ANALISIS PENGARUH VARIASI INTERPASS TEMPERATURE PADA MATERIAL CHROMIUM-MOLYBDENUM SA 387 GRADE 12 DENGAN PENGELASAN FCAW TERHADAP NILAI KEKERASAN DAN STRUKTUR MIKRO

Abstract

The pressure vessel manufacturing process requires a material with high hardenability
because it get a fairly intense pressure treatment. SA 387 Grade 12 cromoly steel is a steel that is often
used in pressure vessel work. Cr-Mo alloy steel has the disadvantage of being susceptible to hydrogen
cracking, so cooling too quickly must be avoided. Interpass temperature here takes an important role
in stabilizing the cooling process during welding. So this research raised the formulation of the
problem; 1) How was the effect of Interpass temperature variations with FCAW welding on hardness
value?, 2) How was the effect of Interpass temperature variation with FCAW welding on
microstructure?. The purpose of this study was to determine the effect of Interpass temperature
variations on FCAW welding on hardness and microstructure values. This research method was an
experiment using 3 specimens with Interpass temperature variations of 100°C, 250°C and 400°C.
Instruments in this study included hardness and micro. From the results of hardness testing, the highest
hardness value in the weld metal area was found in the 100 ° C interpass temperature variation with
an average value of 298.07 HVN and the lowest hardness value was found in the 400 °C interpass
temperature variation with an average value of 248.11 HVN. In micro testing, it was found that the
bainite content was getting less at higher temperatures, namely at the 400 ° C interpass temperature
variation with a value of 59.35% bainite and 40.65% ferrite. The conclusion of this research was that
the variation of interpass temperature had a significant influence on the value of hardness and
microstructure. This research is expected to contribute to industries engaged in the production of
pressure vessels.