CN101532112A - Steel plate for panel with excellent toughness in thickness direction of jug line energy welding heat infection part and manufacturing method thereof - Google Patents

Steel plate for panel with excellent toughness in thickness direction of jug line energy welding heat infection part and manufacturing method thereof Download PDF

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CN101532112A
CN101532112A CN200910126550A CN200910126550A CN101532112A CN 101532112 A CN101532112 A CN 101532112A CN 200910126550 A CN200910126550 A CN 200910126550A CN 200910126550 A CN200910126550 A CN 200910126550A CN 101532112 A CN101532112 A CN 101532112A
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steel plate
inclusion
amount
cooling
thickness
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CN101532112B (en
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盐饱丰明
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Kobe Steel Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—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
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

Abstract

The present invention provides a steel plate for panel with excellent toughness in thickness direction of jug line energy welding heat infection part, containing C, Si, Mn and the like, and Ti, N, B meet the formula (1) to (3), a longitudinal section of the steel plate contains less than 5 per mm<2> of foreign bodies of Ca with a equivalent circle diameter above than 5 [Mu]m, less than 2 per mm<2> of MnS series foreign bodies with a length more than 50 [Mu]m, the C concentration of a center deflection plate part of the steel plate is less than 1.2 times of the integral average C concentration of the steel plate. (1) 1.0 <= [Ti]/[N] <=3.0, (2) 0.0003 <= [N]-[Ti]/3.4 <= 0.0035, (3) -0.0005 <= [B]-{([N]-[Ti]/3.4)*11/14} <= 0.0015, wherein [Ti], [N], [B] are the contents (mass percent) of the Ti, N, B separately.

Description

The steel plate for panel and the manufacture method thereof of the thickness of slab direction tenacity excellent of large-line energy welding heat affected zone
Technical field
For example the present invention relates to the steel plate that the panel (skin plate) of the box column (being also referred to as four sides box column, welding assembly box section post etc.) that the building iron as the high building structure thing uses is suitable for, relating at heat inputs such as carrying out electroslag welding and bight submerged arc welding is large-line energy when welding more than the 400kJ/cm, is subjected to the steel plate of thickness of slab direction tenacity excellent at the position (hereinafter referred to as " HAZ ") of heat affecting.
Background technology
The post that the high building structure thing is suitable for, its manufacturing are by making 4 pieces of long steel plates (panel) become the box column shape long corner portion to be welded, and are being welded with the book office of beam again, the welding diaphragm in post in advance in order to ensure intensity.Carry out these whens welding, expect the welding of individual layer welding bead for the raising that realizes operating efficiency and the shortening of engineering time.Therefore, be large-line energy submerged arc welding about 400～600kJ/cm as the bight of the welding between panel welding will carrying out heat input, and the welding of panel and dividing plate will to carry out heat input be large-line energy electroslag welding about 400～1200kJ/cm.But if carry out large-line energy welding, thickization of metal structure of welding heat affected zone (HAZ) then causes the toughness deterioration of weld part thus.In order to improve vibration strength, it would be better to that the toughness of expectation weld part improves.Particularly heat input is the above large-line energy welding of 400kJ/cm, and different with the electro-gas welding of carrying out on a part of building structure, because the heat input height, speed of cooling is also slow, so the easier deterioration of toughness.
The research that is used to improve the flexible metallography of large-line energy welding heat affected zone is all being carried out all the time, for example has 1) research of applying flexibly TiN; 2) apply flexibly the research of oxide compound; 3) apply flexibly the research etc. of sulfide.
1) in the research of applying flexibly TiN, for example opens the tough property improvement technology of HAZ that proposes to apply flexibly TiN and VN in flat 5-186848 number the spy.Specially in addition open amount ratio [Ti]/[N] that propose to make Ti and N for 2002-266050 number than being 3.5～5.0 to increase the motion that Ti measures with comparing with the N amount.But, be in temperature near the interface (welded bonds) of welding metal and heat affected zone (HAZ) above 1400 ℃.What particularly architectural welding was carried out is the ultra-large linear energy input welding, so the residence time under the high temperature is elongated.Residence time under the high temperature is long more, makes the fusion of TiN particle, and the tough property improvement effect of HAZ reduces more.In addition, if prevent the fusion of such TiN particle and increase Ti amount that strengthen the TiN grain, then thickization of TiN particle causes the toughness deterioration on the contrary.
2) as the research of applying flexibly oxide compound, for example the spy open 2000-80436 number, the spy opens 2000-80437 number and the spy opens 2003-293077 number proposition, applies flexibly the technology of the oxide particle that is added with Mg.But homogeneous disperses the technology of fine oxide compound to be difficult to, and also needs further improvement in order to make on the enterprising line stabilization of industrialization ground.
3), propose to have by adding REM to make the particle dispersive technology (for example spy open 2004-176100 number, spy open 2004-10951 number, spy and open 2003-286540 number) of sulfide, oxide compound and oxysulfide as applying flexibly the technology of sulfide; The content of Ca and S and O is controlled at technology in the scope of parameter of the such fixed patternization of ACR (spy opens 2005-220379 number, spy and opens the 2005-68478 communique in the example) etc. for the particle of applying flexibly CaS.But, apply flexibly the technology of fluidisation thing because need S to a certain degree to measure, thus thickization of sulfide, the toughness deterioration, the inclusion of MnS system causes the toughness deterioration of thickness of slab direction.
So when earthquake, the building structure composition deformation plays a role in the thickness of slab direction tensile stress of welded joint along the post material.Though steel plate is stronger for the stress that acts on (direction parallel with the plate face) in the plate face, reduce at intensity as the stress of the thickness of slab direction of the vertical direction of plate face.Therefore, in order to improve the vibration strength of building structure, wish also to consider the toughness of thickness of slab direction.Above-mentioned prior art can not be stablized and satisfy high tenacity, does not also consider the toughness of thickness of slab direction in addition.In order to estimate the toughness of thickness of slab direction, must extract equidirectional is the pendulum impact test sheet of lengthwise direction, is the test film of lengthwise direction but can not extract with the thickness of slab direction from the steel plate of common jam welding.
Summary of the invention
The present invention carries out in view of above-mentioned this situation, and its purpose is that raising is as the vibration strength of the box column of the reinforcing bar use of building structure.More particularly, be at heat affected zone (HAZ) as the electroslag welding of the submerged arc welding in the box column bight of the welding between panel and panel and dividing plate, improve the toughness of the thickness of slab direction (Z direction) of panel.
