Martensitic steel strip and manufacturing method thereof

Abstract

The invention discloses a martensitic steel strip and a manufacturing method thereof. The martensitic steel strip is prepared from the components in percentage by weight: 0.16-0.26% of C, 0.1-0.5% ofSi, 0.4-1.7% of Mn, less than or equal to 0.02% of P, less than or equal to 0.007% of S, 0.004-0.010% of N, less than 0.001% of Als, 0.001-0.006% of B, 0.007-0.020% of total oxygen [O]< T>, and the balance of Fe and inevitable impurities; the conditions that Mn/S is greater than 250, and one or two of 0.01-0.08% of Nb or 0.1-0.4% of Mo are included need to be met at the same time. Nb, Mo and B elements are selectively added; the alkalinity of slag, the type and melting point of inclusions in steel, the content of free oxygen in molten steel and the content of acid-soluble aluminum Als are controlled in the smelting process. According to the martensitic steel strip and the manufacturing method thereof, the yield strength of the martensitic steel strip is 700-1200 MPa, tensile strength is 1000-1800 MPa, elongation is 3-12%, the martensitic steel strip can be widely applied to the field of high-strength automobile steel, and a wide space is provided for the automobile industry in the aspects of light weight, energy consumption reduction and fuel economy improvement.

Description

technical field [0001] The invention belongs to the continuous casting process, in particular to a martensitic steel strip and a manufacturing method thereof. Background technique [0002] Most of the traditional thin strip steel is produced by multi-pass continuous rolling of the slab with a thickness of 70-200mm. The traditional hot rolling process is: continuous casting + slab reheating and heat preservation + rough rolling + finishing rolling + cooling + Coiling, that is, firstly obtain a cast slab with a thickness of about 200mm through continuous casting, reheat the cast slab and keep it warm, then perform rough rolling and finish rolling to obtain a steel strip with a thickness generally greater than 2mm, and finally process the steel strip Laminar cooling and coiling complete the whole hot rolling production process. If it is necessary to produce a steel strip with a thickness of less than 1.5mm (inclusive), it is relatively difficult, and it is usually completed by...

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

[0011] 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

Images