CN103233161A - Low-yield-ratio high-strength hot-rolled Q&P steel and manufacturing method thereof - Google Patents
Low-yield-ratio high-strength hot-rolled Q&P steel and manufacturing method thereof Download PDFInfo
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Abstract
The invention relates to low-yield-ratio high-strength hot-rolled Q&P steel and a manufacturing method thereof. The steel comprises the chemical components of 0.20-0.40% of C, 1.0-2.0% of Si, 1.5-3.0% of Mn, no more than 0.015% of P, no more than 0.005% of S, 0.02-0.08% of Al, no more than 0.006% of N, 0.005-0.015% of Ti, and balance of Fe and unavoidable impurities. According to the invention, through low-cost component design, on a basis of common C-Mn steel, Si content is increased such that cementite precipitation is inhibited, and austenite grains are micronized through micro-Ti treatment. Also, with a combination of hot continuous rolling process and sectioned cooling process, a structure comprising proeutectoid ferrite, martensite, and residual austenite is obtained. The yield strength is lower than 700MPa, a tensile strength is higher than 1000MPa, a yield ratio is 0.50-0.60, and alloy cost is greatly reduced.
Description
Technical field
The invention belongs to the wear resisting steel field, relate to the high-strength hot-rolled Q﹠amp of a kind of low yield strength ratio; P steel and manufacture method thereof, this hot rolling Q﹠amp; The yield strength of P steel below 700MPa, more than the tensile strength 1000MPa, yield tensile ratio 0.50～0.60.
Background technology
Quenching-partition steel is Q﹠amp; The P steel is the research focus in nearly ten years high-strength steel fields, and its topmost purpose is in the intensity that improves steel, improves the plasticity of steel, namely improves the strength and ductility product of steel.At present, Q﹠amp; The P steel has been known as the important new steel grade of a class in the advanced high-strength steel of the automobile steel field third generation.
Q﹠amp; The main technique of P steel is: steel is heated to complete austenitic area or part austenitic area, after homogenizing is handled for some time, be quenched into a certain temperature between Ms and the Mf (Ms and Mf represent Ms (martensite start) point and end temp respectively) rapidly to obtain to have martensite+residual austenite tissue of a certain amount of residual austenite, stop cold temperature or make carbon atom from oversaturated martensite, in residual austenite, spread enrichment a little more than stopping being incubated certain hour under the cold temperature in quenching subsequently, thereby the stable residual austenite, and then be quenched to room temperature.
Q﹠amp; The research that the P steel is initial and application mainly are conceived to automobile industry to the demand of high-strength high-plasticity steel.From Q﹠amp; The technology implementation procedure of P steel is not difficult to find out, its operational path is comparatively complicated, and steel plate is through after quenching for the first time, need be rapidly heated to a certain temperature and stays for some time.This two-step approach Q﹠amp; P technology is difficult to realize for the hot rolling production process, but the production of hot-rolling high-strength steel is had good reference.In course of hot rolling, can adopt single stage method Q﹠amp; P technology is that press quenching batched to the following certain temperature of Ms after finish to gauge finished.Q﹠amp; P steel typical organization is martensite+a certain amount of residual austenite, so have high strength and good plasticity.
Chinese patent CN102226248A discloses a kind of carbon silicomanganese hot rolling Q﹠amp; The P steel is not handled but carry out little Ti on the design of alloy; Chinese patent CN101775470A discloses a kind of complex phase Q﹠amp; The production technique of P steel is actually a kind of two-step approach and produces Q﹠amp; The technology of P steel; It is Q﹠amp that Chinese patent CN101487096A discloses a kind of two step of usefulness heat treating process production C-Mn-Al; P steel, its principal feature are that unit elongation is very high, but intensity is lower.
Above-mentioned patent adopts heat-treating methods, by can relatively easily controlling ferritic volume fraction in the two-phase region heating, but for the hot continuous rolling process, Heating temperature usually in fully austenitic area and finishing temperature generally more than 780 ℃, and ferriticly begin to separate out temperature mostly below 700 ℃.Therefore, obtaining a certain amount of ferrite by the reduction finishing temperature is difficult to realize in the hot rolling actual production.
