what causes a violent boiling in EAF

1)  a carbon boil - disolved oxygen ppm + carbon = lots of light and heat.

2)any scrap or ferroalloys embebed in slag may cause a violent reaction in the furnace once it gets espontaneously in contact with the molten steel. Also if a deficient refractory repair breaks and any moist is retained under it may cause a violent reaction. 

3)  sudden addition of high-carbon material (pig iron, respectively hot metal) into a steel bath with high oxygen activity has caused sudden formation of CO and the boiling you have observed. I would reconsider the rate and time of addition. 

4)  two things are important,if the furnace is having highly oxydised bath it indicates with flame shoot once hot metal is poured.But the pouring should be controlled or else it may end up with boiling.......slag volume in furnace is important...as its increase in volume and subsequent sudden pouring of hot metal will cause boiling...control of Si in HM is also imp 

5) Bath stratification of temperature or carbon will cause a boil in the EAF during refine. Depending how the furnace is charge could cause problems. If you charge lime or DRI on the bottom and then, charge scrap or hot metal on the top, you will have an reaction around 2800 to 2850 F. 

6) Rust, Moiture, Oxygen, Nitrogen & Hydrogen present in scrap expands many more times of their voulume at high temp and there by reacts with each other causes voilent boiling in EAF 

7)  Basic atmost reason for boil in EAF during refiningis presence of high activity of free oxygen for having a boil surface tension & viscosity of slag must be least. 

8) Before any addition to EAF molten bath should be stable, specially adding pigs or alloys. in both cases it looks that boiling is due to Temperature gradient. or it may be due to high slag volume & carbon boil in most cases.