CN110100030A - The ultrahigh strength hot-rolled steel plate and its manufacturing method of excellent in bending workability - Google Patents
The ultrahigh strength hot-rolled steel plate and its manufacturing method of excellent in bending workability Download PDFInfo
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- CN110100030A CN110100030A CN201780080291.1A CN201780080291A CN110100030A CN 110100030 A CN110100030 A CN 110100030A CN 201780080291 A CN201780080291 A CN 201780080291A CN 110100030 A CN110100030 A CN 110100030A
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- C—CHEMISTRY; METALLURGY
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- 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
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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
- C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
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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
- C21D8/0294—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a localised treatment
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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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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Abstract
One aspect of the present invention is related to a kind of ultrahigh strength hot-rolled steel plate of excellent in bending workability, in terms of weight %, the hot rolled steel plate includes: C:0.18~0.28%, Mn:1.2~2.2%, Si:0.1~0.5%, P:0.005~0.05%, S:0.01% or less, Al:0.01~0.05%, Ti:0.01~0.10%, B:0.001~0.0045%, the Fe and inevitable impurity of N:0.001~0.01% and surplus, in terms of area fraction, microstructure includes 90% or more martensite, 4~10% self tempering martensite and 5% retained austenite below.
Description
Technical field
The present invention relates to the ultrahigh strength hot-rolled steel plates and its manufacturing method of a kind of excellent in bending workability.
Background technique
According to vehicle body and passenger's collisional stabilization and CO2The strict demand of Environmental Regulation etc. needs reality in world wide
Therefore the superhigh intensity and ultra lightweighting of existing vehicle body are actively developing 1.0Gpa grades or more of ultrahigh-strength steel plates.
Major part for bumper reinforcement material and door anti-collision joist etc. as most of automobile body reinforcement material
Have while ultrahigh strength hot-rolled steel plate needs to have high-intensitive and is used for the excellent curved of rolling and forming (Roll Forming)
Bent processability and shape quality.
In order to meet this physical property, vehicle structural members are with steel plate substantially by ferrite (Ferrite), bainite
(Baintie), the combination of martensite (Martensite) and tempered martensite (Tempered Martensite) phase is constituted,
And according to the composition of these phases, it is divided into two-phase (Dual Phase, DP) steel, phase change induction plasticity
(Transformation Induced Plasticity, TRIP) steel, complex tissue (Complex Phase) steel, martensite are strong
Change type superhigh intensity (MART) steel etc. and applied.
The steel is mainly used in the component that high-energy absorption performance is needed when vehicle collision, and e.g., component class, is protected at column class
Dangerous thick stick reinforcement material, curb girder etc., and processed in the way of rolling and forming, it is therefore desirable to the tensile strength with 1.0Gpa or more
And high-elongation.
On the other hand, in order to provide be used as automobile body reinforcement material component tensile strength be 1.2GPa grade or more surpass
High strength steel, has carried out a large amount of research and development, and typical example has patent document 1 to 5.
A kind of superelevation that the tensile strength for vehicle bumper reinforcement material is 1.2GPa grades is disclosed in patent document 1
The manufacturing method of strength cold-rolled steel sheet, method includes the following steps: carrying out homogeneity to aluminum killed steel at 1050~1300 DEG C
After processing, 850~950 DEG C of progress hot finishings on Ar3 transition point, then in 550~650 DEG C of progress hot rolling windings, with
The weight ratio meter of chemical component, add in the aluminum killed steel C:0.15~0.20%, Si:0.3~0.8%, Mn:1.8~
2.5%, Al:0.02~0.06%, Mo:0.1~0.4%, Nb:0.03~0.06%, S:0.02% or less, P:0.02% with
Under, N:0.005% hereinafter, and include steel manufacturing process in the element finish rolling that inevitably contains；With 30~80%
Cold reduction ratio, to the steel plate carry out cold rolling, continuous annealing is then carried out more than A3 temperature；And the steel plate is carried out
600~700 DEG C are slowly cooled to for the first time, then it is quickly cooled to 350 for the second time with -10~-50 DEG C/sec of cooling velocity~
300 DEG C, then carry out Slow cooling in 350~250 DEG C of ranges and kept for 1 minute or more.
A kind of manufacturing method of cold-rolled steel sheet is disclosed in patent document 2, is including in terms of weight %: C:0.05~
0.20%, in the steel of Si:2.5% or less, Mn:3.0% or less and impurity and a small amount of alloying element add Cr:0.3% with
Under, one or more of Mo:0.3% or less, Ni:0.3% or less, to manufacture the intensity with 1180~1400MPa
And the bending of steel plate/distort as the 10mm cold-rolled steel sheet below with excellent in shape.In addition, it is disclosed that using continuously moving back
Burning hot processing equipment is at high temperature rapidly cooled steel plate, then by carrying out overaging in 150~200 DEG C of temperature ranges
Processing is then handled by tempering (tempering) bad to improve plate shape to carry out common water cooling (quenching)
(width direction of steel plate deforms).
A kind of manufacturing method of super high tensile cold-rolled steel plate that tensile strength is 1470MPa grades is disclosed in patent document 3,
To include in terms of weight %: C:0.1~0.6%, Si:1.0~3.0%, Mn:1.0~3.5%, Al:1.5% or less and Cr:
0.003~2.0% cold-rolled steel sheet is heated to Ac3~Ac3+50 DEG C of temperature, is then carried out with 3 DEG C/sec or more of cooling velocity
It is cooling, then by keeping constant temperature in (Ms-100 DEG C)~Bs (bainite start temperature) range, make the cold-rolled steel sheet
The phase fraction of retained austenite before processing is 10% or more, and the length of austenite grain is that short axle is 1 micron or more, average axis
It is 5 or more than (major axis/minor axis) and there is hydrogen embrittlement resistance.
