CN100575529C - The Plate Steel of super large heat input HAZ toughness and parent material toughness for low temperature excellence - Google Patents
The Plate Steel of super large heat input HAZ toughness and parent material toughness for low temperature excellence Download PDFInfo
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- CN100575529C CN100575529C CN200610127470A CN200610127470A CN100575529C CN 100575529 C CN100575529 C CN 100575529C CN 200610127470 A CN200610127470 A CN 200610127470A CN 200610127470 A CN200610127470 A CN 200610127470A CN 100575529 C CN100575529 C CN 100575529C
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Abstract
Under super large heat input welding, also demonstrate good HAZ toughness even provide a kind of, and the Plate Steel of parent material toughness for low temperature excellence, it contains: C:0.030～0.10%, below the Si:1.0%, Mn:0.8～2.0%, below the P:0.03%, below the S:0.01%, Al:0.01～0.10%, Nb:0.015～0.035%, Ti:0.015～0.03%, B:0.0015～0.0035%, and N:0.0055～0.01%, also contain: below the Cu:2.0%, below the Ni:2.0%, below the Cr:1%, below the Mo:0.5%, below the V:0.1%, surplus is made of Fe and unavoidable impurities, and satisfies 2≤[Ti]/[N]≤4, with 40≤(500[C]+32[Si]+8[Mn]-9[Nb]+14[Cu]+17[Ni]-5[Cr]-25[Mo]-34[V]).
Description
Technical field
The present invention relates to a kind of for example Plate Steel of the welded structure of boats and ships and marine structure etc. that is applicable to, relate in particular to heat affected zone (the HeatAffected Zone after the above super large heat input of 50kJ/mm is welded, HAZ) tenacity excellent, and the Plate Steel of parent material toughness for low temperature excellence.
Background technology
In recent years, for example the maximization of container-ship etc. advances, and uses thickness of slab to be the Plate Steel more than the 60mm.In order to weld such Plate Steel expeditiously, requiring to import heat is the above super large heat input welding of 50kJ/mm.
But, if carry out super large heat input welding, then because HAZ is slowly cooled from being heated to the pyritous austenite region, thus exist it to organize thickization, the problem that the remarkable deterioration of HAZ toughness is such.Therefore all the time, have to carry out the restriction of welding heat input.
In order so to obtain good HAZ toughness in the super large heat input welding, for example patent documentation 1 proposes, C content in the Plate Steel is reduced, and the content of the P that restriction is unavoidably sneaked into, in addition the content with Nb and B is controlled at suitable scope (with reference to patent request scope and paragraph 0010).Patent documentation 2 proposes in addition, adds N quite in large quantities in steel, and suitably controls the interpolation balance (with reference to the scope and the paragraph 0013 of patent request) of Ti and B.Patent documentation 3 proposes in addition, makes the TiN that is present in the welding steel contain Nb (with reference to the scope and the paragraph 0009 of patent request) among the inclusion energetically.
[patent documentation 1] spy opens the 2003-166033 communique, patent request scope and paragraph 0010
[patent documentation 2] spy opens the 2005-200716 communique, the scope of patent request and paragraph 0013
[patent documentation 3] spy opens the 2004-218010 communique, the scope of patent request and paragraph 0009
Summary of the invention
But, seek the HAZ flexible and further improve in the field of welding.Described in addition patent documentation is not all considered parent material toughness for low temperature (low-temperature flexibility that refers to mother metal in this manual, below, slightly be written as " low-temperature flexibility ").Therefore the present invention's problem that will solve is, even a kind of 50kJ/mm is provided above super large heat input welding, also demonstrates good HAZ toughness, and the Plate Steel of low-temperature flexibility excellence.
Can solve the Plate Steel of the present invention of described problem, it is characterized in that, contain: the C:0.030～0.10% (meaning of quality %, below identical), Si:1.0% following (not containing 0%), Mn:0.8～2.0%, P:0.03% following (not containing 0%), S:0.01% following (not containing 0%), Al:0.01～0.10%, Nb:0.015～0.035%, Ti:0.015～0.03%, B:0.0015～0.0035%, and N:0.0070～0.01%, contain in addition: Cu:2.0% following (containing 0%), Ni:2.0% following (containing 0%), Cr:1% following (containing 0%), Mo:0.5% following (containing 0%) and V:0.1% following (containing 0%), and Fe and unavoidable impurities, and satisfy following formula (1) and (2)
2≤[Ti]/[N]≤4 …(1)
40≤X value ... (2)
X value=500[C]+32[Si]+8[Mn]-9[Nb]+14[Cu]+17[Ni]
-5[Cr]-25[Mo]-34[V]
(in the formula, [] represents the content (quality %) of each element).
Among Plate Steel of the present invention, from good low-temperature flexibility and HAZ flexible viewpoint, be preferably: (I) temperature range in δ territory is below 40 ℃, and/or (II) in the position of degree of depth t/4 (t=thickness of slab), Ti is that the median size of carbonitride is below the 40nm, and Nb is that the median size of carbonitride is below the 60nm.
