CN104451444A - Low-carbon-equivalent large heat input welding thick steel plate with and preparation method thereof - Google Patents
Low-carbon-equivalent large heat input welding thick steel plate with and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a low-carbon-equivalent large heat input welding thick steel plate and a preparation method thereof. The preparation method comprises the following steps: 1) smelting and casting, wherein the steel plate comprises the following components in percentage by weight: 0.045-0.07% of C, 0.10-0.30% of Si, 1.3-1.6% of Mn, less than or equal to 0.015% of P, 0.001-0.01% of S, 0.2-0.4% of Ni, 0.005-0.035% of Ti, 0.0005-0.01% of Mg, 0.001-0.01% of N, 0.0005-0.005% of B, less than or equal to 0.05% of Al, less than or equal to 0.05% of Ca, less than or equal to 0.02% of REM and the balance of Fe and inevitable impurities and further comprises more than one of less than or equal to 0.03% of Nb or less than or equal to 0.2% of Cr; Ti/N is greater than or equal to 2 but less than or equal to 6, Mg/(Al+Ti) is greater than or equal to 0.024, Ceq is 0.32-0.36% and Bef is 0.0005-0.005%; 2) rolling; 3) cooling. By controlling the (Mg+Ca)/(Al+Ti) ratio and areal density of micron inclusions with the diameter which is greater than or equal to 1 micron as well as the (Mg+Ca)/(Al+Ti) ratio and areal density of submicron inclusions with the diameter which is 0.1-1 micron, for the steel plates with the thickness being 50-70 mm and the base material tensile strength being greater than or equal to 510 MPa, the steel plates are welded with the weld heat input of 200-400kJ/cm, and the average Charpy impact energy of a welding heat affected zone at -40 DEG C reaches 100J above.
Description
Technical field
The present invention relates to welding Plate Steel and manufacture field, particularly a kind of low-carbon-equivalent can Large Heat Input Welding Plate Steel and manufacture method thereof.Be 50 ~ 70mm for thickness of slab, the steel plate of mother metal tensile strength >=510MPa level, be under the condition of 200 ~ 400kJ/cm at weld heat input, the welded heat affecting zone of steel plate has good impelling strength, and the average Charpy-V impact power of-40 DEG C is at more than 100J.This Plate Steel can be applied to the fields such as boats and ships, building and oceanic tectonic thing as welding construction material.
Background technology
In recent years, along with the maximization of the welding structure things such as shipbuilding, building, pressurized vessel, petroleum natural gas pipeline and ocean platform, day by day require the Large Heat Input Welding performance improving Plate Steel, welding efficiency can be improved like this, shorten manufacturing man-hours, reduce manufacturing cost.
After Large Heat Input Welding, the weave construction of welded heat affecting zone steel is destroyed, and austenite crystal is obviously grown up, and easily forms coarse grain zone.Cause brittle tissue to be the ferrite side plate, the upper bainite that are formed in process of cooling in coarse grain zone, thick grain boundary ferrite and be closely close to the perlite of formation at grain boundary ferrite, the carbide formed between the lath of ferrite side plate island-like martensite-austenite constituent element etc.Along with the increase of weld heat input, original austenite grain particle diameter becomes large, and ferrite side plate and upper bainite are organized more flourishing, the size also corresponding increase of grain boundary ferrite, the Charpy-V impact power of welded heat affecting zone will significantly reduce, and it reduce the toughness of welded heat affecting zone.
Under Large Heat Input Welding condition, in order to improve the low-temperature flexibility of Plate Steel welded heat affecting zone, forefathers have carried out a large amount of research work.As Japanese Patent JP5116890 (golden swamp high noon, middle Island bright, this Itou Kentaro of Gang, Jin Guyan: enter greatly Hot and weld with high Zhang power Steel material System product System making method, JP5116890,1976.5.28.) in disclose in the Composition Design of steel, add a certain amount of Ti, N, utilize TiN particle can suppress the deterioration of welding heat influence area toughness, weld heat input can bring up to 50kJ/cm.But when weld heat input reaches more than 200kJ/cm, in welding process, the temperature of welded heat affecting zone will up to 1400 DEG C, be there is solid solution or grows up by TiN particle in part, it suppresses the effect of welded heat affecting zone grain growth by partial disappearance, will cause welding heat influence area toughness deterioration like this.Therefore, only utilize the steel of minuteness particle TiN, be difficult to the Large Heat Input Welding performance improving Plate Steel.
