ASSESSMENT OF MECHANICAL PROPERTIES OF WELDED JOINTS OF DISSIMILAR METALS USING STAINLESS STEELS AND CARBON STEELS

Abstract

The purpose of this work is to evaluate the microstructure and mechanical properties of dissimilar weld joints, using austentic stainless steel electrodes types E308L& E309L, to join C-Mn Steel type 17MN4, DIN 17155. This steel is used in nuclear industries as a boiler tubes plates. Also, a ferritic steel electrode type AWS E7018 has been used in order to compare similar and dissimilar weld joints. Welding of specimens was conducted using shielded metal arc welding process (SMAW). Tensile and Charpy-V impact properties were determined at ambient temperature for the weld joints in the as-welded condition and after aging at 580°Cfor 2, 10, 50 and 1OOhours. Also were measured the ferrite number of weld deposits for E308 and E309 in the as-welded condition. In addition, Vickeres microhardness profiles across the fusion line were measured in as-welded condition, and for 2hr and 1 OOhr at 580°C. Optical and scanning electron microscopy were used to characterize the microstructure and fracture surface morphology. The • results showed that the C-Mn Steel is very sensitive for stress relief and care should be taken to select the proper time ofPWHT. Acicular ferrite

which is the predominant structure of the 7018 weld metal exhibited higher impact energy after 2hrs PWHT. The tendency of martensite formation at the fusion line between HAZ and weld Metal is higher in E308 than in E309. In addition, long period ofPWHT at 580°C showed that the E309L weld metal is susceptible to form higher carbides than the E308L.