Summary of the invention
The object of the present invention is to provide the high-strength hot-rolled Q﹠amp of a kind of low yield strength ratio; P steel and manufacture method thereof, its yield strength are below 700MPa, and tensile strength is more than 1000MPa, and yield tensile ratio is 0.50-0.60, and cost of alloy significantly reduces, and have low yield strength ratio and high-intensity advantage, can be applicable to require yielding and wear-resisting field.
Mentality of designing of the present invention is as follows:
The present invention is by low-cost composition design, on the composition basis of common C-Mn steel, suppress separating out of cementite by improving Si content, little Ti handles refine austenite crystal grain, adopt hot continuous rolling process simultaneously, cooperate the proeutectoid ferrite+martensite+residual austenite tissue that adopts the segmentation process for cooling can obtain to contain a certain amount of volume fraction.By controlling three kinds of out of phase relative contents, can obtain yield strength below 700MPa, the high-strength hot-rolled Q﹠amp of the low yield strength ratio of tensile strength more than 1000MPa; The P steel.
To achieve these goals, the present invention adopts following technical scheme:
The high-strength hot-rolled Q﹠amp of a kind of low yield strength ratio; The P steel, its following chemical components in percentage by weight is: C:0.20%～0.40%, Si:1.0%～2.0%, Mn:1.5%～3.0%, P≤0.015%, S≤0.005%, Al:0.02～0.08%, N≤0.006%, Ti:0.005%～0.015%, all the other are Fe and other unavoidable impurities, the high-strength hot-rolled Q﹠amp of described low yield strength ratio; The yield strength of P steel is below 700MPa, and tensile strength is more than 1000MPa, and its yield tensile ratio is 0.50-0.60.
Preferably, described hot rolling Q﹠amp; In the chemical ingredients of P steel, Si:1.3～1.7%wt.%; Mn:1.8～2.5wt.%; Al:0.03～0.06wt.%; N≤0.004wt.%; Ti:0.008～0.012wt.%; O≤30ppm.
The high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; In the design of P steel chemical composition:
Carbon: carbon is element the most basic in the steel, also is the high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention simultaneously; One of most important element in the P steel.Carbon is as the interstitial atom in the steel, and the intensity that improves steel is played important effect, and yield strength and the tensile strength of steel is had the greatest impact.Generally, the intensity of steel is more high, and unit elongation is more low.The present invention is in order to guarantee to obtain the high tensile steel plate more than the tensile strength 1000MPa, the content of carbon is not less than 0.2wt.% usually in the steel, cross low carbon content can not guarantee steel plate quenching batch the back slowly in the process of cooling carbon from oversaturated martensite to residual austenite fully diffusion, thereby influence the stability of residual austenite.Carbon content in the steel is also unsuitable too high, if carbon content is greater than 0.4wt.%, though can guarantee the high strength of steel, but owing to the objective of the invention is in order to obtain a certain amount of proeutectoid ferrite+martensite+residual austenite tissue, separating out of proeutectoid ferrite must cause rich carbon in the remaining change austenite that does not change, the high carbon martensite unit elongation that this part austenite obtains after quenching is too low, thereby makes the unit elongation of final steel plate reduce.Therefore, carbon content proper in the steel should be controlled at 0.2～0.4wt.%, can guarantee that steel plate has good intensity and plasticity coupling preferably.
Silicon: silicon is element the most basic in the steel, also is one of most important element in the steel of the present invention simultaneously.Compare with traditional hot-rolling high-strength steel, at present the high-strength Q﹠amp of hot rolling; The P base steel originally all is the composition principle of design that adopts high Si.Except C, Si, Mn, do not add or only add a small amount of other alloying elements substantially.Si can suppress separating out of cementite in certain temperature range, but more limited to the restraining effect of εTan Huawu.Thereby Si inhibition cementite is separated out and is made carbon atom diffuse to stable residual austenite in the residual austenite from martensite.Also can suppress separating out of cementite though add higher Al and P, Al content height makes and is easy to stop up the mouth of a river during continuous casting by relatively thickness of molten steel, reduces and water steel efficient; And P content height causes crystal boundary fragility easily, and the impelling strength of steel plate is very low.Therefore, in general, the design of the composition of high Si is still present hot rolling Q﹠amp; One of most important composition principle of design of P steel.The content of Si generally is not less than 1.0wt.%, separates out otherwise can not suppress cementite; The content of Si generally also should not surpass 2.0wt.%, otherwise hot tearing the time appears in steel plate welding easily, and the application of steel plate is caused difficulty, thus in the steel of the present invention the content of Si usually control be preferably 1.3～1.7%wt.% at 1.0～2.0wt.%.
