CN106399820B - A kind of 980MPa grades of hot rolling high-chambering dual phase steel and its manufacturing method - Google Patents
A kind of 980MPa grades of hot rolling high-chambering dual phase steel and its manufacturing method Download PDFInfo
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- CN106399820B CN106399820B CN201610451302.XA CN201610451302A CN106399820B CN 106399820 B CN106399820 B CN 106399820B CN 201610451302 A CN201610451302 A CN 201610451302A CN 106399820 B CN106399820 B CN 106399820B
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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
- 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C21D2211/005—Ferrite
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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
- C21D2211/008—Martensite
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- Heat Treatment Of Sheet Steel (AREA)
Abstract
A kind of 980MPa grades of hot rolling high-chambering dual phase steel and its manufacturing method, the steel chemical composition weight percent are：C：0.15~0.20%, Si：1.0~2.0%, Mn：1.0~2.0%, P≤0.02%, S≤0.005%, O≤0.003%, Al：0.3~1.0%, N≤0.006%, Nb：0.01~0.06%, Ti：0.08~0.20%, remaining is Fe and inevitable impurity, and above-mentioned element need to meet following relationship simultaneously：0.10%≤Nb+Ti≤0.25%, 2.5≤Al/C≤5.0.The microstructure of dual phase steel of the present invention is the Nano-Scaled Carbide of ferrite+transgranular distribution of martensite+ferrite, ferrite average grain size is 5~10 μm, martensite equivalent grain size≤20 μm, Nano-Scaled Carbide size≤10nm, its yield strength >=700MPa, tensile strength >=980MPa, elongation percentage A80>=12%, hole expansibility >=30% shows excellent intensity, plasticity and hole expandability matching, can be applicable to wheel etc. and need favorable forming property and high-strength thinned position.
Description
Technical field
The invention belongs to hot-rolling high-strength steel fields, and in particular to a kind of 980MPa grades of hot rolling high-chambering dual phase steel and its manufacture
Method.
Background technology
Currently, the wheel-use steel material generally use dual phase steel of commercial car especially heavy truck automobile is manufactured, part is economical
The wheel (including wheel rim and spoke) of car also uses steel wheel to reduce cost.Using high strength dual phase steel making wheel
Wheel weight can be effectively reduced, such as compared with 345 steel of common Q, can be dropped using DP600 (i.e. tensile strength 600MPa grades of dual phase steels)
Low wheel weight about 10~15%；And use the DP780 dual phase steels of 780MPa grades of tensile strength that can further decrease wheel weight
About 5~10%.The main 600MPa of the dual phase steel low-intensity dual phase steels below that most of the country wheel shop uses at present, higher
Apply seldom if the dual phase steel such as DP780 of intensity.
The why widely used dual phase steel of automotive wheel, mainly due to low yield strength possessed by dual phase steel itself,
High-tensile, that is, low yield strength ratio, continuous surrender and good formability etc..From the point of view of the trend that wheel industry develops,
The intensity of wheel-use steel material be still totally develop towards higher intensity direction, and at present used in wheel hardness of steel generally not
Height, between 400~600MPa.As national environmental protection regulation is increasingly strict and the national implementation to motor vehicle emission restriction,
In addition to passenger car, the automotive light weight technology in commercial car field also has become the trend of industry development.For this development trend, having must
Higher level such as 780MPa and 980MPa grade hot-rolled dual-phase steel is developed, to meet the future development demand of wheel-use steel material.In addition,
High strength dual phase steel can also be applied to certain automobile structures, such as automotive frame, collision prevention girders.
Due to wheel, this body structure is relative complex, and process is mainly Pressing Deformation, is wanted to the reaming performance of dual phase steel
Ask higher.The hole expandability of high-strength steel and the tensile strength of steel grade, yield strength, yield tensile ratio etc. have substantial connection.In identical tension
Under strength level, the hole expansibility of dual phase steel (i.e. conventional ferrite martensite dual-phase steel) is minimum, followed by the height of bainite type
Qiang Gang is again dual phase steel of ferrite and bainite, and highest hole expansibility is single-phase ferrite high-strength steel.In general, 780MPa
Its hole expansibility of the hot-rolled dual-phase steel of grade is generally 40% hereinafter, majority is below 30%；And 980MPa grades of hot-rolled dual-phase steel its
Hole expansibility is generally below 20%.Low main of the hole expansibility of high-strength dual phase steel is the reason is that ferrite and martensite two in tissue
Phase mechanical property difference is big, and work hardening rate is higher, around punching there are being easy in micro-crack or reaming procedure in ferrite and
Geneva body interface, which forms stress concentration, to be caused to crack.The improvement of high-strength dual phase steel hole expansibility is relatively difficult, this is oneself by it
What the tissue characteristic of body was determined.
