Method and control device for controlling the heat removal from a side plate of a mold

Abstract

The invention concerns a method and a control device for automatically controlling the heat dissipation {dot over (q)} in a mold 200 for casting metal. The heat dissipation of the side plate of a mold is automatically adjusted to a preset set point {dot over (q)} set by suitable variation of the volume flow rate {dot over (V)} of a coolant 300 through the side plate. In accordance with the invention, to avoid the necessity, when different molds are used, of adapting the control of the heat dissipation each time to different thicknesses or coatings of the side plates or to different settings of the side plates during the casting operation or during the casting of different grades of steel, the actual value for the heat dissipation {dot over (q)} during a steady-state casting operation is suitably computed on a current basis from, among other things, the difference in the temperature of the coolant 300 at the coolant outlet and the coolant inlet of the side plate 200 and material constants for the coolant.

1 . A method for automatically controlling the heat dissipation {dot over (q)} in at least one side plate ( 200 ) of a mold for casting metal to a preset set point {dot over (q)} set  by suitable variation of the volume flow rate {dot over (V)} of a coolant ( 300 ) through the side plate ( 200 ) according to a control deviation Δ{dot over (q)} in the form of the difference between the set point and an actual value {dot over (q)} actual  for the heat dissipation, wherein the heat dissipation {dot over (q)} is automatically controlled and the volume flow rate {dot over (V)} is varied during a steady-state casting operation wherein the method is carried out for the side plate ( 200 ) in the form of a narrow-side plate of the mold, wherein, the width and/or the conicity of the narrow-side plate are changed during the casting operation. 
     
     
         2 . A method in accordance with  claim 1 , wherein the actual value for the heat dissipation {dot over (q)} is computed on a current basis from, among other things, the difference between the actual temperature (T out ) of the coolant at the coolant outlet of the side plate and the actual temperature (T in ) of the coolant at the coolant inlet of the side plate ( 200 ) and material constants (ρ, c p ) for the coolant. 
     
     
         3 . A method in accordance with  claim 2 , wherein the heat dissipation is the specific heat dissipation, and the actual value for the specific heat dissipation is computed as follows:
     {dot over (q)} (ρ* V*c   p   *d   v )/ A      
       where
 {dot over (q)}: the heat dissipation [W/m 2 ] 
 ρ: the density of the cooling water [kg/m 3 ] 
 {dot over (V)}: the volume flow rate of the cooling water [L/min] 
 c p : the specific heat of the cooling water (at constant pressure) [kJ/(kg·K)] 
 d v : the temperature difference T out -T in  [K] 
 A: the active cooling surface of the side plate. 
 
     
     
         4 . A method in accordance with  claim 1 , wherein the heat dissipation is the absolute heat dissipation. 
     
     
         5 . A method in accordance with  claim 1 , wherein the actual values for the temperatures (T out , T in ) and/or the volume flow rate {dot over (V)} of the coolant are each measured on a current basis and then averaged or buffered, before they are used in the computation of the actual value for the heat dissipation {dot over (q)} actual . 
     
     
         6 . A method in accordance with  claim 1 , wherein the coolant ( 300 ) is water treated with corrosion inhibitor, glycol or oil, activated water, or distilled water. 
     
     
         7 . A method in accordance with  claim 1 , wherein the set point {dot over (q)} set  for the heat dissipation can be variably preset. 
     
     
         8 . A method in accordance with  claim 1 , wherein the method is carried out separately for two side plates ( 200 ) in such a way that the set points {dot over (q)} set  for their respective heat dissipation values are in a desired ratio to each other. 
     
     
         9 . A method in accordance with  claim 8 , wherein the method is carried out separately for the two opposite narrow-side plates ( 200 ) of the mold in such a way that the heat dissipation for each of the two narrow-side plates is automatically adjusted to the same set point {dot over (q)} set . 
     
     
         10 . A control device ( 100 ) for automatically controlling the heat dissipation {dot over (q)} in a side plate of a mold for casting metal, which comprises:
 a computing unit ( 110 ) for computing an actual value {dot over (q)} actual  for the heat dissipation;   a comparator ( 120 ) for computing a control deviation Δ{dot over (q)} for the heat dissipation by comparing the actual value for the heat dissipation with a preset set point; and   a controller ( 130 ) for converting the current control deviation Δ{dot over (q)} to a suitable variation of the volume flow rate {dot over (V)} of a coolant ( 300 ) through the mold ( 200 ) for automatically controlling the heat dissipation {dot over (q)} of the mold,   
       wherein the computing unit ( 110 ) is designed to compute the actual value for the heat dissipation {dot over (q)} actual  on a current basis from, among other things, the difference between the actual temperature of the coolant ( 300 ) at the coolant outlet of the mold and the actual temperature of the coolant at the coolant inlet of the side plate and material constants (ρ, c p ) for the coolant ( 300 ). 
     
     
         11 . A control device ( 100 ) in accordance with  claim 10 , wherein the computing unit ( 110 ) is designed to compute the actual value for the heat dissipation as follows:
     {dot over (q)} =(ρ* V*c   p   *d   v )/ A      
       where
 {dot over (q)}: the heat dissipation [W/m 2 ] 
 ρ: the density of the cooling water [kg/m 3 ] 
 {dot over (V)}: the volume flow rate of the cooling water [L/min] 
 c p : the specific heat of the cooling water (at constant pressure) [kJ/(kg·K)] 
 d v : the temperature difference T out -T in  [K] 
 A: the active cooling surface of the side plate. 
 
     
     
         12 . A control device ( 100 ) in accordance with  claim 10 , comprising at least one averaging unit ( 140 ) for averaging or buffering the measured actual values with respect to time, before they are supplied to the computing unit ( 110 ).