1974 Volume 60 Issue 1 Pages 85-95
In the earlier paper, the relationship between the austenitizing time and the mechanical properties ofhigh-speed tool steels was reported. In this paper, a similar relationship for the alloy tool steel SKD11 whichis austenitized at 960°C-1080°C for 10-3000sec and tempered at 150°C-550°C has been studied by thesame methods as in the previous paper. The results obtained are as follows;
1. The preferable mechanical properties of the steel SKD11 for cold working are generally obtainedin the hardness range of Rockwell C58 to 60 (Hv 650 to 700) and in the bend strength of over 350kg. Theseproperties can be obtained by the next heat-treatments. A: Austenitized for a long time at lower temperaturenear 1000°C and tempered between 150°C and 200°C. B: Austenitized for a short time at highertemperature between 1040°C and 1080°C and tempered between the same temperatures as A. C: Austenitizedfor a long time at 1040°C to 1080°C and tempered above 500°C.
2. Degrees of austenitizing in the microstructure seems to become larger in the order of B→A→C. Specimensby the treatment A are almost completely austenitized and those by B include some residual ferritein austenite. Those by the treatment C are completely austenitized and have partial grain growth.
3. A specimen by A which has been austenitized for 3000sec at 960°C and tempered at 150°C has themost preferable mechanical properties for cold work tools. This has been confirmed by industrial tests.