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How Leggett & Platt makes steel

6/19/2018

Forming steel and wire into the most widely used sleep support system on the planet is a delicate process. You need wire that is tough. Toughness, as our metallurgist once said, is a combination of being strong and malleable.


Wire must feed through a machine and bend, not break. 

 

To make steel, Leggett & Platt begins by combining 98 parts iron and less than two parts carbon. Our team refines recipes that produce tough, formable wire. A strong and malleable piece of wire will feed through our world-class innerspring-making machines, retaining its durability.

 

Steel comes from iron ore and recycled scrap. Iron ore is mined, crushed, concentrated, made into pig iron, and then impurities are removed. Leggett & Platt’s recycled scrap, which is mainly comprised of automobiles, is separated, sized, mixed together, melted, and then refined.

 

To make steel, our metallurgists formulate a recipe and then add 95% recycled scrap steel to the largest electric furnace in North America. That steel recipe determines how the end product will turn out. We melt the scrap using an electrical arc created by passing a current through solid carbon electrodes. The material liquefies, then a technician checks its initial chemical composition and makes coarse adjustments.

 

Next, the molten steel is transferred into a ladle and then to a ladle-refining furnace where the temperature and chemicals are adjusted. Once those adjustments are made, we transfer the molten steel to the caster, where it’s poured into water-jacketed molds and allowed to solidify into squares about the size of a large man’s fist.

 

Each of these squares, called billets, is about the same length as a Tyrannosaurus Rex. Once poured, billets are cooled for handling and transferred to the rolling mill. At the rolling mills, the billets are reheated, then pass through 27 sets of rolls to reduce the size, creating rod as small as 7/32 of an inch.

 

Once rod is formed, it is sent to Leggett & Platt’s wire mill where it is drawn to the needed gauge and then used for making innersprings.

See related articles: innersprings, manufacturing

Mark Kinsley

Mark Kinsley is Leggett & Platt's Staff Vice President of Marketing for the Bedding Group. Outside the office he enjoys spending time with family, mountain biking, hiking, and snow skiing. Connect with Mark on Twitter via @markkinsley.