Excerpt from the Jan. 2013 Foundry & Management Technology article by John Hall.
Starting a new die Die coating application Die heating, coating
Die coating in gravity diecasting is one of the operational parameters of the casting process that is often overlooked or misunderstood. Die coatings are necessary for three basic reasons.
Coatings provide a protective barrier between the die and the casting to prevent die erosion and wear. Coatings provide some degree of control over the solidification rate and direction. Coatings provide a barrier between the die and casting so that the casting will release from the die.
With proper use, a die coating can be used to control the thermal gradients such that directional solidification can be achieved. This allows a pathway for feed metal to flow into the solidifying structure and compensate for normal metal shrinkage during solidification. This is particularly important in castings with thin sections that expand to thicker sections: The thin areas must remain open to ensure that shrinkage will not occur in the adjacent thick section.Read More