At present two major classes are broadly divided into about high strength dual phase steel：First, the high-strength dual phase steel of cold rolling；Second is that hot rolling is high-strength double
Xiang Gang.The tensile strength of the high-strength dual phase steel of cold rolling has reached 1180MPa at present, and the tensile strength of the high-strength dual phase steel of hot rolling is almost
All do not reach 780MPa or more.On the one hand this difference of the high-strength dual phase steel of cold rolling and the high-strength dual phase steel of hot rolling is user couple
The demand of high-strength dual phase steel is not strong to the product demand of hot-rolled high-strength dual phase steel mainly for cold-rolled products；Followed by hot rolling
There are a great difference in producing line and cold rolling producing line, the products that many can produce in cold rolling producing line, which are placed in hot rolling producing line, to be difficult to
It realizes, needs that the ingredient and technique of steel grade are redesigned and optimized.But it is double to hot-rolled high-strength with the continuous development of industry
The demand of phase steel is inherently more and more.
Invention content
The purpose of the present invention is to provide a kind of 980MPa grades of hot rolling high-chambering dual phase steel and its manufacturing method, the hot rolling is high
Yield strength >=700MPa of reaming dual phase steel, tensile strength >=980MPa, elongation percentage A80>=12%, hole expansibility >=30%, table
Reveal excellent intensity, plasticity and hole expandability matching, can be applicable to wheel etc. and need favorable forming property and high-strength thinned portion
Position.
In order to achieve the above objectives, the technical scheme is that：
The Si of high level is added to ensure to be formed a certain number of iron elements within the limited hot rolling and air cooling time in the present invention
Body tissue and the process window for expanding ferrite formation；It is to improve ferrite driving force is precipitated that higher Al main purposes, which are added,
Ferrite is promoted to be precipitated；It is to make phase in finish rolling stage farthest fining austenite grains that micro Nb main purposes, which are added,
The ferrite that change is formed later is more tiny, is conducive to the intensity and plasticity that improve steel plate；The main purpose that high Ti is added is logical
Cross in the air-cooled stage in the transgranular formation Nano-Scaled Carbide of ferrite (size≤10nm), reinforced ferrite, reduce ferrite with
Performance difference between martensite improves reaming performance.By being accurately controlled to ferrite in tissue and martensite content, obtain
Obtain yield strength >=700MPa, the high strength dual phase steel of tensile strength >=980MPa.
A kind of 980MPa grades of hot rolling high-chambering dual phase steel, chemical component weight percentage are：：C：0.15~0.20%,
Si：1.0~2.0%, Mn：1.0~2.0%, P≤0.02%, S≤0.005%, O≤0.003%, Al：0.3~1.0%, N≤
0.006%, Nb：0.01~0.06%, Ti：0.08~0.20%, remaining is Fe and inevitable impurity, and above-mentioned element is same
When need to meet following relationship：0.10%≤Nb+Ti≤0.25%, 2.5≤Al/C≤5.0.
Preferably, in the chemical composition of the hot rolling high-chambering dual phase steel：C：0.16~0.18%, with weight percent
Meter.
Preferably, in the chemical composition of the hot rolling high-chambering dual phase steel：Si：1.2~1.8%, by weight percentage.
Preferably, in the chemical composition of the hot rolling high-chambering dual phase steel：Mn：1.4~1.8%, by weight percentage.
Preferably, in the chemical composition of the hot rolling high-chambering dual phase steel：Al：0.4~0.8%, by weight percentage.
Preferably, in the chemical composition of the hot rolling high-chambering dual phase steel：Nb：0.03~0.05%, with weight percent
Meter.
Preferably, in the chemical composition of the hot rolling high-chambering dual phase steel：Ti：0.12~0.18%, with weight percent
Meter.
Further, the microstructure of the hot rolling high-chambering dual phase steel is ferrite+body that volume fraction is 20~35%
Fraction be 65~80% the transgranular distribution of martensite+ferrite Nano-Scaled Carbide, ferrite average grain size be 5~
10 μm, martensite equivalent grain size≤20 μm, Nano-Scaled Carbide size≤10nm.
