CN109837459A - The manufacturing method of high-strength steel strip - Google Patents
The manufacturing method of high-strength steel strip Download PDFInfo
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- CN109837459A CN109837459A CN201811416000.4A CN201811416000A CN109837459A CN 109837459 A CN109837459 A CN 109837459A CN 201811416000 A CN201811416000 A CN 201811416000A CN 109837459 A CN109837459 A CN 109837459A
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- hot
- polygonal ferrite
- retained austenite
- steel
- sheet
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 143
- 239000010959 steel Substances 0.000 title claims abstract description 143
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 68
- 230000000717 retained effect Effects 0.000 claims abstract description 54
- 229910001568 polygonal ferrite Inorganic materials 0.000 claims abstract description 53
- 238000000137 annealing Methods 0.000 claims abstract description 48
- 238000000034 method Methods 0.000 claims abstract description 34
- 239000002245 particle Substances 0.000 claims abstract description 34
- 230000009466 transformation Effects 0.000 claims abstract description 26
- 238000010438 heat treatment Methods 0.000 claims abstract description 23
- 229910000734 martensite Inorganic materials 0.000 claims description 39
- 238000005096 rolling process Methods 0.000 claims description 34
- 230000008569 process Effects 0.000 claims description 26
- 238000001953 recrystallisation Methods 0.000 claims description 24
- 238000005098 hot rolling Methods 0.000 claims description 21
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 19
- 230000009467 reduction Effects 0.000 claims description 15
- 230000002829 reductive effect Effects 0.000 claims description 15
- 238000005097 cold rolling Methods 0.000 claims description 11
- 238000005554 pickling Methods 0.000 claims description 10
- 229910052750 molybdenum Inorganic materials 0.000 claims description 8
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- 229910052720 vanadium Inorganic materials 0.000 claims description 6
- 229910052787 antimony Inorganic materials 0.000 claims description 5
- 229910052804 chromium Inorganic materials 0.000 claims description 5
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 230000036961 partial effect Effects 0.000 claims description 4
- 229910052715 tantalum Inorganic materials 0.000 claims description 4
- 229910052718 tin Inorganic materials 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 2
- 238000000265 homogenisation Methods 0.000 abstract description 3
- 239000000523 sample Substances 0.000 description 27
- 229910000859 α-Fe Inorganic materials 0.000 description 23
- 230000000694 effects Effects 0.000 description 14
- 238000012360 testing method Methods 0.000 description 14
- 239000013078 crystal Substances 0.000 description 13
- 230000000996 additive effect Effects 0.000 description 9
- 239000000284 extract Substances 0.000 description 9
- 230000006866 deterioration Effects 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 230000000007 visual effect Effects 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 6
- 238000012545 processing Methods 0.000 description 6
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 5
- 238000001887 electron backscatter diffraction Methods 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 5
- 238000007747 plating Methods 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 229910052725 zinc Inorganic materials 0.000 description 5
- 239000011701 zinc Substances 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 238000005266 casting Methods 0.000 description 4
- 229910001567 cementite Inorganic materials 0.000 description 4
- 238000005336 cracking Methods 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 230000008520 organization Effects 0.000 description 4
- 229910001562 pearlite Inorganic materials 0.000 description 4
- 229910052761 rare earth metal Inorganic materials 0.000 description 4
- 238000005204 segregation Methods 0.000 description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 3
- 239000010960 cold rolled steel Substances 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 3
- 229910052758 niobium Inorganic materials 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 238000004881 precipitation hardening Methods 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 229910001335 Galvanized steel Inorganic materials 0.000 description 2
- 208000037656 Respiratory Sounds Diseases 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 235000013399 edible fruits Nutrition 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000008397 galvanized steel Substances 0.000 description 2
- 238000005246 galvanizing Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 238000007788 roughening Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910001047 Hard ferrite Inorganic materials 0.000 description 1
- 206010040844 Skin exfoliation Diseases 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000005260 alpha ray Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 150000001722 carbon compounds Chemical class 0.000 description 1
- -1 cementite Compound Chemical class 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004453 electron probe microanalysis Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000010813 municipal solid waste Substances 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
-
- 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
-
- 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
- C21D8/0236—Cold rolling
-
- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
-
- 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
-
- 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
-
- 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
- C21D2211/001—Austenite
-
- 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
-
- 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
Abstract
The present invention provides the method that one kind can steadily manufacture the high-strength steel strip that TS >=980MPa, YR >=68%, TS × EL >=22000MPa% mouldability are excellent in volume overall length.When manufacturing high-strength steel strip, using batch kiln, by the outer volume portion of hot-rolled sheet coil with (Ac1+ 20 DEG C of transformation temperature)~(Ac1+ 120 DEG C of transformation temperature) predetermined temperature remain above 21600s and for 129600s condition below, carry out the heating of hot-rolled sheet coil.Thus, the homogenization of structure of steel is realized in volume overall length, and, in the longitudinal direction of manufactured high-strength steel strip, the position in the involute portion of hot-roll annealing coiled sheet will be belonged to as the 1st position, the position in the outer volume portion of hot-roll annealing coiled sheet will be belonged to as the 2nd position, make the area ratio 1.00~1.50 of the area ratio/the 2nd position polygonal ferrite of the polygonal ferrite at the 1st position, the volume fraction of the volume fraction of the retained austenite at the 1st position/the 2nd position retained austenite is 0.75~1.00, the average crystallite particle diameter of the average crystallite particle diameter of the polygonal ferrite at the 1st position/the 2nd position polygonal ferrite is 1.00~1.50.
Description
Technical field
The present invention relates to the manufacturing methods of high-strength steel strip, especially stably obtain be adapted to provide for as automobile,
The mouldability of the purposes for the component that the industrial fields such as electrical equipment use is excellent and has the steel band of high yield ratio.
Background technique
In recent years, from the foothold for environment of preserving our planet, the raising of the fuel economy of automobile becomes important
Project.Therefore, it is thinning by the high intensity of car body materials to realize, the light-weighted trend of car body itself is made to become increasingly living
Jump.
It is however generally that the high intensity of steel plate will lead to the reduction of mouldability, therefore the steel if realizing high intensity
The problems such as mouldability of plate reduces, and generates crackle when molding.Therefore, it is impossible to simply implement being thinning for steel plate.
So, there has long been a desire for that developing the material for having both high-intensitive and high-mouldability.Moreover, being for tensile strength (TS)
The steel plate of 980MPa or more also specially requires impact absorbing energy characteristic such greatly other than the high-mouldability.For improving
Impact absorbing energy, it is effective for improving yield ratio (YR).This is because if yield ratio is high steel plate can be made with low deflection
Efficiently absorb impact energy.
For example, proposing in patent document 1, tensile strength is 1000MPa or more and percentage of total elongation (EL) is 30% or more
, be utilized retained austenite processing induced transformation the high-strength steel sheet with high ductility.
In addition, being proposed in patent document 2 using high Mn steel and by carrying out in ferrite and austenite this 2 phase regions
It is heat-treated and manufactures the high-strength steel sheet of the balancing good of intensity and ductility.Existing technical literature
Patent document
Patent document 1: Japanese Unexamined Patent Application 61-157625 bulletin
Patent document 2:WO2016/067626A1 bulletin
Summary of the invention
Steel plate documented by patent document 1 be by after making with the steel plate austenitizing of C, Si and Mn basis,
Isothermal holding, so-called means of isothermal quenching is carried out in the quenching of bainitic transformation temperature region and is manufactured.In turn, in reality
When applying the means of isothermal quenching, retained austenite is generated since C is enriched with to austenite.However, a large amount of remaining in order to obtain
Austenite, need be more than 0.3% a large amount of C, and more than 0.3% as in C concentration, the reduction of spot weldability is significant, it is difficult to
As automotive sheet functionization.
