CN106119700A - A kind of 1180MPa level precipitation strength type high-strength high-plasticity steel and manufacture method thereof - Google Patents
A kind of 1180MPa level precipitation strength type high-strength high-plasticity steel and manufacture method thereof Download PDFInfo
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- CN106119700A CN106119700A CN201610450214.8A CN201610450214A CN106119700A CN 106119700 A CN106119700 A CN 106119700A CN 201610450214 A CN201610450214 A CN 201610450214A CN 106119700 A CN106119700 A CN 106119700A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Abstract
A kind of 1180MPa level precipitation strength type high-strength high-plasticity steel and manufacture method thereof, this steel chemical composition percentage by weight is: C:0.15～0.20%, Si:0.8～2.0%, Mn:1.5～2.0%, P≤0.015%, S≤0.005%, O≤0.003%, Al:0.4～1.0%, N≤0.005%, Nb:0.03～0.06%, Ti:0.1～0.2%, V≤0.40%, remaining is Fe and inevitable impurity, and needs to meet following relation simultaneously: 0.10%≤Nb+Ti≤0.25%；0.02%≤(Ti 3.42N 3S)/4+V/4.24+Nb/7.74≤0.15%；2.5≤Al/C≤5.0.The microstructure of steel of the present invention is ferrite, bainite and retained austenite, ferrite intracrystalline distribution Nano-Scaled Carbide, ferrite average grain size≤5 μm, Nano-Scaled Carbide size≤10nm；Width≤5 μm of lath of bainite, yield strength >=1000MPa, tensile strength >=1180MPa, elongation percentage >=15%, show high intensity and the high-ductility coupling of excellence.
Description
Technical field
The invention belongs to hot-rolling high-strength steel field, be specifically related to a kind of 1180MPa level precipitation strength type high-strength high-plasticity
Steel and manufacture method thereof.
Background technology
In automobile especially passenger car field, high-strength thinning or vehicle structure lightweight has become automobile factory in the world
The important research direction of business.High-strength from passenger car thinning and lightweight trend is different, the lightweight work progress of commercial car is very
Slowly.Main cause one is owing to the universal surcharge ratio of commercial car is more serious, the designer of the commercial car design margin to structure
The biggest；Meanwhile, commercial car self and loading capacity are the biggest, and after using high-strength steel thinning, rigidity is difficult to ensure that sometimes；Another
Aspect reason is that user it is generally desirable to the intensity at steel plate owing to commercial car is relative to belonging to Price Sensitive customers for passenger car
While raising, price had better not improve too much.Therefore, no matter from the demand willingness that high-strength steel is used or himself
Working ability and price the aspect such as are born and are all made the high-strength thinning of commercial car and weight reduction process make slow progress.But at some
Position need nonetheless remain for using high-strength even super-high strength steel, such as collision prevention girders etc..Along with energy-saving and emission-reduction require constantly strict, commercial car
Processing and user should see clearly industry development trend, the lightweight of commercial car also will be following a kind of trend.Therefore, open
The high-strength steel of volatility excellence also will be following development trend.
At present, tensile strength adds micro-conjunction at the other high-strength steel of 1180MPa higher level in composition design main employing higher carbon
Gold element, generally uses the method that out-line quenching adds tempering in technique.Generally, the property of steel plate after quenching+tempering
Can show as yield strength higher with tensile strength ratio, generally even close to 1.0 more than 0.90, and elongation percentage is generally 10
± 1%.For ensureing user's cold forming processing request, user usually requires that on the basis of keeping more than tensile strength 1180MPa,
The rate that will extend over improves to more than 15%.This is almost for traditional organization design thinking and quenching add lonneal technique
Impossible index.This is because, the most countless theories and result of the test also it was demonstrated that use traditional quenching+
Tempering process manufactures the super-high strength steel of 1180MPa level, and its elongation percentage and hole expansibility index cannot meet user and require.
The most only Japan JFE etc. use nanotechnology exploitation 1180MPa level high-strength steel Japan Patent JP5386961B2 to adopt
Manufacturing 1180MPa level high-strength steel with microalloying ingredient design and sub-sectional cooling and average tempering technique, its tensile strength reaches
To 1180MPa, elongation percentage, up to more than 15%, uses high Nb in the design of its composition, relatively costly, and has a step in manufacturing process
Average tempering technique.
