Improving Cleanliness of 16MnCrS5 Case Hardening Steels by Optimized Active Tundish Flux

Abstract

The aim of this study is to determine the optimal chemical composition of the tundish flux, which can efficiently absorb macro and micro inclusions from 16MnCrS5 case hardening steel. Computation of phase diagram is used as an approach to understand properties and behavior of tundish slags in casting conditions. Thermodynamic computation of steel − slag reactions is performed to find out the capability of different tundish slags to absorb inclusions. Industrial trials are, then, carried out with the slags to verify their functionality, when casting several heats in sequence. Results show that by tailoring tundish slag composition the steel cleanliness can be improved. Basic Ca–Mg–aluminate type slags have potential for wide use, as they can be easily adjusted chemically stable against the steel and have ability to absorb inclusions. The slag optimization is, however, a complex issue depending for example on the steel grade.

Laboratorial Analysis of Inclusions Formed by Reoxidation in Tundish Steelmaking

“…This result indicates that a great reoxidation level was obtained in the TS experiment, since the calculated equilibrium and the experimental results are in good agreement with the types of inclusions formed. The presence of an active slag in the tundish, capable to modify and dissolve inclusions, appears to be a main goal for the future of the steel production, in order to achieve a very high level of steel cleanliness . A good steel cleanliness observed in the TS experiment was deteriorated by the addition of RHA.…”

“…The main function of this slag is to prevent thermal loss and air reoxidation, other functions regarding a good steel cleanliness are desired as well . However in the past years, improving the removal of inclusions has not been a main goal . Together with the TS, the addition of rice husk ash (RHA) is a common practice in order to increase the thermal protection .…”

“…This property has been evaluated and it was confirmed that greater values of B 2 present better results to decrease total oxygen content and improve steel cleanliness in the tundish. Slags with a very high binary basicity are able to avoid reoxidation and are widely employed during the tundish steelmaking . In the past years, the active tundish slag concept became evident.…”

“…In the past years, the active tundish slag concept became evident. An active slag should be capable to modify and remove inclusions instead of being only a minor important source for inclusion control . This slag would be able to provide a good thermal protection, avoid air reoxidation, and modify/remove inclusions.…”

Recycling of Critical Raw Materials in the Nordics

“…[132] [133][134] [135] [136] [137] Finland is currently of particular interest due to its vanadium project. Many iron ores have a naturally high vanadium content.…”