HARDNESS AND IMPACT ENERGY OFTHE TEMPERED SILICON MANGANESE STEELS CONTAINING VANADIUM

This research studied microstructure, hardness and impact energy in oil quenching and tempering conditions of the silicon manganese steel modified with vanadium. The modified steels consist of carbon 0.56-0.64 wt%, silicon 1.80-2.20 wt% and manganese 0.70-1.00 wt% with vanadium content of approximately 0.002 to 0.296 wt%. All samples were casted in sand molds, oil quenching and tempering at various temperatures. All samples were subjected to solution treatment at 845C subsequently oil quenching. It was found that all specimens exhibited martensite structure about 3-5% of retained austenite. Grain size of needle-shape martensite appeared finer when vanadium content increased. Again, average of hardness values increased by 36% from 499 HB to 678 HB. However, impact energy of as quenched steels was not affected by increase of vanadium. In tempering conditions, at tempering temperature of 490, 515 and 540 C followed by air cooling, the tempered structure was obtained. Hardness of specimen tempered at 515C increased with increasing vanadium content by 39% from 404 HB to 562 HB. Impact energy decreased with increasing vanadium content. The maximum decreased by 16.48% found in specimens tempered at 515C.