CN104131225B - Low cost ultralow temperature nickel steel and manufacture method thereof - Google Patents
Low cost ultralow temperature nickel steel and manufacture method thereof Download PDFInfo
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Abstract
Low cost ultralow temperature nickel steel and manufacture method thereof, its composition by weight percent is: C0.04～0.070%, Si≤0.15%, Mn0.80～1.20%, P≤0.010%, S≤0.0020%, Ni5.00～7.00%, Mo0.05～0.25%, Als0.010～0.030%, Ti0.008～0.018%, N≤0.0040%, Ca0.001～0.004%, remaining be Fe and being inevitably mingled with；The present invention uses Mn-low N-ultra micro+Ti in the ultralow Si-of ultralow C-to process the component system of low-alloy steel, control (%Mn) × [7.33 (%Si)+5.16 (%Al)]≤1.0,0.007≤stabilization of austenite Index A u/ two-phase section hardening heat T≤0.009, optimize Controlled Cooling and follow-up special combination Technology for Heating Processing, ultralow temperature nickel steel is made to obtain high ultralow-temperature flexibility, excellent weldability, the welding of relatively high heat-input can be born, there is the anti-high tempering parameter SR embrittlement characteristic of excellence, and can low cost manufacture.
Description
Technical field
The present invention relates to low-carbon (LC) (high intensity) low-alloy steel, particularly to low cost ultralow temperature nickel steel and
Manufacture method, this steel plate yield strength >=550MPa, tensile strength >=650MPa ,-196 DEG C of low temperature punchings
Hit merit monodrome Akv >=100J, Z-direction performance >=35%, be mainly used in LNG tank, liquid peculiar to vessel
Change natural gas storage tank.
Background technology
It is known that low-carbon (LC) (high intensity) low-alloy steel is one of most important structural timber, extensively
It is applied to petroleum natural gas pipeline, ocean platform, shipbuilding, bridge structure, boiler vessel, builds
Among building structure, auto industry, railway transportation and machine-building.Low-carbon (LC) (high intensity) low-alloy rigidity
Can depend on the process system of its chemical composition, manufacture process, wherein intensity, toughness and weldability are
The most important performance of low-carbon (LC) (high intensity) low-alloy steel, it is finally decided by the microscopic structure of finished steel
State.Along with science and technology constantly advances, people are bad to obdurability, weldability and the anti-processing of steel
The property changed is had higher requirement, and i.e. steel plate is significantly increased while maintaining relatively low manufacturing cost
Comprehensive mechanical performance and serviceability, to reduce the consumption of steel and cost-effective, alleviate steel beam column
Own wt, stability and safety.
Start the research climax of development a new generation high-performance steel iron material at present in world wide, passed through
Alloy combination design, innovation controlled rolling/TMCP (including DQ) technology and subsequent heat treatment technique obtain more preferably
Microscopic structure coupling so that steel plate obtain more excellent low-temperature flexibility, strong plasticity and toughness coupling with weldering
Connecing property.
When prior art manufactures the steel plate of-196 DEG C of low temperature transverse impact toughness (single value) >=100J, one
As in steel, to add a large amount of expensive alloying elements nickel, nickel content general control is more than 9.0%, with really
Protect mother metal steel plate and there is the ultralow-temperature flexibility of excellence.Such as " Japan's metallography meeting " 30 (1966), P42；
Ibid., 33 (1969), P856；" Kawasaki Steel skill report ", 18 (1986), P327；" NKK
Skill report ", 111 (1986), P1；" pressure techniques ", 31 (1993), P353；" CAMP-ISIJ ",
9 (1996), P437).But production cost remains high, product competitiveness in the market is low, such as " pressure
Power technology ", 29 (1991), P341.
Secondly, alloy-steel plate is through too high tempering parameter TP >=18.5 × 103(TP=T (20+lgt) postwelding heat
Process (i.e. SR process), steel plate ultralow temperature impact flexibility serious deterioration, show as low-temperature impact work number
Value generally individually less than 47J, seriously jeopardize low temperature LNG storage tank under arms during security reliability,
Bury the hidden danger of major accident.
