CN104619876B - Hot rolled steel plate and manufacture method thereof - Google Patents
Hot rolled steel plate and manufacture method thereof Download PDFInfo
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- CN104619876B CN104619876B CN201380047480.0A CN201380047480A CN104619876B CN 104619876 B CN104619876 B CN 104619876B CN 201380047480 A CN201380047480 A CN 201380047480A CN 104619876 B CN104619876 B CN 104619876B
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 193
- 239000010959 steel Substances 0.000 title claims abstract description 193
- 238000000034 method Methods 0.000 title claims description 67
- 238000004519 manufacturing process Methods 0.000 title claims description 27
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 92
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 41
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 35
- 239000000203 mixture Substances 0.000 claims abstract description 34
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 12
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 11
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 11
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 11
- 238000005496 tempering Methods 0.000 claims abstract description 10
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 7
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims description 167
- 238000005096 rolling process Methods 0.000 claims description 41
- 235000019628 coolness Nutrition 0.000 claims description 26
- 230000008569 process Effects 0.000 claims description 22
- 230000009467 reduction Effects 0.000 claims description 19
- 238000009825 accumulation Methods 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 8
- 239000012535 impurity Substances 0.000 claims description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 239000002994 raw material Substances 0.000 abstract description 11
- 230000000694 effects Effects 0.000 description 27
- 238000012360 testing method Methods 0.000 description 21
- 230000009466 transformation Effects 0.000 description 19
- 229910001566 austenite Inorganic materials 0.000 description 14
- 238000005516 engineering process Methods 0.000 description 13
- 238000005098 hot rolling Methods 0.000 description 11
- 239000002245 particle Substances 0.000 description 11
- 238000010791 quenching Methods 0.000 description 11
- 230000000171 quenching effect Effects 0.000 description 11
- 230000007704 transition Effects 0.000 description 9
- 230000005611 electricity Effects 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 239000006104 solid solution Substances 0.000 description 7
- 229910001568 polygonal ferrite Inorganic materials 0.000 description 6
- 238000009835 boiling Methods 0.000 description 5
- 238000009826 distribution Methods 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 238000005275 alloying Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 3
- 230000033228 biological regulation Effects 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000035939 shock Effects 0.000 description 3
- 238000010583 slow cooling Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 230000006641 stabilisation Effects 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 238000003723 Smelting Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010779 crude oil Substances 0.000 description 2
- 238000009863 impact test Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 235000015170 shellfish Nutrition 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000008186 active pharmaceutical agent Substances 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000036760 body temperature Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 235000013399 edible fruits Nutrition 0.000 description 1
- HQFCOGRKGVGYBB-UHFFFAOYSA-N ethanol;nitric acid Chemical compound CCO.O[N+]([O-])=O HQFCOGRKGVGYBB-UHFFFAOYSA-N 0.000 description 1
- 229910052840 fayalite Inorganic materials 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000007542 hardness measurement Methods 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 238000006396 nitration reaction Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003129 oil well Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 235000019362 perlite Nutrition 0.000 description 1
- 239000010451 perlite Substances 0.000 description 1
- 238000012797 qualification Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
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- 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
- B21B3/02—Rolling special iron alloys, e.g. stainless steel
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- 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
-
- 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
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following 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
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
- C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
- C21D8/1222—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
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
- C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
- C21D8/1261—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest following 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
- 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
-
- 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
- C22C38/002—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
- C22C38/18—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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- 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 low yield ratio, high strength hot rolled steel plate being suitable as steel pipe raw material and excellent in low temperature toughness.Described hot rolled steel plate has following composition: containing C:0.03～0.10%, Si:0.01～0.50%, Mn:1.4～2.2%, below P:0.025%, below S:0.005%, Al:0.005～0.10%, Nb:0.02～0.10%, Ti:0.001～0.030%, Mo:0.01～0.50%, Cr:0.01～0.50%, Ni:0.01～0.50%, and preferably Moeq meets the scope of 1.4～2.2%；And there is following tissue: internal layer be with the bainite ferrite below mean diameter 10 μm as principal phase and in terms of area ratio containing 1.4～15% the length-width ratio lath martensite less than 5.0 as the tissue of the second phase, top layer is the tissue being made up of mutually tempered martensite or the tissue being made up of mutually with tempering bainite tempered martensite phase.
Description
Technical field
The present invention relates to a kind of spiral steel pipe being suitable as used in line pipe or electricity stitches the raw-material low of steel pipe
Yield ratio, high strength hot rolled steel plate and manufacture method thereof.Particularly, the reduction of the yield strength after tubing can be prevented, surrender simultaneously
Than low and can stably ensure excellence low-temperature flexibility.
Background technology
At present, it is being that helical form carrys out the spiral steel pipe of tubing owing to can effectively manufacture the steel pipe of major diameter by roll of steel plate,
Therefore, it is widely used as in recent years carrying crude oil, the line pipe purposes of natural gas.Particularly in the pipeline of long distance delivery,
Raising transfer efficiency is asked to go forward side by side horizontal high voltage, it addition, oil well and gas well are present in cold district mostly sometimes, via cold district
Situation more.Therefore, the line pipe used requires high intensity, high tenacity.Additionally, from buckling resistant, shock resistance
Viewpoint considers, it is desirable to line pipe is low yielding ratio.The yield ratio in the length of tube direction of spiral steel pipe occurs because of tubing hardly
Change, basically identical with the yield ratio as raw-material hot rolled steel plate.Therefore, in order to reduce the line pipe of spiral steel pipe
Yield ratio, needs to reduce the yield ratio as raw-material hot rolled steel plate.
For such requirement, such as, patent documentation 1 has been recorded a kind of excellent in low temperature toughness and low yielding ratio height has been opened
The manufacture method of power line-pipes hot rolled steel plate.In the technology described in patent documentation 1, by heating steel billet to 1180～1300
After DEG C, under conditions of roughing end temp 950～1050 DEG C, finish rolling end temp 760～800 DEG C, carry out hot rolling, with 5～20
DEG C/sec rate of cooling cooling, start natural cooling when reaching 670 DEG C and keep 5～20 seconds, then, with 20 DEG C/sec with
On rate of cooling cooling, less than 500 DEG C at a temperature of winding, be made for hot rolled steel plate, described steel billet contains in terms of weight %
Have C:0.03～0.12%, below Si:0.50%, below Mn:1.70%, below Al:0.070%, possibly together with Nb:0.01～
0.05%, at least one in V:0.01～0.02%, Ti:0.01～0.20%.According to technology described in patent documentation 1,
Hot strength 60kg/mm can be produced2(more than 590MPa), yield ratio are less than 85%, have fracture transition temperature above
Hot rolled steel plate for the high tenacity of less than-60 DEG C.
It addition, recorded the manufacture method of a kind of effective hot rolled steel plate of high intensity low yielding ratio in patent documentation 2.Patent
Technology described in document 2 is the manufacture method of following hot rolled steel plate, and the method includes: steel is heated to 1000～1300
DEG C, the end of extent (EOE) hot rolling of 750～950 DEG C, it is cooled to coiling temperature with rate of cooling 10～50 DEG C/sec, 480～600
DEG C scope batch, described steel contains C:0.02～0.12%, Si:0.1～1.5%, below Mn:2.0%, Al:0.01
～0.10%, possibly together with Mo+Cr:0.1～1.5%.According to the technology described in patent documentation 2, can not carry out from Ovshinsky body temperature
The degree quenching that starts of region and obtaining have based on ferrite, in terms of area ratio 1～the martensite of 20%, yield ratio be
Less than 85% and tubing after the less hot rolled steel plate of yield strength decrement.
It addition, recorded the manufacture method of the low yielding ratio electricity seam steel pipe of a kind of excellent in low temperature toughness in patent documentation 3.
In the technology described in patent documentation 3, slab is carried out hot rolling, be cooled to 500～650 with the rate of cooling of more than 5 DEG C/sec
Batch after DEG C, after this temperature range makes it be detained more than 10 minutes, be cooled to the temperature less than 500 DEG C, make hot rolling
Steel plate, carries out tubing to this hot rolled steel plate and makes electricity seam steel pipe, and the composition of described slab is as follows: containing C in terms of quality %:
0.01～0.09%, below Si:0.50%, below Mn:2.5%, Al:0.01～0.10%, Nb:0.005～0.10%, also contain
Have in below Mo:0.5%, below Cu:0.5%, below Ni:0.5%, below Cr:0.5% is one kind or two or more so that
Mneq meets more than 2.0, and described Mneq is the relation with contents formula of Mn, Si, P, Cr, Ni, Mo.Described in patent documentation 3
Technology, it is possible to produce have with bainite ferrite as principal phase and comprise the martensite of more than 3% and as needed for 1%
The tissue of above retained austenite, fracture transition temperature for less than-50 DEG C, excellent in low temperature toughness and have high plastic deformation suction
The electricity seam steel pipe of receipts ability.
