CN101910437B - Steel for welding structure having welded joint with superior ctod properties in weld heat affected zone - Google Patents

Steel for welding structure having welded joint with superior ctod properties in weld heat affected zone Download PDF

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CN101910437B
CN101910437B CN200880122473.1A CN200880122473A CN101910437B CN 101910437 B CN101910437 B CN 101910437B CN 200880122473 A CN200880122473 A CN 200880122473A CN 101910437 B CN101910437 B CN 101910437B
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welding
structural steel
welding joint
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oxide compound
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CN101910437A (en
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朴永桓
郑弘喆
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Posco Holdings Inc
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Posco Co 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
    • C22C38/001—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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium

Abstract

There is provided welding structural steel including, by weight, 0.01 to 0.2% C, 0.1 to 0.5% Si, 1.0 to 3.0% Mn, 0.01 to 0.1% Ti, 0.5 to 3.0% Ni, 0.0010 to 0.01% B, 0.003 to 0.006% N, 0.030% or less P, 0.005 to 0.05% Al, 0.030% or less S, 0.05% or less O, unavoidable impurities, and the balance of Fe. The Ti, O, N and B satisfy relations of 0.2=Ti/O=0.5, 2<=Ti/N<=5, 5<=O/B<=10 and 0.7<=(Ti+4B)/O<=1.5. A fine structure of a welded joint of the welding structural steel includes acicular ferrite with a structure fraction of 85% or more. In the welded joint, TiO oxides are distributed uniformly in a structure at a spacing of 0.5mu m or less, and have a grain size ranging from 0.01 to 0.1mu m. The number of TiO oxides is 1.0x10<7>/mm<3> or more. The welding structural steel has high strength characteristics in high heat input welding and employs TiO oxides and soluble B, so that the transformation into acicular ferrite is accelerated in a welded metal zone, thereby ensuring superior CTOD properties at the welded joint.

Description

Has steel for welded structures at the welding joint of the most advanced and sophisticated opening displacement excellent performance of Welding Heat-affected Zone Crack
Technical field
The present invention relates to the welding joint of crack tip opening displacement (CTOD) excellent performance; It is used for welded construction; More specifically; Relate to Welded Structural Steel, it can improve the CTOD performance of large-line energy welding joint in submerged arc welding (SAW) process of ship, building, bridge, marine structure, steel pipe and pipeline.
Background technology
Because the continuous rise of global oil price and the variation of Building technology, marine structure be more extreme environment construction down.The marine structure of building at cold district especially, must be used the made that has HS and the most advanced and sophisticated opening displacement of fine crackle (CTOD) at low temperatures.Yet the high-level efficiency welding is essential for welding this high-intensity thick material and in preset time, building up required building.The large-line energy welding technique of thick steel products has appearred being used to weld in this respect.One of the most widely used welding technique is submerged arc welding (SAW).
The big bonding area of SAW helps to reduce welding bead quantity.Therefore, with regard to productivity, SAW is much better than conventional melting pole gas shielded arc welding (GMAW).In at present used SAW technology, the heat of input is in the scope of about 25-45kJ/cm.
Yet in the welding of this large-line energy, the metal experience tissue that is welded solidifies, thereby may form thick columnar organization, and along forming coarse-grain circle ferritic, Wei Shi body ferritic etc. in the coarse grain of austenite grain boundary.Therefore, welding joint possibly become the structure position that impelling strength is degenerated and the most often taken place in institute's welding assembly.Be the welded stability that guarantees to form, need guarantee the CTOD performance of welding base metal through the fine structure of control welding base metal through the large-line energy welding.
For this reason, proposed to strengthen impelling strength through the alloying element or the use slag former that limit welding material.Yet those technology are neither controlled the fine structure and the grain size of welding base metal, also do not control the oxygen or the nitrogen content of welding base metal.Therefore, be difficult to guarantee the impelling strength of welding joint in large-line energy welding process such as SAW.
Summary of the invention
Technical problem
Make the present invention to solve the problems referred to above of this area at present; Therefore one aspect of the present invention provides and contains the element that is useful on the CTOD performance that in large-line energy welds SAW for example, strengthens welding joint and the welding joint of fine structure, and the Welded Structural Steel with this welding joint.
