How To Weld Copper: The Best Techniques

You have to adapt when it comes to welding different types of metal. Welding copper, for example, requires a whole new technique. It can be joined using soldering, but for this article, we are going to focus on welding.

So what is the best way to weld copper?

Properties of Copper and Its Alloys

When working on a job-site, you need to know that the material you are using is fit for the job. Copper has many properties that make it an ideal metal to use, especially if you are welding copper tubing with a large or small diameter.

High Thermal Conductivity

Copper is 8 times more efficient at conducting heat than other metals. When you compare it to aluminum and steel, it conducts heat much better. However, copper welds need to be hot and fast, because while it heats quickly, temperatures dissipate rapidly. It requires twice the heat compared to steel.

Relatively Low Melting Point

Copper has a melting point of 1,083 degrees Celsius (1,984 degrees Fahrenheit), which is high compared to some alloys but compared to carbon steel and other metals, it melts faster. Copper is easy to melt, which is why it is widely used.

High Ductility

Copper can easily form into various shapes, making it the ideal material for tubing in plumbing and air conditioning systems. It can be shaped on-site with relative ease. Thanks to its formability, you can often eliminate elbows and joints in your pipework, making the installation much more robust. To put it simply, there are fewer places to spring a leak.

The only consideration is if you are welding thinner material that needs to maintain its shape, TIG welders might not be the best machine to achieve this.

Noncombustible

Copper will not burn, nor will it decompose and release toxic gasses. You can rely on copper to maintain its shape, structure, and integrity even when you embed it into concrete.

Variety of Applications

Copper has so many applications, from underground water and gas services to oxygen systems.

• Water distribution systems.
• Air conditioning systems.
• Gas furnaces.
• Chilled water mains.
• Refrigerators.
• Heating systems, including solar.
• Fuel-oil systems.
• Non-flammable medical gas systems.

Reliability

Copper is renowned for its reliability in several uses. It is good engineering practice to stick with one material for a mechanical system, and copper is that material of choice. From plumbing to heating and beyond, copper is in demand.

It’s the reason why it is so popular with the heating and cooling industry.

Long-Lasting and Maintenance Free

Copper doesn’t corrode, so it lasts for years, even when placed in inhospitable environments. It never requires painting and natural reactions form over time to protect the integrity of the copper, especially copper tubing.

It complies with all principle building codes for reliability and safety, and copper never transmits fire, reducing the spread of flames.

Copper Is Abundant

The US has plentiful supplies of copper waiting to be mined. It is abundant. That said, almost half the copper in the US comes from recycled scrap material, which is probably why it is so plentiful ⁽¹⁾.

Recycled copper is as usable as virgin copper mined from ore. This recycling and careful management of the natural ore will keep the US self-sufficient in copper stocks for years to come.

Methods of Joining Copper To Copper or To Copper Alloys

There are various ways you can join copper to copper or copper alloys. Determining which method you use is a balance between strength and maximum temperature. Here are the 3 options you have.

Soldering

Soldering differs from welding because you don’t melt the base metal to make the seal; you use a third material called solder, primarily a mix of mostly tin and nickel. This metal melts at 840 degrees Fahrenheit and is applied to the joint, causing it to harden when it cools, forming a strong airtight bond between the two copper pieces.

If you want the strongest joints, silver is the best material to use. The amount of silver in solder metal varies from 15 to 30 percent, and the higher the silver content, the better the joint.

Solder with a higher silver quantity will cost you more, but you also get a higher tensile strength. Another advantage of soldering is the lower heat requirement, which saves the copper pipe from oxidizing on the inside. It saves you having to use nitrogen to purge your pipework.

You would use the soldering method when you are working on thinner material that requires less heat. HVAC units often call for soldering because you are working close to plastic couplings and rubber bushes. Soldering operates at far lower temperatures compared to welding. It is kinder to the base material and easier to control for more detailed work.

Brazing

Brazing is the same method as soldering and involves the same materials and principles. Where it differs is in the temperatures required to melt the solder. Unlike soldering, the filler metal in brazing melts above 840 degrees Fahrenheit, meaning that the increased heat creates a stronger seal.

Brazing is a bit like industrial-strength soldering and is more effective when used with thicker copper. You can minimize the risk of oxidizing the copper by running a mix of neutral nitrogen through the pipework while you are brazing. This removes any oxygen.

