THE EVALUATION OF NON-METALLIC INCLUSIONS IN CALCIUM-TREATED STEEL BY USING ELECTROLYTIC EXTRACTION
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
This study aims on characterization of non-metallic inclusions (oxides and sulfides) in steel with and without Calcium treatment. In this paper, the three-dimensional (3-D) investigation method of inclusions on film filter after Electrolytic Extraction (EE) of steel samples is applied on two different steel grades (280, 316L). Image analysis of non-metallic inclusions is carried out on Scanning Electron Microscope (SEM) images following with inclusion characteristic analysis. Steel samples with calcium treatment in the production process and reference samples was investigated and compared in density, size and composition.
It shows that higher magnification and larger inclusion size correspond to more accurate result. With restriction of equipment and measurement, 2μm is the smallest size could be measured in ×500 magnification within 5% error.
The comparison of distribution of inclusions varies with different zones: center has the largest size with least number of NMI; surface has the smallest size with largest number of NM; middle part has the median properties.
In 316L steel, Ca treatment increases the number of oxides inclusions significantly; the content of Ca and Si in oxides inclusions is also increased. Two shapes of oxides inclusions, oval and elongated ones, are found with Ca treatment.
In 280 steel, the total amount of NMI decreases slightly with Ca treatment; CaS is found in spherical inclusions; Because of earlier formation of larger size spherical inclusions, higher Ca content is found than that in smaller size spherical inclusions.
Place, publisher, year, edition, pages
Steel, Electrolytic Extraction, Non-metallic inclusion, Calcium treatment
Metallurgy and Metallic Materials
IdentifiersURN: urn:nbn:se:kth:diva-191786OAI: oai:DiVA.org:kth-191786DiVA: diva2:957615
Subject / course
Applied Process Metallurgy
Master of Science - Engineering Materials Science
2016-06-09, 14:00 (English)