CN103998636B - Steel material for welding - Google Patents
Steel material for welding Download PDFInfo
- Publication number
- CN103998636B CN103998636B CN201280028721.2A CN201280028721A CN103998636B CN 103998636 B CN103998636 B CN 103998636B CN 201280028721 A CN201280028721 A CN 201280028721A CN 103998636 B CN103998636 B CN 103998636B
- Authority
- CN
- China
- Prior art keywords
- particle
- steel
- welding
- haz
- content
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
This steel material for welding contains, by mass, 0.05% to less than 0.12% of C, 1.40% to 1.80% of Mn, 0.0020% to 0.0080% of S, 0.020% to 0.070% of Al, 0.004% to 0.012% of Ti, 0.0005% to 0.0020% of B, 0.0015% to 0.0030% of Mg, 0.0020% to 0.0050% of N, and 0.0007% to 0.0020% of O, has a weld cracking sensitivity index (Pcm) value of 0.16% to 0.23% and a hardenability index (DI) value of 0.70 to 2.30, and contains 1.0 104 to 3.0 105 per square mm of Mg/Mn-containing sulfide particles having a grain diameter of 0.015 to 0.2 [mu]m, the proportion of Mg relative to the total of Mg and Mn in the Mg/Mn-containing sulfide being 70 to 90% by atom %.
Description
Technical field
The present invention relates to the steel material for welding of the excellent in low temperature toughness of the welded heat affecting zone (Heat AffectedZone: hereinafter referred to as HAZ) in the ultra-large linear energy input welding such as the electro-gas welding of application in the electroslag welding or shipbuilding and bridge etc. applied in the assembling of the box column of Highrise buildings etc.Particularly, even if heat input is more than 200kJ/cm, such as, it is the low-temperature flexibility that about 400 ~ 500kJ/cm also has excellent HAZ.
Background technology
Along with the high stratification of nearest building structure, steel column maximizes.Thereupon, the thickness of slab of the steel used in steel column also increases.When carrying out welding assembly to so large-scale steel column, require with high-duty welding, so the electroslag welding can welding pole Plate Steel with 1 passage is widely used.In addition, in shipbuilding field and bridge field, with 1 passage, also widespread use is able to the electro-gas welding that thickness of slab welds for steel plate more than about 50mm.When carrying out these electroslag welding or electro-gas welding, the scope of typical heat input is 200 ~ 500kJ/cm, for so-called ultra-large linear energy input welds.Such ultra-large linear energy input is welded, different from the Large Heat Input Welding (heat input is lower than 200kJ/cm) such as union-melt weld, the high temperature residence time near welding welded bonds (FL:Fusion Line) or in the thermal process of HAZ acceptance more than 1350 DEG C becomes extremely long.Therefore, the coarsening highly significant of austenite crystal, is difficult to the low-temperature flexibility guaranteeing HAZ.Therefore, be very important problem for the security of the welded steel structure thing such as building structure, boats and ships, bridge guaranteed under such as-20 DEG C such harsh low temperature environments, the low-temperature flexibility of HAZ that improves such ultra-large linear energy input welding.
HAZ(Large Heat Input Welding HAZ about when carrying out Large Heat Input Welding in the past) toughness improve, have many experiences and technology as shown below.But, as mentioned above, heat input be more than 200kJ/cm ultra-large linear energy input welding and Large Heat Input Welding in, HAZ acceptance thermal process, particularly more than 1350 DEG C time residence time differ widely.Therefore, merely the technology of raising Large Heat Input Welding HAZ toughness in the past can not be applied to object domain of the present invention.
About the technology of the toughness of raising Large Heat Input Welding HAZ in the past, if rough classification, then mainly based on two basic fundamentals.Wherein one be utilize the pinning effect of particle in steel prevent austenite crystal coarsening technology, another is the Effective grain size miniaturization technology utilizing austenite crystal intragranular ferrite transformation.
Such as, in non-patent literature 1, just various nitrogen in steel compound and carbide have studied the effect suppressing austenite crystal growth, result discloses: for the steel that with the addition of Ti, generates the minuteness particle of TiN in steel, can effectively suppress the austenite crystal in Large Heat Input Welding HAZ to grow.
Patent Document 1 discloses following technology: containing the Al of 0.04 ~ 0.10%, the Ti of 0.002 ~ 0.02% and 0.003 ~ 0.05% rare earth element (REM:Rare Earth Metal) steel in, make heat input be 150kJ/cm Large Heat Input Welding HAZ toughness improve.This make use of form oxygen/sulfide (composite particles of oxide compound and sulfide) by REM and prevent HAZ from organizing the technology of the effect of coarse when Large Heat Input Welding.
Patent Document 2 discloses following technology: be 0.1 ~ 3.0 μm containing particle diameter, population is 5 × 10
3~ 1 × 10
7individual/mm
3ti oxide compound or Ti oxide compound and Ti nitride complex body in the steel of any one in, in the Large Heat Input Welding HAZ that heat input is 100kJ/cm, played a role as ferrite transformation core by these particles and make HAZ organize miniaturization, thus improving HAZ toughness.
Patent Document 3 discloses following technology: in Large Heat Input Welding HAZ organizes, generate ferrite in crystal grain using the miscible precipitate of TiN and MnS as core appropriate containing in the steel of Ti and S, make HAZ organize miniaturization, improve HAZ toughness thus.
Patent Document 4 discloses following technology: containing the Al of 0.005 ~ 0.08%, the B of 0.0003 ~ 0.0050%, further containing in the steel of more than at least a kind in Ti, Ca, REM of less than 0.03%, by in Large Heat Input Welding HAZ with the oxygen/sulfide of unfused REM and Ca or TiN for starting point, BN is formed in process of cooling, generate ferrite thus, thus improve large-line energy HAZ toughness.
Patent Document 5 discloses following technology: every 1 square millimeter containing 40000 ~ 100000 oxide compounds containing Mg and every 1 square millimeter be in the steel of the complex body formed by oxide compound and the MnS containing Ti of 0.20 ~ 5.0 μm containing 20 ~ 400 particle diameters, improve ultra-large linear energy input welded thin-wall box component toughness by suppressing ferrite transformation in austenite crystal growth and promotion crystal grain.
Patent Document 6 discloses following technology: containing particle diameter be MgO, MgS, Mg(O, S of 0.005 ~ 0.5 μm) in steel of more than two kinds in, by utilize these minuteness particles suppress austenite crystal growth and improve ultra-large linear energy input welded thin-wall box component toughness.
Patent Document 7 discloses following technology: a large amount of be in the steel of (Mg, Mn) S particle of 0.005 ~ 0.5 μm containing particle diameter, improve ultra-large linear energy input welded thin-wall box component toughness by utilizing these minuteness particles to suppress austenite crystal growth.
But there is following problem in above-mentioned technology.
Technology disclosed in non-patent literature 1 take TiN as the technology that the nitride of representative seeks to suppress austenite crystal growth by utilizing.Therefore, can effect be played in Large Heat Input Welding, but in the ultra-large linear energy input welding of the present invention as object, because the residence times of more than 1350 DEG C are very long, so most TiN solid solution, lose the effect suppressing grain growing.In addition, play a role as the starting point that brittle rupture occurs in the TiN of the thick micron-scale that a part is molten remaining ultra-large linear energy input HAZ at-20 DEG C, sometimes make toughness reduce.So this technology can not be applicable to the toughness of the present invention as the ultra-large linear energy input welded thin-wall box component of object.
Technology disclosed in patent documentation 1 is the coarse utilizing the oxygen/sulfide of REM and prevent HAZ when Large Heat Input Welding.Oxygen/sulfide and Nitride Phase ratio, because the stability under the high temperature of more than 1350 DEG C is high, so can maintain the effect suppressing grain growing.But, be difficult to oxygen/sulfide is disperseed imperceptibly.That is, because the individual number density of oxygen/sulfide is low, even if so maintain the pinning effect of each particle, the reduction of the austenite particle diameter of ultra-large linear energy input welded thin-wall box component also has limit, only can not seek toughness thus and improve.In addition, for the oxygen/sulfide of the REM of thick micron-scale, play a role as the starting point that brittle rupture occurs in the ultra-large linear energy input HAZ sometimes at-20 DEG C, toughness is reduced.
