Stainless steel lines, North American Stainless (USA)

U.S. company North American Stainless (NAS), a subsidiary of the Spanish Acerinox Group has erected a modern, high-performance production facility for bright-annealed stainless steel strip in Ghent, Kentucky. It produces up to 95,000 tons per year. SMS group supplied a 20-roll cold rolling mill and a bright annealing line.

The bright annealing line is the country's highest-performance plant of its kind. Here is how it operates: First in line is a two-stage cleaning section designed to clean rolling oil and other contaminants from the cold rolled strip. Next up is recrystallization annealing in an oxygen-free, inert atmosphere with a high hydrogen content. This will create a high-grade, reflective strip surface. Also integrated in the line is a four-high skin pass mill for post-treatment. It will not only improve the strip surface and flatness, but also the metallurgical properties thanks to low-strain hardening. Downstream of this unit, a tension leveler will perfect the strip flatness. Yet this plant is not restricted to tension leveling. It also functions as a pure stretcher for thin-gage strip. Trimming on both sides completes the process.

The technological highlight of the bright annealing line is the fully electric vertical furnace from Drever. It achieves extreme operating efficiency, consuming just 220 kilowatt hours per ton. That is 60 percent lower than conventional designs with a muffle furnace. Our customer will also benefit from the shorter heating section and 50 percent lower bay height. Responsible for the high efficiency is direct heating with electrical heating elements, plus dynamic annealing at up to 1,250°C. The annealing process takes place in a pressurized inert atmosphere (up to 90 percent hydrogen). This attains a low dew point and produces an immaculately reflective surface. NAS will achieve flawless surfaces with our special strip stabilization system that ensures contactless positioning of the strip. To boost production and reduce resource consumption, a mathematical model will automatically adjust all process parameters.