Copper Nickel Alloy – Your Ultimate Guide

Copper Nickel alloy is a category of alloy formed by combining copper and nickel in different compositions. The alloy is also known as cupronickel and was famously referred to by the ancient Chinese as white copper

To boost their strength and corrosion resistance for different industry applications, you will find CuNi alloys enriched with small quantities of iron and manganese among other rare metals.

In this post, we share with you detailed information about copper-nickel alloys.

Let’s begin…

Table of Contents

1.0 The Top 9 Properties of Copper Nickel Alloy

Application of copper nickel alloy

Since copper-nickel alloys have different compositions, they display varying degrees of physical, mechanical, and corrosion resistance properties.

Here are some of the most critical properties of Copper Nickel alloys you should take note of:

1.1 Copper Nickel Is a Sea Water Corrosion Resistant Alloy

CuNi is highly resistant to seawater corrosion and, therefore, excellent for your marine industry projects.

1.2 Good Tensile Strength at High & Low Temperatures

The nickel composition ensures that the strength of copper alloy remains stable even if you subject it to higher temperatures which can be up to 600°C (1,110°F)

Again, CuNi does not lose its tensile strength or become brittle when you subject it to low temperatures. This property makes it suitable for cryogenic applications.

1.3 Impingement Corrosion Resistant

Copper 70/30 is a copper-nickel alloy that is highly resistant to impingement corrosion. This makes it suitable for your seawater piping projects and other marine applications.

1.4 Ductility of Cupronickel

The higher the percentage of copper in your chosen cupronickel, the higher its ductility when annealed.

1.5 Corrosion Resistance

Cupronickel has a protective layer on its surface and this makes it highly resistant to corrosion.

And so, it provides excellent resistance to the effects of moisture, salt solutions, non-oxidizing acids, and gasses

1.6 Cold-working Hardening Ease

CuNi alloys with low nickel compositions will provide you with excellent cold workability for enhanced strength.

1.7 Copper Nickel Alloy Has a Low Temperature Coefficient of Electrical Resistance

Copper-nickel alloy such as CuNi44 has a significantly low temperature coefficient of electrical resistance. This makes it ideal for making precision resistors and voltage regulators.

1.8 Resistance to Biofouling

High copper alloys such as CuNi 90/10 provide excellent marine biofouling resistance making it ideal as your ship-hull cladding alloy metal.

1.9 Good Thermal Conductivity 

Cupronickel also boasts good thermal conductivity. This makes it a perfect material for your heat exchanger and condenser applications

2.0 How You Manufacture Copper Nickel Alloy

metal alloy melting process

To begin your CuNi alloy production process, you should have the right equipment and suitable raw materials. 

Your suitable raw material can be Nickel Oxide ore, Nickel, Copper, wrought copper, or other necessary alloy elements.

Here are the main CuNi manufacturing processes you should take note of:

2.1 Melting Copper Nickel Alloy Compositions

Melting is the first step of your copper-nickel manufacturing process. You need to consider the most suitable temperature ranges in advance based on the composition of the CuNi alloy you are working on.

As nickel composition increases, the tendency of the melting alloy to absorb both hydrogen and oxygen increases. 

Therefore, you should reduce hydrogen absorption and keep the melt carbon-free. You can achieve this through vacuum degassing or electrorefining techniques.

Here are the three major CuNi melting processes you can use:

2.1.1 Electric Arc Melting: 

In this method, you put your wrought CuNi, or nickel oxide in a high-temperature metal or ceramic material. You then place it in a furnace where melting is achieved by electric arc heating.

This is the most cost-effective method if you focus on large-scale processing.

2.1.2 Induction melting:

In this process, you place the wrought copper alloy or compositions in a crucible for induction melting inside a furnace.

It is a more expensive method compared to the arc melting technique.

2.1.3 Blow Torch Melting:

In this technique, you use a blow torch to heat and melt your CuNi compositions or elements. 

Considering that CuNi alloys melt at high temperatures, it is recommended that you use an industrial oxy-acetylene blow torch.

Since the torch is hand-held, this method only allows you to melt small quantities of materials. 

2.2 CuNi Alloying

After melting and getting the desired copper-nickel ingots in their proper ratios, your next step is heating them together to their melting points inside the furnace.

Prior knowledge of the alloy compositions is critical because this will determine the melting points of the elements you are working on.