A kind of manufacturing method of cold-rolled steel sheet that tensile strength is 1.5GPa is disclosed in patent document 4, this method is passed through
Following continuous annealing step: with 1~5 DEG C/sec of heating speed, by the heating of plate blank through cold rolling to [(Ac3-90 DEG C)~
(Ac3 ± 15 DEG C)] temperature range, be then cooled to 500~750 DEG C of temperature for the first time with 1~3 DEG C/sec of cooling velocity
Then range is cooled to the temperature range of [(Ms-120)~460 DEG C] for the second time with 3~50 DEG C/sec of cooling velocity, then protected
It holds isothermal transformation 6~500 seconds, or Slow cooling, in terms of weight %, the slab is carried out with 1 DEG C/sec of cooling velocity below
Include: C:0.10~0.27%, Si:0.001~1.0%, Mn:2.3~3.5%, Al:1.0% or less (except 0%), Cr:
2% or less (except 0%), P:0.02% or less (except 0%), S:0.01% or less (except 0%), N:0.01% or less (0%
Except), B:0.005% or less (except 0%), Ti:0.004~0.03%, Mo:0.02% or less (except 0%), Nb:
0.05% or less (except 0%) and the Fe of surplus and other inevitable impurity.
But according to patent document 1 to 4, due to needing to carry out cold rolling and annealing heat-treatment after hot rolling
(Continuous Annealing Line, CAL) technique, therefore manufacturing cost steeply rises, and for being applied to current quotient
The Vehicular bumper or reinforcement material used in industry, has that tensile strength is relatively low.
In addition, being disclosed in patent document 5 and a kind of hot-forming being to obtain tensile strength by being carried out to cold-rolled steel sheet
The manufacturing method of the superhigh intensity of 1.8GPa, in terms of weight %, the cold-rolled steel sheet includes: C:0.26~0.45%, Mn+Cr:
0.5~3.0%, Nb:0.02~1.0%, content meet 3.42N+0.001≤Ti≤3.42N+0.5 Ti and Si:0.5%
Below, Ni:2% or less, Cu:1% or less, V:1% or less and Al:1% one or more below, and according to circumstances
Include: B:0.01% or less, Nb:1.0% or less, Mo:1.0% or less, Ca:0.001~0.005% it is one or two kinds of with
On.
According to patent document 5, although may insure that tensile strength is the superhigh intensity of 1.8GPa, the steel plate through cold rolling
The hot-forming step of further progress (Hot Press Forming) is needed, therefore manufacturing cost further increases.
Therefore, it is necessary to develop it is a kind of can replace traditional super high tensile cold-rolled steel plate and thermoforming steel, and can be true
It protects higher tensile strength and significantly reduces the ultrahigh strength hot-rolled steel plate and its manufacturing method of manufacturing cost.
(existing technical literature)
(patent document 1) Korean Patent Laid the 2004-0057777th
(patent document 2) Japanese Laid-Open Patent Publication the 2007-100114th
(patent document 3) Korean Patent Laid the 2008-73763rd
(patent document 4) Korean Patent Laid the 2013-0069699th
(patent document 5) Japanese Laid-Open Patent Publication the 2008-0111549th
Summary of the invention
(1) technical problems to be solved
The purpose of one aspect of the present invention is, provides one kind in the direct-connected technique of continuous casting~rolling using without a head continuous
Rolling mode, thus only by hot rolling technology have excellent bendability 1.8GPa grade super strength hot rolled steel plate and its
Manufacturing method.
On the other hand, the technical problems to be solved by the invention are not limited to above-mentioned content.The present invention to be solved
The technical issues of can be understood by the entire content of this specification, and the ordinary skill people of the technical field of the invention
Member will be readily understood that supplementary technology problem of the invention.
(2) technical solution
One aspect of the present invention is related to a kind of ultrahigh strength hot-rolled steel plate of excellent in bending workability, in terms of weight %,
The hot rolled steel plate includes: C:0.18~0.28%, Mn:1.2~2.2%, Si:0.1~0.5%, P:0.005~0.05%,
S:0.01% or less, Al:0.01~0.05%, Ti:0.01~0.10%, B:0.001~0.0045%, N:0.001~
0.01% and surplus Fe and inevitable impurity, in terms of area fraction, microstructure include 90% or more martensite,
4~10% self tempering martensite and 5% retained austenite below.
In addition, another aspect of the present invention relates to a kind of manufacturers of the ultrahigh strength hot-rolled steel plate of excellent in bending workability
Method the described method comprises the following steps: molten steel is casting continuously to form to the sheet billet of 60~120mm, in terms of weight %, and the steel ladle
Contain: C:0.18~0.28%, Mn:1.2~2.2%, Si:0.1~0.5%, P:0.005~0.05%, S:0.01% or less,
Al:0.01~0.05%, Ti:0.01~0.10%, B:0.001~0.0045%, N:0.001~0.01% and surplus Fe
With inevitable impurity；In roughing outlet side, roughing is carried out to the heated sheet billet, so that the edge part temperature of batten
Degree reaches 850~1000 DEG C, to obtain batten；In Ac3+10 DEG C~Ac3+100 DEG C of temperature range, the batten is carried out
Finish rolling, to obtain hot rolled steel plate；The hot rolled steel plate is carried out air-cooled 1~3 second, then with 200 DEG C/sec or more of cooling velocity
It is cooled down, and is wound at Mf-50 DEG C or less；And the rolling hot rolled steel plate is positioned in other two through receiving
Between the hot rolled steel plate of volume, and each step continuously performs.
In addition, the technical solution does not list all features of the invention.Various features and its advantage of the invention
Following specific embodiments are referred to effect to be further understood in detail.
(3) beneficial effect
According to the present invention it is possible to provide using continuous rolling mode without a head in the direct-connected technique of continuous casting~rolling, thus only
There is the 1.8GPa grade super strength hot rolled steel plate and its manufacturing method of excellent bendability by hot rolling technology, not only
It can replace ultrahigh strength hot-rolled steel plate and thermoforming steel, and may insure higher tensile strength, and can significantly drop
Low manufacturing cost.
Detailed description of the invention
Fig. 1 be example 3 winding after slab photo.
Fig. 2 is the photo for shooting the PO material surface of example 3.
