Spheroidal Graphite Iron (SGI)
SG Iron is a type of cast iron that has been treated while molten with an element such as magnesium or cerium to induce the formation of free graphite as nodules or spherulites. This imparts a measurable degree of ductility to the cast metal. The ductile iron family offers the design engineer a unique combination of strength, wear resistance, fatigue resistance, and toughness, as well as excellent ductility characteristics.
Presentation on all types of Cast Iron
SG Iron / Ductile iron is not a single material but is part of a group of materials which can be produced to have a wide range of properties through control of the microstructure. The common defining characteristic is the shape of the graphite — in ductile irons, graphite is in the form of nodules rather than flakes as in grey iron.
The sharp shape of the flakes of graphite creates stress concentration points within the metal matrix. The rounded nodules inhibit the creation of cracks and provide the enhanced ductility that gives the alloy its name. This nodular graphite structure also inhibits the creation of linear cracks, hence the ability to withstand distortion.
Chemical Composition
A typical chemical analysis of this material:
- Carbon — 3.2 to 3.6%
- Silicon — 2.2 to 2.8%
- Manganese — 0.1 to 0.5%
- Magnesium — 0.03 to 0.05%
- Phosphorus — 0.005 to 0.04%
- Sulfur — 0.005 to 0.02%
- Copper — 0.40%
- Iron — balance
Other elements such as copper or tin may be added to increase tensile and yield strength while simultaneously reducing ductility. Improved corrosion resistance can be achieved by replacing 15% to 30% of the iron with varying amounts of nickel, copper, or chromium.
Applications
Ductile iron is specifically useful in many automotive components, where strength needs surpass that of aluminium but do not necessarily require steel. Other major industrial applications include off-highway diesel trucks, Class 8 trucks, agricultural tractors, and oil well pumps.
Specifications
All grades offer better corrosion, wear and heat resistance.
Reference Download
Effect of Basic Chemical Element in SGI (Ductile Iron) — research paper from IJERT:
Chemical Components of Ductile Cast Iron
Chemical components are for reference only — not a strict material standard. Physical properties are the primary evaluation criterion.
| USA | Germany | ISO | C% | Si% | Mn% | P% | S% | Mg% | Cu% | Sn% |
|---|---|---|---|---|---|---|---|---|---|---|
| 60-40-18 | GGG40 | 400-18 | 3.50–3.78 | 2.80–2.85 | 0.2–0.5 | 0.03–0.06 | 0.02–0.035 | 0.020–0.060 | — | — |
| 65-45-12 | GGG40 | 450-10 | 3.30–3.80 | 2.40–2.90 | 0.2–0.5 | 0.03–0.06 | 0.02–0.040 | 0.020–0.060 | — | — |
| 70-50-05 | GGG50 | 500-7 | 3.20–3.60 | 2.30–2.90 | 0.4–0.6 | 0.03–0.06 | 0.02–0.040 | 0.030–0.055 | <0.4 | — |
| 80-60-03 | GGG60 | 600-3 | 3.00–3.50 | 2.40–2.80 | 0.3–0.5 | 0.03–0.06 | 0.02–0.040 | 0.035–0.050 | 0.30–0.40 | — |
| 100-70-03 | GGG70 | 700-2 | 3.65–3.90 | 1.70–1.90 | 0.3–0.5 | <0.06 | <0.03 | 0.035–0.050 | 0.30–0.40 | 0.03–0.06 |
| 120-90-02 | GGG80 | 800-2 | — | — | — | — | — | — | — | — |
Equivalent Grades — International Standards
| Country | Standard | Grade 1 | Grade 2 | Grade 3 | Grade 4 | Grade 5 | Grade 6 | Grade 7 |
|---|---|---|---|---|---|---|---|---|
| ISO | ISO-1083 | 400-15-18 | 450-10 | 500-7 | 600-3 | 700-2 | 800-2 | 900-2 |
| China | GB1348 | QT400-18 | QT450-10 | QT500-7 | QT600-3 | QT700-2 | QT800-2 | QT900-2 |
| USA | ASTM-A536 | 60-40-18 | 60-42-10 / 65-45-12 | 70-50-05 | 80-55-06 / 80-60-03 | 100-70-03 | 120-90-02 | — |
