Zinc Casting

Zinc alloy's high strength and hardness, means that it is the ideal alternative to machined, pressed, stamped and fabricated items. Complex net-shaped zinc housings with precise thin walls give excellent electrical performance and shielding properties to electronic connectors as well as shields, chassis and frames for handheld telecoms & computing equipment. The small, intricate components from our proprietary multi-slide die casting are used in many applications, including mobile phone antennae, portable computers, disk drives, precision interlocking gears, heatsinks, shutter mechanisms in cameras and many other consumer electrical and electronics applications. Our strength in automotive is in electronic and safety critical applications.

Characteristics

• High strength and hardness
• Excellent electrical conductivity
• High thermal conductivity
• Lowest cost raw material
• High dimensional accuracy and stability
• Excellent thin wall capability
• Ability to cold form, which eases joining
• High quality finishing characteristics
• Outstanding corrosion resistance
• Full recyclability

Zinc production, starts with the mining of bulk ores, which often contain a mixture of lead, zinc and silver. Zinc concentrates can then be smelted to about 98% purity, which is acceptible for some general galvanising, but demand for higher purity zinc, as traded on the LME, now means that most zinc is produced electrolytically, to produce High Grade and Special high Grade zinc, with purities of 99.95% and 99.99% respectively - the latter being the benchmark grade for LME contracts.

Zinc is produced extensively in North and South America, Asia, Australia and in Europe. This wide base of producers, combined with the industries' low level of integration between miners and smelters, means the industry has often been slow to react to poor market conditions. In the past, this has led to long periods of over production with producers reluctant to make significant production cutbacks to keep supply and demand in balance. As a result, zinc stocks tend to build up significantly during economic slowdowns and during economic recoveries zinc prices often lag behind the other base metals, while its high levels of stocks are drawdown.

Gravity Die Casting of Zinc Alloys

A recently developed family of zinc foundry alloys suitable for sand, permanent mold, plaster mold, shell mold and investment casting. Many of these alloys also can be die cast in cold chamber machines where strength and/or hardness beyond the properties of AG41A are required. Currently, two alloys are finding increasing application, a 12%-Al alloy (ILZRO 12) and a 27%-Al alloy (Zn-27Al). These two gravity casting zinc alloys have been designed for structural applications and should not be confused with die casting and slush casting alloys, which often are used for decorative gravity cast parts.

The mechanical properties of these zinc alloys make them attractive substitutes for cast iron and copper alloys in many structural and pressure-tight applications. Because zinc is less costly than copper, these zinc alloys have a distinct cost advantage over copper-base alloys. The ease of machining of zinc and its inherent corrosion resistance give it advantages over cast iron.

Zinc gravity casting alloys have attractive foundry properties. Due to their low melting temperatures (below 540°C) and casting temperatures, energy requirements are low. They are readily cast in thin sections - less than 2,5 mm in sand molds. Melting and casting of these alloys are virtually pollution free. No fluxing or degassing is required, and because of the low casting temperatures minimal pollution from the sand mold results.

The 12%- Al alloy is preferred for heavy sections and is suitable for permanent mold casting in both metal and graphite molds. Its permanent mold casting characteristics are similar to those of aluminum permanent mold alloys. The 27%-Al alloy should be specified when higher mechanical properties are required in thin section sand castings. Care should be taken to prevent hot spots in the mold, which contribute to underside shrinkage.

Zinc gravity casting alloys can be used for general industrial applications where strength, hardness, wear resistance or good pressure tightness is required. Zinc alloys often are employed to replace cast iron because of their similar properties and higher machinability ratings. The good bearing and wear characteristics of zinc alloys permit them to be used for bearing bushings and flanges. Other applications in which zinc alloys have been successfully substituted for cast iron or copper alloys include fuel-handling components, pulleys, electrical fittings and hardware components.