阅读说明：本技术 一种980MPa级高成形性冷轧相变诱导塑性钢及其制备方法 (980 MPa-grade high-formability cold-rolled phase-change induced plasticity steel and preparation method thereof ) 是由 李春诚 刘宏亮 佟铁印 李霞 胡小强 冯岗 程宏远 薛文辉 于 2020-02-17 设计创作，主要内容包括：本发明提供了一种980MPa级高成形性冷轧相变诱导塑性钢及其制备方法,钢中化学成分按质量百分比含量为：C：0.15～0.30％,Si：0.50-2.00％,Mn：1.50～2.60％,Nb：0.02-0.08％,Ti：0.02-0.08％,P≤0.05％,S≤0.01％,Al≤0.10％,余量为Fe及不可避免的夹杂物。钢板的生产工艺为：铁水预处理、转炉冶炼、炉外精炼、连铸、加热、控轧控冷、卷取、酸洗、冷轧、连续退火、平整、机能检验、包装出厂。(The invention provides 980MPa grade high-formability cold-rolled phase-change induced plasticity steel and a preparation method thereof, wherein the steel comprises the following chemical components in percentage by mass: c: 0.15-0.30%, Si: 0.50 to 2.00%, Mn: 1.50-2.60%, Nb: 0.02 to 0.08%, Ti: 0.02-0.08%, P is less than or equal to 0.05%, S is less than or equal to 0.01%, Al is less than or equal to 0.10%, and the balance is Fe and inevitable impurities. The production process of the steel plate comprises the following steps: the method comprises the following steps of molten iron pretreatment, converter smelting, external refining, continuous casting, heating, controlled rolling and controlled cooling, reeling, acid washing, cold rolling, continuous annealing, leveling, function inspection and packaging for delivery.)

1. A980 MPa grade high-formability cold-rolled phase-change induced plasticity steel is characterized in that the steel plate is controlled to have the following chemical components in percentage by weight: c: 0.15-0.30%, Si: 0.50 to 2.00%, Mn: 1.50-2.60%, Nb: 0.02 to 0.08%, Ti: 0.02-0.08%, P is less than or equal to 0.05%, S is less than or equal to 0.01%, Al is less than or equal to 0.10%, and the balance is Fe and inevitable impurities.

2. The preparation method of the 980MPa grade high-formability cold-rolled transformation induced plasticity steel according to claim 1, wherein the production process of the steel plate comprises the following steps: the method comprises the steps of molten iron pretreatment, converter smelting, external refining, continuous casting, heating, controlled rolling and controlled cooling, reeling, acid washing, cold rolling, continuous annealing, leveling, function inspection, packaging and delivery, and is characterized in that,

the hot rolling slab is heated at 1240-1290 ℃, rolled at 1120-1170 ℃, rolled at 910-970 ℃ and then cooled in a laminar cooling mode, and the coiling temperature is 530-590 ℃;

the cooling rate is 20-35 ℃/s;

the cold rolling adopts the reduction rate of more than or equal to 50 percent;

the temperature of the heating section of the continuous annealing process is 840-860 ℃, the temperature of the soaking section is 840-860 ℃, the temperature of the slow cooling section is 740-760 ℃, the temperature of the fast cooling section is 390-410 ℃, the temperature of the overaging section is 360-400 ℃, the temperature of the final cooling section is 140-160 ℃, and the steel passing speed in the furnace is 120-140 m/min.

Technical Field

The invention relates to the field of steel production and manufacturing, in particular to 980MPa grade high-formability cold-rolled phase-change induced plasticity steel and a preparation method thereof.

Background

In recent years, with the rising of energy crisis, oil price and the increasing of global greenhouse effect, environmental problems caused by energy and carbon dioxide emission are more emphasized in countries of the world, and various strict measures are proposed and made for control. In the field of automobile industry, coping with environmental problems and improving collision safety are common keywords, and one of the most effective methods is to reduce the self weight of a vehicle body. The use of the high-strength steel can reduce the thickness specification of the steel plate, thereby achieving the purposes of reducing the vehicle weight and improving the safety. Studies by scholars have shown that when the thickness of the steel sheet is reduced by 0.05mm, 0.01mm and 0.15mm, respectively, the weight of the car body is reduced by 6%, 12% and 18%, respectively. However, as more and more high-strength steels are used instead of low-grade steels, problems such as reduction in formability, difficulty in processing, and the like are likely to occur.

At present, the 980 MPa-grade cold-rolled high-strength steel for automobiles mainly comprises dual-phase steel (DP), quenching distribution steel (Q & P), martensitic steel (M) and the like, and the high-strength steel introduces a large amount of martensitic hard phase tissues, so that the strength of the steel is greatly improved. However, the martensite steel and the dual-phase steel have low plasticity at the strength level, need roll forming or simply processed stamping forming parts, and can only replace a small amount of steel types with low forming requirements due to the forming requirements; the quenching distribution steel is composed of martensite + retained austenite or martensite + retained austenite + ferrite, the plasticity is improved and the formability is improved by introducing part of the retained austenite, and the steel is more excellent than martensite steel or dual-phase steel, but the yield strength is higher due to higher martensite proportion, and the requirement on a processed die is higher.

