CN108026618A - Structure high-strength steel plate and its manufacture method - Google Patents

Structure high-strength steel plate and its manufacture method Download PDF

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Publication number
CN108026618A
CN108026618A CN201680052939.XA CN201680052939A CN108026618A CN 108026618 A CN108026618 A CN 108026618A CN 201680052939 A CN201680052939 A CN 201680052939A CN 108026618 A CN108026618 A CN 108026618A
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thickness
slab
steel plate
brittle
vtrs
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CN108026618B (en
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崎本隆洋
半田恒久
伊木聪
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JFE Steel Corp
JFE Engineering Corp
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NKK Corp
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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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • 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
    • 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
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • 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
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • 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
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • 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
    • 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
    • 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
    • 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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • 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

Abstract

The present invention provides the high-strength steel plate that thickness of slab is more than 70mm and brittle-cracking propagation Stopping Ability is excellent.The high-strength steel plate of the present invention is by possessing interior zone (thickness of slab central part region) with high brittle-cracking propagation Stopping Ability and being formed in three layers of the low region of its two outsides brittle-cracking propagation Stopping Ability.That is, thickness of slab t is more than 70mm, brittle-cracking propagation Stopping Ability index Y (12 × I of=vTrs of 1/6t, 1/3t, 1/2t position in thickness of slab direction(100)‑22×I(211)) meet Y1/3t≤0.9Y1/2tAnd Y1/6t≥0.8Y1/2t.It should be noted that vTrs is the fracture transition temperature (DEG C) of V notch Charpy-type tests, I(100)For the X-ray diffraction intensity ratio in (100) face parallel with rolling surface (plate face), I(211)For the X-ray diffraction intensity ratio in (211) face parallel with rolling surface (plate face).

Description

Structure high-strength steel plate and its manufacture method
Technical field
The present invention relates to being suitable as, ship, marine structure, cryopreservation tank and building/civil structure thing etc. is large-scale The structure steel plate and its manufacture method of steel structure purposes, more particularly to the brittleness for the steel plate that thickness of slab is more than 70mm The raising of crack propagation Stopping Ability.
Background technology
For the large-scale steel structure things such as ship, marine structure, cryopreservation tank and building/civil structure thing, In the event of accidents such as the extensive damage associated with brittle fracture, damages, then very big influence is brought on economy, environment.Therefore, For large-scale steel structure thing, from the viewpoint of brittle fracture is prevented, the safety for improving works is usually required that Property.
In recent years, such as Effects of Containers Growing Bigger, argosy is just built or plans as 6000~20000TEU. With the maximization of such ship, it is used as the steel plate of ship hull plate high intensity while wall thickening, begins to use thickness of slab For 50~100mm, yield strength 390N/mm2Level, 470N/mm2The high-strength steel plate of level.It should be noted that TEU (two Ten foot equivalent units, Twenty feet Equivalent Unit) represent to be converted into of the container of 20 feet of length Number, represents the index of the carrying capacity of container ship.
For the steel such as the steel plate used in the large-scale steel structure thing such as such ship, from ensuring works From the viewpoint of security, it is desirable to stop at service temperatures with excellent low-temperature flexibility, excellent brittle-cracking propagation tough Property value.Especially need also to make in the case of just in case producing brittle crack the propagation of brittle crack causing to break on a large scale Stop before splitting, therefore, the brittle-cracking propagation of the steel such as used steel plate stops toughness value (hereinafter also referred to as " crack arrest Performance ") it is important characteristic.
For such situation, develop, manufactured the various steel or large welded structures for improving " crack arrest characteristic " Body.
For example, a kind of structure high-strength thick of excellent in brittle-cracking propagation stopping characteristics is described in patent document 1 Steel plate.In the technology described in patent document 1, C will be contained in terms of quality %：0.03~0.20%, Si：0.03~0.5%, Mn：0.5~2.0%, Al：0.005~0.08% or further contain Ti：0.005~0.03%, Nb：0.005~ 0.05%th, Cu：0.01~0.5%, Ni：0.01~1.0%, Cr：0.01~0.5%, Mo：0.01~0.5%, V：0.001~ 0.1%th, B：Less than 0.003%, Ca：Less than 0.005%, REM：Any one in less than 0.01% or two or more steel original Material is heated to 900~1200 DEG C of temperature, and the temperature carried out in thickness of slab central portion is Ar3Reduction ratio is accumulated at a temperature of more than point It is Ar for more than 30%, in the temperature of thickness of slab central portion3Put following and Ar3Reduction ratio is accumulated within the temperature range of more than -60 DEG C of point For more than 30% rolling, then, less than 600 DEG C are cooled to more than 2 DEG C/sec of cooling velocity, thereby, it is possible to be made to have (100) face X-ray intensity in rolling surface at thickness of slab central portion is than in the rolling surface at more than 2.0 and thickness of slab 1/4 (110) face X-ray intensity than the texture for more than 1.5 steel plate.Such steel plate is applied to the flange of T word connectors During portion, the brittle crack that can make to develop since web portion stops in flange part.In the technology described in patent document 1, So that 1/2 in thickness of slab, the X-ray intensity of 1/4 position of thickness of slab certain surface parallel with rolling surface is than elevated Mode makes specific texture flourishing, changes the direction of propagation of brittle crack, so that crack arrest improves.
In addition, describe in patent document a kind of thickness of slab 50mm of roomy excellent in brittle-cracking propagation stopping characteristics with On steel plate and its manufacture method.In the technology described in patent document 2, C will be contained in terms of quality %：0.15% with Under, Si：Less than 0.60%, Mn：0.80~1.80%, S：0.001~0.05% and containing being selected from Ti：0.005~0.050% Or Nb：At least one of 0.001~0.1%, further contain and be selected from Cu：Less than 2.0%, V：Less than 0.2%, Ni：2.0% Below, Cr：Less than 0.6%, Mo：Less than 0.6%, W：Less than 0.5%, B：Less than 0.0050%, Zr：One in less than 0.5% Kind or two or more steel former materials are heated to 900~1300 DEG C of temperature, and 1000~850 DEG C of temperature is being calculated as with surface temperature In the range of carry out after accumulation reduction ratio is more than 10% rolling, it is that 900~600 DEG C and internal temperature reach to form surface temperature To the state of 50~150 DEG C higher than surface temperature of temperature, then, implement every time reduction ratio as more than 7%, accumulation reduction ratio More than 50% and to roll the hot rolling that end temp is calculated as with surface temperature 800~500 DEG C.It should be noted that hot rolling knot Shu Hou, can be cooled to 400 DEG C with more than 5 DEG C/sec cooling velocities.Thus, following steel plate can be obtained：In thickness of slab central portion The X-ray intensity ratio for locating (211) face in the rolling surface at the position at least 20% region of thickness of slab or (100) face is 1.5 Above, (211) face in the rolling surface in 1/4~1/10 region as thickness of slab or 3/4~9/10 region as thickness of slab Or the X-ray intensity ratio in (100) face is more than 1.3, carry out crisp in the thickness of slab direction section of fracture when roomy ESSO is tested Stopping crack length in the region for 20% width that the front end geometry of property crack propagation stop is formed as thickness of slab central portion Relative to from surface of steel plate for thickness of slab 1/4~1/10 or thickness of slab 3/4~9/10 region maximum crack length at least Shortened and recessed recessed Xian portions on the direct of travel of brittle crack with the length of thickness of slab, conventional difficulty can be made in steel plate Roomy brittle crack under conditions of unstressed reflection also stop propagate.In the technology described in patent document 2, so that At 1/2 of thickness of slab at least 20% region of thickness of slab and the 1/4~1/10 of thickness of slab or 3/4~9/10 region of thickness of slab with The X-ray intensity of the parallel certain surface of rolling surface is adjusted than elevated mode, so that roomy brittle-cracking propagation stops Characteristic improves.
