LEADED STEELA free-machining steel containing about 0.25% lead. Lead does not alloy with iron, but when a stream of finely divided lead is shot at the stream of molten steel to the ingot mold, the lead is distributed in the steel in tiny particles. The lead eases machining without imparting to the steel the unfavorable characteristics given by sulfur or phosphorus. There is little weakening of the physical properties of the steel. The lead forms a layer of liquid lubricant at the chip-tool interface, thus reducing the stress required to overcome friction. Also, by slightly embrittling the steel, lead reduces the deformation stress and serves to initiate microcracks to produce small chips. Ledloy, of Inland Steel Co., contains 0.15 to 0.30% lead in the regular SAE grades of steel. La-Led steel of LaSalle Steel Co. is a low-carbon leaded free-machining steel marketed in cold-finished rounds. Super La-Led steel contains 0.25% lead with up to 0.50 sulfur. Rycut 40 steel, of Joseph T. Ryerson & Son, Inc., is a chromium steel-molybdenum containing 0.15 to 0.35% lead. It can be machined 50% faster than unleaded steel of the same composition. The tensile strength is 129,000 to 200,000 lb/in2 (889 to 1,379 MPa) with elongation of 12 to 21%, depending on the tempering. Ledloy 170, of the same company, is leaded, cold-drawn, seamless tubing. It is a 1015 analysis steel with 0.15 to 0.35% of lead added.
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