Manganese: manganese is element the most basic in the steel, also is one of most important element in the steel of the present invention simultaneously.As everyone knows, Mn is the important element that enlarges the austenite phase region, can reduce the critical quenching rate of steel, stable austenite, and crystal grain thinning is postponed austenite to pearlitic transformation.The present invention is in order to guarantee the intensity of steel plate, and Mn content generally should be controlled more than 1.5wt.%, and Mn content is low excessively, in fs of segmentation cooling during air cooling, supercooled austenite instability, changes the tissue of perlite type easily into; Simultaneously, the content of Mn generally also should not surpass 3.0wt.%, when surpassing 3.0wt.%, the Mn segregation takes place easily during steel-making, hot tearing easily takes place during sheet billet continuous casting simultaneously, is unfavorable for the raising of production efficiency.Therefore, the content of Mn is generally controlled at 1.5～3.0wt.% in the steel of the present invention, is preferably 1.8～2.5wt.%.
Phosphorus: phosphorus is the impurity element in the steel.P is poly-to crystal boundary very easily partially, during the content of P higher (〉=0.1%), forms Fe in the steel
2P separates out around the crystal grain, reduces plasticity and the toughness of steel, so its content is more low more good, general control at 0.015wt.% with better interior and do not improve steel-making cost.
Sulphur: sulphur is the impurity element in the steel.The common formation MnS of being combined with Mn of S in the steel is mingled with, especially when the content of S and Mn is all higher, will form more MnS in the steel, and MnS itself has certain plasticity, MnS reduces the cross directional stretch performance of steel plate along rolling to deforming in the follow-up operation of rolling.So the content of S is more low more good in the steel of the present invention, control in 0.005wt.% usually during actual production.
Aluminium: the effect of aluminium in steel mainly is to carry out deoxidation in steelmaking process.In addition, Al also can the N in steel be combined and be formed AlN, and AlN can crystal grain thinning.The grain fineness number size of steel is directly related with Al content, and Al content is lower than 0.02wt.%, and grain refinement effect is not obvious; Al content is during greater than 0.08wt.%, not only can not crystal grain thinning, and make steel generation greying easily, thus cause the inefficacy of steel plate.Therefore, the content of Al will be controlled in suitable scope in the steel of the present invention, and control gets final product at 0.02～0.08wt.% usually, and preferable range is 0.03～0.06wt.%.
Nitrogen: nitrogen belongs to impurity element in steel of the present invention, and its content is more low more good.N also is inevitable element in the steel, and generally, the residual content of N is between 0.002～0.004wt.% in the steel, and these solid solutions or free N element can be fixed by being combined with the molten Al of acid.In order not improve steel-making cost, the control of the content of N gets final product with interior at 0.006wt.% in the steel of the present invention, and preferable range is less than 0.004wt.%.
Titanium: the add-on of titanium is corresponding with the add-on of nitrogen in steel.The control of the content of Ti and N can form the TiN particle of a large amount of small and disperseds in the steel in steel during hot rolling in lower scope; Ti/N need control and all form TiN with assurance Ti below 3.42 in the steel simultaneously.Tiny and nano level TiN particle with good high-temperature stability effective refine austenite crystal grain in the operation of rolling; If Ti/N is greater than 3.42, then form thicker TiN particle in the steel easily, the impelling strength of steel plate is caused disadvantageous effect, thick TiN particle can become the formation of crack of fracture.On the other hand, the content of Ti can not be too low, otherwise the TiN quantity that forms very little, do not have the effect of refine austenite crystal grain.Therefore, the content of titanium will be controlled in suitable scope in the steel of the present invention, and the add-on of titanium is at 0.005～0.015wt.% usually, and preferable range is 0.008～0.012wt.%.
