International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Dissimilar welding between duplex stainless steel and structural steel is increasingly used in the offshore, petrochemical and energy industries due to the combination of high corrosion resistance and good mechanical strength. This study presents a comparative investigation of two welding procedures for which they were used as filler metal: a BÖHLER Q G 309L-Si solid wire (GMAW 135 process), a FOX core 2209-T1 flux-cored wire (FCAW 136 process) and M21 shielding gas (82% Ar + 18% CO2). The butt joint was performed between 10mm thick plates made of duplex stainless steel UNS S32205 and structural steel S355J2. During tensile testing, failure occurred in the base material, confirming the high strength and good quality of the welded joints. Charpy impact testing revealed high toughness in the weld area for the GMAW 135 process, while excellent toughness was obtained for the GMAW 136 process. Hardness measurements showed a more uniform hardness distribution for the flux-cored wire welds and macrostructural analysis confirmed full penetration of both welds.

The work aimed to evaluate the effect of microalloying titanium in proportions of 1 to 5 wt.% on the microstructure and microhardness of a precipitation-hardenable martensitic stainless steel. The standard chemical composition of martensitic steel 17-4PH was used, to which 1; 2; 3; 4 and 5 wt.% Ti was added, respectively. Microstructural analyses revealed changes in the crystal grains and precipitation effects from the solid solution of the alloy. Microhardness measurements were also performed, which demonstrated that withincreasing Ti content in the alloy the metallic matrix becomes harder. The study confirms that microalloying with Ti is beneficial for the development of martensitic stainless steels to increase mechanical properties, even without the application of subsequent heat treatments.
The results obtained in this work represent a starting point for the development of new customized alloy recipes, adapted to specific applications, where a high value of hardness, as well as microstructural stability or wear resistance are required.