Correlation of HIC Resistance with Penetrator of ERW Welds

A study on the correlation of hydrogen induced cracking (HIC) resistance with penetrator of electric resistance welded (ERW) joints has been investigated in order to improve the resistance to HIC at bond line in API 5L X65 line pipes. It was found that the elongated (Si, Mn, Al) rich oxides inclusions at bond line provided a preferential site for HIC, and their fraction should be lower than 0.03% to have a satisfactory HIC resistance. The combination of high welding speed and high power input was proven to be preferable to lower penetrator ratio, and an optimum ERW condition which presented a special relationship of power input, welding speed, upset force and strip thickness, was suggested to have penetrator ratio at bond line less than 0.02%. This optimum ERW condition successfully led to an excellent HIC resistance at bond line.