It addition, recorded a kind of low yielding ratio high tenacity steel plate in patent documentation 4.Described in patent documentation 4
Technology in, slab is implemented hot rolling, then starts to accelerate cooling within final rolling temperature-50 DEG C, flat with 5～50 DEG C/sec
All rate of cooling water-cooleds, to 400～150 DEG C, then carry out natural cooling, it is hereby achieved that having mean diameter is 10～50 μ
The ferrite of m and be dispersed with the low yielding ratio of line and staff control of bainite of island-like martensite and the high tenacity of 1～20 area %
Steel plate, described hot rolling is preferably heated to 950～1300 DEG C, by (Ar3 transformation temperature+100 DEG C)～(Ar3 transformation temperature+150 DEG C)
The reduction ratio of temperature range be set to more than 10%, final rolling temperature be set to 800～700 DEG C, the composition of described slab is as follows: contain
Have C:0.03～0.15%, below Si:1.0%, Mn:1.0～2.0%, Al:0.005～0.060%, Ti:0.008～
0.030%, N:0.0020～0.010%, below O:0.010%.It should be noted that do not mention the shape of island-like martensite
(bar-shaped, block: aftermentioned).
Prior art literature
Patent documentation
Patent documentation 1: Japanese Laid-Open Patent Publication 63-227715 publication
Patent documentation 2: Japanese Unexamined Patent Publication 10-176239 publication
Patent documentation 3: Japanese Unexamined Patent Publication 2006-299413 publication
Patent documentation 4: Japanese Unexamined Patent Publication 2010-59472 publication
Summary of the invention
The problem that invention is to be solved
But, for the technology described in patent documentation 1, due to before and after natural cooling, particularly after natural cooling
Rate of cooling relatively big, accordingly, it would be desirable to control rapidly and rightly rate of cooling, cooling stops temperature etc., be especially in the presence of into
Manufacture thick hot rolled steel plate and need such problems such as large-scale cooling device.It addition, according to described in patent documentation 1
Technology and the hot rolled steel plate that obtains there is also and has based on the tissue of soft polygonal ferrite, thus be difficult to obtain institute
The such problem of desired high intensity.
It addition, for the technology described in patent documentation 2, still it can be seen that the reduction of yield strength after tubing,
Thus exist and produce the such problem of situation increasing requirement that cannot meet nearest steel strength.
It addition, for the technology described in patent documentation 3, exist not reach and can stably ensure fracture transition temperature
VTrs (the cold district specification for nearest) is the such problem of low-temperature flexibility of less than-80 DEG C such excellences.
It addition, for utilizing the steel plate that the technology described in patent documentation 4 obtains, fracture transition temperature can only be ensured
Degree vTrs is up to the toughness of-30～about-41 DEG C, exist cannot tackle nearest needs raising toughness further requirement this
The problem of sample.
It addition, in recent years, based on the requirement carrying crude oil etc. efficiently, it is desirable to high intensity and the former material of thicker steel pipe
Material.But, there are the following problems: increase for high intensity alloying element amount and have to along with increase wall thickness and
Hot rolled steel plate manufacturing process carries out quenching process.Hot rolled steel plate is due to so that high speed carries in the water-cooled band of limited length
Being rolled into coiled type, therefore thickness of slab is the thickest more needs strong cooling.Accordingly, there exist the case hardness of steel plate bring up to more than necessity this
The problem of sample.
Particularly in the case of such as manufacturing thickness of slab and reach the thick hot rolled steel plate of more than 10mm, due to make when finish rolling plate with
100～250mpm such high speeds are passed through, and the most also make plate similarly with at a high speed by the cooling zone after finish rolling.Therefore, thickness of slab
More it is to increase, needs the cooling carrying out that there is big heat transfer coefficient.Accordingly, there exist following problems: the surface of hot rolled steel plate
Hardness brings up to more than necessity, and compared with inside thickness of slab, hot rolled sheet metal surface hardens, and shows that the situation of uneven distribution increases
Many.The uneven distribution of such hardness also can produce the problem bringing properties of steel pipes uneven.It addition, the distribution of this case hardness
It is because steel plate surface detention is in the transformation boiling temperature region (film boiling and the border of nuclear boiling) of cooling procedure that inequality homogenizes
Produce.In order to avoid above-mentioned situation, need the surface temperature of steel plate not below 500 DEG C, but in the case of thickness of slab is thicker,
Internal rate of cooling is the slowest, it is impossible to form desired interior layer tissue.On the other hand, low by making surface of steel plate temperature be reduced to
The homogenization of case hardness can be realized in the temperature range changing boiling range, but cross section maximum hardness exceedes in terms of HV0.5
300 points.Being improved by this hardness, in the case of tube shape after there is not tubing is bad, properties of steel pipes is bad and cannot
The such problem of tubing is the most substantially changed.
It is an object of the invention to provide the low yield ratio, high strength hot rolled steel plate of a kind of excellent in low temperature toughness, this hot-rolled steel
Plate can solve above-mentioned problem of the prior art, need not implement the heat treatment of complexity, and not carry out large-scale scrap build, suitable
Share and make steel pipe raw material, particularly spiral steel pipe purposes, can prevent the intensity after spiral tubing from reducing.Particularly, this
Bright purpose is to provide a kind of more than thickness of slab 8mm (more preferably more than 10mm) and below 50mm (more preferably below 25mm)
The low yield ratio, high strength hot rolled steel plate of excellent in low temperature toughness." high intensity " mentioned here refers to become with rolling direction 30 degree
The yield strength in direction be more than 480MPa, the situation that hot strength is more than 600MPa of plate width direction, it addition, " low temperature
Tenacity excellent " refer to the situation that fracture transition temperature vTrs is less than-80 DEG C of Charpy-type test, it addition, " low yielding ratio "
Refer to that during the stress-strain diagram being expressed as surrender type continuously, yield ratio is the situation of less than 85%.It addition, " steel plate " includes steel
Plate and steel band.
The method of solution problem
To achieve these goals, the present inventor etc. on affect each of the steel strength after tubing and steel pipe toughness
Planting will be because conducting in-depth research.It is it was found that in the reduction of intensity that tubing causes is the pipe acted on by compression stress
Disappearing of the elongation at yield of the side, tube outside that the reduction of the yield strength that the Bauschinger effect of side, face causes and tensile stress are acted on
Become homeless and cause.
Therefore, the present inventor etc. is further studied, and result is expected, by making being organized as with fine of steel plate
Bainite ferrite is the tissue of principal phase and the lath martensite being dispersed with hard in this bainite ferrite imperceptibly,
After can being made to prevent tubing, particularly intensity after spiral tubing reduce, there is the yield ratio of less than 85% simultaneously, enter
And go back the steel pipe of combined with superior toughness.The present inventor etc. find, make as the raw-material steel of steel pipe by forming such tissue
The work hardening capacity of plate improves, and improves hence with the available sufficient intensity of processing hardening of side, tube outside during tubing, from
And after tubing can being suppressed, particularly intensity after spiral tubing reduce, additionally, by making lath martensite disperse imperceptibly, tough
Property significantly improves.
In addition, it has been found that in order to make can prevent surface of steel plate hardness uneven rising, shape after tube shape excellent
Different and have homogeneous deformation can steel pipe, make surface of steel plate be organized as tempered martensite mutually single-phase or for tempered martensite with
The mixed phase of tempering bainite is effective.
The present invention is based on above-mentioned discovery and studies further and completes.That is, the purport of the present invention is as follows.
(1) a kind of hot rolled steel plate, it has a following composition:
In terms of quality %, containing C:0.03～0.10%, Si:0.01～0.50%, Mn:1.4～2.2%, P:0.025%
Below, below S:0.005%, Al:0.005～0.10%, Nb:0.02～0.10%, Ti:0.001～0.030%, Mo:0.01
～0.50%, Cr:0.01～0.50%, Ni:0.01～0.50%, surplus is made up of Fe and inevitable impurity,
Further, described hot rolled steel plate has a following tissue:
Internal layer be with the bainite ferrite below mean diameter 10 μm as principal phase and in terms of area ratio containing 1.4～
The length-width ratio of 15% lath martensite less than 5.0 as the tissue of the second phase,
Top layer is the tissue being made up of mutually tempered martensite or is made up of mutually with tempering bainite tempered martensite phase
Tissue.