Fig. 3 is transmission electron microscope (TEM) macrograph of example 3, and (a) is 20000 times of photo, is (b) (a)
The middle photo that the part [X] is amplified to 100000 times.
Fig. 4 is in the direct-connected technique of continuous casting~rolling using the schematic diagram of the technique of continuous rolling mode without a head.
Preferred forms
In the following, being illustrated to the preferred embodiment of the present invention.But embodiments of the present invention can be changed to it
His various modes, the scope of the present invention are not intended to be limited to embodiments described below.In addition, embodiments of the present invention be for
More completely illustrate to person of an ordinary skill in the technical field the present invention and provides.
Present inventors have realized that only as long as automobile body reinforcement material can be used as by hot rolling technology manufacture
The tensile strength of component is 1.5GPa grades or more of unimach, so that it may instead of traditional cold-rolled steel sheet and hot rolled sheet,
So as to significantly reduce manufacturing cost, and in order to only be carried out by the hot rolled steel plate that hot rolling technology manufactures 1.8GPa grades
Further investigation.
As a result confirm, continuous rolling mode without a head is used in the direct-connected technique of continuous casting~rolling, and be precisely controlled to point
And manufacturing process, it is 1.8GPa grades of high tensile hot rolled steel sheet so as to manufacture tensile strength, and have thus completed the present invention.
The ultrahigh strength hot-rolled steel plate of excellent in bending workability
In the following, being carried out to the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to an aspect of the present invention detailed
Explanation.
In terms of weight %, the ultrahigh strength hot-rolled steel plate packet of excellent in bending workability according to an aspect of the present invention
Contain: C:0.18~0.28%, Mn:1.2~2.2%, Si:0.1~0.5%, P:0.005~0.05%, S:0.01% or less,
Al:0.01~0.05%, Ti:0.01~0.10%, B:0.001~0.0045%, N:0.001~0.01%, surplus Fe and
Inevitable impurity,
In terms of area fraction, microstructure includes 90% or more martensite, 4~10% self tempering martensite and 5%
Retained austenite below.
Firstly, composition of alloy of the invention is described in detail.In the following, unless otherwise specified, each element content
Unit indicates weight %.
C:0.18~0.28%
The important element of intensity is improved by making tissue become martensite when carbon (C) is rapid cooling after hot rolling.
When C content is less than 0.18%, the intensity of martensite itself is low, it may be difficult to ensure strong needed for the present invention
Degree.On the other hand, when C content is more than 0.28%, due to the excessive rising of weldability and intensity, bendability is reduced.Cause
This, C content is preferably 0.18~0.28%.
In addition, the preferred lower limit of C content can be 0.20%, lower limit still further preferably can be 0.21%.
In addition, the preferred upper limit of C content can be 0.27%, the upper limit still further preferably can be 0.26%.
Mn:1.2~2.2%
Manganese (Mn) inhibits ferritic formation, and improves stabilization of austenite, makes it easy to form low-temperature transformation phase, from
And increase intensity.
When Mn content is less than 1.2%, it may be difficult to ensure intensity needed for the present invention.On the other hand, when Mn content
When more than 2.2%, in the internally and/or externally formation segregated zone of continuous casting steel billet and hot rolled steel plate, cause the generation and expansion of crackle
Exhibition, so that the final mass of steel plate reduces, and weldability and/or bendability possible deviation.Therefore, Mn content is preferably
1.2~2.2%.
In addition, the preferred lower limit of Mn content can be 1.30%, lower limit still further preferably can be 1.4%.
In addition, the preferred upper limit of Mn content can be 2.1%, the upper limit still further preferably can be 2.0%.
Si:0.1~0.5%
Silicon (Si) is the effective element that can ensure intensity in the case where not reducing the ductility of steel plate.In addition, Si is
Promote ferritic formation and encourages C to not changing austenite enrichment to promote the element of the formation of martensite.
When Si content is less than 0.1%, it is difficult to substantially ensure said effect.On the other hand, when Si content is more than 0.5%
When, red oxide skin is generated in surface of steel plate and its trace remains in surface of steel plate after pickling, so that surface quality may drop
It is low.Therefore, Si content is preferably 0.1~0.5%.
P:0.005~0.05%
Phosphorus (P) is the element strengthen with steel.
When P content is less than 0.005%, it is difficult to ensure the effect.On the other hand, when P content is more than 0.05%, partially
Analysis may cause brittleness in crystal boundary and/or alternate crystal boundary.Therefore, the content of P is preferably limited to 0.005~0.05%.
S:0.01% or less
Sulphur (S) is impurity, and S forms MnS non-metallic inclusion in steel and is segregated in continuous casting and solidifying, so as to cause
Heat cracking.Therefore, S content is limited in alap level, is preferably limited to 0.01% or less.But when S content limits
System needs excessively high cost, therefore, can exclude 0% at 0%.
Al:0.01~0.05%
Aluminium (Al) plays the role of the ductility for inhibiting the formation of carbide to increase steel.
When Al content is less than 0.01%, said effect is insufficient.On the other hand, when Al content is more than 0.05%, shape
At a large amount of AlN precipitate, high-temperature ductility is reduced, so as to reduce the edge quality of slab or batten, and is enriched in
The surface of steel plate and make plating be deteriorated.Therefore, Al content is preferably 0.01~0.05%.
Ti:0.01~0.10%
Titanium (Ti) is used as precipitate and nitride forming element, is the element for increasing the intensity of steel.In addition, Ti be by
Setting temperature is formed about TiN to remove the precipitation object amount for being dissolved N and reducing AlN etc., to prevent high-temperature ductility from reducing, drops
The element of the sensibility of raw edge (Edge) crackle of low yield.
When Ti content is less than 0.01%, excessive fine AlN and/or BN precipitate is precipitated, leads to prolonging for block
Malleability reduces, to reduce slab quality.On the other hand, when Ti content is more than 0.10%, coarse TiN precipitate is formed,
To be difficult to expect crystal grain micronized effect, and manufacturing cost rises.Therefore, Ti content is preferably 0.01~0.10%.
