The Influence of Tool Rotational Speed on Mechanical Properties of Friction Stir Welded Dissimilar AA5083-H112/AA6061-T6 Joints

The relatively new and innovative welding technique known as friction stir welding (FSW) has found widespread application in the automotive, railway, and aircraft industries. Due to engineering and financial considerations, welding of dissimilar metals is frequently carried out in these industries. During the friction stir welding process, three tool rotational speeds—910, 1500, and 2280 rpm—were utilized, while the welding speed remained constant at 30 mm/min. Several experimental works, including fractography, tensile tests, and observations of the microstructure, were carried out following welding. Results showed that ultimate tensile strength (UTS) and yield strength (YS) expanded as the tool rotational speed was expanded and the best UTS and YS, typically 228 MPa and 156 MPa at the speed of 2280 rpm. The precipitation of AA6061-T6 in the stir zone (SZ) and the increased degree of mixing were linked to the improved weld strengths.The relatively new and innovative welding technique known as friction stir welding (FSW) has found widespread application in the automotive, railway, and aircraft industries. Due to engineering and financial considerations, welding of dissimilar metals is frequently carried out in these industries. During the friction stir welding process, three tool rotational speeds—910, 1500, and 2280 rpm—were utilized, while the welding speed remained constant at 30 mm/min. Several experimental works, including fractography, tensile tests, and observations of the microstructure, were carried out following welding. Results showed that ultimate tensile strength (UTS) and yield strength (YS) expanded as the tool rotational speed was expanded and the best UTS and YS, typically 228 MPa and 156 MPa at the speed of 2280 rpm. The precipitation of AA6061-T6 in the stir zone (SZ) and the increased degree of mixing were linked to the improved weld strengths

Transformation Behaviour Of Acicular Ferrite In C-Mn Steel Weld Metals Containing Titanium

ABSTRAK The formation of acicular ferrite which gives high strength and good impact toughness in C-Mn steel weld metals has been studied using dilatometry in combination with optical microscopy and transmission electron microscopy (TEM) associated with microanalytical technique, i.e. energy dispersive X-ray (EDX) analysis. The results showed that Ti was essential in promoting acicular ferrite and the complexity of the austenite to ferrite transformation was likely to be associated with interactions between Ti, N, 0 and other alloying elements during welding process Keywords: acicular Ferriete, titaniu

Perilaku Laju Rambatan Retak Fatik Sambungan Spiral Las Busur Rendam Pipa Baja API 5L X-52 yang Mengalami Perlakuan Panas Stress Relief.

Spiral welded steel pipes are widely used for oil/gas (API) transmission. Such pipes are usually produced by forming hot-rolled coil (HRC) steels into tubular products and welding is performed along spirally joining lines using a submerged arc welding (SAW) process. For structural applications, weld metals for API 5L X-52 steel pipes must have high strength, good impact toughness and high resistance to fatigue crack growth. The present investigations aims to study effects of stress relief heat treatment on mechanical properties of submerged arc spiral welded API 5L X-52 steel pipes in particular fatigue crack growth behaviour. Experiments were carried out by heating submerged arc steel weld metals of API 5L X-52 steel pipes to various temperatures, namely 400, 500 and 600 °C for 3 hours. Subsequently, a sequence of tests were conducted including microstructural examination, hardness test, tensile test and fatigue crack growth test. Results of this investigation show that stress relief heat treatment is proved to improve resistance to crack growth. At low AK, the weld metal which is heat treated at 600 °C reveals the highest resistance to fatigue marked its lowest value of A. However, for higher AK, the n value of the weld metal heat treated at 500 °C is the lowest suggesting that this weld metal has optimum resistance to fatigue crack growth. Keywords : API 5L X-52 steel pipes, submerged arc welding and fatigue crack growt

Studi Eksperimental Pengendalian Korosi pada Aluminium 2024-T3 di Lingkungan Air Laut Melalui Penambahan Inhibitor Kalium Kromat (K2CrO4)

