CN105473753B - Steel plate and its manufacture method - Google Patents

Steel plate and its manufacture method Download PDF

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Publication number
CN105473753B
CN105473753B CN201480046492.6A CN201480046492A CN105473753B CN 105473753 B CN105473753 B CN 105473753B CN 201480046492 A CN201480046492 A CN 201480046492A CN 105473753 B CN105473753 B CN 105473753B
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steel plate
less
steel
cooling
thickness
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CN105473753A (en
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村上善明
长谷和邦
荒尾亮
远藤茂
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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
    • C22C38/18—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
    • 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
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
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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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
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    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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    • 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
    • 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

A kind of excellent steel plate of the material homogenieity of the invention provided in Large Heat Input Welding characteristic and steel plate and its manufacture method.A kind of steel plate, it has contains C in terms of quality %：0.030~0.080%, Si：0.01~0.10%, Mn：1.20~2.40%, P：Less than 0.008%, S：0.0005~0.0040%, Al：0.005~0.080%, Nb：0.003~0.040%, Ti：0.003~0.040%, N：0.0030~0.0100%, B：0.0003~0.0030%, the composition being further made up of as needed containing one or both of Cu, Ni, Cr, Mo, V, Ca, Zr, REM above, surplus Fe and inevitable impurity is constituted, also, thickness of slab direction and the amplitude of fluctuation of respective Vickers hardness (HV) on plate width direction：Δ HV is less than 30.A kind of manufacture method, the steel former material that mentioned component is constituted is heated to after 1000~1300 DEG C of temperature, carries out hot rolling, then carries out descale under conditions of the percussive pressure for accelerating the preceding injection stream at surface of steel plate of cooling is faced for more than 1MPa, then, acceleration cooling is carried out.

Description

Steel plate and its manufacture method
Technical field
The present invention relates to be suitable as being used for various steel structures, the spies such as ship, marine structure, building, steel pipe field It is not the steel plate and its manufacture method applied to Large Heat Input Welding.
Background technology
The steel structure used in the fields such as ship, marine structure, building, steel pipe is general smart by solder joints It is processed as the works of intended shape.Therefore, from the viewpoint of security is ensured, these works are except that will ensure as making The characteristic of weld part, mainly joint are also required beyond basic mother metal characteristic, the i.e. intensity of steel, toughness, elongation Intensity, joint toughness are also excellent.
In addition, in recent years, above-mentioned ship, steel structure tend to maximization, therefore used steel are also desirable that high intensity Change, wall thickening, on the other hand, suppress by service cost caused by being significantly increased of steel weight increase such viewpoint also by Concern.Therefore, such design too much will not be become by gradually becoming the intensity using applied steel plate, thickness of slab, and in weldering Connect in construction using high efficiency, the welding methods of large-line energy such as submerged-arc welding, electrogas arc welding, electroslag welding, be manufactured into overall This rationalization.Specifically, premised on the above-mentioned Large Heat Input Welding of application, it is contemplated that intensity and thickness of slab do not have so excessive , about 550~750N/mm is reached in terms of tensile strength as intensity rank2Rank, thickness of slab are the application of below 50mm steel plate It can expand.
Generally, for purposes, above-mentioned intensity level such as characteristic, reduction alloying element and the omission heat treatments for improving steel plate Not, the steel plate of thickness of slab is by combining controlled rolling and accelerating the so-called TMCP technologies of cooling to manufacture.TMCP technologies can Ensure high cooling velocity, therefore have and advantage as strength of parent can be ensured with relatively low composition.On the other hand, with steel Intralamellar part is quenched compared to the surface of steel plate, therefore the hardness compared with inside steel plate near surface of steel plate is uprised sometimes, thickness of slab The hardness distribution in direction produces variation.In addition, accelerating cooling uniform not in steel plate entire surface sometimes, worry in steel plate Property uniform in material, the specifically tensile properties of steel plate bring influence.
