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Thermo-mechanical treatment
process were experimentally studied to obtain finer
austenite grains and higher fatigue strength of
carburized and quench hardened gear parts. A combination
of two operations, a cooling operation to the pearlite
transformation temperature after hot/warm forming
and subsequent short time reheating operation to
the temperature just above the austenite transformation
temperature, was effective in refining austenite
gains. The final austenite grain size of 3 to 15μm
was obtained by the precarburizing method and 15μm
by final carburizing method with SCr420 or SCM420.
These grain refining processes proved to be effective
in improving ductility,toughness and fatigue strength.
This thermo-mechanical
treatment process has a bright prospect of producing
gear parts with higher strength.
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