Solve the steel plate of the present invention of described problem, contain the C:0.02～0.10% (meaning of quality %.Down together.), Si:0.05～0.5%, Mn:1.0～2.0%, Al:0.01～0.05%, Cu:0.05～1.5%, Ni:0.05～1.5%, Ti:0.003～0.02%, B:0.0005～0.0030%, Ca:0.0015～0.0030%, N:0.0040～0.008% and O:0.0005～0.0030%, surplus is iron and unavoidable impurities, P is defined in below 0.015%, S is defined in below 0.0010%, above-mentioned Ti, B, the content of N (quality %) satisfies following formula (1)～(3), in the vertical section of steel plate, the above inclusion of diameter of equivalent circle 5 μ m that contains Ca is 5/mm 2Below, the above MnS of length 50 μ m is that inclusion is 2/cm 2Below, the C concentration of the inclined to one side board in center of steel plate is below 1.2 times of average C concentration of steel plate integral body.
(1)1.0≤[Ti]/[N]≤3.0
(2)0.0003≤[N]—[Ti]/3.4≤0.0035
(3)—0.0005≤[B]—{([N]—[Ti]/3.4)×11/14}≤0.0015
(wherein, [Ti], [N], [B] represent the content (quality %) of Ti, N, B respectively.)
Here the said diameter of equivalent circle meaning is and the circular diameter of object with homalographic.
Steel plate for panel of the present invention also can also contain Cr:0.05～1.5% and/or V:0.005～0.05%.
Steel plate for panel of the present invention can be made in the following way: will satisfy described one-tenth and be grouped into, and satisfy the plate slab of described formula (1)～(3), 1) is heated to 950～1250 ℃, 2) make finishing temperature be 800～900 ℃ be rolled after, 3) carry out air cooling more than 30 seconds, 4) be cooled to temperature below 300 ℃ with the speed of cooling of 1～100 ℃/s thereafter.
Described manufacture method also can be 4) after the cooling below 300 ℃, 5) reheat to 450～600 ℃, carry out air cooling.In addition, this 4) cooling and 5 below 300 ℃) between 450～600 ℃ the reheat and air cooling, also can implement 700～850 ℃ reheat and then with the above speed of cooling of 1 ℃/s carry out to the cooling below 200 ℃.
Steel plate for panel of the present invention, control the amount of each element respectively, also suitably control Ti, B, N content mutual relationship and make the fine dispersion of the nitride of TiN and BN etc., and suppressing the thick MnS that contains Ca inclusion and the deleterious stretching, extension of thickness of slab direction toughness is inclusion, the center segregation that suppresses C in addition, therefore, even when the ultra-large linear energy input welding of carrying out submerged arc welding and electroslag welding etc., also can guarantee the toughness of the thickness of slab direction of welding heat affected zone (HAZ).
Description of drawings
Fig. 1 is the graphic representation of expression " [Ti]/[N] " and HAZ flexible relation.
Fig. 2 is the graphic representation of expression " [N]-[Ti]/3.4 " and HAZ flexible relation.
Fig. 3 is expression " [B]-{ ([N]-[Ti]/3.4) * 11/14} " and the graphic representation of HAZ flexible relation.
Fig. 4 is the summary section of the extraction main points of medelling ground expression welding process and pendulum impact test sheet.
Embodiment
Usually, for the electro-gas welding opposite joint and the submerged arc welding opposite joint that carry out steel plate and steel plate by shipbuilding manufacturers etc., carry out the rolling direction (L direction) of steel plate or the HAZ toughness of rolling right angle orientation (C direction, plate width direction) and estimate.But can not extract with thickness of slab direction (Z direction) on the jam welding joint is the test film of lengthwise direction, can not estimate the HAZ toughness of thickness of slab direction (Z direction).In addition, the reproduction thermal cycling test of the thermal process under the large-line energy welding that simulation is carried out usually, the extraction direction of test film also can only be carried out in L direction or C direction, can't estimate the HAZ toughness of Z direction.
Rolling steel plate shows different states respectively in rolling direction (L direction), rolling right angle orientation (C direction) and thickness of slab direction (Z direction), for example, under rolling effect and the inclusion that stretches exists, or the metal structure that is subjected to operation of rolling situation about existing etc., the HAZ toughness of thickness of slab direction (Z direction) is compared with the toughness deterioration of L direction and C direction, therefore in order to improve the toughness of thickness of slab direction (Z direction), also need the viewpoint of Control and Inclusion Removal and organizational controls.
Therefore, the main starting point of present inventor is, not only make L direction, C direction, but also the large-line energy HAZ toughness of thickness of slab direction (Z direction) is improved, and find when this is studied repeatedly, (i), be grouped into by highly being controlled to from the viewpoint of Control and Inclusion Removal and organizational controls, and (ii), can guarantee thickness of slab direction toughness at the welding heat affected zone of large-line energy welding by control inclusion and structural state directly.
(i) from the Composition Control of the viewpoint of control inclusion and tissue
If, importantly carry out following Composition Control: (i-1) measure and the amount of control Ti, N, B for precipitation state and the solid solution B that controls TiN, BN etc. from controlling the viewpoint of inclusion and tissue; (i-2) in order to control the inclusion that contains Ca, the flexible MnS that can reduce the thickness of slab direction owing to stretching is that inclusion (A is an inclusion) is controlled Ca amount and S amount; (i-3) control C amount etc. in order to suppress MA (martensite austenite constituent, island martensite body).Also have, do not add, guarantee that by interpolation Cu, Ni, B intensity is also very important the deleterious Nb of HAZ toughness.
Particularly because (i-1) control of Ti amount, N amount, B amount is very important, so followingly describe in more detail.
In the present invention, for the precipitation state of controlling TiN, BN etc. and solid solution B amount, make Ti amount, N amount, B amount all satisfy the relation of following formula (1)～(3) and control.
(1)1.0≤[Ti]/[N]≤3.0
(2)0.0003≤[N]—[Ti]/3.4≤0.0035
(3)—0.0005≤[B]—{([N]—[Ti]/3.4)×11/14}≤0.0015
(wherein, [Ti], [N], [B] represent the content (quality %) of Ti, N, B respectively.)
