Smelting and Refining of SPA-H steel

Smelting Process
The molten iron required for smelting SPA-H steel must undergo desulfurization pretreatment. Before entering the converter, the sulfur content of the molten iron is ≤0.010%, and the slag on the surface of the molten iron must be removed. Nickel plates, copper grains or nickel-copper alloys are fed into the converter along with scrap steel. The carbon content at the end of converter smelting is required to be ≤0.06% to prevent overoxidation of SPA-H molten steel. The tapping temperature is controlled at 1640-1660°C, and synthetic slag is first added to the ladle for baking before tapping. Slag stopper and slag ball double block method are used to stop slag and tap steel. During the tapping process, silicon calcium barium, aluminum manganese titanium, silicon manganese, ferrosilicon, medium carbon ferrochromium and ferrophosphorus are added for deoxidation alloying.

LF Refining
During the LF refining process for SPA-H steel, lime and fluorite are added to make slag, and compound deoxidizers, silicon carbide, etc. are used for diffusion deoxidation. The top slag must be white slag before leaving the station. After the composition and temperature of SPA-H molten steel are adjusted to a suitable range, feed the silicon-calcium wire before leaving the station. After feeding the wire, perform a soft argon blowing treatment for a period of time to uniform the temperature and composition of SPA-H molten steel, promote the floating of inclusions, and ensure the quality of SPA-H molten steel.