CN104451402A - 700MPa-grade hot-rolled dual-phase steel and manufacturing method thereof - Google Patents

Abstract

The invention belongs to the technical field of steel and iron material engineering, relates to high-strength hot-rolled dual-phase steel and a manufacturing method thereof, and particularly relates to 700MPa-grade hot-rolled dual-phase steel and the manufacturing method thereof. The 700MPa-grade hot-rolled dual-phase steel comprises the following chemical ingredients in percentage by weight: 0.08-0.12 percent of C, 0.1-0.3 percent of Si, 0.7-1.00 percent of Mn, 0.02-0.06 percent of Alt, 0.60-1.00 percent of Cr, 0.03-0.06 percent of P, 0.02-0.05 percent of Ti, smaller than or equal to 0.005 percent of S, smaller than or equal to 0.006 percent of N and the balance of Fe and inevitable impurities. By controlling a suitable content of C and Si, greatly reducing the content of manganese, adding Cr, Ti and P, strictly controlling the content of S and N, adding no precious micro-alloyed elements Nb and V and no precious alloy such as Mo and Ni, the 700MPa-grade hot-rolled dual-phase steel is greatly lowered in cost.

Description

A kind of 700MPa level hot-rolled dual-phase steel and preparation method thereof

Technical field

The invention belongs to the technical field of ferrous materials engineering, relate to a kind of high-strength hot-rolled two-phase and manufacture method thereof, be specifically related to a kind of 700MPa level hot-rolled dual-phase steel and preparation method thereof.

Background technology

Along with being becoming tight energy day, environmental stress increasingly sharpens, and adds constantly perfect to legislative work for protecting environment of the whole world, facilitates automotive technology development center of gravity towards energy-saving and environmental protection and the development of security aspect.Use modern technologies and method to alleviate the weight of component or car load, under the prerequisite of performances such as ensuring safety, realizing energy-saving and emission-reduction consumption reduction target by loss of weight becomes common recognition.

Dual phase steel refers to the high-strength steel formed primarily of ferrite (F)+a small amount of martensite (M) that soft steel or low-carbon micro steel-alloy obtain through critical zone thermal treatment or cooling controlling and rolling controlling process.Its to have low, the continuous surrender of yield strength, the feature such as yield tensile ratio is low, work hardening rate is higher and unit elongation is larger and by life institute extensive concern.The actual production technique of dual phase steel mainly contains two kinds: heat treating process and hot direct rolling process.By contrast, Hot rolling production dual phase steel operation is simple, cost is low, save man-hour and the energy, be convenient to scale operation, becomes the prefered method of producing dual phase steel.At present, the production method of traditional hot-rolled dual-phase steel can be divided into middle warm rolling to get type Hot rolling and low temperature batches type Hot rolling.But respectively there is shortcoming: when taking middle warm rolling to get type Hot rolling production dual phase steel, compound must add Cr, the alloying elements such as Mo in steel, cost is higher; And when taking low temperature to batch type Hot rolling, due to the complicacy of roller repairing technique, make its more difficult control, be difficult to obtain uniform and stable tissue, and in composition, the content of Si is higher, causes plate surface quality poor.

Can production tensile strength 600MPa(ZL 200610045846.2 with C-Mn-Si set member) and hot-rolled dual-phase steel 540MPa(ZL200610045847.7).But more the hot-rolled dual-phase steel of high intensity levels usually adopts and adds more precious alloy.Such as, disclosure of the invention CN 101279330A is by adding 0.050%Nb or 0.047 ~ 0.049%Nb+0.21 ~ 0.36%Mo element and adopting the hot-rolled dual-phase steel tensile strength of the coiling temperature of 500 ~ 600 DEG C production to reach 700MPa, yield tensile ratio is 0.59 ~ 0.64, but microalloy element content is higher, and production cost is higher.

