Influence of ferromanganese additions on microalloyed engineering steel

• Published in: Ironmaking & steelmaking Vol. 30; no. 1; pp. 73 - 80
• Main Authors: Sjökvist, T., Göransson, M., Jönsson, P., Cowx, P.
• Format: Journal Article
• Language: English
• Published: London, England Taylor & Francis 01.02.2003; SAGE Publications; Maney; Taylor & Francis Ltd
• Subjects: Additives; Alloys; Applied sciences; Carbon; Exact sciences and technology; Experiments; Finite element analysis; Hot rolling; Iron alloys; Iron and steel making; Laboratories; Metals. Metallurgy; Production of metals; Scanning electron microscopy; Steel production; Steel products; Studies; Treatment before gravity die casting and continuous casting; Sweden; Property composition relationship; Microalloyed steel; Treatment ladle; Steel refining; Structural steel; Experimental study; Electric furnace steel; Ferromanganese
• ISSN: 0301-9233; 1743-2812; 1743-2812
• DOI: 10.1179/030192303225009461

Plant trials with the addition of four different low carbon and medium carbon ferromanganese alloys to microalloyed engineering steels have been carried out at Ovako Steel, Hofors, Sweden. The process route for this type of steel at Ovako is electric arc furnace (EAF), ladle arc furnace (LAF), ASEA-SKF vacuum degasser, LAF and finally uphill teeming. For each ferromanganese alloy type, five experiments were accomplished by adding alloy at the ladle furnace station, i.e. 20 charges in total. During the experiments, liquid steel rapid solidification samples were taken to study the behaviour of inclusion formation and removal during ladle treatment. Also, samples for LSHR testing (liquid sampling hot rolling) were acquired for one heat of each of the ferromanganese containing alloys. Microinclusion assessments were carried out according to the method described in Swedish standard SS 111116. Macroinclusion assessments were carried out using immersed ultrasonic testing. Element analysis and mappings were done using a scanning electron microscope to establish the effect of ferromanganese addition on the composition of inclusions present in the steel. In samples taken 3 min after the ferromanganese addition to the LAF, about 30% of the analysed inclusions contain Al 2 O 3 , MnO and MnS. The Al 2 O 3 content is concluded to originate from the deoxidation practice, while MnO and MnS contents are likely to originate from the addition of ferromanganese. The results also show that the addition of ferromanganese alloys leads to an increased amount of macroinclusions in the LAF up to 9 min after alloy addition. Steel samples taken after degassing but just before casting indicate that all the tested ferromanganese alloys give the same result with respect to the studied microinclusion characteristics at the end of ladle treatment. Last, the inclusion composition in the final steel samples is unrelated to the type of ferromanganese alloy used. In this case, the main compositions are Al 2 O 3 -MgO and MnS.