Experiment shows cold rolling enhances tensile strength and toughness in high-nitrogen bearing steel, indicating intricate microstructure relationships.
Cold rolling as an essential processing step prior to heat treatment has been widely employed to achieve precision shape forming of bearings. Herein, the influence of cold rolling on the microstructure of the high‐nitrogen bearing steel X30CrMoN15 is systematically investigated and the effect of the microstructure on mechanical properties is quantified. Quantitative deconvolution of strengthening mechanisms reveals that dislocation strengthening dominates the yield strength enhancement (contributing 63.2% in CR40), supplemented by precipitation strengthening (23.4%) and grain boundary strengthening (18.7%). After cold rolling, specimens exhibit simultaneous increases in strength and toughness, with 30% reduction delivering optimal properties. Ultimate tensile strength increases from 2178 to 2280 MPa, while impact toughness rises from 9.1 to 11.9 J compared to undeformed specimens. Microstructural analysis confirms that dislocation–precipitation synergy governs strength enhancement, while balanced interactions between refined carbonitrides (0.57 μm), martensite refinement (0.60 μm), and retained austenite stabilization (10.37%) drive toughness improvement.
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Sun et al. (2025) studied this question.