Utilize titanyl compound also can improve the toughness of steel Large Heat Input Welding heat affected zone.This is because titanyl compound is at high temperature stablized, not easily there is solid solution.Titanyl compound can play a role as ferritic forming core core simultaneously, fining ferrite grains, and forms the acicular ferrite structure each other with high spud angle crystal grain, is conducive to the toughness improving welded heat affecting zone.At Japanese Patent JP517300, (little Chi permits the method, this Inter expands it, matsuda is clear one, modern Army doubly rectifies name, just pure, mountain pass Fu Ji in normal times, weld the hand Hot shadow Ring Bu Tough The ぐ れ Steel Cai System that continues and make method, JP517300,1993.3.8) in set forth.But there is comparatively small amt and be difficult to Dispersed precipitate two large problems in steel in titanium oxide.If wish the quantity being improved titanium oxide by the titanium content improved in steel, the formation of Large Titanium oxide inclusion certainly will be caused.When the size of titanium oxide particle is greater than 5 μm, the impelling strength of mother metal and welded heat affecting zone will be reduced.Therefore be greater than in the Large Heat Input Welding process of 200kJ/cm at weld heat input, depend merely on the toughness that titanyl compound is still difficult to improve welded heat affecting zone.
The Japanese Patent JP4515430 of Kobe Steel (help two, go out Pu wise man's historical data: weld Hot shadow Ring Bu Tough お I び Mu Cai Tough To Gifted れ Steel material お I び そ System method, JP4515430,2010.5.21 by high bridge.) set forth the method improving thick plates heat affected zone toughness by adding REM, Ca, Zr.In Thermal Cycle process, even if temperatures as high 1400 DEG C, the oxide compound utilizing REM, Ca, Zr deoxidation to generate also can in steel Dispersed precipitate and solid solution does not occur, thus can stop growing up of austenite crystal, thus effectively reduce the size of ferrite crystal grain.Under the weight percent content being greater than 5%, Ti oxide compound when the weight percent content of REM, Ca, Zr oxide compound in inclusion is greater than the condition of 0.3%, the impelling strength of welded heat affecting zone can be improved significantly.
Summary of the invention
The object of this invention is to provide a kind of low-carbon-equivalent can Large Heat Input Welding Plate Steel and manufacture method thereof, and be 50 ~ 70mm for thickness of slab, the steel plate of mother metal tensile strength>=510MPa, is under the condition of 200 ~ 400kJ/cm at weld heat input, has
ve
-40the welded heat affecting zone impelling strength that>=100J is good.
For achieving the above object, technical scheme of the present invention is:
A kind of low-carbon-equivalent of the present invention can Large Heat Input Welding Plate Steel, and its chemical component weight per-cent is: C 0.045 ~ 0.07%, Si 0.10 ~ 0.30%, Mn 1.3 ~ 1.6%, P≤0.015%, S0.001 ~ 0.01%, Ni 0.2 ~ 0.4%, Ti 0.005 ~ 0.035%, Mg 0.0005 ~ 0.01%, N0.001 ~ 0.01%, B 0.0005 ~ 0.005%, Al≤0.05%, Ca≤0.005%, REM≤0.02%, all the other are Fe and inevitable impurity; Wherein, 2≤Ti/N≤6, Mg/ (Al+Ti) >=0.024;
And in steel plate,
Carbon equivalent C
eq0.32% ~ 0.36%, C
eq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15;
Effective boron amount B
ef0.0005 ~ 0.005%, wherein,
When N-Ti × 14.01/47.87≤0, B
ef=B;
As N-Ti × 14.01/47.87>0, B
ef=B-(N-Ti × 14.01/47.87) × 10.81/14.01.
Further, the chemical composition of Plate Steel of the present invention also contains more than one elements in Nb 0.001 ~ 0.03% or Cr≤0.2%, by weight percentage.
In steel plate, diameter is more than or equal to the micron inclusion of 1 μm, inclusion area density>=100/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.8.For the submicron inclusion that diameter is 0.1-1 μm, inclusion area density>=220/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.1.
In the Composition Design of steel of the present invention,
C is the element increasing steel strength.For the TMCP technique of controlled rolling and controlled cooling, in order to stably keep certain strength, the lower limit of C content is 0.045%.But excessively add C, will the toughness of mother metal and welded heat affecting zone be caused to reduce, the upper limit of C content be 0.07%.
