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มนตรี แสงสุริยันต์ ประยูร สุรินทร์

Abstract

This research aims to study the influence of microstructure to creep resistant along the cast-iron metal arc welding line. By preheating the work before welding at 400 ± 10 ° C with 3 types of welding wire, NC astweld 55 (A), Gemini Ni55 (B) and YAWATA Ni Cast 55 (C), each type was applied for 5 samples. The 15 welding samples were prepared as 150x300x25 mm and were notched as the angle 30º. Flat butt joint technique was applied for the sample at 90 A and 22 V.  The individual sample was scratched at speed 112 mm/s. Hardness test was applied for studying with load of 200 gf. Creeping test was operated at 500 ºC with load of 9.8 N. The results showed of A B and C welding wire had a microstructure along the welding line joining with HAZ composed of spheroidal graphite, ferrite, and pearlite phases. At the area of HAZ composed of spheroidal graphite, martensite and ledebulite phases and at the area of welding composed of austenite and co-crystal graphite phase. The average hardness around HAZ area are 465.78, 372.28 and 450.48 HV, respectively. The average elongation at brake point is 11.92%, 12.04% and 17.68%, respectively. Therefore, the welding wire A has maximum hardness. Moreover, the welding wire C is the most toughness mechanical properties because the microstructure at the point where the welded material has a circular graphite phase, that is uniformly distributed in the austenite phase. Furthermore, the amount of austenite phase in the welding wire C is greater than the welding wire A and B.

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บทความวิจัย