CN105102651A - High strength thick steel plate with superior brittle crack arrestability for high heat input welding and method for manufacturing same - Google Patents
High strength thick steel plate with superior brittle crack arrestability for high heat input welding and method for manufacturing same 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
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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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
- 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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- 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
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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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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- 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- 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
- C21D2201/00—Treatment for obtaining particular effects
- C21D2201/05—Grain orientation
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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
- C21D2211/004—Dispersions; Precipitations
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- C—CHEMISTRY; METALLURGY
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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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Abstract
Provided are a high strength thick steel plate, which has superior brittle crack arrestability for high heat input welding that has a plate thickness of 50 mm or greater and is suitably used in marine vessels, and a manufacturing method for the same. The present invention is a thick steel plate and a manufacturing method for the same, wherein the thick steel plate has: a specific component composition, a metal structure composed mainly of ferrite, and an aggregate structure in which the density at the RD//(110) plane at the surface layer of the plate thickness is 1.3 or greater and the density at the RD//(110) plane in the center part of the plate thickness is 1.8 or greater. Charpy fracture appearance transition temperature (vTrs) is -50 DEG C or less at the surface layer and in the center part of the plate thickness.
Description
Technical field
The present invention relates to brittle-cracking propagation stopping characteristics (brittlecrackarrestability) excellent Large Heat Input Welding (highheatinputwelding) high tensile steel plate (high-strengththicksteelplate) and manufacture method thereof, be particularly suitable for the high tensile steel plate of more than the thickness of slab 50mm of boats and ships.
Background technology
For the large structures such as boats and ships, the impact that the accident that brittle rupture (brittlefracture) brings produces economy and environment is very large.Therefore, usually require to improve security, for used steel, require Tough (toughness) and brittle-cracking propagation stopping characteristics Xia use temperature.
The thick-wall materials of high strength is used for ship hull plate (outerplateofship'shull) by the boats and ships such as container-ship, bulk carrier in its structure.Recently, along with the maximization of hull, high-strength thick is further developed, usually, the brittle-cracking propagation stopping characteristics of steel plate has high strength or the tendency that is more deteriorated of thick-wall materials, therefore, also improves further the requirement of brittle-cracking propagation stopping characteristics.
As the method making the brittle-cracking propagation stopping characteristics of steel improve, the method for known increase Ni content, in the storage tank of natural gas liquids (LNG:LiquefiedNaturalGas), uses 9%Ni steel with commercial size all the time.
But the increase of Ni amount has to make cost significantly increase, and therefore, is difficult to the purposes be applied to beyond LNG storage tank.
On the other hand; for do not reach the such pole low temperature (ultralowtemperature) of LNG, for boats and ships or pipeline, thickness of slab is less than the thinner steel of 50mm; TMCP (Thermo-MechanicalControlProcess can be passed through; thermomechanical Controlling Technology) method realizes grain refined and Di Wen Tough improved, thus giving excellent brittle-cracking propagation stopping characteristics.
In addition, propose the steel organizing micronization (ultrafinegrainedsteel) of skin section in patent documentation 1 to make brittle-cracking propagation stopping characteristics improve under the prerequisite not making cost of alloy increase.
The feature of the steel of the excellent in brittle-cracking propagation stopping characteristics that patent documentation 1 is recorded is, the shear lip (plastic deformation area shear-lips) produced in steel thickness of slab skin section when being conceived to brittle-cracking propagation is effective to the raising of brittle-cracking propagation stopping characteristics, make the crystal grain miniaturization of shear lip part, thus the Propagation of Energy that the brittle crack absorbing propagation has.
In addition, in patent documentation 1, following content is described: by the controlled cooling model after hot rolling, thickness of slab surface part is cooled to Ar
3transformation temperature (transformationpoint) below, then, stop controlled cooling model (controlledcooling), thickness of slab surface part is reheated more than (recuperate) to transformation temperature, repeatedly carry out more than 1 time above-mentioned operation, during this period rolling is implemented to steel, make it repeatedly undergo phase transition or process recrystallize thus, generate ultramicrofine ferritic structure (ferritestructure) or bainite structure (bainitestructure) in thickness of slab surface part.
In addition, following content is described: for using ferrite-pearlite (pearlite) as the steel of main body microstructure in patent documentation 2, improve to make brittle-cracking propagation stopping characteristics, importantly two surface elements of steel are made up of the layer with more than 50% ferritic structure, described ferritic structure has that round equivalent grain size (circle-equivalentaveragegrainsize) is less than 5 μm, length-to-diameter ratio (aspectratioofthegrains) is the ferrite crystal grain of more than 2, and suppresses the deviation of ferrite particle diameter.As the method suppressing deviation, the maximum depression rate (maximumrollingreduction) of every 1 passage in finish rolling is set as less than 12%, thus suppresses the recrystallize phenomenon of local.
But, the steel of excellent in brittle-cracking propagation stopping characteristics recorded in patent documentation 1,2 are by carrying out reheating after only steel thickness of slab skin section temporarily being cooled again and implementing processing and specifically organized in reheating, therefore, wayward under actual production scale.Particularly for thickness of slab more than 50mm thick-wall materials for, be the technique large to the load of rolling, cooling apparatus.
On the other hand, describe the miniaturization being not only conceived to ferrite crystal grain in patent documentation 3 but also be conceived to the subgrain (subgrain) be formed in ferrite crystal grain and the TMCP elongation technology that brittle-cracking propagation stopping characteristics is improved.
Specifically, when thickness of slab is the steel plate of 30 ~ 40mm, without the need to carrying out the cooling on steel plate top layer and the complicated temperature such as reheating and control, by following condition, brittle-cracking propagation stopping characteristics is improved: (a) guarantees the rolling condition of fine ferrite crystal grain, b () generates the rolling condition of fine ferrite structure in the part of more than 5% of steel thickness of slab, c () is made texture (texture) flourishing and utilizes heat energy the dislocation (dislocation) introduced by processing (rolling) configured again and form the rolling condition of subgrain in fine ferrite, d () suppresses the cooling conditions of the coarsening of fine ferrite crystal grain and the fine subgrain formed.