Yield strength >=700MPa of hot rolling high-chambering dual phase steel of the present invention, tensile strength >=980MPa, elongation percentage
A80>=12%, hole expansibility >=30%.
In the composition design of steel of the present invention：
Carbon：Carbon is the basic element in steel and one of the important element in the present invention.Carbon expands austenite phase field, surely
Determine austenite.Carbon is as the interstitial atom in steel, and the intensity to improving steel plays very important effect, to the yield strength of steel
It is influenced with tensile strength maximum.In the present invention, it is the tensile strength 980MPa grades high reaming dual phase steel of acquisition, it is necessary to assure carbon
Content is 0.15% or more；But the content of carbon can not be higher than 0.20%, be otherwise difficult to during hot rolling two-stage cooling
Form required amount of ferrite.Therefore, carbon content must control between 0.15~0.20% in steel of the present invention, and preferred scope exists
0.16~0.18%.
Silicon：Silicon is the basic element in steel, while being also one of the important element in the present invention.This is because to obtain
Tensile strength reaches the high-strength dual phase steel of 980MPa or more, on the one hand to control ferritic size and number, while also to improve
The intensity of martensite, this needs the content that carbon and manganese are properly increased in composition design.And carbon and manganese all be expand austenitic area,
The element of stable austenite, (usually≤10s) is difficult to form sufficient amount of iron in very short time during hot rolling and air cooling
Ferritic, this just needs the element silicon for adding high level.The addition of silicon can be obviously promoted ferrite and be formed, and expand ferrite and formed
Process window, purify ferrite；It can also play the role of partial reinforment simultaneously.Silicone content is relatively high in the present invention, most
Low content should reach 1.0% or more, but the content of Si also should not be too high, and the steel plate after otherwise rolling impacts degraded toughness.Therefore,
Silicone content control is between 1.0~2.0% in steel of the present invention, and preferred scope is between 1.2~1.8%.
Manganese：Manganese is also element most basic in steel, while being also one of most important element in the present invention.It is well known that
Manganese is the important element for expanding austenite phase field, can reduce the critical quenching rate of steel, stable austenite, crystal grain thinning pushes away
Slow austenite from being transformed into perlite.In the present invention, it is the intensity for ensureing steel plate, manganese content should be controlled 1.0% or more, manganese
Content is too low, and overcooling austenite is not sufficiently stable, and is easy to be changed into the tissue of pearlite type when air-cooled；Meanwhile the content of manganese
No more than 2.0%, if more than 2.0%, Mn segregations are easy to happen when not only making steel, but also the air-cooled stage is not allowed to be formed after rolling
Sufficient amount of ferrite, while hot tearing is also easy to happen when sheet billet continuous casting.Therefore, Mn contents are controlled 1.0 in steel of the present invention
~2.0%, preferred scope is 1.4~1.8%.
Phosphorus：Phosphorus is the impurity element in steel.Easily in segregation to crystal boundary, in steel when the content of phosphorus higher (>=0.1%), shape
At Fe2P is precipitated around crystal grain, reduces the plasticity and toughness of steel, therefore the lower its content the better, and general control is within 0.02%
Preferably and do not improve steel-making cost.
Sulphur：Sulphur is the impurity element in steel.Sulphur in steel, which is usually combined with manganese, to be formed MnS and is mingled with, especially when sulphur and manganese
Content it is higher when, more MnS will be formed in steel, and MnS itself has certain plasticity, in the follow-up operation of rolling
MnS rolls the transverse tensile property that steel plate is reduced to deforming in edge.Therefore the lower sulfur content the better in steel, when actual production, is usual
Control is within 0.005%.
Aluminium：Aluminium is one of the important alloying element in the present invention.Due to high reaming two-phase hardness of steel according to the present invention
Up to 980MPa or more, the content of carbon and manganese is relatively high in steel, and overcooling austenite is relatively stable, is difficult to be formed in process air cooler
Sufficient amount of ferrite, therefore, it is necessary to more aluminium is added in composition design to promote ferrite to be formed.The additive amount of aluminium
Mainly related with carbon content, carbon content is higher, and the addition of aluminium is also higher.In the present invention in the composition range of carbon, carbon and aluminium
Between should meet the relationships of 2.5≤Al/C≤5.0.Aluminium content is too low, it is difficult to form enough ferrites；Aluminium content is excessively high, continuous casting
Base Longitudinal Surface Cracks are more serious.Therefore, in steel of the present invention aluminium content control between 0.3~1.0%, preferred scope be 0.4~
0.8%.
