CN1989265A - Steel for welded structures excellent in low temperature toughness of weld heat affected zone and method of production of same - Google Patents
Steel for welded structures excellent in low temperature toughness of weld heat affected zone and method of production of same Download PDFInfo
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- CN1989265A CN1989265A CN 200580024252 CN200580024252A CN1989265A CN 1989265 A CN1989265 A CN 1989265A CN 200580024252 CN200580024252 CN 200580024252 CN 200580024252 A CN200580024252 A CN 200580024252A CN 1989265 A CN1989265 A CN 1989265A
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Abstract
A steel for a welded structure excellent in low temperature toughness of a heat affected zone, characterized in that it is produced by a method which comprises providing a molten steel containing, in mass %, 0.03 to 0.12 % of C, 0.05 to 0.30 % of Si, 1.2 to 3.0 % of Mn, 0.015 % or less of P, 0.001 to 0.15 % or S, 0.10 % or less of Cu + Ni, 0.001 to 0.050 % of Al, 0.005 to 0.030 % of Ti, 0.005 to 0.10 % of Nb and 0.0025 to 0.0060 % of N, casting the molten steel by a continuous casting method with a cooling speed in the secondary cooling from a temperature near the solidification point to 800 DEG C of 0.06 to 0.6 DEG C/s, to prepare a cast material, subjecting the cast material to hot rolling and cooling the rolled material from a temperature of 800 DEG C or higher; and a method for producing the above steel for a welded structure. The above steel allows the production of a high strength thick steel plate for a marine structure excellent in weldability and in the low temperature toughness of HAZ, and can be produced at a low cost without the use of a complicated production method.
Description
Technical field
The present invention relates to all good high-strength steel plate and the manufacture method thereof of low-temperature flexibility of weldability and HAZ towards marine structure.In addition, the present invention also can be widely used in building, bridge, shipbuilding, the such field of building machinery.
Background technology
In the past, about as marine structure with the high-strength steel of steel, as the manufacture method of the steel of excellent weldability, known technology has: the speed of cooling by after the control hot rolling, can reduce Pcm as the weldability index.In addition, as HAZ (heat affected zone: the manufacture method of the steel of good-toughness HeatAffected Zone), for example as the spy open that flat 5-171341 communique put down in writing, known technology has: by add Ti in steel, serve as the generation that nuclear will promote intragranular ferrite (IntragranularFerrite:IGF) with Ti oxide compound (to call TiO in the following text).In addition, known technology also has: as the public clear 55-26164 communique of spy and special open that 2001-164333 communique etc. put down in writing, by Ti nitride (to call TiN in the following text) is disperseed in matrix, the grain growth of matrix when suppressing reheat by means of the pinning effect, thus guarantee the toughness of HAZ; And as the spy open that flat 11-279684 communique put down in writing, grain growth when dispersive Ti-Mg oxide compound not only makes reheat by means of the pinning effect in the matrix is suppressed, and generate effect by means of the promotion of IGF and make ferrite realize miniaturization, thereby guarantee the toughness of HAZ.But, make the problem that the technology of the steel of above-mentioned HAZ good-toughness exists and be: require very complicated technology, and cost is higher.
In addition, homodisperse TiO or TiN and HAZ is organized in the technology of miniaturization in making steel also study with regard to best TiO and TiN particulate chemical ingredients value and particle diameter.For example open in the 2001-164333 communique the spy and putting down in writing: for the ratio (Ti/N) of Ti and N is 1.0～6.0 steel, contains 5 * 10 by making in the steel before the welding
5～1 * 10
6Individual/mm
2Particle diameter be the TiN particle of 0.01～0.10 μ m, just can make the steel of HAZ good-toughness.
But, open in the 2001-164333 communique the spy and to put down in writing: make the particles dispersed of target in order to adopt this technology, must between 900～1300 ℃ of strand cooling stages, carry out the ageing treatment more than 10 minutes.Ageing treatment under this high temperature is very difficult, and neither be preferred from the angle consideration of thermo-efficiency and throughput.
On the other hand, opening flat 7-252586 communique according to the spy, generate in steel under the situation of MnS, is the generation that nuclear promotes IGF with MnS in the HAZ tissue, and crystal particle diameter is miniaturization effectively, thereby can guarantee desired toughness.Yet though there is not definite reason, in fact the Mn addition in the practical steel is set at higher limit, thereby resulting MnS amount generates aspect the effect in the promotion of bringing into play IGF to greatest extent and is and inadequate.
In addition, open in the flat 3-264614 communique the spy, interaction about TiN and MnS generation, TiN is designed to play a role as the separating out nuclear of MnS, in addition, in order effectively to utilize these precipitates, following scheme has been proposed also: promptly should the speed of cooling when solidifying in 1000～600 ℃ scope, be set at 5.0 ℃/min (about 0.08 ℃/s) below.But its reason is quantitatively narration not, and therefore, best speed of cooling it be unclear that.