In addition, in patent document 3, the structure of excellent in brittle-cracking propagation stopping characteristics more than thickness of slab 50mm is described With the manufacture method of high-strength steel plate.In the technology described in patent document 3, C will be contained in terms of quality %：0.03~ 0.20%th, Si：0.03~0.5%, Mn：0.5~2.2%, Al：0.005~0.08%, P：Less than 0.03%, S：0.01% with Under, N：Less than 0.0050%, Ti：0.005~0.03% or also containing being selected from Nb：0.005~0.05%, Cu：0.01~ 0.5%th, Ni：0.01~1.0%, Cr：0.01~0.5%, Mo：0.01~0.5%, V：0.001~0.10%, B：0.0030% Below, Ca：Less than 0.0050%, REM：One or more of less than 0.010% steel former material is heated to 900~1150 DEG C of temperature Degree, implements to make adding up to for the accumulation reduction ratio in austenite recrystallization temperature scope and austenite non-recrystallization temperature range More than 65%, make accumulation reduction ratio for more than 20% in the state of thickness of slab central portion is in austenite recrystallization temperature scope, And the rolling that the average reduction ratio for making every a time is less than 5.0%, then, is in austenite in thickness of slab central portion and does not tie again In the state of brilliant temperature range, it is more than 40% and makes the average reduction ratio of every a time be into accumulation reduction ratio is exercised More than 7.0% rolling, then accelerates to be cooled to less than 600 DEG C with more than 4.0 DEG C/sec of cooling velocity.Thus, it is possible to obtain The works high-strength steel plate of excellent in brittle-cracking propagation stopping characteristics as described below：With being organized as ferrite master Body, the aggregation degree in RD//(110) face of skin section are that the aggregation degree in RD//(110) face of more than 1.3, thickness of slab central portion is 1.8 Texture above, the Charpy fracture transition temperature of skin section is less than -60 DEG C, the Charpy fracture transition temperature of thickness of slab central portion For less than -50 DEG C.In the technology described in patent document 3, skin section and thickness of slab central portion make specific texture prosperity from And improve the brittle-cracking propagation stopping characteristics of steel plate.In patent document 3, " aggregation degree in RD//(110) face " refer to by (110) face carries out accumulative and obtains tired relative to the value of the three-dimensional crystal orientation density function of the parallel orientation of rolling direction (RD) Evaluation and divided by accumulative orientation number obtained from value.
In addition, the structure of the excellent in brittle-cracking propagation stopping characteristics of more than thickness of slab 50mm is recorded in patent document 4 With the manufacture method of high-strength steel plate.In the technology described in patent document 4, C will be contained in terms of quality %：0.03~ 0.20%th, Si：0.03~0.5%, Mn：0.5~2.5%, Al：0.005~0.08%, P：Less than 0.03%, S：0.01% with Under, N：Less than 0.0050%, Ti：0.005~0.03% or further containing being selected from Nb：0.005~0.05%, Cu：0.01 ~0.5%, Ni：0.01~1.0%, Cr：0.01~0.5%, Mo：0.01~0.5%, V：0.001~0.10%, B： Less than 0.0030%, Ca：Less than 0.0050%, REM：One or more of less than 0.010% steel former material is heated to 1000~ 1200 DEG C of temperature, implements to make the accumulation reduction ratio in austenite recrystallization temperature scope and austenite non-recrystallization temperature range The accumulation reduction ratio for adding up to more than 65%, making thickness of slab central portion be in the state of austenite recrystallization temperature scope be More than 20%, it is 40% then to make the accumulation reduction ratio that thickness of slab central portion is in the state of austenite non-recrystallization temperature range More than and make thickness of slab central portion be in austenite non-recrystallization temperature range in the state of rolling in initially passage with finally The difference of the rolling temperature of passage be 40 DEG C within rolling, then, with more than 4 DEG C/sec of cooling velocity be cooled to 450 DEG C with Under.Thus, it is possible to obtain be organized as bayesian phosphor bodies, the aggregation degree in RD//(110) face of skin section is more than 1.5 to knit Structure and skin section and the brittle-cracking propagation stopping characteristics that the Charpy fracture transition temperature of thickness of slab central portion is less than -40 DEG C are excellent Good works high-strength steel plate.In the technology described in patent document 4, in skin section and thickness of slab central portion, make spy Fixed texture is flourishing, so as to improve the brittle-cracking propagation stopping characteristics of steel plate.In patent document 4, " RD//(110) face Aggregation degree " refer to the value relative to the three-dimensional crystal orientation density function of the parallel orientation of rolling direction (RD) by (110) face Carry out it is accumulative and obtain aggregate-value and divided by accumulative orientation number obtained from value.
In addition, a kind of " the excellent high-strength steel plate of crack arrest " is recorded in patent document 5.Patent document 5 is remembered The steel plate of load is high-strength steel plate as described below：With containing C in terms of quality %：0.04~0.16%, Si：0.01~ 0.5%th, Mn：0.75~2.5%, Al：0.001~0.1%, Nb：0.003~0.05%, Ti：0.005~0.05%, N： 0.001~0.008%, P, S, Cu, Ni, Mo, V, B, Ca, Mg, REM are limited to below particular value, surplus by Fe and can not be kept away The composition that the impurity exempted from is formed, carbon equivalent Ceq is 0.30~0.50%, has the ferrite that less than 70% is included in terms of area occupation ratio With the microscopic structure of more than 30% bainite, at 1/4 of thickness of slab, crystal orientation difference is more than 15 ° of crystal boundary per single Total length, the i.e. grain boundary density of plane product is 400~1000mm/mm2, there are 15 ° relative to the face vertical with main rolling direction Within angle (100) face area occupation ratio be 10~40%, at 1/2 of thickness of slab, grain boundary density is 300~900mm/ mm2, the area occupation ratio relative to the face vertical with main rolling direction with (110) face of the angle within 15 ° is 40~70%.Need It is noted that in the technology described in patent document 5, as manufacture method, the steel disc of above-mentioned composition is preferably loaded into gas After atmosphere temperature is 1000~1250 DEG C of heating furnace, implementing 4 with thickness of slab neutron moisture meter more than 850 DEG C and below 1150 DEG C Every time reduction ratio of~15 passages is less than 3% and accumulation pressure for every time reduction ratio within 3~30%, 3 passages Rate is 15~70% roughing, and implements 4~15 passages, shape ratio in the case where being calculated as 750~850 DEG C with thickness of slab central temperature Average value be 0.5~1, the finish rolling that accumulation reduction ratio is 40~80%, then, opened from thickness of slab central temperature for more than 700 DEG C Begin to be cooled to less than 550 DEG C with 2~10 DEG C/sec of thickness of slab center cooling velocity.In the technology described in patent document 5, 1/2 of thickness of slab, with 1/4 of thickness of slab, makes the texture development of prosperity, so as to suppress the propagation of brittle crack.
Prior art literature
Patent document
Patent document 1：Japanese Unexamined Patent Publication 2008-045174 publications
Patent document 2：Japanese Unexamined Patent Publication 2012-180590 publications
Patent document 3：Japanese Unexamined Patent Publication 2013-151731 publications
Patent document 4：Japanese Unexamined Patent Publication 2013-151732 publications
Patent document 5：No. 5445720 publications of Japanese Patent No.
The content of the invention
Problem to be solved by the invention
In the technology described in patent document 1~5, make specific location of the texture in thickness of slab direction flourishing, so as to suppress The propagation of brittle crack, improves the brittle-cracking propagation stopping characteristics in steel plate.But using described in patent document 1~5 Technology or there are the following problems：For the high-strength steel plate of more than thickness of slab 70mm, even if being also not carried out keeping The condition of most stringent of condition, unstressed reflection that crackle enters via complete penetration weld etc. in as practical structures Under can also make roomy brittle crack stop as fully excellent brittle-cracking propagation stopping characteristics.
In view of above-mentioned problem of the prior art, passes it is an object of the invention to provide thickness of slab for more than 70mm and brittle crack Broadcast the excellent high-strength steel plate of Stopping Ability and its manufacture method.It should be noted that " high intensity " described herein refers to Yield strength is 400N/mm2Situation above.In addition, " brittle-cracking propagation Stopping Ability is excellent " described herein refers to ship Body design temperature：Brittle-cracking propagation at -10 DEG C stops toughness value Kca-10℃For 9500N/mm3/2Situation above.
The method for solving problem
In order to achieve the above object, the present inventor is conceived to the brittle-cracking propagation of the thickness of slab direction position of steel plate The difference of Stopping Ability, it is overall to the distribution and steel plate of the brittle-cracking propagation Stopping Ability of thickness of slab direction position The relation of brittle-cracking propagation Stopping Ability have made intensive studies.Itself it turns out that, for thickness of slab be more than 70mm thickness For steel plate, there is brittle-cracking propagation Stopping Ability, the thickness of slab direction each position that can significantly increase steel plate entirety The appropriate distribution of the brittle-cracking propagation Stopping Ability at place.
