CN102691006A - High tempering parameter SR embrittlement resistant cryogenic nickel steel and manufacture method thereof - Google Patents
High tempering parameter SR embrittlement resistant cryogenic nickel steel and manufacture method thereof Download PDFInfo
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Abstract
A high tempering parameter SR embrittlement resistant cryogenic nickel steel and a manufacture method thereof. The nickel steel comprises, by weight, 0.025%-0.060% of C, Si no more than 0.15%, 0.45%-0.85% of Mn, P no more than 0.012%, S no more than 0.0020%, 0.10%-0.40% of Cu, 2.80%-3.80% of Ni, 0.10%-0.30% of Cr, 0.05%-0.30% of Mo, 0.040%-0.070% of Als, 0.006%-0.012% of Ti, 0.008%-0.025% of Nb, N no more than 0.0040%, 0.001%-0.003% of Ca, residual iron and unavoidable inclusions. According to optimized controlled rolling and a normalizing plus tempering technology, the nickel steel gains extremely high ultralow temperature toughness, excellent HIC / SCC resistance, weldability and bearing capacity of high heat input welding; besides, the nickel steel has excellent high tempering parameter SR embrittlement resistance characteristic, and is especially suitable for manufacture of large-scale LPG low temperature storage tank, low temperature storage tank for ship and large-scale steel structure for ice ocean and polar region.
Description
Technical field
The present invention relates to Cryogenic Steel and method of manufacture thereof; Be particularly related to the low temperature nickel steel and the method for manufacture thereof of anti-high tempering parameter SR embrittlement; Should anti-high tempering parameter postweld heat treatment (SR) embrittlement, can be than the low temperature nickel steel of large-line energy welding and anti-HIC and SCC, material is used in the manufacturing that is mainly used in LPG low temperature storage tank, low-temperature storage tank for ship.
Background technology
As everyone knows; Low-carbon (LC) (HS) low alloy steel is one of most important structural timber, is widely used among petroleum natural gas pipeline, ocean platform, shipbuilding, bridge structure, boiler vessel, building structure, automotive industry, transportation by railroad and the machinofacture.Low-carbon (LC) (HS) low alloy steel performance depends on the process system of its chemical ingredients, manufacturing processed, and wherein intensity, toughness and weldableness are the most important performances of low-carbon (LC) (HS) low alloy steel, and its final decision is in the microstructure state of finished steel.Along with science and technology constantly advances; People have higher requirement to obdurability, weldableness and the anti-processing deterioration of steel; Promptly when keeping low manufacturing cost, improve the comprehensive mechanical performance and the use properties of steel plate significantly; Practice thrift cost with the consumption that reduces steel, alleviate steel member own wt, stability and security.
Started the research climax that develops high-performance steel iron material of new generation in the world wide at present; Obtain better microstructure coupling through alloy combination design, innovation controlled rolling/TMCP technology and subsequent heat treatment technology; Thereby make steel plate obtain better low-temperature flexibility, strong plasticity and toughness coupling and weldableness, anti-HIC and SCC performance.
When prior art is made the Plate Steel of-101 ℃ of low temperature transverse impact toughness (single value)>=47J, generally will in steel, add the valuable alloying element nickel of a greater number, nickel content generally is controlled at about 3.5%, has excellent low-temperature flexibility to guarantee the mother metal steel plate; But Low Alloy Steel Plate is through too high tempering parameter TP>=18.5 * 10
3(TP=T (20+lgt) postweld heat treatment (being that SR handles), the serious deterioration of steel plate very low temperature impelling strength shows as low-temperature impact work numerical value and generally all is lower than 50J (referring to " ISI ", P101～P106,1971; " Acta Meta ", Vol.13, P591,1965; " J.I.S.I ", Vol.207, P984,1969; " ISI ", P54～P59,1971), seriously jeopardize low temperature LPG storage tank process safe safety under arms, bury the hidden danger of Serious Accident.For this reason, Japan each big steel mill (Nippon Steel, JFE, Sumitomo Metal Industries etc.) drops into a large amount of manpowers and physics; Launch deeply and carefully to study, obtained breakthrough, obtained a large amount of achievements in research; And be successfully applied to production practice, and promptly adopt the carbon content that suitably reduces steel plate, optimize rolling technology; Double normalizing thermal treatment, with reduce content of pearlite in alloy, eliminate the perlite banded structure, control perlite colony size, reduced the degradation of steel plate low-temperature impact toughness behind the high tempering parameter SR significantly; Basically solved under the high tempering parameter SR treatment condition problem of the steel plate-101 ℃ serious deterioration of low-temperature impact toughness.
Yet owing to adopt double normalizing thermal treatment, the manufacturing cycle of steel plate is long, manufacturing cost is high, the more important thing is when steel plate thickness is above above 60mm; Steel plate-101 behind the high tempering parameter SR ℃ low-temperature impact toughness instability, fluctuation is big, and the strength degradation amplitude is big; Plate quality controllability relatively poor (" steel burns ど fragility To and closes the research of The Ru "; 1976, P123～P144, Japanese iron steel association; Ibid, P95～P105, Japanese iron steel association; " iron と steel ", S281,1977; " iron と steel ", S326,1978).
In addition; When adopting the large-line energy welding; More serious deterioration takes place in welded heat affecting zone (HAZ) low-temperature flexibility; The low temperature ductile-brittle transition temperature of heat affected zone (HAZ) is general difficultly to reach very low temperature-101 ℃ (like European patent EP 0288054A2, EP0839921A1, U.S. Pat Patent 4851052) to reach-80 ℃, to say nothing of.