Plate Steel of the present invention can also contain: (a) Ca:0.005% following (not containing 0%) and/or Mg:0.005% following (not containing 0%), (b) Zr:0.1% following (not containing 0%) and/or Hf:0.05 following (not containing 0%) and/or (c) Co:2.5% following (not containing 0%) and/or W:2.5% following (not containing 0%).Plate Steel of the present invention is preferably as the high-tensile steel with the above tensile strength of 490MPa that is suitable for large-scale manufacturings such as container-ship.
Also has " carbonitride " also meaning use of nitrogenate in this specification sheets.
Amazingly be, the amount of each chemical ingredients is in the suitable scope, and satisfy described formula (1) and (2), form by adjusting chemical ingredients in this way, even super large heat input welding, also can demonstrate excellent HAZ toughness, and can access the Plate Steel of low-temperature flexibility excellence.
Description of drawings
Fig. 1 is that HAZ toughness (vE is taked in expression
-40) measure the sketch chart of position of the test film of usefulness.
Fig. 2 is the graphic representation of relation of the temperature range in the X value of expression steel plate No.1～26 of making among the embodiment and δ territory.
Fig. 3 is the graphic representation of the relation of the X value of expression steel plate No.1～26 of making among the embodiment and the median size that Ti is carbonitride.
Fig. 4 is the graphic representation of the relation of the X value of expression steel plate No.1～26 of making among the embodiment and the median size that Nb is carbonitride.
Fig. 5 is the X value and the HAZ toughness (vE of expression steel plate No.1～26 of making among the embodiment
-40) the graphic representation of relation.
Fig. 6 is the X value and the low-temperature flexibility (vE of expression steel plate No.1～26 of making among the embodiment
-60) the graphic representation of relation.
Fig. 7 is the temperature range and the HAZ toughness (vE in the δ territory of expression steel plate No.1～26 of making among the embodiment
-40) the graphic representation of relation.
Fig. 8 is the temperature range and the low-temperature flexibility (vE in the δ territory of expression steel plate No.1～26 of making among the embodiment
-60) the graphic representation of relation.
Fig. 9 is that the Ti of expression steel plate No.1～26 of making among the embodiment is the median size and the HAZ toughness (vE of carbonitride
-40) the graphic representation of relation.
Figure 10 is that the Nb of expression steel plate No.1～26 of making among the embodiment is the median size and the low-temperature flexibility (vE of carbonitride
-60) the graphic representation of relation.
Embodiment
It is the carbonitride granular that present inventors try by making Ti, reaches still good HAZ toughness in super large heat input welding.If the speed of cooling that existing Ti is the dispersion state of carbonitride when being considered to molten steel solidification is certain, just then as long as can determine by the interpolation balance of Ti, N.But the result that present inventors study with keen determination points out, dwindles by the temperature range in δ territory represented in the state graph that makes steel, even identical Ti, N addition, also can make Ti is the carbonitride fine dispersion.
Here so-called " δ territory ", the meaning is the zone that includes δ iron at steel in state graph.Should " zone that comprises δ iron ", except the zone of having only δ iron, also comprise the two-phase zone etc. of δ+γ, the zone of the state different with δ iron.So-called then " δ territory temperature range " is meant the temperature range that comprises δ iron (ceiling temperature in δ territory and lower limit temperature poor).Here in the steel of specific composition, when for example having only the temperature range of δ iron and the temperature range of δ+γ being arranged, the total of these temperature ranges is the temperature ranges in δ territory.The temperature range in this δ territory is imported the comprehensive calculation of thermodynamics software (Thermo-calc can buy from the CRC synthetic study) by the chemical ingredients of steel plate is formed, thereby can be calculated.
In this δ iron, be considered to because the velocity of diffusion of Ti is fast, so the temperature range in δ territory is wide, the time that δ iron exists is elongated, thick Ti is that carbonitride is easy to form.Therefore research is formed the temperature range of dwindling the δ territory by adjusting chemical ingredients, and making Ti is the carbonitride granular.Through the calculating of Thermo-calc,, investigate of the influence of each chemical ingredients to the temperature range in δ territory by being one that benchmark ground only changes the chemical ingredients amount with the special component for this reason.By such research, in the temperature range and correlationship in δ territory, determine the X value of the function representation formed by chemical ingredients.
X value=500[C]+32[Si]+8[Mn]-9[Nb]+14[Cu]+17[Ni]
-5[Cr]-25[Mo]-34[V]
(in the formula, [] represents the content (quality %) of each element.)
Coefficient in the described formula of X value, the variable quantity of the temperature range in the δ territory when making each chemical composition change corresponding to steel from special component.Specifically, the coefficient of [C] they " 500 " for example, the meaning is that the C amount was increased 0.01% o'clock, the temperature range through the calculating δ territory of Thermo-calc reduces about 5 ℃.So the temperature range in X value and δ territory is in roughly inverse proportional relation (its relation is that then the temperature range in δ territory reduces if the X value increases in other words).
