Yoshio Ashida

Effects of Co, Mo and Ti Contents on Age-hardening in 15% Ni Maraging Steels

ABSTRACT Effects of Co, Mo and Ti contents on age-hardening behavior have been investigated. It is found that all of these alloying elements are effective in increasing the peak hardness after aging. From the results of transmission electron microscopic observation of size and distribution of intermetallic compounds and austenite, the hardening mechanism is discussed. It is shown that the Orowans mechanism well explains the hardening behavior in the present case.

Strengthening and toughening of Cr-Ni-Mn-V austenitic hot work tool steels

The effects of alloying elements and heat treatment on the mechanical properties of austenitic hot work tool steels, which were strengthened by the precipitation of VC carbides, were investigated.The replacement of Ni by Mn increased the strength and hardness because the dissolved C and V contents after solution treatment increased. 0.2 pct proof stress more than 120 kg /mm2 and hardness more than HRC45 could be obtained in a 0.5 pct C-10 pct Cr-8 pct Ni-13 pct Mn-2 pct V austenitic steel by solution treatment over 1200 °C and aging at 700 °C for seven hours.Thermomechanical treatment, in which the steels were water quenched immediately after hot rolling at 1150 to 1200 °C and then aged at 700 °C, was most effective in the improvement of ductility and toughness because of grain refinement caused by recrystallization.Step aging treatment, the increases of C and V content, and the addition of B also improved ductility and toughness.