CN100360698C - High strength hot rolled steel sheet and method for manufacturing the same - Google Patents
High strength hot rolled steel sheet and method for manufacturing the same Download PDFInfo
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- CN100360698C CN100360698C CNB2004800055579A CN200480005557A CN100360698C CN 100360698 C CN100360698 C CN 100360698C CN B2004800055579 A CNB2004800055579 A CN B2004800055579A CN 200480005557 A CN200480005557 A CN 200480005557A CN 100360698 C CN100360698 C CN 100360698C
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Abstract
The present invention relates to a high strength hot rolled steel sheet consisting of 0.04 to 0.15% C, 1.5% or less Si, 0.5 to 1.6% Mn, 0.04% or less P, 0.005% or less S, 0.04% or less Al, 0.03 to 0.15% Ti, 0.03 to 0.5% Mo, by mass, and balance of Fe and inevitable impurities, and having a microstructure consisting of ferrite containing precipitates, second phase of bainite and/or martensite, and other phase, wherein the percentage of the ferrite containing precipitates is 40 to 95%, and the percentage of the other phase is 5% or less. For example, the high strength hot rolled steel sheet having a thickness of 1.4 mm shows a tensile strength of 780 MPa or higher, an elongation of 22% or higher elongation, and a hole expansion ratio of 60% or higher, thus the steel sheetis suitable for reinforcing members automobile cabin and crash worthiness members of automobile.
Description
Technical field
The high tensile hot rolled steel sheet that the present invention relates to a kind of wheel house strengthening part that is used for automobile etc. and have the above tensile strength of 780MPa, particularly a kind of stretchiness and put good high tensile hot rolled steel sheet of limit property and manufacture method thereof.
Background technology
In the past, for the wheel house strengthening part of automobile, do not use hot-rolled steel sheet from the viewpoint of plasticity.But, in recent years,, inquiring into always such parts used cheap hot-rolled steel sheet along with increase in demand to the high steel plate of cost low formation.Particularly, compare the hot-rolled steel sheet of surface property difference with cold-rolled steel sheet for invisible such parts are fit to from the outside.In addition, for the parts of anti-collision of front longitudinal etc., use the situation of the hot-rolled steel sheet of tensile strength increasing, but further require high strength with 440-590MPa.
When making hot-rolled steel sheet be applicable to such parts,, need above high tensile of 780MPa and good stretchiness and put limit property as its characteristic.Particularly for putting limit property, need make the hole expansibility as its index is more than 60%.
To reach the raising stretchiness is purpose, opens in the flat 7-62485 communique to disclose the complex tissue steel plate of second phase of the residual austenite of dispersion hard in the ferrite of parent phase the spy.But, use this steel plate, because the ferrite of parent phase is big with second mutually the difference of hardness of residual austenite, thereby can not get the good limit property of putting.
Open in the flat 9-263885 communique the spy and to propose a kind of ferrite precipitation strength that makes parent phase, dwindle and second mutually the martensitic difference of hardness, improve stretchiness and put the complex tissue steel plate of limit property.But the tensile strength of this steel plate is inappropriate less than 780MPa for the wheel house strengthening part of automobile and the parts of anti-the collision.
As the complex tissue steel plate of tensile strength above 780MPa, open a kind of ferrite precipitation strength that makes parent phase of proposition in the flat 5-179396 communique the spy, dwindle the martensite of second phase or the volume fraction of residual austenite and put the steel plate of limit property to reach to improve.Use this steel plate, can reduce the C equivalent, can improve spot weldability and fatigue characteristic, but hole expansibility at the most only 46%, use as the parts of anti-collision of the wheel house strengthening part of automobile and complicated shape, the not talkative limit property of putting is sufficient.
Summary of the invention
The object of the present invention is to provide the above tensile strength of a kind of 780MPa of having, good stretchiness and the good high tensile hot rolled steel sheet of putting limit property of hole expansibility more than 60%.
This purpose can be reached by the following high tensile hot rolled steel sheet of forming of tool: it has in quality % and contains C:0.04-0.15%, below the Si:1.5%, Mn:0.5-1.6%, below the P:0.04%, below the S:0.005%, below the Al:0.04%, Ti:0.03-0.15%, Mo:0.03-0.5%, the chemical constitution that surplus is made of iron and unavoidable impurities, and have by the ferrite that has precipitate, second phase that bainite and/or martensite constituted, the tissue that in addition other constitutes mutually, and to have the ferritic ratio of precipitate be 40-95%, the ratio of other phase is below 5%.
