A Comprehensive Guide to Copper Nickel Alloy

Copper nickel alloy, also known as
cupronickel, is a versatile and widely used metal material with a fascinating combination of properties that make it valuable across various industries. In this comprehensive guide, we will delve into the world of copper nickel alloy, exploring its composition, characteristics, applications, and benefits.

What is Copper Nickel Alloy?

Copper-nickel alloy: It is a copper-based alloy with nickel as the main additive element. It is silvery white with a metallic luster, also called white copper.
Because of the infinite solid solution between copper and nickel, when the nickel content is more than 16 %, the color of the alloy becomes white as silver, and the higher the nickel content, the whiter the color. The content of nickel in the copper-nickel alloy is generally 25 %.

Characteristics of copper nickel alloys

Copper nickel alloy is a metallic material composed of two metal elements: copper and nickel. This alloy is made by smelting copper and nickel and mixing them in a certain proportion. Its importance lies in its ability to provide high strength, high corrosion resistance, thermal stability, good machinability, and surface adhesion.
The structure of copper nickel alloy is composed of a molten mixture, and its microstructure has good fluidity and uniformity, with larger grains and blocky precipitation. It has high corrosion resistance and can maintain good properties in extreme environments. After processing, the corrosion resistance and strength of copper nickel alloys can be increased, making them more durable in various extreme working environments.

• 1. Tensile strength: Copper nickel alloy has a high tensile strength, up to 560 MPa, and a compressive strength of up to 400 MPa.
• 2. Corrosiveness: Copper nickel alloys have excellent corrosion resistance in the air, largely due to the good corrosion resistance of nickel elements in the alloy.
• 3. Stability: Copper nickel alloy has good thermal stability and can be used at higher temperatures, with stronger thermal stress resistance than single metal materials.
• 4. Machinability: Copper nickel alloy has good machinability and excellent drilling and bending properties.
• 5. Surface quality and adhesion: Copper nickel alloy has a good surface finish, strong surface adhesion, and can resist external air and water erosion, ensuring the durability of the coating material.

Classification of copper nickel alloys

Copper-nickel alloys can be divided into manganese white copper, iron white copper, ordinary white copper, aluminum white copper, and zinc white copper. Due to the different content of Ni elements in them, their performance varies, and their applications are also different. Due to its irreplaceable corrosion resistance and superior performance compared to traditional alloys, it has great potential for application.
Table.1 Copper-nickel alloy grades and chemical composition (mass fraction/%)

Classification of copper-nickel alloys	Code	Grade	Cu	Ni	Al	Fe	Mn	Zn	Impurity
Ordinary white copper	C70110	B0.6	allowance	0.57-0.63	−	0.005	−	−	0.1
	C70380	B5	allowance	4.40-5.00	−	0.2	−	−	0.5
	C71050	B19	allowance	18.00-20.00	−	0.5	0.5	0.3	1.8
	C71100	B23	allowance	22.00-24.00	−	0.1	0.2	0.202	1
	C71200	B25	allowance	24.0-26.00	−	0.5	0.5	0.303	1.8
	C71400	B30	allowance	29.00-33.00	−	0.9	1.2	−	2.3
Iron white copper	C70400	BFe5-1.5-0.5	allowance	4.80-6.20	−	1.3-1.7	0.3-0.8	−	1.6
	C70510	BFe7-0.4-0.4	allowance	6.00-7.00	−	0.1-0.7	0.1-0.7	−	0.7
	C70600	BFe10-1-1	allowance	9.00-11.00	−	1.0-1.5	0.5-1.0	0.03	0.7
	C70610	BFe10-1.5-1	allowance	10.00-11.00	−	1.0-2.0	0.5-1.0	−	0.6
	C70620	BFe10-1.6-1	allowance	9.00-11.00	−	1.5-1.8	0.5-1.0	−	0.4
	C70900	BFe16-1-1-0.5	allowance	15.00-18.00	Ti≤0.03	0.5-1.0	0.2-1.0	−	1.1
	C71500	BFe30-1-1	allowance	29.00-32.0	−	0.5-1.0	0.5-1.2	0.03	0.7
	C71511	BFe30-2-2	allowance	29.0-32.00	−	1.7-2.3	1.5-2.5	−	0.6
Manganese white copper	C71512	BMn3-12	allowance	2.00-3.51	0.2	0.2-0.5	11.5-13.5	−	0.5
	C71513	BMn40-1.5	allowance	39.0-41.00	−	0.5	1.0-2.0	−	0.9
	C71514	BMn43-0.5	allowance	42.00-44.00	−	0.15	0.1-1.0	−	0.6
Aluminum white copper	C71515	BAl6-1.5	allowance	5.50-6.50	1.2-1.8	0.5	0.2	−	1.1
	C71516	BAl13-3	allowance	12.00-15.00	2.3-3.0	1	0.5	−	1.9
Zinc white copper	C71517	BZn15-20	62.0-65.0	13.50-16.50	−	≤0.50	≤0.3	allowance	0.9
	C71518	BZn18-18	63.5-66.5	16.50-19.50	−	0.25	0.5	allowance	0.8
	C71519	BZn18-26	53.5-56.5	16.50-19.50	−	≤0.25	≤0.5	allowance	0.8