Publication number CN 102766812 A discloses a kind of 700MPa level low yield strength ratio hot-rolled dual-phase steel steel plate and manufacture method thereof, according to mass percent, containing 0.06% ~ 0.09%C, 1.0% ~ 1.2%Si, 1.10% ~ 1.30%Mn, 0.020% ~ 0.050%Al, 0.4% ~ 0.6%Cr, and surplus Fe.Adopt sub-sectional cooling low-temperature coiling processes.This patent adopts the Si up to 1.0-1.2%, is difficult to the manufacture requirements of the component meeting great surface quality requirement.

Publication number CN 102517496 A discloses a kind of hot rolled ferrite/martensite double phase steel, it is characterized in that, component weight percentages is: C:0.06% ~ 0.10%, Si:0.40% ~ 0.60%, Mn:1.00% ~ 2.00%, P≤0.02%, S≤0.02%, Ti:0.08% ~ 0.12%, all the other are Fe and inevitable impurity, produce the hot-rolled dual-phase steel that a kind of tensile strength reaches 780MPa.In its manufacture method, finishing temperature 800 ~ 850 DEG C, adopt sub-sectional cooling, first paragraph water-cooled cooling rate 30 ~ 50 DEG C/s, is cooled to 650 ~ 700 DEG C, treats temperature 8 ~ 15S subsequently in atmosphere, subordinate phase water-cooled cooling rate >=40 DEG C/s.In this patent, adopt the Composition Design of higher silicon and manganese and high Ti, and do not control N content, the stability of product performance is difficult to ensure; The product of great surface quality is also difficult to obtain; Air cooling time reaches 8-15S, and the common hot rolling line production line that especially short route cooling line length is short is difficult to realize suitability for industrialized production.

Publication number CN 102719732 A discloses a kind of hot-rolled high-strength dual phase sheet steel and manufacture method thereof.The steel plate chemical component weight percentage composition of this invention is: C:0.10 ~ 0.13%, Si:0.85 ~ 1.15%, Mn:1.40 ~ 1.70%, P≤0.015%, S≤0.005%, Al:0.015 ~ 0.035%, N≤0.006%, surplus is iron and inevitable impurity.Steel plate is organized as ferrite+martensitic duplex structure, tensile strength reaches 800MPa rank, this invention adopts Composition Design and the low-temperature coiling processes of high silicon, Gao Meng, and the control difficulty of Surface Quality is larger, and general hot rolling line cannot adopt this technique to produce.

Authorization Notice No. is the patent of invention of CN100441724C, discloses a kind of technique of hot-rolled dual-phase steel, and wherein in molten steel, the weight percent composition (%) of chemical element is designed to: C:0 ~ 0.075%; Si:0.6 ~ 1.0%; Mn:1.5 ~ 2.0%; Cr:0.4 ~ 0.6%; Als:0.010 ~ 0.080%; V:0.02 ~ 0.14%; All the other are Fe and impurity element.Take to prick rear sectional type process for cooling, finishing temperature is 800 ~ 900 DEG C, and coiling temperature is 400 ~ 500 DEG C.Application publication number is the patent of invention of CN101880825A, also disclose a kind of hot-rolled dual-phase steel production technique and according to plate product that this mode of production obtains, this dual phase steel chemical constitution controls by mass percent (%): C:0.06 ~ 0.16%, Si:0.10 ~ 0.50%, Mn:1.00 ~ 2.00%, Al:0.02 ~ 0.06%, Nb:0.01 ~ 0.08%, Ti:0 ~ 0.03%, and limit P≤0.1%, S≤0.005%, surplus is Fe and other element impurity.Take continuous coo1ing technique, finishing temperature is 770-860 DEG C, coiling temperature <350 DEG C.A certain amount of price higher microalloy element Nb, V is all with the addition of and expensive alloying elements Ni, Mo etc. obtain the higher dual phase steel product of tensile strength in the technical process of above-mentioned two patents of invention, add production cost on the one hand, also can impact use propertieies such as the extensibility of steel plate and weldabilities on the other hand.