Summary of the invention
It is an object of the invention to provide a kind of 1180MPa level precipitation strength type high-strength high-plasticity steel and manufacturer thereof
Method, the yield strength >=1000MPa of this high-strength high-plasticity steel, tensile strength >=1180MPa, elongation percentage >=15%, show
Excellent intensity and plasticity coupling, can be applicable to wheel etc. needs favorable forming property and high-strength thinning position.
For reaching above-mentioned purpose, the technical scheme is that
The present invention adds the Si main purpose of high level: first is to expand the work that ferrite during sub-sectional cooling is formed
Skill window, second is being formed and finally obtaining more retained austenite of suppression carbide (mainly cementite)；Add relatively
High Al main purpose is under conditions of carbon and Fe content are of a relatively high, accelerates ferrite Cambium periodicity process；Add relatively
High Ti main purpose be after rolling the air cooling stage formed in ferrite the tiny Nano-Scaled Carbide of disperse with strengthening ferrum element
Body；Additionally, compound Nb and Ti of interpolation can also ensure to obtain tiny austenite at rolling sequence, in order to the air cooling stage after rolling
Obtain the most tiny ferrite；Add higher V main purpose: first is to be improved further by force by the precipitation strength of VC
Degree, second is to soften the follow-up welding point improving super-high strength steel to have good effect.Based on mentioned component and technological design
Thinking, can obtain the 1180MPa level hot rolling super-high strength steel with superhigh intensity and plasticity matched well.
A kind of 1180MPa level precipitation strength type high-strength high-plasticity steel, its chemical component weight percentage ratio is: C:0.15～
0.20%, Si:0.8～2.0%, Mn:1.5～2.0%, P≤0.015%, S≤0.005%, O≤0.003%, Al:0.4～
1.0%, N≤0.005%, Ti:0.1～0.2%, Nb:0.03～0.06%, V≤0.40%, remaining is that Fe is with inevitable
Impurity, and above-mentioned element needs to meet following relation simultaneously: 0.10%≤Nb+Ti≤0.25%, 0.02%≤(Ti-3.42N-
3S)/4+V/4.24+Nb/7.74≤0.15%, 2.5≤Al/C≤5.0.
Preferably, in the chemical composition of described high-strength high-plasticity steel: C:0.16～0.18%, by weight percentage.
Preferably, in the chemical composition of described high-strength high-plasticity steel: Si:1.2～1.8%, by weight percentage.
Preferably, in the chemical composition of described high-strength high-plasticity steel: Mn:1.6～1.8%, by weight percentage.
Preferably, in the chemical composition of described high-strength high-plasticity steel: Al:0.5～0.8%, by weight percentage.
Further, the microstructure of described high-strength high-plasticity steel is ferrite, bainite and retained austenite, ferrite
Intracrystalline distribution Nano-Scaled Carbide, ferrite average grain size≤5 μm, Nano-Scaled Carbide size≤10nm；Bainite plate
Width≤5 μm of bar.
Preferably, width≤3 μm of lath of bainite in the microstructure of described high-strength high-plasticity steel.
Preferably, in the microstructure of described high-strength high-plasticity steel, volume fraction shared by ferrite is 20～35%, shellfish
Volume fraction shared by family name's body is 60～70%, and volume fraction shared by retained austenite is 5～10%.
Yield strength >=the 1000MPa of high-strength high-plasticity steel of the present invention, tensile strength >=1180MPa, elongation percentage
>=15%.
In the composition of steel of the present invention designs:
Carbon: carbon is the basic element in steel, is also one of important element in the present invention.Carbon is former as the gap in steel
Son, plays very important effect to the intensity improving steel, yield strength and the tensile strength impact maximum on steel.In the present invention
In, reach the super-high strength steel of 1180MPa level to obtain tensile strength, except ferrite average grain size must is fulfilled for≤5 μm
Outward, it is necessary to rely on nanometer precipitated phase (size≤10nm) reinforced ferrite intensity further；In addition it is necessary to rely on tiny
Bainite strengthening and the TRIP effect of retained austenite.In steel, carbon content is at least more than 0.15%；Carbon content is the most simultaneously
Can be the highest, if carbon content is more than 0.20%, unfavorable to the welding performance of steel.Therefore, carbon content must control below 0.20%,
And and Nb, meet 0.02%≤(Ti-3.42N-3S)/4+V/4.24+Nb/7.74≤0.15% between Ti and V content.To sum up,
In the present invention, carbon content should control 0.15～0.20%, and preferably scope is 0.16～0.18%.