Aluminium paduan seri 2024-T3 banyak digunakan di industri manufaktur seperti pesawat terbang, otomotif, dan kapal laut karena aluminium merupakan logam ringan dan memiliki sifat mekanik yang baik. Namun demikian aluminium paduan 2024-T3 rentan terhadap korosi bila dioperasikan di lingkungan yang korosif, seperti air laut. Salah satu upaya untuk mengendalikan laju korosi adalah dengan penambahan inhibitor. Penelitian ini bertujuan untuk mempelajari pengaruh inhibitor kalium kromat (K2CrO4) dalam mengendalikan laju korosi Al 2024-T3 di lingkungan air laut. Pada penelitian ini, jenis inhibitor yang dipakai adalah kalium kromat (K2CrO4) yang ditambahkan di media air laut dengan variasi konsentrasi 0,1%; 0,3%; dan 0,5%. Selanjutnya laju korosi diukur dengan menggunakan metode sel potensial tiga elektroda dengan kalomel (Hg2Cl2) jenuh sebagai elektroda baku sedangkan elektroda tambahan digunakan platina (Pt). Sebagai data pendukung dilakukan uji komposisi, uji struktur mikro, uji kekerasan Vickers dan uji tarik. Hasil penelitian ini memperlihatkan bahwa laju korosi Al 2024-T3 di media air laut tanpa inhibitor sebesar 0,0216 mm/tahun. Penambahan inhibitor kalium kromat (K2CrO4) cenderung menurunkan laju korosi dan konsentrasi optimum tercapai pada 0,5% K2CrO4 ditandai dengan laju korosi minimum yaitu sebesar 0,0134 mm/tahun atau terjadi penurunan laju korosi sebesar 38%. Bentuk korosi yang terjadi berupa korosi sumuran (pitting corrosion) yang disebabkan karena rusaknya selaput pasif. Pada kasus ini inhibitor berfungsi menutup selaput pasif yang rusak tersebut sehingga dapat menghambat laju korosi. Kata kunci: aluminium paduan, 2024-T3, air laut, korosi , inhibitor, K2CrO4 Aluminium alloy 2024-T3 is widely used in manufacturing industries such as aircraft, automotive and ship industries due to its light weight and good mechanical properties. However, aluminium alloy 2024-T3 is suffered from corrosion attack when it is operated in corrosive environment such as sea water. One of the corrosion control methods is inhibitor addition. The present investigation aimed to study the effect of K2CrO4 inhibitor on controlling corrosion rate in sea water. In this research, K2CrO4 was added to sea water environment with various concentrations, i.e. 0.1, 0.3 and 0.5%. Subsequently corrosion rates were measured using three-electrode potential technique with saturated calomel (Hg2Cl2) electrode as a reference electrode whereas the auxiliary electrode was platinum (Pt). Additional experiments including compositional analysis, microstructural examination, hardness measurement and tensile test were also carried out to gain better understanding to the mechanism in which corrosion attacks aluminium alloy 2024-T3. Experimental results showed that corrosion rate of aluminium alloy 2024-T3 in sea water without inhibitor is around 0.0216 mm/year. The additions of K2CrO4 inhibitor tended to reduce the corrosion rate until a minimum value was obtained, typically 0.0134 mm/year (or 38% decrease) as the amount of K2CrO4 was 0.5%. The type of corrosion observed in this investigation was pitting corrosion as a result of local damage in passive film. Inhibitor seemed to form thin protective film on metal surface hence reducing corrosion rate. Keywords: aluminium alloy, 2024-T3, sea water, corrosion , inhibitor, K2CrO

Improvement of Andong Horseshoe Quality in Yogyakarta City to Support City Tourism

The Zero Kilometer Point is an important route for andong horses in Yogyakarta City. The renovation and replacement of road material with andesite can cause horses to slip because the horseshoes have not been adjusted to the new road material. If neglected, it can harm the horses and its owners, reducing the tourism industry in Yogyakarta. On the other hand, horseshoes demand is still met by small and medium enterprises (SME) without a well-standardized system. After doing technical testing to the existing horseshoe design, several alternative solutions were obtained for horseshoe redesign (1) by adding rubber pads and (2) serrated without rubber pads. Based on analysis and testing, it was found that horseshoe with the addition of rubber by 40% was able to increase the friction value to 0.54 or 10% from the initial condition. Besides improving the productivity and quality of SME horseshoe products, several solutions should be considered, including (1) change the layout design of SME by implementing 5S lean six sigma principles and (2) apply new methods/technology to maintain the standardization of horseshoe product. Implementation of both solutions will guarantee not only the quality product but also SME production. It is hoped that all the improvements that have been made will increase the quantity and quality of horseshoe products. Then it will also be able to improve the image of Yogyakarta City as a tourist city