Summary of the invention
The invention provides and a kind ofly do not adopt complicated manufacture method and can be with the high-strength steel plate and the manufacture method thereof towards marine structure of low cost manufacturing and weldability and HAZ excellent in low temperature toughness.Main points of the present invention are described below:
(1) steel for welded structures of the excellent in low temperature toughness of a kind of welded heat affecting zone (HAZ), it is characterized in that: this steel is in quality %, contain that C:0.03～0.12%, Si:0.05～0.30%, Mn:1.2～3.0%, P:0.015% are following, S:0.001～0.015%, Cu+Ni:0.10% are following, Al:0.001～0.050%, Ti:0.005～0.030%, Nb:0.005～0.10%, N:0.0025～0.0060%, surplus is made up of iron and unavoidable impurities, and, has the bainite structure more than 80% as structure of steel.
(2) steel for welded structures of the excellent in low temperature toughness of basis (1) described welded heat affecting zone (HAZ), it is characterized in that: this steel is in quality %, contain also that Mo:0.2% is following, V:0.03% is following, Cr:0.5% is following, Ca:0.0035% is following, Mg:0.0050% a kind among following, two or more.
(3) manufacture method of the steel for welded structures of the excellent in low temperature toughness of a kind of welded heat affecting zone (HAZ), it is characterized in that: molten steel is in quality %, contain C:0.03～0.12%, Si:0.05～0.30%, Mn:1.2～3.0%, below the P:0.015%, S:0.001～0.015%, below the Cu+Ni:0.10%, Al:0.001～0.050%, Ti:0.005～0.030%, Nb:0.005～0.10%, N:0.0025～0.0060%, surplus is made up of iron and unavoidable impurities, this molten steel is adopted the Continuous casting process casting, and the secondary refrigerative is set at 0.06～0.6 ℃/s and obtains strand near the speed of cooling to the 800 ℃ zero pour at this moment, then strand is carried out hot rolling.
(4) manufacture method of the steel for welded structures of the excellent in low temperature toughness of basis (3) described welded heat affecting zone (HAZ), it is characterized in that: this steel is in quality %, contain also that Mo:0.2% is following, V:0.03% is following, Cr:0.5% is following, Ca:0.0035% is following, Mg:0.0050% a kind among following, two or more.
(5) manufacture method of the steel for welded structures of the excellent in low temperature toughness of basis (3) or (4) described welded heat affecting zones (HAZ), it is characterized in that: above-mentioned hot-rolled condition is, with the temperature below the above-mentioned strand reheat to 1200 ℃, carry out hot rolling in non-recrystallization temperature district with the accumulation draft more than 40% then, after finishing hot rolling more than 850 ℃, be cooled to below 400 ℃ with 5 ℃/ speed of cooling more than the s from the temperature more than 800 ℃.
(6) manufacture method of the steel for welded structures of the excellent in low temperature toughness of a kind of welded heat affecting zone (HAZ) is characterized in that: in the manufacture method of (5), the steel that above-mentioned hot rolling is obtained cools off, and implements temper at 400～650 ℃ then.
Description of drawings
Fig. 1 has schematically illustrated Mn and the TiN influence to toughness value.
Embodiment
The present invention is for solving above-mentioned problem, by the lower Mn of heavy addition cost of alloy, seek to guarantee low cost and strength and toughness, the promotion of the inhibition effect of thickization of crystal grain that produces based on the pinning effect of TiN by compound use or the IGF that produces based on MnS simultaneously generates effect, seeks to guarantee good HAZ toughness.
Fig. 1 has schematically illustrated Mn and TiN to the influence of toughness value, is accompanied by the increase of Mn, and toughness is improved, and reaches 1.2% when above at the Mn addition especially, and it is obvious that its effect becomes.But the Mn addition surpasses at 2.5% o'clock, and its effect reaches capacity, and is surpassing 3.0% o'clock toughness deterioration on the contrary.In addition, be that the speed of cooling of steel when casting makes TiN dispersive steel about controlling high Mn, in whole M n scope, toughness is improved.
Strand is in the scope of the chemical ingredients shown in (1), contain C:0.08%, Si:0.15%, Mn:2.0%, P:0.008%, S:0.003%, Al:0.021%, Ti:0.01%, Nb:0.01%, N:0.005% in quality %, for this strand, the use calculation of thermodynamics has been predicted the TiN amount that may generate in equilibrium state, and result's volume fraction (volume of volume/steel of TiN) as can be known is 4.08 * 10
-4If crystal particle diameter is
The particle diameter of precipitate is
The volume fraction of precipitate is f, uses the Nishizawa formula of formula l and the volume fraction (4.08 * 10 that had before calculated
-4), then can obtain following result: the particle diameter that has only precipitate is under the situation below the 0.4 μ m, and the crystal particle diameter that is obtained by the pinning effect of precipitate is to it is generally acknowledged below the 100 μ m that can fully guarantee excellent in toughness.Even heat-staple TiN adds and pines for also can not decomposing between the high temperature, short time of welding etc., can suppress thickization of crystal particle diameter, thereby can fully keep and obtain HAZ flexible effect.