In addition, also knownly in controlled rolling, rolling applied to the ferrite after phase transformation and make the method that texture is flourishing, thus brittle-cracking propagation stopping characteristics is improved.The stress that the method relaxes brittle crack front end by producing breach (separation) along the direction parallel with plate face on the surface of fracture of steel improves the resistance to brittle rupture.
Such as, following content is described: make (110) face X-ray intensity ratio (X-rayplaneintensityratiointhe (110) planeshowingatexturedevelopingdegree) be more than 2 by controlled rolling and make the coarse grain justifying equivalent diameter (diameterequivalenttoacircleinthecrystalgrains) more than 20 μm be less than 10%, making resistance to brittle rupture characteristic improve thus in patent documentation 4.
Patent Document 5 discloses a kind of steel plate of steel for welded structures of the excellent in brittle-cracking propagation stopping characteristics as seam, it is characterized in that, the X-ray face strength ratio in (100) face on the rolling surface of thickness of slab inside is more than 1.5, and describes and utilize the angle deviation in mechanical load direction and the crack propagation direction produced by the prosperity of this texture can obtain excellent brittle-cracking propagation stopping characteristics.
Prior art document
Patent documentation
Patent documentation 1: Japanese Patent Publication 7-100814 publication
Patent documentation 2: Japanese Unexamined Patent Publication 2002-256375 publication
Patent documentation 3: Japanese Patent No. 3467767 publication
Patent documentation 4: Japanese Patent No. 3548349 publication
Patent documentation 5: Japanese Patent No. 2659661 publication
Patent documentation 6: Japanese Patent No. 3546308 publication
Non-patent literature
Non-patent literature 1: aboveground etc.: thick hand shipbuilding Steel To お け Ru Long large fragility I splits that Den broadcasts Behavior Move (heavy wall makes the brittle-cracking propagation characteristic of growing up of ship steel), Japanese boats and ships ocean engineering can give a lecture collection of thesis the 3rd phase, 2006, pp359 ~ 362
Summary of the invention
Invent problem to be solved
Recently, in the Large Container Ship more than 6000TEU (Twenty-footEquivalentUnit, twenty-foot equivalent unit), use thickness of slab more than the steel plate of 50mm.In non-patent literature 1, the brittle-cracking propagation stopping characteristics of the steel plate of thickness of slab 65mm is evaluated, and report the result that brittle crack does not stop in the large-scale brittle-cracking propagation stopping test of mother metal.
In addition, in standard ESSO test (ESSOtestcompliantwithWES3003) for examination material, the value (following, to be also recited as Kca (-10 DEG C)) demonstrating the Kca under the use temperature of-10 DEG C is less than 3000N/mm
3/2result, when applying the hull structure of thickness of slab more than the steel plate of 50mm, suggesting and guaranteeing that security becomes problem.
From manufacturing condition, disclosed experimental data, the steel plate of excellent in brittle-cracking propagation stopping characteristics recorded in above-mentioned patent documentation 1 ~ 5 with the steel plate of the thickness of slab of about 50mm for main object.When technology described in patent documentation 1 ~ 5 is applied to the thick-wall materials more than 50mm, the unclear characteristic that can obtain specifying, in hull structure for the characteristic of the crack propagation in thickness of slab direction, must not be verified completely.
On the other hand, along with the wall thickening of steel plate, in welding procedure, apply the Large Heat Input Welding of union-melt weld (submergedarcwelding), electro-gas welding (electrogasarcwelding) and electroslag welding (electroslagwelding) etc. efficient (highefficiency).Usually known, if weld heat input increases, then welding heat affected zone (HeatAffectedZone; HAZ) organize coarsening, therefore, the toughness of welding heat affected zone declines.In order to solve the problem of the toughness reduction caused by such Large Heat Input Welding, have developed high input energy welding steel material, and practical.Such as, Patent Document 6 discloses following technology: by controlling the TiN separated out in steel, prevent the coarsening (coarsening) of welding heat affected zone tissue, simultaneously by the dispersion of ferrite product nucleus, promote ferrite transformation in crystal grain, make welding heat affected zone high malleableize thus.But, although the good-toughness of the welding heat affected zone in Large Heat Input Welding portion, do not consider brittle-cracking propagation stopping characteristics, do not obtain the steel meeting two characteristics.
Therefore, the object of the invention is to, the Large Heat Input Welding high tensile steel plate of the excellent in brittle-cracking propagation stopping characteristics providing the industrial extremely easy technique that can be controlled the texture on thickness of slab direction by optimization composition of steel and rolling condition stably to manufacture and manufacture method thereof.
For the method for dealing with problems
The present inventors conducts in-depth research repeatedly in order to realize above-mentioned problem, even the high-strength steel plate also having an excellent crack propagation stop performance about thick steel sheet obtains following opinion.
1. for the Plate Steel of thickness of slab more than 50mm, the fracture that detailed examination standard ESSO tests, result, when becoming the fracture morphology as shown in Fig. 1 (b), along with the width of brittle crack reduces, the stress magnification factor of crackle leading section reduces, and the crack arrest characteristic of result steel plate improves.The crackle 3 entered from breach 2 that Fig. 1 (a) (b) schematically illustrates standard ESSO test film 1 stops propagating with front end geometry 4 mother metal 5.
2., in order to obtain fracture morphology as above, need the crack arrest characteristic improving thickness of slab skin section and thickness of slab central part.As the method making the crack arrest characteristic of thickness of slab skin section and thickness of slab central part improve, it is effective that thickness of slab skin section and thickness of slab central part Tough are improved.But for the Plate Steel that thickness of slab is such more than 50mm, speed of cooling and draft etc. exist restriction, thus also boundary is existed for raising thickness of slab central part Tough.
3. as the method also making crack arrest characteristic improve except improving toughness, the texture controlling thickness of slab central part is effective, particularly make (110) face gather abreast relative to rolling direction, it is effective for carrying out texture controlling in the mode making the crackle that rolling direction or plate width direction develop depart from obliquely from rolling direction or plate width direction respectively.