Properties and Applications of Copper Nickel Alloy

Ordinary white copper: Copper-nickel binary alloy (i.e., binary white copper) is called ordinary white copper. In ordinary white copper, the letter B represents the amount of nickel added; for example, B5 represents a nickel content of about 5%, and the rest is about copper content. The models include B0.6, B19, B25, and B30. Ordinary white copper is generally a structural copper-nickel alloy. In addition to having high corrosion resistance, it has good comprehensive mechanical properties at high and low temperatures, including good plasticity and toughness. It is generally used as a rod or strip. At the same time, adding trace alloy elements such as Fe, Mn, Zn, and Al to ordinary white copper can meet the special performance requirements in practical applications and better meet industrial needs.
Iron white copper: The most widely used iron white copper is BFe10-1-1 (C70600) and BFe30-1-1 (C71500). When the mass fraction of Ni is 30% and 10%, the passivation range of the alloy is wider, and the corrosion resistance is the best. And this alloy also has strong resistance to seawater erosion and corrosion, known as the “ocean engineering alloy”. The main applications of copper and copper alloys in ocean engineering are shown in Table 2.
Table.2 Main Application Classification of Copper and Copper Alloys in the Field of Marine Engineering

Application category	Application area	Application Type
Heat exchange tube	Seawater desalination	Evaporator and condenser pipe for thermal seawater desalination
	Seawater backflow power generation host	Condenser, oil cooler, heater
	Active Power System of Ocean Ships	Main power system condenser and heat exchanger
	Ocean Ship Power Generation System	Condensors and heat exchangers for ship power generation systems
	Marine engineering auxiliary machinery, etc	Seawater backflow power generation oil cooler and heater
		Auxiliary heat exchanger for ship power
		Heat exchangers for offshore oil production platforms
Pipe for piping system	Pipeline system for seawater direct use	Infusion pipeline for seawater cooling and seawater flushing
	Pipeline network of offshore oil production platforms	Offshore oil production platform official website pipeline
	Pipeline system of marine vessels	Water and infusion pipelines, etc