A large amount of patent documentations are just explained-40 ℃～-60 ℃ low-temperature flexibilities that how to realize the mother metal steel plate; For how under welding conditions; Obtaining good heat affected zone (HAZ) low-temperature flexibility explains lessly; How to guarantee that the low-temperature flexibility of heat affected zone (HAZ) is few when especially adopting the large-line energy welding, like the clear 63-93845 of Japanese Patent, clear 63-79921, clear 60-258410, special flat 4-285119, special flat 4-308035, flat 3-264614, flat 2-250917, flat 4-143246 and U.S. Pat Patent4855106, US Patent5183198, the US Patent4137104 of opening of opening.
Summary of the invention
The object of the present invention is to provide a kind of low temperature nickel steel and method of manufacture thereof of anti-high tempering parameter SR embrittlement; Make the low temperature nickel steel obtain high ultralow-temperature flexibility, good anti-HIC/SCC and weldableness, can bear than large-line energy and weld; This low temperature nickel steel of what is more important has excellent anti-high tempering parameter SR embrittlement characteristic; Be suitable for especially being used as and make large-scale LPG low temperature storage tank, LPG low temperature storage tank peculiar to vessel, ice sea and zone, polar region large-scale steel structure, and can realize low-cost stable suitability for industrialized production in batches.
The concrete technical indicator of this steel plate is: in tempering parameter TP>=19 * 10
3, under the postweld heat treatment condition, steel plate ys 275MPa～375MPa, tensile strength>=490MPa ,-101 ℃ of low-temperature impact work monodrome Akv>=47J, Z be to performance>=35%, and can be than large-line energy welding and anti-HIC and SCC.
The low temperature nickel steel of anti-high tempering parameter SR embrittlement is that difficulty is made one of maximum steel grade in the slab kind; Its reason is that such steel plate not only requires mother metal to have high ultralow-temperature flexibility, good weldableness, anti-HIC and SCC performance; But also require when steel plate still has above-mentioned performance behind too high tempering parameter SR, steel plate also has good anti-welding reheat crack(ing) performance and can stand the large-line energy welding property.
Therefore; The present invention is in gordian technique route and composition technological design; Combine influence-101 ℃ low-temperature flexibility of low temperature nickel steel, anti-HIC/SCC, anti-welding reheat cracking susceptibility, can be softening and the factor of embrittlement than large-line energy weldableness and anti-high tempering parameter SR; Creatively adopted composition system that the low N-ultra micro (Nb+Ti) of Mn-among the ultralow Si-of ultralow C-handles low alloy steel as the basis, suitably improved in the steel acid and dissolve Als content and control its scope, (%C) * (%Si)≤7.5 * 10
-3, Ni equivalent>=2.90%, [(%Cr)+1.5 (%Mo)]/t>=9.0 * 10
-3, the [(%N of 12≤Mn/C≤20,0.80≤Nb/Ti≤1.50,1.5≤Ti/N≤3.0 and Als>=(Mn/C)
Total)-0.292 (%Ti)], Ca handles and the Ca/S ratio be controlled at 1.0～3.0 between and (%Ca) * (%S)
0.28≤1.0 * 10
-3, optimize controlled rolling and follow-up special normalizing+tempering process, make the low temperature nickel steel obtain high ultralow-temperature flexibility, good anti-HIC/SCC and weldableness, can bear than the large-line energy welding, and excellent anti-high tempering parameter SR embrittlement characteristic.
Steel plate of the present invention is 50 feather weight normalizing+tempering delivery attitude low temperature nickel steel, and the microstructure of steel plate is ferritic+a small amount of perlite; In order to ensure delivery attitude low temperature nickel steel-101 ℃ toughness, the steel plate microstructure must be evenly tiny, perlite as the second phase even dispersion be distributed in the ferritic phase and perlite colony size control at≤15 μ m; For the attitude low temperature nickel steel of guaranteeing to deliver goods has good anti-HIC/SSC characteristic, do not allow to exist banded perlite and ribbon sulfide in the steel plate microstructure; For guaranteeing that the low temperature nickel steel has good weldableness and steel plate can bear big heat input welding, steel plate must low carbon content (≤0.10%) and low-carbon-equivalent (IIW≤0.45%, wherein IIW=C+Mn/6+ (Cu+Ni)/15+ (Cr+Mo+V)/5).
Steel plate has the fundamental property that above-mentioned characteristic can satisfy the low temperature nickel steel; But can't bear in the rapid deterioration of high tempering parameter SR condition lower steel plate performance; This deterioration shows as that armor plate strength reduces significantly ,-101 ℃ of ballistic works sharply descend; And along with the increase of tempering parameter, armor plate strength reduces monotonously ,-101 ℃ of impelling strength reduce monotonously.