Si, be element required in steel-making pre-deoxidation process, and can play the effect of strengthening mother metal, therefore the lower limit of Si content is 0.1%.When but Si too high levels is more than 0.3%, the toughness of mother metal being reduced, simultaneously in Large Heat Input Welding process, by promoting the generation of island-like martensite-austenite constituent element, significantly reducing welding heat influence area toughness.Si content range is 0.10 ~ 0.30%.
Mn, can be improved the intensity of mother metal, can play a role again as pre-deoxidation element by solution strengthening.The precipitation of MnS simultaneously can promote the generation of Intragranular Acicular Ferrite, and the lower value of Mn is 1.3%.But too high Mn will cause the center segregation of slab, the sclerosis of Large Heat Input Welding heat affected zone and MA can be caused simultaneously to generate, reduce the toughness of welded heat affecting zone, so the higher limit of Mn controls to be 1.6%.
Ti, by forming Ti
2o
3particle, can promote the generation of Intragranular Acicular Ferrite.Simultaneously Ti and N combine generate TiN particle can growing up at welded heat affecting zone pinning austenite crystal, make mother metal and welded heat affecting zone structure refinement, raising toughness.So as beneficial element, the lower limit of Ti content is 0.005%.But during Ti too high levels, will thick nitride be formed, or impel the generation of TiC, reduce the toughness of mother metal and welded heat affecting zone, so Ti upper content limit is 0.035%.
Mg, the MgO that interpolation Mg can generate fine dispersoid distribution is mingled with, and is mingled with as forming core core, can promotes the precipitation of TiN and MnS using these, suppress growing up and promoting the growth of Intragranular Acicular Ferrite of austenite crystal in Thermal Cycle process, improve the toughness of welded heat affecting zone.Mg content in steel is advisable with 0.0005-0.01%.When Mg content is less than 0.0005%, the quantity of the microinclusions of generation will significantly reduce, and the Mg content simultaneously in microinclusions significantly reduces, and can not meet the requirement of separating out MnS, TiN on inclusion surface.If the effect that Mg content is greater than 0.01%, Mg is saturated, add vaporization losses and the oxidational losses of Mg simultaneously.
The present invention finds, Al and Ti in the Mg of interpolation and molten steel exists the relation of competition deoxidation, when Mg content is too low, during Al and Ti too high levels, be unfavorable for that generation take MgO as the inclusion of main component, for this reason, Mg, Al and Ti content in steel will meet Mg/ (Al+Ti) >=0.024.
N, can form fine Ti nitride, and in Large Heat Input Welding process, can effectively suppress growing up of austenite crystal, its lower limit is 0.001%.But its content is more than 0.006%, will the formation of solid solution N be caused, reduce the toughness of mother metal and welded heat affecting zone.
Meanwhile, keep having suitable Ti/N ratio in steel, its ratio is 2≤Ti/N≤6.When Ti/N is less than 2, the quantity of TiN particle will sharply reduce, and can not form the TiN particle of sufficient amount, to suppress growing up of austenite crystal in Large Heat Input Welding process, reduces the toughness of welded heat affecting zone.When Ti/N is greater than 6, TiN particle coarsening, simultaneously superfluous Ti is easily combined with C and generates thick TiC particle, and these thick particles all likely as the starting point that crackle occurs, reduce the impelling strength of mother metal and welded heat affecting zone.
Al, when Al content is too high in steel, easily generates tufted alumina inclusion, is unfavorable for the generation of fine dispersoid distribution inclusion.Therefore, the upper limit of Al content is 0.05%.
Ca, add the form that Ca can improve sulfide, the oxide compound of Ca and sulfide can also promote the growth of Intragranular Acicular Ferrite, and the oxide compound of Ca and the oxide compound of Al combine the inclusion that can form low melting point, improve the form of inclusion.If the effect that Ca content is greater than 0.005%, Ca is saturated, add vaporization losses and the oxidational losses of Ca simultaneously.Therefore, the upper limit of Ca content is 0.005%.
The interpolation of REM, REM can improve the form of sulfide, and simultaneously the oxide compound of REM and sulfide can suppress growing up of austenite crystal in Thermal Cycle process.But, when the content of REM is greater than 0.02%, generating portion particle diameter is greater than the inclusion of 5 μm, reduces the impelling strength of mother metal and welded heat affecting zone.Therefore, the upper limit of REM content is 0.02%.