Oxygen: oxygen is inevitable element in the steelmaking process, and for the purpose of the present invention, the content of O generally can reach below the 30ppm by after the Al deoxidation in the steel, can not cause the significant adverse influence to the performance of steel plate.Therefore, the control of the O content in the steel of the present invention is got final product with interior at 30ppm.
The high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The manufacture method of P steel comprises the steps:
1) smelting, secondary refining, casting:
Adopt converter or electrosmelting, vacuum oven secondary refining, casting formation strand or ingot casting by following composition, following chemical components in percentage by weight is: C:0.20%～0.40%, Si:1.0%～2.0%, Mn:1.5%～3.0%, P≤0.015%, S≤0.005%, Al:0.02～0.08%, N≤0.006%, Ti:0.005%～0.015%, all the other are Fe and other unavoidable impurities;
2) heating, hot rolling:
The strand that step 1) is obtained or ingot casting are heated to 1100～1200 ℃ and be incubated 1～2h, and start rolling temperature is 1000～1100 ℃, rolling and accumulative total deflection 〉=50% of multi-pass, and main purpose is refine austenite crystal grain; Treat to carry out when the intermediate blank temperature is down to 900～950 ℃ 3～5 rolling and accumulative total deflection 〉=70% of passage subsequently;
3) segmentation cooling:
Rolled piece after the hot rolling between 800～900 ℃ with the quick water-cooled to 500 of cooling rate of 50 ℃/s～600 ℃, air cooling 5～10s then, continue again with the cooling rate of 50 ℃/s is cooled to 100～300 ℃ of a certain temperature between (being between the Ms-Mf) to obtain proeutectoid ferrite+martensite+residual austenite tissue, slowly cool to room temperature after batching at last, obtain the high-strength hot-rolled Q﹠amp of described low yield strength ratio; The P steel.
Preferable, step 2) multi-pass in is rolling be 5～7 times rolling; The speed of batching the slow cooling in back in the step 3) is 8～12 ℃/h.
In above-mentioned proeutectoid ferrite+martensite+residual austenite tissue, the volume percent of its proeutectoid ferrite body tissue is 10～20%, and the volume percent of residual austenite tissue is greater than 5% and less than 10%.
The high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The P steel, design by reasonable component, cooperate the novel process of the hot rolling+segmentation cooling of novelty can obtain the steel plate of excellent combination property simultaneously, namely obtain yield strength below 700MPa, tensile strength is more than 1000MPa, and its yield tensile ratio is 0.50～0.60 the high-strength hot-rolled Q﹠amp of low yield strength ratio; The P steel.
In the segmentation of the present invention cooling, the main purpose of quick water-cooled of fs is to improve the phase driving force of supercooled austenite, be convenient to the follow-up air cooling stage separate out enough proeutectoid ferrites (10～20wt%), to guarantee the low yield strength of steel plate.The composition design of test steel needs higher carbon and manganese so that the carbon after the coiler plate distributes and the stable residual austenite, but then, carbon and manganese also are that austenite stabilizer element is unfavorable for that the air cooling stage after quick water-cooled of fs separates out ferrite, therefore, the proportioning of the composition of alloy and hot rolling, process for cooling must obtain to control well, The faster the better for the water-cooled speed in this stage, and this also is one of innovative point of patent of the present invention;
Steel plate after the fs water-cooled need be through 5～10s air cooling, its main purpose is to separate out a certain amount of proeutectoid ferrite, for guaranteeing the low yield strength of steel plate, the quantity of proeutectoid ferrite should control between 10～20wt% can guarantee lower yield strength; Subordinate phase was quenched and is stopped that cold temperature must be controlled in certain temperature range but not room temperature after air cooling finished, otherwise it is too low to finish distribution and the residual austenite quantity of carbon atom, causes the steel plate unit elongation to reduce.Press quenching technology commonly used at present all is that direct quenching is to room temperature, and another innovative point of the present invention is coiling temperature control in certain low temperature range: can keep on the one hand more austenite (＞5wt%), but the residual austenite instability of this moment, if be cooled to room temperature, residual austenite will be changed its hetero-organization into, therefore add a certain amount of Si element in the composition design and can suppress separating out of carbide in the residual austenite, reduce the consumption of carbon; On the other hand, because the partial potential of carbon atom in martensite is higher than the partial potential in residual austenite, the difference of the partial potential of the two for carbon atom from martensite to residual austenite diffusion motivating force is provided, make the carbon content in the residual austenite significantly increase, thereby make residual austenite at room temperature can stably exist.By the ingenious cooperation of composition proportion and process for cooling, can obtain the steel plate of a certain amount of ferrite+martensite+residual austenite tissue, thus the high-strength hot-rolled Q﹠amp of the low yield strength ratio of obtained performance excellence; The P steel.
