Basic Knowledge – Article Series Part 3 Lightmetal Alloys: Spotlight Zinc
Whether switches, handles, decorative strips, covers or fittings: zinc alloys can be cast into almost any desired shape, not only close to the final dimensions. What are the most common zinc alloys and what properties do they have?
Die Casting with Zinc Alloys
Zinc alloys have long been successfully used in die casting or rolled for mounting on roofs and facades. Modern die casting is one of the special processes that contribute to the fact that zinc can be used in many areas of our lives. This special technology makes new applications possible again and again. They are in demand wherever high stability and high quantities are required. And in addition, the corresponding products often look beautiful.
It is above all these properties that make zinc particularly suitable for die casting:
- high economic efficiency due to very short cycle times, low melting temperature (380-390 °C), minimum draft angles, near-net-shape production and long mold service life
- good casting properties: tightest tolerances of the raw casting (up to approx. IT 8), excellent flow behaviour (thin-wall casting), electrical and electromagnetic shielding
- mechanical material properties (for ZP0410 e.g. tensile strength 300-340 MPa, yield strength (0.2 %) 290-330MPa, modulus of elasticity 85 GPa)
- excellent conditions for surface finishing
- 100% recyclability
During the casting process, precise surface structures can also be integrated, giving the appearance an extraordinary effect. Zinc die casting also offers excellent conditions for surface finishing processes such as galvanic coating (see Figure 1).
As impressively demonstrated by the zinc die casting competition, components made of zinc die cast are high-tech products today, which are used for a wide variety of applications and are used in many areas of daily life, in automotive engineering, mechanical and apparatus engineering, in electrical engineering and electronics as well as in construction and furniture making (see Figure 2). The main part of the zinc used in cars is made up of components and parts made of die cast zinc, for example as belt tensioners, starter motor and windshield wiper motor housings, headlight and exterior mirror supports, as part of the steering column and front sensor for airbags, as door lock cylinders and door handles. Over 100 zinc individual parts stand for mobility, safety and functionality, but also for decorative elements with a high perceived value.
New Zinc Alloys
The product range will continue to grow in the coming years, because zinc die casting allows the implementation of complex geometries with thin wall thicknesses with high reproducibility within narrow tolerances and with high strength values. Quality and quality assurance play a decisive role here - from the standard-compliant zinc die casting alloy to the finished castings.
Further developments of zinc die casting alloys allow the casting of finest wall thicknesses (see Figure 3).
Brass - an Alloy of Zinc and Copper
Brass with its warm golden yellow to yellow-red tones radiates elegance and creates atmosphere. Brass is also used in almost all industrial sectors: In mechanical engineering, apparatus engineering and power station construction it is used for bearings, valves, synchronizer rings, pipes, turbines and blade wheels, in vehicle construction for car radiators and heat exchangers, in precision engineering and instrument construction for measuring and control devices and in electrical engineering and electronics for plug connections, clamp contacts and semiconductor connections. Brass is an alloy of zinc and copper, with the most common compounds having a zinc content of 5 to 45 %.
The colour spectrum ranges from golden red with a high copper content to light yellow with a high zinc content, whereby it is mainly thanks to the zinc content that brass retains its colour for many years: Copper and zinc mix optimally in the melt and remain evenly distributed within each other even when solidifying. Although theoretically an infinite number of alloys between copper and zinc can be produced, in practice the number is limited to about 60 types. This means that largely all desired physical, chemical and technological properties can be produced.
However, not only the two base metals are excellently soluble in each other: numerous other elements such as aluminum, iron, manganese, nickel, silicon and tin can be added to the molten mass, resulting in new alloys with advantageous properties. Brass types with such specific additives are called special brass. Those grades which contain small amounts of lead as a third component for better machinability are also called machining or machining brass.
Brass - and thus also the zinc content in it - is nowadays recycled as a matter of course. Brass scrap is used in both copper and brass production.
Wrought Zinc Alloys - New Fields of Application for Zinc
Wrought zinc alloys are now also available as a cost-effective material alternative, e.g. for building hardware and locking systems. Comparable to aluminum and copper-based wrought materials, solid profiles of various geometries can be produced from a wide range of zinc alloys with homogeneous material characteristics by extrusion and drawing.
Depending on the requirements, high-precision parts and components, e.g. for fittings or locking systems, can be produced by forging or machining (turning, sawing, milling, drilling). The components are excellently suited for surface refinement, but are also distinguished by good functional properties when left unfinished.