| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 100 === Abstract
Cast steel SCW 450 for welded construction has been cast in a considerable volume, in most cases designed bonding together with other materials by welding, so other than the mechanical properties of SC 450 , it requirements of a low temperature impact toughness at 0 ℃with a impact value at least up to 27 J.
The study was designed to explore the effect of intercritical heat treatment on the low temperature impact toughness of cast steel SCW 450. Experimental methods include the furnace cooling and air cooling after austenitizing treatment, the OM and SEM examination of the microstructure of cast steel, impact testing at 0 ℃ and the fracture surface of impact specimens. The relationship of austenite grain size of SCW450 at 920 ℃ with holding times was studied also.
The results show that the pearlite distribution pattern after heat treatment and the ferrite grain size are the most important factors which affect the low temperature impact toughness of SCW450; the original austenite grain size is coarsening with the increase of holding times.
Keywords：Cast steel, Low temperature toughness, Intercritical heat treatment
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