In addition, this high tensile hot rolled steel sheet can be made by the manufacture method of following high tensile hot rolled steel sheet, and the manufacture method of this high tensile hot rolled steel sheet has: the plate slab that above-mentioned one-tenth is grouped into is heated to 1150-1300 ℃ operation, plate slab after the heating is carried out the operation that steel plate is made in hot rolling with the finishing temperature more than the Ar3 transformation temperature, steel plate after the hot rolling once is cooled to the operation of 700-850 ℃ temperature province with the above average cooling rate of 20 ℃/s, the operation that cooled steel plate is once kept surpassing the time of 1s in the temperature province more than 680 ℃, the operation that steel plate after keeping is cooled to the temperature province below 550 ℃ and batches with the above average cooling rate secondary of 30 ℃/s.
Embodiment
Present inventors etc. study being suitable for the wheel house strengthening part of making automobile and the high tensile hot rolled steel sheet of the parts of anti-the collision, and obtain following result.
A) tissue is made of mutually mutually with other the ferrite that has precipitate, second, wherein, second is made of bainite and/or martensite, formations such as other outer thus mutually ferrite that does not have precipitate, perlite, residual austenite, and making the ferritic ratio that has precipitate is 40-95%, the ratio of other phase is 5% when following, can obtain the above tensile strength of 780Mpa, good extensibility and the hole expansibility good limit property of putting more than 60%.
B) precipitate that is present in the ferrite comprises Ti and Mo, its median size be 20nm following, when equispaced 60nm is following, can make ferrite high strength more, can dwindle the ferrite and second mutually the difference of hardness more, can obtain the better limit property of putting.
The present invention is based on above-mentioned opinion and the invention of developing, below its details of explanation.
1) chemical constitution
C:C need increase, put limit property variation but surpass 0.15%: second for more than 0.04% mutually for the tensile strength that obtains more than the 780Mpa.Thereby C is 0.04-0.15%, is preferably 0.04-0.1%, more preferably 0.05-0.08%.
Si:Si is effective for improving extensibility and putting limit property.But Si surpasses 1.5% o'clock remarkable variation of surface property, and the while erosion resistance is variation also.In addition, resistance to deformation during hot rolling increases, and less than the manufacturing of the steel plate of the 1.8mm thickness of slab difficulty that becomes, thereby Si is below 1.5%, is preferably below 1.2%, more preferably 0.3-0.7%.
Mn:Mn need be for more than 0.5% for the tensile strength that obtains more than the 780Mpa, but surpasses 1.6% o'clock remarkable variation of weldability.Thereby Mn is 0.5-1.6%, is preferably 0.8-1.4%.
P:P surpasses at 0.04% o'clock to original austenite (γ) grain boundary segregation, the remarkable variation of low-temperature flexibility, and big its processibility of each diversity change of steel plate significantly descends simultaneously.Thereby P is below 0.04%, is preferably below 0.025%, more preferably below 0.015%.
S:S surpasses at 0.005% o'clock to former γ grain boundary segregation, separates out as MnS, because the remarkable variation of low-temperature flexibility, so the steel plate of using for the automobile that is used for cold district is improper.Thereby S below 0.005%, is preferably below 0.003%.
Al:Al adds as the reductor of steel, is to improving the useful element of purity of steel.In order to obtain such effect, it is ideal that Al is contained more than 0.001%, forms inclusion in large quantities but surpass at 0.04% o'clock, becomes the reason that constitutes surface spots.Thereby Al is below 0.04%.
Ti:Ti strengthens ferrite owing to separating out in ferrite, so be important element aspect the tensile strength that reaches more than the 780Mpa.In addition, because ferrite is strengthened,, improve and put limit property so second mutually the difference of hardness of ferrite and hard is diminished.For this reason, Ti is contained more than 0.03%, but it is saturated to surpass 0.15% o'clock its effect, causes cost to increase.Thereby Ti is 0.03-0.15%, is preferably 0.05-0.12%.
Mo:Mo separates out as carbide, is unusual effective elements making aspect the ferrite reinforcement.When not containing Mo, it is difficult reaching the above tensile strength of 780Mpa.In addition, because ferrite is strengthened,, improve and put limit property so second mutually the difference of hardness of ferrite and hard is diminished.For this reason, Mo is contained more than 0.03%, but it is saturated to surpass 0.5% o'clock its effect, causes cost to increase.Thereby Mo is 0.03-0.5%.
