Papers by Keyword: Welded Seam

Abstract: The article investigates the issues of pipeline transport and the methods of protecting pipelines from corrosion, as well as the manufacture of pipes with internal and external coatings and proceeding construction of pipelines. The main objective of this article is to obtain a reliable and durable pipeline with internal and external coatings, as well as to preserve pipeline capacity and ease its installation.

Abstract: The results of experimental studies of the variation of residual stresses in a frameless tubular node of the offshore stationary platform (OSP) due to technological effects on the metal are presented. It is shown in the paper that the value of the tensile residual stresses in sheet rolled products with 20-50 mm of thickness reaches 80-65 MPa. As a result of the subsequent technological redistribution, the residual stresses change in magnitude and sign, and reach 0.8-1.2 of the yield strength of the base metal. The most unfavorable from the point of view of the serviceability of OSP are the tensile residual stresses in welded joints, the maximum value of which is 350...500 MPa. High temperature tempering after welding does not always lead to the desired result: in the heat-affected zone of the corner joints of nozzles mounting to the waist tube of the node, the residual stresses amount to 120-150 MPa. Preheating temperatures in the range of 120-160⁰С do not have a significant effect on the value of residual welding stresses. For more effective reduction of σ _rs , its value should be 200-450⁰С, depending on the thickness of the joined parts and the strength class of the steel.

Abstract: Enough works in which positive action of the vibration fluctuations imposed both in the course of welding of a design and after it is specified are known. In the article features of influence of low-frequency vibration fluctuations in the course of a welding cycle on properties of welded connections from steel A 516-55 are considered. The conducted pilot studies of influence of vibration influence of a welding bathtub in the course of welding on structure and physico-mechanical properties of metal of welded connections have allowed to prove positive action of this technology which leads to increase in durability and fatigue endurance of welded connections. This fact will allow to expand using of technology of vibration processing in the course of welding for production of the welded equipment of various type.

Abstract: The paper reviews research works on nanoincorporated consumables for welding, surfacing and spraying. Use of metal and compound nanoparticles is considered such as tungsten carbide, tungsten-cobalt carbide, chromium carbide, titanium carbonitride, aluminum oxide and others. It has been proved that inoculation of nanopowders results in modification of metal structure and improves service performance of weld joints.

Abstract: The flaws such as crack or slag inclusion, in the welded seam of header of a 300MW steam turbine generator unit, were detected by the ultrasonic non-destructive inspection. Based on the crack modeling, the finite element method (FEM) was used to calculate and analyze the displacement field, stress field and stress intensity factors of the cracks under the conditions of warm start, cold start and normal operation, and the residual service life was predicted. Analyzing results showed that these flaws would not bring about primary brittle fracture and propagation of crack was harmless to safe in operation.