Identifying the influence of transient thermal tensioning treatments on minimizing distortion and improving fatigue behavior of steel welded

Due to the cost efficiency of welding repairs, the use of transient thermal tensioning (TTT) has begun to be applied to minimize distortion and residual stresses, particularly on thin plates. However, it requires a long preheating time especially on large structures, so that the efficiency of welding process cannot be maximized. Application of TTT treatment using flame heater on TTT treatment which require no preheating time so that welding efficiency can be increased. The aims of this study are to investigate the TTT treatment in reducing distortion, investigate the effect of TTT treatment on tensile strength and hardness, investigate the microstructure and its effect on tensile strength and hardness, investigated the effect of TTT treatment on fatigue crack growth rate. In this research, TTT treatment was performed by flame heating on the both side of weld line integrated in welding process. Temperature in both side plates were controlled and measured using thermocouple. The tests on the weld joints were carried out including distortion measurement, microstructure examination, hardness measurement, tensile test and fatigue test. Results showed that the TTT (60) treatment is the most effective in decreasing the longitudinal distortion which placing the flame heating a 60 mm behind welding torch. It tends to increase the tensile strength of weld metal supported by its increasing hardness. The increase in the percentage of the acicular ferrite phase is linearly related to the tensile strength and hardness of the weld joint. The fatigue behavior could be improved by TTT treatment (60) which is associated with the effect of decreasing residual stress in the weld metal region. This treatment is the best parameter in an effort to increase the welding efficiency of the TTT metho

Mitigating Distortion and Residual Stress by Static Thermal Tensioning to Improve Fatigue Crack Growth Performance of MIG AA5083 Welds

The demand for lightweight structures in ship fabrication to improve performance and fuel savings has led to increasing use of thin-section structures. However, welding such structures often produces problems such as distortion and residual stress. The present investigation is aimed to mitigate distortion and residual stress using static thermal tensioning (STT) to improve fatigue performance in AA 5083 metal inert gas (MIG) welded joints. The STT treatments were performed by cooling the weld zone and its adjacent area during welding whereas both sides away from the weld were heated at various temperatures of 100, 200 and 300 °C to generate thermal gradient. Subsequent experiments including distortion measurements, microscopical examination, hardness and tensile tests, measurements of residual stresses using neutron diffraction method and fatigue crack growth tests combined with SEM fractography were conducted. Results showed that an increase in heating temperature reduced convex longitudinal out of plane distortion. The minimum longitudinal out of plane distortion was achieved at a heating temperature of 200 °C owing to the balance between buckling distortion induced by welding and that generated by static differential heating which opposed the weld distortion. Under such condition, fatigue crack growth performance was improved

Ilmu dan teknologi pengelasan

v, 194 halaman; 23c

Pengaruh Post Weld Heat TreatmentTerhadap Sifat Mekanis dan Korosi Sambungan Las Spiral Saw pada Pipa Baja ASTM A252

Metal joint with welding system is increasingly used. i.e structure, piping or machine constuction. Some of the problems on welding is residual stress dan over hardness can decrease the weld toughness stress corrosion cracking. An effort to solve this problem is PWHT. PWHT has multiple functions, those are to reduces residual stress,increases ductility of HAZ and improves toughness in weld metal and HAZ regions.Heating process with various temperature is expected to make optimum PWHT temperature.This experiment was carried out to know the effect of PWHT torwad the toughness an corrosion of helical welding pipe ASTM A252. The welding process use SAW with groove double V, electrical current 375 A , voltage 35 V and heat input 2,8 kj/mm. Post weld heat treatment was carried out at various temperature 450oC, 550oC and 650oC during 3 hours followed by cooling process in furnace after that, these specimens ware tested the hardness, tensile strength, toughness and corrosion. The Result of research show that increasing of PWHT temperature, can increase the toughness and corrosion resistance of joint weldin, but the tensile strength is decreasre. The optimum PWHT temperature is 550o C with toughness 81 J at 0O C