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Öğe Development of weld lobe for resistance spot-welded TRIP800 steel and evaluation of fracture mode of its weldment(Springer London Ltd, 2016) Emre, Hayriye Ertek; Kacar, RamazanThe weld lobe in spot welding provides an indication of good quality joining and the tolerance of the weld schedule in production stage. In this study, TRIP800 steel was used for the experiments, and welding times of 5, 10, 15, 20, and 25 cycles were selected with welding currents ranging from 1 to 7 kA with an interval of 2 kA and from 7 to 10 kA with an interval of 1 kA. The effect of heat input associated with welding current and welding time on nugget geometry, such as diameter, height, nugget size ratio, and electrode indentation, was determined by optical microscope. The welded specimens were exposed to tensile shear tests. Tensile shear strength and failure mode associated with nugget geometry and electrode indentations were also evaluated and weld lobe was drawn accordingly. It was found that the nugget diameter and nugget size ratio of TRIP800 steel spot welds should be at least 4.5aet and 0.15-0.30, respectively, for pullout failure mode, acceptable shear strength, and surface quality.Öğe Dynamic Strain Aging Behavior of Cobalt-Based Haynes188 Superalloy(Springer, 2024) Nohutcu, Samet; Kacar, RamazanSuperalloys have been developed to meet the need for materials that will serve at high operating temperatures without losing their properties. The three major classes of superalloys are nickel-, iron-, and cobalt-based alloys. Cobalt-based superalloys are used between 650 and 1100 degrees C temperatures due to their wear, creep, oxidation, heat, and corrosion resistance. Haynes 188, an essential family member, is mainly used in gas turbine engines such as combustion chambers, air transfer ducts, fixed blades, exhaust nozzles, and flame holder components. Strengthening is achieved by solid solution or carbide and intermetallic formed in their structures. None of the cobalt-based superalloys are fully solid solution alloys. Almost all contain carbide or intermetallic compounds. This can lead to dynamic strain aging at different service temperatures in the alloy under load, resulting in a reduction in ductility. Considering the temperatures in service conditions, the dynamic strain ageing behavior of Haynes 188 alloy at 25, 250, 400, 550, 700, 850, and 1000 degrees C was thoroughly examined for the first time in this study. The unsteady yielding with different type's serration verified that the dynamic strain ageing is formed in Haynes 188 alloy. Therefore, ductility of alloy decreased in the temperature range of 250-700 degrees C, particularly at 550 degrees C.Öğe Effect of bright annealing process on the properties of TIG welded duplex stainless steel tube(Inderscience Enterprises Ltd, 2015) Kacar, Ramazan; Emre, Hayriye ErtekPassivation is the process of forming a protective oxide film on stainless steel. It is accomplished through an appropriate inline bright annealing process. Duplex stainless steel exhibits optimum mechanical and corrosion properties with the austenite-ferrite phase balance in its structure. However, the ferrite-austenite equilibrium in duplex structure can also be affected by inline bright annealing process, in which the heating of stainless steel to a suitably high temperature in a reducing atmosphere takes place. For this reason, the effect of inline bright annealing process on the microstructure and mechanical properties of TIG welded AISI2205 stainless steel tube was evaluated in this study. The results point out that the structure and mechanical properties of the duplex stainless steel tube are affected by the inline bright annealing process. In light of foregoing findings, the sample that was inline bright annealed in reducing nitrogen gas atmosphere has given optimum mechanical properties.Öğe The effect of CO2 laser beam welded AISI 316L austenitic stainless steel on the viability of fibroblast cells, in vitro(Elsevier Science Bv, 2016) Kose, Ceyhun; Kacar, Ramazan; Zorba, Asli Pinar; Bagirova, Melahat; Allahverdiyev, Adil M.It has been determined by the literature research that there is no clinical study on the in vivo and in vitro interaction of the cells with the laser beam welded joints of AISI 316L biomaterial. It is used as a prosthesis and implant material and that has adequate mechanical properties and corrosion resistance characteristics. Therefore, the interaction of the CO2 laser beam welded samples and samples of the base metal of AISI 316L austenitic stainless steel with L929 fibroblast cells as an element of connective tissue under in vitro conditions has been studied. To study the effect of the base metal and the laser welded test specimens on the viability of the fibroblast cells that act as an element of connective tissues in the body, they were kept in DMEMF-12 medium for 7, 14, 28 days and 18 months. The viability study was experimentally studied using the MTF method for 7, 14, 28 days. In addition, the direct interaction of the fibroblast cells seeded on 6 different plates with the samples was examined with an inverted microscope. The MIT cell viability experiment was repeated on the cells that were in contact with the samples. The statistical relationship was analyzed using a Tukey test for the variance with the GraphPad statistics software. The data regarding metallic