Generally, the higher the composition of nickel or the level of impurities, the higher the melting temperature you should expect

You should thoroughly mix the compositions to ensure your copper-nickel alloy is homogenous.

Note: To ensure that the Molten cupronickel is free from impurities or effects of oxygen or hydrogen, there are treatment methods you ought to consider during the alloying process.

2.3 Casting

metal casting

This process involves pouring the homogenous molten copper-nickel alloy into a mold cavity to solidify and form your desired alloy form or shape. 

After solidification, you remove the cast alloy from the mold or destroy the mold to leave the newly produced copper-nickel form.

You can use the casting technique to produce complex alloy forms that would prove costly by other methods.

Some of the copper alloy casting methods you can adopt based on your capacity and requirements include:

  • Centrifugal Method
  • Die-casting
  • Sand Casting
  • Chill Casting
  • Continuous casting
  • Investment Casting
  • Plaster Casting

2.4 Hot and Cold Working

In the hot working process, you increase the strength of the casted CuNi by changing its shape after subjecting it to heat. You will require temperatures between 850°C to 1,100°C.

The process may involve different techniques such as: forging, rolling, or extrusion.

To ensure that the corrosion resistance of your CuNi is not compromised, you should heat the alloy in a sulfur-free environment. 

However, if your CuNi alloy has a high copper composition, the most suitable approach is cold working.

2.5 Heat Treatment / Annealing

Heat treatment or soft annealing involves heating your CuNi alloy at high temperatures to make it soft and then cooling it slowly. 

You do soft annealing on a cold-worked alloy to relieve stress and improve workability.

The three main stages in this process are the recovery stage, recrystallization, and grain growth stage.

The temperature of recrystallization annealing can range between 620°C to 900°C. This range is determined by your nickel composition, how the CuNi alloy has been cold-worked, and the enhancement metals in your alloy mix.

Note: To avoid contamination by sulfur or carbon elements, you should effectively grease CuNi alloy before heat treatment. Your annealing furnace should also be free from sulfur.

2.6 Machining

Machining is a controlled process to ensure your Cu-Ni alloy component or fitting attains a precise shape and size to suit the intended application.

The main processes entail precision cutting, drilling of fastening holes, and tapping.

The lower the nickel % in your nickel-copper alloy component, the more you will find it challenging to machine.

2.7 Joining & Welding

metal joining by welding

If you are working on different CuNi alloy parts like bars and pipes, you will require to join together some of the already machined parts.

You must keep the parts to be joined clean and free from contaminants like carbon or sulfur-based compounds.

You can join some of your CuNi alloy parts using fasteners such as screws, bolts,  nuts, and rivets.  Other techniques include welding, soldering, or brazing. For some CuNi alloy fittings, you can use special metal adhesives.

When using soldering or brazing techniques, you should use a suitable silver-based brazing metal.

If the nickel composition in your CuNi alloy is 10% and above, you can safely use the Resistance Welding process. 

You can also use the Gas-Metal Arc Welding(GMAW) method with a suitable deoxidized filler metal to join some of your CuNi alloy fittings.

3.0 Advantages & Disadvantages of Copper Nickel Alloy

Due to its unique properties, CuNi alloy boasts several advantages making it a perfect choice for your wide range of applications.  

3.1 The Top 6 Advantages of Copper Nickel Alloy

3.1.1 Resistant to Corrosion and Biofouling 

Cupronickel is highly resistant to moisture or corrosive solutions such as seawater. When you expose it to seawater, it naturally forms a protective layer of cuprous oxide.

Apart from resisting corrosion, the protective film also ensures that seawater organisms do not easily attach themselves to the surface of your CuNi alloy component. 

This makes Cupronickel highly suitable for your piping projects and seawater systems.

3.1.2 Superior Strength 

If you are keen on producing or using a metal alloy part that is tough and with high strength, then CuNi alloy is a perfect choice.

The alloy can withstand heavy loads and pressure for an extended duration without getting distorted. 

3.1.3 Highly Durable

Because it is not affected by a wide range of extreme conditions, it is highly durable and perfect for your shipbuilding projects and other industrial applications.

3.1.4 Stable Performance at High Temperatures

CuNi alloy guarantees you stable performance even at elevated temperatures

You can use Cupronickel to produce system parts for the automotive or aerospace industries where high-temperature operation is critical.