2) tissue
As mentioned above, in order to obtain the wheel house strengthening part of automobile and the desirable stretchiness of the parts of anti-the collision and to put limit property, make second phase that being organized as of steel plate be made of the ferrite, bainite and/or the martensite that have precipitate, and other tissue that constitutes mutually of in addition the ferrite that does not have precipitate, perlite and residual austenite etc., and need to make the ferritic ratio that has precipitate be that the ratio of 40-95%, other phase is below 5%.
Exist the ferritic ratio of precipitate becoming mutually less than second of 40% o'clock hard too much, surpass second of 95% o'clock hard and become very few mutually.Situation in any case all causes stretchiness to descend.
Here, existing the ferrite of precipitate to be meant to exist at intragranular can (TEM) observation of etc.ing of enough transmission electron microscopes and have a ferrite of the fine precipitate of precipitation strength energy.In addition, there is the ferritic ratio of precipitate, can as following, tries to achieve.
That is, at first, the sample from the position of the thickness of slab direction 1/4 of steel plate takes 3 TEM to use carries out tem observation with 1,000,000 times multiplying powers, try to achieve observe precipitate ferrite for whole ferritic area occupation ratios.Then, after grinding the steel plate cross section, carry out etch, observe with 400 times of positions, try to achieve ferritic area occupation ratio by picture processing to thickness of slab direction 1/4 by opticmicroscope with 3% nital.And the ferritic phase of observing precipitate that order is tried to achieve by tem observation is the ferritic ratio that has precipitate to whole ferritic area occupation ratios with by the long-pending of ferritic area occupation ratio that opticmicroscope is tried to achieve.
Remove the ferritic surplus that has precipitate and be by bainite and/or martensite constitute second mutually and the ferrite that does not have precipitate, perlite, residual austenite etc. other mutually, be below 5% but need make the ratio of other phase, be preferably below 3%.
In ferrite, there is the precipitate that comprises Ti and Mo, the median size that makes this precipitate is below the 20nm, be preferably below the 10nm, making the equispaced is below the 60nm, be preferably 40nm when following, with the fixed ferritic hardness of nano hardness instrumentation be 3-8GPa, the hardness of second phase that is made of bainite and/or martensite is 6-13GPa, can dwindle the ferrite and second mutually the difference of hardness, can obtain better stretchiness and put limit property.
The precipitate that exists in ferrite is differentiated its composition by the energy dispersion type x-ray spectrometry device that is equipped among the TEM, regards precipitate as circle by picture processing and obtains diameter, obtains its median size.In addition, by tem observation, number goes out to be present in the precipitate number in the square zone of 300nm, measures the thickness of sample, calculates the volume that number goes out the zone of precipitate number, supposes that the precipitate homodisperse calculates the equispaced of precipitate.
In addition, when making steel plate of the present invention with method of the present invention, the ratio of bainite is below 60%, and martensitic ratio is below 35%.
Here, martensitic ratio, after grinding the steel plate cross section, with 4% picric acid alcohol and 2% sodium pyrosulfate, 1 to 1 blended liquid are carried out etch, position in thickness of slab direction 1/4 is observed by opticmicroscope, measures by picture processing and tries to achieve the martensitic area occupation ratio that is become white by etch.The ratio of bainite is observed with 1000 times with sweep electron microscope, tries to achieve by picture processing.The kind of the phase beyond ferrite, bainite, the martensite is differentiated by above-mentioned sweep electron microscope.In addition, the ratio of other phase is the ratio beyond ferrite, martensite and the bainite that has precipitate.
The ferrite and second mutually the hardness use the nano hardness meter TRIBOSCOPE of Hysitron corporate system, and making depth of indentation is that 50 ± 20nm ground is adjusted and loaded, and measures 10 points respectively in the position of thickness of slab direction 1/4, and they are averaged and try to achieve.In addition, at this moment the length on 1 limit of impression is about 350nm.By such nano hardness meter, can correctly measure the hardness of second phase of the complex tissue steel that in the past can not correctly measure.
3) manufacture method
3.1 slab heating temperature (SRT)
Make with Continuous casting process or ingot casting+cogging method by the slab that above-mentioned composition constitutes.In this slab, after hot rolling, separated out the precipitate (mainly being Ti class carbide) that is used to make the ferrite precipitation strength thickly.Because this thick precipitate is almost strengthened energy, so the slab before hot rolling temporarily melted when heating, need separate out imperceptibly after hot rolling again, therefore, slab need be heated to more than 1150 ℃.In addition, when heating surpasses 1300 ℃ owing to organize thickization, thereby stretchiness and put limit property variation.Thereby SRT is 1150 ℃-1300 ℃, is preferably 1200 ℃-1300 ℃.