During additionally, use high heat-input welding, welding heat affected zone (HAZ) low-temperature flexibility compares
Serious deterioration, the low temperature ductile-brittle transition temperature of heat affected area (HAZ) is typically relatively difficult to reach-165
DEG C, not to mention reach ultralow temperature-196 DEG C.
Existing a large amount of patent documentation only illustrates how to realize-40 DEG C of mother metal steel plate～-60 DEG C of low temperature are tough
Property, for the most under soldering conditions, it is thus achieved that excellent heat affected area (HAZ) low-temperature flexibility illustrates
Less, how to ensure ultralow temperature nickel steel heat affected area (HAZ) especially with high heat-input when welding
-196 DEG C of low-temperature flexibilities are less.(63-93845 as clear in Japan Patent, clear 63-79921, clear 60
-258410, spy is opened flat 4-285119, spy is opened flat 4-308035, flat 3-264614, flat 2-
250917, flat 4-143246 and United States Patent (USP) US Patent4855106, US Patent5183198,
US Patent4137104)
Summary of the invention
It is an object of the invention to provide a kind of low cost ultralow temperature nickel steel and manufacture method thereof, steel plate is bent
Take intensity >=550MPa, tensile strength >=650MPa ,-196 DEG C of low-temperature impact work monodrome Akv >=100J,
Z-direction performance >=35%, is particularly suitable for being used as manufacture Large LNG extremely low temperature tank, LNG peculiar to vessel surpasses
Low-temperature storage tank, ice sea and region, polar region large-scale steel structure, and it is capable of low cost stably batch work
Industry metaplasia is produced.
For reaching above-mentioned purpose, the technical scheme is that
Ultralow temperature nickel steel brittle for anti-high tempering parameter SR is that in slab kind, difficulty manufactures bigger steel
One of kind, its reason is that such steel plate does not require nothing more than mother metal and has high ultralow-temperature flexibility, excellent
Weldability, but also require, at steel plate after too high tempering parameter SR, still there is the same of above-mentioned performance
Time, steel plate also has excellent weldability and can stand high heat-input welding；Therefore on key technology road
On line and Composition And Process design, combine the low-temperature flexibility of-196 DEG C that affect ultralow temperature nickel steel, anti-weldering
Connect reheat cracking susceptibility, can relatively high heat-input weldability and anti-high tempering parameter SR soften with brittle
Factor, creatively have employed in the ultralow Si-of ultralow C-Mn-low N-ultra micro+Ti and process low
Based on the component system of steel alloy, control (%Mn) × [7.33 (%Si)+5.16 (%Al)]≤1.0,
0.007≤stabilization of austenite Index A u/ two-phase section hardening heat T≤0.009, Ca process and Ca/S ratio
Control between 1.0～3.0 and (%Ca) × (%S)0.28≤1.0×10-3, optimize Controlled Cooling and follow-up spy
Different combination Technology for Heating Processing, makes ultralow temperature nickel steel obtain high ultralow-temperature flexibility, excellent welding
Property, can bear relatively high heat-input welding, the low temperature nickel steel of this invention of what is more important have excellence
Anti-high tempering parameter SR embrittlement characteristic, and can low cost manufacture (relatively conventional about 9.0%
The ultralow temperature steel plate of nickel content).
Concrete, the low cost ultralow temperature nickel steel of the present invention, its composition by weight percent is: C:
0.040%～0.070%, Si :≤0.15%, Mn:0.80%～1.20%, P :≤0.010%, S:
≤ 0.0020%, Ni:5.00%～7.00%, Mo:0.05%～0.25%, Als:0.010%～0.030%,
Ti:0.008%～0.018%, N :≤0.0040%, Ca:0.001%～0.004%, remaining be Fe
Inevitably it is mingled with；And mentioned component must simultaneously meet following relation:
(%Mn) × [7.33 (%Si)+5.16 (%Al)]≤1.0；
Ti/N=1.5～3.5；
0.007≤stabilization of austenite Index A u/ two-phase section hardening heat T≤0.009,
Wherein, Au=2.54+40.53 [(%C)+(%N)]+0.43 [(%Cu)+(%Ni)+(%Mn)]
-0.22 (%Al)-2.64 [(%P)+(%S)]-1.26 [(%Cr)+(%Mo)]-(%Si), the unit of T is K；
Ca/S is between 1.00～3.00, and (%Ca) × (%S)0.28≤1.0×10-3；
The low temperature nickel structure of steel obtained is the martensite/bainite+ferrite+austenite island of fine uniform
Complex phase microscopic structure.