S, in the adding procedure of Ca and/or REM, forms sulfide with Ca and/or REM, can also promote that MnS is on oxide particle, or the further precipitation in Ca and REM sulfide particles, thus promotes the formation of Intragranular Acicular Ferrite, and its lower limit is 0.001%.But its too high levels, will cause the center segregation of slab.In addition, when S content is more than 0.01%, will the thick sulfide of forming section, the starting point that these thick sulfide will be formed as crackle, reduces the impelling strength of mother metal and welded heat affecting zone.Therefore, the upper limit of S content is 0.01%.
P, is the impurity element in steel, should reduces as far as possible.Its too high levels, will cause center segregation, and reduce the toughness of welded heat affecting zone, the upper limit of P is 0.015%.
Ni, can improve intensity and the toughness of mother metal, and its lower limit is 0.2%.But because it is expensive, in view of the restriction of cost, its upper limit is 0.4%.
Nb, can the tissue of refinement steel, improves intensity and toughness.But because it is expensive, in view of the restriction of cost, its composition range is 0.001 ~ 0.03%.
Cr, can improve the hardening capacity of steel.For Plate Steel, raising hardening capacity can make up the loss of strength that thickness brings, and improves the intensity of thickness of slab central zone, improves the homogeneity of performance on thickness direction.But too high Cr and Mn adds fashionable simultaneously, the Cr-Mn composite oxides of low melting point can be formed, easily form surface crack in the hot rolling, also can affect the welding property of steel simultaneously.Therefore Cr upper content limit is 0.2%.
C
eq, carbon equivalent directly affects the tensile strength of mother metal, and generally along with the increase of carbon equivalent, the tensile strength of mother metal strengthens.On the other hand, carbon equivalent directly affects again the impelling strength of welded heat affecting zone, and along with the increase of carbon equivalent, the impelling strength of welded heat affecting zone reduces.The present invention is found by research, in order to meet the requirement of mother metal tensile strength >=510MPa simultaneously, and under weld heat input is 200 ~ 400kJ/cm welding conditions, the average Charpy-V impact power of-40 DEG C, the welded heat affecting zone of steel plate reaches the requirement of more than 100J, and carbon equivalent needs to control in rational scope.When carbon equivalent is less than 0.32%, the tensile strength of mother metal can not meet the requirement being more than or equal to 510MPa; When carbon equivalent is greater than 0.36%, can not meet under weld heat input is 200 ~ 400kJ/cm welding conditions, the average Charpy-V impact power of-40 DEG C, the welded heat affecting zone of steel plate reaches the requirement of more than 100J.
B, is improve the effective element of hardening capacity, can promotes the formation of bainite structure, improve the tensile strength of thickness of slab central zone.Meanwhile, by forming BN, the growth of Intragranular Acicular Ferrite can be promoted.As solid solution B, in process of cooling after welding, segregation is in austenite grain boundary, can also suppress the generation of grain boundary ferrite.Therefore in order to ensure the intensity of mother metal and improve the impelling strength of welded heat affecting zone, the lower limit of B content is 0.0005%.But hardening capacity will be caused during B too high levels significantly to rise, and reduce toughness and the ductility of mother metal, reduce the toughness of welded heat affecting zone, its upper limit is 0.005% simultaneously.
B
ef, according to N element bonding force size in steel, first the N in steel is combined with Ti and forms TiN, and remaining N will be combined with B and form BN.The B content that such deduction is combined with N, remaining B is effective boron content.Therefore effective boron (B
ef) can be defined as follows:
When N-Ti × 14.01/47.87≤0, B
ef=B;
As N-Ti × 14.01/47.87>0, B
ef=B-(N-Ti × 14.01/47.87) × 10.81/14.01.
Effective boron content directly affects the hardening capacity of steel, for the intensity improving thickness of slab central zone, improves the homogeneity of performance on thickness direction extremely important.This research finds, effective boron amount needs to control in rational scope, could meet the requirement of the tensile strength of mother metal, mother metal and welded heat affecting zone impelling strength simultaneously.When effective boron is less than 0.0005%, carbon equivalent C can not be met
eqbe under the condition of 0.32% ~ 0.36%, mother metal tensile strength is more than or equal to the requirement of 510MPa; When effective boron is greater than 0.005%, the impelling strength of mother metal and welded heat affecting zone will be reduced.
