In situ boring
The Metalock Engineering Group was selected to carry out boring work by VAI Cosim following good reports on earlier work from their French sister company VAI Clecimand the VAI Group itself. Aceralia, which produces over a million tonnes of steel product annually, needed to get the machining work done as quickly as possible so that the new load cells could be fitted and the mill returned to operation with minimum downtime. Using four boring machines, Metalock was able to complete the machining task in 9 days, working 24 hours a day with a 14-man team. In all over 11 tonnes of metal was removed.
The actual work involved enlarging the eight bores on the four Blaw-Knox mill housings to accept the new capsules from 711.5 mm to 950 mm diameter to a depth of 565 mm from the previous 558 mm finishing with a 50mm radius at the end of each bore. Special single-point turning devices were manufactured to generate the radius and produce the required surface finish.
The tandem mill at Aceralia can be used as an intermediate mill or a finishing mill depending upon production schedules. As an intermediate it would reduce slabs down prior to tempering. As a finishing mill strip product passes through to a tinning line and be capable of producing strip up to 1524 mm wide good quality control and thickness tolerance over the full width is essential. The new screwdown system is enabling these parameters to be more constantly achieved than previously. As screwdown pressure has now been increased with the new equipment Aceralia are planning to produce harder steels on this mill in due course.