CN107849651B - High tensile hot rolled steel sheet - Google Patents
High tensile hot rolled steel sheet Download PDFInfo
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- CN107849651B CN107849651B CN201580082015.XA CN201580082015A CN107849651B CN 107849651 B CN107849651 B CN 107849651B CN 201580082015 A CN201580082015 A CN 201580082015A CN 107849651 B CN107849651 B CN 107849651B
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- rolled steel
- hot rolled
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- ferrite
- steel plate
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 122
- 239000010959 steel Substances 0.000 title claims abstract description 122
- 229910001568 polygonal ferrite Inorganic materials 0.000 claims abstract description 50
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 41
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 29
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 20
- 239000000203 mixture Substances 0.000 claims abstract description 20
- 239000000126 substance Substances 0.000 claims abstract description 19
- 229910001567 cementite Inorganic materials 0.000 claims abstract description 15
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 11
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 10
- 229910052758 niobium Inorganic materials 0.000 claims description 10
- 229910052796 boron Inorganic materials 0.000 claims description 9
- 239000012535 impurity Substances 0.000 claims description 8
- 229910052759 nickel Inorganic materials 0.000 claims description 8
- 229910052750 molybdenum Inorganic materials 0.000 claims description 7
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 229910052797 bismuth Inorganic materials 0.000 claims description 5
- 229910052749 magnesium Inorganic materials 0.000 claims description 5
- 238000001816 cooling Methods 0.000 description 37
- 238000012360 testing method Methods 0.000 description 30
- 238000005096 rolling process Methods 0.000 description 28
- 238000000034 method Methods 0.000 description 22
- 230000009467 reduction Effects 0.000 description 22
- 238000009825 accumulation Methods 0.000 description 16
- 230000000694 effects Effects 0.000 description 16
- 230000008569 process Effects 0.000 description 12
- 238000010438 heat treatment Methods 0.000 description 11
- 238000001556 precipitation Methods 0.000 description 11
- 230000006866 deterioration Effects 0.000 description 10
- 238000005098 hot rolling Methods 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 238000007598 dipping method Methods 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 8
- 238000012545 processing Methods 0.000 description 8
- 229910052719 titanium Inorganic materials 0.000 description 8
- 229910052802 copper Inorganic materials 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 7
- 229910052748 manganese Inorganic materials 0.000 description 7
- 229910052710 silicon Inorganic materials 0.000 description 7
- 229910052720 vanadium Inorganic materials 0.000 description 7
- 238000005246 galvanizing Methods 0.000 description 6
- 239000011701 zinc Substances 0.000 description 6
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 5
- 238000005275 alloying Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 230000009466 transformation Effects 0.000 description 5
- 229910052725 zinc Inorganic materials 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 4
- 229910052791 calcium Inorganic materials 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 238000000399 optical microscopy Methods 0.000 description 4
- 238000005554 pickling Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000000717 retained effect Effects 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000007812 deficiency Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000036961 partial effect Effects 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 208000037656 Respiratory Sounds Diseases 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 229940075614 colloidal silicon dioxide Drugs 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- -1 ore Substances 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000002829 reductive effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000001568 sexual effect Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- 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
-
- 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
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- 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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- 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
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
A kind of high tensile hot rolled steel sheet has defined chemical composition；The polygonal ferrite in terms of the area ratio containing 80% or more is organized, 5% martensite and austenite below is added up to and adds up to 5% pearlite and cementite below, remainder is selected from one or more of bainite ferrite and bainite；By when the standard deviation of the microhardness of existing any 50 polygonal ferrites is denoted as σ HV in the range of distance center face ± 100 μm on plate thickness direction, the σ HV is 30 or less；In the intragranular of the polygonal ferrite, there are 5 × 107A/mm2Above carbide containing Ti, the long side length of 50% or more the carbide containing Ti is relative to ratio, that is, aspect ratio of bond length less than 3 among the carbide containing Ti；Tensile strength is 540MPa or more.
Description
Technical field
The present invention relates to hot rolled steel plate, more particularly to being suitable for being configured to various shapes by punch process etc.
The running gear component of automobile etc., high tensile hot rolled steel sheet that hole expandability is excellent.
Background technique
The hot rolled steel plate manufactured less expensively, the various industrial equipments being widely used in headed by automobile.In recent years,
From the viewpoint of the CO2 emissions limitation associated with global warming countermeasure, it is desirable that improve the fuel-economy of automobile
Property, for the purpose of the lightweight of car body and ensuring crashworthiness, expanding high strength rolled steel in terms of automotive part
The application of plate.
It is self-evident, for the steel plate for automotive part, not only to meet intensity requirement, it is necessary to which satisfaction strikes out
Required various application properties when the shape components of shape, weldability etc..It is and stamping for example, for running gear component
Correlation, the frequency of use for putting side forming and flanging forming are high.Therefore, it for the high tensile hot rolled steel sheet for the component,
Seek excellent hole expandability.In addition, as running gear component, from the viewpoint of ensuring safety, even if being to need mostly
The component being plastically deformed also is avoided in the case where being applied with big load.Therefore, to the steel for being used for running gear component
The demanding yield ratio of plate.
Typically, for high tensile hot rolled steel sheet, in order to have both high yield ratio and excellent hole expandability, make structure of steel at
For by any single-phase tissue constituted of ferrite, bainite ferrite or bainite etc., and consolidating by Mn, Si etc.
The precipitation strength of the carbide or Cu of molten reinforcing, and/or Ti, Nb, V etc. by even tissue is strengthened, and just carries out to this
Research.
For example, patent document 1 disclose it is a kind of be related to the technology of the excellent high tensile hot rolled steel sheet of hole expandability, feature exists
In making substantially to disperse the Ti carbide containing Mo by fine uniform structure in the single-phase tissue constituted of ferrite.But patent document
1 technology, it is necessary to add alloying element extremely expensive as Mo, therefore be unsuitable for volume production from the viewpoint of economy.
Patent document 2 discloses following technology: for the steel added with Ti of Mn, Si containing specified amount, by appropriate
Control makes tissue become ferrite and bainite from hot rolling to cooling down during batching, and makes the fine precipitation of TiC, to make
The elongation percentage of high tensile hot rolled steel sheet is improved with side property is put.But in patent document 2, about as suitable for running gear
The yield ratio of one of characteristic necessary to the hot rolled steel plate of component, does not consider at all.In addition, with the iron element enhanced is precipitated
Body is compared, and bainite shows low yielding ratio, but the bainite containing 50% is allowed in the technology of patent document 2, can be analogized
High yield ratio can not be maintained out.Moreover, ferrite defined in patent document 2, definition is indefinite, it is contemplated that packet
Containing being not polygonal ferrite, so-called bainite ferrite, quasi-polygonal ferrite.As the reason for this is that because are as follows: special
In sharp document 2,720 DEG C of temperature fields below without fully generating polygonal ferrite also allow as the 1st cooling stopping
Temperature.Bainite ferrite, quasi-polygonal ferrite are the tissues for showing the yield ratio lower than polygonal ferrite.
