Method for reducing tertiary cementite precipitation amount of low-carbon cold heading steel wire rod

By adding Ti elements to low-carbon cold heading steel and combining it with specific rolling and cooling processes, the cracking problem caused by the precipitation of tertiary cementite in low-carbon cold heading steel wire rods with large deformation amounts is solved, achieving a balance between high plasticity and strength. It is suitable for cold forming production in the fields of handicrafts, automobiles, and new energy.

CN120666253APending Publication Date: 2025-09-19HUNAN VALIN XIANGTAN IRON & STEEL CO LTD
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Patent Information

Application Number
CN202510848149.3
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-06-24
Publication Date
2025-09-19

AI Technical Summary

Technical Problem

Existing low-carbon cold heading steel wire rods are prone to cracking when producing products with large deformation amounts. This is mainly due to the precipitation of a large amount of tertiary cementite at the grain boundaries and matrix, which leads to a decrease in plasticity and affects the cold forming processing performance.

Method used

By adding Ti element to low carbon cold heading steel and utilizing the affinity between Ti and C to form TiC, combined with two-phase rolling and controlled cooling process, the precipitation and distribution of free cementite at the ferrite grain boundary are reduced. The precipitation and organizational level of tertiary cementite are controlled through finishing mill rolling and Stelmor roller cooling.

Benefits of technology

The wire rod produced has hot-rolled tensile strength ≤350MPa, grain size ≥7.5, and tertiary cementite structure level ≤2.0, which improves the plasticity and cold forming properties of the material and is suitable for the production of products with large deformation.

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Abstract

The invention belongs to the technical field of low-carbon cold forging steel, and discloses a method for reducing the tertiary cementite precipitation amount of a low-carbon cold forging steel wire rod. The wire rod comprises the following chemical components in percentage by mass: 0.01%-0.04% of C, less than or equal to 0.10% of Si, 0.20%-0.30% of Mn, less than or equal to 0.010% of P, less than or equal to 0.008% of S, 0.020%-0.050% of Al, 0.02%-0.04% of Ti and the balance of Fe and inevitable impurities. The production process comprises the steps of continuous casting, heating, rolling, spinning and cooling. By controlling cooling and adding a proper amount of Ti element, the precipitation amount and grade of the tertiary cementite in a ferrite grain boundary are reduced, the tensile strength of the obtained wire rod in a hot rolling state is smaller than or equal to 350 MPa, the grain size is larger than or equal to 7.5 grade, and the structure grade of the tertiary cementite is smaller than or equal to 2.0 grade.
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