Technology described in patent documentation 2 is by making the particle of any one in the complex body of Ti oxide compound or Ti oxide compound and Ti nitride play a role as ferrite transformation core, making HAZ organize miniaturization, thus improves the technology of HAZ toughness.If consider the high-temperature stability of Ti oxide compound, even if then also its effect can be maintained in ultra-large linear energy input welding.But, the caryogenic ferritic crystalline orientation of phase transformation in crystal grain non-fully is random, by the impact of the austenitic crystalline orientation of parent phase.So, in ultra-large linear energy input welding in austenite crystal coarsening, make HAZ organize miniaturization to have limit by means of only phase transformation in crystal grain.In addition, play a role as the starting point that brittle rupture occurs in the Ti oxide compound of thick micron-scale or the ultra-large linear energy input HAZ of the complex body of Ti oxide compound and Ti nitride sometimes at-20 DEG C, toughness is reduced.
Technology disclosed in patent documentation 3 is the technology making ferrite transformation from TiN-MnS miscible precipitate.The method, as Large Heat Input Welding, plays effect when the residence time more than 1350 DEG C is shorter.But, electroslag welding or electro-gas welding such ultra-large linear energy input welding in, the residence time of more than 1350 DEG C is long, because of a large amount of TiN solid solution, ferrite transformation core is disappeared during this period, can not give full play to its effect.In addition, play a role as the starting point that brittle rupture occurs in the TiN-MnS miscible precipitate of the thick micron-scale ultra-large linear energy input HAZ sometimes at-20 DEG C, toughness is reduced.
Technology disclosed in patent documentation 4 makes HAZ organize the technology of miniaturization, even if also can expect the effect of miniaturization in ultra-large linear energy input welding by generating ferrite from the oxygen/sulfide of REM and Ca or the BN be formed at TiN.But the number being difficult to the oxygen/sulfide making REM and Ca increases.In addition, because TiN solid solution is fallen, so the toughness improving ultra-large linear energy input welded thin-wall box component by means of only ferrite transformation has limit.In addition, the oxygen/sulfide of REM and Ca or on TiN, separate out BN ultra-large linear energy input HAZ sometimes at-20 DEG C of the miscible precipitate of thick micron-scale in play a role as the starting point that brittle rupture occurs, toughness is reduced.
Technology disclosed in patent documentation 5 suppressing austenite crystal to grow by utilizing the fine oxide compound containing Mg of 0.01 ~ 0.20 μm, utilizing the complex body be made up of the oxide compound containing Ti of 0.20 ~ 5.0 μm and MnS to promote ferrite transformation in crystal grain, thus improve the technology of ultra-large linear energy input welded thin-wall box component toughness.But, in the generation of the oxide compound containing Ti, need Al amount to suppress below 0.005%, the advantage of the steel of infringement interpolation Al in the past.That is, the Al amount is in the past in the Al deoxidized steel of about 0.010 ~ 0.5%, the exothermic oxidation produced by utilizing the Al in steel and easily can control liquid steel temperature, can cheapness and stably carry out the batch production of steel.As described in Patent Document 5, if Al addition is suppressed below about 0.005%, then need to carry out heating etc. with molten steel heating unit and replace utilizing the exothermic oxidation of Al to control the means of liquid steel temperature.Al in molten steel also has and utilizes the oxygen in air to the effect preventing molten steel from polluting, and in addition, for by forming nitride, well-known Al guarantees that material is effective, if Al amount reduces to less than 0.005%, then damages the advantage that these add Al.
Technology disclosed in patent documentation 6 be containing 0.005 ~ 0.5 μm MgO, MgS, Mg(O, S) in steel of more than two kinds in, by utilizing these minuteness particles to suppress austenite crystal grow, thus the technology of raising ultra-large linear energy input welded thin-wall box component toughness.But need Al amount to suppress below 0.01% in the generation of fine MgO, equally, its problem damages the advantage of above-mentioned interpolation Al.
Disclosed in patent documentation 7, technology is the technology that present inventor etc. makes, it is premised on the Al adding more than 0.015%, a large amount of is in the steel of (Mg, Mn) S particle of 0.005 ~ 0.5 μm containing particle diameter, by utilizing these minuteness particles to suppress austenite crystal to grow, thus improve the technology of ultra-large linear energy input welded thin-wall box component toughness.But, its HAZ toughness improves approved evaluation temperature and is-5 DEG C, for the HAZ toughness guaranteed under-20 DEG C of such harsh low temperature environments, particularly residual to some extent as problem for stably obtaining good value in the Charpy impact test at-20 DEG C.
Prior art document
Patent documentation
Patent documentation 1: Japanese Laid-Open Patent Publication 60-184663 publication
Patent documentation 2: Japanese Laid-Open Patent Publication 60-245768 publication
Patent documentation 3: Japanese Unexamined Patent Publication 2-254118 publication
Patent documentation 4: Japanese Laid-Open Patent Publication 61-253344 publication
Patent documentation 5: Japanese Unexamined Patent Publication 9-157787 publication
Patent documentation 6: Japanese Unexamined Patent Publication 11-286743 publication
Patent documentation 7: Japanese Unexamined Patent Publication 2002-3986 publication
Non-patent literature
Non-patent literature 1: " iron と Steel ", Nippon Steel association issues, the 61st year (1975) o.11, the 65th page
Summary of the invention
The problem that invention will solve
The present invention puts in view of the above problems and proposes.That is, its object is to, premised on the steel adding Al, the heat inputs such as the electro-gas welding of application in the electroslag welding applied in a kind of assembling of box column of high-rise and shipbuilding and bridge etc. are provided to be the steel material for welding of the excellent in low temperature toughness of HAZ in the ultra-large linear energy input welding of more than 200kJ/cm.
The present invention is as described below as the characteristic of the concrete steel material for welding of object.
A necessary preheating temperature during () y shape weld cracking expreiment is less than 25 DEG C.
The welded heat affecting zone (HAZ) of ultra-large linear energy input welding joint during (b) weld heat input 400kJ/cm impart the thermal cycling that the thermal process near to welding welded bonds (FL) simulate time Charpy impact energy be more than 100J at-20 DEG C.
Moreover, when considering the application of above-mentioned component, as described below preferred of the characteristic of mother metal.
C () thickness of slab is 40mm ~ 100mm, especially be 60mm ~ 80mm, in 1/4 (1/4t portion) of the thickness of slab of mother metal, tensile strength is more than 490MPa, is especially more than 510MPa and below 720MPa, yielding stress is more than 355MPa, especially be more than 390MPa, the Charpy impact energy at-40 DEG C is more than 100J.
Moreover, if improve tensile strength, be difficult to guarantee HAZ toughness, so also the upper limit of yielding stress can be defined as 650MPa or 600MPa, the upper limit of tensile strength be defined as 670MPa or 650MPa.Also the steel as object can be defined as Plate Steel.
For the means of dealing with problems
Present inventors etc. are for solving the problem and achieving the above object, for being that the minuteness particle of (Mg, Mn) S of 0.005 ~ 0.5 μm is to the steel of the interpolation Al suppressing austenite crystal to grow by particle diameter disclosed in patent documentation 7, in order to seek the further raising of low-temperature flexibility, to grow headed by the kind of effective particle and the investigation of number suppression austenite crystal, carry out large quantity research.Consequently, new discovery: C content (addition) is strictly restricted to more than 0.05% and lower than 0.12%, Si content is strictly restricted to lower than 0.10%, N content in steel is reduced to less than 0.0050%, O amount in steel is reduced to less than 0.0020%, B content is restricted to 0.0005% ~ 0.0020%, and the hardening capacity of the steel simultaneously can evaluated with hardenability index DI value is defined as the optimum range of 0.70 ~ 2.30, and every 1 square millimeter contains 1.0 × 10
4~ 3.0 × 10
5individual particle diameter is that (Mg, Mn) S of 0.015 ~ 0.2 μm is namely containing the sulfide of Mg and Mn, in addition by ratio shared in the total amount of Mg and Mn for the Mg in (Mg, Mn) S particle in atom % control for 70% ~ 90%, be effective for the low-temperature flexibility in HAZ when improving ultra-large linear energy input welding thus.According to new discovery, the steel material for welding of the excellent in low temperature toughness of the HAZ during a kind of ultra-large linear energy input can be provided premised on the steel adding Al to weld, this completes the present invention.
" steel material for welding " in the present invention is such as equivalent to JIS G3106 " Rolled Steel For Welded Structure ", JIS G3115 " steel heavy plate for pressure vessels ", JIS G3126 " low temperature pressure vessel carbon steel steel plate ".
That is, the present invention adopts following formation.
