Aluminum / Magnesium

One of the most common failure mechanisms when working with melts of Aluminum or Magnesium alloys are heat checking. Gross cracking and corrosion/erosion can also be a problem because of the complex dies used today. Use materials with high temperature strength and good ductility and toughness such as
Uddeholm Orvar Superior, or Uddeholm Dievar.

General

In die casting, melts of different alloys are injected with pressure into a die set and then solidified. Depending on the melt alloy, the dies are subjected to different high thermal and mechanical stresses.

Typical die failures

Die casting dies are exposed to severe thermal and mechanical cyclic loading, which puts high demands on the die material. Thus, there are some phenomena, which restrict die life.

  • Thermal fatigue cracking: The most common die failure in die casting is thermal fatigue cracking. During the die casting process the dies are subjected to alternate heating and cooling leading to high thermal stresses. This gives rise to severe strains in the surface layer of the die, gradually leading to thermal fatigue cracks (known as "heat checking"). Factors influencing thermal fatigue are basic material properties, design, die manufacturing and heat treatment (surface treatment), production parameters and maintenance.
  • Gross cracking: Gross cracking is a temporarily thermal and/or mechanical overloading of the die. It may lead to large cracks and even total failure of the die. Fractures influencing gross cracking are basic material properties, design, die manufacturing and heat treatment, production parameters and maintenance.
  • Indentation: Indentation in the parting lines or cavity surface are a matter of production parameters and basic die material properties.
  • Corrosion: In cases where the cavity surface lacks a protective layer, the cast metal will diffuse into the die surface. At the same time, alloying elements within the die will diffuse from the die surface into the cast metal. These processes can create both dissolution of the steel and intermetallic compounds between the cast metal and the die surface. In cases where severe formation of intermetallic compounds occurs, the cast metal will solder to the die surface. Factors influencing corrosion are production parameters, die design and surface treatment.
  • Erosion: This is a form of hot mechanical wear on the die surface, often in and near the gating area. Erosion epends to a high degree on production parameters and die design. Most commonly a combination of corrosion and erosion damages occur on the die surface.

Die material properties

For the best die performance, the following basic die steel values and properties should be high and good:

  • Hot yield strength
  • Temper resistance
  • Creep strength
  • Ductility
  • Toughness