Reduction in Energy Consumption During Hot Rolling by Roll Bite Lubrication at Hot Strip Mill, Bokaro Steel Plant

Abstract

During hot rolling, the work rolls are subjected to tough conditions due to the presence of heat, scale, cyclic load, shear stress, vibration, etc. Therefore the power consumption is very high during hot rolling. Under such conditions rolls get worn out rapidly through all major modes of wear, i.e. abrasion, adhesion and fatigue. Frictional conditions are more severe at initial stands where bar is given larger thickness reductions. Rolls are therefore changed regularly to maintain proper qualities of HR strips though at the cost of loss in production. In order to reduce the power consumption and roll wear, Roll bite lubrication (RBL) technology has been designed and installed in the initial finishing stands of hot strip mill of Bokaro Steel Plant. The RBL system consisted of oil flow circuit, water flow line, static oil-water mixer, dispersion spray headers, and automatic flow control device. Oil-in-water dispersion was sprayed over the backup rolls, which created a thin oil film on the work rolls for providing lubrication at the bite. A suitable hot rolling oil with good boundary and extreme pressure properties was used as a lubricant.Performance evaluation of RBL has revealed a reduction in the roll force and power consumptions by 5-10% in all grades/sizes of HR coils. The surface quality of rolls has visibly improved and reduction in grinding off-take has been achieved by 10-30%. It has also confirmed that the campaign length of rolling has been increased over 10%.