Investigation of shot blasting and thermal stress relieving processes on residual stresses and corrosion behavior of X60
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Investigation of shot blasting and thermal stress relieving processes on residual stresses and corrosion behavior of X60 steel gas pipelines Alireza Malekahmadi1 · Mohammad Honarpisheh1 Received: 5 March 2020 / Accepted: 24 August 2020 © Springer Nature Switzerland AG 2020
Abstract Corrosion is one of the most common complications in some industries. Two main factors causing corrosion are tensile stress and a corrosive environment, both of which require careful control. The purpose of this research is to achieve an optimal method of increasing corrosion resistance and also reducing tensile residual stress in API X60 gas pipelines. In the present study, residual stress has been examined in samples which have undergone either shot blast or heat treatment operations or both of them. In this research, 4 samples have been studied including: shot blasted, firstly heat treated then shot blasted, firstly shot blasted then heat treated and heat-treated using API-X60 steel pipe to indicate the best method of resistance to corrosion and stress. To investigate these properties, residual stress of these components has been examined by using the Contour Method and corrosion resistance has been studied through the Cyclic Polarization Resistance method. The results showed that the best corrosion resistance happen by the heat-treated sample (almost twice as much as the other methods) and also the most compressive residual stress observe in the firstly shot blasted and then heat-treated sample. Keywords Residual stress · Corrosion resistance · Shot blast · Heat treatment · Contour method · Cyclic polarization resistance
1 Introduction Corrosion along with stress is one of the most common forms of corrosion in industry. The two main factors which cause this kind of corrosion are a corrosive environment and tensile stress. The removal of one of these two factors will eliminate stress corrosion [1]. In industry, to remove the first of these causes, an attempt is made to create a physical barrier in the form of a coating between the corrosive environment and the devices. In order to reduce the impact and the amount of the other key factor, namely tensile stress, measures have to be taken. Therefore, any method that modifies these stresses will directly affect and increase the lifespan of devices and equipment. The methods which are currently being used to reduce these stresses are stress relief by using the ultrasonic method
on welding lines and the shot peening and the shot blast method on all the external parts of the pipes in order to make compressive residual stress on the external surface [2]. Considering the importance of residual stress in relation to stress corrosion, it is obvious, that residual stress measuring methods are able to accurately calculate the degree of tensile strength and the effect of residual stress on stress corrosion [3]. Some studies have been carried out examining the impact of stress corrosion on steel used in API-5L pipes and its connection with residual stress. For example, in stress corrosion crack
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