Find that based on such consideration when manufacturing has the steel plate of various X value and investigates, increase by making the X value, can make Ti is the median size granular of carbonitride, and HAZ toughness is improved.
By the X value is increased, find that also the low-temperature flexibility of steel plate also improves then.It is because by the X value is increased, Ti is that the median size of carbonitride reduces that this phenomenon is inferred, and Nb is the median size minimizing of carbonitride.Nb is why the median size of carbonitride reduces in addition, is considered to because Ti is the carbonitride fine dispersion.Mention reason and be that to separate out Ti on nuclear be carbonitride because Nb is the major part of carbonitride.
Steel plate of the present invention as described, its significant feature are that its chemical ingredients composition satisfies following formula (2) this point:
40≤X value ... (2)
X value=500[C]+32[Si]+8[Mn]-9[Nb]+14[Cu]+17[Ni]
-5[Cr]-25[Mo]-34[V]
(in the formula, [] represents the content (quality %) of each element).
But the present invention is not restricted to such reason (minimizing of the median size of the carbonitride that the minimizing of the temperature range in δ territory brings of inferring, the HAZ toughness that the minimizing of median size brings and the raising of low-temperature flexibility etc.), scope of the present invention is determined according to the scope of claim.Promptly satisfy the Plate Steel of the constitutive requirements of claim scope defined, be contained in the scope of the present invention.
If each chemical ingredients is in proper range, then the X value becomes big more, and Ti is that carbonitride and Nb are median size and the HAZ toughness and the low-temperature flexibility raising more of carbonitride.The following of this X value is limited to 40, is preferably 45, and more preferably 50.The upper limit of X value is determined according to the appropriate amount of each chemical ingredients, is about 160.From the viewpoint that hard phase MA organizes the generation of (martensite-austenitic mixed structure) to suppress, the preferred upper limit of X value is below 75.
In Plate Steel of the present invention, adjust the chemical ingredients composition in the mode that the X value becomes more than 40, making Ti system and Nb thus is that carbonitride is trickle.But, broken as if the balance of Ti amount and N amount, then the toughness of steel plate, particularly HAZ toughness deterioration.[Ti] specifically/[N] surpasses at 4 o'clock, and it is thick that Ti is that carbonitride becomes, and HAZ toughness reduces.If instead it is lower than 2, then because of the influence of excessive N, low-temperature flexibility and HAZ toughness reduce.Therefore steel plate of the present invention also has a feature, except the described formula (2) of regulation X value, also satisfying following formula (1), thereby realizes the balance that Ti amount and N measure.The preferred lower limit of being somebody's turn to do [Ti]/[N] is 2.5, and preferred upper limit is 3.5.
2≤[Ti]/[N]≤4 …(1)
(in the formula, [] represents the content (quality %) of each element.)
From the flexible viewpoint, it is trickle that Ti in the Plate Steel of the present invention system and Nb are that carbonitride is preferably.Therefore the Ti in the Plate Steel of the present invention is a carbonitride, is preferably below the 40nm, and more preferably below the 35nm, more preferably below the 30nm, Nb is a carbonitride, is preferably below the 60nm, more preferably below the 55nm, more preferably below the 50nm.
Ti of the present invention is the value of the median size of carbonitride and Nb carbonitride, be the value of measuring as follows: at first, with transmission electron microscope (TEM), to observe the condition of multiplying power more than 60,000 times, more than field of view 2.0 * 2.0 μ m, more than observation 5 places, place, observe position (t=thickness of slab) as the partial depth t/4 of the thermal process of representing steel plate.Measure the area of each carbonitride in this visual field then, calculate the diameter of equivalent circle of each carbonitride by this planimeter.The value that the diameter of equivalent circle of each carbonitride of arithmetical mean (addition is average) is obtained is the median size of carbonitride as Ti system of the present invention or Nb.
Also have, which how to be differentiated is that Ti is that carbonitride or which are that Nb is a carbonitride, be to determine that according to the composition that becomes the main body of each carbonitride particle (composition of the content (quality %) of conduct maximum beyond carbon and nitrogen) it can utilize energy dispersion type X-ray analyzer (EDX) decision.Also have, because can not measure excessively trickle carbonitride, so so-called carbonitride of the present invention is limited to more than the 5nm.
Plate Steel of the present invention as described is characterized in that, its chemical ingredients composition satisfies the relation of described formula (1) and (2).But,,, then can not reach excellent HAZ toughness and low-temperature flexibility if the content of each chemical ingredients (each element) is not in the proper range even satisfy the relation of described formula (1) and (2).Therefore Plate Steel of the present invention, its feature also be, except satisfying described formula (1) and (2), the amount of each chemical ingredients will be in the proper range as following record.Below, respectively chemical ingredients is described.
