1. BACKING SAND IN TUNDISH
USAGE OF OLIVINE as
BACKING SAND IN TUNDISH
24/09/2007
24/09/2007

2. TUNDISHES ; are machines which, continuously provide molten metal to mold and adjust amount of incoming metal to mold
ladle
Tundish

3. Interior of tundishes could be molded by two ways; hot molding and cold molding. In cold molding magnesite based plates are used as tundish coating and laying of plates are made without heat treatment. In hot molding, tundish coating is made by tundish mortar and heat treated. After heat treatment, there is a colling period for hardening of material. Cold molding is better economical than hot molding and requires less time. Downside of cold molding is it requires more workmanship.

4. This photograph shows a tundish, before its refractory coating applied, from a big steel mill in Turkey.
Cold molding is utilized for tundish coating. Tundish is about 7m long and have about 30 Ton capacity

5. Tundish Coating
(Magnesite based plates)
Tundishes have 2 layers; tundish coating and wall. Olivine sand is used as a backing material to fill in between of wall and coating
Tandişler çalışma astarı ve emniyet astarı olmak üzere iki kısımdan oluşurlar. Olivin kumu ise burada emniyet astarı ile çalışma astarı arasında dolgu malzemesi olarak kullanılır.
Tundish Impact
Wall
Wall

6. Wall is coated with 12 cm refractory cement which has high alumina content

7. Magnesite based plates used in coating

8. This photo shows the usage of olivine sand as a filler
This photo shows the usage of olivine sand as a filler. Olivine sand protects wall of tundish due to its high melting point. Application of olivine is not a complicated process and not requires a lot of workmanship. Steps are as follow;
1- Bottom of emptied tundish is filled with 0-2mm or 1-3mm olivine sand.

9. 2) Filled olivine is levelled to whole surface with 10 cm thickness
2) Filled olivine is levelled to whole surface with 10 cm thickness. After levelling process, magnesite plates are molded on bottom.

10. 3) After molding of plate to bottom surface, side surfaces are molded with magnesite based plates. It is important to put 10 cm gap between wall and coating

11. 4) This 10 cm gap is filled with olivine sand in order to protect wall
4) This 10 cm gap is filled with olivine sand in order to protect wall. Olivine sand is a refractory material with high melting point(1750 °C). Olivine protects wall with its this property and reduces maintanence costs of tundish.

12. 5) After olivine sand filling process, gaps between plates are troweled with refractory mortar. olivine sand Olivin dolgu kumunun tatbikinden sonra plaka araları yüksek ısıya dayanıklı refrakter harçlarla sıvanır ve sıvanın kuruması için bir gün bekletilir.
Refractory mortar

13. 6) Tundish impact is placed under where molten metal comes from ladle

14. After all these processes, molding of tundish with refractory material is finished. Tundish is now ready for upcoming casting processes. After 30 casting process, tundish coating is replaced with new one.