BFe10-1-1 and BFe30-1-1-1 alloys have excellent resistance to seawater erosion and corrosion, high heat transfer coefficient, excellent mechanical/welding performance, and inhibition of marine microbial adhesion. They are widely used in cooling water pipes for ship main and auxiliary equipment, fire pipelines for offshore oil production platforms, heat exchangers for power plants, condensers for coastal nuclear power plants, and brine heaters for seawater desalination multi-stage flash evaporation devices. At the same time, BFe30-1-1 alloy has higher strength and is also used in high-strength structural components such as shafts, fasteners, valve stems, and flanges of some marine devices. The development of BFe30-2-2 alloy with good resistance to seawater erosion corrosion and sand corrosion is to address the problem of high sand content in the seawater of the East China Sea. The mechanical properties of BFe10-1-1 and BFe30-1-1-1 alloy pipes in the hard state should meet the following requirements: tensile strength ≥ 370MPa, yield strength ≥ 150MPa, elongation ≥ 18%, and Vickers hardness ≥ 85; Corrosion resistance: The corrosion amount (50 ℃, 3.5% NaCl seawater) is ≤ 0.025mm/a and no pitting corrosion is allowed.
Manganese white copper: Manganese white copper (BMn3-12 alloy) has a moderate resistance coefficient, low resistance temperature coefficient, and is relatively stable. Due to its good electrical performance, BMn3-12 alloy can make standard resistors and other precision instrument resistance components. With the development of the times, the precision requirements of instruments are becoming increasingly high, so research on this alloy must continue to change the alloy composition and content. Qin Fangli et al. used annealing, horizontal extrusion failure, and drawing processes to endow BMn3-12 alloy with special coherent twin boundaries, which can improve the strength of the material without affecting its conductivity. BMn40-1.5 alloy is an electrical copper-nickel alloy applied earlier than BMn3-12 alloy. Due to its small resistance temperature coefficient, it has a good heat resistance and can be used over a wide temperature range. Compared to BMn3-12 alloy, BMn40-1.5 alloy has a higher thermoelectric potential for copper, making it suitable for precision resistors, sliding resistors, starting and regulating transformers and resistance strain gauges for AC applications.
Aluminum white copper: Aluminum white copper has high strength and good plasticity and toughness. Among them, BAl13-3 alloy is commonly used to make high-strength corrosion-resistant parts, and BAl16-1.5 alloy is used to manufacture flat springs with important applications. For a long time, to improve the performance of aluminum white copper, a small amount of trace elements have been added to create a strengthening matrix for aluminum white copper, which has good conductivity while maintaining high strength to meet practical application requirements. Due to its high strength, high conductivity, and excellent wear resistance, aluminum white copper can be a potential material for lead frames and wear-resistant components.

Zinc white copper: Zinc white copper (BZn18-18, BZn15-20 alloy) is also known as “German silver”. Due to its excellent tensile strength, fatigue resistance, and corrosion resistance, zinc white copper is mainly used as a shell for components or crystals, medical equipment, construction materials, and wind instrument shells.

Use temperature of copper-nickel alloy materials

Copper-nickel alloy is a common high-temperature material widely used in various industrial fields. It has excellent high temperature and oxidation resistance and can maintain good mechanical strength and chemical stability in high temperature environments. The following will explain the use temperature of copper-nickel alloy materials.

• 1. Temperature range: The temperature range of copper-nickel alloy materials is usually between room temperature and high temperature; the specific temperature depends on the composition of the alloy and processing technology. Generally, copper-nickel alloy materials can be used normally at room temperature and withstand higher temperatures, generally up to 800 °C or more. Under appropriate conditions, some special copper-nickel alloy materials, such as nickel-aluminum bronze, can even be used at high temperatures of more than 1000 °C.
• 2. High temperature performance: copper-nickel alloy materials of high temperature performance is determined by their alloy composition and microstructure. Nickel in the alloy can improve the heat resistance of the alloy so that it can maintain good mechanical properties and chemical stability at high temperatures. In addition, the preparation process and heat treatment process of the alloy will also have an impact on the high temperature resistance.
• 3. Antioxidant properties: copper-nickel alloy materials have good antioxidant properties and can prevent the occurrence of oxidation reactions in a high temperature environment. The presence of copper and nickel elements can form a layer of dense oxide surface layer, effectively preventing further erosion of oxygen. This oxide surface layer also has a certain self-repairing ability and can be formed again after the oxide layer is damaged.

To summarize, copper-nickel alloy materials are usually used in the temperature range between room temperature and high temperature and can be used in high temperature environments above 800°C. It has good high temperature resistance. It has good high temperature and oxidation resistance and can maintain good mechanical properties and chemical stability in high temperature environments. This makes copper-nickel alloy materials widely used in aerospace, chemical, electric power, and other fields.