In addition, patent document 2 is to be annealed by 2 phase regions to control phase fraction, the partial size of ferrite and austenite, and control
C and Mn amount in austenite phase, to be successfully formed to the epoch-making of the effective retained austenite phase of strain-induced transformation
Invention.However, especially being incited somebody to action in use batch kiln in practice in the steel plate of manufacture scene patent document 2 to be manufactured
When hot-rolled sheet coil is heated to specified temperature, the temperature for rolling up immediate vicinity is not easy to rise, and is unable to reach specified temperature, therefore,
The involute portion of hot-roll annealing coiled sheet after intermittent heating, is unable to get destination organization, generates characteristic in the longitudinal direction of volume
Deviation and occur yield rate be deteriorated the problem of.
The present invention is to the invention that invention is improved documented by above patent document 2, and its purpose is to provide one
Even if kind using batch kiln heating hot-rolled sheet coil in the case where, also can volume overall length steadily manufacture TS >=
The method of the excellent high-strength steel strip of 980MPa, YR >=68%, TS × EL >=22000MPa% mouldability.
The present inventor etc. in order to realize the above subject, in order to volume overall length on steadily being manufactured property it is excellent and
High-strength steel strip with high yield ratio and tensile strength, to the manufacturing method of steel plate especially in batch kiln
Further investigation has been repeated in heating condition.Its result has obtained following opinion: by with by the outer volume portion of hot rolled coil with (Ac1
+ 20 DEG C of transformation temperature)~(Ac1+ 120 DEG C of transformation temperature) predetermined temperature remain above 21600s and for the 129600s time below
Condition carry out batch kiln in hot rolled plate annealing operation, it may be advantageous to realize desired purpose.The present invention is base
It is completed in above-mentioned opinion.
That is, purport composition of the invention is as follows.
[1] a kind of manufacturing method of high-strength steel strip, which is characterized in that there is following process:
By the process of heating steel billet to 1100 DEG C~1300 DEG C, the steel billet has as follows at being grouped as: in terms of quality %
Containing C:0.030%~0.250%, Si:0.01%~3.00%, Mn: greater than 4.20% and it is 6.00% or less, P:
0.001%~0.100%, S:0.0001%~0.0200%, N:0.0005%~0.0100%, Al:0.010%~
2.000% and Ti:0.005%~0.200%, and remainder is made of Fe and inevitable impurity；
The process that above-mentioned steel billet is obtained into hot rolled plate with 750 DEG C~1000 DEG C of finish rolling outlet side temperature progress hot rollings；
By above-mentioned hot rolled plate with 300 DEG C~750 DEG C processes batched and hot-rolled sheet coil is made of coiling temperature；
Next, implementing pickling to the hot rolled plate of above-mentioned hot-rolled sheet coil and except the process of descale；
Above-mentioned hot-rolled sheet coil is heated in batch kiln, the hot rolled plate annealing of hot-roll annealing coiled sheet is made
Process；
Thereafter, by the hot-roll annealing plate of above-mentioned hot-roll annealing coiled sheet with 50% or less reduction ratio carries out cold rolling and obtains cold rolling
The process of plate；And
Thereafter, by above-mentioned cold-reduced sheet with Ac1Transformation temperature~(Ac1+ 100 DEG C of transformation temperature) predetermined temperature keep 20 seconds~900
Second, it cools down thereafter and carries out cold-reduced sheet annealing, the process for obtaining high-strength steel strip,
It wherein, is with by the outer volume portion of above-mentioned hot-rolled sheet coil in the hot rolled plate annealing operation that above-mentioned batch kiln carries out
With (Ac1+ 20 DEG C of transformation temperature)~(Ac1+ 120 DEG C of transformation temperature) predetermined temperature be remained above 21600 seconds and for 129600 seconds or less
Condition carry out,
In the longitudinal direction of above-mentioned high-strength steel strip, will belong to the position in the involute portion of above-mentioned hot-roll annealing coiled sheet as
1st position will belong to the position in the outer volume portion of above-mentioned hot-roll annealing coiled sheet as the 2nd position, will belong to above-mentioned hot-roll annealing plate
The position of the central portion of volume as the 3rd position,
The structure of steel at above-mentioned 3rd position contains polygonal ferrite in terms of the area ratio: 15%~55%, non-recrystallization iron element
Body: 8% or more, martensite: 15%~30%, contain retained austenite in terms of volume fraction: 12% or more,
Moreover, the face of the area ratio of the polygonal ferrite at above-mentioned 1st position/above-mentioned 2nd position polygonal ferrite
Product rate is 1.00~1.50, the body of volume fraction/above-mentioned 2nd position retained austenite of the retained austenite at above-mentioned 1st position
Product rate is 0.75~1.00,
Also, in above-mentioned 3rd position, the average crystallite particle diameter of polygonal ferrite is 4.0 μm hereinafter, martensite is averaged
Crystallization particle diameter be 2.0 μm hereinafter, the average crystallite particle diameter of retained austenite be 2.0 μm hereinafter,
Moreover, the average crystallite particle diameter of the polygonal ferrite at above-mentioned 1st position/above-mentioned 2nd position polygon iron is plain
The average crystallite particle diameter of body is 1.00~1.50,
Moreover, the Mn amount (quality %) in retained austenite is divided by the Mn in polygonal ferrite in above-mentioned 3rd position
Measuring value obtained by (quality %) is 2.00 or more.
[2] manufacturing method of the high-strength steel strip according to above-mentioned [1], which is characterized in that mentioned component is formed with matter
Measure % meter further containing selected from Nb:0.005%~0.200%, B:0.0003%~0.0050%, Ni:0.005%~
1.000%, Cr:0.005%~1.000%, V:0.005%~0.500%, Mo:0.005%~1.000%, Cu:0.005%
~1.000%, Sn:0.002%~0.200%, Sb:0.002%~0.200%, Ta:0.001%~0.010%, Ca:
0.0005%~0.0050%, at least one kind of member in Mg:0.0005%~0.0050% and REM:0.0005%~0.0050%
Element.
In accordance with the invention it is possible to volume overall length on stably obtain TS >=980MPa, YR >=68%, TS × EL >=
The excellent high-strength steel strip of the mouldability of 22000MPa%.Therefore, by answering high-strength steel strip made according to the present invention
For such as automotive structural members, so as to realize the improvement of the light-weighted fuel economy based on car body, therefore, industry
On utility value it is very big.
Specific embodiment
(at being grouped as)
Firstly, in the present invention, it is illustrated to by steel band at being grouped as the reasons why being limited to above range.It should say
It is bright, steel, blank the symbol at % involved in being grouped as indicate quality %.In addition, steel band at the remainder being grouped as
For Fe and inevitable impurity.
C:0.030%~0.250%
C is to generate the low-temperature phases such as martensite and in a disguised form intensity is made to rise necessary element.In addition, and to raising
The stability of retained austenite improves the effective element of ductility of steel.Here, when C amount is less than 0.030%, it is difficult to ensure institute
The martensite volume needed, is unable to get required intensity.Further, it is difficult to ensure sufficient remained austenite content, it is unable to get good
Ductility.On the other hand, if excessively adding C more than 0.250%, the martensite volume of hard becomes excessive, in geneva
The crystal boundary Micro-v oid of body increases, and the propagation being cracked, bendability, stretch flange are easy in bend test and hole expansion test
It reduces.In addition, the excessive addition of C makes the hardening of weld part and heat affected zone become significant, reduce the mechanical property of weld part,
Therefore the deterioration such as spot weldability, arc welding.By these viewpoints, C amount is set as 0.030%~0.250% range.Preferably
0.080%~0.200% range.
