A Study on Lap Joint Welding of Thin Plate ASTM F1684 Using Fiber Laser Welding

The International Maritime Organization (IMO) has developed stricter regulations on emission standards for sulfur oxides, etc., and the demand for Liquefied Natural Gas (LNG) is increasing as an alternative to satisfy these standards. This study relates to fiber laser welding, an approach which offers high-speed welding and low welding deformation for ASTM F1684, which has a low coefficient of thermal expansion (CTE) even in a cryogenic environment. In this study, through three preliminary experiments using 0.25 mm thick Invar, the conditions required to secure sufficient penetration depth and back bead were identified. Through the cross-sectional observation analysis, the welding conditions without defects were identified and the trend of penetration shape according to increasing welding speed was identified. Following a lap joint laser welding experiment under the secured conditions, the mechanical properties were evaluated through the shear strength test and the heat influence range of a fiber laser was identified through the temperature measurement of a welding part. As a result, it was confirmed that the shear strength of the lap joint laser welding part was 86.8% that of the base metal.

A Study on Fiber Laser Welding of High-Manganese Steel for Cryogenic Tanks

As the environmental regulations on ship emissions by the International Maritime Organization (IMO) become stricter, the demand for a ship powered by liquefied natural gas (LNG) is rapidly increasing worldwide. Compared to other materials, high-manganese steel has the advantages of superior impact toughness at cryogenic temperatures, a low thermal expansion coefficient, and a low-cost base material and welding rod. However, there is a limitation that the mechanical properties of a filler material are worse than those of a base material that has excellent mechanical properties. To solve these shortcomings, a basic study was performed to apply fiber laser welding with little welding deformation and no filler material to high-manganese steel. The relationship between laser welding parameters and penetration shapes was confirmed through cross-section observation and analysis by performing a bead on plate (BOP) test by changing laser power and welding speed, which are the main parameters of laser welding. In addition, the welding performance was evaluated through mechanical property tests (yield strength, tensile strength, hardness, cryogenic impact strength) of a welding part after performing the high-manganese steel laser butt welding experiment. As a result, it was confirmed that the yield strength of a high-manganese steel laser welding part was 97.5% of that of a base metal, and its tensile strength was 93.5% of that of a base metal.

A Study on Cross-Shaped Structure of Invar Material Using Cold Wire Laser Fillet Welding (PART I: Feasibility Study for Weldability)

With the need for eco-friendly energy increasing rapidly due to global environmental issues, there is a rapidly increasing demand for liquefied natural gas (LNG). LNG is liquefied at minus 163 degrees Celsius, and its volume decreases to 1/600, giving it a relatively higher storage and transport efficiency than gaseous natural gas (NG). The material for the tanks that store cryogenic LNG must be a material with high impact toughness at cryogenic temperatures. Invar, which contains 36% nickel and has a very low coefficient of thermal expansion, is used for the membranes and corner structures of LNG cargo holds. The cross-shaped Invar structure used in an LNG cargo hold is manufactured through manual tungsten inert gas (TIG) fillet welding, which causes welding distortion and weldability problems. This study is a feasibility study that aims to reduce welding distortion, increase weldability with welding speed, and reduce the steps in an existing process by half by replacing the existing manufacturing method with automatic fiber laser fillet welding. Laser welding using fiber laser parameters are controlled for 1.5 and 3.0 mm thick Invar materials and weldability is secured through cross-section observation. Then, the optimal welding conditions with top and back beads secured are derived through a trial and error method.

