Ganwarich Pluphrach

DOI: 10.14456/sjst-psu.2016.60

pp. 357 - 363

Abstract

This research explains the results of microstructure and mechanical property investigations of four drop forging
microalloyed HSLA steels, ME Wrench 1, ME Wrench 2, ME Wrench 3, and ME Wrench 4. The purpose was to find the
influence of vanadium (0.121, 0.119, 0.120, and 0.210%) and niobium (0.00045, 0.00055, 0.00052, and 0.00057%) content on the
microstructures of ME Wrench 1 in comparison to ME Wrench 2, 3, and 4. It has been found that the group of ME Wrench 1
shows most evenly distributed proeutectoid ferrite as highest volume fraction and finest prior austenite grain size in theirs
structure. At the highest vanadium intensity and nitrogen appearance of ME Wrench 1 V(CN) precipitation dispersion occurs
in non-random way. Effective yield stresses have been controlled by applying different mean ferrite grain size according to
Hall-Petch equation. It has also been noted that grain size and yield stress are in good correlation.