Design of Composite Ladle Shroud for Improving Thermal Shock Resistance

A ladle shroud is one of the functional refractories for continuous casting,which undergoes severe thermal shock by molten steel when used without pre-heating.The composite ladle shroud with an insulating liner presents excellent thermal shock resistance.Finite element simulation is an effective method to explore the maximum thermal stress for predicting the thermal shock resistance of ladle shrouds.In this paper,the influence of the lining materials and the structure of ladle shrouds on the thermal stress distribution is systematically researched.The working mechanism of the lining material on the body material is also presented.Lining materials with low thermal expansion,elastic modulus and thermal conductivity are helpful to improve the thermal shock resistance and an optimum lining thickness is suggested.The lining material can both serve as thermal resistance for the body material to buffer the thermal stress,and apply a strain load to the body material by the thermal strain to increase the stress.

Multiphase flow inside a four-strand continuous casting tundish using three types of ladle shrouds

Numerical and physical models have been built and validated to study the multiphase flow inside three ladle shrouds and a four-strand tundish.A conventional straight ladle shroud and two types of trumpet-shaped ladle shroud(TLS)have been comparatively investigated.The maximum velocity at ladle shroud outlet reduces from 1.3 to 0.5 m/s,which indicates a quieter tundish pool.It is demonstrated that the use of a TLS can also decrease the maximum surface velocity from 0.16 to 0.13 m/s,which reduces the tendency of forming tundish open eye.The flow pattern and mixing behavior are improved inside the tundish,especially in enlarging the plug volume from 6.61%to 9.04%.The difference between the near and far outlets is narrowed when the TLS is applied.A computational program was developed to calculate characteristic parameters of different ladle shroud designs,and a dimensionless index was proposed to evaluate their mass and inner volume.Plant trials have been carried out,and the results showed that TLS can reduce level fluctuation in the pouring zone,which is beneficial to promoting better protective performance from secondary contamination and heat loss during continuous casting.

Behaviors of fine bubbles in the shroud nozzle of ladle and tundish

Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish.The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation intundish, are studied. The results show that the maximum sizes of the bubbles in the water and steelflow within the shroud in the length of 1.2 m are 0.70-1.44 mm and 1.53-3.16 mm respectively whenthe flow rates are 0.006-0.016 m^3/s; the terminal velocities of fine bubbles in the water andmolten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.