Productivity improvement with hot wire GTAW for 18%Ni maraging steel for fabrication of rocket motor casing

Abstract

ABSTRACT Maraging steel is a high-strength high-fracture toughness material presently being welded by conventional GTAW for the manufacturing of large rocket motor cases. However, this process has a limitation of low speed, low deposition and less productivity. Scum formation and lack of fusion, porosities are the key defects in GTAW welding. To increase the productivity and quality of the of maraging steel welding alternative and modified GTAW processes, hot wire GTAW (HW-GTAW) is attempted. For comparison, study on conventional GTAW & HW-GTAW process was performed. Mechanical properties and microstructure characterisation have been done. The productivity improvement by using hot wire process over conventional GTAW is discussed. Microstructure consists of martensite and small amount of reverted austenite in various zones. Relatively lower amount of reverted austenite in HW-GTAW process due to lesser number of passes (reduced heat input) is responsible for improved mechanical properties.