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Öğe Determination of diffusable hydrogen in duplex stainless stell welds(2001) Kaçar, R.The risk of hydrogen cracking in steel welds depends on a number of interrelated factors, the most important of which is the hydrogen content that originates from the welding consumable. In designing a welding procedure to avoid cracking, it is necessary to define the hydrogen level associated with a given welding consumable, using standard methods. In this study, the Oerlikon/Yanaco hydrogen gas analysis method, which is widely used to determine the hydrogen content of ordinary ferritic steel welds, was modified, and thus the time-temperature relationship of hydrogen evolution from duplex stainless steel weld metal at 200, 400, 600 and 950°C was investigated experimentally and determined theoretically on the basis of BS 6693 samples. It was found that diffusible hydrogen evolution from weld metal heated at 400°C for 24 hours was completed experimentally and theoretically. In conclusion, the diffusible hydrogen amount which is potentially hazardous in the long term in duplex stainless steel weld metal can be easily determined by modification of the Oerlikon/Yanaco methods.Öğe Effect of solidification mode and morphology of microstructure on the hydrogen content of duplex stainless steel weld metal(Elsevier Ltd, 2004) Kaçar, R.The evolution rate of hydrogen from a duplex weld depends on sample geometry, temperature and microstructure. These factors have important consequences for the determination of hydrogen in duplex stainless steel welds. Because of the low hydrogen diffusibility and high hydrogen solubility in austenite, a standard method (BS 6693: 1988) which existed to determine the hydrogen content of ferritic steel welds as a means of assessing welding consumables, is not suitable for duplex welds. As a result of extensive research, a modified test method has been used involving encapsulation of the weld sample in Pyrex, evolution at 400 °C for 24 h, and followed by hydrogen analysis in an Oerlikon/Yanaco gas chromatograph. In this present work, the effect of solidification mode and microstructure on weld hydrogen content, and the evolution of hydrogen from such welds has been investigated by using experimental electrodes which are designed to give varying ferrite/austenite ratio in the welds. It was found that the measured weld hydrogen contents were almost constant since they arose from the flux/binder combinations which were the same for each type of experimental electrodes. Thus, the potential hydrogen from each type was the same and similar amounts became trapped during the rapid solidification of the weld pool, irrespective of final ferrite content. © 2003 Elsevier Ltd. All rights reserved.Öğe Effect of static strain aging on the fatigue behavior of S275JRC steel(Carl Hanser Verlag, 2017) Bülbül, A.; Kaçar, R.; Emre, H.E.In this study, the effect of static strain aging on the fatigue behavior of a mild steel (S275JRC) was evaluated. For this purpose, the 5 % prestrained mild steel was aged at a temperature of 160 °C for different intervals. The aging behavior was determined primarily for the as-received (AR) as well as in the homogenization and normalizing heat treated (H+N heat treated) condition. The yield stresses before and after aging process as well as the hardness values of the aged steels were measured for the assessment of the strain aging progress. The dynamic mechanical behavior of strain aged samples was also determined by fatigue test under the dynamic loads. An increase in the yield strength due to strain aging and hardness induced improvement in fatigue strength of the steel were observed. © Carl Hanser Verlag GmbH & Co. KGÖğe The effect of weld current intensity and welding time resistance spot weld of duplex stainless steel(2011) Durgut, E.; Kaçar, R.In this study, effects of welding current intensity and welding time on the resistance spot weld quality of AISI 2205 duplex stainless steel was investigated in detail. To this purpose, the tensile shear load bearing capacity and the hardness profile of weldment were determined. The microstructure of welded samples was evaluated so the relationship between the microstructure and mechanical properties were determined. It was found that the mechanical properties of the welded samples were varied depending on the welding time and weld current intensity.Öğe Effect of welding speed on the mechanical properties and microstructure of laser welded AISI 316L stainless steel(Gazi Universitesi Muhendislik-Mimarlik, 2015) Köse, C.; Kaçar, R.In this study, AISI 316L (X2CrNiMo17-12-2) austenitic stainless steel plates were joined with CO2 Laser Beam Welding (LBW) method. The welding process were carried out in 50% Ar+50% He shielding gas atmosphere by using 3500W laser power for 90-180-270 cm/min different welding speeds. The samples were joined autogenously in butt welding position without using filler metal. In order to determine the mechanical properties of welded joints, the tensile, charpy impact and three point bending tests were applied. In addition, the hardness of the welded sample was measured on the cross section. The microstructure characterization of welded samples was carried out using with optical microscope, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), elementel mapping and X-ray diffraction (XRD) analysis. As a result of this study, it was found that the mechanical properties of AISI 316L weldment recovered and the microstructure morphology of weld metal altered by increasing laser welding speed due to high cooling rate.Öğe Fatigue behaviours of friction welded drill pipes(2013) Emre, H.E.; Kaçar, R.The drilling pipes are used under the different load in the service condition. In this study, N80-N80 similar drill pipes and N80-42CrMo4, N80-S355J2 dissimilar steel pipes were welded with friction welding process. The fatigue behavior of welded samples was investigated and the results were interpreted by considering the hardness values and tensile strength. It was found that the fatigue behaviour of friction welded samples recovered by the increasing tensile strength and hardness.