CN100503866C - Steel having improved toughness in welding heat-affected zone and its production - Google Patents

Steel having improved toughness in welding heat-affected zone and its production Download PDF

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Publication number
CN100503866C
CN100503866C CNB2006101281703A CN200610128170A CN100503866C CN 100503866 C CN100503866 C CN 100503866C CN B2006101281703 A CNB2006101281703 A CN B2006101281703A CN 200610128170 A CN200610128170 A CN 200610128170A CN 100503866 C CN100503866 C CN 100503866C
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steel
contain
rem
oxide compound
toughness
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CN1932062A (en
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出浦哲史
杉村朋子
水渡英昭
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Kobe Steel Ltd
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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
    • C22C38/06—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
    • C22C38/001—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
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

Provided is a steel having improved toughness in welding heat-affected zone and its producing method. The steel contains: carbon of 0.01-0.2% (wt., follows are the same), silicon less than 0.5% (exclusion of 0% ), manganese less than 2.5% (exclusion of 0% ), phosphor less than 0.02% (inclusion of 0% ), sulphur less than 0.015% (inclusion of 0% ), aluminum less than 0.01% (inclusion of 0% ), REM of 0.001-0.1% and/or calcium of 0.0003-0.02% and zirconium of 0.001-0.05%, and as oxides containing of REM oxide and/or CaO and ZrO<SUB>2</SUB>.

Description

The steel of the tenacity excellent of welded heat affecting zone and method for making thereof
Technical field
The present invention relates to when welding is used in the steel of bridge, high-rise and boats and ships etc., be subjected to heat affecting position (below, be called " welded heat affecting zone " or " HAZ ") tough property improvement steel and method for making thereof.
Background technology
Be used in the desired characteristic of steel of bridge, high-rise and boats and ships etc., the increasingly stringent that becomes in recent years requires good especially toughness.These steel are general many by welded joint, still, particularly exist HAZ to be subjected to heat affecting and the such problem of the easy deterioration of toughness when welding.This toughness deterioration manifests greatly and all the more significantly along with the input heat in when welding becomes, and its reason is considered to be, if the input heat during welding becomes big, then the speed of cooling of HAZ is slack-off, and hardenability reduces and generates thick island martensite body.Therefore, in order to improve the toughness of HAZ, the input heat when doing one's utmost to suppress to weld gets final product.On the other hand, improving on the welding operation efficient, then expecting the employing of the big heat input welding process of for example electro-gas welding connection (electrogas arc welding) and solder flux brass welding process etc.
Therefore, when adopting big heat to import welding process, also can suppress the steel of HAZ flexible deterioration even proposed.For example in patent documentation 1, propose to have, be suppressed at thickization of the austenite grain of the HAZ portion generation when carrying out heat input welding greatly by trickle TiN dispersion is separated out again, thus the steel of inhibition HAZ toughness deterioration.But when studying, present inventors find, if welding metal arrives the high temperature more than 1400 ℃, then among the HAZ particularly in the position of approaching welding metal (hereinafter referred to as " welded bonds (bond) " portion), because the heat that bears during welding, above-mentioned TiN solid solution disappears, thereby can not suppress the toughness deterioration.
On the other hand, in patent documentation 2,, disclose the form that exists of oxide compound contained in the control steel and nitride as the technology that the toughness that makes mother metal and HAZ improves.In the document, disclose by being used in combination Ti and Zr, make the generation of trickle oxide compound and nitride and the toughness of mother metal and HAZ is improved, generate in order to make so trickle oxide compound and nitride, can add Ti and Zr successively.But when studying, present inventors find, in order further to improve the toughness of HAZ, though distinguishing to increase oxide amount, but in above-mentioned patent documentation 2 disclosed technology, in order to increase oxide amount, will heavy addition Ti and Cr, will form the carbide of Ti and Zr etc. so, the toughness of steel (mother metal) reduces on the contrary.
So present inventors take the lead in having proposed in patent documentation 3, even the time be subjected under the situation of pyritous heat affecting in welding, the steel that the toughness of HAZ can deterioration yet.These steel are to make La 2O 3-SiO 2Be oxide compound, Ce 2O 3-SiO 2Be oxide compound and La 2O 3-Ce 2O 3-SiO 2The composite oxides that are oxide compound etc. are dispersed in the steel, these composite oxides because in molten steel, exist with aqueous, so even in steel fine dispersion, and when welding, be subjected to heat affecting and also can solid solution do not disappear, the toughness of HAZ is improved.In the document, disclose then, can in the molten steel of having adjusted dissolved oxygen content, add La and Ce, then add Si again for above-mentioned composite oxides are generated.In addition, in the document, also disclose, in the steel tissue, TiN has been separated out, further improved the toughness of HAZ thus by making steel contain Ti.So for such TiN is generated, disclose to have in the above-mentioned molten steel that closes oxide compound to generation and added Ti.
[patent documentation 1] special public clear 55-26164 communique
[patent documentation 2] spy opens 2003-213366 branch newspaper
[patent documentation 3] spy opens the 2005-48265 communique
Summary of the invention
Present inventors, at the disclosed technology that takes the lead in as patent documentation 3, be conceived to the oxide compound of the composition beyond the composite oxides of above-mentioned composition, the divided oxide that makes the composition different with above-mentioned patent documentation 3 be dispersed in the flexible problem that whether can improve HAZ in the steel thus study repeatedly.That is, the objective of the invention is to, the steel and the method for making thereof of the toughness excellence of HAZ (welded heat affecting zone) is provided, it is to be dispersed in the steel by the divided oxide that makes the composition different with the steel of above-mentioned patent documentation 3 propositions to realize.