That is, find：In order to improve the brittle-cracking propagation Stopping Ability of steel plate entirety, firstly, it is necessary to be made by possessing Interior zone (thickness of slab central part region) with high brittle-cracking propagation Stopping Ability and crisp in contrast in its two outside Property three layers of the relatively low region of crack propagation Stopping Ability composition steel plates.For such steel plate, find： In the case where brittle crack develops (propagation), height difference is produced near the border at the position in thickness of slab central part and its two outside, Crackle front end is developed in the form of branching into three layers of brittle crack, therefore, thick according to the combination of the thickness of each layer and its characteristic The brittle-cracking propagation Stopping Ability of steel plate entirety greatly changes.
Therefore, the present inventor expects, using index Y (DEG C) defined in following formula can easily to thickness of slab direction everybody The brittle-cracking propagation Stopping Ability put is evaluated.
Y=vTrs-12 × I(100)-22×I(211)…(A)
Wherein, vTrs：The fracture transition temperature (DEG C) of V notch Charpy-type tests,
I(100)：The X-ray diffraction intensity ratio in (100) face parallel with rolling surface (plate face),
I(211)：The X-ray diffraction intensity ratio in (211) face parallel with rolling surface (plate face).
Index Y is the fracture transition temperature (vTrs) based on Charpy-type test and considers to brittle-cracking propagation The raising of Stopping Ability bring the development degree of the texture of influence and in order to stopping toughness institute for improving brittle-cracking propagation The parameter that the fracture transition temperature (vTrs) needed is defined and is imported by a part of the present inventor.Be conducive to improve brittle crack It is flourishing to propagate the texture of Stopping Ability, I(100)、I(211)During increase, index Y is changed into low temperature.
Index Y is used as the index of the brittle-cracking propagation Stopping Ability of thickness of slab direction each position, new hair by the present inventor It is existing：Cause the brittle-cracking propagation Stopping Ability index Y at 1/6 position of thickness of slab especially by adjustment1/6t, thickness of slab 1/ Brittle-cracking propagation Stopping Ability index Y at 3 positions1/3tAnd the stopping property of the brittle-cracking propagation at 1/2 position of thickness of slab Can index Y1/2tMeet following (1) formulas and (2) formula, the brittle-cracking propagation stopping toughness value Kca for forming whole thickness is significantly carried High steel plate.
Y1/3t≤0.9Y1/2t…(1)
Y1/6t≥0.8Y1/2t…(2)
The interior zone (thickness of slab central part region) that formula (1) refers to have high brittle-cracking propagation Stopping Ability is at least time And region between two 1/3 positions of thickness of slab and exist.In addition, formula (2), which refers to exist in two outsides of the interior zone, has phase To the region of relatively low brittle-cracking propagation Stopping Ability.Here, Y1/2t、Y1/3tAnd Y1/6tLess than zero.
First, to being illustrated as the basic experimental result of the present invention.
In order to make the characteristic of thickness of slab direction each position change, composition, manufacturing condition etc. are made various changes, made The various steel plates of more than thickness of slab 70mm.From obtained each steel plate, the ESSO test film (rulers of whole thickness are cut It is very little：T × 500 × 500mm), and cut using thickness of slab direction each position as center thickness of slab 20mm subtracts thick ESSO test films (ruler It is very little：20×500×500mm).
Then, using these test films, according to brittle crack Crack Arrest Design policy (juridical person Nippon Kaiji Kyokai BJ Office, In September, 2009) appendix A, implement temperature-gradient type ESSO experiment, obtain each steel plate whole thickness and thickness of slab direction everybody Put place, crack stop temperature and brittle-cracking propagation stop the relation of toughness value Kca.
It is from obtained result, the example of the steel plate of thickness of slab 85mm is shown in Figure 1.
The steel plate that brittle-cracking propagation Stopping Ability is shown in Fig. 1 is 1/3 in 1/2 position of thickness of slab and thickness of slab The thickness of slab interior zone put show high brittle-cracking propagation stop toughness value Kca, its two outside thickness of slab 1/6 position Place show than above-mentioned low brittle-cracking propagation stop it is toughness value Kca, being formed by three layers, show thickness of slab direction everybody Put the steel plate of the distribution of the brittle-cracking propagation Stopping Ability at place.
It should be noted that it is to use thickness of slab that the brittle-cracking propagation of thickness of slab direction position, which stops toughness value Kca, It is that the test film of 20mm obtains as a result, in order to exclude the influence of thickness of slab, according to Japan welding association standard WES 3003, using by Thickness of slab coefficient of effect f (t) defined in following formula,
F (t)=1-0.05 (t-30)；t≤35mm
=54/65-3t/1300；35mm≤t≤100mm,
Kca (following, the Kca obtained by the test film using thickness of slab 20mmT=20mm) by following formula it is scaled thickness of slab 85mm's KcaT=85mm, it is shown in Figure 1.
KcaT=85mm=KcaT=20mm×f(85)/f(20)。
According to Fig. 1, the distribution for such brittle-cracking propagation Stopping Ability for showing thickness of slab direction position Steel plate for, the brittle-cracking propagation of whole thickness stops toughness value Kca and shows to be significantly higher than thickness of slab direction each position The brittle-cracking propagation at place stops the value of toughness value.
It should be noted that for the steel plate, from thickness of slab direction each position (1/6 position of thickness of slab, 1/3 of thickness of slab Put, 1/2 position of thickness of slab) cut V according to the regulation of JIS Z 2242 in a manner of test film length direction is rolling direction and lack Mouth Charpy-type test piece, obtains the fracture transition temperature vTrs of thickness of slab direction position.In addition, the thickness of slab with the steel plate Direction each position (1/6 position of thickness of slab, 1/3 position of thickness of slab, 1/2 position of thickness of slab) cuts experiment for the mode of aspect of measure Piece, using X-ray diffraction method, obtains the X-ray diffraction intensity ratio in (100) face parallel with rolling surface (plate face) and (211) face. By these values, the index Y (Y of above-mentioned (A) formula calculating thickness of slab direction position are used1/6t、Y1/3t、Y1/2t) when, Y1/6t=-129 ℃、Y1/3t=-168 DEG C, Y1/2t=-170 DEG C, it is satisfied by above-mentioned (1) formula, (2) formula.
That is, find：For the steel plate of more than thickness of slab 70mm, in order to meet above-mentioned (1) formula and (2) formula, to thickness of slab The distribution of the brittle-cracking propagation Stopping Ability of direction position is adjusted, and is configured with being formed with thickness of slab center position Put as center and the interior zone with high brittle-cracking propagation Stopping Ability of 1/3 thickness with total thickness of slab and In its 1/3 with total thickness of slab of two outsides with relatively low brittle-cracking propagation Stopping Ability compared with interior zone Different three layers of brittle-cracking propagation Stopping Ability region, on thickness of slab direction of thickness, this is for being made whole thickness Brittle-cracking propagation is important for stopping the steel plate of toughness value Kca high.
The present invention is based on above-mentioned opinion and is further studied and complete.That is, purport of the invention is as described below.
[1] a kind of structure high-strength steel plate, it is characterised in that thickness of slab t is more than 70mm, and following (a) formula is defined Thickness of slab 1/2t positions at brittle-cracking propagation Stopping Ability index Y1/2tThickness of slab 1/3t defined in (DEG C), following (b) formula Brittle-cracking propagation Stopping Ability index Y at position1/3tIt is crisp at thickness of slab 1/6t positions defined in (DEG C) and following (c) formula Property crack propagation Stopping Ability index Y1/6t(DEG C) meets following (1) formulas and (2) formula.
Y1/3t≤0.9Y1/2t…(1)
Y1/6t≥0.8Y1/2t…(2)
Y1/2t=(vTrs)1/2t-12×{I(100)}1/2t-22×{I(211)}1/2t‥(a)
Y1/3t=(vTrs)1/3t-12×{I(100)}1/3t-22×{I(211)}1/3t‥(b)
Y1/6t=(vTrs)1/6t-12×{I(100)}1/6t-22×{I(211)}1/6t‥(c)
Wherein, (vTrs)1/2t、(vTrs)1/3t、(vTrs)1/6tFor the V notch Charpy-type tests of thickness of slab position Fracture transition temperature (DEG C),
{I(100)}1/2t、{I(100)}1/3t、{I(100)}1/6tX for (100) face parallel with plate face of thickness of slab position is penetrated Line diffracted intensity ratio,
{I(211)}1/2t、{I(211)}1/3t、{I(211)}1/6tX for (211) face parallel with plate face of thickness of slab position is penetrated Line diffracted intensity ratio.
