Copper and copper alloy welding
Copper and its alloys have been of great technical and social importance for almost 6,000 years. Today, copper is the metal of the energy transition, powering renewable systems, improving energy efficiency, and offering infinite recyclability as a sustainable material. However, welding this "material of choice" requires specific metallurgical knowledge.
When welding pure copper, it is imperative that the material is oxygen-free. While these copper grades are typically deoxidized with phosphorus, even a low phosphorus content can negatively impact electrical conductivity. Therefore, for electrotechnical parts intended for welding, SE-Cu deoxidized with elements such as lithium or boron should be used instead.
The excellent thermal conductivity of copper necessitates high preheating temperatures and a concentrated, intense heat input during the welding process. Together with its more than 400 alloys, copper remains the material of choice for many innovative developments in modern life. This includes critical applications in industrial engineering, energy technology, architecture, and information and communication technology.
The family of copper alloys is huge, ranging from brass and bronze to complex copper-nickel compositions. Because these materials are used globally, they are categorized under different international standards, such as the European EN (using CW/CC prefixes) and the American UNS systems.
To provide you with the most up-to-date and comprehensive overview of these alloy classifications and their corresponding welding consumables, we have compiled a detailed database.
The European standard system uses the prefix “CW” for wrought alloys (such as sheets, bars, or wires) and the prefix “CC” for cast alloys. This is followed by three digits and a letter (e.g., ‘CW004A’ or “CW008A”).
System CEN/TC 133 - Materials as well as other, non-standardized materials. However, the numbers have been assigned in advance in such a way as to avoid confusion with CEN materials as far as possible. This means that not every material subgroup begins with the number “1”. For example, copper alloys begin with 001, but various copper alloys begin with 100, copper-aluminum alloys with 300, copper-zinc alloys with 500, etc., as shown in Table.
| material groups | Number ranges for items 3, 4, and 5 |
Material group identifier |
Number range for materials preferred by CEN |
|---|---|---|---|
| Copper | 001-999 | A | 001-049A |
| 001-999 | B | 050-099B | |
| Cu + max 5% alloying elements |
001-999 | C | 100-149 °C |
| 001-999 | D | 150-199 D | |
| Cu + more than 5% alloying elements |
001-999 | E | 200-249 E |
| 001-999 | F | 250-299 °F | |
| copper-aluminium alloys |
001-999 | G | 300-349G |
| copper-nickel alloys | 001-999 | H | 350-399H |
| Copper-nickel-zinc alloys |
001-999 | J | 400-449J |
| Copper-tin alloys | 001-999 | K | 459-499K |
| Copper-zinc alloys, binary |
001-999 | L | 500-549L |
| 001-999 | M | 550-599 Mio. | |
| Copper-zinc-lead alloys |
001-999 | N | 600-649N |
| 001-999 | P | 650-699P | |
| Copper-zinc alloys, complex |
001-999 | R | 700-749R |
| 750-799S | |||
| Copper materials that are not standardized by CEN/TC 133 |
800-999 | ALS* | 800-999* |
System: The Unified Numbering System (UNS) is a system established in the USA. For copper and copper alloys, the prefix C (for “copper”) is used, followed by five digits (e.g., C10100 or C11000).
Unified Numbering System (UNS) Alloy Designations
Wrought Copper Alloy Families
- C100xx-C150xx Commercially Pure Cu
- C151xx-C199xx Age Hardenable Cu (w/ Cd, Be, Cr, Fe)
- C2xxxx Cu-Zn alloys – Brasses
- C3xxxx Cu-Zn-Pb alloys – Lead (Plumb) brasses
- C4xxxx Cu-Zn-Sn alloys – Tin bronzes
- C5xxxx Cu-Sn and Cu-Sn-Pb Phosphor bronze alloys
- C6xxxx Cu-Al and Cu-Si Bronzes
- C7xxxx Cu-Ni Copper Nickel and Cu-Ni-Zn Nickel Silver
Cast Copper Alloy Families
- C800xx-C811xx Commercially Pure Coppers
- C813xx-C828xx 95-99% Copper
- C833xx-C899xx Cu-Zn alloys containing Sn, Pb, Mn, or Si
- C9xxxx Other alloys, including tin bronze, aluminum bronze, copper nickel
| Material | EN Number | UNS Number |
| CuBe2 | CW101C | C17200 |
| CuCo1NiBe | CW103C | - |
| CuCo2Be | CW104C | C17500 |
| CuCr1 / CuCr1-C | CW105C / CC104C | C18200 / C181500 |
| CuCr1Zr | CW106C | C18150 |
| CuFe2P | CW107C | C19400 |
| CuNi1P | CW108C | C19000 |
| CuNi1Si | CW109C | C19010 |
| CuNi2Be | CW110C | C17510 |
| CuNi2Si | CW111C | C70260 |
| CuNi3Si1 | CW112C | C70250 |
| CuZr | CW120C | C15000 |
| Material | EN Number | UNS Number |
| CuAG0.1 | CW013A | C11600 |
| CuMg0.4 | CW128C | C18665 |
| CuPb1P | CW113C | C18700 |
| CuSP | CW114C | C14700 |
| CuSi1 | CW115C | C65100 |
| CuSi3Mn1 | CW116C | C65500 |
| CuSn0.15 | CW117C | C14410 |
| CuTeP | CW118C | C14500 |
| CuZn0.5 | CW119C | - |
Brass:
Brass alloys contain zinc (Zn) as the primary alloying element, along with at least 50 per cent copper. Other alloying elements may also be present. For instance, lead-containing alloys must not be welded, as lead evaporation is harmful to health.
