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Öğe Analysis of mechanical and microstructural characteristics of AISI 430 stainless steel welded by GMAW(Redakcia Kovove Materialy, 2022) Acar, İsmail; Çevik, Bekir; Gülenç, BehçetThe use of stainless steels in the machine manufacturing industry is increasing day by day. Due to the poor corrosion properties of especially unalloyed and low-alloy steels, stainless steels are among the preferred materials in industrial applications because of their superiorities such as high corrosion resistance, very good forming and welding capabilities, hygiene and aesthetic appearance. The welding requirements of stainless steels with such widespread use potential are inevitable. For this reason, studies on welding joining stainless steels are important. In this study, AISI 430 ferritic stainless steel materials were joined using different shielding gas combinations through the gas metal arc welding (GMAW) method. In the welding operations, pure argon (100 % Ar), 97 % Ar + 3 % H-2, and 93 % Ar + 7% H-2 gas combinations were used. The effect of shielding gas combined with the mechanical and metallographic tests applied to the welded sheets on the mechanical and microstructural properties of AISI 430 stainless steel was investigated. In the results obtained from the study, a noticeable grain coarsening occurred in the microstructure of the weld metal and HAZs with the addition of H-2 to the Ar gas during the welding process. The highest tensile strength was obtained from the joints welded with 97 % Ar+3 % H-2 mixture gas. As a result of the tensile test, a rupture occurred in the base metal in all welded samples. No crack or tear defect was found in the weld zone due to the bending test.Öğe Analysis of Welding Groove Configurations on Strength of S275 Structural Steel Welded by FCAW(Gazi Univ, 2018) Çevik, BekirThe quality of welded joints depends on many factors such as welding current, voltage, welding speed, shielding gas type, and welding position. One of these factors is the welding groove design. This is because different stresses (tensile, compression, bending, etc.) can occur on the weldments. For this reason, while designing welded constructions, it is important to join them with the most appropriate welding groove configuration by considering the stresses the welded joints can be exposed to. In this study, the effect of the welding groove configuration on the mechanical and metallurgical properties of S275 structural steel joined by flux cored arc welding (FCAW) method was investigated. For this purpose, different welding groove configurations were formed for structural steel sheets. Tensile, bending, and hardness tests were performed to determine the mechanical properties of the weldments. In addition, metallographic investigations were carried out to determine the metallurgical properties of the weld zones. As a result of the tests, the effect of the welding groove configuration on the mechanical and metallurgical properties of the welded joints was determined. As a result of the microstructure studies, different structures such as grain boundary ferrite, widmanstatten ferrite and acicular ferrite were determined to form in the weld metal and coarse grained zone. It was determined that hardness of the weld metal was higher than HAZ and base metal in all welding groove configurations. As a result of the tensile and bending tests, the highest tensile and bending strengths were obtained from the samples welded by X-2 type welding groove configuration after the base metal. Furthermore, the X-type welding groove configurations showed better mechanical properties than the K-type welding groove configurations.Öğe The effect of cold and hot reformation process to mechanical properties of deformed automobile chassis material(Kaunas Univ Technol, 2016) Gülenç, Behçet; Kocaman, Hamit; Çevik, Bekir; Durgutlu, Ahmet; Fındık, TayfunVehicles are damaged as a result of traffic accidents. Chassis and body parts of damaged vehicles are reformed by using cold and hot deformation methods. High-strength low alloy (HSLA) steel material coated (galvanised) with S320GD+Z quality (DIN EN 10326) zinc, which is used in chassis production, was used in this study. Steel sheet materials were damaged. Damaged automotive chassis material was reformed with cold and hot reformation processes. Tensile, notch impact, bending and hardness tests were applied to the reference material which were not deformed and materials to which reformation process was applied. In the light of obtained results, the effect of reformation process on mechanical properties of automotive sheet was determined.