For guaranteeing the performance of low temperature nickel steel under high tempering parameter SR condition, the design of low temperature nickel steel microscopic structure is different from common low temperature steel plate fully.Show that through researching and analysing in a large number the origin cause of formation that influences high tempering parameter SR low temperature nickel rigidity ability deterioration is steel Medium pearlite content, perlite colony size and distribution thereof, ferrite grain size; Along with steel Medium pearlite content increases, perlite colony size increases and skewness increases, high tempering parameter SR low temperature nickel rigidity can deterioration increase the weight of; Through low temperature nickel steel microstructure evolution process observation analysis under high tempering parameter SR condition is found, along with the rapid deterioration of steel plate low-temperature flexibility is grown up in carbide gathering in perlite colony trident crystal boundary place; And perlite colony size is big more, and perlite colony trident crystal boundary place carbide gathering coarsening rate is faster, carbide is thick more, and low temperature nickel steel toughness deterioration is serious more; Also find through observational study, when the perlite skewness, when especially zonal arrangement occurring; The not only anti-HIC/SCC deterioration in characteristics of low temperature nickel steel, and anti-high tempering parameter SR embrittlement ability extreme deterioration are promptly in the perlite accumulation area; Perlite colony trident crystal boundary place carbide coarsening rate is faster, size is thicker, One's name is legion and be state of aggregation and distribute, and under the effect of tension stress, these trident crystal boundary place carbide become the forming core point of crackle; And along with perlite colony size increases; Trident crystal boundary place carbide size is just big more, and the tiny crack size of forming core is also just bigger, quantity is many more, causes extremely deterioration of steel plate low-temperature flexibility; In addition; The performance of ferrite grain size after to the high tempering parameter SR of low temperature nickel steel also influences very big; Along with ferrite grain size increases, the performance degradation speed behind the high tempering parameter SR of low temperature nickel steel strengthens and appears the trend of rapid deterioration, and along with ferrite grain size increases; The perlite size increases, distributes uneven more, further promotes the deterioration of performance behind the high tempering parameter SR of low temperature nickel steel.Be low-temperature flexibility and the obdurability coupling of improving low temperature nickel steel under the high tempering parameter SR condition; The microstructure of anti-high tempering parameter PWHT low temperature steel plate should be has that content of pearlite in alloy is few, perlite colony size is tiny and be evenly distributed, do not allow to occur banded perlite, and the whole microstructure of low temperature nickel steel is evenly tiny; Best situation is to suppress the appearance of pearlitic structure, substitutes perlite with granular bainite, and forming evenly, tiny granular bainite disperse is distributed in the tiny and uniform ferritic parent phase.
Achieve the above object, steel plate composition of the present invention designs as follows:
The low temperature nickel steel of anti-high tempering parameter SR embrittlement, its composition weight percent is:
C：0.025％～0.060％
Si：≤0.15％
Mn：0.45％～0.85％
P：≤0.012％
S：≤0.0020％
Cu：0.10％～0.40％
Ni：2.80％～3.80％
Cr：0.10％～0.30％
Mo：0.05％～0.30％
Als：0.040％～0.070％
Ti：0.006％～0.012％
Nb：0.008％～0.025％
N：≤0.0040％
Ca：0.001％～0.003％
All the other are Fe and inevitably are mingled with;
And above-mentioned constituent content must satisfy following relation simultaneously:
12≤Mn/C≤20, guaranteeing steel plate after SR handles, uniform crystal particles is tiny and be higher than 50% at least-101 ℃ of following Charpy bar fracture fiber rates; Reduce content of pearlite in alloy, refine pearlite colony size, promote granular bainite to separate out, improve the anti-high tempering parameter SR embrittlement of steel plate;
(%C) * (%Si)≤9.0 * 10
-3, when improving low temperature nickel steel intrinsic plasticity and toughness, the refinement ferrite grain size improves and impacts the platform ability on the steel plate, and the M/A island is separated out, is reduced M/A island quantity, improves M/A island form among the inhibition HAZ, improves the toughness of welded H AZ;
Ni equivalent >=2.90% reduces the P-N power that under the low temperature move in ferritic dislocation 1/2＜111＞(110), has higher mobility, improves the steel plate ultralow-temperature flexibility to guarantee-101 ℃ of following ferritics 1/2＜111＞(110) dislocation; According to experimental study research and quantum mechanics first principle analysis, cast out high order power item and simplify and to draw: (%Cu)+0.37 (%Mn)-0.32 (%Mo)-0.27 (%Cr)-1.1 (%Si) of Ni equivalent=(%Ni)+0.21;
[(%Cr)+1.5 (%Mo)]/t>=9.0 * 10
-3, the reinforced ferrite crystal boundary, prevent the crystal boundary brittle failure, suppress perlite and form, promote the granular bainite phase transformation, improve low temperature nickel hardness of steel and-101 ℃ of toughness excessive descent under the high tempering parameter condition; Wherein t is a steel plate thickness, and unit is mm.
Ti/N between 1.5～3.0 and Als>=(Mn/C) [(%N
Total)-0.292 (%Ti)] can bear than large-line energy welding, HAZ excellent in low temperature toughness to guarantee the low temperature nickel steel;
0.80≤Nb/Ti≤1.50, guarantee Ti (C, N), Nb (C; N) particle is tiny, in steel, suppresses slab heating and welded H AZ grain growth with the even dispersion distributions; Refinement low temperature nickel steel microscopic structure and weldableness guarantee that steel plate HAZ is good under big heat input welding conditions;
Ca/S between 1.00～3.00 and (%Ca) * (%S)
0.28≤1.0 * 10
-3, inclusion content of steel few and evenly disperse slightly in steel; Improve low temperature nickel steel plasticity and toughness and welded H AZ toughness.
The tissue of low temperature nickel steel of the present invention is ultra-fine uniform axle ferritic+little granular bainite and the perlite that wait.
