Everything You Need to Know About Welding Copper

Picture of welder. Photo courtesy of Alexas_Fotos from Pixabay

Copper is known for its exceptional conductivity and corrosion resistance, which makes it uniquely suited for many applications across various industries.

However, copper also presents some unique challenges due to its high thermal conductivity and susceptibility to oxidation. 

 

Jump to a section: Uses | Types | Safety | Tools and Equipment | Preparation | Techniques | Challenges and Solutions | Post-Welding Process | Tips | FAQs 

 

Uses of Copper Welding

Copper is a metal with very unique properties that make it perfectly suited for many different applications in various industries.

Electrical Industry 

Copper is the preferred material for electrical components like busbars, cables, and electrical connections. Welding copper makes strong, reliable connections in many electrical systems.

Heating and Air 

The high thermal conductivity of copper makes it ideal for use in heat exchangers in HVAC systems, refrigeration units, and industrial machinery. Welding is an essential part of fabrication and repair of heat exchangers. 

Plumbing and Piping Systems 

Copper pipe often appears in plumbing systems due to its corrosion resistance. Welding copper ensures durable, long-lasting, leak-proof connections in plumbing installation.

Aerospace

Copper is widely used in critical aerospace components like heat shields, electrical connectors, and propulsion systems. Welding copper ensures secure welds with the structural rigidity required for aerospace, aviation, and defense applications.

Art 

Copper is also malleable, which helps metal artists create complex designs with strength and precision.

Types of Copper

There are several types and grades of copper, each with distinct characteristics that make them suited to different applications.

Pure Copper 

The most common type is pure copper, which is rated at a minimum of 99.9% copper content. Pure copper is often used in electrical wiring, connectors, and pipes due to its excellent conductivity of both thermal and electrical energy.

Brass 

Brass is copper alloyed with zinc. Easily identifiable by its golden color, brass is used in a wide array of applications — from plumbing fixtures and decorative applications to musical instruments.

Bronze 

Bronze is copper alloyed with tin. Bronze is commonly used in bearings, metal sculptures, and many marine applications due to its high strength and corrosion resistance. 

Copper–Nickel Alloys 

Copper alloyed with nickel is used in coins, many marine applications, and heat exchangers, due to its excellent thermal conductivity, as well as in pipes, due to its high corrosion resistance.  

Safety Precautions

Prior to cutting, fabricating, and welding copper, it is important to address potential hazards and methods of mitigation to ensure welder safety.

Personal Protective Equipment (PPE)

At a minimum, use safety glasses with side shields, a welding hood, and sturdy welding gloves. 

Welders should use a welding jacket or a long-sleeve shirt of either denim, cotton, or canvas cloth material (never polyester or synthetics) to cover any exposed skin. Sturdy leather work boots with safety toes are also recommendable.

Ventilation and Fume Control

Always perform welding operations in a well-ventilated area and avoid breathing in the fumes generated by the welding process. If necessary, use a fume extractor or PAPR hood, such as if working in a confined space where other methods of ventilation are impractical.

Copper Welding Tools and Equipment

Welding Machines

It is possible to weld copper using several different welding processes. However, the power source should be capable of producing a smooth, consistent arc while welding at the required amperages.

TIG Welders 

TIG or GTAW is commonly used for welding copper due to its capability to provide precise control of the welding parameters. 

A good TIG welding machine for welding copper should include high-frequency capabilities to initiate the arc and have high-amperage capabilities to weld thicker sections of copper.

MIG Welders

It is possible to use MIG or GMAW to weld thick sections of copper due to the higher deposition rates that are achievable with the MIG welding process. A MIG welding machine with pulse welding capabilities may prove beneficial in welding copper because it allows for better control of the heat input, lowering the risk of distortion in the workpiece, overheating, and burn-through.

Resistance Spot Welding

Another good option for welding copper alloys, resistance spot welding is often used for joining thin sheets or wires and electrical components.

A resistance spot welding power source should be capable of producing high currents within short amounts of time to create a strong weld.

Oxy-Acetylene Welders

Still a popular choice for welding copper is the OAC (oxy-acetylene) welding process, due to its simplicity, low cost of equipment and set-up, and high degree of operator control. To weld copper with the OAC process, all you need is a set of oxygen and acetylene bottles, torch hose and regulators, and a torch with the right size tip. 

Copper’s high degree of thermal conductivity means it may be necessary to preheat the copper to ensure better weld penetration and minimize the risk of distortion to the workpiece and cracking in the weld.