According to formula 1, in order to obtain having the strand that crystal particle diameter is the tissue below the 100 μ m, the particle diameter that must make precipitate is below 0.4 μ m.For this reason, be necessary to control the speed of cooling of strand, be 0.06 ℃/more than the s, be preferably 0.08 ℃/more than the s, more preferably 0.1 ℃/more than the s.Because thickness of slab is even the speed of cooling between the same strand also produces very big difference.Particularly the temperature head of casting billet surface and strand central part is bigger, and the process that stands temperature also has nothing in common with each other.But speed of cooling is limited to certain scope as can be known.Therefore, by the speed of cooling of control strand, only become possibility than the control of the TiN of decision before then making by Ti/N.
On the other hand, to generate under the situation of inhibition effect of the grain growth that the TiN of effect in the time can not giving full play to by welding produce be effective especially in the promotion of the IGF that is produced by MnS.Be that TiN because of heating dissolving has taken place.Mn and MnS according to heavy addition in steel of the present invention about 2.0% generate this fact in higher humidity province, the steel that the MnS growing amount of steel of the present invention under welding temperature measured before than Mn addition being increases to some extent, in the cooling of result after welding, the generation frequency of IGF increases.Therefore, HAZ tissue miniaturization effectively.
In addition, can list various methods, but in order to ensure toughness for the manufacturing of slab with high strength and high tenacity, DQT method preferably, promptly directly quench after hot rolling (DQ) implements tempering (T) then and handles.But it is once to cool off the back reheat and keep the operation of certain hour under this temperature that T handles, thereby causes the rising of cost.Consider from the angle that reduces cost, think to avoid as far as possible T to handle.But steel of the present invention needn't be implemented T and handle and just can guarantee good toughness, thereby does not increase cost and just can make high performance steel plate.But, have under the flexible situation in special requirement, handle by implementing T, can access the more good steel of toughness.
Describe with regard to qualification reason of the present invention below.The qualification reason of the composition of steel of the present invention at first, is described." % " in below forming means quality %.
C is for guaranteeing the necessary element of intensity, need to add more than 0.03%, reduce but heavy addition probably causes the HAZ flexible, so its higher limit being set at 0.12%.
Si uses as reductor, be effective elements aspect the intensity that increases steel by solution strengthening, but when content was lower than 0.05%, its effect is less, on the other hand, when content surpasses 0.30%, HAZ toughness generation deterioration then.Therefore, Si is defined as 0.05～0.30%.In addition, further preferred content is 0.05～0.25%.
Mn is to the high strength effective elements for the intensity that increases steel.In addition, Mn combines with S and generates MnS, and MnS becomes the product nucleus of IGF and promotes the miniaturization of welded heat affecting zone, can suppress HAZ flexible deterioration by this.Therefore,, guarantee the toughness of welded heat affecting zone simultaneously, need content more than 1.2% in order to keep desired intensity.But addition that it is generally acknowledged Mn surpasses at 3.0% o'clock, and deterioration takes place toughness on the contrary.Therefore, Mn is defined as 1.2～3.0%.In addition, the Mn amount is preferably 1.5～2.5%.
The P segregation makes the toughness deterioration of steel in crystal boundary, thereby preferably as far as possible with its reduction, but, can allow until 0.015%, therefore is defined as below 0.015%.
S mainly forms MnS and is present in the steel, has to make the rolling cooled effect of organizing miniaturization, contains the toughness and the ductility that will make the thickness of slab direction more than 0.015% and reduces.Therefore, S must be below 0.015%.In addition, for MnS being used as the product nucleus of IGF and obtaining the micronize effect, S must add more than 0.001%.Therefore, S is defined as 0.001～0.015%.
Cu is the effective element that was used to guarantee intensity in the past, but it causes the reduction of hot workability.For fear of this problem, added and the roughly the same Ni of Cu addition in the past always.But Ni is the very expensive element of cost, and therefore, the heavy addition of Ni may become the essential factor that the target that can not reach steel of the present invention is a cost degradation.So in steel of the present invention,, do not have a mind to add Cu and Ni based on the thought of guaranteeing intensity by Mn.But, using steel scrap to make under the situation of slab, probably sneak into inevitably separately about 0.05%, therefore, Cu+Ni is defined as below 0.10%.
Al is the same with Si to be to be used for the necessary element of deoxidation, can not carry out deoxidation fully being lower than at 0.001% o'clock, is surpassing 0.050% and make HAZ toughness generation deterioration during excessive interpolation.Therefore, Al is defined as 0.001～0.050%.
Ti to make in order combining with N and to form TiN in the steel, preferably adds more than 0.005%.But, surpass at 0.030% o'clock at the addition of Ti, will make thickization of TiN, probably reduce inhibition effect as thickization of crystal grain the object of the invention, that produce by TiN.Therefore, Ti is defined as 0.005%～0.030%.
Thereby Nb has and enlarges the effect that austenitic non-recrystallization zone promotes the ferrite grain refining, is simultaneously to generate the Nb carbide and the element of guaranteeing intensity, therefore need contain more than 0.005%.But, when the addition of Nb surpasses 0.10%, then be easy to generate the HAZ embrittlement that causes because of the Nb carbide, so Nb is defined as 0.005～0.10%.
N forms TiN in steel in order to combine with Ti, need to add more than 0.0025%.But,, so during heavy addition, probably cause HAZ flexible deterioration even N also has very large effect as the solution strengthening element.Therefore, obtain the effect of TiN to greatest extent in order to cause bigger influence for HAZ toughness, the upper limit of N is set at 0.0060%.
