Cryogenic Properties

Copper and copper alloys were the first metals used in the fabrication of low-temperature equipment for the liquefaction and storage of cryogenic fluids. Copper and many copper alloys retain ductility at low temperatures. Their unusual properties of retaining ductility at low temperatures and exhibiting good thermal conductivity is advantageous for heat exchangers and other components in cryogenic plants and in low-temperature processing and storage equipment.

The table below shows that 90-10 and 70-30 Cu-Ni alloys become stronger while still retaining good ductility as temperatures decline. They also retain excellent impact properties.

Average Properties of Copper-Nickels at Low Temperatures
AlloyTest temperature, °KElastic propertiesPlastic Properties
UniaxialTriaxial
No.Name And treat-mentYoungs Modulus 106psi (5%)Tensile Strength psiYield Strength psiElongation % in 4DReduction in Area %Notch tensile Strength (KT=5.0) psiImpact Charpy Energy Absorbed, ft-lb
706 90-10
Cu-Ni,
(ann-ealed)		 295 17.7 49,600 21,400 37 79 65,000 114
195 54,700 24,700 42 77 73,100 113
76 19.5 72,000 24,800 50 77 87,200 115
20 82,500 30,200 50 73 96,800 116
4 20.5 80,600 24,900 53 73 100,000
715 70-30
Cu-Ni,
(ann-ealed)		 295 22.0 57,800 18,700 47 68 79,400 115
195 68,000 22,200 48 70 90,500 114
76 23.0 89,800 31,600 52 70 112,900 114
20 103,100 38,100 51 66 127,600 114
4 23.2 104,600 40,100 48 65 130,500

Taken from CDA Application Data Sheet 144/8R.
Data spread in most instances was 1%.

Stress-strain diagrams for 90-10 and 70-30 copper-nickels are illustrated below.

Figure 1 . Copper Alloy No. 706 (Annealed)Stress-strain diagram for Copper Alloy No. 706 (Annealed)
Figure 2 . Copper Alloy No. 715 (Annealed) Stress-strain diagram for Copper Alloy No. 715 (Annealed)

References

  1. Low Temperature Properties of Copper and Copper Alloys, Application Data Sheet 104/5, CDA, .
  2. Mechanical Properties of Copper and Copper Alloys at Low Temperatures, Application Data Sheet 144/8 R, CDA, .