Nitrogen：Belong to impurity element in the present invention, the lower content the better.Nitrogen is also inevitable element in steel, is led to
In the case of often, if without Special controlling in steelmaking process, the residual content of nitrogen in steel is usually≤0.006%.These solid solutions
Or free nitrogen must be fixed by forming certain nitride, otherwise free nitrogen-atoms is non-to the impact flexibility of steel
Chang Buli, and the sawtooth for being readily formed during belt steel rolling overall length splits defect.It is micro- by adding in the present invention
Secondary element titanium is allowed to be combined with nitrogen to form stable TiN to fixed nitrogen-atoms.Therefore, content control exists in steel of the present invention
It is within 0.006% and more lower better.
Niobium：Niobium is also one of the key element in the present invention.Since 980MPa and the above rank hot continuous rolling dual phase steel are usual
Need to be added higher silicon to promote to roll the formation of air-cooled section of ferritic phase, and the addition of high silicon would generally improve martensitic phase
Brittleness.Although content≤0.20% of carbon itself in the present invention, after a certain amount of ferrite is precipitated, the carbon in ferrite
Atom can be discharged, into the austenite not changed so that carbon content is enriched in remaining austenite, and finally formed martensite is real
Border carbon content is higher, and martensite brittleness is larger, and the addition of high silicon has then been further exacerbated by this brittleness.Therefore, high Si types hot rolling
The low-temperature impact toughness of dual phase steel is usually relatively low, in order to improve the impact flexibility of the high high-strength dual phase steel of Si types as far as possible.Alloy at
Set up separately in meter and micro niobium is added, the impact flexibility of dual phase steel can be effectively improved by crystal grain thinning.Two sides are played in the addition of niobium
Face acts on：First, in hot stage, the niobium of solid solution plays solute effect of dragging to Austenite Grain Growth；Second is that in the finish rolling stage
By the carbonitride pinning austenite grain boundary of niobium, fining austenite grains, and the ferrite to finally changing and martensite rise
To refining effect, dual phase steel impact flexibility is improved.Therefore, content of niobium control is 0.01~0.06% in the present invention, preferred scope
0.03~0.05%.
Titanium：Titanium is one of the important element in the present invention.Titanium mainly plays two in the present invention：First, with steel
Impurity element nitrogen combines and forms TiN, plays nitrogen fixation effect；Second is that coordinating with niobium, the work of best fining austenite grains is played
With.The nitrogen-atoms to dissociate in steel is very unfavorable to the impact flexibility of steel, and trace amount of titanium, which is added, to fix free nitrogen, but in this hair
The content of bright middle titanium should not be excessive, is otherwise easy to form larger-size TiN, and the impact flexibility to steel is also unfavorable；Experiment
It proves, only an addition niobium does not add titanium in steel, and continuous casting billet is easy to happen chink in continuous casting production process, and addition trace amount of titanium then can be with
It is effectively improved chink problem；Meanwhile as long as the control of the content of niobium and titanium is in the ingredients of 0.10%≤Nb+Ti≤0.25% in the present invention
In range, you can play good grain refinement effect and cost is relatively low.Therefore, Ti content scope control exists in steel of the present invention
0.08~0.20%, preferred scope is 0.12~0.18%.
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
Can generally 30ppm be reached afterwards hereinafter, significant adverse will not be caused to influence the performance of steel plate.Therefore, the oxygen in steel is contained
Amount control is within 30ppm.
The manufacturing method of 980MPa grades of hot rolling high-chambering dual phase steel of the present invention comprising following steps：
1) it smelts, cast
It smelted, refined by above-mentioned chemical composition, being cast as strand or ingot casting；
2) strand or ingot casting heating
1230~1300 DEG C of heating temperature, 1~2 hour heating time；
3) hot rolling+sub-sectional cooling+is batched
Start rolling temperature is 1080~1200 DEG C, carried out at 1050 DEG C or more 3~5 passage roughing and accumulative deflection >=
50%；Intermediate base waits for that temperature is 900~950 DEG C, then carries out 3~5 passage finish rolling and accumulative deflection >=70%；Finish to gauge temperature
Degree be 800~900 DEG C, after finish to gauge with the cooling rate of >=100 DEG C/s by steel plate water cooling to 650~750 DEG C；Air-cooled 5~10 seconds
Afterwards, then with the cooling rate water cooling of 30~50 DEG C/s to 200 DEG C or less it batches, is cooled to room temperature with the cooling rate of≤20 DEG C/h after batching.
