Heavy multi-pass TIG welding

Abstract

This study aims to find the maximum, usable, feed limit at different arc-energies and use the findings in multi-pass welding planning for robotic welding, taking into consideration the high controllability of robot movements. A combined studies using numerical analyses and practical experiments to calculate the feed limits for different arc energies. Each weld where analysed both mathematical, physical and thru observation. The combined results for one experiment will form the bases for the next set of experiments. Two feed limits was discovered, one for room temperature metal and one for pre-heated metal. For welding on materials in room temperature, the arc was able to melt the filler, and make a complete fusion with the parent metal, when the energy requirement for melting the filler was under 20 per cent of the total arc energy. For welding on pre-heated metals the energy requirement for the filler was 23 – 24 per cent. The feed limits where tested and confirmed when welding with 2.6 kJ/s (300 A), 2.2 kJ/s (250 A) and 1.6 kJ/s (200 A). Welding at the feed limit, on pre heated metals, produced good welds at arc speed up to 5 millimetres per second. Part of the result is a preliminary welding procedure specification for a specific groove based on the findings in the experiments. It is recommended that the feed limits are tested when welding with filler of different thickness.