Öğe Effect of Continuous and Pulsed Currents on Microstructural Evolution of Stainless Steel Joined by TIG Welding(Carl Hanser Verlag, 2015) Durgutlu, Ahmet; Fındık, Tayfun; Gülenç Behçet; Çevik, Bekir; Kaya, Yakup; Kahraman, NizamettinIn this study, AISI 316L series austenitic stainless steel sheets were joined by tungsten inert gas welding method in continuous and pulsed currents. Regarding microstructural investigation and hardness values of weld metal, samples were welded to investigate the effect of current type on grain structures of weld metal. Results showed that samples welded by using pulsed current had considerable different properties compared to the samples welded by using continuous current. While the weld metals of joinings obtained by using continuous current displayed a coarse-grained and columnar structure, weld metals obtained by using pulsed current had a finer-grained structure. It was also found that hardness values of samples, which were welded with continuous and pulsed current, were quite different.Öğe The effect of pure argon and mixed gases on microstructural and mechanical properties of S275 structural steel joined by flux-cored arc welding(Redakcia Kovove Materialy, 2018) Çevik, BekirStudies on the use of various welding methods and equipment (electrode, welding wire, welding powder, etc.) in welding of steels have intensively continued nowadays. Flux-cored arc welding technology is one of the welding methods which have mostly been investigated and applied to different metals in recent years. In this study, the effect of different shielding gases on microstructural and mechanical properties of S275 structural steel joined by flux-cored arc welding was examined. Pure argon (100% Ar) and a mixed gas (86% Ar, 12% CO2, 2% O-2) were used as shielding gas in welding processes. A double V groove of 50(degrees) was opened on steel sheets. Welding processes were performed horizontally by using a 1.2 mm-diameter rutile flux-cored wire. Tensile, hardness, and bending tests were used to determine mechanical properties of welded samples. In addition, metallographic examinations were performed to determine microstructural properties of weld zones. As a result of the tensile test, the highest mechanical properties were obtained from weld seams by the mixed gas. There were crack and rupture defects in weld zone as a result of bending tests. In all welding parameters, the hardness of weld metal was higher than that of the heat affected zone (HAZ) and base metal. The microstructure studies revealed that grain coarsening occurred in HAZ.Öğe The effect of shielding gas on weldability of the AISI 420 martensitic stainless steel(Walter De Gruyter Gmbh, 2023) Acar, İsmail; Çevik, Bekir; Gülenç, BehçetMost of weld defects occurring in the welding of martensitic stainless steels are caused by the presence of hydrogen. Thus, the effects of hydrogen in the weld zone need to be well-understood to estimate the quality and service life of martensitic stainless steel joints. In the present study, AISI 420 martensitic stainless steel materials were welded by using different combinations of shielding gas via the gas metal arc welding (GMAW) method. It is known that shielding gases also play a critical role in heat input, cooling rate, microstructure of weld seam, weld defects, and mechanical properties besides drying of molten weld pool. Thus, it is important to investigate the effects of shielding gases and gas combinations on the welding of martensitic stainless steels in the welding process. In the present study, 100 % Ar, 97 % Ar + 3 % H-2 and 93 % Ar + 7 % H-2 gas combinations were employed. The welded sheets were subjected to the metallographic examination as well as hardness, tensile, and bending tests. The effect of the tests and the combination of shielding gas on the mechanical and microstructural properties of AISI 420 stainless steel was investigated. The results indicated that a noticeable grain coarsening occurred in the microstructure of the weld metal and heat affected zones (HAZs) after the addition of H-2 into the Ar gas during the welding process. The highest tensile strength was obtained from the joints with 100 % Ar gas. As a result of the tensile test, rupture occurred in the base metal-HAZ transition zone in all the welded samples. In the joints welded with 97 % Ar + 3 % H-2 and 93 % Ar + 7 % H-2 gas combinations, fracture occurred in the base metal-HAZ transition zone during the bending test.