[C：0.030～0.10％]
Being the necessary element of intensity that is used to guarantee steel plate, is the element that is used for making the temperature range in δ territory of the state graph of steel to dwindle effectively in addition.The C amount is lower than at 0.030% o'clock and can not guarantees intensity.On the other hand, if the C amount surpasses 0.10%, then the second phase MA of hard tissue becomes too much, and base metal tenacity and HAZ toughness reduce.Therefore the C amount is defined as 0.030～0.10%.The preferred lower limit of C amount is 0.040%, and preferred upper limit is 0.080%.
[Si:1.0% following (not containing 0%)]
Si is the intensity effective elements that is used to guarantee steel plate, preferably adds more than 0.10% for this reason.But if excessively add Si, then the MA tissue is a large amount of generates, and base metal tenacity and HAZ toughness reduce, therefore need be with its upper limit as 1.0%.Si amount preferred upper limit is 0.8%, more preferably below 0.6%.
[Mn：0.8～2.0％]
Mn improves hardenability, is the effective elements of guaranteeing the intensity of steel plate.The Mn amount is lower than at 0.8% o'clock, can't give full play to the effect that intensity is guaranteed.On the other hand, if the Mn amount surpasses 2.0%, then base metal tenacity and HAZ toughness reduce.Therefore the Mn amount is defined as 0.8～2.0%.The preferred lower limit of Mn amount is 1.00%, more preferably more than 1.50%.On the other hand, the preferred upper limit of Mn amount is 1.80%.
[P:0.03% following (not containing 0%)]
As the P of impurity element, because bring disadvantageous effect can for base metal tenacity and HAZ toughness, so its content is preferably few as much as possible.Therefore the P amount is below 0.03%, to be preferably below 0.010%.But in industrial production, be difficult to make the P amount in the steel to become 0%.
[S:0.01% following (not containing 0%)]
Because S forms MnS and element that ductility is reduced, particularly in high tension steel, it is big that disadvantageous effect becomes, so its content is preferably the least possible.Therefore the S amount is below 0.01%, to be preferably below 0.005%.But in industrial production, be difficult to make the S amount in the steel to become 0%.
[Al：0.01～0.10％]
Al is the element with following effect: deoxidation; With granular base metal tenacity is improved by microstructure.Add the Al more than 0.01% in order to bring into play such effect fully.But if excessively add Al, then base metal tenacity and HAZ toughness reduce on the contrary, so are limited to 0.10% on it.The preferred lower limit of Al amount is 0.020%.On the other hand, its preferred upper limit is 0.060%, more preferably below 0.040%.
[Nb：0.015～0.035％]
Nb is used to make the hardenability of base material to improve and the effective elements that improves the intensity of steel plate.In order to give full play to this effect, needing the Nb amount is more than 0.015%.But if excessively add Nb, then base metal tenacity and HAZ toughness reduce, and therefore its upper limit amount are defined as 0.035%.The Nb amount is preferably more than 0.020%, is preferably below 0.030%, more preferably below 0.025%.
[Ti：0.015～0.03％]
Ti and N form trickle nitride, thickization of the austenite grain of the HAZ during with the inhibition welding (so-called (pinning) effect of blocking), thus the HAZ flexible is improved effective elements.Add the Ti more than 0.015% in order to bring into play such effect fully.But if Ti is excessive, HAZ toughness deterioration on the contrary then is defined as 0.03% on therefore will the Ti amount.The Ti amount is preferably more than 0.018%, below 0.025%.
[B：0.0015～0.0035％]
B is in super large heat when welding input, and at HAZ, particularly near in conjunction with (bond) portion, generating with BN is the intracrystalline ferrite of nuclear, and also has the fixed action of solid solution N, is to improve the important element of HAZ toughness.In the present invention, in order to give full play to this effect, and make B contain manyly, reach more than 0.0015% than the content in the common Plate Steel.But if B amount is excessive, because form thick bainite structure during super large heat input welding, so HAZ toughness deterioration on the contrary.Therefore will be defined as 0.0035% on the B amount.The B amount is preferably more than 0.0020%, below 0.0030%.
[N：0.0055～0.01％]
N is the element with following effect, and it combines with Ti and forms trickle carbonitride, and thickization of austenite grain improves HAZ toughness when suppressing super large heat input welding.If the N amount is very few, then can't give full play to described effect, therefore will be defined as 0.0055% under it.On the other hand,, bring disadvantageous effect then for base metal tenacity and HAZ toughness, therefore will be defined as 0.01% on it if the N amount is excessive.The preferred lower limit of N amount is 0.0060%, more preferably more than 0.0070%.The preferred upper limit of N amount is 0.0090% in addition, more preferably below 0.0080%.