Present inventors are for being the steel of different composition with composition that above-mentioned patent documentation 3 proposes, for the toughness that can improve welded heat affecting zone is studied repeatedly.It found that, by compound interpolation REM and/or Ca and Zr in steel, when measuring the composition of the contained whole oxide compounds of these steel, if be adjusted into oxide compound and/or CaO and the ZrO that contains REM 2, then can improve the toughness of welded heat affecting zone, in addition, by compound again interpolation Ti in the system of composition so, when measuring the contained whole acidulants of described steel and form, contain the Ti oxide compound if be adjusted into, then the toughness of welded heat affecting zone further improves, thereby has finished the present invention.
Promptly, the so-called steel of the present invention that can solve above-mentioned problem, have following main points, contain: the C:0.01～0.2% (meaning of " quality % ", below identical), Si:0.5% following (not containing 0%), Mn:2.5% following (not containing 0%), with (do not contain 0%) below the N:0.01%, satisfy: P:0.02% following (containing 0%), S:0.015% following (containing 0%), with (contain 0%) below the Al:0.01%, and contain respectively: REM:0.001～0.1% and/or Ca:0.0003～0.02%, and Zr:0.001～0.05%, and in measuring these steel, during the composition of contained whole oxide compounds, contain oxide compound and/or the CaO of REM as oxide compound, and ZrO 2
Described steel, the composition of contained whole oxide compounds (in this manual, being sometimes referred to as oxide compound in the steel) will add up to as 100% o'clock in measuring these steel, and that preferably satisfies the oxide compound of REM and/or CaO adds up to more than 5% ZrO 2Be more than 5%.
Described steel, as other element, also contain Ti:0.08% following (not containing 0%), and in measuring described steel during the composition of contained whole oxide compounds, preferably contain the Ti oxide compound, can further improve the toughness of welded heat affecting zone by containing Ti.Described steel contain under the situation of Ti, when measuring the composition of whole oxide compounds, satisfy more than 3% as the preferred Ti oxide compound of oxide compound.
Described steel, as other element, also preferably contain from by the element of selecting more than one the following group that constitutes: (do not contain 0%) below the Cu:2%, (do not contain 0%) below the Ni:3.5%, (do not contain 0%) below the Cr:3%, (do not contain 0%) below the Mo:1%, (do not contain 0%) below the Nb:0.25%, (do not contain 0%) below the V:0.1% and (do not contain 0%) below the B:0.005%, by containing the intensity that these elements can improve mother metal.Also have, the surplus of described steel can be Fe and unavoidable impurities.
The steel that the present invention relates to for example, in the molten steel that dissolved oxygen content is adjusted into 0.0020～0.010% scope, add at least a element and the Zr that select from the group that is made of REM and Ca, just can make.Above-mentioned steel preferably in the molten steel that dissolved oxygen content is adjusted into 0.0020～0.010% scope, add at least a element and Ti and the Zr that select especially when containing Ti from the group that is made of REM and Ca.In this case, preferably in the above-mentioned molten steel of adjusting dissolved oxygen content, add at least a element and the Zr that from the group that constitutes by REM and Ca, selects earlier, add Ti again.
According to the present invention since in steel compound interpolation REM and/or Ca and Zr, in measuring these steel, during the composition of contained whole oxide compounds, be adjusted into the oxide compound and/or CaO and the ZrO that contain REM 2, therefore, the divided oxide of the composition different with the steel of proposition in the above-mentioned patent documentation 3 is dispersed in the steel, can improve the toughness of welded heat affecting zone (HAZ).Particularly by the above-mentioned oxide compound of the present invention regulation, even reach the high temperature of 1400 ℃ of levels can not disappear in steel in solid solution yet, so when welding steel of the present invention, be not limited to little～middle heat input welding, even in big heat input welding, also can prevent the toughness deterioration of welded heat affecting zone (HAZ).
Embodiment
Steel of the present invention is characterized in that, particularly contain REM and/or Ca and Zr respectively as alloying element, when measuring the composition of whole oxide compounds contained in these steel again, it is characterized by, and contain oxide compound and/or CaO and the ZrO of REM as oxide compound 2
At first, the oxide compound that steel of the present invention contain is described.Steel of the present invention during the composition of contained whole oxide compounds, contain oxide compound and/or CaO and the ZrO of REM in measuring these steel 2By when measuring the composition of the contained whole oxide compounds of these steel, contain oxide compound and/or CaO and the ZrO of REM 2, compare with the flexible situation that Zr formation oxide compound improves HAZ with adding REM, Ca respectively separately, can reduce addition for each element of steel.And, if in steel with the combination of above-mentioned oxide compound or composite oxides and contain, the absolute magnitude of the whole oxide compounds that contain in the steel is increased.Therefore, can prevent becomes the sulfide of REM of reason of toughness deterioration of steel (mother metal) and the sulfide of Ca or the carbide of Zr and generates because of excessive REM, Ca and the Zr of adding, so can suppress the toughness deterioration of mother metal, the toughness of HAZ is improved.
