Research of weldability of pipe steel X65QS ordered for sour service
The increase of being developed oil and gas fields with a high content of hydrogen sulfide causes a great demand for large-diameter pipes resistant to sulfide stress corrosion cracking. At the same time, in the weld adjacent zone of the pipes, the resistance against that type of cracking is lower in comparison with the base metal. Studies of the influence of welding thermal cycles to the microstructure, toughness and resistance to sulfide stress corrosion cracking of X65QS steel used for production of large diameter pipes for oil and gas transport are shown in this paper. The studies were carried out by standardized methodology of simulation of welding process by controlled induction heating and subsequent cooling of the samples. It was accompanied by further metallographic analysis and set of mechanical and corrosion tests. The results of conducted research defined the interval of cooling rate in the heat affected zone that provides the best toughness and resistance against sulfide stress corrosion cracking for X65QS steel. The directions for ensuring the required cooling rate with respect to automatic submerged multi-arc welding under factory conditions and