Chemistry key to optimizing use of turnings, borings in electric furnace charge

Feb 01, 2010 | 05:53 AM | Michael Marley

The use of turnings and borings varies from mill to mill, depending on the melter's experience and preference. But for all mills, chemistry is key.

Some mills might use only a small fraction in their melt, or they'll specify alloy-free turnings in the scrap purchased from outside suppliers. Still others have different ways of buying, storing and charging turnings and borings into their electric-arc furnaces.

There are two different types of briquetting. One is specifically for borings, while the other can be used for combinations of borings and turnings. Hot briquettes are made at Ferrous Processing & Trading Co.'s Zalev yard in Windsor, Ontario. Louis Padnos Iron & Steel Co. also makes both hot and cold briquettes at its facility in Holland, Mich. Many more scrapyards and industrial plants make the cold-pressed briquettes.

Some melters prefer the hot briquette over the colder puck because it has better physical properties, holds together much better and is a more robust product, travels better and doesn't disintegrate and fall apart as easily as the cold briquette. But many of the cold briquettes are made at steel mills and, thus, don't have far to go to the melt shop.

What they give up with the hot briquetting process is some part of the carbon, one scrap buyer said. It is oxidized in the process, so while loose borings typically have a 2- or 2.5-percent carbon content, hot briquettes of borings range from 1.9- to 2-percent carbon. "That's one of the key reasons we melt borings," he said. "We are after the carbon."....