Hot-rolled steel sheet and molten galvanized steel sheet

TWI932212BActive Publication Date: 2026-07-11NIPPON STEEL CORPORATION
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Patent Information

Application Number
TW114116395
Authority / Receiving Office
TW · TW
Patent Type
Patents
Current Assignee / Owner
Priority Date
2024-04-30
Filing Date
2025-04-30
Publication Date
2026-07-11
Estimated Expiration
2045-04-29

AI Technical Summary

Technical Problem

Hot-rolled steel sheets with molten zinc coatings suffer from liquid metal embrittlement (LME) due to zinc penetration into grain boundaries during fusion, leading to cracking, and existing solutions like Zn-Al-Mg coated steel sheets may not provide sufficient resistance.

Method used

A hot-rolled steel sheet with a specific chemical composition (C: 0.030~0.110%, Si: 0.01~0.50%, Mn: 0.50~1.50%, P: <0.025%, S: <0.010%, Al: 0.010~0.070%, N: <0.0070%, Ti: 0.055~0.200%, Nb: 0.030~0.150%, B: 0.0010~0.0050%, V: 0~0.20%, Cr: 0~1.00%) and microstructure, featuring an area fraction of toughened granules over 85%, with residual vostanite grain boundaries having a length of 1.20 to 5.00 mm per 100 μm × 100 μm unit and B segregation degree of 40 or higher, enhances LME resistance.

Benefits of technology

The proposed steel sheet exhibits excellent resistance to LME, maintaining strength and workability while suppressing grain boundary cracking.

✦ Generated by Eureka AI based on patent content.

Smart Images

  • Figure IMG-2_DRAW_114116395-A0304-14-0001-1
    Figure IMG-2_DRAW_114116395-A0304-14-0001-1
  • Figure IMG-2_DRAW_114116395-A0304-14-0001-2
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  • Figure IMG-2_DRAW_114116395-A0304-14-0002-3
    Figure IMG-2_DRAW_114116395-A0304-14-0002-3
Patent Text Reader

Abstract

This invention provides hot-rolled steel sheets exhibiting excellent resistance to LME (Low Metal Effluent Metabolism). The hot-rolled steel sheets disclosed herein, by mass%, contain, but are not specified, the following components: C: 0.030–0.110%, Si: 0.01–0.50%, Mn: 0.50–1.50%, P: less than 0.025%, S: less than 0.010%, Al: 0.010–0.070%, N: less than 0.0070%, Ti: 0.055–0.070%. The composition is 0.200%, Nb: 0.030~0.150%, B: 0.0010~0.0050%, V: 0~0.20%, and Cr: 0~1.00%, with the remainder consisting of Fe and impurities. The area ratio of the toughened fertilizer particles is 85% or more. In the surface region from the surface of the hot-rolled steel plate to a depth of 0.2 mm in the plate thickness direction, the total length of the residual vostanite grain boundaries of BO2- is 1.20~5.00 mm per 100 μm × 100 μm unit, and the B segregation of the residual vostanite grain boundaries is 40 or more.
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