Welding of API 5L-X80 steel with different cooling rates

This study aims to investigate the influence of cooling rate on API 5L-X80 steel, extracted from a circular section of pipeline, welded using the automated MAG process with two wires, one solid and one tubular metal-cored wire. To obtain different cooling rates, five different preheating temperatures were used. Double V bevels with noses were then welded at five different preheating and interpass temperatures. The mechanical and metallurgical properties of the welded bevels were evaluated using tensile, bending, impact (Charpy-V), and hardness (Vickers) tests. The results of the mechanical tests were higher than the minimums defined by the standard, with very interesting results. There was a good correlation between the hardness, tensile, and impact tests. The mechanical tests and metallurgical analyses showed that the combined effect of time and temperature created significant changes in the results. The mechanical properties of the welded joints were higher than the minimum requirements of the API 5L standard.