Method for manufacturing 550MPa-level high-strength atmospheric corrosion resistant steel strip through strip continuous casting

Abstract

The invention provides a method for manufacturing a 550MPa-level high-strength atmospheric corrosion resistant steel strip through strip continuous casting. The method comprises the following steps of: 1) smelting, wherein molten steel comprises the following chemical components: 0.03-0.08% of C, not more than 0.4% of Si, 0.6-1.5% of Mn, 0.07-0.22% of P, not more than 0.01% of S, not more than 0.012% of N, 0.25-0.8% of Cu, 0.3-0.8% of Cr, 0.12-0.4% of Ni, at least one of microalloy elements including 0.01-0.08% of Nb, 0.01-0.08% of V, 0.01-0.08% of Ti and 0.1-0.4% of Mo, and the balance of Fe and inevitable impurities; 2) strip continuous casting: directly casting a cast strip with thickness of 1-5mm; 3) strip cooling, wherein the cooling rate is more than 20 DEG C / s; 4) online hot rolling of the cast strip, wherein the hot rolling temperature is 1050-1250 DEG C, the reduction rate is 20-50% and the deformation rate is more than 20s<-1>; online austenite recrystallization happens after hot rolling; and the hot-rolled strip is 0.5-3.0mm in thickness; and 5) cooling and coiling, wherein the cooling rate is 10-80 DEG C / s, and the coiling temperature is 570-720 DEG C. The microstructure of the obtained steel strip is mainly formed by fine polygonal ferrite and pearlite.

Description

technical field [0001] The invention relates to thin strip continuous casting technology, in particular to a manufacturing method of thin strip continuous casting 550MPa high-strength atmospheric corrosion-resistant steel strip, the yield strength of the steel strip is ≥550MPa, the tensile strength is ≥650MPa, and the elongation is ≥22%, 180 ° The bending performance is qualified, and it has excellent strong-plastic matching. The microstructure of the steel strip is mainly composed of fine polygonal ferrite and pearlite. Background technique [0002] Atmospheric corrosion-resistant steel or weathering steel refers to low-alloy structural steel that has a protective rust layer that is resistant to atmospheric corrosion and can be used to manufacture steel structures such as vehicles, bridges, towers, and containers. Compared with ordinary carbon steel, weathering steel has better corrosion resistance in the atmosphere. Compared with stainless steel, weathering steel has only...

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Problems solved by technology

[0008] (1) Long process flow, high energy consumption, many units and equipment, and high infrastructure costs lead to high production costs

[0009] (2) Atmospheric corrosion-resistant steel contains a relatively high content of phosphorus, copper and other elements that are easy to segregate to improve the atmospheric corrosion resistance of the steel strip. The traditional process is easy to cause macro-segregation of phosphorus, copper and other elements due to the slow solidification and cooling speed of the billet. As a result, the anisotropy of the slab and the appearance of macroscopic cracks lead to a low success rate

As a result, the weather resistance of the steel strip is not high

[0011] (4) In the traditional process, since the microalloying elements cannot remain in solid solution during the hot rolling process, partial precipitation occurs, resulting in an increase in the strength of the steel, which will significantly increase the rolling load, increase energy consumption and roll consumption, and damage equipment Larger, thus limiting the economical and practical production of high-strength weathering steel hot-rolled product thickness range, usually ≥ 2mm

Continuing cold rolling of traditional hot-rolled products can further reduce the thickness of the steel strip, but the high strength of the hot-rolled steel strip makes cold rolling difficult

One is that the high cold rolling load has higher requirements on equipment and greater damage; the other is that the second phase precipitated by alloy elements in the hot rolled product significantly increases the recrystallization annealing temperature of the steel strip after cold rolling

[0012] (5) In the traditional process, when producing high-strength products containing microalloying elements, the principle of deformation and refinement of austenite grains is usually used. Therefore, the starting temperature of finish rolling is usually lower than 950°C, and the finish rolling temperature is around 850°C , rolling at a lower temperature, coupled with the increase in deformation with the rolling process, will lead to a significant increase in the strength of the steel strip, which will also significantly increase the difficulty and consumption of hot rolling

This not only increases the investment cost, but also significantly increases the floor area of ​​the thin strip continuous casting and rolling production line, reducing the advantages of the production line

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