In addition, the Heating temperature of steel billet is too short if be lower than 1100 ℃ and soaking time, then is unfavorable for the homogenizing of alloying element; And when temperature is higher than 1200 ℃, not only improved manufacturing cost, and make the heating quality of steel billet descend to some extent.Therefore, the heating and temperature control of steel billet is proper at 1100～1200 ℃.
Equally, the soaking time of heating also needs control within the specific limits.Soaking time is too short, and the diffusion of solute atoms such as Si, Mn etc. is abundant inadequately, and the heating quality of steel billet can not get guaranteeing; Soaking time is long to make that then austenite crystal is thick and has improved manufacturing cost, so the soaking time of heating should be controlled between 1～2 hour.Heating temperature is more high, and corresponding soaking time can suitably shorten.
Production technique of the present invention can be used for making yield strength≤700MPa, tensile strength 〉=1000MPa, and thickness is at the high-strength hot-rolled Q﹠amp of the low yield strength ratio of 3～12mm; The P wear-resisting steel plate has unit elongation (＞8%) preferably simultaneously, and this steel plate shows excellent strong plasticity coupling, brings the beneficial effect of the following aspects thus:
1, the high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The P steel plate, its cost of alloy significantly reduces.Compare with traditional low-alloy high-strength steel, do not add any noble metal element such as Nb, V, Cu, Ni, Mo etc., greatly reduce cost of alloy.Adopt hot continuous rolling process production also can further to reduce production costs than with the production of slab line, therefore, the production cost of steel plate is very low;
2, the high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The P steel plate, its mechanical property excellence, the comprehensive use cost of user reduces.Because the yield strength of steel plate is lower, and the tensile strength height, yield tensile ratio is low, and a largest benefit of bringing thus is that many high-strength steel users need not to transform existing processing units just can carry out technologies such as bending to steel plate, has save the expense of reforming equipment; The loss of grinding tool, the work-ing life of prolongation grinding tool etc. have also been reduced simultaneously;
3, adopt steel plate of the present invention to have low cost, low yield strength ratio and high strength advantage, be particularly suitable for and carry out bending and forming and to require wear-resisting field steel plate, the metastable state residual austenite that keeps in the steel, under conditions such as abrasive wear, can change martensite into, further improve the wear resistance of steel plate.
Description of drawings
Fig. 1 is the high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The technological process of production figure of P steel;
Fig. 2 is the high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The rolling technology figure of P steel;
Fig. 3 is the high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The P steel roll back process for cooling figure;
Fig. 4 is the typical metallograph of embodiment of the invention 1# test steel;
Fig. 5 is the typical metallograph of embodiment of the invention 3# test steel;
Fig. 6 is the typical metallograph of embodiment of the invention 5# test steel;
Fig. 7 is the typical metallograph of embodiment of the invention 7# test steel.
Embodiment
Below in conjunction with specific embodiment technical scheme of the present invention is described in further detail.
The high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The manufacture method of P steel, its technological process of production is: converter or electrosmelting → vacuum oven secondary refining → strand (ingot) → steel billet (ingot) reheat → hot rolling+segmentation process for cooling → coil of strip, as shown in Figure 1.