Mo, V, Cr are the raising effective elements to hardening capacity, for the micronized effect of organizing that TiN is produced reaches optimum, also can select as required to contain a kind, two or more.Wherein V can make with the form of VN with TiN and organize micronized effect to reach optimum, and has the precipitation strength that makes VN and be able to promoted effect.Moreover, by containing Mo, V, Cr, can reduce Ar
3Point, thereby the micronized effect of ferrite crystal grain is expected further increase.In addition,, can control the form of MnS, and further improve low-temperature flexibility, so under the situation of being strict with the HAZ characteristic, can select to add Ca by the interpolation of Ca.Moreover Mg has that the austenite crystal that suppresses HAZ is grown up and the effect that makes its grain refining, and its result is improved HAZ toughness, therefore under the strict especially situation of HAZ toughness, can select to add Mg.Their addition is respectively that Mo:0.2% is following, V:0.03% following, Cr:0.5% is following, Ca:0.0035% is following, below the Mg:0.0050%.
On the other hand, add to surpass 0.2% Mo and surpass under the situation of 0.5% Cr, it is generally acknowledged infringement weldability and toughness, and cause the rising of cost, add to surpass under the situation of 0.03% V because infringement weldability and toughness, so with it as the upper limit.In addition, add to surpass under the situation of 0.0035% Ca, because the degree of cleaning of infringement steel have improved hydrogen embrittlement (being that hydrogen is induced crackle) susceptibility, so be set at the upper limit with 0.0035%.Being added on of Mg surpasses at 0.005% o'clock, and the effect surplus of austenite grain refining is also less, and also is not very wise move aspect cost, therefore is set at the upper limit with 0.005%.
The reason that structure of steel is set at the bainite structure more than 80% is: though be low alloy steel, in order to ensure HAZ toughness and obtain full intensity, must be based on bainite structure, it is 80% just can realize above-mentioned purpose when above.Preferred bainite structure is more than 85%, and further preferred bainite structure is more than 90%.
Secondly, just creating conditions of steel of the present invention describes.
About casting the cooling of back steel billet, be preferably 0.06～0.6 ℃/s near the speed of cooling that is cooled to 800 ℃ the zero pour.According to the Nishizawa formula, for the crystal particle diameter that will be obtained by the pinning effect of precipitate maintains below the 100 μ m, the particle diameter of precipitate is necessary for below the 0.4 μ m.Be to realize this point, need 0.06 ℃/ strand speed of cooling more than the s in cast sections.Even the heat-staple TiN that exists stands the heating of the after this welding high temperature short period of time of etc.ing and also can not decompose, therefore, when the heating of welding etc., also be expected to produce the pinning effect, thereby can guarantee the toughness of HAZ.But when the speed of cooling of steel billet was too fast, the amount of fine precipitate increased, and probably caused the embrittlement of steel billet.Therefore, about casting the speed of cooling of back strand, be defined as 0.06～0.6 ℃/s near the speed of cooling to the 800 ℃ zero pour.In addition, be preferably 0.10～0.6 ℃/s.
About Heating temperature, the temperature below 1200 ℃ is necessary.As its reason, be because be heated to and surpass 1200 ℃ high temperature side, controlled chilling speed and there is dissolved possibility once more in the precipitate that generates when solidifying thus.In addition, also because become purpose mutually to finish, 1200 ℃ is fully, it is generally acknowledged that also can be prevented thickization of crystal grain that produces in advance this moment.In view of the above, Heating temperature is defined as below 1200 ℃.
The present invention need carry out hot rolling with the accumulation draft more than 40% in non-recrystallization temperature district.As its reason, be because the increase of the draught in non-recrystallization temperature district helps the miniaturization of austenite crystal in the operation of rolling, the result has the effect that makes the ferrite crystal grain miniaturization and improve mechanical property.Such effect becomes obvious when the accumulation draft of non-recrystallization zone reaches 40% when above.Therefore, the accumulation draft with non-recrystallization zone is defined as more than 40%.
In addition, strand must be cooled to below 400 ℃ from the temperature more than 800 ℃ with the above speed of cooling of 5 ℃/s after more than 850 ℃ hot rolling being finished.As from refrigerative reason more than 800 ℃, be because, consider it is disadvantageous from the angle of hardening capacity, thereby might can not obtain desired intensity from being lower than 800 ℃ when beginning to cool down.In addition, when speed of cooling is lower than 5 ℃/s, can not expect to obtain to have the steel of even microstructure, therefore, consequently quicken the refrigerative effect and reduce.In addition, when generally being cooled to below 400 ℃, phase transformation is fully finished.Moreover, in steel of the present invention,, therefore do not implement T especially and handle and can use as steel even be cooled to continuously can guarantee sufficient toughness below 400 ℃ with the above speed of cooling of 5 ℃/s yet.Based on above-mentioned reason, as creating conditions of steel of the present invention, make steel billet after finishing hot rolling more than 850 ℃, limit from the temperature more than 800 ℃ and be cooled to below 400 ℃ with 5 ℃/ speed of cooling more than the s.
