Studies on solidification, aging and forgeability of modified stainless steels

The present study is concerned with a comparative evaluation of three Fe-Cr -Ni steels with different compositions. These are: (1) Fe-0.2C-18.2Mn-1 8.5 Cr-0.83Si-0.7Mo-0.15Ni-0.6N; (2) Fe-0.16C-18.5Mn-1 8.4Cr-0.33Si-1.7Mo-0.09N i; (3) Fe-0.07C-1.08Mn-21.6Cr-0.63Si-0.14Mo-9.63Ni. Four types of studies w ere conducted on each of these steers for their characterization, vii.: (a) solidification behavior by cooling curve analysis, (b) non-isothermal phas e transformation through dilatometric study; (c) isothermal phase transform ations at 500, 650 and 800 degrees C; (d) forgeability studies at 1050+/-50 and 800+/-50 degrees C. Depending on the chemistry, the melting point of the steels vary. Steel I i s the highest melting point alloy (1530+/-10 degrees C). Steel 2 melts at 1 510+/-10 degrees C and Steel 3 has the lowest melting point of 1430+/-10 de grees C. Dilatometric study reveals that at slow cooling condition (10 degr ees C/min) Steel 2 undergoes major phase transformations at two different r anges of temperatures, i.e., at 1070-1040 and 600-550 degrees C. This type of transformation was not observed in the other two steels. Steel 3 softens during holding at 1150 degrees C, Steel I is insensitive to aging treatmen t at 500 and 650 degrees C but undergoes pearlitic transformation on aging at 800 degrees C. Similarly, Steel 2 is sensitive at 650 and 800 degrees C. But Steel 3 shows little aging response at any of the temperatures. Steels 1 and 2 are forgeable at 1050+/-50 and 800+/-50 degrees C, respectively. T he forgeability of Steer 3 is poor compared to that of the other two steels and fails with opening up of large cracks. It may be concluded that Steel 1 shows better properties compared to other two compositions of steel. (C) 2000 Elsevier Science S.A. All rights reserved.