3.1.5 Superior Electrical & Thermal Conductivity

If you require a metal alloy part with good thermal conductivity, cupronickel is the best metal alloy to consider.

3.1.6 Easy & Cost-effective to Fabricate

Because copper-nickel is highly ductile and comes in different forms and sizes, you will find it easy to fabricate.

 What’s more, the alloy can be easily cold-worked making your fabrication process less costly.

3.2 Disadvantages: 

While Cupronickel boasts a wide range of beneficial properties, it also has some drawbacks that you should be aware of when making your selection  

Let’s find out…

3.2.1 Copper Nickel Alloy is Expensive

You will find cupronickel more expensive compared to other metals like stainless steel. This is partly because copper is difficult to find.

And so, by choosing CuNi alloy for your industry application, you have to dig deeper into your pocket

3.2.2 Difficulty in Getting Suitable Pure Alloy Compositions

The quality of your final CuNi alloy is determined by the purity of your raw materials. 

You may find this a challenge forcing you to take costly precautions during manufacturing. 

3.2.3 Welding  is Demanding

Welding your  Cupronickel alloy fittings is not always easy.  Because of the alloy’s complex nature, you must have the right welding equipment and special consumables. You also require professional welding skills to ensure your joints are precise and durable.

Further, you need to thoroughly clean and dry the surfaces you want to weld to avoid possible contamination or residues that may affect the quality of the welds.

3.2.4 Require Clean Fabrication Environment

Unlike other common metals, nickel-copper alloy requires a much cleaner fabrication surface. This is because it can easily pick up residue or contaminants during the process. 

These can negatively affect the final quality and integrity of your application fittings or components.

4.0 Common Types of Copper-nickel Alloys 

If you are sourcing cupronickel for your industrial applications, you will be amazed by the diverse range of its alloy compositions.

CuNi alloys fall into two major categories namely:

  • Marine CuNi Alloys
  • Non-Marine CuNi  Alloys 

So, the type of CuNi alloy you choose should be guided by your application requirement.

Here are some of the most common types of nickel-copper alloys to consider for your projects:

4.1 Marine Types of Cupronickel Alloys

These CuNi alloys will provide your fittings with superior resistance to corrosion and high strength to suit marine environment applications. 

Some of the most common types are:

4.1.1 Cupronickel 90/10

Composed of 10% nickel and is highly suitable for your marine engineering projects. Supplied as a  wrought cupronickel,  it guarantees high corrosion and biofouling resistance.

When enriched with Iron and manganese, you have a superior CuNil alloy with enhanced resistance to water flow and seawater corrosion.

The alloy is an ideal choice for your marine and other industrial applications such as marine water cooling systems, condenser tubes for power plants, and heat exchangers.

4.1.2  CuNi 70/30

This CuNi alloy is made of 70% copper and 30% nickel. It provides superior strength and a higher water flow resistance compared to copper 90/10!

The alloy is enhanced with manganese and iron for improved corrosion resistance.  You find it commonly used in marine and other industrial sectors.

4.1.3 CuNi 66/30/2/2 

This alloy is an improved type of copper 70/30. It is made of  66% copper with both iron and manganese constituting 2% each. 

The alloy comes in a tube form and is suitable where your application requires excellent resistance to high water flow rates. It is the ideal CuNi alloy type to choose for your power plant’s condenser tubes among other industrial applications.

 4.1.4 CuNi 80/20

This CuNi alloy consists of 20% nickel and is easy to fabricate.  Based on your industry requirements, you can purchase it as a bar, tube, or wire.

With its excellent corrosion resistance,  you will find it suitable for a wide range of marine engineering and electronic applications.

You can use it in the manufacture of condensers and heat exchanger tubes. You can also use its wire in the electronics industry in the production of resistors among others.

4.2 Non-Marine Cupro Nickel Alloys

4.2.1 Cupronickel 55/45

 Also known as constantan or Eureka, the alloy constitutes 55% copper and 45% nickel.

And so, if you are in the manufacture of thermocouples,  resistors, or rheostats,  this is the ideal cupro-nickel alloy wire worth considering. 

4.2.2 CuNi 66/34

Composed of 34% nickel, this CuNi alloy boasts low electrical resistance with excellent corrosion resistance. 