Preparation method of copper-nickel alloy

Cu-Ni alloy, also known as common white copper, solid-state copper, and nickel, can be an unlimited solid solution, so the organization of the copper-nickel alloy at room temperature for the α single solid solution. Cu-Ni alloy has good electrical conductivity, thermal conductivity, good strength and excellent plasticity, high corrosion resistance, and high ductility, and the color is beautiful, with deep-drawn performance, in the decorative arts and crafts, electrical appliances, ship instrumentation parts, chemical machinery parts and medical devices and other fields to be widely used. Medical equipment and other fields to be widely used. At the same time, the copper-nickel alloy is also an important resistance and thermocouple alloy, Cu-Ni alloy also has good resistance to seawater corrosion and resistance to the adhesion of marine organisms’ performance and is widely used in shipbuilding, the electric power industry, marine engineering, ships, seawater piping systems, and condensers. Due to the nickel-platinum resistance to artificial sweat, salt spray, and other media corrosive and plastic processing performance is very strong, the mint processing performance also occupies a certain advantage. Therefore, copper-nickel alloys have been widely used in many fields due to their excellent performance. We will introduce the preparation methods of Cu-Ni alloys.

Preparation method of Cu-Ni alloy

(1) Arc melting and mechanical alloying

Cao Zhongqiu et al. used arc melting and mechanical alloying method to prepare Cu-50N and Cu-70Ni (atomic fraction) alloys with large differences in grain size and high nickel content, respectively. Arc melting Cu-Ni alloys are protected by argon, a non-self-consuming arc furnace repeatedly melting pure metal raw materials, and then vacuum annealing (24h) to eliminate the stresses, and the grain size of 50 μm-100 μm obtained. The mechanical alloying process to prepare nanocrystalline Cu-Ni alloys mainly includes ball milling and hot pressing. Specific steps: Pure copper powder and pure nickel powder (mass fraction ≥99.99%) with a particle size of less than 100 μm were mixed proportionally and put into the QR-1SP planetary ball mill for ball milling, and argon was used as a protective gas to prevent the samples from being oxidized. To avoid overheating, every ball milling 1h needs to stop for 30min, a total of 60h needed to ball milling. Finally, the ground powder will be put into φ20mm graphite mold and then put into a 0.06Pa vacuum furnace, at 750 ℃, 60MPa pressure to keep 10min, and then with the cooling of the furnace and then vacuum annealing. By comparing the oxidation behaviors of the two in the air at 800℃, it was found that the oxidation rate of the mechanical alloying method was higher than that of the arc melting method for Cu-50Ni alloy. Still, it was the opposite for Cu-70Ni alloy.

(2) Powder co-penetration method

Due to the large difference between the melting point of copper and nickel, if the melting method for the preparation of copper-nickel alloys, there will be on the mechanical properties of the material, corrosion resistance, and process performance unfavorable dendritic segregation phenomenon, the production needs to be supplemented by the diffusion of the annealing process to give the elimination. The metal powder co-infiltration process can effectively alleviate the phenomenon of dendritic segregation.
Song Yuqiang et al. studied the structural and performance characteristics of Cu-Ni alloys under different preparation process conditions, and the preparation process parameters included powder size, mixing mode and time, pressing pressure and rate, whether the second warm pressure and warm pressure temperature, sintering temperature and holding time, etc. According to the different process parameters, the Cu-Ni alloys could be produced by a diffusion annealing process, effectively alleviating dendrite segregation. According to the selected process parameters, the specimen preparation process is divided into two kinds: the first one, mixing – cold pressing – sintering – cooling – sintered body; the second one, mixing – primary cold pressing – secondary warm pressing – cooling – sintering – cooling – sintered body. According to the pre-set process conditions, take out the pure Cu powder, pure Ni powder and mix, put into the grinder grinding, in the WE-30B hydraulic universal experimental machine on the press, in the unprotected atmosphere conditions will be put into the SX210-12 box-type resistance furnace sintering, change the sintering temperature and holding time, the sintering temperature depends on the Cu-Ni alloy phase diagram.

(3) Liquid phase reduction method

Liquid-phase reduction method has the advantages of simple operation, easy powdering process, and easy control of the powder grain size so that the reaction components to achieve molecular-level mixing liquid-phase reduction method for the nanopowder preparation has been studied. Zhu Ximing et al. applied the liquid phase reduction method for the first time to prepare nanoscale Cu-Ni alloy. The main reagents used (all analytically pure): NiSO₄-6H₂O; CuSO₄-5H₂O; N₂H₄-H₂O; PVP; NaBH₄; CH₃CH₂OH; CH₃COCH₃. The preparation process: the reagent PVP was put into the mixed solution of NiSO₄-6H₂O and CuSO₄-5H₂O, and then a complexing agent was added, and the reaction solution was obtained. Finally, add hydrazine solution and sodium borohydride; when the reaction is over, wash with ethanol acetone, separate, and dry at room temperature, and the product can be obtained.

