Gas Shielded Arc Welding of High Carbon Steel (Report 1)

Effects of Shielding Gas Compositions on Properties of Weld Metals

Abstract

Hot cracking susceptibility of weld metals by angle expanding type cracking test (gas mixture ratio; 0, 20, 40%), chemical compositions of weld metals by bead welding (0, 10, 20, 30, 40, 50%) and mechanical properties, chemical compositions of weld metals by narrow gap butt welding (gap; 10 mm, 0, 20%) in the flat position and vertical position have been investigated for CO₂-O₂, Ar-CO₂, Ar-O₂ gas shielded arc welding of high carbon steel (0.65%C, 0.O26%S). The results obtained are as follows:
(1) Appropriate shielding gas composition concerning hot cracking susceptibility is CO₂+20%O₂. In case of Ar-CO₂, Ar-O₂ shielding gases, hot cracking susceptibility increase as increasing gas mixture ratio.
(2) In case of bead welding, carbon contents of weld metals increase 0.24%, to 0.34% as increasing gas mixture ratio. Contents of Si, Mn, Ti decrease as increasing gas mixture ratio. Decreasing tendency of these elements are in order of Ar-O2, CO2-O2 and Ar-CO2. Hot cracking are not recognized in the weld .metals:
(3) In case of narrow gap welding, weld metals with sound mechanical properties (tensile test, impact test) are obtained by CO2+20%O2. Carbon contents of weld metals for butt welding in the flat position are about 0.14-0.15% and for vertical welding are about 0.18% and hot cracking are not recognized in the weld metals.