The reason of the relation of above-mentioned about determining (1)～(3), the limit describes with reference to Fig. 1～3 limits.Fig. 1～3 are 0.04%C-0.15%Si-1.35%Mn-0.008%P-0.001%S-0.030%Al-0.6%Cu-0.6%Ni-0.6%Cr-0.0020%Ca-0.0015%O for making basal component, and Ti, N, the B quantitative changeization of making so as shown in table 1, carry out the toughness evaluation for such steel plate, and the relation of the Composition Control of arrangement and Ti-N-B.Below, describe for the manufacture method and the HAZ flexible evaluation procedure of the steel plate that is used for Fig. 1～3.
At first, the manufacture method for the steel plate that is used for Fig. 1～3 describes.The steel that is adjusted into the amount shown in the table 1 for composition casts continuously, obtains the slab (deoxidation is carried out Al deoxidation and RH deoxidation treatment with converter) of thick 280mm.Also have, during continuous casting, dwindle depress roller gap (distance of upside roller and downside roller) near the position that finishes and depress solidifying.Then,, depress and become the slab (breakdown slab) of thickness 230mm, be cooled to room temperature behind the slab reheat to 1200 ℃.In addition, described slab is rolled down to thickness of slab 60mm, quickens cooling with the speed of cooling of 9 ℃/s thereafter with 850 ℃ of 1100 ℃ of Heating temperatures, outlet temperature.
Secondly, describe for HAZ flexible evaluation procedure.At first begin to make the thermal cycling test sheet by the steel plate of making according to aforementioned main points.Secondly, near the tissue of the embrittlement region the welding molten thread (Fusion Line) that reproduces the heat input 800kJ/cm that is equivalent to electroslag welding, and implement to reproduce the Thermal Cycle test.Reproduce in the Thermal Cycle test at this, after 30 seconds, cool off so that be 730 seconds such speed of cooling 800～500 ℃ cooling time with 1400 ℃ of maintenance thermal cycling test sheets.Extracting with thickness of slab direction (Z direction) from the thermal cycling test sheet is the V otch standard test sheet (JIS Z 2242) of lengthwise direction, carries out pendulum impact test (JIS Z2242 impacts sword radius 2mm) with 0 ℃ test temperature, and trying to achieve absorption can vE 0
Fig. 1 is expression " [Ti]/[N] " and vE 0The graphic representation of relation, Fig. 2 is expression " [N]-[Ti]/3.4 " and vE 0The graphic representation of relation, Fig. 3 is expression " [B]-{ ([N]-[Ti]/3.4) * 11/14} " and vE 0The graphic representation of relation.
Table 1
Figure A200910126550D00091
※ 1 BK value=[B]-{ ([N]-[Ti]/3.4) * 11/14}
(1)1.0≤[Ti]/[N]≤3.0
Based on Fig. 1, [Ti]/[N] is decided to be more than 1.0, below 3.0." [Ti]/[N] " has relation with TiN dispersion of particles state.The TiN particle has prevent the austenite particle thick and turns usefulness into and promote the effect from the phase transformation in the austenite crystal in process of cooling, and HAZ toughness improves under these effects.The TiN particle is disperseed imperceptibly in a large number, and HAZ toughness improves more.By making [Ti]/[N] more than 1.0, can increase fine TiN particle, HAZ toughness improves.On the other hand, if " [Ti]/[N] " surpasses 3.0, thickization of TiN particle then, the number of TiN particle reduces, and HAZ toughness sharply reduces.The preferred lower limit of " [Ti]/[N] " is 1.5 (preferred especially 2.0), is limited to 2.9 (preferred especially 2.8) on preferred.
(2)0.0003≤[N]—[Ti]/3.4≤0.0035
Based on Fig. 2, " [N]-[Ti]/3.4 " are decided to be more than 0.0003, below 0.0035.
Fig. 2 represents " [N]-[Ti]/3.4 " and vE 0Relation." [Ti]/3.4 " expression Ti and N with stoichiometric ratio in conjunction with the time the employed N amount of TiN.Therefore " [N]-[Ti]/3.4 " meaning is to deduct the employed N amount of TiN from total N content, and promptly TiN generates the remaining free N amount in back.The bonding force of N and Ti is strong, and TiN preferably generates during casting.In the process of cooling after the heat when soldered, free N (TiN generates the remaining N in back) combines with B, separates out as BN then.If in other words, then the meaning of " [N]-[Ti]/3.4 " also is can the remaining N that separating out of BN effectively plays a role be measured.BN is also the same with TiN, if suitably make it to disperse, then promotes from the phase transformation in the austenite crystal HAZ toughness to be improved.
The value of " [N]-[Ti]/3.4 " hour, free N amount is few, so the BN deficiency, and HAZ toughness is low.If the value of " [N]-[Ti]/3.4 " reaches more than 0.0003, BN is suitably disperseed, HAZ toughness is increased sharply.If " [N]-[Ti]/3.4 " surpass 0.0035, then free N surplus can not increase HAZ toughness deterioration as the free N of BN fixed on the other hand.The preferred lower limit of " [N]-[Ti]/3.4 " is 0.0005 (preferred especially 0.0008), and preferred upper limit is 0.0025 (preferred especially 0.0020).
(3)—0.0005≤[B]—{([N]—[Ti]/3.4)×11/14}≤0.0015
Based on Fig. 3, " [B]-{ ([N]-[Ti]/3.4) * 11/14} " (hereinafter referred to as BK value) is decided to be more than-0.0005, below 0.0015.The BK value is the B amount of separating out as BN that deducts from total B amount, and the meaning is that BN separates out the remaining solid solution B amount in back.But the BK value is not represented the absolute value of solid solution B amount, but the size of relativity ground expression solid solution B amount.Solid solution B amount (BK value) is many more, and HAZ toughness improves more, and strength of parent also improves in addition.Therefore the BK value be decided to be-more than 0.0005.On the other hand, if solid solution B amount (BK value) is too much, then can hinder promotion from the phase transformation in the austenite crystal.If the BK value surpasses 0.0015, then therefore the rapid deterioration of toughness schedules the BK value below 0.0015.The preferred lower limit of BK value is-0.0003 (preferred especially 0.0000), and preferred upper limit is 0.0012 (preferred especially 0.0010).
