Abstract
The aim of this research paper is to investigate the efficiency of dissimilar friction welded super duplex stainless steel SAF 2507 and mild steel joints. The joints were obtained using rotary friction welding process. Friction pressure and forging pressure are varied in three different cases but rotational speed and friction time are kept constant .The joints were subjected to tensile strength and metallographic study. The tensile strength of welded joints compared to that of SDSS SAF 2507 and mild steel in as received condition. The joint efficiency were calculated .The tensile strength and joints efficiency decreased with increasing friction pressure and forging pressure .The results attributed to change in mechanical, physical properties ,and micro structural changes of welded joints like change in ferrite to austenite percent, precipitation of carbides and nitrides ,sigma phase,….etc. Key words: Friction welding, super duplex stainless steel, tensile strength
Highlights
Duplex stainless steels DSS are iron (Fe)-Chromium (Cr)-Nickel (Ni) alloy with approximately equal volume fraction of ferrite and austenite .Ferritic stainless steels have high yield strength and good stress corrosion resistance but show brittleness and poor ductility, while austenitic stainless steels have high toughness, but they are sensitive in local corrosion in chloride environment and have low yield strength [1]
Satyanarayanan et al [5]studied the effect of roughness of faying surface of austenitic stainless steel on friction welded dissimilar joints with ferritic stainless steel, they found that notch tensile strength will increase with increasing roughness up to critical value and thereafter a descending trend is noted .A.Kurt [6] studied mechanical properties of dissimilar friction welded mild steel and bronze joints and they reported that the tensile strength of dissimilar joint can reach 70% of base metal strength
Large number of friction welded dissimilar material have been reported up to date the information about dissimilar friction welded super duplex stainless and mild steel is very scare .The aim of this study is to examine efficiency of dissimilar friction welded( super duplex stainless steel SAF 2507 – mild steel ) joints
Summary
Duplex stainless steels DSS are iron (Fe)-Chromium (Cr)-Nickel (Ni) alloy with approximately equal volume fraction of ferrite and austenite .Ferritic stainless steels have high yield strength and good stress corrosion resistance but show brittleness and poor ductility, while austenitic stainless steels have high toughness, but they are sensitive in local corrosion in chloride environment and have low yield strength [1]. Duplex stainless steels and mild steel are widely used materials due to their excellent mechanical and physical properties .In engineering applications and under some particular circumstance the welding of these two dissimilar materials is mandatory and it is important to produce high quality joints between them .Among different types of welding technique to join materials, friction welding is more acceptable compared to fusion welding processes because of advantages such as high material saving ,low production time limited heat effected zone .Friction welding can be used for welding similar and dissimilar counterparts even with a great difference in mechanical and metallurgical properties like melting point(tungsten and copper),low melting point materials (copper and aluminum) and material strength (stainless steel and pure aluminum)[3].Friction welding classified as a solid state joining process in which bonding is produced at a temperature lower than the melting point of base materials .The most important parameters in friction welding are friction pressure, forging pressure, friction time ,and rotational speed. A. Hascalik et al [7] studied fatigue behavior and tensile strength of friction welded dissimilar AISI 304 austenitic –AISI 4340 ferritic stainless steel joints and concluded that the tensile strength and fatigue endurance will decrease with increasing rotational speed during friction welding process. Eder Padun Alves et al [8] reported that tensile strength of dissimilar friction welded AISI 304 stainless steel and AA 1050 aluminum is higher than that of fusion welding processes
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