In addition, embodiment shows as described later, if suitably at least a element and the Zr dissolved oxygen content of selecting before added in control from the group that is made of REM and Ca, even the addition as many as of REM, Ca and Zr to a certain degree, oxide compound is formed, therefore do not have the sulfide of REM and the sulfide of Ca or the carbide of Zr and generate.So in addition oxide compound, even because the time be subjected to heat affecting and the high temperature that forms 1400 ℃ of levels also can not disappear in solid solution in welding, so can prevent to weld the time in thickization of HAZ portion austenite grain, consequently can prevent the toughness deterioration of HAZ.
Steel of the present invention, or contain (a) REM oxide compound and/or CaO and ZrO 2, perhaps contain the composite oxides that (b) contains REM and/or Ca and Zr, or contain (c) REM oxide compound and/or CaO and ZrO 2, and also contain the composite oxides that comprise REM and/or Ca and Zr and get final product.What is called comprises the composite oxides of REM and/or Ca and Zr, for example can enumerate: contain REM and Zr composite oxides, contain Ca and Zr composite oxides, contain the composite oxides of REM and Ca and Zr etc.
Steel of the present invention preferably except above-mentioned oxide compound, also contain the Ti oxide compound.That is, in measuring described steel, during the composition of contained whole oxide compounds, contain Ti 2O 3And Ti 3O 5, TiO 2Get final product.Because by containing the Ti oxide compound, can exempt to make the oxide amount that is dispersed in the steel further to increase, so can further improve the toughness of HAZ.
Above-mentioned Ti oxide compound can make it as oxide alone (Ti 2O 3, Ti 3O 5And TiO 2) in steel, contain, also can for example be included in the above-mentioned composite oxides (promptly contain REM and Zr composite oxides, contain Ca and Zr composite oxides, contain the composite oxides of REM, Ca and Zr) contain as composite oxides.
Above-mentioned steel, the composition of contained whole oxide compounds will add up to as 100% o'clock in measuring these steel, and that preferably satisfies the oxide compound of REM and/or CaO adds up to more than 5% ZrO 2Be more than 5%.Its reason is the oxide amount that improves in order to ensure the toughness that helps HAZ.The preferred oxide compound of REM and/or adding up to more than 10% of CaO are more preferably more than 15%, more preferably more than 20%.On the other hand, preferred ZrO 2Be more than 10%, more preferably more than 15%, more preferably more than 20%.
Contain at above-mentioned steel under the situation of Ti oxide compound, during the composition of contained whole oxide compounds, preferred Ti oxide compound satisfies more than 0.3% in measuring these steel.More preferably more than 1%, more preferably more than 3%, be preferably especially more than 5%, most preferably be more than 10%.Also have, though the Ti oxide compound in steel as Ti 2O 3, Ti 3O 5And TiO 2Exist, but, measure the composition of whole oxide compounds contained in the steel, need only whole Ti oxide compounds as Ti 2O 3The value that converts satisfies above-mentioned scope and gets final product.
Steel of the present invention, in measuring these steel during the composition of contained whole oxide compounds, the oxide compound of REM and/or CaO, ZrO 2With Ti oxide compound (Ti 2O 3) total be more than 55%.The total of these oxide compounds is lower than at 55% o'clock, helps the oxide amount deficiency of the toughness raising of HAZ, can not substantially improve the toughness of HAZ.More preferably more than 60%, more preferably more than 65%.
Also have, all the remaining composition of the composition of oxide compounds is not defined especially, but can be SiO for example 2, MnO and Al 2O 3Preferred SiO 2, Al 2O 3Be lower than 5% with the composition of MnO " other " in addition.
The composition of the oxide compound that steel are contained, by with (the Electron Probe X-rayMicro Analyzer: electron rays mini-probe X-ray analyzer) observe the cross section of steel, the inclusion of confirming in the field of view is carried out quantitative analysis and can measure of EPMA for example.The observation of EPMA, for example acceleration voltage is 20kV, and the test portion electric current is 0.01 μ A, and the field of view area is 1～5cm 2, the composition of the central part of the wavelength dispersion beam split quantitative analysis inclusion by characteristic X-ray.
As the size of the inclusion of analytic target, maximum diameter is more than the 0.2 μ m, analyzes number and is at least 100.
The analytic target element is Al, Mn, Si, Ti, Zr, Ca, La, Ce and O, adopt known substance, the X ray intensity of each element and the relation of concentration of element are tried to achieve as the pre-calibration line, from X ray intensity and the described lubber-line that obtains by inclusion as analytic target, concentration of element contained in the inclusion as analytic target is carried out quantitatively, is that inclusion more than 5% is as oxide compound with oxygen level.But, when an inclusion is observed a plurality of element, be ratio from the X ray intensity of the existence of representing these elements, be converted into the oxide alone of each element and calculate the composition of oxide compound.In steel of the present invention, so the resulting quantitative result of each oxide compound is averaged then, become the average composition of oxide compound.
Next, illustrate that the one-tenth in the steel of the present invention (mother metal) is grouped into.Steel of the present invention is characterized in that, contain REM:0.001～0.1% and/or Ca:0.0003～0.02% and Zr:0.001～0.05%.Stipulate the reasons are as follows of this scope.