Measure control about (i-2) Ca amount, S, (i-3) interpolation of C amount control and Cu, Ni, B etc., explanation in the back.
The (ii) direct control of inclusion and structural state
If the viewpoint that improves from the HAZ toughness that makes the thickness of slab direction, then (ii-1) importantly reduces and contains thick Ca inclusion, and the MnS that (ii-2) reduces stretching, extension is an inclusion, (ii-3) alleviates center segregation.
(ii-1) contain the reduction of thick Ca inclusion
Contain thick Ca inclusion, particularly particle diameter (diameter of equivalent circle) containing the Ca inclusion and can cause disadvantageous effect more than 5 μ m to HAZ toughness.Therefore in the present invention, making the above inclusion of diameter of equivalent circle 5 μ m is 5/mm 2Below, be preferably 4/mm 2Below, 3/mm more preferably 2Below.Also have the lower limit of inclusion number to be not particularly limited, for example also can be 0.1/mm 2About (0.5/mm particularly 2About).
As the inclusion that contains Ca that prevents object that constitutes thickization, comprise the whole inclusiones that contain Ca, particularly as the inclusion of easy thickization (therefore should emphasis control), except that the CaS sulfides is inclusion, also can enumerate the complex inclusion with oxide compound, with complex inclusion of nitride etc.
In order to reduce the thick Ca inclusion that contains, except control steel product ingredient (particularly Ca amount, S amount), oxygen level, the control degassing treatment time is also effective.
Also have, the thick number that contains the Ca inclusion is based on the viewpoint result of the vertical section of steel plate.Be the thick number that contains the Ca inclusion, it is tried to achieve is to utilize EPMA and FE-SEM etc. to observe this cross section, extracts to contain the Ca inclusion, measures its particle diameter (diameter of equivalent circle).
(ii-2) MnS of Shen Zhaning is the reduction of inclusion
If owing to the rolling MnS that stretches is inclusion (A is an inclusion), the above MnS of particularly long 50 μ m is that inclusion exists, the interface peel of the base material iron of this inclusion and steel plate then, and the starting point that this part becomes the destruction generation makes the toughness deterioration of thickness of slab direction.Being made the MnS more than the long 50 μ m for this prevents is that inclusion is 2/cm 2Below, be preferably 1/cm 2Below, 0.5/cm more preferably 2Below.
Exist if the MnS that stretches is an inclusion (A is an inclusion), lamellar tearing (lamellar tear) crackle (for example " new building structural steel " steel construction is published, p.88～92) then can take place when welding as can be known.But, improving in this viewpoint at the HAZ of thickness of slab direction, MnS is that the influence of inclusion is not clear and definite quantitatively, and has obtained clear and definite in the present invention first.
For the MnS that reduces stretching, extension is an inclusion, effectively control steel product ingredient (particularly Ca amount, S amount).Ca make the big inclusion of length of MnS system be changed to CaS separately or with the complex inclusion of CaS, make it balling, have the effect of shortening length.
The MnS that stretches is the number of inclusion, is to try to achieve by the vertical section of opticmicroscope (multiplying power for example is about 100 times) mensuration steel plate.
(ii-3) center segregation alleviates
If the chemical ingredients generative center segregation of steel plate, then welding heat affected when feeding through near the thickness of slab center, the tissue generation great variety of the segregation portion at this thickness of slab center (chemical ingredients multiviscosisty portion), hard such as island martensite body (MA), martensite, bainite generate in a large number at the face with plate face equality.Destroy from this MA during to thickness of slab direction stress application, so the HAZ toughness of thickness of slab aspect deterioration greatly.In order to prevent HAZ flexible deterioration, need alleviate center segregation.The degree of this segregation can be estimated by the degree of segregation of C.If the ratio of (the C concentration of center segregation portion)/(the average C concentration of steel plate integral body) surpasses 1.2, then the generation of MA is many, HAZ toughness deterioration.Therefore will be defined as 1.2 on the ratio of (the C concentration of center segregation portion)/(the average C concentration of steel plate integral body).The preferable range of the ratio of (the C concentration of center segregation portion)/(the average C concentration of steel plate integral body) is below 1.1.
With the MnS that stretches is that inclusion (A is an inclusion) is the same, when center segregation takes place, lamellar tearing crackle (aforementioned " new building structural steel " steel construction is published, p.88～92) can take place also when welding as can be known.But in this viewpoint of the tough property improvement of the HAZ of thickness of slab direction, the influence of center segregation does not have the clear and definite of quantitative property, and has obtained clear and definite in the present invention first.
The degree of center segregation, casting temp, casting roll clearance control that can be by continuous casting, the reheat of block are rolling etc. makes it to change.In more detail, can alleviate center segregation more to the difference of the pouring temperature of mold and temperature of solidification is more little, for the casting roll gap, depress by dwindling depress roller gap (distance of upside roller and downside roller) near the position that finishes solidifying of molten steel, can alleviate center segregation.In addition, by to the block reheat, make the diffusion of center segregation composition with heat, rolling by depressing again, can pressure in conjunction with the gap of solidifying of central part, can alleviate center segregation.
The C concentration of center segregation portion presents different values according to measuring method.Therefore, in order to carry out quantitative control, need earlier unified measuring method.For example, in order to analyze atomic little zone by EPMA, analytical value is easy to generate deviation.Therefore in the present invention, measure the C concentration of center segregation portion by following such method.
The vertical section of cutting steel plate is carried out macro etch and is presented the center segregation thing, cuts out steel from this multiviscosisty position with specific thickness, and the cutting powder is carried out chemical analysis, thus the C concentration of decision center segregation portion.Cutting out thickness is thickness of slab * 0.02.For example, if thickness of slab is 100mm, then cutting out thickness is 100 * 0.02=2mm.It is comparatively convenient to use in cutting out with the drill bit of thickness of cutting same diameter.But when cutting out thickness with the decision of the relation of thickness of slab, existence thickness in view of the above obtains the situation of the instrument of suitable bit diameter, and in addition if every kind of thickness of slab all changes bit diameter, then operation effectiveness reduces, and cuts out situation of difficult.Therefore if the steel plate of thickness of slab 50～100mm then send out also and can be set at 1～1.2mm cutting out thickness (bit diameter).In addition, also can make center segregation portion exposing surface and cut, the C concentration that luminescence analysis (カ Application ト バ Star Network) decides center segregation portion is carried out on its surface.
