Manufacturing method for easily pickled steel with low yield ratio by thin slab casting and rolling

Abstract

The invention discloses a manufacturing method for easily pickled steel with a low yield ratio by thin slab casting and rolling. The method comprises the steps of molten iron desulfurizing, converter smelting, refining, thin slab continuous casting, slab soaking, hot continuous rolling, laminar cooling, coiling and air-cooling, wherein the slab soaking temperature is 1160 DEG C to 1200 DEG C; finish rolling is directly carried out for seven times in the hot continuous rolling process, and screw-down rate for the seven times is as follows in sequence: 50-60%, 50-60%, 52-58%, 45-50%, 20-25%, 13-18% and 9-13%; the final rolling temperature is 870 DEG C to 890 DEG C; the temperature after laminar cooling is 580 DEG C to 610 DEG C; and the components of the slag are as follows in percentages by weight: 0.045-0.065% of C, not more than 0.05% of Si, 0.40-0.60% of Mn, not more than 0.015% of P, not more than 0.010% of S, and the balance of iron and inevitable impurities. According to the manufacturing method disclosed by the invention, the yield ratio of the easily pickled steel is effectively reduced without the addition of extra noble alloy elements.

Description

technical field [0001] The invention belongs to the technical field of hot-rolled steel strip production, and specifically refers to a method for manufacturing thin slab continuous casting and rolling low-yield-strength-ratio easy pickling steel. Background technique [0002] The production of pickled steel by thin slab continuous casting and rolling technology can realize mass production of products with thickness specifications less than 1.6mm, which is conducive to the realization of "replacing cold with heat", which is an advantage that cannot be replaced by conventional hot rolling technology. However, due to the thin slab continuous casting and rolling process and the characteristics of microstructure evolution, such as hot rolling large reduction, laminar rapid cooling, and a large amount of dispersed precipitation of nitrides, oxides and sulfides, compared with conventional hot-rolled pickled steel , Thin slab continuous casting and rolling products have finer grains...

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Problems solved by technology

However, the above two methods do not need to add precious alloys or microalloying elements, which are improved compared with the previous methods, but the disadvantage is that in order to achieve a lower yield ratio (below 0.8), both preparation methods require Higher coiling target temperature (above 650°C), while the coiling temperature is too high, will increase the thickness of iron oxide scale to a certain extent, and significantly promote Fe 2 o 3 formation, due to the three possible structures of iron oxide scale (FeO, Fe 2 o 3 and Fe 3 o 4 ), Fe 2 o 3 The most difficult pickling, so Fe produced in large quantities after coiling at too high a temperature 2 o 3 Will significantly increase the difficulty of subsequent pickling of pickled steel

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