| Germany / Austria | DIN-1693 | GGG40 | — | GGG50 | GGG60 | GGG70 | GGG80 | — |
| European | EN-1563 | EN-GJS-400-15/18 | EN-GJS-450-10 | EN-GJS-500-7 | EN-GJS-600-3 | EN-GJS-700-2 | EN-GJS-800-2 | EN-GJS-900-2 |
| Japan | JISG5502 | FCD400 | FCD450 | FCD500 | FCD600 | FCD700 | FCD800 | — |
| Italy | UNI-4544 | GS370-17 | GS400-12 | GS500-7 | GS600-2 | GS700-2 | GS800-2 | — |
| France | NFA32-201 | FGS370-17 | FGS400-12 | FGS500-7 | FGS600-2 | FGS700-2 | FGS800-2 | — |
| UK | BS2789 | 400/17 | 420/12 | 500/7 | 600/7 | 700/2 | 800/2 | 900/2 |
| India | IS1865 | SG370/17 | SG400/12 | SG500/7 | SG600/3 | SG700/2 | SG800/2 | — |
| Spain | UNF | FGE38-17 | FGE42-12 | FGE50-7 | FGE60-2 | FGE70-2 | FGE80-2 | — |
| Belgium | NBN830-02 | FNG38-17 | FNG42-12 | FNG50-7 | FNG60-2 | FNG70-2 | FNG80-2 | — |
| Australia | AS1831 | 300-17 / 400-12 | — | 500-7 | 600-3 | 700-2 | 800-2 | — |
| Sweden | SS14 07 | 0717-02 | — | 0727-02 | 0732-03 | 0737-01 | 0864-03 | — |
| Norway | NS11-301 | SJK-400.3 / SJK-400 | — | SJK-500 | SJK-600 | SJK-700 | SJK-800 | — |
Grade Charts by Standard
ASTM A536 — 1993 (USA)
| ANSI/ASTM Grade | UNS | Tensile Strength σ≥ / MPa | Yield Strength σ≥ / MPa | Elongation δ≥ (%) |
|---|---|---|---|---|
| 60-40-18 | F32800 | 414 | 276 | 18 |
| 65-45-12 | F33100 | 448 | 310 | 12 |
| 80-55-06 | F33800 | 552 | 379 | 6.0 |
| 100-70-03 | F34800 | 689 | 483 | 3.0 |
| 120-90-02 | F36200 | 827 | 621 | 2.0 |
| Special Purpose Grades | ||||
| 60-42-10 | — | 415 | 290 | 10 |
| 70-50-05 | 485 | 345 | 5.0 | |
| 80-60-03 | 555 | 415 | 3.0 | |
GB/T 1348 — 1998 (China)
| Grade | Tensile Strength σb≥ / MPa | Yield Strength σ0.2≥ / MPa | Elongation δ5≥ (%) | Hardness HBS |
|---|---|---|---|---|
| QT400-18 / QT400-18-LT* | 400 | 250 | 18 | 130–180 |
| QT400-15 | 400 | 250 | 15 | 130–180 |
| QT450-10 | 450 | 310 | 10 | 160–210 |
| QT500-7 | 500 | 320 | 7 | 170–230 |
| QT600-3 | 600 | 370 | 3 | 190–270 |
| QT700-2 | 700 | 420 | 2 | 225–305 |
| QT800-2 | 800 | 480 | 2 | 245–335 |
| QT900-2 | 900 | 600 | 2 | 280–360 |
DIN 1693 — 1997 (Germany)
| Grade | Material No. (W-Nr.) | Tensile Strength σb≥ / MPa | Yield Strength σ0.2≥ / MPa | Elongation δ≥ (%) |
|---|---|---|---|---|
| GGG-40 | 0.7040 | 400 | 250 | 15 |
| GGG-50 | 0.7050 | 500 | 320 | 7 |
| GGG-60 | 0.7060 | 600 | 380 | 3 |
| GGG-70 | 0.7070 | 700 | 400 | 2 |
| GGG-80 | 0.7080 | 800 | 500 | 2 |
EN 1563 — 1997 (European Standard)
| Symbol | Number | Tensile Strength σ≥ / MPa | Yield Strength σ≥ / MPa | Elongation δ≥ (%) |
|---|---|---|---|---|
| EN GJS 350-22 | EN JS1010 | 350 | 220 | 22 |
| EN GJS 350-22-LT* | EN JS1015 | 350 | 220 | 22 |
| EN GJS 400-18 | EN JS1020 | 400 | 250 | 18 |
| EN GJS 400-18-LT* | EN JS1025 | 400 | 240 | 18 |
| EN GJS 400-15 | EN JS1030 | 400 | 250 | 15 |
| EN GJS 450-10 | EN JS1040 | 450 | 310 | 10 |
| EN GJS 500-7 | EN JS1050 | 500 | 320 | 7 |
| EN GJS 600-3 | EN JS1060 | 600 | 370 | 3 |
| EN GJS 700-2 | EN JS1070 | 700 | 420 | 2 |
| EN GJS 800-2 | EN JS1080 | 800 | 480 | 2 |
| EN GJS 900-2 | EN JS1090 | 900 | 600 | 2 |
ISO 1083 — 1987 (International)
| Grade | Tensile Strength σb≥ / MPa | Yield Strength σ0.2≥ / MPa | Elongation δ≥ (%) | Hardness HBS |
|---|---|---|---|---|
| 900-2 | 900 | 600 | 2 | 280–360 |
| 800-2 | 800 | 480 | 2 | 245–335 |
| 700-2 | 700 | 420 | 2 | 225–305 |
| 600-3 | 600 | 370 | 3 | 190–270 |
| 500-7 | 500 | 320 | 7 | 170–230 |
| 450-10 | 450 | 320 | 10 | 160–210 |
| 400-15 | 400 | 250 | 15 | 130–180 |
| 400-18 / 400-18 AL* | 400 | 250 | 18 | 130–180 |
| 350-22 | 350 | 220 | 22 | ≤150 |