(4) Molding and injection molding method

Molding is one of the most common methods in pressurized forming and can be used to prepare various material systems. However, there are still some shortcomings in applying this method; for example, the size and shape of the product are limited and prone to compositional segregation and other defects. Molding method for the preparation of Cu-10Ni alloy: the first Cu powder and Ni powder according to the mass ratio of 9:1 mix, and then use the standard tensile mold will be pressed into shape, pressing pressure of 400MPa. in the tube furnace sintering billet under the atmosphere of hydrogen, can be produced Cu-10Ni alloy samples.
Metal injection molding can produce high-density, high-precision, complex shapes of the structural parts and can be directly mass production. Therefore, applying injection molding technology to preparing copper-based alloys and parts production is a high-performance, high-efficiency, and low-cost production path. However, TORRALBA et al., in the study of high-speed steel, found that the injection molding alloy than the traditional molding alloy sintering process is complex, sintering dimensional shrinkage is large, the need for strict control of the process.
Injection molding method for the preparation of Cu-10Ni alloy: Cu, Ni mixed powder to add oil-based polymer binder, binder components include paraffin, polypropylene, peanut oil, and castor oil, powder loading rate of 57% (volume fraction). 160 ℃ in the refiner on the mixer for 3h, you can get the injection molding feed. In injection material in BOY50T2 injection molding machine injection molding, you can get the standard tensile specimen blanks, injection temperature 150 ℃, and injection pressure 70MPa-90MPa. In dichloromethane, on the solvent degreasing, degreasing temperature of 40 ℃, solvent degreasing, and thermal degreasing two-step degreasing method, thermal degreasing can be stripped out of the residual binder. Finally, the Cu-10Ni alloy samples were sintered under a hydrogen atmosphere.

Welding process of copper-nickel alloy

We analyzed the weldability of copper-nickel alloys, the defects prone to occur in the welding process, and the welding difficulties in process weldability, and summarized the welding techniques and parameters of manual tungsten argon arc welding (GTAW) and electrode arc welding (SMAW) in the welding of copper-nickel alloys in combination with the actual welding process. Through the copper-nickel alloy (UNS C70600) manual tungsten tungsten arc welding (GTAW) and electrode arc welding (SMAW) process evaluation test, to verify the reasonableness and applicability of the welding techniques and welding process parameters, and summarized to obtain high-quality Cu-Ni alloy welding joints.
Welding considerations for obtaining quality Cu-Ni alloy welded joints are summarized.

Cu-Ni alloy weldability analysis

Weldability
Weldability refers to the metal materials in the use of certain welding processes, including welding methods, welding materials, welding specifications and welding structure form and other conditions, to obtain the degree of difficulty of excellent welded joints. Can be divided into process weldability and the use of weldability, copper-nickel alloy, nickel can be unlimited solid solution in copper, with a single alpha-phase organization, there is no phase transition in the heating and cooling process, so there is no tendency to quench, and do not need to preheat before welding. There is high plasticity and toughness, so the tendency of cold cracking is small. In general, the weldability of copper-nickel alloy is relatively good, but there are some difficulties.
Analysis of welding difficulties

• (1) Due to its high coefficient of linear expansion, it is easier to weld deformation and larger welding stress.
• (2) Welded joints have a greater tendency to thermal cracking.
• (3) Due to the large thermal conductivity of copper-nickel alloy, the cooling rate of the weld is too large, welding is prone to porosity, mainly hydrogen-induced porosity and oxidation reaction porosity.
• (4) The welding process is prone to thermal embrittlement and crystallization cracks.

