ABSTRACT
The question of weldability has a direct bearing on the use of nickel alloys and high alloy special stainless steels in the manufacture of chemical plant and proc ess equipment, offshore technology, as well as environmental and energy tech nologies. The safety and service life of equipment and plant is largely deter mined by the quality of the welded joints. The requirements specified by the operators are usually demanding. The selection of the materials to be used must take into account the subsequent operating conditions such as the process medium, temperature and pressure. However, optimum results can only be ob tained if design and fabrication are harmonized with the welding characteristics of the materials to be used. The selection of suitable welding filler materials and welding processes plays a decisive role and must be considered from the very beginning of component design. An ideal welding design provides for troublefree assembly in the workshop and also on site. The weld arrangement and geometry must be selected so that the welder has sufficient freedom of move ment during his work to make welds with flat profiles, no slag inclusions and without excessive root penetration whilst maintaining the correct heat input for the material. If the number of welds in a component is high, it is advantageous to use mechanized welding processes. Experience is available, for example, from critical applications on the use of the GTAW process with cold or hot filler wire. This is discussed in more detail below. In general, however, preliminary tests have to be carried out in regions subjected to severe corrosion attack to deter mine the welding process and suitable filler. With manual processes the qualifi cations of the personnel must be considered in addition to the welding process. It is essential that well trained and reliable personnel are used, preferably with qualifications in accordance with DIN 8561 for non-ferrous metal welders.