3.2 hot rolling finishing temperature
When hot rolling slab, when the regional end of ferrite+austenitic two-phase was rolling, the distortion in the ferrite was residual, causes the deterioration of stretchiness.Thereby final rolling temperature is that finishing temperature need be for more than the Ar3 transformation temperature that becomes the austenite one phase zone.
In addition, the Ar3 transformation temperature is subjected to the influence of the composition of steel plate, for example uses following formula (1) expression.
Ar3＝910-203×[C]
1/2+44.7×[Si]-30×[Mn]+31.5×[Mo] ...(1)
Here, the amount (quality %) of [M] expression element M.
3.3 the cooling conditions after rolling
By the hot rolled steel plate, in order to make the ferritic ratio that has precipitate is more than 40%, need once be cooled to 700-850 ℃ temperature province with the average cooling rate more than the 20 ℃/s, more than the preferred 50 ℃/s, then keep surpassing the time of 1s, preferably keep more than the 3s in the temperature province more than 680 ℃.Less than 20 ℃/s and when keeping temperature less than 680 ℃, the motivating force of ferrite transformation is little at average cooling rate, is 1s when following in the hold-time in addition, and the ferrite transformation deficiency of time can not obtain existing the ferrite of the precipitate more than 40%.
In addition, for the time that keep to surpass 1s in the temperature province more than 680 ℃, once be cooled to 700-850 ℃ temperature province with the above average cooling rate of 20 ℃/s after, for example also can carry out air cooling.
And then, in ferrite, there is the precipitate that comprises Ti and Mo, for the median size that makes this precipitate is below the 20nm, making the equispaced is below the 60nm, preferably once be cooled to 700-850 ℃ and satisfy more than (SRT/3+300) ℃, the temperature province below (SRT/8+700) ℃.This be because, because the different fusing amount differences that are present in the Ti class carbide in the slab of SRT, so the particle diameter of the precipitate of separating out in cooling and interval are subjected to the influence of SRT greatly.
After the temperature province more than 680 ℃ keeps surpassing the time of 1s, second phase that formation is made of bainite and/or martensite, for the ratio that makes other phase is below 5%, need average cooling rate secondary above with 30 ℃/s, that preferred 50 ℃/s is above be cooled to below 550 ℃, preferred below 450 ℃, more preferably batch after the temperature province below 350 ℃.
Embodiment
Have the steel A-U of chemical constitution of table 1 with the converter melting after, make slab, under the condition of table 2-1,2-2, carry out hot rolling, produce the steel plate 1-34 of thickness of slab 1.4mm with continuous casting.In addition, the Ar3 of table 1 point is the value of obtaining from above-mentioned formula (1).And, in above-mentioned method, carried out parsing, the measurement of hardness of tissue and precipitate.And then, from taking the JIS5 test film, abide by JIS Z 2241 and carry out tension test with the orthogonal direction of the rolling direction of steel plate, try to achieve tensile strength (TS), stretchiness (EL).In addition, put limit property, carry out drifiting test, measured hole expansibility (λ) according to Japanese iron and steel alliance standard JFST 1001 in order to estimate.
Target value of the present invention is TS 〉=780MPa, EL 〉=22%, λ 〉=60%.
The results are shown among table 3-1, the 3-2.
In as the steel plate 1,5,9 of example, 11-13,18-19,21-23,25-26,28-34, all be TS 〉=780MPa, EL 〉=22%, λ 〉=60%, its intensity height, stretchiness and to put limit property good as can be known.
