ACID CLEANING METHOD OF HIGH Si HIGH Mn-CONTAINING HOT ROLLED STEEL SHEET AND MANUFACTURING METHOD OF HIGH Si HIGH Mn-CONTAINING STEEL SHEET

摘要

To provide a high Si high Mn-containing hot rolled steel sheet capable of removing grain boundary oxide layer formed on a surface of a hot roll steel sheet with high efficiency.SOLUTION: An acid cleaning method of a high Si high Mn-containing hot rolled steel sheet includes a process for impregnating a hot rolled steel sheet by hot rolling steel containing, by mass%, Si:1.0% or more and Mn 1.5% or more, and winding the same at a temperature of 550°C or more into an acid cleaning liquid of 2 or more acid cleaning tank in order, in which concentration of copper ion contained in the acid cleaning liquid in one or more acid cleaning tank after second tank in an order of impregnation of the hot rolled steel sheet is 10 ppm or less. The method preferably includes a measurement process for measuring concentration of copper ion in the acid cleaning liquid held in one or more acid cleaning tank after the second tank in the order of impregnation of the hot rolled steel sheet and a process for controlling the concentration of the copper ion in the acid cleaning liquid held in the acid cleaning tank to 10 ppm or less based on the concentration of copper ion measured in the measurement process.SELECTED DRAWING: Figure 1