In the composition of steel plate of the present invention designs:
C, on the impact flexibility of ultralow temperature nickel steel, high tempering parameter SR is brittle and weldability impact is very big,
From improving the low-temperature impact toughness of ultralow temperature nickel steel, anti-high tempering parameter SR embrittlement and weldability angle,
Wish that in steel, C content is advisable than relatively low；But it is from the intensity of steel plate, prior from course of hot rolling with quench
The microstructures Control angle of fire process, C content is unsuitable too low, and too low C content causes austenite crystal
Boundary's mobility is high, and this brings bigger problem to the uniform thinning microstructure of hot rolling and quenching, is easily formed mixed crystal
Tissue, the most too low C content also results in Grain-boundary Junctions and makes a concerted effort to reduce, causes steel plate low-temperature impact toughness low
Under, welding heat affected zone low-temperature impact toughness deterioration；Comprehensive above factor, the content of C controls
Between 0.040%～0.070%.
Si promotes deoxidation of molten steel and can improve the intensity of ultralow temperature nickel steel, but uses Al deoxidation
Molten steel, the deoxidation of Si is little, although Si can improve the intensity of ultralow temperature nickel steel, but Si
Roughening steel plate microstructure seriously damages the intrinsic toughness of ultralow temperature nickel steel, anti-high tempering parameter SR
Embrittlement and weldability, especially under relatively high heat-input welding condition, Si not only promotes that M-A island is formed,
And the M-A island size that formed is big, skewness, seriously damages welding heat affected zone (HAZ)
Low-temperature flexibility and anti-fatigue performance, therefore the Si content in steel should control low as far as possible, it is contemplated that
The economy of steelmaking process and operability, Si content controls≤0.15%.
Mn as alloying element in ultralow temperature nickel steel except improving intensity and in addition to improving toughness, also have
Expand austenite phase field, reduce Ac1、Ac3、Ar1、Ar3Point temperature, refines steel plate crystallite dimension,
Increase the position between bainite/martensite lath to angle, it is often more important that under the conditions of high Ni content,
Mn can be greatly improved the quenching degree of steel plate, refines bainite/martensite colony size, improves ultralow
The low-temperature flexibility of temperature nickel steel；But add too much Mn and can increase steel plate internal segregation degree, reduce super
The uniformity of low temperature nickel steel mechanical property and-196 DEG C of toughness, increase ultralow temperature nickel steel temper brittleness especially
Anti-high tempering parameter SR embrittlement characteristic, deteriorates steel plate relatively high heat-input weldability.And the weldering of little heat input
When connecing, welding heat affected zone is easily formed brittle tissue such as martensite etc.；Therefore, Mn content range control
System is between 0.80%～1.20%.
P is mingled with-196 DEG C of impact flexibility to ultralow temperature nickel steel, anti-high tempering parameter as harmful in steel
SR is brittle and weldability has huge detrimental effect；Require the lowest more good in theory, but consider
The logistics of steel-making condition, steel-making cost and steel mill is smooth and easy, it is desirable to P content controls≤0.010%.
S is mingled with-196 DEG C of impact flexibility to ultralow temperature nickel steel as harmful in steel (especially laterally low temperature is tough
Property), anti-high tempering parameter SR embrittlement detrimental effect the biggest；Additionally, S is combined with Mn in steel,
Forming MnS field trash, in the hot rolling, the plasticity of MnS makes MnS along rolling to extension, shape
Become along rolling to MnS field trash band, the serious infringement horizontal low-temperature impact toughness of steel plate, Z-direction performance,
Anti-high tempering parameter SR embrittlement and weldability, produce hot short master in S or course of hot rolling simultaneously
Want element；Require the lowest more good in theory, but in view of steel-making condition, steel-making cost and steel mill
The smooth and easy principle of logistics, it is desirable to S content controls≤0.0020%.