Table 1
| Steel | Chemical ingredients (quality %) | The Ar3 point (℃) | |||||||
| C | Si | Mn | P | S | Al | Mo | Ti | ||
| A | 0.04 | 0.57 | 1.17 | 0.013 | 0.003 | 0.030 | 0.09 | 0.12 | 863 |
| B | 0.05 | 1.02 | 0.82 | 0.013 | 0.002 | 0.039 | 0.1 8 | 0.13 | 891 |
| C | 0.07 | 0.61 | 0.81 | 0.012 | 0.002 | 0.031 | 0.07 | 0.05 | 861 |
| D | 0.09 | 0.37 | 0.54 | 0.014 | 0.003 | 0.035 | 0.42 | 0.11 | 863 |
| E | 0.06 | 0.14 | 0.94 | 0.014 | 0.001 | 0.026 | 0.14 | 0.07 | 843 |
| F | 0.08 | 0.54 | 1.52 | 0.014 | 0.002 | 0.035 | 0.24 | 0.08 | 839 |
| G | 0.02 | 0.58 | 1.36 | 0.012 | 0.004 | 0.038 | 0.11 | 0.10 | 870 |
| H | 0.05 | 0.40 | 0.40 | 0.015 | 0.003 | 0.037 | 0.14 | 0.09 | 875 |
| I | 0.07 | 0.81 | 0.80 | 0.012 | 0.005 | 0.039 | 0.002 | 0.12 | 869 |
| J | 0.07 | 0.93 | 1.10 | 0.011 | 0.002 | 0.025 | 0.16 | 0.02 | 870 |
| K | 0.12 | 0.85 | 0.75 | 0.015 | 0.003 | 0.032 | 0.08 | 0.13 | 858 |
| L | 0.15 | 0.72 | 1.02 | 0.012 | 0.003 | 0.038 | 0.06 | 0.06 | 835 |
| M | 0.17 | 0.80 | 0.70 | 0.010 | 0.002 | 0.038 | 0.11 | 0.09 | 845 |
| N | 0.12 | 1.16 | 1.22 | 0.024 | 0.003 | 0.031 | 0.12 | 0.10 | 859 |
| O | 0.09 | 1.48 | 1.00 | 0.013 | 0.002 | 0.029 | 0.15 | 0.09 | 890 |
| P | 0.07 | 0.62 | 0.64 | 0.012 | 0.003 | 0.030 | 0.15 | 0.14 | 870 |
| Q | 0.06 | 1.10 | 0.97 | 0.032 | 0.004 | 0.030 | 0.20 | 0.07 | 887 |
| R | 0.08 | 1.06 | 0.92 | 0.019 | 0.003 | 0.032 | 0.17 | 0.09 | 878 |
| S | 0.06 | 0.65 | 1.13 | 0.014 | 0.002 | 0.032 | 0.16 | 0.11 | 860 |
| T | 0.07 | 0.81 | 0.62 | 0.033 | 0.003 | 0.035 | 0.06 | 0.04 | 876 |
| U | 0.10 | 1.02 | 0.75 | 0.027 | 0.002 | 0.035 | 0.30 | 0.06 | 878 |
Underscore: beyond the invention scope
Table 2-1
| Steel plate | Steel | SRT (℃) | Finishing temperature (℃) | Speed of cooling (℃/s) | Once the cooling stop temperature (℃) | SRT/8+700 (℃) | SRT/3+300 (℃) | Hold-time (s) | Secondary cooling beginning temperature (℃) | The secondary speed of cooling (℃/s) | Coiling temperature (℃) | Remarks |
| 1 | A | 1200 | 880 | 50 | 750 | 850 | 700 | 5 | 720 | 50 | 40 | Example |
| 2 | A | 1200 | 880 | 30 | 750 | 850 | 700 | 5 | 720 | 20 | 40 | Comparative example |
| 3 | A | 1100 | 880 | 50 | 750 | 838 | 667 | 5 | 720 | 50 | 40 | Comparative example |
| 4 | A | 1200 | 840 | 50 | 750 | 850 | 700 | 5 | 720 | 50 | 40 | Comparative example |
| 5 | B | 1250 | 900 | 40 | 780 | 856 | 717 | 4 | 740 | 40 | 70 | Example |
| 6 | B | 1250 | 900 | 10 | 780 | 856 | 717 | 4 | 740 | 40 | 70 | Comparative example |
| 7 | B | 1250 | 900 | 40 | 650 | 856 | 717 | 4 | 580 | 40 | 70 | Comparative example |
| 8 | B | 1250 | 900 | 40 | 780 | 856 | 717 | 1 | 760 | 40 | 70 | Comparative example |
| 9 | C | 1270 | 880 | 60 | 740 | 859 | 723 | 6 | 700 | 60 | 120 | Example |
| 10 | C | 1270 | 880 | 60 | 740 | 859 | 723 | 6 | 700 | 60 | 600 | Comparative example |
| 11 | D | 1180 | 950 | 70 | 840 | 848 | 693 | 7 | 800 | 70 | 400 | Example |
| 12 | E | 1230 | 870 | 90 | 820 | 854 | 710 | 7 | 780 | 60 | 240 | Example |
| 13 | F | 1250 | 910 | 30 | 790 | 856 | 717 | 6 | 740 | 30 | 320 | Example |
| 14 | G | 1280 | 890 | 40 | 720 | 860 | 727 | 5 | 700 | 40 | 40 | Comparative example |
Underscore: beyond the invention scope
Table 2-2