In order to solve the above problems, in the past since, be used as a ring of TMCP technologies, it is proposed that various solutions, for example Patent Document 1 discloses method as described below：It is 3~12 DEG C/sec of such ratios by cooling velocity control when accelerating cooling Relatively low cooling velocity, the hardness for thus suppressing surface relative to thickness of slab central part is raised.In addition, disclosed in patent document 2 The manufacture method of the small steel plate of the material difference in thickness of slab direction as described below：In cooling procedure, separated out in ferrite Progress is standby in temperature range, thus makes the duplex structure for being organized as ferrite and bainite of steel plate, reduces top layer and plate The difference of the hardness of thick central part.In addition, from the oxide skin character and steel plate for being conceived to surface of steel plate acceleration cooling when it is cold But from the viewpoint of speed, method as described below is disclosed in patent document 3,4：Descale is carried out before cooling is faced, So as to reduce the inhomogeneous cooling caused by oxide skin character, improve plate profile.These technologies can be interpreted ensuring material The technology of the high toughening by bringing crystal grain miniaturization can be realized while matter uniformity.
On the other hand, as described above, tending to the large-line energy weldering of application and construction efficiency high in the welding procedure of steel plate Connect.However, in the welding heat affected zone (also referred to as HAZ [Heat Affected Zone]) formed by Large Heat Input Welding, The crystal grain micronized effect that can occur to be brought as above-mentioned various controlled rollings, accelerated cooling process simultaneously disappear caused by joint The reduction of toughness, the reduction of the strength of joint caused by the formation in welding joint softened region, it is desirable to pair solved the above problems in the lump Plan.
As the countermeasure being wherein especially widely known by the people, it there are more stable in high temperature range by making in welding TiN fine dispersions suppress in steel the coarsening of austenite crystal technology, as described in Patent Document 5 like that by The method for the reduction for adding appropriate Ti, B in steel to make up joint low-temperature flexibility.
Furthermore disclosed seek to take into account steel by optimizing the Nb additions in steel like that as described in Patent Document 6 The method of the high intensity and joint characteristic of plate, particularly HAZ toughness.But, with large-line energy of the patent document 5,6 for representative The influence that welding game method is brought to the homogenieity of steel plate material is not verified also.
Prior art literature
Patent document
Patent document 1：Japanese Patent Publication 7-116504 publications
Patent document 2：No. 3911834 publications of Japanese Patent No.
Patent document 3：Japanese Unexamined Patent Publication 9-57327 publications
Patent document 4：No. 3796133 publications of Japanese Patent No.
Patent document 5：Japanese Unexamined Patent Publication 2005-2476 publications
Patent document 6：Japanese Unexamined Patent Publication 2011-074448 publications
The content of the invention
Invent problem to be solved
The present invention be in view of above-mentioned present situation and develop, together provide steel plate of the thickness of slab for below 50mm and its favourable Manufacture method, the steel plate possesses each characteristic required by Large Heat Input Welding connector portions, and by reducing the thickness of slab of steel plate The variation of the hardness of direction and plate width direction and cause steel plate material, particularly its through thickness tensile properties improve.
Method for solving problem
In order to solve above-mentioned problem, the present invention is optimized to the composition design as Large Heat Input Welding countermeasure On the basis of, the manufacturing condition for improving the material homogenieity in steel plate is studied, and be directed to meet Defined homogenieity and the material threshold value that should possess has carried out what is obtained after many experiments and research.I.e. the present invention is：
1. a kind of Large Heat Input Welding characteristic and the excellent steel plate of material homogenieity, it is characterised in that with matter Amount % meters contain C：0.030~0.080%, Si：0.01~0.10%, Mn：1.20~2.40%, P：Less than 0.008%, S： 0.0005~0.0040%, Al：0.005~0.080%, Nb：0.003~0.040%, Ti：0.003~0.040%, N： 0.0030~0.0100%, B：0.0003~0.0030%, the composition that surplus is made up of Fe and inevitable impurity is constituted, and And, thickness of slab direction and the amplitude of fluctuation of respective Vickers hardness (HV) on plate width direction：Δ HV is less than 30.