Si:0.01%~3.00%
Si improves ferritic work hardening capacity, therefore is to ensuring the effective element of good ductility.If Si
For amount less than 0.01%, then its additive effect becomes insufficient, therefore lower limit is set as 0.01%.On the other hand, the Si more than 3.00%
Excessive addition not only cause the embrittlement of steel, but also cause the deterioration of surface texture due to the generation of red rust etc..Therefore, Si
Amount is set as 0.01%~3.00% range.Preferably 0.20%~2.00% range.
Mn: greater than 4.20% and be 6.00% or less
Mn is extremely important element in the present invention.Mn is to make the stabilized element of retained austenite, good to ensuring
Ductility it is effective.Moreover, Mn is also the element that increase the intensity of steel.In addition, passing through remnants
Mn enrichment in austenite, it can be ensured that 2% or more the ε phase with hcp structure, moreover, retained austenite can be made with body
Product rate is calculated as 12% or more to be ensured in large quantities in this way.Mn amount of this effect in steel first appears when being more than 4.20%.It is another
Aspect, Mn amount are more than 6.00% excessive the main reason for being added to cost increase.From such a viewpoint, Mn amount is set
For greater than 4.20% and be 6.00% range below.Preferably 4.80%~6.00% range.
P:0.001%~0.100%
P is effective to solution strengthening, is the element that can be added according to required intensity.In addition, and promotion ferrite
Phase transformation, to the effective element of the complex tissueization of steel plate.Such effect in order to obtain, needs to make the P amount in steel plate be
0.001% or more.On the other hand, if P amount is more than 0.100%, it will lead to the deterioration of weldability, and carry out to zinc coat
Make the reduction of alloying speed when Alloying Treatment, damages the quality of zinc coat.Therefore, P amount is 0.001%~0.100%, preferably
For 0.005%~0.050% range.
S:0.0001%~0.0200%
S makes steel embrittlement in hot-working in cyrystal boundary segregation, and there is and make the part of steel plate in the form of sulfide
Deformability reduces.Therefore, S amount is for 0.0200% hereinafter, preferably 0.0100% hereinafter, more preferably 0.0050% or less.
But consider from the restriction in production technology, making S amount is 0.0001% or more.Therefore, S amount is 0.0001%~0.0200%
Range.Preferably 0.0001%~0.0100%, more preferably 0.0001%~0.0050% range.
N:0.0005%~0.0100%
N is the element for deteriorating the ageing resistance of steel.Especially N amount is more than 0.0100%, then the deterioration of ageing resistance becomes
Significantly.Therefore, the N amount the few the more preferred, but considers from the restriction in production technology, and making N amount is 0.0005% or more.Therefore, N amount
It is 0.0005%~0.0100%, preferably 0.0010%~0.0070% range.
Al:0.010%~2.000%
Al is to expand two phase regions of ferrite and austenite, and the reduction to annealing temperature dependence is stable material quality
Improve effective element.In addition, Al also plays a role as deoxidier, to the effective element of the maintenance of the cleannes of steel.However,
If Al amount, less than 0.010%, additive effect becomes insufficient, therefore makes lower limit 0.010%.On the other hand, more than 2.000%
The risk that generates of steel disc crackle of a large amount of addition when can improve continuously casting, reduce manufacturing.From such viewpoint
It sets out, the range that Al amount when addition is 0.010%~2.000%.Preferably 0.200%~1.200% range.
Ti:0.005%~0.200%
Ti is addition element important in the present invention.Ti is not only effective to the precipitation-hardening of steel, and ensure it is required not
Recrystallization ferrite content and contribute effectively to the high yield ratioization of steel plate.In addition, by utilizing the non-recrystallization for comparing hard
Ferrite can also reduce the difference of hardness with the 2nd phase of hard (martensite or retained austenite), facilitate stretch flange
It improves.Also, these effects are obtained by the addition that Ti amount is 0.005% or more.On the other hand, if the Ti amount in steel plate is super
0.200% is crossed, then the martensite volume of hard becomes excessive, increases in the Micro-v oid of the crystal boundary of martensite, in bend test and expansion
The propagation that hole is cracked when testing is easy to carry out, and the bendability of steel plate, stretch flange reduce.Therefore, the additive amount of Ti is
0.005%~0.200% range.Preferably 0.010%~0.100% range.
More than, essential component is illustrated, it still, in the present invention, in addition to this, can also be suitably containing following
The element.
Nb:0.005%~0.200%
Nb is effective to the precipitation-hardening of steel, and additive effect is obtained at 0.005% or more.In addition, the effect with Ti addition
Fruit similarly ensures required non-recrystallization ferrite content and facilitates the high yield ratioization of steel plate.In addition, being compared by utilizing
The non-recrystallization ferrite of hard, it is possible to reduce the difference of hardness with the 2nd phase of hard (martensite or retained austenite) also helps
In the raising of stretch flange.On the other hand, if Nb amount is more than 0.200%, the martensite volume of hard becomes excessive, in geneva
The Micro-v oid of the crystal boundary of body increases, and the propagation being cracked in bend test and when hole expansion test is easy to carry out.As a result, steel plate
Bendability, stretch flange reduce.In addition, the main reason for also becoming cost.Therefore, it when adding Nb, is set as
0.005%~0.200% range.Preferably 0.010%~0.100% range.
B:0.0003%~0.0050%
B, which has, to be inhibited to generate from austenite grain boundary and grows ferritic effect, and flexible tissue control is able to carry out
System, therefore can according to need and be added.Its additive effect is obtained at 0.0003% or more.On the other hand, if B amount is more than
0.0050%, then the mouldability of steel plate reduces.Therefore, when adding B, it is set as 0.0003%~0.0050% range.It is preferred that
For 0.0005%~0.0030% range.
Ni:0.005%~1.000%
Ni is to make the stabilized element of retained austenite, to ensuring that good ductility is effective, moreover, being strong by being dissolved
The element changed and increase the intensity of steel.Its additive effect is obtained at 0.005% or more.On the other hand, if addition is more than
1.000%, then the martensite volume of hard becomes excessive, increases in the crystal boundary Micro-v oid of martensite, bend test and hole expansion test
The propagation that Shi Rongyi is cracked.As a result, the bendability of steel plate, stretch flange reduce.In addition, and cost master
Want reason.Therefore, when adding Ni, it is set as 0.005%~1.000% range.
Cr:0.005%~1.000%, V:0.005%~0.500%, Mo:0.005%~1.000%
Cr, V and Mo improve the balance of intensity and ductility due to having the function of, can according to need and are added
Add.Its additive effect is obtained in Cr:0.005% or more, V:0.005% or more and Mo:0.005% or more.On the other hand, if
Making Cr be more than 1.000%, V respectively is more than that 0.500% and Mo is more than 1.000% and excessively adds, then the martensite of hard
Quantitative change is too much, is easy the propagation being cracked in the crystal boundary Micro-v oid increase of martensite, bend test and hole expansion test.Its
As a result, the bendability of steel plate, stretch flange reduce.In addition, the main reason for also becoming cost increase.Therefore, this is being added
When a little elements, it is set to Cr:0.005%~1.000%, V:0.005%~0.500% and Mo:0.005%~1.000%
Range.
Cu:0.005%~1.000%
Cu is the effective element of reinforcing to steel.Its additive effect is obtained at 0.005% or more.On the other hand, if adding
Add more than 1.000%, then the martensite volume of hard becomes excessive, increase in the crystal boundary Micro-v oid of martensite, in bend test and
The propagation being cracked is easy when hole expansion test.As a result, the bendability of steel plate, stretch flange reduce.Therefore, in addition Cu
When, it is set as 0.005%~1.000% range.