4. be more than 20% by the accumulation draft under the state that makes to be in austenite recrystallization temperature district at thickness of slab central part, and the average draft making every 1 passage is in addition, less than 5.0%, realizes the miniaturization of the tissue of thickness of slab skin section.Then, be more than 40% by the accumulation draft under the state that makes to be in austenite non-recrystallization humidity province at thickness of slab central part, and make the average draft of every 1 passage be more than 7%, Tough and the texture prosperity of thickness of slab central part can be made, thus above-mentioned tissue can be realized.
5. as the method for the toughness in raising Large Heat Input Welding portion, effectively make the fine division of the complex sulfide of TiN, CaS and MnS, suppress the grain growing because welding when being exposed to high temperature, and in process of cooling afterwards, promote phase transformation in crystal grain, thus at room temperature make heat affected zone organize miniaturization.
The present invention carries out having studied in the enterprising step in obtained opinion basis.That is, the present invention is:
1. the Large Heat Input Welding high tensile steel plate of an excellent in brittle-cracking propagation stopping characteristics, it is characterized in that, steel composition is in mass % containing C:0.03 ~ 0.15%, below Si:0.50%, Mn:1.0 ~ 2.0%, below P:0.030%, S:0.0005 ~ 0.0040%, Al:0.005 ~ 0.10%, Ti:0.004 ~ 0.030%, below N:0.0036 ~ 0.0075%, Ca:0.0005 ~ 0.0030%, below O:0.0040%, and, Ca, O, each content of S meets following formula (1), surplus is made up of Fe and inevitable impurity, metal structure is based on ferrite, the aggregation degree with RD//(110) face in thickness of slab skin section is more than 1.3, the aggregation degree in the RD/ in thickness of slab central part/(110) face is the texture of more than 1.8, the summer of thickness of slab skin section and thickness of slab central part is less than-50 DEG C than fracture transition temperature vTrs,
0＜(Ca－(0.18+130×Ca)×O)/1.25/S≤0.8···(1)
Wherein, in formula (1), Ca, O, S are content (quality %).
2. the Large Heat Input Welding high tensile steel plate of the excellent in brittle-cracking propagation stopping characteristics according to 1, it is characterized in that, the summer of thickness of slab skin section and thickness of slab central part meets following (2) formula than the aggregation degree in fracture transition temperature and RD//(110) face
VTrs
(top layer)+ 1.9 × vTrs
(1/2t)-6 × I
rD//(110) [top layer]-84 × I
rD//(110) [1/2t]≤-350 (2)
Wherein, in formula (2),
VTrs
(top layer): the summer of thickness of slab skin section than fracture transition temperature (DEG C),
VTrs
(1/2t): the summer of thickness of slab central part (t/2) than fracture transition temperature (DEG C),
I
rD//(110) [top layer]: the aggregation degree in RD//(110) face of thickness of slab skin section,
I
rD//(110) [1/2t]: the aggregation degree in RD//(110) face of thickness of slab central part (t/2),
It should be noted that, t is thickness of slab (mm).
3. the Large Heat Input Welding high tensile steel plate of the excellent in brittle-cracking propagation stopping characteristics according to 1 or 2, it is characterized in that, steel composition is in mass % further containing one or more in Nb:0.003 ~ 0.050%, below Cu:0.5%, below Ni:1.0%, below Cr:0.5%, below Mo:0.5%, below W:0.4%, below V:0.2%, B:0.0003 ~ 0.0030%.
4. the Large Heat Input Welding high tensile steel plate of the excellent in brittle-cracking propagation stopping characteristics according to any one of 1 ~ 3, it is characterized in that, steel composition is in mass % further containing one or more in Mg:0.0005 ~ 0.0050%, Zr:0.001 ~ 0.020%, REM:0.001 ~ 0.020%.
5. the manufacture method of the Large Heat Input Welding high tensile steel plate of an excellent in brittle-cracking propagation stopping characteristics, it is characterized in that, to 1 be had, the former material of steel of the composition according to any one of 3 or 4 is heated to the temperature of 900 ~ 1150 DEG C, implement to add up to more than 65% at the accumulation draft of austenite recrystallization temperature district and austenite non-recrystallization humidity province, accumulation draft under the state that thickness of slab central part is in austenite recrystallization temperature district is more than 20%, and the average draft of every 1 passage is the rolling of less than 5.0%, then, the accumulation draft carried out under the state being in austenite non-recrystallization humidity province at thickness of slab central part is more than 40%, and the average draft of every 1 passage is the rolling of more than 7.0%, then, less than 600 DEG C are cooled to the speed of cooling of 4.0 DEG C/more than s.
6. the manufacture method of the Large Heat Input Welding high tensile steel plate of the excellent in brittle-cracking propagation stopping characteristics according to 5, is characterized in that, being cooled to after below 600 DEG C, having further and being tempered to A
c1the operation of the temperature that point is following.
Invention effect
According to the present invention, obtain that texture on thickness of slab direction is suitably controlled, the Large Heat Input Welding high tensile steel plate of excellent in brittle-cracking propagation stopping characteristics and manufacture method thereof.Apply the present invention to more than thickness of slab 50mm, the preferably thickness of slab steel plate more than 50mm, more preferably more than thickness of slab 55mm, further preferred more than thickness of slab 60mm, playing more significant superiority relative to the steel of prior art, is therefore effective.And, such as, in shipbuilding field, in the strength deck bilge construction of large-scale container-ship, bulk carrier, by being applied to hatch side coaming, deck member, contribute to the security improving boats and ships, therefore, industrially extremely useful.
Accompanying drawing explanation
Fig. 1 is the figure schematically representing the fracture morphology that thickness of slab is tested more than the standard ESSO of the Plate Steel of 50mm, and (a) is the figure of top view test film, and (b) is the figure of the fracture representing test film.
Embodiment
In the present invention, 1. steel compositions, 2. thickness of slab skin section and central part Tough and texture, 3. metal structure and 4. manufacturing conditions are specified.
1. steel composition
Below, the preferred chemical composition in the present invention is described.In explanation, % is quality %.
C：0.03～0.15％
C is the element of the intensity improving steel, in the present invention, in order to ensure the intensity expected, needs containing more than 0.03%.On the other hand, during more than 0.15%, not only weldability is deteriorated, and Dui Tough also has detrimentally affect.Therefore, C is made to be 0.03 ~ 0.15%.Be preferably 0.05 ~ 0.15%.
