Abstract
We study the difference in the maximum stress on a cylinder surface σ max using the measured surface heat transfer coefficient h m instead of its average value h a during quenching. In the quenching temperatures of 200, 300, 400, 500, 600 and 800°C, the maximum surface stress σ mmax calculated by h m is always smaller than σ amax calculated by h a, except in the case of 800°C; while the time to reach σ max calculated by h m (f mmax) is always earlier than that by h a (f amax). It is inconsistent with the traditional view that σ max increases with increasing Biot number and the time to reach σ max decreases with increasing Biot number. Other temperature-dependent properties also have a small effect on the trend of their mutual ratios with quenching temperatures. Such a difference between the two maximum surface stresses is caused by the dramatic variation of h m with temperature, which needs to be considered in engineering analysis.
Acknowledgement
This work is supported by the National Natural Science Foundation of China [grant number 11102208], [grant number 11232013], [grant number 11472285] and [grant number 11572326].