Carry out research to the impelling strength of Plate Steel welded heat affecting zone under raising Large Heat Input Welding condition to find, under the condition of Mn, Si, Ti, Al, Mg, Ca and REM complex deoxidization, can promote that diameter is more than or equal to a large amount of generations of the microns oxide particle of 1 μm, easily separate out MnS, TiN on their surface, the formation of Intragranular Acicular Ferrite can be brought out thus.In addition, can also promote that diameter is a large amount of generations of the submicron inclusion such as nitride, sulfide of 0.1-1 μm, these submicron inclusiones can suppress growing up of austenite crystal in Large Heat Input Welding process, therefore significantly can improve the impelling strength of welded heat affecting zone.
The present invention determines suitable component and the quantity of inclusion.The components utilising SEM-EDS of inclusion analyzes, and after carrying out grinding and mirror polish for sample, utilize SEM carry out observing for inclusion and analyze, the composition of each specimen holder foreign material is the mean value 10 being chosen arbitrarily to inclusion analysis result.Utilize SEM to choose visual field continuously for 50 under the multiplying power of 1000 times to observe, observed visual field area is greater than 0.27mm
2.The area density of inclusion is the calculation result of observed the amount of inclusions and visual field area.
The present invention is found by a large amount of experimental studies, particle diameter in steel is more than or equal to the micron inclusion of 1.0 μm, when the ratio of (Mg+Ca) in inclusion/(Al+Ti) weight percent content is more than or equal to 1.8, MgO in inclusion, CaO oxide components is higher, the oxide compound simultaneously easily forming Mg-Ca-Al-Ti is core, the complex inclusion that MnS, TiN and BN separate out in inclusion periphery.Such micron inclusion, on the one hand easy in steel Dispersed precipitate, be conducive to the increase of the amount of inclusions; On the other hand, the generation of the Intragranular Acicular Ferrite taking inclusion as core can be promoted, thus improve the Large Heat Input Welding performance of Plate Steel.Meanwhile, can also suppress take Al as the tufted aluminate of main component, or the formation of large-scale aluminate, improves welding heat influence area toughness.This is because the starting point that tufted and large-scale alumina inclusion easily generate as crackle causes the generation of crackle, reduce Low Temperature Impact Toughness of Heat-affected Zone.In addition, when the area density of micron inclusion is less than 100/mm
2time, micron inclusion can not play the effect of induction Intragranular Acicular Ferrite growth effectively.Therefore, need to control micron composition of inclusions, make (Mg+Ca)/(Al+Ti)>=1.8, area density>=100/mm
2.
For the submicron inclusion that particle diameter in steel is 0.1 ~ 1.0 μm, (Mg+Ca) when/(Al+Ti) ratio of weight percent content is more than or equal to 1.1, the submicron inclusion of this composition, is conducive to Dispersed precipitate, promotes the formation of a large amount of submicron inclusion.In Thermal Cycle process, such submicron inclusion particle can the growing up of pinning welded heat affecting zone austenite crystal effectively, improves the toughness of welded heat affecting zone.When the area density of submicron inclusion is less than 220/mm
2time, submicron inclusion can not play the effect of pinning welded heat affecting zone Austenite Grain Growth effectively.Therefore, need to control submicron inclusion and formed, make its composition meet (Mg+Ca)/(Al+Ti)>=1.1, area density>=220/mm
2.
Low-carbon-equivalent of the present invention can the manufacture method of Large Heat Input Welding Plate Steel, comprises the steps:
1) smelt, cast
Become base by following compositions smelting, refining, continuous casting, the chemical component weight per-cent of steel is:
C 0.045 ~ 0.07%, Si 0.10 ~ 0.30%, Mn 1.3 ~ 1.6%, P≤0.015%, S0.001 ~ 0.01%, Ni 0.2 ~ 0.4%, Ti 0.005 ~ 0.035%, Mg 0.0005 ~ 0.01%, N0.001 ~ 0.01%, B 0.0005 ~ 0.005%, Al≤0.05%, Ca≤0.005%, REM≤0.02%, all the other are Fe and inevitable impurity, and the chemical composition of steel plate meets 2≤Ti/N≤6, Mg/ (Al+Ti) >=0.024;
And in steel plate, carbon equivalent C
eq: 0.32% ~ 0.36%, effective boron amount B
ef: 0.0005 ~ 0.005%; Wherein, C
eq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15.When N-Ti × 14.01/47.87≤0, B
ef=B; As N-Ti × 14.01/47.87>0, B
ef=B-(N-Ti × 14.01/47.87) × 10.81/14.01;
2) rolling
Strand is heated to 1050 ~ 1250 DEG C, breaking down temperature is higher than 930 DEG C, and accumulative draft is greater than 30%; Final rolling temperature is less than 930 DEG C, and accumulative draft is greater than 30%;
3) cool
The speed of cooling of 1-30 DEG C/s is adopted surface of steel plate temperature to be begun to cool down to less than 500 DEG C from more than 750 DEG C.
