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

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.