Causes of Mold Surface Peeling After Repeated Aluminum Casting Cycles

Mold surface peeling is a common aging failure phenomenon in the later stage of repeated aluminum alloy casting production, which directly leads to casting surface pits, blemishes and dimensional deviation, seriously reducing product qualification rate. Industrial fault statistics show that three core factors cause 92% of mold surface peeling problems. The primary factor is cyclic thermal fatigue stress: the mold repeatedly switches between 180-220℃ preheating state and 680℃ high-temperature molten aluminum contact state, and the alternating temperature difference generates continuous tensile and compressive stress, leading to gradual fatigue shedding of the mold surface metal structure, accounting for 58% of total peeling faults. The second factor is failure of the nitriding hardened layer: when the surface nitride layer thickness is lower than the standard 0.3-0.5mm (less than 0.25mm), the protective ability is insufficient, and cyclic high-temperature friction and impact cause hardened layer peeling, accounting for 24% of faults. In addition, long-term residual release agent on the mold surface will produce slow chemical corrosion on the metal microstructure, causing local peeling; excessive polishing maintenance will wear off the surface dense protective layer, reducing surface structural compactness; unstable casting pressure with fluctuation exceeding ±0.05MPa will cause unbalanced mold surface load and accelerate fatigue peeling. Targeted control of the above factors can reduce mold surface peeling failure rate by 89%.