AOD-slag at Sandvik Materials Technology in Sandviken is disintegrating to a fine powder during cooling as a consequence of a volume increase caused by a phase transformation. The slag becomes a powder that's hard to handle because of dusting, the environment that is closeby take a beating. On top of that the slag must be landfilled and cannot be used as secondary material. In general most slags have a great potential to be used in as construction material in different applications around the society after used by the steel industry. In Sandviks case the disintegration stops that from being possible. To prevent disintegration of AOD-slag serveral things can be done, such as new additives or change of slag composition. In this project a new composition of the slag has been obtained from a decrease of lime addition. Then the slag composition can be moved outside of the area of disintegration by the volume increase. The change had to be done without jeopardize the quality of the steel or the lining material in the AOD. Potential steels were choosen for trials with lowered addition of lime after a present value analysis were established. The early analysis was conducted by slag samples from different steels in the AOD, these samples created the foundation of method further on. The full scale tries were conducted in three campaigns with different follow-ups. The results shows that there is possible to reduce the lime addtive to the AOD and by that receive a solid slag and at the same time produce high quality steel. With reduced lime addition the basicity is lowered. With lowered basicity the results shows that the sulphur removal gets worse as well as the reduction of chromium. The method established in this thesis does no go well with all steels except some pinpointed steel types with less demands on high sulphur removal. / AOD-slaggen vid Sandvik Materials Technology i Sandviken sönderfaller till ett fint pulver under svalning som en konsekvens av en fasomvandling av dikalciumsilikat där en volymexpansion sker. Slaggen som blir pulver blir svårhanterlig på grund av att den dammar, närmiljön försämras till följd. Dessutom måste slaggen deponeras och kan inte användas som ett sekundärt material. Generellt anses slagg har stor potential att användas till andra applikationer i samhället efter användning i stålindustrin. I Sandviks fall sätter sönderfallet stopp för det. För att undvika sönderfall av AOD-slaggen kan en rad olika saker göras som tillsatser eller ändring av sammansättning. I det här projektet har en ny slaggsammansättning uppnåtts genom minskning av kalktillsatsen till slaggen. Då kunde slaggens sammansättning flyttas från området för sönderfall genom volymexpansion. Förändringen var tvungen att ske utan att äventyra stålets kvalité eller infodringen i AOD:n. Potentiella stålsorter valdes ut för försök med mindre kalktillsats efter att en nuvärdesbild hade etablerats. Nuvärdesbilden bestod av provtagning av slagg från charger i AOD:n och den bidrog till metoden för försöken. Fullskaleförsöken utfördes i tre kampanjer med olika typer av uppföljning. Resultaten visar att det är möjligt att minska kalkmängden till AOD:n och därmed få en stabil slagg och samtidigt producera ett fullgott stål. Genom minskad kalktillsats sänks basiciteten och det gör slaggen mindre basisk. Resultaten visar att svavelraffineringen blev sämre. Kromreduceringen blev också något sämre. Metoden framtagen i det här projektet fungerade inte för alla stålsorter utan det är framförallt några utvalda stål med lägre krav på svavelrening.

Surface treatment processes of stainless steel, such as pickling, produces acidic waste water consisting of Na⁺, Cl⁻, F⁻, NO⁻3, SO42-, PO43-, Fe3+, Cr6+ and Ni2+. At Sandvik ABs steel works in Sandviken, this waste water is treated and neutralized using slaked lime before being released into the lake Storsjön. The aim of this report was to make a literary review of previous work in using slag as a neutralizing agent for acidic waste water. Furthermore, to see if it’s possible to replace some or all of the slaked lime in the neutralization process with slag and to study what slag that might be suitable to use. Since the waste water contains HF acid, the focus of this report was on different materials used for fluoride adsorptions. The literary study showed that the fluoride adsorption process with BOF slag, quick lime and magnesium oxide as adsorbents were endothermic. Therefore, it benefitted from an increased temperature. Furthermore, the literature study showed that many materials follow a pseudo-second-order kinetic model as well as a Langmuir or Freundlich isotherm for a fluoride adsorption. A previous experiment showed that a mixture of BF slag and slaked lime had the best HF acid neutralization among the tested materials. A fluoride adsorption experiment was made at different temperatures (25 – 55 °C) by using a slag from an aluminium reduced steel melt and a slag from a silicon reduced steel melt from the AOD converter in Sandviken. The silicon reduced steel melt slag showed an increase of fluorides in the solution, due to the presence of calcium fluoride in the slag. This was observed for all temperatures. The aluminium reduced steel melt slag also increased the fluoride content in the solution at 25 and 30 °C. At higher temperatures the fluoride content in the solution decreased with 93.6 to 94.9 %. Na⁺, Cl⁻, F⁻, NO⁻3, SO42-, PO43-, Fe3+, Cr6+, and Ni2+