(1) steel material for welding of a scheme of the present invention, contain in mass %: more than C:0.05% and lower than 0.12%, Mn:1.40% ~ 1.80%, S:0.0020% ~ 0.0080%, Al:0.020% ~ 0.070%, Ti:0.004% ~ 0.012%, B:0.0005% ~ 0.0020%, Mg:0.0015% ~ 0.0030%, N:0.0020% ~ 0.0050%, O:0.0007% ~ 0.0020%, following element is restricted to: Si: lower than 0.10%, below Ca:0.0005%, below REM:0.0005%, below P:0.01%, below Cu:1.0%, below Ni:1.5%, below Cr:0.6%, below Mo:0.4%, below Nb:0.02%, below V:0.06%, remainder comprises Fe and inevitable impurity, the welding crack sensibility index represented by following formula 1 and Pcm value are 0.16% ~ 0.23%, the hardenability index represented by following formula 2 and DI value are 0.70 ~ 2.30, every 1 square millimeter contains 1.0 × 10
4individual ~ 3.0 × 10
5individual particle diameter is the sulfide containing Mg and Mn of 0.015 μm ~ 0.2 μm, described containing in the sulfide of Mg and Mn, the ratio of Mg shared by the total amount of Mg and Mn counts 70% ~ 90% with atom %.
Pcm=[C]+[Si]/30+ [Mn]/20+ [Cu]/20+ [Ni]/60+ [Cr]/20+ [Mo]/15+ [V]/10+5 × [B] formula 1
DI=0.367 × ([C]
1/2) × (1+0.7 × [Si]) × (1+3.33 × [Mn]) × (1+0.35 × [Cu]) × (1+0.36 × [Ni]) × (1+2.16 × [Cr]) × (1+3.0 × [Mo]) × (1+1.75 × [V]) × (1+1.77 × [Al]) formula 2
Wherein, [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], [Al], [B] represent the content represented with quality % of C, Si, Mn, Cu, Ni, Cr, Mo, V, Al, B respectively.
(2) in the steel material for welding described in above-mentioned (1), also below Ni:0.7% can be restricted to further in mass %.
(3) in the steel material for welding described in above-mentioned (1) or (2), also below Cu:0.5%, below Cr:0.3%, below Mo:0.10% can be restricted to further in mass %.
(4) in the steel material for welding according to any one of above-mentioned (1) ~ (3), also can thickness of slab be 40mm ~ 100mm, yielding stress is more than 355MPa, tensile strength is 490MPa ~ 720MPa.
Invention effect
Steel material for welding according to such scheme of the present invention, is applied by welding in applicable works at ultra-large linear energy input, can the extremely high welded structure of fabrication reliability, and its effect in industry member is extremely large.
Embodiment
Below, the steel material for welding of an embodiment of the invention is described.
The steel material for welding of present embodiment is by by having a large amount of manufacture actual achievements and premised on steel of manufacture method manufacture comprising Al deoxidation for excellent mass production processes.
The relation to the tissue of ultra-large linear energy input welded thin-wall box component and toughness such as present inventor has carried out detailed investigation.Consequently, even if draw the organizational controls of directly application Large Heat Input Welding HAZ in the past or the method for toughness raising, ultra-large linear energy input welded thin-wall box component toughness also confined conclusion.In addition, also found: for raising toughness, need to make the remarkable miniaturization of the austenite crystal of ultra-large linear energy input welded thin-wall box component (grain refined).
In the miniaturization of austenite crystal, the pinning effect of particle in steel is utilized to be effective.But, even if if think in nitride that more than the most stable TiN long-time heating to 1350 of heat DEG C, its major part also melts, and loses pinning effect, so the application in ultra-large linear energy input welding of nitride has limit.So, the particle of high temperatures must be utilized.But, for REM or the Ca oxide compound (also comprising oxygen/sulfide) of conventional art, although the stability under high temperature is higher, it is very difficult for these oxide compounds being dispersed in steel imperceptibly with the degree of the austenite crystal coarsening fully suppressing ultra-large linear energy input welded thin-wall box component.
In the past, in Al deoxidized steel, add the Mn of about 0.2 ~ the 2% and S of about 0.002 ~ 0.02% as everyone knows, form MnS.Because this MnS at high temperature melts away, so the particle making austenite crystal miniaturization can not be become.Present inventors etc. have carried out comparative study to various particle premised on Al deoxidized steel, found that: the sulfide containing Mg and Mn i.e. (Mg, Mn) S particle is at high temperature stablize and is the particle of applicable fine dispersion.In addition, to the particle mainly particle of less than 0.2 μm suppressing the austenite crystal growth of HAZ to play effect, but pass through the content etc. of control Mn, Mg, S, Al, can make fine (Mg, Mn) S in large quantities fine dispersion in steel.
But the approved evaluation temperature utilizing (Mg, Mn) S particle to improve the effect of HAZ toughness is so far-5 DEG C.That is, the HAZ toughness under-20 DEG C of harsh like this low temperature environments or problem is guaranteed.If toughness evaluation temperature is-20 DEG C of such low temperature, the miniaturization of the austenite crystal of HAZ is then utilized to be restricted to the effect improving toughness, only by the technical knowledge of raising HAZ toughness disclosed in patent documentation 7, the HAZ toughness at being difficult to stably to obtain-20 DEG C.
For this problem, present inventor etc. are for improving toughness further and having carried out large quantity research.Consequently new discovery: ratio shared in the total of control Mg at Mg and Mn in (Mg, Mn) S particle, and then on the basis strictly limiting C content, Si content, B content, N content, O content, by strictly limiting the hardening capacity represented with DI value, the further raising of HAZ low-temperature flexibility can be sought.
Below detailed content is described.
Present inventors etc. are with regard to the ratio of Mg and Mn in (Mg, Mn) S particle, and find that the ratio of Mg more increases, particle is at high temperature more stable, have the effect of strong suppression austenite crystal growth.The sulfide of (Mg, Mn) S particle identified by patent documentation 7 to be Mn be main body, if being the ratio of Mg and Mn is that 5% ~ 40%(is converted into atom % in % by weight Mg, then Mg is 10.6% ~ 60.1%) particle.These particles are the particle compositions close to MnS unstable under high temperature compared with the MgS of high temperatures, and the stability under the high temperature of therefore particle is insufficient, and the HAZ toughness at can not stably making-20 DEG C becomes good.But find: as long as can think that more than 70% of Mn in MnS is replaced into ratio shared in the total amount of (Mg, Mn) S particle of Mg, Mg and Mn namely in particle counts 70%≤Mg≤90%, 10%≤Mn≤30% (Mg, Mn) S particle with atom %, at high temperature just highly stable, and easily disperse imperceptibly.(Mg, Mn) S particle so is at high temperature stablized, and the reason of easily disperseing imperceptibly is now not clear.
Present inventor etc. is comprised in the inventor of patent documentation 7.The ultra-large linear energy input high tension steel of patent documentation 7, in manufacturing process, with the addition of Mg before adding enough Al amounts.The new discoveries such as present inventor: when adding Mg before adding enough Al amounts, the ratio that Mg exists with the form of thick oxide compound increases, and the ratio of the Mg in (Mg, Mn) S particle that result is fine declines.That is, the sulfide of (Mg, Mn) disclosed in patent documentation 7 S particle to be Mn be main body, if being the ratio of Mg and Mn is that 5% ~ 40%(is converted into atom % in % by weight Mg, then Mg is 10.6% ~ 60.1%) particle.Be somebody's turn to do (Mg, Mn) S particle stability at high temperature insufficient, sometimes the γ crystal grain part coarsening in FL portion.Even the austenite crystal that a part is thick, average austenite particle diameter is also particulate, the toughness at therefore can meeting-5 DEG C.But; the thick ferrite crystal grain of the austenite crystal that the part that results from-20 DEG C is thick or bainite crystal grain etc. become the starting point that fracture occurs, so (Mg, Mn) S particle that Mn disclosed in employing patent documentation 7 is main body is difficult to stably improve toughness.
Present inventor etc. for improve particle further high temperature under stability and implement large quantity research.Consequently find: by adding the Al of more than 0.020% before adding Mg, confirming being mixed into of Ca, REM to suppress to add Mg again after below 0.0005%, obtain based on atom % Mg and the atomic ratio of Mg high (Mg, Mn) S particle Absorbable organic halogens.And known: in the scope of the chemical composition of the steel material for welding of the present embodiment so manufactured, different from (Mg, Mn) S particle identified by patent documentation 7, generate (Mg, Mn) S particle of the stability further increased under high temperature, namely the ratio of Mg and Mn counts the high sulfide of the atomic ratio of Mg of 70%≤Mg≤90%, 10%≤Mn≤30% with atom %.In addition, also found: the HAZ toughness at-20 DEG C can being improved by adopting such particle.
