Lead Alloy

any of the alloys for which lead is the base metal. Lead alloys are divided into two main groups, depending on whether the percentage of the alloying element is low or high. The low-percentage group includes alloys made with additions of Fe, Cu, Sb, Sn, Cd, or Ca in concentrations that do not reduce, and that in certain cases increase, the corrosion resistance of lead and that substantially increase lead’s creep strength and long-term strength. The high-percentage group comprises lead alloys containing appreciable amounts of elements that increase the strength, hardness, and antifriction properties of lead and that lower the melting point of lead and reduce shrinkage during casting. Like lead, most lead alloys, with the exception of those containing more than 0.1 percent Ca, Mg, Li, K, or Na, exhibit a high corrosion resistance upon exposure to air and water and to most dilute inorganic acids at room temperature and low temperatures. Lead alloys are stable in concentrated acetic, chloroacetic, and citric acids. The stability in organic acids decreases in the presence of oxygen. Chlorine (up to 100°C), hydrogen sulfide, and sulfurous gas have a negligible effect on lead alloys. Lead alloys having a low percentage of alloying element are highly stable in soils containing salts of silicic, carbonic, and sulfuric acids.

Of all the elements used in lead alloys, only Ca and Te impart added strength under plastic deformation. Because of a low re-crystallization temperature, lead, when alloyed with other elements, softens immediately during rolling, extrusion, drawing, and other types of processing carried out at room temperature. Additives substantially increase the creep strength, long-term strength, recrystallization temperature, and stability of lead in sulfuric acid. With the addition of 0.05 percent Te, losses in lead from the action of sulfuric acid are reduced by a factor of 10.

Lead alloys with Te (0.03–0.06 percent), Cu (0.04–0.08 percent), and Sb (0.5–2.0 percent) are used in the manufacture of sheet material, pipes, and other semifinished products. They are also used as lining for vats and other types of acid-resistant apparatus and for pipes. Lead alloyed with Te (0.04–0.06 percent), Ca (0.03–0.07 percent), Sn (1.0–2.0 percent), and Sb (0.4–0.8 percent) is used as sheathing for low-voltage and power cables. Fusible lead alloys are generally binary, ternary, or more complex eutectics of lead with In, Sn, Bi, Sb, Cd, and Hg. The Pb-Sn, Pb-Ag, and Pb-Sn-Sb systems provide a series of soft solders (melting points 185°-305°C), which are characterized by good adhesion to many metals and alloys and high corrosion resistance. Lead tinning—lead alloyed with 0.5–1 percent Zn or Sn—is used to protect iron alloys from corrosion. It is also used in bearings before babbiting. Ternary lead alloys with Sb (8–23 percent) and Sn (2–7 percent) are used in printing. Bearing lead alloys from the Pb-Sb-Sn, Pb-Sb-Sn-Cu, and Pb-Ca-Na systems have a variety of uses. Owing to their high density and good casting properties, lead alloys containing 0.1–1.5 percent Sb, 0.06–0.2 percent As, and 0.02–0.04 percent Na are used for casting shot, and alloys with 0.3–3 percent Sb are used for casting bullet cores. Plates for lead storage batteries are made from lead alloys containing 6–9 percent Sb.