Embodiment
The high-strength hot-rolled Q﹠amp of the low yield strength ratio of embodiment 1-9; The manufacturing of P steel specifically comprises the steps:
1) smelting, secondary refining, casting:
Chemical ingredients according to each steel in the table 1 adopts converter or electrosmelting, vacuum oven secondary refining, casting formation strand or ingot casting; Slab thickness 120mm;
2) heating, hot rolling:
The strand that step 1) is obtained or ingot casting are heated to 1100～1200 ℃ and be incubated 1～2h, start rolling temperature is 1000～1100 ℃, 5～7 passage hot rollings and accumulative total deflection 〉=50% of depressing greatly treat to carry out when the intermediate blank temperature is down to 900～950 ℃ 3～5 rolling and accumulative total deflection 〉=70% of passage subsequently; Its hot rolling technology as shown in Figure 2; Heating and hot-rolled process parameter that each embodiment is concrete are as shown in table 2;
3) segmentation cooling:
Rolled piece after the hot rolling between 800～900 ℃ with the quick water-cooled to 500 of the cooling rate of＞50 ℃/s～600 ℃, air cooling 5～10s then, continue again to be cooled to 100～300 ℃ of a certain temperature between (being between the Ms-Mf) to obtain a certain amount of ferrite+martensite+a certain amount of residual austenite tissue with the cooling rate of＞50 ℃/s, slowly cool to after batching at last room temperature (cooling rate be 8～12 ℃/h), obtain the high-strength hot-rolled Q﹠amp of low yield strength ratio of each embodiment; The P steel; It rolls the back process for cooling as shown in Figure 3; Each embodiment is concrete, and to roll back process for cooling parameter as shown in table 2.
After testing, the high-strength hot-rolled Q﹠amp of low yield strength ratio of embodiment 1-9 acquisition; The mechanical property of P steel is as shown in table 3; Embodiment 1,3,5 and 7 the high-strength hot-rolled Q﹠amp of low yield strength ratio; The typical metallograph of P steel respectively as shown in Figure 4 to 7.
From the high-strength hot-rolled Q﹠amp of the low yield strength ratio of Fig. 4～Fig. 7; Can clearly be seen that on the typical metallograph of P steel, the tissue of steel plate be mainly needle-like or etc. axle shape proeutectoid ferrite+martensite+residual austenite.According to the X-ray diffraction result as can be known, the content of residual austenite is respectively 5.47%, 6.14%, 5.56% and 6.82% in embodiment 1,3,5 and No. 7 steel plates.Needle-like or etc. the volumn concentration of axle shape proeutectoid ferrite all between 10～20%.In 500～600 ℃ temperature range, it is more low to stop cold temperature, more easy formation needle-like proeutectoid ferrite; It is more high to stop cold temperature, axle such as easy formation shape proeutectoid ferrite more, and the two all can satisfy performance requriements.Therefore, the microtexture of steel plate of the present invention be needle-like or etc. axle shape proeutectoid ferrite+martensite+residual austenite.Because the existence of residual austenite makes steel plate undergo phase transition induced plastic (TRIP) effect in stretching or wear process, thereby has improved the wear resistance of steel plate.
As known from Table 3, the high-strength hot-rolled Q﹠amp of low yield strength ratio of the present invention; The P steel plate, its yield strength≤700MPa, tensile strength 〉=1000MPa, its yield tensile ratio is 0.50～0.60, has simultaneously＞8% unit elongation preferably, this steel plate shows excellent strong plasticity coupling.
