EFFECT OF WELDING PARAMETERS ON THE STRUCTURE, PROPERTIES AND SILT EROSION IN 1314 MARTENSITIC STAINLESS STEEL

Abstract

In the present study investigations have been carried out on the effect of various weld parameters on structure,mechanical properties and silt erosion behaviour of CA-6NM martensitic stainless steel (commonly known as 13/4 stainless steel). The steel has a nominal composition :- C:0.06 max. Mn:1.00, Si : 1.00, Cr : 11.5-14.0, Ni 3.5 - 4.5, S : 0.04, P : 0.04 and Mo : 0.4 - 1.00. In view of its high hardness and toughness it has a relatively high resistance to erosion under silt laden water. This steel is currently in use almost in all hydroelectric power projects in India in the fabrications of under water parts. Due to high silt in the Himalayan region, there is rapid damage of under water parts which leads to frequent shut downs of the power projects. The repair welding of these under water parts has to be carried out quite often. However, no standard practice has yet been developed for effective repair welding of these components. The work involves collections of field data on the present practice of repair welding in various hydroelectric projects in India as well as experimental studies with an aim to develop high erosion resistance in the repair welded components. The cast plates of 13/4 steel were given a standard heat treatment which comprised of austenitizing at 1050°C for 4 hours followed by Oil quenching and a subsequent tempering treatment at 620°C for 4 hours. Shielded metal arc welding was carried out on single V-groove at 60° using 444 L (martensitic stainless steel) electrodes as well as 309 Mo (austenitic stainless steel) electrodes.