New macrosegregation criteria for quality problems in continuous casting of steel

Abstract

To estimate the quality condition in continuously cast steel slabs, simple but accurate macrosegregation criteria have been proposed. The formation of macrosegregation phenomena in continuous casting of peritectic carbon steels has been investigated by metallographic study of collected slab samples. The metallographic study involved plant trails to collect the slab samples and to prepare them for chemical macrosegregation analysis. The experimental results show a fluctuation of carbon between positive and negative segregation with distance from slab surface based on the cooling conditions experienced by the slab. Via mathematical analysis, formulae of average macrosegregation level ASL, its fluctuation level FSL and its segregation quality number SQN have been developed. The results calculated by these formulae show good agreement with the description of the formation mechanisms of different continuous casting defects and their locations. Therefore, these calculations illustrated that macrosegregation criteria and their distributions can be considered by experimental, simple and vital tools to evaluate the conditions of surface and inner qualities in continuously cast steel slabs. The mechanisms of these criteria with some mechanisms of continuous casting defects have been explained and discussed.

Macrosegregation Quality Criteria and Mechanical Soft Reduction for Central Quality Problems in Continuous Casting of Steel

“…This idea has already been demonstrated by many investigators [1]- [11]. These and similar early models revealed important insights into the most frequent surface and internal defects [12]- [21]. For example, Samarasekera et al [1] [2], have developed mathematical analyses of the thermal distortion of continuous casting billet molds and the influence of mold behavior on the production of these casters.…”

“…In order to examine slab quality in various cooling zones of continuous casting of steel, macrosegregation criteria were developed based on El-Bealy approach explained in Ref. [21]. As result of complex segregation interactions of different alloying elements, this approach should be extended into multi segregated elements.…”

“…Many important related aspects of continuous casting have been modeled in depth and discussed elsewhere [12]- [21], including heat transfer [12] [13], solidification [14], fluid flow and the molten steel pool and inclusion removal [15], bulging and solid shell resistance of the strand [16] [17], crack predication [18]- [20], and quality criteria [21].…”

The Influence of Centerline Segregation on the Mechanical Performance and Microstructure of X70 Pipeline Steel

“…In the final strip, the segregation is evident through banding of the microstructure, especially in the region of centerline, where the enrichment of elements including carbon, manganese, molybdenum, and chromium could increase the hardenability of the strip and result in formation of the harder microstructural features. Over the years, various slab assessing systems have been defined . These systems are applicable to measure slab quality considering factors such as segregation and internal cracks .…”

“…Over the years, various slab asse-ssing systems have been defined. [4][5][6][7][8] These systems are applicable to measure slab quality considering factors such as segregation and internal cracks. [3] Traditionally, the severity of centerline segregation is rated by the "Mannesmann standard" [9] of which the segregation ratings are scaled from level 1 to 5 and the degree of segregation increases with the rating.…”