Table 1 unit: weight percent
| Embodiment | C | Si | Mn | P | S | Al | N | Ti | O |
| 1 | 0.20 | 1.77 | 2.95 | 0.005 | 0.0033 | 0.043 | 0.0033 | 0.011 | 0.0028 |
| 2 | 0.23 | 1.98 | 2.81 | 0.008 | 0.0032 | 0.028 | 0.0038 | 0.012 | 0.0023 |
| 3 | 0.25 | 1.37 | 2.25 | 0.006 | 0.0034 | 0.051 | 0.0042 | 0.013 | 0.0027 |
| 4 | 0.27 | 1.01 | 2.63 | 0.007 | 0.0035 | 0.035 | 0.0044 | 0.010 | 0.0025 |
| 5 | 0.30 | 1.54 | 2.24 | 0.010 | 0.0029 | 0.022 | 0.0058 | 0.014 | 0.0028 |
| 6 | 0.32 | 1.25 | 2.05 | 0.015 | 0.0030 | 0.079 | 0.0033 | 0.012 | 0.0024 |
| 7 | 0.35 | 1.63 | 1.74 | 0.013 | 0.0027 | 0.065 | 0.0041 | 0.010 | 0.0029 |
| 8 | 0.38 | 1.16 | 1.88 | 0.009 | 0.0023 | 0.073 | 0.0046 | 0.005 | 0.0026 |
| 9 | 0.40 | 1.42 | 1.55 | 0.011 | 0.0031 | 0.058 | 0.0040 | 0.008 | 0.0030 |
Table 2
The mechanical property of table 3 steel plate
Claims (6)
1. high-strength hot-rolled Q﹠amp of low yield strength ratio; The P steel, its following chemical components in percentage by weight is: C:0.20%～0.40%, Si:1.0%～2.0%, Mn:1.5%～3.0%, P≤0.015%, S≤0.005%, Al:0.02～0.08%, N≤0.006%, Ti:0.005%～0.015%, all the other are Fe and other unavoidable impurities; Described hot rolling Q﹠amp; The yield strength of P steel is below 700MPa, and tensile strength is more than 1000MPa, and its yield tensile ratio is 0.50～0.60.
2. the high-strength hot-rolled Q﹠amp of low yield strength ratio as claimed in claim 1; The P steel is characterized in that, described hot rolling Q﹠amp; In the chemical ingredients of P steel, Si:1.3～1.7%wt.%; Mn:1.8～2.5wt.%; Al:0.03～0.06wt.%; N≤0.004wt.%; Ti:0.008～0.012wt.%; O≤30ppm.
3. the high-strength hot-rolled Q﹠amp of low yield strength ratio as claimed in claim 1 or 2; The manufacture method of P steel specifically comprises the steps:
1) smelting, secondary refining, casting:
Adopt converter or electrosmelting, vacuum oven secondary refining, casting formation strand or ingot casting by following composition, its following chemical components in percentage by weight is: C:0.20%～0.40%, Si:1.0%～2.0%, Mn:1.5%～3.0%, P≤0.015%, S≤0.005%, Al:0.02～0.08%, N≤0.006%, Ti:0.005%～0.015%, all the other are Fe and other unavoidable impurities;
2) heating, hot rolling:
The strand that step 1) is obtained or ingot casting are heated to 1100～1200 ℃ and be incubated 1～2h, start rolling temperature is 1000～1100 ℃, rolling and accumulative total deflection 〉=50% of multi-pass treats to carry out when the intermediate blank temperature is down to 900～950 ℃ 3～5 rolling and accumulative total deflection 〉=70% of passage subsequently;
3) segmentation cooling:
Rolled piece after the hot rolling between 800～900 ℃ with the quick water-cooled to 500 of cooling rate of 50 ℃/s～600 ℃, air cooling 5～10s then, continue again with the cooling rate of 50 ℃/s is cooled to a certain temperature between 100～300 ℃ to obtain proeutectoid ferrite+martensite+residual austenite tissue, slowly cool to room temperature after batching at last, obtain the high-strength hot-rolled Q﹠amp of described low yield strength ratio; The P steel.
4. the high-strength hot-rolled Q﹠amp of low yield strength ratio as claimed in claim 3; The manufacture method of P steel is characterized in that step 2) in multi-pass rolling be 5～7 times rolling; The speed of batching the slow cooling in back in the step 3) is 8～12 ℃/h.
5. the high-strength hot-rolled Q﹠amp of low yield strength ratio as claimed in claim 3; The manufacture method of P steel is characterized in that, the high-strength hot-rolled Q﹠amp of the low yield strength ratio of acquisition; In the P steel, the volume percent of its proeutectoid ferrite body tissue is 10～20%, and the volume percent of residual austenite tissue is greater than 5% and less than 10%.
6. as the high-strength hot-rolled Q﹠amp of the arbitrary described low yield strength ratio of claim 3～5; The manufacture method of P steel is characterized in that, the high-strength hot-rolled Q﹠amp of the low yield strength ratio of acquisition; The yield strength of P steel is below 700MPa, and tensile strength is more than 1000MPa, and yield tensile ratio is 0.50～0.60.
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