2. Large Heat Input Welding characteristic and the excellent steel plate of material homogenieity as described in 1, it is characterised in that with matter Amount % meters also contain Cu：Less than 1.00%, Ni：Less than 1.00%, Cr：Less than 1.00%, Mo：Less than 0.50%, V：0.10% More than one or both of below.
3. Large Heat Input Welding characteristic and the excellent steel plate of material homogenieity as described in 1 or 2, it is characterised in that with Quality % meters also contain Ca：0.0005~0.0050%, Zr：0.001~0.020%, REM：One in 0.001~0.020% Plant or two or more.
4. the manufacture method of a kind of Large Heat Input Welding characteristic and the excellent steel plate of material homogenieity, the plate of the steel plate Thick direction and the amplitude of fluctuation of respective Vickers hardness (HV) on plate width direction：Δ HV is less than 30, the spy of the manufacture method Levy and be, the steel former material of the composition composition any one of 1~3 is heated to after 1000~1300 DEG C, hot rolling is carried out, passes through The percussive pressure of injection stream at surface of steel plate is deoxygenated to make injection stream impact surface of steel plate under conditions of more than 1MPa Change skin, then, immediately using the average cooling rate of steel plate as the average cooling of more than 10 DEG C/sec, steel plate stopping temperature be 200~ 600 DEG C of condition carries out acceleration cooling.
5. the manufacture method of the steel plate as described in 4, it is characterised in that accelerate after cooling stopping, below Ac1 transformation temperatures It is tempered.
Invention effect
According to the present invention it is possible to obtain the excellent steel plate of both material homogenieity and Large Heat Input Welding joint characteristic and It is exceedingly useful in its manufacture method, industry.
Embodiment
Hereinafter, limitation of the invention condition is illustrated.It should be noted that the % in chemical composition is matter Measure %.
C：0.030~0.080%
C be improve steel intensity element, in order to ensure as the intensity needed for structural steel, it is necessary to add More than 0.030%.When on the other hand, more than 0.080%, island-like martensite is easily generated in Large Heat Input Welding HAZ, therefore The upper limit is set as 0.080%.Preferably 0.040~0.070% scope.
Si：0.01~0.10%
Si is the element added as deoxidier during steel-smelting melting, it is necessary to add more than 0.01%.But, it is more than When 0.10%, island-like martensite is generated in Large Heat Input Welding HAZ, easily causes the reduction of toughness.Therefore, Si is set as 0.01~0.10% scope.
Mn：1.20~2.40%
The element of the Mn intensity for being raising steel plate mother metal same with C, in order to ensure as the intensity needed for structural steel, needing Add more than 1.20%.And it is cheap compared with other alloying components, therefore addition is effective on one's own initiative.But, it is more than When 2.40%, quenching degree becomes over, base metal tenacity reduction, and damages weldability.Therefore, Mn amounts be set as 1.20~ 2.40%.Preferably 1.50%~2.20% scope.
P：Less than 0.008%
P is one of element for containing as impurity in steel.But, in order to reduce steel plate mother metal and large-line energy HAZ portions Toughness, be set as less than 0.008%.In terms of economy when considering raw material melting, preferably drop within the bounds of possibility It is low.
S：0.0005~0.0040%
It is one of element for containing as impurity in steel that S is same with P.It is different from P, with sulphur such as MnS, CaS, REM-S In the presence of the mode of compound, as ferritic generation core, the effect that large-line energy HAZ portions toughness of sening as an envoy to is improved is showed Really.The effect is effective when adding more than 0.0005%.On the other hand, a large amount of sulfide of generation can be caused by being excessively added, So that base metal tenacity is reduced.Therefore, S amounts are set as 0.0005~0.0040% scope.
