Abstract
Carbides in tool steels rapidly quenched from liquid state are extremely fine compared with those in commercial forged tool steels. Therefore, it may be well expected that rapidly quenched tool steels have different heat treatment characteristics from those of forged steels.
In this paper, this was confirmed experimentally using splats, extruded bars made from atomized powders, and beads by electron beam or transfer plasma melting of high speed steel, cold work die steel, and hot work die steel.
The results are summarized as follows.
1) Splats and beads of SKD 1 and SKD 11 cold work die steels showed a hardness value of above HRC 60 by being quenched from an austenitizing temperature as low as 850°C.
2) Canning extruded SKH9 showed a hardness value higher than HRC 63, by being quenched from an austenitizing temperature as low as 950°C, while splats did not show such high hardness values.
3) The high hardness values obtained at low austenitizing temperatures may be considered to be highly dependent on the carbides which were so fine as to easily dissolve into austenite.
