THE INFLUENCE OF MICROSTRUCTURAL FACTORS AND HEAT TREATMENT ON THE CORROSION RESISTANCE OF REINFORCING STEEL CLASS A 600
Currently, hot rolled bar reinforcement class A600 of low-alloy steels in the delivery condition has a high tendency to this very specific kind of destruction as stress corrosion cracking under tension (SCC). However, there are cases of collapse of pre-stressed concrete structures, in most cases initiated corrosion cracking under stress, put the problem this type of fracture is particularly acute. In stress corrosion cracking cracks occur, the occurrence of which depends not only on the structural state of the material, the type and level of stress, but also on the degree of aggressiveness of the environment in which the operation occurs. In this regard, it is very important to establish how the corrosion resistance of class A600 reinforcing steel varies depending on the change in the chemical composition, microstructure, the level of applied and residual micro-stresses, and various modes of heat treatment. The purpose of this paper is to study the effect of the above factors on the resistance of low-alloyed reinforcing steel class A600 stress corrosion cracking It is shown that the sensitivity of the reinforcement to stress corrosion cracking is largely determined by the chemical composition (mainly carbon content), the type of microstructure and the level of residual micro-stresses. The influence of heat treatment regimes on the corrosion resistance of A600-grade reinforcing steel in nitrates solutions is investigated. It is shown that the use of additional heat treatment (normalization and improvement) increases the corrosion resistance of steel. High corrosion resistance steel reinforcement has only a carbon content at the lower limit of the vintage composition, which is provided by the structure of homogeneous bainite with mechanical properties at the level of strength class A600. With higher mechanical properties, the steel reinforcement has lower corrosion resistance.