The invention of Authorization Notice No. CN 101130847B provides a kind of medium thin slab continuous casting and rolling dual phase sheet steel and manufacture method thereof.Steel plate composition (% by weight) is C:0.04% ~ 0.11%, Si:0.02% ~ 1.5%, Mn:0.6% ~ 2.50%, Cr:0.02% ~ 2.0%, also Mo, Nb or Ti can be contained, S, P are more low better, and surplus is Fe and inevitable impurity; Control exit temperature at finishing 800 ~ 950 DEG C in its manufacture method, be cooled to less than 650 DEG C and batch, be of the present inventionly cooled to three sections of coolings, I section target temperature >=720 DEG C, cooling rate 10 ~ 20 DEG C/s; II section air cooling time is greater than 2 seconds; III section is cooled to coiling temperature with the speed of cooling being greater than 10 DEG C/s.This invention belong to dual phase steel that tensile strength is 600MPa rank and also its industrial production cost higher.

Publication number CN 101880825 A discloses ultra-fine crystal hot-rolled dual phase steel and the manufacturing method of plate thereof thereof of a kind of more than tensile strength 750MPa.The steel plate chemical component weight percentage composition of this invention is: C:0.060 ~ 0.16%, Si:0.10 ~ 0.50%, Mn:1.00 ~ 2.00%, P≤0.1%, S≤0.005%, Al:0.02 ~ 0.06%, Nb:0.01 ~ 0.08%, Ti:0 ~ 0.03%, surplus is iron and inevitable impurity.Its manufacture method adopts strict two benches controlled rolling, and finishing temperature is 770 ~ 860 DEG C, rolls rear employing continuous coo1ing, cooling rate 30 ~ 40 DEG C/s, coiling temperature < 350 DEG C, this invention adopts the Composition Design of microalloying on the basis of low C height Mn, and production cost is still higher; Require very high to controlled rolling in this manufacture method, the Unhydrated cement rolling reduction of less than 950 DEG C requires > 70% and adopts low temperature finish to gauge, and common Hot Rolling Mill realizes difficulty.

In view of the above problems, the present invention, by controlling suitable C, Si content, significantly reduces Fe content, adopts chromium alloying and adds the Composition Design of appropriate cheap titanium, adopt the cooling controlling and rolling controlling process matched, produce the hot-rolled dual-phase steel of the high comprehensive performance of 700MPa level.

Summary of the invention

The object of the invention is to provide a kind of 700MPa level hot-rolled dual-phase steel and preparation method thereof for high-strength vehicle structural steel to fatigue property and the higher requirement of impact property and the factor such as with low cost, the present invention is by controlling suitable C, Si content, significantly reduce Fe content, by adding Cr, Ti and P, strict control S, N content, do not add the valuable microalloy element of Nb, V, also the precious alloys such as Mo, Ni are not added, significantly reduce cost, adopt cooling controlling and rolling controlling process, obtain 700MPa level hot-rolled high-strength dual phase steel; It is finally organized as ferrite+martensitic stucture.

Technical scheme of the present invention is: a kind of 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.08 ~ 0.12%, Si 0.1 ~ 0.3%, Mn 0.7 ~ 1.00%, Alt 0.02 ~ 0.06%, Cr 0.60 ~ 1.00%, P0.03 ~ 0.06%, Ti 0.02 ~ 0.05%, S≤0.005%, N≤0.006%, surplus is Fe and inevitable impurity.

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.09 ~ 0.11%, Si 0.15 ~ 0.25%, Mn 0.70 ~ 0.9%, Alt 0.02 ~ 0.06%, Cr 0.70 ~ 0.9%, P 0.03 ~ 0.05%, Ti 0.03 ~ 0.05%, S≤0.005%, N≤0.006%, surplus is Fe and inevitable impurity.

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.105%, Si 0.16%, Mn 0.82%, Alt 0.04%, Cr 0.77%, P 0.047%, Ti 0.038%, S 0.003%, N 0.0036%, surplus is Fe and inevitable impurity.

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.088%, Si 0.13%, Mn 0.83%, Alt 0.032%, Cr 0.69%, P 0.052%, Ti 0.037%, S 0.003%, N0.0033%, surplus is Fe and inevitable impurity.

