Weldability and toughness evaluation of pressure vessel quality steel using the shielded metal arc welding (SMAW) process

The present study was carried out to assess the weldability properties of A STM A537 Cl.1 pressure-vessel quality steel using the shielded metal are we lding (SMAW) process, Implant and elastic restraint cracking (ERC) tests we re conducted under different welding conditions to determine the cold crack ing susceptibility of the steel. The static fatigue limit values determined for the implant test indicate adequate resistance to cold cracking even wi th unbaked electrodes. The ERC test, however, established the necessity to rebake the electrodes before use, Lamellar tearing tests carried out using full-thickness plates under three welding conditions showed no incidence of lamellar tearing upon visual examination, ultrasonic inspection, and four- section macroexamination. Lamellar tearing tests were repeated using machin ed plates, such that the central segregated band located at the midthicknes s of the plate corresponded to the heat-affected zone (HAZ) of the weld. On ly in one (no rebake, heat input: 14.2 kJ cm(-1), weld restraint load: 42 k g mm(-2)) of the eight samples tested was lamellar tearing observed. This w as probably accentuated due to the combined effects of the presence of loca lized packets of a hard phase (bainite) and a high hydrogen level (unbaked electrodes) in the weld joint. Optimal welding conditions were formulated b ased on the above tests. The weld joint was subjected to extensive tests an d found to exhibit excellent strength (tensile strength: 56.8 kg mm(-2), or 557 MPa), and low temperature impact toughness (7.4 and 4.5 kg-m at -20 de grees C for weld metal, WM, and HAZ) properties. Crack tip opening displace ment tests carried out for the WM and HAZ resulted in delta(m) values 0.36 and 0.27 mm, respectively, which indicates adequate resistance to brittle f racture.