As everyone knows, carbon is very big to the impelling strength of low temperature nickel steel, high tempering parameter SR embrittlement and weldableness influence, from the low-temperature impact toughness that improves the low temperature nickel steel, anti-high tempering parameter SR embrittlement and weldableness angle, hopes that C content is relatively lower in the steel to be advisable; But intensity from steel plate; Prior microstructures Control angle from course of hot rolling and normalizing process, C content should not be low excessively, crosses low C content and cause the austenite grain boundary mobility high; This brings big problem for the even thinning microstructure of hot rolling and normalizing; Be prone to form mixed grain structure, cross low C content simultaneously and also cause the crystal boundary bonding force to reduce, cause that the steel plate low-temperature impact toughness is low, welded heat affecting zone low-temperature impact toughness deterioration; Comprehensive above factor, the content of C is controlled between 0.025%～0.060%.
Si promotes deoxidation of molten steel and can improve the intensity of low temperature nickel steel that still adopt the molten steel of Al deoxidation, the desoxydatoin of Si is little; Though Si can improve the intensity of low temperature nickel steel, the intrinsic toughness of Si heavy damage low temperature nickel steel, anti-high tempering parameter SR embrittlement and weldableness are especially under the large-line energy welding conditions; Si not only promotes the M-A island to form; And the M-A island size that forms is big, skewness, the low-temperature flexibility and the anti-fatigue performance of heavy damage welded heat affecting zone (HAZ), so the Si content in the steel should be controlled lowly as far as possible; Consider the economy and the operability of steelmaking process, Si content is controlled at≤and 0.15%.
Mn as alloying element in the low temperature nickel steel except that improving intensity and improving the toughness, also have the austenite of expansion phase region, reduce Ac
1, Ac
3, Ar
1, Ar
3The point temperature; Refinement ferrite crystal grain and perlite sheet spacing, homogenizing perlite distribute, refine pearlite colony size and the perlite amount of separating out that reduces (Mn reduces the activity quotient of C in austenite) and improve the effect of anti-high tempering parameter SR embrittlement; The more important thing is under high Ni content condition; Mn can greatly improve the hardening capacity of steel plate, suppresses perlite and separates out, and improves the performance of the high tempering parameter SR of low temperature nickel steel; Can increase the inner segregation degree of steel plate but add too much Mn, reduce the homogeneity and-101 ℃ of toughness of low temperature nickel steel mechanical property; And improve the hardenability of steel plate, influence steel plate than the large-line energy weldableness.And during the welding of little heat input, welded heat affecting zone is prone to form crisp sclerous tissues such as martensite, upper bainite; Under the Ultra-low carbon design conditions, the Mn upper content limit is moved on can be suitably, and Mn content is controlled between 0.45%～0.85%.
P has huge detrimental effect as harmful-101 ℃ of impelling strength to the low temperature nickel steel, anti-high tempering parameter SR embrittlement and weldableness of being mingled with in the steel; It is low more good more to require in theory, but considers that the logistics of steel-making condition, steel-making cost and steelworks is smooth and easy, require P content be controlled at≤0.012%.
S as harmfully in the steel be mingled with-101 ℃ of impelling strength (especially laterally low-temperature flexibility) to the low temperature nickel steel, anti-high tempering parameter SR embrittlement detrimental effect is very big; In addition; S combines with Mn in steel, forms the MnS inclusion, in course of hot rolling; The plasticity-of MnS makes MnS along rolling to extension; Form along rolling to MnS inclusion band, the horizontal low-temperature impact toughness of heavy damage steel plate, Z are to performance, anti-high tempering parameter SR embrittlement and weldableness, and S produces hot short principal element in the course of hot rolling simultaneously; It is low more good more to require in theory, but considers the smooth and easy principle of logistics of steel-making condition, steel-making cost and steelworks, require S content be controlled at≤0.0020%.
As austenite stabilizer element, add a spot of Cu and can improve anti-HIC/SSC property under intensity and the low acidity environment of low temperature nickel steel simultaneously, improve-101 ℃ of toughness and do not damage its anti-high tempering parameter SR embrittlement and weldableness; But when adding too much Cu (＞0.40%), in hot rolling and normalizing treatment process, ε-Cu that small and dispersed takes place is precipitated (Cu solid solubility in ferritic about about 0.45%) ,-101 ℃ of toughness of infringement low temperature nickel steel also possibly cause copper brittleness simultaneously; If but add Cu content very few (＜0.10%), invalid to anti-HIC/SSC under raising intensity, toughness and the low acidity, so Cu content is controlled between 0.10%～0.40%.
Ni is that steel plate obtains good ultralow-temperature flexibility, the anti-indispensable alloying element of high tempering parameter SR embrittlement, and Ni has ferritic dislocation mobility under the coldcondition of raising, promotes that the ferritic dislocation takes place to hand over slippage, improves the intrinsic plasticity and toughness of ferritic steel for low temperature service plate; Add Ni simultaneously in the steel and can also reduce the copper brittleness generation, alleviate the cracking of course of hot rolling.Therefore theoretically, Ni content is high more within the specific limits good more in the steel, but Ni is a kind of very expensive alloying element, produces angle in batches from low cost, and suitable add-on is 2.80%～3.80%.