Al：0.005~0.080%
Al is the element in order to carry out deoxidation to steel and add, it is necessary to contain more than 0.005%.On the other hand, add big When 0.080%, field trash amount becomes excessive, and making the toughness of mother metal reduces.Therefore, Al is set as 0.005~0.080% model Enclose.It is preferably set to 0.010~0.060%.
Nb：0.003~0.040%
Nb has the effect for expanding non-recrystallization humidity province by addition, the strength and toughness for ensuring steel plate mother metal For be effective element.But, when addition is less than 0.003%, the effect above is small, on the other hand, and addition is more than 0.040% When, island-like martensite is generated in Large Heat Input Welding HAZ, toughness is reduced.Therefore, Nb is set as 0.003~0.040% Scope.Preferably 0.005~0.025% scope.
Ti：0.003~0.040%
Ti is separated out in solidification in the form of TiN, especially for the thick of the austenite crystal for suppressing welding heat affected zone Bigization and high toughening as the Large Heat Input Welding HAZ such as ferritic phase change core is exceedingly useful element.In order to obtain The effect above is, it is necessary to add more than 0.003%.On the other hand, when addition is more than 0.040%, the TiN of precipitation becomes thick, difficult To obtain the effect above.Therefore, Ti is set as 0.003~0.040% scope.Preferably 0.005~0.025% scope.
N：0.0030~0.0100%
N is essential elements for above-mentioned TiN generation and the formation of B nitride described later, is most heavy in the present invention One of element wanted.Contribute effectively to improve toughness to generate these nitride in Large Heat Input Welding HAZ portions, need To contain more than 0.0030%.On the other hand, when addition is more than 0.0100%, sometimes due to weld heat input condition causes TiN Solid solution N amounts increase in the region of dissolving so that the toughness reduction in welded thin-wall box component portion.Therefore, N be set as 0.0030~ 0.0100% scope.Preferably 0.0040~0.0070% scope.
B：0.0003~0.0030%
B concentrates on crystal boundary in the presence of with solid solution condition so that it is guaranteed that quenching degree, help to ensure strength of parent, Simultaneously in the presence of in the form of B nitride, played a role as ferrite core, improve Large Heat Input Welding HAZ tough Property, B contributes to above-mentioned two aspects effect.Therefore, B is one of most important element in the present invention.Content is less than 0.0003% When, it is impossible to the former effect is obtained, also, when adding more than 0.0030%, the solid solution B more than B nitride is largely present so that and it is big Heat input welded thin-wall box component toughness is reduced.Therefore, B is set as 0.0003~0.0030% scope.
The basis of the present invention is constituted as described above, surplus is made up of Fe and inevitable impurity.Further improve In the case of desired characteristic, one or both of Cu, Ni, Cr, Mo, V above alternatively element can be added.
Cu：Less than 1.00%
Cu is in order that the element that intensity increases and can added.But, addition be more than 1.00% when, because of red brittleness so that The character on steel plate mother metal surface is deteriorated.Therefore, in the case of addition, its amount is preferably set to less than 1.00% scope.
Ni：Less than 1.00%
Ni is that the intensity that can make mother metal increases while the element of toughness can also be improved.Situation of the addition more than 1.00% Under, effect saturation, and economically become unfavorable.Therefore, in the case of addition, its amount is preferably set to less than 1.00% model Enclose.
Cr：Less than 1.00%
Cr is in order that intensity increases and effective element.But, when addition is more than 1.00%, base metal tenacity is deteriorated. Therefore, in the case of addition, its amount is preferably set to less than 1.00% scope.
Mo：Less than 0.50%
Mo is effective element for increase strength of parent.But, when addition is more than 0.50% so that toughness is notable It is deteriorated, and damages economy.Therefore, in the case of addition, its amount is preferably set to less than 0.50% scope.
V：Less than 0.10%
V is effective element for increase strength of parent.But, when addition is more than 0.10% so that toughness is notable It is deteriorated.Therefore, in the case of addition, its amount is preferably set to less than 0.10% scope.
