The new generation of high power fiber lasers presents several benefits for industrial purposes, namely high power with low beam divergence, flexible beam delivery, low maintenance costs, high efficiency and small implantation space. This paper presents preliminary results of weld beads produced on thick X100 pipeline carbon-steel plates with an 8 kW fiber laser. Weld bead geometry was evaluated and transition between conduction and deep penetration welding modes was investigated.

The thermal or process efficiency in gas metal arc welding (GMAW) is a crucial input to numerical models of the process and requires the use of an accurate welding calorimeter. In this paper, the authors compare a liquid nitrogen calorimeter with an insulated box calorimeter for measuring the process efficiency of Fronius cold metal transfer, Lincoln surface tension transfer and RapidArc, Kemppi FastRoot and standard pulsed GMAW. All of the controlled dip transfer processes had a process efficiency of y85% when measured with the liquid nitrogen calorimeter. This value was slightly higher when welding in a groove and slightly lower for the RapidArc and pulsed GMAW. The efficiency measured with the insulated box calorimeter was slightly lower, but it had the advantage of a much smaller random error.

Since the installation of an ITER-like wall, the JET programme has focused on the consolidation of ITER design choices and the preparation for ITER operation, with a specific emphasis given to the bulk tungsten melt experiment, which has been crucial for the final decision on the material choice for the day-one tungsten divertor in ITER. Integrated scenarios have been progressed with the re-establishment of long-pulse, high-confinement H-modes by optimizing the magnetic configuration and the use of ICRH to avoid tungsten impurity accumulation. Stationary discharges with detached divertor conditions and small edge localized modes have been demonstrated by nitrogen seeding. The differences in confinement and pedestal behaviour before and after the ITER-like wall installation have been better characterized towards the development of high fusion yield scenarios in DT. Post-mortem analyses of the plasma-facing components have confirmed the previously reported low fuel retention obtained by gas balance and shown that the pattern of deposition within the divertor has changed significantly with respect to the JET carbon wall campaigns due to the absence of thermally activated chemical erosion of beryllium in contrast to carbon. Transport to remote areas is almost absent and two orders of magnitude less material is found in the divertor.

Installation of new pipelines is predicted to grow at a rapid rate over the next twenty years, due in part to

Laser welding has two distinctive modes, keyhole and conduction mode. Keyhole mode is characterized by deep penetration and high welding speeds, while conduction mode has higher quality welds with no defects or spatter. This study focuses on the transition from conduction to keyhole mode by increasing power density and using different beam diameters and interaction times. Based upon the results it was possible to evaluate that there is a transition mode between conduction and keyhole mode. The results show that the transition between conduction and keyhole mode is not defined by a single power density value. This transition has a range of power densities that depend on the beam diameter and on the interaction time. This study allows the identification of the power density that limits conduction mode, based on parameters such as beam diameter and interaction time instead of a single power density value independent of these parameters.