Method for smelting steel for oil and gas well expansion pipe

The invention discloses a method for smelting steel for an oil and gas well expansion pipe, and belongs to the technical field of smelting and continuous casting control. The method comprises the following steps: molten iron is subjected to KR desulfurization, the desulphurized molten iron is deslagged sufficiently, the deslagged molten iron is subjected to dephosphorization and desilicication in a dephosphorization converter, slag blocking is carried out to obtain desulphurized, dephosphorized and desiliconized molten iron, the desulphurized, and dephosphorized and desiliconized molten iron is subjected to decarbonization smelting in a converter, wherein slag blocking is carried out before and after a tapping process, and premelted slag is added into a steel ladle in the tapping process for tapping desulphurization; RH vacuum refining is conducted on the obtained molten iron, so that the dehydrogenation, inclusion removal and micro calcium treatment is completed; and low-degree-of-superheat fully protective