Below Si:0.50%
Si is effective as deoxidant element and as the strengthening element of steel, but when content is less than 0.01%, may not have its effect.On the other hand, during more than 0.50%, not only damage the surface texture of steel, Er Qie Tough is deteriorated.Therefore, its addition is less than 0.50%.Be preferably the scope of 0.01 ~ 0.40%.
Mn：1.0～2.0％
Mn adds as strengthening element.When being less than 1.0%, its effect is insufficient.On the other hand, during more than 2.0%, make the degraded toughness of weld part.Therefore, Mn is made to be 1.0 ~ 2.0%.Be preferably the scope of 1.1 ~ 1.8%.
Below P:0.030%
P is the impurity be unavoidably mixed into, and during more than 0.030%, the toughness of mother metal and weld part is reduced.Therefore, the upper limit is made to be 0.030%.
S：0.0005～0.0040％
In order to generate required CaS or MnS, S is necessary for more than 0.0005%.On the other hand, during more than 0.0040%, make the degraded toughness of mother metal.Therefore, S is made to be 0.0005 ~ 0.0040%.
Al：0.005～0.10％
Al works as reductor, needs containing more than 0.005% for this reason.But containing during more than 0.10%, Hui Shi Tough reduces, and welding metal Bu Tough is made to reduce when welding.Therefore, Al is defined as the scope of 0.005 ~ 0.10%.Be preferably 0.005 ~ 0.08%, more preferably 0.02 ~ 0.06%.
Ti：0.004～0.030％
For Ti, by the interpolation of trace, form nitride, carbide or carbonitride, suppress the austenitic coarsening of welding heat affected zone, and/or promote ferrite transformation as ferrite transformation core, have thus and make crystal grain miniaturization and the effect improving Mu Cai Tough.Its effect is obtained by the interpolation of more than 0.004%.But containing during more than 0.030%, make TiN particle coarsening, make mother metal and welding heat affected zone Tough reduce thus.Therefore, make Ti be 0.004 ~ 0.030% scope.Be preferably the scope of 0.006 ~ 0.028%.
N：0.0036～0.0075％
N is the necessary element of the TiN guaranteeing necessary amount.Cannot obtain sufficient TiN when being less than 0.0036% to measure, toughness of welded zone is deteriorated.When being greater than 0.0075%, when being subject to Thermal Cycle there is solid solution again, the excessive generation of solid solution N in TiN, thus toughness is significantly deteriorated.Therefore, N amount is set to 0.0036 ~ 0.0075%.Be preferably the scope of 0.0037 ~ 0.0068%.
Ca：0.0005～0.0030％
Ca is the element by the fixing of S with the effect improving toughness.In order to play this effect, need the Ca containing more than 0.0005%.But, even if more than 0.0030% containing effective also saturated.Therefore, in the present invention, Ca is defined as the scope of 0.0005 ~ 0.0030%.
Below O:0.0040%
O contains in steel as inevitable impurity, becomes oxide compound and separates out, the cleanliness factor of steel is reduced when solidifying.Therefore, preferably O is reduced as much as possible in the present invention.Particularly when O content is more than 0.0040%, CaO system inclusion coarsening and base metal tenacity is declined.Therefore, O is made to be less than 0.0040%.
In the present invention, the formula (1) below demand fulfillment.
0＜(Ca－(0.18+130×Ca)×O)/1.25/S≤0.8···(1)
Wherein, in formula (1), Ca, O, S are content (quality %).
Ca, O and S need the mode of the relation of (1) to satisfy equation and contain.Now, form CaS separated out and has the complex sulfide of MnS is become.This complex sulfide plays function as the core of ferrite transformation, and therefore the tissue of welding heat affected zone is micronized, and the toughness of welding heat affected zone is improved thus.When the value of (Ca-(0.18+130 × Ca) × O)/1.25/S is less than 0, CaS is crystallization not, and therefore S separates out with the form that MnS is independent.Extend in the rolling of this MnS when steel plate manufactures thus cause base metal tenacity to reduce, and at the welding heat affected zone MnS as the main starting point of the present invention, melting occurring, therefore cannot realize fine dispersion.On the other hand, when the value of (Ca-(0.18+130 × Ca) × O)/1.25/S is greater than 0.8, S is fixed by Ca substantially, and the MnS worked as ferrite product nucleus does not separate out on CaS, therefore cannot realize sufficient toughness and improve.The preferable range of the value of (Ca-(0.18+130 × Ca) × O)/1.25/S is 0.10 ~ 0.8%.
It is more than the preferred basal component composition in the present invention.But in order to improve characteristic further, can containing more than one in Nb, Cu, Ni, Cr, Mo, W, V, B.
Nb：0.003～0.050％
Nb with the form of NbC when ferrite transformation or the time of reheating separate out, contribute to high strength.And have the effect making Unhydrated cement expand in the rolling of austenitic area, contribute to the grain refined of ferrite and bainite, therefore the improvement of ， Dui Tough is also effective.This effect is played, therefore containing being sometimes preferably set to more than 0.003% by the Nb containing more than 0.003%.But during more than 0.050% interpolation, thick NbC separates out, and leads the reduction causing Tough on the contrary, therefore containing sometimes preferably making its upper limit be 0.050%.Be more preferably the scope of 0.005 ~ 0.040%.
Cu、Ni、Cr、Mo、W
Cu, Ni, Cr, Mo, W are the element of the hardening capacity improving steel.Directly contribute to the intensity after rolling to improve, and can add in order to functions such as Ti Gao Tough, hot strength or weathering resistancies.Their effect by playing containing more than 0.01%, therefore, when containing, be preferably more than 0.01%.But, excessively containing sometimes, Tough, weldability can be made to be deteriorated, therefore, when containing, preferably make that the upper limit of Cu is 0.5%, the upper limit of Ni is 1.0%, the upper limit of Cr is 0.5%, the upper limit of Mo is 0.5%, the upper limit of W is 0.4% respectively.
Below V:0.2%
V is by making with the form precipitation strength of V (C, N) element that the intensity of steel improves, in order to play this effect, and can containing more than 0.001%.But containing during more than 0.2%, Hui Shi Tough reduces.Therefore, when containing V, be preferably set to less than 0.2%, be more preferably set to the scope of 0.001 ~ 0.10%.
