Characterization, Mechanism and Control Measures of V Segregation in Continuous Casting Billet of C-Mn Steel
- PDF / 3,320,962 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 115 Downloads / 296 Views
ODUCTION
LARGE raw materials for heavy equipment are usually produced by ingot casting. With the development of continuous casting, the dimension of continuous casting billets has been significantly enlarged. Currently, many large continuous casting billets have been used as the raw materials for heavy equipment. However, V segregation appearing in large steel billets usually induces non-uniform distribution of solute, microstructures and porosities. In particular, even after hot deformation, V segregation can still result in segregate bands in the forgings.[1] Hence, the quality of the continuous casting billet is seriously deteriorated by the V segregate. It is urgent to solve this problem. Several formation mechanisms for V segregation have been proposed by previous investigations on ingots. In the 1920s, V segregation was recognized as the flow channel of the segregated melt from the head of the ingot driven by the solidification contraction.[2] Although the flow channel from the head of the ingot was not supported by later experimental results,[3] the suction of the enriched melt driven by solidification XIAOPING MA and DIANZHONG LI are with the Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016 China. Contact e-mail: [email protected] Manuscript submitted August 29, 2018. Article published online March 27, 2019. METALLURGICAL AND MATERIALS TRANSACTIONS B
contraction was approved.[4] Sharing the same mechanism with macrosegregation, some researchers suggested that V segregation may be produced by thermo-solutal convection.[5,6] Some other researchers proposed that V segregation is closely related to the settlement of eqiuaxed grains.[7] Recently, a physical simulation of the effect of settlement of eqiuaxed grains on V segregation was reported.[8] In 1976, it was recognized that V segregation is the filled fissure in the equiaxed dendritic zone. Flemings proposed that the metallostatic pressure can produce fissures along shear planes.[9] In 1977, Alberny proposed that the dendritic sag can result in a V pattern of enriched melt in the equiaxed dendritic zone.[10] Some reports have focused on V segregation in continuous casting billets.[1,11,13,14] It was observed that V segregation only exists in the equiaxed grain zone of the billet.[1,11] Tomono suggested the following formation mechanism for V segregation in continuous casting billets. The enriched liquid between the equiaxed crystals is sucked in and flows downwards. With the forcible movement of the piling equiaxed crystals to the billet center, the enriched liquid accumulates along some planes.[11] Abbott proposed that V segregation is induced by hot tearing and erosion of the solid by flowing segregated liquid.[14] In addition, in relation to V segregation, the solute segregation, microstructures, inclusions and porosity in continuous casting were also investigated.[15–17]
VOLUME 50B, JUNE 2019—1161
Some detailed information remains to be clarified further, such as the dispersion of V segre
Data Loading...
