en Research Paper Research Paper <font face="TimesNewRomanPS-BoldItalicMT"><font face="TimesNewRomanPS-BoldItalicMT"><p align="left"><font size="2">Abstract: </font></p><p align="justify"><font size="2">mechanical properties of AISIH 13 hot-work tool steel have been studied. Cast samples made of the modified new steel </font><font size="2">were homogenized and austenitized at different conditions, followed by tempering at the specified temperature ranges. </font><font size="2">Hardness, red hardness, three point bending test and Charpy impact test were carried out to evaluate the mechanical </font><font size="2">properties together with characterizing the microstructure of the modified steel using scanning electron microscope. </font><font size="2">The results show that niobium addition modifies the cast structure of Nb–alloyed steel, and increases its maximum </font><font size="2">hardness. It was found that bending strength bending strain, impact strength, and red hardness of the modified cast </font><font size="2">steel are also higher than those of the cast H13 steel, and lower than those of the wrought H13 steel. </font></p></font></font><font face="TimesNewRomanPS-ItalicMT"><font face="TimesNewRomanPS-ItalicMT"><font size="2">In this research, the effects of partially replacing of vanadium and molybdenum with niobium on the</font></font></font> Hot-work tool steel, H13, Nb, niobium, NbC, mechanical properties. 22 29 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-3-123&slc_lang=en&sid=1 A. Noorian 180031947532846001437 180031947532846001437 No Sh. Kheirandish * kheirandish@iust.ac.ir 180031947532846001438 180031947532846001438 Yes H. Saghafian 180031947532846001439 180031947532846001439 No