Technical Pages - Iron & Steel

Calcium Treatment Of Liquid Steel To Facilitate Thin Slab Casting Process And Cleaner Flat Products.

Thin slab (50mm-70mm) casting technology was devloped by SMS, Germany and MDH, Germany during mid-eighties. NUCOR, USA established the first commercial scale Thin Slab Custer at their Crawfords Ville Plant in 1989, while Arvedi, Italy adopted MDH Thin Slab Technology in the early nineties.

Full scale PROCESS DEVELOPMENT and PRODUCT DEVELOPMENT efforts commenced at NUCOR alongwith technology experts from SMS, Germany. Considerable R & D contributions have evolved process standardization, and eventual commercial success which has led to the adoption of Thin Slab Casting (SMS - CSP) Technology by as many as 15 New Steelmakers all over the world. The growth pattern has been very impressive, thanks to the Intensive metallurgical development efforts for process development and product quality improvement through judicious application of CALCIUM TREATMENT TECHNOLOGY

Thin Slab Casting Process employs a specially designed sub-entry Nozzle (SEN) with varying cross-section - circular at the top, gradually flattening into a rectangular shape at the pouring end. The susceptibility to the alumina build up at the seat area and walls of SEN is extremely high and appropriate countermeasures are not taken, the SEN develops progressive wall blockage leading to serious clogging, and termination of casting process.

CALCIUM TREATMENT has provided the most effective COUNTERMEASURE. With appropriate sequential process steps at Ladle Refining Station / or after LF-VD treatment, the precision treatment with CA - Si or Ca-Fe or special purpose Ca based CORED WIRE provides the most stable and sustainable 'Chemistry' which, alongwith standard process control measures at the Caster, facilitates SMOOTHENING OF THIN SLAB CASTING PROCESS WITH CONSISTENT CASTING SPEED AND LEAST DISTURBANCE DUE TO INTERMITTENT / PARTIAL CLOGGING.

CALCIUM in liquid steel (Al-killed or Al-Si killed) provides "SACRIFICIAL" MARGIN TO RENET WITH ANY' 'Oxygen' due to 'ingress' or tundish slag contamination, and thus protects the ALUMINIUM level and prvents ALUMINA formation. Marginal generation of Ca-aluminates do not influence the casting process. The product 'Oxygen' level is thus maintained fairly low, resulting in much cleaner steel.

CALCIUM TREATMENT IS 'MANDATORY" FOR EXCELLENT CASTABILITY AND SUPERIOR PRODUCT QUALITY.