Abstract
The mass effect and the hardenability of ADI, using a specially designed apparatus for end-quench test in austempering, were studied. Two types of cone shape specimens were applied for austempering treatment. The changes of Vickers hardness, microstructure, morphology of bainite and retained austenite with distance from quench end at given temperature were investigated with first type of cone shape specimen. The shape of bainite changes and hardness of bainite lowers on the border of pearlite because of increase of transformation temperature.
Hardenability of iron alloyed with Mo and/or Cu was evaluated with second type of cone shape specimen. A multiple linear regression analysis using the pearlite free half-cooling time data was performed to quantify the effects of Cu and/or Mo on suppression of the pearlite transformation. Half-cooling time is defined as the time required to cool from the austenitizing temperature to the temperature which is midway between the austenitizing temperature and austempering temperature.
Moreover predicting the micro-structure and hardness of ADI was tried by the heat flow analysis with personal computer. Basing on predetermined end-quench data, the prediction in the way of simulating temperature distribution at pearlite free or 50 % pearlite plus ferrite half-cooling time after dipping into austempering bath by SOLDIA-EX was well coincident with practical ADI.
