Abstract: A tuyere assembly is provided which is especially useful in pneumatic steelmaking processes employing submerged blowing. This improved tuyere provides oxidizing or other gases at supersonic velocities while concomitantly employing pressures only slightly above that of the metal bath. Such supersonic velocities are achieved by the insertion, into a conventional tuyere, of a generally pear-shaped, double-cone object so as to provide a limiting throat section followed by an expansion chamber which permits the gases to exceed sonic velocity. By achieving supersonic velocities without the use of high inlet pressures, (i) a material decrease in refractory wear is achieved and (ii) higher gas flow rates are permitted without the occurrence of "spitting".