Silicon: silicon is also the basic element in steel, is also simultaneously one of important element in the present invention.This is because, obtain
Obtaining tensile strength and reach the high-strength high-plasticity steel of more than 1180MPa, on the one hand to control ferritic size and quantity, utilization is received
Rice separates out and improves ferritic intensity；The most also to improve the intensity of bainite by refinement lath of bainite.This needs becoming
Set up the content properly increasing carbon and manganese in meter separately, and carbon and manganese are all to expand austenitic area, the element of stable austenite.In hot rolling
In very short time in process air cooler, (generally≤10s) is difficult to form sufficient amount of ferrite, and this is accomplished by adding higher containing
The element silicon of amount.The addition of silicon can be obviously promoted ferrite and be formed, and expands the process window that ferrite is formed, and purifies ferrite,
May also operate as partial reinforcement effect simultaneously.Silicon another important function in steel is the shape of cementite in suppression phase transition process
Become, be conducive to improving the content of final residual austenite.These effects of silicon must when its content reaches more than 0.8% just table
Reveal to come；But the content of silicon also should not be the highest, otherwise steel plate degraded toughness.Therefore, in steel silicone content be normally controlled in 0.8～
Between 2.0%, preferably scope is between 1.2～1.8%.
Manganese: manganese is element most basic in steel, is also one of most important element in the present invention simultaneously.It is known that manganese
It is the important element expanding austenite phase field, the critical quenching rate of steel, stable austenite, crystal grain thinning can be reduced, postpone
Austenite from being transformed into perlite.In the present invention, for ensureing the high intensity of steel plate, Fe content should control more than 1.5%, manganese
Content is on the low side, and overcooling austenite is not sufficiently stable, and is easily changed into the tissue of pearlite type in cooling process air cooler；Meanwhile, manganese
Content is general also no more than 2.0%, if more than 2.0%, is susceptible to manganese segregation, easily occurs simultaneously during sheet billet continuous casting during steel-making
Hot tearing.Therefore, in steel of the present invention, Fe content controls 1.5～2.0%, and preferably scope is 1.6～1.8%.
Phosphorus: phosphorus is the impurity element in steel.Phosphorus easily segregation is on crystal boundary, in steel during the content of phosphorus higher (>=0.1%),
Form Fe2P separates out around crystal grain, reduces the plasticity of steel and toughness, therefore phosphorus content is the lowest more good, and general control is 0.015%
Within preferably and not improve steel-making cost.
Sulfur: sulfur is the impurity element in steel.Sulfur in steel is generally combined formation MnS and is mingled with, especially when sulfur and manganese with manganese
Content the highest time, steel will form more MnS, and MnS itself have certain plasticity, in the follow-up operation of rolling
MnS, along rolling to deforming, reduces the transverse tensile property of steel plate.In high Ti steel, sulfur can also become Ti with Ti and C-shaped4C2S2
Compound, consumes part Ti so that the effectively quantity of Ti reduces, and affects final precipitating reinforcing effect.Therefore, in steel, sulfur contains
Measure the lowest more good, within being normally controlled in 0.005% during actual production.
Aluminum: aluminum is one of important element in the present invention.Due to high-strength high-plasticity steel involved in the present invention, its tension is strong
Degree reaches more than 1180MPa, and in steel, the content of carbon and manganese is of a relatively high, and overcooling austenite is relatively stable, is difficult in process air cooler
Form sufficient amount of ferrite, accordingly, it would be desirable to add more aluminum when composition designs to promote that ferrite is formed.Adding of aluminum
Dosage is the most relevant with carbon content, and carbon content is the highest, and the addition of aluminum is the highest.In the present invention in the composition range of carbon, carbon
And 2.5≤Al/C≤5.0 relation should be met between aluminum.Aluminum content is too low, it is difficult to form enough ferrites；Aluminum too high levels,
Continuous casting billet Longitudinal Surface Cracks is the most serious.Therefore, in steel of the present invention, aluminum content controls between 0.4～1.0%, and preferably scope is
0.5～0.8%.
