The two dimensional numerical model is established with adding shrouding gas holes around traditional lance oxygen Laval tube for a 90 t LD injecting auxiliary oxygen to protect main oxygen jet and form coherent state

of traditional oxygen lance and coherent lance the oxygen jet velocity distribution at jet axis and the flow characteristics of liquid steel and impact depth in pool with different lance level are analyzed. Results show that as compared with traditional oxygen lance at same lance level the attenuation of jet of coherence oxygen lance is slower

the impact force is stronger and the depth of impact pit is deeper； with lance level 30De (De-diameter of oxygen lance outlet) the max impact depth of coherent lance is just the same that of traditional lance with lance level 20De and the average impact depth of coherent lance with lance level 40De is corresponding to that of traditional lance with lance level 20De.