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Preliminary investigation of forged brackets produced of S355 J2+(N) steel is presented in this research work. Performed investigation was intended to approve predicted production technology. First, all stages in the complex production process chain were defined, starting from the construction of the forging die, heating of the pieces of raw material, preforming, forging of the piece, frying and stress relieving. Confirmation of the proposed production parameters was performed with an application of appropriate computer program DEFORM F3 Ver10. After performing the forging process, mechanical and microstructural investigations of the produced forging parts were done. These investigations confirmed that preliminary proposed forging process meets all requirements concerning quality of the forged brackets. It means that undesirable forging defects were not detected and mechanical properties (tensile strength and hardness) of the forgings are in accordance with standard requirements.

Basic idea in this research work is to check prescribed quality requirement of steel pipes welded by implementation of high frequency contact welding process (HFCW). These pipes are intended for natural gas transportation. As a raw material for pipes production was used X60M steel coils with thickness of 6.5 mm. Outer diameter of pipe is Φ508 and length 12000 mm. Preliminary welding procedure is given based on personal experience and technical knowledge. Special attention was paid to the most important welding parameters: current frequency, voltage and welding speed. After performing of welding additional heat treatment (normalization) of the welded pipes (joints) was performed at the temperature of 900 0 C.

The heat input during conventional arc welding processes can be readily calculated knowing the power taken from the power source. The efficiency coefficient can be taken from the appropriate literature standards. Here, the intention of the performed research work was to develop a procedure for determination of heat input in arc and laser welding processes implementing Adams equation - modified Rykalin equation for two dimensional heat distributions (2-D). To realize this idea, it is necessary to determine two characteristic temperatures points in the HAZ with known peak temperature, and to determine distance between them. Implementing measured values for distance in Adams’ equation, heat input in arc welding can be directly determined in arc welded joints.In laser beam welding, the absorption of the beam in the metal is not known, so that the welding heat input cannot be calculated directly, and direct implementation of Adam’s equation is not possible i.e. absorption coefficient has to be determined first, and after that calculation of heat input is possible.The peak temperatures corresponding to specific microstructures can be obtained by performing welding simulation, by the Gleeble 1500 simulator in our case. As one of the peak temperatures, the melting temperature can be used corresponding to the fusion line, so that at least one characteristic peak temperature such as coarse grain zone, fine grin zone, intercritical zone, recrystallization, has to be determined by the simulation.Performed research showed that obtained values for heat input using Adam’s equation correspond pretty well with standard equation for heat input in arc welding.