Cold Flow

Cold Flow appears on the surface of a casting in a few different forms. In its worst form, it shows up as a series of curved linear marks on the surface, quite pronounced. In its more benign form, it appears as a diffuse region of spotty marks, as if it has been abraded.

As the name suggests, Cold Flow is caused when some of the metal in the cavity has lost too much heat and has begun to solidify before the cavity has filled. What you see on the surface of the casting are the boundaries between the cold metal and the hotter, liquid metal flowing around it.

Cold Flow is a particular problem in zinc alloy castings which need to be subsequently polished and electroplated. The small furrows and pits created by the cold flow are amplified against the flat shiny surface and turn the casting into a costly reject.

HotFlo! engineers have experience in solving Cold Flow problems with techniques such as:

• Die thermal control
• Shot profile analysis
• Cooling channel modification
• Changes to runners and gates
• Changes to die layout

To find out more, contact us by email today.