Öğe Effect of tool material on microstructure and mechanical properties in friction stir welding(Carl Hanser Verlag, 2016) Çevik, Bekir; Özçatalbaş, Yusuf; Gülenç, BehçetAlthough the number of experimental studies investigating the effect of friction stir welding (FSW) parameters on joining properties have increased recently, there are not sufficient numbers of studies on the effect of the stirring tool material in friction stir welding. This study investigated the effect of stirring tool materials on microstructure, mechanical properties and residual stress of joints. Samples of 7075-T651 Al alloys were joined by FSW using uncoated and TiN-coated X210Cr12 alloy steel stirring tools. The welding processes were performed at rotational speeds of 900, 1250 and 1600 rpm and at a welding speed of 60 mm x min(-1). Mechanical and metallographic tests were applied to the welded joints and residual stress analysis was performed using the hole drilling method. The best mechanical properties were determined in the welded samples joined by the uncoated tool at a rotational speed of 900 rpm. It was also determined that the TiN-coated tool negatively affected the mechanical and metallurgical properties of the weldements. Moreover, the highest longitudinal residual stresses were specified in the joining performed by the uncoated tool.Öğe Effect of welding processes on mechanical and microstructural properties of S275 structural steel joints(Carl Hanser Verlag, 2018) Çevik, BekirS275 structural steel is a popular low carbon steel type that can be used in many different general engineering and structural applications. These steels are widely used in steel construction, maintenance, machinery and manufacturing industries. Welded joints of this steel used in the mentioned industrial areas are important. In this study, 10-mm thick S275 structural steel sheets were joined by using gas metal arc welding (GMAW) and flux cored arc welding (FCAW) methods. Tensile, bending, and hardness tests were performed to determine the mechanical properties of the welded samples. In addition, metallographic investigations were carried out to determine the microstructural properties of the weld zones. As a result of the microstructural studies, it was found that different structures such as grain boundary ferrites, polygonal ferrites, Widmanstatten ferrites and acicular ferrites are formed in the weld metal and coarse-grained region. It was determined that the hardness of the weld metal was higher than HAZ and base metal in all welding parameters. The highest tensile and bending strengths were obtained from those samples joined by using the FCAW method. As a result of the tensile test, separation occurred in the transition region between the weld metal coarse-grained regions.Öğe The effect of welding speed on mechanical and microstructural properties of 5754 Al (AlMg3) alloy joined by laser welding(Iop Publishing Ltd, 2018) Çevik, Bekir; Gülenç, Behçet5754 (AlMg3) alloys have advantages such as good strength, perfect corrosion resistance and cold forming in addition to the low specific density. Because of these advantages, they are commonly used in automotive, chemical and food industries, and especially in the vessel and yacht industry. However, in spite of having such important and common areas of usage, it is very difficult to join Al and its alloys by traditional welding methods. This study focused on joining of 5754 Al alloy materials, which are hard to be joined by the traditional welding methods but have common areas of usage, by using the laser welding method. Laser welding method has many advantages such as the low heat input, deep penetration, low residual stress, and distortion compared to traditional welding methods. For this purpose, 3 mm thick 5754 Al alloy sheets were joined by using the laser welding method. The welding processes was carried out selecting three welding speeds (3, 4.8, and 6 m min(-1)). The macrostructure, microstructure, hardness, tensile, and impact strength properties of the samples taken from the welded joints were examined. It was observed that micro-porosity and micro-void defects formed in the microstructure of the weld metal. The rate and size of these defects increased with increasing welding speed. The increase in the welding speed decreased the amount of the accumulated metal and the penetration rate. The mechanical properties were also negatively affected by the increase in the welding speed.