CN103805869B - A kind of high-strength hot-rolled Q & P steel and manufacture method thereof - Google Patents
A kind of high-strength hot-rolled Q & P steel and manufacture method thereof Download PDFInfo
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- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 abstract description 4
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Abstract
A kind of high-strength hot-rolled Q & amp; P steel and manufacture method thereof, does is its chemical component weight per-cent: C0.20 ~ 0.50%, Si? 0.8 ~ 2.0%, Mn? 1.5 ~ 3.0%, P≤0.015%, S≤0.005%, Al0.02 ~ 0.08%, N≤0.006%, Ti? 0.005 ~ 0.015%, Cr? 0.5 ~ 1.5%, all the other are Fe and inevitable impurity.The present invention is on the component base of traditional C-Mn steel; cementite is suppressed to be separated out by carrying high Si content; the lath martensite that austenite grain size when simultaneously adding the Ti control heating of trace is tiny when quenching to obtain; add a certain amount of Cr element improve the hardening capacity of steel plate and postpone the transformation of allocated phase residual austenite to bainite; thus realize low cost and produce high-strength hot-rolled wear resisting steel, its tensile strength & gt; 1500MPa, has good unit elongation (& gt simultaneously; 10%), excellent strong plasticity coupling is shown.
Description
Technical field
The invention belongs to wear resisting steel and manufacture field, particularly one high-strength hot-rolled Q & P steel and manufacture method thereof, its tensile strength >1500MPa, unit elongation >10%.
Background technology
Quenching-partition steel and Q & P steel are the study hotspots in last decade high-strength steel field.
At present, Q & P steel has been acknowledged as the advanced high-strength steel of the automobile steel field third generation.The main technique of Q & P steel is: steel is heated to complete austenitic area or partial austenitic district, after Homogenization Treatments for some time, rapid quench is to M
sand M
f(M
sand M
frepresent Ms (martensite start) point and end temp respectively) between a certain temperature to obtain the martensite+residual austenite body tissue with a certain amount of residual austenite, stop cold temperature in quenching or make carbon atom in residual austenite, spread enrichment from oversaturated martensite a little more than held for some time under stopping cold temperature subsequently, thus stable residual austenite, and then be quenched to room temperature.The relative content of martensite and residual austenite generally determines the final performance of steel, and can stop cold temperature and adjusted by controlling quenching.By the steel after this art breading, there is very high intensity and good plasticity usually, namely there is very high strength and ductility product.Its tensile strength can reach more than 2000MPa, and unit elongation >=10%.The typical organization of Q & P steel when room temperature is lath martensite and film like residual austenite, sometimes may contain a small amount of plate martensite and massive martensite.Q & P steel mechanical property determines primarily of the carbon content in the width of sheet of lath martensite and film like residual austenite, martensite and residual austenite percent by volume.
The concept of Q & P steel is once proposition, and many research groups have all carried out detailed and deep research to this class new steel grade from theoretical and test aspect in the world, and wherein the most famous is the Speer seminar of Colorade USA mining industry university.
Comprehensive existing achievement in research is not difficult to find, the operational path of test is substantially all adopt heat-treating methods or two-step approach, namely steel is after austenitizing, first carries out quenching and then reheated by steel to after being incubated for some time under stop cold temperature a little more than quenching, is finally quenched to room temperature again.This operational path is concerning proper the production of cold rolling or pot galvanize product.But for Hot Strip Rolling, due in section cooling and the ability that do not reheat process fast between batching or reheat entire volume after batching.Therefore, under current domestic hot continuous rolling produces line equipment condition, produce Q & P steel according to two-step approach and almost can not realize, the one-step technology route that section cooling can only be adopted to be quenched to certain temperature then carry out batching.
Chinese patent CN102226248A describes a kind of carbon silicomanganese hot rolling Q & P steel, but design of alloy is not carried out micro-Ti process and add Cr element, and the tensile strength of steel plate is starkly lower than 1400MPa.Chinese patent CN101775470A describes a kind of production technique of complex phase Q & P steel, is actually the technique that a kind of two-step approach produces Q & P steel.Chinese patent CN101487096A describes one two-step thermal processing method and produces C-Mn-Al system Q & P steel, and its principal feature is that unit elongation is very high, but intensity is lower.
Summary of the invention
The object of this invention is to provide a kind of high-strength hot-rolled Q & P steel and manufacture method thereof, designed by reasonable component, adopt hot continuous rolling process can produce the grade high-strength hot-rolled wear resisting steel of tensile strength >1500MPa, there is good unit elongation (>10%) simultaneously, show excellent strong plasticity coupling.
