Cupronickel

What Is Cupronickel?

Cupronickel is a copper-based alloy with nickel as the main additive element. It is silver-white with metallic luster, hence the name Cupronickel.

Copper and nickel can be infinitely dissolved in each other to form a continuous solid solution, that is, regardless of the ratio of each other, it is always an α-single-phase alloy.

When nickel is melted into red copper and the content exceeds 16%, the color of the resulting alloy becomes as white as silver. The higher the nickel content, the whiter the color. The nickel content in cupronickel is generally 25%.

Advantages and disadvantages

Pure copper and nickel can significantly improve the strength, corrosion resistance, hardness, electrical resistance and pyroelectricity, and reduce the temperature coefficient of resistivity. Therefore, compared with other copper alloys, the mechanical and physical properties of cupronickel are exceptionally good, with good ductility, high hardness, beautiful color, corrosion resistance, and deep drawing performance.

It is widely used in shipbuilding, petrochemical industry, electrical appliances, instrumentation, medical equipment, daily necessities, handicrafts and other fields, and it is also an important resistance and thermocouple alloy.

The disadvantage of copper-nickel alloy is that the main added element-nickel is a scarce strategic material, and the price is relatively expensive.

Nickel cupronickel (also called white copper), uses: crystal oscillator component shell, crystal shell, sliding sheet for potentiometer, medical machinery, building materials, etc.

classification

Complex cupronickel

Cupronickel alloys with elements such as manganese, iron, zinc, and aluminum are called complex cupronickel (that is, cupronickel above ternary), including iron cupronickel, manganese cupronickel, zinc cupronickel and aluminum cupronickel, etc. In the complex cupronickel, the second main element symbol and the component number group other than the copper content indicate the content of various elements. For example, BMn3-12 means that the nickel content is about 3% and the manganese content is about 12%.

There are 4 types of complex cupronickel:

• ①Iron white copper: The models are BFe5-1.5(Fe)-0.5(Mn), Bfe10-1(Fe)-1(Mn), Bfe30-1(Fe)-1(Mn). The amount of iron added in the cupronickel is not more than 2% to prevent corrosion and cracking. It is characterized by high strength, and the ability to resist corrosion, especially the corrosion of flowing seawater, can be significantly improved.
• ②Manganese white copper: The models are BMn3-12, BMn4.0-1.5, BMn43-0.5. The manganese cupronickel has a low temperature coefficient of resistance, can be used in a wide temperature range, has good corrosion resistance and good workability.
• ③Zinc white copper: The models are BZn18-18, BZn18-26, BZn18-18, BZn15-12 (Zn)-1.8 (Pb), BZn15-24 (Zn)-1.5 (Pb).
• Zinc-nickel alloy has excellent comprehensive mechanical properties, excellent corrosion resistance, good cold and hot processing formability, easy to cut, and can be made into wires, bars and plates for the manufacture of instruments, meters, medical equipment, daily necessities and communications. Precision parts.
• ④Aluminum white copper: The models are Bal13-3 and Bal16-1.5. It is an alloy formed by adding aluminum to a copper-nickel alloy with a density of 8.54-0.3. The performance of the alloy is related to the ratio of the amount of nickel to the amount of aluminum in the alloy. When Ni:Al=10:1, the alloy performance is the best.

Commonly used aluminum white copper is Cu6Ni1.5Al, Cul3Ni3Al, etc., which are mainly used for various high-strength corrosion-resistant parts in shipbuilding, electric power, chemical and other industrial sectors.

Ordinary copper-nickel alloy

Copper-nickel binary alloy (ie, binary white copper) is called ordinary white copper. In ordinary copper-nickel alloy, the letter B indicates the content of nickel, such as: B5 indicates that the nickel content is about 5%, and the rest is about the copper content. Models are B0.6, B19, B25, B30.

Industrial copper-nickel alloy

Industrial cupronickel is divided into two categories: structural cupronickel and precision resistance alloy cupronickel (electrical cupronickel).

(1) Structural white copper:

Structural white copper is characterized by good mechanical properties and corrosion resistance, and beautiful color. Among the structural cupronickel, the most commonly used are B30, B10 and zinc cupronickel. In addition, there are aluminum cupronickel, iron cupronickel and niobium cupronickel and so on. B30 has the strongest corrosion resistance in cupronickel, but it is more expensive.