The reasons why design and manufacture technology of the present invention, is as follows：
For the high-strength steel of high Ti precipitation strengths type, heating temperature is a critically important technological parameter.With it is general
Logical high-strength steel is compared, and the high higher heating temperature of Ti steel (>=1230 DEG C) main purpose is dissolved as far as possible in the slab of heating
More Ti atoms.Since the carbonitride solid solubility temperature of Ti is usually very high (>=1300 DEG C), in steel-making or continuous casting and rolled
The different phase of journey can be precipitated, and the Ti contents that this allows for finally can be used to play the role of precipitation strength are just very low.Therefore, must
It must ensure that high heating temperature is possible to obtain more nano-carbides in air-cooled phase process after rolling, therefore the present invention wants
Ask the minimum heating temperature of steel plate it is necessary >=1230 DEG C；The upper limit of heating temperature is actually accessible or can according to live heating furnace
The temperature born is limited, and heating temperature does not set upper limit requirement in principle；In order to save energy consumption, usually actual highest is heated
Temperature is controlled at≤1300 DEG C.Steel heating process schematic diagram of the present invention is referring to Fig. 1.
For high Ti steel, the heating time of slab for heating temperature, influences much smaller.Theoretically
For, as long as heating temperature reaches the balance solution temperature of the carbonitride of Ti, solution rate is very fast.Therefore in this stage,
Heating time is mainly to ensure that slab can be grilled thoroughly uniformly as main target.Certainly, heating time can not be too long, otherwise
The carbonitride of the undissolved Ti of high temperature very likely occurs to be roughened and grow up, the carbonitride of these coarse Ti is in austenite
Grain boundaries are precipitated, and reduce the bond strength of crystal boundary, are easy during heating, and disconnected base phenomenon occurs in heating furnace for slab.
Therefore, according to slab thickness difference, heating time is normally controlled in 1~2 hour.
Rolling mill practice schematic diagram of the present invention is referring to Fig. 1.In rolling mill practice design, in roughing and finish rolling stage, rolled
The rhythm of journey should be rapidly completed as possible, to reduce the precipitation in roughing and finish rolling stage Ti to the greatest extent.This is because roughing especially
It is that finish rolling is in austenitic area, is received mostly tens in the carbide or carbonitride size of the Ti that final rolling temperature section is precipitated
Rice, it is little to final precipitating reinforcing effect, but have great role to the refinement of austenite grain.Therefore, roughing and finish rolling rank
Section should be completed as early as possible so that more nanoscales (≤10nm) carbide is precipitated in the air-cooled stage in ferrite after rolling；Open rolling temperature
Degree control is 1080~1200 DEG C, and 3~5 passage roughing and accumulative deflection >=50% are carried out at 1050 DEG C or more；Main mesh
Be fining austenite grains.
Present invention cooling rate of Ying Yigao after finish to gauge be quickly cooled to stop cooling temperature (stopping cold temperature) 650~
750℃.This is because if cooling velocity is slower after rolling, the austenite of steel plate internal distortions can be in a short period of time
Recrystallization process is completed, austenite grain is grown up at this time.In subsequent cooling procedure iron occurs for relatively coarse austenite
When ferritic phase transformation, the ferrite crystal grain formed along original austenite grain boundaries is more coarse, usually between 10~20 μm, to carrying
The intensity of high steel plate is unfavorable.The present invention is tiny isometric ferrite and martensitic structure to the microstructure mentality of designing of steel.It wants
Reach the tensile strength rank of 780MPa, the size of ferrite crystal grain must be controlled at 10 μm hereinafter, this just needs steel plate at end
Cold temperature is stopped in required centre when must be quickly cooled down after rolling.Since the present invention is mild steel, ferrite transformation driving force
Greatly, it is easy to be formed.Therefore, the cooling velocity after finish to gauge answers sufficiently fast (>=100 DEG C/s), avoids forming iron element in cooling procedure
Body.