Ni is that steel plate obtains excellent ultralow-temperature flexibility, the brittle indispensable conjunction of anti-high tempering parameter SR
Gold element, Ni has the P-N power of ferrite dislocation motion under reduction condition of ultralow temperature, improves ultralow
Ferrite dislocation mobility under the conditions of temperature, promotes ferrite dislocation generation commutative Banach aglebra, improves ferrite low
The intrinsic plasticity and toughness of temperature steel plate；The most theoretically, in steel, Ni content is the highest
The best, but Ni is a kind of expensive alloying element, produces angle in batches from low cost, suitable
Addition is 5.00%～7.00%.
Mo, as ferrite grain boundaries intensified element, has suppression low temperature nickel steel height tempering parameter SR brittle
With softening, the intensity of raising ultralow temperature nickel steel, in steel, the appropriate Mo that adds can reduce C further
Content, the bainite/martensite substructure form reduced in ultralow temperature nickel steel, improve ultralow temperature nickel steel
While-196 DEG C of toughness and weldability, improve the anti-high tempering parameter SR of ultralow temperature nickel steel brittle, because of
This is for the ultralow temperature nickel steel of anti-high tempering parameter, and Mo alloying is indispensable；But as excess adds
Add, the weldability of infringement steel plate, the especially weldability under the conditions of high heat-input；Therefore Mo suitably adds
Dosage is 0.05%～0.25%.
Als in steel plate can fix the freedom [N] in steel, reduces welding heat affected zone (HAZ) freely
[N], has refinement steel plate microscopic structure (AlN anchoring effect) and (includes welding heat affected with eliminating in steel
District) effect of solid solution N；But the Als adding excess in steel not only can form a large amount of disperse in steel
Needle-like Al2O3Field trash, infringement steel plate low-temperature impact toughness and cracking resistance, crack arrest；And promote back
Fire is brittle, damage high heat-input weldability and welding point abnormal structure occurs, becomes split according to steel plate
System analyzes, and optimum Al s content controls between 0.010%～0.030%.
The Ti purpose adding trace in steel is that N is combined in steel, generates the TiN grain that stability is the highest
Son, refines mother metal steel plate microscopic structure, improves the impact flexibility of steel used at ultra-low temperature and anti-high tempering parameter
SR is brittle；Additionally, suppression welded thin-wall box component district Austenite Grain Growth and change second-order phase transition product,
Improve the low-temperature flexibility of Large Heat Input Welding HAZ.The Ti content added in steel to contain with the N in steel
Flux matched, the principle of coupling is that TiN can not separate out in liquid molten steel and must separate out in solid phase；
Therefore the Precipitation Temperature of TiN must assure that less than 1400 DEG C, according to log [Ti] [N]=-16192/T
+ 4.72 additions that may determine that Ti.When adding, Ti content is very few, forms TiN number of particles not
Foot, is not enough to suppress the Austenite Grain Growth of HAZ and change second-order phase transition product and improve big line
The low-temperature flexibility of energy welded thin-wall box component；When addition Ti content is too much, TiN Precipitation Temperature is more than 1400
DEG C, part TiN granule separates out large-sized TiN particle, this large scale during solidification of molten steel
TiN particle not only can not suppress the Austenite Grain Growth of HAZ, becomes rising of crack initiation on the contrary
Initial point；Therefore the optimum controling range of Ti content is 0.008%～0.018%.
