Weld joint properties of nitrogen-alloyed austenitic stainless steel using multi-pass GMA welding
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(2020) 20:82
ORIGINAL ARTICLE
Weld joint properties of nitrogen‑alloyed austenitic stainless steel using multi‑pass GMA welding Naveen Kumar1 · Navneet Arora1 · S. K. Goel2 Received: 6 March 2020 / Revised: 5 June 2020 / Accepted: 22 June 2020 © Wroclaw University of Science and Technology 2020
Abstract The welding of nitrogen (0.29 wt%)-alloyed austenitic steel (grade 23-8-N) was performed with gas metal arc welding process. Solution treatment was performed at 950 °C and 1150 °C on base metal prior to weld. Base metal after second treatment has maximum ultimate tensile strength of 942 MPa and impact toughness 66 J. The microstructures of different zones of the weld joint were characterized using an optical microscope and field scanning electron microscope (FESEM). The microhardness, tensile and impact toughness tests of the weldments were conducted along with weld ferrite evaluation. ER2209 duplex filler metal used for welding has lower C and N content which changed the weld solidification mode. Weld has microstructure containing austenite + ferrite. Being a strong austenite former, nitrogen caused minimum ferrite near weld–HAZ interface while maximum ferrite content was observed at weld centre. Weld metal has minimum while base metal has maximum microhardness. UTS (892 MPa) and impact strength (96 J) of weld made on 1150 °C solution-treated base metal were maximum as compared to other weld joints. Keywords 23-8-N nitronic steel · ER 2209 duplex filler · Solution treatment · Characterization · Carbide · Hardness · Ferrite
1 Introduction Alloying with nitrogen improves the corrosion resistance and mechanical properties of austenitic stainless steels (ASS) and duplex steels. There are several grades of steels available with varying nitrogen content. Any steel is called high-nitrogen steel (HNS) if it contains more than 0.4 wt% of N [1]. Nickel content of steel used for producing medical equipment causes allergy and other side effects to the human body, so it is necessary to abolish the nickel content of the equipment. Nitrogen is gaining attention as a replacement of nickel in steels due to its lower price and easy availability. Moreover, being a strong austenite stabiliser, it improves the mechanical strength without affecting the ductility and impact toughness properties. Further, nitrogen addition to ASS is found to decrease the stacking fault energy (SFE)
* Naveen Kumar [email protected] 1
Mechanical and Industrial Engineering Department, Indian Institute of Technology, Roorkee, Roorkee, India
Star Wire (India) Ltd, Faridabad, India
2
and improve the work-hardening capability of these materials. In the last few years, nitrogen-containing ASS are getting much attention due to their superior properties [2]. Sometimes these steels are called ‘Nitronic steels’ depending upon the nitrogen content (≤ 0.4 wt%). The optimum content of nitrogen in Cr–Mn austenitic stainless steels improves mechanical and tribological properties [3]. In recent studies, new grades of nitronic steels (21-4-N and 23-8-N
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