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

It was examined the developing of Specifications for high durability and large diameter electric welded straight -seam pipes used in unique constructions including that they worked in heavy climate conditions. It was demonstrated that the pipes, made with high cleaned from harmful admixture thick sheets treated by thermo mechanical rolling and accelerated cooling, possess very high cold-resistant, crack-resistant, fire-resistant and high resistant against propagation of fatigued cracks. It was installed that such pipes possess high resistant against mechanical aging and they have high level of parameters defined the resistant against the seismic loadings. In accordance with the results of researches there were developed Specifications with the suitable guarantee provided operational reliability of unique constructions made with electric straight- seam pipes.

Due to technological particularities of low carbon low alloy API 5L X80 steels producing they have strong texture and its inhomogeneity on plate thickness. Charpy impact tests at ambient and negative temperatures and investigation of texture of samples of API 5L X80 steel were performed. By the method of X-ray structural analysis DPF, IPF and ODF were obtained. Texture components and their volume fraction were determined. It was shown that correlation between volume fractions of main texture components, misoriented grains fraction and DBTT exists. As a result analysis of texture parameters allowed characterization of effect of texture on cold resistance of low carbon low alloy API 5L X80 steel.

Investigation of low carbon microalloyed API 5L X80 steels for electric-welded pipes applied in building of metallic structures of different complexity. Problems of weldability of these steels and effect of technological and structural factors on mechanical properties of weld seams have been considered. Also mechanical characteristics at cyclic loading of the steels are considered.