Nitrogen: nitrogen belongs to impurity element in the present invention, its content is the lowest more good.Nitrogen is also inevitable element in steel,
Under normal circumstances, if not carrying out Special controlling in steelmaking process, the residual content of nitrogen in steel is generally≤0.005%.These are solid
Molten or free nitrogen element must be fixed by forming certain nitride, the otherwise free nitrogen-atoms impact flexibility to steel
The most unfavorable, and the sawtooth being readily formed total length during belt steel rolling splits defect.By adding in the present invention
Strong carbide or nitride forming element Ti, form stable TiN thus fixed nitrogen atom.Therefore, the content of nitrogen controls
Within 0.005% and the lowest more good.
Niobium: niobium is one of most important element in the present invention.Niobium is compound with titanium to be added heating and operation of rolling austenite
Grain refining effect is the most notable, niobium and titanium be combined interpolation after the effect of fining austenite grains much larger than single niobium, titanium and vanadium
The effect added.After niobium adds in steel, when high temperature such as the heating steel billet stage, solute strong between niobium and the crystal boundary of solid solution
Effect of dragging can refine austenite crystal during heating steel billet；At rolling sequence, owing to niobium has the work of raising recrystallization temperature
With, compare titanium, vanadium, aluminum element, the effect that niobium improves recrystallization temperature is the strongest, by rolling on recrystallization temperature
System, can obtain the austenite of tiny hardening, and its equivalent grain size is little, and dislocation density is high, permissible during ferritic transformation
Obtain the most tiny ferrite crystal grain；Meanwhile, (Nb, Ti) (C, the N) of the 20-40nm formed at rolling sequence can more enter one
Step fining austenite grains.The Ovshinsky containing high dislocation density more tiny when fine austenite crystal grain during high-temperature heating and rolling
Body crystal grain ensures the ferritic abundant refinement of phase-change product and strengthening during cooling phase-change.The content of niobium is at least up to
More than 0.03% just has the effect significantly improving recrystallization temperature；The addition of niobium is also unsuitable too much, is normally controlled in
Less than 0.06%.Niobium also should meet 0.10%≤Nb+Ti≤0.25% with the interpolation of titanium.
Titanium: titanium is one of important element in the present invention.Titanium has the strongest adhesion with C, N, S atom in steel.The present invention
Composition mentality of designing be primarily intended to obtain the Nano-Scaled Carbide of small and dispersed rather than nitride.Titanium is big with the adhesion of nitrogen
Adhesion between titanium and carbon, in order to reduce the formation amount of TiN in steel as far as possible, the content of nitrogen in steel should control the lowest more
Good.Add high level titanium main purpose be in order at austenite during ferritic transformation, in ferrite or bayesian
Body is formed more Nano-Scaled Carbide；Similarly, adding higher vanadium main purpose is to be formed more in bainite
Nano vanadium carbide particle, improves the effect of dispersion-strengtherning further.
In the present invention, key element carbon, titanium, sulfur and vanadium should meet certain relation that is 0.02%≤(Ti-3.42N-3S)/4
+ V/4.24+Nb/7.74≤0.15% could obtain ferrite and bainite precipitation strength super-high strength steel.Demonstrate,prove through lot of experiments
Real, carbon and titanium, sulfur, the content of vanadium must meet above-mentioned relation, and the Nano-Scaled Carbide otherwise formed in steel can not at utmost be sent out
Wave in disperse educt strengthening effect or steel and be likely to occur a small amount of pearlitic structrure so that the intensity of steel plate is difficult to reach
The high intensity of 1180MPa.The optimal Precipitation Temperature of Nano-Scaled Carbide is the most closely related with the content of titanium, sulfur and vanadium.Warp
Crossing Theoretical Calculation and test confirms, within the temperature range of 650～750 DEG C, titanium can play the content of optimal precipitating reinforcing effect
Scope is between 0.10～0.20%.