REM, Ca and Zr are oxide compound and CaO, the ZrO that helps to form REM in steel 2Perhaps composite oxides and improve the flexible element of HAZ.In steel of the present invention, REM and Ca can distinguish separately or and use.
REM is contained more than 0.001%, be preferably more than 0.006%, more preferably more than 0.010%.But if excessively add, then the sulfide of REM generates, and therefore the toughness deterioration of mother metal should be suppressed at it below 0.1%.Be preferably below 0.09%, more preferably below 0.08%.Also have, in the present invention, so-called REM is meant the meaning that contains lanthanum family (lantanoid) element (15 kinds of elements from La to Ln) and Sc (scandium) and Y (yttrium), in these elements, also preferably contain and from the group that constitutes by La, Ce and Y, select at least a element, more preferably contain La and/or Ce.
Ca should contain more than 0.0003%, is preferably more than 0.0005%, more preferably more than 0.0008%.But if excessively add, the sulfide of then thick Ca generates, and therefore the toughness deterioration of mother metal should be suppressed at it below 0.02%.Be preferably below 0.015%, more preferably below 0.01%.
Zr should contain more than 0.001%, is preferably more than 0.003%, more preferably more than 0.005.But if excessively add, the carbide of then thick Zr generates, and therefore the toughness deterioration of mother metal should be suppressed at it below 0.05%.Be preferably below 0.04%, more preferably below 0.03%.
Steel of the present invention except comprising REM and/or Ca and Zr, as fundamental element, also comprise C:0.01～0.2%, Si:0.5% following (not containing 0%), Mn:2.5% following (not containing 0%) and N:0.01% following (not containing 0%).Stipulate the reasons are as follows of this scope.
C is the indispensable element of intensity that is used to guarantee steel (mother metal), in order to make this effect performance, need contain more than 0.01%.C is contained more than 0.02%, more preferably more than 0.03%.But if it surpasses 0.2%, generate the island martensite body in a large number at HAZ when then welding, not only cause the toughness deterioration of HAZ, also can bring disadvantageous effect to weldability.Therefore, C need be suppressed at below 0.2%, preferably below 0.18%, more preferably below 0.15%.
Si has desoxydatoin, and helps the element of the intensity raising of steel (mother metal).In order to make such effect performance effectively, preferably contain more than 0.02%, more preferably more than 0.05%, further preferably contain more than 0.1%.But if it surpasses 0.5%, then therefore the weldability of steel (mother metal) and base metal tenacity deterioration need be suppressed at it below 0.5%.Preferably be suppressed at below 0.45%, more preferably below 0.4%.Also have, when pursuing the HAZ high tenacity, Si preferably is suppressed at below 0.3%.More preferably below 0.05%, further preferably below 0.01%.But, suppress the Si amount if so, though the toughness of HAZ improves the tendency that has intensity to reduce.
Mn is the element that helps the intensity raising of steel (mother metal), in order to make this effect performance effectively, preferably contains more than 0.5%.More preferably contain more than 0.7%, more preferably more than 0.8%.But if it surpasses 2.5%, then make the weldability deterioration of steel (mother metal), therefore it need be suppressed at below 2.5%.Preferably be suppressed at below 2.3%, more preferably below 2%.
N is the element of separating out nitride (for example ZrN and TiN etc.), and this nitride can prevent to promote ferrite transformation, so help to improve the toughness of HAZ in thickization of the austenite grain of HAZ generation when welding.In order to make this effect performance effectively, preferably contain more than 0.002%, more preferably more than 0.003%.Because the many more granulars that can promote the austenite grain more of N, so the toughness of HAZ is improved the effect that plays effectively.But if it surpasses 0.01%, then solid solution N amount increases the toughness deterioration of mother metal.Therefore, N need be suppressed at below 0.01%, is preferably below 0.009%, more preferably below 0.008%.
Steel of the present invention except that containing above-mentioned element, also satisfy P:0.02% following (containing 0%), S:0.008% following (containing 0%) and Al:0.01% following (containing 0%), stipulate the reasons are as follows of this scope.
P is the element of easy segregation, particularly the crystal grain boundary segregation in steel and make the toughness deterioration.Therefore, P need be suppressed at below 0.02%, is preferably below 0.018%, more preferably below 0.015%.
S combines with Mn and generates sulfide (MnS), is the deleterious element that makes the deteriorated ductility of the toughness of mother metal and thickness of slab direction.S combines with La and Ce and generates LaS and CeS in addition, hinders the generation of oxide compound.Therefore, S should be suppressed at below 0.015%, preferably below 0.012%, more preferably below 0.008%, particularly preferably in below 0.006%.
Al is the strong element of deoxidation power, if excessively add then reduced oxide, thereby is difficult to generate the oxide compound of hope.Therefore, Al need be suppressed at below 0.01%, is preferably below 0.0090%, more preferably below 0.0080%.
Steel of the present invention though contain above-mentioned element, as other element, also preferably contain Ti:0.08% following (not containing 0%).Stipulate the reasons are as follows of this scope.
Ti generates the nitride of TiN etc. and Ti oxide compound and the element that helps the toughness of HAZ to improve in steel.In order to make this effect performance effectively, Ti is contained more than 0.005%, more preferably more than 0.007%, further preferred more than 0.01%.But if excessively add, then the toughness deterioration of steel (mother metal) therefore should be suppressed at it below 0.08%.Preferably below 0.07%, more preferably below 0.06%.