Öğe Friction stir spot weldability of Al-Cu-Al material couple(2011) Kaçar, R.; Emre, H.E.; Demir, H.; Gündüz, S.Recently joining of metallic materials has gained a big importance. The problem can arise joining of advanced and new materials especially in industry. Thus, the solid state bonding methods have become much more popular effective in joining such materials. One of them is friction stir spot welding. In this study, 5754 quality aluminum couple using interlayer copper were joined by friction stir spot welding method using 1000 and 1600 rpm pin rotation for 3 and 5 second time intervals. The mechanical and metallurgical properties of weldment determined. The finding from this study compared with result that was obtained from FSSW Al-Al couple. The mechanical properties of FSSW welded Al-Cu-Al couple found better than Al-Al weldment.Öğe In vitro bioactivity and corrosion properties of laser beam welded medical grade AISI 316L stainless steel in simulated body fluid(Electrochemical Science Group, 2016) Köse, C.; Kaçar, R.AISI 316L stainless steel sheet was joined by CO2 laser beam welding method. In order to determine in vitro bioactivity and corrosion properties of the laser beam welded and non-welded samples were immersed in Simulated Body Fluid (SBF) for 1, 3, 7, 14, 21, 28 days. The bone-like apatite formation was investigated on the surface of the weld area and non-welded samples. Also, corrosion resistance of the laser beam welded and non-welded samples were determined via weight loss method. No corrosion mechanisms were observed in the heat affected zone (HAZ), weld metal of laser beam welded joints, and base material. © 2016 The Authors.Öğe Increasing the strength of AISI 430 ferritic stainless steel by static strain ageing(2009) Kaçar, R.; Gündüz, S.In this study, the strain ageing behaviour of AISI 430 ferritic stainless steel is investigated. A certain part of the as-received ferritic stainless steel test pieces was pre-strained for 5 % in tension, then aged at 100, 200, 300, and 400 °C for 30 min in a furnace. The other part was solution heat-treated at 950 °C for 15 minutes, water quenched and pre-strained for 2 or 5 % in tension, then aged at 100, 200, 300, and 400 CC for 30 min. UTS (ultimate tensile strength), ? Y(increase in yield strength due to strain ageing), percentage elongation and yield point elongation measurements were employed to investigate the effect of strain ageing on the mechanical properties. The experimental work has revealed that different ageing temperatures significantly affect the mechanical properties of the AISI 430 ferritic stainless steel.Öğe An investigation of microstructure/property relationships in dissimilar welds between martensitic and austenitic stainless steels(Elsevier Ltd, 2004) Kaçar, R.; Baylan, O.The metallurgical characteristics, tensile, hardness, toughness and corrosion resistance of dissimilar welds between X5CrNi18-10 grade austenitic and X20CrMo13 grade martensitic stainless steel have been evaluated. Both austenitic and duplex stainless steel electrodes were used to join this combination, using multipass manual metal arc welding process. Defect free welds were made with each welding consumable. It was found that the tensile strength of weldment, which was produced by duplex electrode (E2209-17), was slightly lower than that of austenitic electrode (E308L-16). The toughness of the both E2209-17 and E308L-16 deposits was acceptable even at low temperature regardless of heat input. Hardness was increased in both welds made with E2209-17 duplex and E308L-16 austenitic electrode along the X20CrMo13/weld metal fusion boundary due to heat annealing and then following high cooling rate. The pitting corrosion resistance of the weld metal made with E308L-16 and E2209-17 filler metal was found acceptable. Although, heat affected zone in the weldment and X20CrMo13 base metal were affected by electrolytic corrosion. This investigation has shown that both filler metals can be used to join austenitic stainless steel to the martensitic stainless steel. © 2003 Elsevier Ltd. All rights reserved.Öğe Resistance spot weldability of deformed TRIP800 steel: Various parameters were investigated for obtaining optimum tensile shear strength, weld button geometry, and electrode indentation(American Welding Society, 2016) Emre, H.E.; Kaçar, R.In order to simulate automotive manufacturing conditions, the spot weldability of cold-deformed, in tension by 10%, TRIP800 steels was investigated in this study. Tensile shear strength and failure mode associated with button geometry and electrode indentations were also evaluated, and weld lobe was drawn for resistance spot-welded deformed TRIP800 steel. The microstructure of the weldment was evaluated and the hardness profile of the weldment was also determined. It was found that the properties of the weldment are directly related to parameters used for the process and deformation of base metal prior to welding. It was found that the button diameter and button size ratio of deformed TRIP800 steel spot welds should be at least 4t and 0.14-0.30, respectively, for pullout failure mode, acceptable shear strength, and surface quality. Copyright © 2016 by American Welding Society in both printed and electronic formats.Öğe Strengthening of 6063 aluminium alloy by strain ageing(2008) Gündüz, S.; Kaçar, R.In this study, the artificial ageing behaviour of 6063 Al-alloy is investigated. A certain part of the aluminium test pieces was solution heat treated (SHT) at 520°C for 2 h, water quenched, then aged at 180°C for 1, 3, 5, 7, 9 and 15 h and the other part was pre-strained for 2 % in tension shortly after the solution heat treatment (SHTP), then aged at 180°C for 1, 3, 5, 7, 9, 15 h in a furnace. Tensile strength, flow stress at 3 %, microhardness and electrical conductivity measurements were employed to investigate the effect of artificial ageing on the mechanical properties of Al-alloy. The variations in ageing time have improved the mechanical properties of the 6063 Al-alloy, whereas the ductility has decreased. The experimental work has revealed that different ageing times at 180°C play a very important role in the precipitation hardening process of the 6063 Al-alloy.
