Measurement and Simulation of Low Carbon Steel Alloy Deposit Temperature in plasma Arc Welding Additive Manufacturing

Abstract

Additive manufacturing has the potential to produce near-net shape parts directly from weld metal. Prior work has proved that it is possible to directly manufacture components with complex geometric features and with good productivity. However, under high productivity conditions, deposit temperature increases to a level that it is no longer possible to develop appropriate deposit microstructure and therefore mechanical properties. In this study, Plasma Arc welding was used to produce experimental deposits of 1018 low carbon steel under various conditions. An analytical heat flow model was developed to study the influence of interlayer wait time on deposit temperature and therefore grain size and hardness. The results of the model indicated that as wall height increased, the rate of deposit heat removal by conduction to the substrate decreased leading to a higher preheat temperature after a fixed interlayer wait time causing grain size to increase as wall height increased. However, the model results also show that as wall height increased, the deposit surface area from which heat energy is lost via convection and radiation increased. The model also demonstrated that the use of a means of forced convection to rapidly remove heat from the deposit could be an effective way to boost productivity and maintain smaller grain size and therefore higher hardness and strength in the deposit.