Silicon Brasses

Overview

Silicon brasses are part of the subgroup of high strength brasses. These materials contain less than 20% zinc and less than 6% silicon. The silicon brasses are solid solution strengthened. These silicon brasses are typically chosen because of their high strength and moderately high corrosion resistance. The conductivity of the silicon brasses is much less than that of unalloyed copper. The silicon red brasses are used for valve stems where corrosion and high strength are critical. The wrought silicon red brasses are designated as UNS C69400 through C69710. Included in this category are the silicon red bronzes. These alloys are similar to the silicon red brasses except they contain very low concentrations of zinc. The silicon red bronze alloys are designated UNS C47000 through C66100. The cast silicon red brasses are C87300 to C87900. Silicon brass castings exhibit moderate strength and very good aqueous and atmospheric corrosion resistance. They are used in applications such as bearings, gears, and intricately shaped pump and valve components.

The silicon red brasses are single phase alloys. The zinc and silicon contents of the silicon brasses and bronzes are low enough that the alloying elements remain in solid solution. The microstructure of the cast material contains cored dendrites of alpha copper solid solution containing zinc and silicon. The coring occurs because the alloys solidify over a wide temperature range, which allows segregation of the alloying elements. The zinc and silicon composition varies form zero at the center of the dendrite to a maximum at the outer edge. The subsequent working and annealing breaks up the dendrites and results in a structure consisting of equiaxed, twinned grains of alpha solid solution. The microstructure of the wrought materials consists of equiaxed, twinned grains of alpha copper solid solution.

The microstructure of leaded silicon red brass is similar to the unleaded alloys with exception of lead particles distributed in the grain boundaries and inter dendritic areas. The lead solidifies as globules in the grain boundaries because it is practically insoluble in solid copper.

NOTE: The file size of the Larger and Largest View of the Micrographs are substantially larger than the thumbnail shown. The Larger View images range in size from 11K to 120K depending on the image. The Largest View images range in size from 125K to almost 500K.

Nominal Composition: Cu 80.0-83.0, Si 3.4-5.4, Zn 12.0-13.0, Fe 0.20, Pb 0.30 Larger View of Micrograph Largest View of Micrograph	Alloy Family:	Silicon brasses
	Product Form:	Wrought
	Processing:
	Etchant:
	Scale Line Length:	~ 50Microns
	Alloy:	C69400
	Temper:
	Material:	Silicon red brass
	Source:	University of Florida

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