B:0.001~0.0045%
Boron (B) is the element for increasing the harden ability of steel.
When B content is less than 0.001%, said effect is insufficient, when B content is more than 0.0045%, makes austenite again
Crystallization temperature rises, and weldability is made to be deteriorated.In addition, the precipitate of excessive BN etc. is precipitated, high-temperature ductility is caused to reduce, from
And the edge quality possible deviation of slab and/or batten (Bar plate).Therefore, B content is preferably 0.001~0.0045%.
In addition, the preferred lower limit of B content can be 0.0015%, the preferred upper limit can be 0.004%.
N:0.001~0.01%
Nitrogen (N) is stabilization of austenite and nitride forming element.
When N content is less than 0.001%, said effect is insufficient.On the other hand, it when N content is more than 0.01%, is precipitated
Excessive nitride, causes high-temperature ductility to reduce, so that the edge quality of slab and/or batten (Bar plate) may become
Difference.In addition, intensity may be decreased since the size of precipitate is thicker big.Therefore, N content is preferably 0.001~0.01%.
Residual components of the invention are iron (Fe).But it may be from raw material or ambient enviroment in general manufacturing process
In be inevitably mixed into undesirable impurity, therefore, it is impossible to exclude the impurity.These impurity are for general manufacturing process
It is known for technical staff, therefore entire contents not specifically mentioned in the present specification.
At this point, other than above-mentioned composition of alloy, in terms of weight %, can also further include Nb:0.001~
0.05%, one or more of Cr:0.5~1.0%, Mo:0.001~0.05% and Sb:0.005~0.02%.
Nb:0.001~0.05%
Niobium (Nb) is to miniaturize effective element to the intensity rising of steel plate and partial size.
When Nb content is less than 0.001%, it may be difficult to ensure said effect, when Nb content is more than 0.05%, be formed
Excessive NbC, (Ti, Nb) CN etc., so as to cause the black brittleness of continuous casting steel billet.Therefore, Nb content be preferably 0.001~
0.05%.
Cr:0.5~1.0%
Chromium (Cr) plays Solid Solution Strengthened Steel and to form martensite by postponing bayesian phase transformation while cooling to help
Effect.
When Cr content is less than 0.5%, said effect is insufficient.On the other hand, when Cr content is more than 1.0%, manufacture
Cost increase, and the ductility reduction of steel plate.Therefore, Cr content is preferably 0.5~1.0%.
Mo:0.001~0.05%
Molybdenum (Mo) be by solution strengthening and form nano-precipitation and strengthen yield strength, and by intercrystalline strengthening come
Improve the effective component of impact flexibility and bendability.
When Mo content is less than 0.001%, it is difficult to obtain said effect, when Mo content is more than 0.05%, effect will
Saturation, and ductility may be decreased.Therefore, Mo content is preferably 0.001~0.05%.
Sb:0.005~0.02%
Antimony (Sb) is the element for playing the role of inhibiting to generate hot rolling scale defects.
When Sb content is less than 0.005%, it is difficult to ensure said effect, when Sb content is more than 0.02%, manufacturing cost
Increase and processability is deteriorated, and the problems such as Sb may cause edge crack as low melting point element.Therefore, Sb content is preferred
It is 0.005~0.02%.
In addition, include one or more of Cu, Ni, Sn and Pb as residual elements other than the composition of alloy,
Summation can be 0.2 weight % or less.Residual elements are derived from the impurity element for being used as the waste material of raw material in process for making, when it
When summation is more than 0.2%, it is possible to create the face crack of sheet billet and the surface quality for reducing hot rolled steel plate.
In addition, the Ceq of described C, Si, Mn, P and S defined by following relationship 1 can be 0.25~0.45.
Relational expression 1:Ceq=C+Si/30+Mn/20+2P+3S
(in the relational expression 1, each element symbol is the value that each element content is indicated with weight %.)
The relational expression 1 is for ensuring that the ingredient relational expression of the weldability of steel plate, in the present invention, by the Ceq (carbon
Equivalent) value control is 0.25~0.45, and so as to ensure excellent resistance spot welding, and it is excellent to assign weld part
Mechanical-physical character.
When Ceq is less than 0.25, harden ability is low, to be difficult to ensure required tensile strength.On the other hand, when Ceq is super
When 0.45, weldability be may be decreased, and be likely difficult to obtain the physical property of intact weld part.It is preferred that control
It is made point so that Ceq meets 0.25~0.45 range.
In the following, microstructure of the invention is described in detail.
In terms of area fraction, microstructure of the invention includes 90% or more martensite, 4~10% self tempering geneva
Body and 5% retained austenite below.
Martensite is for ensuring superhigh intensity, when martensite fractions are less than 90%, it may be difficult to ensure required stretching
Intensity.
When self tempering martensite is less than 4%, bendability possible deviation, when self tempering martensite is more than 10%,
It is likely difficult to ensure required tensile strength.
On the other hand, retained austenite is phase unstable under room temperature, and it is strong to improve to be changed into martensite in processing
Degree and processability, still, when retained austenite is more than 5%, the amount that when processing is changed into martensite is more, thus since volume is swollen
It is swollen and lead to deformation of products, and it is uneven to may cause hardness.On the other hand, even if in the case that retained austenite is 0%,
Superhigh intensity and bendability needed for the present invention is also ensured, therefore, its lower limit is not particularly limited.
At this point, lath (lath) short axle spacing of the martensite can be 5 μm or less.
Lath (lath) the short axle spacing of martensite may influence intensity and bendability, and work as the lath of martensite
(lath) when short axle spacing is more than 5 μm, it may be difficult to ensure required intensity and bendability.
In addition, microstructure of the invention can also further include 4.5% ferrite below in terms of area fraction.
When ferritic area fraction is more than 4.5%, it may be difficult to ensure tensile strength, therefore, ferritic area
Score is preferably 4.5% or less.On the other hand, even if being also ensured needed for the present invention in the case that ferrite is 0%
Therefore superhigh intensity and bendability are not particularly limited the lower limit of ferritic area fraction.