You can use the alloy to manufacture low-temperature heating cables, low-resistance circuit breakers, and low-voltage electrical parts among others.

4.2.3 Copper-nickel 75/25 

This CuNi alloy type is composed of 25% nickel and is extensively used in coinage. 

Because of its durability and cost-effectiveness, you will find also its use in industrial and energy transfer sectors. 

5.0 Applications of Copper-nickel Alloys

Applications of  CuNi alloys generally fall into two major categories of marine and non-marine applications. Let’s dig deeper into some of the alloy applications you ought to know.

5.1 Marine Industry Applications of Copper Nickel Alloy

Use of CuNi in Shipbuilding

Copper nickel alloy is known for its unique thermal and electrical properties, corrosion and biofouling resistance, and strength. You will, therefore, find it useful in different sectors within the marine industry.

5.1.1 Shipbuilding and Repair

Copper-nickel alloys and especially CuNi 90/10 and CuNi 70/30 are commonly used to clad ships or boat hulls.  It is also used in making firefighting components, and seawater cooling systems.

5.1.2 Seawater Condenser | Desalination Plant | Cryogenic Industry

Because of their corrosion resistance and thermal properties, you will find Cupronickel alloys such as CuNi 90/10 and CuNi 70/30  used in the manufacture of seawater condensers and heat exchangers among other fittings. The alloys also find their application in desalination plants where they are used to produce evaporator tubes. 

Because of its excellent ductility, good thermal conductivity, stable performance even under extremely low temperatures, you will CuNi alloys are used as storage boxes for cryogenic fluids

5.1.3 Power Generation Plant & Off-shore Facilities

Another sector where you will find CuNi alloy parts being used is the power generation industry. 

This is because of their efficient heat transfer which makes them suitable for power plant piping systems, heat exchangers, and condensers. 

And so, if you are in the power generation industry, the main CuNi alloys you will find useful for your sector are CuNi 90/10, CuNi 70/30, and CuNi 66/30/2/2

You will also find CuNi alloys useful in offshore oil and gas facilities

5.1.4 Piping Systems

CuNi alloy is widely used in seawater piping systems due to its superior resistance to corrosion and biofouling. You will find this alloy in the form of cupronickel pipes or fitting components.

5.2.1 Coinage Industry

Because cupronickel is highly durable with no-tarnish properties, you will appreciate why its CuNi 66/34 alloy finds its application in the coinage industry.

5.2.2 Electronics Industry

Cupronickel has a significantly low-temperature coefficient of electrical resistivity. And so you will CuNI 55/45 alloy type used in high-precision resistors and thermocouples.

5.2.3 Automotive Industry

Cupronickel is used in the vehicles’ cooling system. It is also used in the brake tubing of cars.

6.0 Different Forms of Copper Nickel Alloy 

As you shop for your Copper Nickel Alloys, you will find them in different forms, sizes, and colors appearances to suit your project needs.In terms of appearance, the more nickel composition your alloy has, the more silvery it will appear.  

Here are some of the most common industrial forms  of copper-nickel alloy in the market:

  • CuNi Bars
  • CuNi Plates
  • CuNi Sheets
  • CuNi Wire
  • CuNi Tubing
  • CuNi Pipes
  • CuNi Coil
  • CuNi Strips
  • CuNi Flanges
  • CuNi Forgings
  • CuNi Balls
  • CuNi Billets

7.0 Tuolian Metal – Copper-nickel Alloy Manufacturer

Are you searching for high-quality CuNi alloy types and forms for your marine, industrial or automotive industry?

Tuolian Metal is a leading manufacturer of a wide range of copper-nickel alloys for your wide range of marine and industry applications.  

The company boasts modern manufacturing technology and technical expertise to respond to your cupronickel industry needs. Do you have questions or inquiries about copper-nickel alloys? 

Contact us today for a Quick response! 

Other Relevant Links:

  • Metal Calculators
  • Monel Metal
  • Cupronickel for Automotive
  • Cupronickel for Marine
  • Cupronickel for Oil & Gas Plants
  • Cupronickel Sheets
  • Cupronickel Tubes

One Stop Stainless Steel Supply.

Whether you need stainless steel materials for your business or fabrication projects, TuoLian is your best supplier. You can find all types, grades, and thicknesses based on your needs. Guaranteed that we provide the best quality at a reasonable cost.
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