As ferrite stabilizer; Adding a spot of Cr (≤0.30%) can be under the condition of not damaging low temperature nickel steel-101 ℃ impelling strength and weldableness; Improve the intensity behind delivery attitude low temperature nickel hardness of steel and the high tempering parameter SR, obdurability, the strong plasticity improved behind the high tempering parameter SR of low temperature nickel steel are mated; Can adopt Cr to substitute portion C, reduce the C content of steel plate, not reduce under the strength condition, improve the low-temperature flexibility of steel plate, anti-high tempering parameter SR embrittlement and weldableness; In addition, Cr improves the hardening capacity of low temperature nickel steel, suppresses perlite and forms, granular bainite phase transformation in the process air cooler after the promotion normalizing; Therefore for anti-high tempering parameter low temperature nickel steel, the Cr alloying is indispensable.If but add Cr content very few (＜0.100%), and above-mentioned effect is less, adds too much (＞0.30%), deterioration low temperature nickel steel-101 ℃ toughness and weldableness, so Cr content is controlled between 0.10%～0.30%.
Mo is as ferritic grain-boundary strengthening element; Have and suppress the high tempering parameter SR of low temperature nickel steel embrittlement and intensity softening, that improve Ultra-low carbon normalizing low temperature nickel steel; An amount of Mo of interpolation can further reduce C content, reduce the content of pearlite in alloy in the low temperature nickel steel in steel; When improving low temperature nickel steel-101 ℃ toughness and weldableness; Even tiny perlite colony size and further improve the anti-high tempering parameter SR embrittlement of low temperature nickel steel, therefore for the low temperature nickel steel of anti-high tempering parameter, the Mo alloying is indispensable; In addition; Mo increases substantially the hardening capacity of low temperature nickel steel; Granular bainite phase transformation in the process air cooler after the formation of strongly inhibited perlite, the promotion normalizing, (be perlite colony trident crystal boundary, this is in the long-time high temperature SR process to reduce high tempering parameter embrittlement source; Carbide is separated out, grows up, is thickened along crystal boundary, becomes the flaw shaped epipole).But like excessive interpolation (＞0.25%), the weldableness of infringement steel plate, the weldableness under the especially big hot initial conditions; Therefore the suitable addition of Mo is 0.05%～0.30%.
Als in the steel plate is the freedom [N] in the steel fixedly; Reduce welded heat affecting zone (HAZ) free [N]; Promote ferritic to separate out in the welding refrigeration cycle that (AlN that separates out in advance can be used as ferritic nucleation site; The microstructure of refinement HAZ), improvement is than the low-temperature impact toughness effect of large-line energy welded H AZ; But add excessive Als not only can form a large amount of disperses in steel needle-like Al in the steel
2O
3Inclusion, infringement steel plate low-temperature impact toughness, anti-high tempering parameter PWHT embrittlement and weldableness, according to the system anlysis of steel plate composition, optimum Al s content is controlled between 0.040%～0.070%.
The Ti purpose that adds trace in the steel be with steel in N combines, generate the very high TiN particle of stability, refinement mother metal steel plate microstructure and perlite colony size are improved the impelling strength of Cryogenic Steel and are resisted high tempering parameter SR embrittlement; In addition, inhibition welded H AZ district austenite crystal is grown up and is changed the second-order phase transition product, improves the low-temperature flexibility of large-line energy welded H AZ.The Ti content that adds in the steel will contain flux matched with the N in the steel, and the principle of coupling is that TiN can not separate out in liquid molten steel and must in solid phase, separate out; Therefore the separating out temperature and must guarantee to be lower than 1400 ℃ of TiN, according to log [Ti] [N]=-16192/T+4.72 can confirm the add-on of Ti.When adding Ti content very few (＜0.006%), it is not enough to form the TiN number of particles, and the austenite crystal that is not enough to suppress HAZ is grown up and changed the second-order phase transition product and improve the low-temperature flexibility of large-line energy welded H AZ; When adding Ti content too much (＞0.012%); TiN separates out temperature above 1400 ℃; Part TiN particle is separated out large-sized TiN particle in the solidification of molten steel process, this large size TiN particle not only can not suppress the austenite crystal of HAZ grows up, and becomes the starting point of crack initiation on the contrary; Therefore the optimum controling range of Ti content is 0.006%～0.012%.
The Nb element purpose of adding trace in the steel is to carry out controlled rolling, and the microstructure of refinement mother metal steel plate, perlite colony size, homogenizing perlite distribute; Exist optimum matching interval between Nb content range and the C content range, in this interval, when Nb brought into play best controlled rolling, highly malleablized effect, Nb was less to the infringement of steel plate weldableness; Therefore, when adopting the design of Ultra-low carbon composition, the Nb content range can suitably improve, with intensity, toughness, the anti-high tempering parameter SR embrittlement and softening of guaranteeing Cryogenic Steel; When the Nb addition is lower than 0.008%, can not effectively bring into play the above-mentioned effect of Nb in the Ultra-low carbon content steel plate; When the Nb addition surpasses 0.025%, bring out under the large-line energy welding conditions that upper bainite (Bu) forms and Nb (C, N) secondary is separated out embrittling effect, the low-temperature flexibility of heavy damage large-line energy welded heat affecting zone (HAZ); Therefore Nb content is controlled between 0.008%～0.025%, when obtaining best controlled rolling effect, even tiny ferritic and perlite colony, does not damage the toughness of large-line energy welded H AZ again.