On the other hand, the tensile strength of hot rolled steel plate according to the present invention can be 1.8Gpa or more, and bending machining
Property can be 3 or less.
Bendability (R/t) indicates the minimum bending radius (R) that will not crack after 90 ° of bend tests divided by steel
The value of plate thickness (t) can be preferably applied to the insurance as automobile body reinforcement material when bendability is 3 or less
The manufacture of thick stick reinforcement material and door anti-collision joist etc..It is highly preferred that bendability can be 2.5 or less.
In addition, the thickness of hot rolled steel plate according to the present invention can be 2.0mm or less.
In addition, the thickness deviation (Crown) of the width direction of hot rolled steel plate according to the present invention can be 40 μm or less.Its
In, the thickness deviation (Crown) of width direction indicates the difference between thickness and center part thicker at edge 25mm.
The manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability
In the following, to the manufacturing method of the ultrahigh strength hot-rolled steel plate of the excellent in bending workability of another aspect of the present invention into
Row is described in detail.
The manufacturing method of the ultrahigh strength hot-rolled steel plate of the excellent in bending workability of another aspect of the present invention includes following
Step: the molten steel for meeting above-mentioned composition of alloy is casting continuously to form to the sheet billet of 60~120mm；In roughing outlet side, to heated
The sheet billet carries out roughing so that the edge part temperature of batten reaches 850~1000 DEG C, to obtain batten；At Ac3+10 DEG C
~Ac3+100 DEG C of temperature range carries out finish rolling to the batten to obtain hot rolled steel plate；The hot rolled steel plate is carried out air-cooled
It 1~3 second, is then cooled down with 200 DEG C/sec or more of cooling velocity, and wound at Mf-50 DEG C or less；And it will be through
The hot rolled steel plate of winding is positioned between other two rolling hot rolled steel plates, and each step continuously performs.
Each step continuously performs expression and utilizes continuous rolling mode without a head in the direct-connected technique of continuous casting~rolling.
So-called manufacturing process (the small-sized steel using sheet billet as the new steel and iron manufacturing technique to attract attention in recent years
Factory's technique) be the direct-connected technique of continuous casting~rolling, in terms of the operational characteristic for, the technique is in the width direction of band and length side
Upward temperature deviation is small, so as to manufacture the good phase-change organization's steel of material deviation, therefore as the potential technique of tool
And it attracts attention.
The direct-connected technique of continuous casting~rolling has traditional intermittent mode (batch type) and newly developed without a head continuous
Rolling mode.
Roll bending in the case where intermittent mode, in order to make up the difference between casting speed and mill speed, before finishing mill
Finish rolling is executed after being wound in case, consequently, it can happen oxide skin fissility reduces, surface quality is reduced, and in life
The problems such as generating plate is broken when producing steel plate below with a thickness of 3.0mm.
Techniques different from intermittent mode in the case where continuous rolling mode without a head, not having winding before finish rolling, therefore
Although solving the problem in intermittent mode, in order to make up the difference between casting speed and mill speed, need more
It accurately controls.
Fig. 4 is the figure for showing the example in the direct-connected technique of continuous casting~finish rolling using the technique of continuous rolling mode without a head.?
The sheet billet a with a thickness of 50~150mm is manufactured in conticaster 100, due to not rolling up between roughing mill 400 and finishing mill 600
Plate case, can continuous rolling steel plate, so that logical plate is excellent, plate risk of breakage is very low, so as to produce with a thickness of 3.0mm
Thin object below.There is (the Roughing Mill Scale of roughing scale breaker 300 before roughing mill 400
Breaker, RSB), and there is (the Finishing Mill Scale of roughing scale breaker 500 before finishing mill 600
Breaker, FSB), to easily remove oxide skin, and in the subsequent process pickled hot steel plate when can produce surface matter
Measure excellent pickling oiling (Pickled&Oiled, PO) material.In addition, the mill speed in finish rolling step, in a steel plate
Difference can be realized the speed rollings such as isothermal for 5% or less, so that the temperature deviation of steel plate width, length direction significantly reduces,
Cooling can be accurately controlled in runout table 600 (Run Out Table, ROT), so as to manufacture the excellent steel of material deviation
Plate.
In the following, each step is described in detail.
Continuous casting step
The molten steel for meeting above-mentioned composition of alloy is casting continuously to form to the sheet billet of 60~120mm.
When the thickness of the sheet billet is more than 120mm, it is difficult to high-speed casting, and in roughing, rolling load increases,
When the thickness of the sheet billet is less than 60mm, the sharp temperature drop of slab, to be difficult to form uniform tissue.Although can
With additional setting heating equipment to solve described problem, but this will increase production cost, therefore preferably exclude as far as possible.Cause
This, the thickness of sheet billet is preferably 60~120mm.
At this point, the continuous casting step can use the covering slag that basicity is 1.0 or more to execute.Wherein, basicity indicates CaO
The ratio between (%)/SiO2 (%).
In general, added ingredient is more in order to ensure high intensity for high strength steel, thus the sensibility of linear flaws
It is very high.Therefore, when the covering slag using basicity less than 1.0, heat output is high, since steel slab surface is forced to cool down, generates
The sensibility of linear flaws is got higher, it is therefore preferable that the covering slag for the use of basicity being 1.0 or more.
In addition, the casting speed of the continuous casting can be 4~8mpm.
The reason that casting speed is set as 4mpm or more is that high-speed casting is connected with the operation of rolling and constituted, and
In order to ensure target termination temperature, need it is predetermined more than casting speed.In addition, there are slab generations when casting speed is slow
The risk of segregation, when the segregation occurs, it is difficult to ensure intensity and processability, and sent out in width direction or length direction
The risk of greenwood matter deviation increases.When casting speed is more than 8mpm, since molten steel face is unstable and job success ratio may drop
It is low.
