CN108396237A

CN108396237A - High-plasticity cold-rolled sheet and production method thereof

Info

Publication number: CN108396237A
Application number: CN201710064848.4A
Authority: CN
Inventors: 吕家舜; 李峰; 杨洪刚; 周芳; 刘仁东
Original assignee: Angang Steel Co Ltd
Current assignee: Angang Steel Co Ltd
Priority date: 2017-02-05
Filing date: 2017-02-05
Publication date: 2018-08-14
Anticipated expiration: 2037-02-05
Also published as: CN108396237B

Abstract

The invention provides a high-plasticity cold-rolled sheet and a production method thereof, and the high-plasticity cold-rolled sheet comprises the following chemical components: 0.10-0.60% of C, 0.50-3.5% of Si, 1.50-3.50% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, 0.02-3.00% of Al, less than or equal to 0.50% of Cr, less than or equal to 3.00% of Ni, less than or equal to 0.50% of Cu, less than or equal to 1.50% of Mo, less than or equal to 0.50% of V, less than or equal to 0.20% of Ti, and. And in the hot rolling process, the coiling temperature is controlled in a bainite transformation temperature interval to obtain a metallographic structure taking lath bainite as a main body, the steel plate after cold rolling is heated to an austenite temperature region in a continuous annealing production line and then is subjected to heat preservation for a period of time, then bainite isothermal quenching is carried out to obtain the steel plate taking the lath bainite and residual austenite as main structures, and then carbon distribution treatment is carried out. The steel has a metallographic structure with residual austenite uniformly distributed in a fine-grained bainite matrix, and has excellent plasticity, welding performance, forming performance, hole expansion performance and flange extending performance.

Description

A kind of high-ductility cold-reduced sheet and its production method

Technical field

The invention belongs to cold-rolled steel sheet manufacturing technology field, more particularly to a kind of high intensity obtained using bainitic transformation High-ductility cold-reduced sheet and its production method.

Background technology

In order to improve the service efficiency of steel, the energy, resource consumption of the saving steel during manufacturing and use, The scientific research personnel of various countries develops the various high strength steels with excellent comprehensive performance in succession in recent decades, wherein having generation Table has dual phase steel, TRIP steel, TWIP steel, martensite steel, bainitic steel, Multiphase Steel, thermoforming steel, Q＆P steel etc..With it is common High-strength steel is compared, and AHSS steel formability is good, and S. E. A. is high, anticollision concavity energy is good, and baking and hardening performance, adds yield strength The advantages that work hardening ratio is high and fatigue behaviour is good, good application prospect is shown in automobile, machine-building, building etc..

But full geneva is obtained after being hot pressed into shaped steel molding in existing steel in addition to martensite steel is without the concern for plasticity Body tissue does not have outside plasticity, and other steel grades obtain preferable plasticity by two ways：Pass through the preferably soft phase of plasticity and plasticity The poor hard matched well for being combined to obtain plasticity and intensity, this kind of ladle include dual phase steel, bainitic steel, Multiphase Steel etc.； Improve the overall deformation ability of steel by the deformation induced plasticity of retained austenite, while there is also soft phase and hard phases in steel Combination, this kind of ladle include TRIP steel, TWIP steel, Q＆P steel etc..

Although preferable plasticity, the widely different two-phase of deformability can be obtained by the combination of soft phase and hard phase (ferrite+martensite) interface is easily cracked in osseotomy site in forming process, and stretch flange formability forming property is not good enough, especially After Flash Butt Welding, martensitic phase temper softening easily occurs at heat affected area (HAZ), while fatigue strength is low.

Existing bainite Plate Production patent for example application number 201010283882.9,201110383478.3, 201210195411.1,201210268312.1 primarily directed to hot rolled steel plate production.201010283882.9 disclosing one Kind high-elongation high strength low carbon bainibic steel plate and its production method, chemical composition C0.06-0.18%, Si0.55%- 1.70%, Mn1.1-1.7, also contains the alloying elements such as some Nb, V, Ti, Cr, Ni, Mo, Cu, technique be controlling hot rolling roll and Control cooling, subsequently carries out some heat treatments；It is organized as bainite, martensite and retained austenite.201110383478.3 carrying For a kind of ultralow-carbon bainite steel plate and its manufacturing method, chemical composition is C≤0.03%, Si≤0.15%%, Mn1.2- 1.6%, also contain the alloying elements such as some Nb, V, Ti, Cu, Ni, B, ultra-low carbon bainite is obtained using the method for controlled rolling and controlled cooling Steel plate, and 500-600 DEG C of temper is carried out, finally it is organized as tempering ultra-low carbon bainite+disperse educt object. A kind of ultralow-carbon bainite steel plate and its manufacturing method disclosed in 201210195411.1, it is similar with 201110383478.3, only It is that C content is slightly higher, Mn contents 3.0-4.5% is very high, without containing noble elements such as Cu, Ni.201210268312.1 then providing One kind plate containing B bainitic steel and its manufacturing method, chemical composition C0.20-0.35%, Si0.6-1.6%%, Mn1.5- 2.0%, additionally contain Ti, B, Al and impurity element, be organized as bainite, finished product is hot rolled plate.