In the case of further improving desired characteristic, can mentioned component composition in further addition Ca, Zr, More than one or both of REM alternatively element.
Ca：0.0005~0.0050%, Zr：0.001~0.020% and REM：0.001~0.020%
S in steel is fixed and had the effect for improving the toughness of steel plate by Ca, Zr, REM.Member is formed as strong sulfide When the Ca of element is more than 0.0005%, further with regards to Zr and REM respective effect can be obtained when adding more than 0.001%. But, when the respective amount addition of Ca, Zr, REM is more than 0.0050%, 0.020%, 0.020%, it is mingled with object amount increase in steel, Make degraded toughness on the contrary.Therefore, in the case of adding these elements, preferably Ca is set as that 0.0005~0.0050%, Zr is set It is set as 0.001~0.020% scope for 0.001~0.020%, REM.
The amplitude of fluctuation of respective Vickers hardness (HV) on thickness of slab direction and plate width direction：Δ HV is less than 30
The regulation is one of most important necessary condition in the present invention, and the homogenieity, particularly female steel plate to material are complete The tensile properties of thickness bring very big influence.For the variation width of respective Vickers hardness (HV) on thickness of slab direction and plate width direction Spend (Δ HV) to be more than for 30 steel plate, preferentially occur necking down at the relatively low position of its hardness during the tension test of female steel plate, Therefore the tensile properties of through thickness are significantly reduced.Therefore, the amplitude of fluctuation (variation) of hardness with Vickers be set as 30 with Under scope, be preferably set to less than 20.The excellent steel plate of the material homogenieity that such steel plate is considered as in steel plate.Hardness is tried Proved recipe method is described in detail in embodiment.
The steel that there is mentioned component to constitute for the method melting of the conventional methods such as converter or electric furnace is preferably used, passes through continuous metal cast process Or the steel former materials such as the steel billet that is manufactured for steel plate are made in the process of the conventional method such as ingot casting method.Hereinafter, for advising in the present invention The restriction reason of fixed steel plate manufacturing condition is illustrated.Steel temperature in the present invention is set as surface and the central part of steel The mean temperature of (1/2 of thickness of slab).
Heating-up temperature：1000~1300 DEG C
The steel former material such as steel billet after casting is cooled to after room temperature or is fitted into being held in the state of high temperature in heating furnace, It is more than 1000 DEG C to make steel former material temperature., will mainly from the viewpoint of making the dissolving of Nb carbonitrides, fully ensuring solid solution Nb The lower limit set of the heating-up temperature of steel former material is 1000 DEG C.In addition, steel former material temperature is higher than in the case of 1300 DEG C, during heating Coarsening occurs for austenite crystal, and harmful effect is brought to base metal tenacity, therefore the upper limit is set as 1300 DEG C.Need explanation It is that steel former material temperature preferably is 1000~1250 DEG C, is more preferably 1050~1200 DEG C.
Accumulation reduction ratio is more than 40% rolling in non-recrystallization humidity province
Steel billet after heating after hot rolling, is controlled rolling in recrystallization temperature area in non-recrystallization humidity province.Again Rolling in crystallization temperature area is implemented preferred to by austenite crystal miniaturization when heating, expect with it is more than 1 passage, it is excellent Accumulation reduction ratio is selected to be carried out for more than 20%.The control implemented after hot rolling in the recrystallization temperature area in non-recrystallization humidity province System rolling is in the case where its reduction ratio is small, it is impossible to obtain defined base metal tenacity.Therefore, by rolling in non-recrystallization humidity province The lower limit of the accumulation reduction ratio of system is defined as 40%.In addition, reduction ratio is preferably higher.But, industrially about 80% reaches the upper limit.
It should be noted that the lower limit temperature in recrystallization temperature area in addition to being influenceed by steel composition also by crystal grain The influence of footpath, processing course, dependent variable etc., is about in the range of 800~950 DEG C.Examined by carrying out trial test in advance Examine, thus, it is possible to deduce above-mentioned lower limit temperature.