Roughing step
Roughing is carried out to heated sheet billet in roughing outlet side so that the edge part temperature of batten reach 850~
1000 DEG C, to obtain batten.
When the edge part temperature in roughing outlet side batten is lower than 850 DEG C, a large amount of AlN precipitate etc. is generated, thus
High-temperature ductility reduces, and the sensibility for generating edge crack may become very high.On the other hand, when in roughing outlet side batten
Edge part temperature when being more than 1000 DEG C, sheet billet central part temperature is excessively high, a large amount of sour water type oxide skin is generated, thus pickling
Rear surface quality possible deviation.
At this point, the roughing may be performed that so that roughing entrance side sheet billet surface temperature reach 1000~
1200℃。
When the surface temperature in roughing entrance side sheet billet is lower than 1000 DEG C, roughing load increases, and in roughing
In batten edge part, there may be crackles in journey, in this case, may cause the edge part defect of hot rolled steel plate.Another party
Face remains hot rolling oxide skin, so that hot rolling surface quality may be decreased when the surface temperature is more than 1200 DEG C.
At this point, can further include following steps: before the roughing, with the pressure of 100~200bar or more,
To the heated sheet billet spray cooling water, with scale removal；After the roughing, pass sequentially through the batten
First row and secondary series, with scale removal, the first row is with the pressure injection cooling water of 50~250bar, the secondary series
With the pressure injection cooling water of 100~300bar.
For example, before roughing, can from roughing scale breaker (Roughing Mill Scale Breaker, with
It is known as " RSB " down) nozzle, sprays 40 DEG C of cooling waters below to heated sheet billet with the pressure of 100~200bar, to go
Except surface scale makes the thickness of oxide skin reach 200 μm hereinafter, and can use essence before finish rolling after roughing
Roll the first row nozzle and second of scale breaker (Finishing Mill Scale Breaker, hereinafter referred to as " FSB ")
The surface scale of column nozzle removal batten makes the thickness of oxide skin reach 20 μm or less.
When the pressure of cooling water is less than 100bar before roughing, in a large amount of sour water type oxide skins of sheet billet remained on surface etc.,
To pickling rear surface quality possible deviation, when the pressure of cooling water is more than 200bar before roughing, batten lip temperature is sharply
It reduces, the risk for generating edge crack is high.
When the pressure of the nozzle of the first row and secondary series is respectively smaller than 50 and 100 after roughing, it is unable to fully remove
Oxide skin, surface of steel plate generates a large amount of spindle, squama shape oxide skin after finish rolling, so that pickling rear surface quality may become
Difference.On the other hand, when the pressure that the pressure of the first row nozzle is more than the nozzle of 250bar or the secondary series is more than
When 300bar, final rolling temperature becomes too low, can not obtain effective austenite score, so as to be difficult to ensure required stretching
Intensity.
In addition, due to being difficult to only by the nozzle of first row come abundant scale removal, in finish rolling there may be for
It is the spindle oxide skin of critical defect for product, it is therefore preferable that being come using first row as described above and secondary series nozzle
Scale removal.
Hot-rolled step
In Ar3+10 DEG C~Ar3+100 DEG C of temperature range, finish rolling is carried out to the batten, to obtain hot rolled steel plate.
When final rolling temperature is lower than Ar3+10 DEG C, the load of roller is greatly increased when hot rolling, and energy consumption increases, and operates
It slows, when width direction temperature deviation occurs, is locally reduced to Ar3 hereinafter, pro-eutectoid ferrite may simultaneously occur, from
And it may be unable to fully obtain required martensite volume after the cooling period.
In addition, when more than Ar3+100 DEG C at a temperature of carry out finish rolling when, due to coarse grains, high intensity can not be obtained,
It is sufficiently martensitic in order to obtain, it needs to further increase cooling velocity.
Cooling and winding step
The hot rolled steel plate is carried out air-cooled 1~3 second, is then cooled down with 200 DEG C/sec or more of cooling velocity, and
It is wound at Mf-50 DEG C or less.
After finish rolling to slab carry out be within air-cooled 1~3 second because the slab internal residual stress that generates of when removal finish rolling and
It miniaturize martensite lath and is cooled to the temperature of Ar3 or more.When air cooling time was less than 1 second, production when not can be removed finish rolling
Residual stress inside raw slab, thus the shape possible deviation in winding.On the other hand, when air cooling time is more than 3 seconds,
It is likely to form pro-eutectoid ferrite, to may be unable to ensure after the completion of cooling sufficiently martensitic.
When cooling velocity is less than 200 DEG C/sec after air-cooled, due to passing through ferrite and bainite nose (Nose), Ke Nengwu
Method ensures sufficiently martensitic tissue.In addition, when the winding temperature is more than Mf-50 DEG C, it is difficult to martensitic structure is obtained, and
And a large amount of self tempering martensite is formed by the possible self tempering (Auto Tempering) of the cooling martensitic structure obtained,
So as to be difficult to obtain required tensile strength.
Load step
The rolling hot rolled steel plate is positioned between other more than two rolling hot rolled steel plates.
There is a large amount of residual water in the surface and inside of the hot rolled steel plate of low temperature winding, execute in this state smooth
When (Skin Pass), due to snugly into each other between residual water and oxide skin, fatal indentation may be generated in steel slab surface and lacked
It falls into.
When between the hot rolled steel plate that rolling hot rolled steel plate is positioned in other more than two windings, it can remove
Water is remained, and due to partial martensite self tempering, it can be ensured that self tempering martensite.
At this point, can further include following steps: at 50~150 DEG C, being carried out to the hot rolled steel plate of mounting flat
Whole rolling.
It is to be easy to correct hot rolled steel plate because passing through warm-rolling effect at 50~150 DEG C by the skin pass rolling temperature limiting
Shape.
On the other hand, following steps be can further include: pickling processes are carried out to the hot rolled steel plate of mounting, with
Obtain pickling oiling (Pickled&Oiled, PO) material.In general, as long as processing method used in hot rolling acid-cleaning technique
It can use, therefore be not particularly limited.
Specific embodiment
In the following, the present invention is described in more detail by embodiment.But following embodiment is only for saying in more detail
Bright example of the invention, and it is not intended to limit interest field of the invention.This is because interest field of the invention is by claim
The content recorded in book and the content thus rationally derived determine.
