than 0.0001%, more preferably add more than 0.0005%.On the other hand, add Mg if surpass 0.010% ground, the then easy aggegation of oxide compound, thickization bring the deterioration of HIC property or the flexible of mother metal and HAZ to descend sometimes.So preferably the upper limit with the Mg amount is defined as below 0.010%.
Y, Hf, Re:Y, Hf, Re and Ca are same, are the elements that the generation that generates the MnS of sulfide, the elongation of subtend rolling direction suppresses, helps to improve HIC-resistance.For obtaining so effect, preferably add Y, Hf, Re more than 0.0001%, more preferably add more than 0.0005%.On the other hand, if the amount of Y, Hf, Re surpasses 0.0050%, then oxide compound increases, if aggegation, thickization then damage HIC-resistance, thereby preferably the upper limit is defined as below 0.0050%.
In addition, in the present invention, respectively maximum Mn degree of segregation, Nb degree of segregation and Ti degree of segregation are defined as below 2.0, reach below 4.0 below 4.0.
Through maximum Mn degree of segregation is defined as below 2.0, the hardness that can suppress center segregation portion rises, and improves the low-temperature flexibility of center segregation portion.In addition,, then can suppress the generation of the Nb (C, N) of aggregation,, then can suppress the generation of the TiN of aggregation, all can prevent the deterioration of the low-temperature flexibility of center segregation portion if the Ti degree of segregation is defined as below 4.0 if the Nb degree of segregation is defined as below 4.0.
Maximum Mn degree of segregation is that the Mn with respect to the maximum of the center segregation portion of the average Mn amount except that center segregation portion of steel plate and steel pipe measures, and can utilize probe diameter is defined as the EPMA of 2 μ m or the Mn concentration distribution that CMA mensuration is obtained steel plate and steel pipe.About Nb degree of segregation and Ti degree of segregation too; Utilization is defined as probe diameter EPMA or the CMA of 2 μ m; Measured Nb concentration distribution and Ti concentration distribution respectively, the Nb that obtains the maximum that obtains with respect to the making center segregation portion equalization of the amount of the average N b except that center segregation portion of steel plate and steel pipe measures the Ti amount (Ti degree of segregation) of the maximum that obtains with respect to the making center segregation portion equalization of the amount of the average T i except that center segregation portion of (Nb degree of segregation) and steel plate and steel pipe.
Below, the method that suppresses maximum Mn degree of segregation, Nb degree of segregation and Ti degree of segregation is described.
Suppress the segregation of Mn, Nb and Ti, the light pressure during finally solidifying in the continuous casting is best suited for.Light pressure when finally solidifying is that the even portion of solidifying of inhomogeneous cooling when resulting from casting for elimination implements with the mixed existence of not solidifying portion, thus, can make it take place equably finally to solidify at width.
" if 40 ° of faces " the aggregation degree of 100} surpasses 4.0, then can be observed whole oblique rock-candy structure, can not satisfy 85% DWTT ductile fracture rate, so with { the aggregation metric of 100} is decided to be below 4.0.
In continuous casting, usually steel billet is carried out water-cooled, but the cooling of the end of width is fast, the cooling of the central part of width is reinforced.Therefore, even solidify, at 1/4 one of width, solidify also and postpone, in the remaining portion of not solidifying of inside steel billet at the end and the central part of the width of steel billet.Therefore, at the width of steel billet, solidify portion and the portion of not solidifying inhomogeneous, for example, the shape of solidifying portion and the interface of not solidifying portion at width sometimes for the W type.Solidify if produce so in that width is uneven, then encourage segregation, hardness improves, and makes the low-temperature flexibility deterioration.
Relative therewith, in continuous casting, if the light pressure when finally solidifying, then the portion of not solidifying is extruded, and it is solidified at width equably.In addition, if produced the uneven after-applied light pressure of solidifying at width, the resistance to deformation of the portion of solidifying of then resulting from is big, can not push the portion of not solidifying effectively.
Therefore, in order not produce so solidifying of W type, preferably according to the distribution at width of finally solidifying the center solid rate in the position of strand, Yi Bian control draught, Yi Bian gently press.Thus, even also can suppress center segregation, can reduce maximum Mn degree of segregation, Nb degree of segregation, Ti degree of segregation more at width.