The stopping cooling temperature of first stage need to control within the scope of suitable temperature, this is because hot continuous rolling producing line strip
The speed of service is fast, the limited length of water cooling stage, it is impossible to carry out air-cooled for a long time.The cold temperature of stopping of first stage controls as possible
Optimum temperature section is precipitated in ferrite, it is 650~750 DEG C that the present invention, which controls stopping cooling temperature,；In the air-cooled stage, while into
Two processes are precipitated in row ferrite forming core and Nano-Scaled Carbide, and the ferrite formed at this time has higher intensity, and rear
The continuous martensite formed difference in mechanical property is smaller；The water cooling main purpose of second stage is to form required martensite,
The water quenching speed of second stage should control between 30~50 DEG C/s, and excessively high cooling velocity can cause martensitic phase inside steel plate
Stress when change is excessive, causes belt plate shape bad.The stopping cooling temperature of second stage water cooling is controlled at≤200 DEG C,
Specific cooling technique schematic diagram is as shown in Figure 2.
The present invention coordinates innovative hot rolling technology by ingenious rational composition design, is precipitated using nanometer strong
Change enhancing ferrite intensity, reduces the performance difference between ferrite and martensite, to improve the hole expandability of high-strength dual phase steel
Can, obtain the hot-rolled dual-phase steel of high intensity, good, the high hole expansibility of plasticity.The microstructure of steel plate of the present invention is tiny nanometer
Precipitation strength ferrite (i.e. the Nano-Scaled Carbide of the transgranular distribution precipitation size≤10nm of ferrite+ferrite) and martensite,
Wherein, ferrite average grain size is 5~10 μm, martensite equivalent grain size≤20 μm.In composition design, pass through reason
By analysis and experimental study, the total amount of Nb and Ti should meet 0.10%≤Nb+Ti≤0.25%, while coordinate required rolling
Technique could obtain the high-strength hot-rolled nanometer of low yield strength ratio and ferrito-martensite dual phase steel is precipitated.
Beneficial effects of the present invention：
(1) present invention uses the composition design thinking of relatively economical, while coordinating existing hot continuous rolling producing line that can give birth to
Output has low yield strength ratio hot rolling high-chambering dual phase steel.
(2) present invention produces yield strength >=700MPa, tensile strength >=980MPa, elongation percentage A80>=12%, reaming
Rate >=30%, and the hot-rolled high-strength dual phase sheet steel of thickness≤6mm, the steel plate show excellent high intensity, plasticity and reaming
Property matching, have both low yield strength ratio, can be applied to wheel etc. needs high-strength thinned component, has a good application prospect.
Description of the drawings
Fig. 1 is present invention heating and rolling mill practice schematic diagram.
Fig. 2 is roller repairing process schematic representation of the present invention.
Fig. 3 is that TEM photos are precipitated in the transgranular typical nanometer of ferrite in 3 steel plate tissue of the embodiment of the present invention.
Specific implementation mode
With reference to embodiment, the present invention will be further described.
Table 1 is the ingredient of steel of the embodiment of the present invention, and table 2 is the fabrication process parameters of steel of the embodiment of the present invention, and table 3 is this hair
The performance of bright embodiment steel.
Technological process of the embodiment of the present invention is：Converter or electric furnace smelting → vacuum drying oven double refining → strand or ingot casting → steel
Rear sub-sectional cooling → coil of strip is rolled in base (ingot) heating → hot rolling+, and wherein key process parameter is referring to table 2.
From the figure 3, it may be seen that the Nano-Scaled Carbide size of the transgranular precipitation of iron element is about 5 ± 1nm in steel plate tissue of the present invention, and
It is arranged in certain rule.Make iron just because of the Nano-Scaled Carbide that the size being precipitated inside ferrite crystal grain is only 5 ± 1nm
Ferritic intensity greatly improves, and reduces the performance difference between ferrite and martensite, improves ferrito-martensite dual phase steel
Hole expansibility, obtain intensity and reaming and match good advanced high-strength steel.
As known from Table 3, the present invention can produce 980MPa grades high reaming dual phase steel, and the yield strength of the dual phase steel >=
700MPa, tensile strength >=980MPa, elongation percentage A80>=12%, hole expansibility >=30%, hence it is evident that higher than the reaming of traditional dual phase steel
Rate (usually≤20%) shows excellent intensity, plasticity and hole expandability matching, be particularly suitable for wheel etc. need reaming flange and
High-strength thinned field.