| Steel plate | Steel | SRT (℃) | Finishing temperature (℃) | Speed of cooling (℃/s) | Once the cooling stop temperature (℃) | SRT/8+700 (℃) | SRT/3+300 (℃) | Hold-time (s) | Secondary cooling beginning temperature (℃) | The secondary speed of cooling (℃/s) | Coiling temperature (℃) | Remarks |
| 15 | H | 1270 | 915 | 40 | 740 | 859 | 723 | 4 | 700 | 40 | 200 | Comparative example |
| 16 | I | 1200 | 885 | 50 | 760 | 850 | 700 | 4 | 710 | 50 | 310 | Comparative example |
| 17 | J | 1190 | 900 | 70 | 710 | 849 | 697 | 6 | 690 | 70 | 150 | Comparative example |
| 18 | K | 1250 | 880 | 30 | 750 | 856 | 717 | 7 | 715 | 30 | 450 | Example |
| 19 | L | 1220 | 860 | 50 | 790 | 853 | 707 | 8 | 750 | 50 | 400 | Example |
| 20 | M | 1250 | 870 | 40 | 750 | 856 | 717 | 6 | 720 | 80 | 350 | Comparative example |
| 21 | N | 1200 | 890 | 80 | 800 | 850 | 700 | 11 | 755 | 100 | 200 | Example |
| 22 | O | 1270 | 910 | 100 | 820 | 859 | 723 | 15 | 780 | 60 | 500 | Example |
| 23 | P | 1200 | 920 | 30 | 810 | 850 | 700 | 7 | 775 | 60 | 300 | Example |
| 24 | P | 1200 | 920 | 30 | 870 | 850 | 700 | 9 | 825 | 60 | 300 | Comparative example |
| 25 | Q | 1230 | 900 | 90 | 780 | 854 | 710 | 5 | 755 | 70 | 420 | Example |
| 26 | R | 1210 | 930 | 60 | 800 | 851 | 703 | 6 | 770 | 60 | 370 | Example |
| 27 | R | 1210 | 930 | 60 | 860 | 851 | 703 | 6 | 830 | 60 | 370 | Comparative example |
| 28 | S | 1155 | 880 | 50 | 850 | 844 | 685 | 5 | 830 | 80 | 350 | Example |
| 29 | S | 1220 | 880 | 50 | 750 | 853 | 707 | 5 | 740 | 80 | 350 | Example |
| 30 | S | 1250 | 880 | 50 | 700 | 856 | 717 | 5 | 690 | 80 | 350 | Example |
| 31 | T | 1220 | 900 | 40 | 830 | 853 | 707 | 10 | 780 | 50 | 100 | Example |
| 32 | T | 1200 | 920 | 40 | 780 | 850 | 700 | 3 | 810 | 50 | 300 | Example |
| 33 | T | 1180 | 920 | 40 | 780 | 848 | 693 | 3 | 815 | 50 | 550 | Example |
| 34 | U | 1230 | 890 | 60 | 750 | 854 | 710 | 7 | 730 | 60 | 520 | Example |
Underscore: beyond the invention scope
Table 3-1
| Steel plate | Steel | Tissue | The mechanical testing value | Precipitate | Hardness | Remarks | ||||||||
| The ratio of F (%) | Second phase | The ratio of other phase (%) | Other phase | TS (MPa) | EL (％) | λ (％) | Median size (nm) | Equispaced (nm) | Ferrite (GPa) | Second phase (GPa) | ||||
| The ratio of B (%) | The ratio of M (%) | |||||||||||||
| 1 | A | 70 | 0 | 30 | 0 | - | 822 | 24 | 71 | 10 | 40 | 6.3 | 8.1 | Example |
| 2 | A | 65 | 10 | 10 | 15 | P | 760 | 20 | 65 | 9 | 38 | 4.6 | 8.4 | Comparative example |
| 3 | A | 50 | 0 | 20 | 30 | f | 715 | 25 | 58 | 13 | 50 | 2.8 | 8.1 | Comparative example |
| 4 | A | 60 | 0 | 20 | 20 | f | 781 | 18 | 57 | 10 | 36 | 2.1 | 8.7 | Comparative example |
| 5 | B | 80 | 0 | 20 | 0 | - | 813 | 24 | 65 | 11 | 42 | 5.2 | 8.7 | Example |
| 6 | B | 15 | 0 | 30 | 55 | f | 751 | 24 | 47 | 13 | 35 | 2.6 | 8.8 | Comparative example |
| 7 | B | 10 | 0 | 20 | 70 | f | 654 | 24 | 34 | 8 | 22 | 2.2 | 8.5 | Comparative example |
| 8 | B | 10 | 20 | 70 | 0 | - | 924 | 17 | 45 | 10 | 31 | 2.1 | 9.0 | Comparative example |
| 9 | C | 60 | 10 | 30 | 0 | - | 843 | 23 | 73 | 9 | 33 | 7.1 | 8.1 | Example |
| 10 | C | 60 | 20 | 0 | 20 | P | 736 | 20 | 78 | 7 | 35 | 2.2 | 5.5 | Comparative example |
| 11 | D | 55 | 45 | 0 | 0 | - | 823 | 22 | 84 | 14 | 49 | 6.1 | 7.2 | Example |
| 12 | E | 70 | 28 | 0 | 2 | f | 782 | 23 | 89 | 15 | 30 | 7.6 | 7.1 | Example |
