Mechanical properties of submerged arc welds with metal powder addition

This paper deals with welding procedure test results achieved with submerged arc welding (SAW) employing metal powder addition. The effect of metal powder on welding productivity and on the mechanical properties of joints was studied using two different metal powder addition techniques - forward feeding and wire feeding. The test materials were two microalloyed structural steels FcE355HEW (Re 355 ³ MPa) and FeE460TM (Re ³ 460 MPa) welded with Mn, MNMo and TiB-type consumables. The test results demonstrated that the metal powder addition methods studied provide the welding industry with an effective solution for increasing the productivity of welding. Improvements of 50-100 % in productivity were possible without any noticeable loss in the mechanical properties of the welded joints. Sound, fusion and crack-free welds were produced with both methods studied. The decrease of penetration due to metal powder feeding was compensated for by increasing the welding current by 100-200 A above the adequate level for conventional SA welding tested for reference. Metal powder drying was not found necessary to avoid hydrogen-induced cracking of welds with the steels studied. Charpy-V notch and CTOD tests indicated that the toughness of joints welded with metal powder addition were either improved or remained practically unchanged in comparison with conventional SAW. Good weld metal toughness was achieved with favourable oxygen contents and the addition of alloying elements effective in producing acicular ferrite. The nitrogen contents of the welds were not found to increase with metal powder addition. HAZ toughness was not changed by metal powder addition, because the effect of metal powder addition on weld cooling time t 8/5 remained negligible in the heat input range studied.