A material with great conducting properties, copper has a wide range of applications. A major reason for this is that copper is a good conductor of both heat and electricity. However, this can sometimes make it hard to weld copper.
Copper ore was the first one successfully smelted some five-thousand years ago. Today, copper is the metal that is holding our world together. Okay, maybe that is a bit of an exaggeration. However, the point is that copper is an incredibly important metal with many applications so learning how to weld copper is in your interest.
The importance of copper can be gauged from its global demand. According to Freedonia, the global demand for copper is expected to increase by 4.2% during the current year to reach 36 million metric tons, valued at over $260 billion. Freedonia also expects India to become the fastest-growing market for copper by the end of the year with China being a close second. As for the United States, the advances in construction spending are likely to increase the demand for copper in the country.
It isn’t just Freedonia that expects the demand for copper to grow in the future; McKinsey also expects the same to happen. According to a report published in Forbes, demand for copper is expected to grow from 23.6 million tons in 2018 to just 30 million tons by 2027.
From the above, it is clear that Copper is a highly sought-after metal today. There are several reasons for this including the metal’s thermal and electrical conductivity, malleability, high ductility, and resistance to corrosion. Considering the importance of the metal and its wide applications, you need to learn how to weld copper. We will be teaching you that here.
The Different Methods for Welding Copper
Copper can be welded via several methods. However, we’re only going to discuss the most common techniques in this article about teaching how to weld copper. These include Gas Metal Arc Welding (GMAW), Gas tungsten Arc Welding (GTAW), and Manual Metal Arc Welding (MMAW). Following is an explanation of each.
Gas Metal Arc Welding (GMAW)
Also called MIG welding, Gas Metal Arc Welding (GMAW) follows the SMAW system for welding. This means that the filler material used in this welding technique is an electrode. However, there is a difference between the two methods; while a series of short rods are used by SMAW as the consumable electrode, the GMAW method automatically feeds a continuous ‘wire’ to the welding torch at a speed defined by the user. Additionally, there is a regulated setting for feeding the shielding gas.
When using the GMAW method to weld copper, it is recommended that you use ERCu copper electrodes. The use of Aufhauser Deoxidized Copper is also recommended; this is a copper alloy or filler material with a 985 purity. The thickness of the copper section that you need to weld will determine the gas mixture needed. Generally, argon is used for thickness up to 6mm. For thickness that exceeds this, a mixture of helium and argon is used. In the GMAW method for welding copper, you need to deposit the filler metal with narrow weave or stringer beads; this can be done using spray transfer.
Gas Tungsten Arc Welding (GTAW)
Also called TIG welding, Gas Tungsten Arc Welding (GTAW) welds copper in a way similar to most arc welding processes; this means that GTAW involves the use of electric arc for heating and melting both the copper piece being and the filler material.
As the molted weld pool cools and solidifies, it is protected from atmospheric effects by introducing a shielding gas such as argon or helium at the torch’s tip. While GTAW is similar to many arc welding processes, it does not weld like arc welding methods that pass the electric arc to the copper being weld using consumable electrodes.
Instead, GTAW uses a non-consumable electrode to create a weld joint between the workpieces; it can do this with or without filler material. Also, in many other arc welding methods, the filler material is used as the electrode carrying the electric arc to the copper being weld. However, separate filler wire is used in the Gas Tungsten Arc Welding method. Also, it isn’t at all necessary to introduce a filler material while the GTAW method is used to weld copper.
The GTAW methods can successfully weld copper pieces with a thickness of up to 16mm. The filler wired recommended for this method is any metal having a composition similar to the base metal. Argon shielding gas is preferred for copper sections with a thickness of up to 1.6mm. For workpieces that exceed this level of thickness, a mixture of helium and argon is used.
When compared to argon, a mixture of helium and argon allows higher travel speeds and deeper perforation at a similar welding current. To provide the copper piece being weld with helium’s good perforation characteristics together with argon’s arc stability properties, the mixture commonly used is 25%Ar/75% He. Lastly, forehand welding is recommended when performing this method on a piece of copper with narrow weave or stringer beads.
Manual Metal Arc Welding (MMAW)
This method is mainly used to perform repair or maintenance welding on copper and copper alloys. The filler material recommended for this is method is ECuSn-C electrode. Another recommendation is using Direct Current electrode positive (DC+) with a stringer bead technique. When this filler material is used, the MMAW method can help in the following:
- Welding copper to other metals
- Small repair of thin copper pieces
- Weld joints with restricted access
These are the three most common methods used to weld copper. Now that you have basic information on each method, you can pick a technique/method that is most suited to your needs and the job being performed. However, regardless of the method you choose to weld copper, you need to follow some basic steps to produce an effective weld. We discuss these steps in the next section.
The Key Steps in Welding Copper
When welding copper on your own, you need to know the critical steps involved in effectively welding copper. There are 11 steps involved in DIY copper welding. By performing these steps in the following order, you will be able to produce an extremely durable copper weld.
When looking to weld copper on your own, the first thing that you need to do is ensure your safety. No matter what metal you’re welding, you need to take proper precautions before you start welding. Failure to do so can put you at the risk of injury.
So, what are the possible precautions you can take before you start welding copper? You need to put on safety gear, ensure there’s no flammable item around you, and work in a clean area or area free from foreign materials. Taking safety precautions is especially important when welding copper; this is because copper is an extremely good conductor of electricity and you can get an electric shock if you handle the metal with bare hands.
In addition to the risk of an electric shock, welding copper can expose you to toxic gases. So, you shouldn’t stop at leather gloves and safety garments to ensure your safety when welding copper. Instead, you should include a respirator mask and eye protection in your safety gear as well.