The span of control of N is corresponding with the span of control of Ti, and for than the large-line energy welding steel, Ti/N is best between 1.5～3.5.N content is crossed low and during the Ti too high levels, generates that the TiN number of particles is few, size is big, can not play the effect of the weldableness of improving steel, and is harmful to weldableness on the contrary; But during the N too high levels, free [N] increases in the steel, especially sharply increases heavy damage HAZ low-temperature flexibility, the weldableness of deterioration steel than heat affected zone (HAZ) under the large-line energy welding conditions free [N] content; In addition, when N content was higher, the steel slab surface severe crack caused slab to scrap when serious.Therefore N content be controlled at≤0.0040%.
Steel is carried out Ca to be handled; On the one hand can pure molten steel; On the other hand sulfide in the steel is carried out denaturing treatment, make it to become non deformable, stablize tiny spherical sulfide, suppress S red brittleness, improve steel plate impelling strength and Z to performance, improve the anisotropy of steel plate impelling strength.What of Ca add-on are depended on the height of S content in the steel, and the Ca add-on is low excessively, and treatment effect is little; The Ca add-on is too high, and (O, S) oversize, fragility also increases, and can become the fracture crack starting point, reduces the low-temperature flexibility of steel, also reduces purity of steel simultaneously, pollutes molten steel to form Ca.General control Ca content is pressed ACR=(wt%Ca) [1-1.24 (wt%O)]/1.25 (wt%S), and wherein ACR is a sulfide inclusion shape control index, be advisable between the span 1.0～3.0, so the span of control of Ca content is 0.001%～0.003%.
The method of manufacture of the low temperature nickel steel of anti-high tempering parameter SR embrittlement of the present invention is characterized in that, comprises the steps:
A) smelt, cast
Press mentioned component and smelt, continuous casting is adopted in casting, and the light draft of continuous casting is controlled between 3%～7%, and the basket pouring temperature is between 1530 ℃～1560 ℃, and is cold a little less than the two cold employings, and the specific water is controlled at≤0.60L/ ton * min;
B) slab heating
After coming out of the stove, 1050 ℃～1150 ℃ of Heating temperatures, slab adopt high-pressure water descaling;
C) rolling, the steel plate overall compression ratio is slab thickness/Finished Steel plate thickness >=3.60
Fs is common rolling, and it is rolling to adopt big rolling pass draft to carry out rapid Continuous, guarantees that the deformation metal takes place dynamically/static recrystallize, rolling pass draft >=8%, accumulative total draft >=45%, refine austenite crystal grain;
Subordinate phase adopts non-recrystallization controlled rolling TMR; 770 ℃≤controlled rolling start rolling temperature≤820 ℃; Rolling pass draft>=8%, non-recrystallization district accumulative total draft>=50%, 730 ℃≤finishing temperature≤780 ℃; Further attitude steel plate microstructure is rolled in refinement, for normalizing homogenous superfine microstructure lays the foundation;
D) rolling back steel plate is cheated or the case slow cooling, and the steel plate retarded cooling process is slow cooling 36 hours at least more than 300 ℃, guarantees that the H atomic diffusion goes out steel plate in the steel, prevents that hydrogen from causing delayed cracking, improves steel plate HIC and SSC characteristic; Steel plate goes out burial pit or case immediately;
E) normalizing
Normalizing temperature is 800 ℃～850 ℃, and the normalizing hold-time is 20～40min; Weak accelerated cooling process is adopted in the steel plate back of coming out of the stove, average cooling rate≤2 ℃/s; Opening cold temperature is 790 ℃～840 ℃, and cooling stops temperature≤500 ℃, along with natural air cooling to room temperature;
F) tempering
The steel plate tempering temperature is that the plate temperature is 595～635 ℃; Tempering hold-time >=(0.65～1.0) * Finished Steel plate thickness; The soaking time that the tempering hold-time picks up counting when reaching tempering temperature for the steel plate core temperature, unit time is min, steel plate thickness unit is mm; Tempering finishes back steel plate natural air cooling to room temperature.
Further, adopt air-cooled after the step e) steel plate is come out of the stove.
The composition system according to the present invention, the High Nickel Steel steel slab surface is prone to crack, and continuous casting process is adopted in casting, continuous casting process emphasis control trough casting temperature, light draft and two cold but patterns; The light draft of continuous casting is controlled between 3%～7%, and the basket pouring temperature is between 1530 ℃～1560 ℃, to improve the continuously cast bloom center segregation with loose; Cold a little less than the two cold employings, the specific water is controlled at≤0.60L/ ton * min, to improve High Nickel Steel continuously cast bloom surface crack.
Adopt high-pressure water descaling after 1050 ℃～1150 ℃ of slab heating temperatures, slab are come out of the stove, de-scaling is de-scaling not to the utmost repeatedly;
For guarantee that the low temperature nickel steel microscopic structure is evenly tiny, perlite and granular bainite disperse distribute steel plate overall compression ratio (slab thickness/Finished Steel plate thickness) >=3.60.
Fs is common rolling, and it is rolling to adopt big rolling pass draft to carry out rapid Continuous, guarantees that the deformation metal takes place dynamically/static recrystallize, accumulative total draft >=45%, refine austenite crystal grain.
Subordinate phase adopts non-recrystallization controlled rolling TMR; 770 ℃≤controlled rolling start rolling temperature≤820 ℃; Rolling pass draft>=8%, non-recrystallization district accumulative total draft>=50%, 730 ℃≤finishing temperature≤780 ℃; Further attitude steel plate microstructure is rolled in refinement, for normalizing homogenous superfine microstructure lays the foundation.
