Spheroidizing annealing is a critical heat treatment process for high-carbon steels to balance hardness and machinability. This study develops a rapid spheroidizing annealing process by employing low-temperature pretreatment followed by subcritical heating. The key is to utilize carbide precipitates from non-equilibrium phases (e.g., martensite/lower bainite) as nucleation sites, thereby accelerating spheroidization. At an optimized pretreatment temperature of 400 °C, the process achieves a homogeneous spheroidized microstructure with a hardness of 206.7 HV, comparable to that obtained via conventional prolonged annealing. This method significantly reduces processing time and energy consumption.

In this paper, high-silicon K52 and API X52 were studied comparatively, which were with similar yield strength. The results showed that K52 with high-silicon and low-manganese asked for higher tensile strength, lower yield ratio and higher impact energy than API X52. K52 was successfully producted with more content of Nb, V, Ti and so on, which is with high tensile strength, low yield ratio and high impact energy. The oxide scale of K52 was more thichness because of the high-silic. The thickness of oxide scale could be reduced by the lower tapping temperature during hot rolling. The inclusion of silicon oxide was bad fot the toughness of welding line, which was forming during the welding process.The squeeze amount should be increased to improve the impact energy of welds.