The performance of aluminum cupronickel is similar to that of B30, and the price is low, and it can be used as a substitute for B30. Zinc cupronickel was produced and used in China in the 15th century and is called “Chinese silver”. The so-called nickel silver or German silver also belongs to this type of zinc cupronickel.

Zinc can be dissolved in a large amount of copper and nickel, resulting in solid solution strengthening and corrosion resistance. After adding lead, zinc-nickel alloy can be smoothly cut and processed into various precision parts, so it is widely used in instruments and medical devices. This alloy has high strength and corrosion resistance, good elasticity, beautiful appearance and low price.

The aluminum in the aluminum cupronickel can significantly improve the strength and corrosion resistance of the alloy, and its precipitates can also produce precipitation hardening.

Structural copper-nickel alloy is widely used in the manufacture of precision machinery, chemical machinery and ship components.

(2) Copper-nickel alloy for precision resistance alloy (electrician copper-nickel alloy):

Copper-nickel alloy (electrical white copper) for precision resistance alloy has good thermoelectric properties. BMn 3-12 manganese copper, BMn 40-1.5 constantan, BMn 43-0.5 test copper and new constantan with manganese instead of nickel (also known as nickel-free manganese cupronickel, containing 10.8-12.5% ​​manganese, 2.5-4.5% aluminum, Iron 1.0～1.6%) is manganese cupronickel with different manganese content.

Manganese cupronickel is a precision resistance alloy. This kind of alloy has high resistivity and low temperature coefficient of resistivity, and is suitable for making standard resistance components and precision resistance components. It is a material used to manufacture precision electrical instruments, rheostats, meters, precision resistors, strain gauges, etc. Constantan and Kaotong have high thermoelectric potential and can also be used as thermocouples and compensation wires.

The main purpose

Among copper alloys, cupronickel is widely used as corrosion-resistant structural parts in shipbuilding, petroleum, chemical, construction, electric power, precision instruments, medical equipment, musical instruments and other sectors because of its excellent corrosion resistance and easy molding, processing and welding. . Certain cupronickel has special electrical properties, which can be used to make resistance elements, thermocouple materials and compensation wires. Non-industrial cupronickel is mainly used to make decorative crafts.

Distinguish white copper and silver

Because cupronickel jewelry is similar to pure silver jewelry in terms of color and workmanship. Some unscrupulous merchants take advantage of consumers’ ignorance of silver jewellery and sell cupronickel jewellery as sterling silver jewellery in order to obtain huge profits.

So, how to distinguish sterling silver jewelry or copper-nickel jewelry?

It is understood that the general sterling silver jewelry will be marked with the words S925, S990, XX pure silver, but the cupronickel jewelry does not have such a mark or the mark is very unclear; a needle can be used to mark the surface of the silver; while the copper texture is tough and not It is easy to scratch; the color of silver is slightly yellowish silvery white, which is due to the easy oxidation of silver. After oxidation, it will appear dark yellow, while the color of cupronickel is pure white, and green spots will appear after a period of time.

In addition, if you drop a drop of concentrated hydrochloric acid on the inner side of silver jewelry, a white moss-like silver chloride precipitate will be formed immediately, while cupronickel does not appear this situation.

Main varieties

Ordinary copper-nickel alloy mainly has four alloy grades such as B0.6, B5, B19, and B30. Commonly used are B19 and B30, and there are more grades in the American standard.

The cupronickel rod is a continuous solid solution formed by Cu and Ni, with a face-centered cubic lattice. When the temperature is lower than 322 degrees, the copper-nickel phase diagram has a relatively wide composition and temperature range for metastable decomposition. Add a third element such as Fe, Cr, Sn, Ti, Co, Si, Al to the Cu-Ni alloy. It can change the composition, temperature range and location of metastable decomposition, and also improve certain properties of the alloy.

Ordinary cupronickel has good cold and hot workability. It can be smoothly processed into various shapes such as plates, bands, tubes, rods, shapes, and wires. The welding performance is good, and it can be used for soft and hard brazing, gas shielded arc welding and resistance welding. The cutting performance is 20% of the free-cutting brass HPb63-3.

Ordinary cupronickel has good corrosion resistance, medium strength, high plasticity, can be processed under cold and hot pressure, and good electrical properties. In addition to being used as a structural material, it is also an important high resistance and thermocouple alloy.