بررسي اتصال غير مشابه فولاد زنگ نزن آستنيتي AISI316 به فولاد كم كربن St37 با استفاده از جوشكاري اصطكاكي اغتشاشي

چكيده انگليسي :

Investigation on AISI 316 austenitic stainless steel to low carbon steel St 37 dissimilar joint by friction stir welding Hossein Khosrovaninezhad h khosrovaninezhad@ma iut ac ir Date of Submission January 18 2014 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Morteza Shamanian Professor shamanian@cc iut ac irAhmad Rezaeian Assistant Professor a rezaeian@cc iut ac irAbstract In the present study microstructural and texture development mechanical properties and corrosionbehavior of dissimilar jointing between austenitic stainless steel AISI 316 and low carbon steelSt 37 by friction stir welding has been investigated The welding was carried out with rotationalspeeds of 400 600 800 rpm and linear speeds of 50 100 150 mm min The microstructure wascharacterized by scanning electron microscopy SEM and optical microscopy Possible phasetransformations were determined using X ray diffraction technique and electron diffractionspectroscopy Also changes in texture of the joints were studied using electron backscatterdiffraction EBSD technique Tensile test shear punch test and microhardness measurements wereconducted to evaluate the mechanical properties of the joints Also corrosion behavior of the jointswere assessed using Tafel polarization and Immersion tests The results showed that using frictionstir welding joints without defects were produced In addition no carbide and brittle phases weredetected at the joining boundary Microstructural investigations showed that the significantdecrease in grain size was occurred in the stir zone of the austenitic stainless steel for samplewelded at rotational speed of 600 rpm and linear speed of 50 mm min EBSD technique showedtexture has been modified to direction of compact planes and orientations Tensile test resultsdemonstrated that failure was occurred in the weld metal for samples welded at rotational speed of400 rpm for all linear speeds Whereas failure was occurred in the St 37 base metal for sampleswelded at rotational speeds of 600 800 rpm and linear speeds of 50 100 150 mm min According tothe shear punch test the highest ultimate shear strength as well as yield shear strength wasachieved for sample welded at rotational speed of 600 rpm and linear speed of 50 mm min whilethe mentioned sample showed the least elongation In addition the highest microhardness wasmeasured in the stir zone of austenitic stainless steel sample welded with the above mentionedwelding condition The results of corrosion behavior evaluation showed similar corrosion behavioras of St 37 base metal but the corrosion potential and the corrosion current density of weld metalswere higher in comparison to St 37 base metal Also the results of immersion test demonstratedthat the stir zone of St 37 steel side had the lowest resistance to pitting due to increase ofdislocations density and grain boundaries in this region Keywords dissimilar joint austenitic stainless steel AISI 316 low carbon steel friction stirwelding EBSD

خسرواني نژاد، حسين

بررسي اتصال غير مشابه فولاد زنگ نزن آستنيتي AISI316 به فولاد كم كربن St37 با استفاده از جوشكاري اصطكاكي اغتشاشي

EBSD