Technical scheme
One aspect of the present invention provides the Welded Structural Steel that comprises welding joint; Said welding joint contains by weight: the N of the Ni of the Mn of the C of 0.01-0.2%, the Si of 0.1-0.5%, 1.0-3.0%, the Ti of 0.01-0.1%, 0.5-3.0%, the B of 0.0010-0.01%, 0.003-0.006%, 0.030% or the Al of P still less, 0.005-0.05%, 0.030% or S still less, 0.05% or O still less, unavoidable impurities, and the iron of surplus.Wherein Ti, O, N and B satisfy relational expression 0.2≤Ti/O≤0.5,2≤Ti/N≤5,5≤O/B≤10 and 0.7≤(Ti+4B)/O≤1.5.Said welding joint also can contain and is selected from one or more following elements: the Mo of the V of the Cu of 0.1-2.0%, the Nb of 0.0001-0.1%, 0.005-0.1%, the Cr of 0.05-1.0%, 0.05-1.0%, the W of 0.05-0.5% and the Zr of 0.005-0.5%.Said welding joint also can contain REM or both of Ca, the 0.005-0.05% of 0.0005-0.05%.
The fine structure of said welding joint can comprise that organizing mark is 85% or more acicular ferrite, and all the other be polygonal ferrite and other grain boundary ferrites.Said welding joint can comprise with 0.5 μ M or littler spacing and is evenly distributed on the TiO oxide compound in the structure.The size of microcrystal of said TiO oxide compound can be 0.01-0.1 μ M.The quantity of TiO oxide particle can be 1.0 * 10 7/ mm 3Or it is more.
Beneficial effect
Welded Structural Steel with welding joint of the present invention has excellent intensity and CTOD performance, thereby even under severe cold, also can show excellent stability.
Embodiment
Hereinafter will describe the present invention.
Through the kind of the oxide compound of---the CTOD performance of known its butt welded seam metal area is effective---to influence acicular ferrite and big or small research repeatedly, the contriver has known that amount and the CTOD value of amount, the acicular ferrite of grain boundary ferrite in the weld-metal zone change according to the existence of TiO and solubility B.
Welded Structural Steel of the present invention based on above-mentioned research is characterised in that fully:
1), large-line energy uses TiO in welding the welding base metal of for example submerged arc welding (SAW);
2) the restriction oxide compound is distributed as 1.0 * 10 7/ mm 3Or higher, the size of oxide compound is 0.01-0.1 μ M (micron).
3) guarantee TiO and solubility B in the welding joint, accelerating transformation, thereby guarantee 85% or more acicular ferrite, thereby strengthen the toughness of welding zone to acicular ferrite.
1.TiO oxide compound control
When keeping Ti/O and O/B ratio rightly, the TiO oxide compound can distribute rightly.The appropriate distribution of this TiO oxide compound can be accelerated the transformation of TiO oxide compound to acicular ferrite, and prevents austenite crystal chap in the process of setting of welding base metal.When temperature descended, the appropriate TiO oxide compound that distributes was as the heterogeneous nucleation site of acicular ferrite in austenite crystal.Therefore, acicular ferrite can form before crystal boundary forms at grain boundary ferrite.Because the formation of this a large amount of acicular ferrites, the toughness of welding joint can significantly strengthen.
For this reason, need the meticulous of TiO oxide compound and distribution equably.In this respect, the inventor is known: size, content and the distribution of required TiO oxide compound can obtain through the ratio of optimizing Ti/O and O/B.According to the present invention, Ti/O and O/B are limited in respectively in the scope of 0.2-0.5 and 5-10, the known acquisition up to 1.0 * 10 in said scope 7/ mm 3Or more size is the TiO oxide compound of 0.01-0.1 μ m.
2. the fine structure of welding joint
When a large amount of TiO oxide compounds that obtain in the above described manner were distributed in the welding joint rightly, in the process of cooling of weld-metal zone, the transformation to acicular ferrite was accelerated in the crystal grain before crystal boundary takes place to change.Therefore, the invention is characterized in, in welding joint, form 85% or more acicular ferrite through guaranteeing a large amount of acicular ferrites.
3. the effect of solubility boron (B) in the welding joint.
The contriver knows that the oxide compound in being evenly distributed on welding joint, the solubility B that is present in the welding joint also diffuses to crystal boundary, has reduced the energy of crystal boundary and has suppressed the formation of crystal boundary place grain boundary ferrite.The transformation of intragranular to acicular ferrite quickened in inhibition to grain boundary ferrite forms, thereby helps to strengthen the CTOD performance in the welding joint.