Sn:0.002%~0.200%, Sb:0.002%~0.200%
From tens μm or so of thickness area for inhibiting the steel plate surface layer generated by the nitridation of surface of steel plate and oxidation
From the perspective of decarburization, Sn and Sb can be added as needed.In this way, surface of steel plate can be prevented by inhibiting nitridation and oxidation
Martensite volume is reduced, to ensuring that TS, stable material quality are effective.The effect in order to obtain needs to add 0.002% or more respectively.
On the other hand, if excessively addition will lead to the reduction of toughness more than 0.200%.Therefore, it when adding Sn, Sb, sets respectively
For 0.002%~0.200% range.
Ta:0.001%~0.010%
Such as Ti, Nb, Ta also generates alloy carbide and alloy carbonitride and facilitates the high intensity of steel.In addition,
It also has the effect that a part is solid-solution in Nb carbide and Nb carbonitride, generates compound as (Nb, Ta) (C, N)
Precipitate stabilizes the raising of the intensity of the steel plate based on precipitation-hardening to inhibit the coarsening of precipitate.Here, Ta
Additive effect is obtained and making 0.001% or more content of Ta.On the other hand, even if excessively adding Ta, addition effect
Fruit is also saturated, and cost of alloy also increases.Therefore, when adding Ta, it is set as 0.001%~0.010% range.
Ca:0.0005%~0.0050%, Mg:0.0005%~0.0050%, REM:0.0005%~0.0050%
Ca, Mg and REM are to improve sulfide to hole expandability (stretch flange to and making the Form Sphere of sulfide
Property) the effective element of adverse effect.The effect in order to obtain needs to add 0.0005% or more respectively.On the other hand, respectively
Excessive addition more than 0.0050% can cause the increase of field trash etc., cause surface and internal flaw of steel plate etc..Therefore,
When adding Ca, Mg and REM, it is set to 0.0005%~0.0050% range.
(structure of steel)
In the present invention, by suitably controlling the heating condition in batch kiln, asked so as to improve in previous become
The deviation of tissue and characteristic in the longitudinal direction of the volume of topic.Here, in this specification, in the length of manufactured high-strength steel strip
On edge direction, the position for belonging to the involute portion of hot-roll annealing coiled sheet is known as the 1st position, the outer volume of hot-roll annealing coiled sheet will be belonged to
The position in portion is known as the 2nd position, and the position for belonging to the central portion of hot-roll annealing coiled sheet is known as the 3rd position.Here, " hot rolling is moved back
The involute portion of fiery coiled sheet " refers to the range from the end of the inside of hot-roll annealing coiled sheet until in longitudinal direction 150m." hot rolling
The outer volume portion of annealing coiled sheet " refers to the range from the end in the outside of hot-roll annealing coiled sheet until in longitudinal direction 150m." heat
Roll annealing coiled sheet central portion " refer to hot-roll annealing coiled sheet involute portion and the position other than outer volume portion.
In the present invention, the index of the deviation as tissue, using the area ratio/the of the polygonal ferrite at the 1st position (A)
The area ratio of the polygonal ferrite at 2 positions, the 1st position (B) retained austenite volume fraction/the 2nd position residual austenite
Average crystallite particle diameter/the 2nd position polygonal ferrite of the volume fraction of body and the polygonal ferrite at the 1st position (C)
They are defined as defined range by average crystallite particle diameter this 3.By by these than control in range as described below, from
And improve the characteristic deviation in previous problematic volume longitudinal direction, the especially characteristic in hot-roll annealing coiled sheet curls inward portion
Deterioration obtains not having excellent characteristic devious in volume overall length.
The area ratio of the polygonal ferrite at the 3rd position (central portion): 15%~55%
In order to ensure sufficient ductility, in present invention, it is desirable to making the area ratio of the polygonal ferrite at the 3rd position
15% or more.On the other hand, it in order to ensure the intensity of 980MPa or more, needs the area of the polygonal ferrite at the 3rd position
Rate inhibits below 55%.It is preferred that being calculated as 20%~50% range with the area ratio.In addition, being not only the 3rd in the present invention
Position, and the area ratio of the polygonal ferrite in the 1st position (involute portion) and the 2nd position (outer volume portion) be preferably also 15%~
55%, more preferably 20%~50%.It should be noted that the polygonal ferrite in the present invention refers to more soft and is imbued with extension
The ferrite of property.
The index (A) of tissue deflection
The area ratio ratio (involute portion/outer volume portion) of polygonal ferrite: 1.00~1.50
Also, for the area ratio of the polygonal ferrite, by making the 1st position (involute portion)/the 2nd position (outer volume portion)
Ratio be that can be obtained between 1.00~1.50 and do not have the steel band of individual deviation, high yield rate in volume overall length.Preferably 1.00
~1.20 range.
The ferritic the area ratio of non-recrystallization at the 3rd position (central portion): 8% or more
In the present invention it is important that the ferritic the area ratio of non-recrystallization is 8% or more.Although here, non-recrystallization iron
Ferritic generally rises effectively the intensity of steel plate, but will lead to the significant ductility reduction of steel plate, thus mostly when subtracted
It is few.But in the present invention, by ensuring good ductility using polygonal ferrite and retained austenite, also, actively
Ground utilize harder matter non-recrystallization ferrite, without for example in terms of the area ratio more than 30% as a large amount of geneva
Body ensures that the TS of desired steel plate, moreover, reducing the biphase interface amount of polygonal ferrite and martensite, therefore
It can be improved yield strength (YP), the yield ratio (YR) of steel plate.Above effect in order to obtain, needs to make non-recrystallization ferrite
The area ratio be 8% or more.Preferably 10% or more.It should be noted that the non-recrystallization ferrite in the present invention refers in crystal grain
The interior ferrite containing less than poor 15 ° of the strain of crystalline orientation, is than the above-mentioned polygonal ferrite hard for being imbued with ductility
Ferrite.In addition, the upper limit of the ferritic the area ratio of non-recrystallization is not particularly limited in the present invention, preferably 20% or so.
The area ratio of the martensite at the 3rd position (central portion): 15%~30%
In order to realize the TS of 980MPa or more, need to make 15% or more the area ratio of the martensite at the 3rd position.Another party
Face needs the area ratio by the martensite at the 3rd position to be limited in 30% or less in order to ensure good ductility.
In addition, for the area ratio of the martensite, preferably the 1st position (involute portion)/the 2nd position (outer volume portion) ratio is
1.00~1.30, the steel band for not having individual deviation, high yield rate in volume overall length can be obtained as a result,.
Here, the calculating of the area ratio of martensite can carry out in the following way.That is, being with the 3rd position (central portion)
It represents, in the rolling direction, sample is extracted in the middle position of front end and tail end from steel band, on board width direction, from
Board width central part extracts sample and uses 3vol.% after grinding the plate thickness section (L section) parallel with rolling direction of the sample
Nital corrosion (is equivalent to from surface of steel plate in 1/4 position that depth direction is plate thickness) 1/4 position of plate thickness
The visual field for being observed 40 μm of 50 μ m in 10 visuals field or so with 2000 times of multiplying power using SEM (the microcosmic mirror of scanning electron), is obtained
Organization chart picture.In the organization chart picture, the tissue (substrate of grey is presented in ferrite (polygonal ferrite and non-recrystallization ferrite)
Both tissue), martensite is presented the tissue of white, therefore can identify.Based on the obtained organization chart picture, Media is used
The Image-Pro of Cybernetics company calculates the area ratio of the martensite in 10 visuals field, averagely these the area ratios and finds out.
