K-CARBIDES PRECIPITATION IN TWO HIGH MANGANESE ALLOYS
Two high Mn alloys marked A (24Mn-1.2C-12Al) and B (28Mn-0.7C-8.6Al) were laboratory hot rolled. After rolling in material A coarser k-carbides were detected, sporadically on the austenite grains boundaries and more frequently on the ferrite ones. Reason was un-balanced Mn a C contents in superposition with the rolling deformations and finishing rolling temperature of 950°C. Hardness corresponded to 432HV30 on average. Using light microscope no carbides on grains boundaries were observed in B both after rolling and followed aging at 500°C/6´. After 6 minutes of aging the hardness of B was approx. by 9 % higher unlike the rolled state. The X-ray analysis nucleation of nano-size kcarbides confirmed. After aging of B at 500°C/30´ and/or 60´some coarser k-carbides were detected on ferrite-austenite boundaries and/or austenite-austenite interface. The hardness went up and corresponded to 343 and/or 350HV30. From the X-ray and microstructure analyses follows the 30´ and/or 60´ dwell supported both very fine and coarser k-carbides precipitation. The calculated stacking fault energies (SFE) of both materials complete all solution. The A showed by 9 mJ.m -2 higher SFE than the B. In the A alloy lower Mn content and higher Al one resulted to 2.8 times higher ferrite volume fraction in comparison with the B alloy.
Phase Equilibria in Fe-Mn-Al-C Alloys
Phase constitutions of Fe-(20-30)wt%Mn-(0-10)wt%Al-C alloys have been investigated by electron probe microanalysis and transmission electron microscopy. The phase relations between austenite and perovskite carbide, (Fe, Mn)3AlC in the temperature range of 900-1 200°C have been carefully examined. An L12-type ordered structure, which was reported to be formed in rapidly solidified alloys as a metastable phase has not been detected in specimens aged at temperatures above 600°C.
Trends in kiln drives
The heart of the cement plant is the rotary kiln, and continuous quality production of cement clinker depends on the continuous accurate performance of the rotary kiln drive.