As above-mentioned, the significant feature that has in the present invention is (i-1) the one-tenth component between control Ti-B-N; (ii) directly control inclusion and structural state, but (i-2) control Ca amount, S amount and (i-3) C amount, Cu amount, Ni amount, B amount are also very important in addition comprise these control, and the one-tenth that suitably designs steel plate is grouped into also very important.The one-tenth of steel plate of the present invention is grouped into and limits and the reasons are as follows.
(C：0.02～0.10％)
C is the needed element of intensity that is used to guarantee steel plate.The C amount is lower than at 0.02% o'clock, can not guarantee intensity.On the other hand, if the C amount surpasses 0.10%, then the welding heat affected zone when large-line energy welds (HAZ) is easy to generate the hard tissue that is called as island martensite body (MA), HAZ toughness deterioration.Therefore the C amount is decided to be 0.02～0.10%.The preferred lower limit of C amount is 0.03%, and preferred upper limit is 0.09%.
(Si：0.05～0.5％)
Si is the needed element of deoxidation.The Si amount is lower than at 0.05% o'clock, and the effect of deoxidation can not effectively be brought into play.On the other hand, if measuring, Si surpasses 0.5%, then the weldability deterioration.Therefore the Si amount is decided to be 0.05～0.5%.The preferred lower limit of Si amount is 0.1%, and preferred upper limit is 0.4%.
(Mn：1.0～2.0％)
Mn guarantees the intensity of steel plate, and also is that flexible is improved effective elements.The Mn amount is lower than at 1.0% o'clock, can not guarantee the intensity and the toughness of steel plate.On the other hand, if measuring, Mn surpasses 2.0%, then the weldability deterioration.Therefore the Mn amount is decided to be 1.0～2.0%.The preferred lower limit of Mn amount is 1.2%, and preferred upper limit is 1.8%.
(P:0.015% is following)
P is the element of unavoidably sneaking into as impurity element, but if the P amount surpasses 0.015%, then makes the toughness deterioration, therefore makes to be limited to 0.015%.The preferred upper limit of P amount is 0.013%.
(S:0.0010% is following)
S is the element of unavoidably sneaking into as impurity element, and S can become the inclusion of MnS and CaS system, makes the mother metal performance degradation of thickness of slab direction, and these inclusiones become and destroy the starting point that takes place, and makes HAZ toughness deterioration.MnS is an inclusion after rolling, exists with the state that stretches in each position of thickness of slab central part and thickness of slab direction.And carry out large-line energy when welding, because welding heat affected, the MnS of stretching, extension is the interface peel of the base material iron of inclusion and steel plate, becomes to destroy the starting point that takes place, and makes the HAZ toughness deterioration of thickness of slab direction.In addition the MnS of Shen Zhaning be inclusion easily with the coexistence of center segregation portion, as if with island martensite body (MA) adjacency, then can further make HAZ toughness.If the S amount is superfluous, thickization of inclusion of then aforesaid MnS system and CaS system, the number of inclusion also increases, and therefore becomes the place of destroying the starting point that takes place and increases HAZ toughness deterioration.Therefore make the S amount on be limited to 0.0010%.The preferred upper limit of S amount is 0.009%.
(Al：0.01～0.05％)
Al is the element that plays a role as reductor.The Al amount is lower than at 0.01% o'clock, and the effect of deoxidation can't be brought into play effectively.On the other hand, if the Al amount surpasses 0.05%, then make the toughness deterioration.Therefore the Al amount is decided to be 0.01～0.05%.The preferred lower limit of Al amount is 0.02%, and preferred upper limit is 0.04%.
(Cu：0.05～1.5％)
Cu is effective to the rising of intensity, is the little element of HAZ flexible deterioration.The Cu amount is lower than at 0.05% o'clock and can not guarantees intensity.On the other hand, if measuring, Cu surpasses 1.5%, then the weldability deterioration.Therefore the Cu amount is decided to be 0.05～1.5%.The preferred lower limit of Cu amount is 0.2%, and preferred upper limit is 1%.
(Ni：0.05～1.5％)
Ni is effective to the rising of intensity, is the little element of HAZ flexible deterioration.The Ni amount is lower than at 0.05% o'clock and can not guarantees intensity.On the other hand, if measuring, Ni surpasses 1.5%, then the weldability deterioration.Therefore the Cu amount is decided to be 0.05～1.5%.The preferred lower limit of Cu amount is 0.2%, and preferred upper limit is 1.3%.
(Ti：0.003～0.02％)
Ti improves very effective elements to the HAZ flexible.By TiN is disperseed imperceptibly in a large number, applying welding heat near fluxing point the time, utilize its pinning effect and prevent from thickization of austenite particle diameter from when cooling, to play a role on the other hand, make HAZ organize miniaturization as the ferrite/bainite karyogenesis point in the austenite crystal.Ti amount is lower than at 0.003% o'clock, can not fully guarantee to be used to bring into play the number of the TiN of such effect.On the other hand, if Ti amount surpasses 0.02%, thickization of TiN then, the number of TiN reduces.Therefore, the Ti amount is decided to be 0.003～0.02%.The preferred lower limit of Ti amount is 0.005%, and preferred upper limit is 0.018%.
(B：0.0005～0.0030％)
The B trace just rises effectively to intensity down, and the same with Ti be to HAZ flexible raising effective elements.In austenite grain boundary solid solution segregation hardenability is improved during cooling after rolling, intensity is improved.In addition, at welding heat affected zone, if population reduces the TiN particle in case fuse under near the high temperature more than 1400 ℃ the molten thread, then can't separate out again, with respect to this, separate out as BN in the process of cooling of B after welding heating, work, make HAZ organize miniaturization as the ferrite/bainite karyogenesis point in the austenite crystal.In order to bring into play such effect, the following of B amount is limited to 0.0005%.On the other hand, surpass 0.0030% if contain, the solid solution capacity surplus of B then, weldability, HAZ toughness deterioration, thus B on be limited to 0.0030%.The preferred lower limit of B amount is 0.001%, and preferred upper limit is 0.0025%.