In addition, polygonal ferrite and the ferritic the area ratio of non-recrystallization can be found out in the following way.That is, from rear
Sample is extracted in the specified position stated, and 1/4 position of plate thickness of the plate thickness section (L section) parallel with rolling direction of the sample is supplied
It is observed in EBSD below.Use EBSD (Electron BackScatter Diffraction；Electron ray backscattering is spread out
Penetrate method) identify the poor wide-angle crystalline substance for being 15 ° or more of poor 2 ° of crystalline orientation or more low-angle boundary, the crystalline orientations arrived less than 15 °
Boundary.Then, using the ferrite for containing low-angle boundary in crystal grain as non-recrystallization ferrite, IQ Map is made.Then, from system
At IQ Map 10 visuals field are extracted with 40 μm of 50 μ m of the visual field after, find out the face of low-angle boundary and high-angle boundary respectively
Product, to calculate polygonal ferrite and the ferritic area of non-recrystallization respectively, find out 10 visuals field polygonal ferrite and
The ferritic the area ratio of non-recrystallization.Then, these average the area ratios find out above-mentioned polygonal ferrite and non-recrystallization iron element
The area ratio of body.In the ferritic the area ratio of the polygonal ferrite and non-recrystallization that find out the 3rd position (central portion), represent
Central portion, in the rolling direction, the middle position of front end and tail end from steel band extract above-mentioned sample, in board width direction
On, above-mentioned sample is extracted from board width central part.In the polygon for finding out the 1st position (involute portion) and the 2nd position (outer volume portion)
When ferrite and the ferritic the area ratio of non-recrystallization, each position is represented, in the rolling direction, from the 1st position side of steel band
The position of end 100m and the position of end 100m from the 2nd position side extract above-mentioned sample, on board width direction, from plate
Extract above-mentioned sample in widthwise central portion.
The volume fraction of retained austenite in 3rd position (central portion): 12% or more
In the present invention, in order to ensure sufficient ductility, need to make the volume fraction 12% of the retained austenite at the 3rd position
More than.Preferably 14% or more.In addition, the upper limit of the volume fraction of the retained austenite at the 3rd position does not limit especially in the present invention
System, but since the retained austenite thin and unstable at separating/enriching of C, the Mn small to the effect for improving ductility etc. increase,
Therefore it is preferably set to 50% or so.
The index (B) of tissue deflection
The volume fraction ratio (involute portion/outer volume portion) of retained austenite: 0.75~1.00
Moreover, for the volume fraction of retained austenite, it is important that by the 1st position (involute portion)/the 2nd position (outer volume portion)
Ratio control between 0.75~1.00, can be obtained do not have the steel band of individual deviation, high yield rate in volume overall length as a result,.
Here, the volume fraction of retained austenite is by the way that the sample extracted from aftermentioned specified position is ground to plate thickness side
To 1/4 face (be equivalent to from surface of steel plate depth direction be plate thickness 1/4 face), the diffraction X in 1/4 face of plate thickness is penetrated
Line intensity is measured and finds out.Incident X-rays use MoK alpha ray, find out { 111 } of retained austenite, { 200 },
{ 220 }, the integrated intensity at the peak in { 311 } face relative to ferritic { 110 }, { 200 }, { 211 } face peak integrated intensity
The intensity ratio of all 12 kinds of combinations, using their average value as the volume fraction of retained austenite.Finding out the 3rd position (center
Portion) retained austenite volume fraction when, central portion is represented, in the rolling direction, from the front end and tail end of steel band
Between position extract above-mentioned sample, on board width direction, extract above-mentioned sample from board width central part.Finding out, the 1st position is (interior
Volume portion) and the 2nd position (outer volume portion) retained austenite volume fraction when, each position is represented, in the rolling direction, from steel band
Above-mentioned sample is extracted in the position of the end 100m at the 1st position side and the position of the end 100m from the 2nd position side, in board width side
Upwards, above-mentioned sample is extracted from board width central part.
The average crystallite particle diameter of the polygonal ferrite at the 3rd position (central portion): 4.0 μm or less
The miniaturization of the crystal grain of polygonal ferrite facilitates the raising of YP, TS.Therefore, in order to ensure high YP and height
YR and required TS, need to make 4.0 μm of average crystallite particle diameter of the polygonal ferrite at the 3rd position or less.Preferably
3.0 μm or less.In addition, the lower limit of the average crystallite particle diameter of the polygonal ferrite at the 3rd position does not limit especially in the present invention
System, industrially preferably 0.2 μm or so.In addition, in the present invention, be not only the 3rd position, and the 1st position (involute portion) and
The average crystallite particle diameter of the polygonal ferrite at the 2nd position (outer volume portion) be preferably also 4.0 μm hereinafter, more preferably 3.0 μm with
Under, more preferably 0.2 μm or so or more.
The index (C) of tissue deflection
The average crystallite particle diameter ratio (involute portion/outer volume portion) of polygonal ferrite: 1.00~1.50
Also, for the average crystallite particle diameter of polygonal ferrite, need the 1st position (involute portion)/the 2nd position is (outer
Volume portion) ratio control between 1.00~1.50, can be obtained do not have individual deviation, high yield rate in volume overall length as a result,
Steel band.
The average crystallite particle diameter of the martensite at the 3rd position (central portion): 2.0 μm or less
The miniaturization of the crystal grain of martensite facilitates the raising of bendability and stretch flange (hole expandability).Therefore, it is
Ensure high bendability, high stretch flange (high hole expandability), needs to inhibit the average crystallite particle diameter of the martensite at the 3rd position
At 2.0 μm or less.Preferably 1.5 μm or less.In addition, in the present invention, the lower limit of the average crystallite particle diameter of the martensite at the 3rd position
It is not particularly limited, industrial preferably 0.05 μm or so.
The average crystallite particle diameter of the retained austenite at the 3rd position (central portion): 2.0 μm or less
The miniaturization of the crystal grain of retained austenite facilitates the raising of ductility and bendability and stretch flange (expand
Permeability) raising.Therefore, it in order to ensure good ductility, bendability, stretch flange (hole expandability), needs to make the 3rd position
Retained austenite average crystallite particle diameter be 2.0 μm or less.Preferably 1.5 μm or less.In addition, in the present invention, the 3rd position
The lower limit of the average crystallite particle diameter of retained austenite is not particularly limited, and industrial preferably 0.05 μm or so.
In addition, polygonal ferrite, martensite and the average crystallite particle diameter of retained austenite can be asked in the following way
Out.That is, sample is extracted from aftermentioned specified position, by the plate of the parallel plate thickness section of the rolling direction in the sample (L section)
Thick 1/4 position is for observation below.Using above-mentioned Image-Pro, polygon iron is found out with 50 μ m, 40 μm of 1 visual field
Each area of ferritic grain, martensite grain and retained austenite grain calculates equivalent diameter, each particle in the average visual field
Partial size and find out.It should be noted that martensite and retained austenite are identified with the Phase Map of EBSD.In addition, of the invention
In, when finding out above-mentioned average crystallite particle diameter, measure the sample of 0.01 μm or more of partial size.This is because less than 0.01 μm
Sample does not impact the present invention.When finding out the average crystallite particle diameter of each phase at the 3rd position (central portion), center is represented
Portion, in the rolling direction, the middle position of front end and tail end from steel band extract above-mentioned sample, on board width direction,
Above-mentioned sample is extracted from board width central part.In the polygon iron element for finding out the 1st position (involute portion) and the 2nd position (outer volume portion)
When the average crystallite particle diameter of body, each position is represented, in the rolling direction, from the position of the end 100m of the 1st position side of steel band
Above-mentioned sample is extracted with the position of the end 100m from the 2nd position side, on board width direction, from the extraction of board width central part
State sample.