B：0.0003～0.0030％
B is the element of the hardening capacity improving steel with trace.In order to play this effect, can containing more than 0.0003%.But, containing during more than 0.0030%, weld part Tough is reduced, therefore, when containing B, is preferably set to less than 0.0030%.Be more preferably the scope of 0.0003 ~ 0.0026%.
In the present invention, in order to make characteristic improve, in mentioned component composition, more than one of Mg, Zr, REM can be contained further.
Mg：0.0005～0.0050％
Mg is the element with the effect being improved toughness by the dispersion of oxide compound, can add as required.By this effect can be played containing more than 0.0005%, therefore when containing, be preferably set to more than 0.0005%.Even if but content also can be saturated more than 0.0050% effect, therefore, when adding Mg, addition is preferably made to be 0.0005 ~ 0.0050%.
Zr：0.001～0.020％
For Zr, in steel, form oxide compound, disperseed by its oxide compound and have and make organizing miniaturization thus improving the effect of toughness of welding heat affected zone, also can not damage effect of the present invention even if add, therefore can add as required.By this effect can be played containing more than 0.001%, therefore when containing, be preferably set to more than 0.001%.But effect is saturated when excessively adding, and forms the degraded toughness that thick inclusion makes mother metal, therefore when adding, the upper limit of addition is preferably made to be 0.020%.
REM：0.001～0.020％
REM forms oxide compound in steel, is had and makes organizing miniaturization thus improving the effect of toughness of welding heat affected zone, also can not damage effect of the present invention, therefore can add as required even if add by the dispersion of its oxide compound.By this effect can be played containing more than 0.001%, therefore when containing, be preferably set to more than 0.001%.But effect is saturated when excessively adding, and forms the degraded toughness that thick inclusion makes mother metal, therefore when adding, the upper limit of addition is preferably made to be 0.020%.
In the present invention, in order to make Ca with the form crystallization of CaS, need the amount reducing the O strong with the bonding force of Ca before Ca adds in advance, the remaining oxygen amount before preferred Ca adds is less than 0.0050%.As the method reducing remaining oxygen amount, the method strengthening degassed or input reductor etc. can be taked.
Surplus beyond mentioned component is Fe and inevitable impurity.
2. thickness of slab skin section and central part Tough and texture
In the present invention, for the crackle developed along horizontal directions (in the face of steel plate direction) such as rolling direction or rolling vertical direction, in order to obtain the fracture morphology of the Fig. 1 that can improve crack propagation stop performance, be suitably defined in the aggregation degree in thickness of slab skin section and central part Tough and RD//(100) face.
First, Mu Cai Tough is well the prerequisite of the development for suppressing crackle.For steel plate of the present invention, as the toughness of thickness of slab skin section and central part, the summer of regulation thickness of slab skin section and thickness of slab central part is less than-50 DEG C than fracture transition temperature vTrs.
In addition, by making the texture in RD//(100) face flourishing, cleavage surface (cleavageplane) is gathered obliquely relative to crackle principal direction, by the effect that the stress producing the brittle crack front end that small crackle branch causes relaxes, brittle-cracking propagation Stopping Ability improves.For the nearest thickness of slab for the ship hull plate such as container-ship and bulk carrier more than 50mm thick-wall materials, guarantee safety of structure in obtain as target Kca (-10 DEG C)>=6000N/mm
3/2brittle-cracking propagation Stopping Ability when, need to make the aggregation degree in the RD/ in thickness of slab skin section/(110) face be more than 1.3, preferably more than 1.6, and make the aggregation degree in the RD/ in thickness of slab central part/(110) face be more than 1.8, preferably more than 2.0.Therefore, in the present invention, the aggregation degree in the RD/ in thickness of slab skin section/(110) face is the aggregation degree in more than 1.3, preferably more than 1.6, the RD/ in thickness of slab central part/(110) faces is more than 1.8, preferably more than 2.0.
On the other hand, when aggregation degree due to the RD/ in thickness of slab skin section or thickness of slab central part/(110) face is greater than 4.0, texture is too flourishing, the clear and definite branch of brittle crack and fine crackle branch not occurs, is difficult to play the brittle-cracking propagation Stopping Ability brought by the stress alleviation effects of brittle crack front end.Therefore, the aggregation degree in RD//(110) face in the aggregation degree in the RD/ in thickness of slab skin section/(110) face and thickness of slab central part is all preferably less than 4.0.
At this, the aggregation degree in RD//(110) face of thickness of slab skin section or thickness of slab central part refers to following numerical value.First, gather the sample of thickness of slab 1mm from thickness of slab skin section or thickness of slab central part, mechanical mill/electrolytic polishing is carried out to the face parallel with plate face, thus, prepare the test film of X-ray diffraction.It should be noted that, when thickness of slab skin section, the face close with most surface is ground.Use this test film, adopt and use the radiogenic X-ray diffraction device of Mo, enforcement X-ray diffraction measures, and obtains (200), (110) and (211) pole figure, tries to achieve three-dimensional crystals orientation density function by Bunge method by obtained pole figure calculating.Then, by obtained three-dimensional crystals orientation density function, recorded by Bunge, at ψ
2=0 ° ~ 90 ° add up in the sectional view of 19 with 5 ° of intervals, accumulation (110) face reaches the value of the three-dimensional crystals orientation density function of parallel orientation relative to rolling direction, obtain accumulated value, the value that this accumulated value obtains divided by the number of the orientation of above-mentioned accumulation is called the aggregation degree in RD//(110) face.
Except the regulation of above-mentioned Mu Cai Tough and texture, the Xia of preferred thickness of slab skin section and thickness of slab central part meets following (2) formula Bi the aggregation degree in Tough value and RD//(110) face.
