High strength thin steel sheet excelling in weldability and process for producing the same

Abstract

Provided are a high strength thin steel sheet having tensile strength of about 800 MPa or more, and a manufacturing method thereof. The thin steel sheet is mainly used for construction materials, home appliances, and automobiles. The thin steel sheet has excellent plating char not acteristic, welding characteristic, bending workability, and hole expansion ratio. The thin steel sheet includes, in weight %, C: 0.02-0.20%, Si: 1.5% or less, Mn: 1.5-3.0%, P: 0.001-0.10%, S: 0.010% or less, SoLAl: 0.01-0.40%, N: 0.020% or less, Cr: 0.3-1.5%, B: 0.0010-0.0060%, Sb: 0.001-0.10%, and including at least one material selected from the group consisting of Ti: 0.003-0.08%, Nb: 0.003-0.08%, and Mo: 0.003-0.08%, and includes Fe and other inevitable impurities as a remainder. Here, Si, Mn, B, Sb, P, and S meet conditions of 5 < (Si / Mn + 150B) / Sb < 20 and C + Mn / 20 + Si / 30 + 2P + 4S < 0.27. Also, the manufacturing method can secure workability of the thin steel sheet.

Description

technical field [0001] The present invention relates to a high-strength thin steel sheet having a tensile strength of about 800 MPa or more, which is mainly used for building materials, home appliances, and automobiles, and a manufacturing method thereof, and more particularly, to a steel sheet having excellent plating characteristics. , weldability, bending workability, hole expansion ratio (HER), and high tensile strength high-strength thin steel plate and a manufacturing method thereof. Background technique [0002] Recently, steel sheets for automobiles are required to have higher strength in order to improve fuel economy or durability. In consideration of collision safety and passenger protection, high-strength steel plates having a high strength of about 800 MPa are increasingly used for main structures or reinforcement materials of automobiles. However, since the formability and welding characteristics are lowered due to the high strength of the steel sheet, the deve...

AI Technical Summary

Problems solved by technology

In the case of manufacturing a steel sheet having a high strength of 800 MPa or more in an actual process, the cold rolling characteristics are significantly lowered due to the high strength of the hot strip as an intermediate material

In addition, since the heat treatment conditions of rapid cooling should be used in the annealing process, the workability is also significantly reduced

Japanese Patent Laid-Open No. 2005105367 does not fully consider these issues

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