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Niobium,a traditional microalloying element for the production of HSLA steels,is usually added in amounts not more than 0.100-10 in the form of Standard Ferroniobium ( FeNb STD).Despite dissolving readily,the addition of FeNb requires a good control of some parameters such as temperature,time and particle size.Earlier studies on a laboratory scale have shown that the kinetics of dissolution of ferroniobium in liquid steel is controlled by heat transfer to the particles and that its dissolution rate increases by increasing the temperature or decreasing the particle size.Taking advantage of using very fine particles,CBMM developed a new briquetting process in order to agglomerate FeNb fines smaller than 2 mm to make them tough enough for easy handling during their addition to the molten steel.This paper aims at comparing the dissolution rate of briquetted FeNb in relation to the lumpy material as well as to describe the mechanism of dissolution at the briquette/steel interface.Industrial results showed that the total dissolution of briquettes and lumpy material occur in less than 10 minutes at 1570% and the yield of the niobium addition was higher than 98% for both.The briquettes of FeNb dissolved faster than the lumpy material of the same equivalent diameter.It was also observed that the dissolution rate of the briquettes and the lumpy material increased for higher temperatures.The dissolution mechanism at the interface was similar for both materials.