(2) hot rolled steel plate described in above-mentioned (1), wherein, described composition is in terms of quality %, defined by following formula (1)
Moeq meets the composition of scope of 1.4～2.2%,
Moeq (%)=Mo+0.36Cr+0.77Mn+0.07Ni (1)
(content (quality %) of wherein, Mn, Ni, Cr, Mo: each element).
(3) above-mentioned (1) or (2) described in hot rolled steel plate, wherein, in addition to above-mentioned composition, possibly together with selected from following composition
In one kind or two or more: below Cu:0.50%, below V:0.10%, below B:0.0005%, described content is quality %.
(4) above-mentioned (1)～(3) according to any one of hot rolled steel plate, wherein, in addition to above-mentioned composition, possibly together with Ca:
0.0005～0.0050%, described content is quality %.
(5) above-mentioned (1)～(4) according to any one of hot rolled steel plate, wherein, the size of described lath martensite is to the maximum
Below 5.0 μm, average out to 0.5～3.0 μm.
(6) above-mentioned (1)～(5) according to any one of hot rolled steel plate, wherein, away from case depth 0.5mm position, thickness of slab direction
The hardness put is less than the 95% of thickness of slab direction maximum hardness.
(7) manufacture method of a kind of hot rolled steel plate, the method includes: steel are implemented hot-rolled process, refrigerating work procedure, batches
Operation and make hot rolled steel plate,
Wherein, described steel have following composition: in terms of quality %, containing C:0.03～0.10%, Si:0.01～
0.50%, Mn:1.4～2.2%, below P:0.025%, below S:0.005%, Al:0.005～0.10%, Nb:0.02～
0.10%, Ti:0.001～0.030%, Mo:0.01～0.50%, Cr:0.01～0.50%, Ni:0.01～0.50%, remaining
Measure and be made up of Fe and inevitable impurity；
Described hot-rolled process is as follows: by described heat steel to heating-up temperature 1050～1300 DEG C, to the steel after this heating
Material implement roughing, laminate base, the accumulation reduction ratio of the temperature province that this sheet billet is implemented in less than 930 DEG C be 50% with
On finish rolling, make hot rolled steel plate；
Described refrigerating work procedure is as follows: get started cooling after finish rolling terminates, and following cooling is implemented in described cooling successively,
Once cooling: be cooled to martensitic phase transformation with surface thermometer with the average cooling rate of more than 100 DEG C/sec and start
Temperature below temperature,
Cooling twice: after this once cools down and terminates, makes its temperature more than 600 DEG C be detained 1 second with surface thermometer
More than clock,
Three coolings: after this cooling twice terminates, with thickness of slab central part thermometer, with the cooling speed of average 5～30 DEG C/sec
Degree is cooled to the cooling of the temperature province of 600～450 DEG C and stops temperature, and
Four coolings: with thickness of slab central part thermometer, with the rate of cooling of average less than 2 DEG C/sec from these three times coolings
Cooling stops temperature and is cooled to coiling temperature, or makes it stop temperature to the temperature of coiling temperature in the cooling of these three times coolings
Area stay more than 20 seconds；
Described coiling process is as follows: batch coiling temperature 450 DEG C is carried out above with surface thermometer.
(8) manufacture method of the hot rolled steel plate described in above-mentioned (7), wherein, described composition is in terms of quality %, by following formula
(1) Moeq defined meets the composition of scope of 1.4～2.2%,
Moeq (%)=Mo+0.36Cr+0.77Mn+0.07Ni (1)
(content (quality %) of wherein, Mn, Ni, Cr, Mo: each element).
(9) above-mentioned (7) or (8) described in the manufacture method of hot rolled steel plate, wherein, in addition to above-mentioned composition, possibly together with choosing
One kind or two or more in following composition: below Cu:0.50%, below V:0.10%, below B:0.0005%, described content
For quality %.
(10) above-mentioned (7)～(9) according to any one of the manufacture method of hot rolled steel plate, wherein, in addition to above-mentioned composition,
Possibly together with Ca:0.0005～0.0050%, described content is quality %.
The effect of invention
According to the present invention, particularly can get following low yield ratio, high strength hot rolled steel plate, it is preferably as spiral
Steel pipe raw material, the intensity after tubing reduces less, and the uneven distribution of case hardness disappears, and section hardness also reduces, and makes
Tube shape and homogeneous deformation during pipe can be excellent, and the yield strength becoming the direction of 30 degree with rolling direction is more than 480MPa, plate
The hot strength of cross direction is more than 600MPa, and fracture transition temperature vTrs of Charpy-type test is less than-80 DEG C, and surrender
Ratio is less than 85%, excellent in low temperature toughness.And, the low yield ratio, high strength hot rolled steel plate of the present invention need not be implemented particularly
Heat treatment, can easily and inexpensively manufacture.Therefore, the present invention can industrially play effect excellent especially.It addition, according to this
Invention, also have can inexpensively and be easily manufactured the line pipe laid with reel pipelaying vessel metbod (リ Le バ ジ method) and will
Seek the line pipe electricity consumption seam such effect of steel pipe of shock resistance.If it addition, by the low yield ratio, high strength hot-rolled steel of the present invention
Plate is used as raw material, the most also has and also is able to create the excellent construction of shock resistance and the high intensity spiral shell of bay component
The rotation such effect of steel-pipe pile.It addition, employ the spiral steel pipe of such hot rolled steel plate due to the yield ratio in length of tube direction
Relatively low, therefore, also there is the such effect of high strength steel pile tube that can also apply to high added value.
Accompanying drawing explanation
Fig. 1 is the explanation of the relation of the cooling twice in the cooling after schematically illustrating the generation of lath martensite and hot rolling
Figure.
Detailed description of the invention
First, the composition restriction reason of hot rolled steel plate of the present invention is illustrated.Hereinafter, unless otherwise specified, matter
Amount % is the most only designated as %.
C:0.03～0.10%
C separates out with the form of carbide, and the intensity being contributed to steel plate by precipitation strength is increased.It still passes through crystal grain
Miniaturization also contributes to the element that the toughness of steel plate improves.Additionally, C has to be solid-solution in steel makes stabilization of austenite, thus promote
Enter the effect of the formation of not covert austenite.In order to obtain these effects, need the C containing more than 0.03%.On the other hand, contain
Having more than the C of 0.10% to make to be formed on crystal boundary the tendency of thick cementite and strengthen, toughness reduces.Therefore, C is defined to 0.03
～the scope of 0.10%.It should be noted that C is preferably 0.04～0.09%.
Si:0.01～0.50%
Si contributes to the intensity of steel plate by solution strengthening to be increased.It addition, by forming hard second phase (such as, horse
Family name's body) and contribute to yield ratio and reduce.In order to obtain these effects, need the Si containing more than 0.01%.On the other hand, contain
Si more than 0.50% can make the generation of the iron scale containing fayalite become notable, and steel plate appearance character reduces.Therefore,
Si is defined to the scope of 0.01～0.50%.It should be noted that Si is preferably 0.20～0.40%.
Mn:1.4～2.2%
Mn solid solution makes the quenching degree of steel improve, thus promotes the generation of martensite.It addition, Mn is to make bainite ferrite
Starting temperature of transformation reduces, and is contributed to the element of the raising of steel plate toughness by the miniaturization of tissue.In order to obtain these effects
Really, the Mn containing more than 1.4% is needed.On the other hand, the toughness of welding heat affected zone can be made to drop containing the Mn having more than 2.2%
Low.Therefore, Mn is defined to the scope of 1.4～2.2%.It should be noted that from stably generating the such viewpoint of lath martensite
Considering, Mn is preferably 1.6～2.0%.
Below P:0.025%
P solid solution and contribute to the increase of armor plate strength, but make toughness reduce simultaneously.Therefore, in the present invention, it is preferred to P makees
Reduce as much as possible for impurity.But, can allow to 0.025%.Therefore, P is defined to less than 0.025%.It should be noted that
P is preferably less than 0.015%.Refining cost can be made to steeply rise owing to excessively reducing P, the most preferably more than 0.001%.
Below S:0.005%
S forms the thick sulfide-based field trashes such as MnS in steel, produces rupturing of slab etc..It addition, make moulding of steel plate
Property reduce.Such phenomenon becomes notable when containing the S having more than 0.005%.Therefore, S is defined to less than 0.005%.Need
Illustrating, S is preferably less than 0.004%.Even if it should be noted that S content is that zero % is the most out of question, but excessively reducing S
Refining cost can be made to steeply rise, the most preferably more than 0.0001%.