[Cu:2.0% following (containing 0%)]
Cu improves hardenability and the element that helps toughness to improve, can add as required.Be considered in addition have equally with C the temperature range in δ territory is dwindled, making Ti is the effect of carbonitride granular.For the such effect of performance fully, the Cu amount recommends to be preferably more than 0.20%, more preferably more than 0.40%.But if the Cu amount is excessive, then base metal tenacity and HAZ toughness have the tendency of reduction, therefore will be defined as 2.0% on it.The Cu amount is preferably below 1.0%.
[Ni:2.0% following (containing 0%)]
Ni is also the same with Cu to be improved hardenability and helps intensity to improve, and is that the temperature range that makes the δ territory is dwindled effective elements, can add as required.For the such effect of performance fully, the Ni amount recommends to be preferably more than 0.20%, more preferably more than 0.40%.But if the Ni amount is excessive, then base metal tenacity and HAZ toughness have the tendency of reduction, therefore will be defined as 2.0% on it.The Ni amount is preferably below 1.0%.
[Cr:1% following (containing 0%)]
Cr is also the same with Cu to be to improve hardenability and the element that helps intensity to improve, can add as required.For the such effect of performance fully, the Cr amount recommends to be preferably more than 0.20%, more preferably more than 0.40%.But if the Cr amount is excessive, then because base metal tenacity and HAZ toughness reduce, so will be defined as 1% on it.The preferred upper limit of Cr amount is 0.80%.
[Mo:0.5% following (containing 0%)]
The intensity that Mo makes except improving hardenability still is used to prevent the temper brittleness effective elements improving, and can add as required.For the such effect of performance fully, the Mo amount recommends to be preferably more than 0.05%, more preferably more than 0.10%.But if the Mo amount is excessive, then therefore base metal tenacity and HAZ toughness deterioration will be defined as 0.5% on it.The Mo amount is preferably below 0.30%.
[V:0.1% following (containing 0%)]
V is to have the element that improves hardenability and temper softening opposing effect by a spot of interpolation, can add as required.For the such effect of performance fully, the V amount recommends to be preferably more than 0.01%, more preferably more than 0.02%.But if the V amount is excessive, then therefore base metal tenacity and HAZ toughness deterioration will be defined as 0.1% on it.The V amount is preferably below 0.05%.
Plate Steel of the present invention is made of Fe and unavoidable impurities except that described composition basically.But the present invention does not get rid of the Plate Steel that contains other elements, in scope of the present invention, in the scope of not destroying effect of the present invention, comprises the Plate Steel of the composition element that contains other yet.
For example in Plate Steel of the present invention, except that described composition, contain as required as inferior also effective, according to the kind that contains composition, can further improve the steel plate characteristic, that is: (a) Ca:0.005% following (not containing 0%) and/or Mg:0.005% following (not containing 0%), (b) Zr:0.1% following (not containing 0%) and/or Hf:0.05% following (not containing 0%) and/or (c) Co:2.5% following (not containing 0%) and/or W:2.5% following (not containing 0%).
[Ca:0.005% is following and/or Mg:0.005% is following]
Ca and Mg are the elements with the effect that makes the raising of HAZ toughness.In detail, Ca reduces by the anisotropy that reduction brings the morphology Control of the inclusion of MnS balling, and HAZ toughness is improved.On the other hand, Mg forms MgO, suppresses thickization of the austenite grain of HAZ, and HAZ toughness is improved.In order to give full play to such effect, preferably in steel plate, preferably contain the Mg more than the Ca and/or 0.0001 more than 0.0005%.But if their amount is excessive, then make base metal tenacity and HAZ toughness deterioration on the contrary, therefore the upper limit that Ca and/or Mg are contained sometimes is decided to be 0.005% respectively.The preferred upper limit of Ca amount is 0.0030%, and the preferred upper limit of Mg amount is 0.0035%.
[Zr:0.1% is following and/or Hf:0.05% is following]
Because Zr and Hf and Ti are made like nitride, thickization of the austenite grain of the HAZ when suppressing welding is so be to the tough property improvement effective elements of HAZ.In order to give full play to such effect, recommend the Zr amount to be preferably more than 0.001%, the Hf amount is preferably more than 0.0005%.But if their amount is excessive, then make base metal tenacity and HAZ toughness deterioration on the contrary, when therefore containing them, be defined as 0.1% on the Zr amount, be defined as 0.05% on the Hf amount.
[Co:2.5% is following and/or W:2.5% is following]
Co and W have the hardenability of making to improve, with the element of the effect of the intensity that improves steel plate.In order to give full play to such effect, one of them or both are contained more than 0.2% separately.But if their amount is excessive, then base metal tenacity and HAZ toughness deterioration, so the upper limit of their amount is decided to be 2.5% respectively.
Plate Steel of the present invention, it can be made in view of the above: the steel that will satisfy the prerequisite of described chemical ingredients amount, [Ti]/[N] and X value, according to common smelting process melting, after cooling off this molten steel and becoming slab, heat and hot rolling with common condition, (Q-tempering according to circumstances) then quenches.