Brazing is also better for bridging larger gaps compared to soldering and welding.

Welding

Welding melts the base metal as well as a filler material to create robust joints. Because of the extreme heat involved, welding is the best way to ensure the strongest tensile joint. The cost of materials increases with each method, making welding the most expensive option.

The two most common welding styles for copper are MIG and TIG. MIG welding is easier to master, but less precise. It also limits you on the thickness of the copper you can work with. TIG welding is more accurate and penetrates deeper for thicker material, but it is infinitely harder to master. It requires two hands, so the welder machine is typically controlled using a foot pedal.

Welding is the most industrial form of joining copper pieces and best reserved for the thickest material where a high tensile weld is most needed. You wouldn’t want to use a welder to repair a HVAC or refrigeration unit due to the delicate nature of the mechanics and the extreme heat involved with the process.

Also, welding is the most dangerous to undertake, requiring expensive specialist equipment to protect you from harm.

How To TIG Weld Copper

Follow our simple step-by-step guide to TIG welding copper.

1. Take Precautions

Whenever you undertake a dangerous pursuit, you should always protect yourself. What you need is the following:

• Safety goggles.
• Safety helmet.
• Protective welding jacket to protect you from flash and arc fire.
• Flame-resistant welding gloves. Leather is one of the best materials for protection.
• Heavy-duty work boots with protective toe-caps.
• Welding respirator if working indoors.
• Fire extinguisher.

This is not a wish list of protective items. It should be the number one priority and the first thing you should think about before welding. It’s the reason we made it the first point in our guide.

2. Work in a Ventilated Area

Wherever possible, you should work in a ventilated area. If you struggle to do this, you should take precautions and wear an N95 face mask. These differ from ordinary face masks because they remove 95 percent of all pollutants, which means you protect your lungs.

Brass has a high zinc content, so avoid it where possible. Zinc fumes are noxious and can give you flu-like symptoms. At best, the effects pass, but prolonged exposure could lead to permanent health issues.

3. Electricity Kills

Avoid electric shocks. It kills lots of people every year and is entirely avoidable. Make sure you wear insulated boots and inspect your gloves to make sure they have no holes. Welding equipment should be adequately grounded and never left switched on. Always disconnect the power when the welder is off to avoid accidents.

Also, make sure that the conditions are dry. Welding in damp conditions can be deadly.

4. Choose the Right Copper

Try and choose copper that is clean and unpainted. Paint and other surfaces can produce poisonous fumes, especially if the paint is lead-based. If you must do this, always wear a respirator.

The best course of action is to clean the copper as best you can. Try and choose oxygen-free copper. It helps to protect the copper from oxidation, and it will keep its color after welding. The good news is that oxygen-free copper is the most commonly available.

5. Avoid Alloys

Alloys can be welded, but they react differently depending on their ingredients. Only experienced welders should weld with copper alloys. Zinc-based copper alloys reduce weldability and also boil at lower temperatures, producing toxic gasses that can cause long-term health defects.

6. Get the Ratios Right

Gas ratios and temperatures vary on the style of welding and the thickness of the material. If the copper is under 2 mm, you should use argon gas and 160 amps. For thicker copper, up the amps and add helium to the gas mix.

7. Make Sure You Preheat

Thanks to copper’s high thermal conductivity, preheating is necessary. Preheating can range in temperature from 50 degrees Fahrenheit to over 700 degrees Fahrenheit, depending on the thickness of the metal.

Insert the copper into a furnace until the right temperature is reached. Alternatively, you can use a blowtorch. Preheating helps the copper to cool steadily and reduces cracking.

8. Put on Your Safety Gear

Now is the best time to put on your safety gear. You are ready to initiate the arc.

9. Initiate the Arc

Hold the arc steady for a few seconds until the puddle forms. Keep the torch at about 70 degrees from the base metal.

10. Add Filler

Now the puddle has appeared, prod the filler into the pool of molten metal. As the filler melts, it mixes with the two melted coppers and forms a seal as it cools.

11. Be Quick

If the puddle lingers for too long, it increases the risk of the copper oxidizing. This prevents a clean weld, so be quick with the welding.