Al:0.005～0.10%
Al works as deoxidizer.It addition, Al is the effective element of N to the fixing reason becoming strain aging.For
Obtain these effects, need the Al containing more than 0.005%.On the other hand, oxygen in steel can be made containing the Al having more than 0.10%
Compound increases and makes the toughness of mother metal and weld part reduce.During it addition, the steel such as slab, steel plate are heated in heating furnace, hold
Easily form nitration case on top layer, it is possible to cause the increase of yield ratio.Therefore, Al is defined to the scope of 0.005～0.10%.Need
It is noted that Al is preferably less than 0.08%.
Nb:0.02～0.10%
Nb is solid-solution in steel, or separates out with the form of carbonitride, and the coarsening of suppression austenite grain has simultaneously and presses down
The effect of austenite grain recrystallization processed, makes austenite be possibly realized in the rolling of not re-crystallization temperature province.It addition, Nb is still with carbon
The form of compound or carbonitride separates out imperceptibly and contributes to the element that the intensity of steel plate increases.In cooling after hot rolling,
In the dislocation introduced because of hot rolling, the form with carbide or carbonitride separates out, and the core as γ → α phase transformation works, and promotees
The intragranular entering bainite ferrite generates, and contributes to fine block non-transformed austenite or even fine block martensite
Generation.In order to obtain these effects, need the Nb containing more than 0.02%.On the other hand, excess is containing having more than 0.10%
Deformation drag when Nb there is a possibility that hot rolling increases and is difficult to hot rolling.It addition, excess causes conduct containing the Nb having more than 0.10%
The increase of the yield strength of the bainite ferrite of principal phase, it is difficult to guarantee the yield ratio of less than 85%.Therefore, Nb is defined to 0.02
～the scope of 0.10%.It should be noted that Nb is preferably 0.03～0.07%.
Ti:0.001～0.030%
N is fixed as nitride by Ti, contributes to preventing slab from rupturing.It addition, Ti has the form with carbide imperceptibly
The effect separated out and make armor plate strength increase.In order to obtain such effect, need the Ti containing more than 0.001%.The opposing party
Face, contains, if a large amount of, the Ti having more than 0.030%, then makes bainite ferrite transformation temperature excessively increase, and the toughness of steel plate reduces.
Therefore, Ti is defined to the scope of 0.001～0.030%.It should be noted that Ti is preferably 0.005～0.025%.
Mo:0.01～0.50%
Mo has the effect that and is favorably improved quenching degree, and the C in bainite ferrite is introduced non-transformed austenite
In, promote that martensite is formed by improving the quenching degree of non-transformed austenite.Additionally, Mo be solid-solution in steel by solid solution strong
Change and contribute to the element that armor plate strength increases.In order to obtain these effects, need the Mo containing more than 0.01%.The opposing party
Face, can be formed containing the Mo having more than 0.50% and need above martensite, and the toughness of steel plate reduces.It addition, the unit that Mo is high price
Element, a large amount of containing causing material cost to steeply rise.Thus, Mo is defined to the scope of 0.01～0.50%.It should be noted that
Mo is preferably 0.10～0.40%.
Cr:0.01～0.50%
Cr has makes γ → α phase transformation delay, and is favorably improved quenching degree, promotes the effect that martensite is formed.In order to obtain
Such effect, needs the Cr containing more than 0.01%.On the other hand, can produce containing the Cr having more than 0.50% and make weld part many
Produce the tendency of defect.Therefore, Cr is defined to the scope of 0.01～0.50%.It should be noted that Cr be preferably 0.20～
0.45%.
Ni:0.01～0.50%
Ni is favorably improved quenching degree, promotes that martensite is formed.Additionally, be still favorably improved the element of toughness.In order to
Obtain these effects, need the Ni containing more than 0.01%.On the other hand, even if containing the Ni having more than 0.50%, its effect is satisfied
With, also cannot expect the effect matched with content, therefore be economically disadvantageous.Therefore, Ni is defined to 0.01～0.50%
Scope.It should be noted that Ni is preferably 0.30～0.45%.
Above-mentioned composition is basis, but in the present invention, it is preferred to adjusts above-mentioned one-tenth in the range of above-mentioned containing
Point so that the Moeq defined with following formula (1) meets the scope of 1.4～2.2%,
Moeq (%)=Mo+0.36Cr+0.77Mn+0.07Ni (1)
(content (quality %) of wherein, Mn, Ni, Cr, Mo: each element).
Moeq be represent cooled operation after remain in the index of quenching degree of non-transformed austenite in steel plate.Moeq is low
In 1.4% time, the quenching degree of non-transformed austenite is not enough, becomes perlite etc. in coiling process later mutually.On the other hand,
If Moeq is more than 2.2%, then generating and need above martensite, toughness reduces.Therefore, Moeq be preferably limited to 1.4～
The scope of 2.2%.If Moeq is more than 1.5%, then become low yielding ratio, and then deformation energy improves.Therefore, Moeq is more preferably
It is more than 1.5%.
In the present invention, can contain the most further in above-mentioned composition range selected from below Cu:0.50%,
One kind or two or more and/or Ca:0.0005～0.0050% in below V:0.10%, below B:0.0005% is as selecting
Element.
One kind or two or more in below Cu:0.50%, below V:0.10%, below B:0.0005%
Cu, V, B all contribute to the element of steel plate high intensity, can select as required containing.
V, Cu contribute to the high intensity of steel plate by solution strengthening or precipitation strength.It addition, B segregation in crystal boundary,
The high intensity of steel plate is contributed to by improving quenching degree.In order to obtain such effect, preferably comprise Cu:0.01% with
Upper, more than V:0.01%, more than B:0.0001%.On the other hand, weldability can be made containing V to reduce more than 0.10%.Containing B ultrasonic
Crossing 0.0005% can make the toughness of steel plate reduce.Hot-workability can be made containing Cu to reduce more than 0.50%.Therefore, in the feelings contained
Under condition, it is preferably limited to below Cu:0.50%, below V:0.10%, below B:0.0005%.
Ca:0.0005～0.0050%
Ca is the element making thick sulfide be considered as spherical sulfide and contributing to controlling oxide morphology, can basis
Needs contain.In order to obtain such effect, preferably comprise more than Ca:0.0005%.On the other hand, exceed containing Ca
0.0050% can make the cleannes of steel plate reduce.Therefore, in the case of containing, be preferably limited to Ca:0.0005～
The scope of 0.0050%.
In addition to mentioned component, surplus is made up of Fe and inevitable impurity.As inevitable impurity, can permit
Permitted below N:0.005%, below O:0.005%, below Mg:0.003%, below Sn:0.005%.
Then, the tissue restriction reason of the low yield ratio, high strength hot rolled steel plate of the present invention is illustrated.
The low yield ratio, high strength hot rolled steel plate of the present invention has above-mentioned composition, additionally, thickness of slab direction face side layer (with
Under, be the most sometimes only called top layer) and thickness of slab direction inner face side layer (following, be the most sometimes only called internal layer) there is different tissues.
By so there is different tissues in thickness of slab direction each position, when making steel pipe, possess low yielding ratio and homogeneous deformation energy.This
" thickness of slab direction face side floor (top layer) " described in refers to be less than away from the surface of steel plate back side degree of depth district of 1.5mm in thickness of slab direction
Territory.It addition, " thickness of slab direction inner face side layer (internal layer) " refer in thickness of slab direction from the surface of steel plate back side to inside depth 1.5mm with
On region.
Thickness of slab direction face side layer (top layer) presents tempered martensite phase homogeneous structure or tempered martensite phase and tempering shellfish
The line and staff control of family name's body phase.By forming such tissue, the hardness of thickness of slab direction face side can be made to reduce and possess excellence
Homogeneous deformation energy.Pipe shapes owing to being flexural deformation, and therefore the distance at distance thickness of slab center is the most remote, and the processing in thickness of slab direction becomes
Shape is the biggest, and thickness of slab is the thickest more notable, therefore adjusts textura epidermoidea critically important.