Plate Steel of the present invention, because of control X value the temperature range in δ territory is dwindled, so be and Nb is the median size of carbonitride by forming slab with common condition cooling molten steel (for example with 0.1～2.0 ℃/second speed of cooling cooling), just can forming fully little Ti from 1500 ℃ to 1100 ℃.But, in order to form trickleer carbonitride, preferably make the cooling water inflow and the method for cooling change of casting machine, the speed of cooling when solidifying is improved.
The present invention relates to Plate Steel, so-called Plate Steel defines as JIS in this field, and referring generally to thickness of slab is more than the 3.0mm.But the thickness of slab of Plate Steel of the present invention is preferably more than the 20mm, more preferably more than the 40mm, more preferably more than the 60mm.Mentioning reason is because Plate Steel of the present invention even import welding because heat is input as the super large heat of 50kJ/mm, also demonstrates good HAZ toughness, so even thickness of slab is thick, by the input heat being increased and can welding expeditiously.
[embodiment]
Below, enumerate embodiment and be described more specifically the present invention, but the present invention is not limited by the examples below certainly, if before can meeting the scope of purport described later suitably changed and implement certainly can, these all are contained in the scope of technology of the present invention.
Steel with the composition shown in the table 1, according to common smelting process melting, this molten steel is cooled to 1100 ℃ and after becoming slab, being heated to 1100 ℃ carries out hot rolling from 1500 ℃ with 0.1～2.0 ℃/minute speed of cooling, and according to circumstances carry out tempering, produce the high-tensile steel of thickness of slab 60mm.
Form [Ti]/[N] that calculate and X value and the value (in table, being designated as " δ territory ") of the temperature range in the δ territory that calculates by Thermo-calc by the chemical ingredients of steel plate, show by table 2.
Make as described in addition in the steel plate, measure the median size that Ti is a carbonitride, the median size that Nb is carbonitride, tensile strength, low-temperature flexibility and these results of HAZ toughness table 2 demonstration of steel plate according to following main points.
[Ti is that carbonitride and Nb are the median size of carbonitride]
With transmission electron microscope (TEM),, observe the position (t=thickness of slab) of degree of depth t/4 to observe the condition of multiplying power more than 60,000 times, more than field of view 2.0 * 2.0 μ m, more than observation 5 places, place.Measure the area of each carbonitride in this visual field then, calculate the diameter of equivalent circle of each carbonitride by this planimeter.The diameter of equivalent circle of each carbonitride is done sums on average (addition is average), and the Ti system or the Nb that calculate in each steel plate are the median size of carbonitride.
[tensile strength]
Take the JIS4 test film in the position of degree of depth t/4 (t=thickness of slab), carry out tension test, measure tensile strength in view of the above.In this embodiment, tensile strength be 490MPa above for qualified.
[low-temperature flexibility]
Take the JIS4 test film in the position of degree of depth t/4 (t=thickness of slab), carry out pendulum impact test at-60 ℃, measuring absorption can (vE
-60).In this embodiment, tensile strength be 150kJ above for qualified.
[HAZ toughness]
Heat 50kJ/mm welds (electro-gas welding electrogas arc welding) with input, takes JIS4 test film (incision site from weld part to the 0.5mmHAZ side) from position shown in Figure 1, carries out the hammering blow test at-40 ℃, measures that absorb can (vE
-40).In this embodiment, tensile strength be 200J above for qualified.
[table 1-1]
[table 1-2]
[table 1-3]
[table 2-1]
| Steel plate No. | [Ti]/[N] | The X value | The δ territory (℃) | Ti is carbonitride (nm) | Nb is carbonitride (nm) | Tensile strength (MPa) | Low-temperature flexibility vE -60(J) | HAZ toughness vE -40(J) |
| 1 | 2.7 | 50.4 | 32 | 37 | 51 | 580 | 165 | 238 |
| 2 | 4.0 | 52.0 | 30 | 41 | 64 | 594 | 163 | 227 |
| 3 | 3.7 | 48.8 | 34 | 42 | 65 | 578 | 160 | 236 |