Patent document 3 discloses a kind of ratio by reducing Mn content and controlling the C being precipitated as cementite, comes
The high tensile hot rolled steel sheet added with Ti for improving toughness and hole expandability.But the hot rolled steel plate of patent document 3, imagining
It, cannot such as 75% or more in this way in the high strength steel of 540MPa or more in the case where being applied to running gear component
High yield ratio.
In addition, patent document 4 discloses a kind of technology of high tensile hot rolled steel sheet excellent about hole expandability, wherein drop
Low Mn and Si content, also, a certain amount of Ti and B is added to inhibit the coarsening of TiC.But B has inhibition austenite
The effect of recrystallization, if therefore with the compound addition of Ti that has same effect, rolling loads when hot rolling rise significantly,
The load for incurring hot-rolling mill increases.Therefore, there is the danger for causing operation failure in the technology of patent document 4.In addition, containing as B
Amount only varies by several ppm, and the intensity of final product just greatly changes, it is therefore necessary to which the steel containing B is unsuitable for volume production.
Patent document 5 discloses a kind of high tensile hot rolled steel sheet with high yield ratio and excellent hole expandability, wherein
Steel containing a large amount of Si, Mn and Ti is cooling with cooling condition appropriate, so that tissue is become granular bainite ferrite list
Phase constitution.But in the technology of patent document 5, granular bainite ferritic structure, needs containing a large amount of in order to obtain
Si, Mn, therefore there are problems that incurring cost of alloy increase.
Citation
Patent document
Patent document 1: Japanese Laid-Open 2002-322540 bulletin
Patent document 2: Japanese Laid-Open 2007-009322 bulletin
Patent document 3: the flat 10-287949 bulletin of Japanese Laid-Open
Patent document 4: Japanese Laid-Open 2012-026032 bulletin
Patent document 5: Japanese Laid-Open 2004-307919 bulletin
Summary of the invention
The present invention is completed in view of status as described above.The subject of the invention is to provide with high yield ratio and excellent
Hole expandability high tensile hot rolled steel sheet.High intensity in the present invention refers to that tensile strength (TS) is 540MPa or more.
Ti is less expensive, also, ought contain microly and just embody significant precipitation strength sometimes.The present inventor is excellent in order to realize
Different hole expandability makes the tissue of hot rolled steel plate based on polygonal ferrite, by this as premise.Moreover, the present inventor
Following research work is carried out, it may be assumed that in the polygonal ferrite subject organization with excellent hole expandability, in order to improve intensity
And it is effectively utilized the precipitation strength of Ti.In addition, for as the main body of tissue and Ti precipitate has been precipitated using polygonal ferrite
High tensile hot rolled steel sheet containing Ti, the method that sharp study improves hole expandability.As a result, having obtained opinion below.
The present inventor determines the micro- hard of each ferrite grain of the steel with the tissue based on polygonal ferrite
Degree.Its result is it is found that its hardness is meaningfully different by the grain determined.And then find: by reducing each ferrite grain
The deviation of hardness can improve hole expandability significantly.
In addition, the present inventor uses the transmission electron microscope observing intragranular of the polygonal ferrite of the inferior sample of hole expandability.
Itself as a result, it has been found that, the Ti system carbide of the nonequiaxial shape of many elongations has been precipitated along ferritic specific orientation, this
Adverse effect is caused to hole expandability.The shape almost without Ti carbide influenced the report of hole expandability, the carbonization of Ti system in the past
Mechanism that the shape of object impacts hole expandability is simultaneously indefinite.But presumption with etc. axis shapes Ti system carbide compared with, it is non-
Etc. axis shapes Ti system carbide and the ferritic matching of parent phase it is high, big matching strain is had accumulated around it, therefore push away
Determine to deteriorate hole expandability since matching strain encourages the extension of the crackle in reaming processing.
It is completed the present invention is based on above-mentioned opinion.Its main idea described below.
(1) hot rolled steel plate that a scheme of the invention is related to, chemical composition in terms of quality % containing C:0.010%~
0.200%, Si:0.001%~2.50%, Mn:0.001%~1.50%, P:0.050% or less, S:0.010% or less, N:
0.0070% or less, Al:0.001%~0.50%, Ti:0.050%~0.30%, V:0%~0.50%, Nb:0%~
0.090%, Cr:0%~0.50%, Ni:0%~0.50%, Cu:0~0.50%, Mo:0%~0.50%, B:0%~
0.0050%, Ca:0%~0.01%, Mg:0%~0.01%, Bi:0%~0.01%, surplus are Fe and impurity, are organized with face
Product rate meter contain 80% or more polygonal ferrite, add up to 5% martensite and austenite below and add up to 5%
Pearlite and cementite below, remainder be selected from one or more of bainite ferrite and bainite, will be in plate thickness
On direction in the range of distance center face ± 100 μm the microhardness of existing any 50 above-mentioned polygonal ferrites standard
When deviation is denoted as σ HV, above-mentioned σ HV is 30 hereinafter, there are 5 × 10 in the intragranular of above-mentioned polygonal ferrite7A/mm2Above contains
Ti carbide, the long side length of 50% or more the carbide containing Ti is relative to the ratio of bond length among above-mentioned carbide containing Ti
Aspect ratio is less than 3；Tensile strength is 540MPa or more.
(2) hot rolled steel plate according to above-mentioned (1), above-mentioned chemical composition can also be containing selected from V in terms of quality %:
0.010%~0.50%, Nb:0.001%~0.090%, Cr:0.001%~0.50%, Ni:0.001%~0.50%, Cu:
0.001%~0.50%, one or more of Mo:0.001%~0.50%, B:0.0001%~0.0050%.
(3) hot rolled steel plate according to above-mentioned (1) or (2), above-mentioned chemical composition can also contain choosing in terms of quality %
From one or more of Ca:0.0001%~0.01%, Mg:0.0001%~0.01%, Bi:0.0001%~0.01%.
(4) according to described in any item hot rolled steel plates of above-mentioned (1)~(3), it can have dip galvanized on surface.
Above scheme according to the present invention can be manufactured inexpensively with the high-strength of high yield ratio and excellent hole expandability
Spend hot rolled steel plate.In addition, the steel plate that above scheme of the invention is related to, in automotive part, particularly running gear component etc.
