LAUSR

H13 steel (0.4C-5Cr-1.2Mo-1V steel) is the most widely used hot work die steel and used in hot rolling, hot extrusion and hot forging because of its combination of notable hot strength and remarkable toughness, especially the thermal fatigue resistance. H13 steel exhibits excellent mechanical properties after being quenched at 1 050°C and tempered twice at 600°C.1) To further improve the performance of H13 steel, laser surface hardening,2) deep cryogenic treatment,3) and Nb microalloying4) have also been employed. Nb microalloying has been widely used in refining grain size and improving strength and impact toughness of steels.5,6) The total substitution of vanadium in H13 steel by 0.07 wt.% niobium can effectively suppress grain growth and coarsening MC carbide.7) According to Elias’s results, the partial substitution of vanadium by niobium does not lead any significant change in the hardness of the H13 hot work tool steel, on the contrary, the new steel has a smaller austenite grain size and a finer second carbide size distribution, Effect of Nb Content on the Behavior of Primary Carbides in 0.4C-5Cr-1.2Mo-1V Steel