The alloying element (hereinafter, % is meant wt%) of Welded Structural Steel of the present invention will be described below in more detail.
The content of C is in the scope of 0.01-0.2%.
C with 0.01% or more amount add intensity and welding hardness to guarantee welding base metal.Yet C content surpasses 0.2% may significantly reduce weld signature and impelling strength under the large-line energy condition, and causes the cold cracking of welding joint.Therefore, the content of C is limited in the scope of 0.01-0.2%.
The content of Si is in the scope of 0.1-0.5%.
Addition element Si is in order to play desoxydatoin.Si content is lower than 0.1% may cause desoxydatoin deficiency in the welding base metal.In addition, very little Si may cause the flowability of welding base metal to descend unfriendly.On the other side, Si content surpasses 0.5% may accelerate the transformation of martensitic-austenitic in the welding base metal (M-A constituent element) tissue, thereby reduces low-temperature impact toughness and welding crack sensibility is had adverse influence.Therefore, Si content is limited in the scope of 0.1-0.5%.
The content of manganese (Mn) is in the scope of 1.0-3.0%.
Mn is the alloying element of a kind of effective enhancing desoxydatoin and intensity.According to the present invention, Mn is with the form deposition around the MnS of TiO, thereby forms the Ti composite oxides, accelerated to help the generation of the acicular ferrite that the toughness of weld-metal zone strengthens.Yet Mn content too much may generate the low-temperature transformation tissue.Therefore, the manganese that adds as many as 3.0%.
The content of titanium (Ti) is in the scope of 0.01-0.1%.
Ti combines to form meticulous Ti oxide compound and meticulous TiN deposition with oxygen (O).
Therefore, Ti is considered to extremely important in the present invention.For obtaining said meticulous TiO oxide compound and TiN composite precipitation, need adding 0.01% or more Ti.Yet Ti content too much may cause thick TiO oxide compound and the thick sedimentary formation of TiN, and it may cause adverse influence to the performance of welding zone.Therefore, the Ti that adds as many as 0.1%.
The content of nickel (Ni) is in the scope of 0.5-3.0%.
Ni strengthens the intensity and the toughness of matrix effectively through solution hardening.Therefore, adding 0.5% or more Ni.Yet Ni content too much significantly increases hardness and high temperature rimose risk.Therefore, the Ni that adds as many as 3.0%.
The content of boron (B) is in the scope of 0.0010-0.01%.
B strengthens hardening capacity.B need add 0.0010% or more, also therefore suppresses the transformation to crystal grain ferrite with segregation on crystal boundary.Yet B content is not too much guaranteed further effect and is significantly increased welding hardness, thereby accelerates the transformation of M-A tissue.This may cause the cold cracking in the welding process and reduce toughness.Therefore, the B that adds as many as 0.01%.
The content of nitrogen (N) is in the scope of 0.003-0.006%.
N is the deposition of a kind of formation such as TiN and the element that increases the sedimentary amount of meticulous TiN.Particularly, N influences the sedimentary particle diameter of TiN, spacing and distribution significantly, the incidence of the composite precipitation of influence and oxide compound, and sedimentary high-temperature stability.Therefore, N content is set at 0.003% or higher.Yet N content does not guarantee to produce further effect above 0.006% and increase is present in the amount of the soluble nitrogen in the welding base metal, thereby damage toughness.Therefore, the content of N is limited in the scope of 0.003-0.006%.
The content of phosphorus (P) is 0.030% or lower.
P is a kind of high temperature rimose impurity element that in welding process, causes.Therefore, can control P content low as much as possible.Especially, be enhanced toughness and reduce cracking, can add the P of as many as 0.03%.
The content of aluminium (Al) is in the scope of 0.005-0.05%.
Al is a kind of reductor and the content that reduces oxygen in the welding base metal (O).Al combines to form meticulous AIN deposition with solubility N.Therefore, adding 0.005% or more Al.Yet Al content too much causes forming thick Al 2O 3, its blocking-up is to the formation of the essential TiO of enhanced toughness.Therefore, the Al that adds as many as 0.05%.
The content of sulphur (S) is 0.030% or lower.
Need S to form MnS.The S that adds as many as 0.030% is with deposition MnS composite precipitation thing.S content surpasses 0.030% can form for example FeS of low melting component, and it may cause the high temperature cracking.
