Oxygen-free copper

Oxygen-free copper is much easier to weld than regular copper because you don't have to worry about hydrogen disease. With regular copper, hydrogen from the flame or moisture reacts with copper oxide at the grain boundaries, creating steam that tears the structure apart. You don't have that with OF copper. Still, you have to watch out: the material conducts heat extremely well, so the weld zone cools quickly, leading to stress and cracks. Therefore, preheating is mandatory, and the surface must be clean and grease-free before welding. For TIG welding, use DC with electrode negative and argon or helium as shielding gas. For filler material, best use oxygen-free copper wire. For gas welding, avoid hydrogen-containing flames – use a neutral or slightly reducing flame, otherwise you'll create the problem yourself.