Uneven in cooling experience, such as in the case of receiving the cooling by transition boiling region, hot rolled steel plate office
Portion produces hardness and improves, thus it is uneven to produce hardness.Such problem can be the mutually single-phase group of tempered martensite by making top layer
Knit or line and staff control for tempered martensite phase and tempering bainite phase avoids.It should be noted that in line and staff control
In the case of, the mixed proportion of tempered martensite phase and tempering bainite phase is not particularly limited, the viewpoint processed from temper softening
Consider, preferably make in terms of area ratio tempered martensite be mutually 60～100%, make tempering bainite be 0 mutually in terms of area ratio
～40%.It should be noted that above-mentioned tissue can by manufacturing condition by the temperature province of less than in finish rolling 930 DEG C
Accumulation reduction ratio is set to implement following cooling successively in more than 50%, and the refrigerating work procedure after finish rolling terminates and obtain, described
Cool down as follows: be cooled to martensite start temperature (Ms with surface thermometer with the average cooling rate of more than 100 DEG C/sec
Point) the once cooling of following temperature；After this once cools down and terminates, make its temperature more than 600 DEG C with surface thermometer
It is detained the cooling twice of more than 1 second；After this cooling twice terminates, with thickness of slab central part thermometer, with average 5～30 DEG C/
The rate of cooling of second is cooled to the cooling of the temperature province of 600～450 DEG C and stops cooling down for three times of temperature；And with thickness of slab center
Portion's thermometer, stops temperature with the rate of cooling of average less than 2 DEG C/sec from the cooling of these three times coolings and is cooled to coiling temperature,
Or make it stop temperature to the temperature province of coiling temperature in the cooling of above-mentioned three coolings and be detained four times of more than 20 seconds
Cooling.It addition, tissue and area ratio can be observed by the method described in embodiment described later, measure, identify, calculate.
Additionally, the hardness away from surface of steel plate 0.5mm position is preferably the 95% of thickness of slab direction maximum hardness in thickness of slab direction
Below.That is, tube shape after the processability guaranteeing hot rolled steel plate and tubing so from the viewpoint of, it is important that do not make thickness of slab
The direction hardness away from surface of steel plate 0.5mm position reaches the maximum hardness in thickness of slab direction.It should be noted that thickness of slab direction is
High rigidity is preferably calculated as more than 165 with vickers hardness hv 0.5.Additionally, it is preferred that be less than 300, more preferably 280 with
Under.It should be noted that above-mentioned hardness can be by implementing once in refrigerating work procedure after finish rolling terminates in manufacturing condition
Cooling and cooling twice and obtain, described once cooling is with the average cooling rate of more than 100 DEG C/sec with surface thermometer
Being cooled to martensite and in a disguised form start temperature (Ms point) temperature below, described cooling twice is after this once cools down and terminates, with
Surface thermometer makes its temperature more than 600 DEG C be detained more than 1 second.It addition, hardness can be by remembering in aftermentioned embodiment
The method carried measures.
On the other hand, thickness of slab direction inner face side layer (internal layer) presents the tissue formed mutually by principal phase with second, and this tissue is
Using bainite ferrite as principal phase and be dispersed with as the second phase length-width ratio less than 5.0 lath martensite.Here, main
Refer to the phase in terms of area ratio with the occupied area of more than 50% mutually.Bainite ferrite is preferably in terms of area ratio
More than 85%, more preferably more than 88.3%.Bainite ferrite as principal phase is to have the bottom tissue that dislocation density is high
Phase, it comprises acicular ferrite, acicular ferrite.It should be noted that it is close without dislocation in bainite ferrite
Spend extremely low polygonal ferrite and standard (plan) polygonal ferrite with bottom tissues such as tiny subgrains.Need explanation
, in order to ensure desired high intensity, need in as the bainite ferrite of principal phase, separate out fine carbonitride.
It addition, have the mean diameter of below 10 μm as the bainite ferrite of principal phase.If mean diameter becomes big, then more than 10 μm
The processing hardening of the low deformed region less than 5% can be insufficient, and yield strength reduces because of bending machining during spiral tubing.Logical
Cross and make the average particle diameter became of principal phase fine, even in the case of containing more martensite, it is also possible to guarantee desired
Low-temperature flexibility.
And, the second phase in internal layer be in terms of area ratio 1.4～15% length-width ratio less than 5.0 block geneva
Body.Lath martensite described in the present invention be in the cooling procedure after rolling at old γ grain circle or old γ intragranular by non-phase transformation
The martensite that austenite generates.In the present invention, such lath martensite is made to be scattered in old γ grain circle or the shellfish as principal phase
Between family name's body ferrite grain and bainite ferrite grain.Martensite is harder compared with principal phase, can add man-hour at bainite ferrum
Ferritic introduces a large amount of mobile dislocation, such that it is able to make yield behavior become continuous surrender type.It addition, martensite has compares bayesian
The higher hot strength of body ferrite, therefore can realize low yielding ratio.It addition, be that length-width ratio is less than 5.0 by making martensite
Lath martensite, can introduce more mobile dislocation in bainite ferrite around, thus play improving deformation energy
Effect.When the length-width ratio of martensite is more than 5.0, become bar-shaped martensite (non-lath martensite), it is impossible to realize desired
Low yielding ratio, but bar-shaped martensitic phase in terms of area ratio can be allowed to be less than 30% for martensite total amount.Lath martensite
More than the 70% of martensite total amount preferably it is calculated as with area ratio.It should be noted that length-width ratio can be by aftermentioned embodiment
Described in method measure.
In order to obtain such effect, need to dissipate the lath martensite of more than 1.4% with area ratio score.Block geneva
When body is less than 1.4%, it is difficult to guarantee desired low yielding ratio.On the other hand, if lath martensite is super in terms of area ratio
Cross 15%, then low-temperature flexibility substantially reduces.Therefore, lath martensite is defined in the scope of 1.4～15%.Additionally, it is preferred that be
Less than 10%.It should be noted that second is divided by beyond lath martensite, it is also possible to containing with area ratio be calculated as 7.0% with
The bainite etc. of lower degree.
It should be noted that above-mentioned tissue can pass through the temperature province of less than in finish rolling 930 DEG C in manufacturing condition
Accumulation reduction ratio be set to more than 50% and refrigerating work procedure after finish rolling terminates in implement following cooling successively and obtain, institute
State cooling as follows: be cooled to martensite start temperature with surface thermometer with the average cooling rate of more than 100 DEG C/sec
The once cooling of (Ms point) temperature below；After this once cools down and terminates, make its temperature more than 600 DEG C with surface thermometer
Degree is detained the cooling twice of more than 1 second；After this cooling twice terminates, with thickness of slab central part thermometer, with average 5～30
DEG C/sec the cooling of the rate of cooling temperature province that is cooled to 600～450 DEG C stop three times of temperature coolings；And with thickness of slab
Central part thermometer, stops temperature with the rate of cooling of average less than 2 DEG C/sec from the cooling of these three times coolings and is cooled to batch temperature
Degree, or make its above-mentioned three times cooling cooling stop temperature to coiling temperature temperature province be detained more than 20 seconds four
Secondary cooling.
It addition, the size of lath martensite is preferably at most below 5.0 μm, average out to 0.5～3.0 μm.If block horse
The average-size of family name's body coarse to more than 3.0 μm, then easily becomes the starting point of brittle break, or readily facilitates the biography of be full of cracks
Broadcasting, low-temperature flexibility reduces.If it addition, average-size is less than 0.5 μm, then particle is meticulous and make the peritropous bayesian of mobile dislocation
Introduction volume in body ferrite reduces.If it addition, maximum is more than 5.0 μm, then toughness reduces.Therefore, the chi of lath martensite
Very little be preferably at most below 5.0 μm, average out to 0.5～3.0 μm.It should be noted that for size, by long edge lengths and short
The 1/2 of edge lengths sum is as " diameter ".And, the maximum therein is set to " maximum " of lath martensite size, by right
The value that " diameter " of obtained each particle carries out arithmetic average and obtain is set to " averagely " of lath martensite size.Need
Bright, martensite to be determined is set to more than 100.
It should be noted that above-mentioned tissue can pass through the temperature province of less than in finish rolling 930 DEG C in manufacturing condition
Accumulation reduction ratio be set to more than 50% and refrigerating work procedure after finish rolling terminates in implement following cooling successively and obtain, institute
State cooling as follows: be cooled to martensite start temperature with surface thermometer with the average cooling rate of more than 100 DEG C/sec
The once cooling of (Ms point) temperature below；After this once cools down and terminates, make its temperature more than 600 DEG C with surface thermometer
Degree is detained the cooling twice of more than 1 second；After this cooling twice terminates, with thickness of slab central part thermometer, with average 5～30
DEG C/sec the cooling of the rate of cooling temperature province that is cooled to 600～450 DEG C stop three times of temperature coolings；And with thickness of slab
Central part thermometer, stops temperature with the rate of cooling of average less than 2 DEG C/sec from the cooling of these three times coolings and is cooled to batch temperature
Degree, or make its above-mentioned three times cooling cooling stop temperature to coiling temperature temperature province be detained more than 20 seconds four
Secondary cooling.
It should be noted that tissue, area ratio and mean diameter can be seen by the method described in aftermentioned embodiment
Examine, measure, identify, calculate.
Then, the preferable production process of the low yield ratio, high strength hot rolled steel plate of the present invention is illustrated.
In the present invention, to have above-mentioned composition steel implement hot-rolled process, refrigerating work procedure, coiling process and make heat
Rolled steel plate.