12. Slow the Cooling Process

Speeding the cooling process increases the risk of cracking and weakens the weld. When it comes to cooling, the slower the better. The longer the weld reduces in temperature, the higher the tensile strength of the joint. It’s a bit like allowing a steak to rest after cooking.

This is where preheating helps to maintain the integrity of the metal. If you are indoor welding, air-cooling is acceptable. Avoid splashing water on the weld. Moisture weakens the weld and could increase oxidation.

Once you finish, turn the welder off and unplug at the wall. If it is safe, remove your safety gear. Don’t try and pick up the copper unless you are sure it has cooled completely.

Top Tips for Welding Copper

Add Helium

If the welding isn’t smooth, up the helium to 100 percent. It has a higher power than argon and allows you to apply higher heat values to the copper.

Protect Your Feet

Use metatarsal guards over your laces to protect your upper foot and ankle from falling objects. Also, make sure your boots are insulated to reduce instances of electric shock.

Stay Dry

Wet clothes increase the chances of electric shocks and rising moisture levels will compromise your weld’s integrity. Wear dry clothes and avoid moisture, even perspiration.

Insulate the Copper

If you are welding in cold conditions, insulation for the welded metal might stop it from cracking. Fiberglass blankets are the easiest way to stop the copper cooling rapidly. You could also stack sandbags around the copper to help it cool slowly.

Welding Copper FAQs

Can I Weld Copper With a Mig Welder?

You can use a MIG welder to weld copper. Using a silicon bronze welding wire makes joining the copper easier. You can also polish out the yellowish color to match the copper color for an invisible join.

Do You Weld or Solder Copper?

You can solder and braze copper. It needs a filler material like tin or silver-based solder, but the process differs from welding because the filler melts and not the base metal. With welding, the base metals are also melted to create a stronger joint.

How Do You Weld Thin Copper?

You use a technique called spot welding. Spot welding reduces prolonged contact with the sheet copper which minimizes distortion and overheating. While copper has a melting temperature of over 1,800 degrees Fahrenheit, the sheet material is more prone to warping.

Can Copper Be Spot Welded?

You need to select a class 13 or 14 electrodes. Pure tungsten electrodes are the most commonly used.

Is Copper Easy to Weld?

Copper is easier to weld than other materials, but it’s not easier to work with. The best method for welding stainless steel is to preheat the surface to prevent cracking.

The trickiest thing about welding copper is its high thermal conductivity. This means your copper surface will heat up quickly, so you must work fast before the temperature dissipates.

Welding copper means working fast and at high temperatures since it needs double the amount of heat compared to steel materials.

But copper melts relatively fast, which can be considered an advantage when you have to weld it.

What Type of Welding Is Used for Copper?

The best way to get good results when welding copper is to use MIG or TIG welding, with the latter being the superior option. The exact steps for TIG welding copper can differ based on the copper used.

When you work with copper thinner than 2 mm, you need 160 amps of power and argon gas. If your copper is thicker than 2 mm, use helium alongside argon.

How Do You Clean Copper Before Welding?

Cleaning copper before welding is easy and doesn’t require a lot of materials. You must ensure the copper has no paint residue, dirt, debris, oil, or grease on its surface.

These could release toxic fumes when in contact with the high welder temperatures, so you have to get them out of the way.

The simplest way to do so is to use a bronze wire brush and scrub the surface of the copper. You can also use degreasing agents to eliminate potential chemicals and oils. Keep the brush handy and use it even after each deposited weld run.

Can I Weld Copper to Steel?

You can weld copper to steel, even if these materials have different and unique properties. This brings up potential problems, especially once you understand that copper has a higher thermal conductivity.

Is Welding Copper Toxic?

According to the CDC, being exposed to copper fumes can cause metal fume fever. If you have it, you will experience nausea, a metallic taste, and irritation of your upper respiratory tract.

You can prevent this by using a respirator when welding copper. An N95 mask should avoid any potential inhaling of copper fumes, thus allowing you to work in an environment that’s not detrimental to your health. Remember to ensure proper ventilation of your working space.

Why We Love Copper

Copper is a great material to weld with. It is versatile, formable, easy to work with, and it doesn’t corrode. It’s the reason why copper is always in demand, both as a building material and as an HVAC and refrigeration stalwart.

But that doesn’t mean that copper is easy to weld. Far from it! It takes skill, the right temperature and gas mix, and the right choice of copper.