FORECASTING OF THE MECHANICAL PROPERTIES OF METAL WELDED CONNECTIONS OF PIPELINES AND TANKS, TAKING INTO ACCOUNT THE TIME PARAMETER OF WELDING

Аннотация

The article presents the results of experimental studies of the relationship between the welding reference
variables (chemical composition of welding materials, welded elements, welding conditions), the structure formed
in the welded joint, its basic mechanical properties (ductility, strength, impact toughness), and crack resistance
parameters. The research consisted in carrying out standard and special tests, as well as studying the structure of
the metal after heat treatment at various cooling rates. To confirm the established relationships, tests of
circumferential welded joints of pipes and sheets of tanks, welded according to the technologies used in the
Transneft PJSC, were carried out.
As a result, a model has been developed for predicting the mechanical properties of welded joints according
to data of various levels. It was elucidated the quantitative effect of the cooling rate and structure parameters on
the main mechanical properties of the welded joint. Also, empirical expressions were obtained connecting the
group of mechanical properties of the metal (the ratio of the yield strength to the tensile strength, relative
elongation, impact toughness), combined into a "complex coefficient of durability", and the metal crack resistance
parameters used in the force criterion of fracture mechanics.
The greatest practical effect from the implementation of the developed model is achieved with the
introduction of differentiated decreasing coefficients within the framework of computation for strength and
durability, depending on the level of data on the welded joint used in the calculations.