In more use put side forming in also have excellent hole expandability.Therefore, especially facilitate car body in automotive field
Lightweight and ensure crashworthiness.
Detailed description of the invention
Fig. 1 is the schematic diagram for indicating the example of tupe of hot rolling.
Fig. 2 is the example of the heat treatment mode in the alloyed hot-dip zinc-coated production line for indicating to use in example 2
Schematic diagram.
Fig. 3 A is the figure for indicating an example of microhardness distribution for the polygonal ferrite being measured in embodiment 1.
Fig. 3 B is the figure for indicating an example of microhardness distribution for the polygonal ferrite being measured in embodiment 1.
Specific embodiment
(hereinafter sometimes referred to present embodiment relates to the high tensile hot rolled steel sheet being related to below to one embodiment of the present invention
And hot rolled steel plate) be described in detail.
Hot rolled steel plate of the present embodiment,
(a) chemical composition contains C:0.010%~0.200%, Si:0.001%~2.50%, Mn in terms of quality %:
0.001%~1.50%, P:0.050% or less, S:0.010% or less, N:0.0070% or less, Al:0.001%~
0.50%, Ti:0.050%~0.30% is selected from V:0.50% or less, Nb:0.090% or less, Cr also according to needing to contain:
0.50% or less, Ni:0.50% or less, Cu:0.50% or less, Mo:0.50% or less, B:0.0050% or less, Ca:0.01%
Below, Mg:0.01% or less, Bi:0.01% or less one or more of, surplus be Fe and impurity；
(b) it organizes the polygonal ferrite in terms of the area ratio containing 80% or more, add up to 5% martensite below and Austria
Family name's body and 5% pearlite and cementite below is added up to, remainder is among bainite ferrite and bainite
More than one；
(c) will in the range of distance center face ± 100 μm on plate thickness direction existing any 50 above-mentioned polygon iron
When the standard deviation of the microhardness of ferritic is denoted as σ HV, above-mentioned σ HV is 30 or less；
(d) in the intragranular of above-mentioned polygonal ferrite, there are 5 × 107A/mm2Above carbide containing Ti, above-mentioned carbon containing Ti
The long side length of 50% or more the carbide containing Ti is relative to ratio, that is, aspect ratio of bond length less than 3 among compound；
(e) tensile strength is 540MPa or more.
The chemical composition > of < steel plate
Firstly, being illustrated to the reasons why chemical composition for limiting hot rolled steel plate of the present embodiment.Below, it is specified that
" % " of chemical composition all " quality % ".
[C:0.010%~0.200%]
C is the high intensity necessary element that steel plate is realized by precipitation strength or solution strengthening.In order to obtain
C content is set as 0.010% or more by the effect.Preferably 0.020% or more, further preferably 0.040% or more.It is another
Aspect can inhibit the generation of polygonal ferrite, and cementite easy to form when C content excess.Additionally, there are polygon
The tendency that the difference of hardness of the ferritic each crystal grain of shape also becomes larger.As a result, hole expandability deteriorates.In addition, weldability is also significantly bad
Change.Therefore, C content is set as 0.200% or less.Preferably 0.130% hereinafter, further preferably 0.110% or less.
[Si:0.001%~2.50%]
Si is solution strengthening element, is to the effective element of the high intensity of steel plate.Effect in order to obtain, by Si content
It is set as 0.001% or more.Preferably 0.01% or more, more preferably 0.04% or more.On the other hand, when Si content excess,
Island oxide skin, surface quality deterioration can be generated.Therefore, Si content is set as 2.50% or less.Preferably 1.30% hereinafter, more
Preferably 0.80% or less.[Mn:0.001%~1.50%]
Mn is to improve effective element to the intensity of steel plate.In addition, it is also to be consolidated in the form of MnS by the S in steel
The fixed element to inhibit the thermal embrittlement caused by being dissolved S.Mn content is set as 0.001% or more by these effects in order to obtain.
Preferably 0.10% or more, more preferably 0.45% or more.On the other hand, when Mn content excess, from austenite to ferrite
Phase change delay, it becomes difficult to obtain the polygonal ferrite of 80 area % or more, hole expandability deterioration.Therefore, Mn content is set
It is 1.50% or less.Preferably 1.00% hereinafter, more preferably 0.80% or less.
[P:0.050% or less]
P is the element that contains as impurity, makes the weldability and toughness deterioration of steel plate.It is therefore preferable that P content is few.But
It is that, in the case where P content is more than 0.050%, above-mentioned influence becomes significantly, therefore the deterioration as weldability and toughness is not
Significant range and P content is set as 0.050% or less.Preferably 0.020% hereinafter, more preferably 0.010% or less.
[S:0.010% or less]
S is the element contained as impurity, forms MnS in steel, deteriorates the hole expandability of steel plate.It is therefore preferable that S contains
Amount is few.But in the case where S content is more than 0.010%, above-mentioned influence becomes significantly, therefore the deterioration as hole expandability
Inapparent range and S content is set as 0.010% or less.Preferably 0.0050% hereinafter, more preferably 0.0020% or less.
[N:0.0070% or less]
N is impurity and the element contained, forms coarse nitride in steel, deteriorates the hole expandability of steel plate significantly.
It is therefore preferable that N content is few.But in the case where N content is more than 0.0070%, above-mentioned influence becomes significantly, therefore conduct
The inapparent range of the deterioration of hole expandability and N content is set as 0.0070% or less.Preferably 0.0050% or less.
[Al:0.001%~0.50%]
Al is the effective element of deoxidation to steel.Al content is set as 0.001% or more by the effect in order to obtain.It is another
Aspect, when Al content is more than 0.50%, not only effect is saturated, and also incurs increased costs.Therefore, Al content is set as 0.50%
Below.Preferably 0.20% hereinafter, more preferably 0.10% or less.
[Ti:0.050%~0.30%]
Ti is that carbide is formed in steel, by the element of ferrite equably precipitation strength.In addition, it be also have it is following
The element of effect: solid solution C amount is reduced by being precipitated as TiC, hinders the precipitation for the cementite for deteriorating hole expandability.Cause
This, is especially important element in hot rolled steel plate of the present embodiment.When Ti content is lower than 0.050%, effect
It is insufficient, therefore Ti content is set as 0.050% or more.Preferably 0.100% or more, more preferably 0.130% or more.It is another
Aspect, when Ti content is more than 0.30%, toughness deteriorates significantly, and incurs unnecessary increased costs.Therefore, Ti is contained
Amount is set as 0.30% or less.Preferably 0.25% hereinafter, more preferably 0.20% or less.