Öğe Effect of welding speed on the mechanical properties and weld defects of 7075 Al alloy joined by FSW(Redakcia Kovove Materialy, 2016) Çevik, Bekir; Özçatalbaş, Yusuf; Gülenç, BehçetIn this study, 7075-T651 Al alloys were joined by friction stir welding (FSW) at a fixed rotational speed and different welding speeds. The stirring tool used in the welding processes was comprised of a shoulder of 20 mm in diameter and modified M6 x 1 HSS hand taps used as pins. The FSW was performed at a rotational speed of 1600 rpm and at welding speeds of 20, 40, and 60 mm min(-1). Mechanical and metallographic tests were carried out on the welded joints and the effects of the welding speed on the mechanical and metallurgical properties of the welded specimens were investigated. Welding speed significantly affected the microstructure and mechanical properties of the joining. Results showed that the average grain size of the weld nugget was reduced as welding speed was increased. In addition, it was found that high welding speed negatively affected the mechanical properties of the weld nugget.Öğe The Effects of Critical Welding Parameters on Tensile-Shear Properties of Friction Stir Spot Welded Polyethylene(Gazi Univ, 2017) Çevik, Bekir; Gülenç, Behçet; Durgutlu, AhmetThe aim of this study was to investigate the weldability of high density polyethylene via friction stir spot welding method. Polyethylene sheets were joined with dwell times of 60 to 100 s, three different pin profiles (M6x1, M6x1.25, M6x1.5) and pin lengths of 3.75 to 4.75 mm by using rotational speed of 900 rpm and delay time of 45 s. During welding processes, the temperatures were measured under the welding centers. The tensile-shear tests were performed to welded samples. Also, macrostructures of welding nuggets were examined. The small welding nuggets were formed by using the lower dwell time. The melting in welding nugget occurred in the all dwell times during the welding. The dwell time affected on the friction temperature. The key (pin) hole closed when sufficient friction temperature (dwell times of 80 and 100 s). The pin profiles directly affected the welding quality. Large screw pitch range of the pin and the small pin length from 4.5 mm negatively affected the weld fracture load. Pin length of the stirring tool directly affected the quality of welding.Öğe The effects of welding speed on the microstructure and mechanical properties of marine-grade aluminium (AA5754) alloy joined using MIG welding(Redakcia Kovove Materialy, 2019) Çevik, Bekir; Koç, M.AA5754 aluminium alloys are commonly used in marine and offshore applications as well as in shipbuilding equipment. It is of great importance to weld this alloy in these industrial areas. This study investigated the penetration, microstructure, and mechanical properties of AA5754 Al alloy sheets that were joined using robotic metal inert gas (MIG) welding at different welding speeds. The joints were welded at three welding speeds by keeping the welding current constant, and then macrostructure and microstructure of the samples taken from these joints were examined Afterward, their hardness, tensile and bending tests were carried out. It was found that the increase in the welding speed decreased the amount of accumulated metal and the penetration rate. Formation of macro- and micro-porosities was observed in the root sections of the weld seams. It appeared that the welding speed increased, the quantity and size of these defects increased, and the mechanical properties were negatively affected by the increase in the welding speed.