VTrs
(top layer)+ 1.9 × vTrs
(1/2t)-6 × I
rD//(110) [top layer]-84 × I
rD//(110) [1/2t]≤-350 (2)
Wherein, in formula (2),
VTrs
(top layer): the summer of thickness of slab skin section is than fracture transition temperature (DEG C)
VTrs
(1/2t): the summer of thickness of slab central part is than fracture transition temperature (DEG C)
I
rD//(110) [top layer]: the aggregation degree in RD//(110) face of thickness of slab skin section
I
rD//(110) [1/2t]: the aggregation degree in RD//(110) face of thickness of slab central part
By meeting above-mentioned (2) formula, more excellent brittle-cracking propagation Stopping Ability can be obtained.
3. metal structure
In the present invention, metal structure is based on ferrite.At this, in the present invention, metal structure with ferrite be main body refer to that the area percentage of ferritic phase is entirety more than 60%.As long as the area percentage of the total of bainite, martensite (comprising island-like martensite), perlite etc. is less than 40% then can to accept in surplus.
In tissue based on ferrite, when obtaining the metal structure based on ferrite according to the rolling condition in the rolling of common austenitic area, although obtain as Mu Biao Tough, but transformation time fully exists time after rolling from austenite to ferrite transformation, therefore, the texture obtained becomes unordered, cannot realize the aggregation degree in RD//(110) face in as the thickness of slab skin section of target be more than 1.3, preferably more than 1.6, the aggregation degree in RD//(110) face of thickness of slab central part is more than 1.8, preferably more than 2.0.Therefore, as described later, by design rolling condition, even the tissue based on ferrite, the aggregation degree that also can obtain RD/ in thickness of slab skin section/(110) face is more than 1.3, preferably more than 1.6, the aggregation degree in RD//(110) face of thickness of slab central part is more than 1.8, preferably more than 2.0.
4. manufacturing condition
Below, the preferred manufacturing condition in the present invention is described.
As manufacturing condition, the preferably Heating temperature, hot-rolled condition, cooling conditions etc. of the former material of regulation steel.Particularly about hot rolling, preferably except except the accumulation draft of the total in austenite recrystallization temperature district and austenite non-recrystallization humidity province, the situation being also in austenite recrystallization temperature district to thickness of slab central part and the situation being in austenite non-recrystallization humidity province respectively provide the average draft of accumulation draft and every 1 passage.By these regulations, for the aggregation degree of the summer in the thickness of slab skin section of Plate Steel and thickness of slab central part than fracture transition temperature vTrs and RD//(110) face, the characteristic expected can be obtained.
First, the molten steel of above-mentioned composition is carried out melting by converter etc., make the former material of steel (steel billet) by continuous casting etc.
Then, after preferably former for steel material being heated to the temperature of 900 ~ 1150 DEG C, hot rolling is carried out.For terrible to good good Tough, reduce Heating temperature, reduce rolling before crystallization particle diameter be effective.But when Heating temperature is lower than 900 DEG C, the time of the rolling carrying out austenite recrystallization temperature district can not be guaranteed fully.In addition, during more than 1150 DEG C, austenite crystal is greatly thicker, and not only Dao Zhi Tough reduces, and oxidational losses is remarkable, and yield rate reduces.Therefore, Heating temperature is preferably 900 ~ 1150 DEG C.From the view point of Tough, the scope of preferred Heating temperature is 1000 ~ 1100 DEG C.
Usually, when obtaining the metal structure based on ferrite by implementing the rolling of common austenitic area, although obtain the Tough as order mark, time after rolling from austenite to ferrite transformation, transformation time fully exists, therefore, the texture obtained becomes unordered.Therefore, using the rolling of common austenitic area cannot realize in the present invention as the aggregation degree in RD/ in the thickness of slab skin section of target/(110) face be more than 1.3, preferably more than 1.6, the aggregation degree in RD//(110) face in thickness of slab central part is more than 1.8, preferably more than 2.0.Therefore, in the present invention, be preferably as follows described regulation hot-rolled condition, thus, even the tissue based on ferrite, the aggregation degree that also can obtain RD/ in thickness of slab skin section/(110) face is more than 1.3, preferably more than 1.6, the aggregation degree in RD//(110) face of thickness of slab central part is more than 1.8, preferably more than 2.0.
For hot rolling, first preferably carry out the accumulation draft of thickness of slab central part under the state being in austenite recrystallization temperature district and be more than 20% and the rolling of the average draft less than 5.0% of every 1 passage.By making this accumulation draft be more than 20%, austenite grain refined, the metal structure finally obtained also grain refined ， Tough improves.On the other hand; by making the average draft of every 1 passage in this temperature range be less than 5.0%; strain can be introduced near the particularly top layer of steel; thus; the aggregation degree in the RD/ in thickness of slab skin section/(110) face can be made to be more than 1.3, preferably more than 1.6; and then thickness of slab skin section grain refined, can obtain thickness of slab skin section Tough and improve effect.
Then, accumulation draft more than 40% under the state that is in austenite non-recrystallization humidity province in the temperature of thickness of slab central part is preferably carried out and the average draft of every 1 passage is the rolling of more than 7.0%.Be more than 40% by making the accumulation draft in this temperature range, the texture of thickness of slab central part can be made fully flourishing, and, by making the average draft of every 1 passage be more than 7.0%, the aggregation degree in the RD/ of thickness of slab central part/(110) face can be made to be more than 1.8, preferably more than 2.0.
In addition, as making above-mentioned austenite recrystallization temperature district and austenite non-recrystallization humidity province altogether overall, accumulation draft is preferably more than 65%.By making overall accumulation draft be more than 65%, can guarantee that sufficient draught ， Tough and aggregation degree can realize target values for tissue.
For austenite recrystallization temperature district and austenite non-recrystallization humidity province, can be held by the preliminary experiment carried out there is steel that this one-tenth is grouped into giving the heat/processing course making condition change.
It should be noted that, the end temp of hot rolling is not particularly limited.But from the view point of rolling efficiency, preferably in austenite non-recrystallization humidity province, make it terminate.