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.096%, Si 0.28%, Mn 0.75%, Alt 0.040%, Cr 0.65%, P 0.043%, Ti 0.036%, S 0.002%, N0.0027%, surplus is Fe and inevitable impurity.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 90 ~ 250mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 90 ~ 250mm is heated to 1200 ~ 1300 DEG C by gained thickness, soaking time 1 ~ 3 hour, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1100 ~ 1180 DEG C, finishing temperature 1000 ~ 1100 DEG C, and finish rolling stage start rolling temperature is 980 ~ 1080 DEG C, and finishing temperature is 800 ~ 880 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 650 ~ 700 DEG C with the cooling rate of 25 ~ 100 DEG C/s, air cooling 2 ~

8S, is then cooled to target coiling temperature with the cooling rate of 25 ~ 100 DEG C/s and batches;

(4) coiling technique: coiling temperature is less than 250 DEG C; Gained finished product thickness is 2 ~ 6mm.

In described finished product, ferrite volume fraction is 75 ~ 85%, and Martensite Volume Fraction is 15 ~ 25%.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1240 DEG C by gained thickness, soaking time 2 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%,

Finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1130 DEG C, finishing temperature 1070 DEG C, and 3 passes become the intermediate blank of 30mm, and finish rolling stage start rolling temperature is 1040 DEG C, and finishing temperature is 870 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 692 DEG C with the cooling rate of 86 DEG C/s, air cooling 7S, then with 83 DEG C

The cooling rate of/s is cooled to target coiling temperature and batches;

(4) coiling technique: coiling temperature is 136 DEG C; Gained finished product thickness is 2.6mm.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1250 DEG C by gained thickness, soaking time 2.5 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1160 DEG C, finishing temperature 1060 DEG C, and 3 passes become the intermediate blank of 30mm, and finish rolling stage start rolling temperature is 1040 DEG C, and finishing temperature is 860 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 686 DEG C with the cooling rate of 77 DEG C/s, air cooling 6S, then with 72 DEG C

The cooling rate of/s is cooled to target coiling temperature and batches;

(4) coiling technique: coiling temperature is 112 DEG C; Gained finished product thickness is 3mm.

Beneficial effect of the present invention is: C: the important element improving the intensity of steel, the too low then tensile strength of C content is not enough, C content is too high, and ferrite forms the incubation period and incubation time that need to grow very much, be unfavorable for the acquisition of the cooling after rolling and final tissue, and welding property and forming property worsen, carbon content scope of the present invention is narrower, and 0.08 ~ 0.12%, preferably 0.09 ~ 0.11%.

Si: deoxidant element, simultaneously in steel, play solution strengthening effect, the too low strengthening effect of content is too weak, and content too great surface quality is restive, therefore controls 0.10 ~ 0.30%, and preferably 0.15 ~ 0.25%.

Mn: improve yield strength and hardening capacity, the too low undercapacity causing body body stability difficult to understand and steel, too high meeting makes the plasticity of steel and weldability decline, manganese is stable austenite tissue and reinforced alloys element, meanwhile, manganese can also increase the hardening capacity of steel, reduces the critical cooling velocity that bainite and martensite is formed, can effectively reduce the speed of cooling of rolling first paragraph water-cooled in rear sub-sectional cooling, be beneficial to and obtain bainite or martensitic stucture.But manganese has higher segregation tendency, the present invention, by significantly reducing Fe content, avoids the disadvantageous effect of manganese segregation to tissue and processing characteristics, therefore controls 0.70 ~ 1.00%, preferably 0.70 ~ 0.90%.

S: the impurity element in steel, comparatively large to plasticity and Influence of Fatigue Properties, content is more low better.

P: solution strengthening element, adds appropriate P and can promote ferritic generation and keep intensity and moulding well balanced, therefore control 0.03 ~ 0.06%, and preferably 0.03 ~ 0.05%.

Cr: the element improving hardening capacity, be conducive to austenitic stable, too high then ductility deteriorates, too low then hardening capacity reduces, and undercapacity, therefore controls 0.60 ~ 1.00%, and preferably 0.70 ~ 0.90%.