As known from Table 3, compared with the conventional ferrite martensite dual-phase steel of same intensity rank, steel plate of the present invention has more
High yield strength and slightly higher tensile strength, this is mainly due to present in the ferrite of steel plate tissue of the present invention it is a large amount of more
Caused by dissipating tiny nano TiC precipitation strength, yield tensile ratio is slightly above conventional ferrite martensite dual-phase steel, with traditional iron element
The yield tensile ratio of body bainite dual-phase steel is close.
Claims (10)
1. a kind of 980MPa grades of hot rolling high-chambering dual phase steel, chemical component weight percentage are：C：0.15~0.20%, Si：
1.0~2.0%, Mn：1.0~2.0%, P≤0.02%, S≤0.005%, O≤0.003%, Al：0.3~1.0%, N≤
0.006%, Nb：0.01~0.06%, Ti：0.08~0.20%, remaining is Fe and inevitable impurity, and above-mentioned element is same
When need to meet following relationship：0.10%≤Nb+Ti≤0.25%, 2.5≤Al/C≤5.0；The hot rolling high-chambering dual phase steel
Microstructure is the Nano-Scaled Carbide of ferrite+transgranular distribution of martensite+ferrite, wherein volume fraction shared by ferrite
It is 20~35%, ferrite average grain size is 5~10 μm, Nano-Scaled Carbide size≤10nm；Volume shared by martensite
Score is 65~80%, martensite equivalent grain size≤20 μm.
2. 980MPa grades of hot rolling high-chambering dual phase steel according to claim 1, which is characterized in that the hot rolling high-chambering is double
In the chemical composition of phase steel：C：0.16~0.18%, by weight percentage.
3. 980MPa grades of hot rolling high-chambering dual phase steel according to claim 1, which is characterized in that the hot rolling high-chambering is double
In the chemical composition of phase steel：Si：1.2~1.8%, by weight percentage.
4. 980MPa grades of hot rolling high-chambering dual phase steel according to claim 1, which is characterized in that the hot rolling high-chambering is double
In the chemical composition of phase steel：Mn：1.4~1.8%, by weight percentage.
5. 980MPa grades of hot rolling high-chambering dual phase steel according to claim 1, which is characterized in that the hot rolling high-chambering is double
In the chemical composition of phase steel：Al：0.4~0.8%, by weight percentage.
6. 980MPa grades of hot rolling high-chambering dual phase steel according to claim 1, which is characterized in that the hot rolling high-chambering is double
In the chemical composition of phase steel：Nb：0.03~0.05%, by weight percentage.
7. 980MPa grades of hot rolling high-chambering dual phase steel according to claim 1, which is characterized in that the hot rolling high-chambering is double
In the chemical composition of phase steel：Ti：0.12~0.18%, by weight percentage.
8. according to 980MPa grades of hot rolling high-chambering dual phase steels of claim 1-7 any one of them, which is characterized in that the hot rolling
Yield strength >=700MPa of high reaming dual phase steel, tensile strength >=980MPa, elongation percentage A80>=12%, hole expansibility >=30%.
9. such as the manufacturing method of claim 980MPa grades of hot rolling high-chambering dual phase steels of 1-7 any one of them comprising as follows
Step：
1) it smelts, cast
It smelted by any one of the claim 1-7 chemical compositions, refined, be cast as strand or ingot casting；
2) strand or ingot casting heating
1230~1300 DEG C of heating temperature, 1~2 hour heating time；
3) hot rolling+sub-sectional cooling+is batched
Start rolling temperature is 1080~1200 DEG C, and 3~5 passage roughing and accumulative deflection >=50% are carried out at 1050 DEG C or more；
Intermediate base waits for that temperature is 900~950 DEG C, then carries out 3~5 passage finish rolling and accumulative deflection >=70%；Finishing temperature is
800~900 DEG C, after finish to gauge with the cooling rate of >=100 DEG C/s by steel plate water cooling to 650~750 DEG C；After air-cooled 5~10 seconds, then
It is batched to 200 DEG C or less with the cooling rate water cooling of 30~50 DEG C/s, is cooled to room temperature with the cooling rate of≤20 DEG C/h after batching.
10. the manufacturing method of 980MPa grades of hot rolling high-chambering dual phase steel according to claim 9, which is characterized in that described
Yield strength >=700MPa of hot rolling high-chambering dual phase steel, tensile strength >=980MPa, elongation percentage A80>=12%, hole expansibility >=
30%.
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