It should be noted that the manufacture method of the steel used is not particularly limited, converter, electric furnace etc. are preferably used usual
Known method of smelting carries out melting, is made by the molten steel of above-mentioned composition by generally well-known method of smelting such as continuous casting processes
The steel such as slab.
Obtained steel are implemented hot-rolled process.
Hot-rolled process is following operation: by having the heat steel of above-mentioned composition to heating-up temperature 1050～1300 DEG C, real
Executing roughing, laminate base, the accumulation reduction ratio of the temperature province that then this sheet billet is implemented in less than 930 DEG C be 50% with
On finish rolling, make hot rolled steel plate.
Heating-up temperature: 1050～1300 DEG C
As it has been described above, the steel used in the present invention must contain Nb, Ti.Desired in order to be guaranteed by precipitation strength
High intensity, need to make their thick carbide, nitride etc. temporarily to melt, then make its fine precipitation.Therefore, steel
Heating-up temperature be set to more than 1050 DEG C.During less than 1050 DEG C, the non-solid solution of each element, it is impossible to obtain desired armor plate strength.
On the other hand, if it exceeds 1300 DEG C and reach a high temperature, then produce the coarsening of crystal grain, steel plate toughness reduces.Therefore, steel
Heating-up temperature is defined to 1050～1300 DEG C.
The steel being heated to above-mentioned heating-up temperature implement roughing and the base that laminates.The condition of roughing limits the most especially
Fixed, as long as be able to ensure that the condition of the sheet billet of desired size shape.
Obtained sheet billet, followed by finish rolling, makes the hot rolled steel plate of desired size shape.Finish rolling be
The rolling that accumulation reduction ratio is more than 50% of the temperature province of less than 930 DEG C.
The accumulation reduction ratio of the temperature province below 930 DEG C: more than 50%
For miniaturization and the fine dispersion of lath martensite of the bainite ferrite in interior layer tissue, will be at 930 DEG C
The accumulation reduction ratio of following temperature province is set to more than 50%.The accumulation reduction ratio of the temperature province below 930 DEG C is less than
When 50%, drafts is not enough, it is impossible to guarantee the fine bainite ferrite as principal phase in interior layer tissue.It addition, become rush
The dislocation separating out position of the NbC etc. entering to generate the core of γ → α phase transformation is insufficient, and the intragranular of bainite ferrite generates deficiency,
Cannot be used in form the bulk of lath martensite and non-phase transformation γ is fine and most dispersion and remain.Therefore, by finish rolling
The accumulation reduction ratio of the temperature province of less than 930 DEG C is defined to more than 50%.It should be noted that preferably accumulation reduction ratio is
Less than 80%.Even if reduction ratio increases more than 80%, its effect reaches saturated, and the generation separated also becomes apparent, sometimes
The absorption causing Charpy-type test can reduce.
It should be noted that consider from viewpoints such as steel plate toughness, armor plate strength, rolling loads, the rolling of finish rolling terminates temperature
Degree is preferably 850～760 DEG C.If the rolling end temp of finish rolling reaches a high temperature, then in order to make at 930 DEG C more than 850 DEG C
The accumulation reduction ratio of following temperature province is more than 50%, needs to increase the drafts of every a time, sometimes results in rolling
The increase of load.On the other hand, if the low temperature that temperature is less than 760 DEG C, then rolling generates ferrite, causes tissue, precipitation
The coarsening of thing, makes low-temperature flexibility, intensity reduce sometimes.
Next obtained hot rolled steel plate implements refrigerating work procedure.
Refrigerating work procedure is to get started cooling after finish rolling terminates, and implements following cooling successively: with surface thermometer with 100
Average cooling rate more than DEG C/sec is cooled to the once cooling of martensite start temperature (Ms point) temperature below；?
This once cools down after terminating, and makes its temperature more than 600 DEG C delay cooling twice of more than 1 second with surface thermometer；?
After this cooling twice terminates, with thickness of slab central part thermometer, it is cooled to 600～450 with the rate of cooling of average 5～30 DEG C/sec
DEG C the cooling of temperature province stop three times of temperature coolings；And with thickness of slab central part thermometer, with average less than 2 DEG C/sec
Rate of cooling stop temperature from the cooling of these three times coolings and be cooled to coiling temperature, or make its cold in above-mentioned three coolings
But stopping temperature to the temperature province of coiling temperature to be detained more than 20 seconds for four times and cool down, above-mentioned coiling process is with surface temperature
Degree meter is in the coiling temperature 450 DEG C operation batched carried out above.
After finish rolling terminates, within 15 seconds, preferably immediately begin to cooling.
In once cooling, it is cooled to martensitic phase transformation with surface thermometer with the average cooling rate of more than 100 DEG C/sec
Start temperature (Ms point) below.Once the rate of cooling in cooling refers to the temperature range with surface thermometer 600～450 DEG C
Averagely.Once cooled down by this, martensitic phase homogeneous structure or martensitic phase and bainite phase can be formed on steel plate top layer
Line and staff control.The upper limit of the average cooling rate once cooled down does not limits.Can also be according to the energy of the chiller used
Power cools down with higher speed.It should be noted that be stranded in martensite start temperature, (Ms point, with surface temperature
Meter) following time sets according to desired surface texture, within can being 10 seconds, within preferably 7 seconds.As
Fruit is detained for a long time in the temperature province that Ms point is following, then become that martensitic phase is single-phase or martensitic phase and bainite phase
The region of line and staff control excessively increases, and the thickness of slab ratio that desired tissue occupies reduces.
Once cooling after implement cooling twice, in cooling twice, do not implement particularly to cool down, but by from
Internal backheat or heating make it be detained more than 1 second in the temperature being calculated as more than 600 DEG C with surface temperature.By this secondary
Cooling down, martensitic phase, bainite are tempered mutually, and textura epidermoidea becomes tempered martensite phase homogeneous structure or tempered martensite phase
Line and staff control with tempering bainite phase.In surface of steel plate temperature less than 600 DEG C, the holdup time less than in the case of 1 second, table
The tempering of layer tissue is insufficient.Therefore, the temperature that cooling twice is set to being calculated as more than 600 DEG C with surface of steel plate temperature is detained 1
Process more than second.It should be noted that be detained more than 2 seconds at a temperature of preferably more than 600 DEG C.More than 600 DEG C
At a temperature of the upper limit of holdup time be not particularly limited.But, from three cooling conditions substantially ensuring that thickness of slab central part
And from the viewpoint of suppressing the generation of polygonal ferrite, preferably less than 6 seconds.It should be noted that make surface of steel plate temperature
The method of the temperature that degree is warmed up to more than 600 DEG C includes: utilizes the method for the heat within thickness of slab direction and uses external heat
The method etc. of equipment, but be not particularly limited.After defining steel plate textura epidermoidea by once cooling and cooling twice, implement
Three coolings, are formed with bainite ferrite as principal phase, with layer tissue in steel plate that lath martensite is the second phase.
The rate of cooling of three coolings at thickness of slab central part with generation temperature province that is 750～600 of polygonal ferrite
DEG C average rate of cooling be calculated as the scope of 5～30 DEG C/sec.When average cooling rate is less than 5 DEG C/sec, being organized into of internal layer
Tissue for polygonal ferrite main body, it is difficult to guarantee the desired tissue with bainite ferrite as principal phase.On the other hand,
If using the average cooling rate quenching more than 30 DEG C/sec, then alloying element concentration in non-transformed austenite is insufficient,
Cooling later cannot carry out fine dispersion at lath martensite to desired amount, it is difficult to make and there is desired low surrender
Hot rolled steel plate than the low-temperature flexibility of, desired excellence.Therefore, the rate of cooling of thickness of slab central part be defined to 5～30 DEG C/
Second, preferably 5～25 DEG C/sec.It should be noted that the temperature of thickness of slab central part can surface temperature based on steel plate, cooling
The water temperature of water and the water yield etc. are obtained by Calculation of Heat Transfer etc..
Cooling in three coolings stops temperature and is set to the temperature of 600～450 DEG C of scopes.It is higher than upper that cooling stops temperature
When stating the high temperature of temperature range, it is difficult to guarantee the tissue of the desired internal layer with bainite ferrite as principal phase.On the other hand,
When cooling stopping temperature is the low temperature less than said temperature region, non-phase transformation γ is basically completed phase transformation, thus is difficult to ensure that expectation
The lath martensite of amount.
