Effect of cerium oxide flux on active flux TIG welding of 800 MPa super steel

The effect of cerium oxide on penetration, microstructure and mechanical properties of BS700MC super steel weld was investigated. Cerium oxides changed the penetration of the weld via changing the Marangoni convection in the weld pool, and the heat input was different with different content of cerium oxide. The results demonstrate a gradual decrease of the heat input as the content of cerium oxide increased from 0 to 15%. The heat input increased significantly for the content of cerium oxide surpassed 15%. A certain amount of the cerium oxides changed the microstructures of the welds by transiting the cerium element from the flux layers to the weld metal. The content of acicular ferrites reached the maximum when the cerium oxide content was 15%, the strength, low-temperature impact and micro-hardness achieved their optimal value accordingly. As the content of cerium oxide is less or more than the optimal value, the content of proeutectoid ferrites increased, and the values of the mechanical properties of the weld deteriorated.