EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

PERT has developed and patented a new concept for the composite rolls for long product rolling mills, called LLR Rolls (Long – Life Rolling Rolls). LLR Rolls, allows mounting of cast iron, HSS or carbide rings on a shaft made of special alloyed steel, in order to increase the grooves working life and to decrease, consequently, the plant downtimes for stands changing operations. The transmissible torque is also highly increased due to the use of steel ring-holder shaft making theoretically impossible the roll neck failures. The new and patented ring locking system is the main advantage introduced by LLR Rolls, as the using of traditional hydraulic locking system is avoided as well as the mechanical pins or keys. In fact, the torque is transmitted from the shaft to a special designed spacer and from the spacer directly to the rolling rings. A mechanical coupling between shaft and spacer and between spacer and rings is used, so the torque is transmitted not by friction, as per hydraulic locking system. Thanks to the above mentioned innovative locking system, rings changing operations are extremely easy and faster to perform, avoiding the use of any hydraulic or heating tool. In addition, the slipping of the ring is impossible also with high rolling loads, due to the mechanical coupling of the group shaft-spacer-rings. Avoiding the hydraulic locking system and practically avoiding a longer thread on the shaft (used to pre-load the shaft, permitting the torque transmission by friction), which occupies a lot of space, it is possible to utilize almost the full rolls barrel length, increasing the number of grooves, decreasing, in this way, the plant downtimes due to stands replacements. In addition, LLR Rolls doesn’t need a very high axial locking force, so the shaft damages are totally avoided. LLR Rolls consist of: - Heat treated ring – holder shaft, made of alloyed steel - Patented ring locking system and spacer - Rolling ring (cast iron or carbide) - Ring nut for axial clamping The main advantages introduced by using LLR Rolls, are : - Patented coupling between rings and shaft - Mechanical locking system instead of hydraulic system - Lower plant downtimes - Increased productivity of the rolling mill and excellent surface finishing of final products through precise dimension control during rolling - The shaft can be reused, only the worn ring must be replaced. - Improved quality and tolerances of the final products, thanks to the use of carbide rings - Reduced number of rings as a spare (compared with cast iron rolls) - Free from ring slippage even under high rolling torque - Simple assembling and disassembling operations for rings changing