Further, the chemical composition of described Plate Steel also contains more than one elements in Nb 0.001 ~ 0.03% or Cr≤0.2%, by weight percentage.
In steel plate, diameter is more than or equal to the micron inclusion of 1 μm, inclusion area density>=100/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.8; For the submicron inclusion that diameter is 0.1-1 μm, inclusion area density>=220/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.1.
Steel plate thickness of slab 50 ~ 70mm that the present invention obtains, mother metal tensile strength >=510MPa, under weld heat input is 200 ~ 400kJ/cm welding conditions, the average Charpy-V impact power in-40 DEG C, welded heat affecting zone of steel plate reaches more than 100J.
The present invention in rolling and process for cooling,
When Heating temperature before rolling is less than 1050 DEG C, the carbonitride of Nb can not solid solution completely.When Heating temperature is greater than 1250 DEG C, growing up of austenite crystal will be caused.
Breaking down temperature is higher than 930 DEG C, and accumulative draft is greater than 30%, is because more than this temperature, recrystallize occurs, can fining austenite grains.When accumulative draft is less than 30%, the thick austenite crystal formed in heat-processed also can be remaining, reduces the toughness of mother metal.
Final rolling temperature is less than 930 DEG C, and accumulative draft is greater than 30%, is that austenite recrystallize does not occur, the dislocation formed in the operation of rolling, can work as the core of ferrite forming core because at such temperatures.When accumulative draft is less than 30%, the dislocation formed is less, is not enough to the forming core bringing out acicular ferrite.
The speed of cooling of 1-30 DEG C/s is adopted to begin to cool down to less than 500 DEG C by surface of steel plate temperature from more than 750 DEG C after finish rolling, to ensure that mother metal has suitable intensity and toughness.When speed of cooling is less than 1 DEG C/s, the strength degradation of mother metal, can not meet the demands; When speed of cooling is greater than 30 DEG C/s, the toughness of mother metal reduces, and can not meet the demands.
Beneficial effect of the present invention:
The present invention takes suitable Composition Design and Control and Inclusion Removal technology, by for Ti/N, Mg/ in steel (Al+Ti) ratio, and B
efand C
eqcarry out conservative control, and diameter is more than or equal to area density and chemical composition (Mg+Ca)/(Al+Ti) ratio of the micron inclusion of 1 μm, area density and chemical composition (Mg+Ca)/(Al+Ti) ratio of the submicron inclusion of diameter 0.1-1 μm carry out conservative control, can solidify with in phase transition process, the growth of Intragranular Acicular Ferrite is promoted on these inclusion surfaces, or suppress growing up of austenite crystal, improve the Large Heat Input Welding performance of Plate Steel.Steel plate thickness specification manufactured by the present invention is 50 ~ 70mm, mother metal tensile strength>=510MPa, is that under the welding conditions of 200 ~ 400kJ/cm, welded heat affecting zone has at weld heat input
ve
-40the Large Heat Input Welding performance that>=100J is good.
Embodiment
Below in conjunction with embodiment, the present invention will be further described.
Table 1 is chemical composition, Ti/N, B of the embodiment of the present invention and comparative example
ef, C
eqwith Mg/ (Al+Ti) ratio.Table 2 is the mother metal mechanical property of the embodiment of the present invention and comparative example, inclusion characteristic and welded heat affecting zone impelling strength.
Low-carbon-equivalent of the present invention can the manufacture method of Large Heat Input Welding Plate Steel be: smelt, refining and continuous casting, and the chemical composition obtaining strand is as shown in table 1; Then strand is heated to 1050 DEG C ~ 1250 DEG C, breaking down temperature is 1000 ~ 1150 DEG C, and accumulative draft is 50%; Final rolling temperature is 700 ~ 850 DEG C, and accumulative draft is 53 ~ 67%%; The speed of cooling of 4-8 DEG C/s is adopted to begin to cool down to less than 500 DEG C by surface of steel plate temperature from more than 750 DEG C after finish rolling, to ensure that mother metal has suitable intensity and toughness.