(Ca：0.0015～0.0030％)
Ca make the big inclusion of length of MnS system become independent CaS inclusion or with the complex inclusion of CaS, make it balling, have the effect of shortening length, be the element that helps the improvement of thickness of slab directivity characteristics.The complex inclusion of formation and TiN at high temperature becomes stable microinclusions in addition, improves HAZ toughness.In order to arrive this effect, the following of Ca amount is limited to 0.0015%.On the other hand, if Ca amount surpasses 0.0030%, then contain thickization of inclusion of Ca, quantity also increases, HAZ toughness deterioration, so the Ca amount on be limited to 0.0030%.The preferred lower limit of Ca amount is 0.0017%, and preferred upper limit is 0.0029%.
(N：0.0040～0.008％)
N becomes the oxide particle of TiN and BN, is the HAZ flexible is improved effective elements.The N amount is lower than at 0.0040% o'clock, improves HAZ flexible effect and can not bring into play.On the other hand, if N amount surpasses 0.008%, solid solution N surplus then, HAZ toughness deterioration.Therefore the N amount is 0.0040～0.008%.The preferred lower limit of N amount is 0.0045%, and preferred upper limit is 0.007%.
(O：0.0005～0.0030％)
O is if add superfluously, and then the alumina series inclusion increases, and contains thickization of oxide compound of Ca, and quantity also increases, and therefore makes HAZ toughness deterioration.Therefore the O amount on be limited to 0.0030%.The preferred upper limit of O amount is 0.0025%.O can be remaining inevitably in steelmaking process in addition, is limited to 0.0005% under therefore.
The one-tenth of steel plate of the present invention is grouped into as above to be stated, and surplus is iron and unavoidable impurities.
The present invention also can also contain Cr:0.05～1.5% and/or V:0.005～0.05% as other elements.Below describe for these compositions.
(Cr：0.05～1.5％)
Cr is to intensity rising effective elements.In order to bring into play this effect, recommend the Cr amount to be preferably more than 0.05%, more preferably more than 0.5%.On the other hand, if the Cr amount is superfluous, then therefore the weldability deterioration is preferably below 1.5%, more preferably below 1%.
(V：0.005～0.05％)
V makes effective elements in the raising of intensity and toughness.In order to bring into play such effect, recommend the V amount to be preferably more than 0.005%, more preferably more than 0.01%.On the other hand, if the V amount is superfluous, then therefore HAZ toughness deterioration is preferably below 0.05%, more preferably below 0.04%.
Steel plate of the present invention can be made in the following way: will be heated to 950～1250 ℃ about the steel billet that above-mentioned chemical ingredients amount and Ti, N, B satisfy the important document of following formula (1)～(3) formula, make finishing temperature be 800～900 ℃ be rolled after, carry out the air cooling more than 30 seconds, be cooled to temperature below 300 ℃ with the speed of cooling of 1～100 ℃/s thereafter.
(Heating temperature when rolling: 950～1250 ℃)
Because need make austenite structure phase transformation equably, so the Heating temperature during steel billet rolling need be more than 950 ℃.On the other hand, if Heating temperature is too high, thickization of austenite crystal diameter then, the toughness deterioration is limited to 1250 ℃ on therefore.The preferred lower limit of Heating temperature is 1000 ℃, and preferred upper limit is 1200 ℃.
(finishing temperature: 800～900 ℃)
In order to ensure toughness, finishing temperature preferably can import the temperature of phase transformation (deformation bands) in austenite crystal in the non-recrystallization territory, on be limited to 900 ℃.On the other hand, if finishing temperature becomes over-drastic low temperature, then the sound anisotropy in the ultrasonic test is big, produces disadvantage on the checking efficiency of weld part, is limited to 800 ℃ under therefore.The preferred lower limit of finishing temperature is 820 ℃, and preferred upper limit is 870 ℃.
(air cooling more than 30 seconds after rolling)
Behind rolling the finishing, between the cooling (water-cooled etc.) that begins acceleration cooling (direct quenching (DQ)), need carry out air cooling more than 30 seconds.Can make the surface temperature homogenization of steel plate reduce material deviation in the steel plate by this air cooling, and cooling beginning temperature is reduced, yield tensile ratio (YR) is reduced.The preferred air cooling time is more than 60 seconds.
(speed of cooling: 1～100 ℃/s)
The fast more intensity of speed of cooling after rolling rises more, thus speed of cooling be 1 ℃/more than the s.On the other hand, if speed of cooling is too fast, then become hard tissue, the toughness deterioration is limited to 100 ℃/s on therefore.The preferred lower limit of speed of cooling is 3 ℃/s, preferred upper limit be 30 ℃/s (be preferably especially 15 ℃/s).
(cooling stops temperature: below 300 ℃)
To stop temperature low more in cooling, can become low temperature phase change tissue, and intensity rises more, cools off therefore that to stop temperature be below 300 ℃.It is below 200 ℃ that preferred cooling stops temperature.
(tempering (T))
In manufacture method of the present invention, also can to quicken so as described above the cooling (direct quenching) steel plate for example off-line carry out tempering.Make hard tissue softening by tempering, this can further improve toughness.
The preferred reheat temperature of tempered condition: 450～600 ℃, method of cooling: air cooling.When the reheat temperature was lower than 450 ℃, if hard tissue softening insufficient was on the other hand above 600 ℃, then tensile strength (TS) reduces, and the situation that is lower than specification intensity is arranged, and compare with the reduction amount of tensile strength (TS), the reduction of yield strength (YS) is little, and yield tensile ratio (YR) rises.
(from the quenching of two phase regions (Q '))
Between described acceleration cooling (direct quenching) and tempering, also can implement quenching (Q ') from ferritic-austenitic two phase regions.From the quenching of two phase regions (Q ') is effective means especially on low YRization.
The reheat temperature is Ac 1Point above (for example more than 700 ℃), Ac 3Point following (for example below 850 ℃).By with the steel plate reheat to two phase region (Ac 1Point is above, Ac 3Point is following), a part of austenitizing of steel plate tissue, all the other are softening, ferriteization.Then by quenching, austenite becomes the hard phase, can make hard phase and ferritic phase appropriate balance, can hang down YRization.Preferred reheat temperature is more than 700 ℃, below 850 ℃.Preferred quenching conditions is speed of cooling: 1 ℃/more than the s, cooling end temp: below 200 ℃.Therefore steel plate toughness deterioration under as-quenched condition that two-phase is quenched carries out tempering as hereinbefore usually.