Alt: deoxidant element, can reduce the oxide inclusion in steel and pure steel, is conducive to the forming property improving steel plate; Too high levels will cause ductility deteriorates, therefore control 0.02 ~ 0.06%.

Ti: V-N steel element, plays crystal grain thinning, dispersion-strengthened action, is combined improves sulfide inclusion form with sulphur, can fix nitrogen unnecessary in steel simultaneously; Too low effect is not obvious, too high unnecessary.Therefore control 0.02 ~ 0.05%, preferably 0.03 ~ 0.05%.

A kind of 700MPa level hot-rolled dual-phase steel that the present invention produces, yield strength>=400MPa, tensile strength>=700MPa, unit elongation A ₅₀>=20%, this steel plate does not add the noble elements such as Nb, V, Mo, Ni, and saved production cost, production method is convenient operation also.Have higher intensity, plastotype and plasticity, the use properties such as good extensibility, weldability, clod wash, meets the requirement that the automobile component manufactures such as automobile traveling parts, structural part and stiffener are higher, meets the demand for development of automotive light weight technology.

Embodiment

Below by embodiment, the present invention will be described in detail.

Embodiment 1

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.105%, Si 0.16%, Mn 0.82%, Alt 0.04%, Cr 0.77%, P 0.047%, Ti 0.038%, S 0.003%, N 0.0036%, surplus is Fe and inevitable impurity.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1280 DEG C by gained thickness, soaking time 2 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1180 DEG C, finishing temperature 1100 DEG C, and 3 passes become the intermediate blank of 32mm, and finish rolling stage start rolling temperature is 1060 DEG C, and finishing temperature is 880 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 693 DEG C with the cooling rate of 25 ~ 100 DEG C/s, air cooling 3S, be then cooled to target coiling temperature with the cooling rate of 89 DEG C/s and batch;

(4) coiling technique: coiling temperature is 89 DEG C; Gained finished product thickness is 2.3mm.

The yield strength 489MPa of this embodiment 1 resulting structures steel, tensile strength 732MPa, unit elongation A ₅₀21%

Embodiment 2

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.088%, Si 0.13%, Mn 0.83%, Alt 0.032%, Cr 0.69%, P 0.052%, Ti 0.037%, S 0.003%, N0.0027%, surplus is Fe and inevitable impurity.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1240 DEG C by gained thickness, soaking time 2 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1130 DEG C, finishing temperature 1070 DEG C, and 3 passes become the intermediate blank of 30mm, and finish rolling stage start rolling temperature is 1040 DEG C, and finishing temperature is 870 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 692 DEG C with the cooling rate of 86 DEG C/s, air cooling 7S, be then cooled to target coiling temperature with the cooling rate of 83 DEG C/s and batch;

(4) coiling technique: coiling temperature is 136 DEG C; Gained finished product thickness is 2.6mm.

The yield strength 463MPa of this embodiment 2 resulting structures steel, tensile strength 739MPa, unit elongation A ₅₀22%

Embodiment 3

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.096%, Si 0.28%, Mn 0.75%, Alt 0.040%, Cr 0.65%, P 0.043%, Ti 0.036%, S 0.002%, N0.0042%, surplus is Fe and inevitable impurity.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1250 DEG C by gained thickness, soaking time 2.5 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1160 DEG C, finishing temperature 1060 DEG C, and 3 passes become the intermediate blank of 30mm, and finish rolling stage start rolling temperature is 1040 DEG C, and finishing temperature is 860 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 686 DEG C with the cooling rate of 77 DEG C/s, air cooling 6S, be then cooled to target coiling temperature with the cooling rate of 72 DEG C/s and batch;

(4) coiling technique: coiling temperature is 112 DEG C; Gained finished product thickness is 3mm.