In the present invention, after above-mentioned once cooling～three coolings, four times coolings are implemented.Cool down three times is cold
But stopping temperature to the cooling of the temperature province of coiling temperature, to be shown schematically in Fig. 1 using thickness of slab central part thermometer cold as four times
But.As it is shown in figure 1, four times are cooled to Slow cooling.By this temperature province uses Slow cooling, the alloying element such as C enter one
Step be diffused in non-phase transformation γ, non-phase transformation γ stabilisation and generate lath martensite easily by cooling afterwards.Such
Slow cooling is following cooling: with thickness of slab central part thermometer with average less than 2 DEG C/sec, preferably with less than 1.5 DEG C/sec
Rate of cooling stops temperature from the cooling of three times above-mentioned coolings and is cooled to coiling temperature, or makes it in three times above-mentioned coolings
Cooling stop temperature to coiling temperature temperature province be detained more than 20 seconds.If with average more than the rate of cooling of 2 DEG C/sec
Stop temperature from the cooling of cooling twice and be cooled to coiling temperature, then the alloying element such as C does not diffuses adequately into non-phase transformation γ
In, the stabilisation of non-phase transformation γ is insufficient, such as the cooling being represented by dotted lines in Fig. 1, remains in bainite ferrum element with non-phase transformation γ
Form between body becomes bar-shaped, it is difficult to generate desired lath martensite.
Carry out it should be noted that these four times coolings preferably stop water filling at the back segment of runout table.For thickness of slab relatively
For thin steel plate, in order to ensure desired cooling condition, preferably by completely remove remain on steel plate cooling water, set
Put insulation cover etc. to be adjusted.Additionally, in order to ensure in the above-mentioned temperature province delay time of more than 20 seconds, the most right
Transporting velocity is adjusted.
After four coolings, hot rolled steel plate implements coiling process.
Coiling process is in the coiling temperature 450 DEG C operation batched carried out above with surface thermometer.
When coiling temperature is less than 450 DEG C, it is impossible to realize desired low yielding ratio.Therefore, coiling temperature is defined to 450
More than DEG C.By using above-mentioned operation, preset time more than can be detained in the temperature province that ferrite and austenite coexist.
Using utilize above-mentioned manufacture method to manufacture hot rolled steel plate as tubing raw material, make through common tubing operation
Spiral steel pipe, electricity seam steel pipe.Tubing operation is not particularly limited, and common operation all can be applied.
Below, based on embodiment, the present invention is illustrated in further detail.
Embodiment
The molten steel of composition shown in table 1 is made slab (thickness 220mm) with continuous casting process, makes steel.Then, by this
A little heat steel, to the heating-up temperature shown in table 2, carry out roughing, after the base that laminates, implement this sheet billet with shown in table 2
Condition carry out finish rolling and make the hot-rolled process of hot rolled steel plate (thickness of slab: 8～25mm).For obtained hot rolled steel plate,
Finish rolling implements immediately after terminating and cools down the refrigerating work procedure that constitutes by being once cooled to four times shown in table 2.After refrigerating work procedure, real
The coiling process executed and be rolled into coiled type under the coiling temperature shown in table 2, then carrying out natural cooling.
Taked test film by obtained hot rolled steel plate, implement structure observation, tension test, impact test, hardness examination
Test.
Test method is as follows.
(1) structure observation
Structure observation test film is taken so that rolling direction cross section (L cross section) is for seeing by obtained hot rolled steel plate
Examine face.Test film is polished, carries out nitric acid ethanol corrosion, use optical microscope (multiplying power: 500 times) or ultramicroscope
(multiplying power: 2000 times) carries out structure observation, shooting.Use image analysis apparatus by the macrograph of obtained internal layer to tissue
Kind, the tissue ratio (area ratio) of each phase, mean diameter be determined.It should be noted that for top layer, only by
Macrograph has carried out the qualification of tissue types.
In interior layer tissue, the mean diameter of bainite ferrite as principal phase is obtained with the process of chopping according to JIS G 0552.
It should be noted that the length-width ratio of martensite particle is (long with the length in the direction of the i.e. particle diameter of the length direction in each particle maximum
Limit) and the perpendicular ratio of length (minor face) in direction, (long limit)/(minor face) calculate.By the length-width ratio martensite less than 5.0
Particle is defined as lath martensite.Length-width ratio is martensite referred to as " bar-shaped " martensite of more than 5.0.It addition, for block horse
For the size of family name's body, the long edge lengths of each for lath martensite particle and the 1/2 of bond length sum are set to diameter, to gained
To the diameter of each particle carry out arithmetic average, as the average-size of the lath martensite in steel plate.It should be noted that will
Value maximum in the diameter of each particle of lath martensite is set to the maximum of the size of lath martensite.The martensite particle recorded
It is set to more than 100.
(2) tension test
With draw direction, as right angle orientation, (plate width direction) and draw direction become with rolling direction with rolling direction respectively
The mode in the direction of 30 degree takes tension test sheet (the complete thick test film of API-5L defined from obtained hot rolled steel plate
(wide 38.1mm, GL50mm)), implement tension test according to the regulation of ASTM A 370, obtain tensile properties (yield strength
YS, hot strength TS).
(3) impact test
Take V recessed with the rolling direction mode as right angle orientation with test film length direction from obtained hot rolled steel plate
Mouth test film, implements Charpy-type test according to the regulation of ASTMA 370, has obtained fracture transition temperature vTrs (DEG C).
(4) hardness test
From obtained hot rolled steel plate, take hardness measurement test film, use Vickers (test force: 4.9N)
(load: 500g) determine section hardness.It is measured continuously along thickness of slab direction with 0.5mm interval from surface of steel plate, obtains
At thickness of slab direction (depth direction) hardness away from 0.5mm position, surface and the maximum hardness in thickness of slab direction.Then, by plate
The maximum hardness in thick direction is less than 300, hardness away from case depth 0.5mm position is relative to the maximum hardness in thickness of slab direction
The situation that ratio is less than 95% to be evaluated as hardness distribution good.
Then, using obtained hot rolled steel plate as pipe raw material, spiral steel pipe has been manufactured by spiral tubing operation (outer
Footpath: φ 1067mm).Taked tension test sheet (set by API in the mode that draw direction is pipe circumferential direction by obtained steel pipe
Test film), according to ASTMA 370 regulation implement tension test, determine tensile properties (yield strength YS, hot strength
TS).Δ YS (30 ° of YS of=steel pipe YS-steel plate) is calculated, the degree that the intensity causing tubing reduces by obtained result
Evaluated.
Obtained result is shown in table 3.
Example of the present invention is all not carried out special heat treatment and defines low yield ratio, high strength high-toughness hot-rolled steel sheet, its with
Rolling direction becomes the yield strength in the direction of 30 degree to be more than 480MPa, the hot strength of plate width direction is more than 600MPa, disconnected
Mouth transition temperature vTrs is less than-80 DEG C, has the toughness of excellence, and its yield ratio is less than 85%.On the other hand, for partially
For the comparative example of the scope of the invention, toughness reduces, or cannot guarantee low yielding ratio, it is impossible to obtain having desired characteristic
Hot rolled steel plate.
It addition, after the hot rolled steel plate of example of the present invention becomes steel pipe at tubing, the intensity that tubing causes reduces the most relatively
Few, it is preferred as spiral steel pipe or electricity seam steel pipe raw material.
Claims (10)
1. a hot rolled steel plate, it has a following composition:
In terms of quality %, containing C:0.03～0.10%, Si:0.01～0.50%, Mn:1.4～2.2%, P:0.025% with
Under, below S:0.005%, Al:0.005～0.10%, Nb:0.02～0.10%, Ti:0.001～0.030%, Mo:0.01～
0.50%, Cr:0.01～0.50%, Ni:0.01～0.50%, surplus is made up of Fe and inevitable impurity, and,
Described composition is the forming of scope that the Moeq defined in terms of quality %, by following formula (1) meets 1.4～2.2%,
Moeq (%)=Mo+0.36Cr+0.77Mn+0.07Ni (1)
Wherein, the content (quality %) of Mn, Ni, Cr, Mo: each element,
Further, described hot rolled steel plate has a following tissue:
Internal layer is containing 1.4～15% with the bainite ferrite below mean diameter 10 μm as principal phase and in terms of area ratio
The length-width ratio lath martensite less than 5.0 as the tissue of the second phase,
Top layer is the tissue being made up of mutually tempered martensite or the group being made up of mutually with tempering bainite tempered martensite phase
Knit.
Hot rolled steel plate the most according to claim 1, wherein, in addition to above-mentioned composition, possibly together with 1 in following composition
Plant or two or more: below Cu:0.50%, below V:0.10%, below B:0.0005%, described content is quality %.
Hot rolled steel plate the most according to claim 1, wherein, in addition to above-mentioned composition, possibly together with Ca:0.0005～
0.0050%, described content is quality %.
