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

The main objective of this paper is to get an accurate result of the mechanical characteristics of welded joints of structural steel performed with two different types of filler material, wire, which are characterized by: simple welding technology, low structural changes of the basic materials, as well as lower cost of welds. The whole research is conducted in accordance with European standards for welding. Research has been conducted on two standard plates made of constructive steel S355J2 + N Z15, with a thickness of 15mm, according to standard EN ISO 15614-1. Both plates are welded with solid wire and metal cored wire under the protection of a gas mixture based on argon, and the whole process is supported by standard documentation. Destructive tests have been performed to determine the welded joints’ quality and influence of different filler materials, such as tensile test, impact test, and hardness test in the weld and heat-affected zone. The experimental results confirm that the gas metal arc welding of structural steel in the protection of inert gas with solid and metal cored wire is a procedure that ensures the quality and safety of welded joints and retention properties of the base material after the welding process.

An experimental study of the geometrical characteristics of the cross sections of the thermally affected areas obtained by electron beam welding of carbon steel 45 is made. The thermally affected zone and the molten area of the welds from non-stainless steels corresponds to a zone where the physical-mechanical properties and the microstructure of the processed material are changed after the processing. The process parameters that were changed during the experiments are: welding speeds were 0.5, 1.0 and 1.5 cm/sec, the beam current was changed in the range of 30 – 133 mA and the focus position was changed from 72 mm above the sample surface to 62 mm below the sample surface. The accelerating beam voltage was 50 kV. The geometry of the weld in the cases of a deep penetrating electron beam and narrow thermally affected zone is investigated. Electron beam welding process parameter optimization is performed, based on the estimation of regression models. In such way the electron beam optical systems can be tested and the specific quality requirements for the welds obtained by electron beam welding can be fulfilled

High-frequency electric resistance welding is one of the most common process for production of longitudinal seam welded carbon steel pipes suitable for line pipe, casing and tubing. In this pipe production process, the hot rolled strip goes into the forming mill where it is gradually cold formed into a tubular shape in several stages of forming rolls and its edges are continuously joined by a combination of localized electrical resistance heating and forge pressure. High frequency electric resistance welding generally involves high temperature, forge pressure and subsequent cooling, and as the result of this thermal cycle occurs significant microstructural changes. These microstructural changes provides a wealth of information on weld seam quality and edge preparation of hot rolled strips.

In this paper, microstructural changes in the forge weld area during high frequency electric resistance welding (HFERW) of longitudinal seam welded pipes Ø114.3×5.21mm were investigated.