ion release were identified with the ICP-MS method after the laser welded and main material samples were kept in cell culture medium for 18 months. The cell viability of the laser welded sample has been detected to be higher than that of the base metal and the control based on 7th day data. However, the laser welded sample's viability of the fibroblast cells has diminished by time during the test period of 14 and 28 days and base metal shows better viability when compared to the laser welded samples. On the other hand, the base metal and the laser welded sample show better cell viability effect when compared to the control group. According to the ICP-MS results of the main material and laser welded samples which were kept in the cell culture medium for 18 months, it was determined that the Fe, Ni and Cr ion concentration released to the cell culture medium from the laser welded test sample was less than that of the main material. (C) 2015 Elsevier B.V. All rights reserved.Öğe An effect of environment temperature and pre-heat treatment on the electrofusion welding of polyethylene natural gas pipes(Gazi Univ, Fac Engineering Architecture, 2018) Najafigharehtapeh, Asghar; Kacar, RamazanThe standard recommends for electrofusion welding of polyethylene pipes, used for natural gas and water transportation network to be carried out at the temperature from -5 degrees C up to +30 degrees C. In this study, an effect of the environment temperature on the properties of weldment is investigated. For this purpose, high density polyethylene (PE100) pipes were joined with electrofusion welding method at the various environment temperatures (room temperature, 0, -10, -20 and -30 degrees C) as received condition and by using preheat treatment (60 degrees C). According to standard, leaking and crushing test has been carried out and the double decohesion peeling test has been also applied for determining the strength of weldment. Thus, decohesion toughness, K, and nominal energy E-n, for decohesion of weldment calculated. Conclusively, the strength of the weldment increased meanwhile the ductility decreased by increasing crystalline amount in weld region associate to increasing environment temperature. It was determined that the pre-heat treatment process affected positively features of weldment which was joined in low environment temperature meanwhile; the strength of weldment joined at room temperature is affected negatively.Öğe Effect of heat treatment on the properties of plasma arc welded TRIP800 steel(Walter De Gruyter Gmbh, 2022) Karaoglu, Busra; Kacar, RamazanIn this study, the effect of heat treatment applied at various temperatures on the properties of plasma arc welded TRIP800 steel has been examined extensively. For this purpose, the low temperature heat treatment was carried out at -50, -20, and 0 degrees C for 2 h on a set of welded samples. Moreover, the heat treatment process was also applied for 2 h at various temperatures (i.e., 100, 200, 300, 400, 500, 600, 800, and 1000 degrees C) for another group of plasma arc welded TRIP800 steels. In addition, the properties of a set of samples without any heat treatment were determined in as-welded condition for a comparison. The mechanical properties of all samples were determined, and microstructures of samples were evaluated. As a result, the low temperature heat treatment applied at the specified temperatures did not have a significant effect on the ultimate tensile strength, and ductility of the joint but affected the yield strength positively. Besides, the ultimate tensile strength of heat treated samples also diminished with increasing processing temperature. It was found that the yield strength of the heat treatment applied samples showed an increase up to 500 degrees C, while the samples tested at 500 and 600 degrees C showed pronounced yielding behavior.Öğe Effect of Post Weld Heat Treatment Process on Microstructure and Mechanical Properties of Friction Welded Dissimilar Drill Pipe(Univ Fed Sao Carlos, Dept Engenharia Materials, 2015) Emre, Hayriye Ertek; Kacar, RamazanIn this study, N80-42CrMo4 dissimilar drill pipes were welded by a roto-friction welding machine. A set of welded samples were tested as-welded condition. Another set of welded samples were post weld heat treated (stress relief annealing) at the temperature of 600 degrees C, for 20 min. and then tested. The microstructures of the as-welded and stress relief annealed samples were examined by optical microscope and SEM. The properties of the all welded samples were determined by hardness measurement, tension and V notch-impact tests. The high hardness especially in the weld interface resulted in low toughness. As a conclusion, the stress relief annealing treatment caused a little decrease in yield strength and ultimate tensile strength, but increase in the elongation. The ductility of samples also increased after annealing treatment which is very important for static and dynamic loads.