[2] the structure high-strength steel plate as described in above-mentioned [1], wherein, thickness of slab is below 100mm.
[3] the structure high-strength steel plate as described in above-mentioned [1] or [2], wherein, above-mentioned brittle-cracking propagation stopping property Can index Y1/3t(DEG C) is less than -150 DEG C.
[4] the structure high-strength steel plate as any one of above-mentioned [1]~[3], wherein, have：
Contain C in terms of quality %：0.03~0.20%, Si：0.03~0.5%, Mn：0.5~2.5%, P：0.03% with Under, S：Less than 0.01%, Al：0.005~0.08%, Nb：0.005~0.05%, Ti：0.005~0.03%, N：0.0050% Below and surplus is made of what Fe and inevitable impurity were formed；With
To be calculated as using volume fraction more than 80% bainite mutually as main body, the second phase by total volume fraction as less than 20% The tissue formed more than one or both of ferritic phase, pearlite, martensite of (including 0%).
[5] the structure high-strength steel plate as described in above-mentioned [4], wherein, above-mentioned composition is in terms of quality % also containing choosing From Ni：0.05~3%, Cu：0.05~1.5%, Cr：0.02~1.0%, Mo：0.005~1.0%, V：0.002~0.10%, B：More than one or both of 0.0002~0.003%.
[6] the structure high-strength steel plate as described in above-mentioned [4] or [5], wherein, above-mentioned composition is also contained in terms of quality % Have and be selected from Ca：0.0005~0.003%, REM：One or both of 0.0005~0.010%.
[7] a kind of manufacture method of structure high-strength steel plate, wherein, heating process and Hot-roller are implemented to steel former material Sequence, is made the steel plate that thickness of slab t is more than 70mm, and the manufacture method is characterized in that,
Above-mentioned steel former material is set as having and contains C in terms of quality %：0.03~0.20%, Si：0.03~0.5%, Mn： 0.5~2.5%, P：Less than 0.03%, S：Less than 0.01%, Al：0.005~0.08%, Nb：0.005~0.05%, Ti： 0.005~0.03%, N：Less than 0.0050% and the steel former material formed that is made of Fe and inevitable impurity of surplus,
Above-mentioned heating process is set as the steel former material being heated to the process of the temperature of 900~1200 DEG C of heating-up temperature,
Above-mentioned hot-rolled process is set as following process：It is being calculated as with surface temperature within the temperature range of 1000~850 DEG C Implement the once rolling that accumulation reduction ratio is less than 9%, then, be calculated as with surface temperature within the temperature range of 900~600 DEG C Implement that every time reduction ratio is more than 7%, accumulation reduction ratio is more than 55% and rolling end temp is calculated as 800 with surface temperature ~550 DEG C of secondary rolling, then, according to 5 DEG C/sec of the average out to for the temperature range that 790~540 DEG C are calculated as with surface temperature with On cooling velocity be cooled to 450~400 DEG C cooling stop temperature,
The brittle-cracking propagation Stopping Ability index Y that thickness of slab direction each position is made meets following (1) formulas and following (2) formulas Steel plate.
Y1/3t≤0.9Y1/2t…(1)
Y1/6t≥0.8Y1/2t…(2)
Wherein, Y1/2t=(vTrs)1/2t-12×{I(100)}1/2t-22×{I(211)}1/2t‥(a)
Y1/3t=(vTrs)1/3t-12×{I(100)}1/3t-22×{I(211)}1/3t‥(b)
Y1/6t=(vTrs)1/6t-12×{I(100)}1/6t-22×{I(211)}1/6t‥(c)
It should be noted that (vTrs)1/2t、(vTrs)1/3t、(vTrs)1/6tTried for the V notches Charpy of thickness of slab position The fracture transition temperature (DEG C) tested,
{I(100)}1/2t、{I(100)}1/3t、{I(100)}1/6tX for (100) face parallel with plate face of thickness of slab position is penetrated Line diffracted intensity ratio,
{I(211)}1/2t、{I(211)}1/3t、{I(211)}1/6tX for (211) face parallel with plate face of thickness of slab position is penetrated Line diffracted intensity ratio.
[8] manufacture method of the structure high-strength steel plate as described in above-mentioned [7], wherein, above-mentioned composition is with quality % Meter, which also contains, is selected from Ni：0.05~3%, Cu：0.05~1.5%, Cr：0.02~1.0%, Mo：0.005~1.0%, V： 0.002~0.10%, B：More than one or both of 0.0002~0.003%.
[9] manufacture method of the structure high-strength steel plate as described in above-mentioned [7] or [8], wherein, above-mentioned composition is with matter Amount % meters, which also contain, is selected from Ca：0.0005~0.003%, REM：One or both of 0.0005~0.010%.
Invention effect
In accordance with the invention it is possible to easily manufacture thickness of slab be more than 70mm, yield strength 400N/mm2The above and ship Body design temperature：Brittle-cracking propagation at -10 DEG C stops toughness value Kca-10℃For 9500N/mm3/2Brittle crack above passes The excellent high-strength steel plate of Stopping Ability is broadcast, industrially plays significant effect.In addition, by by the present invention high intensity Steel plate is applied to the hatch side coaming in the strength deck portion structure of large-scale container ship, bulk carrier, in the component of deck, Also help to improve the so very big effect of the security of ship.
Brief description of the drawings
Fig. 1 is that ESSO result of the tests are stopped toughness value Kca by brittle-cracking propagation to stop temperature with brittle-cracking propagation Spend the figure shown in the relation of Tk.
Embodiment
The high-strength steel plate of the present invention is thick 1/3 comprising thickness of slab middle position and thickness of slab in the section of thickness of slab direction The thickness of slab central portion region of degree have high brittle-cracking propagation Stopping Ability, its two outside thickness of slab 1/3 thickness it is each Exterior lateral area has shows brittle crack on relatively low thickness of slab directions brittle-cracking propagation Stopping Ability, at three layers Propagate the steel plate of the distribution of Stopping Ability.By make thickness of slab central portion two outside region in exist show with thickness of slab The region of the different brittle crack development in the region in centre portion, the development of brittle crack is different in each layer, as a result, for example, with Have in whole thickness compared with the uniform steel plate of the identical brittle-cracking propagation Stopping Ability of thickness of slab central portion, steel plate Overall brittle-cracking propagation stops toughness value and improves.
For the high-strength steel plate of the present invention, as described above, showing that brittleness is split on three layers of thickness of slab direction The distribution of line propagation Stopping Ability, i.e. the brittle-cracking propagation Stopping Ability index Y of each thickness of slab direction position meet following (1) formula and following (2) formulas.
Y1/3t≤0.9Y1/2t…(1)
Y1/6t≥0.8Y1/2t…(2)
Here, Y1/2tIt is the brittle-cracking propagation Stopping Ability index at thickness of slab 1/2t positions, with following (a) Shi Laiding Justice.
Y1/2t=(vTrs)1/2t-12×{I(100)}1/2t-22×{I(211)}1/2t‥(a)
(here, (vTrs)1/2t：The fracture transition temperature (DEG C) of V notch Charpy tests at thickness of slab 1/2t positions, {I(100)}1/2t：X-ray diffraction intensity the ratio, { I in (100) face parallel with plate face at thickness of slab 1/2t positions(211)}1/2t：Thickness of slab The X-ray diffraction intensity ratio in (211) face parallel with plate face at 1/2t positions).It should be noted that the height for the present invention For strength thick steel plates, in order to ensure high brittle-cracking propagation toughness value, preferably Y in whole thickness1/2tMeet -150 DEG C with Under.
In addition, Y1/3tIt is the brittle-cracking propagation Stopping Ability index at thickness of slab 1/3t positions, with following (b) Shi Laiding Justice.