The content of oxygen (O) is 0.05% or lower.
O and Ti react in the process of setting of welding joint and form the Ti oxide compound, and it accelerates in welding base metal the transformation to acicular ferrite.Yet O content too much causes producing other oxide compounds, for example thick Ti oxide compound and FeO, thus the butt welded seam metal area has adverse influence.Therefore, the O that adds as many as 0.05%.
Ti/O is in the scope of 0.2-0.5.
The Ti/O value can cause the growth of austenite crystal in the welding base metal to be suppressed less than 0.2 and to change the required Ti oxide compound of acicular ferrite into not enough.Particularly, the mark of contained Ti is low in the TiO oxide compound, can cause the TiO oxide compound to lose its effect as acicular ferrite nucleation site.Therefore, the mark that strengthens the effective acicular ferrite of toughness in the welded heat affecting zone is descended.On the other side, the Ti/O value surpasses 0.5 pair of growth that suppresses austenite crystal in the welding base metal does not have any further effect, reduces the ratio of alloying element contained in the oxide compound on the contrary, thereby causes TiO to lose its effect as acicular ferrite nucleation site.Therefore, the ratio of Ti/O is limited in the scope of 0.2-0.5.
Ti/N is in the scope of 2-5.
The Ti/N ratio reduces the sedimentary amount of TiN that forms in the TiO deposition less than 2 meetings, thereby make to accelerate to change into the effective acicular ferrite of enhanced toughness is become difficult.On the other side, Ti/N surpasses 5 not to be guaranteed any further effect and increases impelling strength.Therefore, Ti/N is limited in the scope of 2-5.
O/B is in the scope of 5-10.
The O/B value less than 5 cause solubility B quantity not sufficient, and solubility B suppresses the transformation to grain boundary ferrite through diffusing to austenite grain boundary in the process of cooling after welding.On the other side, the O/B value surpasses 10 and does not guarantee the amount of any further effect and increase solubility N, thereby damages the toughness of welded heat affecting zone.Therefore, O/B is limited in the scope of 5-10.
(Ti+4B)/O is in the scope of 0.7-1.5.
In the present invention, (Ti+4B)/value of O causes the amount of solubility N to increase less than 0.7, thereby the toughness of butt welded seam metal area strengthens disadvantageous effect is arranged.On the other side, (Ti+4B)/value of O surpasses 1.5 and causes precipitating the for example quantity not sufficient of TiN and BN.
For enhancing has the mechanical property of the steel of the above-mentioned composition of the present invention, add the element that one or more are selected from niobium (Nb), vanadium (V), copper (Cu), molybdenum (Mo), chromium (Cr), tungsten (W) and zirconium (Zr) in addition.
The scope of the content of Cu is 0.1-2.0%.
Cu is dissolved in the matrix to gain in strength through solution hardening.Therefore, Cu is effective with toughness to gaining in strength.For this reason, adding 0.1% or more Cu.Yet the content of Cu surpasses the hardness of 2.0% increase weld-metal zone, therefore reduces toughness and causes the high temperature of welding base metal to ftracture.Therefore, the content of Cu is limited in the scope of 0.1-2.0%.
If add Cu and Ni jointly, their total content is limited in 3.5% or lower so.The total content of Cu and Ni surpasses 3.5% significantly increases hardening capacity, infringement toughness and welding characteristic.
The content of Nb is in the scope of 0.0001-0.1%.
Nb is a kind of element that strengthens hardening capacity.Particularly, Nb is to reducing Ar 3Even temperature is effective with the formation range that under low rate of cooling, enlarges acicular ferrite structure, thereby helps effectively to obtain acicular ferrite structure.Be to realize the effect of gaining in strength, can add 0.0001% or more Nb.Yet Nb content surpasses 0.1% and accelerates the formation that weld-metal zone M-A organizes in the welding process, and it may reduce the toughness of weld-metal zone.Therefore, the content of Nb is limited in the scope of 0.0001-0.1%.
The content of V is in the scope of 0.005-0.1%.
V is a kind of through forming the element of VN deposition quickening ferritic transformation.Can add 0.005% or more V.Yet V content too much may form for example carbide of hard phase (hard phase) in the weld-metal zone, thus the toughness of infringement weld-metal zone.Therefore, the content of V is limited in the scope of 0.005-0.1%.
The content of Cr is in the scope of 0.05-1.0%.