Öğe Farklı Özlü Tel Kullanılarak Birleştirilen S275 Yapı Çeliğinin Mekanik ve Mikroyapı Özelliklerinin İncelenmesi(Gazi Univ, 2017) Çevik, BekirÖzlü teller, iç kısımlarına yerleştirilen ve toz halindeki çeşitli bileşenlerden oluşmaktadır. Özü oluşturan bileşenlerin amaca göre değiştirilebilmesi sayesinde özlü teller çok yönlü kullanım özelliklerine sahiptirler. Günümüzde değişik kaynak yöntemleri ve değişik malzemeler için geliştirilmiş olan özlü teller (elektrotlar) bulunmaktadır. Bu nedenle özlü tel ark kaynak yönteminde özlü tel elektrotlarla yapılan mekanize kaynak da gittikçe önem kazanmaktadır. Özlü tel ark kaynak yönteminde farklı koruyucu gazlar ve karışımları ile kullanımı konusunda araştırmalar devam etmektedir. Bu çalışmada, S275 yapı çeliği levhalar özlü tel ark kaynak yöntemi ile rutil ve bazik özlü teller kullanılarak ticari saflıktaki argon atmosferinde birleştirilmiştir. Bu amaçla 10 mm kalınlıktaki S275 çelik levhalara 70o çift V kaynak ağız formu oluşturulmuştur. Kaynaklı numunelerin mekanik ve mikroyapı özelliklerini belirlemek için çekme ve sertlik testi ile metalografik incelemeler yapılmış ve saf argon gazının farklı özlü teller ile kullanılabilirliği araştırılmıştır. Yapılan çekme testi sonucunda en yüksek mekanik özellikler bazik özlü tel ile yapılan kaynak dikişlerinden elde edilmiştir. Çekme testi esnasında kaynaklı numunelerdeki ayrılma, genellikle de geçiş bölgesine yakın yerlerde meydana gelmiştir. Bütün kaynak parametrelerinde, kaynak metali sertliğinin ısının tesiri altında kalan bölge (ITAB) ve esas metalden yüksek olduğu görülmüştür. Mikroyapı çalışmaları sonucunda ITAB’ta tane irileşmesinin meydana geldiği tespit edilmiştir.Öğe Farklı Özlü Tel Kullanılarak Birleştirilen S275 YapıÇeliğinin Mekanik ve Mikroyapı Özelliklerininİncelenmesi(2017) Çevik, BekirÖzlü teller, iç kısımlarına yerleştirilen ve toz halindeki çeşitli bileşenlerden oluşmaktadır. Özü oluşturan bileşenlerin amaca göre değiştirilebilmesi sayesinde özlü teller çok yönlü kullanım özelliklerine sahiptirler. Günümüzde değişik kaynak yöntemleri ve değişik malzemeler için geliştirilmiş olan özlü teller (elektrotlar) bulunmaktadır. Bu nedenle özlü tel ark kaynak yönteminde özlü tel elektrotlarla yapılan mekanize kaynak da gittikçe önem kazanmaktadır. Özlü tel ark kaynak yönteminde farklı koruyucu gazlar ve karışımlarıile kullanımı konusunda araştırmalar devam etmektedir. Bu çalışmada, S275 yapı çeliği levhalar özlü tel ark kaynak yöntemi ile rutil ve bazik özlü teller kullanılarak ticari saflıktaki argon atmosferinde birleştirilmiştir. Bu amaçla 10 mm kalınlıktaki S275 çelik levhalara 70o çift V kaynak ağız formu oluşturulmuştur. Kaynaklı numunelerin mekanik ve mikroyapı özelliklerini belirlemek için çekme ve sertlik testi ile metalografik incelemeler yapılmış ve saf argon gazının farklı özlü teller ile kullanılabilirliği araştırılmıştır. Yapılan çekme testi sonucunda en yüksek mekanik özellikler bazik özlü tel ile yapılan kaynak dikişlerinden elde edilmiştir. Çekme testi esnasında kaynaklı numunelerdeki ayrılma,genellikle de geçiş bölgesine yakın yerlerde meydana gelmiştir. Bütün kaynak parametrelerinde, kaynak metali sertliğinin ısının tesiri altında kalan bölge (ITAB) ve esas metalden yüksek olduğu görülmüştür. Mikroyapı çalışmaları sonucunda ITAB'ta tane irileşmesinin meydana geldiği tespit edilmiştir.Öğe Friction Stir Welding of 7075-T651 Aluminium Alloy(Carl Hanser Verlag, 2016) Çevik, Bekir; Özçatalbaş, Yusuf; Gülenç, BehçetThe microstructural changes, mechanical properties and residual stress distribution of 7075-T651 Al alloy joined using friction stir welding were investigated in this study. Welding was performed at 900, 1 250, and 1 600 rev/min and 20, 40, and 60 mm/min welding speeds. Mechanical tests were carried out on the welded joints in addition to microstructural examinations performed using a scanning electron microscope. Furthermore, residual stress distribution of the joints was determined by the hole drilling method. Generally, higher tensile strength was obtained at medium rotational and welding speeds. Tunnel defects were formed in the root of the weld seam. At high welding speeds, insufficient filling in the joints led to microvoids and large grain bands on the retreating side of the weld seam. The tensile strength of the welded specimens decreased at the rate of 26-45 % compared to the reference material. Lower residual stresses were determined in the specimens joined at a high rotational speed.