LAJU PENDINGINAN PENGELASAN BAJA CARBON SEDANG PADA TEMPERATUR LINGKUNGAN BERBEDA

The quality of welding results is influenced by the shape of the microstructure of the welding material especially in the HAZ region. The shape of the welding microstructure is largely determined by the cooling rate of the weld material. The cooling rate of the weld is greatly influenced by the heat input from the arc and the ambient temperature. This study aimed to determine the effect of different environmental temperatures on the cooling rate of welding results. Welding of GMAW fillets on medium carbon steel plates S50C, with variations in welding currents 90 A, 100A and 110A and carried out at variations in environmental temperature of 15oC, 10oC and 5oC. Temperature data on the middle, welding part is taken with a digital thermometer to compare the effect of each variable. The test results show that the greater the welding current, the slower the cooling rate. Similarly, an increase in ambient temperature causes a decrease in the weld metal's cooling rate.

Vibration Fracture Mechanism and Optimization Design of Array Power Supply for Near-Space SAR

The random vibration failure of an array power supply for near-space SAR was analyzed. The fracture mechanism and the fracture reason of fracture formation in the specimen were investigated. The results show that antishock MOS pin breaks first, and the power supply is still in the working state during the process of random vibration. This caused dischargings at the tip of the fracture and melting of the tip of the broken pin which form a river-shaped fracture and granular tissue. The plastic fracture with typical dimple morphology of the pins for the resistor tube occurred during the random vibration. The intergranular fracture appeared at the welding part of the electronic components for array power supply, which presented a brittle fracture mechanism. The fracture was dominated by a ductile fracture for components when the stress produced by the vibration was close to the yield strength of the material. The fracture was dominated by a brittle fracture for components when the stress produced by the vibration was far beyond the yield strength of the material. A simulation evaluation system based on the high-confidence model was proposed. The stress of the electronic components for array power supply and its welding was much lower than the allowable strength of the material by the optimization of the structure and the form of the welding for the array power supply. The sample was successfully tested and verified without any further fracture problems.

OPTIMALISASI DESAIN DAN POSISI JIG WELDING GUNA MENGURANGI SPATTER PADA PRODUKSI HALF OUTER COMP MENGGUNAKAN METODE DMAIC

ABSTRAKPenelitian ini dilakukan pada salah satu produsen spare part otomotif PT. XYZ memiliki permasalahan dan menjadi perhatian serius pada bagian pengelasan adanya produk cacat yang dapat menurunkan nilai dan kualitas produk sehingga banyak produk yang ditolak oleh konsumen karena tidak sesuai dengan standar, dimana banyak terdapat kotoran las (Spatter) yang menmpel pada Joint Exhaust produk Half Outer Comp merupakan bagian komponen dari knalpot sehingga mengurangi produktifitas produksi pada bagian inspeksi akhir, permasalahan di atas dianggap perlu dilakukan penelitian untuk mencari penyebab hal tersebut. Beberapa langkah dilakukan guna memperbaiki cacat yang ada yaitu langkah awal dilakukan observasi dan wawancara ke bagian produksi, metode yang digunakan untuk pengolahan data hasil observasi menggunakan metode DMAIC (Define, Measure, Analisys, Improve, Control), kemudian dilakukan optimalisasi dan modifikasi Jig Welding dengan mendesain ulang menggunakan perangkat software Solidwork versi 2018, kemudian mengubah posisi Jig sebelumnya vertikal menjadi horizontal agar supaya pada saat pengelasan Spatter tidak langsung jatuh ke Joint Exhaust dan memberikan penahan tambahan pada Jig guna mengurangi jumlah Spatter menempel pada Half Outer Comp. Pada penelitian ini diperoleh hasil dimana jumlah Spatter yang menempel pada Joint Exhaust sangat berkurang dan memperoleh hasil produk yang lebih baik sehingga meningkatkan produktivitas pada bagian inspeksi akhir sebelumnya 58,33% menjadi sebesar 83.33%. Kata Kunci : Optimalisasi, Spatter, DMAIC, Desain, Solidwork 2018 ABSTRACTThis research was conducted at one of the automotive spare part manufacturers PT. XYZ has a problem and is a serious concern on the welding part of the presence of defective products that can reduce the value and quality of the product so that many products are rejected by consumers because it does not comply with standards, where there is a lot of welding dirt (Spatter) which attaches to the Joint Exhaust Half Outer Comp product is a component of the muffler so as to reduce production productivity at the final inspection, the above problems are considered necessary to do research to find the cause of it. Several steps were taken to correct existing defects, namely the initial steps carried out observation and interviews to the production department, the method used for processing the observation data using the DMAIC method (Define, Measure, Analysis, Improve, Control), then optimization and modification of Jig Welding with redesign using the 2018 Solidwork software tool, then changing the position of the previous vertical jig to horizontal so that when welding Spatter does not directly fall into the Joint Exhaust and provide additional support to the Jig to reduce the number of Spatter attached to the Half Outer Comp. In this study the results obtained where the number of Spatter attached to the Joint Exhaust is greatly reduced and obtain better product results thereby increasing productivity in the previous final inspection section of 58.33% to 83.33%. Keywords : Optimization, Spatter, DMAIC, Design, Solidwork 2018