In 3rd position (central portion) by the Mn amount (quality %) in retained austenite divided by the Mn in polygonal ferrite
It measures and is worth obtained by (quality %): 2.00 or more
Be extremely important that in the 3rd position in the present invention, make by the Mn amount (quality %) in retained austenite divided by
Value obtained by Mn amount (quality %) in polygonal ferrite is 2.00 or more.This is because in order to ensure good ductility,
The stable retained austenite for needing to be enriched with Mn increases.In addition, in the present invention, by the Mn amount (quality %) in retained austenite
Divided by value obtained by the Mn amount (quality %) in polygonal ferrite the upper limit there is no limit, from the viewpoint for ensuring stretch flange
It sets out, preferably 16.0 or so.
Mn amount (quality %) in retained austenite and the Mn amount (quality %) in polygonal ferrite can be by as follows
Mode is found out.That is, the representative as the 3rd position (central portion), in the rolling direction, from the front end and tail end of steel band
Between position extract sample, on board width direction, from board width central part extract sample, by the sample for EPMA
(Electron Probe Micro Analyzer；Electron probe micro-analysis instrument) observation, rolled in 1/4 position of plate thickness
The distribution of the Mn of each phase of direction section processed carries out quantification.Then, 30 retained austenite grains and 30 iron elements are analyzed
The Mn amount of body grain.It is then possible to which the Mn amount found out by the result of the analysis is averaged and is found out.
Here, microstructure of the invention other than above-mentioned polygonal ferrite, martensite etc., also has blocky iron
Usually existing carbon in the steel plates such as ferritic, acicular ferrite, bainite ferrite, tempered martensite, pearlite and cementite
Compound (not including the cementite in pearlite).If these tissues are calculated as 10% range below with the area ratio, even if containing
Effect of the invention will not be damaged.
In addition, in the present invention, preferably in terms of the area ratio containing 2% or more the ε phase with hcp structure.Here, largely containing
The steel of ε phase with hcp structure has the risk of embrittlement.However, if as in the present invention by suitable ε with hcp structure
Phase fine dispersion then ensures the flat of good intensity and ductility in ferrite and the ferritic crystal boundary of non-recrystallization and crystal grain
Excellent damping performance is shown while weighing apparatus.
In addition, the Phase Map that EBSD can be used in ε phase, martensite and retained austenite with hcp structure is known
Not.In addition, there is no limit for the upper limit of the area ratio of ε phase, but has a possibility that embrittlement, therefore preferably 35% is left in the present invention
It is right.By meeting above-mentioned condition, can make to belong between processing induced transformation (TRIP) phenomenon for the main reason for improving ductility
Embody the generation that so-called stable retained austenite may be implemented until the processing final stage of steel plate with having a rest.
(manufacturing condition)
The manufacturing method of high-strength steel strip of the invention is with following process: the heating steel billet that will be formed with mentioned component
Process；The process that above-mentioned hot rolling of steel billet is obtained into hot rolled plate；The process that above-mentioned hot rolled plate is batched and hot-rolled sheet coil is made；
Next, implementing pickling to the hot rolled plate of above-mentioned hot-rolled sheet coil and except the process of descale；By above-mentioned hot-rolled sheet coil in interval
Formula heating furnace is heated and is made the hot rolled plate annealing operation of hot-roll annealing coiled sheet；Thereafter, by above-mentioned hot-roll annealing plate
The hot-roll annealing plate cold rolling of volume and the process for obtaining cold-reduced sheet；Thereafter, cold-reduced sheet annealing is implemented to above-mentioned cold-reduced sheet and obtains height
The process of strength steel strips.Hereinafter, being illustrated to manufacturing condition and its restriction reason.
The heating temperature of steel billet: 1100 DEG C~1300 DEG C
In the heating period of steel billet (or being blank), existing precipitate can be with coarse in finally obtained steel plate
Precipitate form exist, intensity is not contributed.Ti, Nb system precipitate being precipitated when therefore, to casting need to carry out again
Melting.Here, not only carbide is difficult to adequately be dissolved, but also can produce when the heating temperature of steel billet is less than 1100 DEG C
Dangerous the problems such as increasing of accident occurs when hot rolling caused by the raw increase because of rolling load.Therefore, the heating temperature of steel billet needs
It to be 1100 DEG C or more.In addition, to blank surface layer bubble, segregation the defects of control, reduce the cracking, recessed of surface of steel plate
It is convex and from the perspective of realizing smooth surface of steel plate, the heating temperature of steel billet is also required to be 1100 DEG C or more.On the other hand, steel
When the heating temperature of base is more than 1300 DEG C, along with the increase of amount of oxidation, oxide skin loss increases.Therefore, the heating temperature of steel billet
Degree needs to be 1300 DEG C or less.Therefore, the heating temperature of blank needs to be 1100 DEG C~1300 DEG C.Preferably 1150 DEG C~1250
DEG C range.
Gross segregation in order to prevent, steel billet are preferably manufactured with continuous casting process, can also pass through ingot casting method, the casting of thin stock material
Method etc. is made to manufacture.In addition, following method can be used in the present invention: after manufacturing steel billet, temporarily it is cooled to room temperature, thereafter, then
Spend the existing method heated.Moreover, in the present invention, can also unquestionably using in the state of not being cooled to room temperature with temperature
The state of piece is packed into heating furnace, or slightly carries out the energy saving works such as the direct sending rolling Direct Rolling rolled immediately after thermal protection
Skill.When laminating base in addition, steel billet passes through roughing system under typical conditions, but heating temperature being set low, from preventing hot rolling
When accident from the perspective of, the further combustion thin plate base such as rod heater is used preferably before finish rolling.
The finish rolling outlet side temperature of hot rolling: 750 DEG C~1000 DEG C
Steel billet after heating, which carries out hot rolling by roughing system and finish rolling, becomes hot rolled plate.At this point, if Finishing temperatures are super
1000 DEG C are crossed, then the production quantity of oxide (oxide skin) increased dramatically, the interface roughness of substrate and oxide, implement pickling, cold
The surface quality of steel plate after rolling has the tendency that deterioration.In addition, partially there is the residue etc. of hot rolling oxide skin after pickling, then
Adverse effect is caused to ductility, the stretch flange of steel plate.Moreover, crystallization particle diameter becomes over coarse sometimes, when processing, is pressed
The surface of product is roughening.On the other hand, when Finishing temperatures are less than 750 DEG C, rolling load increases, and austenite is not being tied again
Reduction ratio under crystalline state is got higher.As a result, the set tissue in steel plate exception is flourishing, the intra-face anisotropy in final product
Become significant, not only the uniformity (stable material quality) of material is impaired, but also the ductility of steel plate also reduces itself.Therefore, originally
Invention needs to make 750 DEG C~1000 DEG C of finish rolling outlet side temperature of hot rolling.Preferably 800 DEG C~950 DEG C of range.
Coiling temperature: 300 DEG C~750 DEG C
Coiling temperature is the average value of the coiling temperature of the hot rolled coil overall length after hot rolling.If the coiling temperature after hot rolling is more than
750 DEG C, then the ferritic crystallization particle diameter of hot rolled plate tissue becomes larger, it is difficult to ensure required intensity.On the other hand, after hot rolling
Coiling temperature less than 300 DEG C when, hot rolling plate strength rises, and the rolling load in cold rolling increases, or generates plate shape not
It is good, therefore productivity reduces.So the coiling temperature after hot rolling needs for 300 DEG C~750 DEG C.Preferably 400 DEG C~650 DEG C
Range.
