To make steel, Leggett & Platt combines 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, while 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.
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. 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.
Leggett & Platt controls every aspect of our innerspring-making process. It begins at Sterling Steel in Illinois, home to the largest electric furnace in North America. Each year we melt nearly a million tons of recycled scrap steel into billets. From there we make rod and draw it into wire at our own mills.
The wire used to produce Leggett & Platt innersprings is made using high-carbon steel, a designation that requires a ratio at least .04% carbon and 99.6% iron. As you can see, a little carbon goes a long way when it comes to creating steel.
We pull the steel rod through a series of steel-jacked, tungsten carbide wire-drawing dies. The first wire die is slightly smaller in diameter than the steel rod. Each subsequent die the wire is pulled through gets smaller and smaller, like nesting dolls, until finally we pull the wire through the die that creates its resting diameter. In addition to elongating and reducing the diameter, drawing the wire down creates a smooth, bright surface and increases wire's hardness, tensile strength, and elastic limit.
The steel wire used in Leggett & Platt's high-quality innersprings makes each coil sturdy and resilient, even after years of use.
Unlike imitators, our coils are tempered using heat or electricity so they bounce back to their original shape. After a coil is turned and shaped into its final form, tempering the spring realigns the molecular structure to ensure the coil won't sag or settle.
Depending on a person's weight, coils yield as weight is applied, creating an initial feeling of comfort with a feeling of support as the person's body rides down into the unit. Different body types require unique levels of firmness and support to get the sleep they need. Engineering a variety of firmness and support characteristics is a process that can be controlled with changes to wire tensile, gauge, coil turns, and coil connectors.
Innersprings support and conform to the contours of your body. Infinite pressure relief means your body will sag. When sinking occurs, your body loses proper spinal alignment, which can lead to muscles tensing and fighting for a stable position. Support is a critical factor in finding a relaxed position that leads to deep sleep.
Your mattress should feel the same way every day. It's well known in the mattress industry that cheap foams break down and lead to body impressions. Leggett & Platt innersprings are tested for durability because we want people to enjoy consistent sleep. Mattresses packed with low-density foam and other cheap materials often do not last. Leggett & Platt is tenacious with internal testing and has monitored the results of millions of units being sold and used in the real world. All that testing and caring about our quality means we can prove our products are durable and deliver great sleep, night after night.
Also, we've been roll-packing our products for years and have proven our innerspring's bounce-back characteristics. If you're building beds for shippable eCommerce programs, we have durable, comfortable components that are roll-pack-ready.