Öğe Gas tungsten arc welding of 7075 aluminum alloy: microstructure properties, impact strength, and weld defects(Iop Publishing Ltd, 2018) Çevik, BekirPrecipitation-hardened 7075 (Al-Zn-Mg-Cu) aluminum alloys have low specific density and high strength. Because of these advantages, they are commonly used as construction materials in the aerospace industries. Even though they have such important and common areas of usage, their weldability is quite difficult. It is important to weld this alloy used in these industrial areas. In this study, 3 mm-thick 7075-T651 aluminum alloy materials were joined using different welding currents via gas tungsten arc welding (GTAW) method. The metallographic examinations were carried out to determine macrostructural and microstructural properties of the weld zones. Also, notch impact and hardness tests were performed to determine the mechanical properties of the welded samples. The results obtained as a result of the tests were evaluated and interpreted. The grain size of the weld center increased due to heat input occurring with increase of the welding current. Micro cracks (hot cracking) occurred in the roots of welding seams. The increase in the welding current affected the hardness distribution of the weld zone. The impact strength of the welded sample was negatively affected by the grain coarsening and micro cracks in the welding seam.Öğe Influence of welding parameters on the fracture of PE300 polyethylene friction stir spot welds(Carl Hanser Verlag, 2016) Çevik, BekirIn this study, polyethylene specimens were welded by using friction stir spot welding (FSSW) technique. Welding process was carried out by a rotation of 460 and 900 rpm. Under constant friction force, five different dwell times (20, 40, 60, 80 and 100 s), four different delay times (15, 30, 45 and 60 s) and three different pin profiles (M6 x 1, M6 x 1.25 and M6 x 1.5) were used. During the welding process, temperature measurements under the welding cenetrs were performed using a four multichannel K type digital thermometer. Tensile shear tests were used to characterize the samples. Tensile performance of the samples was significantly affected by the welding parameters.Öğe Microstructure and mechanical properties of friction stir welded dissimilar 5754-H111-6013-T6 aluminum alloy joints(Carl Hanser Verlag, 2019) Yürük, Ali; Çevik, Bekir; Kahraman, NizamettinAluminum alloys exhibit good strength, excellent corrosion resistance and good forming properties along with low specific density. Due to these superior properties, they are widely used in the automotive, chemical, and food industries, especially in shipbuilding and the yacht industry. It is important to join these alloys used in the mentioned industrial areas. However, it is very difficult to join Al and its alloys via traditional welding methods despite its widespread use. In this study, 5754-H111 and 6013-T6 aluminum alloys were joined by friction stir welding. Welding operations were carried out at 1250 rpm using welding feed rates of 12.5, 25, and 32 mm x min(-1). Metallographic investigations were carried out to determine the microstructural and macrostructural properties of the weld zones. Tensile, bending, and hardness tests were also performed to determine the mechanical properties of the welded samples. The results obtained as a result of the tests were evaluated and interpreted. Micro-void defects were found to occur in the weld metal-HAZ transition zones. It was established that the welding speed affected the tensile strength. The highest tensile strength was obtained at a feed rate of 25 mm x min(-1). It was determined that no cracking or fraction occurred in the welded samples as a result of the bending test.Öğe Tarımsal mekanizasyonda kullanılan 30MnB5 bor çeliğinin kaynak sonrası soğutma rejiminin mekanik ve mikroyapı özelliklerine etkisi(2024) Çevik, Bekir30MnB5 çeliği tarımsal mekanizasyon endüstrisinde sertlik, mukavemet, darbe ve aşınma direnci istenen uygulamalarda kullanılabilen bir çelik türüdür. Günümüz endüstrisinde ekonomik faktörlerin giderek önem kazanması tarımsal mekanizasyonda daha uzun ömürlü tarım makinelerinin üretilmesini gerektirmektedir. Bu nedenle tarımsal mekanizasyonda kullanılan söz konusu çeliğin kullanımı ve kaynaklı birleştirilmesi önem arz etmektedir. Bu çalışmada, 30MnB5 çelikleri MAG kaynak yöntemiyle birleştirilmiş ve üç farklı (havada, suda ve yağda) soğutma rejiminde soğutulmuştur. Soğutma rejimine bağlı olarak kaynaklı 30MnB5 çeliğinin mekanik ve makro/mikroyapı özelliklerindeki değişimi tespit etmek için tahribatsız (görsel muayene, sıvı penetrant testi), tahribatlı (darbe, eğme, sertlik testleri) ve metalografik testler yapılmıştır. Görsel muayene ve sıvı penetrant testi sonucunda kaynak dikişlerinde herhangi bir makro ve mikro hataya rastlanmamıştır. Kaynaklı numunelerde soğutma rejimine bağlı olarak mekanik ve mikroyapı özelliklerindeki değişimler gözlemlenmiştir.