The yield strength 452MPa of this embodiment 3 resulting structures steel, tensile strength 727MPa, unit elongation A ₅₀23%

Embodiment 4

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.093%, Si 0.18%, Mn 0.86%, Alt 0.032%, Cr 0.72%, P 0.048%, Ti 0.026%, S 0.003%, N0.0037%, surplus is Fe and inevitable impurity.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1250 DEG C by gained thickness, soaking time 2 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1150 DEG C, finishing temperature 1070 DEG C, and 3 passes become the intermediate blank of 33mm, and finish rolling stage start rolling temperature is 1030 DEG C, and finishing temperature is 860 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 677 DEG C with the cooling rate of 71 DEG C/s, air cooling 5S, be then cooled to target coiling temperature with the cooling rate of 69 DEG C/s and batch;

(4) coiling technique: coiling temperature is 173 DEG C; Gained finished product thickness is 4mm.

The yield strength 446MPa of this embodiment 4 resulting structures steel, tensile strength 718MPa, unit elongation A ₅₀27%

Embodiment 5

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.104%, Si 0.27%, Mn 0.89%, Alt 0.033%, Cr 0.77%, P 0.033%, Ti 0.042%, S 0.001%, N0.0029%, surplus is Fe and inevitable impurity.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1260 DEG C by gained thickness, soaking time 2 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1170 DEG C, finishing temperature 1070 DEG C, and 3 passes become the intermediate blank of 34mm, and finish rolling stage start rolling temperature is 1030 DEG C, and finishing temperature is 850 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 682 DEG C with the cooling rate of 58 DEG C/s, air cooling 4S, be then cooled to target coiling temperature with the cooling rate of 53 DEG C/s and batch;

(4) coiling technique: coiling temperature is 146 DEG C; Gained finished product thickness is 5mm.

The yield strength 459MPa of this embodiment 5 resulting structures steel, tensile strength 721MPa, unit elongation A ₅₀27%

Embodiment 6

Described 700MPa level hot-rolled dual-phase steel, comprise the chemical composition of following weight percent: C 0.115%, Si 0.25%, Mn 0.95%, Alt 0.038%, Cr 0.88%, P 0.0392%, Ti 0.048%, S 0.001%, N0.0034%, surplus is Fe and inevitable impurity.

The preparation method of described 700MPa level hot-rolled dual-phase steel, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1240 DEG C by gained thickness, soaking time 2 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1130 DEG C, finishing temperature 1020 DEG C, and 3 passes become the intermediate blank of 45mm, and finish rolling stage start rolling temperature is 1010 DEG C, and finishing temperature is 830 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 658 DEG C with the cooling rate of 43 DEG C/s, air cooling 3S, be then cooled to target coiling temperature with the cooling rate of 36 DEG C/s and batch;

(4) coiling technique: coiling temperature is 107 DEG C; Gained finished product thickness is 6mm.

The yield strength 453MPa of this embodiment 6 resulting structures steel, tensile strength 738MPa, unit elongation A ₅₀29%.

A kind of 700MPa level hot-rolled dual-phase steel cost of the present invention is lower, there is higher intensity, plastotype and plasticity, the use properties such as good extensibility, weldability, clod wash, be suitable for the processing and manufacturing of the automobile component such as automobile traveling parts, structural part and stiffener, particularly processing characteristics and fatigue property are had to the parts of high request, manufacture method of the present invention is workable, has higher application value.

Claims (9)

1. a 700MPa level hot-rolled dual-phase steel, it is characterized in that, comprise the chemical composition of following weight percent: C 0.08 ~ 0.12%, Si 0.1 ~ 0.3%, Mn 0.7 ~ 1.00%, Alt 0.02 ~ 0.06%, Cr 0.60 ~ 1.00%, P0.03 ~ 0.06%, Ti 0.02 ~ 0.05%, S≤0.005%, N≤0.006%, surplus is Fe and inevitable impurity.

2. 700MPa level hot-rolled dual-phase steel according to claim 1, it is characterized in that, comprise the chemical composition of following weight percent: C 0.09 ~ 0.11%, Si 0.15 ~ 0.25%, Mn 0.70 ~ 0.9%, Alt 0.02 ~ 0.06%, Cr 0.70 ~ 0.9%, P 0.03 ~ 0.05%, Ti 0.03 ~ 0.05%, S≤0.005%, N≤0.006%, surplus is Fe and inevitable impurity.