Steel of the present invention, in order to improve intensity, contain from more than one the element that goes out by the following group selection that constitutes also effective: (do not contain 0%) below the Cu:2%, (do not contain 0%) below the Ni:3.5%, (do not contain 0%) below the Cr:3%, (do not contain 0%) below the Mo:1%, (do not contain 0%) below the Nb:0.25%, (do not contain 0%) below the V:0.1% and (do not contain 0%) below the B:0.005%.Stipulate the reasons are as follows of this scope.
Cu is the element that makes the steel solution strengthening, in order to make this effect performance effectively, preferably contains more than 0.05%, more preferably more than 0.1%, more preferably more than 0.2%.Particularly, except solution strengthening, also bring into play the timeliness precipitation strength, can improve intensity significantly if made more than 0.6%.But contain if surpass 2%, the then toughness deterioration of steel (mother metal), so Cu can be suppressed at below 2%, preferably below 1.8%, more preferably below 1.6%.
Ni improves steel strength, and effectively the toughness that makes steel is improved the element that works, and in order to make such effect performance, preferably contains more than 0.05%, more preferably more than 0.1%, more preferably more than 0.2%.Ni is many more to be preferred more, but because it is expensive element, so from the viewpoint of economy, preferably it is suppressed at below 3.5%, more preferably below 3.3%, more preferably below 3%.
Add Cr in order to improve intensity, preferably contain more than 0.01%, more preferably more than 0.02%, more preferably more than 0.03%.But if it surpasses 3% weldability deterioration, so Cr preferably is suppressed at below 3%, more preferably below 1.5%, further preferably below 1%.
Add Mo in order to improve intensity, preferably contain more than 0.01%.Be recommended as and more preferably contain more than 0.02%, further preferred more than 0.03%.But make the weldability deterioration if it surpasses 1%, therefore preferred Mo is below 1%, is recommended as more preferably to be suppressed at below 0.9%, further preferably below 0.8%.
Add Nb in order to improve intensity, preferably contain more than 0.005%, more preferably more than 0.01%, more preferably more than 0.03%.But, because, make the toughness deterioration of mother metal, so preferably Nb is suppressed at below 0.25%, more preferably below 0.23%, more preferably below 0.2% if it surpasses 0.25% carbide (NbC) separates out.
Add V in order to improve intensity, preferably contain more than 0.005%, more preferably contain more than 0.01%, more preferably more than 0.03%.But if surpassing 0.1% weldability, it worsens, and the toughness deterioration of mother metal, therefore preferred V is below 0.1%, more preferably it is suppressed at below 0.08%, further preferably below 0.06%.
B can improve the intensity of steel, and in when welding heated HAZ refrigerative process, combine with N in the steel and separates out BN, and promotion is from the ferrite transformation of austenite intragranular.In order to make such effect performance effectively, preferably contain more than 0.0003%, more preferably more than 0.0005%, more preferably more than 0.0008%.But if it surpasses 0.005%, then make the toughness deterioration of steel (mother metal), therefore preferred B is below 0.005%.More preferably below 0.004%, more preferably below 0.003%.
Steel of the present invention, as must composition and contain, surplus can be Fe and unavoidable impurities (for example, Mg, As and Se etc.) with above-mentioned element.
Next, the method for making that can be fit to adopt when making steel of the present invention is described.Steel of the present invention for example in the molten steel of dissolved oxygen content being adjusted to 0.0020～0.010% scope, add at least a element and the Zr that select, and can make from the group that is made of REM and Ca.
That is, if in the molten steel of suitably having controlled dissolved oxygen content, at least a element and Zr that compound interpolation is selected from the group that is made of REM and Ca are just can make the oxide compound of regulation generate.At this moment if above-mentioned dissolved oxygen content is lower than 0.0020%, even at least a element and Zr that compound interpolation is selected from the group that is made of REM and Ca, because oxygen quantity not sufficient, so the oxide amount that can not guarantee to help the toughness of HAZ to improve, and can't form the REM of oxide compound and Ca forms sulfide, Zr forms carbide and makes the toughness deterioration of mother metal.Dissolved oxygen content before the above-mentioned element of compound interpolation is preferably adjusted to more than 0.0025%, more preferably more than 0.0030%.But, if dissolved oxygen content surpasses 0.010%,,, not only be not preferred on the melting operation, but also can generate the oxide compound of thick REM and the oxide compound of Ca so the reaction of oxygen in the molten steel and above-mentioned element becomes acutely then because the oxygen amount in the molten steel is too much, and ZrO 2Therefore dissolved oxygen content should be suppressed at below 0.010%, preferably below 0.008%, more preferably below 0.007%.
The compound interpolation after at least a element of selecting from the group that is made of REM and Ca and Zr, the composition that the interpolation alloying element is adjusted steel gets final product.
Also have, when in the above-mentioned molten steel of adjusting dissolved oxygen content, adding above-mentioned element, at least a element and Zr that compound interpolation is selected from the group that is made of REM and Ca get final product, for example when compound interpolation REM and Ca, (a) can be after in the molten steel of having adjusted dissolved oxygen content, adding REM and Ca and Zr, add alloying element and adjust the composition of steel, (b) also can in the molten steel of having adjusted dissolved oxygen content, add REM (or Ca) and Zr after, add Ca (or REM) alloying element in addition and adjust the composition of steel, then add Ca (or REM).