The steel that contains mentioned component forms steel billet through continuous casting after the melting in steel making working procedure, steel billet is carried out reheat and implements heavy plate rolling, forms steel plate.In such cases, the reheat temperature of steel billet is defined as more than 1000 ℃, with the recrystallization temperature district depress than be defined as more than 2, with the non-recrystallization district depress than be defined as more than 3, so carry out heavy plate rolling.And then, after rolling end, carry out water-cooled, but beginning temperature, water-cooled is preferably the above temperature of Ar3 point, in addition, preferably water-cooled is stopped temperature and be defined as 250～600 ℃.Being lower than under 250 ℃ the situation, crack sometimes.As long as stipulate TR for this reason, just can form bainite+martensite branch rate is the microstructure more than 90%.And, can make average original austenite particle diameter below 10 μ m.
The measuring method of average original austenite particle diameter is according to the measuring method of the E112 of ASTM.If what make the recrystallization temperature district depresses than is lower than 2, and make 3 ground of depressing than being lower than in non-recrystallization district carry out heavy plate rolling, then can not make average original austenite particle diameter below 10 μ m.If average original austenite particle diameter reaches more than the 10 μ m, then can not satisfy 85% DWTT ductile fracture rate.So, average original austenite particle diameter is defined as below the 10 μ m.
Have, the recrystallization temperature district is the TR that rolling back produces recrystallize, under the composition of steel of the present invention, generally above 900 ℃ again.On the other hand, the non-recrystallization humidity province is the TR that does not produce recrystallize and ferrite transformation after rolling, under the composition of steel of the present invention, is generally 750～900 ℃.Recrystallization temperature district rolling is called the rolling or roughing of recrystallize, non-recrystallization humidity province rolling is called the rolling or finish rolling of non-recrystallization.
After non-recrystallization is rolling, through beginning water-cooled, water-cooled is stopped temperature being defined as more than 250 ℃ from the temperature more than Ar3 ℃, the highest hardness that can make center segregation thus is below 400Hv.In addition, then same if make water-cooled stop temperature more than 400 ℃, the martensite part of the hard after the phase transformation is decomposed, and can hardness be suppressed at below the 350Hv.In addition, reduce, need to add alloys more, thereby be preferably below 600 ℃ if water-cooled stops the too high then intensity of temperature.
At last, the method for length below 0.01mm of the not pressure contact portion that makes steel plate discussed.As stated, when the solidifying of strand, be accompanied by solidification shrinkage and generate pore.At this moment, if gaseous constituents such as H are many, then in pore, contain more gaseous constituent.If make the H amount below 0.00025%, then almost there is not pressure contact portion, also can make its length below 0.1mm even exist.Relative therewith, if the H amount surpasses 0.00025%, then remaining more thick not pressure contact portion, generating length is the above not pressure contact portion of 0.1mm, becomes the reason of the occurrence features deterioration of fracture.
Have, the hydrogen amount is from 2 molten steel after refining, to take analytical sample again, with the value of rare gas element fusing thermal conductivity test method determination.
Embodiment
Then, embodiments of the invention are discussed.
After the thick bloom of the 240mm of the chemical ingredients that will have table 1 is heated to 1100～1250 ℃, under the recrystallization temperature more than 900 ℃, carry out hot rolling.And then in the hot rolling of carrying out the non-recrystallization humidity province from 900 ℃ to 750 ℃ TR.Then, begin water-cooled more than 750 ℃, under 400～500 ℃ temperature, water-cooled is being stopped, so making the steel plate of multiple thickness of slab.Thus, the microstructure of steel plate has obtained bainite and martensitic total branch rate is the tissue more than 90%.
Then, after having carried out C compacting, U compacting, O compacting, position the welding of weldering, interior outside, carry out expander then, form steel pipe.
From these steel plates and steel pipe, take tension test sheet, DWT test film, macroanalysis sheet, supply with each test.The DWT test is carried out according to API5L3.Measure the degree of segregation of Mn, Nb, Ti from the macroanalysis sheet.Probe diameter is 2 μ m, presses the wide mensuration area of total thickness * 20mm and implements.And the measurement of hardness of enforcement center segregation.With the load-carrying is that 25g measures the hardness at the highest position of Mn concentration.The result of steel plate sees table 2, and the result of steel pipe sees table 3.