| 13 | F | 60 | 40 | 0 | 0 | - | 801 | 22 | 87 | 13 | 29 | 4.9 | 7.3 | Example |
| 14 | G | 80 | 0 | 20 | 0 | - | 698 | 24 | 72 | 9 | 21 | 2.3 | 4.6 | Comparative example |
Underscore: beyond the invention scope
F: have the ferrite of precipitate, f: do not have the ferrite of precipitate, B: bainite, M: martensite, P: perlite
Table 3-2
| Steel plate | Steel | The mechanical testing value | Precipitate | Hardness | Remarks | |||||||||
| The ratio of F (%) | Second phase | The ratio of other phase (%) | Other phase | TS (MPa) | EL (％) | λ (％) | Median size (nm) | Equispaced (nm) | Ferrite (GPa) | Second phase (GPa) | ||||
| The ratio of B (%) | The ratio of M (%) | |||||||||||||
| 15 | H | 50 | 50 | 0 | 0 | - | 671 | 25 | 61 | 8 | 24 | 2.2 | 5.9 | Comparative example |
| 16 | I | 60 | 40 | 0 | 0 | - | 731 | 20 | 63 | 14 | 31 | 2.1 | 5.8 | Comparative example |
| 17 | J | 60 | 0 | 40 | 0 | - | 852 | 22 | 43 | 6 | 81 | 2.8 | 10.1 | Comparative example |
| 18 | K | 75 | 10 | 11 | 4 | f | 980 | 22 | 63 | 7 | 27 | 5.1 | 8.6 | Example |
| 19 | L | 65 | 5 | 30 | 0 | - | 982 | 23 | 61 | 11 | 30 | 4.9 | 8.7 | Example |
| 20 | M | 37 | 5 | 58 | 0 | - | 1001 | 15 | 28 | 14 | 27 | 4.8 | 8.9 | Comparative example |
| 21 | N | 70 | 5 | 25 | 0 | - | 831 | 23 | 61 | 12 | 36 | 7.1 | 12.1 | Example |
| 22 | O | 80 | 20 | 0 | 0 | - | 812 | 25 | 68 | 16 | 41 | 4.6 | 7.8 | Example |
| 23 | P | 68 | 17 | 15 | 0 | - | 822 | 23 | 67 | 13 | 30 | 5.4 | 9.0 | Example |
| 24 | P | 32 | 42 | 23 | 3 | f | 862 | 23 | 42 | 23 | 71 | 2.6 | 10.2 | Comparative example |
| 25 | Q | 60 | 35 | 5 | 0 | - | 800 | 22 | 64 | 10 | 38 | 4.7 | 8.1 | Example |
| 26 | R | 75 | 20 | 5 | 0 | - | 840 | 24 | 65 | 9 | 36 | 5.3 | 8.5 | Example |
| 27 | R | 30 | 32 | 17 | 21 | f | 815 | 24 | 37 | 25 | 66 | 2.2 | 9.1 | Comparative example |
| 28 | S | 62 | 24 | 14 | 0 | - | 815 | 22 | 60 | 26 | 68 | 2.4 | 8.1 | Example |
| 29 | S | 72 | 17 | 11 | 0 | - | 861 | 24 | 79 | 9 | 28 | 6.9 | 8.7 | Example |
| 30 | S | 64 | 6 | 30 | 0 | - | 883 | 22 | 60 | 9 | 69 | 2.4 | 8.6 | Example |
| 31 | T | 82 | 5 | 13 | 0 | - | 792 | 22 | 62 | 16 | 51 | 3.5 | 13.0 | Example |
| 32 | T | 45 | 20 | 35 | 0 | - | 964 | 24 | 60 | 9 | 30 | 5.8 | 12.1 | Example |
| 33 | T | 40 | 60 | 0 | 0 | - | 826 | 22 | 64 | 10 | 36 | 5.1 | 8.5 | Example |
| 34 | U | 61 | 34 | 5 | 0 | - | 801 | 23 | 67 | 9 | 32 | 5.7 | 8.9 | Example |
Underscore: beyond the invention scope
F: have the ferrite of precipitate, f: do not have the ferrite of precipitate, B: bainite, M: martensite, P: perlite
Claims (3)
1. high tensile hot rolled steel sheet, have in quality % and contain C:0.04-0.15%, below the Si:1.5%, Mn:0.5-1.6%, below the P:0.04%, below the S:0.005%, below the Al:0.04%, Ti:0.03-0.1 5%, Mo:0.03-0.5%, the chemical constitution that surplus is made of iron and unavoidable impurities, and have by the ferrite that has precipitate, second phase that bainite and/or martensite constitute, with aforementioned other tissue that constitutes mutually in addition, and the ferritic ratio that has described precipitate is 40-95%, the ratio of described other phase is below 5%, and the precipitate that is present in the ferrite comprises Ti and Mo, the median size of described precipitate is below the 20nm, and the equispaced is below the 60nm.
