Leaded Tin Bronze Cast Alloys – Copper Tin Lead Alloys (UNS C90200 to C91700) Compositions

Sep 20 2012

Topics Covered

Introduction
Composition

Introduction

Tin bronzes or copper tin alloys are well known for their corrosion resistance property. UNS C90200 to C91700 are designations allotted to cast tin bronzes.

Tin bronzes are more ductile and stronger than semi red and red brasses. They have low friction and high wear resistance when placed against steel. The structure of alpha copper is retained by tin bronzes containing 15.8% of tin.

Tin is considered as a solid solution strengthener in copper despite its low solubility in copper under room temperature. These copper tin alloys are hence regarded as single phase alloys due to slow transformations or absence of transformations under the room temperature.

Lead plays a significant role in tin bronzes as it helps in improving pressure tightness and machinability and also decreases ductility and tensile strength of the tin bronzes. A balance in strength and machinability of the tin bronzes can be obtained by adjusting the composition in the tin bronzes. Tin bronzes that are high leaded comprise a slow fail mechanism that prevents seizing and galling on a temporary basis. During the operation of this mechanism lead leaks out of the alloy and gets smeared over the journal’s surface.

UNS C92200-C94500 are designations allotted to the cast leaded tin bronzes. The cast tin bronzes have a microstructure provided with cored dendrites. These dendrites are capable of increasing tin because of their composition gradient.

The nonleaded materials along with lead particles in the inter-dendritic boundaries have a microstructure that is similar to that of the leaded tin bronzes. The lead solidifies as pure lead in the grain boundaries and does not solidify in solid copper.

Tin bronzes are used in fittings, bearings, piston rings, gears and valves.

Composition

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

Copper Alloy No. Cu Sn Pb Zn Fe Sb Ni S P Al Si Mn Other Named Elements Status Inactive Date
C922001 86.0-90.02 5.5-6.5 1.0-2.0 3.0- 5.0 .25 .25 1.03 .05 .054 .005 .005 - - Active
C922101 86.0-89.02 4.5-5.5 1.7-2.5 3.0-4.5 .25 .20 .7- 1.03 .05 .034 .005 .005 - - Active
C922201 86.0-88.02 5.0-6.0 1.5-2.5 3.0-5.5 .25 - .50- 1.03 - .05 - - - - Active
C923001 85.0-89.02 7.5-9.0 .30-1.0 2.5- 5.0 .25 .25 1.03 .05 .054 .005 .005 - - Active
C923101 Rem.2 7.5-8.5 .30-1.5 3.5-4.5 - - 1.03 - - .005 .005 .03 - Active
C924001 86.0-89.02 9.0-11.0 1.0-2.5 1.0- 3.0 .25 .25 1.03 .05 .054 .005 .005 - - Active
C924101 Rem.2 6.0-8.0 2.5-3.5 1.5-3.0 .20 .25 .203 - - .005 .005 .05 - Active
C925001 85.0-88.02 10.0-12.0 1.0-1.5 .50 .30 .25 .8- 1.53 .05 .304 .005 .005 - - Active
C926001 86.0-88.52 9.3-10.5 .8-1.5 1.3- 2.5 .20 .25 .73 .05 .034 .005 .005 - - Active
C926101 Rem.2 9.5-10.5 .30-1.5 1.7-2.8 .15 - 1.03 - - .005 .005 .03 - Active
C927001 86.0-89.02 9.0-11.0 1.0- 2.5 .7 .20 .25 1.03 .05 .254 .005 .005 - - Active
C927101 Rem.2 9.0-11.0 4.0- 6.0 1.0 .20 .25 2.03 .05 .104 .005 .005 - - Active
C928001 78.0-82.02 15.0-17.0 4.0- 6.0 .8 .20 .25 .83 .05 .054 .005 .005 - - Active
C928101 78.0-82.02 12.0-14.0 4.0-6.0 .50 .50 .25 .8- 1.23 .05 .054 .005 .005 - - Active
C929001 82.0-86.02 9.0-11.0 2.0-3.2 .25 .20 .25 2.8- 4.03 .05 .504 .005 .005 - - Active

1Cu + Sum of named elements, 99.3% min.
2In determining Cu min., Cu may be calculated as Cu + Ni.
3Ni value includes Co.
4For continuous castings, P shall be 1.5%, max.

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