Effect of Heat Sinks on Cooling Time to Weld Interpass Temperature

Materials and Production Engineering, Faculty of Technology, University of Oulu, Pentti Kaiteran Katu 1, 90570 Oulu, Finland

Corresponding author: Juhani.Laitila@Oulu.fi

Abstract

In high- and ultrahigh-strength steel welding, interpass cooling time is an important factor affecting productivity and welding costs. Usually, welding heat input is restricted to meet the relatively short recommended cooling times between 800 and 500 °C (t8/5), which are prescribed by the need to meet weld strength and toughness properties. This, in turn, leads to the need for multipass welding with the interpass waiting times needed for the weld to cool to a sufficiently low interpass temperature. Welding productivity is affected by both the number of passes and the interpass waiting time. With a view to minimizing the total number of passes needed for a given preparation, it is beneficial for the interpass temperature to be as low as possible as this permits higher heat input for a given t8/5. On the other hand, low interpass temperature requires longer interpass waiting times. Therefore, this research concerns the potential of introducing copper heat sinks adjacent to the weld to reduce the time it takes for the weld to cool down to the interpass temperature. It is demonstrated that, in the case of a butt weld in a 6 mm thick base plate MAG welded with a weld energy of 1 kJ/mm and an interpass temperature of 100 °C, copper heat sinks almoust halve the interpass waiting time. This can have a marked effect on the overall productivity when welding highand ultrahigh-strength steels and increase their attractiveness for steel construction.