Copper-nickel alloy welding process

Welding method
Considering the site construction situation and the requirements for welding quality, manual tungsten argon arc welding (GTAW) and manual electrode arc welding (SMAW) are used.
Selection of welding materials
(1) welding wire and welding rod selection
According to the above analysis of the weldability of copper-nickel alloy, copper-nickel alloy itself does not contain deoxidizing elements, in order to avoid the generation of porosity, it is generally chosen to contain trace amounts of Si, P or Ti and other deoxidizing agent welding consumables.
(2) Protective gas
From an economic point of view, in order to ensure the quality of the weld, to avoid porosity in the weld, tungsten argon arc welding (GTAW) using pure argon protection. If you need to increase the protective gas penetration, increase the weld depth, you can add an appropriate amount of nitrogen. In this paper, the selection of argon.
Welding process
(1) Welding preparation
Due to the poor wettability of copper-nickel alloy, it is recommended to try to use a single side of 30-35 ° bevel angle. As the yield strength of copper-nickel alloy is relatively low, the coefficient of linear expansion is large, so the welding will produce a large transverse shrinkage deformation, so that the assembly gap is narrowed, or even become zero, on the welding of single-sided welding double-sided molding caused by greater difficulties. Therefore, before welding should ensure sufficient assembly clearance, if necessary, you can use the positioning block to ensure that the equipment gap. Recommended assembly clearance of 3-4mm.
(2) Position welding
Position welding wire should be the same as the formal weld wire used, position welding weld thickness and number should be as little as possible. Position welding weld shall not exceed the thickness of the formal weld, and no welding defects are allowed. In the bottoming welding, tack welding must be completely melted.
3) Bottom Welding
The bottoming weld adopts GTAW, and the welding should adopt small specifications as much as possible. Before bottoming welding, the pipe should be filled with argon on the back first, and try to ensure that the oxygen content in the pipe is less than 0.5%. Avoid porosity or weld being oxidized during welding. During the welding process, when the back weld is not affected by the arc, before stopping the back protection. For larger diameter pipe, bottoming welding adopts symmetrical bottoming method (see Figure 1 for the order of bottoming welding) to avoid deformation. Smaller diameter pipe, and filler welding can be used and filler welding consistent welding sequence (filler welding sequence see Figure 1).

Figure.1 Welding sequence diagram
For larger diameter pipe, two people can be used at the same time from 9 points and 6 points of symmetrical welding, after the arc is initiated at 9 points, the arc is first slightly preheated on the start of the arc, and then filler wire welding. Filler wire to reciprocating motion intermittently fed into the molten pool arc area in front of the molten pool, drip drip into the molten pool. The wire feeding speed should be uniform, not fast and slow. Arc from 6 points, due to the position in the back welding, coupled with the copper water mobility, wettability is poor, the root is prone to concave, it is used to fill the wire method, that is, the wire from the bottom of the bevel into the use of the arc heat will be melted wire. When closing the arc, welding to the end of the weldment, the angle between the torch and the weldment should be reduced, so that the arc heat is concentrated in the wire, increase the amount of wire melting to fill the arc pit. After stopping the arc, the argon gas is shut off with a delay of about 10S to prevent the molten pool from being oxidized at high temperatures. When welding joints, the quality of the weld at the arc pit should be checked first to ensure that the weld is free of oxide skin and other defects. When starting the arc, it should be 15-20mm to the right of the arc pit, move slowly, and then continue to filler weld after the arc pit slowly melts to form a molten pool.
4) Filler welding
The filler welding sequence is shown in Figure 1. In order to avoid burning through the bottoming weld channel, it is recommended that the thickness of the argon arc layer reaches 3-4mm after the use of manual electrode arc welding. When manual electrode arc welding, according to the flux properties of the electrode, select DC reverse connection to increase the stability of the arc. Welding process should be used short arc welding, narrow weld path, that is, the width of the weld is not easy to more than 3 times the diameter of the core, the thickness of the weld is not easy to more than 3mm, in order to achieve excellent protection effect, the electrode angle should be kept as far as possible between 80-90 °. Before welding a layer for the next layer of welding, the application of stainless steel wire or copper wire brush or aluminum-based grinding wheel must carefully clean the surface of the weld channel oxide film, spatter, weld slag, and other impurities affecting the quality of welding.
Due to the low strength of copper-nickel alloy, relatively soft, in the use of grinding wheel grinding defects are easy to defects dense, not easy to judge the defects and identify defects have been removed, so in the welding of thick-walled pipe, in order to ensure the quality of welding, should be in the thickness of the weld to reach the appropriate position after the nondestructive testing. The defects in the weld are partitioned and removed.