3. 700MPa level hot-rolled dual-phase steel according to claim 1, it is characterized in that, comprise the chemical composition of following weight percent: C 0.105%, Si 0.16%, Mn 0.82%, Alt 0.04%, Cr 0.77%, P 0.047%, Ti 0.038%, S 0.003%, N 0.0036%, surplus is Fe and inevitable impurity.

4. 700MPa level hot-rolled dual-phase steel according to claim 1, it is characterized in that, comprise the chemical composition of following weight percent: C 0.088%, Si 0.13%, Mn 0.83%, Alt 0.032%, Cr 0.69%, P 0.052%, Ti 0.037%, S 0.003%, N 0.0033%, surplus is Fe and inevitable impurity.

5. 700MPa level hot-rolled dual-phase steel according to claim 1, it is characterized in that, comprise the chemical composition of following weight percent: C 0.096%, Si 0.28%, Mn 0.75%, Alt 0.040%, Cr 0.65%, P 0.043%, Ti 0.036%, S 0.002%, N 0.0027%, surplus is Fe and inevitable impurity.

6. a preparation method for 700MPa level hot-rolled dual-phase steel according to any one of claim 1 to 5, comprises the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 90 ~ 250mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 90 ~ 250mm is heated to 1200 ~ 1300 DEG C by gained thickness, soaking time 1 ~ 3 hour, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1100 ~ 1180 DEG C, finishing temperature 1000 ~ 1100 DEG C, and finish rolling stage start rolling temperature is 980 ~ 1080 DEG C, and finishing temperature is 800 ~ 880 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 650 ~ 700 DEG C with the cooling rate of 25 ~ 100 DEG C/s, air cooling 2 ~ 8S, be then cooled to target coiling temperature with the cooling rate of 25 ~ 100 DEG C/s and batch;

(4) coiling technique: coiling temperature is less than 250 DEG C; Gained finished product thickness is 2 ~ 6mm.

7. the preparation method of 700MPa level hot-rolled dual-phase steel according to claim 6, it is characterized in that, in described finished product, ferrite volume fraction is 75 ~ 85%, and Martensite Volume Fraction is 15 ~ 25%.

8. the preparation method of 700MPa level hot-rolled dual-phase steel according to claim 6, is characterized in that, comprise the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1240 DEG C by gained thickness, soaking time 2 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1130 DEG C, finishing temperature 1070 DEG C, and 3 passes become the intermediate blank of 30mm, and finish rolling stage start rolling temperature is 1040 DEG C, and finishing temperature is 870 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 692 DEG C with the cooling rate of 86 DEG C/s, air cooling 7S, be then cooled to target coiling temperature with the cooling rate of 83 DEG C/s and batch;

(4) coiling technique: coiling temperature is 136 DEG C; Gained finished product thickness is 2.6mm.

9. the preparation method of 700MPa level hot-rolled dual-phase steel according to claim 6, is characterized in that, comprise the following steps: first molten iron is through KR desulfurization process; Then smelt and LF refining treatment through converter routine, the strand that last continuous casting becomes 135mm thick, strand obtains 700MPa level hot-rolled dual-phase steel through hot continuous rolling; Wherein said hot continuous rolling comprises following technique:

(1) heating process: be that the strand of 135mm is heated to 1250 DEG C by gained thickness, soaking time 2.5 hours, is then rolled;

(2) rolling technology: adopt two-stage control rolling, wherein rough rolling step single pass draft >=20%, total reduction is >=70%, and finish rolling stage draft is >=75%; Rough rolling step start rolling temperature is 1160 DEG C, finishing temperature 1060 DEG C, and 3 passes become the intermediate blank of 30mm, and finish rolling stage start rolling temperature is 1040 DEG C, and finishing temperature is 860 DEG C; Rolling cools after completing;

(3) process for cooling: adopt cooling speed change cooling technique, be cooled to 686 DEG C with the cooling rate of 77 DEG C/s, air cooling 6S, be then cooled to target coiling temperature with the cooling rate of 72 DEG C/s and batch;

(4) coiling technique: coiling temperature is 112 DEG C; Gained finished product thickness is 3mm.