Vanadium: vanadium is one of key element in the present invention.Vanadium is similar with titanium, due to its carbonitride consolidating in austenite
Solubility is relatively big, and generally separates out in ferrite.Use low-carbon (LC) titaniferous, its maximum pulling strength that can reach of vanadium steel only
800～about 900MPa, to continue to improve the intensity of ferrite-bainite type high-strength steel, it is necessary to improve carbon content, but carbon contains
When the result that amount increase brings is high temperature section air cooling, there is banding pearlite in tissue；Vanadium is also carbide, adds
Enter appropriate vanadium and can fix unnecessary carbon, be possible not only to further function as precipitating reinforcing effect, but also avoid high temperature air cooling
Time pearlite formation.Additionally, 1180MPa level high-strength steel involved in the present invention in follow-up welding process it can also happen that joint
Ruckbildung, adds appropriate vanadium and can preferably solve this problem.According to theory analysis and experimental study, the content of vanadium
Should control in the range of≤0.4%, and and Nb, Ti, N, S and C between should meet certain relation that is 0.02%≤(Ti-
3.42N-3S)/4+V/4.24+Nb/7.74≤0.15%.
Oxygen: oxygen is inevitable element in steelmaking process, for the purpose of the present invention, in steel the content of oxygen by aluminium deoxidation it
The most typically can reach less than 0.003%, the performance of steel plate is not resulted in significant adverse impact.Therefore, by the oxygen in steel
Content controls within 0.003%.
The manufacture method of 1180MPa level precipitation strength type high-strength high-plasticity steel of the present invention, it comprises the steps:
1) smelt, cast
Carry out smelting by above-mentioned chemical composition, refine, be cast as strand or ingot casting；
2) strand or ingot casting heating
Heating-up temperature >=1230 DEG C, heat time heating time 1～2 hours；
3) hot rolling+sub-sectional cooling+batch
Start rolling temperature is 1080～1200 DEG C, 1000 DEG C of 3～5 passage roughing carried out above and accumulative deflection >=
50%；Intermediate blank treats that temperature temperature is 900～950 DEG C, carries out 3～5 passage finish rolling and accumulative deflection >=80%；Finishing temperature
Be 800～900 DEG C, finish to gauge terminate after with the cooling rate of >=100 DEG C/s by steel plate water-cooled to 650～750 DEG C；Air cooling 5～after 10 seconds,
Batch to 350～500 DEG C with the cooling rate water-cooled of >=100 DEG C/s again, after batching, be cooled to room temperature with the cooling rate of≤20 DEG C/h.
The reason of the design and manufacture technology of the present invention is as follows:
For the high-strength steel of high Ti precipitation strength type, heating-up temperature is a critically important technological parameter.With general
Logical high-strength steel is compared, and high Ti steel design higher heating-up temperature (>=1230 DEG C) main purpose of the present invention is the slab in heating
Middle solid solution Ti as much as possible atom.Owing to the carbonitride solid solubility temperature of Ti is usual the highest (>=1300 DEG C), making steel or connecting
The different phase of casting and the operation of rolling all can separate out, and this allows for just finally can be used to play the Ti content of precipitation strength effect
The lowest.It is therefore necessary to ensure high heating-up temperature its is possible to obtain in air cooling phase process more nano-scale carbon after rolling
Compound, therefore, the minimum heating-up temperature of application claims steel plate is necessary >=and 1230 DEG C；The upper limit of heating-up temperature heats according to scene
The actual accessible temperature maybe can born of stove is limited, and heating-up temperature does not the most set upper limit requirement.For energy efficient, logical
Often actual maximum heating temperature is controlled at≤1300 DEG C.
For high Ti steel, the heat time heating time of slab, its impact was much smaller for heating-up temperature.In theory
For, as long as heating-up temperature reaches the balance solution temperature of the carbonitride of Ti, its dissolution velocity is very fast.Therefore in this stage,
Heat time heating time is mainly to ensure that slab can be grilled thoroughly as main target uniformly.Certainly, heat time heating time can not be oversize, otherwise
Very likely there is roughening and grow up in the carbonitride of the undissolved Ti of high temperature, the carbonitride of these thick Ti is at austenite
Grain boundaries separates out, and reduces the bond strength of crystal boundary, and easily in heating process, slab occurs disconnected base phenomenon in heating furnace.Cause
This, different according to slab thickness, heating-up temperature is normally controlled in 1～2 hour.
