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Relationship between grain size and fracture toughness of tool steel
Author(s) -
Pacyna Jerzy,
Mazur Adam
Publication year - 1986
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.198600828
Subject(s) - fracture toughness , materials science , grain size , toughness , metallurgy , grain growth , composite material , fracture (geology) , austenite , cracking , microstructure
The aim of this study was to examine the effect of grain size, regulated by means of austenitizing temperature, on the process of hot‐work tool steel cracking. Fracture toughness ( K lc ) of this steel depended on the ratio of the average linear intercept of grain ( L̄ ) and the diameter of the plastic strain zone formed ahead of the propagating crack ( d y ). Investigations were supplemented by the fractographic analysis. The dependence of the K lc one the ratio L̄ : d y has been confirmed. In the subcritical range, when L̄ : d y <1, the grain growth causes rapid decrease of fracture toughness. In an overcritical range, when L̄ : d y >1, grain growth resulting from the increase of austenitizing temperature causes stoppage of the decrease of fracture toughness and can even lead to increase. Thus, tools requiring the highest hardness can be quenched from possibly high temperatures without fear of any disadvantageous influence upon the toughness of even a strong grain growth. In the critical range, when L̄ : d y ≈1, fracture toughness of tool steel reached minimum.