For achieving the above object, technical scheme of the present invention is:
The present invention is on the component base of traditional C-Mn steel, cementite is suppressed to be separated out by carrying high Si content, the lath martensite that austenite grain size when simultaneously adding the Ti control heating of trace is tiny when quenching to obtain, add a certain amount of Cr element improve the hardening capacity of steel plate and postpone the transformation of allocated phase residual austenite to bainite, thus realize low cost and produce high-strength hot-rolled wear resisting steel.
Particularly, one of the present invention high-strength hot-rolled Q & P steel, its chemical component weight per-cent is: C0.20% ~ 0.50%, Si0.8% ~ 2.0%, Mn1.5% ~ 3.0%, P≤0.015%, S≤0.005%, Al0.02 ~ 0.08%, N≤0.006%, Ti0.005% ~ 0.015%, Cr0.5% ~ 1.5%, all the other are Fe and inevitable impurity.
In the Composition Design of steel of the present invention:
Carbon is element the most basic in steel, is also one of most important element in the present invention simultaneously.Carbon, as the interstitial atom in steel, plays very important effect to improving the intensity of steel, has the greatest impact to the yield strength of steel and tensile strength.If the content of carbon is lower than 0.2% in steel, when not adding other alloying elements, the intensity of hot rolling Q & P steel is difficult to reach very high intensity as more than 1500MPa; And in the process of batching isothermal, carbon is not enough to ensure the stability of residual austenite when room temperature from the degree that martensite spreads enrichment to austenite.If the carbon content in steel is greater than 0.5%, although can ensure there are enough carbon atoms to enrichment in austenite batching in isothermal process, cause M because carbon content is high
sand M
fpoint reduces, and under identical processing condition, the content of residual austenite increases, and the carbon concentration in corresponding residual austenite also can reduce, and stability reduces.In addition, the too high impelling strength to steel plate of carbon content and weldability etc. have disadvantageous effect.Therefore, in steel, carbon content control can ensure that in the scope of 0.20-0.50% steel plate has good high strength and good plasticity coupling.
Silicon is element the most basic in steel, is also one of most important element in the present invention simultaneously.Compared with traditional hot-rolling high-strength steel, high strength Q & P steel is substantially all the Composition Design principle adopting high silicon at present.The main purpose adding high silicon in Q & P steel is in the precipitation of batching slow cooling stage suppression cementite, promotes carbon enrichment in residual austenite, stable austenite.If the add-on of silicon in steel is lower than 0.8%, then steel is being quenched into M
s-M
fbetween to batch carbide precipitate in annealing process as cementite, reduce the carbon content in residual austenite, make residual austenite become unstable.Continuing to progressively cool in the process of room temperature, residual austenite is likely decomposed, and causes disadvantageous effect to the performance of steel; On the other hand, the content of silicon in steel can not be too high, if silicone content is more than 2.0%, easily forms the oxide compound of silicon, make steel generation brittle rupture in steel.Therefore, in steel, the content of silicon controls at 0.8-2.0%, and preferable range is between 1.2-1.8%.
Manganese, is the element expanding austenite phase field, can reduces the critical cooling velocity of steel, stable austenite, postpones austenite to pearlitic transformation.In the present invention, for ensureing the intensity of steel plate, the content of manganese generally should control more than 1.5%; On the other hand, Fe content can not be too high, and as more than 3.0%, the intensity of steel plate easily reduces on the contrary, and this mainly improves austenitic stability because Fe content increases, and is quenched into M
sand M
fbetween obtain many residual austenites, reduce the intensity of steel plate.Therefore, in the present invention, the content general control of manganese can obtain the good steel plate of over-all properties between 1.5-3.0%.
Phosphorus is the impurity element in steel.In steel time the content of phosphorus higher (>=0.1%), form Fe2P and separate out around crystal grain, reduce the plasticity of steel and toughness, therefore its content is more low better, general control within 0.015% better and do not improve steel-making cost.
Be present in around the crystal grain of steel with the eutectiferous form of FeS-Fe when sulphur content is higher in steel, reduce the mechanical property of steel, its content and seemingly Phosphorus, be also more low better, usually control within 0.005% during actual production;
Aluminium, the effect of aluminium in steel mainly carries out deoxidation in steelmaking process.In addition, aluminium also can be combined formation AlN by the nitrogen in steel, if the content of nitrogen in steel is higher, the titanium added is not enough to the fixed nitrogen atomic time, and aluminium also can play the effect of fixed nitrogen.Therefore, in steel, the content of aluminium will control, in suitable scope, usually to control at 0.02-0.08%, and preferable range is 0.03-0.06%.