Morphology Control and center segregation in order to alleviate inclusion in addition, control, the control of casting temp, the control in casting roll gap, the reheat in treatment time that further carries out the RH degassing in above-mentioned manufacture method is rolling also very important.
The control in the treatment time of the RH degassing is effective to the size of controlled oxidation system inclusion, and the preferred treatment time is about 20～30 minutes.
The rolling control to center segregation of the control reheat in the control of casting temp, casting roll gap is effective.About casting temp, can alleviate center segregation more to poor (the △ T) of the pouring temperature of mold and temperature of solidification is more little, the scope of preferred △ T is about 15～25 ℃.About the casting roll gap, depress by dwindling depress roller gap (distance of upside roller and downside roller) near the position that finishes solidifying of molten steel, can alleviate center segregation.The degree closely in depress roller gap is, (depress gradient hour) is " little " when if the total length of establishing the configuration of traversing depress roller is slowly dwindled, be " greatly " solidifying when just dwindling in finishing when big (depress gradient) quickly, be " standard " then preferably to dwindle therebetween with " greatly " or " standard ".In addition, particularly during utmost point Plate Steel (thickness of slab is more than the 80mm), reheat block and spread equal thermal treatment rollingly can alleviate center segregation by depressing.Depressing rolling preferred Heating temperature is about 1200 ℃, and preferred draft is about 10～20%.
Steel plate of the present invention, the HAZ toughness of the thickness of slab direction when carrying out large-line energy, tensile strength (TS) excellence, (YR) is low for yield tensile ratio.Therefore as if the panel of the box column that steel plate of the present invention is used for use, then can significantly improve the vibration strength of box column as building iron.
The thickness of slab of steel plate of the present invention for example is about 30～100mm, about preferred 40～80mm.Tensile strength for example is about 490～740MPa.Yield tensile ratio (YR) for example is about 65～80%.
[embodiment]
Below, enumerate embodiment and be described more specifically the present invention, but the present invention is not limited by following embodiment certainly, can certainly be before can being fit to be suitably changed enforcement in the scope of aim described later, these all are included in the scope of technology of the present invention.
Behind the steel with the composition shown in the converter melting table 2, carry out deoxidation with the method shown in the table 3, after casting continuously with the condition shown in the table 3, with the condition reheat block shown in the table 3, depress and be rolled down to intermediate slab thickness, with condition table 3 shown in be hot-rolled down to the thickness of slab of regulation, quicken cooling thereafter.The steel plate of a part is with this state or carry out 2 and carry out tempering after quenching mutually.
Figure A200910126550D00191
Figure A200910126550D00201
For the steel plate of above-mentioned such manufacturing, measure by following main points.
(mensuration that contains the Ca inclusion)
In the mensuration that contains the Ca inclusion, use FE-SEM.With 1000 times multiplying powers measure the vertical section of steel plates the t/4 position (t: the zone of mensuration arbitrarily thickness of slab) (about 300 μ m * 300 μ m), extract the inclusion that contains Ca, the number of the inclusion that statistical equivalence circular diameter 5 μ m are above.Be determined in 10 visuals field and carry out, the number (totals of 10 visual field parts) of the inclusion that obtains is converted into every 1mm 2Number.
(MnS is the mensuration of inclusion)
At MnS is in the mensuration of inclusion, uses opticmicroscope.Observe the t/4 position of vertical section of steel plates and t/2 position (t: (about 15mm * 15mm), the MnS more than the statistical length 50 μ m is the number of inclusion in the zone of mensuration arbitrarily thickness of slab) with 100 times multiplying powers.Carry out respectively the t/4 position and the t/2 position that are determined at the vertical section of steel plate, and each 5 visual field adds up to 10 visuals field, is that the number (totals of 10 visual field parts) of inclusion is converted into every 1cm with the MnS that obtains 2Number.
(mensuration of the C concentration of center segregation portion)
Cross-section steel plate, central authorities cut out sample from width, carry out macro etch and reveal segregation portion.Macro etch uses nitric acid and alcoholic acid mixed solution (about nitric acid 5～15%) to carry out.By this macro etch, can make segregation portion be the black emersion.This segregation portion of bit cutting with bit diameter 1～1.2mm carries out chemical analysis by wet analysis to this cutting powder.Try to achieve (the C concentration of center segregation portion)/(the average C concentration of steel plate integral body) as the center segregation degree by calculating then.
(HAZ flexible mensuration)
In the toughness of welded-joint is estimated, select the steel plate that obtains in the foregoing description as panel.As shown in Figure 4, the dividing plate of thickness of slab 50mm and panel configuration in T type matrix tool, are carried out electroslag welding by condition shown below to it.From the connection section of panel and welding metal, the thickness of slab direction of extracting panel is the pendulum standard shock test sheet (JIS Z 2242) of lengthwise direction in the prolongation of the thickness of slab 1/2 of dividing plate.On the welding molten thread of test film (Fusion Line), incision otch lengthwise direction is the V otch of welding direction, follows JIS Z 2242, carries out pendulum impact test under 0 ℃ of test temperature.Measuring absorption for 3 test films can (vE 0), try to achieve its mean value.Absorbing can (vE 0) welded-joint more than 70J is qualified.
(electroslag welding condition)
Heat input: 850kJ/cm
Welding current: 380A
Weldingvoltage: 52V
Welding speed: 14mm/ branch
(mensuration of tensile strength)
Extract No. 4 test films of JIS Z 2201 from t (thickness of slab)/4 position of steel plate, follow JIS Z 2241 and measure tensile strength (TS), yield strength (YS), try to achieve yield tensile ratio (YR).Trial speed during tension test is 10N/mm 2Second.Above qualified of tensile strength (TS) 490MPa, yield tensile ratio (YR) is qualified below 80%.
These results are displayed in Table 4.