In addition, in hot rolling, roughing plate can be engaged with each other in the present invention and continuously carry out finish rolling.In addition, can also
Temporarily to batch roughing plate.Moreover, part or all of finish rolling can be set as moistening to reduce rolling load when hot rolling
Sliding rolling.From the viewpoint of the homogenization of plate profile, the homogenization of material, it is also effective for being lubricated rolling.In addition,
Coefficient of friction when lubrication and rolling is preferably 0.10~0.25.
Pickling is carried out to the hot rolled plate of the hot-rolled sheet coil by process manufacture.Since pickling can remove surface of steel plate
Oxide, therefore for ensuring that the good chemical treatability of final product high-strength steel sheet, plating quality are important.This
Outside, pickling can carry out once, being also segmented into multiple progress.
Hot rolled plate annealing: by the outer volume portion of hot-rolled sheet coil with (Ac1+ 20 DEG C of transformation temperature)~(Ac1+ 120 DEG C of transformation temperature) rule
Determine temperature to remain above 21600s and be 129600s or less
In the present invention, the annealing of hot-rolled sheet coil is carried out using batch kiln, at this point, extremely important in the present invention
It is the outer volume portion by hot-rolled sheet coil with (Ac1+ 20 DEG C of transformation temperature)~(Ac1+ 120 DEG C of transformation temperature) predetermined temperature remain above
21600s and be the 129600s time below.The annealing temperature of hot rolled plate annealing is being less than (Ac1+ 20 DEG C of transformation temperature) or be more than
(Ac1+ 120 DEG C of transformation temperature) in the case where, or in the case where the retention time being less than 21600s, without without outstanding in steel band
It is to be difficult to ensure the body of sufficient retained austenite after the final anneal in the enrichment of the Mn into austenite of its front end
Product rate, ductility reduction.On the other hand, if remaining above 129600s, not only the enrichment of the Mn in austenite is saturated and organizes
Coarsening, and become cost increase the main reason for.Therefore, the annealing of hot-rolled sheet coil be by the outer volume portion of hot-rolled sheet coil with
(Ac1+ 20 DEG C of transformation temperature)~(Ac1+ 120 DEG C of transformation temperature) predetermined temperature remain above 21600s and for 129600s it is below when
Between.Retention time is preferably 25000s or more.
In addition, being cooled to room temperature after above-mentioned heat treatment.Cooling means and cooling velocity at this time does not have special provision, excellent
Select the furnace being set as in batch anneal cold or air cooling.
50% or less the reduction ratio of cold rolling:
In cold rolling of the invention, make 50% or less reduction ratio.If being more than to implement cold rolling under 50% reduction ratio,
Coarse polygonal ferrite is generated when heat treatment.As a result, soft phase is obtained in steel plate, strength-ductility balanced drop
It is low.In addition, the bendability and stretch flange (hole expandability) of steel plate also reduce.In addition, the reduction ratio in cold rolling is preferably 30%
More than.
Cold-reduced sheet annealing: by cold-reduced sheet with Ac1Transformation temperature~(Ac1+ 100 DEG C of transformation temperature) predetermined temperature in 20~900s
Between keep
When carrying out the annealing of cold-reduced sheet, it is extremely important that cold-reduced sheet in the present invention in Ac1Transformation temperature~(Ac1Phase transformation
+ 100 DEG C of point) temperature region keep 20~900s.The annealing temperature of cold-reduced sheet is being less than Ac1Transformation temperature is more than (Ac1Phase transformation
+ 100 DEG C of point) when or the retention time be less than 20s when, the enrichment without the Mn into austenite, it is difficult to ensure adequately
The volume fraction of retained austenite, ductility reduction.On the other hand, when remaining above 900s, the ferritic area of non-recrystallization
Rate reduces, and the biphase interface amount of ferrite and the 2nd phase of hard (martensite and retained austenite) increases, and YP is reduced, and YR
It reduces.
Embodiment
By with shown in table 1 at being grouped as and remainder is melted with converter by the steel that Fe and inevitable impurity are constituted
Refining, is made blank with continuous casting process.It is handled under the conditions of resulting blank is various shown in the table 2 and obtains cold-rolled steel
Band (CR).In addition, further implementing zinc-plated processing to a part of cold-rolled steel sheet.In addition, being bathed as galvanizing by dipping, in galvanizing by dipping
In steel band (GI), bathed using Al:0.19 mass % containing zinc, in addition, using Al in alloyed hot-dip zinc-coated steel band (GA):
0.14 mass % is bathed containing zinc.It is set as 465 DEG C of bath temperature, plating adhesion amount is 45g/m in every single side2(two sides plating).Moreover,
In GA, the Fe concentration in coating layer is adjusted in a manner of becoming 9 mass of mass %~12 %.
To the obtained steel band, the average crystallite particle diameter of the microstructure at the 3rd position (central portion) and each phase is carried out
The result of investigation is shown in table 3, in addition, by the microstructure to the 1st position (involute portion) and the 2nd position (outer volume portion) and each phase
The result that average crystallite particle diameter is investigated is shown in table 4.In turn, by the tensile properties to the steel band at the 3rd position (central portion), expansion
The result that permeability is investigated is shown in table 5.In addition, surface texture and productivity (the logical plate to steel band are also described in table 5 together
Property) result investigated.In addition, by the tensile properties to the steel band in the 1st position (involute portion) and the 2nd position (outer volume portion) and
The result that hole expandability is investigated is shown in table 6.
It should be noted that Ac1Transformation temperature is found out using following formula.
Ac1Transformation temperature (DEG C)=751-16 × (%C)+11 × (%Si) -28 × (%Mn) -5.5 × (%Cu) -16
× (%Ni)+13 × (%Cr)+3.4 × (%Mo)
Here, (%C), (%Si), (%Mn), (%Ni), (%Cu), (%Cr) and (%Mo) is in the steel of each element
Content (quality %).
Tension test is using the JIS for extracting sample in the way of right angle orientation by the rolling direction of draw direction and steel plate
No. 5 test films were carried out according to JIS Z 2241 (2011), measured YP, YR, TS and EL.It should be noted that YR is by YP divided by TS
And value expressed as a percentage.In addition, in the present invention, YR >=68%, and TS × EL >=22000MPa%, moreover, in TS:
At 980MPa grades, EL >=26% is judged as well, at TS:1180MPa grades, EL >=22% is judged as well, in TS:
At 1470MPa grades, the case where EL >=18%, is judged as good.It should be noted that TS:980MPa grades are that TS is in the present embodiment
Steel plate of the 980MPa more than and less than 1180MPa, TS:1180MPa grades are that TS is steel of the 1180MPa more than and less than 1470MPa
Plate, TS:1470MPa grades are that TS is steel plate of the 1470MPa more than and less than 1760MPa.
Hole expandability was carried out according to JIS Z 2256 (2010).After obtained each steel plate is cut to 100mm × 100mm,
The hole of diameter 10mm is punched out with gap 12% ± 1%.It then, is 9ton by kiss gating-feeder using the mould of internal diameter 75mm
In the state of (88.26kN), by the formed punch push-in hole of 60 ° of circular cones, measurement generates cracking boundary bore dia.In turn, by following
Formula finds out limit hole expansibility λ (%), evaluates hole expandability according to the value of the limit hole expansibility.
Limit hole expansibility λ (%)={ (Df- D0)/D0}×100
Wherein, DfAperture (mm) when being generated for cracking, D0For initial stage aperture (mm).It should be noted that in the present invention, in TS:
At 980MPa grades, λ >=20% is judged as well, at TS:1180MPa grades, λ >=15% is judged as well, in TS:
At 1470MPa grades, the case where λ >=10%, is judged as good.