| 4 | 2.7 | 50.4 | 32 | 36 | 51 | 574 | 165 | 242 |
| 5 | 2.8 | 51.5 | 31 | 33 | 54 | 588 | 164 | 227 |
| 6 | 2.0 | 49.8 | 32 | 32 | 49 | 544 | 161 | 233 |
| 7 | 2.7 | 52.0 | 30 | 33 | 53 | 582 | 169 | 232 |
| 8 | 3.5 | 49.7 | 32 | 40 | 60 | 586 | 162 | 244 |
| 9 | 2.0 | 48.8 | 33 | 33 | 49 | 588 | 158 | 240 |
| 10 | 2.7 | 43.7 | 37 | 36 | 57 | 580 | 155 | 211 |
| 11 | 2.9 | 64.8 | 20 | 29 | 42 | 610 | 203 | 288 |
| 12 | 2.8 | 64.1 | 21 | 30 | 44 | 615 | 193 | 275 |
[table 2-2]
| Steel plate No. | [Ti]/[N] | The X value | The δ territory (℃) | Ti is carbonitride (nm) | Nb is carbonitride (nm) | Tensile strength (MPa) | Low-temperature flexibility vE -60(J) | HAZ toughness vE -40(J) |
| 13 | 2.7 | 65.7 | 19 | 29 | 42 | 620 | 211 | 281 |
| 14 | 2.7 | 55.1 | 28 | 34 | 49 | 605 | 173 | 259 |
| 15 | 2.9 | 71.9 | 14 | 25 | 39 | 640 | 242 | 295 |
| 16 | 2.8 | 47.2 | 34 | 37 | 55 | 600 | 159 | 235 |
| 17 | 2.7 | 43.7 | 37 | 40 | 58 | 605 | 154 | 231 |
| 18 | 2.7 | 49.6 | 32 | 34 | 54 | 600 | 163 | 241 |
| 19 | 2.7 | 51.5 | 31 | 35 | 51 | 600 | 165 | 235 |
| 20 | 2.7 | 51.5 | 31 | 35 | 52 | 580 | 164 | 232 |
| 21 | 2.5 | 49.5 | 32 | 33 | 53 | 577 | 162 | 240 |
| 22 | 2.4 | 49.9 | 32 | 34 | 50 | 580 | 163 | 242 |
| 23 | 2.6 | 56.9 | 26 | 32 | 47 | 635 | 177 | 257 |
[table 2-3]
| Steel plate No. | [Ti]/[N] | The X value | The δ territory (℃) | Ti is carbonitride (nm) | Nb is carbonitride (nm) | Tensile strength (MPa) | Low-temperature flexibility vE -60(J) | HAZ toughness vE -40(J) |
| 24 | 2.7 | 35.9 | 43 | 44 | 61 | 535 | 124 | 143 |
| 25 | 2.7 | 32.9 | 46 | 44 | 67 | 470 | 95 | 108 |
| 26 | 2.7 | 27.0 | 50 | 48 | 70 | 460 | 70 | 75 |
| 27 | 2.9 | 85.4 | 3 | 21 | 28 | 630 | 67 | 53 |
| 28 | 2.7 | 81.2 | 4 | 19 | 26 | 580 | 62 | 73 |
| 29 | 2.9 | 46.4 | 35 | 38 | 58 | 610 | 73 | 86 |
| 30 | 2.6 | 43.1 | 38 | 36 | 59 | 540 | 53 | 58 |
| 31 | 2.7 | 77.2 | 9 | 20 | 33 | 620 | 74 | 68 |
| 32 | 2.7 | 81.5 | 4 | 19 | 26 | 630 | 69 | 65 |
| 33 | 2.7 | 42.1 | 38 | 39 | 58 | 610 | 63 | 49 |
| 34 | 2.0 | 41.8 | 39 | 34 | 55 | 550 | 152 | 92 |
| 35 | 6.4 | 42.1 | 38 | 62 | 92 | 555 | 62 | 79 |
| 36 | 2.7 | 49.2 | 33 | 36 | 55 | 540 | 158 | 72 |
| 37 | 2.9 | 42.5 | 38 | 43 | 60 | 565 | 66 | 81 |
| 38 | 3.0 | 41.8 | 39 | 40 | 61 | 550 | 163 | 58 |
| 39 | 1.4 | 42.2 | 38 | 31 | 48 | 530 | 69 | 55 |
| 40 | 2.6 | 160.5 | 0.3 | 17 | 24 | 690 | 72 | 109 |
The prerequisite of each chemical ingredients amount of the present invention is satisfied in steel plate No.1～24.Steel plate No.25 and 26 in addition, its C amount is lower than the lower limit of the present invention's regulation, but the prerequisite of other the amount of being divided into all satisfies.Relation, X value and the Ti of these steel plates of Fig. 2～4 expression No.1～26 the X values and the temperature range in δ territory is that the relation of averaged particles of carbonitride and X value and Nb are the relation of the median size of carbonitride.As shown in Figure 2, the temperature range in X value and δ territory is in good correlationship (being the inverse proportional relation specifically substantially).In addition by Fig. 3 and Fig. 4 as can be known, along with the X value increases, the median size of carbonitride reduces.
The X value and the HAZ toughness (vE of Fig. 5～8 expression steel plate No.1～26
-40) relation, X value and low-temperature flexibility (vE
-60) relation, the temperature range and the HAZ toughness (vE in δ territory
-40) relation and the temperature range and the low-temperature flexibility (vE in δ territory
-60) relation.By these figure as can be known, along with the X value increases, promptly the temperature range along with the δ territory reduces, and the HAZ toughness of steel plate and low-temperature flexibility improve.The X value is the steel plate (temperature range in δ territory is at the steel plate below 40 ℃) more than 40 then, its vE
-40More than 200J, vE
-60More than 150J, have good HAZ toughness and low-temperature flexibility.This be considered to because, adjust the chemical ingredients composition by become mode more than 40 with X value, the temperature range in δ territory narrows down, consequently the diffusion of Ti is suppressed, Ti is that carbonitride and Nb are that the median size of carbonitride is suppressed.