In principle, arc welding of these Cu-Zn alloys is not possible because zinc evaporates easily. The concentrated heat generated during this process can lead to the weld pool overheating, causing the partial pressure of zinc to rise above 1 atm (101.325 kPa). This can result in high porosity, which reduces the strength of the weld seam. It is also dangerous for the welder.
Therefore, oxyacetylene welding is the only recommended method for welding brass. Filler metals containing aluminium (Al) or silicon (Si) have proven to be suitable, and welding should be carried out with an excess of oxygen.
Bronze:
Historically, bronze is a collective term for a variety of copper alloys.
In a precise technical sense, the term bronze is used exclusively for copper-tin alloys (CuSn).
It was copper-tin alloys that gave the Bronze Age its name.
In metallurgy, the term is now only used in conjunction with the main alloying element: it then refers to antimony bronze, arsenic bronze, aluminum bronze, lead bronze, or manganese bronze. Phosphorus bronze is also a tin bronze, but the phosphorus content in the metal is low.
Tin bronzes are standardized copper-tin alloys that are essentially divided into two categories based on their different requirements and properties:
- Wrought alloys (max. 9% tin) are suitable for forming processes.
- Casting alloys (9% to 13% tin) are suitable for foundry work.
- Special case are Bell bronzes containing around 20% (maximum 22%) tin.
Unalloyed copper is single-phase and can be work-hardened by forming. Most copper alloys are also single-phase, depending on the quantity of alloying elements. They can also be work-hardened if ductility is sufficient.
By adding elements such as Cr, Ni with Si or P or Sn, Be, Co, etc., copper material can be precipitation hardened.
Similar to steel, a thermally influenced area, the heat-affected zone, is created in copper materials by the application of heat in addition to the weld zone.
The resulting grain coarsening and the width of this zone depend on the level of heat input and the preheating temperature. In materials with a Face-Centered Cubic (FCC) lattice or structure (e.g. pure copper), the grain growth is lower, since these metals are thermally more stable than materials with a Body-Centered Cubic (BCC) lattice.
Heating and cooling can produce undesirable microstructures.
The following materials are susceptible to this:
- Materials with impurities that form low-melting phases or embrittling precipitates,
- Precipitation hardening materials,
- Alloys with a large solidification interval, which have crystal-segregated areas after welding.
- Plumb (Pb) (Lead) improves fluidity but reduces tensile strength and ductility, so even small amounts are harmful as these alloys tend to be brittle when hot
- Nickel (Ni) increases toughness while maintaining strength and ensures that strength is less dependent on the wall thickness of the casting. Nickel also makes casting alloys more corrosion resistant.
- iron (Fe) in small quantities improves the hardenability of wrought alloys and produces a finer grain.
- Copper-tin-zinc (red brass) Zinc additives are very important for copper-tin casting alloys. Many of these alloys contain zinc as a third alloying element and make up the group of copper-tin-zinc casting alloys (red brass).
- Copper-tin-Plumb (cast tin-plumb bronzes) The lead content in copper-tin-lead casting alloys is usually much higher than that of tin. Strength and elongation decrease slightly with lead additions above 1.5%.
- Copper-tin-nickel (~nickel silver) Copper-tin and copper-tin-zinc casting alloys occasionally contain nickel as an alloying element. Nickel contents of up to approx. 2.5% improve toughness while maintaining approximately the same strength properties and reduce the dependence of strength on wall thickness (wall thickness influence). They also increase the corrosion resistance of the casting alloys.
- Copper-tin-phosphorus Small amounts of phosphorus are added to achieve deoxidation of the copper-tin melt and prevent the formation of tin oxide.
