Compacted Graphite Iron: Part One


Compacted graphite iron (CGI) along with lamellar graphite iron and spheroidal graphite iron define the three main classes of cast iron according to morphology.
CGI displays very useful properties for a range of engineering applications with the tensile strength and elastic modulus being considerably higher than grey cast irons (75% and 35% respectively).

Cast iron is a family of alloys divided into several classes, defined by their graphite morphology and metallic matrix structure. There are mainly three different classes of cast irons classified by their graphite morphology; lamellar graphite iron (LGI), compacted graphite iron (CGI) and spheroidal graphite iron (SGI). LGI, commonly known as gray iron or flake graphite iron has a stable eutectic with graphite shaped as lamellas or flakes, see Figure 2a. In Figure 2c, SGI is illustrated.

It is also called ductile iron or nodular cast iron and has a stable eutectic with the graphite shaped as spheroids or nodules. The third class of cast iron is CGI which has a stable eutectic with a worm‐like shaped graphite, also called compacted graphite or vermicular graphite, see Figure 2b.

Figure 2: Microstructure of (a) gray iron, (b) CGI and (c) ductile iron

Compacted graphite iron (CGI) can be considered as a promising engineering material which contains graphite particles in compacted (vermicular) form. CGI shows intermediate mechanical and physical properties between grey and ductile irons. For instance, it possesses 70% higher tensile strength, 35% higher elastic modulus and nearly double fatigue strength of grey cast irons.

Thus it includes an optimal combination of different properties like strength, ductility and thermal conductivity which have lead to a distinctive attention during recent years. Because of these properties, CGI found a significant role in production of automotive engines, machine parts and also many different applications. Nowadays, several methods of casting of CGI products have been developed, trying to find the best method to have a precise control on the final microstructure.

The ISO 16112 international standard for CGI provides for five grades of CGI, ranging from a minimum tensile strength of 300 MPa to 500 MPa (GJV 300 to GJV 500). For each of these grades, the microstructure specification requires a nodularity range of 0-20%.

Pearlite content can be chosen to suit the application, with the GJV 300 Grade being fully ferritic and the GJV 500 Grade being fully pearlitic. Flake graphite is inadmissible. As with grey iron and ductile iron, specific alloying elements can be added to enhance high temperature strength, wear resistance or other properties.

A full range of heat treatments, including austempering, can also be applied. Typical chemistry ranges are provided below, although the chemical specification of CGI castings is subordinate to mechanical properties.

Figure 1: a) CGI microstructure containing 10% nodularity and b) Deep-etched SEM micrographs show the complex coral-like graphite in three-dimensions

Table 1: Mechanical and Physical properties of 10% Nodularity CGI – ISO 16112


1. A.Berglund: Criteria for Machinability Evaluation of Compacted Graphite Iron Materials, Doctoral thesis, KTH Royal Institute of Technology, Department of Production Engineering Machine and Process Technology, Stockholm, Sweden 2011, ISSN 1650-1888, ISBN 978-91-7501-159-2;

2. H.H. Hooshyar: Thermal analysis of compacted Graphite Iron, Chalmers University of Technology, Diploma work no 60/2011 Department of Materials and Manufacturing Technology, SE-412 96 Gothenburg, Sweden;

3. Compacted Graphite Iron-Material Data Sheet, SinterCast, Supermetal CGI,, Accessed March 2017;

기술 자료 검색

검색할 어구를 입력하십시오:

검색 범위



Total Materia는 다양한 나라와 규격에 따른 금속학 이미지에 대한 정보를 포함하고 있습니다.

메뉴 표시줄에 특별히 디자인된 금속학 탭을 이용하여, 금속학 데이터가 포함된 관심 재질을 리스트에서 선택하실 수 있습니다.

또한 금속학 데이터는 표준 빠른 검색을 통해 찾을 수 있으며 규격 내 소그룹 페이지를 통해 이용 가능한 관련 자료들이 표시됩니다.

재질명을 '재질'창에 입력하신 후 규격을 알고 계신다면 규격을 선택하고 '검색' 버튼을 클릭합니다.

미세 구조에 대한 일반적인 정보가 관련 관심 재질의 화학 조성과 함께 출력됩니다.

구조의 세부 범위를 보여주는 여러 배율에서의 이미지가 가능하다면 제공됩니다.

다양한 조건을 선택할 수 있으며, '조건 선택' 메뉴를 사용하여 다양한 공정 및 열처리에 따른 금속학 이미지를 보여줍니다.

Total Materia 데이터베이스를 사용해 보실 수 있는 기회가 있습니다. 저희는 Total Materia 무료 체험을 통해 150,000명 이상의 사용자가 이용하고 있는 커뮤니티로 귀하를 초대합니다.