The span of control of N is corresponding with the span of control of Ti, for relatively Large Heat Input Welding steel plate,
Ti/N is optimal between 1.5～3.5.N content is too low and during Ti too high levels, generates TiN particle
Quantity is few, size is big, it is impossible to plays the effect of the weldability improving steel, is harmful to weldability on the contrary；
But when N content is too high, in steel, freely [N] increases, hot shadow under the conditions of the most relatively Large Heat Input Welding
Ring district (HAZ) freely [N] content to sharply increase, serious infringement HAZ low-temperature flexibility, deteriorate the weldering of steel
Connecing property；During additionally, N content is higher, slab surface cracks is serious, causes slab to scrap time serious.
Therefore N content controls≤0.0040%.
Steel is carried out Ca process, on the one hand on the other hand sulfide in steel can be entered with pure molten steel
Row degenerative treatments, is allowed to become non deformable, stablizes tiny spherical sulfide, the heat of suppression S
Fragility, improve steel plate impact flexibility and Z-direction performance, the anisotropy of steel plate impact flexibility improved.Ca
The number of addition, depends on the height of S content in steel, and Ca addition is too low, and treatment effect is not
Greatly；Ca addition is too high, forms Ca (O, S) oversize, and fragility also increases, and can become fracture
Crack initiation point, reduces the low-temperature flexibility of steel, the most also reduces purity of steel, pollutes molten steel.One
As control Ca content press ACR=(wt%Ca) [1-1.24 (wt%O)]/1.25 (wt%S), wherein ACR
For sulphide inculsion shape control characteristic, therefore the span of control of Ca content is 0.001%～0.004%.
Particularly, in present component designs, (%Mn) × [7.33 (%Si)+5.16 (%Al)]≤1.0,
This is one of key technology of the present invention point.
Si and Al promotes the conjugation segregation between Mn, C, P, S, causes steel plate internal segregation serious,
Damage steel plate endoplasm viability and uniformity, cause Plate Welding, temper embrittlement and low-temperature flexibility big
Amplitude reduction.
The present invention, by controlling (%Mn) × [7.33 (%Si)+5.16 (%Al)]≤1.0, suppresses ultralow temperature nickel steel
Intralaminar part segregation, improve the ultralow temperature anti-temper brittleness of nickel steel plate, be improved particularly anti-high tempering parameter SR
Brittle characteristic, refinement mother metal steel plate and welding heat affected zone bainite/martensite colony size, increase
Position between bainite/martensite lath increases the resistance of cracks can spread to angle, improves ultralow temperature nickel steel
The cracking resistance of plate, crack arrest characteristic (i.e. low-temperature flexibility).
It addition, in present component designs,
0.007≤stabilization of austenite Index A u/ two-phase section hardening heat T≤0.009, wherein Au=
2.54+40.53 [(%C)+(%N)]+0.43 [(%Cu)+(%Ni)+(%Mn)]-0.22 (%Al)-2.64 [(%P)
+ (%S)]-1.26 [(%Cr)+(%Mo)]-(%Si), the unit of T is K, and this is key technology of the present invention point
One of, by between stabilization of austenite index and ferrite+austenite two-phase section hardening heat
Join, it is thus achieved that reasonable quantity, be evenly distributed, geomery suitable high stability austenite island, this
Austenite island has a conclusive effect for ultralow temperature steel plate:
A) under the conditions of-196 DEG C, austenite has excellent chemistry, mechanical stability, in variousization
Learn under the effect with power, martensitic phase transformation does not occur, exists as face-centered cubic plasticity and toughness phase Dispersed precipitate
In steel；
B) this austenite island is as crack blunting device, when cracks can spread to austenite island, austenite
There is plastic deformation, absorb crack tip stress field energy, be passivated crack tip, prevent crackle and enter one
Step extension, improve ultralow temperature nickel steel plate cracking resistance, crack arrest characteristic (i.e. low-temperature flexibility)；
C) austenite island has segmentation bainite/martensite lath effect, refines bainite/martensite plate
Bar size, improves the ultralow-temperature flexibility of steel plate；
D) austenite island has purification ferritic phase effect (bainite/martensite lath is ferritic phase),
I.e. eliminate brittle interstitial element C, the N etc. in ferritic phase, improve bainite/martensite lath ultralow
Temperature intrinsic plasticity and toughness.