Y1/3t=(vTrs)1/3t-12×{I(100)}1/3t-22×{I(211)}1/3t‥(b)
(here, (vTrs)1/3t：The fracture transition temperature (DEG C) of V notch Charpy tests at thickness of slab 1/3t positions, {I(100)}1/3t：X-ray diffraction intensity the ratio, { I in (100) face parallel with plate face at thickness of slab 1/3t positions(211)}1/3t：Thickness of slab The X-ray diffraction intensity ratio in (211) face parallel with plate face at 1/3t positions).
In addition, Y1/6tIt is the brittle-cracking propagation Stopping Ability index at thickness of slab 1/6t positions, with following (c) Shi Laiding Justice.
Y1/6t=(vTrs)1/6t-12×{I(100)}1/6t-22×{I(211)}1/6t‥(c)
(here, (vTrs)1/6t：The fracture transition temperature (DEG C) of V notch Charpy tests at thickness of slab 1/6t positions, {I(100)}1/6t：X-ray diffraction intensity the ratio, { I in (100) face parallel with plate face at thickness of slab 1/6t positions(211)}1/6t：Thickness of slab The X-ray diffraction intensity ratio in (211) face parallel with plate face at 1/6t positions).
In the case where being unsatisfactory for above-mentioned (1) formula, the brittle-cracking propagation Stopping Ability of 1/3 position of thickness of slab reduces, and has The thickness in the thickness of slab central portion region of high brittle-cracking propagation Stopping Ability is thinning, it is thus impossible to ensure desired whole thick The brittle-cracking propagation of degree stops toughness value Kca.It should be noted that the brittle-cracking propagation stopping property at thickness of slab 1/3t positions Can Y1/3tPreferably less than -150 DEG C.
On the other hand, in the case where being unsatisfactory for above-mentioned (2) formula, the brittle-cracking propagation Stopping Ability of 1/6 position of thickness of slab Excessively improve, the development of brittle crack becomes identical with thickness of slab central portion region, can not be formed and be branched off into three layers of brittle crack Fracture, it is thus impossible to ensure that the brittle-cracking propagation of desired whole thickness stops toughness value Kca.
For the above situation, in the present invention, the brittle-cracking propagation Stopping Ability being defined at thickness of slab 1/3t positions Y1/3t, brittle-cracking propagation Stopping Ability Y at thickness of slab 1/2t positions1/2tAnd the brittle-cracking propagation at thickness of slab 1/6t positions Stopping Ability Y1/6tMeet the steel plate of above-mentioned (1) formula and (2) formula.Such steel plate is that have desired height in whole thickness Brittle-cracking propagation stop the steel plate of toughness value Kca.In addition, crackle front-end branches are showed for three in order to stably be made Layer brittle crack fracture, whole thickness have high brittle-cracking propagation toughness value steel plate, preferably further meet Y1/6t≤0.7Y1/2t。
It should be noted that if meeting the steel plate of above-mentioned condition, it is formed, tissue need not be particularly limited to, preferably Being made has：Contain C in terms of quality %：0.03~0.20%, Si：0.03~0.5%, Mn：0.5~2.5%, P：0.03% with Under, S：Less than 0.01%, Al：0.005~0.08%, Nb：0.005~0.05%, Ti：0.005~0.03%, N：0.0050% Contain below or optionally and be selected from Ni：0.05~3%, Cu：0.05~1.5%, Cr：0.02~1.0%, Mo：0.005~ 1.0%th, V：0.002~0.10%, B：It is more than one or both of 0.0002~0.003%, and/or, selected from Ca：0.0005 ~0.003%, REM：One or both of 0.0005~0.010% and surplus be made of Fe and inevitable impurity Composition；With by the bainite that more than 80% is calculated as using volume fraction mutually less than 20% is added up to by volume fraction as principal phase, the second phase The high-strength thick steel of the tissue formed more than one or both of ferritic phase, pearlite, martensite of (including 0%) Plate.
Hereinafter, first, the restriction reason preferably constituted is illustrated.Hereinafter, it is abbreviated with forming relevant quality % For %.
C：0.03~0.20%
C contributes to the increased element of intensity, in order to ensure the present invention steel plate desired intensity, it is necessary to contain More than 0.03%.When on the other hand, containing having more than 0.20%, the toughness of welding heat affected zone reduces.Therefore, C content is defined to 0.03~0.20% scope.It is preferably 0.05~0.09% it should be noted that from the viewpoint of texture controlling.Into one Step is preferably 0.05~0.07%.
Si：0.03~0.5%
Si is to play a role and occur to be dissolved and contribute to the increased element of intensity as deoxidier.In order to obtain this The effect of sample is, it is necessary to contain more than 0.03%.On the other hand, largely containing more than 0.5% can make the tough of welding heat affected zone Property reduce.Therefore, Si contents are defined to 0.03~0.5% scope.It should be noted that preferably 0.14~0.28%.Into One step is preferably 0.14~0.17%.
Mn：0.5~2.5%
Mn be by the raising of solution strengthening, quenching degree and contribute to intensity increase and also contribute to toughness raising, And the flourishing element of phase transformation texture.Such effect is, it is necessary to contain more than 0.5% in order to obtain.On the other hand, containing super When 2.5%, it is possible to cause the reduction of base metal tenacity.Therefore, Mn contents are defined to 0.5~2.5% scope.Need to illustrate , it is preferably 1.5~2.4%.More preferably 1.8~2.0%.
P：Less than 0.03%
P is to be present in as impurity in steel, be segregated in generations such as crystal boundaries and dysgenic element is brought to base metal tenacity, It is preferred that reduce as far as possible.However, it is possible to allow to 0.03%.Therefore, P content is defined to less than 0.03%.It should be noted that Preferably less than 0.006%.On the other hand, it is industrially more than 0.0001% from the viewpoint of dephosphorization cost.
S：Less than 0.01%
S is to exist in steel in the form of sulfide-based field trash, make hot-workability, base metal tenacity, mother metal ductility etc. The element of reduction, is preferably reduced as far as possible.However, it is possible to allow to 0.01%.Therefore, S contents are defined to less than 0.01%.Need It is noted that preferably less than 0.003%.On the other hand, it is industrially 0.0001% from the viewpoint of desulphurization cost More than.
Al：0.005~0.08%
Al plays a role as deoxidier, and has with reference to and by separate out in the form of AlN with nitrogen and suppress the thick of crystal grain The effect of change.Such effect is, it is necessary to contain more than 0.005% in order to obtain.On the other hand, largely contain more than 0.08% When, oxide system is mingled with object amount increase, and the cleanliness factor of steel reduces.Therefore, Al content is defined to 0.005~0.08% scope. It should be noted that preferably 0.02~0.04%.
Nb：0.005~0.05%
Nb be by precipitation strength and contribute to intensity increase and have the function that suppression austenite recrystallization, make Obtaining the processing (rolling) in austenite non-recrystallization temperature range becomes the element of miniaturization that is easy, contributing to crystal grain.In order to Such effect is obtained, it is necessary to contain more than 0.005%.On the other hand, largely containing more than 0.05% can form precipitate Amount becomes the tendency of excessive toughness reduction.Therefore, Nb contents are defined to 0.005~0.05% scope.It should be noted that Preferably 0.02~0.04%.
Ti：0.005~0.03%
Ti forms nitride and suppresses the coarsening of austenite grain, contribute to the crystal grain miniaturization of mother metal, make mother metal tough Property improve, and additionally aid the tissue miniaturization of welding heat affected zone, improve the toughness of welding heat affected zone.In order to obtain Such effect is, it is necessary to contain more than 0.005%.When on the other hand, containing having more than 0.03%, cause the reduction of toughness.Therefore, Ti contents are defined to 0.005~0.03% scope.It should be noted that preferably 0.008~0.015%.
N：Less than 0.0050%
N and Ti, Nb etc. contribute to base metal tenacity, welding with reference to and by contribute to the miniaturization of crystal grain in the form of nitride The raising of the toughness of heat affected zone.Such effect is, it is necessary to contain more than 0.002%, but contain and have more than in order to obtain When 0.0050%, cause the toughness of weld part to reduce.Therefore, N content is defined to less than 0.0050%.
Mentioned component is basis, still, in the present invention it is possible to further containing choosing on the basis of basic composition From Ni：0.05~3%, Cu：0.05~1.5%, Cr：0.02~1.0%, Mo：0.005~1.0%, V：0.002~0.10%, B：It is more than one or both of 0.0002~0.003%, and/or, selected from Ca：0.0005~0.003%, REM：0.0005~ One or both of 0.010% is used as optional elements.