UNS C70600 Welding Process Evaluation

Base material
The base material used for process evaluation is UNS C70600 (Φ88.9×7.62), UNS C70600 (Cu90-Ni10) is a typical ωNi10% copper-nickel alloy, which belongs to PNO.34 in ASME.
Welding consumables
According to the chemical composition of UNS C70600, ECuNi-B (electrode) and ERCuNi (wire) are used.
Welding process parameters
The process evaluation process parameters are shown in Table 3.

Table.3 Welding process parameters

Layer/channel		Underlay 1/1	Fill 2/2	Fill 3/3	7-10
Welding method		GTAW	GTAW	SMAW	SMAW
Filler metal	Category	ERCuNi	ERCuNi	ECuNi-B	ECuNi-B
	Diameter (mm)	2	2	3.2	3.2
Electrical characteristics	Type & Polarity	DCEN	DCEN	DCEP	DCEP
	Current/A	100-120	120-140	80-115	80-110
	Voltage/V	11-14	11-15	22-25	22-25
Gas flow rate/L/min	Front	15-25	15-25	/	/
	Back	15-25	15-25	/	/
Welding speed/cm/min		5-7	6-8	7-10	7-10

Mechanical performance testing

According to the requirements of GB 50236, the weld is subjected to tensile test and bending test, the opposite bend and back bending specimen according to GB/T232-2010 after 180 ° bending, no cracks, in line with the standard requirements. After room temperature stretching, the specimen was broken at the fusion line and the base material, the tensile strength are greater than the base material, respectively, 325MPa and 335MPa, in line with the standard requirements.

Field welding recommendations

Due to the special characteristics of copper, as a non-ferrous metal, the usual welding method is generally gas welding, manual tungsten argon arc welding and electrode arc welding application is less, coupled with its unique weldability, there is a welding difficulties. In order to ensure the quality of welding, the following recommendations:

• Cultivate welders with the ability to weld non-ferrous metals and pass the corresponding qualification examination.
• Before welding, you must carefully clean up around the weld to remove oxide film, water, oil and other impurities.
• When argon arc welding, strictly control the flow of protective gas.
• When welding electrode arc welding, strictly control the baking of the electrode, when welding, the electrode must be placed in the insulated bucket, take it with you.
• Arc welding, to prevent overheating and oxidation of the weld channel to produce porosity, so it is prohibited to knock off the slag too early.

Use short arc welding and narrow welding path, and the thickness of molten metal in each layer should be less than 3mm.
Through the analysis of the weldability of white copper and process tests, the following conclusions are drawn:

• White copper weldability is good, no preheating before welding, but in order to improve the fluidity of copper water and weld shaping, can be preheated at 150 ℃.
• When white copper is welded, it is easy to produce porosity, thermal cracks and deformation.
• For the weldability of white copper, reasonable welding process parameters and preventive measures to prevent porosity, thermal cracks and welding deformation are developed through tests, ensuring cleanliness around the weld before welding, strictly observing process discipline, controlling the flow of shielding gas, the baking temperature of the welding rod, and controlling the thickness of the single-layer weld.
• The process evaluation test was carried out according to GB 50236, and the specimen of UNS C70600 Φ88.9×7.92 was subjected to radiographic inspection, and the quality grade of the weld was not less than Class II. The tensile test and bending test are qualified, indicating that the manual tungsten argon arc welding (GTAW) and manual electrode arc welding (SMAW) processes are feasible.

Heat treatment of white copper

Aluminum white copper BAl2-3 can be heat treated and strengthened. After solid solution at 900 ℃, it is cold rolled by 50%. After aging at 550 ℃, its strength can reach 800-1000MPa, and the solid solution state is only 250-350MPa.
Due to severe intergranular segregation in white copper ingots, homogenization annealing is necessary. The homogenization annealing system for white copper is as follows:

• B19, B30, temperature 100-1050 ℃, time 3-4 hours;
• BMn3-12, temperature 830-870 ℃, time 2-3h;
• BMn40-1.5, temperature 1050-1150 ℃, time 3-4 hours;
• BZn15-20, temperature 940-970 ℃, time 2-3h.