In sum, by stabilization of austenite Index A and ferrite+austenite two-phase section quenching temperature
Coupling between degree T, it is achieved steel plate is the key of ultralow-temperature flexibility under the conditions of-196 DEG C；Also it is to realize
Low nickel-content (5.00%～7.00%) relatively substitutes high nickel content (more than 9.0%), and manufacture is greatly lowered
The key technology of cost.
Ca/S is between 1.00～3.00 and (%Ca) × (%S)0.28≤1.0×10-3, inclusion content of steel
Less and uniformly slightly disperse is in steel, refinement steel plate and micro-group of high heat-input welding heat affected zone
Knit；Improve ultralow temperature nickel steel plate and welding heat affected zone cracking resistance, crack arrest characteristic.
The low cost ultralow temperature nickel steel of the present invention and manufacture method thereof, it comprises the steps:
1) smelt, cast
Smelt by above-mentioned composition, casting uses continuous casting process, and Continuous Casting Soft Reduction rate controls 3%～7%
Between, basket pouring temperature is between 1520 DEG C～1550 DEG C, to improve continuous casting billet center deviation
Analysis is with loose；Two cold employings are weak cold, and specific water controls at≤0.60L/ (ton × min)；
2) slab heating temperature 1050 DEG C～1150 DEG C, slab uses high-pressure water descaling after coming out of the stove, and de-scaling is not
To the greatest extent can de-scaling repeatedly；
3) rolling, steel plate overall compression ratio i.e. slab thickness/finished steel plate thickness >=4.00
First stage is common rolling, uses and rolls uninterruptedly, it is ensured that shape changing metal occurs dynamic
State/Static Recrystallization, the first stage adds up reduction ratio >=50%, fining austenite grains；
Second stage uses recrystallization controlled rolling RCR, controlled rolling start rolling temperature 780 DEG C～840 DEG C, rolls
Percentage pass reduction >=8% processed, recrystallization zone adds up reduction ratio >=50%, finishing temperature 740 DEG C～800
℃；
4) normalizing+quenching
Normalizing temperature is 780 DEG C～820 DEG C, and the normalizing retention time is 10～20min, steel plate after normalizing
Natural air cooling is to room temperature；Hardening heat is 650 DEG C～700 DEG C, quenching the retention time be 15～
25min, steel plate quenching is to room temperature；
5) tempering
Temperature is 600～650 DEG C, and tempering hold times is 30～60min, and tempering terminates rear steel
Plate natural air cooling is to room temperature.
According to present component system, high nickel steel steel slab surface is easily generated crackle, steel making working procedure emphasis work
Skill is continuous casting process, and continuous casting process priority control trough casting temperature, slighter compress rate and two are cold but
Pattern；Continuous Casting Soft Reduction rate controls between 3%～7%, basket pouring temperature at 1520 DEG C～
Between 1550 DEG C, to improve continuous casting billet center segregation with loose；Two cold employings are weak cold, and specific water controls
At≤0.60L/ (ton × min), to improve high nickel steel continuous casting billet face crack.
Slab heating temperature 1050 DEG C～1150 DEG C, slab uses high-pressure water descaling after coming out of the stove, and de-scaling is not
To the greatest extent can de-scaling repeatedly；
The most tiny for guaranteeing ultralow temperature nickel steel microscopic structure, steel plate overall compression ratio (slab thickness/finished product
Steel plate thickness) >=4.00.
First stage is common rolling, uses big rolling pass reduction ratio to roll uninterruptedly
Making, it is ensured that shape changing metal occurrence dynamics/Static Recrystallization, the first stage adds up reduction ratio >=50%, carefully
Change austenite crystal.
Second stage uses recrystallization controlled rolling RCR, 780 DEG C≤controlled rolling start rolling temperature≤840 DEG C, rolls
Percentage pass reduction >=8% processed, recrystallization zone adds up reduction ratio >=50%, 740 DEG C≤finishing temperature≤800 DEG C,
State steel plate microscopic structure is rolled in refinement further, lays the foundation for uniform quenching super-refinement microscopic structure.