Thereby, must under 400～650 ℃ tempering temperature, carry out requiring extra high toughness under the situation of enforcement temper after the hot rolling.Under the situation of carrying out temper, tempering temperature is high more, and the motivating force of grain growth is big more, and when surpassing 650 ℃, it is obvious that grain growth becomes.In addition, it is generally acknowledged that the temper that is lower than 400 ℃ can not fully obtain its effect.Based on these reasons, carrying out after the hot rolling under the situation of temper, be limited under 400～650 ℃ the temper condition and carry out tempering.
Embodiment
Narrate with regard to embodiments of the invention below.
The molten steel that will have a chemical ingredients of table 1 is cast with the secondary speed of cooling shown in the table 2 and is obtained slab, and the steel billet that obtains is carried out hot rolling and obtains steel plate with the condition shown in the table 2, has carried out various tests for the mechanical property of estimating this steel plate afterwards.Tensile test specimen cuts the JIS4 test piece from the 1/4t position of each steel plate thickness of slab, has estimated YS (0.2% yield strength), TS, El.Base metal tenacity cuts the test piece of 2mmV type breach from the 1/4t position of each steel plate thickness of slab, carries out the summer than (Charpy) shock test at-40 ℃, can value estimate with the shock absorption that obtains.About HAZ toughness, be that the steel of the reproduction thermal cycling test of 10kJ/mm can value be estimated in the shock absorption that-40 ℃ Charpy impact test obtains to have implemented to be equivalent to weld heat input.In addition, the speed of cooling the during casting shown in the table 2 is the speed of cooling during from secondary cooling that the practical situation of solidifying calculate.In addition, the bainite mark shown in the table 3 adopts organizing of nital corrosive steel to be estimated by observing under opticmicroscope.For for simplicity, the part beyond grain boundary ferrite and the MA is used as bainite structure.
Table 3 has been concluded the mechanical property of various steel.Steel 1～22 expression be steel plate as example of the present invention.From table 1 and table 2 significantly as can be seen, these steel plates satisfy chemical ingredients and each important document of creating conditions, and as shown in table 3, as can be known the characteristic good of mother metal, also have high tenacity even weld with bigger heat input ,-40 ℃ summer reaches more than the 150J than striking energy value.In addition, when also in specialized range, adding Mo, V, Cr, Ca, Mg as can be known,, also can obtain good toughness even implement temper.
On the other hand, steel 23～36 expressions is to break away from comparative example of the present invention.These steel are respectively because Mn amount (steel 23,28), C measures (steel 32,33), Nb measures (steel 24,35), Ti measures (steel 25), Si measures (steel 26), Al measures (steel 34), N measures (steel 27), Mo and V amount (steel 29), Cr measures (steel 27), Ca and Mg amount (steel 31), speed of cooling during casting (steel 25), temper (steel 30), accumulation draft (steel 28,32), reheat temperature (steel 31), cooling after rolling begins temperature (steel 36), and bainite mark (steel 32,35) therefore condition and different with steel of the present invention we can say that deterioration has taken place HAZ toughness.
Table 1
| Chemical ingredients (mass%) | ||||||||||||||||
| C | Si | Mn | P | S | Al | Ti | Nb | N | Cu+Ni | Mo | V | Cr | Ca | Mg | ||
