| Hardness, tensile properties and impact toughness of 0.07C-1.4Mn-0.08Nb and 0.07C-1.4Mn-0.09V steels, which had been cold rolled by different degrees, were studied after aging treatment at 600℃ for varying period of times. By increasing aging times, there appeared two peaks of hardness values or strength. Aging time, which caused the hardness peaks, were independent of cold rolling degree and were constant for the same steel. When compared at the same hardness level, ductility and impact Goughness of the samples of secondary hardness peak were much better than that of the samples of primary hardness peak. Test results of mechanical properties are discussed in relation with the precipitation particle size and its distribution, coherency of the particles, and recrystallization. |
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