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

The steel for the production of welded pipes must possess good weldability to achieve high efficiency and effectiveness of the production process in production lines (in line) and ground, during welding of pipes in long distance pipelines and in lower temperature conditions. The main focu of this research was on weldability assessment of API Grade X52 steel at low temperature (0°C), which is used for the production of welded pipes, respectively pipelines. Carbon equivalent (C_E), mechanical testing and metallographic analysis of the welded joint were conducted in order to assess the weldability. The results of mechanical tests and metallographic analysis show that steel API Grade X52, at low temperature (0°C) has excellent weldability, so the pipes produced can be welded in long distance pipelines, easy and unhindered, thereby ensuring high production efficiency and effectiveness.

In the work a mathematical model for the non-stationary motion of liquid homogeneous viscous mixtures through pipelines is constructed. The corresponding integral equations expressing the laws of conservation of mass, momentum and energy are deriving, from which, in turn, we get the corresponding differential equations. The formulation of the initial and boundary conditions is given; the necessary additional relations that close the corresponding system of differential equations are indicated. A numerical algorithm for solving such a system is proposed. The corresponding numerical examples are given.