Cast material

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Cast materials are materials that are particularly well suited for casting . They are also called casting alloys or casting alloys respectively. The counterpart are wrought alloys , which are particularly suitable for forming ( forging , rolling ). Cast materials are usually expressly designated as such, for example aluminum cast alloys, aluminum die cast alloys (for the die casting process ) or the copper alloys gunmetal and bronze cast . Iron materials are an important exception : the wrought alloys are called steel , the cast alloys are cast iron (at least 2% carbon, usually around 4.3%) and cast steel (less than 2% carbon, usually significantly less).

Casting materials are mainly used for molding , i.e. for casting in molds that approximate the final component shape. Wrought alloys are also cast, but into bars , slabs and rods that are further processed by forming. For it is the ingot casting and continuous casting used.

The standardized material names usually begin with a G (cast) or international with C (from English cast = cast).

Before casting, casting materials are subjected to a special melt treatment.

Important alloy elements

Casting alloys usually have good castability . These are mostly eutectic alloys or near-eutectic alloys that have a particularly low melting point , which leads to low energy requirements for melting, as well as low temperature loads on the molds, crucibles and tools. In addition, the eutectic alloys have a defined melting point, while other alloys have a melting range in which one part of the material is solid and another part is liquid. This melting interval favors casting defects and leads to a coarse-grained structure and thus poor mechanical properties ( hardness , strength ). In the near-eutectic alloys, the melting interval is small.

During the solidification of most materials decreases the volume, while in silicon (and water increases). Silicon is an important alloying element for many cast materials because it reduces the change in volume.

Important cast materials

The most important casting material is cast iron , which makes up about 75% of the total production in the foundry. In addition to carbon , silicon is also important alloying elements. There are numerous types of cast iron, but the most important is lamellar graphite cast iron . Special types of steel that are suitable for casting are known as cast steel ; however, it is of little importance. Cast steel and cast iron are also summarized under the term cast iron materials . The second most important cast material are aluminum alloys . Their most important alloying elements are silicon, magnesium and copper. Magnesium , copper , tin and zinc are also important as casting materials in foundries . Titanium alloys are rarely used because of their very high melting point. In addition, the titanium melt reacts very quickly with the oxygen in the air.

Cast iron materials

Iron materials contain iron and carbon as the main element . The cast iron materials also contain silicon and in some cases other elements such as phosphorus , which further lowers the melting temperature.

  • Cast steel (standardized designation GS)
  • Cast iron (the names begin with GJ (from English Iron ))
    • Gray cast iron / gray cast iron: With this type, the carbon is present as graphite , which gives the fracture surfaces a gray color.
      • Cast iron with lamellar graphite (designation according to European standard (EN): GJL, according to DIN (old) GG (gray cast)): The standard type with lamellar graphite. It has only low tensile strength , cannot be forged, but it can be cast very well and is inexpensive
      • Cast iron with vermicular graphite (GJV): A transition grade to the following grade
      • Cast iron with nodular graphite (EN: GJS (nodular cast iron) DIN: GGG (globular gray cast iron)): In this type, the graphite forms small spheres, which gives the material high strength and makes it malleable.
    • Malleable cast iron (GJM (from English Malleable ))

Non-ferrous cast materials

They contain a non-ferrous metal as their main element . The most important are aluminum and magnesium . Nor otherwise be used tin , zinc and copper and its alloys, bronze and brass . Titanium alloys can only be cast with great effort.

The aluminum alloys that are used for casting include in particular the aluminum-silicon alloys which have a share of over 90%.

The standardized abbreviations usually contain a "G" for cast or a "C" for cast (English for cast). Cast aluminum alloys, for example, start with AC followed by a number according to international standards, with GA (cast, aluminum) according to DIN followed by the chemical composition. According to DIN, there are additional designations for light metal casting alloys, such as S for sand cast, D for die cast.

literature

Individual evidence

  1. ^ Bernhard Ilschner, Robert Singer: Material science and manufacturing technology - properties, processes, technologies , Springer, 5th edition, 2010, p. 350
  2. ^ Bernhard Ilschner, Robert Singer: Material science and manufacturing technology - properties, processes, technologies , Springer, 5th edition, 2010, p. 350.
  3. ^ Bernhard Ilschner, Robert Singer: Material science and manufacturing technology - properties, processes, technologies , Springer, 5th edition, 2010, p. 350
  4. ^ Bernhard Ilschner, Robert Singer: Material science and manufacturing technology - properties, processes, technologies , Springer, 5th edition, 2010, p. 350
  5. ^ Eberhard Roos, Karl Maile: Material science for engineers - basics, application, testing , Springer, 4th edition, 2011.
  6. ↑ Hans-Jürgen Bargel, Günter Schulze (Ed.): Material science , Springer, 11th edition, 2012, p. 284.
  7. ↑ Berns, Theisen, p. 157.
  8. ↑ Jürgen Ruge, Helmut Wohlfahrt: Technology of Materials - Production, Processing, Use , Springer, 9th edition, 2013, p. 286.