Disclosure of Invention

In order to solve the problems, the invention provides 980MPa grade high-formability cold-rolled transformation induced plasticity steel.

The technical scheme provided by the invention is as follows:

the invention provides 980MPa grade high-formability cold-rolled phase-change induced plasticity steel and a preparation method thereof, wherein the steel plate is prepared by controlling the following chemical components in percentage by weight: c: 0.15-0.30%, Si: 0.50 to 2.00%, Mn: 1.50-2.60%, Nb: 0.02 to 0.08%, Ti: 0.02-0.08%, P is less than or equal to 0.05%, S is less than or equal to 0.01%, Al is less than or equal to 0.10%, and the balance is Fe and inevitable impurities.

A preparation method of 980MPa grade high-formability cold-rolled transformation induced plasticity steel comprises the following steps: the method comprises the following steps of molten iron pretreatment, converter smelting, external refining, continuous casting, heating, controlled rolling and controlled cooling, reeling, acid washing, cold rolling, continuous annealing, leveling, function inspection and packaging for delivery.

The preparation process comprises the following specific steps:

smelting by adopting a converter smelting method to obtain molten steel, wherein the molten steel comprises the following chemical components in percentage by mass: c: 0.15-0.30%, Si: 0.50 to 2.00%, Mn: 1.50-2.60%, Nb: 0.02 to 0.08%, Ti: 0.02-0.08%, P is less than or equal to 0.05%, S is less than or equal to 0.01%, Al is less than or equal to 0.10%, and the balance is Fe and inevitable impurities.

(1) Firstly, removing impurity elements or recycling valuable elements before adding molten iron into a steel making furnace, and smelting by adopting a converter smelting method to obtain molten steel, wherein the molten steel comprises the following chemical components in percentage by mass: c: 0.15-0.30%, Si: 0.50 to 2.00%, Mn: 1.50-2.60%, Nb: 0.02 to 0.08%, Ti: 0.02-0.08%, P is less than or equal to 0.05%, S is less than or equal to 0.01%, Al is less than or equal to 0.10%, and the balance of Fe and inevitable impurities;

(2) refining outside the furnace, namely performing continuous casting by using a conventional continuous casting machine to obtain a continuous casting billet; then, carrying out a hot rolling process, wherein the heating temperature of a hot rolled plate blank is 1240-1290 ℃, the initial rolling temperature is 1120-1170 ℃, the final rolling temperature is 910-970 ℃, and a laminar cooling mode is adopted after rolling, and the coiling temperature is 530-590 ℃;

(3) the method comprises the following steps of (1) entering an acid washing process, removing oxides on the surface of a hot rolled steel plate by a conventional acid washing method, wherein the cooling rate is 20-35 ℃/s;

(4) entering a cold rolling process, wherein the cold rolling adopts a reduction rate of more than or equal to 50 percent;

(5) entering a continuous annealing process, wherein the temperature of a heating section of the continuous annealing process is 840-860 ℃, the temperature of a soaking section is 840-860 ℃, the temperature of a slow cooling section is 740-760 ℃, the temperature of a fast cooling section is 390-410 ℃, the temperature of an overaging section is 360-400 ℃, the temperature of a final cooling section is 140-160 ℃, and the steel passing speed in the furnace is 120-140 m/min;

(6) and finally, flattening the steel after the continuous annealing process by using a flattening machine to improve the plate shape so that the surface of the steel is flatter, and performing functional inspection and packaging to leave a factory.

The total design of C-Si-Mn system is adopted, a small amount of microalloy elements Nb and Ti are added to improve the microstructure and the sizes of different phases, and the mechanical property of transformation induced plasticity steel (TRIP) is realized through the volume fractions of ferrite, bainite and residual austenite. The production method can be realized on a continuous annealing production line, achieves high strength and high plasticity, simultaneously reduces yield strength, improves formability, solves the problems of larger strength difference of soft and hard phases, lower rapid cooling temperature, complex heat treatment process and the like, has lower yield strength than Q & P steel, better plasticity than DP steel and easier formability than M steel, and is a representative product of advanced high-strength steel.

Compared with the prior art, the plastic steel obtained by the working procedures has the advantages that the production control is relatively simple, the characteristics of strong quick cooling capacity and longer overaging section of the continuous annealing unit are fully exerted, and the heating and cooling technological parameters are easy to realize. In addition, the invention does not need to add elements such as noble alloys Cr, Mo and the like, has lower raw material and production cost and extremely high added value, has the mechanical properties of high strength, high plasticity and high formability, can better meet the requirement of processing more complicated parts and has wide future market prospect.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.