Surface treatment of steel sheet prior to heat treatment operations by passing it past an oxy-fuel burner and spraying with solid particles of carbon dioxide as a substitute to degreasing operations

摘要

Surface treatment of a steel sheet (1) prior to heat treatment by passing through a furnace incorporating preheating and heating zones, consists of first treating the sheet by passing it at a distance of between 2D and 6D from the flame of at least one oxy-fuel burner, where D is the diameter of the equivalent burner orifice. The sheet is then treated by spraying with carbon dioxide in the form of solid particles and/or snow, in a manner to remove a substantial part of the grease present on the surface of the sheet and which has been previously softened by the effect of the oxy-fuel burner. The term diameter (D) of the equivalent burner orifice has the following significance: (a) in the case of burners with coaxial injection of combustion agent and fuel, the diameter (D) is defined as being the largest diameter of the two injection conduits for combustion agent and fuel arranged coaxially; (b) in the case of burners with separate jets for combustion agent and fuel, this diameter is defined by the formula D = lorth + lpar/5, where lorth is the maximum distance between the orifices of the fuel and combustion agent jets according to a direction perpendicular to the surface of the sheet and lpar is the maximum distance between the fuel and combustion agent orifices in the direction parallel to the sheet.