Cr strengthens hardening capacity and intensity.Cr with 0.05% or still less amount add fashionable nothing and significantly act on, and when Cr content surpasses 1.0%, may damage the toughness of weld-metal zone.
The content of Mo is in the scope of 0.05-1.0%.
Mo is a kind of element that strengthens hardening capacity and intensity.Can add 0.05% or more Mo to guarantee intensity.Yet the upper limit of Mo content is restricted to 1.0% with the sclerosis of inhibition weld-metal zone and the cold cracking in the welding.
The content of W is in the scope of 0.05-0.5%.
W is effective to enhancing high temperature intensity and deposition.Therefore, can add 0.05% or more W.Yet the toughness that W content surpasses 0.5% butt welded seam metal area has adverse influence.Therefore, the content of W is limited in the scope of 0.05-0.5%.
The content of Zr is limited in the scope of 0.005-0.5%.
Can add 0.005% or more Zr, because it is effective to strengthening intensity.Yet the toughness that Zr content surpasses 0.5% butt welded seam metal area has adverse influence.Therefore, the content of Zr is limited in the scope of 0.005-0.5%.
According to the present invention, can add Ca and/or REM to suppress the growth of original austenite grains.
The effect of Ca and/or REM is the element that can in welding process, stablize welding arc and form oxide compound in the weld-metal zone.In addition, Ca and/or REM suppress the growth of austenite crystal in the process of cooling and accelerate intragranular ferritic transformation, thereby strengthen the toughness of weld-metal zone.For this reason, can add 0.0005% or more Ca, and 0.005% or more REM.Yet Ca content surpasses 0.05% above 0.05% with REM content and causes forming big oxide compound, and it may make toughness reduce.Cerium (Ce), lanthanum (La), yttrium (Y) and/or hafnium (Hf) can be used for REM.
Describe fine structure and the oxide compound that constitutes Welded Structural Steel of the present invention now in detail.
Main tissue: mark is 85% or more acicular ferrite
According to the present invention, the fine structure of the weld-metal zone that after the SAW process, forms comprises that mark is 85% or more acicular ferrite.Acicular ferrite structure both can obtain HS; Also can obtain low temperature CTOD performance; Conjunctive tissue unlike ferritic and bainite---its assurance favourable to the CTOD performance but butt welded seam metal area intensity is relatively poor, also unlike the conjunctive tissue of M-A tissue and bainite---and it provides the HS of weld-metal zone but is relatively poor and have high cold cracking susceptibility to the assurance of the CTOD performance of mechanical property such as weld-metal zone.The remaining tissue of weld-metal zone can comprise polygonal ferrite and a small amount of grain boundary ferrite.
Oxide compound: particle diameter is that 0.5 μ m or littler TiO oxide compound distribute with 0.5 μ m or littler spacing equably, and the particle diameter of TiO oxide compound and threshold value are respectively 0.01-0.1 μ m (micron) and 1.0 * 10 7/ mm 3
Usually, be present in the transformation of fine structure of kind, size and the numbers of poles earth effect weld-metal zone of the oxide compound in the weld-metal zone.Particularly, SAW weld-metal zone experience is solidified, thereby can make grain coarsening, and can form coarse-grain circle ferritic, Wei Shi body ferritic etc. from crystal boundary, and it may make the performance of weld-metal zone significantly descend.According to the present invention, for preventing said decline, the TiO oxide compound is evenly distributed in the welding region with 0.5 μ m or littler spacing, and the particle diameter and the threshold value of TiO oxide compound is restricted to 0.01-0.1 μ m and 1.0 * 10 respectively 7/ mm 3Or it is more.If the particle diameter of said oxide compound is less than 0.01 μ m, so said oxide compound just can not be accelerated in the SAW weld-metal zone transformation to acicular ferrite.On the other hand,, so locking action (being that the grain growing suppresses) decline of austenite crystal and the effect of said oxide compound are similar to thick non-metallic inclusion if particle diameter surpasses 0.1 μ m, thus the CTOD performance of infringement weld-metal zone.
Welded Structural Steel of the present invention also can be competent at multiple welding process except that SAW.Particularly, the large-line energy welding process of preferred high rate of cooling is because the high rate of cooling of weld-metal zone helps the fine distribution of said oxide compound and make tissue become meticulous.For the same reason, the cooling of steel and copper substrate can be used for improving the rate of cooling of welding joint.Yet, it should be noted that known technology is used for the present invention just to simple modification of the present invention, should be understood to include within the scope of the invention.