Titanium, add-on is corresponding with the add-on of nitrogen in steel.In steel, Ti/N controls to be advisable in the stoichiometric ratio less than 3.42 of TiN.If Ti/N is greater than 3.42, then easily form thicker TiN particle in steel, cause disadvantageous effect to the impelling strength of steel plate, 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 formed very little, do not have the effect of fining austenite grains.Therefore, in steel, the content of titanium will control in suitable scope, and the add-on of usual titanium controls between 0.005-0.015%, and preferable range controls at 0.008-0.012%.
Chromium is the important element in the present invention.Chromium to add in steel the hardening capacity improving steel on the one hand, and chromium greatly can reduce the spread coefficient of carbon in austenite on the other hand, can significantly postpone steel in quenching-distribution process residual austenite to the transformation of bainite.If the content of chromium is lower than 0.5%, need not be not obvious to the transformation postponement of bainite to postponing residual austenite; If the content of chromium is higher than 1.5%, it is substantially saturated to the effect of bainite transformation that chromium postpones residual austenite, therefore in steel, the content of chromium controls between 0.5-1.5%;
Nitrogen, belongs to impurity element in the present invention, and its content is more low better.Nitrogen is also inevitable element in steel, and under normal circumstances, the residual content of nitrogen in steel is between 0.002-0.004%, and these nitrogen elements can by being combined with dissolved aluminum and Ti and fixing.In order to not improve steel-making cost, the content of nitrogen controls within 0.006%, and preferable range is for being less than 0.004%.
Oxygen, be inevitable element in steelmaking process, for the purpose of the present invention, in steel, the content of oxygen is by generally reaching below 30ppm after aluminium deoxidation, significant adverse can not be caused to affect on the performance of steel plate.Therefore, by the Control for Oxygen Content in steel within 30ppm.
The manufacture method of a kind of high-strength hot-rolled Q & P steel of the present invention, it comprises the steps:
1) smelt, cast
Adopt converter or electrosmelting by following compositions, chemical component weight per-cent is: C0.20 ~ 0.50%, Si0.8 ~ 2.0%, Mn1.5 ~ 3.0%, P≤0.015%, S≤0.005%, Al0.02 ~ 0.08%, N≤0.006%, Ti0.005 ~ 0.015%, Cr0.5 ~ 1.5%, all the other are Fe and inevitable impurity; Through vacuum oven secondary refining, be cast as steel billet or steel ingot;
2) heat
Steel billet or Heating Steel Ingots temperature: 1100 ~ 1200 DEG C, soaking time: 1 ~ 2 hour;
3) rolling
Start rolling temperature: 1000 ~ 1100 DEG C, the large pressure of multi-pass more than 950 DEG C and accumulative deflection >=50%, intermediate blank treats that temperature is to 900 ~ 950 DEG C, then carries out last 3 ~ 5 passes subsequently;
4) cool
Separate out at ferrite and start on temperature namely between 850 ~ 900 DEG C, be cooled to 100 ~ 300 DEG C with the cooling rate of >50 DEG C/s, acquisition martensite+residual austenite body tissue, slowly cools to room temperature after finally batching.
In manufacture method of the present invention:
Steel billet (ingot) Heating temperature: 1100 ~ 1200 DEG C, soaking time: 1 ~ 2 hour, start rolling temperature: 1000 ~ 1100 DEG C, the large pressure of multi-pass more than 950 DEG C and accumulative deflection>=50%, main purpose is fining austenite grains; Intermediate blank treats that temperature is to 900-950 DEG C, then carries out a last 3-5 passes subsequently; Separate out at ferrite and start to be cooled to 100-300 DEG C of (M with the cooling rate of >50 DEG C/s between 850-900 DEG C on temperature
s-M
fbetween) a certain temperature to obtain martensite+a certain amount of residual austenite body tissue, slowly cool to room temperature after finally batching.
Preferably, the thickness of intermediate blank and the Thickness Ratio of final steel plate, generally more than 3.0, can ensure deformation uniformity.