Öğe The effect of preheat & post weld heat treatment on the laser weldability of AISI 420 martensitic stainless steel(Elsevier Sci Ltd, 2014) Kose, Ceyhun; Kacar, RamazanThe martensitic stainless steels are widely used in many industries with their excellent mechanical properties and sufficient corrosion resistance. These steels usually are used for a wide range of applications like nuclear power plants, steam generators, mixer blades, pressure vessels, turbine blades, surgical tools, instrument manufacturing and so on. Contrary to good mechanical and corrosion properties of martensitic steels, poor weldability and cold cracking sensitivity are major problems that are faced in joining of these steels. In this study, the weldability of AISI 420 (X30Cr13) martensitic stainless steel by CO2 laser beam welding method has been investigated. Effects of pre and post weld heat treatments on mechanical properties and microstructure of laser welded AISI 420 martensitic stainless have also been determined. As a conclusion, it was determined that pre and post weld heat treatments sufficiently improved the mechanical properties of the welds. (C) 2014 Elsevier Ltd. All rights reserved.Öğe The effect of process parameter on the properties of spot welded cold deformed AISI304 grade austenitic stainless steel(Elsevier Science Sa, 2009) Karci, Feramuz; Kacar, Ramazan; Gunduz, SuleymanThe electrode force, weld current, and weld time are three essential parameters of the resistance spot welding process. This paper deals with the characterization and understanding the effect of weld time and the influence of different weld atmospheres in the resistance spot weldability of AISI304 grade stainless steel deformed in tension by 5%, 10%. or 20%. Therefore, the microstructure of the weldment was evaluated and the hardness and tensile shear load bearing capacity of weldment were also determined. It was found that the final mechanical properties of weldment are directly related to the parameters of the process used, knowing the weld time and rate of deformation prior to welding. (C) 2008 Elsevier B.V. All rights reserved.Öğe Effect of Quenching Rate and Pre-strain on the Strain Ageing Behaviors of 7075 Aluminum Alloys(Univ Fed Sao Carlos, Dept Engenharia Materials, 2015) Kacar, Ramazan; Guleryuz, KemalThe mechanical properties of aluminum alloys are strongly dependent on the thermo-mechanical process so, the strain ageing behavior of 7075 Al-alloy was investigated in this study. A set of test pieces was solution heat treated at 480 degrees C for 2 h, water quenched (SHTWQ) then pre-strained for 8% in tension. The test samples were aged at 140 degrees C for 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 24, 48, 72 and 96 h in a furnace. The other set of test samples were solution heat treated at 480 degrees C for 2 h, quenched in sand (SHTSQ) then pre-strained for 8% in tension. They were also aged at 140 degrees C for same intervals. The effect of strain ageing, on the mechanical properties of Al-alloy, was investigated by mean of hardness, and tensile tests. The results shown that, the quenching rate after solution heat treatment, ageing time and temperature, as well as pre-strain, play a very important role in the precipitationhardening associated with ageing process of the 7075 Al-alloy.Öğe Effect of static strain aging on the fatigue behavior of S275JRC steel(Carl Hanser Verlag, 2017) Bulbul, Ahmet; Kacar, Ramazan; Emre, Hayriye ErtekIn 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 degrees 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.Öğe THE EFFECT OF WELD CURRENT INTENSITY AND WELDING TIME RESISTANCE SPOT WELD OF DUPLEX STAINLESS STEEL(Gazi Univ, Fac Engineering Architecture, 2011) Durgut, Erkan; Kacar, RamazanIn 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 Effects of welding methods on the mechanical properties of joining dissimilar steel couple(Gazi Univ, Fac Engineering Architecture, 2018) Kacar, Ramazan; Emre, Hayriye Ertek; Isineri, Ali Umit; Najafigharehtapeh, AsgharIn this study, the weldability of wear resistant hardox steel to austenitic stainless steel with shielded metal arc welding (SMAW) and gas metal arc welding (GMAW) methods was investigated and an effect of welding method on the mechanical properties and microstructure of weldment was examined. According to standard, welding groove was prepared for Hardox 400-AISI 304 steel couple that was multi pass welded in butt position by using GMAW and SMAW methods. The mechanical properties of the weldments were determined by tensile, three point bending and V-notch impact tests. In addition, hardness measurement and microstructure evaluation was carried out on the cross section of weldment. According to findings; the tensile strength, weld metal notch impact toughness and ductility of the samples joined with the GMAW method were determined higher than those joined with SMAW.Öğe Factors Affecting Kinetics of Strain Aging in S275JRC Steel(Univ Fed Sao Carlos, Dept Engenharia Materials, 2017) Bulbul, Ahmet; Kacar, RamazanThe materials parameter i.e. microstructure as well as the processing factors i.e. aging time and temperature, the amount of plastic deformation, and residual stresses affecting the kinetic of strain ageing in the S275JRC steel were investigated in detail. For this purpose, 5 % pre-strained steel was aged at 160 degrees C for different intervals. The ageing behavior was determined for the as-received (AR) and homogenization & normalizing heat treated (H+N heat treated) conditions. The yield stresses before and after aging process and, the hardness values of the aged steels were considered to calculate strain aging progress. It was shown that a noticeable increase in the yield strength, tensile strength and hardness values was observed for aged AR and H+N heat treated specimens. Moreover, the repetitive increase in the yield and ultimate tensile strength was believed to be a result of strain ageing.