Impact Pressure of Water in Hydraulic Descaling during Hot Strip Mill Rolling

Hydraulic descaling is commonly used to remove scale formed during reheating and continuous rolling of steel strips. On an experimental survey of parameters which affect the descaling behaviour, impact pressure was measured precisely both by spraying over a plasticine ( a modelling material) on the basis of design of experiments and by using a pressure converter. It was found that the impact pressure has good correlations with the water consumption V at a pressure of 9.8 MPa, water pressure P, rolling speed v and distance H between the material and the nozzle. The thickness loss Δt of plasticine and the impact pressure p by hydraulic descaling can be then expressed by the descaling parameters as follows; Δt = 2 000 PV/ ( vH2 ) ( cm, correlation coefficient : 0.94) p = 5.64 PV/H2(MPa) The impact pressure calculated from the equation is in excellent agreement with H. HOJAS' results. Since the impact pressure required to remove the primary scale is much higher than secondary scale, a careful set up of the conditions is essential to complete the descaling.