Abstract
The behaviour of retained austenite in hardened high-carbon high-chromium steel containing 2.17% carbon and 12.57% chromium, has been studied by means of micro-structure, hardness measurement and magnetic analysis. And then the isothermal transformation diagrams of this steel at two maximum heating temperatures were determined. These results are summarized as follows: (1) From 10% to nearly 100% of retained austenite is contained at room temperature in the specimens oil-quenched from various temperatures between 900° and 1200°. (2) The quenching temperature has a large effect on Ms point, and this point is below the room temperature when the quenching temperature is higher than 1150°. (3) The retained austenite in specimens oil-quenched from below 1100° decomposes into bainite or pearlite during subsequent heating at two temperatures, about 200 and 600°, but that formed at the quenching temperature above 1150° decomposes only into pearlite at about 600°. (4) As the tempering time at 550° is longer, the temperature, at which the retained austenite begins to transform during cooling from the tempering temperature, becomes higher. (5) As shown in the isothermal transformation diagrams (Fig. 8), austenite is meta-stable in the intermediate zone.