Also known: if the evaluation temperature of toughness is-20 DEG C of such low temperature, then at-5 DEG C, unquestioned fine brittle relative toughness produces detrimentally affect, sometimes hinders the stabilization of toughness.Present inventors etc. have found: by reducing in the toughness evaluation at-5 DEG C the amount not finding dysgenic little and a small amount of island-like martensite (brittle microstructures of hard and martensite and austenitic mixed phase: MA) further, the toughness at-20 DEG C can significantly improve.And found: reduce island-like martensite, except strictly controlling C content, suppression Si content and strict control B content and N content, it is also effective for controlling with the index that DI value represents.
In HAZ when (Mg, Mn) S particle high by the atomic ratio of above-mentioned Mg suppresses austenite crystal to grow, the ferrite and pearlite of particulate becomes the microstructure of main body.It is believed that: in such tissue, island-like martensite disperses imperceptibly, low to harmful degree of toughness.But, at-20 DEG C, have the detrimentally affect to toughness, therefore need above-mentioned restriction.In addition, the restriction of DI value is also effective from making ferritic structure form more this point of particulate.
In addition, if-20 DEG C time the insufficient formation particulate of ferritic structure, then the detrimentally affect of a small amount of island-like martensite or a small amount of oxide compound described later or nitride increases.Present inventors etc. have found: for making the abundant miniaturization of ferrite (grain refined), only utilize (Mg, Mn) S particle to suppress austenite crystal to grow also insufficient, and the carrying out of ferrite transformation is postponed is important.By forming the tissue and the generation of suppression island-like martensite that contain the more bainite of the ferrite of particulate, the perlite of particulate and particulate, Absorbable organic halogens ground improves the HAZ toughness under low temperature.
When being suppressed austenite crystal growth by (Mg, Mn) S particle, carry out ferrite transformation because austenite crystal interfacial area is greatly and easily superfluous.So, make ferritic size and a point rate optimizing be important by making the carrying out of ferrite transformation postpone.To this, present inventor etc. are as the means making the carrying out of ferrite transformation postpone, and new discovery utilizes the restriction of above-mentioned DI value etc. to be effective.In addition, carry out again repeatedly studying, result new discovery: in order to more stably obtain utilizing DI value etc. to improve the effect of toughness, strictly control C content, Si content and DI value and reduce in the toughness evaluation at-5 DEG C not find that the oxide compound of dysgenic micron-scale and the amount of nitride are effective.In addition, also new discovery: in order to the amount of the oxide compound and nitride that control this micron-scale, the higher limit strictly limiting O content, Ti content and N content whole is effective.
The nitride utilizing TiN such or oxide compound to suppress as the coarsening of austenite crystal or in crystal grain the ferritic product nucleus of phase transformation conventional art in, be difficult to strictly to limit the higher limit that O content, Ti content, N content are whole.For the steel material for welding of present embodiment, owing to utilizing sulfide i.e. (Mg, Mn) S particle to suppress the coarsening of austenite crystal, so the whole higher limit of O content, Ti content, N content strictly can be limited.
In addition, in the present embodiment, the particle diameter of (Mg, Mn) S particle and individual number density (number of per unit area) are important.
In the present embodiment, the particle diameter of (Mg, Mn) S particle is defined as 0.015 ~ 0.2 μm.When lower than 0.015 μm, the effect of austenite crystal growth is suppressed to reduce.The lower limit of preferred particle diameter is 0.020 μm.On the other hand, if the particle surpassing 0.2 μm increases, then the Mg amount in steel is restricted, and the number of result minuteness particle significantly reduces, and suppresses the effect of austenite crystal growth to reduce.The upper limit of preferred particle diameter is 0.15 μm, more preferably 0.12 μm.
In addition, be every 1 square millimeter in the number of (Mg, Mn) S particle of the size of 0.015 ~ 0.2 μm be 1.0 × 10
4when more than individual, suppress the Be very effective of austenite crystal growth.The lower limit of preferred particle number is every 1 square millimeter is 3.0 × 10
4more than individual, preferred lower value is every 1 square millimeter is 4.0 × 10
4more than individual.On the other hand, 3.0 × 10 are increased to
5individually above need to add Mg, infringement economy, so be every 1 square millimeter by the ceiling restriction of the number of (Mg, Mn) S particle be 3.0 × 10 superfluously
5individual.Preferred higher limit is every 1 square millimeter is 2.0 × 10
5individual.
For the measuring method of particle number, make from steel plate (steel material for welding) and extract replica, with the transmission electron microscope (TEM) with characteristic X-ray detector (EDX) at least 1000 μm
2above area estimation is of a size of the particle number of 0.015 ~ 0.2 μm, is then converted into the number of per unit area.Such as, when 1 visual field being set to 100mm × 80mm to observe with the multiplying power of 20,000 times, the viewing area due to every 1 visual field is 20 μm
2, so at least observe 50 visual fields.If the number of the particle of now 0.015 ~ 0.2 μm is (1000 μm, 50 visual fields
2) in be 100, then particle number can be scaled every 1 square millimeter is 1 × 10
5individual.
Then, how many (Mg, Mn) S particle existence determined in the particle of number is measured.When particle number is many, owing to reaching more than 1000, so identify it is troublesome operation one by one to all particles.Therefore, as long as at least identify whether be (Mg, Mn) S, obtain it and there is ratio, be multiplied by (Mg, Mn) there is ratio of S by the particle number formerly obtained and obtain the number of (Mg, Mn) S particle to the particle of more than 20 by following condition.Such as, be 1 × 10 relative to above-mentioned particle number and every 1 square millimeter
5individual, (Mg, Mn) S to there is ratio be 90% when, it is 9 × 10 that the number of (Mg, Mn) S particle is defined as every 1 square millimeter
4individual.
Then, carry out describing to the authentication method of (Mg, Mn) S particle.In the present embodiment, by Mg and Mn respectively relative to the ratio of the total amount of Mg and Mn in (Mg, Mn) S particle, 70%≤Mg≤90% and 10%≤Mn≤30% is defined as in atom %.As long as just play austenite crystal micronized effect based on the sulfide of Mg, Mn, thus the element detecting beyond Mg, Mn also it doesn't matter.In addition, sometimes detect from particle trace O, as long as but the ratio of S and O counts 95%≤S with atom %, contained O be lower than 5% trace just can see (Mg, Mn) S particle as.But even if the ratio of S and O counts 95%≤S with atom %, contained O, lower than 5%, when identifying that particle is evident as the complex body of MnS and MgO, can not see (Mg, Mn) S particle as.The ratio of Mg and Mn and the ratio of S and O are obtained quantitatively by EDX.The beam diameter used when this is quantitative is 0.001 ~ 0.02 μm, and tem observation multiplying power is 50,000 ~ 1,000,000 times, carries out quantitatively the optional position in fine (Mg, Mn) S particle.
When making extraction replica (extraction replica) from steel plate, when being difficult to the number measuring (Mg, Mn) S particle at precipitate, such as cementite or the alloy carbonitride etc. because generating beyond multiple (Mg, Mn) S particle being of a size of 0.015 ~ 0.2 μm, the particle solid solution beyond (Mg, Mn) S is made by keeping about 60 seconds at 1400 DEG C, then ferritic thermal cycling is generated by giving quenching or giving in quenching midway, make cementite or the few sample of alloy carbonitride, also can make extraction replica thus.
(Mg, Mn) S particle is owing at high temperature stablizing, even if so give above-mentioned thermal cycling, its result also can not change.
In order to by the particle dispersion of above-mentioned such size and number in steel, in the present embodiment, as the chemical composition of steel material for welding, the content of restriction Mg, Mn, S and Al as described below.
Mg：0.0015%～0.0030%
Mg is required element for generation (Mg, Mn) S particle.Mg content lower than 0.0015% time, (Mg, Mn) S particle of required number can not be obtained.In addition, the ratio of the Mg in (Mg, Mn) S particle also reduces.In order to generate fine (Mg, Mn) S particle of more, more preferably add more than 0.0018% or more than 0.0020%.Containing during more than 0.0030%, Mg easily generates oxide compound, and (Mg, Mn) S measures saturated, and the effect improving HAZ toughness is also saturated, and infringement economy, so its higher limit is defined as 0.0030%.Consider economy, also its upper limit can be defined as 0.0027% or 0.025%.
Mn：1.40%～1.80%
Mn is the element forming (Mg, Mn) S particle, is therefore required element.By containing the Mn of more than 0.2%, fine (Mg, Mn) S particle can be disperseed in a large number, but in order to fully obtain (Mg, Mn) S particle containing 10%≤Mn≤30%, need containing more than 1.40%.In addition, lower than 1.40% time, for guaranteeing that intensity and HAZ toughness are also disadvantageous.In order to improve HAZ toughness, also the undergage of content can be decided to be 1.45% or 1.50%.On the other hand, if Mn is more than 1.80%, the easy coarsening of (Mg, Mn) S particle, makes HAZ toughness reduce, so using 1.80% as the upper limit.For improving HAZ toughness, also its upper limit can be defined as 1.75% or 1.70%.
