Industrial Trials on the Cleanliness Improvement, Microstructure Refinement and Performance Enhancement of Rare‐Earth‐Treated 75Cr1 Steel

Abstract

The effects of rare‐earth treatment on cleanliness, corrosion resistance, microstructure, and mechanical properties of 75Cr1 steel are investigated by industrial trial. In the results, it is shown that the appropriate La–Ce addition can effectively remove oxygen and sulfur elements in steel, and total oxygen (T.O) and S contents decrease by 45% and 33%, respectively. After La–Ce treatment, the typical inclusions in steel are transformed from (Mg–Al–O)–CaS composite inclusions to RExSy–CaS inclusion with a small amount of Al2O3. The number and average size of inclusions in steel are significantly reduced, and the morphology of inclusions changes from irregular shape to spherical shape, which contributes to the improvement of the corrosion resistance of 75Cr1 steel. Furthermore, the pearlite spacing and the grain size are refined, the tensile and yield strengths are significantly enhanced in the test of La–Ce‐treated steel. The 75Cr1 steels are fabricated in small batches, which avoids the nozzle clogging resulted by rare‐earth treatment during continuous casting. It implies that rare‐earth treatment to improve the quality of 75Cr1 steel shows the strong industrial applicability.