On rolling mill practice designs, in order to coordinate the composition of high Ti design, the heating-up temperature of steel billet necessary sufficiently high (as >=
1230 DEG C) to ensure to have Ti atom as much as possible to be solid-solubilized in slab；In roughing and finish rolling stage, the rhythm of the operation of rolling should
It is rapidly completed, it is to avoid at roughing and the Carbonitride Precipitation of finish rolling stage too much Ti as far as possible.Should be with high cooling rate after finish to gauge terminates
(>=100 DEG C/s) rapid water is cooled to two-phase section and two-phase section air cooling 5～10 seconds, main purpose be formed at air cooling ferritic
During separate out the most tiny TiC.This is because, if rate of cooling is relatively slow after rolling terminates, the Ovshinsky of steel plate internal distortions
Body can be completed in a relatively short time partial, re-crystallization process, and now austenite crystal is grown up.Relatively coarse austenite
When cooling procedure generation ferrite transformation subsequently, the ferrite crystal grain of formation is the thickest, generally between 10～20 μm,
Unfavorable to the intensity improving steel plate.Rolling mill practice schematic diagram of the present invention sees Fig. 1.Steel plate organization design thinking of the present invention is nanometer
Precipitation strength ferrite, bainite and residual austenite soma.
The high intensity of steel plate is from two aspects: one is nanometer precipitation strength ferrite, and two is tiny bainite.According to warp
The Orowan mechanism of allusion quotation, nano-carbide to the contribution of intensity about between 200～400MPa.But only nanometer precipitation strength
Being nowhere near, the high intensity of steel plate must also come from tiny bainite.The intensity rank of 1180MPa to be reached, ferrite
The size of crystal grain must control below 5 μm, and the width of lath of bainite must be below 0.5 μm, preferably below 0.3 μm,
This is accomplished by steel plate must be quickly cooled to two-phase section after finish to gauge terminates, and is quickly cooled to after 5～10s air coolings again
350～500 DEG C carry out bainite transformation and precipitation.Therefore, the rate of cooling after strip steel finish to gauge should sufficiently fast (>=100 DEG C/s),
Avoid being formed ferrite in continuous cooling process, and should be forming part is tiny in strip steel process air cooler ferrite and receive
Meter level carbide, the austenite that remaining part does not changes is further continued for the cooling rate with >=100 DEG C/s and is cooled to 350～500 DEG C soon, with
The nanometer carrying out bainitic transformation or VC separates out, and slow cooling to room temperature obtains the retained austenite of 5～10%, and concrete cooling technique is shown
It is intended to as shown in Figure 2.
The present invention is designed by ingenious rational composition, coordinates the hot rolling technology of novelty can obtain intensity and plasticity simultaneously
Excellent 1180MPa level nanometer precipitation strength super-high strength steel.Steel plate be organized as nanometer precipitation strength ferrite, bainite and residual
Remaining austenite, ferrite average grain size be≤5 μm, and ferrite form be the spindle-type such as closely, and a large amount of disperses of distribution of its intracrystalline are thin
Little Nano-Scaled Carbide (size≤10nm).While tensile strength reaches 1180MPa high intensity, steel plate has >=15%
High-elongation.
On composition designs, the interpolation main purpose one of high Ti content is to coordinate refinement heating and Austria of rolling sequence with Nb
Family name's body crystal grain, next to that for the Nano-Scaled Carbide tiny at ferrite diffusion-precipitation main during strip coiling, rise
To strong precipitating reinforcing effect；Adding a certain amount of V is then the quantity in order to increase nanometer precipitated phase further, plays higher
Dispersion-strengthened effect；And the design of carbon content should proof strength, also to match with the content of Nb, Ti and V simultaneously, it is necessary to
Meet following relation: 0.02%≤(Ti-3.42N-3S)/4+V/4.24+Nb/7.74≤0.15%, coordinate simultaneously required by
Rolling mill practice, the final acquisition ferrite of nanometer precipitation strength, bainite and the microstructure of retained austenite composition, obtain height
Intensity high-ductility advanced person's high-strength steel.
Beneficial effects of the present invention:
(1) present invention uses the composition mentality of designing of relatively economical, coordinates existing hot continuous rolling to produce line simultaneously and just can give birth to
Output has nanometer precipitation strength type advanced person's high-strength steel of superhigh intensity and high-elongation.
(2) present invention produces yield strength >=1000MPa, tensile strength >=1180MPa, elongation percentage >=15%, and thickness
The hot rolling precipitation strength type high-strength high-plasticity steel plate of degree≤6mm, this steel plate shows high intensity and the plasticity coupling of excellence, can
It is applied to automobile chassis, crossbeam, center pillar, side bar etc. and needs high-strength thinning place, have broad application prospects.
