Pengelasan pada Stainless Steel dengan Tipe yang Berbeda Menggunakan Resistance Spot Welding untuk Aplikasi Gerbong Kereta

Salah satu jenis proses pengelasan yang banyak digunakan di dunia industri Kereta Api adalah proses <em>resistance spot welding</em>. Proses pengelasan ini mempunyai banyak keunggulan pada pengelasan pelat tipis dengan menggunakan sambungan tumpang yang diaplikasikan pada <em>side wall</em> kereta api. Penelitian ini dilakukan dengan tujuan untuk mengetahui pengaruh variasi parameter pengelasan yang meliputi <em>current</em>, <em>weld time</em>, dan <em>pulsation</em> terhadap <em>shear strength</em>, struktur mikro dan diameter <em>nugget</em>. Material yang digunakan adalah material SA-240 tipe 304 dan SA-240 tipe 201 dengan ketebalan 2 mm untuk material SA-240 tipe 304 dan tebal 3 mm untuk material SA-240 tipe 201. Pengujian <em>shear strength</em> diperoleh parameter<em> resistance spot welding</em> semakin tinggi, maka nilai <em>shear strength </em>juga semakin tinggi. Strukturmakro didapatkan semakin tinggi <em>current</em>, <em>weld time</em>, dan <em>pulsation</em>, maka <em>nugget</em> semakin lebar. Sedangkan pada hasil uji mikro pada daerah <em>base metal</em> struktur yang tebentuk adalah <em>austenite</em>, sedangkan pada daerah HAZ dan <em>weld metal</em> adalah struktur <em>ferrit</em> dan <em>austenite</em>. Ukuran butir pada daerah HAZ yang semakin mendekat ke daerah <em>weld metal</em> ukuran butirnya menjadi semakin besar. Struktur mikro yang terbentuk pada <em>weld metal</em> bentuknya memanjang (<em>columnar grains</em>) ke daerah yang mengalami pembekuan paling akhir.

Resistance spot welding of additively manufactured maraging steels Part II: Failure behavior

Application of maraging steels via selective laser melting process in the automotive industry was unavoidably involved in the resistance spot welding with conventional steels. Due to the rapid cooling rate of welding process, selective laser melted maraging steels with unique chemical components and stack microstructure could induced the different microstructural evolution, resulting in the complicated fracture behavior in the spot welds. This paper developed a FEA model to predict the fracture mode of spot welds of DP600 to maraging steel and the effect of test conditions and printing orientations were studied. A method was proposed to calculate the material properties of fusion zone by introducing the combined effect of melting DP600 and maraging steels via selective laser melting, resulting in the accurate prediction of fracture mode and strength of spot welds. An interlayer with lower strength was found around the fusion zone and the fracture path propagated in the region, resulting in the partial interfacial failure of spot welds. Meanwhile, the printing orientation had no significant effect on the fracture mode and strength of spot welds, but the different material properties of maraging steels could affect the fracture displacement of spot welds. These findings could pave a way to guide the application of maraging steels via selective laser melting process in multiple industries, especially in the automotive industry.

Resistance spot welding of additively manufactured maraging steels Part I: Nugget formation

Application of additively manufactured steels is unavoidably involved in the resistance spot welding with conventionally manufactured steels. However, the microstructural evolution of an additive manufactured steel at high temperatures is still unknown, especially for the rapid solidification process. This paper investigated the microstructural evolution of a selective laser melted maraging steel during the rapid solidification process via resistance spot welding. Asymmetrical fusion zone with boat shape was found in the spot weld due to the rougher surface and larger electrical resistance of maraging steel via selective laser melting process. The rapid expansion of fusion zone at end of welding process was caused by the carbide formation at the heat-affected zone of maraging steel via selective laser melting process. Besides, printing orientation affected the surface roughness of a selective laser melted maraging steel and subsequently significantly influence the early stage of formation of fusion zone of additively manufactured maraging steel. We expect that our findings will pave the way to the future application of additively manufactured steels in the industries.

OPTIMALISASI PARAMATER RESISTANCE SPOT WELDING UNTUK PENGELASAN TIGA TUMPUK LEMBAR BAJA SPCC

In the automotive industry, the latest breakthroughs and innovations are strongly influenced bymaintaining and increasing production results so that the use and application of technology is anabsolute must, as is welding technology. Thin sheet-shaped components are found in many car bodies.One of the methods used in joining plate sheets is to use the resistance spot welding method, which is awelding process that is only carried out at a certain point using copper electrodes. In the welding method,maintaining quality in order to produce products and services that can meet the needs and expectationsof consumers related to the product's life time or service. SPCC steel (Cold Roller Stell Sheet) is one ofthe most widely used materials in car body welding applications. The characteristics and mechanicalproperties of SPCC steel from the results of the three-sheet welding were examined using the parametersof welding current, welding time, welding distance. The results showed that the increase in current wouldaffect the diameter of the electrode traces and the nuggets that were formed. The greater the current used,the larger the diameter of the trail, so that the optimum pull-shear load is at a current of 6.5 kA at adistance of 20mm with a value of 365.53 MPa, also the highest hardness value is in the nugget area witha hardness value of 595, 14 HVN at a current of 6.5 kA and from the results of measuring grain diameterin microstructural testing for the HAZ area the best at a welding current of 6.5 kA. Because the smallerthe weld grain diameter, the greater the strength of the weld joint. Then the data from the results of theshear-shear test are analyzed using the Taguchi method, and the most effective parameters in the tensilesheartest with a combination of A (6.5) B (1.5) C (15) and from the experimental results for tensile loads.slide obtained 397 MPa.