Prepare the Surface
Surface preparation for welding copper means keeping the weld area free of grease, oil, paint, dirt, and other foreign particles before you start to weld. Why do you need to keep the weld area free of these particles? Because the weld can crack if they get mixed in with the metal. Additionally, they may contain harmful chemicals such as sulfur, phosphorus, and lead.
In addition to the weld area, you should clean the copper as well before you start to weld. How can you clean the weld area and the copper? With a bronze wire brush and an appropriate cleaning agent. First wire brush with then de-grease using the cleaning agent. Also, make sure to remove the oxide film that forms during welding with a wire brush after depositing each weld run.
Why is it important to preheat copper before you can start welding? Because this metal has high thermal conductivity. This is especially important if the thickness of the copper metal is more than 0.01 inch. You should preheat all segments that needed to be welded uniformly.
Since copper can conduct heat rapidly from the weld joint into the base metal surrounding it, a high preheat is required to weld the thick copper sections. The temperature will depend on the metal’s thickness and can range between 50° to 752° F.
However, if you’re welding copper alloy, then you can skip this section because the thermal diffusivity, in this case, is much lower compared to copper. In case you are welding copper and not copper alloy, you need to select the appropriate preheat for your application. You must pay special attention to the copper being welder, its base metal thickness, the welding process, and even the weldment’s overall mass.
In addition to the above, another important thing to do is restrict the heat to a localized area as much as you can; this will help you to ensure that not too much of the material is in a temperature range that leads to a loss in ductility. Moreover, you should maintain the preheat temperature until the joint has been welded. After you start to weld, the heat of the preheated copper starts to dissipate, and this lowers the risk of cracking.
Considering Joint Design
Another important step in welding copper effectively is a joint design consideration. What does this entail? Firstly, you need to consider the distance between the joints. Ideally, you should control this distance to within certain tolerances based in the parent metal and the brazing alloy used. However, the optimum gap for joints is between 0.04 and 0.20mm.
Another important consideration here is a joint overlap. The ideal joint overlap will at least three times thicker than the thinnest part that you need to join. You should try to use as less material as possible since this will help you to achieve the desired strength.
Adjust the Flame
If you want to produce an effective copper weld, then you must adjust the flame appropriately. The best thing to do here would be to use a neutral flame. What does a neutral flame mean? A neutral flame is a flame adjusted to allow the same amounts of acetylene and oxygen to mix at the same rate. Another critical thing to do here is clearly defining the white inner cone and ensuring there is no haze.
Remove the Flux
You must remove the residue in one of the following ways if the flux has been used:
- Brushing with wire and steaming
- Brushing with wire and using hot water to rinse
- Diluting in hot caustic soda dip
If you fail to completely remove the flux, then this may lead to the weakening and even failure of the joint.
Choose Filler Material
Choosing the right filler material is one of the most critical steps in welding copper effectively. Choosing the right filler material helps in welding a copper piece that is stronger than the base metal. The best or most suitable filler material for welding copper will depend on the metal’s resistance to corrosion, how much strength you required in the joint, the operating temperature, and the costs involved.
For the best results, you should choose a filler metal with Silicon (Si) or Manganese (Mn) content acting as a deoxidant. This is regardless of whether you’re using the GMAW, the GTAW, or MMAW method for welding copper.
When it comes to filler materials for welding copper, the most recommended and commonly used materials are ErCu and ErCuSi-A. The former facilitates fluidity as it contains both Si and Mn with Tin (Sn). On the other hand, you should go for ErCuSi-A filler material if you want to weld P-oxidized copper; it is also a good option for when welding hard-pitch copper that contains both Si and MN as deoxidants.
Choose an Appropriate Shielding Gas
Another key step in welding copper effectively is choosing an appropriate shielding gas for the weld. What options do you have? Generally, the most suitable shielding gases for welding copper are Helium, Argon, or a mixture of both.
Which shielding gas among these is the most appropriate for you will depend on the thickness of the piece you’re working on. Having said that, a shielding gas that is being increasingly used today for welding copper is 100% Helium gas. So, you want to go for this option over the others.
Choose a Welding Technique
We’ve already gone through the three main techniques/method used to weld copper. Based on the information provided above, you need to pick a welding technique that is best suited to welding job at hand. In other words, you need to choose a welding technique that is most suitable for your filler material and application.
Ensure Proper Use of Heat and Gas When Welding
If you use the GTAW method to weld copper with a thickness of less than 2mm, then the shielding gas you should use is Argon; you should use this shielding gas with a current 160 amps. However, you should increase the level of current with an increase in the thickness of the metal. Also, the preferred shielding gas and preheating temperature changes with the welding method.
For example, if you use the GTAW method to weld copper having a thickness of 0.196-inch, then the preheat temperature you need to maintain is 50°C while using a mix of helium and argon with a current of up to 300 amps.
On the other hand, you need maintain a preheat temperature between 10 and 100°Cwhile using argon as the shielding gas with a current of 240 amps if you use the gas metal arc welding (GMAW) to weld copper.
If you’re looking for better results and faster welding, then we would recommend you to for 100% Helium. This shielding gas will produce better heat levels and better weld quality than any other gas whether you’re using the GMAW, GTAW, or MMAW method.
Use the Right Position
The eleventh and final step in welding copper effectively is using the right position to weld. When it comes to welding copper, the best position is a horizontal seam or down-hand. This makes it easier to weld copper as less skill is needed to perform the job.
As seen above, there are several different methods and procedures involved in the welding of copper. You must understand each method and procedure thoroughly to produce an effective copper weld which is the ultimate aim.