Accompanying drawing explanation
Fig. 1 is that the present invention heats and rolling mill practice schematic diagram.
Fig. 2 is roller repairing process schematic representation of the present invention.
Fig. 3 is that in the embodiment of the present invention 3 steel plate, the typical nanometer of ferrite intracrystalline separates out TEM photo.
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 is the fabrication process parameters of embodiment of the present invention steel, and table 3 is this
The performance of bright embodiment steel.
Embodiment of the present invention technological process is: converter or electric furnace smelting → vacuum drying oven double refining → strand or ingot casting → steel
Base (ingot) heating → hot rolling+roll rear sub-sectional cooling → coil of strip, wherein key process parameter sees table 2.
Fig. 3 is that in the embodiment of the present invention 3 steel plate, the typical nanometer of ferrite intracrystalline separates out TEM photo.Can from Fig. 3
Going out, the Nano-Scaled Carbide size that ferrum element intracrystalline separates out is about 6 ± 1nm.Just because of the internal nanometer separated out of ferrite crystal grain
Level carbide substantially increases the intensity of steel plate, and together improves the plasticity of steel plate with the retained austenite in steel.
As known from Table 3, use the yield strength of the high-strength steel that composition provided by the present invention and processing route obtain >=
1000MPa, tensile strength >=1180MPa, elongation percentage >=15%, hence it is evident that be better than the extension of traditional quenching+tempering type high-strength steel
Rate.Intensity and plasticity that steel plate of the present invention is good mate the shellfish coming from the fine ferrite of its nanometer precipitation strength, high intensity
The retained austenite (percentage by volume is 5～10%) of family name's body and high level, just because of the composition of these excellent performances
The cooperation of phase so that steel plate has intensity and the plasticity coupling of excellence, can apply and automobile chassis, structural member, wheel, collision prevention girders
Deng parts.
Claims (14)
1. a 1180MPa level precipitation strength type high-strength high-plasticity steel, its chemical component weight percentage ratio is: C:0.15～
0.20%, Si:0.8～2.0%, Mn:1.5～2.0%, P≤0.015%, S≤0.005%, O≤0.003%, Al:0.4～
1.0%, N≤0.005%, Ti:0.1～0.2%, Nb:0.03～0.06%, V≤0.40%, remaining is that Fe is with inevitable
Impurity, and above-mentioned element needs to meet following relation simultaneously:
0.10%≤Nb+Ti≤0.25%；
0.02%≤(Ti-3.42N-3S)/4+V/4.24+Nb/7.74≤0.15%；
2.5≤Al/C≤5.0。
1180MPa level precipitation strength type high-strength high-plasticity steel the most according to claim 1, it is characterised in that described height
In the chemical composition of intensity high-ductility steel: C:0.16～0.18%, by weight percentage.
1180MPa level precipitation strength type high-strength high-plasticity steel the most according to claim 1, it is characterised in that described height
In the chemical composition of intensity high-ductility steel: Si:1.2～1.8%, by weight percentage.
1180MPa level precipitation strength type high-strength high-plasticity steel the most according to claim 1, it is characterised in that described height
In the chemical composition of intensity high-ductility steel: Mn:1.6～1.8%, by weight percentage.
1180MPa level precipitation strength type high-strength high-plasticity steel the most according to claim 1, it is characterised in that described height
In the chemical composition of intensity high-ductility steel: Al:0.5～0.8%, by weight percentage.
6., according to the 1180MPa level precipitation strength type high-strength high-plasticity steel described in any one of claim 1-5, its feature exists
In, the microstructure of described high-strength high-plasticity steel is ferrite, bainite and retained austenite, ferrite intracrystalline distribution nanometer
Level carbide, ferrite average grain size≤5 μm, Nano-Scaled Carbide size≤10nm, width≤5 μ of lath of bainite
m。
1180MPa level precipitation strength type high-strength high-plasticity steel the most according to claim 6, it is characterised in that described height
Width≤3 μm of lath of bainite in the microstructure of intensity high-ductility steel.
8. according to the 1180MPa level precipitation strength type high-strength high-plasticity steel described in claim 6 or 7, it is characterised in that described
In the microstructure of high-strength high-plasticity steel, volume fraction shared by ferrite is 20～35%, and volume fraction shared by bainite is 60
～70%, volume fraction shared by retained austenite is 5～10%.