Hot rolled steel plate of the present embodiment, substantially composition are: containing above-mentioned chemical component, surplus include Fe and
Impurity.But in order to further increase intensity, hole expandability, can also in range as shown below containing selected from V, Nb, Cr,
One or more of Ni, Cu, Mo, B, Ca, Mg, Bi replace a part of Fe.But due to these elements be not necessarily required containing,
Therefore its lower limit is 0%.Here, so-called impurity means: when industrialness manufactures steel by the raw materials such as ore, waste material and
Other factors and mixed ingredient.
[V:0.010%~0.50%]
V is the element for forming carbide in steel in the same manner as Ti.In addition, V is the dissolution compared with Ti in austenite
Degree product is big, to the effective element of the high intensity of steel plate.Therefore, although it is at high price compared with Ti, also it can according to need
To contain.When V content is lower than 0.010%, said effect cannot be sufficiently obtained, therefore the said effect to be obtained the case where
Under, V content is set as 0.010% or more.Preferably 0.070% or more, more preferably 0.140% or more.On the other hand, work as V
When content becomes excessive, cost increase can be incurred, even therefore contain V the case where, V content is also set as 0.50% or less.
[Nb:0.001%~0.090%]
Nb is to form carbide in steel in the same manner as Ti, to the effective element of the high intensity of steel plate.Therefore, although with
Ti also can according to need to contain compared at high price.When Nb content is lower than 0.001%, cannot sufficiently obtain above-mentioned
Effect, therefore in the case where said effect to be obtained, Nb content is set as 0.001% or more.On the other hand, when Nb content mistake
When amount, the plastic anisotropy of steel plate increases, hole expandability deterioration.Therefore, even Nb content, is also set as by the case where containing Nb
0.090% or less.
[Cr:0.001%~0.50%]
[Ni:0.001%~0.50%]
[Cu:0.001%~0.50%]
[Mo:0.001%~0.50%]
[B:0.0001%~0.0050%]
Cr, Ni, Cu, Mo, B are to the effective element of the high intensity of steel plate.Therefore, it can according to need and individually contain
It is a kind of or contain two or more compoundly.If obtaining said effect, need to be set to Cr:0.001% or more,
Ni:0.001% or more, Cu:0.001% or more, Mo:0.001% or more, B:0.0001% or more.On the other hand, these yuan
Element, the ferrite transformation delay after hot rolling is made in the same manner as Mn.Therefore, difficult in the tissue of hot rolled steel plate when content excess
To obtain being calculated as 80% or more polygonal ferrite, the hole expandability deterioration of hot rolled steel plate with the area ratio.Therefore, even containing
Its content is also set to Cr:0.50% or less, Ni:0.50% or less, Cu:0.50% or less, Mo by the case where each element:
0.50% or less, B:0.0050% or less.Preferably Cr:0.20% or less, Ni:0.20% or less, Cu:0.20% or less, Mo:
0.09% or less, B:0.0040% or less.
[Ca:0.0001%~0.01%]
[Mg:0.0001%~0.01%]
[Bi:0.0001%~0.01%]
Ca and Mg contributes to the element of the fine dispersion of steel inclusion, and Bi is that Mn, the Si etc. lowered in steel is replaced
The element of the microscopic segregation of type alloying element.It, can root since the hole expandability that any element both contributes to steel plate improves
Individually contain compoundly containing one kind or by two or more according to needs.If obtaining said effect, need to contain respectively
0.0001% or more.On the other hand, when the content excess of these elements, ductility deterioration, even therefore the case where contain,
Also the content of each element is set to 0.01% or less.
The tissue > of < hot rolled steel plate
Then, the reasons why tissue for limiting hot rolled steel plate of the present embodiment, is illustrated.
[the area ratio of polygonal ferrite: 80% or more]
Polygonal ferrite is that the raising to hole expandability is effectively organized.In order to ensure hole expandability, by polygonal ferrite
The area ratio be set as 80% or more.Preferably 90% or more, more preferably 95% or more.The area ratio of polygonal ferrite can also
Think 100%, that is, hot rolled steel plate of the present embodiment may be that polygonal ferrite is single-phase.
[the area ratio of martensite and austenite it is total: 5% or less]
When the area ratio of martensite and austenite is when adding up to more than 5%, hole expandability deteriorates significantly.Therefore, by geneva
The total of the area ratio of body and austenite is set as 5% or less.Preferably 2% or less.In addition, total the area ratio may be
0% (that is, without martensite and austenite).In addition, austenite said here, is so-called retained austenite.
[the area ratio of pearlite and cementite it is total: 5% or less]
When the area ratio of pearlite and cementite is when adding up to more than 5%, hole expandability deteriorates significantly.Therefore, by pearly-lustre
The total of the area ratio of body and cementite is set as 5% or less.Preferably 3% hereinafter, more preferably 1% or less.In addition, total
The area ratio may be 0% (that is, without pearlite and cementite).
[tissue of remainder]
The tissue of remainder (its surplus) other than the above, be selected from one of bainite ferrite and bainite with
On.But in the case where total the area ratio of above-mentioned tissue is 100%, bainite ferrite and bainite are not contained.
Above-mentioned tissue can be such that tissue shows, then according to its group by corroding the sample cut from hot rolled steel plate
Photo is knitted to be identified.
The polygonal ferrite generated by diffusivity mechanism does not have internal structure in intragranular, also, crystal boundary becomes
Straight line or arc-shaped.On the other hand, bainite ferrite, bainite have internal structure, also, having grain-boundary shape is needle
Shape and the tissue clearly different from polygonal ferrite.Therefore, polygonal ferrite, bainite or bainite ferrite, can be by
Macrograph judges that the macrograph is rotten with nital by the presence or absence of grain-boundary shape and internal structure
After erosion, obtained using optical microscopy.Do not show clearly there are internal structure and grain-boundary shape be acicular tissue
In the case where (quasi-polygonal ferrite), counted as bainite ferrite.
In addition, tissue can be positively identified since cementite and pearlite can be corroded to black.
In addition, the macrograph obtained using optical microscopy is carried out by the sample for having carried out homogeneous corrosion is used
Image analysis can calculate total the area ratio of retained austenite and martensite.
In the present embodiment, the tissue of steel plate is showing the representative tissue of steel plate, plate thickness 1/4 depth
It is observed position.
[existing any 50 polygonal ferrites is aobvious in the range of distance center face ± 100 μm on plate thickness direction
The standard deviation HV:30 or less of microhardness]
As described above, by reducing the deviation of the hardness of each ferrite grain, the hole expandability of hot rolled steel plate can be made aobvious
Land raising.Specifically, measurement distance center face (plate thickness central portion comprising steel plate, with plate thickness direction on plate thickness direction
The face vertically intersected) hardness (microhardness) of existing arbitrary 50 polygonal ferrites in the range of ± 100 μm, it will
When the standard deviation of its microhardness is denoted as σ HV, by making σ HV 30 hereinafter, excellent hole expandability can be obtained.Therefore, by σ
HV is set as 30 or less.Since standard deviation is small preferably, the lower limit of σ HV is 0.