Öğe FATIGUE BEHAVIOURS OF FRICTION WELDED DRILL PIPES(Gazi Univ, Fac Engineering Architecture, 2013) Ertek Emre, Hayriye; Kacar, RamazanThe 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 In Vitro Bioactivity and Corrosion Properties of Laser Beam Welded Medical Grade AISI 316L Stainless Steel in Simulated Body Fluid(Esg, 2016) Kose, Ceyhun; Kacar, RamazanAISI 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.Öğe Interactions Between Fibroblast Cells and Laser Beam Welded AISI 2205 Duplex Stainless Steel(Kaunas Univ Tech, 2018) Kose, Ceyhun; Kacar, Ramazan; Zorba, Asli Pinar; Bagirova, Melahat; Abamor, Emrah Sefik; Allahverdiyev, Adil M.Because of their high mechanical strength, excellent corrosion resistance and good weldability, duplex stainless steels are mostly used in industries such as oil, chemistry, petrochemistry, food and occasionally used in medical industry. These properties have enabled us to use duplex stainless steels in biomedical applications recently. Accordingly, duplex stainless steel material can be highly important to examine the toxic effect on the cells. In this study, the effect of the AISI 2205 duplex stainless steels which are joined by CO2 laser beam welding on viability of L929 fibroblast cells has been studied in vitro for the first time. For this aim, the cells were kept in DMEM/F-12 (Thermofisher Scientific 31331-028) medium for 7 days. The viability study was experimentally studied using the MTT (Thiazolyl Blue Tetrazolium Bromide) method for 7 days. The cell viability of the laser beam welded sample has been detected to be higher than that of the base metal and the control based on 7th day data. According to the obtained results, it was revealed that laser beam welded and base metal AISI 2205 duplex stainless steel has been found suitable to study for biomedical applications.Öğe Mechanical Properties of Laser Welded 2205 Duplex Stainless Steel(Carl Hanser Verlag, 2014) Kose, Ceyhun; Kacar, RamazanDuplex stainless steel is widely used in the oil, chemical industry and to a lesser extent in the medical industry, because of the high mechanical properties, corrosion resistance and good weldability. In this study, AISI 2205 (22Cr5Ni3Mo) duplex stainless steel samples were joined using the CO2 laser beam welding method. In order to determine the mechanical properties of the welded joints, tensile tests were applied and the hardness of the welded sample was measured on the cross-section. The microstructure characterization of welded samples was also carried out using optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Although, the mechanical properties of welded samples were found acceptable, the final microstructure of the welded metal and the heat affected zone (HAZ) were significantly affected by the ferrite phase due to the low heat input that caused high cooling rates, respectively.Öğe Mechanical properties of plasma arc welded AISI304LN austenitic stainless steel at various temperatures(Taylor & Francis Ltd, 2023) Kacar, Ramazan; Emre, Hayriye Ertek; Nohutcu, SametAISI 304 grade austenitic stainless steels are widely used in a wide variety of fields such as chemical, automobile, food industries, etc. due to their good mechanical properties and corrosion resistivity. In this study, AISI 304LN austenitic stainless-steel couples were joined with plasma arc welding. The effect of temperature on the mechanical properties, formability and fracture morphologies of joints was evaluated. For this purpose, tensile testing of the joints was carried out in the temperature range of -50 degrees C, and 25 degrees C-850 degrees C. Thus, the ultimate tensile strength, (UTS), yield strength, (YS) and elongation (EL%) amounts of welded joints were determined. The fracture morphologies of the tensile test samples were examined. It was observed that the rupture (except 850 degrees C) occurred from the weld metal. The highest formability was obtained in the samples tested at 850 degrees C. In addition, the existence range of dynamic strain aging (DSA) of the plasma arc welded samples was also investigated. The unsteady plastic flow between the yield and the ultimate tensile of the sample subjected to the tensile test at 250-550 degrees C are evaluated as signs of DSA.Öğe Microstructure and property relationships in resistance spot weld between 7114 interstitial free steel and 304 austenitic stainless steel(Journal Mater Sci Technol, 2006) Hasanbasoglu, Ahmet; Kacar, RamazanDue to the differences in physical, chemical and mechanical properties of the base metals, the resistance spot welding of dissimilar materials is generally more challenging than that of similar materials. The influence of the primary welding parameters affecting the heat input such as peak current on the morphology, microhardness, and tensile shear load bearing capacity of dissimilar welds between 304 grades austenitic and 7114 grade interstitial free steel has been investigated in this study. The optimum welding parameters producing maximum joint strength were established at a peak current of 9 kA, where the electrode force is kept 6x10(-5) Pa and weld time is kept constant 17 cycles, respectively. The primary cause of weakening the weldment is identified as the excessive grain growing region of heat affected zone (HAZ) in case of 7114 grade interstitial free steel.
