Some specifications and applications require that the inside weld bead must be cold worked and in level with the surrounding base metal. This is most common for hygienic and heat exchanger tubes, but we also perform this on some of the small diameter ANSI and ISO pipe.
A bead worked weld offers advantages at orbital welding, roller expansion into tube-sheets, easier flow, easier cleaning and less risk for deposits.
The operation is made in-line before heat treatment, the coldworked weldstructure will thereby recrystallize and homogenise faster at the annealing process, which improves the corrosion resistance.
Laser welded tubes have a very low inside bead height (< 0.15 mm), which means that the requirement for bead working can be excluded, as the excess weld volume outside the base material, actually is less in comparison with a bead worked TIG-welded tube.