Illustrate the specific measuring method of σ HV below.As Determination of Hardness sample, use: to the rolling direction of steel plate
Section carries out mirror ultrafinish, and then is chemically ground to remove the machined layer on surface layer using colloidal silicon dioxide,
Corrode the sample for displaying crystal boundary with nital afterwards.Microhardness is measured using following methods: being used
Small Determination of Hardness device (trade name: FISCHERSCOPEHM2000XYp), on plate thickness direction distance center face ±
Existing randomly selected 50 polygonal ferrites (each crystal grain) in the range of 100 μm, by 136 ° of quadrangle cone shape of apex angle
Vickers indenter be pressed into intragranular in such a way that its impression is not overlapped with ferrite grain boundaries.
Loading of pressing in is set as 20N.The standard deviation HV of microhardness is found out by 50 obtained data.
[the carbide containing Ti existing for the intragranular of polygonal ferrite: 5 × 107A/mm2More than]
[50% or more of the carbide containing Ti existing for polygonal ferrite intragranular, long side/short side aspect ratio are less than
3]
Hot rolled steel plate of the present embodiment contains 5 × 10 in the intragranular of polygonal ferrite7A/mm2Above contains
Ti carbide.When being 5 × 107A/mm2When following, precipitation strength is insufficient, becomes intensity deficiency.On the other hand, it is not necessary that
Set upper limit, but usually will not be more than 1 × 10 if it is above-mentioned composition range11A/mm2。
In addition, being calculated as by making in number ratio among the carbide containing Ti existing for the intragranular of the polygonal ferrite
50% or more carbide containing Ti is that long side length is less than relative to the ratio (aspect ratio indicated with long side/short side) of bond length
3 carbide can obtain excellent hole expandability.It is preferred that: containing Ti carbide of long side/short side aspect ratio less than 3 exists
2/3 or more is accounted among the carbide containing Ti of polygonal ferrite intragranular.The ratio of containing Ti carbide of the aspect ratio less than 3 can also
Think 100%.
The ratio of containing Ti carbide of the aspect ratio less than 3, can be obtained by following methods: in the incidence side for making electron ray
To parallel with ferritic 001 > of < of parent phase, and utilize transmission electron microscope (multiplying power: 200000 times) observation at least 100 or more
When carbide containing Ti, relative to the sum of the observed carbide containing Ti, carbon of long side/short side aspect ratio less than 3 is found out
Compound.
In the present embodiment, so-called carbide containing Ti is the carbide containing Ti, can also be also containing in V, Nb
More than one.That is, also including: the crystal structure (NaCl type structure) with the carbide containing Ti, also, some positions of Ti are by V
Or the state that Nb has been replaced.
[dip galvanized]
Hot rolled steel plate of the present embodiment also can have well known dip galvanized on the surface thereof.Hot-dip
Zinc layers are also possible to carry out the alloyed hot-dip zinc-coated layer of alloying.With dip galvanized, rust can be inhibited
Generation, therefore hot rolled steel plate corrosion resistance improve.
The mechanical property > of < steel plate
[tensile strength (TS): 540MPa or more]
[the ratio (yield ratio) of tensile strength (TS) and 0.2% endurance (YS): 75% or more]
[product (TS λ) of tensile strength (TS) and the hole expansibility specified in JFST1001 (λ): 50000MPa% with
On]
It is mechanical special as it if meeting performance stringent required by automobile high-strength hot rolled steel plate in recent years
Property, preferably: tensile strength TS is 540MPa or more, also, the ratio (YR (yield ratio)) of tensile strength TS and 0.2% endurance YS is
75% or more, also, the product (TS λ) of the tensile strength TS and hole expansibility λ specified in JFST1001 is 50000MPa%
More than.Hot rolled steel plate of the present embodiment will all be met high as described above by control chemical composition and tissue
Tensile strength, yield ratio and tensile strength-reaming sexual balance (TS λ) are used as target.
Tensile strength is preferably 590MPa or more.In addition, the fatigue of weld part is special when tensile strength is more than 1180MPa
Property deterioration, therefore preferably 1180MPa or less.
Then, to obtain hot rolled steel plate of the present embodiment, preferred manufacturing method is illustrated.If using
Manufacturing method comprising (A) below~(D) process then can steadily manufacture hot rolled steel plate of the present embodiment, because
This is preferably.
(A) by the heating of plate blank obtained by the molten steel of the chemical composition with above range to 1200 DEG C of degree；
(B) by the slab being heated to become 50% or more in 1050 DEG C or more 1150 DEG C accumulation reduction ratios below
Mode carries out roughing；
(C) by the steel plate after roughing to become 20%~80%, final passage in 1050 DEG C of accumulation reduction ratios below
The mode that reduction ratio becomes 15%~35% also, finally the temperature (Finishing temperatures) of passage becomes 930 DEG C or more carries out essence
It rolls；
(D) thereafter, for hot rolled steel plate, i) as primary cooling, by the final passage temperature of finish rolling~(720 DEG C≤MT of MT
≤ 830 DEG C) temperature region so that average cooling rate is cooling as the condition of 30 DEG C/s or more, thereafter, ii) as secondary cold
But, by the temperature region of MT~Tx (720 DEG C≤Tx < MT) so that average cooling rate becomes 10 DEG C/s condition below and carries out
Cooling is by t (second)=5 [Mn]2Defined t seconds or more (here, [Mn] is the Mn content that unit is quality %.), then,
Iii) conduct cools down three times, by the temperature region of secondary cooling finishing temperature Tx~CT (450 DEG C≤CT≤650 DEG C) so that average
Cooling velocity is cooling as the condition of 30 DEG C/s or more, is cooled to after CT, batches to hot rolled steel plate.
Its reason is illustrated below.
< heating process >
In heating process, by the heating of plate blank with chemical composition as described above to 1200 DEG C of degree.From influencing
The solid solution condition of the carbide formers such as the precipitation density of the carbide containing Ti of polygonal ferrite intragranular, Ti, Nb, V inhibits
From the perspective of the formation of coarse carbide, desired performance in order to obtain, heating temperature is preferably 1150 DEG C to 1250
DEG C temperature range.
< roughing operation >
The slab being heated becomes hot rolled steel plate by the hot-rolled process including roughing operation and finishing rolling step.It is making
When making hot rolled steel plate of the present embodiment, temperature, reduction ratio etc. are controlled preferably in each process of roughing and finish rolling.