[table 4]
Steel grade Steel plate No. Tensile strength TS (MPa) Yield tensile ratio YR (%) The number that contains the Ca inclusion more than the 5 μ m is (individual/mm 2) The number of the MnS type impurity that 50 μ m are above is (individual/cm 2) The center segregation degree ※1 Z direction welding joint toughness vE 0(J)
A 1 530 75 2.5 0.5 1.05 148
A 2 480 72 2.0 0 1.10 134
A 3 485 70 2.5 0 1.10 139
A 4 550 81 2.0 0.5 1.10 129
A 5 470 71 2.0 0.5 1.05 114
A 6 480 75 1.5 0 1.05 146
A 7 520 78 2.0 0 1.10 156
A 8 570 74 2.0 0 1.10 164
B 9 570 77 1.5 0.5 1.10 143
C 10 640 77 2.5 0 1.00 154
C 11 670 83 2.0 0.5 1.05 124
C 12 610 76 2.0 0.5 1.05 143
D 13 650 75 2.5 0 1.05 151
E 14 590 77 1.0 0 1.10 119
F 15 610 75 2.0 1.0 1.25 32
G 16 510 72 1.5 0 1.25 41
H 17 560 77 2.0 3.5 1.05 51
I 18 570 79 1.0 4.5 1.10 46
J 19 540 75 7.0 2.5 1.10 34
K 20 510 73 2.0 0.5 1.05 31
L 21 530 75 2.5 0.5 1.15 25
M 22 570 77 3.0 0 1.10 29
N 23 550 76 2.5 0 1.05 16
O 24 540 75 6.0 1.0 1.05 42
P 25 550 77 2.0 0.5 1.05 49
Q 26 510 70 1.5 0.5 1.10 21
R 27 590 78 2.0 0 1.05 16
※ 1 center segregation degree=(the C concentration of center segregation portion)/(the average C concentration of steel plate integral body)
The steel plate No.1,7～10 of table 4,12～14 uses is to satisfy one-tenth of the present invention to be grouped into steel A～E with mutual relational expression (1)～(3) of Ti, B, N, manufacturing method according to the invention is made, contain the Ca inclusion, MnS is that the number of inclusion and the C concentration of center segregation portion satisfy important document of the present invention, therefore demonstrate good thickness of slab direction HAZ toughness, mother metal characteristic (tensile strength, yield tensile ratio) is also good.
Heating temperature when the steel plate No.2 of table 4 is rolling is low, so the low example of the tensile strength of mother metal, and steel plate No.3 is that finishing temperature is low, so the low example of the tensile strength of mother metal.Steel plate No.4 and 11 is because rolling end back is short to the refrigerative air cooling time, thus cooling beginning temperature height, the YR height of mother metal.Steel plate No.5 does not use water-cooled and is to use air cooling after rolling end, so speed of cooling is slow, and the tensile strength of mother metal is low.Steel plate No.6 is because cooling stops the temperature height, so the tensile strength of mother metal is low.
Steel plate No.15, the 16th, center segregation degree (the C concentration of center segregation portion)/(the average C concentration of steel plate integral body) height, so the low example of Z direction welding joint toughness.Steel plate No.17～19 are because the long MnS clevis foreign material of length exist in a large number, so the welding joint toughness of Z direction is low.In addition, steel plate No.19,24 is because the thick Ca inclusion that contains exists in a large number, so the welding joint toughness of Z direction is low.Steel plate No.20～23,25～27 because the balance (preceding formula (1)～(3)) of Ti, N, B not in the scope of the present invention's regulation, so the welding joint toughness of Z direction is low.

Claims (6)

1. steel plate is characterized in that % contains in quality:
C：0.02～0.10％、
Si：0.05～0.5％、
Mn：1.0～2.0％、
Al：0.01～0.05％、
Cu：0.05～1.5％、
Ni：0.05～1.5％、
Ti：0.003～0.02％、
B：0.0005～0.0030％、
Ca：0.0015～0.0030％、
N:0.0040～0.008% and
O：0.0005～0.0030％，
Surplus is iron and unavoidable impurities,
P is defined in below 0.015%, and S is defined in below 0.0010%,
And the mass percentage content of above-mentioned Ti, B, N satisfies following formula (1)～(3),
In the vertical section of steel plate, the above inclusion of diameter of equivalent circle 5 μ m that contains Ca is 5/mm 2Below, the above MnS of length 50 μ m is that inclusion is 2/cm 2Below,
The C concentration of the inclined to one side board in center of steel plate is below 1.2 times of average C concentration of steel plate integral body,
(1)1.0≤[Ti]/[N]≤3.0
(2)0.0003≤[N]—[Ti]/3.4≤0.0035
(3)—0.0005≤[B]—{([N]—[Ti]/3.4)×11/14}≤0.0015
Wherein, [Ti], [N], [B] represent the mass percentage content of Ti, N, B respectively.
2. steel plate according to claim 1 is characterized in that, also contains Cr:0.05～1.5% in quality %.
3. steel plate according to claim 1 is characterized in that, also contains V:0.005～0.05% in quality %.
4. method of making the steel plate described in the claim 1～3, it is characterized in that, comprise following operation: steel billet is heated to 950～1250 ℃, make finishing temperature be 800～900 ℃ be rolled after, carry out the air cooling more than 30 seconds, be cooled to temperature below 300 ℃ with the speed of cooling of 1～100 ℃/s thereafter.
5. steel plate manufacture method according to claim 4 is characterized in that, after described cooling below 300 ℃, air cooling is carried out in reheat to 450～600 ℃.
6. steel plate manufacture method according to claim 4 is characterized in that, after described cooling below 300 ℃, order is carried out:
(1) 700～850 ℃ reheat and then with the above speed of 1 ℃/s carry out to the cooling below 200 ℃,
(2) 450～600 ℃ reheat and the air cooling that carries out then.
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JP3668713B2 (en) * 2001-11-26 2005-07-06 株式会社神戸製鋼所 High tensile steel plate with excellent weldability and uniform elongation
JP4096839B2 (en) * 2003-08-22 2008-06-04 Ｊｆｅスチール株式会社 Manufacturing method of high yield thick steel plate with low yield ratio and excellent toughness of heat affected zone
JP2005187853A (en) * 2003-12-24 2005-07-14 Jfe Steel Kk Method for producing high strength thick steel plate excellent in toughness in extra-high heat input welded-heat affected part
JP2005213534A (en) * 2004-01-27 2005-08-11 Jfe Steel Kk Method for producing steel material excellent in toughness at welding heat affected zone

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104131225A (en) * 2014-07-30 2014-11-05 宝山钢铁股份有限公司 Ultralow temperature nickel steel with low cost and manufacturing method thereof
CN104131225B (en) * 2014-07-30 2016-08-24 宝山钢铁股份有限公司 Low cost ultralow temperature nickel steel and manufacture method thereof

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CN101532112B (en) 2011-09-21

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