In addition, from the viewpoint of the uniformity of tissue, rolling end temp is preferably more than Ar3 transformation temperatures.
Accelerate the implementation of the descale before cooling
The preceding injection stream impact surface of steel plate by making HI high impact pressure of cooling is accelerated to carry out descale facing.In order to make Into the excellent steel plate of the property uniform in material in steel plate, it is necessary to reduce the variation of the hardness in steel plate, particularly steel plate is being kept The variation for suppressing the hardness of skin section while the intensity of inside is critically important.
For the steel plate after rolling, sometimes because descale before rolling and in rolling etc. causes oxygen on width The thickness for changing skin produces inequality.In addition, in the case of oxidation skin depth, part oxide skin occurring sometimes and peels off.Carried out after rolling cold When but, changed if scale thickness is present, the cooling velocity of surface of steel plate can also change according to its thickness, steel plate table The hardness in face can also change according to its cooling velocity.In order that steel plate high intensity, increase accelerates cooling speed during cooling Degree is effective.But, in the cooling carried out with high cooling velocity, scale thickness becomes to the influence that surface hardness is brought Significantly, so if scale thickness has inequality, then the variation of hardness increases and the property uniform in material in steel plate is deteriorated.
In the present invention, implement descale using the injection stream of HI high impact pressure before acceleration cooling is faced, skin depth will be aoxidized Degree is equably thinned to less than 15 μm, so that cooling velocity does not produce larger difference.That is, the oxygen of the steel plate after acceleration is cooled down Change in the case that skin thickness is less than 15 μm, the hardness in thickness of slab direction is varied to up to below Δ HV30 and plate width direction The variation of hardness similarly reaches below Δ HV30.
It is difficult to accelerate the scale thickness of the steel plate before cooling to be measured to facing.But, accelerate the oxide skin before cooling Thickness can be found by carrying out descale before cooling is faced so that cold according to accelerating the scale thickness after cooling to estimate But the scale thickness of the steel plate after is less than 15 μm, it is hereby achieved that intended effect.By utilizing height before cooling is faced The injection stream of percussive pressure carries out descale, uniform in material in the intensity and steel plate under high cooling velocity thus, it is possible to take into account Property.
Descale pressure (percussive pressure of the injection stream at surface of steel plate)：More than 1MPa
In the present invention, using the percussive pressure of the injection stream at surface of steel plate as more than 1MPa condition before acceleration cooling is faced Descale is carried out, so that the scale thickness of the steel plate after cooling is less than 15 μm.The impact of injection stream at surface of steel plate Force down when 1MPa, descale is insufficient and produces oxide skin inequality sometimes, and surface hardness, which is produced, to be changed, therefore injection stream Percussive pressure is set as more than 1MPa.Descale is carried out using water under high pressure.It should be noted that injection stream at surface of steel plate When percussive pressure is more than 1MPa, also had no problem even if using other injection streams.More preferably more than 2MPa.
The average cooling rate of steel plate：More than 10 DEG C/sec
Acceleration cooling after descale is implemented in order to ensure the intensity of steel plate., it is necessary to select in cooling is accelerated Select while ensuring the condition of the material homogenieity of steel plate skin section.The average cooling rate of steel plate is less than in the case of 10 DEG C/sec, Even the top layer face after descale, the cooling of surface region also becomes uneven, and the variation with the hardness inside steel plate increases Greatly.Therefore, average cooling rate is defined as more than 10 DEG C/sec.In addition, preferred average cooling rate is more than 15 DEG C/sec. It should be noted that from the viewpoint of the uniformity of resulting metal structure, it is generally desirable to which cooling down start temperature is preferably It is more than Ar3 transformation temperatures.But, when such as thickness of slab is relatively thin, it is transported to acceleration by descale after the end of rolling Temperature reduction occurs during cooling device, cooling start temperature is sometimes less than Ar3 transformation temperatures.In order that the influence does not hinder conduct The present invention target hardness homogenieity, accelerate cooling start temperature be preferably rolling end temp~(rolling end temp- 30 DEG C) in the range of.
