تاثير پارامترهاي جوشكاري بر خواص مكانيكي و ساختار ميكروسكوپي فولاد زنگ نزن آستنيتي 316 جوش داده شده به روش اصطكاكي اغتشاشي

چكيده انگليسي :

The Effect of Welding Parameters on Mechanical Properties andMicrostructure of Austenitic Stainless Steel AISI 316 Welded by Friction Stir Welding Masood Eslami M eslami@me iut ac ir Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohsen Safavi Mosafavi@cc iut ac irAbstract Friction stir welding is one of the new solid state welding methods Recently extensive researches havebeen performed on stainless steel welding using this method In this research the effect of the tool rotationaland traverse speed on mechanical properties and microstructure of austenitic stainless steel AISI 316 wasexamined Plates with dimension of 150 100 2 mm were joined by this method The rotational speeds weredetermined to be 630 800 and 1000 RPM and traverse speeds as 55 63 and 80 mm min Tungsten carbidewith conical pin profile with the lower diameter of 5 and upper diameter of 5 5mm was used as the toolmetal During the studies the tool angle of 0 was kept constant Full penetrated and defect free butt weldedjoints were successfully produced under all applied welding conditions In order to study mechanicalproperties the tensile impact and hardness tests were performed and in order to study microstructure opticalmicroscope and scanning electron microscope were used The joints showed a higher tensile strength yieldstrength and hardness than the base metal The impact test results showed that this method reduce the impactproperty of metal and with increasing of traverse and rotational speeds fracture energy has reduced Thehardness test results showed that this mechanical property has been improved and with increasing traverseand rotational speeds the hardness increased too Study of tensile test results showed the improvement ofyield and tensile strengths Increasing rotational and traverse speed the yield and tensile strengths haveincreased first and decreased finally Metallurgical tests showed that the friction stir welding improved themicrostructure and made the grains forming austenitic phase smaller and has improved the metallurgicalproperties Improving the microstructure has improved the hardness tensile strength and yield strengthproperties too In the stir zone of the austenitic stainless steel a refined grain structure with some features ofdynamic recrystallization was evidenced Also intermetallic compounds and their effects on the mechanicalproperties of the joints were investigated Response surface method has used for analyzing hardness tensileand yield strength and fracture energy test results The response surface method helps for predicting the testresults and analysis the results with increasing the tool rotational and traverse speed at the same time and alsohelps for determining the mechanical property that the welding parameters have the most effect on it Mechanical tests analysis using the response surface method showed that increasing rotational and traversespeed has reduced the tensile strength and fracture energy of specimens but has improved the hardness Response surface method analysis showed that the effect of the tool rotational and traverse speed on thehardness is more than fracture energy tensile strength and yield strength Keywords Friction stir welding Stainless steel Traverse and rotational speed Mechanical and metallurgicalproperties

اسلامي، مسعود

تاثير پارامترهاي جوشكاري بر خواص مكانيكي و ساختار ميكروسكوپي فولاد زنگ نزن آستنيتي 316 جوش داده شده به روش اصطكاكي اغتشاشي

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