Cold-rolled steel sheet, pressed parts, and method for manufacturing the same

The cold-rolled steel sheet with optimized chemical composition and manufacturing process addresses high spheroidization and hardenability challenges, achieving efficient and cost-effective production for complex pressing applications.

JP2026510409APending Publication Date: 2026-04-02BAOSHAN IRON & STEEL CO LTD
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Patent Information

Authority / Receiving Office
JP · JP
Patent Type
Applications
Current Assignee / Owner
Filing Date
2024-03-28
Publication Date
2026-04-02

AI Technical Summary

Technical Problem

Existing steel materials for automobile parts face challenges in achieving high spheroidization rates, poor plasticity, and insufficient hardenability, leading to increased production costs and complex pressing requirements.

Method used

A cold-rolled steel sheet with specific chemical compositions and a manufacturing process that includes controlled hot rolling, bell annealing, and temper rolling, resulting in a microstructure with uniformly distributed spherical cementite particles and a spheroidization rate of ≥90%, allowing for excellent plasticity and low strength, and enabling martensitic structure formation at lower cooling rates.

Benefits of technology

The solution achieves a high spheroidization rate, excellent plasticity, and low strength, reducing production costs while meeting complex pressing requirements and enabling efficient heat treatment with improved hardenability.

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Abstract

The present invention discloses a cold-rolled steel sheet, which contains Fe and inevitable impurities, and further contains the following chemical elements in the following mass percentages, namely, C: 0.06 to 0.10 wt%, Si: 0.01 to 0.5 wt%, Mn: 1.6 to 2.5 wt%, Al: 0.01 to 0.07 wt%, Cr: 0.5 to 1.0 wt%, Mo: 0.1 to 0.3 wt%, Ti: 0.01 to 0.05 wt%, Nb: 0.001 to 0.03 wt%, B: 0.0001 to 0.005 wt%, 0 < N ≤ 0.006 wt%. The microstructure of the cold-rolled steel sheet is such that spherical cementite particles are uniformly distributed in a single-phase ferrite matrix, among which the spheroidization rate of the spherical cementite is ≥ 90%. Correspondingly, the present invention further discloses a manufacturing method of the cold-rolled steel sheet and a pressed part manufactured from the cold-rolled steel sheet.
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