Abstract
The microstructure and mechanical properties of an API 5CT L80 casing grade steel (0.24C 0,4Si 1.4Mn CrNiCu) have been studied after performing weld thermal simulations (with and without subsequent tempering) applying a thermal cycle weld simulator. Specimens were subjected to three different peak temperatures (1300 °C, 1150 °C, 950 °C) and five different cooling rates (1 °C/s, 3 °C/s, 5 °C/s, 10 °C/s, 60 °C/s) through the austenite transformation temperature range. Based on the microstructure, hardness values, and toughness properties of the simulated specimens, thermal cycles were selected and recommended for welding of L80 components by the SAG-FW (shielded active gas forge welding) method.
Highlights
Welding of high carbon equivalent (i.e. >0.53) steels has always been a challenge in the engineering industry
Large pearlite colonies were occasionally located close to the grain boundary ferrite, but mostly the microstructure consisted of a fine mixture of pearlite and Widmanstätten ferrite plates/needles
For specimen 1300(1), the phase transformation to Widmanstätten ferrite and pearlite occurred in the temperature range ~670–550 °C
Summary
Welding of high carbon equivalent (i.e. >0.53) steels has always been a challenge in the engineering industry. >0.53) steels has always been a challenge in the engineering industry. The stringent requirements for oil and gas applications demand better processing methods and excellent weld quality for safety and environment care. After an oil/gas well has been drilled, a pipe (casing) is inserted into the borehole to support its walls from caving. Steel tubes for casing applications must have high. Recommended for publication by Commission IX - Behaviour of Metals Subjected to Welding. AMR Engineering AS, Rosenkrantzgata 61B, N-3018 Drammen, Norway Threaded connections are commonly used, but these may leak if they are deformed when they are expanded downhole, which is an important reason for selecting forge welded connectors
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