Use combination Technology for Heating Processing as follows: normalizing temperature is 780 DEG C～820 DEG C, the normalizing retention time
Being 10～20min, after normalizing, steel plate natural air cooling is to room temperature；Hardening heat is 650 DEG C～700 DEG C,
The quenching retention time is 15～25min (steel plate quenching is to room temperatures)；Temperature is 600～650 DEG C,
Tempering hold times is 30～60min, and tempering terminates rear steel plate natural air cooling to room temperature.
Beneficial effects of the present invention:
The present invention designs at key technology route and Composition And Process, combines and affects ultralow temperature nickel steel
The low-temperature flexibility of-196 DEG C, anti-welding reheat cracking sensitivity, can relatively high heat-input weldability and anti-height
Tempering parameter SR softens and brittle factor, creatively have employed Mn in the ultralow Si-of ultralow C-
Based on-low N-ultra micro+Ti processes the component system of low-alloy steel, control
(%Mn) × [7.33 (%Si)+5.16 (%Al)]≤1.0,0.007≤stabilization of austenite Index A u/ two-phase section
Hardening heat T≤0.009, Ca process and Ca/S ratio controls between 1.0～3.0 and
(%Ca) × (%S)0.28≤1.0×10-3, optimize Controlled Cooling and follow-up special combination Technology for Heating Processing,
Ultralow temperature nickel steel is made to obtain high ultralow-temperature flexibility, excellent weldability, relatively high heat-input can be born
Welding, it is even more important that the anti-high tempering parameter SR that the low temperature nickel steel of the present invention has excellence is crisp
Change characteristic, and can low cost manufacture (steel plate of relatively conventional ultralow temperature 9.0% nickel content), especially
It is suitable for being used as manufacture Large LNG extremely low temperature tank, LNG extremely low temperature tank peculiar to vessel, ice sea and pole
Ground region large-scale steel structure, and be capable of low cost and stablize bulk industrial production.
The present invention realizes part substitute nickel with manganese, uses relatively low nickel-content to produce ultralow temperature steel plate, than routine
Ultralow temperature steel plate nickel content reduces by 2%～4%, and manufacturing cost is greatly lowered, and product has the strongest
Competitiveness.
Accompanying drawing explanation
Fig. 1 is the steel plate microscopic structure of embodiment of the present invention E.
Detailed description of the invention
Below in conjunction with embodiment and accompanying drawing, the present invention will be further described.
Table 1 is the composition of embodiment of the present invention steel, and table 2, table 3 are the manufacture of embodiment of the present invention steel
Technique, table 4, table 5 are the performance of embodiment of the present invention steel.
Embodiment of the present invention manufacturing process is as follows:
TDS molten iron deep desulfuration → converter smelting → LF → RH (feeding Si-Ca silk) → continuous casting
→ recrystallization is cut → heated to (use slighter compress technique) → slab finishing → slab scale fire that rolls off the production line
Controlled rolling (RCR) → steel plate heap slow cooling/hole slow cooling → AUT/MUT → swarf, crop end
→ rough polishing ball goes surface of steel plate oxide skin → austenite one phase district quenching+austenite biphase with ferrite
District's quenching+tempering heat treatment (Q+Q'+T) → sampling and performance test → cut scale steel plate → surface
Quality and apparent size, identify and detect → dispatch from the factory.
As seen from Figure 1, the martensite/bainite+ferrum being organized as fine uniform of embodiment of the present invention steel
The complex phase microscopic structure on ferritic+austenite island, thus ensure that ultralow temperature nickel steel has high ultralow temperature
Toughness, excellent weldability, can bear relatively high heat-input welding and the anti-high tempering parameter SR of excellence
Embrittlement characteristic.
