Wire rod
A wire rod with controlled chemical composition and microstructure achieves high strength and ductility through single annealing, addressing deformation resistance and mold wear issues while reducing costs and emissions.
WO2026154661A1PCT designated stage Publication Date: 2026-07-23NIPPON STEEL CORPORATION
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Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NIPPON STEEL CORPORATION
- Filing Date
- 2025-01-17
- Publication Date
- 2026-07-23
AI Technical Summary
Technical Problem
Wire rods made of low alloy steel containing Mn and Cr have high deformation resistance and low ductility, leading to mold wear and processing cracks during cold forging, and multiple annealing cycles increase manufacturing costs and CO2 emissions.
Method used
A wire rod with a specific chemical composition and microstructure, including bainite and martensite, is subjected to a single annealing cycle at controlled temperatures and drawing processes to achieve high strength and ductility, reducing deformation resistance and manufacturing costs.
Benefits of technology
The solution provides a wire rod with equivalent strength and workability to double annealing cycles, improving cold forgeability and reducing manufacturing costs and emissions.
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Abstract
This wire rod has a chemical composition consisting of 0.10-0.60% of C, 0.01-0.45% of Si, 0.30-1.00% of Mn, 0.030% or less of P, 0.001-0.050% of S, 0.001-0.080% of Al, 0.85-1.50% of Cr, 0.0010-0.0200% of N, 0.004% or less of O, and the balance made up of Fe and impurities. When D is the diameter of the wire rod, the metal structure of a part at 1 / 4 D contains bainite in an area ratio of 96% or more. In cases where the area ratio of bainite is less than 100%, the balance is made up of martensite. The wire rod has a half-value width of the diffraction peak of the (211) plane of 2.20° or more and a reduction of area of 30.0% or more when an X-ray diffraction pattern is measured by Cr-Kα rays using an X-ray stress diffraction device with respect to a part at 1 / 4 D in a cross-section in the length direction.
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