Mold oscillation

Mold oscillation is necessary to minimize friction and sticking of the solidifying shell, and avoid shell tearing, and liquid steel breakouts, which can wreak havoc on equipment and machine downtime due to clean up and repairs. Friction between the shell and mold is reduced through the use of mold lubricants such as oils or powdered fluxes. Oscillation is achieved either hydraulically or via motor-driven cams or levers which support and reciprocate (or oscillate) the mold.

Mold oscillating cycles vary in frequency, stroke and pattern. However, a common approach is to employ what is called "negative strip", a stroke pattern in which the downward stroke of the cycle enables the mold to move down faster than the section withdrawal speed. This enables compressive stresses to develop in the shell that increase its strength by sealing surface fissures and porosity.


Depth of Oscillation Crack & Transverse Crack :

         T = (Vc/pie*h*f)*(1/180*f)
where,
f = frequency (oscillation per time)
Vc = Casting Speed
h = Oscillation Stroke

Negative Strip :

        Ns = [(Vc- Os)/Os]*100

where,
         Os = oscillation Speed = Vc * 1.25

Frequency :

          f = [(.788*  Vc)/2*S.L]

where,
S.L = Stoke Length

Total Cycle Time = 60/f

Negative strip time = Total Cycle Time * 20%

Specific water consumption : 

     total water consumption/(Vc*perimeter)

Degree of bulging :

  f = c*[(p.l^4)/(e.d^3)]
where,
 p = Ferrostatic pressure
 l =  roll pitch
 d = strand shell thickness 
 e = modulus of elasticity
 v = casting speed