In this paper are characterized problems of high strength steel weldability in underwater wet welding conditions. Water as a welding environment intensifies action of unfavourable factors which influence susceptibility to cold cracking of welded steel joints. The susceptibility to cold cracking of S355J2G3 steel and S500M steel in wet conditions was experimentally estimated (by using Tekken test). It was concluded that the steels in question are characterized by a high susceptibility to formation of cracks in welds. Usefulness of the proposed Temper Bead Welding technique (TBW) was experimentally verified as a method for improving weldability of the steels in the analyzed conditions.

Thermo-mechanically rolled S460ML steel was chosen for welding in underwater wet welding conditions by covered electrodes. The main aim of this study was to check the weldability for fillet welds in a water environment by controlled thermal severity (CTS) tests and to check the influence of temper bead welding (TBW) on the weldability of the investigated steel. Non-destructive and destructive tests showed that S460ML steel has a high susceptibility to cold cracking. In all joints, hardness in the heat-affected zone (HAZ) was extended to the 400 HV10 values. Microscopic testing showed the presence of microcracks in the HAZ of all welded joints. TBW was chosen as the method to improve the weldability of the investigated steel. This technique allows for the reduction of the maximum hardness in the HAZ below the critical value of 380 HV10, as stated by the EN-ISO 15614-1:2017. It was determined that for S460ML steel, from the point of view of weldability, the pitch between two beads should be in the range 75%–100%. Also, if the pitch between two beads increases, the hardness, grain size, and number of cracks decreases. In all specimens where the hardness of the HAZ was below 380 HV10, there were no microcracks.

Friction stir welding (FSW) of polymeric materials has recently attracted significant attention. Herein, we present the effect of the tool pin profile on the FSW of high-density polyethylene (HDPE) joints through joint experimental analysis and thermomechanical simulations. For analysis of pin profile effects on the thermomechanical properties of HDPE joints, frustum (FPT), cubic (CPT), and triangular (TPT) pin shapes were selected in this study. This research investigated the heat generation of the parts of the different tools as well as heat flux (internal and surface). The results revealed that the heat generation in pins with more edges (cubic (96 °C) and triangular (94 °C)) was greater than in pins with a smooth shape (frustum (91 °C)). The higher heat generation caused the heat flux on the surface of the HDPE from the cubic pin profile to be greater than for other joints. Due to the properties of HDPE, higher heat generation caused higher material velocity in the stirring zone, where the velocity of the materials in TPT, CPT, and FPT pins were 0.41 m/s, 0.42 m/s, and 0.4 m/s, respectively. The simulation results show sharp-edged pins, such as triangular and cubic, lead to over-stirring action and internal voids formed along the joint line. Furthermore, the simulation results indicated that the size of the stirred zones (SZs) of the FPT, TPT, and CPT samples were 17 mm², 19 mm², and 21 mm², respectively, which is around three times the corresponding values in the HAZ.

El método de desplazamiento de la glicerina se utilizó para determinar el contenido de hidrógeno difundido en el metal depositado. Las muestras se soldaron en aire y en agua con electrodos recubiertos de rutilo. En la primera parte, las se soldaron inmediatamente después de abrir el paquete con los electrodos. Posteriormente, los electrodos se almacenaron en paquetes abiertos en el ambiente de laboratorio durante 3 años. Pasado este tiempo, se realizó la segunda parte de las muestras. Los resultados de las mediciones de la cantidad de hidrógeno difundido en el metal depositado varió de 32,61 a 39,95 ml/100 g para muestras soldadas al aire y de 51,50 a 61,34 ml/100 g para muestras soldadas en agua. Los análisis estadísticos se realizaron utilizando el software Statistica, módulo ANOVA (análisis de varianza de una vía) con un supuesto nivel de validez α=0,05. La normalidad fue verificada por el ensayo Shapiro-Wilk. La homogeneidad de la varianza se verificó mediante el ensayo Levene. En la etapa siguiente, se realizaron análisis post-hoc. El objetivo fue determinar si los promedios son significativamente diferentes. Se utilizaron los ensayos Scheffe, Tukey, NIR Fisher, Newman-Keuls y Duncan. Los posibles cambios en el contenido de hidrógeno difundido en el metal depositado, resultante del tiempo de almacenamiento de los electrodos, se determinaron mediante el ensayo “t” de Student. Los resultados del análisis estadístico muestran que el tiempo de almacenamiento de los electrodos no tiene una influencia significativa en el contenido de hidrógeno difundido en el metal depositado, independientemente del sistema de apantallamiento utilizado en la soldadura.

The article presents the results of the effect of parameters of underwater local dry chamber welding on the properties of padding welds. The effect of heat input and the type of shielding gas on the structure and hardness of welds was established. the functions for estimating the maximum hardness of the heat affected zone have been also elaborated