Improving the resistance to hot cracking during the welding of nickel-based alloys using cold wire submerged arc welding processes

摘要

Because of its high heat input, submerged arc welding (SAW) is generally not utilised for the joining of chrome-nickel steels and nickel-based steels for industrial installations (e.g. power stations, petrochemical installations, turbines and industrial furnaces). Preference is given to the gas-shielded arc welding processes, frequently with a pulsed arc. However, SAW might, with its high weld quality and deposition rate, constitute an alternative with particular economic viability in so far as process modifications which guarantee a higher resistance to hot cracking due to a decreased heat input are available. In addition to the simple way of reducing the energy per unit length by increasing the welding speed, one more demanding but more effective approach lies in the direct extraction of molten pool heat by adding cold wire. The objective of the tests on the Alloy 617 and Alloy 625 nickel-based alloys was to make a statement about the weldability and economic viability of cold wire SAW, in the thin wire technique as well. One important aspect was the influence of the cold wire feed not only on the weld geometry and the distortion but also on the chemical composition of the weld metal and thus on the inclination to hot cracking too. The hot cracking tests were carried out using MVT procedures. It was possible to achieve a high process reliability by optimising the cold wire feed.