Inclusion Control on Mechanical Performance Optimization in G17CrMoV5-10 Heat-Resistant Cast Steel Through AOD Refining and Deoxidation Strategies

Abstract High-temperature Cr–Mo–V cast steels are widely used in applications above 540 °C, where microstructural stability and mechanical performance are critical. This study investigates the influence of casting route and deoxidation practice on inclusion characteristics, microstructure, and mechanical behavior of G17CrMoV5-10 cast steel. Quantitative analysis revealed a significant reduction in inclusion areal fraction from 0.751 to 0.031% (~96%), accompanied by a transformation from irregular multiphase inclusions to spherical Ca–Al–O-based morphologies. In addition, pronounced grain refinement ( G = 11.65 → 14.54) and a more dispersed carbide distribution were observed, with carbide number density increasing from 745 to 1082 and average size decreasing from ~0.393 to ~0.240 µm 2 after AOD processing. These microstructural changes led to measurable improvements in mechanical properties. At room temperature, yield strength increased from 540 to 572 MPa and tensile strength from 661 to 684 MPa, while impact energy increased from ~87 J to ~125 J. At 550 °C, yield strength increased from 352 to 396 MPa and tensile strength from 394 to 442 MPa, while elongation decreased from 31.8 to 23.2%, indicating a strength–ductility trade-off. The results indicate that the observed improvements are governed by the combined effects of processing route, inclusion modification, grain refinement, and microstructural evolution, rather than a single dominant factor. This study provides a comprehensive quantitative evaluation of inclusion evolution, grain refinement, carbide distribution, and mechanical behavior at both room and elevated temperatures.