IMPROVEMENT OF TECHNOLOGY FOR PRESSING PROCESS OF STAINLESS STEEL PIPES

Abstract

the method of producing pipes on pressing units is most effective in the production of pipes from low-plasticity steel grades. These include, in particular, steel grades with increased corrosion resistance and cold resistance, which are currently in demand for the development of oil and gas fields in the Far North. But even the use of a pressing process with a favorable stress state scheme, as experience has shown, does not completely eliminate problems with metal destruction. When hot pressing pipes from complex-alloy steel grades, one of the problems is the poor quality of the outer surface, caused by localized destruction of the metal in the form of surface cracks. To predict the probability of occurrence of ruptures on the outer surface of pipes and to search for technical solutions to prevent them, the phenomenological theory of destruction of metals and alloys during pressure treatment is taken as a basis, the foundations of which are laid in the works of V. L. Kolmogorov and A. A. Bogatov. At the same time, the influence of the main process factors on the quality of the surface of hot-pressed pipes is considered. In particular, an analysis of the influence of the granulometric composition and viscosity of the lubricants used is performed. Permissible temperature ranges for deformation of complex-alloy steel grades are considered. The nature of the change along the deformation center of the main characteristics of the stress-strain state is analyzed. Particular attention is paid to the study of the influence of the plasticity of the press tool shape on the degree of resource exhaustion. The studies were carried out using computer modeling using the finite element method and experimental studies on modern testing equipment. As a result of such a comprehensive analysis, the main factors influencing the occurrence of ruptures of the outer surface of pipes during hot pressing were identified. An assessment of the degree of influence of each of them was made and technical proposals were developed to minimize the likelihood of ruptures.