Description
The content variation in the grade is done to achieve precedence over the 90/10 grade in terms of better strength and stability. The grade is delivered in a very pure form. Like the 90/10 grade, even the copper-nickel 70/30 has an alpha phase structure since nickel becomes soluble in the copper phase. Although complete homogeneity is not obtained due to the addition of other alloying elements, the grade almost becomes a balanced compound with a homogenized phase structure. Grade 70/30 has high strength and better ductility. The microstructure of the grade provides it with high thermal as well as physical stability.
A considerably high impact strength is obtained from the grade to be used in dynamic applications. After noting its corrosion resistance in polluted and turbulent streams of water, it showed commendable corrosion resistance. The grade is specifically used in imbalanced environments like variable pressures, temperatures, higher velocity flow, and turbulence. A high resistance to cracking due to corrosion is obtained. The grade can be used conveniently up to 370°C for relevant applications. The possession’s ratio of the grade is slightly higher when compared to standard austenitic steels with exceptional toughness and elastic properties. The grade also has fine electric resistance and electric properties to be used in marine power applications apart from its corrosion resistance underwater.
In fact, it is widely used in electrical engineering space as cables, anodes in TV tubes, and resistors. The grade can be hot-worked and cold-worked very conveniently. Hot working processes like forging can be carried out at 930-1040°C, with subsequent annealing for grain refinement. The grade comes in the group of corrosion-resistant and moisture-resistant alloys that suitably resist acids, salt solutions, organic solutions, and alkalis.
Chemical Properties
| Grade | Cu | Fe | Pb | Mn | Ni | Zn | |
| 70-30 | Min./Max. | Rem. | 0.4-1.0 | 0.05 | 1.0 | 29.0-33.0 | 1.0 |
| Nominal | 69.5 | 0.50 | – | – | 30.0 | – |
Physical Properties
| Density | 8.95 gram/ cm3 or 0.325 ln per inch3 |
| Elastic Modulus | 126 000 |
| Poissons Ratio | 0.34 |
| Melting Point | 1170 to 1240oC or 2140 to 2265 oF |
| Shears MODULUS (N/MM2) | 57.0 GPa 8270 ksi |
| Specific heat capacity | 0.09 cal/goC or 0.09 Btu/lb oF |
| Thermal conductivity | 0.07 cal cm/cm2 s oC or 178 BTU ft/ft2 h oF |
| Electrical conductivity at -269oC or -452oF (annealed) | 0.34 ohm/mm2/m or 207 ohms (circ mil per ft) |
MECHANICAL PROPERTIES
| Standard | 70-30 |
| UNS | C71500 |
| WERKSTOFF NR. | 2.0882 |
| EN | 12451 CuNi 30 Mnlfe CW354H |
| BS | 2871 |
| DIN | 1785 CuNi 30 Mnlfe |
| AFNOR | CuNi 30 Mnlfe |
Standards Specifications
PIPES & TUBES
| Summary | Standards |
| Standard Specification for Copper and Copper-Alloy Seamless Condenser Tubes and Ferrule Stock | ASTM B111 |
| Standard Specification for Copper and Copper-Alloy Seamless Condenser and Heat Exchanger Tubes With Integral Fins | ASTM B359 |
| Standard Specification for U-Bend Seamless Copper and Copper Alloy Heat Exchanger and Condenser Tubes | ASTM B395 |
| Standard Specification for Welded Copper-Nickel Pipe | ASTM B467 |
| Standard Specification for Welded Copper and Copper-Alloy Heat Exchanger Tube | ASTM B543 |
| Standard Specification for Seamless and Welded Copper–Nickel Tubes for Water Desalting Plants | ASTM B552 |
Forms of Supply
Piping and tubing, fittings and flanges, washers.
Corrosion Resistance
The grade delivers exceptional performance in marine service applications and general as well as aggressive attacks in normal seawater. The grade performs well even under polluted water as well as streams of water with higher velocities (up to 4.5 m/s). It can resist moist air or steam efficiently like general copper nickel grades. The grade is almost insensitive to stress corrosion cracking. Acids like phosphoric acid, sulphuric acid, and other mild organic acids can be suitably resisted. It can be attacked by cyanides, halide group acids, and nitric acid but can resist alkaline chlorides, sulfates, and nitrates. Environments containing wet or dry gases like chlorine, bromine, and carbon dioxide can be indisputably resisted.
Heat Treatment
The grade is normally annealed after procedures to remove internal stresses and refine the grain structure. It is usually done at around 650- 820°C, followed by appropriate quenching. The grade has a wide range of applications under highly uncertain environments. Hence, scrupulous annealing after procedures is required.
Weldability
The copper-nickel grade has no carbon content, hence its properties and procedures in welding are different from standard stainless steels. It has great welding properties in coated metal arc welding, gas-shielded arc welding, seam welding, butt welding, spot welding and satisfactory welding in oxyacetylene.
Machining
The grade comes in the category of moderate or sometimes poor machining category alloys. The chips formed while machining are long, hard, and tough to remove. Also, sometimes the surface gets damaged while machining. The normal machining rate of the grade is 20%.
Applications
Heat exchanger and cooling plant, flexible metal hose, weld wire and boiler parts, pumps and valves, refrigerator and condenser components, pressure vessels, process equipment, evaporator tubes, propeller sleeves, distiller tubes, tube sheets and baffles, tanks, vats, welding backing rings, pump bodies and parts, salt water piping, and pipe fittings.
Possible Grade Alternatives
GRADE COPPER NICKEL 70/30
| Grade | Cu | Fe | Pb | Mn | Ni | Zn | |
| 70-30 | Min./Max. | Rem. | 0.4-1.0 | 0.05 | 1.0 | 29.0-33.0 | 1.0 |
| Nominal | 69.5 | 0.50 | – | – | 30.0 | – |