Selected from Ni：0.05~3%, Cu：0.05~1.5%, Cr：0.02~1.0%, Mo：0.005~1.0%, V： 0.002~0.10%, B：More than one or both of 0.0002~0.003%
Ni, Cu, Cr, Mo, V, B are to make the increased element of intensity, can select as needed containing it is one or two kinds of with On.
Ni is that also have to improve toughness and in the case of containing Cu prevent on the basis of generation solid solution increases intensity The only element of the effect of fire check.Such effect is, it is necessary to contain more than 0.05% in order to obtain.On the other hand, more than 3% The surging of material cost can be caused by largely containing.Therefore, in the case of containing Ni, Ni contents are preferably limited to 0.05~3% Scope.It should be noted that more preferably 0.2~1%.
Cu is that solid solution occurs and contributes to the increased element of intensity, and such effect is, it is necessary to contain 0.05% in order to obtain More than.When on the other hand, containing having more than 1.5%, intensity excessively increases and toughness reduces.Therefore, in the case of containing Cu, Cu Content is preferably limited to 0.05~1.5% scope.It should be noted that more preferably 0.2~0.5%.
Cr is that solid solution occurs and contributes to the increased element of intensity, and such effect is, it is necessary to contain 0.02% in order to obtain More than.On the other hand, more than 1.0% largely containing sometimes, the toughness of welding heat affected zone reduces.Therefore, in the feelings containing Cr Under condition, Cr contents are preferably limited to 0.02~1.0% scope.It should be noted that more preferably 0.1~0.6%.
Mo occurs solid solution or further forms carbide and have the function that inhibition strength reduction.It is such in order to obtain Effect is, it is necessary to contain more than 0.005%.On the other hand, the toughness that can cause welding heat affected zone is largely contained more than 1.0% Reduce.Therefore, in the case of containing Mo, Mo contents are preferably limited to 0.005~1.0% scope.It should be noted that more Preferably 0.005~0.01%.
V is that solid solution occurs or further forms precipitate (carbide) and contributes to the increased element of intensity.To be terrible To such effect, it is necessary to contain more than 0.002%.On the other hand, even if containing having more than 0.10%, effect also saturation, it is impossible to Expect the effect being consistent with content, therefore, it is unfavorable economically to become.Therefore, in the case of containing V, V content preferably limits For 0.002~0.10% scope.It should be noted that more preferably 0.002~0.02%.
B is that segregation occurs, improve quenching degree with micro containing and contributes to the increased element of intensity in crystal boundary.In order to Such effect is obtained, it is necessary to contain more than 0.0002%.On the other hand, more than 0.003% largely containing sometimes, toughness is on the contrary Reduce.Therefore, in the case of containing B, B content is preferably limited to 0.0002~0.003% scope.It should be noted that More preferably 0.0002~0.001%.
Selected from Ca：0.0005~0.003%, REM：One or both of 0.0005~0.010%
Ca, REM are to contribute to the member that ductility, toughness improve by the form control action of sulfide-based field trash Element.Such effect is, it is necessary to contain Ca in order to obtain：More than 0.0005%, REM：More than 0.0005%.On the other hand, even if Ca：More than 0.003%, REM：Contain more than 0.010%, effect also saturation, it is impossible to expect the effect being consistent with content, because This, it is unfavorable economically to become.Therefore, in the case of containing one or both of Ca, REM, it is preferably limited to Ca： 0.0005~0.003%, REM：0.0005~0.010% scope.
Surplus beyond mentioned component is made of Fe and inevitable impurity.It should be noted that as inevitable Impurity, As can be allowed：Less than 0.03%, Sb：Less than 0.01%, Sn：Less than 0.02%, Pb：Less than 0.01%, Bi： Less than 0.01%.
Then, to the present invention high-strength steel plate tissue limit the reason for illustrate.
The high-strength steel plate of the present invention has above-mentioned composition and in the thickness of slab direction whole region in addition to steel plate top layer To be calculated as using volume fraction more than 80% bainite mutually as principal phase, the second phase by total volume fraction as less than 20% (including 0%) the tissue formed more than one or both of ferritic phase, pearlite, martensite.
It is 400N/mm to keep yield strength under conditions of more than thickness of slab 70mm2High intensity and high tenacity above, The high-strength steel plate of the present invention is mutually used as principal phase using bainite.When principal phase is the phase beyond bainite phase, for thickness of slab 70mm For steel plate as above, it is difficult to have above-mentioned high intensity and high tenacity concurrently.It should be noted that described herein is " main Phase " refers to account for more than 80% phase in terms of volume fraction.
For the high-strength steel plate of the present invention, the second phase beyond principal phase be set as total volume fraction for 20% with Under (including 0%) more than one or both of ferritic phase, pearlite, martensite.Second phase is super in terms of volume fraction When crossing 20% and becoming a large amount of, it is impossible to ensure desired high intensity.Therefore, it is less than 20% that the second phase, which is defined to total volume fraction, (including 0%) is selected from more than one or both of ferritic phase, pearlite, martensite.It should be noted that the second phase bag Include and be calculated as 0% with volume fraction.I.e., it is possible to it is 100% bainite phase.
Then, the preferable manufacture method of the high-strength steel plate of the present invention is illustrated.
In the present invention, heating process and hot-rolled process are implemented to the steel former material of above-mentioned composition and is made more than thickness of slab 70mm Steel plate.It should be noted that the manufacture method of steel former material need not be particularly limited to, from the viewpoint of productivity, preferably such as Lower method：The molten steel of above-mentioned composition is subjected to melting using the common smelting furnace such as converter, passes through the common casting such as continuous metal cast process Slab is made in method, and steel former material is made.It should be noted that can certainly be made up of ingot casting-split rolling method method steel disc and Steel former material is made.
Then implement the heating process for hot rolling to obtained steel former material.In heating process, steel former material is heated To the temperature that heating-up temperature is 900~1200 DEG C.
Heating-up temperature：900~1200 DEG C
When heating-up temperature is less than 900 DEG C, thermal change form drag becomes excessive, the load of milling train is increased, it is difficult to be made predetermined The steel plate of shape.On the other hand, when heating-up temperature is changed into high temperature more than 1200 DEG C, oxidation becomes notable and yield rate drops It is low, and coarse grains, it is impossible to ensure desired high tenacity.Therefore, heating-up temperature is defined to the temperature of 900~1200 DEG C of scopes Degree.It is preferably 1050~1150 it should be noted that from the viewpoint of the phase transformation texture with desired aggregation degree is formed ℃.In addition, in the case where the temperature of steel former material remains able to implement the high temperature of the degree of hot rolling, can be not to the steel former material It is additionally carried out in the state of heating or carries out to implement hot rolling after in the stove of short time loading.
Hot-rolled process is implemented to the steel former material after heating.Hot-rolled process be set as including once rolling, it is secondary rolling and The process of cooling after rolling.
Once rolling is set as accumulating reduction ratio within the temperature range of being calculated as 1000~850 DEG C using surface temperature as 9% Following rolling.
By implementing once to roll within this temperature range, austenite grain will not coarsening and homogenize, therefore, phase transformation The uneven reduction of texture.When rolling temperature is calculated as the temperature more than 1000 DEG C with surface temperature, the excessive coarsening of austenite grain, Even if desired tissue can not be formed by hot rolling afterwards.On the other hand, rolling temperature is less than 850 DEG C with land surface pyrometer When, become austenite non-recrystallization temperature range, harmful effect is brought to the homogenization of crystal grain.Therefore, once rolling is set as Carried out within the temperature range of being calculated as 1000~850 DEG C with surface temperature.
In addition, accumulation reduction ratio increase in the temperature range and during more than 9%, it is impossible to ensure the expectation in secondary rolling Reduction ratio, it is impossible to realize the distribution of the brittle-cracking propagation Stopping Ability in desired thickness of slab direction.For the above reasons, once Rolling is defined to be calculated as accumulating reduction ratio using surface temperature within the temperature range of 1000~850 DEG C as less than 9% rolling.Need It is noted that in once rolling, from the viewpoint of the whole grain of austenite grain, every time reduction ratio is preferably set It is about 3%~about 5%.
In addition, secondary rolling is set as every time reduction ratio within the temperature range of being calculated as 900~600 DEG C with surface temperature For more than the 7%, rolling that accumulation reduction ratio is more than 55% and rolling end temp is 800~550 DEG C.