In the above-mentioned molten steel of adjusting dissolved oxygen content, at least a element that compound interpolation is selected from the group that is made of REM and Ca and the order of Zr are not specially limited, for example (a) can be after adding at least a element of selecting from the group that is made of REM and Ca, add Zr again, (b) can be after adding Zr, add at least a element of from the group that constitutes by REM and Ca, selecting again, (c) the also at least a element and the Zr that from the group that constitutes by REM and Ca, select of compound interpolation simultaneously.When compound interpolation REM and Ca, (d) can after having added REM (or Ca), add Zr again, then add Ca (or REM), (e) also can compound interpolation REM of while and Ca and Zr.
The interpolation order of Ti when steel of the present invention contain Ti is not specially limited, in the molten steel of having adjusted dissolved oxygen content, the compound interpolation after at least a element of from the group that constitutes by REM and Ca, selecting and Zr, (a) can when the composition of steel is adjusted, add Ti in the lump, (b) also can after the composition adjustment of steel, add Ti.Be preferably in the molten steel of having adjusted dissolved oxygen content, add at least a element and Zr and the Ti that from the group that constitutes by REM and Ca, select.In this case, preferred elder generation adds at least a element and the Zr that select from the group that is made of REM and Ca in the molten steel of having adjusted dissolved oxygen content, add Ti again.If in the molten steel of having adjusted dissolved oxygen content, add Ti, then at first form the Ti oxide compound, still, because the interfacial energy of Ti oxide compound and molten steel is little, so the size of the Ti oxide compound that forms becomes trickle.Then, by at least a element and the Zr that compound interpolation is selected from the group that is made of REM and Ca, the oxygen of REM is thing and CaO, ZrO 2, be that product nucleus is grown up with above-mentioned Ti oxide compound, so being the number of particle, the result increases, it is big that the thickization inhibition effect of austenite grain becomes.
So, by the dissolved oxygen content in the molten steel of converter and electric furnace initial refining, surpass 0.010% usually.Therefore in method for making of the present invention, before at least a element and Zr that compound interpolation is selected from the group that is made of REM and Ca, perhaps add before the Ti, the dissolved oxygen content in the molten steel need be adjusted to above-mentioned scope.As the method for adjusting dissolved oxygen content, can enumerate the method etc. that for example adopts RH formula degassing a refining unit to carry out the method for vacuum C deoxidation and add the deoxidation element of Si, Mn, Ti and Al etc., can certainly these methods of appropriate combination adjust dissolved oxygen content.In addition, also can adopt casting ladle heating-type a refining unit and simple type molten steel treatment facility etc., substitute RH formula degassing a refining unit and adjust dissolved oxygen content.In this case, because can't utilize the adjustment of the dissolved oxygen content of vacuum C deoxidation, so, can adopt the method for the deoxidation element that adds Si etc. for the adjustment of dissolved oxygen content.When adopt adding the method for deoxidation element of Si etc., can when tapping, add casting ladle the deoxidation element from converter.
The mode of the REM that adds in molten steel, Ca, Zr and Ti is not specially limited, for example as REM, can add pure La, pure Ce and pure Y etc., perhaps pure Ca, pure Zr, pure Ti also have Fe-Si-La alloy, Fe-Si-Ce alloy, Fe-Si-Ca alloy, Fe-Si-La-Ce alloy, Fe-Ca alloy, Ni-Ca alloy etc. in addition.In addition, also can in molten steel, add mishmetal (misch metal).So-called mishmetal is the mixture of cerium family rare earth element, specifically, contains the Ce about 40～50%, about 20～40% La.But, in mishmetal, because contain Ca mostly, so when mishmetal contains Ca, need satisfy the scope of the present invention's regulation as impurity.
The molten steel that so carries out the composition modulation and obtain, carries out hot rolling according to ordinary method again and gets final product after becoming slab (slab) according to the ordinary method continuous casting.
The steel of the present invention that so obtain, for example can use as the material of the works of bridge, high-rise and boats and ships etc., much less little～middle heat input welding, even in big heat input welding, also can prevent the toughness deterioration of welded heat affecting zone.
[embodiment]
Below, illustrate in greater detail the present invention by embodiment, but following embodiment and non-limiting character of the present invention also can suitably change enforcement in the scope of aim described later before can being fit to, these all are contained in technical scope of the present invention.
Experimental example 1
With 240 tons of converters with the molten iron refining after, tap to casting ladle from this converter, while carry out the composition adjustment and secondary refining is carried out in the temperature adjustment.Here, in casting ladle, the method for deoxidation according to shown in the following table 1 is adjusted into the dissolved oxygen content shown in the following table 1.After this, add element by the order shown in the following table 1.Then add remaining alloying element as required, finally be adjusted to the composition shown in the following table 2.Also have, adopt RH formula degassing a refining unit to take off H and take off S etc. in the secondary refining.
Following table 1 is expressed as order, method of deoxidation, the dissolved oxygen content that branch is adjusted.In addition, in following table 2, the one-tenth of the adjusted steel of expression composition is grouped into.Also have, in following table 1, add with following form respectively: La is that the form of Fe-La alloy, form, REM that Ce is the Fe-Ce alloy are the form that contains the mishmetal of La about 50% and about 25% Ce; Ca is that form, the Zr of Ni-Ca alloy or Ca-Si alloy or Fe-Ca press-powder body is that Zr monomer, Ti are the form of Fe-Ti alloy.But element is not added in "-" expression in the following table 2." be lower than " in addition though the meaning is not add element, because contain inevitably, so the scope below quantitation limit is detected.