S：0.0020%～0.0080%
S is required element for generation (Mg, Mn) S particle.S content lower than 0.0020% time, the quantity not sufficient of (Mg, Mn) S particle, so be decided to be 0.0020% by undergage.In order to generate fine (Mg, Mn) S particle of more, more preferably add more than 0.0025% or more than 0.0030%.On the other hand, if containing more than 0.0080%, the ratio of the Mg then in (Mg, Mn) S particle reduces, stability under the high temperature of particle is insufficient, therefore the number of fine (Mg, Mn) S particle of less than 0.2 μm reduces, and γ crystal grain (austenite crystal) micronized effect of ultra-large linear energy input welded thin-wall box component reduces.And, generate thick (Mg, Mn) S particle, play a role as the starting point that brittle rupture occurs.Therefore low temperature HAZ toughness declines.So its higher limit is defined as 0.0080%.The higher limit of preferred S amount is 0.0070%.For improving HAZ toughness, also its upper limit can be defined as 0.0065%, 0.0060% or 0.0055%.
Al：0.020%～0.070%
Al is required element for (Mg, Mn) S particle suppressing Mg to generate thick oxide compound, make Mg generation fine.Therefore, the content of more than 0.020% is necessary.In order to generate fine (Mg, Mn) S particle of more, more preferably add the Al of more than 0.025% or more than 0.030%.On the other hand, if containing more than 0.070%, then easily generate the brittle microstructures of hard and martensite and austenitic mixed phase (MA:Martensite-Austenite Constituent) at HAZ, or it is brittle to produce the HAZ that solid solution Al causes, therefore HAZ toughness declines.So, the upper limit is defined as 0.070%.The higher limit of preferred Al amount is 0.060%.In order to improve HAZ toughness, also its upper limit can be defined as 0.055% or 0.050%.
Below Ca:0.0005% and below REM:0.0005%
It is necessary for generating fine (Mg, Mn) S particle in the present embodiment.Therefore preferably reduce the content of the sulfide forming element beyond Mg, Mn as far as possible.If the sulfide forming element beyond Mg, Mn is superfluous, then can not obtain (Mg, Mn) S particle of sufficient amount.Representational element is Ca and REM, needs them to be defined as less than 0.0005%.Therefore the higher limit of Ca and REM is restricted to 0.0005%.Preferred higher limit is 0.0003%.Their lower limit does not need special restriction, and their lower limit is 0%.
HAZ toughness not only organizes the reduction of the reduction of miniaturization or thick cementite or island-like martensite and thick oxide compound or nitride according to austenite crystal miniaturization and intragranular, and can greatly change according to the content of alloying element.In addition, in order to ensure as the intensity of the mother metal needed for works or toughness, preferably containing suitable alloying element.Therefore, for alloying element other than the above (chemical composition), limit their content (addition) based on following reason.
More than C:0.05% and lower than 0.12%
C is the element improving strength of parent.Lower than 0.05% time to improve the effect of strength of parent little, so using 0.05% as lower limit.The lower value of preferred C content is 0.06%.On the other hand, if C content contains more than 0.12%, then cementite or island-like martensite because becoming the starting point of brittle rupture increase, thus HAZ toughness is declined.Particularly, for the low-temperature flexibility at-20 DEG C, even if more a small amount of little cementite or island-like martensite also easily become the starting point of brittle rupture, HAZ toughness is sometimes made to decline, so need strictly to limit for the upper limit of C content.The higher limit of preferred C content is 0.10% or 0.09%, and the higher limit of preferred C content is 0.08% further.
Si: lower than 0.10%
If containing Si, then in the microstructure of HAZ, easily generate brittle microstructures and the island-like martensite phase of hard.This island-like martensite makes the low-temperature flexibility deterioration of HAZ, so be defined as Si content lower than 0.10%.Preferred content is low, but be reduced to by Si content can sometimes along with cost increase lower than 0.03%, in such cases, preferably using 0.03% as lower limit.The lower limit of Si amount does not need special restriction, and its lower limit is 0%.Moreover, in order to improve HAZ toughness, do not wish containing Si, as long as but lower than 0.10%, also Si can be added wittingly.
Ti：0.004%～0.012%
Ti mainly improves the effect of the lifting hardening capacity that B produces, so be effective to the rising of strength of parent and the miniaturization of HAZ tissue.In the miniaturization of HAZ tissue, importantly guarantee that solid solution B measures, by solid solution B, the ferrite transformation of ultra-large linear energy input HAZ is postponed, thus make HAZ organize miniaturization.Because solid solution N fixes with TiN form by Ti, suppress the generation of BN, so can guarantee that solid solution B measures.In addition, the miniaturization organized for the HAZ organizing miniaturization (grain refined) and be heated to less than 1350 DEG C of the mother metal brought by the effect utilizing TiN to suppress austenite crystal to grow also is effective.But, lower than 0.004% time, these effects can not be obtained, so lower value is defined as 0.004%.In order to really play the effect that these add Ti, also its undergage can be decided to be 0.005% or 0.006%.On the other hand, if contained more than 0.012%, then generate thick TiN, it becomes the starting point that fracture occurs, and therefore HAZ toughness declines.So, higher limit is defined as 0.012%.The higher limit of preferred Ti amount is 0.010% or 0.009%, and the higher limit of preferred Ti amount is 0.008% further.
B：0.0005%～0.0020%
B plays the significant effect improving intensity when implementing controlled cooling model, it is to the effective element of raising strength of parent.In addition, in ultra-large linear energy input HAZ, solid solution B makes ferrite transformation postpone, so be effective to the miniaturization of microstructure.But, content lower than 0.0005% time, the effect of the intensity that can not be improved, so be defined as 0.0005% by lower value.In order to really play the effect that these add B, also its undergage can be decided to be 0.0007% or 0.008%.On the other hand, if contained more than 0.0020%, then separate out thick B nitride or carbon boride, this becomes the starting point of fracture, so make HAZ toughness decline.Therefore, higher limit is defined as 0.0020%.The higher limit of preferred B amount is 0.0017%, and the higher limit of preferred B amount is 0.0015% or 0.0013% further.
N：0.0020%～0.0050%
If N content is high, then easily generate thick TiN or (Ti, Nb) (C, N).These particles become the starting point that brittle rupture occurs.In evaluation at-20 DEG C of ultra-large linear energy input HAZ, even if the TiN of several μm or (Ti, Nb) (C, N) also becomes the starting point that brittle rupture occurs, cause the decline of HAZ toughness, so will strictly control.In addition, if solid solution N measures height, generate BN, solid solution B is measured and reduces, so be not preferred.If solid solution B measures reduction, then solid solution B makes ferrite transformation postpone, and makes HAZ organize the effect of miniaturization or improves the effect reduction of strength of parent.Particularly, in the steel material for welding of present embodiment, in order to not generate thick TiN, Ti content is defined as less than 0.012%, so easily increase can not be measured with the form of TiN by the solid solution N that Ti fixes.Therefore, need just strictly to limit N content from initial.Therefore, higher limit is defined as 0.0050%.Preferred higher limit is 0.0045% or 0.0040%, is more preferably 0.0030%.Preferred N content is low, but N content is reduced to and sometimes can brings cost increase lower than 0.0020%, so using 0.0020% as lower limit.In order to avoid cost increase, also can using 0.0023% or 0.0026% as its lower limit.
O：0.0007%～0.0020%
If O content is high, then easily generate multiple thick oxide compound.Thick oxide compound becomes the starting point that fracture occurs, and HAZ toughness is declined.In addition, even if when the Al content before interpolation Mg is more than 0.020%, when because of on equipment or the topsoil of molten steel that causes of the operational special reason such as improper etc. and make oxygen amount more than 0.0020%, increased by the Mg amount that thick oxide compound consumes.Consequently, the Mg ratio in sometimes fine (Mg, Mn) S particle declines, and the number of (Mg, Mn) S particle reduces, and HAZ toughness declines.Therefore the upper limit of O content is defined as 0.0020%.Preferred higher limit is 0.0018% or 0.0016%.Preferred O content is low, but is reduced to by O content and sometimes can brings cost increase lower than 0.0007%, so using 0.0007% as lower limit.In order to avoid cost increase, also its undergage can be decided to be 0.0009% or 0.0011%.