Existing open source information is also the achievement in research for hot rolled steel plate, rarer cold-rolled high-strength bainitic steel mostly The report of plate.

In order to improve the performance of bainitic steel, increase the deformability of bainite structure itself, the present invention is by improving shellfish The deformability of family name's body itself so that lath of bainite can deform upon during deformation, become to improve steel plate Mutually coordinated and cooperation during shape between various crystal grain, deformability substantially improve.

Invention content

The object of the present invention is to provide it is a kind of can be improved steel plate in deformation process between various crystal grain it is mutually coordinated with Cooperation has excellent plasticity, reaming performance, the cold rolling bainite steel plate of Extending flange Perfor and its production method.

The technical solution taken of the present invention is：

A kind of high-ductility cold-reduced sheet, chemical composition mass percent are：C 0.10%~0.60%, Si 0.50%~ 3.5%, Mn1.50%~3.50%, P≤0.020%, S≤0.010%, Al 0.02%~3.00%, Cr≤0.50%, Ni ≤ 3.00%, Cu≤0.50%, Mo≤1.50%, V≤0.50%, Ti≤0.20%, Nb≤0.20%, surplus are Fe and other Inevitable impurity；

Cold-reduced sheet metallographic structure is ferrite bainite+retained austenite, and retained austenite is uniformly distributed in lath of bainite Between and lath of bainite inside, the percent by volume of bainite structure is 55%~85%, the volume basis of retained austenite Than being 15%~45%.

A kind of production method of high-ductility cold-reduced sheet, for the steel of the ingredient after smelting, casting, hot rolling, pickling, hot rolling is whole Temperature control is rolled in austenitic area, and the beginning of cooling temperature is controlled in austenitic area, and 20 DEG C/s of cooling velocity after rolling ＞ are cooled to institute The bainite transformation temperature for stating steel, is then batched, and hot rolled steel plate is organized as ferrite bainite+retained austenite；Steel plate acid-washing, Continuous annealing, heating speed >=10 DEG C/s of continuous annealing production line are carried out after cold rolling, heating temperature is 700~930 DEG C, heat preservation 10~60s of time, rapid cooling, rapid cooling cooling velocity >=30 DEG C/s, rapid cooling temperature control in bainite transformation area immediately thereafter, and 20~300s of this temperature is cooled to 300~400 DEG C of temperature range and further completes C distribution, is finally cooled to room later Temperature.

The present invention selects the reason of above-mentioned each feature and its design parameter as follows：

Hot rolling finishing temperature is controlled in austenitic area, and the speed to be not less than 20 DEG C/s is cooled to Bainite Region and batches, really Guarantor obtains the metallographic structure of ferrite bainite+retained austenite.

The heating speed of continuous annealing production line is not less than 10 DEG C/s, and heating temperature is 700~930 DEG C, soaking time 10 ~60 seconds, then rapid cooling, rapid cooling cooling velocity were not less than 30 DEG C/s immediately, in bainite transformation area, then rapid cooling temperature controls Slow cooling is to room temperature after this temperature 20~300 seconds.It is heated to austenitic area heat preservation, it is therefore intended that obtain uniform austenite Tissue；Less than 700 DEG C, steel plate is unable to austenitizing, is higher than 930 DEG C, will make austenite grain coarsening, and cause armor plate strength Decline, easily causes broken belt in stove；Quenching velocity is less than 30 DEG C/s, it is impossible to obtain B+A tissues；It is main group that must obtain B+A The reason of knitting is, distribution of the C atoms from B into A can be realized in subsequent assigning process, obtains the A of rich carbon, hardening heat In bainite transformation temperature section, the too low obtained A amounts of temperature are less for control, and are susceptible to M tissues.

