Plastic moulds are plastic moulds which are made of 45 steel, P20, 718 and other plastic die steels. The analysis of the failure of plastic mold can better guide the research and development of die steel. The failure forms of plastic moulds are:
1, wear and corrosion of the cavity surface
1) the plastic melt is flowing in the mold cavity with certain pressure. The solidified plastic parts are removed from the mold, which will cause friction to the mold surface and cause wear.
2) the reinforced resin filler in the plastic will produce scour, wear and corrosion on the surface of the mold cavity.
3) at the same time, the chlorine, fluorine and other components in the plastic processing are heated to decompose the corrosion gas HCl and HF.
These cross effects will cause damage to the coating or protective layer on the surface of the cavity, resulting in wear and corrosion.
2. Failure of plastic deformation
1) plastic mold cavity surface compression and heating can cause plastic deformation failure, especially when small mold works on large tonnage equipment, it is prone to overload plastic deformation.
2) the strength and toughness of the material used in plastic mould are not enough, and the deformation resistance is low.
3) the hardened layer of the plastic mold cavity surface is too thin, the deformation resistance is insufficient or the working temperature is higher than the tempering temperature, and the phase change softening occurs.
These will result in die surface depression, wrinkles, pitting, angular heap collapsed damage.
3, the fracture of plastic mould
1) the shape of the plastic mold is complicated with many corners, thin wall and other parts, and the local stress concentration in these parts will cause fracture phenomenon.
2) the structural stress, thermal stress or insufficient tempering caused by temperature difference, the residual austenite is transformed into martensite at the temperature, causing local volume expansion and producing tissue stress in the mold.