Abstract: Disclosed is to an improvement apparatus of surface roughness of hot/cold rolled stainless steel coils and the method thereof. The present invention provides an improvement apparatus of surface roughness of hot/cold rolled stainless steel coils including a water spray unit for spraying water on a surface of a cast stainless steel slab; a cutting unit for cutting the stainless steel slab; and a high-pressure water spray having at least one nozzle in a region where the stainless steel slab is cut by the cutting unit and discharged and installed to be symmetric in upper and lower parts of the stainless steel slab; and a roller brush installed to be in contact with and symmetric in the upper and lower parts of the stainless steel slab passed through the water spray so as to rotate at a high speed.

Abstract: A converter includes a side wall, and a tapping hole placed at the side wall to allow passage of molten steel. A refractory plug is axially spaced apart from the tapping hole with a predetermined distance. The distance between the refractory plug and the tapping hole is in the range of 3-5 d where d indicates the inner diameter of the tapping hole. The refractory plug has one or more heat resisting steel tubes. When the molten steel is discharged through the tapping hole of the converter to the ladle, 0.1-0.4 Nm3/min of inert gas is introduced into the converter through the refractory plug to prevent leakage of the carried over slag.