In table 1～3, steel 1～22 and 34 is the present invention's example.Show clearly like table 2 and table 3, the maximum hardness of the center segregation portion of these steel plates is that 400Hv is following, the length of pressure contact portion is not below the 0.1mm, has obtained the ductile fracture rate more than 85% through the DWT test.Relative therewith, steel 23～33 and 35～37 is for breaking away from the comparative example of the inventive method.That is to say, steel 23～30th, basal component is at extraneous example of the present invention, steel 31 for S/Ca 0.5 or more, have the example of the MnS of more extensionization, steel 32 is to make the not example of length more than 0.1mm of pressure contact portion because of the H amount above 2.5ppm.In these comparative examples, about steel plate (table 2) and steel pipe (table 3), the ductile fracture rate all is lower than 85% in the DWT test.The H amount of steel 33 surpasses 2.5ppm, and pressure contact portion does not surpass 0.1mm, and therefore the ductile fracture rate is lower than 85% in DWTT.40 ° of faces of steel 35 { the aggregation degree of 100} surpasses 4.0, and the ductile fracture rate is lower than 85%.The element of the basal component of steel 36 outside scope of the present invention, and 40 ° of faces { the aggregation degree of 100} surpasses 4.0, so the ductile fracture rate is lower than 85%.The degree of segregation of the Nb of steel 37, the degree of segregation of Ti surpass 4.0, and 40 ° of faces { the aggregation degree of 100} surpasses 4.0, thereby the ductile fracture rate is lower than 85%.
Table 3
Utilize possibility on the industry
According to chemical ingredients of the present invention and method of manufacture, the maximum hardness that can limit center segregation portion reaches the not length of pressure contact portion.Effect can be made the line-pipes steel plate and the line-pipes steel pipe of excellent in low temperature toughness thus.Consequently, the security of line pipe increases substantially, and utilizes possibility high on the industry.
Claims (14)
1. the effective steel plate of the high-strength line-pipe of an excellent in low temperature toughness is characterized in that,
In quality %, contain:
C：0.03～0.08％、
Si：0.01～0.5％、
Mn：1.6～2.3％、
Nb：0.001～0.05％、
N：0.0010～0.0050％、
Ca：0.0001～0.0050％，
Following element is limited in:
Below the P:0.015%,
Below the S:0.0020%,
Ti：0.001～0.030％、
Below the Al:0.030%,
Below the O:0.0035%,
Surplus comprises Fe and unavoidable impurities element,
Satisfy S/Ca＜0.5, and then,
The maximum hardness of center segregation portion is limited in below the 400Hv;
And then, with the limitation of length of the not pressure contact portion of center segregation portion below 0.1mm;
And then, will be with rolling direction axle, to rolling surface tilt 40 ° the position { the aggregation degree of 100} is limited in below 4.0;
Tensile strength is more than the 600MPa.
2. the effective steel plate of the high-strength line-pipe of excellent in low temperature toughness according to claim 1 is characterized in that, in quality %, further contain in the following element more than a kind or 2 kinds:
Ni：0.01～2.0％、
Cu：0.01～1.0％、
Cr：0.01～1.0％、
Mo：0.01～0.60％、
W：0.01～1.0％、
V：0.01～0.10％、
Zr：0.0001～0.050％、
Ta：0.0001～0.050％、
B：0.0001～0.0020％。
3. the effective steel plate of the high-strength line-pipe of excellent in low temperature toughness according to claim 1 and 2 is characterized in that, in quality %, further contain in the following element more than a kind or 2 kinds:
REM：0.0001～0.01％、
Mg：0.0001～0.01％、
Y：0.0001～0.005％、
Hf：0.0001～0.005％、
Re：0.0001～0.005％。
4. according to the effective steel plate of the high-strength line-pipe of each the described excellent in low temperature toughness in the claim 1～3, it has bainite+martensitic stucture.
5. the effective steel plate of the high-strength line-pipe of excellent in low temperature toughness according to claim 4, wherein, the median size of the original austenite parent phase of said bainite+martensitic stucture is below the 10 μ m.
6. according to the effective steel plate of high-strength line-pipe of claim 4 or 5 described excellent in low temperature toughness, wherein, the ferritic branch rate in said bainite+martensitic stucture is lower than 10%.
7. according to the effective steel plate of the high-strength line-pipe of each the described excellent in low temperature toughness in the claim 1～6, it is characterized in that the maximum Mn degree of segregation of center segregation portion is below 2.0, the Nb degree of segregation is below 4.0, the Ti degree of segregation is below 4.0.
