How do you weld a copper pipe

Weld a copper pipe

Welding or soldering copper pipes?

Basically, copper can be welded very well. However, depending on the application and with pipe thicknesses of up to 3 mm, methods such as soldering copper pipes are more likely to be used. A distinction must be made here between soft and hard soldering of copper pipes. Depending on the application, it may even be that a copper pipe may not be welded, but only soft-soldered.

The peculiarities of copper in welding

When welding, the thermal properties in particular must be taken into account, i.e. the expansion and contraction during cooling. In addition, like other non-ferrous metals, copper has the property of absorbing and binding gases when heated, as is the case with welding. Together, these two effects can quickly lead to an inferior weld seam.

Copper alloys are also to be considered individually

The welding of copper and copper alloys, including copper pipes, is therefore limited to welding processes that offer adequate protection. These would be the following welding processes in particular:

  • MIG welding
  • TIG welding
  • electric arc welding by hand (limited)

The electric arc welding of copper pipes

Manual arc welding alone illustrates the problem quite well. On the one hand, the copper must be preheated due to the rapid heat dissipation. As a result, only short seams or small copper workpieces can be welded using this welding technique. In addition, the filler metal must preferably have a slag-forming property. The slag protects against the binding of gases and other atmospheric influences such as contact with oxygen.

TIG and MIG welding of copper pipes

MIG and TIG welding are therefore preferred for larger welding projects. In particular, powerful TIG welding machines can be used without preheating. However, this requires really good specialist knowledge and experience. Welding with inert gases (as opposed to active gases in MAG welding) means that these inert gases protect against atmospheric influences and at the same time do not react to copper.

Pay attention to the composition of copper alloys

There are additional restrictions when welding copper alloys because, depending on the alloys used, multiphase copper alloys can also be formed. Many copper alloys are single-phase, while alloys with lead, for example, are always two-phase, as the lead forms its own phase.

Differentiation between single and multi-phase copper alloys or copper pipes

Single-phase metals can be welded much better. Metals with a short cross grid are easier to weld than with a hexagonal cross grid (htp). When welding multiphase metals, for example a copper alloy with lead, the welding is impaired by the phase that is more difficult to weld. As a rule, this means more brittle weld seams and significantly poorer cold formability.

The oxygen content of copper materials

Another important factor is the oxygen content. Copper metals in particular, for which electrical conductivity is to be used, tend to be rich in oxygen and are therefore more difficult to weld. Copper for plant and equipment construction, on the other hand, has a higher proportion of phosphorus and is much easier to weld.

The main standards for welding copper pipes

In order for you to be able to weld copper, it is extremely important to take into account the various standards. We have therefore listed the most important standards in connection with welding copper pipes for you:

  • DIN CEN / TS 13388 overview of copper and copper alloys
  • DIN EN 1982 copper and copper alloys, cast metals
  • DIN 8552-3 weld seam preparation, joint shapes copper and copper alloys, gas fusion and inert gas welding
  • DIN EN 14640 welding consumables, welding wire, solid wire for fusion welding of copper and copper alloys

Of course, the rules are much more comprehensive. This is only a small excerpt from the standards relating to welding of copper and copper alloys. Welding copper pipes therefore requires a high level of specialist knowledge and, of course, relevant experience is also extremely helpful.

Compared to welding copper, other processes such as soldering or pressing copper pipes are more common. Welding is mainly used in industrial applications and is of subordinate importance for do-it-yourselfers in many areas. However, if you actually need to weld copper pipes, the help of specialists who also have the appropriate welding equipment is highly recommended.