CSP process-based manufacturing method of economical hot-rolled dual-phase steel with high surface quality

Abstract

The invention relates to a CSP process-based manufacturing method of economical hot-rolled dual-phase steel with high surface quality, which solves the problems that the existing economical hot-rolled dual-phase steel has serious surface iron scales and instable structure property control. The technical scheme comprises molten iron desulfurization, converter blowing, argon blowing, refining, continuous casting, soaking, finish rolling, cooling and coiling. The steel comprises the following chemical components in percentage by weight: 0.03 to 0.065 percent of C, 0.45 to 0.55 percent of Si, 1.20 to 1.55 percent of Mn, less than or equal to 0.012 percent of S, less than or equal to 0.020 percent of P, 0.015 to 0.060 percent of Als, and the balance of Fe and inevitable impurities. In the manufacturing method, the plate blank tapping temperature of a soaking furnace is controlled to be between 1,180 and 1,200 DEG C in the soaking step, the oxygen content volume percent in the furnace is 3.5 to 5.0 percent, the time inside the furnace is 30 to 50 minutes, and the plate blank after soaking is subjected to high-pressure water descaling and then is subjected to the finish rolling. The dual-phase steel produced by the manufacturing method has stable structure property control, no obvious iron scales on the surface, and excellent performance indexes.

Description

technical field [0001] The invention relates to a steel manufacturing process, in particular to a manufacturing method of an economical hot-rolled dual-phase steel with good surface quality based on a CSP process. Background technique [0002] Dual-phase steel refers to low-carbon steel or low-carbon alloy steel obtained by critical zone heat treatment or controlled cooling process, mainly composed of ferrite (F) and a small amount (volume fraction less than 20%) of martensite (M) Advanced High Strength Steel. The so-called economical hot-rolled dual-phase steel specifically refers to the hot-rolled dual-phase steel obtained by using ordinary C-Si-Mn components without adding precious alloy elements such as Cr and Mo, and through strict controlled rolling and controlled cooling processes. [0003] In the manufacture of dual-phase steel, compared with the conventional hot-rolling production line, the thin slab continuous casting and rolling production line (CSP process) has ...

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Problems solved by technology

[0004] Due to its low cooling capacity, the traditional hot rolling process can only produce medium-temperature coiled hot-rolled dual-phase steel (this steel needs to add a certain amount of alloying elements, such as Cr, Mo, etc.), and the above literature shows that the thin slab The continuous casting and rolling process, taking advantage of its strong cooling capacity, can produce low-temperature coil-type hot-rolled dual-phase steels that cannot be produced by traditional hot-rolling processes (that is, economical hot-rolled dual-phase steels, without adding alloy elements, reducing However, in the actual production process, it was found that the dual-phase steel produced by this process has problems such as serious red oxide scale on the surface and unstable control of microstructure and properties.

After analysis, the main reasons are as follows: (1) Due to the consideration of the finishing rolling bite and the compactness of the process, it is impossible to apply large vertical roller scale breaking between the soaking furnace and the finishing mill on the thin slab continuous casting and rolling production line, Compared with the conventional hot rolling production line, there are fewer descaling passes, and there is only ordinary high-pressure water descaling before finishing rolling, so the problem of scale defects is more serious; (2) The content control of Si in the steel composition is in a dilemma: In the production of economical hot-rolled dual-phase steel, a high Si content control (above 0.6%) can increase the nucleation rate of ferrite, promote the enrichment of C, reduce the difficulty of controlled cooling process, and increase the control of microstructure and properties. Stability, but there is also the problem that due to the high content of Si, the iron oxide scale is prone to unclean removal. The reason is that when the Si content is high, the iron oxide scale is prone to cracks, and the temperature drop near the crack is faster, and the temperature is lower. The stripping property of the steel becomes poor, and it is difficult to remove; while the Si content is controlled at a low level (below 0.4%), although the problem of red oxide scale on the surface can be reduced to a certain extent, but it also brings about the low Si content, which reduces the ferrite. The nucleation rate is unfavorable to the enrichment of C, which increases the difficulty of the controlled cooling process, and the stability of the structure and properties of the steel cannot be effectively guaranteed in the actual production process; The difficulty of the cold process can also avoid the problem of poor peelability due to cracks on the surface of the iron oxide scale. However, when the Si content is within this range, ferrous silicate is easily produced between the steel matrix and the iron oxide scale. This kind of sticky substance is easy to pin the iron oxide scale on the steel substrate, resulting in a large area of ​​iron oxide scale that cannot be removed, so this range is usually not considered

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