Improving the Mill Productivity through Technological Interventions at CRM of Rourkela Steel Plant

摘要

Cold Rolling Mill (CRM) complex of Rourkela Steel Plant (RSP) was set up in 1968. The CRM has two pickling lines which use sulphuric acid as pickling medium. Production level at pickling lines were significantly low as its speed was restricted to 60-70% of its rated value due to inferior quality of HR coil and improper bath conditions. Pickled coils produced at this line were also observed to have inferior surface quality. Cold rolling of these coils at the Tandem Mill with deficient roll cooling system was leading to higher occurrence of strip breakage and inferior shape of the coils. These problems resulted in lower productivity of the cold rolling mill. Various technological measures were taken both at the Pickling Line and at the Tandem Mill to improve their operating conditions. These measures include introduction of improved scale washing system at Pickling Line and heat exchanger in acid regeneration plant to improve pickling bath condition. To address these deficiencies of graphite block heat exchanger, new generation 'tantalum shell and tube heat exchanger' has been introduced in pickling lines. An automatic temperature control system was also designed and installed to control pickling bath temperature within ±2C of the desired bath temperature. Roll cooling system at Tandem Mill was modified to reduce thermal- crown of work rolls at the stands 4 and 5, which helped in improving shape of coils and reducing strip breakages. With these measures, productivity of the cold rolling mill through Pickling Line 2 - Tandem Mill route could be increased by 25-30%. There was also reduction in diversion on account of bad shape of CR coils by about 30%.