Abstract: A blast pipe for delivering refining oxygen to the space above a metal bath in a refining operation is presented. The blast pipe is positioned in a gas supply duct and is provided with a pressure regulating valve. The blast pipe comprises a fixed straight wall portion along which the gas flows in a linear path. The straight wall portion terminates at a sharp edge, constituting a portion of the blast pipe exit orifice. A bent wall segment is located adjacent to and downstream of the straight wall portion and connects the remainder of the straight wall portion to the exit orifice. The bent wall segment preferably has a convergent configuration, upstream of the sharp edge, and a divergent configuration downstream thereof. The exit orifice, in cross section, has the shape of a rectangle, one of the long sides of which constitutes the sharp edge.