Rolling back steel plate is cheated (case) slow cooling, and the steel plate retarded cooling process is slow cooling 36 hours at least more than 300 ℃, guarantees that the H atomic diffusion goes out steel plate in the steel, prevents that hydrogen from causing delayed cracking, improves steel plate HIC and SSC characteristic; Steel plate goes out burial pit (case) immediately.
The employing normalizing process is following: normalizing temperature is 800 ℃～850 ℃, and the normalizing hold-time is 20～40min; Weak accelerated cooling process (air-cooled) is adopted in the steel plate back of coming out of the stove, and opening cold temperature is 790 ℃～840 ℃, and cooling stops temperature≤500 ℃, along with natural air cooling to room temperature.
Steel plate tempering temperature (plate temperature) is 595～635 ℃; Tempering temperature was limit on the upper side when steel plate was relatively thin, tempering temperature was limit on the lower side when steel plate was thicker relatively; Tempering hold-time >=(0.65～1.0) * Finished Steel plate thickness; The soaking time that the tempering hold-time picks up counting when reaching the tempering target temperature for the steel plate core temperature, unit time is min; Tempering finishes back steel plate natural air cooling to room temperature.
Beneficial effect of the present invention
The present invention is in gordian technique route and composition technological design; Combine influence-101 ℃ low-temperature flexibility of low temperature nickel steel, anti-HIC/SCC, anti-welding reheat cracking susceptibility, can be softening and the factor of embrittlement than large-line energy weldableness and anti-high tempering parameter SR; Creatively adopted composition system that the low N-ultra micro (Nb+Ti) of Mn-among the ultralow Si-of ultralow C-handles low alloy steel as the basis, suitably improved in the steel acid and dissolve Als content and control its scope, (%C) * (%Si)≤7.5 * 10
-3, Ni equivalent>=2.90%, [(%Cr)+1.5 (%Mo)]/t>=9.0 * 10
-3, the [(%N of 12≤Mn/C≤20,0.80≤Nb/Ti≤1.50,1.5≤Ti/N≤3.0 and Als>=(Mn/C)
Total)-0.292 (%Ti)], Ca handles and the Ca/S ratio be controlled at 1.0～3.0 between and (%Ca) * (%S)
0.28≤1.0 * 10
-3Optimize controlled rolling and follow-up special normalizing+tempering process; Make the low temperature nickel steel obtain high ultralow-temperature flexibility, good anti-HIC/SCC and weldableness, can bear than large-line energy and weld; The low temperature nickel steel of this invention of what is more important has excellent anti-high tempering parameter SR embrittlement characteristic, is suitable for especially being used as making large-scale LPG low temperature storage tank, LPG low temperature storage tank peculiar to vessel, ice sea and zone, polar region large-scale steel structure, and can realizes low-cost stable suitability for industrialized production in batches.
The concrete technical indicator of this steel plate is: in tempering parameter TP>=19 * 10
3(TP=T (20+lgt); Wherein TP is a tempering parameter; T postweld heat treatment temperature, temperature unit are K; T be postweld heat treatment time, unit time for hour) under the postweld heat treatment condition; The steel plate ys is controlled at 275MPa～375MPa, tensile strength>=490MPa ,-101 ℃ of low-temperature impact work monodrome Akv>=47J, Z to performance>=35%, and can be than large-line energy welding and anti-HIC and SCC.
The successful implementation of the present invention's technology; Not only broken Japanese steel mill to of the monopolization of such high added value steel grade technology with product; Filled up domestic blank; Finish the low temperature nickel steel situation under one's control of high tempering parameter SR, for the lifting of China's slab manufacturing technology, catch up with and surpass the international high standards and made contribution; And eliminated of the infringement of the monopolic profits of external steel mill great number to Chinese equipment manufacture, promote update and the design of China's low-temperature equipment production product, the fast lifting of manufacturing technology; In addition; External inlet plate can't guarantee delivery date, forces the user before design paper comes out, and orders in advance to have certain size surplus steel plate; So that after design paper comes out; The plate size that requires according to design paper requires the cutting steel plate, causes the huge waste of material, and production domesticization back the problems referred to above can be solved comprehensively.
Description of drawings
Fig. 1 is steel plate microstructure (10.5 grades of the grain fineness numbers) photo of embodiment of the invention E.
Embodiment
Below in conjunction with embodiment and accompanying drawing the present invention is further specified.
The manufacturing process of embodiment is: TDS molten iron deep desulfuration → converter smelting → LF → RH (feed Si-Ca silk) → continuous casting (adopt and gently depress technology) → slab roll off the production line finishing → slab scale fire cut → heat → controlled rolling (TMR) → weak acceleration cooling (adopting air-cooled) → steel plate piles slow cooling/hole slow cooling → AUT/MUT → swarf; Crop end → thick ball blast removes surface of steel plate oxide debris → normalizing+tempering heat treatment (N+T) → sampling and performance test → cut scale steel plate → surface quality and apparent size; Identify and detect → dispatch from the factory.
The one-tenth of the embodiment of the invention shown in the table 1 is grouped into.Table 2, table 3 are the ME of the embodiment of the invention.Table 4 is the plate property of the embodiment of the invention.The performance of steel plate (600 ℃ * 22 hours) behind the high tempering parameter SR of the present invention shown in the table 5.