Steel plate after terminating for rolling, is preferably cooled to less than 600 DEG C with the speed of cooling of 4.0 DEG C/more than s.By making speed of cooling be 4.0 DEG C/more than s, can fine grained structure be obtained and can not make to organize coarsening, the excellent toughness as target can be obtained.When speed of cooling is less than 4.0 DEG C/s, organize coarsening, cannot obtain as Mu Biao Tough.By making cooling stop temperature to be less than 600 DEG C, the carrying out of recrystallize can be avoided, by hot rolling and cooling afterwards, the texture of obtained expectation can be maintained.When cooling stops temperature higher than 600 DEG C, even if recrystallize also can carry out after cooling stops, the texture expected can not be obtained.It should be noted that, above-mentioned speed of cooling and cooling stop temperature being set to the temperature of the thickness of slab central part of steel plate.The temperature of thickness of slab central part is tried to achieve by analog calculation etc. by thickness of slab, surface temperature and cooling conditions etc.Such as, by using method of finite difference, calculating the temperature distribution in thickness of slab direction, obtaining the temperature of the thickness of slab central part of steel plate.
Steel plate after terminating for cooling, also can implement temper.By implementing tempering, steel plate Tough can be improved further.Tempering temperature is set to A in steel plate medial temperature
c1point is following implements temper, thereby, it is possible to do not damage by rolling, the tissue cooling the expectation obtained.In the present invention, obtain A by following formula
c1point (DEG C).
A
c1point=751-26.6C+17.6Si-11.6Mn-169Al-23Cu-23Ni+24.1Cr+22.5Mo+23 3Nb-39.7V-5.7Ti-895B
In above-mentioned formula, each symbol of element is content (quality %) in steel, not containing being sometimes set to 0.
The medial temperature of steel plate is also same with the temperature of thickness of slab central part, is obtained by analog calculation etc. by thickness of slab, surface temperature and cooling conditions etc.
Embodiment
The molten steel (steel mark A ~ R) of each composition shown in table 1 is carried out melting by converter, makes the former material of steel (the thick 250mm of steel billet), be hot-rolled down to thickness of slab 50 ~ 80mm, then, cool by continuous metal cast process, what obtain No.1 ~ 30 supplies examination steel.For a part, also implement tempering after the cooling period.Hot-rolled condition shown in table 2, cooling conditions and tempered condition.
Table 2
Note 1: underscore represents outside the scope of the invention.
Note 2: " recrystallize γ district's accumulation draft " refers to the accumulation draft of thickness of slab central part under the state being in austenite recrystallization warm area.
Note 3: " the average draft in recrystallize γ district " refers to the average draft of every 1 passage of thickness of slab central part under the state being in austenite recrystallization temperature district.
Note 4: " non-recrystallization γ district's accumulation draft " refers to the accumulation draft of thickness of slab central part under the state being in austenite non-recrystallization humidity province.
Note 5: " the average draft in non-recrystallization γ district " refers to the average draft of every 1 passage of thickness of slab central part under the state being in austenite non-recrystallization humidity province.
Note 6: " overall accumulation draft " refers to that merging thickness of slab central part is being in the state of austenite recrystallization warm area and is being in the overall accumulation draft of state of austenite non-recrystallization humidity province.
For obtained Plate Steel, cut the JIS14A test film of Φ 14 by 1/4 of thickness of slab with the length direction of test film and rolling direction mode at a right angle, carry out tension test, measure yield-point (YS), tensile strength (TS).
Mirror ultrafinish is carried out to the thickness of slab cross section parallel with mill length direction of gained Plate Steel, then by metal structure that observation by light microscope presents through corrosion.
In addition, in order to evaluate toughness value, (following by thickness of slab skin section and thickness of slab central part, sometimes thickness of slab central part is designated as 1/2t portion) cut JIS4 shock test sheet in the mode that the direction of the major axis of test film is parallel with rolling direction, carry out Charpy impact test, obtain fracture transition temperature (vTrs) respectively.At this, the shock test sheet of thickness of slab skin section is the test film making the degree of depth being distance surface of steel plate 1mm apart from nearest face, surface.
Then, in order to evaluate brittle-cracking propagation stopping characteristics, standard ESSO test (temperature-gradient type ESSO tests) is carried out, the Kca value (Kca (-10 DEG C)) at obtaining-10 DEG C.
In order to evaluate Large Heat Input Welding characteristic, retaining wall on slope (groove angle 20 °) is implemented to for examination steel plate, use commercially available Cryogenic Steel pneumoelectric welding wire, make joint by the electro-gas welding (EGW) of Large Heat Input Welding (300 ~ 750kJ/cm).Then, for surface and the 1mm position, the back side in thickness of slab direction, use welded bonds portion to introduce the Charpy impact test sheet of breach, obtain test temperature be-20 DEG C at absorption energy: vE-20 DEG C (3 mean value), evaluate HAZ toughness thus.
In addition, the aggregation degree in RD//(110) face of thickness of slab skin section and thickness of slab central part is obtained as follows.First, cutting the sample of thickness of slab 1mm from thickness of slab skin section or thickness of slab central part, by carrying out mechanical mill/electrolytic polishing to the face parallel with plate face, preparing the test film of X-ray diffraction.It should be noted that, when thickness of slab skin section, grind the face close to most surface.Use this test film, adopt and use the radiogenic X-ray diffraction device of Mo, enforcement X-ray diffraction measures, and obtains (200), (110) and (211) pole figure, obtains three-dimensional crystals orientation density function by Bunge method from obtained pole figure calculating.Then, by obtained three-dimensional crystals orientation density function, recorded by Bunge, at ψ
2=0 ° ~ 90 ° add up in the sectional view of 19 with 5 ° of intervals, accumulation (110) face reaches the value of the three-dimensional crystals orientation density function of parallel orientation relative to rolling direction, obtain accumulated value, the value that this accumulated value obtains divided by the number of the orientation of above-mentioned accumulation is called the aggregation degree in RD//(110) face.
These test-results shown in table 3.Thickness of slab skin section and thickness of slab central part Tough value (fracture transition temperature vTrs) and texture within the scope of the invention for examination steel plate (manufacturing No.1 ~ 13) when, Kca (-10 DEG C) is 6000N/mm
3/2above, excellent brittle-cracking propagation Stopping Ability is demonstrated.And, the absorption energy of welding heat affected zone: the vE-20 DEG C of excellent value demonstrating more than 125J.In addition, the Xia of skin section and thickness of slab central part meets the confession examination steel plate (manufacturing numbering 1 ~ 13) of (2) formula Bi Tough value (fracture transition temperature) and RD//(110) aggregation degree, compared with trying steel plate (manufacturing numbering 14) with the confession not meeting (2) formula, obtain high Kca (-10 DEG C) value.In addition, these are for trying the metal structure of steel plate (manufacturing No.1 ~ 14) all based on ferrite.