Cooling stops temperature：200~600 DEG C are calculated as with steel plate mean temperature
Accelerate to be cooled to 200~600 DEG C of temperature range as bainitic transformation, make steel plate inside phase transformation ( It is bainitic transformation in the present invention) it is the microscopic structure that can obtain prescribed strength.When cooling stops temperature higher than 600 DEG C, bayesian Body phase becomes incomplete, it is impossible to obtain sufficient intensity.In addition, when cooling stops temperature less than 200 DEG C, particularly in skin section meeting Generate a part of martensite or island-like martensite (MA), it is impossible to obtain the property uniform in material in steel plate, the tensile properties of through thickness Reduction.Therefore, accelerate the cooling of cooling to stop temperature and be set as 200~600 DEG C in terms of steel plate mean temperature.The phase in order to obtain The strength and toughness of prestige, accelerates cooling to be tempered after stopping below Ac1 transformation temperatures.Ac1 transformation temperatures can pass through following formula Obtain.Wherein, in formula, each element symbol represents the content (quality %) of each element.
Ac1=751-26.6C+17.6Si-11.6Mn-169Al-23Cu-23Ni+24.1Cr+22.5M o+233Nb- 39.7V-5.7Ti-895B
Embodiment
Hereinafter, effect of the present invention is described in detail by embodiment.Utilize the steel constituted converter melting table 1 Suo Shi Afterwards, steel billet (steel former material) is made by continuous metal cast process, by the controlled rolling shown in table 2,3, accelerates cooling condition to produce thickness Spend the steel plate for 20~50mm.It should be noted that in table 1, steel numbering system 1~10 is embodiments of the invention, steel numbering system 11 ~15 comparative example for some in composition composition outside the scope of the present invention.In addition, in table 2,3, the son behind steel numbering system Numbering A is the controlled rolling based on the present invention, the situation of cooling condition, and sub- numbering B1, B2 is some in manufacturing condition at this Comparative example outside the scope of invention.
For the steel plate manufactured by above-mentioned composition and manufacturing process, the through thickness that parallel portion width is 25mm is cut Tension test sheet, according to JIS Z 2241 (1998) regulation implement tension test, obtain tensile strength (being designated as TS below) and Through thickness elongation (percentage of total elongation).It should be noted that as object present invention assumes that for high-strength steel sheet, therefore its is strong Degree target is set to TS：550N/mm2More than, through thickness elongation values are with required by the steel generally for same intensity rank More than 20% is target.
In addition, associating for the elongation values in clearly above-mentioned through thickness tension test and the hardness change value of steel plate, For with the section that rolling direction is right angle, according to JIS Z 2244, determine Vickers hardness, obtain the hardness distribution in thickness of slab direction It is distributed with the hardness of plate width direction.For thickness of slab direction, the hardness of whole thickness is determined with 1mm spacing, for plate width direction, The hardness of whole width is determined with 20mm spacing.It should be noted that the hardness of plate width direction in top layer 1mm positions (away from table Position on the inside of layer 1mm), t/4 positions (position of thickness of slab 1/4), t/2 positions (thickness of slab central part) be measured.All steel plates All be that the variation of the hardness at the 1mm positions of top layer shows maximum, thus the hardness of plate width direction variation in top layer 1mm positions Evaluated.It should be noted that test load during Determination of Hardness is set as 10kgf (98N) and constant.
In addition, the toughness in order to evaluate Large Heat Input Welding HAZ, width 80mm × length 80mm is cut from above-mentioned steel plate × thickness 15mm test film, is heated to after 1450 DEG C cooling down 800~500 DEG C with 250 seconds, assigns after above-mentioned heat treatment, each to cut out 3 2mmV type breach Charpy test pieces are taken, Charpy-type test is carried out as described above.It should be noted that impact test Temperature is set as -40 DEG C, and its toughness target is set as in terms of the absorption energy average value (being designated as vE-40 DEG C below) at -40 DEG C More than 50J.