In the roughing operation of hot rolling, the accumulation reduction ratio in 1050 DEG C~1150 DEG C is preferably set as 50% or more.
When the accumulation reduction ratio in 1050 DEG C~1150 DEG C is lower than 50%, tissue becomes uneven sometimes, σ HV becomes larger, hole expandability
It reduces.Accumulation reduction ratio in the present invention is: the accumulation on the basis of the entrance plate thickness before initial passage, relative to the benchmark
The hundred of drafts (difference of the outlet plate thickness after the final passage in the entrance plate thickness and rolling before initial passage in rolling)
Divide rate.In addition, accumulation reduction ratio, is dividually calculated respectively by roughing, finish rolling.That is, the accumulation reduction ratio of roughing, is in roughing
Initial passage before entrance plate thickness and roughing in final passage after outlet plate thickness difference percentage, the accumulation of finish rolling
Reduction ratio is the hundred of the difference of the outlet plate thickness after the final passage in the entrance plate thickness and finish rolling before the initial passage in finish rolling
Divide rate.
< finishing rolling step >
It is preferably 20%~80% in 1050 DEG C of accumulation reduction ratios below in the finishing rolling step of hot rolling.When 1050
When DEG C accumulation reduction ratio below is more than 80%, the anisotropy of the tissue of finally obtained hot rolled steel plate is significantly changed.The situation
Under, σ HV becomes larger sometimes, hole expandability reduces.Speculate this due to: the segregation of the crystalline orientation of ferrite grain has encouraged difference of hardness.
On the other hand, when 1050 DEG C of accumulation reduction ratios below are lower than 20%, austenite partial size coarsening, and to austenite
Strain accumulation is insufficient, and thus the ferrite transformation after finish rolling is suppressed, finally obtained polygonal ferrite divide rate (score) and
A possibility that standard deviation of the microhardness of polygonal ferrite is detached from desired range, and hole expandability deteriorates gets higher.
[the reduction ratio of final passage: 15%~35%]
The reduction ratio of final passage is preferably set to 15%~35%.When the reduction ratio of final passage is more than 35%, tissue
Anisotropy significantly change, as a result, sometimes σ Hv become larger, hole expandability reduce.Therefore, the reduction ratio of final passage is set as
35% or less.More preferably 25% or less.On the other hand, when the reduction ratio of final passage is lower than 15%, to answering for austenite
Become accumulation deficiency, the ferrite transformation after finish rolling is suppressed, and finally obtained polygonal ferrite divides rate and polygonal ferrite
The standard deviation of microhardness be detached from desired range, a possibility that hole expandability deteriorates, gets higher.
[Finishing temperatures: 930 DEG C or more]
Finishing temperatures (steel billet temperature after the final passage of finish rolling) are preferably set to 930 DEG C or more.Work as Finishing temperatures
When lower than 930 DEG C, in finally obtained hot rolled steel plate, the anisotropy of tissue is easy significantization, as a result, there are σ Hv changes
Greatly, a possibility that hole expandability reduces.On the other hand, as Finishing temperatures are got higher, austenite partial size coarsening, and to Ovshinsky
The strain of body is accumulated insufficient, and thus the ferrite transformation after finish rolling is suppressed, and finally obtained polygonal ferrite divides rate and more
A possibility that standard deviation of the ferritic microhardness of side shape expands, and hole expandability deteriorates gets higher.It is therefore preferable that will finishing temperature
The upper limit of degree is set as 1000 DEG C of degree.
< cooling process >
After above-mentioned finish rolling, hot rolled steel plate is implemented to cool down.
Temperature region in final passage temperature~720 DEG C of finish rolling, i) by the carbide containing Ti that is precipitated in ferrite
Grow up polygonal ferrite intragranular caused by (coarsening) the density of carbide containing Ti variation and ii) in polygon iron element
The variation of long side/short side aspect ratio of the carbide containing Ti existing for body intragranular becomes larger.Therefore, by the final passage temperature of finish rolling~
It is effective that average cooling rate in 720 DEG C of temperature region, which is set as 30 DEG C/s obtaining desired aspect of performance,.
In turn, after above-mentioned cooling, in 830 DEG C~720 DEG C of temperature region, with correspondingly true according to the Mn amount contained
The fixed desired time, hot rolled steel plate is cooling with low average cooling rate, this is promoting ferrite transformation and carbon containing Ti
The precipitation of compound is in the standard deviation of the microhardness of finally obtained polygonal ferrite point rate and polygonal ferrite
It is effective in terms of desired range.
Thereafter, further progress is cooling, then batches hot rolled steel plate.At that time, if cooling velocity is lower than 30 DEG C/s or volume
Taking temperature is more than 650 DEG C, then in cooling or after batching, carbide containing Ti in hot rolled steel plate exceedingly coarsening, sometimes
It is difficult to ensure desired intensity.On the other hand, in the case where making coiling temperature lower than 450 DEG C, control precision of coiling temperature
It reduces, therefore not preferably.Therefore, coiling temperature is set as to 450~650 DEG C of range, also, with defined average cooling speed
Du or more come to be cooled to coiling temperature be effective.
It, will be smart that is, in cooling process after finish rolling, preferably: for the hot rolled steel plate after finish rolling, i) as primary cooling
The temperature region of final passage temperature~MT (720 DEG C≤MT≤830 DEG C) is rolled so that average cooling rate becomes 30 DEG C/s or more
Condition it is cooling, thereafter, ii) be used as secondary cooling, by the temperature region of MT~Tx (720 DEG C≤Tx < MT) so that average cooling
Speed becomes 10 DEG C/s cooling condition below and is cooled down as defined in following formula 1 t seconds or more, then, iii) as three times
It is cooling, by the temperature region of secondary cooling finishing temperature (Tx) to CT (450 DEG C≤CT≤650 DEG C) so that average cooling rate at
It is cooling for the cooling condition of 30 DEG C/s or more, it is batched in 450~650 DEG C of temperature regions.
[t (second)=5 [Mn]2] formula 1
Here, [Mn] is the Mn content that unit is quality %.
In the case where manufacturing hot rolled steel plate of the present embodiment, it can according to need and be further equipped with work below
Sequence.
< plating process >
After coiling process, can also have the galvanizing by dipping work for implementing galvanizing by dipping processing to above-mentioned hot rolled steel plate
Sequence.By implementing galvanizing by dipping processing, coating is formed in surface of steel plate, the corrosion resistance of steel plate can be made to improve.In addition, in hot dipping
It, can also be by implementing Alloying Treatment, to form alloyed hot-dip zinc-coated layer in surface of steel plate after zinc-plated processing.In addition,
At that time, in order to inhibit the strength reduction of steel plate, the maximum heating temperature in annealing before galvanizing by dipping dipping be preferably 800 DEG C with
Under.About other galvanizing by dipping conditions, observe a usual practice method.