Fig. 9 and Figure 10 represent that the Ti of steel plate No.1～26 is the median size and the HAZ toughness (vE of carbonitride in addition
-40) relation and the Nb median size and the low-temperature flexibility (vE that are carbonitride
-60) relation.By these figure as can be known, the median size along with carbonitride diminishes HAZ toughness and low-temperature flexibility raising.Particularly by shown in Figure 9, be below the 40nm if Ti is the median size of carbonitride, vE then
-40Can reach more than the 200J, by shown in Figure 10, be below the 60nm if Nb is the median size of carbonitride, then vE
-60Can reach more than the 150J.
By be summarized in the table the result as can be known, satisfy steel plate No.1～23 of the prerequisite of each chemical ingredients amount of the present invention, [Ti]/[N] and X value, tensile strength, low-temperature flexibility and HAZ tenacity excellent.With respect to this, satisfy the prerequisite of each chemical ingredients amount of the present invention basically, but do not satisfy steel plate No.24～26 of the prerequisite of 40≤X value, low-temperature flexibility or low temperature and HAZ toughness both sides are insufficient.Steel plate No.25 and 26 in addition, its C amount is lower than 0.030%, and tensile strength is also insufficient.
No.27～33,35,37 and 40 of each of the prerequisite of the higher limit of discontented unabridged version invention specified chemical composition amount are because excessively contain a certain item of chemical ingredients, so low-temperature flexibility and HAZ flexible both sides are all insufficient.Any one steel plate of the prerequisite of the lower value of each chemical ingredients amount of opposite discontented unabridged version invention regulation, toughness is also insufficient.Specifically just to be lower than the steel plate No.34 or 38 that lower value contains Ti or N, because the Ti carbonitride is not formed fully, so HAZ toughness is insufficient.Same just to be lower than the steel plate No.36 that lower value contains B, because BN is not fully formed, so HAZ toughness is insufficient.Steel plate No.39 in addition, its [Ti]/[N] is lower than 2, because of the influence toughness of excessive N insufficient.
Claims (6)
1. the thickness of heat affected zone toughness and parent material toughness for low temperature excellence is the above Plate Steel of 20mm, it is characterized in that, and in quality %,
Contain: C:0.030～0.10%, Si:1.0% following but do not contain 0%, Mn:0.8～2.0%, P:0.03% is following but do not contain 0%, S:0.01% is following but do not contain 0%, Al:0.01～0.10%, Nb:0.015～0.035%, Ti:0.015～0.03%, B:0.0015～0.0035% and N:0.0070～0.01%
Also contain: Cu:2.0% is following and contain 0%, Ni:2.0% is following and contain 0%, Cr:1% is following and contain 0%, Mo:0.5% is following and contain 0% and V:0.1% following and contain 0%, and Fe and unavoidable impurities, and satisfy following formula (1) and (2)
2≤[Ti]/[N]≤4 …(1)
40≤X value ... (2)
X value=500[C]+32[Si]+8[Mn]-9[Nb]+14[Cu]+17[Ni]
-5[Cr]-25[Mo]-34[V]
In the formula, [] represents the mass percentage content of each element.
2. thickness according to claim 1 is the above Plate Steel of 20mm, it is characterized in that the temperature range in δ territory is below 40 ℃.
3. thickness according to claim 1 and 2 is the above Plate Steel of 20mm, it is characterized in that, in the position of degree of depth t/4, Ti is that the median size of carbonitride is that 40nm median size following, that Nb is carbonitride is that wherein t represents thickness of slab below the 60nm.
4. thickness according to claim 1 and 2 is the above Plate Steel of 20mm, it is characterized in that, in quality %, also contains: Ca:0.005% following but do not contain 0% and/or Mg:0.005% following but do not contain 0%.
5. thickness according to claim 1 and 2 is the above Plate Steel of 20mm, it is characterized in that, in quality %, also contains: Zr:0.1% following but do not contain 0% and/or Hf:0.05% following but do not contain 0%.
6. thickness according to claim 1 and 2 is the above Plate Steel of 20mm, it is characterized in that, in quality %, also contains: Co:2.5% following but do not contain 0% and/or W:2.5% following but do not contain 0%.
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| CN101559541B (en) * | 2009-05-19 | 2011-06-08 | 武汉钢铁(集团)公司 | Test method and device for weld seam alloying in gas shielded welding |
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| CN103695777B (en) * | 2013-12-20 | 2016-06-22 | 宝山钢铁股份有限公司 | The steel plate of a kind of welding heat influence area toughness excellence and manufacture method thereof |
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