- Copper aluminum CuAl alloys contain Al as the main alloying additive (two-component alloys) and often other alloying elements such as Fe, Ni, Sn, and Mn (multi-component alloys).
Two-component alloys are generally more suitable for welding than multi-component alloys.
Material properties relevant to welding.
In terms of their physical properties, copper materials are just as easy to weld as steel materials. However, one disadvantage is the general tendency of non-ferrous metals to absorb atmospheric gases during welding. This impairs the mechanical and technological quality of the weld seam. Therefore, all areas where temperatures exceeding 600 K occur during welding must be protected from air ingress using inert shielding gases (fusion welding process) or other suitable measures (e.g., coatings in resistance welding processes).
Other properties important for the welding of copper are thermal conductivity and thermal expansion. Compared to unalloyed steel, pure copper has
- approximately 6 times higher thermal conductivity at room temperature and 15 times higher at 1000 °C,
- 1.4 times higher thermal expansion
- approximately twice as much shrinkage during solidification.
The high thermal conductivity means that a large part of the welding energy introduced is dissipated into the surrounding base material. The dissipated energy is not available for melting the base material.
There are numerous processes available for welding copper materials.
Due to the high thermal conductivity of unalloyed and low-alloy copper materials in particular, either processes with a high energy density, such as laser or electron beam welding, should be used, or the workpieces should be preheated. The preheating temperature depends on the conductivity of the material and the size of the component. Fluxes can be used to produce clean, flawless weld seams and to protect the root side. They are applied to the workpiece surface before welding, dissolve the existing oxide layers during heating, and prevent new ones from forming. Fluxes are usually paste-like and consist of boron compounds with additives of oxide-dissolving metal salts.
Special fluoride-containing fluxes are used for CuAl alloys. Special fluoride-containing fluxes are used for CuAl alloys.
Their use is limited to conventional fusion welding processes such as oxyacetylene, manual arc, and TIG welding. Fluxes must always be used for gas and manual arc welding. However, fluxes are rarely used for TIG welding and are no longer used at all for MIG welding, even though they are generally recommended for gas-shielded welding. When working with high preheating temperatures (from approx. 300 °C), they should be used to protect the edges of the weld flanks. For multi-layer welds (sheet thickness > 10 mm), it is advantageous to apply a thin coat of flux to the filler materials as well.
The surface-cleaning effect of the flux can be enhanced or even replaced by the use of the arc. When welding copper alloys containing aluminum, attaching the electrode to the positive pole cleans the surface of the dense, firmly adhering Al oxide layers. With this technique, the electrode is subjected to high thermal stress due to the high speed of the impacting electrons, which is why alternating current is usually used. The negative current components reduce the thermal stress on the electrode, while the desired cleaning effect takes place in the positive phases.
Pure copper to copper alloy
When welding copper with copper alloys, the differences in strength properties at elevated temperatures and in physical properties (thermal conductivity and expansion, heat of fusion and melting temperature) must be taken into account. Recommendations for some technically significant material combinations are given in the table.
| Material 1 | Material 2 | Welding process | Filler Metal | Remark |
| Copper | CuSi2Mn, CuSi3Mn | TIG / MIG | CEWELD CuSi3 | from > 10 mm sheet thickness preheat Cu side (300 -400°C) |
| Copper | CuZn-alloy | TIG / MIG TIG / MIG |
CEWELD CuSn6 CEWELD CuSn |
Depending on wall thickness, preheat Cu side (200 -500°C) |
| Copper | CuSn-alloy | TIG / MIG | CEWELD CuSn6 | |
| Copper | CuNi-alloy | TIG / MIG | CEWELD CuNi30Fe | |
| Copper | CuAl-alloy | TIG / MIG TIG / MIG |
CEWELD CuSn6 CEWELD CuAl8Ni2 |
The buttering technique must be used. Buffering can be done on either the copper or steel side. In both cases, use a pure nickel electrode. For the final welding of the joint, use either Inconel-type or bronze-type electrodes, depending on which side the buttering layer is applied to.
