Effect of As-Cast Structure and Macrosegregation on Mechanical Properties in Direct-Quenched Low-Alloy Ultrahigh-Strength Steel

Abstract

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.

Kinetic Aspects of Phosphorus Removal from Electromagnetically Levitated 600 MPa Steel Droplets

“…Steel is a critical material used in the construction industry, and this has a significant effect on industrial development. With the continuous innovation and development of the construction industry, the market demand for steel has increased, and the performance requirements for steel by the industry have also increased [1]. A key factor that affects the performance is steel strength, including yield strength and tensile strength [1].…”

“…With the continuous innovation and development of the construction industry, the market demand for steel has increased, and the performance requirements for steel by the industry have also increased [1]. A key factor that affects the performance is steel strength, including yield strength and tensile strength [1]. Since regular strength steel can no longer meet the requirements of the market, 600 MPa steel has been developed.…”