(embodiment)
To with shown in following table 1 at the molten steel being grouped as, using the manufacturing condition recorded in following table 2, even
In the direct-connected technique of casting~rolling (slab thickness: 93mm, casting speed: 5.8mpm), thickness is obtained with continuous rolling mode without a head
For the hot rolled steel plate of 1.4mm, skin pass rolling then is executed at 100 DEG C, to manufacture hot rolled steel plate.
Pickling processes are carried out to obtain PO material to the hot rolled steel plate, then measure and evaluate microstructure, mechanical-physical
Whether property cracks, the thickness deviation of width direction (Crown), whether generates PO material indentation defect and PO material surface
Quality, and be documented in following table 3.
For microstructure, is observed using scanning electron microscope (SEM) and transmission electron microscope (TEM) and measure horse
The area ratio of family name's body (M), self tempering martensite (AT) and ferrite (F).For retained austenite (RA), use is electron backscattered
Diffraction (Electron BackScatter Diffraction, EBSD) device measuring the area ratio.In addition, for following table 3
Lath spacing describes the lath short axle spacing using the photo measurement martensite of transmission electron microscope shooting and is averaged
Value.
Yield strength (YS), tensile strength (TS) and yield ratio (YR) as mechanical-physical character are at width W/4
The value for taking JIS5 test piece to measure on the basis of 90 ° of directions relative to rolling direction.
For bendability, it is bent by making bending radius (R) divided by the value 2.5 of steel plate thickness (t), and at 90 °
Whether whether cracking after test to be evaluated, and describe in following table 3 crackle and generate.
For whether generating linear flaws and edge crack, confirmed for the first time in batten and roll bending by naked eyes, then
Utilize the surface defects detection device (Surface Defect Detector, SDD) as surface defects detection device (Detector)
Second of confirmation of device.
For the thickness deviation (Crown) of width direction, the thickness at edge 25mm and central part are measured and described
Difference between thickness.Wherein, thickness deviation criterion of acceptability can be 40 μm or less.
For judging whether to generate the indentation defect of PO material, is confirmed for the first time in roll bending by naked eyes, then utilize SDD the
Secondary-confirmation.
The evaluation criterion of PO material surface quality is as follows.
Zero: glossiness width direction average deviation is 10% or less
△: glossiness width direction average deviation is 10~20%
X: glossiness width direction average deviation is more than 20%
On the other hand, Ar3 is to indicate ferrite transformation start temperature in table 2, and Mf indicates martensitic traoformation final temperature,
Ar3 and Mf is the value calculated using thermodynamic software i.e. JmatPro V-9 is commonly used.
[table 1]
In the table 1, Ceq=C+Si/30+Mn/20+2P+3S, in the relational expression, each element symbol is with weight
Measuring % indicates the value of each element content.
[table 2]
In the table 2, roughing scale breaker (Roughing Mill Scale Breaker, RSB) be roughing it
Preceding cooling water sprays pressure, finish rolling scale breaker (Finishing Mill Scale Breaker, FSB) be roughing it
Cooling water afterwards sprays pressure.
In addition, if mounting indicates whether to be positioned in rolling hot rolled steel plate between other steel plates of two windings.
[table 3]
In the table 3, M indicates that martensite (Martensite), AT indicate self tempering martensite (Auto Tempered
Martensite), RA indicates that retained austenite (Retained Austeniste), F indicate ferrite (Ferrite) tissue.
All meet the examples 1~6 of condition proposed in the present invention meet 1.8GPa or more tensile strength and 2.5 with
Under bendability.
In addition, compare example 1~3 and example 4~6, meet in the present invention it is further proposed that roughing before and after it is cold
But the example 1~3 of water injection pressure may insure bendability and superhigh intensity, and may insure excellent surface matter
Amount
Fig. 1 be example 3 winding after roll bending shape, Fig. 2 is the PO material that pickling is carried out to the hot rolled steel plate of example 3
Surface picture can be confirmed that winding shape and surface quality are excellent.
Fig. 3 is transmission electron microscope (TEM) macrograph of example 3, and (a) is 20000 times of photo, is (b) (a)
The middle photo that the part [X] is amplified to 100000 times.From this result, 1 μm of martensite lath below imperceptibly develops good
Good, there are 100nm fine aciculiform globular cementites (lower end photo arrow) below inside coarse lath, it is known that exists certainly
Tempered martensite.
Comparative example 1 does not meet the basicity condition proposed in the present invention, to generate line style crackle since surface is strong cold.
Comparative example 2 to 4 does not meet the cooling condition proposed in the present invention, from without the material needed for meeting.
Comparative example 5 does not meet the final rolling temperature proposed in the present invention, from without the material needed for meeting.
Comparative example 6 is the example for being not carried out the mounting proposed in the present invention, is generated curved since self tempering martensite is few
Bent crackle, and indentation defect occurs in skin pass rolling due to there is residual water inside lath, surface quality becomes
Difference.
Excessive AlN, BN etc. is precipitated since batten lip temperature is low in comparative example 7 and 8, and high-temperature ductility reduces, therefore produces
Raw edge crack.
The carbon content of comparative example 9 is more than 0.28%, therefore bendability is deteriorated.
Comparative example 10 and 11 does not meet the ingredient proposed in the present invention, therefore tensile strength is deteriorated.
Comparative example 12 to 15 does not meet for controlling the content of Al, Ti, B and N of edge crack in the present invention, therefore produces
Raw edge crack, poor surface quality.
Furthermore it is possible to confirm, the stretching of the ferritic comparative example 2~5,10~12 and 15 of 4.5 area % is comprised more than
Intensity difference.
It is illustrated above by reference to embodiment, still, it will be understood by those skilled in the art that not departing from claim
In the range of the thought and field of the invention recorded in book, the present invention can be carry out various modifications and be changed.
