Keyhole TIG welding of 3-mm-thick 10MnNiCr steel plates

The stable K-TIG butt welding of 3-mm-thick 10MnNiCr steel plates was achieved with the welding speed of 650–700 mm/min and the welding current of 355–370 A. The keyhole behaviours and stability were investigated by industrial cameras; it was found that the size of the keyhole outlet has an essential relationship with the stability of the keyhole. The appropriate outlet length of a stable keyhole is 5–7 mm. The microstructure and the mechanical properties of the welded joint were studied. The weld structures are dominated by granular and striped bainite. The structures in the superheated zone contain granular bainite, striped bainite, and retained austenite. The recrystallization and the incomplete crystallization zone structures are mainly lamellar and granular pearlite. The tensile samples of the welded joint broke in the base metal area, which indicates the K-TIG welded joint is qualified.