According to steel plate technical characterstic of the present invention, the present invention by the modular design of rational alloying element with
Controlled Cooling, specific combination Technology for Heating Processing combine, and ultralow temperature nickel steel can obtain the super of excellence
Low-temperature flexibility, anti-high tempering parameter SR are brittle and soften, and steel plate can bear relatively large-line energy
Welding, thus saved the cost that user's component manufactures, shorten the time that user's component manufactures；By
Need not add any equipment in ultralow temperature nickel steel production process of the present invention, manufacturing process is succinct, raw
Product process control is easy, (especially cost of alloy and tradition ultralow temperature nickel steel phase the most cheap for manufacturing cost
Ratio, reduces more than about 1500 yuan/ton).
Along with China's sustained economic development, increasing to petroleum gas demand, will go into operation recently
The second west to east gas pipeline project, go out river pipeline, Sino-Russian pipeline, Myxocyprinus asiaticus construction are exactly best illustration,
The height of ultralow temperature LNG storage tank is will appear from building for lacking the Deposits in Eastern Coastal China area of petroleum resources
Tide, as the crucial tank body material of ultralow temperature LNG storage tank---the ultralow temperature of anti-high tempering parameter SR
Nickel steel, has wide market prospect.
Claims (2)
1. low cost ultralow temperature nickel steel, its composition by weight percent is:
C:0.040%～0.070%
Si :≤0.15%
Mn:0.80%～1.20%
P :≤0.010%
S :≤0.0020%
Ni:5.00%～7.00%
Mo:0.05%～0.25%
Als:0.010%～0.030%
Ti:0.008%～0.018%
N :≤0.0040%
Ca:0.001%～0.004%
Remaining for Fe and is inevitably mingled with；And mentioned component must simultaneously meet following relation:
(%Mn) × [7.33 (%Si)+5.16 (%Al)]≤1.0；
Ti/N=1.5～3.5；
0.007≤stabilization of austenite Index A u/ two-phase section hardening heat T≤0.009,
Wherein, Au=2.54+40.53 [(%C)+(%N)]+0.43 [(%Cu)+(%Ni)+(%Mn)]
-0.22 (%Al)-2.64 [(%P)+(%S)]-1.26 [(%Cr)+(%Mo)]-(%Si), the unit of T is K；
Ca/S is between 1.00～3.00, and (%Ca) × (%S)0.28≤1.0×10-3；
The low temperature nickel structure of steel obtained is the martensite/bainite+ferrite+Ovshinsky of fine uniform
The complex phase microscopic structure on body island.
2. the manufacture method of low cost ultralow temperature nickel steel as claimed in claim 1, is characterized in that, including
Following steps:
1) smelt, cast
Composition as described in claim 1 is smelted, casting uses continuous casting process, Continuous Casting Soft Reduction rate
Controlling between 3%～7%, basket pouring temperature is between 1520 DEG C～1550 DEG C；Two
Cold employing is weak cold, and specific water controls at≤0.60L/ (ton × min)；
2) slab heating temperature 1050 DEG C～1150 DEG C, slab uses high-pressure water descaling, de-scaling after coming out of the stove
Not to the utmost can de-scaling repeatedly；
3) rolling, steel plate overall compression ratio i.e. slab thickness/finished steel plate thickness >=4.00
First stage is common rolling, uses and rolls uninterruptedly, first stage accumulative pressure
Rate >=50%；
Second stage uses recrystallization controlled rolling, controlled rolling start rolling temperature 780 DEG C～840 DEG C, rolling
Percentage pass reduction >=8%, recrystallization zone adds up reduction ratio >=50%, finishing temperature 740 DEG C～800
℃；
4) normalizing+quenching
Normalizing temperature is 780 DEG C～820 DEG C, and the normalizing retention time is 10～20min, steel after normalizing
Plate natural air cooling is to room temperature；Hardening heat is 650 DEG C～700 DEG C, quenching the retention time be
15～25min, steel plate quenching is to room temperature；
5) tempering
Temperature is 600～650 DEG C, and tempering hold times is 30～60min, after tempering terminates
Steel plate natural air cooling is to room temperature.
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| AU2017353259B2 (en) * | 2016-11-02 | 2022-12-22 | Salzgitter Flachstahl Gmbh | Medium-manganese steel product for low-temperature use and method for the production thereof |
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