Laser Welders

Laser welding is often used for welding copper due to the high welding speeds with minimal heat input that offers high production rates with minimal distortion of the base metal.

A laser welding machine should offer high power output with precise control over the laser beam to ensure a consistent, quality weld.

Filler Materials

Deoxidized copper filler rods (typically called ERCu) are common for welding pure copper and copper alloys. These rods are typically made of high-purity copper to ensure metallurgical compatibility with the base metal to make it easier to obtain consistently high-quality welds. 

Silicon bronze filler rods (ERCuSi) are another popular choice for welding copper and copper alloys. These rods contain copper, silicon, and small traces of other elements to produce welds with high ductility and corrosion resistance. 

Many other copper and copper alloy filler rods are available on the market for specific welding applications. There are brass and bronze filler rods for welding different grades of brass and bronze alloys.

Copper filler rods are available for the GTAW, GMAW, and OAC welding processes in various diameters to suit different material thicknesses and specific applications.

Shielding Gas

Argon is the most common shielding gas for welding copper with either the TIG or MIG welding process, due to its low cost and effectiveness. Argon is inert, affordable, and does not react with molten metal.

Helium is used on thicker sections of copper because an arc shielded with helium is hotter and enables deeper penetration and higher travel speeds. 

Protective Gear

With any arc welding process, a welding hood with the proper shade of lens is important to enable the welder to see the molten weld puddle clearly while protecting the welder from the harmful effects of the UV rays emitted by the arc welding process. 

If you will be using the oxy-acetylene welding process, it is fine to wear welding goggles or a face shield with a shade #5 rating.

You should always wear safety glasses with side shields when cutting, welding, or grinding. 

You should also wear sturdy welding gloves with cuffs to protect the hands and wrists from sparks and burns from hot metal.

 Other safety apparel may include:

• Ear plugs
• Welding jacket or long-sleeve shirt of denim or cotton (never polyester or synthetics)
• Steel-toed work boots

Preparation

Workpiece preparation is a critical step in any welding process to ensure consistent, quality welds. Some of the steps to prepare the materials to weld include:

Cleaning

You should clean both the base metal and filler metals to ensure they are free of surface impurities like oil, paint, dirt, and grease that could adversely impact weld quality.

Remove any oxidation observed on the surface of the base metal with a wire brush, sanding pad, or some type of abrasive, either by hand or with the aid of a grinder. 

It’s important to clean filler metals to remove surface oxides. A Scotch-Brite pad is a quick and effective means of cleaning copper filler rods.

Preheating

Copper’s high rate of thermal conductivity means a preheat may help keep the base metal at a relatively uniform temperature, which enables deeper weld penetration, reduces stress from distortion, and minimizes the risk of crack formation. 

Joint Design and Fit-Up

Quality workmanship is often made or lost in the fit-up stage of the welding operation. To ensure a good weld, take the time to ensure the joint is uniform and all pieces to be joined are in firm contact. If you require extra time to fill a gap in the joint due to poor fit-up, the extra heat input from welding in one area for too long may result in the overheating of the workpiece or possibly even burn through.

Copper Welding Techniques

There are several processes available for welding copper. Let’s take a closer look at some of the more common copper welding processes, the special techniques, and some of the advantages and drawbacks of each. 

TIG Welding

Steps and Techniques

1. Clean and prepare the workpiece.
2. Select the correct Tungsten electrode — typically a 2% thoriated Tungsten will maintain a good, steady arc. 
3. Set the machine to the proper parameters, amperage, gas flow, voltage, etc., as per the thickness of the copper base material to be welded and the size of the filler metal. 
4. Keep a steady arc while welding with sufficient amperage to ensure full penetration and complete fusion in the weld joint.

Advantages

• TIG welding offers a high degree of operator control over the welding parameters, such as changing the heat, travel speed, and rate of feed of the filler metal into the weld puddle.
• The TIG welding process produces clean welds that, when performed correctly, require minimal post-weld cleaning.

Disadvantages

• TIG welding may be slow, with lower deposition rates, which may make it a less-than-ideal choice for welding processes with thicker sections of material where higher rates of production are preferred. 
• TIG welding requires a comparatively higher degree of welder skill and experience to make consistent, high-quality welds.

