Papers by Keyword: Environmental Cracking

Abstract: The exploitation of high acid wells is facing severe corrosion challenges in the A and B gas fields in Sichuan, thus using lined steel pipe is a reliable and cost-effective anti-corrosion measure. However, lined steel pipe welding involves dissimilar steel welding, and anti-corrosion performances will be affected if the welding process is unreasonable. So it is necessary to make evaluation for corrosion of lined steel pipe. In this paper, taking welding gap of L245/825 lined steel pipe as example, the anti-SSC performances of L245/825 straight and ring welding gaps in NACE A solution were studied by CR method, and anti-cracking performances of them were evaluated by laboratory experiments. Then corrosion performances of L245/825 lined steel pipe welding gaps and L360NCS carbon steel were studied in the corrosive environment found in the Tian Dong 5-1 high sour gas well. Laboratory and field tests show that straight and ring welding gaps of L245/825 lined steel pipe have good anti-environment and anti-cracking performances of electrochemical corrosion in the high acid environment. The technology of welding process selected in the paper is reliable. Research results provide references for welding operation of L245/825 lined steel pipe in high sour gas fields.

Abstract: The influence of short-term heat treatments on the environmental cracking and impact properties of a 7050-T7451 friction stir weld were investigated. Prisms, cut transverse to the welding direction, were exposed for minutes at temperatures between 100 oC and 800 oC in an oven or exposed to a propane torch flame and/or water / air quenched. A significant increase in the environmental cracking resistance (ductility ratio from 0.2 to 0.9) was observed for samples exposed to temperatures below the solutionizing limit, but between 240 oC and 280 oC. The fracture location changed from the “soft” heat affected zones to the nugget. Furthermore, the weld exhibited a decrease in the Charpy impact adsorbed energy as compared to the weld unaffected parent metal. An increase in the temperature improved the adsorbed energy, while a temperature decrease promoted the brittleness and reduced the adsorbed energy. The flow contours, also called onion ring bands, present within the nugget, represented a preferential fracture path during impact. The high temperature treatments followed by water quenching did not significantly improved the resistance to impact.