Causes for the Damages of Glass Molds

Since the cavity surface of the cast iron glass mold directly contacts high temperature molten glass, it is subjected to chemical corrosion, abrasion and alternating hot and cold stress. Used at 500-700℃, it is also subjected to serious oxidization. Frequent mechanical impact between the mold components also causes damages. 

The causes for the damages of glass mold include: 

1) Fatigue 

It is found that there are a lot of fatigue cracks on the cavity surface of the damages molds. Those cracks are caused by the fatigue between the alternating hot and cold stress and mold components. Molds are usually made of brittle cast iron materials, which contain a lot of graphite. The graphite is a crack source. The graphite is prone to crack by the external thermal stress and cyclic impact forces. Once there are a lot of fatigue cracks generated on the cavity surface, small spalling will be generated. 

 

2) Mechanical impact

Frequent mechanical impact between mold components is the second reason for the damage of molds. During processing and transport, impact may cause brittle fracture damages. During use, impact force and abnormal mechanical operation or residual hard glass on the parting surface will also cause the damages of molds. 

 

3) Oxidization and corrosion

At its service temperature (500-700℃), cast iron molds have the trend of thermal growth, oxidization and peeling. Meanwhile, during use, the cavity surface of molds directly contacts high temperature molten glass. Molten glass has serious chemical corrosion on the cavity surface.