MIG Welding

Steps and Techniques

1. Prepare the workpiece by cleaning the surfaces, making sure you remove any oils, grease, paint, or other potential contaminants.
2. Select the proper welding wire for the specific copper or copper alloy. Choose the diameter best suited for the material thickness and welding position the job will require.
3. Set the welding machine, and adjust the amps, volts, wire feed speed, and shielding gas flow for the material thickness and welding wire.
4. Move the MIG gun in a steady and controlled manner, paying close attention to work and travel angle. Adjust as needed to attain a uniform and symmetrical weld puddle. 
5. Visually inspect the completed weld for defects, such as incomplete fusion, porosity, undercut, and underfilled welds, and repair as necessary. 

Advantages

• MIG welding offers higher deposition rates, which enables the welder to achieve higher rates of production, especially on thicker sections of material.
• MIG welding is a semi-automatic welding process, meaning the wire is fed at a consistent rate into the molten weld puddle. This makes it easier for the welder to maintain a high degree of consistency. 
• The semi-automatic nature of the MIG welding process means it is easier to learn than some other welding processes (like stick and TIG welding, for example), which makes it well-suited for beginner welders.

Disadvantages 

• MIG welding offers minimal operator control, which makes it harder for a welder to adjust for inconsistencies in the weld joint. 
• MIG welding requires more equipment and consumables than some other forms of welding — for example, tips, liners for the MIG gun, nozzles, welding wire, shielding gas, hoses, etc. 

Resistance Spot Welding

Steps and Techniques

1. Prepare the workpiece by ensuring you have removed all surface impurities. 
2. Fit up the pieces to be spot welded by clamping them together firmly, with no gaps between the mating surfaces.
3. Apply the electrodes with firm pressure to the pieces you will be welding.
4. Weld the copper workpieces together by applying the current through the copper base metal at the desired location. The sudden, rapid localized heating will cause the copper to melt and flow at the point of contact, forming a spot weld between the two copper workpieces.
5. Allow the completed weld to cool before performing an inspection.

Advantages

• Resistance spot welding is a fast process, which is ideal for high-volume production applications.
• Resistance spot welding creates a strong and reliable joint. 
• The fact that no filler metal is added to the weld joint means the completed welds are clean and require no post-weld cleaning.
• Ease of use. Resistance spot welding requires only minimal skill and training.

Disadvantages

• Equipment cost is comparatively higher than the equipment for other welding processes.
• Resistance welding is limited in joint configurations, only allowing for simple lap joints.
• Resistance welding is only suited for materials of limited thickness and is not well suited for thick sections of copper. 

Oxy-Acetylene Welding

Steps and Techniques

1. Clean and prep the copper base, taking care to remove any surface impurities and oxidation.
2. Set up the workpieces by securing them in clamps or fixtures.
3. Ignite the welding torch and adjust the flame until you have achieved a neutral or slightly carburizing flame.
4. Preheat the copper base to the required temperature (this may vary depending on the thickness of the material), ensuring the entire workpiece is at a relatively uniform temperature.
5. Direct the inner cone of the flame to the weld joint and apply heat until the base metal is brought to the molten state.
6. Add copper filler at a rate that ensures complete fusion with the copper base metal. Add filler metal until the weld is the required size or depth. 

Advantages 

• Low cost of equipment. Oxy-acetylene welding only requires bottles, regulators, and hoses with a torch, making it significantly more affordable than other welding processes that require more expensive power sources.
• Oxy-acetylene welding is highly portable, which makes it well-suited for remote locations or locations where accessibility is limited.

Disadvantages

• Oxy-acetylene welding requires a higher degree of welding skill and experience to master controlling the heat and adding filler rods to produce quality welds.
• Oxy-acetylene welding is slower than some other common welding processes, making it poorly suited to jobs requiring high rates of production. 

Laser Welding

Steps and Techniques

1. Prepare the copper workpieces to be joined, making sure the surfaces are clean and free of any surface-level contaminants and oxidation that could adversely affect weld quality. 
2. Focus the laser beam onto the weld joint and add the filler metal (if required) into the weld joint. Note that a shielding gas (typically argon, sometimes helium) will protect the weld puddle from atmospheric contamination.             

Advantages

• Laser welding is a fast welding process, with high travel speeds, making it an excellent choice for high-production jobs.
• The high travel speed associated with laser welding means the heat input is minimal, which reduces the risk of distortion in the workpiece.
• Since there is no contact with the copper workpiece in laser welding, there is little to no chance of contamination or damage to the base metal.
• Laser welding is highly versatile and suitable for a wide range of copper thicknesses and weld joints.