Below P:0.010%
P brings embrittlement of grain boundaries, the element harmful to toughness.Therefore, preferred P content is low.If contained more than 0.010%, even if made the austenite crystal miniaturization of HAZ by (Mg, Mn) S particle, HAZ low-temperature flexibility also declines, so be restricted to 0.010%.Be preferably less than 0.009%, be more preferably less than 0.008%.The lower limit of P amount there is no need special restriction, and its lower limit is 0%.
Below Cu:1.0%
Cu is to the effective element of raising strength of parent, also can contain Cu, if but contain more than 1.0%, then make HAZ toughness decline.So, Cu content is restricted to less than 1.0%.Be preferably less than 0.8%, be more preferably less than 0.7%, more preferably less than 0.5%.Cu is mixed into as inevitable impurity sometimes when molten steel manufactures from scrap iron etc., but there is no need to limit its lower limit especially, and its lower limit is 0%.
Below Ni:1.5%
Ni has the effect improving strength of parent by improving hardening capacity, and then improves toughness.Therefore, also Ni can be contained.But Ni is the element of high price, if contained more than 1.5% ground, damages economy, so Ni content is restricted to less than 1.5%.Be preferably less than 1.2%, be more preferably less than 1.0%, more preferably less than 0.7%.Ni is mixed into as inevitable impurity sometimes when molten steel manufactures from scrap iron etc., but its lower limit there is no need special restriction, and its lower limit is 0%.
Below Cr:0.6%
Cr has effect for raising strength of parent, therefore also can contain Cr.But, if contained more than 0.6%, then generate island-like martensite at HAZ, HAZ toughness declined.So, Cr content is restricted to less than 0.6%.Be preferably less than 0.4%, be more preferably less than 0.3%.Cr is when molten steel manufactures, and be sometimes mixed into as inevitable impurity from scrap iron etc., but its lower limit there is no need special restriction, its lower limit is 0%.
Below Mo:0.40%
Mo has effect for raising strength of parent, therefore also can contain Mo.But, if contained more than 0.40%, then generate sclerotic tissue at HAZ, HAZ toughness declined.So, Mo content is restricted to less than 0.40%.Be preferably less than 0.25%, be more preferably less than 0.10%.Mo is mixed into as inevitable impurity sometimes when molten steel manufactures from scrap iron etc., but its lower limit there is no need special restriction, and its lower limit is 0%.
Below Nb:0.020%
Nb is for raising strength of parent and organize miniaturization to be effective element, so also can contain Nb.But if contained more than 0.02%, then the precipitation of the Nb carbonitride in HAZ is remarkable, makes HAZ toughness decline.So, Nb content is restricted to less than 0.020%.Be preferably less than 0.018%, be more preferably less than 0.016%.Nb is mixed into as inevitable impurity sometimes when molten steel manufactures from scrap iron etc., but its lower limit there is no need special restriction, and its lower limit is 0%.
Below V:0.060%
V is for raising strength of parent and organize miniaturization to be effective element, so also can contain V.But if contained more than 0.060%, then the precipitation of the carbonitride in HAZ is remarkable, makes HAZ toughness decline.So, V content is restricted to less than 0.060%.Be preferably less than 0.050%.V is mixed into as inevitable impurity sometimes when molten steel manufactures from scrap iron etc., but its lower limit there is no need special restriction, and its lower limit is 0%.
In addition, in the steel material for welding of present embodiment, due to necessary preheating temperature during y shape weld cracking expreiment is defined as less than 25 DEG C, so the Pcm value represented by following formula 1 is defined as less than 0.23%.Be more preferably less than 0.22% or less than 0.21%.On the other hand, if Pcm value is lower than 0.16%, then sometimes can not obtain good strength of parent or good strength of joint, so the lower value of Pcm value is defined as 0.16%.Preferred lower value 0.17%.
Pcm=[C]+[Si]/30+ [Mn]/20+ [Cu]/20+ [Ni]/60+ [Cr]/20+ [Mo]/15+ [V]/10+5 × [B] formula 1
In addition, in the steel material for welding of present embodiment, in order to the hardening capacity by improving the HAZ after ultra-large linear energy input welding, reducing ferritic phase temperature, thus making ferrite miniaturization, so the hardenability index DI value represented by formula 2 is defined as more than 0.70.HAZ toughness can be improved by making the ferrite miniaturization in ultra-large linear energy input HAZ.That is, DI lower than 0.70 time, even if austenite particle diameter is particulate, also insufficient from the ferritic miniaturization of austenite phase transformation, also make toughness decline.Be more preferably 0.75.On the other hand, if DI value is more than 2.30, then HAZ sclerosis, HAZ toughness declines, so higher limit is defined as 2.30.The higher limit of preferred DI value is 1.50, more preferably 1.30.
DI=0.367 × ([C]
1/2) × (1+0.7 × [Si]) × (1+3.33 × [Mn]) × (1+0.35 × [Cu]) × (1+0.36 × [Ni]) × (1+2.16 × [Cr]) × (1+3.0 × [Mo]) × (1+1.75 × [V]) × (1+1.77 × [Al]) formula 2
In above-mentioned formula 1, formula 2, [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], [Al], [B] represent the content represented with quality % of C, Si, Mn, Cu, Ni, Cr, Mo, V, Al, B respectively.
The steel material for welding of present embodiment contains or limits mentioned component, and remainder comprises iron and inevitable impurity.But, in the welding steel of present embodiment, except mentioned component, also can contain following alloying element to improve the object such as intensity, toughness of steel itself further, or contain following alloying element as the inevitable impurity from auxiliary materials such as scrap iron.
Because Sb damages HAZ toughness, preferred Sb content [Sb] is less than 0.005%, is more preferably less than 0.003%, most preferably is less than 0.001%.
Because Sn damages HAZ toughness, preferred Sn content [Sn] is less than 0.005%, is more preferably less than 0.003%, most preferably is less than 0.001%.
Because As damages HAZ toughness, preferred As content [As] is less than 0.005%, is more preferably less than 0.003%, most preferably is less than 0.001%.
In addition, in order to give full play to the above-mentioned effect of mentioned component, preferably Zr, Co, Zn and W are restricted to less than 0.01% or less than 0.005% respectively.
The lower limit of Sb, Sn, As, Zr, Co, Zn and W does not need restriction, and the lower limit of each element is 0%.In addition, even if with the addition of the alloying element (such as Si, Ca, REM, P, Ni, Cr, Mo, Nb, V and Sb) specified without lower limit wittingly, or be mixed into as inevitable impurity, as long as its content is within claims, be just interpreted as these steel within claims of the present invention.
The effect of the raising HAZ toughness in the steel material for welding of present embodiment not only in ultra-large linear energy input welding effectively, and also effective in Large Heat Input Welding (such as more than 100 and lower than the degree of 200kJ/cm).
Then, the manufacture method of the steel material for welding of present embodiment is described.
As the melting method of steel, such as, liquid steel temperature being defined as less than 1650 DEG C, is less than 0.01% by molten steel O concentration guidelines, is less than 0.02% by molten steel S concentration guidelines, in this case, adds the Al of more than 0.020% before adding Mg.Now, confirming being mixed into of Ca, REM to suppress for adding Mg again after lower than 0.0005%, after the content that have adjusted other element as required, by casting, can obtain the strand of the minuteness particle containing (Mg, Mn) S in steel thus, the ratio of the Mg in described minuteness particle shared by the total amount of Mg and Mn counts 70% ~ 90% with atom %.
If the Al not by adding more than 0.020% before adding Mg reduces the oxygen amount in molten steel, then the Mg added thereafter is consumed with the form of thick oxide compound, and the Mg amount therefore becoming fine (Mg, Mn) S particle reduces.Consequently, the Mg/Mn ratio in (Mg, Mn) S particle reduces, and the stability under the high temperature of (Mg, Mn) S particle is declined.Therefore, the Al adding more than 0.020% before adding Mg is particularly important.
Even if when not adding Ca, REM wittingly, the refractory materials also sometimes used from ladle or the flux or the slag that add with the object such as desulfurization, alloy raw material is medium is mixed in molten steel.Therefore, being mixed into of Ca, REM is suppressed to be important below 0.0005%.In order to be less than 0.0005% by the suppression that is mixed into of Ca, REM, Ca, REM contained in refractory materials, flux, slag or alloy raw material etc. amount is managed.Or whether the stable form of oxide compound etc., shape and be difficult to be mixed in molten steel and manage are formed to Ca, REM.Do not need the lower limit limiting Ca and REM, its lower limit is 0%.