In table 4, above-mentioned steel plate mother metal characteristic and Large Heat Input Welding HAZ toughness evaluation results are shown.By thickness of slab direction With the amplitude of fluctuation of respective Vickers hardness (HV) on plate width direction：Δ HV is less than 30 and TS：550N/mm2Above, it is complete thick Spend elongation values：More than 20%, which is considered as mother metal, evaluates good.For the steel numbering system 1~10 as example of the present invention and son numbering A Speech, mother metal and Large Heat Input Welding HAZ characteristic have obtained good value, on the other hand, for steel numbering system 1~10 and son volume For number B1, B2, although chemical composition is defined as in the scope of the present invention, therefore large-line energy HAZ characteristic is satisfactory, by In manufacturing condition, therefore the characteristic of mother metal is poor outside the scope of the present invention.On the other hand, for (the sub- numbering A of steel numbering system 11~15 With B1, B2) for, composition range is outside the scope of the present invention, therefore the poor toughness in Large Heat Input Welding HAZ portions.
[table 4]
Table 4
Note 1：It is the situation for meeting following 3 conditions that mother metal, which is evaluated as zero,.Even if having 1 when being unsatisfactory for, mother metal evaluation ×.
Thickness of slab direction and the amplitude of fluctuation of respective Vickers hardness (HV) on plate width direction：Δ HV is less than 30.
Mother metal TS：550N/mm2More than.
Mother metal elongation：More than 20%
Note 2：It is that (vE-40 DEG C) of absorption energy average value at -40 DEG C is more than 50J that large-line energy HAZ, which is evaluated as zero,.

Claims (5)

1. a kind of steel plate, it is characterised in that with containing C in terms of quality %：0.030~0.080%, Si：0.01~ 0.10%th, Mn：1.20~2.40%, P：Less than 0.008%, S：0.0005~0.0040%, Al：0.005~0.080%, Nb： 0.003~0.040%, Ti：0.003~0.040%, N：0.0030~0.0100%, B：0.0003~0.0030%, surplus by The composition composition that Fe and inevitable impurity are constituted, also, thickness of slab direction and respective vickers hardness hv on plate width direction Amplitude of fluctuation：Δ HV is less than 30.
2. steel plate as claimed in claim 1, it is characterised in that also contain Cu in terms of quality %：Less than 1.00%, Ni： Less than 1.00%, Cr：Less than 1.00%, Mo：Less than 0.50%, V：More than one or both of less than 0.10%.
3. steel plate as claimed in claim 1 or 2, it is characterised in that also contain Ca in terms of quality %：0.0005~ 0.0050%th, Zr：0.001~0.020%, REM：More than one or both of 0.001~0.020%.
4. a kind of manufacture method of steel plate, the thickness of slab direction of the steel plate and the change of respective vickers hardness hv on plate width direction Dynamic amplitude：Δ HV is less than 30, and the manufacture method is characterised by, by according to any one of claims 1 to 3 into packet Into steel former material be heated to after 1000~1300 DEG C, hot rolling is carried out in recrystallization temperature area, then in non-recrystallization humidity province It is interior to carry out the rolling that accumulation reduction ratio is more than 40%, it is more than 1MPa's by the percussive pressure of the injection stream at surface of steel plate Under the conditions of make injection stream impact surface of steel plate to carry out descale, then, immediately using the average cooling rate of steel plate as 10 DEG C/ The condition that second is above, the average cooling stopping temperature of steel plate is 200~600 DEG C carries out acceleration cooling.
5. the manufacture method of steel plate as claimed in claim 4, it is characterised in that accelerate after cooling stopping, in Ac1 transformation temperatures It is tempered below.
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