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

The work is performed by analysing spiral welded joints Helical Submerged Arc Welding and their most common errors, which they occur during the submerged arc welding process and can be detected by non-destructive tests. Pipelines were made of structural alloy steel, hot-rolled. Welded defects were detected by X-ray method. A microstructural test was carried out to detect internal errors of the weld joint. Mechanical tests were used to determine the effect on change of properties. After detecting errors on the end X-ray, they were welds subsequently corrected. Destructive or non-destructive testing of gas pipeline welds has its justification, mainly for safety reason.

During the injection molding procedure of plastics, the gear pumps in their work are exposed to the effect of elevated pressure and temperature. On one of these pump there has been frequent downtime due to breakage of the driven gear. Gears which were installed as standard spare parts had stood out in operation for three months. On a sample of a broken gear were perfomed laboratory examinations (metallographic examinations, hardness control on cross-section and surface of the fracture was examined). Conclusion was that it was high quench hardening of a steel of which a part is made, the most likely cause of the fracture of a standard gear. In order to extend the useful life, two test gear are made from steel for cementation 20MnCr5. By applying the appropriate parameters of thermal chemical treatment useful life of the gear is significantly extended, after which the test gears have worked for nine months from the moment of installation.

In this paper the laboratory tests on the selected steel for cementation 20MnCr5 was perfomed. The influence of the contact load resistance to the adhesion wear of high-temperature carbonitrided MnCr steels was analyzed. As a representative example was selected a tribosystem drive/driven gear of reducers in which are expressed high contact loads. For the purposes of these tests, the samples were first high-temperature carbonitrided, and then they are carried to the appropriate chemical and metallographic analysis, control of the surface hardnesses and the resistance to the adhesion wear. The aim of this paper was to observe the representative tribosystem as much possible to define its working parameters in order to determine the optimum conditions for testing the influence of the contact load on resistance to the adhesion wear. The analysis results show that high-temperature carbonitrided steel where the atmosphere of furnace at the beginning of carburizing was enriched with nitrogen, and finally with carbon showed significantly greater resistance to the adhesion wear compared to steel that at the beginning of carburizing had atmosphere of furnace rich in carbon, and finally with nitrogen.