بررسي ريز ساختار و خواص مكانيكي اتصال فولاد St37 - فولاد CK60به وسيله جوشكاري انفجاري

چكيده انگليسي :

81Investigation of Microstructure and Mechanical Properties of St37 Ck60 Steel Joints by Explosive welding Majid Yazdani majid yazdani@ma iut ac ir 14 Jan 2015 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Mohammad Reza Toroghinejad toroghi@cc iut ac irAbstractThe aim of the present study was to investigate the microstructure and mechanicalproperties of a Ck60 St37 composite plate produced by explosive welding technique Theexplosive ratio and stand off distance were set to be 1 7 and 1 5t t flyer thickness respectively In as welded condition mechanical tests such as shear and impact tests aswell as microhardness measurements were conducted Then stress relieved treatment wereperformed at different temperatures In order to compare results with as welded condition mechanical properties were evaluated on the stress relieved samples In addition in orderto have wear resistance samples various hardening treatments was applied consistingnormalizing oil quenching water quenching and tempering at 200 400 and 600 C Then wear and shear tests were carried out on the above heat treated samples Optical andscanning electron microscopy observations revealed a wavy morphology at the bondinginterface In addition locally melted zones were formed along the interface However samples which were subjected to the heat treatment did not show any sign of the localmelted zones adjacent to the interface It was also found that at 650 and 700 C the grainslocated at the interface were coarsened The results also showed that even after thehardening treatment the wavy morphology was observed at the interface and the ferrite perlite structure was transformed to martensite structure on the Ck60 side However on theSt37 side the ferrite perlite structure was remained unchanged Microhardness resultsshowed that the maximum hardness was obtained near the explosively welded interface When stress relieving treatment was performed at 600 C the hardness values weredecreased while the maximum hardness was still measured to be near the interface Also it was also seen that at 650 and 700 C hardness was significantly decreased near theinterface mainly due to the grain coarsening took place on the both sides of the interface Shear tests on the welded metals also showed that the average shear strength for as weldedand stress relieved conditions were higher than that of the values reported as the standardlevels implying that composite plates could be safely used Water quenching caused theleast shear strength whereas tempering at 600 C resulted in the maximum shear strengthlevel The results of the impact tests for as welded and stress relieved condition showedthat heat treatment at the three temperatures led in greater absorbed energy The bondingstrength was determined in two ways one with the cladding metal in tension and the otherwith the cladding metal in compression Bending test results showed that these joints couldbe safely used when the cladded metal was under compression otherwise it would befractured Moreover wear test showed that samples which water quenched and tempered at200 C exhibited greater wear resistance than the samples subjected to oil quenching andtempering at 200 400 C Finally by considering both wear resistance and shear strength oil quenching and tempering at 400 C were found to give rise the optimum conditions Keywords Explosive welding Stress relieving Microstructure Wear resistance

يزداني، مجيد

بررسي ريز ساختار و خواص مكانيكي اتصال فولاد St37 - فولاد CK60به وسيله جوشكاري انفجاري

آزاد سازي تنش , مقاومت به سايش