Thermal Balance

Thermal Die Management

• Casting and forging processes require a proper thermal management and lubrication of the die
• After the die is opened and the forged or casted part is removed, the spraying process is started.
• There are two different process strategies:
  
  Selective Spraying – spray cooling and lube application are separated into two steps;
  - Cooling with water only,
  - Application of lubricant – here the highest concentration possible should be selected (depending on media rheology) for the most effective process
  
  Combined spraying – a relatively highly diluted lubricant dispersion or emulsion is used for spray cooling AND lube application in one spraying step. This kind of process is mainly used in pressure die casting or fast running forging processes.

• In order to be able to apply the lubricant, the surface temperature has to be lowered to a level which is allowing proper film building; The typical temperature range is 150 to 250 °C – some lubricants are allowing temperatures up to 400 °C
• The required layer thickness of the applied lubricant depends on type of lubricant and tribological requirements. 

Process Target:

• Thermal Balance Qin = Qout
  Ideally the spraying process, in many cases in combination with internal die cooling, leads to thermal balance.

The Key to Effective Spray Cooling:

• Small droplets with
• high, optimized velocity and
• high spraying density [l/m²s]

Spraying Parameter

• Nozzle-type, -geometry and -size
• Pressure (air/media)
• Spraying distance and –angle
• Spraying strategy (static/dynamic)
• Spraying time
• Lubricant settings (1-liquid process)

→ Best cooling performance is achieved when the condition of ‚nucleate boiling‘ is achieved when the cooling agent is in contact with the die

→ Only a well-defined parameter setup will show best efficiency!