9., according to the 1180MPa level precipitation strength type high-strength high-plasticity steel described in any one of claim 1-8, its feature exists
In, the yield strength >=1000MPa of described high-strength high-plasticity steel, tensile strength >=1180MPa, elongation percentage >=15%.
10. the manufacture method of 1180MPa level precipitation strength type high-strength high-plasticity steel as described in any one of claim 1-9, its
Comprise the steps:
1) smelt, cast
Chemical composition as described in any one of claim 1-5 carries out smelting, refine, be cast as strand or ingot casting；
2) strand or ingot casting heating
Heating-up temperature >=1230 DEG C, heat time heating time 1～2 hours；
3) hot rolling+sub-sectional cooling+batch
Start rolling temperature is 1080～1200 DEG C, at 1000 DEG C of 3～5 passage roughing carried out above and accumulative deflection >=50%；
Intermediate blank treats that temperature temperature is 900～950 DEG C, then carries out 3～5 passage finish rolling and accumulative deflection >=80%；Finishing temperature is
800～900 DEG C, finish to gauge terminate after with the cooling rate of >=100 DEG C/s by steel plate water-cooled to 650～750 DEG C；Air cooling 5～after 10 seconds, then
Batch to 350～500 DEG C with the cooling rate water-cooled of >=100 DEG C/s, after batching, be cooled to room temperature with the cooling rate of≤20 DEG C/h.
The manufacture method of 11. 1180MPa level precipitation strength type high-strength high-plasticity steel according to claim 10, its feature
Being, the microstructure of described high-strength high-plasticity steel is ferrite, bainite and retained austenite, and the distribution of ferrite intracrystalline is received
Meter level carbide, ferrite average grain size≤5 μm, Nano-Scaled Carbide size≤10nm, width≤5 of lath of bainite
μm。
The manufacture method of 12. 1180MPa level precipitation strength type high-strength high-plasticity steel according to claim 11, its feature
It is, width≤3 μm of lath of bainite in the microstructure of described high-strength high-plasticity steel.
13. according to the manufacture method of the 1180MPa level precipitation strength type high-strength high-plasticity steel described in claim 11 or 12, its
Being characterised by, in the microstructure of described high-strength high-plasticity steel, volume fraction shared by ferrite is 20～35%, bainite institute
Accounting for volume fraction is 60～70%, and volume fraction shared by retained austenite is 5～10%.
14. according to the manufacturer of the 1180MPa level precipitation strength type high-strength high-plasticity steel described in any one of claim 10-13
Method, it is characterised in that the yield strength >=1000MPa of described high-strength high-plasticity steel, tensile strength >=1180MPa, elongation percentage
>=15%.
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| CN109576594A (en) * | 2017-09-29 | 2019-04-05 | 宝山钢铁股份有限公司 | A kind of hot rolling magnetic yoke steel and its manufacturing method |
| CN109576592A (en) * | 2017-09-29 | 2019-04-05 | 宝山钢铁股份有限公司 | A kind of hot rolling magnetic yoke steel and its manufacturing method |
| CN109576593A (en) * | 2017-09-29 | 2019-04-05 | 宝山钢铁股份有限公司 | A kind of hot rolling magnetic yoke steel and its manufacturing method |
| CN113195771A (en) * | 2018-12-18 | 2021-07-30 | Posco公司 | High-strength hot-rolled steel sheet having excellent formability and method for producing same |
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| CN105154769A (en) * | 2015-09-18 | 2015-12-16 | 宝山钢铁股份有限公司 | 780 MPa hot-rolled high-strength steel with high hole expansion ratio and manufacturing method thereof |
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| CN109576594A (en) * | 2017-09-29 | 2019-04-05 | 宝山钢铁股份有限公司 | A kind of hot rolling magnetic yoke steel and its manufacturing method |
| CN109576592A (en) * | 2017-09-29 | 2019-04-05 | 宝山钢铁股份有限公司 | A kind of hot rolling magnetic yoke steel and its manufacturing method |
| CN109576593A (en) * | 2017-09-29 | 2019-04-05 | 宝山钢铁股份有限公司 | A kind of hot rolling magnetic yoke steel and its manufacturing method |
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| CN113195771A (en) * | 2018-12-18 | 2021-07-30 | Posco公司 | High-strength hot-rolled steel sheet having excellent formability and method for producing same |
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