Peningkatan Produktivitas Proses Welding Manual Pedal Brake A PT XXX Dengan Metode Analisa Elemen Kerja & Waktu Baku

Indonesia saat ini menduduki posisi kedua dalam penjualan kendaraan bermotor di pasar otomotif dengan angka penjualan mencapai 1,22 juta unit (2014). Hal ini menandakan bahwa sektor industri otomotif Indonesia saat ini sangat berkembang pesat dibandingkan tahun-tahun sebelumnya. PT XXX adalah salah satu vendor dari ATPM yang bergerak dalam pembuatan stamping & welding part untuk komponen otomotif baik kendaraan roda 2 maupun roda 4. Salah satu hasil produksi welding part PT XXX adalah Pedal Brake A yang merupakan komponen otomotif kendaraan roda 2 dari salah satu ATPM terbesar di Indonesia. Semakin tingginya permintaan atas item Pedal Brake A ini menjadi problem tersendiri bagi PT XXX dimana tuntutan akan peningkatan produktifitas tanpa penamabahan aset menjadi kebijakan utama di perusahaan ini. Pada penelitian ini, peningkatan produktifitas dapat dicapai dengan metode analisa elemen kerja. Efisiensi dan efektifitas dari gerakan proses kerja dinilai masih kurang dan perlunya perbaikan. Elemen kerja yang tidak efektif di singkirikan dan kombinasi kerja antara masing-masing tangan ditingkatkan. Salah satu tools yang digunakan adalah peta tangan kanan & kiri. Dengan segala aspek perbaikan berdasarkan prinsip ekonomi gerakan. Dari penelitian ini diperoleh kesimpulan bahwa produktifitas naik mencapai 20,95% yaitu 735 unit menjadi 889 unit. Pengurangan operator proses dari 2 orang menjadi 1 orang. Peningkatan produktifitas ini di dapatkan dengan cara menghilangkan elemen kerja yang tidak efektif, merubah layout, modifikasi alat kerja, dan merubah proses kerja Pedal Brake A.

EXPERIMENTAL STUDY OF BEAMS WITH EMBOSSED WEB

In order to reduce the weight and the material cost in the steel structures, a study on the slender sectional design has been continuously carried out. Steel beams with corrugated web have been widely used in the steel structures. The welding part between the corrugated web and the flange, however, is not straight, which makes the production costs increased. In order to compensate for this drawback, steel beam with an intaglio and embossed web (IEB) was invented by Innovation & Smart Heavy Industry Co., Ltd., South Korea. Plain plate is pressed to keep the upper and lower boundary of the web straight. This makes it possible to weld the flange and the embossed web by the automatic welding machine. In this study, four types of specimens were tested for comparison with plain H-shaped steel beam. Experimental results showed that the maximum load of the IEB specimens is about 1.3 times larger than that of the H-shaped steel beams. This is because the tension field action of embossed web significantly increased the post-buckling strength.