Adopt electro-gas (enclosed) welding to implement a time welding for the steel plate of different thickness, weld heat input is 200 ~ 400kJ/cm.The welded bonds of thickness of slab 1/2 gets impact specimen, and import v-notch and carry out impelling strength detection, at-40 DEG C, carry out the Charpy impact test of three samples, the data of welded heat affecting zone impelling strength are the mean value of three measuring results.
From table 1 and table 2, in embodiment, carry out Composition Control according to the determined chemical composition ranges of the present invention, and control Ti/N ratio is 2≤Ti/N≤6, Mg/ (Al+Ti)>=0.024, carbon equivalent C
eq0.32% ~ 0.36%, effective boron amount Bef:0.0005 ~ 0.005%.In addition, control diameter and be more than or equal to the micron inclusion of 1 μm, area density>=100/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.8; Diameter is the submicron inclusion of 0.1-1 μm, area density>=220/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.1.
In comparative example 1 ~ 3, in steel, Mg content is all less than 0.0005%, all can not meet the requirement of Mg/ (Al+Ti) >=0.024.Comparative example 2 and 3 can not meet effective boron amount B
ef: the component requirements of 0.0005 ~ 0.005%.Simultaneously, comparative example 1 to 3 can not meet area density and (Mg+Ca)/(Al+Ti) ratio that diameter is more than or equal to the micron inclusion of 1 μm, and diameter is the area density of the submicron inclusion of 0.1-1 μm and the requirement of (Mg+Ca)/(Al+Ti) ratio.In addition, in comparative example 3, Ti/N ratio can not meet requirement of the present invention.
Table 2 lists tensile property and the impelling strength of mother metal in embodiment and comparative example, and the impelling strength of welded heat affecting zone.The yield strength of mother metal, tensile strength and elongation are the mean value of twice test data, and mother metal and-40 DEG C, welded heat affecting zone Charpy-V impact power are the mean value of three test datas.
As can be seen from the table, the mother metal mechanical property of embodiment and comparative example does not have obvious difference, and the thickness specification that can meet manufactured steel plate is 50 ~ 70mm, the requirement of mother metal tensile strength >=510MPa.Be under the condition of 200 ~ 400kJ/cm at weld heat input,-40 DEG C, welded heat affecting zone Charpy-V impact power is tested, the value of embodiment 1 ~ 8 is 152,168,225,102,186,122,157,220 (J) respectively, and the value of comparative example 1,2,3 is 12,17,7 (J).The impelling strength of embodiment welded heat affecting zone is significantly improved, and can meet the requirement of 200 ~ 400kJ/cm Large Heat Input Welding.
The present invention takes suitable Composition Design, determines Ti/N and Mg/ (Al+Ti) ratio suitable in steel, and B
efand C
eqand diameter is more than or equal to micron inclusion area density and chemical composition (Mg+Ca)/(Al+Ti) ratio of 1 μm, diameter is that the submicron inclusion area density of 0.1-1 μm and chemical composition (Mg+Ca)/(Al+Ti) ratio carry out conservative control, like this can solidify with phase transition process in promote the growth of Intragranular Acicular Ferrite on these inclusiones surface, or suppress growing up of austenite crystal, improve the Large Heat Input Welding performance of Plate Steel.The thickness specification of manufactured steel plate is 50 ~ 70mm, and mother metal tensile strength>=510MPa, under weld heat input is 200 ~ 400kJ/cm welding conditions, welded heat affecting zone has
ve
-40the Large Heat Input Welding performance that>=100J is good.This technology can be used in the manufacturing processed of the Plate Steels such as boats and ships, building and oceanic tectonic thing, for improving the Large Heat Input Welding performance of Plate Steel.
Claims (8)
1. low-carbon-equivalent can a Large Heat Input Welding Plate Steel, and its chemical component weight per-cent is:
C 0.045～0.07％，
Si 0.10～0.30％，
Mn 1.3～1.6％，
P≤0.015％，
S 0.001～0.01％，
Ni 0.2～0.4％，
Ti 0.005～0.035％，
Mg 0.0005～0.01％，
N 0.001～0.01％，
B 0.0005～0.005％，
Al≤0.05％，
Ca≤0.005％，
REM≤0.02％，
All the other are Fe and inevitable impurity; Wherein, 2≤Ti/N≤6, Mg/ (Al+Ti) >=0.024;
And in steel plate,
Carbon equivalent C
eq: 0.32% ~ 0.36%, C
eq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15;
Effective boron amount B
ef: 0.0005 ~ 0.005%;
When N-Ti × 14.01/47.87≤0, B
ef=B;
As N-Ti × 14.01/47.87>0, B
ef=B-(N-Ti × 14.01/47.87) × 10.81/14.01.