By Fig. 1, visible content of pearlite in alloy is little in the steel of the present invention, and perlite colony size is tiny, perlite is evenly distributed with granular bainite, does not especially have banded perlite, and assurance low temperature nickel steel has good anti-high tempering parameter SR embrittlement characteristic.
In sum; The present invention combines with non-recrystallization controlled rolling, special thermal treatment technology through the unitized design of rational alloying element, and the low temperature nickel steel can obtain excellent low-temperature flexibility, anti-high tempering parameter SR embrittlement with softening, and steel plate can bear than large-line energy and welds; Thereby practiced thrift the cost that the user member is made; Shortened the time that user's member is made, for the user has created very big value, thereby this type of low temperature nickel steel product that is high added value, green environmental protection; Owing to need not add any equipment in the low temperature nickel steel production process of the present invention, ME is succinct, production process control is easy, therefore cheap for manufacturing cost, has the very high performance-price ratio and the market competitiveness; And technological adaptability is strong, can promote to all Heavy Plate Production producers with HTFX.
Along with China's sustained economic development; Increasing to the oil and gas demand; The transfering natural gas from the west to the east two wires that is about to recently to go into operation, to go out river pipeline, Sino-Russian pipeline, Sino-Kazakhstan pipeline construction be exactly best illustration; The climax that low temperature gas-holder LPG, LNG will occur building for the Deposits in Eastern Coastal China area that lacks hydrocarbon resources, as the crucial tank body material of low temperature gas-holder LPG, LNG---the low temperature nickel steel of anti-high tempering parameter SR has vast market prospect.
Claims (3)
1. resist the low temperature nickel steel of high tempering parameter SR embrittlement, its composition weight percent is:
C：0.025％～0.060％
Si：≤0.15％
Mn：0.45％～0.85％
P：≤0.012％
S：≤0.0020％
Cu：0.10％～0.40％
Ni：2.80％～3.80％
Cr：0.10％～0.30％
Mo：0.05％～0.30％
Als：0.040％～0.070％
Ti：0.006％～0.012％
Nb：0.008％～0.025％
N：≤0.0040％
Ca：0.001％～0.003％
All the other are Fe and inevitably are mingled with;
And above-mentioned constituent content must satisfy following relation simultaneously:
12≤Mn/C≤20；
(％C)×(％Si)≤9.0×10
-3；
Ni equivalent >=2.90%, (%Cu)+0.37 (%Mn)-0.32 (%Mo)-0.27 (%Cr)-1.1 (%Si) of Ni equivalent=(%Ni)+0.21;
[(%Cr)+1.5 (%Mo)]/t>=9.0 * 10
-3, wherein t is a steel plate thickness, unit is mm;
Ti/N between 1.5～3.0 and Als>=(Mn/C) [(%N
Tota1)-0.292 (%Ti)];
0.80≤Nb/Ti≤1.50；
Ca/S between 1.00～3.00 and (%Ca) * (%S)
0.28≤1.0 * 10
-3
2. the method for manufacture of the low temperature nickel steel of anti-high tempering parameter SR embrittlement as claimed in claim 1 is characterized in that, comprises the steps:
A) smelt, cast
Press mentioned component and smelt, continuous casting is adopted in casting, and the light draft of continuous casting is controlled between 3%～7%, and the basket pouring temperature is between 1530 ℃～1560 ℃, and is cold a little less than the two cold employings, and the specific water is controlled at≤0.60L/ ton * min;
B) slab heating
After coming out of the stove, 1050 ℃～1150 ℃ of Heating temperatures, slab adopt high-pressure water descaling;
C) rolling, the steel plate overall compression ratio is slab thickness/Finished Steel plate thickness >=3.60
Fs is common rolling, adopts big rolling pass draft to carry out continuous rolling, guarantees that the deformation metal takes place dynamically/static recrystallize, rolling pass draft >=8%, accumulative total draft >=45%, refine austenite crystal grain;
Subordinate phase adopts non-recrystallization controlled rolling TMR, 770 ℃≤controlled rolling start rolling temperature≤820 ℃, rolling pass draft>=8%, accumulative total draft>=50%, 730, non-recrystallization district ℃≤finishing temperature≤780 ℃;
D) rolling back steel plate is cheated or the case slow cooling, and the steel plate retarded cooling process is slow cooling 36 hours at least more than 300 ℃, and steel plate goes out burial pit or case immediately;
E) normalizing
Normalizing temperature is 800 ℃～850 ℃, and the normalizing hold-time is 20～40min; Weak accelerated cooling process is adopted in the steel plate back of coming out of the stove, average cooling rate≤2 ℃/s, and opening cold temperature is 790 ℃～840 ℃, and cooling stops temperature≤500 ℃, and the steel plate natural air cooling is to room temperature subsequently;
F) tempering
The steel plate tempering temperature is that the plate temperature is 595～635 ℃; Tempering hold-time >=(0.65～1.0) * Finished Steel plate thickness; The soaking time that the tempering hold-time picks up counting when reaching tempering temperature for the steel plate core temperature, unit time is min, steel plate thickness unit is mm; Tempering finishes back steel plate natural air cooling to room temperature.
3. the method for manufacture of the low temperature nickel steel of anti-high tempering parameter SR embrittlement as claimed in claim 2 is characterized in that, adopts air-cooled after the step e) steel plate is come out of the stove.
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