8. the effective steel pipe of the high-strength line-pipe of an excellent in low temperature toughness is characterized in that,
Mother metal contains in quality %:
C：0.03～0.08％、
Si：0.01～0.5％、
Mn：1.6～2.3％、
Nb：0.001～0.05％、
N：0.0010～0.0050％、
Ca：0.0001～0.0050％，
Following element is limited in:
Below the P:0.015%,
Below the S:0.002%,
Ti：0.001～0.030％、
Below the Al:0.030%,
Below the O:0.0035%,
Surplus comprises Fe and unavoidable impurities element,
Satisfy S/Ca＜0.5, and then,
The maximum hardness of center segregation portion is limited in below the 400Hv;
And then, with the limitation of length of the not pressure contact portion of center segregation portion below 0.1mm;
And then, will be with rolling direction axle, to rolling surface tilt 40 ° the position { the aggregation degree of 100} is limited in below 4.0;
Tensile strength is more than the 600MPa.
9. the effective steel pipe of the high-strength line-pipe of excellent in low temperature toughness according to claim 8 is characterized in that, in quality %, further contain in the following element more than a kind or 2 kinds:
Ni：0.01～2.0％、
Cu：0.01～1.0％、
Cr：0.01～1.0％、
Mo：0.01～0.60％、
W：0.01～1.0％、
V：0.01～0.10％、
Zr：0.0001～0.050％、
Ta：0.0001～0.050％、
B：0.0001～0.0020％。
10. according to Claim 8 or the effective steel pipe of the high-strength line-pipe of 9 described excellent in low temperature toughness, it is characterized in that, in quality %, further contain in the following element more than a kind or 2 kinds:
REM：0.0001～0.01％、
Mg：0.0001～0.01％、
Y：0.0001～0.005％、
Hf：0.0001～0.005％、
Re：0.0001～0.005％。
11. the effective steel pipe of the high-strength line-pipe of each the described excellent in low temperature toughness according to Claim 8～10, it has bainite+martensitic stucture.
12. the effective steel pipe of the high-strength line-pipe of each the described excellent in low temperature toughness according to Claim 8～11, wherein, the median size of the original austenite parent phase of said bainite+martensitic stucture is below the 10 μ m.
13. the effective steel pipe of the high-strength line-pipe of described excellent in low temperature toughness according to Claim 8～12, wherein, the ferritic branch rate in said bainite+martensitic stucture is lower than 10%.
14. the effective steel pipe of the high-strength line-pipe of each the described excellent in low temperature toughness according to Claim 8～13 is characterized in that, the maximum Mn degree of segregation of restriction center segregation portion is below 2.0, the Nb degree of segregation is below 4.0, the Ti degree of segregation is below 4.0.
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- 2010-09-01 BR BR112012004577A patent/BR112012004577A2/en not_active Application Discontinuation
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| JP2008163455A (en) * | 2006-12-04 | 2008-07-17 | Nippon Steel Corp | Weld steel pipe with excellent low-temperature toughness for high-strength thick-walled line pipe and process for producing the same |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103215513A (en) * | 2013-04-25 | 2013-07-24 | 宝山钢铁股份有限公司 | Corrosion-resistant gathering and transportation line pipe and manufacturing method thereof |
| CN104651714A (en) * | 2013-11-19 | 2015-05-27 | 新日铁住金株式会社 | Steel sheet |
| CN104651714B (en) * | 2013-11-19 | 2017-05-10 | 新日铁住金株式会社 | Steel sheet |
| CN106103778A (en) * | 2014-03-28 | 2016-11-09 | 株式会社神户制钢所 | The effective steel plate of high-strength line-pipe of excellent in low temperature toughness and the effective steel pipe of high-strength line-pipe |
| CN106103778B (en) * | 2014-03-28 | 2019-03-22 | 株式会社神户制钢所 | The effective steel plate of the high-strength line-pipe of excellent in low temperature toughness and the effective steel pipe of high-strength line-pipe |
| CN103898407A (en) * | 2014-04-09 | 2014-07-02 | 武汉钢铁(集团)公司 | 600MPa hot-rolled ribbed steel bar and preparation method thereof |
| CN103898407B (en) * | 2014-04-09 | 2016-07-06 | 武汉钢铁(集团)公司 | 600MPa hot rolled ribbed bars and preparation method thereof |
| CN108456834A (en) * | 2018-03-05 | 2018-08-28 | 石英楠 | A kind of high-strength line-pipe steel and preparation method thereof with the precipitate containing Ti |
| CN108456834B (en) * | 2018-03-05 | 2020-04-24 | 白婷婷 | High-strength pipeline steel containing Ti precipitates and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2011027900A1 (en) | 2011-03-10 |
| JP5131714B2 (en) | 2013-01-30 |
| BR112012004577A2 (en) | 2016-04-05 |
| JPWO2011027900A1 (en) | 2013-02-04 |
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