Heterogeneous Austenite Grain Growth in ASTM A213–T91 Steel

Abstract

Heterogeneous grain growth during austenitization in ASTM A213-T91 steel has been studied using a Gleeble 3500 thermomechanical simulator. Starting from a uniform, fine austenite grain size distribution after 1 min austenite holding time, a heterogeneous austenite grain size distribution was observed after 15 min austenite holding time at 1 060°C and 1 080°C. The state of precipitation of second phase particles was studied in detail as a function of austenitization time. The particle size distribution changed towards a bimodal feature as a function of time whereas the count frequency of the coarse precipitates increased and the count frequency of fine precipitates diminished with time. V-rich precipitates were dissolved during austenitization and only Nb-rich particles remained after 15 min austenitizing time. The experimental observations on the evolution of the austenite grain size distribution are rationalized on the basis of the Gladman's approach to abnormal grain growth.

Heterogeneous austenite grain growth in martensitic 9cr steel: Coupled influence of initial metallurgical state and heating rate

“…The results correspond to the series of samples heated to austenite at a rate of 30°C s −1 , and determined that precipitates are MX type carbonitrides. Composition measurements are clearly located around Nb rich values, in agreement with previous results indicating that Nb rich phases are the only stable ones in austenite at high temperatures 34. However, even considering that the size of the particle sample taken in each case could bias the obtained results, an incipient trend is observed in Fig.…”

“…Composition measurements are clearly located around Nb rich values, in agreement with previous results indicating that Nb rich phases are the only stable ones in austenite at high temperatures. 34 However, even considering that the size of the particle sample taken in each case could bias the obtained results, an incipient trend is observed in Fig. 11 that indicates a V enrichment of the precipitated phases after the complete thermal cycle when the time in the tempering step is increased.…”

Evolution of Minor Phases in a P91 Steel Normalized and Tempered at Different Temperatures

“…These latter precipitates present smaller size than the Nb-rich ones, and they are formed at tempering temperatures of 600 °C and above. Zavaleta-Gutiérrez et al (2007) observed the type I, type II and type III MX precipitates. The type I and type II precipitates correspond respectively to the Nb-rich and the V-rich precipitates found in the present investigation.…”

Effects of Cooling Rate after Hot Forging on Precipitation of Fine Particles during Subsequent Normalizing and Austenite Grain Growth during Carburization of Al- and Nb-microalloyed Case-hardening Steel

“…1) However, such high-temperature carburization can cause abnormal austenite (γ ) grain growth 2) and, accordingly, degrade the fatigue performance and toughness of the steel components. The abnormal grain growth can be prevented by the addition of micro-alloying elements to form pinning particles, including AlN, 3,4) Nb(C,N), 3,[5][6][7][8][9][10][11] TiN 12) and V(C,N), 13) where TiN or a combination of AlN and Nb(C,N) are most commonly used in industrial applications.…”