Tundish nozzle is key thermal equipment during the steel continuous casting process.
Generally tundish nozzles include tundish metering nozzles, quick exchangeable nozzles etc. When compared to lining refractories, request to materials of tundish nozzles are more strict, as tundish nozzles are crushed and eroded by molten steel continuously under high temperature.
Tundish nozzles are generally composite with two parts : Al2O3-C outer and Zirconia inserts. Raw materials for outer are white corundum and flake graphite, make Phenolic Resin as binding agent; zirconia inserts are made from Magnesium stabilized zirconia. Generally service life is over 6 hrs.
With development of steel producing process and steel grades, request to tundish nozzles are increasing too. Classic nozzles could not meet demands. Regarding to present situation, Long Keter technical team together with production engineers make improvement to the nozzles from different sides.
1.From crystalline components: crystallines of the fired zirconia inserts mainly include ZrO3 cubic, ZrO2 tetragonal and ZrO2 monoclinic phase. ZrO2 Stabilization ratio influence service life a lot. In order to increase the ratio and avoid crack result from phase transform, we improved producing technology as following:
a.Prolong the holding time during firing
b.Increase ratio of cubic ZrO2 phase
With measures above, product quality is highly improved. No cracks happen to the products after 6 min. Complete oxygen Firing testing ( photos as below).
Compared to product produced by the famous international refractory group. Cracks happen after 1 min. Firing test(Photo as below).
2.When tundish nozzles are applied to some severe conditions, such as being used without preheating、high Mo steel etc., impurities inside the molten steel will react with MgO, result in low refractoriness phase MgSiO4. To solve this problem, Yttrium stabilized zirconia combined with Magnesium stabilized zirconia is used as raw materials, as a result performance is improved.
Besides, to get better performance, we still advise to do preheating before tundish nozzles are applied. Preheating for 2-3 hrs from room temperature to 250-300 ℃ could help to avoid cracks caused by cold casting and improve performance efficiently.
Keep “ Make Energy Efficiency Easier” in mind, Long Keter is dedicated to producing, developing and researching of tundish nozzles, and aim to offer most helpful industrial solutions to all clients!