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

This study examines how thermal and mechanical effects influence hardness distribution in 4, 6, and 8 mm AA5754 aluminum plates welded using TIG with AC and DC currents. Vickers hardness (HV0.01) was measured alongside tensile tests to evaluate weld performance. Results show that AC welding produces higher but more variable hardness, while DC welding yields more stable profiles. Notably, thinner plates (4 mm) showed minimal hardness differences between current types due to faster cooling. Strain hardening increased hardness up to 125 HV and reduced variation. The extent of hardness stabilization and heat-affected zone size depended on plate thickness. Although current type influenced hardness distribution, it had little effect on fracture toughness.

The paper presents an informational measurement system for measuring electricity consumption from a three-phase grid during welding of AA6060-T66 aluminium alloy cylindrical workpieces using the TIG (Tungsten Inert Gas) method. In addition to electricity consumption, the developed system can also monitor other related electrical quantities that give an image of the load that the consumer exerts on the grid. The importance of knowing these quantities is reflected in the fact that it can provide us with information about the energy efficiency of the method, as well as the possibility to determine the economic benefits of the chosen process and technology with the knowledge of the welding input parameters. These electricity consumption values affect the sustainability and have an impact on the environment. Energy input also directly affects the quality of the welded joint, which is reflected in penetration, formed microstructure and mechanical properties. Also, knowing this information opens up opportunities to compare performance with other methods. The paper presents the development of such a system, which includes the necessary hardware components, communication and software through which data acquisition is performed.

Mechanical and electrometrical behavior of dissimilar welds between low Carbone steel (X70) and Carbone steel (42CrMo4), were studied using a combination of optical and electron microscopy. Thus, the influence of weld parameters on fusion zone and heat affected zone was investigated using two filler metals and two weld currents. The results of our work show that alternative TIG welding presents the butter combination between metallurgical and Mechanical comportment, also it was established in this study, that nickel alloy filler has the best electromecanical behavior for these types of welds.

This investigation was performed on the request of the Company for production of the solar systems collectors. Subject of the investigation is the segment of the solar stainless steel collector for the heating water in the swimming pool. The system was installed in the private property and was in use until August 2015 (about one month after installation) when it was disconnected for a period of about one month. After that system was restarted again and it was noticed that many cracks appeared in vertical tubes φ8 mm of collector manufactured of S304 stainless steel. In the horizontal pipes made of S316 steel cracks were not detected. This investigation should give the answer what is the reason for appearing of cracks in stainless steel pipes for pretty short period of exploitation.

Bimetallic weld techniques have progressed a great deal in the last decade. In this work, the effect of the filler metal composition on microstructure and mechanical behavior of dissimilar HSLA-X70/304L stainless steels weld joint is investigated. The dissimilar weld joints are fabricated using austenitic, duplex and low Carbone filler metal. The mechanical behavior is investigated through microhardness, charpy impact and tensile test.

The results show that, the weld metal composition has a great influence on mechanical properties and microstructure of weldments, in particular the grain size and phases nature, changes with filler metal composition. In addition presence of martensitic slats in the FZ when using the low Carbone filler metal, detailed microstructure examination is carried out and related to the mechanical behavior of the dissimilar joints.