| Steel of the present invention | 1 | 0.07 | 0.10 | 1.8 | 0.005 | 0.003 | 0.022 | 0.010 | 0.027 | 0.0050 | 0.04 | - | - | - | - | - |
| 2 | 0.08 | 0.05 | 1.9 | 0.004 | 0.002 | 0.018 | 0.010 | 0.018 | 0.0044 | 0.02 | - | - | 0.3 | 0.0026 | - | |
| 3 | 0.08 | 0.10 | 2.1 | 0.004 | 0.004 | 0.02 | 0.025 | 0.020 | 0.0048 | 0.05 | - | - | - | - | 0.0034 | |
| 4 | 0.06 | 0.13 | 2.7 | 0.004 | 0.003 | 0.015 | 0.010 | 0.019 | 0.0046 | 0.03 | - | - | - | - | - | |
| 5 | 0.06 | 0.22 | 2.2 | 0.004 | 0.004 | 0.022 | 0.010 | 0.040 | 0.0046 | 0.00 | - | - | - | 0.0033 | - | |
| 6 | 0.06 | 0.14 | 2.3 | 0.004 | 0.004 | 0.02C | 0.010 | 0.020 | 0.0039 | 0.01 | - | - | - | - | - | |
| 7 | 0.09 | 0.13 | 1.8 | 0.004 | 0.002 | 0.016 | 0.018 | 0.010 | 0.0037 | 0.02 | - | - | - | - | - | |
| 8 | 0.08 | 0.10 | 1.8 | 0.004 | 0.003 | 0.031 | 0.011 | 0.020 | 0.0044 | 0.06 | - | 0.01 | - | - | - | |
| 9 | 0.09 | 0.15 | 1.6 | 0.005 | 0.002 | 0.012 | 0.011 | 0.008 | 0.0035 | 0.02 | - | - | - | 0.0025 | - | |
| 10 | 0.03 | 0.18 | 2.0 | 0.004 | 0.004 | 0.003 | 0.022 | 0.052 | 0.0044 | 0.01 | 0.08 | - | 0.2 | - | - | |
| 11 | 0.06 | 0.25 | 2.0 | 0.004 | 0.004 | 0.019 | 0.010 | 0.019 | 0.0049 | 0.00 | - | 0.03 | - | - | - | |
| 12 | 0.07 | 0.10 | 2.0 | 0.004 | 0.003 | 0.010 | 0.010 | 0.019 | 0.0044 | 0.07 | 0.03 | 0.01 | - | - | - | |
| 13 | 0.05 | 0.18 | 1.9 | 0.003 | 0.003 | 0.021 | 0.010 | 0.018 | 0.0042 | 0.02 | - | - | 0.1 | - | - | |
| 14 | 0.12 | 0.08 | 1.5 | 0.004 | 0.004 | 0.001 | 0.006 | 0.019 | 0.0044 | 0.01 | - | - | - | 0.0028 | - | |
| 15 | 0.08 | 0.15 | 1.3 | 0.004 | 0.003 | 0.042 | 0.011 | 0.020 | 0.0046 | 0.03 | - | - | - | - | - | |
| 16 | 0.10 | 0.09 | 2.2 | 0.004 | 0.004 | 0.016 | 0.029 | 0.019 | 0.0038 | 0.01 | - | - | - | - | 0.0026 | |
| 17 | 0.04 | 0.16 | 1.9 | 0.003 | 0.003 | 0.021 | 0.012 | 0.019 | 0.0042 | 0.03 | - | - | - | - | - | |
| 18 | 0.06 | 0.15 | 1.5 | 0.004 | 0.003 | 0.018 | 0.015 | 0.020 | 0.0041 | 0.01 | - | - | - | - | - | |
| 19 | 0.07 | 0.12 | 1.3 | 0.003 | 0.002 | 0.014 | 0.009 | 0.014 | 0.0038 | 0.02 | - | - | - | - | - | |
| 20 | 0.05 | 0.18 | 1.8 | 0.003 | 0.003 | 0.015 | 0.013 | 0.018 | 0.0046 | 0.02 | - | - | - | 0.0025 | 0.0031 | |
| 21 | 0.07 | 0.13 | 1.6 | 0.004 | 0.003 | 0.017 | 0.012 | 0.019 | 0.0051 | 0.05 | - | - | - | 0.0029 | 0.0028 | |
| 22 | 0.08 | 0.19 | 1.5 | 0.003 | 0.002 | 0.019 | 0.020 | 0.022 | 0.0039 | 0.03 | - | - | - | 0.0022 | 0.0026 | |
| Comparative steel | 23 | 0.09 | 0.15 | 1.1 | 0.004 | 0.002 | 0.016 | 0.010 | 0.026 | 0.0047 | 0.04 | - | - | - | - | - |
| 24 | 0.09 | 0.10 | 1.5 | 0.004 | 0.003 | 0.018 | 0.010 | 0.108 | 0.0046 | 0.02 | - | - | - | - | - | |
| 25 | 0.09 | 0.05 | 1.5 | 0.004 | 0.003 | 0.016 | 0.033 | 0.020 | 0.0040 | 0.02 | - | - | - | - | - | |
| 26 | 0.08 | 0.36 | 2.0 | 0.004 | 0.003 | 0.020 | 0.011 | 0.009 | 0.0034 | 0.05 | - | - | - | 0.0027 | - | |
| 27 | 0.08 | 0.15 | 2.0 | 0.004 | 0.003 | 0.015 | 0.011 | 0.011 | 0.0070 | 0.02 | - | - | 0.6 | - | - | |
| 28 | 0.08 | 0.15 | 3.2 | 0.004 | 0.003 | 0.01 | 0.011 | 0.020 | 0.0042 | 0.00 | - | - | - | - | 0.0027 | |
| 29 | 0.08 | 0.15 | 2.0 | 0.004 | 0.003 | 0.01 | 0.011 | 0.020 | 0.0037 | 0.03 | 0.16 | 0.09 | - | - | - | |
| 30 | 0.09 | 0.16 | 2.0 | 0.005 | 0.002 | 0.018 | 0.010 | 0.021 | 0.0032 | 0.01 | - | - | - | - | - | |
| 31 | 0.08 | 0.19 | 1.6 | 0.005 | 0.003 | 0.005 | 0.010 | 0.017 | 0.0036 | 0.04 | - | - | - | 0.0038 | 0.0052 | |
| 32 | 0.02 | 0.12 | 1.6 | 0.005 | 0.003 | 0.016 | 0.011 | 0.018 | 0.0035 | 0.06 | - | - | - | - | - | |
| 33 | 0.16 | 0.10 | 1.1 | 0.005 | 0.004 | 0.018 | 0.011 | 0.019 | 0.0041 | 0.05 | - | - | - | - | - | |
