Chrome Copper UNS C81500

Lead-freeCDA C81500 High Conductivity Precipitation Hardenable Master Alloy for Cr Additions Elevated Temperature Strength

Chrome copper (98.7% Cu, 1.3% Cr) per CDA C81500. High conductivity high-strength master alloy for chromium additions. Solidus 1967F liquidus 1985F. 2-20 ingot.

Solidus

1,967°F (1,075°C)

Liquidus

1,985°F (1,085°C)

Density

0.319 lbs/in³ (8.82 g/cm³)

Primary Elements

Cu · Cr

Nominal Composition

1.3% Cr, 98.7% Cu

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Product Overview

Chrome Copper UNS C81500 is a copper-chromium alloy with a nominal composition of 98.7% Cu and 1.3% Cr, conforming to CDA number 81500. Solidus is 1967F (1075C) and liquidus is 1985F (1085C). Density is 0.319 lbs/in3 (8.82 g/cm3). The chromium addition provides a combination of high electrical conductivity, good strength, and corrosion resistance that makes this alloy unique among copper alloys. This alloy is used for resistance welding electrodes, electrical contacts, circuit breaker components, and heat exchanger fins where high conductivity combined with elevated-temperature strength is required. It also serves as a master alloy for introducing chromium into copper casting alloys where chromium additions improve corrosion resistance, grain refinement, and mechanical properties. Thermal conductivity of 182 Btu/ft2/ft/hr/F at 68F reflects the minimal impact of chromium on copper’s thermal properties. Supplied in 2-20 lb ingots for both engineering casting applications and master alloy use.

Available Forms

2-20 Ingot

Product Code

4989

Technical Info

Thermal Properties

Melting Point (Solidus)1,967°F (1,075°C)

Melting Point (Liquidus)1,985°F (1,085°C)

Physical Properties

Density (imperial)0.319 lbs/in³

Density (metric)8.82 g/cm³

Primary ElementsCu · Cr

SpecificationCDA C81500

Lead FreeYes

Key Features

High ConductivityPrecipitation HardenableMaster Alloy for Cr AdditionsElevated Temperature Strength

Solubility Note

Dissolves readily in molten copper and copper alloy heats at standard pouring temperatures providing controlled chromium addition with minimal oxidation loss.

Nominal Composition

98.7% Cu
1.3% Cr

Frequently Asked Questions

Common technical inquiries regarding Chrome Copper UNS C81500

C81500 achieves the combination of high electrical conductivity (approximately 80% IACS after precipitation hardening) and elevated-temperature strength (tensile strength approximately 51 ksi) that is essential for resistance welding electrodes. Standard copper is too soft and deforms under welding pressure; brass and bronze alloys sacrifice conductivity needed for current transmission. Chrome copper's precipitation-hardened Cr phase provides strength without significantly impeding electron transport.

The precipitation hardening sequence for C81500 is: (1) solution anneal at 1850-1900F followed by water quench; (2) cold work 20-40% to introduce dislocations that accelerate precipitation kinetics; (3) age at 850-950F for 2-4 hours to precipitate Cr2Cu particles. After aging conductivity recovers to 80-85% IACS while hardness reaches 75-90 HRB. Skipping the cold work step results in incomplete precipitation and lower final hardness.

C81500 is used as a master alloy when the target alloy requires a precise small chromium addition to copper, brass, or bronze heats — for example adding 0.1-0.5% Cr to a copper-nickel alloy for corrosion resistance improvement or grain refinement. The 1.3% Cr content allows accurate charge calculation for these small additions. It is preferred over the 10% Chrome Copper when the target chromium addition level is very low and fine control is needed.