By internal high-pressure forming, processes are understood in which tube-shaped workpieces and hollow profiles are formed with active means support. Using a method of internal high-pressure forming, hollow profile components having improved properties may be manufactured to high precision which, using other methods, could not be implemented, or only implemented at far higher expenditure. For the successful application of the method, besides the selection of suitable components and working materials, knowing the process control limitations is important. For example, too low an internal pressure and, simultaneously, too great a shifting of the tube ends, may lead to unfolding or buckling of the workpiece, whereas strong inside pressure at too little feeding of the tube ends may result in failure by rupturing or bursting.
In addition to seamless and welded tube, alternative tube-shaped semi-finished goods are also successfully formed using this combination of methods, besides various steel materials nonferrous metals also being used. In particular, for manufacturing fittings in piping construction, use is made of oxygen-free copper types deoxidized using phosphorus, having the EN abbreviation Cu-DHP for uses specifying a residual phosphorus content of 0.015 to 0.040%. DHP copper is easily welded and brazed, and is the most important type of copper in machine, equipment and pipe construction.
Although copper is very ductile, that is, easily cold formed, and demonstrates increasing work hardening during cold forming, problems may arise during internal high-pressure forming in the form of wrinkles and cracks. These defects cannot only be attributed to the method parameters.