Big Machine Makes Big Debut for Large BloomsDec 22, 2014
TimkenSteel is embracing its status as a standalone organization: In October, just four months since its spin-off from the century-old bearings and specialty steel group, the steelmaker’s Faircrest Plant in Canton, OH, launched production of continuous cast jumbo blooms on its new vertical caster — the largest continuous bloom caster in the world. The first product deliveries were made in early November.
The $200-million project was announced by Timken Co. in 2012, part of a more detailed program, now complete, that increased throughput and finished qualities for the larger-dimension products supplied by TimkenSteel, including forging billets.
“It complements our large-bar strategy,” Faircrest steelmaking manager Jim Sanders explained during a tour of the caster complex. “The caster itself gives us a lot of production efficiency, which we needed for our larger-section sizes.”
The large dimensional capabilities are what makes the caster unique, Sanders emphasized, and it influences every aspect of the design, from its physical presence to the technological “bells and whistles that ensure high-quality steel.”
The three-strand machine designed and built by SMS Concast AG rises 270 ft from below ground to a casting deck five stories above, where 175-ton ladles arrive from the adjacent electric melt shop to start the process of pouring 2,900°F molten steel.
A rotating turret positions the ladle above the tundish (i.e., the vessel that holds the steel above the threes casting nozzles, reducing turbulence as casting commences into the strands.) SMS incorporated hydraulic oscillation to manage flow; electromagnetic stirring in the mold and in the strand below the mold (F-EMS); as well as “dynamic soft reduction,” the model-based control package that ensures effective management of solidification once the steel enters the molds, including the center porosity and central segregation of defects.
A top-fed dummy bar system is used to start and stop casting; pinch roll units in the strand manage bloom shape control during the descent; strand containment and strand guiding technology help to propel the product, and secondary cooling and in-line quenching of the blooms promote solidification.
Each ladle is poured out in about 70 minutes, according to the steelmaker, though casting speeds vary among the roughly 300 different grades TimkenSteel produces, as well as the 18×24-in. or 11×17-in. bloom dimensions.
The caster has no bending function in the run-out section, in respect to the sizes, dimensions, and metallurgical qualities of the products TimkenSteel supplies. Instead of bending, the blooms descend the five stories, 90 feet below ground, at which point the products are cut to length and shifted to a hydraulic transfer table that levels them from a vertical to a horizontal plane, at the same time raising them back to grade. Next, overhead cranes transfer the still hot and still solidifying ingots to a cooling bed.
The three-strand caster is designed with an option to add a fourth strand, but TimkenSteel’s initial goal is to process 60% of its EAF output through the caster by the end of 2015. The steelmaker continues to offer bottom-poured ingots for customers whose products require that solidification quality.
Both ingots and blooms are quenched and processed further, including shaping and densifying products prior to rolling in the in-line forge press started up last year. That system — the only one of its kind in North America — enhances the center “soundness” of large bars that are integral to TimkenSteel’s production strategy.