On the other hand, for become to be grouped into or manufacturing condition outside the scope of the invention, the Tough of steel plate or texture do not meet regulation of the present invention for examination steel plate (manufacturing numbering 15 ~ 30), the value of Kca (-10 DEG C) is less than 6000N/mm
3/2, and/or the absorption energy of welding heat affected zone: vE-20 DEG C is less than 100J, therefore poor than the present invention's example.
Table 3
Note 1: underscore represents outside the scope of the invention.
Note 2:(2) formula vTrs
(top layer)+ 1.9 × vTrs
(1/2t)-6 × I
rD//(110) [top layer]-84 × I
rD//(110) [1/2t]≤-350
VTrs
(top layer): the fracture transition temperature (DEG C) of thickness of slab skin section,
VTrs
(1/2t): the fracture transition temperature (DEG C) of thickness of slab central part (t/2),
I
rD//(110) [top layer]: RD//(110) aggregation degree of thickness of slab skin section,
I
rD//(110) [1/2t]: RD//(110) aggregation degree of thickness of slab central part (t/2)
Note 3:1/2t portion represents thickness of slab central part.
Label declaration
1 standard ESSO test film
2 breach
3 crackles
4 front end geometry
5 mother metals
Claims (6)
1. the Large Heat Input Welding high tensile steel plate of an excellent in brittle-cracking propagation stopping characteristics, it is characterized in that, steel composition is in mass % containing C:0.03 ~ 0.15%, below Si:0.50%, Mn:1.0 ~ 2.0%, below P:0.030%, S:0.0005 ~ 0.0040%, Al:0.005 ~ 0.10%, Ti:0.004 ~ 0.030%, below N:0.0036 ~ 0.0075%, Ca:0.0005 ~ 0.0030%, below O:0.0040%, and, Ca, O, each content of S meets following formula (1), surplus is made up of Fe and inevitable impurity, metal structure is based on ferrite, the aggregation degree with RD//(110) face in thickness of slab skin section is more than 1.3, the aggregation degree in the RD/ in thickness of slab central part/(110) face is the texture of more than 1.8, the summer of thickness of slab skin section and thickness of slab central part is less than-50 DEG C than fracture transition temperature vTrs,
0＜(Ca－(0.18+130×Ca)×O)/1.25/S≤0.8…(1)
Wherein, in formula (1), Ca, O, S are mass percentage.
2. the Large Heat Input Welding high tensile steel plate of excellent in brittle-cracking propagation stopping characteristics according to claim 1, it is characterized in that, the summer of thickness of slab skin section and thickness of slab central part meets following (2) formula than the aggregation degree in fracture transition temperature and RD//(110) face
VTrs
(top layer)+ 1.9 × vTrs
(1/2t)-6 × I
rD//(110) [top layer]-84 × I
rD//(110) [1/2t]≤-350 ... (2)
Wherein, in formula (2),
VTrs
(top layer): the summer of thickness of slab skin section than fracture transition temperature (DEG C),
VTrs
(1/2t): the summer of thickness of slab central part (t/2) than fracture transition temperature (DEG C),
I
rD//(110) [top layer]: the aggregation degree in RD//(110) face of thickness of slab skin section,
I
rD//(110) [1/2t]: the aggregation degree in RD//(110) face of thickness of slab central part (t/2),
It should be noted that, t is thickness of slab (mm).
3. the Large Heat Input Welding high tensile steel plate of excellent in brittle-cracking propagation stopping characteristics according to claim 1 and 2, it is characterized in that, steel composition is in mass % further containing one or more in Nb:0.003 ~ 0.050%, below Cu:0.5%, below Ni:1.0%, below Cr:0.5%, below Mo:0.5%, below W:0.4%, below V:0.2%, B:0.0003 ~ 0.0030%.
4. the Large Heat Input Welding high tensile steel plate of the excellent in brittle-cracking propagation stopping characteristics according to any one of claims 1 to 3, it is characterized in that, steel composition is in mass % further containing one or more in Mg:0.0005 ~ 0.0050%, Zr:0.001 ~ 0.020%, REM:0.001 ~ 0.020%.
5. the manufacture method of the Large Heat Input Welding high tensile steel plate of an excellent in brittle-cracking propagation stopping characteristics, it is characterized in that, claim 1 will be had, the former material of steel of the composition according to any one of 3 or 4 is heated to the temperature of 900 ~ 1150 DEG C, implement to add up to more than 65% at the accumulation draft of austenite recrystallization temperature district and austenite non-recrystallization humidity province, accumulation draft under the state that thickness of slab central part is in austenite recrystallization temperature district is more than 20%, and the average draft of every 1 passage is the rolling of less than 5.0%, then, the accumulation draft carried out under the state being in austenite non-recrystallization humidity province at thickness of slab central part is more than 40%, and the average draft of every 1 passage is the rolling of more than 7.0%, then, less than 600 DEG C are cooled to the speed of cooling of 4.0 DEG C/more than s.
6. the manufacture method of the Large Heat Input Welding high tensile steel plate of excellent in brittle-cracking propagation stopping characteristics according to claim 5, is characterized in that, being cooled to after below 600 DEG C, having further and being tempered to A
c1the operation of the temperature that point is following.
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Also Published As
| Publication number | Publication date |
|---|---|
| KR20150119281A (en) | 2015-10-23 |
| JP5598617B1 (en) | 2014-10-01 |
| CN105102651B (en) | 2018-01-05 |
| BR112015021658A2 (en) | 2017-07-18 |
| KR20170117235A (en) | 2017-10-20 |
| JPWO2014155439A1 (en) | 2017-02-16 |
| TW201502282A (en) | 2015-01-16 |
| TWI500774B (en) | 2015-09-21 |
| WO2014155439A1 (en) | 2014-10-02 |
| KR101984531B1 (en) | 2019-05-31 |
| PH12015501681A1 (en) | 2015-10-19 |
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