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Study of Mechanical Behavior in Austenitic Stainless Steel 316 LN Welded Joints

D Harish Kumar1 and A Somi Reddy2
1.KITS, Warangal 506371, Andhra Pradesh, India.
2.Vivekananda Institute of Technology & Science, Karimnagar 505001, Andhra Pradesh, India.

Abstract—Low carbon grade type 316 austenitic stainless steel, alloyed with nitrogen designated as 316 LN SS exhibit superior strength at ambient and high temperatures, excellent corrosion resistance to replace other expensive materials. Austenitic stainless steel get sensitized during welding. The problem of sensitization can be over come by decreasing the carbon content. Reducing the carbon content would cause drastic reduction in mechanical properties. Replacing much of the carbon with nitrogen can offset this deterioration in mechanical properties. Nitrogen in solid solution is the most beneficial alloying element in promoting high strength in austenitic SS without sacrificing their good ductility and toughness. The upper limit of nitrogen is set on considerations of minimizing scatter in mechanical properties and improving weldability. Phosphorous, sulphur and silicon are treated as impurities having adverse effects on weldability. The selection of the material is based on its good combination of tensile, creep strength, ductility and its high resistance to stress corrosion cracking and sensitization. Nickel content has been known as an element that stabilizes austenite and increases toughness. Nitrogen has diverse effects on the microstructure and solidification cracking behavior of type 316 stainless steel. In the present paper an attempt has been made to present the influencing factors on the weldability of 316 LN SS. The welding processes such as single pass activated TIG (A-TIG), multi-pass activated TIG (MP-TIG) welding and Laser welding were discussed in relation to the 316 LN austenitic stainless steel. Residual stresses are a system of self-equilibrating stresses, which may exist when it is free from external loads or forces. The existence of such stresses have been analyzed and compared. Non-destructive techniques have been used for measuring residual stresses and defects in welding. The purpose of this review is to investigate weldability of 316 LN SS, study the beneficial effect on fully austenitic steels with particular emphasis on nitrogen-alloyed and stabilized stainless steels.

Index Terms—Austenitic stainless steel, Sensitization, Weldability, Residual stresses, Hot cracking and nitrogen

Cite: D Harish Kumar and A Somi Reddy, "Study of Mechanical Behavior in Austenitic Stainless Steel 316 LN Welded Joints," International Journal of Mechanical Engineering and Robotics Research, Vol.2, No. 1, pp. 37-56, January 2013.