Abstract

Total Cost of Ownership (TCO) of converter refractories is a complex subject involving material selection, reline labour, fluxes mix, process control, maintenance and production planning. Analysis of the total cost of refractories per tonne of liquid steel provides complete view when combined with material performance appraisal. This work enhances TCO analysis by employing LaCam in wear rate measurement and material performance assessment.

Laser scans provide information on refractory wear while wear trend analysis enables identification of outliers, projection of life of refractory products, and adjustment of maintenance practice. Comparison of the wear trends complemented with relevant process parameters helps identify the best performing materials and design converter lining with uniform wear rate. Furthermore, LaCam makes possible calculation of life of each converter repair, allowing appraisal of different material types and applications. As a result, fast wearing areas can be eliminated and application of refractory repairs optimised, leading to significant savings. Campaign costs analysis combines information about refractories performance, and relevant process costs e.g. reline labour, fluxes mix, availability, maintenance; and aids optimisation of all refractories related costs. Short term, the TCO model throws more light on the total cost of refractories per tonne of liquid steel, and indicates the optimum lining service life. Long term, the analysis can be used to define the cheapest converter refractories strategy including lining life requirement, use of slag splashing, selection of fluxes or application of repair materials.

Application of the TCO analysis resulted in a number of improvements at Tata Steel in Port Talbot. Cold iron was identified as the type of scrap causing heavy wear in the impact pad area, and its charge was reduced accordingly. The lining design was improved by installing pitch bonded materials from one supplier in the bottom, and resin bonded materials from another supplier in the barrel and upper cone. Selection of repairs giving the highest value in use was possible thanks to direct comparison of self-flowing and gunning materials. Finally, the lining life expectation was aligned with appropriate costs leading to application of the refractory technology at the lowest cost possible.

The TCO approach linked the converter refractories interdependent costs – initial costs (reline labour, safety lining, working lining), process costs (scrap composition, fluxes, yield, reheating), maintenance costs (slag conditioning, slag splashing, refractory repairs) – and helped design optimum converter lining strategy.