| 34 | 0.07 | 0.12 | 1.5 | 0.004 | 0.004 | 0.054 | 0.010 | 0.022 | 0.0035 | 0.02 | - | - | - | - | - | |
| 35 | 0.05 | 0.06 | 1.3 | 0.005 | 0.003 | 0.024 | 0.011 | 0.002 | 0.0044 | 0.01 | - | - | - | - | - | |
| 36 | 0.04 | 0.14 | 1.6 | 0.005 | 0.006 | 0.015 | 0.011 | 0.018 | 0.0026 | 0.03 | - | - | - | - | - | |
Table 2
| Thickness of slab (mm) | Speed of cooling during casting (℃/s) | Create conditions | ||||||
| The reheat temperature (℃) | Accumulation draft (%) | Cooling beginning temperature (℃) | Speed of cooling (℃/s) | Tempering temperature (℃) | ||||
| Steel of the present invention | 1 | 60 | 0.18 | 1150 | 50 | 848 | 6 | - |
| 2 | 60 | 0.08 | 1100 | 40 | 832 | 10 | - | |
| 3 | 60 | 0.23 | 1150 | 50 | 842 | 12 | - | |
| 4 | 60 | 0.41 | 1150 | 40 | 821 | 5 | - | |
| 5 | 60 | 0.09 | 1200 | 60 | 847 | 10 | - | |
| 6 | 60 | 0.19 | 1150 | 50 | 816 | 10 | - | |
| 7 | 60 | 0.22 | 1150 | 40 | 822 | 8 | 500 | |
| 8 | 80 | 0.11 | 1150 | 50 | 834 | 10 | 550 | |
| 9 | 60 | 0.09 | 1150 | 40 | 850 | 10 | - | |
| 10 | 60 | 0.10 | 1150 | 50 | 844 | 10 | - | |
| 11 | 60 | 0.32 | 1150 | 60 | 812 | 9 | - | |
| 12 | 60 | 0.15 | 1150 | 50 | 834 | 10 | - | |
| 13 | 50 | 0.12 | 1150 | 40 | 844 | 15 | - | |
| 14 | 50 | 0.16 | 1150 | 50 | 847 | 10 | - | |
| 15 | 60 | 0.24 | 1150 | 50 | 826 | 18 | - | |
| 16 | 60 | 0.19 | 1150 | 50 | 809 | 10 | - | |
| 17 | 80 | 0.12 | 1150 | 40 | 819 | 8 | - | |
| 18 | 60 | 0.16 | 1200 | 50 | 815 | 6 | - | |
| 19 | 50 | 0.15 | 1150 | 50 | 843 | 10 | - | |
| 20 | 60 | 0.21 | 1200 | 40 | 820 | 16 | - | |
| 21 | 60 | 0.18 | 1150 | 60 | 831 | 12 | - | |
| 22 | 50 | 0.16 | 1150 | 40 | 816 | 9 | - | |
| Comparative steel | 23 | 60 | 0.08 | 1150 | 40 | 810 | 10 | - |
| 24 | 60 | 0.13 | 1150 | 50 | 805 | 8 | - | |
| 25 | 60 | 0.02 | 1150 | 50 | 824 | 10 | - | |
| 26 | 60 | 0.10 | 1150 | 60 | 813 | 10 | - | |
| 27 | 60 | 0.09 | 1150 | 50 | 842 | 5 | - | |
| 28 | 60 | 0.07 | 1150 | 30 | 822 | 10 | - | |
| 29 | 60 | 0.08 | 1150 | 50 | 816 | 12 | - | |
| 30 | 80 | 0.15 | 1150 | 50 | 841 | 10 | 660 | |
| 31 | 60 | 0.09 | 1250 | 50 | 830 | 10 | - | |
| 32 | 60 | 0.10 | 1150 | 35 | 826 | 9 | - | |
| 33 | 60 | 0.09 | 1150 | 50 | 813 | 3 | - | |
| 34 | 60 | 0.09 | 1150 | 50 | 818 | 10 | - | |
| 35 | 60 | 0.09 | 1150 | 50 | 835 | 10 | - | |
| 36 | 60 | 0.09 | 1150 | 50 | 740 | 10 | - | |
Table 3
| The mother metal tissue | The mother metal characteristic | The HAZ characteristic | ||||||
| Bainite mark (%) | Intensity | Toughness | Toughness | |||||
| YS (MPa) | TS (MPa) | EL (％) | YR (％) | vE-40(J) (Av) | vE-40(J) (Av) | |||
| Steel of the present invention | 1 | 85 | 480 | 648 | 22 | 74 | 272 | 170 |
| 2 | 91 | 508 | 706 | 21 | 72 | 258 | 161 | |
| 3 | 96 | 556 | 762 | 18 | 73 | 261 | 163 | |
| 4 | 99 | 592 | 789 | 21 | 75 | 250 | 155 | |
| 5 | 95 | 553 | 747 | 19 | 74 | 260 | 163 | |
| 6 | 94 | 532 | 739 | 22 | 72 | 259 | 162 | |
| 7 | 81 | 525 | 611 | 17 | 86 | 269 | 168 | |
| 8 | 80 | 502 | 597 | 20 | 84 | 271 | 169 | |
| 9 | 89 | 501 | 686 | 22 | 73 | 273 | 171 | |
| 10 | 80 | 457 | 601 | 18 | 76 | 268 | 167 | |
| 11 | 86 | 485 | 655 | 20 | 74 | 267 | 167 | |
| 12 | 88 | 500 | 676 | 16 | 74 | 265 | 166 | |
| 13 | 82 | 446 | 619 | 23 | 72 | 268 | 168 | |
| 14 | 97 | 576 | 769 | 19 | 75 | 271 | 169 | |
| 15 | 81 | 437 | 615 | 21 | 71 | 284 | 178 | |
| 16 | 98 | 627 | 825 | 17 | 76 | 255 | 159 | |
| 17 | 86 | 426 | 553 | 20 | 77 | 273 | 170 | |
| 18 | 84 | 420 | 553 | 18 | 76 | 281 | 175 | |
| 19 | 81 | 408 | 517 | 22 | 79 | 285 | 178 | |
| 20 | 87 | 439 | 577 | 21 | 76 | 274 | 171 | |
| 21 | 91 | 459 | 621 | 23 | 74 | 276 | 173 | |
| 22 | 84 | 480 | 639 | 20 | 75 | 277 | 173 | |
| Comparative steel | 23 | 83 | 453 | 629 | 17 | 72 | 249 | 41 |