Embodiment
Now through following embodiment and form to of the present invention some/exemplary arrangement carries out detailed description.
Pass through the elementary composition weld-metal zone of SAW manufactured with 30-45kJ/cm or higher heat input like following table 1.The ratio of alloying element of weld-metal zone that can show effect of the present invention is as shown in table 2.
Take out the sample that is used to assess said weld-metal zone mechanical property from middle portion with the weld-metal zone of aforementioned manner welding.Use the sample of the sample of KS Standard No.4 (KS B 0801) as tension test.Ram speed with 100mm/min is carried out said tension test.The CTOD sample is based on the BS7448-1 standard manufacture, and at the center of SAW weld-metal zone fatigue crack is set.
Use image analyzer and electron microscope size, quantity and spacing through some count measurement remarkably influenced weld metal pieces flexible oxide compound.At 100mm 2Last assessment surface to be tested.In addition, through after said SAW process, said weld metal pieces being processed into the CTOD sample and in the CTOD testing apparatus, carrying out the assessments that CTOD tests the CTOD performance of carrying out said SAW weld-metal zone at-10 ℃.
Table 1
Figure BPA00001162582200101
Figure BPA00001162582200111
Figure BPA00001162582200121
(the * unit of representative " ppm ")
Table 2
Figure BPA00001162582200131
Table 3
Figure BPA00001162582200161
As shown in table 3, weld-metal zone constructed in accordance has up to 2 * 10 8/ mm 3Or more TiO oxide compound, and compared steel has 4.3 * 10 6/ mm 3Or TiO oxide compound still less.Therefore can find out: compare with compared steel, the size of invention steel composite precipitation thing is very all even meticulous, and sedimentary quantity significantly increases.In the fine structure of invention steel, the mark of the acicular ferrite of existence is 85% or higher.In said SAW process, the invention ladle contains intragranular acicular ferrite and polygonal ferrite, and the mark of acicular ferrite is 85% or higher.Therefore, the invention steel has the weld-metal zone CTOD performance excellent than compared steel.

Claims (7)

1. the Welded Structural Steel that comprises welding joint, said welding joint comprise, by weight:
The N of the Ni of the Mn of the C of 0.01-0.2%, the Si of 0.1-0.5%, 1.0-3.0%, the Ti of 0.01-0.1%, 0.5-3.0%, the B of 0.0010-0.01%, 0.003-0.006%, 0.030% or the Al of P still less, 0.005-0.05%, 0.030% or S still less, 0.05% or O still less, unavoidable impurities; And the iron of surplus
Wherein Ti, O, N and B satisfy relational expression: 0.2≤Ti/O≤0.5,2≤Ti/N≤5,5≤O/B≤10 and 0.7≤(Ti+4B)/O≤1.5; The fine structure of wherein said welding joint comprises that organizing mark is 85% or higher acicular ferrite, and all the other are polygonal ferrite and other grain boundary ferrites.
2. the Welded Structural Steel of claim 1, wherein said welding joint comprises that also one or more are selected from the W of the Mo of the Cr of the V of the Nb of the Cu of following element: 0.1-2.0%, 0.0001-0.1%, 0.005-0.1%, 0.05-1.0%, 0.05-1.0%, 0.05-0.5% and the Zr of 0.005-0.5%.
3. the Welded Structural Steel of claim 2, wherein when common when adding Cu and Ni in said Welded Structural Steel, Cu in the said welding joint and the total content of Ni are 3.5% or still less.
4. the Welded Structural Steel of claim 1, wherein said welding joint also comprises the Ca of 0.0005-0.05%, the REM of 0.005-0.05%, or comprises both.
5. the Welded Structural Steel of one of claim 1-4, wherein said welding joint comprise with 0.5 μ m or littler spacing and are evenly distributed on the TiO oxide compound in the structure.
6. the Welded Structural Steel of claim 5, wherein in said welding joint, the particle size range of TiO oxide compound is 0.01-0.1 μ m.
7. the Welded Structural Steel of claim 5, wherein in said welding joint, the quantity of TiO oxide fine particle is 1.0 * 10 7/ mm 3Or it is more.
CN200880122473.1A 2007-12-24 2008-12-23 Steel for welding structure having welded joint with superior ctod properties in weld heat affected zone Active CN101910437B (en)

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