< others process >
Hot rolled steel plate of the present embodiment can also conventionally carry out pickling after hot-rolled process.In addition,
For leveling, promote oxide skin removing, skin-pass can also be implemented before pickling or after pickling.Implement the feelings of skin-pass
Elongation under condition do not provide particularly, but preferably 0.1% more than or lower than 3.0%.
Embodiment
Illustrate the embodiment of the present invention below.
[embodiment 1]
There is the steel of chemical composition shown in table 1 in laboratory melting, cast out slab, with mode shown in FIG. 1 progress
Heating, cooling, is batched at hot rolling.At this point, the condition of each process is as shown in table 2.In table 2, SRT, R1, R2, R3, FT, MT, t,
CT respectively indicates following items.
SRT: slab heating temperature
R1: in 1050 DEG C or more 1150 DEG C of accumulation reduction ratios below
R2: in 1050 DEG C of accumulation reduction ratios below
R3: the reduction ratio in finally processing passage
FT: final rolling temperature
MT: primary cooling stopping temperature
T: secondary cooling time
CT: coiling temperature
The hot rolled steel plate pickling that will be obtained in this way, for the condition for being shown as " plating " in the column with " processing " of table 3,
Implement galvanizing by dipping and then produces JIS5 tensile sample from the direction vertical with the rolling direction of hot rolled steel plate.Use the examination
Sample carries out tension test, determines yield strength (YS), tensile strength (TS), yield ratio (YR), percentage of total elongation (EL).
In addition, carrying out hole expansion test according to Nippon Steel alliance standard " 1001 hole expansion test method of JFS T ", determine
Hole expansibility (λ).
In addition, the sample in the rolling direction section comprising hot rolled steel plate is produced, by the rolling direction section phase with the sample
When face using nital corrode, then, using optical microscopy or scanning electron microscope, in 1/4 depth of plate thickness
Position, shoot the macrograph obtained in 300 μm of 300 μ m of visual field, carried out tissue characterization.It is shone by obtained tissue
Piece calculates the area ratio of each tissue using enumeration (point counting) method.Polygonal ferrite and bainite, bayesian
Body ferrite judged by the presence or absence of grain-boundary shape and internal structure, by the tissue identification for corroding to black be cementite and
Pearlite.In addition, having carried out the sample of homogeneous corrosion for using, the macrograph obtained using optical microscopy carries out figure
As parsing, total the area ratio of retained austenite and martensite is thus calculated.
In addition, producing film sample from each hot rolled steel plate, ferrite grain is observed using transmission electron microscope (multiplying power: 200000 times)
The carbide containing one or more of Ti, V, Nb of interior precipitation, has found out a number density and aspect ratio is 3 ratios below.
In addition, being determined using method above-mentioned aobvious for the steel for the polygonal ferrite for having obtained 80 area % or more
The standard deviation of microhardness.As 1, Fig. 3 A shows the measurement result of the microhardness of test piece number (Test pc No.) 14, and Fig. 3 B shows test piece number (Test pc No.)
The measurement result of 15 microhardness.
Obtained result is shown in table 3 and table 4.In table 3 and table 4, V α, VP θ, VMA, B, BF, σ HV indicate following items.
The empty column expression of tissue is not observed.
V α: ferritic the area ratio
VP θ: total the area ratio of pearlite and cementite
VMA: total the area ratio of martensite and austenite
B, BF: bainite and bainite ferrite
σ HV: the standard deviation of ferrite microhardness
Test piece number (Test pc No.) 1~3,5~6,11,17~19,22,25~34, chemical composition and tissue all present invention provide that
In range, therefore desired mechanical property is obtained.On the other hand, test piece number (Test pc No.) 4,10,12~16,20~21,24,36, σ HV
Be more than present invention provide that the upper limit, as a result, not obtaining desired mechanical property.Test piece number (Test pc No.) 7,8,18,36, polygon
Ferritic the area ratio be lower than present invention provide that lower limit, as a result, not obtaining desired mechanical property.Test piece number (Test pc No.) 9, horse
The area ratio of family name's body and austenite it is total be greater than present invention provide that the upper limit, as a result, not obtaining desired mechanical special
Property.The area ratio of test piece number (Test pc No.) 36,38, pearlite and cementite it is total be greater than present invention provide that the upper limit, as a result,
To desired mechanical property.
In addition, test piece number (Test pc No.) 7,8,12,23,24,35,38, carbide number density is small, in addition, test piece number (Test pc No.) 7,8,12,23,
24,36, aspect ratio is that the ratio of 3 carbide below containing Ti becomes more, does not obtain desired mechanical property.
Test piece number (Test pc No.) 37, toughness is low, is broken in sample processing, therefore can not be tested.
[embodiment 2]
Secondly, implementing Fig. 1 for A~C and G, H this 5 steel grades among the steel with chemical composition shown in table 1
Shown in hot rolling and cooling.Thereafter, implement descale processing, do not implement cold rolling, it is real using continuous heat simulator
The heat treatment of the alloyed hot-dip zinc-coated production line of simulation of mode shown in Fig. 2 is applied.At this point, the condition of each process such as 5 institute of table
Show.In table 5, RA, LTH, DIP, GA indicate following items.
RA: maximum heating temperature
LTH: low temperature keeps temperature
DIP:Zn bath temperature
GA: alloying temperature
From the hot rolled steel plate obtained in this way, JIS5 tensile sample has been produced from the direction vertical with rolling direction.It uses
The sample carries out tension test, determines yield strength (YS), tensile strength (TS), yield ratio (YR), percentage of total elongation (EL).Separately
Outside, hole expansion test is carried out according to Nippon Steel alliance standard " 1001 hole expansion test method of JFS T ", determines hole expansibility (λ).
In addition, producing the sample in the rolling direction section comprising steel plate, calculated respectively using method same as Example 1
The area ratio of tissue.
In addition, producing film sample from each hot rolled steel plate, using transmission electron microscope (multiplying power: 200000 times), ferrite is observed
The carbide containing one or more of Ti, V, Nb that intragranular is precipitated, has found out a number density and aspect ratio is 3 ratios below
Example.For having obtained the steel of the polygonal ferrite of 80 area % or more, the mark of microhardness is determined using method above-mentioned
Quasi- deviation.