[table 1]
No. Method of deoxidation Dissolved oxygen content (quality %) The interpolation order of element
1 By Si and Mn deoxidation 0.0035 Zr→REM
2 By Si and Mn deoxidation 0.0025 REM→Zr→Ca
3 By Si and Mn deoxidation 0.0025 Zr→Ca
4 By Si and Mn deoxidation 0.0037 REM and Zr while → Ti
5 By Si and Mn deoxidation 0.0045 Zr→REM→Ca→Ti
6 By Si and Mn deoxidation 0.0043 REM→Zr→Ti
7 By the Mn deoxidation 0.0076 REM→Zr→Ca→Ti
8 By Si and Mn deoxidation 0.0031 REM, Zr, Ti are simultaneously
9 By Si and Mn deoxidation 0.0055 Zr→La→Ti
10 By Si and Mn deoxidation 0.0039 Ti→Zr→Ce
11 By Si and Mn deoxidation 0.0052 Ti → REM and Zr while → Ca
12 By Si and Mn deoxidation 0.0045 Ti→REM→Zr
13 By Si and Mn deoxidation 0.0031 Ti→Zr→Ca
14 By Si and Mn deoxidation 0.0070 Ti→Zr→REM
15 By Si and Mn deoxidation 0.0135 Zr
16 By Si and Mn deoxidation Zr
17 By Si and Mn deoxidation 0.0220 REM→Ti
18 By Si and Mn deoxidation 0.0025 REM→Ti→Ca
19 By the Al deoxidation 0.0005 Ti→Ca
20 By Si and Mn deoxidation 0.0035 Ti→REM
21 By Si and Mn deoxidation 0.0032 Ti
22 By Si and Al deoxidation 0.0015 Ti→REM
23 By Mn and Al deoxidation 0.0013 Ti→REM→Zr→Ca
Figure C200610128170D00171
With continuous casting machine the adjusted molten steel of composition is cast as slab, sample under the cross-sectional cut of D/4 (wherein D is the thickness of the slab) position of this slab.Adopting Shimadzu Seisakusho Ltd.'s system " EPMA-8705 (device name) ", with 600 times of specimen surfaces of observing under the cutting, is precipitate more than the 0.2 μ m to maximum diameter, and its one-tenth of quantitative analysis is grouped into.Observation condition is that acceleration voltage is that 20kV, test portion electric current are that 0.01 μ A, field of view area are 1～5cm 2, to analyze number be 100, by the wavelength dispersion beam split of characteristic X-ray, the central part of quantitative analysis inclusion be divided into composition.The analytic target element is Al, Mn, Si, Ti, Zr, Ca, La, Ce and O, adopt known substance, the gamma intensity of each element and the relation of concentration of element are tried to achieve as the pre-calibration line, then, according to the gamma intensity that obtains from described precipitate and described lubber-line and the concentration of element of its precipitate is carried out quantitatively.
Among the quantitative result that obtains, oxygen level be precipitate more than 5% as oxide compound, the average composition after average as oxide compound.The average composition of the whole oxide compounds of following table 3 expression.Also have, the oxide compound of Ti oxide compound and REM, if represent metallic element by M, then its in steel with M 2O 3, M 3O 5And MO 2Form exist, but be that whole oxide compounds is converted into M 2O 3, measure composition.In addition, when an inclusion observes a plurality of element,, be converted into the oxide alone of each element and calculate the composition of oxide compound from the ratio of the X ray intensity of the existence of representing these elements.
The result who observes said sample with EPMA is that observed oxide compound most is the composite oxides that contain the composite oxides of REM and/or Ca and Zr or also comprise Ti, still, as oxide alone, has also generated oxide compound, CaO, the ZrO of REM 2, Ti 2O 3
Then,, simulate big heat input welding, carried out the welding shown in following and reproduced test in order to estimate the toughness that welding the time is subjected to the HAZ of heat affecting.Test is reproduced in welding, and being becomes 1400 ℃ mode with the sample under the slab cutting with integral body to heat, and keeps cooling off after 5 seconds in this temperature.Speed of cooling is adjusted according to the mode that from cooling time of 800 ℃ to 500 ℃ is 300 seconds.
The impact characteristics of cooled sample by carrying out the pendulum impact test of V otch, is measured-40 ℃ absorption energy (vE -40) estimate.VE -40For being qualified (HAZ toughness is good) more than the 150J.Following table 3 expression measurement result.
Figure C200610128170D00191
Can carry out following investigation from table 2～3.The example of the prerequisite of the present invention regulation is satisfied, because steel contain oxide compound and/or CaO and the ZrO of REM in No.1～14th 2So, can access the good steel of toughness of welded heat affecting zone.Particularly there is Ce No.10～14 because generate in the steel 2O 3And La 2O 3And/or CaO and ZrO 2, also have Ti in addition 2O 3So the toughness of welded heat affecting zone improves extraordinarily.
