600MPa class chromium/niobium-containing hot-rolled dual-phase steel plate and production method thereof

Abstract

The invention provides a 600MPa class chromium / niobium-containing hot-rolled dual-phase steel plate and a manufacturing method thereof. The steel plate comprises the following chemical components in percentage by weight: 0.050-0.10 percent of C, 0.050-0.50 percent of Si, 1.0-1.80 percent of Mn, 0.010-0.080 percent of Als, 0.30-1.20 percent of Cr, 0.010-0.050 percent of Nb, less than 0.020 percent of P and less than 0.005 percent of S. The method comprises the following steps: heating a continuous casting billet to the temperature of 1200+ / -20 DEG C, and preserving heat for 1-3 hours, the rough rolling opening temperature is 1040-1100 DEG C, the finish rolling and finishing temperature is 860-920 DEG C; rapidly cooling the steel plate to ferrite for changing in a rapid temperature zone at a rapid cooling speed of more than 40 DEG C per second, wherein the air-cooling starting temperature is 680-720 DEG C, the time is 5-10 seconds; and rapidly cooling the steel plate to be 480-550 DEG C for rolling at a cooling rate of 50 DEG C per second after air cooling. According to the method, the cost can be greatly reduced, large-scale production of medium thin slabs on a continuous casting tandem rolling line is realized, the hot-rolled dual-phase steel plate of ferrite and martensite is obtained, Rp0.2 is 413MPa, Rm is 640MPa, A80 is 20.8 percent, and the n is 0.19.

Description

technical field [0001] The invention belongs to the field of metallurgical technology, and particularly relates to a hot-rolled dual-phase steel plate containing chromium and niobium with a tensile strength reaching 600 MPa on a medium-thin slab continuous casting and rolling line and a manufacturing method thereof. Background technique [0002] The dual-phase steel composed of a large amount of ferrite and a small amount of martensite has the advantages of good strength-plastic ratio and excellent formability. Its products can be widely used in moving components and safety components of automobiles, such as wheels, chassis, Bumpers etc. In 1994, the World Iron and Steel Association formulated the Ultra Light Steel Body Program (ULSAB), in which dual-phase steel will account for 74.3% of the total mass of the car body. With the rapid development of industry, the demand for the use of resources and the environment has increased rapidly. In the iron and steel industry, in ord...

AI Technical Summary

Problems solved by technology

At present, various steel mills and research institutions have developed multiple levels of hot-rolled dual-phase steel plates, but there are two main problems: one is that the composition contains relatively high Si elements or precious alloying elements (such as Mo), which makes the steel Problems such as poor surface quality and high composition make it difficult to enter the market

The second is that the cooling process is complex and difficult to control, resulting in large fluctuations in the performance of the steel plate. For Si-Mn series hot-rolled dual-phase steel, there are still problems such as low coiling temperature and high requirements for coiling equipment.

[0005] Publication No. CN101130847A discloses a method for producing hot-rolled dual-phase steel plates on a medium-thin slab continuous casting and rolling line. Through reasonable composition design and hot-rolling process cooperation, coiling can be performed in a medium-temperature region to obtain dual-phase Steel plate, but the composition of the steel plate contains 0.001-0.7% Mo element, resulting in higher cost

[0006] Publication No. CN101717886A proposes a hot-rolled dual-phase steel plate with a tensile strength of 650 MPa and its manufacturing method. Although its cost is low and the cooling process after rolling is relatively simple, the Si content in its composition is relatively high, reaching 0.5- 1.2%, which will lead to surface quality problems of the steel plate. At the same time, the coiling temperature is required to be lower than 300°C, which has higher requirements on the coiling capacity and cooling capacity of the equipment.

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