Journal
METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE
Volume 52, Issue 1, Pages 95-106Publisher
SPRINGER
DOI: 10.1007/s11663-020-01997-4
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Funding
- University of Oulu including Oulu University Hospital
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The study investigated the effect of as-cast structure and macrosegregation on the mechanical properties of a low-alloy martensitic ultrahigh-strength aluminum killed and calcium treated steel cast at different superheats. It was found that higher superheat led to more intense interdendritic segregation, causing pronounced positive segregation in specific zones. Hot-rolled samples showed local variations in hardness correlated with carbon content variations, and the CET zone had a tendency to reduce impact toughness values.
The effect of as-cast structure and macrosegregation on the mechanical properties of a direct-quenched low-alloy martensitic ultrahigh-strength aluminum killed and calcium treated steel cast at different superheats was studied. Samples from the castings were laboratory hot rolled with two different finishing rolling temperatures to distinguish the effect of hot rolling. Using optical emission spectrometry, the steel composition was analyzed as a function of slab thickness in order to detect the variations in steel chemistry due to macrosegregation. Further, hardness profiles, prior austenite grain sizes and tensile and impact toughness were determined for the hot-rolled specimens. It was found that interdendritic segregation was more intense at the higher superheat, which led to more pronounced positive segregation in the columnar-to-equiaxed transition (CET) zone, and negative segregation between CET and the centerline. These macrosegregation patterns were inherited by the hot-rolled samples causing local variations in hardness, which followed the variations in carbon content. However, altering the superheat had a minor effect on the nominal transformed microstructures and nominal prior austenite grain sizes. This occurred because of the interdendritic segregation induced composition variations both enlarged and decreased by turns the grain sizes. The CET also reduced measured impact toughness values.
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