As the evaluation to steel band, the surface texture of logical plate, final annealing plate when to hot rolling and cold rolling and production
Rate is evaluated.
Logical plate when as hot rolling and cold rolling increases the danger caused an accident when rolling because of the increase of rolling load
The case where be judged as bad.Show the results of the evaluation table 5.
As the surface texture of final annealing plate, by steel plate table the defects of the bubble, the segregation that not can control blank surface layer
The cracking in face, concave-convex the case where increasing, being unable to get smooth surface of steel plate, are judged as bad.In addition, for final annealing plate
Surface texture, the production quantity of oxide (oxide skin) increased dramatically, the interface of substrate and oxide is roughening, pickling, cold
After rolling surface quality deterioration the case where and pickling after partially there is a situation where that the residue etc. of hot rolling oxide skin is also judged as
It is bad.Show the results of the evaluation table 5.
As productivity, generate the shape defect of hot rolled plate to (1), (2) needed to enter next process into
The case where shape correction of row hot rolled plate, the times cost such as situation of retention time length of (3) annealing are commented
Valence.Also, the case where any one of not meeting (1)~(3), is judged as " good ", will meet any one of (1)~(3)
The case where be judged as " bad ".Measurement result is remembered together in table 5.
Table 2
Underscore: expression is outside the scope of the present invention
* HOT: hot rolled steel plate (no plating), CR: cold-rolled steel sheet (no plating) GI: hot-dip galvanized steel sheet is (without zinc-plated alloy
Change processing), GA: alloyed hot-dip galvanized steel plate
Table 3
Underscore: expression is outside the scope of the present invention
F: polygonal ferrite, F*: non-recrystallization ferrite, RA: retained austenite, M: martensite, P: pearlite, θ: carbon
Compound (cementite etc.)
ε: the ε phase with hcp structure
Table 4
Underscore: expression is outside the scope of the present invention
F: carbide (cementite etc.) ε: pearlite, θ: retained austenite, P: polygonal ferrite, RA: there is hcp structure
ε phase
Table 5
Table 6
According to result above it is found that can be obtained in volume overall length according to the present invention, TS >=980MPa, YR >=68%, TS ×
The excellent high-strength steel strip of the mouldability of EL >=22000MPa%.On the other hand, in a comparative example, in YR, TS, EL and λ
At least one characteristic is poor, or deterioration in characteristics occurs on volume front end or tail end.
Utilization possibility in industry
It according to the present invention, also can be steady even if in the case where carrying out the heating of hot-rolled sheet coil using batch kiln
Surely excellent high-strength of TS >=980MPa, YR >=68% and TS × EL >=22000MPa% mouldability in volume overall length is manufactured
Spend steel band.Therefore, it by the way that high-strength steel strip of the invention is applied to such as automotive structural members, may be implemented light based on car body
Quantify the improvement of caused fuel economy, the utility value in industry is very big.
Claims (2)
1. a kind of manufacturing method of high-strength steel strip, which is characterized in that have following process:
By the process of heating steel billet to 1100 DEG C~1300 DEG C, wherein the steel billet has as follows at being grouped as: in terms of quality %
Containing C:0.030%~0.250%, Si:0.01%~3.00%, Mn: greater than 4.20% and it is 6.00% or less, P:
0.001%~0.100%, S:0.0001%~0.0200%, N:0.0005%~0.0100%, Al:0.010%~
2.000% and Ti:0.005%~0.200%, and remainder is made of Fe and inevitable impurity；
The process that the steel billet is obtained into hot rolled plate with 750 DEG C~1000 DEG C of finish rolling outlet side temperature progress hot rollings；
By the hot rolled plate with 300 DEG C~750 DEG C processes batched and hot-rolled sheet coil is made of coiling temperature；
Next, implementing pickling to the hot rolled plate of the hot-rolled sheet coil and except the process of descale；
The hot-rolled sheet coil is heated in batch kiln, the hot rolled plate lehr attendant of hot-roll annealing coiled sheet is made
Sequence；
Thereafter, by the hot-roll annealing plate of the hot-roll annealing coiled sheet with 50% or less reduction ratio carries out cold rolling and obtains cold-reduced sheet
Process；And
Thereafter, by the cold-reduced sheet with Ac1Transformation temperature~(Ac1+ 100 DEG C of transformation temperature) predetermined temperature keep 20 seconds~900 seconds,
Thereafter it cools down and carries out cold-reduced sheet annealing, the process for obtaining high-strength steel strip,
Wherein, the hot rolled plate annealing operation be by the outer volume portion of the hot-rolled sheet coil with (Ac1+ 20 DEG C of transformation temperature)~(Ac1
+ 120 DEG C of transformation temperature) predetermined temperature be remained above 21600 seconds and for 129600 seconds it is below under the conditions of carry out,
Also, in the longitudinal direction of the high-strength steel strip, the position that will belong to the involute portion of the hot-roll annealing coiled sheet is made
For the 1st position, the position in the outer volume portion of the hot-roll annealing coiled sheet will be belonged to as the 2nd position, the hot-roll annealing will be belonged to
The position of the central portion of coiled sheet as the 3rd position,
The structure of steel at the 3rd position is to contain polygonal ferrite in terms of the area ratio: 15%~55%, non-recrystallization iron element
Body: 8% or more, martensite: 15%~30%, contain retained austenite in terms of volume fraction: 12% or more,
Moreover, the area ratio of the area ratio of the polygonal ferrite at the 1st position/the 2nd position polygonal ferrite
It is 1.00~1.50, the volume fraction of volume fraction/the 2nd position retained austenite of the retained austenite at the 1st position
It is 0.75~1.00,
In addition, the average crystallite particle diameter of polygonal ferrite is for 4.0 μm hereinafter, the average crystallite of martensite in the 3rd position
Partial size be 2.0 μm hereinafter, the average crystallite particle diameter of retained austenite be 2.0 μm hereinafter,
Also, the average crystallite particle diameter of the polygonal ferrite at the 1st position/the 2nd position polygonal ferrite
Average crystallite particle diameter is 1.00~1.50,
Moreover, in the 3rd position, the Mn amount in terms of quality % in retained austenite divided by polygonal ferrite with matter
Measuring value obtained by % meter Mn amount is 2.00 or more.
2. the manufacturing method of high-strength steel strip according to claim 1, which is characterized in that described at being grouped as with quality %
Meter further containing selected from Nb:0.005%~0.200%, B:0.0003%~0.0050%, Ni:0.005%~1.000%,
Cr:0.005%~1.000%, V:0.005%~0.500%, Mo:0.005%~1.000%, Cu:0.005%~
1.000%, Sn:0.002%~0.200%, Sb:0.002%~0.200%, Ta:0.001%~0.010%, Ca:
0.0005%~0.0050%, at least one kind of member in Mg:0.0005%~0.0050% and REM:0.0005%~0.0050%
Element.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111334720A (en) * | 2020-03-30 | 2020-06-26 | 邯郸钢铁集团有限责任公司 | High Al wear-resistant steel strip with good cold formability and production method thereof |
| CN111349771A (en) * | 2020-04-22 | 2020-06-30 | 马鞍山钢铁股份有限公司 | 980 MPa-grade cold-rolled Q & P steel with excellent plasticity and manufacturing method thereof |
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| CN111349771A (en) * | 2020-04-22 | 2020-06-30 | 马鞍山钢铁股份有限公司 | 980 MPa-grade cold-rolled Q & P steel with excellent plasticity and manufacturing method thereof |
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