Efficient long-service-life single-runner secondary combustion oxygen lance and using method

The invention discloses an efficient long-service-life single-runner secondary combustion oxygen lance which comprises a lance body and a lance head. The gun body comprises an outer pipe, a middle pipe and a central pipe, and the gun head comprises a gun head end part and a water diversion disc; a circle of main blowing holes and a circle of auxiliary blowing holes are uniformly formed in the end part of the gun head in the circumferential direction; the lowest points of the outlet outer edges of all the main blowing holes are located on the bottom edge of the main hole conical surface, the highest points of the outlet outer edges of all the auxiliary blowing holes are located on the top edge of the main hole conical surface, the lowest points of the outlet outer edges of all the auxiliary blowing holes are located on the bottom edge of the auxiliary hole conical surface, and the highest points of the outlet outer edges of all the auxiliary blowing holes are located on the top edge of the auxiliary hole conic