If the Heating temperature of steel billet lower than 1100 DEG C and soaking time too short, be then unfavorable for the homogenizing of alloying element; And when temperature is higher than 1200 DEG C, not only increase manufacturing cost, and the heating quality of steel billet is declined to some extent.Therefore, the Heating temperature general control of steel billet is proper at 1100 ~ 1200 DEG C.
Similarly, soaking time also needs to control within the specific limits.Soaking time is too short, and solute atoms is as abundant not in the diffusion of Si, Mn etc., and the heating quality of steel billet can not be guaranteed; Soaking time is long, make austenite crystal thick and improve manufacturing cost, therefore soaking time should control between 1 ~ 2 hour.Heating temperature is higher, and corresponding soaking time can suitably shorten.
Beneficial effect of the present invention:
1. the cost of alloy of steel plate of the present invention significantly reduces.The present invention, compared with traditional low-alloy high-strength steel, does not add noble metal element as Nb, V, Cu, Ni, Mo etc., and the trace alloying element Ti of interpolation is not only cheap, and add-on is very low.Although alloying elements cr add-on is more, Cr is compared with above-mentioned several alloying element, and price is still very low.In addition, adopt hot continuous rolling process to produce the production of ratio slab line and also can reduce production cost further.Therefore, the production cost of steel plate is very low.
2. the mechanical property of steel plate of the present invention significantly improves, and customer using cost reduces, and the tensile strength of steel plate is significantly improved compared with traditional low-alloy high-strength steel with unit elongation.Therefore, use the field of slab wear resisting steel can use the ultrahigh-strength wear-resistant steel of more Thin Specs at some, weight reduction, reduces costs.
3. the steel plate adopting the present invention to produce has low cost superstrength and high rigidity advantage, be particularly suitable for the field needing to improve wear resistance, the residual austenite (more than 5%) particularly retained in steel, martensite can be changed under the conditions such as abrasive wear, improve the wear resistance of steel plate further.
Accompanying drawing explanation
Fig. 1 is process flow sheet of the present invention.
Fig. 2 is the metallographic microstructure photo of the embodiment of the present invention 2 steel plate.
Fig. 3 is the metallographic microstructure photo of the embodiment of the present invention 4 steel plate.
Fig. 4 is the metallographic microstructure photo of the embodiment of the present invention 6 steel plate.
Embodiment
Below in conjunction with accompanying drawing, the present invention will be further described.
See Fig. 1, technical process of the present invention: adopt converter or electrosmelting, through vacuum oven secondary refining, be cast as steel billet or steel ingot; Heating, steel billet or Heating Steel Ingots temperature: 1100 ~ 1200 DEG C, soaking time: 1 ~ 2 hour; Rolling, start rolling temperature: 1000 ~ 1100 DEG C, the large pressure of multi-pass more than 950 DEG C and accumulative deflection >=50%, intermediate blank treats that temperature is to 900 ~ 950 DEG C, then carries out last 3 ~ 5 passes subsequently; Cooling, separate out at ferrite and start on temperature namely between 850 ~ 900 DEG C, be cooled to 100 ~ 300 DEG C with the cooling rate of >50 DEG C/s, acquisition martensite more than+5% residual austenite body tissue, slowly cools to room temperature after finally batching.
Embodiment of the present invention composition is see table 1, and technique and performance are see table 2.
Table 1 unit: weight percent
Table 2
Fig. 2 and Fig. 3 gives the typical metallograph that embodiment 2 and 4 tests steel.Fig. 4 is the metallographic microstructure photo of the embodiment of the present invention 6 steel plate.
As can be seen from metallograph, the tissue of steel plate is mainly lath martensite.According to X-ray diffraction result, the content of embodiment 2,4,6 detecting residual austenite in steel plate is respectively 6.11%, 8.40% and 13.55%.Therefore, the microtexture of light plate of the present invention is lath martensite+a small amount of residual austenite.Due to the existence of more residual austenite, make steel plate in draw-texture process, undergo phase transition induced plastic (TRIP) effect, improve tensile strength and the plasticity of steel plate, make steel plate have good wear resistance.
Claims (8)
1. a high-strength hot-rolled Q & P steel, its chemical component weight per-cent is: C0.20 ~ 0.50%, Si1.2 ~ 1.8%, Mn1.5 ~ 3.0%, P≤0.015%, S≤0.005%, Al0.02 ~ 0.08%, N≤0.004%, Ti0.005 ~ 0.015%, Cr0.5 ~ 1.5%, O≤30ppm, all the other are Fe and inevitable impurity; The microstructure of hot rolling Q & P steel is tiny lath martensite+residual austenite body tissue, tensile strength >=1500MPa, unit elongation >10%.