2. the manufacture method of a high tensile hot rolled steel sheet, it has following operation:
To have in quality % contain C:0.04-0.15%, below the Si:1.5%, Mn:0.5-1.6%, below the P:0.04%, below the S:0.005%, below the Al:0.04%, Ti:0.03-0.15%, Mo:0.03-0.5%, the plate slab of the chemical constitution that surplus is made of iron and unavoidable impurities is heated to the operation of 1150-1300 ℃ temperature province;
Plate slab after the described heating is carried out hot rolling with the finishing temperature more than the Ar3 transformation temperature and make the operation of steel plate;
Steel plate after the described hot rolling once is cooled to the operation of 700-850 ℃ temperature province with the above average cooling rate of 20 ℃/s;
Described cooled steel plate is kept surpassing 1s and the operation of following time of 15s in the temperature province more than 680 ℃; With
The operation that steel plate after the described maintenance is cooled to the temperature province below 550 ℃ and batches with the above average cooling rate secondary of 30 ℃/s.
3. the manufacture method of high tensile hot rolled steel sheet as claimed in claim 2, steel plate after the hot rolling once is cooled to 700-850 ℃ and satisfied with more than the high 300 ℃ temperature of SRT/3, than the temperature province below the high 700 ℃ temperature of SRT/8, here, SRT represents the Heating temperature of plate slab.
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| EP2559783A1 (en) * | 2010-05-31 | 2013-02-20 | JFE Steel Corporation | High-strength hot-rolled steel plate exhibiting excellent stretch flangeability and fatigue resistance properties, and production method therefor |
| EP2617851A1 (en) * | 2010-09-17 | 2013-07-24 | JFE Steel Corporation | High-strength hot-rolled steel sheet having superior punchability and method for producing same |
| CN109182700A (en) * | 2018-11-06 | 2019-01-11 | 鞍钢股份有限公司 | The low yield strength ratio hot rolled steel plate and its manufacturing method of automobile reaming function admirable |
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| CN1257933A (en) * | 1998-11-10 | 2000-06-28 | 川崎制铁株式会社 | Hot-rolled steel plate having superfine grains for machining, and mfg. method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| EP2559783A1 (en) * | 2010-05-31 | 2013-02-20 | JFE Steel Corporation | High-strength hot-rolled steel plate exhibiting excellent stretch flangeability and fatigue resistance properties, and production method therefor |
| EP2559783A4 (en) * | 2010-05-31 | 2014-04-09 | Jfe Steel Corp | High-strength hot-rolled steel plate exhibiting excellent stretch flangeability and fatigue resistance properties, and production method therefor |
| US9222155B2 (en) | 2010-05-31 | 2015-12-29 | Jfe Steel Corporation | Method for manufacturing high strength hot-rolled steel sheet having excellent stretch flangeability and fatigue resistance |
| EP2617851A1 (en) * | 2010-09-17 | 2013-07-24 | JFE Steel Corporation | High-strength hot-rolled steel sheet having superior punchability and method for producing same |
| EP2617851A4 (en) * | 2010-09-17 | 2014-04-09 | Jfe Steel Corp | High-strength hot-rolled steel sheet having superior punchability and method for producing same |
| CN109182700A (en) * | 2018-11-06 | 2019-01-11 | 鞍钢股份有限公司 | The low yield strength ratio hot rolled steel plate and its manufacturing method of automobile reaming function admirable |
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