| Abstrakt: |
The effect of tempering temperature on the mechanical properties of medium carbon armor steels through double quenching-tempering (DQT) with respect to the conventional quenching and tempering (CQT) was investigated. In CQT, the test samples were initially subjected to austenization at 850°C with the holding time of 45 minutes followed by oil quenching and then were tempered for 60 minutes at the temperatures of 200, 400, and 600°C followed by oil- quenched. While in DQT, the samples obtained through CQT were then reheat-treated with the same austenization and tempering conditions at that of CQT. The samples were then tested by the tensile test, microvickers Hardness test, and Charpy V-notch impact test. The microstructure characterization by OM revealed that DQT with the first tempering temperatures of 200 and 400°C led to finer prior-austenite grain size (PAGS) than that of CQT while DQT with the first tempering temperature of 600°C produced slightly larger PAGS than CQT. The finest PAGS was obtained in DQT condition with the first tempering temperature of 200°C. In the DQT, the toughness and hardness are increased with decreasing the average PAGS. PAGS did not have a clear and significant effect on the value of yield strength, UTS, and elongation as there was no distinct trend and remarkable change in the values as PAGS changed. At the DQT's second tempering stage, increasing the second tempering temperature improved toughness and elongation, yet reduced the yield strength, UTS, and hardness. The first tempering temperature of 200°C achieves the most optimum mechanical properties in all second tempering temperature variants at the DQT process. [ABSTRACT FROM AUTHOR] |
