Increasing corrosion and mechanical resistance destruction of welding cover capacities water towers

Abstract

The paper considers standard methods for determining the corrosion and mechanical characteristics of pipes and their welded joints, steel shell structures for water supply to consumers. It was found that sharp fluctuations in the values of microhardness in the zone of thermal influence of the welded joint exceed the baseline values in the middle part of the weld and the base metal of the pipe. The obtained results can be used to test the performance of carbon steel steels designed for the construction of water towers of long service life in corrosive environments. Under the action of the temperature gradient on the outer surfaces of the walls of the water tank tensile stresses occur, and on the inner surfaces-compressive, which is a favorable factor that reduces the risk of corrosion. Temperature stresses that occur in the case of temperature inhomogeneity along the contour of the cylindrical tank are unfavorable. Stresses from the weight load are small and do not have a significant effect on the destruction of the steel tank, because they are compressive. The value of technological final stresses was determined experimentally by mechanical strain gauge according to the classical method, as well as with the help of electric strain gauges and ultrasonic method according to the method of E. O. Paton Electric Welding Institute (PWI). It has been experimentally established that the most dangerous final welding stresses in assembly seams, the value of which for the longitudinal stress component is close to or exceeds the yield strength , and for the transverse – close to the yield strength , while on steel plates VSt3 of the same thickness . It is likely that welding during installation in conditions of rigid compression of the metal causes an increased level of final stresses. The magnitude and sign of the final stresses significantly depends on the method of installation. Even during block installation, when the water tower is mounted from several pre-annealed blocks, the connection between the mounting ring seams in some areas of the base metal near these seams during fitting creates significant stresses (up to 17.6 kgf / mm2), in some areas – up to 6 kgf / mm2. When sheet assembly stresses can reach a level close to the yield strength.