Welding a copper pipe

Like other metals, copper can also be welded. In principle, this also makes it possible to weld copper pipes. However, the very specific properties of copper and copper alloys in welding must be taken into account. In the following article we have summarized everything worth knowing about welding copper pipes for you.

Welding or soldering copper pipes?

In principle, copper can be welded very well. However, depending on the application and pipe thicknesses of up to 3 mm, methods such as brazing copper pipes are more likely to be used. Here, a distinction must be made between brazing and brazing copper pipes. Depending on the application, it may even be that not welded, but a copper pipe may only be soldered.

The peculiarities of copper during welding

During welding, the thermal properties must be taken into account, ie expansion and contraction upon cooling. In addition, copper, like other non-ferrous metals, has the property of absorbing and binding gases when heated, as is the case with welding. In interaction, these two effects can quickly lead to an inferior weld.

Copper alloys are also to be considered individually

Therefore, the welding of copper and copper alloys, including copper pipes, is limited to such welding processes, which provide adequate protection. These are in particular the following welding processes:

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

Electric arc welding of copper pipes

Already handwelding demonstrates the problem pretty well. On the one hand, the copper has to be preheated due to the rapid heat dissipation. As a result, only short seams or small copper workpieces can be welded by means of this welding technique. In addition, the welding filler must have a preferably slag-forming property. The slag protects against the binding of gases and other atmospheric influences such as oxygen contact.

TIG and MIG Welding of copper pipes

Therefore, MIG and TIG welding are preferred for larger welding projects. In particular, with powerful TIG welders can be worked without preheating. However, this requires really good knowledge and experience. Welding with inert gases (compared 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

Additional restrictions on the welding of copper alloys are the result that, depending on the alloys used, multiphase copper alloys can also be produced. Many copper alloys are single-phase, whereas lead-based alloys, for example, are always biphasic, as the lead forms its own phase.

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

Single-phase metals are significantly easier to weld. In this case, metals with krz cross lattice are better weldable than with hexagonal cross lattice (htp). When welding multiphase metals, for example, a copper alloy with lead, welding is impaired by the worse to be welded phase. As a rule, this means more brittle welds and a significantly lower cold workability.

The oxygen content of copper materials

Another important factor is the oxygen content. In particular, copper metals, in which the electrical conductivity is to be used, are rather rich in oxygen and therefore less suitable for welding. By contrast, copper for plant and equipment construction tends to have a high proportion of phosphorus and is much easier to weld.

The most important standards for welding copper pipes

In order to be able to weld copper, consideration of the various standards is extremely important. Therefore, we have listed the most important standards in connection with the welding of 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 forms Copper and copper alloys, gas melt and gas-shielded arc welding
  • DIN EN 14640 Welding additive, welding wire, solid wire for fusion welding of copper and copper alloys

Of course, the regulations are much more comprehensive. This is just a small excerpt from the standards relating to the welding of copper and copper alloys. Thus, the welding of copper pipes requires a maximum of specialist knowledge and, of course, appropriate experience is extremely helpful.

Tips & TricksOver welding copper, other methods such as soldering or pressing copper pipes are more common. Welding is mainly used in industrial applications and is of minor importance to home improvement in many areas. However, if you actually need to weld copper pipes, it would be highly recommended to have the help of professionals who also have the proper welding equipment.
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