On the other hand, No.15～23rd, the example of arbitrary prerequisite of disengaging the present invention regulation.No.15～2 particularly are not because contain oxide compound and/or CaO and the ZrO of REM in the steel 2Any, so the poor toughness of welded heat affecting zone.No.23 is that Mn measures outside specialized range of the present invention, and dissolved oxygen content is also few in addition.
Experimental example 2
Above-mentioned experimental example 1 resulting No.6,12,19 slab are carried out hot rolling, obtain the steel plate of thick 30mm.
Adopting Shimadzu Seisakusho Ltd.'s system " EPMA-8705 (device name) ", with respect to the vertical cross section of the rolling direction of the steel plate that obtains, is that precipitate quantitative analysis its one-tenth 0.2 μ m more than be grouped into to maximum diameter with 600 times of observations.Observation condition is that acceleration voltage is that 20kV, test portion electric current are that 0.01 μ A, field of view area are 3～5cm 2, to analyze number be 100, by the wavelength dispersion beam split of characteristic X-ray, according to the step identical with above-mentioned experimental example 1, quantitative analysis precipitate central part be divided into composition.Also have, the observation place is D/4 (wherein D is the thickness of the slab) position of steel plate.
With the oxygen level among the resulting quantitative result be precipitate more than 5% as oxide compound, average average composition as oxide compound.The average composition of the whole oxide compounds of following table 4 expression.Also having, when by an inclusion observation a plurality of element being arranged, is the ratio from the X ray intensity of the existence of representing these elements, is converted into the oxide alone of each element and calculates the composition of oxide compound.
The result who observes with EPMA is that observed oxide compound is the composite oxides that contain REM and/or Ca and Zr mostly, perhaps also comprises the composite oxides of Ti, still, as oxide alone, has also generated oxide compound, CaO, the ZrO of REM 2, Ti 2O 3
Then,, simulate big heat input welding, carry out the welding shown in following and reproduce test in order to estimate the toughness that welding the time is subjected to the HAZ of heat affecting.Test is reproduced in welding, and being becomes 1400 ℃ mode with the sample under the slab cutting with integral body to heat, and keeps cooling off after 5 seconds in this temperature.Speed of cooling is adjusted according to the mode that from cooling time of 800 ℃ to 500 ℃ is 300 seconds.
The impact characteristics of cooled sample by carrying out the pendulum impact test of V otch, is measured-40 ℃ absorption energy (vE -40) estimate.VE -40For being qualified (HAZ toughness is good) more than the 150J.Following table 4 expression measurement result.
From following table 4 and above-mentioned table 3 as can be known, from the impact characteristics of steel plate cutting test film down, be roughly same degree with the impact characteristics of sample under cutting from slab, even hot rolling does not change HAZ toughness yet.

Claims (7)

1, a kind of steel of tenacity excellent of welded heat affecting zone is characterized in that, in quality %, contain:
C：0.01～0.2％；
Below the Si:0.5%, but do not contain 0%;
Below the Mn:2.5%, but do not contain 0%;
Below the N:0.01%, but do not contain 0%,
And satisfy:
Below the P:0.02%, and contain 0%;
Below the S:0.015%, and contain 0%; With
Below the Al:0.01%, and contain 0%, and,
Contain REM:0.001～0.1% and/or Ca:0.0003～0.02% and Zr:0.001～0.05% simultaneously, and Fe and unavoidable impurities,
And, contain oxide compound and/or CaO and the ZrO of REM as oxide compound in the steel 2
And in quality %, in the oxide compound, the total content of the oxide compound of described REM and/or CaO is more than 5% in steel, and the content of the oxide compound of described REM is below 73.1%, and the content of described CaO is below 38.5%, described ZrO 2Content be more than 5% below 78.1%.
2, steel according to claim 1 is characterized in that, described steel, and it is following but do not contain 0% also to contain Ti:0.08%, and also contains the Ti oxide compound as oxide compound in the steel.
3, steel according to claim 2 is characterized in that, in quality %, in steel in the oxide compound, the content of described Ti oxide compound is more than 0.3% below 13.1%.
4, according to claim 1 or 3 described steel, it is characterized in that, in quality %, described steel, also contain from by more than one elements of selecting the following group that constitutes:
Below the Cu:2%, but do not contain 0%;
Below the Ni:3.5%, but do not contain 0%;
Below the Cr:3%, but do not contain 0%;
Below the Mo:1%, but do not contain 0%;
Below the Nb:0.25%, but do not contain 0%;
Below the V:0.1%, but do not contain 0%; With
Below the B:0.005%, but do not contain 0%.
5, the manufacture method of the steel of the tenacity excellent of the described welded heat affecting zone of a kind of claim 1 is characterized in that,
In quality %, in the molten steel that dissolved oxygen content is adjusted into 0.0020～0.010% scope, add at least a element and the Zr that from the group that constitutes by REM and Ca, select.
6, the manufacture method of the steel of the tenacity excellent of the described welded heat affecting zone of a kind of claim 2 is characterized in that,
In quality %, in the molten steel that dissolved oxygen content is adjusted into 0.0020～0.010% scope, add at least a element, Ti and the Zr that from the group that constitutes by REM and Ca, select.
7, manufacture method according to claim 6 is characterized in that, to described dissolved oxygen content in the adjusted molten steel, is added at least a element and the Zr that selects earlier from the group that is made of REM and Ca, adds Ti again.
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