leometwu的部落格

明/暗 視場各一張. Bright / Dark field as a pair for each magnification.  Forged and annealed.  You see this giant grains only once in a blue moon. Fine pearlite nodules in an island of  Bainite inside a giant grain. Abnormal grain growth resulted from  12 passes of reheating to 1150C while trying to forge a chunk of steel into shape .  Hardness after quenching was said to be "as usual". But the tooling failed prematurely at about  10 thousand strokes----only 1/3 that of a normal (ASTM No 7 grain size )tool life in that factory.