2. low-carbon-equivalent as claimed in claim 1 can Large Heat Input Welding Plate Steel, it is characterized in that, the chemical composition of described Plate Steel also containing one or more elements in Nb 0.001 ~ 0.03% or Cr≤0.2%, by weight percentage.
3. low-carbon-equivalent as claimed in claim 1 or 2 can Large Heat Input Welding Plate Steel, it is characterized in that, in steel plate, diameter is more than or equal to the micron inclusion of 1 μm, inclusion area density>=100/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.8; For the submicron inclusion that diameter is 0.1-1 μm, inclusion area density>=220/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.1.
4. the low-carbon-equivalent as described in claim 1 or 2 or 3 can Large Heat Input Welding Plate Steel, it is characterized in that, described Plate Steel mother metal tensile strength >=510MPa, under weld heat input is 200 ~ 400kJ/cm welding conditions, the welded heat affecting zone of steel plate at the average Charpy-V impact power of-40 DEG C at more than 50J.
5. low-carbon-equivalent can the manufacture method of Large Heat Input Welding Plate Steel, comprises the steps:
1) smelt, cast
Become base by following compositions smelting, refining, continuous casting, the chemical component weight per-cent of steel is: C 0.045 ~ 0.07%, Si 0.10 ~ 0.30%, Mn 1.3 ~ 1.6%, P≤0.015%, S0.001 ~ 0.01%, Ni 0.2 ~ 0.4%, Ti 0.005 ~ 0.035%, Mg 0.0005 ~ 0.01%, N 0.001 ~ 0.01%, B 0.0005 ~ 0.005%, Al≤0.05%, Ca≤0.005%, REM≤0.02%, all the other are Fe and inevitable impurity; This chemical composition meets 2≤Ti/N≤6, Mg/ (Al+Ti) >=0.024; Further,
In steel plate, carbon equivalent C
eq: 0.32% ~ 0.36%,
C
eq＝C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15；
Effective boron amount B
ef: 0.0005 ~ 0.005%;
When N-Ti × 14.01/47.87≤0, B
ef=B;
As N-Ti × 14.01/47.87>0, B
ef=B-(N-Ti × 14.01/47.87) × 10.81/14.01;
2) rolling
Strand is heated to 1050 ~ 1250 DEG C, breaking down temperature is higher than 930 DEG C, and accumulative draft is greater than 30%; Final rolling temperature is less than 930 DEG C, and accumulative draft is greater than 30%;
3) cool
The speed of cooling of 1-30 DEG C/s is adopted surface of steel plate temperature to be begun to cool down to less than 500 DEG C from more than 750 DEG C.
6. low-carbon-equivalent as claimed in claim 5 can the manufacture method of Large Heat Input Welding Plate Steel, it is characterized in that, the chemical composition of described Plate Steel also containing one or more elements in Nb 0.001 ~ 0.03% or Cr≤0.2%, by weight percentage.
7. the low-carbon-equivalent as described in claim 5 or 6 can the manufacture method of Large Heat Input Welding Plate Steel, it is characterized in that, in steel plate, diameter is more than or equal to the micron inclusion of 1 μm, inclusion area density>=100/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.8; For the submicron inclusion that diameter is 0.1-1 μm, inclusion area density>=220/mm
2, chemical composition meets (Mg+Ca)/(Al+Ti)>=1.1.
8. the low-carbon-equivalent as described in claim 5 or 6 or 7 can the making method of Large Heat Input Welding Plate Steel, it is characterized in that, the steel plate mother metal tensile strength >=510MPa obtained, under weld heat input is 200 ~ 400kJ/cm welding conditions, the welded heat affecting zone of steel plate at the average Charpy-V impact power of-40 DEG C at more than 50J.
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| CN115612919A (en) * | 2022-08-28 | 2023-01-17 | 武汉科技大学 | Acid-resistant and hydrogen-resistant X70 pipeline steel and preparation method thereof |
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