Electromagnetic cold crucible continuous casting of CP-Ti ingots: surface quality, microstructure and mechanical properties

To achieve the efficient, continuous, and high-quality production of titanium alloy ingots, this study developed a novel electromagnetic cold crucible continuous casting (ECCCC) process suitable for the short-process production of titanium alloys. The effects of withdrawal rate on the evolution of thermal-solidification behavior, microstructure, defects, surface stability, and mechanical response were systematically elucidated through a combination of experiments and numerical simulations. With increasing withdrawal rate, the prior β grain size and the thickness of the precipitated α lamellae were refined by 79.6% and 48.3%, respectively, accompanied by a marked reduction in the anisotropy of the mechanical properties within the ingots. The highest elongation of 34.5% was obtained at 2.5 mm/min. The tensile strength reached a maximum of 341.5 MPa at 5 mm/min because of microstructural refinement. Meanwhile, the elongation anisotropy decreased from 41.8% to 5.8% as the withdrawal rate increased. In addition, although increasing the withdrawal rate improved production efficiency, it significantly reduced the internal densification of the ingots and markedly deteriorated the surface quality. Specifically, both porosity and average pore size increased substantially, the machining depth required for surface turning increased from 1.6 to 3.3 mm, and the ingot yield decreased from 95.5% to 90.8%. This work establishes a withdrawal-rate-dependent processing window for the ECCCC of commercially pure titanium (CP-Ti) ingots and provides guidance for balancing production efficiency, ingot quality, and mechanical performance in the continuous casting of reactive titanium materials.