A thin-gauge martensitic steel strip and its manufacturing method

Abstract

A thin-gauge martensitic steel strip and its manufacturing method, the composition weight percent of which is: C: 0.16‑0.26%, Si: 0.1‑0.5%, Mn: 0.4‑1.7%, P≤0.02%, S≤0.007% , N: 0.004‑0.010%, Als: <0.001%, total oxygen [O] T : 0.007‑0.020%; the balance is Fe and other unavoidable impurities, and at the same time: containing one or both of Cu: 0.1‑0.6% or Sn: 0.005‑0.04%; containing Nb: 0.01‑0.08%, Mo: one or two of 0.1‑0.4%; Mn / S>250. The invention utilizes residual Sn, Cu and other elements in scrap steel to smelt molten steel, and selectively adds microalloying elements such as Nb / Mo to the steel; during the smelting process, the alkalinity of slag, the type of inclusions in steel and the melting point are controlled , free oxygen content in molten steel, and acid-soluble aluminum Als content; then twin-roll thin strip continuous casting is performed to cast the cast strip, which is obtained by online hot rolling and rapid cooling by gas atomization.

Description

technical field [0001] The invention belongs to a continuous casting process, in particular to a thin-gauge martensitic steel strip and a manufacturing method thereof. Background technique [0002] In the traditional steel production process, tin (Sn) and copper (Cu) are typical residual elements or harmful elements in steel. It is very difficult and expensive to fully remove Sn and Cu during the steelmaking process. Once the steel contains Sn , Cu, basically can not be completely eliminated, only by diluting molten steel to reduce the content of Sn, Cu, which all lead to the increase of the smelting cost of iron and steel products. [0003] In recent years, due to the continuous recycling of scrap steel, there are more and more scrap steel resources, and electricity prices have continued to decrease. Sn and Cu in steel are easy-to-segregate elements, which are easily enriched at the grain boundary to cause defects such as cracks. Therefore, the content of Sn and Cu element...

AI Technical Summary

Problems solved by technology

At the same time, the contact of high-temperature strip steel with cooling water will cause many problems: first, water spots (rust spots) will be formed on the surface of the strip steel, which will affect the surface quality; second, the cooling water used for laminar flow cooling or spray cooling It is easy to cause uneven local cooling on the surface of the strip, resulting in uneven microstructure inside the strip, resulting in uneven properties of the strip and affecting product quality; third, uneven local cooling on the surface of the strip will cause deterioration of the shape of the strip , affecting the shape quality

[0014] However, due to the rapid solidification process characteristics of thin strip continuous casting, the produced steel generally has the problems of uneven structure, low elongation, high yield ratio, and poor formability; The grains have obvious inhomogeneity, which will lead to the inhomogeneous structure of the final product obtained after austenite transformation, resulting in unstable performance of the product

Therefore, it is difficult and challenging to use a thin strip continuous casting production line to produce some high-strength products required by the automotive industry and the petrochemical industry. Therefore, when using thin strip continuous casting to produce high-strength martensitic steel, the traditional composition should be copied Craftsmanship cannot be produced and requires a breakthrough in composition and craftsmanship

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