By implementing secondary rolling within this temperature range, can promote to stop brittle-cracking propagation in thickness of slab interior zone The only prosperity for the texture that performance improves.
Within the temperature range of being calculated as 900~600 DEG C with surface temperature, surface of steel plate is nearby changed into two-phase temperature range, It is austenite region inside steel plate, when implementing the rolling that every time reduction ratio is more than 7%, rolling strain is intensively imported Inside steel plate, the prosperity of texture can be promoted.As a result, in thickness of slab central portion region, stop for improving brittle-cracking propagation Performance is effective, the X-ray diffraction intensity ratio raising in (100) face parallel with plate face (rolling surface), (211) face.Every time pressure When lower rate is less than 7%, rolling strain is weak to the importing inside steel plate, can not form desired texture.It should be noted that from true Protect from the viewpoint of the width of the texture developed region in desired thickness of slab central portion, every time reduction ratio is preferably set to 9% More than.
In addition, when the reduction ratio accumulation in the temperature range is less than 55%, in thickness of slab central portion region for improving brittleness Crack propagation Stopping Ability is effective, parallel with plate face (rolling surface) after phase transformation (100) face, the X-ray diffraction in (211) face are strong Degree is than being less than desired value, it is impossible to ensures desired brittle-cracking propagation Stopping Ability.Therefore, secondary rolling is defined to table Within the temperature range of surface thermometer is 900~600 DEG C every time reduction ratio be more than 7%, accumulation reduction ratio be more than 55% Rolling.It should be noted that preferably, every time reduction ratio is more than 9%, and reduction ratio is accumulated for more than 60%.Separately On the one hand, from the viewpoint of the excessive load load to milling train, every time reduction ratio is preferably less than 15%, in addition, accumulation Reduction ratio is preferably less than 75%.
It should be noted that the rolling end temp of secondary rolling is set as 800~550 DEG C of temperature.Rolling terminates temperature Spend for high temperature more than 800 DEG C when, the prosperity of texture becomes inadequate.On the other hand, when rolling end temp less than 550 DEG C, The plastic strain accumulated in crystal grain becomes excessive, and toughness reduces, it is thus impossible to ensure desired brittle-cracking propagation stopping property Energy.
After hot rolling, according to the cooling speed of more than 5 DEG C/sec of the average out to of the temperature range of 790~540 DEG C of land surface pyrometer The cooling that degree is cooled to 450~400 DEG C stops temperature.
It is cooled slow when cooling velocity after hot rolling is less than 5 DEG C/sec, even if under composition within the scope of the present invention also not The tissue untill thickness of slab 1/2t positions can be made to become the tissue that bainite is mutually principal phase.It should be noted that cooling velocity The upper limit need not be particularly limited to, and from the viewpoint of the generation for suppressing martensitic phase, be preferably set to less than 30 DEG C/sec.It is in addition, flat Equal cooling velocity is preferably 5~15 DEG C/sec.
In addition, when cooling stops temperature more than 450 DEG C, the amount of the second phase beyond bainite phase is exceeded in terms of volume fraction 20%, it is impossible to ensure desired steel plate tissue.When on the other hand, less than 400 DEG C, there is martensitic phase, it is impossible to ensure it is expected Steel plate tissue.For the above reasons, the cooling setpoint after hot rolling is according to the temperature of 790~540 DEG C of land surface pyrometer The cooling that the cooling velocity of more than 5 DEG C/sec of the average out to of scope is cooled to 450~400 DEG C stops temperature.
Embodiment
The molten steel formed table 1 Suo Shi is subjected to melting using converter, slab (wall thickness is made using continuous metal cast process：300mm), make Into steel former material.To the heating process of condition shown in these steel former material implementation tables 2 and including once rolling, secondary rolling and cooling Hot-rolled process, is made the steel plate of thickness of slab shown in table 2.
Table 2
* the accumulation reduction ratio) being calculated as with surface temperature within the temperature range of 1000~850 DEG C
*) the accumulation reduction ratio within the temperature range of 900~600 DEG C is calculated as with surface temperature
* *) surface temperature
* * *) average cooling rate within the temperature range of 790~540 DEG C is calculated as with surface temperature
Test film is cut from obtained steel plate, implements structure observation, tension test, impact test, texture determination examination Test, the intensity, brittle-cracking propagation Stopping Ability index Y to each steel plate are evaluated.It should be noted that test method is such as It is lower described.
(1) structure observation
Structure observation is cut from the thickness of slab direction each position (1/6t, 1/3t, 1/2t of thickness of slab) of obtained steel plate to use Test film, in a manner of viewing surface is in parallel with rolling direction section in the section of thickness of slab direction, is ground, corrodes (corruption Lose liquid：Nital), utilize light microscope (multiplying power：500 times) or scanning electron microscope (multiplying power：1000 times) see Tissue is examined, is shot.It should be noted that the overview setup of tissue is more than each 2 visual field.
Using obtained macrograph, the tissue of each phase obtains each visual field by the identification and image analysis of tissue Percentage (volume %), arithmetic average, the tissue as the position of the steel plate are carried out by the tissue percentage in each visual field Percentage.
(2) tension test
From the thickness of slab direction each position (thickness of slab of obtained steel plate in a manner of test film length direction is rolling direction 1/6t, 1/3t, 1/2t) cut No. 4 test films of JIS, the regulation according to JIS Z 2241 carries out tension test, obtains stretching Characteristic (yield strength YS, tensile strength TS).
(3) impact test
Regulation according to JIS Z 2242 is in a manner of test film length direction is parallel with rolling direction from obtained thickness The thickness of slab direction each position (1/6t, 1/3t, 1/2t of thickness of slab) of steel plate cuts V notch Charpy-type test pieces, according to JIS Z 2242 regulation implements Charpy-type test, obtains fracture transition temperature vTrs (DEG C).
(4) texture determination is tested
Abreast cut out with plate face from the thickness of slab direction each position (1/6t, 1/3t, 1/2t of thickness of slab) of obtained steel plate Take X-ray diffraction test film (size：1.5mm thickness × 24mm width × 25mm length), be with aspect of measure (24 × 25mm) The mode of thickness of slab direction each position, implements mechanical lapping and chemical grinding, after removing machined layer, is measured using X-ray diffraction method (100) face, the X-ray diffraction intensity in (211) face.It should be noted that preparing random experiment piece, similarly measure X-ray and spread out Penetrate intensity.The ratio between X-ray diffraction intensity of obtained X-ray diffraction intensity and random experiment piece is obtained respectively, as thickness of slab X-ray diffraction intensity ratio, the X-ray diffraction intensity ratio in (211) face in (100) face parallel with plate face of direction position.
On obtained as a result, by thickness of slab 1/6t positions the results are shown in table 3, the result of thickness of slab 1/3t positions is shown In table 4, by thickness of slab 1/2t positions the results are shown in table 5.
Then, according to obtained as a result, using following formula to thickness of slab direction each position (the 1/ of thickness of slab of each steel plate 6t, 1/3t, 1/2t each position) brittle-cracking propagation Stopping Ability index Y evaluated.
Y=vTrs-12 × I(100)-22×I(211)…(A)
Wherein, vTrs：The fracture transition temperature (DEG C) of Charpy-type test,
I(100)：The X-ray diffraction intensity ratio in (100) face parallel with rolling surface (plate face),
I(211)：The X-ray diffraction intensity ratio in (211) face parallel with rolling surface (plate face).
The index Y of obtained thickness of slab direction position is shown in table 3~5 in the lump.Then, using obtained plate The index Y of thick direction position, to whether meeting following (1) formulas, (2) formula is evaluated, and situation about meeting is evaluated as "○", "×" is evaluated as by situation in addition.Will be obtained evaluation result is shown in table in 6.
Y1/3t≤0.9Y1/2t…(1)
Y1/6t≥0.8Y1/2t…(2)
In addition, ESSO test films (whole thickness) are cut from each steel plate, according to brittle crack Crack Arrest Design policy (financial group Legal person Nippon Kaiji Kyokai BJ Office (2009)) appendix A, implement temperature-gradient type ESSO experiment, obtain vessel designs temperature：-10℃ Under the brittle-cracking propagation of whole thickness stop toughness value Kca-10℃.By the obtained ESSO results tested and brittle crack The result for propagating Stopping Ability index Y is shown in Table 6 together.