Hot rolled steel plate the most according to claim 2, wherein, in addition to above-mentioned composition, possibly together with Ca:0.0005～
0.0050%, described content is quality %.
5. according to the hot rolled steel plate according to any one of Claims 1 to 4, wherein, the size of described lath martensite is to the maximum
Below 5.0 μm, average out to 0.5～3.0 μm.
6. according to the hot rolled steel plate according to any one of Claims 1 to 4, wherein, away from case depth 0.5mm position, thickness of slab direction
Hardness is thickness of slab direction maximum hardness less than 95%.
Hot rolled steel plate the most according to claim 5, wherein, the hardness away from case depth 0.5mm position, thickness of slab direction is plate
Less than the 95% of thick direction maximum hardness.
8. a manufacture method for hot rolled steel plate, the method includes: steel are implemented hot-rolled process, refrigerating work procedure, coiling process
And make hot rolled steel plate,
Wherein, described steel have following composition: in terms of quality %, containing C:0.03～0.10%, Si:0.01～0.50%,
Mn:1.4～2.2%, below P:0.025%, below S:0.005%, Al:0.005～0.10%, Nb:0.02～0.10%,
Ti:0.001～0.030%, Mo:0.01～0.50%, Cr:0.01～0.50%, Ni:0.01～0.50%, surplus by Fe and
Inevitably impurity is constituted；Further,
Described composition is the forming of scope that the Moeq defined in terms of quality %, by following formula (1) meets 1.4～2.2%,
Moeq (%)=Mo+0.36Cr+0.77Mn+0.07Ni (1)
Wherein, the content (quality %) of Mn, Ni, Cr, Mo: each element,
Described hot-rolled process is as follows: by described heat steel to heating-up temperature 1050～1300 DEG C, real to the steel after this heating
Executing roughing, laminate base, and the accumulation reduction ratio of the temperature province that this sheet billet is implemented in less than 930 DEG C is more than 50%
Finish rolling, makes hot rolled steel plate；
Described refrigerating work procedure is as follows: get started cooling after finish rolling terminates, and following cooling is implemented in described cooling successively,
Once cooling: be cooled to martensite start temperature with the average cooling rate of more than 100 DEG C/sec with surface thermometer
Following temperature,
Cooling twice: after this once cools down and terminates, with surface thermometer make its temperature more than 600 DEG C be detained 1 second with
On,
Three coolings: after this cooling twice terminates, with thickness of slab central part thermometer, the rate of cooling with average 5～30 DEG C/sec is cold
The cooling of the temperature province of but to 600～450 DEG C stops temperature, and
Four coolings: with thickness of slab central part thermometer, with the rate of cooling of average less than 2 DEG C/sec from the cooling of these three times coolings
Stop temperature and be cooled to coiling temperature, or make it stop temperature to the temperature province of coiling temperature in the cooling of these three times coolings
It is detained more than 20 seconds；
Described coiling process is as follows: batch coiling temperature 450 DEG C is carried out above with surface thermometer.
The manufacture method of hot rolled steel plate the most according to claim 8, wherein, in addition to above-mentioned composition, possibly together with being selected from down
That states in composition is one kind or two or more: below Cu:0.50%, below V:0.10%, below B:0.0005%, described content is matter
Amount %.
The manufacture method of hot rolled steel plate the most according to claim 8 or claim 9, wherein, in addition to above-mentioned composition, possibly together with Ca:
0.0005～0.0050%, described content is quality %.
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| CA3007073C (en) | 2016-01-27 | 2020-08-25 | Jfe Steel Corporation | High-strength hot-rolled steel sheet for electric resistance welded steel pipe and manufacturing method therefor |
| KR101830437B1 (en) * | 2016-04-25 | 2018-02-20 | 현대자동차주식회사 | High toughness, heat-treated steel pipe having a three-layer structure and manufacturing method thereof |
| JP6624103B2 (en) * | 2017-02-06 | 2019-12-25 | Ｊｆｅスチール株式会社 | High strength hot rolled steel sheet and method for producing the same |
| JP6394841B1 (en) * | 2017-02-17 | 2018-09-26 | Ｊｆｅスチール株式会社 | High strength hot rolled steel sheet and method for producing the same |
| BR112019018215A2 (en) * | 2017-04-28 | 2020-06-23 | Nippon Steel Corporation | HIGH-RESISTANCE STEEL PLATE AND SAME PRODUCTION METHOD |
| KR102031450B1 (en) * | 2017-12-24 | 2019-10-11 | 주식회사 포스코 | High strength steel sheet and manufacturing method for the same |
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| KR102555312B1 (en) * | 2019-03-29 | 2023-07-12 | 제이에프이 스틸 가부시키가이샤 | Electric resistance steel pipe, manufacturing method thereof, and steel pipe pile |
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| JP2510187B2 (en) | 1987-03-17 | 1996-06-26 | 川崎製鉄株式会社 | Method for producing hot-rolled steel sheet for low-yield ratio high-strength line pipe with excellent low temperature toughness |
| DE19612818C2 (en) * | 1996-03-30 | 1998-04-09 | Schloemann Siemag Ag | Process for cooling warm-rolled steel profiles |
| JPH10176239A (en) | 1996-10-17 | 1998-06-30 | Kobe Steel Ltd | High strength and low yield ratio hot rolled steel sheet for pipe and its production |
| JP5011773B2 (en) | 2005-03-24 | 2012-08-29 | Ｊｆｅスチール株式会社 | Manufacturing method of low yield ratio ERW steel pipe with excellent low temperature toughness |
| JP5223379B2 (en) * | 2007-03-08 | 2013-06-26 | 新日鐵住金株式会社 | High strength hot rolled steel sheet for spiral pipe with excellent low temperature toughness and method for producing the same |
| KR101257547B1 (en) * | 2007-07-23 | 2013-04-23 | 신닛테츠스미킨 카부시키카이샤 | Steel pipes excellent in deformation characteristics and process for manufacturing the same |
| GB0719457D0 (en) * | 2007-10-04 | 2007-11-14 | Skf Ab | Heat-treatment process for a steel |
| JP5162382B2 (en) | 2008-09-03 | 2013-03-13 | 株式会社神戸製鋼所 | Low yield ratio high toughness steel plate |
| EP2392681B1 (en) * | 2009-01-30 | 2019-03-13 | JFE Steel Corporation | Heavy gauge, high tensile strength, hot rolled steel sheet with excellent hic resistance and manufacturing method therefor |
| CA2749409C (en) * | 2009-01-30 | 2015-08-11 | Jfe Steel Corporation | Thick high-tensile-strength hot-rolled steel sheet having excellent low-temperature toughness and manufacturing method thereof |
| JP5499731B2 (en) | 2009-01-30 | 2014-05-21 | Ｊｆｅスチール株式会社 | Thick high-tensile hot-rolled steel sheet with excellent HIC resistance and method for producing the same |
| JP5679114B2 (en) * | 2011-02-24 | 2015-03-04 | Ｊｆｅスチール株式会社 | Low yield ratio high strength hot rolled steel sheet with excellent low temperature toughness and method for producing the same |
| JP6006477B2 (en) * | 2011-06-24 | 2016-10-12 | 株式会社神戸製鋼所 | Method for producing high-strength steel sheet excellent in balance between low-temperature toughness and strength, and control method thereof |
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2013
- 2013-09-11 KR KR1020157007700A patent/KR101702794B1/en active IP Right Grant
- 2013-09-11 IN IN772DEN2015 patent/IN2015DN00772A/en unknown
- 2013-09-11 CN CN201380047480.0A patent/CN104619876B/en active Active
- 2013-09-11 JP JP2014510588A patent/JP5605527B2/en active Active
- 2013-09-11 US US14/428,217 patent/US20150232970A1/en not_active Abandoned
- 2013-09-11 WO PCT/JP2013/005388 patent/WO2014041802A1/en active Application Filing
- 2013-09-11 EP EP13837646.2A patent/EP2871254B1/en active Active
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| US20150232970A1 (en) | 2015-08-20 |
| BR112015005419A2 (en) | 2017-07-04 |
| KR101702794B1 (en) | 2017-02-03 |
| EP2871254A1 (en) | 2015-05-13 |
| WO2014041802A1 (en) | 2014-03-20 |
| KR20150038747A (en) | 2015-04-08 |
| CN104619876A (en) | 2015-05-13 |
| EP2871254B1 (en) | 2020-06-24 |
| JP5605527B2 (en) | 2014-10-15 |
| IN2015DN00772A (en) | 2015-07-03 |
| EP2871254A4 (en) | 2015-11-18 |
| JPWO2014041802A1 (en) | 2016-08-12 |
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