Linde oxyfuel remelting technology speeds shift to automotive aluminum

With the demand for automotive aluminum accelerating in the U.S., Linde LLC is focusing its global expertise in oxyfuel technology on improving both the casthouse processing and heat treating of aluminum and aluminum alloy products.

At the Aluminum Show 2015 in Detroit, November 11 and 12, Linde will introduce advanced Linde Low-Temperature Oxyfuel (LTOF) technology for remelting aluminum, and highlight research into the Linde Direct Flame Impingement (DFI) process which uses oxyfuel to assist in the heat treating of aluminum sheet.

Secondary aluminum processors serving the automotive industry can quickly improve productivity with Linde LTOF technology, which can be installed or retrofitted to virtually any aluminum remelt operation to improve fuel efficiency, boost melting rates, and reduce the generation of nitrous oxides (NOx) associated with air-fuel combustion.

"We developed Low-Temperature Oxyfuel technology to meet the challenge of maintaining or increasing remelting rates with high levels of solid charge materials, typical of secondary aluminum operations in the U.S," said Tony Palermo, Program Manager, Metallurgy, Linde LLC

For continuous annealing and solution heat treatment of aluminum sheet, Linde REBOX® DFI technology, now in commercial development, retrofits to the annealing section of the line and could significantly boost throughput rates for the annealing furnace. Linde presented results of DFI heating conducted at its European test laboratory at TMS 2015 in March.

Aluminum sheet annealing

Linde has been developing REBOX DFI technology for continuous annealing of aluminum sheet for several years. Because of aluminum's low melting point and the restricted range for various types of heat treatments, temperature control is critical to sheet property and surface quality.

With Linde DFI technology, oxyfuel flames directly heat the metal strip. The process can achieve heat transfer rates up to 10 times higher than those for conventional fuel-fired furnaces. The Linde REBOX DFI technology has been boosting productivity of continuous steel hot-dip galvanizing and stainless steel annealing lines for nearly 10 years and millions of tons, with capacity increases in excess of 25 percent.

Boosting secondary aluminum

Characterized by lower flame temperatures, Linde LTOF technology enables more uniform heating than other combustion techniques, as well as the increased radiative heat transfer efficiency typical of oxyfuel combustion. Uniform heating also reduces incidences of localized overheating, which has been associated with yield loss.

"Recycled aluminum feedstock will be increasingly critical to meet demand, so this is a win-win-win for auto companies, aluminum companies, and the environment," Palermo said.