Table 3
*)B：Bainite phase, F：Ferritic phase, P：Pearlite, M：Martensitic phase
**)Y1/6t=(vTrs)1/6t-12×{I(100)}1/3t-22×{I(211)}1/6t ··(c)
Table 4
*)B：Bainite phase, F：Ferritic phase, P：Pearlite, M：Martensitic phase
**>Y1/3t=(vTrs)1/3t-12×{I(100)}1/3t-22×{I(211)}1/3t ··(b)
Table 5
*)B：Bainite phase, F：Ferritic phase, P：Pearlite, M：Martensitic phase
**)Y1/2t=(vTrs)1/2t-12×{I(100)}1/2t-22×{I(211)}1/2t ··(a)
Table 6
*）Y1/3t≤0.9Y1/2t …(1)
**)Y1/6t≥0.8Y1/2t …(2)
* * will（1）Formula and（2) situation that formula all meets is set as "○", will be set as "×" in addition
The brittle-cracking propagation Stopping Ability index Y of thickness of slab direction each position (1/6t, 1/3t, 1/2t) meet (1) formula and (2) example of the present invention of the particular kind of relationship of formula is that yield strength YS is 400N/mm2Above and temperature：Whole thickness at -10 DEG C The brittle-cracking propagation of degree stops toughness value Kca-10℃For 9500N/mm3/2There is the above high brittle-cracking propagation to stop property The high-strength steel plate of energy.On the other hand, the brittle-cracking propagation Stopping Ability index Y in thickness of slab 1/3t portions is high temperature, thickness of slab side The particular kind of relationship of (1) and (2) formula is unsatisfactory for the brittle-cracking propagation Stopping Ability index Y of each position (1/6t, 1/3t, 1/2t) Comparative example in, Kca-10℃Less than 9500N/mm3/2, the reduction of brittle-cracking propagation Stopping Ability.

Claims (9)

1. a kind of structure high-strength steel plate, it is characterised in that thickness of slab t is more than 70mm, thickness of slab defined in following (a) formula Brittle-cracking propagation Stopping Ability index Y at 1/2t positions1/2tDefined in (DEG C), following (b) formula at thickness of slab 1/3t positions Brittle-cracking propagation Stopping Ability index Y1/3tBrittle crack defined in (DEG C) and following (c) formula at thickness of slab 1/6t positions Propagate Stopping Ability index Y1/6t(DEG C) meets following (1) formulas and (2) formula,
Y1/3t≤0.9Y1/2t…(1)
Y1/6t≥0.8Y1/2t…(2)
Y1/2t=(vTrs)1/2t-12×{I(100)}1/2t-22×{I(211)}1/2t‥(a)
Y1/3t=(vTrs)1/3t-12×{I(100)}1/3t-22×{I(211)}1/3t‥(b)
Y1/6t=(vTrs)1/6t-12×{I(100)}1/6t-22×{I(211)}1/6t‥(c)
Wherein, (vTrs)1/2t、(vTrs)1/3t、(vTrs)1/6tFor the fracture of the V notch Charpy-type tests of thickness of slab position Transition temperature (DEG C),
{I(100)}1/2t、{I(100)}1/3t、{I(100)}1/6tX-ray for (100) face parallel with plate face of thickness of slab position is spread out Penetrate intensity ratio,
{I(211)}1/2t、{I(211)}1/3t、{I(211)}1/6tX-ray for (211) face parallel with plate face of thickness of slab position is spread out Penetrate intensity ratio.
2. structure high-strength steel plate as claimed in claim 1, wherein, thickness of slab is below 100mm.
3. structure high-strength steel plate as claimed in claim 1 or 2, wherein, the brittle-cracking propagation Stopping Ability refers to Mark Y1/3t(DEG C) is less than -150 DEG C.
4. such as structure high-strength steel plate according to any one of claims 1 to 3, wherein, have：
Contain C in terms of quality %：0.03~0.20%, Si：0.03~0.5%, Mn：0.5~2.5%, P：Less than 0.03%, S： Less than 0.01%, Al：0.005~0.08%, Nb：0.005~0.05%, Ti：0.005~0.03%, N：Less than 0.0050% And surplus is made of what Fe and inevitable impurity were formed；With
The bainite that more than 80% is calculated as using volume fraction mutually (is wrapped as main body, the second phase by total volume fraction as less than 20% Include the tissue formed more than one or both of ferritic phase, pearlite, martensite 0%).
5. structure high-strength steel plate as claimed in claim 4, wherein, the composition is also contained in terms of quality % to be selected from Ni：0.05~3%, Cu：0.05~1.5%, Cr：0.02~1.0%, Mo：0.005~1.0%, V：0.002~0.10%, B： More than one or both of 0.0002~0.003%.
6. structure high-strength steel plate as described in claim 4 or 5, wherein, the composition is in terms of quality % also containing choosing From Ca：0.0005~0.003%, REM：One or both of 0.0005~0.010%.
7. a kind of manufacture method of structure high-strength steel plate, wherein, implement heating process and hot-rolled process, system to steel former material Into the steel plate that thickness of slab t is more than 70mm, the manufacture method is characterized in that,
The steel former material is set as having and contains C in terms of quality %：0.03~0.20%, Si：0.03~0.5%, Mn：0.5 ~2.5%, P：Less than 0.03%, S：Less than 0.01%, Al：0.005~0.08%, Nb：0.005~0.05%, Ti：0.005 ~0.03%, N：Less than 0.0050% and the steel former material formed that is made of Fe and inevitable impurity of surplus,
The heating process is set as the steel former material being heated to the process of the temperature of 900~1200 DEG C of heating-up temperature,
The hot-rolled process is set as following process：Implement within the temperature range of being calculated as 1000~850 DEG C with surface temperature The once rolling that reduction ratio is less than 9% is accumulated, then, is implemented within the temperature range of being calculated as 900~600 DEG C with surface temperature Every time reduction ratio is more than 7%, accumulation reduction ratio is more than 55% and rolling end temp be calculated as 800 with surface temperature~ 550 DEG C of secondary rolling, then, according to more than 5 DEG C/sec of the average out to for the temperature range that 790~540 DEG C are calculated as with surface temperature Cooling velocity be cooled to 450~400 DEG C cooling stop temperature,
The brittle-cracking propagation Stopping Ability index Y that thickness of slab direction each position is made meets the thickness of following (1) formulas and following (2) formulas Steel plate,
Y1/3t≤0.9Y1/2t…(1)
Y1/6t≥0.8Y1/2t…(2)
Wherein, Y1/2t=(vTrs)1/2t-12×{I(100)}1/2t-22×{I(211)}1/2t‥(a)
Y1/3t=(vTrs)1/3t-12×{I(100)}1/3t-22×{I(211)}1/3t‥(b)
Y1/6t=(vTrs)1/6t-12×{I(100)}1/6t-22×{I(211)}1/6t‥(c)
It should be noted that (vTrs)1/2t、(vTrs)1/3t、(vTrs)1/6tFor the V notch Charpy tests of thickness of slab position Fracture transition temperature (DEG C),
{I(100)}1/2t、{I(100)}1/3t、{I(100)}1/6tX-ray for (100) face parallel with plate face of thickness of slab position is spread out Penetrate intensity ratio,
{I(211)}1/2t、{I(211)}1/3t、{I(211)}1/6tX-ray for (211) face parallel with plate face of thickness of slab position is spread out Penetrate intensity ratio.
8. the manufacture method of structure high-strength steel plate as claimed in claim 7, wherein, the composition is gone back in terms of quality % Containing selected from Ni：0.05~3%, Cu：0.05~1.5%, Cr：0.02~1.0%, Mo：0.005~1.0%, V：0.002~ 0.10%th, B：More than one or both of 0.0002~0.003%.
9. the manufacture method of structure high-strength steel plate as claimed in claim 7 or 8, wherein, the composition is with quality % Meter, which also contains, is selected from Ca：0.0005~0.003%, REM：One or both of 0.0005~0.010%.
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CN109023137A (en) * 2018-09-04 2018-12-18 南京钢铁股份有限公司 A kind of high-strength steel sheet that brittle crack crack arrest characteristic is excellent and its manufacturing method
CN111500931A (en) * 2020-05-22 2020-08-07 包头钢铁（集团）有限责任公司 Preparation method of Q460 hot-rolled round steel for rare earth low-temperature-resistant automobile parts

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