Disadvantages

• Laser welding equipment is often significantly more expensive to purchase and maintain, especially in high-powered and certain automated applications, often making it cost-prohibitive for all but large manufacturers.
• Laser welding systems require a significant amount of training and technical expertise to set up and operate.
• Laser welding typically requires a precise fit and is somewhat unforgiving in joint inconsistency, particularly in automated applications.

Common Challenges and Solutions

As with any metal, copper has unique characteristics and, therefore, its own set of challenges to work with.

Porosity

Porosity can occur due to insufficient cleaning before welding or inadequate shielding. Ensure the surface is clean and free of contaminants, and use weld curtains or barriers to protect from wind if welding outdoors. Check the gas flow and connections for leaks to maintain proper shielding.

Distortion

Distortion is common when welding thin copper sections, usually due to excessive heat. To minimize it, weld in small increments at different locations to dissipate heat, or increase the travel speed to reduce heat input.

Cracking

Cracks can result from thermal stress, hydrogen embrittlement, or poor technique. Preheating the workpiece can reduce thermal stress and remove moisture. Ensure proper welding parameters and consider better joint design to prevent cracks.

Weak Welds (caused by incomplete fusion, incomplete penetration, etc.) 

Weak welds can be due to incomplete penetration or fusion. Check that the heat is sufficient for full penetration, and ensure there are no voids in the weld. The weld should be properly sized and filled to handle stress.

Contamination

Contamination often stems from poor cleaning. Ensure both the workpiece and filler metal are clean before welding to avoid defects like porosity and cracking.

Inconsistent Beads

Inconsistent weld size and penetration can weaken the joint. Practice consistent technique or consider using automated processes like MIG welding for better uniformity. 

Post-Welding Process

Now the weld is complete, there are some final steps to take to ensure top-notch workmanship.

Inspecting the Weld

Visually inspect the completed weld at all visible surfaces, looking for any potential defects, like cracks, fusion voids, incomplete penetration (if the root side is still visible), porosity, and underfill. Check the weld is of sufficient size.

If you find any defects, grind out the defective area and re-weld. Don’t forget to preheat prior to performing repairs.

Cleaning the Weld Area

Clean the weld using a wire brush or sanding pad. For processes like MIG welding, remove any splatter with a sanding pad.

Post-Weld Heat Treatment

Apply post-weld heat treatment to relieve stress, eliminate hydrogen embrittlement, and improve weld properties.

Tips and Best Practices

The following items are some good workmanship habits you should practice to achieve optimal results when welding copper. 

Maintaining Equipment

You must clean all welding equipment and keep it well maintained to ensure you produce sound, quality welds consistently. Regular maintenance of welding equipment includes:

• Checking for wear and tear on nozzles, torch tips, hoses, and regulators.
• Checking electrical connections for frayed or burnt and damaged cables.
• Ensuring proper gas flow, if applicable, to the process and checking for leaks in gas hoses and connections.
• Using compressed air to blow dust and dirt out of the power source. 
• Make sure the immediate area where you store the machine keeps it sheltered from dirt, dust, debris, and moisture.

Consistent Heat Application

Preheat the workpiece and maintain a uniform temperature during welding to reduce cracking risk and improve fusion.

Proper Filler Material Selection

Choose the right filler metal based on the base metal's composition, joint design, and required properties. Common options include pure copper, brass, bronze, and some silver alloys.

Controlling Oxidation

Oxidation can affect weld quality. Clean the base metal thoroughly before welding to remove any oxidation and ensure a strong, defect-free weld. 

FAQ

What is the most common process for welding copper?

TIG welding is commonly used for copper and its alloys because it produces precise, high-quality welds with minimal heat input. Oxy-acetylene welding is also popular due to its low equipment cost and portability, making it ideal for hard-to-reach areas.

Why is preheating so important in welding copper?

Copper's high thermal conductivity can cause rapid cooling and high thermal stress. Preheating slows the cooling rate, reduces stress, and helps achieve complete fusion between base and filler metals.

What are the best ways to prevent oxidation in copper?

To prevent oxidation, start by thoroughly cleaning the copper using a wire brush, sanding pad, or an abrasive tool. For larger workpieces, use a wire wheel or abrasive disk. If you're using MIG or TIG welding, ensure proper shielding gas (usually argon) is used to protect the weld from oxygen.

Featured photo courtesy of  D-Vu // Pixabay