Leaded Phosphor Bronze Alloys - Wrought Alloys (UNS C53400 to C54400)

Topics Covered

Introduction

Phosphor bronzes consist of 0.01 to 0.35% of phosphorous and 0.5 to 11% of tin. Stiffness and wear resistance of these alloys can be increased by the addition of phosphorous. Tin is added to these alloys to increase strength and corrosion resistance. The phosphor bronzes are designated as UNS C50100 to C54200. Leaded phosphor bronzes are designated as UNS C53400 to C54400.

Phosphor bronzes have high fatigue resistance, high corrosion resistance, excellent spring qualities, good solderability, and high formability. They are used in electrical products, diaphragms, spring washers, and corrosion resistant bellows. Leaded phosphor bronzes have high fatigue resistance, high strength, high wear resistance, good machinability, and high corrosion resistance. They find applications in thrust washers, sleeve bearings, and cam followers.

Effect of Alloying Additions

Alloying elements are added to the basic copper-zinc alloys in order to improve machinability, increase wear resistance, strength, and corrosion resistance. Lead is most commonly added to brasses in order to modify their properties. Alpha-beta brasses are added with about 3% of lead in order to give them free- machining properties. Lead does not form solid solution with zinc and copper, but it is present as a dispersed discontinuous phase, which is distributed all over the alloy. In the absence of beta phase, lead is not added to wrought alpha brasses as it results in cracking during hot working.

Composition

The composition of leaded phosphor bronze alloys is outlined in the following table.

¹Cu + sum of named elements, 99.5% min.
²Cu + sum of named elements, 99.8% min.
³Ni value includes Co.