For Buffering CEWELD E NiTi3 / NiCro 600
| Material 1 | Material 2 | Strain | Welding process | Filler Metal | Remark |
| Copper | Unalloyed steel | Subordinate | TIG / MIG TIG / MIG TIG / MIG |
CEWELD CuSn6 CEWELD CuAl8 CEWELD CuNi30Fe |
Cu side to approx. 200-500 °C preheat |
| Copper | Unalloyed steel or austeniti | high | TIG / MIG TIG / MIG |
CEWELD NiTi3 CEWELD Nicro600 |
CU side with Tig and NiTi3 or buffer Nicro600, preheat to approx. 200 - 300 °C without preheating connect with Nicro600 |
| CuMn2 | Unalloyed steel | - | TIG / MIG TIG / MIG TIG / MIG |
CEWELD CuSn6 CEWELD CuAl8 CEWELD CuAl8Ni2 |
Steel side with MIG pulsed arc and CuSn- or CuAl- additional buffers; joint welding with CuSn or CuAl additive |
| CuZn-alloy | Unalloyed steel | - | TIG / MIG TIG / MIG |
CEWELD CuSn6 CEWELD CuAl8 |
Steel side with MIG pulsed arc and CuSn- or CuAl- additional buffers; joint welding with CuSn or CuAl additive |
| CUSn-alloy | Unalloyed steel | - | TIG / MIG TIG / MIG |
CEWELD CuSn CEWELD CuSn6 |
Steel side with MIG pulsed arc and CuSn6P buffer; joint welding with CuSn6P or CuSn1 |
| CuNi-alloy | Unalloyed steel | - | TIG / MIG | CEWELD NiCu30Mn | Buffer steel side with NiCu additive for manual arc welding and TIG |
| CuAl-alloy | Unalloyed steel | - | TIG / MIG TIG / MIG |
CEWELD CuAl8 CEWELD CuAl8Ni2 |
Steel side MIG pulse arc with CuAl additive buffers |
This unusual combination is problematic because the cast iron contains high levels of sulphur and phosphorus, which can react with the copper. For this reason, buttering the cast iron side is strongly recommended with CEWELD NiFe 60-40
Most Ni-based alloys are sensitive, and it has even been suggested that Monel is sensitive when temperature and stress conditions are especially unfavourable. In this specific case, it is probably hot cracks that have been filled with copper, similar to eutectic healing. Nevertheless, the lower strength of the copper phase reduces the strength of the entire joint.
To avoid all such problems, use the buttering technique. The buttering layer should be applied to the copper side. Final welding should then be performed using an electrode suitable for the other material.
CEWELD E NiTi3 / NiCro 600
Arc welding is not recommended for these combinations. However, Al-bronze electrodes or Si-bronze electrodes can be used as a temporary solution. Nevertheless, despite the utmost care during welding, brittle structures can form in the weld metal. Added to this is the aforementioned problem of porosity and the danger to the welder.
It is therefore better to use oxyacetylene welding or brazing.
When welding Sn-bronze directly to steel using butt or fillet welds, there is a risk of incomplete fusion. Aside from copper penetration, this reduces the strength of the joint. This can be avoided by buttering the steel side with a bronze layer and then welding it to the bronze side with the same electrode, or by buttering the bronze side with a nickel electrode if copper penetration cannot be allowed.
In this combination, it is important that the alloy content of the weld metal is not diluted too much by the liquid copper during welding. The risk of cracking increases with a decrease in alloy content.
Sn-bronze, Si-bronze and, in particular, Al-bronze electrodes are satisfactory in this respect.
Oxy-acetylene welding is the preferred process for this combination. However, it is possible to achieve acceptable welds in most situations with careful welding techniques, such as minimising heat input and avoiding localised heat concentrations. At least, this method produces far better results than welding pure brass joints.
Bronze electrodes can be used in constructions exposed only to low static stress loads and not too high temperatures. The steel side should then be coated with a bronze layer and welded to the bronze side, typically using the same electrode. Otherwise, a nickel insulating layer must be applied to the bronze side.
Most bronze electrodes are good for welding this combination. Al-bronze consumables show the best tolerance to dilution while Sn-bronze is the most sensitive in this respect.
For this combination, CuNi 70/30 electrodes are preferred. Monel types may also be used.
When welding copper-nickel to stainless steel, the buttering technique must be used, along with inserts (an intermediate piece of ferritic steel or Monel), followed by bilateral joining. The joint between the copper-nickel and the steel insert can be welded using CuNi or Monel electrodes.
Monel-type consumables can be used to weld this joint directly, but the safest method is to coat the copper-nickel side with Monel and then weld it to the other side using Inconel types. This avoids mixing too much chromium (Cr) and iron (Fe) with the Monel weld metal, which can cause cracking.
A buttering technique is required for this unusual combination.
Cu-30% Ni-type consumables make the best welds. Sn-bronze electrodes also make fairly safe welds.
Cu-30% Ni-type consumables make the best welds. Sn-bronze electrodes also make fairly safe welds.
This combination may occur, for instance, in shipbuilding, and it can be successfully welded using the 'buttering' technique. First, the copper-nickel side should be coated with Sn-bronze, and then it can be welded to the bronze side using either Al- or Si-bronze electrodes.