| 24 | 98 | 591 | 778 | 17 | 76 | 230 | 38 | |
| 25 | 88 | 498 | 682 | 21 | 73 | 231 | 38 | |
| 26 | 95 | 549 | 753 | 11 | 73 | 206 | 34 | |
| 27 | 94 | 533 | 740 | 21 | 72 | 173 | 29 | |
| 28 | 99 | 721 | 962 | 16 | 75 | 148 | 25 | |
| 29 | 97 | 538 | 769 | 16 | 70 | 195 | 33 | |
| 30 | 85 | 560 | 651 | 26 | 86 | 208 | 35 | |
| 31 | 87 | 495 | 669 | 31 | 74 | 227 | 38 | |
| 32 | 67 | 339 | 471 | 24 | 72 | 243 | 40 | |
| 33 | 98 | 628 | 884 | 16 | 71 | 228 | 38 | |
| 34 | 81 | 446 | 612 | 16 | 73 | 236 | 39 | |
| 35 | 66 | 337 | 456 | 16 | 74 | 253 | 42 | |
| 36 | 73 | 378 | 525 | 16 | 72 | 240 | 40 | |
According to the present invention, can obtain the steel of high level, wherein be inhibited, and HAZ toughness is extremely stable by thickization of crystal grain of welding the HAZ that produces.
Claims (6)
1. the steel for welded structures of the excellent in low temperature toughness of a welded heat affecting zone, it is characterized in that: this steel is in quality %, contain that C:0.03～0.12%, Si:0.05～0.30%, Mn:1.2～3.0%, P:0.015% are following, S:0.001～0.015%, Cu+Ni:0.10% are following, Al:0.001～0.050%, Ti:0.005～0.030%, Nb:0.005～0.10%, N:0.0025～0.0060%, surplus is made up of iron and unavoidable impurities, and, has the bainite structure more than 80% as structure of steel.
2. the steel for welded structures of the excellent in low temperature toughness of welded heat affecting zone according to claim 1, it is characterized in that: this steel is in quality %, contain also that Mo:0.2% is following, V:0.03% is following, Cr:0.5% is following, Ca:0.0035% is following, Mg:0.0050% a kind among following, two or more.
3. the manufacture method of the steel for welded structures of the excellent in low temperature toughness of a welded heat affecting zone, it is characterized in that: molten steel is in quality %, contain C:0.03～0.12%, Si:0.05～0.30%, Mn:1.2～3.0%, below the P:0.015%, S:0.001～0.015%, below the Cu+Ni:0.10%, Al:0.001～0.050%, Ti:0.005～0.030%, Nb:0.005～0.100%, N:0.0025～0.0060%, surplus is made up of iron and unavoidable impurities, this molten steel is adopted the Continuous casting process casting, and the secondary refrigerative is set at 0.06～0.6 ℃/s and obtains strand near the speed of cooling to the 800 ℃ zero pour at this moment, then strand is carried out hot rolling.
4. the manufacture method of the steel for welded structures of the excellent in low temperature toughness of welded heat affecting zone according to claim 3, it is characterized in that: this steel is in quality %, contain also that Mo:0.2% is following, V:0.03% is following, Cr:0.5% is following, Ca:0.0035% is following, Mg:0.0050% a kind among following, two or more.
5. according to the manufacture method of the steel for welded structures of the excellent in low temperature toughness of claim 3 or 4 described welded heat affecting zones, it is characterized in that: described hot-rolled condition is, with the temperature below the described strand reheat to 1200 ℃, carry out hot rolling in non-recrystallization temperature district with the accumulation draft more than 40% then, after finishing hot rolling more than 850 ℃, be cooled to below 400 ℃ with 5 ℃/ speed of cooling more than the s from the temperature more than 800 ℃.
6. the manufacture method of the steel for welded structures of the excellent in low temperature toughness of a welded heat affecting zone, it is characterized in that: in the manufacture method of claim 5, the steel that described hot rolling is obtained cools off, and implements temper at 400～650 ℃ then.
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