The reason of the order of addition of control Al and Mg described above and the mixed volume of Ca, REM is described.Only in steel, add Mg, almost can not generate (Mg, Mn) S particle.Its reason is that Mg is strong deoxidant element, sometimes becomes oxide compound.In addition, even if the Mg high a large amount of interpolation that is vapour pressure in molten steel is also difficult to the element effectively utilized in molten steel.Therefore, it is very important for preventing the Mg of the trace of about 0.0015 ~ 0.0030% to be consumed in the form of the oxide, generating (Mg, Mn) S particle.Add Al content when to add Al before Mg lower than 0.020% time, fully can not obtain the number of (Mg, Mn) S particle.Mg is now mainly with MgAl
2o
4or exist in the form of the oxide as MgO.In addition, Mg is consumed in the formation of oxide compound, so the ratio of the Mg in (Mg, Mn) S particle shared by the total amount of Mg and Mn also declines.
On the other hand, when making Al content be more than 0.020% before adding Mg, Al can be utilized to carry out deoxidation of molten steel fully, stably the oxygen amount in molten steel can be reduced to less than 0.0020%.Consequently, oxide amount reduces, and the composition of oxide compound is also with Al
2o
3for main body, MgO reduces, so most of Mg exists as (Mg, Mn) S particle.That is, by adding the Al of more than 0.020% before adding Mg, fine (Mg, Mn) S particle can be generated in a large number.
In addition, for generating fine (Mg, Mn) S particle, preferably reduce the content of the sulfide forming element beyond Mg, Mn as far as possible.Representational element is that Ca and REM, Ca or REM and Mg compare, and is easily combined with oxygen or sulphur, easily forms thick oxygen/sulfide.Even if added the Al of more than 0.020% before adding Mg, if Ca or REM is mixed in molten steel more than 0.0005% ground, then a large amount of generation comprises the thick oxygen/sulfide of Ca or REM and Al, is also difficult to stably obtain fine (Mg, Mn) S particle even if add thereafter Mg.In addition, even if among the interpolation Mg after the Al that with the addition of more than 0.020% or when being mixed into Ca or REM after adding Mg, if their mixed volume is more than 0.0005%, be also difficult to stably obtain fine (Mg, Mn) S particle.
About the heating after casting, rolling, heat-treat condition, as long as according to the mechanical property as target of female steel, Q-tempering etc. after temporarily cooling after direct quenching and tempering, rolling after suitable selection such as controlled rolling and controlled cooling, rolling.
Embodiment
Below embodiments of the invention are shown.Utilize converter steel-smelting, manufacturing thickness by continuous casting is the slab of 320mm.The chemical composition of the A1 ~ A52 of steel grade shown in table 1, table 2.For the steel grade A1 ~ A24 in table 1, before adding Mg, add the Al of more than 0.020%, be after less than 0.0005% confirming the suppression that is mixed into of Ca, REM, then add Mg.For steel grade A27 ~ A35, A37 ~ A42, A45 ~ A52 in table 2, before adding Mg, add the Al of more than 0.020%, be after less than 0.0005% confirming the suppression that is mixed into of Ca, REM, then add Mg.Steel grade A36 in table 2 added Al before interpolation Mg, but Al content is now lower than 0.020%.Steel grade A43 to add the Al of more than 0.020% before Mg adding, but with surplus be mixed into Ca state under add Mg.Steel grade A44 to add the Al of more than 0.020% before Mg adding, but with surplus be mixed into REM state under add Mg.Steel grade A25, A26 add Al after interpolation Mg.
Adopt manufacture method, thickness of slab, the mother metal characteristic of the slab with the chemical composition of steel grade A1 ~ A52 and the steel (steel No.1 ~ 52) that manufacture shown in table 3, table 4 and utilize welding to reproduce the joint toughness evaluation result of thermal cycling.As shown in table 3, table 4, make steel plate with controlled rolling and controlled cooling method, Q-tempering method, direct quenching and tempering legal system, thickness of slab is 40 ~ 100mm.About strength of parent (yielding stress and tensile strength), from 1/4 (1/4t portion) of thickness of slab, gather No. 4 pole tension test sheets specified in JIS Z2241 in the direction (L direction) parallel with rolling direction, evaluate with the method specified in JIS Z2241.About base metal tenacity, the shock test sheet specified JIS Z2242 is gathered from 1/4t portion in the direction (C direction) at a right angle with rolling direction, Charpy impact energy (vE-40) at obtaining-40 DEG C by the method specified in JIS Z2242, then evaluates.About weldability, by the method specified in JIS Z3158, be that 1.7kJ/mm carries out coating welding (also referred to as manual metal-arc welding) with heat input, obtain the preheating temperature prevented needed for root crack, then evaluate.About the evaluation of joint toughness, gather charpy impact test sheet by the test film of the thermal cycling from ultra-large linear energy input welding when imparting that to reproduce heat input be 500kJ/cm, evaluate.As thermal cycling, keep 30 seconds at peak temperature is 1400 DEG C, be then cooled to less than 100 DEG C with the speed of cooling of 1 DEG C/sec.Shock test is carried out (vE-20) at-20 DEG C, evaluates toughness by 9 mean values repeatedly and Schwellenwert.In addition, the sample of the thermal cycling of less than 100 DEG C is quenched to after 100 seconds to imparting maintenance at peak temperature is 1400 DEG C, determine austenite particle diameter, in addition, determine the particle number that particle diameter is (Mg, Mn) S particle of 0.015 ~ 0.2 μm according to the method described above.Now, the ratio determining the Mg in the particle of number shared in the total amount of Mg and Mn counts 70% ~ 90% with atom %., about each particle, the value of the average gained of the ratio (atom %) containing the Mg in the sulfide particles of Mg and Mn being 0.015 ~ 0.2 μm is shown particle diameter in table 3, table 4 as a reference.
About the target value of each characteristic, mother metal yielding stress is defined as more than 355MPa, mother metal tensile strength is defined as 490MPa ~ 720MPa, the vE-40 of mother metal is defined as more than 100J, the vE-20 of the thermal cycling necessary preheating temperature is defined as less than 25 DEG C, imparting the welding of reproduction ultra-large linear energy input is defined as more than 150J in mean value, is defined as more than 100J in Schwellenwert.
As table 3, table 4 express, steel No.1 ~ 24 all do not meet necessary preheating temperature, the target value of HAZ toughness reproduced in the thermal cycling of ultra-large linear energy input welding, every 1 square millimeter containing 1.0 × 10
4individual above particle diameter is (Mg, Mn) S particle of 0.015 ~ 0.2 μm, to be austenite particle diameter the be particulate of less than 150 μm.Moreover tensile strength is also up to more than 490MPa.
On the other hand, steel No.28,29 and 30,33,37,41, the respective C content of 50, Si content, P content, Al content, B content, DI value exceed higher limit, even austenite crystal, mean value, the Schwellenwert of HAZ toughness also all do not meet target value.Steel No.32,39, the respective Mn content of 45, Ti content, N content exceed higher limit, in addition steel No.31,40,47,49 because of DI value not enough, and can not target value be met at both the Schwellenwert of HAZ toughness or Schwellenwert and mean value.Steel No.34,36, the S content of 42, Al content, Mg containing quantity not sufficient, the number of (Mg, Mn) S particle is few, and austenite crystal is thick, and mean value, the Schwellenwert of HAZ toughness all can not meet target value.Steel No.35,43,44, the S content of 46, Ca content, REM content, O content is superfluous, the number of (Mg, Mn) S particle is few, and austenite crystal is thick, and mean value, the Schwellenwert of HAZ toughness all can not meet target value.The Pcm value of steel No.48 exceedes higher limit, can not meet the target value less than 25 DEG C of necessary preheating temperature.Steel No.25,26 with the addition of Al after with the addition of Mg, and the number of (Mg, Mn) S particle is few, and austenite crystal is thick, although the mean value of HAZ toughness can meet target value, Schwellenwert can not meet target value.Steel No.38 can not obtain organizing micronized effect because of Ti containing quantity not sufficient, can not meet the mean value of HAZ toughness, the target value of Schwellenwert.Steel No.51 exceedes the upper limit because of Cu content, and steel No.52 exceedes the upper limit, so HAZ toughness can not meet target value because of Cr content, Nb content, V content.Steel No.27,31,38,40, the yielding stress of the mother metal of 47 and tensile strength do not meet target value.
Utilizability in industry
According to steel material for welding of the present invention, be applied by welding in applicable works at ultra-large linear energy input, can the extremely high welded structure of fabrication reliability, it is extremely large in the effect of industry member.