2. high-strength hot-rolled Q & P steel as claimed in claim 1, it is characterized in that, described Al content is 0.03 ~ 0.06%, weight percent meter.
3. high-strength hot-rolled Q & P steel as claimed in claim 1, it is characterized in that, described Ti content is 0.008 ~ 0.012%, weight percent meter.
4. a manufacture method for high-strength hot-rolled Q & P steel, it comprises the steps:
1) smelt, cast
Adopt converter or electrosmelting by following compositions, chemical component weight per-cent is: C0.20% ~ 0.50%, Si0.8% ~ 2.0%, Mn1.5% ~ 3.0%, P≤0.015%, S≤0.005%, Al0.02% ~ 0.08%, N≤0.006%, Ti0.005% ~ 0.015%, Cr0.5% ~ 1.5%, all the other are Fe and inevitable impurity; Through vacuum oven secondary refining, be cast as steel billet or steel ingot;
2) heat
Steel billet or Heating Steel Ingots temperature: 1100 ~ 1200 DEG C, soaking time: 1 ~ 2 hour;
3) rolling
Start rolling temperature: 1000 ~ 1100 DEG C, the large pressure of multi-pass more than 950 DEG C and accumulative deflection >=50%, intermediate blank treats that temperature is to 900 ~ 950 DEG C subsequently, then carries out last at least 3 passes; The thickness of intermediate blank and the Thickness Ratio of final steel plate are more than 3.0;
4) cool
Between ferrite precipitation starts to be 850 ~ 900 DEG C on temperature, be cooled to 100 ~ 300 DEG C with the cooling rate of >50 DEG C/s, obtain tiny lath martensite+residual austenite body tissue, after finally batching, slowly cool to room temperature; The hot rolling super intensified abrasion-proof steel plate tensile strength >=1500MPa obtained, unit elongation >10%.
5. the manufacture method of high-strength hot-rolled Q & P steel as claimed in claim 4, it is characterized in that, described Si content is 1.2 ~ 1.8%, weight percent meter.
6. the manufacture method of high-strength hot-rolled Q & P steel as claimed in claim 4, it is characterized in that, described Al content is 0.03 ~ 0.06%, weight percent meter.
7. the manufacture method of high-strength hot-rolled Q & P steel as claimed in claim 4, is characterized in that, described N content≤0.004%, weight percent meter.
8. the manufacture method of high-strength hot-rolled Q & P steel as claimed in claim 4, it is characterized in that, described Ti content is 0.008 ~ 0.012%, weight percent meter.
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| EP3686296B8 (en) | 2017-09-20 | 2024-12-11 | Baosteel Zhanjiang Iron & Steel Co., Ltd. | Softening method for high-strength q & p steel hot roll |
| CN108165890B (en) * | 2018-01-09 | 2020-08-11 | 北京科技大学 | Preparation method of low-cost high-strength nano bainite wear-resistant steel ball |
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| CN109536843B (en) * | 2019-01-04 | 2020-08-25 | 武汉钢铁有限公司 | Nitrogen-containing dual-phase corrosion-resistant wear-resistant hot rolled steel and production method thereof |
| CN111607735B (en) * | 2020-06-28 | 2021-10-01 | 武汉钢铁有限公司 | Hot-rolled wear-resistant steel with Brinell hardness of more than or equal to 420 and production method thereof |
| CN111607741B (en) * | 2020-06-28 | 2021-10-22 | 武汉钢铁有限公司 | Hot-rolled wear-resistant steel with Brinell hardness of more than or equal to 370 and production method thereof |
| CN112813348A (en) * | 2020-12-30 | 2021-05-18 | 钢铁研究总院 | Air-cooled martensite and retained austenite complex-phase medium manganese rail steel and preparation method thereof |
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| JP3680674B2 (en) * | 1999-01-28 | 2005-08-10 | 住友金属工業株式会社 | Machine structural steel and machine structural parts with excellent machinability and toughness |
| JP5883211B2 (en) * | 2010-01-29 | 2016-03-09 | 株式会社神戸製鋼所 | High-strength cold-rolled steel sheet with excellent workability and method for producing the same |
| CN102560272B (en) * | 2011-11-25 | 2014-01-22 | 宝山钢铁股份有限公司 | Ultrahigh-strength abrasion-resistant steel plate and manufacturing method thereof |
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