Abstract
Extensive studies are being carried out with high speed steel made from atomized powders, mainly for the establishment of mass production technique and the investigation of various properties of such steels. Almost no literature has been published on the metallographic study of the steels rapidly quenched from liquid state. Therefore, the solidification process during quenching of tool steels from liquid state was studied in this work.
Microscopic observation, X-ray diffraction and electron probe microanalysis were performed on the atomized powders, thin plates by splat cooling, and beads made by several methods such as electron beam and transfer-plasma melting. The materials studied included high speed steels, cold work die steels and hot work die steels.
The results are summarized as follows.
(1) When high speed steels and die steels were quenched from liquid state, carbides were crystallized in the form of extremely fine particle or plate.
(2) Quenched from liquid state, high speed steels were crystallized in the following steps.
Primary γ, γ+cabide eutectic
(3) Hot work die steel was crystallized in the same process as high speed steels but no β-ferrite was found.
(4) Carbides crystallized in SKH9, SKH54 high speed steels and SKD61 hot work die steels were not M6C+MC type but M2C+MC type.