Claims (5)
1. a steel material for welding, is characterized in that, contains in mass %:
More than C:0.05% and lower than 0.12%,
Mn：1.40％～1.80％、
S：0.0020％～0.0080％、
Al：0.020％～0.070％、
Ti：0.004％～0.012％、
B：0.0005％～0.0020％、
Mg：0.0015％～0.0030％、
N：0.0020％～0.0050％、
O：0.0007％～0.0020％，
Following element is restricted to:
Si: lower than 0.10%,
Below Ca:0.0005%,
Below REM:0.0005%,
Below P:0.01%,
Below Cu:1.0%,
Below Ni:1.5%,
Below Cr:0.6%,
Below Mo:0.4%,
Below Nb:0.02%,
Below V:0.06%,
Remainder comprises Fe and inevitable impurity;
The welding crack sensibility index represented by following formula 1 and Pcm value are 0.16% ~ 0.23%;
The hardenability index represented by following formula 2 and DI value are 0.70 ~ 2.30;
Every 1 square millimeter contains 1.0 × 10
4~ 3.0 × 10
5individual particle diameter is the sulfide containing Mg and Mn of 0.015 μm ~ 0.2 μm;
Described containing in the sulfide of Mg and Mn, the ratio of Mg shared by the total amount of Mg and Mn counts 70% ~ 90% with atom %,
Pcm=[C]+[Si]/30+ [Mn]/20+ [Cu]/20+ [Ni]/60+ [Cr]/20+ [Mo]/15+ [V]/10+5 × [B] formula 1
DI=0.367 × ([C]
1/2) × (1+0.7 × [Si]) × (1+3.33 × [Mn]) × (1+0.35 × [Cu]) × (1+0.36 × [Ni]) × (1+2.16 × [Cr]) × (1+3.0 × [Mo]) × (1+1.75 × [V]) × (1+1.77 × [Al]) formula 2
Wherein, [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], [Al], [B] represent the content represented with quality % of C, Si, Mn, Cu, Ni, Cr, Mo, V, Al, B respectively.
2. steel material for welding according to claim 1, is characterized in that, is restricted to further in mass %:
Below Ni:0.7%.
3. steel material for welding according to claim 1 and 2, is characterized in that, is restricted to further in mass %:
Below Cu:0.5%,
Below Cr:0.3%,
Below Mo:0.10%.
4. steel material for welding according to claim 1 and 2, is characterized in that,
Thickness of slab is 40mm ~ 100mm;
Yielding stress is more than 355MPa;
Tensile strength is 490MPa ~ 720MPa.
5. steel material for welding according to claim 3, is characterized in that,
Thickness of slab is 40mm ~ 100mm;
Yielding stress is more than 355MPa;
Tensile strength is 490MPa ~ 720MPa.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP2012/082373 WO2014091604A1 (en) | 2012-12-13 | 2012-12-13 | Steel material for welding |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103998636A CN103998636A (en) | 2014-08-20 |
| CN103998636B true CN103998636B (en) | 2015-07-22 |
Family
ID=49595850
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201280028721.2A Active CN103998636B (en) | 2012-12-13 | 2012-12-13 | Steel material for welding |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JP5321766B1 (en) |
| KR (1) | KR101488633B1 (en) |
| CN (1) | CN103998636B (en) |
| WO (1) | WO2014091604A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2637546C1 (en) * | 2013-11-07 | 2017-12-05 | ДжФЕ СТИЛ КОРПОРЕЙШН | Method of friction stir welding for high-strength thin-sheet or thick-sheet steel |
| JP6447253B2 (en) * | 2015-03-06 | 2019-01-09 | 新日鐵住金株式会社 | High strength steel for welding |
| JP7206701B2 (en) * | 2018-08-28 | 2023-01-18 | 日本製鉄株式会社 | steel plate |
| JP7206700B2 (en) * | 2018-08-28 | 2023-01-18 | 日本製鉄株式会社 | steel plate |
| JP6813127B1 (en) * | 2019-11-13 | 2021-01-13 | 日本製鉄株式会社 | Steel |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101163807A (en) * | 2005-03-17 | 2008-04-16 | 住友金属工业株式会社 | High tension steel plate, welded steel pipe and method for production thereof |
| CN102197154A (en) * | 2009-05-21 | 2011-09-21 | 新日本制铁株式会社 | Steel material for welding and method for producing same |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1179380B1 (en) * | 1999-08-06 | 2009-10-14 | Sumitomo Metal Industries, Ltd. | Martensite stainless steel welded steel pipe |
| JP4336020B2 (en) * | 2000-04-05 | 2009-09-30 | 新日本製鐵株式会社 | Cold-rolled steel sheet that prevents material deterioration in welds and weld heat-affected zones |
| JP3782645B2 (en) * | 2000-06-20 | 2006-06-07 | 新日本製鐵株式会社 | High strength steel for super large heat input welding |
| JP4276574B2 (en) * | 2004-04-12 | 2009-06-10 | 新日本製鐵株式会社 | Thick steel plate with excellent toughness of heat affected zone |
| JP5842314B2 (en) * | 2009-09-16 | 2016-01-13 | Ｊｆｅスチール株式会社 | High heat input welding steel |
-
2012
- 2012-12-13 KR KR1020137032745A patent/KR101488633B1/en active IP Right Grant
- 2012-12-13 CN CN201280028721.2A patent/CN103998636B/en active Active
- 2012-12-13 WO PCT/JP2012/082373 patent/WO2014091604A1/en active Application Filing
- 2012-12-13 JP JP2013515597A patent/JP5321766B1/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101163807A (en) * | 2005-03-17 | 2008-04-16 | 住友金属工业株式会社 | High tension steel plate, welded steel pipe and method for production thereof |
| CN102197154A (en) * | 2009-05-21 | 2011-09-21 | 新日本制铁株式会社 | Steel material for welding and method for producing same |
Also Published As
| Publication number | Publication date |
|---|---|
| CN103998636A (en) | 2014-08-20 |
| JPWO2014091604A1 (en) | 2017-01-05 |
| WO2014091604A1 (en) | 2014-06-19 |
| KR101488633B1 (en) | 2015-01-30 |
| JP5321766B1 (en) | 2013-10-23 |
| KR20140090565A (en) | 2014-07-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102119236B (en) | Steel plate for line pipes with excellent strength and ductility and process for production of same | |
| JP5950045B2 (en) | Steel sheet and manufacturing method thereof | |
| CN101652495B (en) | Steel material having excellent high temperature properties and excellent toughness, and method for production thereof | |
| CN102703808B (en) | Steel for 300MPa-grade automobile structural part and production method for steel | |
| CN102803536B (en) | Pearlite-based high-carbon steel rail having excellent ductility and process for production thereof | |
| CN101657555B (en) | Steel material having excellent high-temperature strength and toughness, and method for production thereof | |
| CN102459656B (en) | Process for producing thick high-strength steel plate with excellent toughness of heat-affected zone in high heat input welding and thick high-strength steel plate with excellent toughness of heat-affected zone in high heat input welding | |
| CN105189803A (en) | Abrasion resistant steel plate having low-temperature toughness and hydrogen embrittlement resistance, and manufacturing method therefor | |
| CN104087829A (en) | Steel material for high heat input welding | |
| CN103998636B (en) | Steel material for welding | |
| CN104870676A (en) | Low-yield-ratio high-strength cold-rolled steel sheet and method for manufacturing same | |
| JP5445723B1 (en) | Ultra high strength steel plate for welding | |
| CN101348881A (en) | Low cost high performance X70 pipeline steel and production method thereof | |
| JP5692138B2 (en) | High strength steel for super high heat input welding with excellent low temperature toughness in heat affected zone | |
| CN106244926A (en) | A kind of containing vanadium steel used for vehicle transmission shaft and production method thereof | |
| CN106574316B (en) | The manufacturing method of high input energy welding steel plate | |
| CN105750760A (en) | Steel Material For Welding | |
| JP5818343B2 (en) | Thick steel plate with excellent toughness in weld heat affected zone | |
| JP7205619B2 (en) | steel | |
| JP6277885B2 (en) | High strength steel for welding | |
| JP5053187B2 (en) | Perlite high carbon steel rail with excellent ductility | |
| JP3513001B2 (en) | Ultra-high heat input welding High-strength steel for welding with excellent heat-affected zone toughness | |
| JP2017155290A (en) | Sour resistant steel sheet | |
| WO2020208710A1 (en) | Steel material | |
| JP6277886B2 (en) | High strength steel for welding |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CP01 | Change in the name or title of a patent holder | ||
| CP01 | Change in the name or title of a patent holder |
Address after: Tokyo, Japan Patentee after: Nippon Iron & Steel Corporation Address before: Tokyo, Japan Patentee before: Nippon Steel Corporation |