پديد آورنده :
جعفري، حميد
عنوان :
جوشكاري مقاومتي نقطه اي فولاد زنگ نزن آستنيتي 304L فوق ريز دانه/ نانو ساختار توليد شده به روش ترمومكانيكي مارتنزيت و ارزيابي خواص منطقه اتصال
مقطع تحصيلي :
كارشناسي ارشد
محل تحصيل :
اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد
صفحه شمار :
چهارده، 91ص.: مصور، جدول، نمودار
يادداشت :
ص.ع. به فارسي و انگليسي
استاد راهنما :
فتح اله كريم زاده، محمد حسن عباسي
توصيفگر ها :
فرايند ترمومكانيكي پيشرفته , پرتو الكتريكي برگشتي ﴿EBSD﴾
تاريخ نمايه سازي :
94/2/1
استاد داور :
مرتضي شمعانيان، احمد كرمانپور
تاريخ ورود اطلاعات :
1396/09/26
چكيده انگليسي :
92 Resistance spot welding of ultra fine grained nanostructured 304Laustenitic stainless steel produced by martensite thermomechanical process and evaluation of weldment properties Hamid Jafari hamid jafari@ma iut ac ir Date of submission January 18 2015 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Fathallah Karimzadeh karimzadeh f@cc iut ac irMohammad Hasan Abbasi abbasi32@cc iut ac irAbstractIn this research in order to eliminate poor mechanical properties of austenitic 304L stainlesssteels and utilize useful capabilities of these alloys in industry firstly an ultrafine grained nanostructured AISI 304L steel was produced by martensite thermomechanical processing Thealloy was then welded by resistance spot welding method The samples were prepared indimensions of 80 40 10 mm and then cold rolled to 90 reduction in thickness Subsequently to get ultra fine fine grained austenitic structure the samples were annealed at 700 C and900 C for 5 to 360 minutes The produced samples containing various grain sizes wereresistance spot welded with different parameters of current 6 to 35 KA electrode force 4 KNand welding time 6 to 18 cycle 0 1 0 3 s For phase analysis X ray diffraction XRD andferitscope techniques were applied during cold roll and annealing process Investigation ofmicrostructures was carried out using optical microscope as well as scanning electronmicroscope SEM Electron backscatter diffraction was used for studying weld microstructure XRD pattern of rolled samples exhibited the transformation of austenite to martensite while forannealed samples it was reverse Microstructure of annealed samples showed that annealing at700 C for 120 minutes leads to ultra fined nanostructured with grain size of 400 nm and also annealing at 900 C for 5 and 180 minutes leads tow steel with grain size of 3 and 12 micron respectively Tensile strength of ultra fine sample its elongation and hardness were 1060 MPa 48 and 330 VHN respectively Studies of weld nugget structure obtained by EBSD provedthe existence of casting structure around the weld spot via formation of austenite matrix inaddition to 3 delta ferrite phase During shear tensile test the fracture occurred in twodistinct modes including interfacial and or pullout failure The pullout failure is the most idealtype of failure in tensile shear test The most tensile shear peak load of weld spot of ultra finedsamples was 12000 N while its hardness was 250 VHN obtained through welding with 30 to35 KA currents 18 cycles 0 3 s welding time and 4 KN 80MPa electrode force The Resultsfor different welded samples which had various grain sizes showed that by increasing of grainsize the fracture load decreases Also the hardness of ultra fined sample in comparison withother samples which had grain sizes of 3 12 micron and as received steel was more Studyingthe fracture surfaces of the weld nugget in both cases showed that the occurred failure was aductile failure with the formation of dimples Tensile direction of dimples in line of appliedforce showed that the failure of the weld nugget had a shear tensile nature Keywords 304L stainless Steel Ultra fine Grained nano structured Resistance Spot Welding Advanced Thermomechanical Process Electron Backscatter Diffraction EBSD
استاد راهنما :
فتح اله كريم زاده، محمد حسن عباسي
استاد داور :
مرتضي شمعانيان، احمد كرمانپور