Obtained result is shown in table 6.Test piece number (Test pc No.) 39~42,44~47, chemical composition and tissue all present invention provide that
In the range of, obtain desired mechanical property.On the other hand, test piece number (Test pc No.) 43, σ HV be more than present invention provide that the upper limit,
As a result, not obtaining desired mechanical property.Test piece number (Test pc No.) 48, polygonal ferrite the area ratio be lower than present invention provide that under
Limit, as a result, not obtaining desired mechanical property.
Industrial availability
In accordance with the invention it is possible to be manufactured inexpensively the high strength rolled steel with high yield ratio and excellent hole expandability
Plate.Moreover, it relates to steel plate, what is more used in automotive part, particularly running gear component etc. puts side
Also there is excellent hole expandability in forming.Therefore, industrially, particularly automotive field facilitate car body lightweight and really
Protect crashworthiness.
Claims (5)
1. a kind of high tensile hot rolled steel sheet, which is characterized in that chemical composition is contained in terms of quality %
C:0.010%~0.200%,
Si:0.001%~2.50%,
Mn:0.001%~1.50%,
P:0.050% or less,
S:0.010% or less,
N:0.0070% or less,
Al:0.001%~0.50%,
Ti:0.050%~0.30%,
V:0%~0.50%,
Nb:0%~0.090%,
Cr:0%~0.50%,
Ni:0%~0.50%,
Cu:0%~0.50%,
Mo:0%~0.50%,
B:0%~0.0050%,
Ca:0%~0.01%,
Mg:0%~0.01%,
Bi:0%~0.01%,
Surplus be Fe and impurity,
Organize the polygonal ferrite in terms of the area ratio containing 80% or more, add up to 5% martensite and austenite below, with
And add up to 5% pearlite and cementite below, remainder be selected from one of bainite ferrite and bainite with
On,
Will in the range of distance center face ± 100 μm on plate thickness direction existing any 50 polygonal ferrites it is aobvious
When the standard deviation of microhardness is denoted as σ HV, the σ HV be 30 hereinafter,
In the intragranular of the polygonal ferrite, there are 5 × 107A/mm2Above carbide containing Ti, the carbide containing Ti it
In 50% or more the carbide containing Ti long side length relative to bond length ratio, that is, aspect ratio less than 3,
Tensile strength is 540MPa or more.
2. high tensile hot rolled steel sheet according to claim 1, which is characterized in that the chemical composition is contained in terms of quality %
Selected from V:0.010%~0.50%, Nb:0.001%~0.090%, Cr:0.001%~0.50%, Ni:0.001%~
0.50%, one of Cu:0.001%~0.50%, Mo:0.001%~0.50%, B:0.0001%~0.0050% with
On.
3. high tensile hot rolled steel sheet according to claim 1 or 2, which is characterized in that the chemical composition is in terms of quality %
Containing selected from one of Ca:0.0001%~0.01%, Mg:0.0001%~0.01%, Bi:0.0001%~0.01% with
On.
4. high tensile hot rolled steel sheet according to claim 1 or 2, which is characterized in that there is dip galvanized on surface.
5. high tensile hot rolled steel sheet according to claim 3, which is characterized in that there is dip galvanized on surface.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP2015/071845 WO2017022025A1 (en) | 2015-07-31 | 2015-07-31 | High-strength hot-rolled steel sheet |
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| CN107849651B true CN107849651B (en) | 2019-09-03 |
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| US (1) | US20180209007A1 (en) |
| EP (1) | EP3330394B1 (en) |
| JP (1) | JP6485549B2 (en) |
| KR (1) | KR102079968B1 (en) |
| CN (1) | CN107849651B (en) |
| BR (1) | BR112018000633A2 (en) |
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| WO (1) | WO2017022025A1 (en) |
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| WO2018055098A1 (en) * | 2016-09-22 | 2018-03-29 | Tata Steel Ijmuiden B.V. | A method of producing a hot-rolled high-strength steel with excellent stretch-flange formability and edge fatigue performance |
| CN110656292A (en) * | 2018-06-28 | 2020-01-07 | 上海梅山钢铁股份有限公司 | 440 MPa-level tensile strength low-yield-ratio high-hole-expansibility hot-rolled steel plate |
| CN109047692B (en) * | 2018-08-22 | 2021-01-26 | 江阴兴澄特种钢铁有限公司 | Ultrathin high-strength steel plate capable of being used at-60 ℃ and manufacturing method thereof |
| CN114096692A (en) * | 2019-07-09 | 2022-02-25 | 杰富意钢铁株式会社 | Seamless steel pipe having excellent sulfuric acid dew point corrosion resistance and method for producing same |
| KR102643337B1 (en) * | 2019-07-10 | 2024-03-08 | 닛폰세이테츠 가부시키가이샤 | high strength steel plate |
| CN112522568A (en) * | 2019-09-19 | 2021-03-19 | 宝山钢铁股份有限公司 | Fire-resistant weather-resistant steel plate/belt and manufacturing method thereof |
| JP7295470B2 (en) * | 2020-01-17 | 2023-06-21 | 日本製鉄株式会社 | steel plate and pipe |
| CN115298342B (en) * | 2020-03-19 | 2023-11-17 | 日本制铁株式会社 | steel plate |
| EP4137592A4 (en) * | 2020-04-17 | 2023-10-25 | Nippon Steel Corporation | High-strength hot-rolled steel sheet |
| EP3925771A1 (en) * | 2020-06-16 | 2021-12-22 | SSAB Technology AB | High strength steel product and method of manufacturing the same |
| CN113005352B (en) * | 2021-02-08 | 2022-04-12 | 大连理工大学 | Method for strengthening and toughening martensitic steel by adding nano TiC |
| KR20240096056A (en) * | 2022-12-19 | 2024-06-26 | 주식회사 포스코 | Steel plate and method for manufactureing the same |
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- 2015-07-31 US US15/744,690 patent/US20180209007A1/en not_active Abandoned
- 2015-07-31 EP EP15900339.1A patent/EP3330394B1/en active Active
- 2015-07-31 BR BR112018000633-5A patent/BR112018000633A2/en not_active Application Discontinuation
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Also Published As
| Publication number | Publication date |
|---|---|
| US20180209007A1 (en) | 2018-07-26 |
| CN107849651A (en) | 2018-03-27 |
| EP3330394A4 (en) | 2018-12-19 |
| WO2017022025A1 (en) | 2017-02-09 |
| JP6485549B2 (en) | 2019-03-20 |
| MX2018001140A (en) | 2018-04-20 |
| EP3330394B1 (en) | 2020-08-26 |
| KR102079968B1 (en) | 2020-02-21 |
| EP3330394A1 (en) | 2018-06-06 |
| BR112018000633A2 (en) | 2018-09-18 |
| KR20180019736A (en) | 2018-02-26 |
| JPWO2017022025A1 (en) | 2018-05-31 |
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