Ladle to Tundish Transfer Improvements at JL Specialty Steel

摘要

In the last two years, the melt-shop and caster at J&L specialty steel has been involved in a large campaign to achieve a world-class quality products. For this intent, a large study was conducted to assess all possible root-causes of primary related (laminations) defects on finished coils. One of the sources of inconsistency identified was the ladle to tundish transfer. Laminations were identified to come from a number of sources and only those related to re-oxidation in the ladle to tundish transfer were addressed in this paper. For this specific case, a stepwise approach was utilized to virtually eliminate all possible sources of re-oxidation between the ladle and the tundish, including ladle shrouding and turbulence in the tundish. Because other process improvements were taken place simultaneously, every step was trialed independently by comparing to our existing practice. Operational, cost and quality concerns were evaluated together and in every case the best practice was selected, verified and standarized before moving to the next step. Overall, we have found that the most robust practice to-date can be achieved by: 1. using a turbulence suppressing pad with no additional furniture in the tundish 2. using a simple shroud design with an argon ring on top 3. use an appropriate gasket between the ladle slide-gate and the ladle shroud 4. careful inspection of the plates on the ladle slide-gate. Along with other projects, the results of this study have significantly reduced the incidence of laminations on the J&L finished coils, and the retreat rate of coils is at an all-time low. Costs benefits were evident at all levels, such as reduction of retreat material, improved scheduling and faster delivery to customers.