top of page

Gravity Die Casting

Production Technique 

​

Gravity die casting is a typical permanent mold casting process, in which the molten metal is poured into the pre-heated die cavity and the cavity is filled by the force that comes from earth gravity.  In gravity die casting, permanent metal moulds are used, mostly consisting from two or more parts. With the use of a pour spoon a liquid metal will be poured into the coquille mould to fabricate the casted part. The material choice of the moulds (mostly a steel kind) depends of the melting point of the metal that is to be melted.

Coquille casting is a very suitable technique for relatively simple geometries and the surface quality of the products is usually high. Because of the simplicity of this technique, small series are possible.

Gravity Die Casting.png

Technical details: 

​

  • The dimensional tolerances are listed in table DCTG 8 (standard ISO 8062-3). For wall thickness, table DCTG9 should be used. 

  • The weight can vary from a couple of grams to approximately 50 kg.

  • The surface roughness is in general below Ra= 7 μm.

  • The minimal wall thickness depends on the design of the part but it is recommended to take at least 5 mm.

​

Materials

Aluminium Alloys

​

  • A356

A356 is one of the most common gravity casting alloys.  It has excellent fluidity, corrosion resistance, can be welded and heat treated (T5 and T6) to improve the casting's mechanical properties.

​

 

  • A380

A380 is a common type of aluminum alloy in gravity casting, with great casting performance and some excellent mechanical and thermal properties, as well as a good economy. It exhibits excellent fluidity, pressure tightness, and resistance to hot cracking, which makes it even suitable for the aerospace industry. A380 has a long history, it is one of the longest-used metals but remains in extensive use in the current. You can find this alloy in auto parts, industrial parts, and building tools. A380 is an ideal material for gravity casting. The anti-soldering properties during the die casting process are beneficial to extend the life of casting molds. A380 aluminum casts are strong at high temperature and corrosion-resistant, can retain complex shapes and high accuracy.  A380 aluminum alloy is a suitable material for the fabrication of consumer tools, frames, buckets, hardware, handles, knobs, pump fixtures,  housings, valves, fittings, electronic equipment, engine brackets and gearbox cases.

​

 

  • 6061

Among the various useful aluminium alloys, aluminium alloy 6061 is typically characterized by properties such as fluidity, castability, corrosion resis- tance and high strength–weight ratio. 6061 is an alloy that can be heat treated. The alloy has also a very good weldability.

A356 gravity.png
A380 gravity.png
6061 gravity.png
zamak 3 gravity.png
zamak 5 gravity.png
zamak 7 gravity.png

Zinc Alloys

​

The Zinc alloys that are commonly used for gravity casting are often referred to as ZAMAK. The name ZAMAK comes from  the basic metallurgy of the alloy group: Z-Zinc, A-Aluminum, MA-Magnesium, and K-Kupfer (German for Copper). ZAMAK 3 is the most common alloy for gravity casting. With a combination of superior mechanical properties and low melting/manufacturing costs, it fulfills the needs for most applications. Other ZAMAK alloys include  ZAMAK 5, and ZAMAK 7. Common to each alloy is a consistent Aluminum content range, however, the alloys differ in specification by varying amounts of copper, magnesium, and nickel – resulting in different mechanical and physical properties.

 

  • ZAMAK 3

No. 3 alloy is usually the first choice when considering ZAMAK. Its excellent balance of desirable physical and mechanical properties, superb castability and long-term dimensional stability are the reasons why ZAMAK 3 is the most commonly used ZAMAK- alloy. ZAMAK 3 also offers excellent finishing characteristics for plating, painting and chromate treatments.

​

 

  • ZAMAK 5

ZAMAK 5 alloy castings are marginally stronger and harder than ZAMAK 3. However, these improvements are tempered with a reduction in ductility which can affect formability during secondary bending, riveting, swaging or crimping operations. ZAMAK 5 contains an addition of 1% copper which accounts for these property changes. The alloy is widely used and does exhibit excellent castability characteristics, as well as, improved creep performance over ZAMAK 3. Because of ZAMAK 3’s wide availability, material specifiers often strengthen components by design modifications instead of using ZAMAK 5. However, when an extra measure of tensile performance is needed, ZAMAK 5 alloy castings are recommended. The alloy is readily plated, finished and machined, comparable to ZAMAK 3 alloy.

 

 

  • ZAMAK 7

ZAMAK 7 alloy is a modification of ZAMAK 3 alloy in which lower magnesium content is specified in order to increase the fluidity. To avoid problems with inter-granular corrosion lower levels of impurities are called for and a small quantity of nickel is specified. ZAMAK 7 has slightly better ductility than ZAMAK 3 with other properties remaining at the same level. The alloy is therefore popular for those special cases where the customer wants thin-walled components requiring a good surface finish. However, research testing has shown that metal and die temperatures have a bigger effect than changing alloys. Close attention to control of the die casting process parameters is important so as to eliminate defects and achieve consistent quality.

​

bottom of page