C content in steel plate is controlled in C0.10%~0.60%, and C can be with stable austenite, the too low armor plate strength of carbon content Deficiency, and be enriched with into retained austenite in the not enough C atoms of the process of distribution, obtained stability of retained austenite is not Foot, too high levels will be unfavorable to processability, welding performance.

The control of Si contents is too low in 0.50%~3.5%, Si contents, can not hinder the precipitation of cementite, play stabilization The effect of austenite, silicone content is excessively high, will cause selective oxidation of the surface of steel plate in annealing process, the oxide shadow of generation Ring the surface quality and aftertreatment technology of steel plate.

The control of Mn contents in 1.50%~3.50%, Mn is austenite stabilizer element, and Mn contents are too low, the intensity of steel and Quenching degree is insufficient, and Mn too high levels may cause austenite volume to increase, and the banded structure of Mn too high levels steel is extremely serious, Influence the homogeneity of performance.

P≤0.020%, it is more fewer better, it is determined according to steel making ability and economy.

S≤0.010%, it is more fewer better, it is determined according to steel making ability and economy.

Al controls have the function of Si elements in 0.02%~3.00%, Al elements, but too high levels will cause to make steel, The problems of casting process, such as oxide is mingled with, nozzle blockage.

Cr≤0.50%, certain Cr contents can move to right C curve, reduce the critical cooling rate of quenching, but content mistake Height, quenching degree increase, and cause the reduction even disappearance of remained austenite content after quenching.

Ni≤3.00%, certain nickel content can improve the comprehensive mechanical performance of steel, improve the stability of austenite, contain It measures and excessively high causes cost increase.

Cu≤0.50%, Cu element are very strong austenite formers, are not also dissolved in cementite, and remnants are conducive to The content of retained austenite can be improved in the formation of austenite, in addition can improve intensity, while improving corrosion resistance.

Mo≤1.50%, Mo are a kind of ferrite formers, and reduce bainite transformation initial temperature, while being prolonged strongly Slow phase transformation of the austenite to ferrite and pearlite, too high levels cause cost increase.

V≤0.50%, Ti≤0.20%, Nb≤0.20%, these three elements all have the function of precipitation strength, but content It is unsuitable excessively high.One or two can be selected when actual needs addition.

Beneficial effects of the present invention are：

Have the advantages that intensity is high, reaming performance is good using steel plate produced by the invention, and efficiently solves industrialization The process route of production.Steel plate yield strength is more than 800MPa, tensile strength >=1000MPa, elongation >=25%, λ >=40.

Specific implementation mode

The chemical composition of embodiment steel is shown in Table 1, and embodiment production process processing parameter and performance are shown in Table 2.

The chemical composition wt% of 1 steel of table

2 production process processing parameter of table and performance

Claims

1. a kind of high-ductility cold-reduced sheet, which is characterized in that its chemical composition mass percent is：C 0.10%~0.60%, Si 0.50%~3.5%, Mn 1.50%~3.50%, P≤0.020%, S≤0.010%, Al 0.02%~3.00%, Cr≤ 0.50%, Ni≤3.00%, Cu≤0.50%, Mo≤1.50%, V≤0.50%, Ti≤0.20%, Nb≤0.20%, surplus For Fe and other inevitable impurity；

Cold-reduced sheet metallographic structure is ferrite bainite+retained austenite, and retained austenite is uniformly distributed between lath of bainite And inside lath of bainite, the percent by volume of bainite structure is 55%~85%, and the percent by volume of retained austenite is 15%~45%.

2. a kind of production method of high-ductility cold-reduced sheet as described in claim 1, which is characterized in that the steel of the ingredient is through smelting After refining, casting, hot rolling, pickling, hot rolling finishing temperature control is controlled in austenitic area, is rolled in austenitic area, the beginning of cooling temperature Postcooling speed 20 DEG C/s of ＞, are cooled to the bainite transformation temperature of the steel, then batch, hot rolled steel plate is organized as lath Bainite+retained austenite；Carry out continuous annealing after steel plate acid-washing, cold rolling, heating speed >=10 DEG C of continuous annealing production line/ S, heating temperature are 700~930 DEG C, 10~60s of soaking time, thereafter rapid cooling immediately, rapid cooling cooling velocity >=30 DEG C/s, rapid cooling Temperature controls in bainite transformation area, and in 20~300s of this temperature, is cooled to 300~400 DEG C of temperature range later C distribution is further completed, room temperature is finally cooled to.