About copper-nickel alloy
1. Classification of copper-nickel alloys
Table 1 shows the grade and elemental composition of cupronickel alloy. Cupronickel can be divided into manganese cupronickel, iron cupronickel, ordinary cupronickel, aluminum cupronickel and zinc cupronickel. Due to the different content of Ni element, its properties are different, and the application occasions are also different. different. Because of its irreplaceable corrosion resistance and many properties superior to traditional alloys, it has great application potential.
2. Properties and applications of copper-nickel alloys
Ordinary white copper is generally a structural copper-nickel alloy. In addition to its high corrosion resistance, it also has good comprehensive mechanical properties at high and low temperatures, that is, good plasticity and toughness. It is generally used as rods or strips. At the same time, adding some trace alloy elements such as Fe, Mn, Zn and Al on the basis of ordinary white copper can achieve special performance requirements in practical applications and better meet industrial needs. The most widely used iron-nickel copper is BFe10-1-1 (C70600) and BFe30-1-1 alloy pipes. The mechanical properties in the hard state should meet: tensile strength ≥ 370MPa, yield strength ≥ 150MPa, elongation ≥ 18% , Vickers hardness ≥ 85; corrosion resistance: corrosion amount (50°C, 3.5% NaCl seawater) ≤ 0.025mm/a, pitting corrosion is not allowed. Manganese white copper (BMn3-12 alloy) has a moderate resistance coefficient, a small resistance temperature coefficient and is relatively stable. Due to its good electrical properties, BMn3-12 alloy can be used to make standard resistors and resistive components of other precision instruments. With the development of the times, the requirements for the precision of instruments are getting higher and higher, so the research on this alloy cannot stop at changing the alloy composition and content [6]. Through annealing, horizontal extrusion failure and drawing processes, BMn3-12 alloy has special coherent twin boundaries, which can improve the strength of the material without affecting the conductivity of the material. BMn40-1.5 alloy is an electrical copper-nickel alloy that was used earlier than BMn3-12 alloy. Because of its smaller temperature coefficient of resistance, it has better heat resistance and can be used in a wider temperature range. Compared with BMn3-12 alloy, BMn40-1.5 alloy has a higher thermoelectric potential against copper, so it is suitable for precision resistors, sliding resistors, starting and regulating transformers and resistance strain gauges for AC [8]. Aluminum-nickel copper has both high strength and good plasticity and toughness. Among them, BAl13-3 alloy is often used to make higher-strength corrosion-resistant parts, and BAl16-1.5 alloy is used to make flat springs with important uses. For a long time, in order to improve the performance of aluminum-nickel copper, a small amount of trace elements are often added to create a strengthened matrix of aluminum-nickel copper, which has good conductivity while maintaining high strength to meet practical application requirements. Because aluminum-nickel copper has high strength, high electrical conductivity and good wear resistance, it can be used as a potential material for lead frames and wear-resistant parts [9-11].
Zinc cupronickel (BZn18-18BZn15-20 alloy) is also called "German silver" [12]. Because zinc-nickel copper has the advantages of good tensile strength, fatigue resistance, and corrosion resistance, it is mainly used as shells of components or crystals, medical equipment, construction materials, and wind instrument shells [13].
3. Copper-nickel alloy performance requirements
With the rapid development of my country's marine shipbuilding industry, offshore oil and gas industry, marine mining, marine power and seawater desalination industries, the requirements for materials are becoming higher and higher [16]. Among them, copper-nickel alloy pipes are mostly used. Copper alloy condenser pipes for ships have long been working in high temperature, high pressure and highly corrosive cooling medium - seawater environment. Therefore, it is no longer enough for the chemical composition, mechanical properties, and seawater corrosion resistance of the product to meet the requirements. Strict requirements must also be placed on geometric dimensional accuracy, process performance, internal organization and other indicators. At the same time, copper-nickel alloy pipes are also required to have good corrosion resistance. , high heat transfer coefficient, large diameter, high precision, excellent mechanical welding technology, and good ability to inhibit the adhesion of marine microorganisms [17] and other characteristics.