Description of symbols
A: slab b: roll bending
100: conticaster 200: heater
300: roughing scale breaker (Roughing Mill Scale Breaker, RSB)
400: roughing mill
500: finish rolling scale breaker (Finishing Mill Scale Breaker, FSB)
600: finishing mill 700: runout table
800: high-speed cutting machine 900: winder
Claims (19)
1. a kind of ultrahigh strength hot-rolled steel plate of excellent in bending workability,
In terms of weight %, the hot rolled steel plate includes: C:0.18~0.28%, Mn:1.2~2.2%, Si:0.1~0.5%, P:
0.005~0.05%, S:0.01% or less, Al:0.01~0.05%, Ti:0.01~0.10%, B:0.001~0.0045%,
The Fe and inevitable impurity of N:0.001~0.01% and surplus, in terms of area fraction, microstructure includes 90% or more
Martensite, 4~10% self tempering martensite and 5% retained austenite below.
2. the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 1, wherein
In terms of weight %, the hot rolled steel plate is further included: Nb:0.001~0.05%, Cr:0.5~1.0%, Mo:0.001
One or more of~0.05% and Sb:0.005~0.02%.
3. the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 1, wherein
It include one or more of Cu, Ni, Sn and Pb, the residual elements summation as residual elements in the hot rolled steel plate
For 0.2 weight % or less.
4. the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 1, wherein
It is 0.25~0.45 by the Ceq that following relationship 1 defines in the hot rolled steel plate,
Relational expression 1:
Ceq=C+Si/30+Mn/20+2P+3S
In the relational expression 1, each element symbol is the value that each element content is indicated with weight %.
5. the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 1, wherein
The lath short axle spacing of the martensite is 5 μm or less.
6. the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 1, wherein
In terms of area fraction, the microstructure further includes 4.5% ferrite below.
7. the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 1, wherein
The tensile strength of the hot rolled steel plate is 1.8Gpa or more, bendability be 3 hereinafter,
The bendability indicates the minimum bending radius (R) that will not crack after 90 ° of bend test divided by steel plate
The value of thickness (t).
8. the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 1, wherein
The hot rolled steel plate with a thickness of 2.0mm or less.
9. the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 1, wherein
The thickness deviation of the width direction of the hot rolled steel plate is 40 μm or less.
10. a kind of manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability, comprising the following steps:
Molten steel is casting continuously to form to the sheet billet of 60~120mm, in terms of weight %, the molten steel includes: C:0.18~0.28%, Mn:
1.2~2.2%, Si:0.1~0.5%, P:0.005~0.05%, S:0.01% or less, Al:0.01~0.05%, Ti:0.01
~0.10%, the Fe of B:0.001~0.0045%, N:0.001~0.01% and surplus and inevitable impurity；
In roughing outlet side, roughing is carried out to the heated sheet billet so that the edge part temperature of batten reach 850~
1000 DEG C, to obtain batten；
In Ac3+10 DEG C~Ac3+100 DEG C of temperature range, finish rolling is carried out to the batten, to obtain hot rolled steel plate；
The hot rolled steel plate is carried out air-cooled 1~3 second, is then cooled down with 200 DEG C/sec or more of cooling velocity, and in Mf-
50 DEG C or less are wound；And
The rolling hot rolled steel plate is positioned between other two rolling hot rolled steel plates,
And each step continuously performs.
11. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, wherein
The continuous casting step is executed using the covering slag that basicity is 1.0 or more.
12. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, wherein
The casting speed of the continuous casting is 4~8mpm.
13. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, wherein
The roughing execution is so that the surface temperature in roughing entrance side sheet billet reaches 1000~1200 DEG C.
14. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, further
The following steps are included:
Before the roughing, with the pressure of 100~200bar or more, to the heated sheet billet spray cooling water, with
Scale removal；
After the roughing, the batten is made to pass sequentially through first row and secondary series, with scale removal, the first row with
The pressure injection cooling water of 50~250bar, the secondary series is with the pressure injection cooling water of 100~300bar.
15. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, further
The following steps are included:
At 50~150 DEG C, skin pass rolling is carried out to the hot rolled steel plate of mounting.
16. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, further
The following steps are included:
Pickling processes are carried out to the hot rolled steel plate of mounting, to obtain pickling oiling steel i.e. PO material.
17. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, wherein
In terms of weight %, the molten steel is further included: Nb:0.001~0.05%, Cr:0.5~1.0%, Mo:0.001~
One or more of 0.05% and Sb:0.005~0.02%.
18. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, wherein
In the molten steel, include one or more of Cu, Ni, Sn and Pb, and the residual elements summation as residual elements
For 0.2 weight % or less.
19. the manufacturing method of the ultrahigh strength hot-rolled steel plate of excellent in bending workability according to claim 10, wherein
It is 0.25~0.45 by the Ceq that following relationship 1 defines in the molten steel.
Relational expression 1:
Ceq=C+Si/30+Mn/20+2P+3S
In the relational expression 1, each element symbol is the value that each element content is indicated with weight %.
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| KR20160177802 | 2016-12-23 | ||
| KR10-2016-0177802 | 2016-12-23 | ||
| PCT/KR2017/014891 WO2018117552A1 (en) | 2016-12-23 | 2017-12-15 | Ultra-high strength hot-rolled steel sheet having excellent bending processability and method for manufacturing same |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112522580A (en) * | 2019-09-19 | 2021-03-19 | 宝山钢铁股份有限公司 | Martensitic steel strip and manufacturing method thereof |
| CN112846115A (en) * | 2020-12-31 | 2021-05-28 | 浦项(张家港)不锈钢股份有限公司 | Smelting and casting process of titanium-chromium-nickel-containing semi-austenite precipitation hardening stainless steel |
| CN114196874A (en) * | 2020-09-18 | 2022-03-18 | 宝山钢铁股份有限公司 | 1000MPa cold-rolled super-strong steel tensile sample and manufacturing method thereof |
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Also Published As
| Publication number | Publication date |
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| CN110100030B (en) | 2021-04-20 |
| KR20190095459A (en) | 2019-08-14 |
| WO2018117552A1 (en) | 2018-06-28 |
| KR102209592B1 (en) | 2021-01-29 |
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