The different heat treatment processes of white copper have a significant impact on its performance. BMn3-12 used for precision instruments should undergo stress relieving annealing to stabilize the resistance.
BMn40-1.5 working at high temperatures should undergo short-term annealing, water cooling, or air cooling at higher temperatures of 750-850 ℃.
Zinc white copper BZn15-20 used for manufacturing elastic components can be annealed at a low temperature of 325-375 ℃.
The intermediate annealing temperature (℃) of white copper processed parts needs to be appropriately reduced as the effective thickness (mm) decreases, as listed below:
B19, B25

• 750-780 ℃ (>5mm), 700-750 ℃ (15-mm);
• 620-700 ℃ (0.5-1mm), 530-620 ℃ (<0.5mm).

BZn15-20  bmN3-12

• 700-750 ℃ (greater than 5mm), 680-730 ℃ (1-5mm);
• 600-700 ℃ (0.5-1mm), 520-600 ℃ (<0.5mm).

BAl6-1.5, BAl13-3

• 700-750 ℃ (>5mm), 700-730 (1-5mm);
• 580-700 ℃ (0.5-1mm), 550-600 ℃ (<0.5mm).

BMn40-1.5

• 800-850 ℃ (>5mm), 750-800 ℃ (1-5mm);
• 600-750 ℃ (0.5-1mm), 550-600 ℃ (<0.5mm).

The annealing temperature of finished copper bars and wires also varies with the different states of “semi hard and soft” before annealing, as listed below:
BZn15-20

• Bar, semi hard at 400-420 ℃, soft at 650-700 ℃;
• Wire rod Φ 0.3- Φ 6.0, soft 650-700 ℃.

BMn3-12

• Wire rod Φ 0.3- Φ 6.0, soft 500-540 ℃.

BMn40-1.5

• Wire rod Φ 0.3- Φ 0.8, soft 670-680 ℃;
• Wire rod Φ 0.85- Φ 2.0, soft 690-700 ℃;
• Wire rod Φ 2.1- Φ 6.0, soft 710-730 ℃.

What is the difference between copper-nickel alloys and nickel-copper alloys?

Copper-nickel alloys and nickel-copper alloys are often mistaken for the same material, but in fact, they differ to some degree in chemical composition, mechanical properties, and application scenarios.
Differences in chemical composition
The ratio of copper to nickel in copper-nickel alloys is usually between 90/10 and 70/30, with traces of iron, manganese, cobalt, and other elements, which provide good corrosion resistance, electrical conductivity, and strength. And nickel-copper alloy in the content of nickel is usually more than 60%, the content of copper is not more than 40%, with better high temperature resistance and oxidation resistance.
Therefore, copper-nickel alloys are often used in manufacturing marine engineering, nuclear equipment, chemical equipment, and other fields. In contrast, nickel-copper alloys often manufacture aero-engines, gas turbines, and other high-temperature and high-pressure equipment.
Differences in mechanical properties
Copper-nickel alloys have high ductility and toughness, excellent corrosion resistance, and can be adapted to various environmental applications. On the other hand, Nickel-copper alloys have higher hardness, strength, and fatigue resistance and are suitable for use in high-temperature, high-pressure and corrosive environments.
Therefore, when choosing the right material, you must choose according to the actual application scenarios and mechanical performance requirements.
Differences in application scenarios
Copper-nickel alloys are often used in ships, marine engineering, chemical equipment, metal decoration, and other fields. For example, copper-nickel tubes are often used in desalination, submarine oil, gas extraction, and other marine engineering fields.
While nickel-copper alloy is used in aviation, aerospace, petrochemical, and other high-temperature and high-pressure equipment fields, nickel-based alloys are often used to manufacture aviation engines, gas turbines, and other high-temperature and high-pressure equipment.
Conclusion
Copper-nickel alloys and nickel-copper alloys differ to a certain extent in chemical composition, mechanical properties, and application scenarios. In the actual application, it is necessary to choose according to the specific application scenarios and mechanical performance requirements to achieve the best performance and effect.