Quantitative assessment of segregates in continuously cast slabs by electron probe microanalysis

Abstract

Due to the limited solubility of individual elements in the crystal lattice of steel, an enrichment of the residual melt and furthermore a formation of micro and macro segregates will appear during solidification of the steel melt. Depending on the chemical composition of the steel, the operation parameters of the casting plant and the slab dimension, the segregates will be formed with different intensities. The knowledge of the segregation effects is imperative for further processing of slabs and the subsequent products. The electron probe micro analyser (EPMA) makes feasible an objective assessment of the segregates due to solidification over the entire slab thickness. This is carried out by concentration mapping (CM), which is a method for the quantitative determination of element distributions over certain areas on the sample. In this paper some results taken from an investigation on steel grade 13 CrMo 4-5 are presented, and some casting technological measures derived from these results are proposed. Quantitative Bewertung der Seigerung inStrangguBbrammen mit Elektronenstrahlmikroanalyse. Bedingt durch die begrenzte L6slichkeit einzelner Elemente im Kristallgitter des Stahles kommt es bei der Erstarrung zur Anreicherung der Restschmelze und im weiteren zur Mikro-und Makroseigerung. Abhii.ngig von der Stahlzusammensetzung, den GieBparametern, der GieBanlage und dem Brammenformat sind die Seigerungen unterschiedlich stark ausqspraqt. Ein quantitatives Wissen Ober die Seigerungen ist daher fOr die Weiterverarbeitung der Brammen und der hergestellten Produkte eine zwingende Notwendigkeit. Die Mikrosonde erm6glicht es, eine quasiobjektive, mikroanalytische Beurteilung der Prlrnarstruktur Ober die Brammendicke durchzutuhreno Dies erfolgt mit Hilte einer quantitativen Bestimmung einzelner Elemente Ober vorgegebene Flachen (Concentration Mapping). Untersuchungsergebnisse und die daraus abzuleitenden MaBnahmen werden am Beispiel der Stahlsorte 13CrM04-5 srlautert.abstract d

Methods for Assessment of Slab Centre Segregation as a Tool to Control Slab Continuous Casting with Soft Reduction

“…Very pronounced segregations will lead to a banded structure in the hot rolled band or heavy plates. [8][9][10] Centre segregations tend to be irregular both across the slab and along the slab's longitudinal axis. Figure 2 shows the slab samples taken from a slab for the purpose of comparing the segregation indexes.…”

“…[8][9][10] To determine the macrosegregation, the microprobe scans an area of 40ϫ40 mm with a step size of 95 mm between the measuring points. This furnishes a relatively good image of the area where segregation occurs.…”

Structure of Continuously Cast Ingots of Unalloyed and Low Alloy Steels and Its Evolution as a Result of Hot Working

“…Aby zobrazować strukturę krzepnięcia, należy ujawnić obraz dendrytów wykrystalizowanych z fazy ciekłej. Stosowane są w tym celu metody ujawniające rozsegregowanie pierwiastków pomiędzy w przestrzenie międzydendrytyczne i ramiona dendrytów: "mapowanie" rozkładu pierwiastków metodą skaningowej mikroskopii elektronowej [22,41], odwzorowanie segregacji siarki za pomocą odbitek Baumanna oraz wytrawianie chemiczne odczynnikami ujawniającymi segregację określonych pierwiastków, np. odczynnikiem Oberhoffera obrazującym rozkład fosforu.…”

Experimental investigation concerning the development of distortion potential during the production of 20MnCr5

“…The metallographic macro structure illustrates an inhomogeneous element distribution due to macro-and micro-segregations, which are considerably affected by the solidification conditions. Such differences concerning the primary structure were found also at other steel qual-ities and casting formats and were affected by the melting and solidification conditions [8,9]. An anisotropical length change during phase transformations could be identified as a cause of the development of the preferred direction and amount of the curvature [10,5].…”